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	summary
	abstract	Brine sludge is an industrial waste generated in chloral alkali industry. The generated brine sludge waste is dumped into landfills and contains barium sulphate, calcium carbonate, magnesium hydroxide, sodium chloride, clay, and toxic elements like chromium, zinc, copper, and vanadium, therefore posing an environmental threat. Consequently, there is an urgent need to convert toxic brine sludge waste into its non-toxic form. The present invention thus aims to achieve total utilization of this brine sludge for making functionalized brine sludge material useful for a broad application spectrum.
	abstract	The present invention relates to the use of a mixed carbonate of formula AB(CO3)2, in which A and B are different and chosen from alkali metals, alkaline-earth metals and rare earths, for the containment of radioactive carbon. This use may for example involve a process comprising: mixing CO2 having a radioactive carbon to be contained, or a simple carbonate of an alkali, alkaline-earth or rare-earth metal having a radioactive carbon to be contained, with an aqueous solution of a mixture of ACln and BClm or with an aqueous solution of a mixture of A(OH)n, and B(OH)m in order to obtain a precipitate of AB(CO3)2, where n and m are integers sufficient to compensate for the charge of A and B respectively; recovery of the AB(CO3)2 precipitate in powder form; and then pressing and sintering of the powder at a 20 temperature below the decarbonation temperature of the mixed carbonate manufactured in order to obtain sintered pellets of mixed carbonates for the containment of the radioactive carbon.
	summary
	description	This application claims priority from U.S. patent application Ser. No. 14/195,890, filed Mar. 4, 2014, which claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Ser. No. 61/781,245, filed Mar. 14, 2013, entitled IN-CONTAINMENT SPENT FUEL STORAGE TO LIMIT SPENT FUEL POOL WATER MAKEUP. This invention is also related to U.S. patent application Ser. No. 14/195,878, entitled Apparatus for Passively Cooling a Nuclear Plant Coolant Reservoir, Attorney docket NPP 2012-003, filed Mar. 4, 2014. The present invention relates to a passive spent fuel cooling system for a nuclear power plant and more specifically to in-containment spent fuel storage to limit spent fuel pool water make-up. The secondary side of nuclear reactor power generating systems creates steam for the generation of saleable electricity. For reactor types such as pressurized water reactors or liquid metal cooled reactors, the primary side comprises a closed circuit which is isolated and in heat exchange relationship with a secondary circuit for the production of useful steam. For reactor types such as boiling water reactors or gas cooled reactors, the gas used for generating saleable electricity is heated directly in the reactor core. A pressurized water reactor application will be described as an exemplary use of the concepts claimed hereafter; though it should be appreciated that other types of reactors may benefit equally from the concepts disclosed herein as well. The primary side of a pressurized water reactor system comprises a reactor vessel enclosing a core internal structure that supports a plurality of fuel assemblies containing fissile material, the primary circuit within heat exchange steam generators, the inner volume of a pressurizer, pumps and pipes for circulating pressurized water; the pipes connecting each of the steam generators and pumps to the reactor vessel independently. Each of the parts of the primary side comprising a steam generator, a pump and a system of pipes, which are connected to the vessel, form a loop of the primary side. For the purpose of illustration, FIG. 1 shows a simplified pressurized water nuclear reactor primary system, including a generally cylindrical reactor pressure vessel 10 having a closure head 12 enclosing a nuclear core 14. A liquid reactor coolant, such as water, is pumped into the vessel 10 by pumps 16 through the core 14 where heat energy is absorbed and is discharged through a heat exchanger 18, typically referred to as a steam generator, in which heat is transferred to a utilization circuit (not shown) such as a steam driven turbine generator. The reactor coolant is then returned to the pump 16 completing the primary loop. Typically, a plurality of the above-described loops are connected to a single reactor vessel 10 by reactor coolant piping 20. Pressurized water nuclear reactors are typically refueled on a 12-18 month cycle. During the refueling process, a portion of the irradiated fuel assemblies within the core are removed and replenished with fresh fuel assemblies which are relocated around the core. The removed spent fuel assemblies are typically transferred under water out of the reactor containment 22 to a separate building that houses a spent fuel pool, figuratively shown in FIG. 1 and designated by reference character 24, in which these radioactive fuel assemblies are stored. The water in the spent fuel pool is deep enough to shield radiation to an acceptable level and prevents the fuel rods within the fuel assemblies from reaching temperatures that could breach the cladding of the fuel rods which hermetically house the radioactive fuel material and fission products. Cooling continues at least until the decay heat within the fuel assemblies is brought down to a level where the temperature of the assemblies is acceptable for dry storage. Events in Japan's Fukushima Dai-ichi Nuclear Power Plant reinforced concerns over the possible consequences of the loss of power over an extended period to the systems that cool spent fuel pools. As a result of the tsunami, there was a loss of off-site and on-site power which resulted in a station blackout period. The loss of power shut down the spent fuel pool cooling systems. The water in some of the spent fuel pools dissipated through vaporization and evaporation due to a rise in the temperature of the pools, heated by the highly radioactive spent fuel assemblies submerged therein. Without power over an extended period to pump replacement water into the pools the fuel assemblies could potentially become uncovered, which could, theoretically, raise the temperature of the fuel rods in those assemblies, possibly leading to a breach in the cladding of those fuel rods and the possible escape of radioactivity into the environment. More recently designed passively cooled nuclear plants, such as the AP1000® nuclear plant design offered by Westinghouse Electric Company LLC, Cranberry Township, Pa., which utilizes passive safety systems, has been evaluated to be able to continue to provide cooling for at least three days following an extreme event like the one at Fukushima. It is an object of this invention to modify the way spent fuel is handled and stored so that the spent fuel can be cooled for at least ten days following a Fukushima type of event. It is a further object of this invention to provide such cooling passively to enable a commercial 1,100 megawatt nuclear plant to provide core and spent fuel cooling using passive means for ten or more days. These and other objects are achieved by a nuclear steam supply system having a nuclear reactor primary coolant loop enclosed within a hermetically sealed containment. The containment includes a nuclear reactor vessel for supporting and housing a plurality of nuclear fuel assemblies within a core. The nuclear reactor vessel is supported within the containment as part of the nuclear reactor primary coolant loop. A refueling cavity extends above the nuclear reactor within the containment. An in-containment refueling water storage tank is supported within the containment outside of the refueling cavity, at an elevation above the core for, upon command, flooding at least a portion of the refueling cavity with the coolant in furtherance of refueling the reactor vessel. The in-containment refueling water storage tank has a full level substantially at which a volume of the refueling coolant is maintained during normal reactor operation. An irradiated nuclear fuel assembly storage tank is supported within the containment below a portion of the refueling cavity. The irradiated nuclear fuel assembly storage tank is configured with fuel assembly storage racks for storing irradiated nuclear fuel within the containment outside the core when the reactor vessel is in operation and the refueling cavity is drained. The irradiated nuclear fuel assembly storage tank is configured to selectively place a nuclear fuel assembly storage tank cooling conduit, connected to the irradiated nuclear fuel assembly storage tank, in fluid communication with the in-containment refueling water storage tank or the refueling cavity. In one embodiment, a portable lower reactor internals storage rack is configured to fit on a lid of the irradiated nuclear fuel assembly storage tank when the lid is closed, for storing the reactor lower internals when they are removed from the nuclear reactor vessel. The lower internals storage rack is configured to be removed from the lid when access is needed to an interior of the irradiated nuclear fuel assembly storage tank to store nuclear fuel. In still another embodiment, the irradiated nuclear fuel assembly storage tank includes a lid for covering and sealing an access opening in the top of the irradiated nuclear fuel assembly storage tank wherein the lid is coupled to a wall of the irradiated nuclear fuel assembly storage tank through a hinge that is configured to swing the lid out of the way of the access opening when in a fully open position, to load or unload a nuclear fuel assembly into or out of an interior of the irradiated nuclear fuel assembly storage tank. Preferably, the irradiated nuclear fuel assembly storage tank includes a long-term nuclear fuel assembly storage tank and a short-term nuclear fuel assembly storage tank that are each configured to separately store fuel assemblies. Desirably, the long-term nuclear fuel assembly storage tank has an interior including a plurality of fuel assembly racks that are accessed through a first access opening sealed by a removable first lid and the short-term nuclear fuel assembly storage tank has an interior including a plurality of fuel assembly racks that are respectively accessed through corresponding individual fuel assembly rack opening lids that are supported within a second access opening in the short-term nuclear fuel assembly storage tank. Each of the fuel assembly rack opening lids in the short-term nuclear fuel assembly storage tank cover a corresponding opening in the plurality of fuel assembly racks in a closed position and provide access to the corresponding opening in an open position. In one arrangement, the second access opening includes a second lid that seals the second access opening and seats above the individual fuel assembly rack opening lids. Preferably, the long-term nuclear fuel assembly tank is a cylindrical tank and the short-term nuclear fuel assembly storage tank is a vaulted tank with a liner. In another embodiment, the fluid communication between the irradiated nuclear fuel assembly storage tank and the in-containment refueling coolant storage tank is configured to flow by natural circulation. Preferably, the fluid communication between the irradiated nuclear fuel assembly storage tank and the refueling cavity is also configured to flow by natural circulation. This invention also contemplates a method of refueling a nuclear steam supply system having a nuclear reactor primary coolant loop enclosed within a hermetically sealed containment. The containment includes a nuclear reactor vessel for supporting and housing a plurality of nuclear fuel assemblies within a core. The nuclear reactor vessel is supported within the containment as part of the nuclear reactor primary loop. A refueling cavity extends above the nuclear reactor vessel within the containment and an in-containment refueling coolant storage tank is supported within the containment outside the refueling cavity at an elevation above the core for, upon command, flooding at least a portion of the refueling cavity with a refueling coolant in furtherance of refueling the reactor vessel. The in-containment refueling coolant storage tank has a full level substantially at which a volume of the refueling coolant is maintained during normal reactor operation. An irradiated nuclear fuel assembly storage tank is supported within the containment below a portion of the refueling cavity. The irradiated nuclear fuel assembly storage tank is configured with fuel assembly storage racks for storing irradiated nuclear fuel within the containment outside of the core when the reactor vessel is in operation and the refueling cavity is drained. The irradiated nuclear fuel assembly storage tank is also configured to selectively place a nuclear fuel assembly storage tank coolant conduit, connected to the irradiated nuclear fuel assembly storage tank, in fluid communication with the in-containment refueling coolant storage tank or the refueling cavity. The method includes the steps of: flooding the refueling cavity with the coolant from the refueling coolant storage tank; removing a head from the reactor vessel; opening a lid on the irradiated nuclear fuel assembly storage tank; removing at least some of the fuel assemblies from the core into the irradiated nuclear fuel assembly storage tank; closing the lid on the irradiated fuel assembly storage tank; loading a number of new fuel assemblies into the core; closing the head on the reactor vessel; draining the refueling cavity into the in-containment refueling coolant storage tank; and starting up the reactor with at least some of the removed fuel assemblies from the core stored in the irradiated nuclear fuel assembly storage tank. In one embodiment, the method includes the steps of configuring the irradiated nuclear fuel assembly storage tank coolant conduit in fluid communication with the refueling cavity after the refueling cavity is flooded; and configuring the irradiated nuclear fuel assembly storage tank coolant conduit in fluid communication with the in-containment refueling coolant storage tank after the refueling cavity is drained. In another embodiment, the method further includes the steps of operating the nuclear steam supply system for an operating cycle; shutting down the reactor vessel; flooding the refueling cavity with the coolant from the refueling coolant storage tank; removing a head from the reactor vessel; opening a lid on the irradiated nuclear fuel assembly storage tank; moving at least some of the fuel assemblies within the irradiated fuel assembly storage tank to a spent fuel pool outside the containment; removing at least some of the fuel assemblies from the core into the irradiated nuclear fuel assembly storage tank; closing the lid on the irradiated fuel assembly storage tank; loading a number of new assemblies into the core; closing the head on the reactor vessel; draining the refueling cavity into the in-containment refueling coolant storage tank; and starting up the reactor with at least some of the fuel assemblies removed from the core stored in the irradiated nuclear fuel assembly storage tank. Preferably, the irradiated nuclear fuel assembly storage tank includes a long-term nuclear fuel assembly storage tank and a short-term nuclear fuel assembly storage tank. The long-term nuclear fuel assembly storage tank and the short-term nuclear fuel assembly storage tank are each configured to separately store fuel assemblies. In such an embodiment the step of removing at least some of the fuel assemblies from the core into the irradiated nuclear fuel assembly storage tank includes the steps of: identifying the fuel assemblies within the core that are not to be returned to the core; removing at least some of the fuel assemblies in the core that are not to be returned to the core to the long-term nuclear fuel assembly storage tank; and removing at least some of the fuel assemblies in the core that are to be returned to the core to the short-term nuclear fuel assembly storage tank. In a further embodiment, the short-term nuclear fuel assembly storage tank includes a fuel assembly rack having compartments with each compartment having an opening into which one of the fuel assemblies can be loaded, with each compartment having a separate cover which can be individually moved to an open or closed position, including the step of opening only one cover at a time with the remaining covers closed as the fuel assembly is loaded into the corresponding compartment. In an additional embodiment, the reactor vessel has a lower internals and the long-term nuclear fuel assembly storage tank has a lid with a removable lower internals storage stand that fits on top of the lid. In such an embodiment, the method further includes the steps of: fitting the lower internals storage stand to the lid after the fuel assemblies that are not to be returned to the reactor vessel are loaded into the long-term nuclear fuel assembly storage tank; removing the lower internals from the reactor vessel after all the fuel assemblies have been removed from the core; and placing the lower internals into the removable lower internals storage stand. In such an embodiment the method may also include the steps of: replacing the lower internals into the reactor vessel; and removing the lower internals storage stand from the lid before opening the lid. As previously mentioned, in the unlikely event of a Fukushima type of occurrence the AP1000® plant is designed to utilize passive safety systems, such as the passively cooled containment 22 shown in FIG. 2, to continue to provide cooling for at least three days. One of the safety systems for accomplishing that objective is the passive containment cooling system illustrated in FIG. 2. The passive containment cooling system 22 surrounds the AP1000® nuclear steam supply system, including the reactor vessel 10, steam generator 18, pressurizer 26 and the main coolant circulation pump 16; all connected by the piping network 20. The containment system 22, in part, comprises a steel dome containment vessel enclosure 28 surrounded by a concrete shield building 30 which provides structural protection for the steel dome containment vessel 28. The major components of the passive containment cooling system are a passive containment cooling water storage tank 32, an air baffle 34, air inlet 36, air exhaust 38 and water distribution system 40. The passive containment cooling water storage tank 32 is incorporated into the shield building structure 30, above the steel dome containment vessel 28. An air baffle 34 located between the steel dome containment vessel 28 and the concrete shield building 30 defines the cooling air flow path which enters through an opening 36 in the shield building 30 at an elevation approximately at the top of the steel dome containment 28. After entering the shield building 30, the air path travels down one side of the air baffle 34 and reverses direction around the air baffle at an elevation adjacent the lower portion of the steel dome containment vessel and then flows up between the baffle and the steel dome containment vessel 28 and exits at the exhaust opening 38 in the top of the shield building 30. The exhaust opening 38 is surrounded by the passive containment cooling water storage tank 32. In the unlikely event of an accident, the passive containment cooling system provides water that drains by gravity from the passive containment cooling water storage tank 32 and forms a film over the steel dome containment vessel 28. The water film evaporates thus removing heat from the steel dome containment vessel 28. The passive containment cooling system is capable of removing sufficient thermal energy, including subsequent decay heat, from the containment atmosphere following a Design Basis event resulting in containment pressurization, such that the containment pressure remains below the design value with no operator action required for at least 72 hours. The air flow path that is formed between the shield building 30, which surrounds the steel dome containment vessel 28, and the air baffle 34 results in the natural circulation of air upward along the containment vessel's outside steel surface. This natural circulation of air is driven by buoyant forces when the flowing air is heated by the containment steel surface and when the air is heated by and evaporates water that is applied to the containment surface. The flowing air also enhances the evaporation that occurs from the water surface. In the event of an accident, the convective heat transfer to the air by the containment steel surface only accounts for a small portion of the total heat transfer that is required, such total heat transfer being primarily accomplished by the evaporation of water from the wetted areas of the containment steel surface, which cools the water on the surface, which then cools the containment steel, which then cools the inside containment atmosphere and condenses steam within the containment. In order to maintain a sufficient transfer of heat from the steel dome containment vessel 22 to limit and reduce containment pressure, after the initial three days following a postulated Design Basis event, the AP1000® passive containment cooling system requires that the water continues to be applied to the containment outside steel surface. The water is provided initially by the passive gravity flow mentioned above. After three days, water is provided by active means initially from onsite storage and then from other onsite or offsite sources. A more detailed understanding of this containment cooling process can be found in U.S. patent application Ser. No. 13/444,932, filed Apr. 12, 2012. In addition, the AP1000® has passive systems to assure that the fuel assemblies in the core remain covered with coolant. In the unlikely event of a primary coolant loop leak, these systems are automatically activated. 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. Since 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 automatically depressurized in the event of a major coolant loss so that coolant water may be added from an in-containment refueling water storage tank, at the ambient pressure within the nuclear reactor containment dome 28. Thus, as shown in FIG. 3, there are two sources of coolant makeup for a loss of coolant in the AP1000® nuclear reactor system. An inlet of the high pressure core makeup tank 42 is coupled by valves to the reactor coolant inlet or cold leg 44. The high pressure core makeup tank 42 is also coupled by motorized valves and check valves to a reactor vessel injection inlet 46. The high pressure core makeup tank 42 is operable to supply additional coolant to the reactor cooling circuit 20, at the operational pressure of the reactor, to make up for relatively small losses. However, the high pressure core makeup tank 42 contains only a limited supply of coolant, though, as can be appreciated from FIG. 3, there are two core makeup tanks in the system. A much larger quantity of coolant water is available from the in-containment refueling water storage tank 48, at atmospheric pressure due to a vent, which opens from the tank 48 into the interior of the containment building 28. U.S. patent application Ser. No. 12/972,568, filed Dec. 20, 2010 (U.S. Publication No. 2012/0155597, published Jun. 21, 2012), and assigned to the Assignee of this application, describes in more detail how the reactor system is depressurized so that cooling water can be drained from the in-containment refueling water storage tank 48 into the reactor vessel 10. This invention is an improvement upon the other safety systems of the AP1000® plant by extending the capability to provide spent fuel pool cooling by minimizing the decay heat emanating from the spent fuel in the spent fuel pool. This is accomplished by storing the spent fuel, not to be reused in the reactor vessel, inside the reactor containment 22 for one whole fuel cycle before this spent fuel is transferred to the spent fuel pool. Due to the decreased decay heat level in the spent fuel pool, the water contained in the spent fuel pool resulting from storing the off-loaded spent fuel in the containment for one fuel cycle, the cask loading pit, and the fuel transfer canal have sufficient heat capacity to extend the coping time (time before water is boiled off and the stored spent fuel is uncovered). The decay heat of the spent fuel stored inside the containment will have no impact on the peak containment pressure following an accident, since, as will be explained below, this fuel must first heat the in-containment refueling water storage tank water before contributing to the containment mass and energy. Also, the extra decay heat from the spent fuel stored inside the containment will have only a small impact on the long term passive containment cooling system performance (ideally, the drain rate from the passive containment cooling water storage tank 32 could be adjusted to account for the extra decay heat from the spent fuel stored inside the containment, but this adjustment would only be approximately seven grams per megawatt of extra decay heat). One preferred embodiment of this invention is to have the irradiated fuel removed from the reactor vessel 10 and stored inside the containment in a “tank” located below the 98 foot 1 inch elevation of the refueling cavity floor as schematically shown in FIG. 4. Preferably, two “tanks” are provided; one for the spent fuel which will not be returned to the reactor vessel (shown as the long-term storage tank identified by reference character 50 in FIGS. 4-8), and one for the irradiated fuel assemblies that will be returned to the reactor vessel and utilized during the subsequent fuel cycle (shown as the short-term storage tank 52 in FIG. 4-8). In this embodiment, the first of these tanks is located beneath the lower core internals storage stand. The lower internals storage stand is modified so that it can be placed on top of the long-term tank cover 56 (shown in FIGS. 6 and 8) when/if the lower internals need to be removed from the reactor vessel 10. The lower internals storage stand 54 will normally be stored outside the refueling cavity. The upper internals storage stand is shown in FIG. 8 adjacent the fuel transfer machine 76 and the long-term storage tank 50. Preferably, the top of the tanks would be at elevation 98 feet, 1 inch, and would have a closure lid 56, 58 (shown in FIGS. 6 and 8), and will be deep enough to accommodate 14-foot long AP1000® fuel assemblies and provide sufficient water above the fuel for shielding; resulting in the tank bottom being at approximately the 76-foot elevation. The tanks 50, 52 are equipped with a water inlet pipe 66 attached to or extending to the tank bottom and a top mounted water discharge line 68. The tank is designed such that water would naturally circulate from the tank bottom connection, to the tank upper connection driven by the spent fuel decay heat. The short-term storage tank 52 is provided for the irradiated fuel that is temporarily removed from the reactor vessel during refueling. Each of the tanks 50, 52, respectively, have fuel racks 62, 64 with individual cells for each fuel assembly that maintains the spacing between assemblies. Since the short-term storage fuel assemblies are offloaded and then must be reloaded into the reactor vessel 10, it is desirable to equip the short-term storage tank 52 with a closure head, such as lid 56 that can be easily opened and closed. Desirably, this includes a permanently installed lid above each of the fuel rack 64 cells that has individual, small covers 60 or hatches for each fuel assembly. The fuel racks 64 are accessed through corresponding individual fuel rack opening lids 60 that are supported within an access opening 90 in the short-term nuclear fuel assembly storage tank 52. The irradiated nuclear fuel assembly storage tank 50 includes a lid 56 for covering and sealing an access opening 88 in the top of the irradiated nuclear fuel assembly storage tank 50 wherein the lid 56 is coupled to a wall 84 of the top of the irradiated nuclear fuel assembly storage tank 50 through a hinge 86 that is configured to swing the lid 56 out of the way of the access opening 88 when in a fully open position, to load or unload a nuclear fuel assembly into or out of an interior of the irradiated nuclear fuel assembly storage tank 50. The tank bottom and upper piping 66, 68, respectively, each contain valves 72 that could be positioned so that both the bottom inlet pipe 66 and the top discharge pipe 68 are aligned with either the water in the refueling cavity 70, during refueling operations, or the water in the in-containment refueling water storage tank 48, when the refueling cavity is drained during shutdown or during normal plant operation. As shown in FIGS. 4 and 5, the valves 72 are located in a valve room 74 preferably under the in-containment refueling water storage tank 48 and can be accessed either from the adjacent loop compartment or via a vertical access tunnel (to prevent flood-up and not impact current containment flood-up levels). In FIGS. 6, 7 and 8 the long-term tank 50 is shown as a cylindrical tank with a sealable lid 56 designed to withstand hydrostatic pressure from the in-containment refueling water storage tank; while the short-term tank 52 is shown as a vaulted tank with a liner. Having the most recent offloaded fuel from the reactor vessel 10 remain inside the containment and with the spent fuel not being transferred to the spent fuel pool for a full fuel cycle, greatly reduces the spent fuel pool decay heat load such that the coping time, the time required heat and boil off the water available above the spent fuel in the spent fuel pool, is greatly extended; and could be further extended if the spent fuel pool was cooled by air, as explained in co-pending application Ser. No. 14/195,878, filed concurrently herewith. The spent fuel inside the containment can utilize the existing passive containment cooling system, previously described to provide heat removal with water assisted evaporation or air-only cooling, as appropriate. It should also be appreciated that the adoption of just the long-term storage tank 50 inside the containment, with no short-term tank, can extend the AP1000® plant's coping time. In this case, during normal operation, the most recent core offload would remain inside the containment, thus reducing the decay heat load in the spent fuel pool. During a full core offload, the fuel assemblies that will be reloaded into the reactor vessel are temporarily placed in the spent fuel pool. During this time, the passive containment cooling water storage tank can be aligned to the spent fuel pool to extend its coping time; while the decay heat from the offloaded fuel assemblies in the long-term storage tank 50 can be transferred to the atmosphere by air only cooling of the containment shell 28. The method of using the two tanks as part of the refueling operation is as follows. After the reactor vessel head 12 is removed and the refueling cavity 70 is filled with water, the long-term spent fuel storage tank 50 lower inlet 66 and upper discharge lines 68 are aligned with the refueling cavity 70 switching the cooling water naturally circulating through the tank from the in-containment refueling water storage tank water to the refueling cavity water. The same operation would apply to the short-term spent fuel storage tank 52. The means currently employed to actively cool the cavity water is then turned on, and the active cooling of the in-containment refueling water storage tank water is shut off. When the reactor vessel upper internals are removed and refueling is to commence, the closure head 56 of the long-term storage tank 50 (storing the spent fuel from the previous refueling outage) is opened and the spent fuel in this tank is removed by the fuel transfer machine 76 and transferred by way of the fuel transfer tube 78 to the spent fuel pool 24 schematically shown in FIG. 1. Operations will then commence on defueling the reactor vessel 10 and the fuel which will not be used in the next fuel cycle will be placed inside the long-term storage tank 50, and the tank lid 56 replaced and fastened. The remaining fuel in the reactor vessel 10 would then be removed if there was to be a full core offload, and placed into the short-term fuel storage tank 52. When and if the refueling cavity is to be drained during the outage, fuel from the short-term fuel storage tank 52 is to be moved to the spent fuel pool 24 prior to the refueling cavity being drained. The long-term storage tank 50 is again aligned with the in-containment refueling water storage tank, switching the natural circulation cooling water flow from the refueling cavity to the in-containment refueling water storage tank. The means of actively cooling the in-containment refueling water storage tank water would also be turned on, and the active cooling of the refueling cavity water would be shut off. When refueling the vessel was to begin, the tanks would be realigned to the reactor refueling cavity as it was filled with water. The fuel from the short-term irradiated fuel storage tank 52 would then be reloaded into the reactor vessel 10 and new fuel from the spent fuel pool would be added to the reactor vessel. Following the refueling of the reactor vessel 10 and as the water in the refueling cavity 70 is being transferred to the in-containment refueling water storage tank 48, the long-term spent fuel storage tank 50 is aligned so that cooling flow was naturally circulated from/to the in-containment refueling water storage tank 48. The means of actively cooling the refueling cavity water would also be turned off, and the active cooling of the in-containment refueling water storage tank water would be turned on. In addition, when the long-term irradiated fuel storage tank 50 and/or the short-term fuel storage tank 52 is in operation with natural circulation to either the refueling cavity or the in-containment refueling water storage tank to cool the spent fuel, the refueling cavity or the in-containment refueling water storage tank water should be cooled and maintained at or below 100° F. (37.8° C.) to minimize evaporation and/or fogging inside the containment. Should the reactor vessel lower internals need to be removed (after all the fuel in the reactor vessel has been removed), the lower internals storage stand 54 is to be placed over the long-term spent fuel storage tank 50 and the lower internals are stored as normal. Due to the large amount of heat from the spent fuel that will be added to the cavity or the in-containment refueling water storage tank, pumped cooling will need to be provided for each water body. Preferably, the pumps take suction from the top of these tanks with a suction line located just below the normal water level and the cooling return line should have a siphon break in order to avoid the possibility of draining the cavity or the in-containment refueling water storage tank should a line break occur (similar to the current spent fuel pool suction and return line). This suction line location enables the heated water to be drawn from the refueling cavity or the in-containment refueling water storage tank without first heating up the entire water volume. Since the pump suction line should be located near the normal full refueling cavity or in-containment refueling water storage tank water level, respectively, 82, 80, and since the refueling cavity 70 or the in-containment refueling water storage tank 48 cooling is a continuous operation (during most of the refueling and during normal operation), pumps and heat exchangers separate from the spent fuel system and normal residual heat removal system pumps and heat exchangers, should be provided. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.
044144750	abstract	Shielding container assembly for storing weak to medially active waste in a storage barrel, including a shielding container having a substantially square cross section surrounding the storage barrel, the shielding container having two pairs of oppositely-disposed sections, one of the pairs having symmetrical projections formed thereon and the other of the pairs having chamfers formed thereon, the projections and chamfers effecting anchoring of the containers when stacked close to each other.
	claims	1. A device for measuring back pressure in open-ended chemical reactor tubes, comprising:a rigid wand body having upper and lower ends and including a frame member at said lower end;a plurality of hollow tube bodies mounted on said frame member,a tubular elastic sleeve mounted over the outer surface of each of said hollow tube bodies, each tubular elastic sleeve having a top and a bottom;top and bottom ferrules clamping the top and bottom of each tubular elastic sleeve against its respective hollow tube body;an inflation gas path extending to the interior of each tubular elastic sleeve for inflating the respective sleeve;a plurality of paths for providing controlled gas flow through said plurality of hollow tube bodies; anda pressure sensor in fluid communication with at least one of said hollow tube bodies. 2. A device for measuring back pressure in open-ended chemical reactor tubes as recited in claim 1, wherein the top ferrule extends below the frame member. 3. A device for measuring back pressure in open-ended chemical reactor tubes as recited in claim 1, and further including means for adjusting the spacing between the plurality of hollow tube bodies and for fixing the positions of the plurality of hollow tube bodies relative to said rigid wand body. 4. A device for measuring back pressure in open-ended chemical reactor tubes as recited in claim 3, and further comprising an additional hollow tube body mounted on said wand by a flexible mounting means which permits its insertion into a reactor tube independently of said plurality of hollow tube bodies; an additional tubular elastic sleeve mounted over said additional hollow tube body; an additional inflation path extending to the interior of said additional tubular elastic sleeve for inflating said sleeve; and an additional path for providing controlled gas flow through said additional hollow tube body. 5. A device for measuring back pressure in open-ended chemical reactor tubes as recited in claim 1; wherein each of said hollow tube bodies has an outer surface and an inner surface, said outer surface defining a recess, and said inner surface defining an internal fluid path, wherein said inflation gas path includes an inflation tube lying within the recess between one of said ferrules and the hollow tube body.
	description	FIG. 1 is a side view showing the arrangement of the first embodiment of an X-ray mask according to the present invention. FIGS. 2A to 2C depict the states in the use of the X-ray mask and mask pattern protection members shown in FIG. 1, in which FIG. 2A is a side view in the storage state, FIG. 2B is a side view in the preparation state in which the X-ray mask is unloaded, and FIG. 2C is a side view upon unloading the X-ray mask. Referring to FIG. 1, an X-ray mask 1 used in this embodiment is a transmission type X-ray mask in which an Au mask pattern 3 serving as an absorber for absorbing X-rays is formed on a 2-xcexcm thick SiC membrane 2 having an Si substrate as a support member 4. Mask pattern protection members 5 are set on both surfaces of the X-ray mask 1 after defect inspection of the X-ray mask 1 to form a dust-proof space. Each mask pattern protection member 5 is formed of a 1-mm thick plastic plate subjected to an antistatic treatment. Since the mask pattern protection members 5 can transmit visible light, the state of the mask pattern 3 on the X-ray mask 1 can be visually observed while the protection members 5 are attached to the X-ray mask 1. In the transmission type X-ray mask 1, the membrane 2 that transmits X-rays tends to deform due to the pressure difference between the dust-proof space and atmosphere since it is very thin. In order to prevent this deformation, small holes 6 for adjusting the inner pressure of the dust-proof space are formed on the mask pattern protection members 5. As shown in FIG. 2A, the X-ray mask 1 is loaded into a mask cassette 7 with the mask pattern protection members 5 attached, and is stored and transported in this state. In this manner, foreign matter can be prevented from becoming attached to the X-ray mask 1 during storage and transportation, and the X-ray mask 1 can be prevented from being damaged upon handling it, especially, upon taking out the X-ray mask 1 from the mask cassette 7 so as to load the X-ray mask 1 into an exposure apparatus. As an exposure apparatus in which the X-ray mask 1 of this embodiment is used, a proximity gap type equal-magnification exposure apparatus using sychrotron radiation light as a light source is used. The X-ray mask 1, a mask stage on which the X-ray mask 1 is mounted, a wafer, a wafer stage, and devices such as a shutter for controlling X-ray irradiation are set in a reduced-pressure helium atmosphere, and are shielded from an optical system set in a vacuum by an X-ray window. For this reason, the exposure apparatus has a preliminary evacuation chamber for substituting the atmosphere upon loading the X-ray mask 1 into the exposure apparatus. In the preliminary evacuation chamber, a mask carrier (not shown) for storing a plurality of X-ray masks 1 is arranged, and X-ray masks 1 are stored in mask slots 8 of the mask carrier one by one (FIG. 2B). Each mask slot 8 has a mechanism (not shown) for forming gaps 9 between the support member of the X-ray mask 1 and the mask pattern protection members 5. When the atmosphere in the preliminary evacuation chamber is substituted by helium, the pressures in the gaps between the X-ray mask 1 and the mask pattern protection members 5 are simultaneously reduced via the forming gaps 9 and the gaps are substituted by helium. When exposure is performed, a desired X-ray mask 1 is taken out from the corresponding mask slot 8 by the mask carrier, and is carried to a predetermined position in the exposure apparatus. At this time, the mask pattern protection members 5 are detached from the X-ray mask 1 inside the mask slot 8, as shown in FIG. 2C, and the X-ray mask 1 alone is loaded. The X-ray mask 1 is chucked at a predetermined position in the exposure apparatus by a mask chucking mechanism for holding the mask in position, and is subjected to alignment adjustment with respect to a wafer and exposure. Upon completion of exposure, the X-ray mask 1 is conveyed to the position of the mask carrier, and is stored in the mask slot 8. At this time, the mask pattern protection members 5 are stored in the mask slot 8. When the X-ray mask 1 that has already been subjected to exposure is to be unloaded outside the exposure apparatus, the interior of the preliminary evacuation chamber that stores the mask slot 8 is caused to leak to air. At this time, the gas present between the mask pattern protection members 5 and the X-ray mask 1 is simultaneously leaked to air via the gaps 9. Thereafter, the gaps 9 between the X-ray mask 1 and the mask pattern protection member 5 are removed inside the mask slot 8, and the X-ray mask 1 and the mask pattern protection members 5 can be unloaded outside the exposure apparatus while being in tight contact with each other. Note that various methods of loading the X-ray mask 1 into the exposure apparatus are available. However, the present invention is not limited to a specific method as long as a means, which can change the pressure in the dust-proof space between the X-ray mask 1 and the mask pattern protection members 5 simultaneously with large changes in pressure of the atmosphere therearound so as to keep the same pressure as that of the atmosphere is used. Also, the mask pattern protection members 5 may be detached from the X-ray mask 1 in the preliminary evacuation chamber, during loading, or at the exposure position. FIGS. 3A and 3B show the arrangement of the second embodiment of an X-ray mask according to the present invention, in which FIG. 3A is a side view of the mask attached with a mask pattern protection member, and FIG. 3B is a side view showing the state wherein the mask pattern protection member is retreated from the optical paths of exposure light and alignment light. An X-ray mask 11 used in this embodiment is a reflection type mask, in which a Crxe2x80x94C multilayered film reflection layer 13 is formed on an SiC substrate 12, and a mask pattern 14 is formed on the layer 13 by patterning an Au layer that absorbs X-rays to have a desired pattern. Combinations of materials, film thicknesses, and the like of the reflection layer 13 of the reflection type mask are appropriately selected in correspondence with the wavelength used. Typical combinations of the materials include: Mo-Si, W-Si, and the like (in the vicinity of a wavelength of 13 nm); or W-C, Ni-C, and the like (in the vicinity of a wavelength of 5 nm). An alignment mark 15 for alignment adjustment is formed on the peripheral portion of the mask pattern 14. A mask pattern protection member 16 is formed of a 1-mm thick plastic plate subjected to an antistatic treatment, and has vent holes 17 on the three side surfaces except for the upper surface (FIGS. 3A and 3B depict the lower surface alone). When the mask pattern protection member 16 is set, the mask pattern 14 and the alignment mark 15 are protected. An exposure apparatus that uses the X-ray mask 11 of this embodiment uses X-rays having a wavelength of 0.7 nm, and the interior of the exposure apparatus is evacuated to a vacuum of about 10xe2x88x924 Pa. For this purpose, the exposure apparatus has a preliminary evacuation chamber used for loading the X-ray mask 11 into the exposure apparatus as in the first embodiment. A series of processes from when the X-ray mask 11 is loaded into the exposure apparatus until it is unloaded outside the exposure apparatus after exposure will be described in turn below. Note that the mask pattern protection member 16 is attached to the X-ray mask 11 after the mask 11 is subjected to defect inspection, as in the first embodiment, and the X-ray mask 11 is stored in the mask cassette with the mask pattern protection member 16 attached during transportation and storage. The X-ray mask 11 is taken out from the mask cassette with the mask pattern protection member 16 attached and is stored in each of mask slots (not shown) of a mask carrier inside the preliminary evacuation chamber. At this time, the preliminary evacuation chamber is partitioned from the exposure apparatus to shield air communications, and the interior of the preliminary evacuation chamber is set at the atmospheric pressure. A desired number of X-ray masks 11 are stored in the mask slots, and the interior of the preliminary evacuation chamber is evacuated. At this time, the dust-proof space inside the mask pattern protection member 16 is also evacuated via the vent holes 17 (FIG. 3A) and is set at the same degree of vacuum as that inside the preliminary evacuation chamber. When the interior of the preliminary evacuation chamber has reached the predetermined degree of vacuum, the vacuum partition wall between the exposure apparatus and the preliminary evacuation chamber is opened, and the X-ray mask 11 with the mask pattern protection member 16 attached is carried to a predetermined position in the exposure apparatus by a mask carrier. The mask pattern protection member 16 is kept attached until the X-ray mask 11 is chucked by a mask chuck mechanism for holding the mask in position to prevent foreign matter from becoming attached to the X-ray mask 11 during carrying. On the other hand, a moving means 18 for retreating the mask pattern protection member 16 from the exposure optical path is arranged in the exposure apparatus, and removes the mask pattern protection member 16 from the exposure optical path after the X-ray mask 11 is chucked. At this time, the mask pattern protection member 16 is withdrawn so as not to disturb the alignment adjustment optical path. After the mask pattern protection member 16 is retreated, the exposure apparatus performs alignment adjustment using alignment light L2. Upon completion of the alignment adjustment, the exposure apparatus performs exposure using exposure light L1 (FIG. 3B). Upon completion of the alignment adjustment and exposure, the moving means attaches the mask pattern protection member 16 to the X-ray mask 11 again, and the X-ray mask 11 is returned to the mask carrier in this state to be stored into the mask slot. Note that the mask pattern protection member 16 can also prevent foreign matter from becoming attached to the X-ray mask 11 even during carrying inside the exposure apparatus. When the X-ray mask 11 is unloaded outside the exposure apparatus after a series of exposure processes have been completed, the vacuum partition wall of the preliminary evacuation chamber is closed again, and the interior of the preliminary evacuation chamber alone is caused to leak to air. At this time, the dust-proof space in the mask pattern protection member 16 is simultaneously leaked via the vent holes 17, thus preventing the X-ray mask 11 and the mask pattern protection member 16 from being damaged by the pressure difference. Therefore, since the mask pattern protection member 16 is attached to the X-ray mask 11 of this embodiment not only outside the exposure apparatus but also inside the exposure apparatus in which foreign matter becomes attached to the X-ray mask due to the flow of the atmosphere inside the apparatus produced by evacuation or air supply, attachment of foreign matter can be greatly eliminated. Note that the mask pattern protection member 16 preferably has a closed structure for preventing entrance of foreign matter. However, when the vent holes 17 are formed like in this embodiment, ventilation other than via the vent holes 17 is preferably cut off, and the vent holes 17 also preferably have a structure that can prevent entrance of foreign matter. Accordingly, the vent holes 17 are preferably not open to the entrance routes of foreign matter, i.e., to the surfaces opposing the upper surface in the exposure apparatus and air supply/exhaust ports. Furthermore, more preferably, the ventilation channel is curved not to allow easy entrance of foreign matter onto the mask pattern 14. When the ventilation channel is designed to have a more complex structure, the conductance of the ventilation channel must be taken into consideration so as not to produce any pressure difference between the interior of the mask pattern protection member 16 and the surrounding atmosphere. It is also effective to arrange a filter, a mesh, or the like on each vent hole 17 to prevent entrance of foreign matter or to arrange a mechanism for adsorbing foreign matter having entered the ventilation channel. Such a structure can also be applied to the pressure adjustment small holes in the mask pattern protection members described in the first embodiment. The third embodiment of the present invention will be described below. In the third embodiment, a reflection type mask similar to that in the second embodiment is used, and vent holes have lids which are free to open/close. FIGS. 4A to 4C show the arrangement of the third embodiment of an X-ray mask according to the present invention, in which FIG. 4A is a side view showing the storage state, FIG. 4B is a side view showing the state inside a preliminary evacuation chamber, and FIG. 4C is a side view showing the state upon alignment adjustment and exposure. Referring to FIG. 4A, a mask pattern protection member 26 for protecting a mask pattern 23 is attached onto an X-ray mask 21, and vent holes 27 with lids 28 are formed on the side surfaces of the mask pattern protection member 26. Each lid 28 is biased by a spring to close so as to prevent foreign matter from entering via the vent hole 27 when the mask 21 is present outside the exposure apparatus. In such a state, the X-ray mask 21 is stored in a mask slot 29 in a preliminary evacuation chamber. Inside the preliminary evacuation chamber, lid open/close pins 20 formed on the mask slot are inserted to press the one-end portions of the lids 28, thereby opening the lid 28 (FIG. 4B). Upon evacuating the interior of the preliminary evacuation chamber, the interior of the mask pattern protection member 26 is also evacuated via the vent holes 27, and is kept at the same pressure as that of the atmosphere inside the preliminary evacuation chamber. Upon exposure, the X-ray mask 21 with the mask pattern protection member 26 attached is carried from the preliminary evacuation chamber to the predetermined position inside the exposure apparatus by a mask carrier. The mask pattern protection member 26 is kept attached until the X-ray mask 21 is chucked by a mask chuck mechanism for chucking the mask, thus preventing foreign matter from becoming attached to the X-ray mask 21 during its carrying. Upon executing alignment adjustment and exposure, the mask pattern protection member 26 is retreated from the optical paths of exposure light and alignment light by the same moving means as that in the second embodiment (FIG. 4C). After the exposure, the mask pattern protection member 26 is returned to the original position on the X-ray mask 21 by the moving means, and the X-ray mask 21 is carried into the preliminary evacuation chamber by the mask carrier. The interior of the preliminary evacuation chamber is caused to leak and is set at the atmospheric pressure. At the same time, the interior of the mask pattern protection member 26 is also set at the atmospheric pressure via the vent holes 27. Thereafter, the lid open/close pins 20 are removed to close the lids 28, and the X-ray mask 21 is ready to unload from the exposure apparatus. Note that the lids 28 may be opened only when the atmospheres in the exposure apparatus and preliminary evacuation chamber largely change, or may be kept open in the apparatus and chamber. An opening/closing mechanism of the lids 28 may be arranged in the preliminary evacuation chamber, or may be added to the carrying mechanism of the mask carrier. Furthermore, the mask pattern protection member 26 preferably has a closed structure for preventing entrance of foreign matter. However, when the vent holes 27 are formed like in this embodiment, ventilation other than via the vent holes 27 is preferably cut off, and the vent holes 27 also preferably have a structure that can prevent entrance of foreign matter. Accordingly, the vent holes 27 are preferably not open to the entrance routes of foreign matter, i.e., to the surfaces opposing the upper surface in the exposure apparatus and air supply/exhaust ports. Furthermore, more preferably, the ventilation channel is curved not to allow easy entrance of foreign matter onto the mask pattern 23. When the ventilation channel is designed to have a more complex structure, the conductance of the ventilation channel must be taken into consideration so as not to produce any pressure difference between the interior of the mask pattern protection member 26 and the atmosphere therearound. It is also effective to arrange a filter, a mesh, or the like on each vent hole 27 to prevent entrance of foreign matter or to arrange a mechanism for adsorbing foreign matter having entered the ventilation channel. In this embodiment, a transmission type mask similar to that in the first embodiment is used, and a pellicle is attached to the mask. FIGS. 5A and 5B show the arrangement of the fourth embodiment of an X-ray mask according to the present invention, in which FIG. 5A is a side view showing the storage state, and FIG. 5B is a side view showing the state upon alignment adjustment and exposure. Referring to FIG. 5A, a pellicle 35 is attached onto an X-ray mask 31 via a pellicle support member 34, and a mask pattern protection member 36 is attached thereon. Vent holes 37 with lids 38 are formed on the side surfaces of the mask pattern protection member 36, and, for example, the interior of the member 36 is evacuated by opening the lids 38 when the pressure in the exposure apparatus changes due to evacuation, as in the third embodiment. In this arrangement, the X-ray mask 31 is stored in a mask slot (not shown) of a mask carrier in a preliminary evacuation chamber while the pellicle 35 and the mask pattern protection member 36 are kept attached thereto. When exposure is performed, the X-ray mask 31 is carried to the predetermined position in the exposure apparatus by the mask carrier, and the mask pattern protection member 36 is detached from the X-ray mask 31 after the X-ray mask 31 is chucked by a chuck mechanism. After alignment adjustment with respect to a wafer 39 is done, exposure is performed using exposure light L1, as shown in FIG. 5B. Upon completion of exposure, the mask pattern protection member 36 is attached again to the X-ray mask 31, and they are stored in the mask slot by the mask carrier. Note that the X-ray mask 31 is stored in a mask cassette (see FIG. 1) when it is carried outside the exposure apparatus. At this time as well, the mask 31 is stored in the mask cassette while the pellicle 35 and the mask pattern protection member 36 are kept attached thereto. In the proximity gap type exposure apparatus that uses the X-ray mask 31 of this embodiment, since foreign matter attached on the pellicle 35 is also transferred onto the wafer 39, the mask pattern protection member 36 must protect the pellicle 35 and the X-ray mask 31 at the same time. When the mask pattern protection member 36 is attached onto the pellicle 35 like in this embodiment, foreign matter can be prevented from becoming attached to the X-ray mask 31 and the pellicle 35, thus reducing defects produced in the transferred pattern. Not only can the X-ray mask 31 and the pellicle 35 be prevented from being damaged, but also the interior of the exposure apparatus can be prevented from being contaminated when the X-ray mask 31 or pellicle 35 is damaged. Since the mask pattern protection member 36 is attached not only inside but also outside the exposure apparatus, the X-ray mask 31 and the pellicle 35 can be prevented from being damaged. Note that the mask pattern protection member 36 is preferably kept attached to the X-ray mask 31 except for exposure and alignment adjustment. With the above-mentioned effects, even when the protection member 36 is attached/detached inside the mask carrier, sufficient effects can be assured. FIG. 6 is a sectional view of an X-ray mask structure of this embodiment. The X-ray mask structure is made up of a 2-mm thick Si holding frame 41, an X-ray transparent 2.0-xcexcm thick SiC membrane 42 formed by CVD, an Au X-ray absorber 43 formed by plating, and an SiC reinforcing member 44 adhered to the holding frame 41 by an adhesive 45. On the reinforcing member 44, a front-side thin film 47 formed on a frame member 46 was mounted by using an easily detachable adhesive 49 to have an interval of 5 xcexcm from the membrane 42. The frame member 46 was formed of Al to have holes 48 for pressure adjustment. Filters for preventing entrance of dust were attached to these holes 48. The front-side thin film 47 was formed of a polyimide to have a thickness of 0.8 xcexcm, and its flatness was controlled to 1 xcexcm or less. A rear-side thin film 51 formed on a frame member 50 was mounted on the reinforcing member 44 by an easily detachable adhesive (not shown) to have an interval of 5 mm from the membrane 42. The frame member 50 was formed of Al to have holes 52 for pressure adjustment. Filters for preventing entrance of dust were attached to these holes 52. The rear-side thin film 51 was formed of a polyimide to have a thickness of 0.8 xcexcm as in the front-side thin film 47. The thin films can be attached during an exposure operation. As described above, since the thin films are mounted on the X-ray mask structure by the easily detachable adhesive to form a dust-proof space, dust can be prevented from directly becoming attached to the mask, and can also be prevented from becoming attached to portions between the adjacent lines of a high-aspect pattern, thus transferring the mask pattern with high precision. Also, the number of times of washing of the mask can be minimized or reduced to zero, and the membrane can be prevented from being damaged or deteriorating due to washing. Even when dust becomes attached to the thin films, dust can be easily inspected by light, and a dust removal process can be easily done by washing or exchanging the thin films. When dust becomes attached to the rear-side thin film, it often has no influence on exposure depending on its material or size, and the dust removal process need not often be performed. Furthermore, since the polyimide has a higher tenacity than SiC, even when the membrane is damaged, the thin films can serve as scattering prevention films that can prevent the membrane from being scattered. As described above, a high-performance X-ray mask structure which can avoid the influence of dust and is suitable for mass production can be provided. An X-ray mask structure was fabricated following substantially the same procedure as in the fifth embodiment, except that a front-side thin film 47 and a rear-side thin film 51 consist of polyphenylene sulfite as a conductive polymer and a radiation-resistant polymer. In addition to the effects of the fifth embodiment, since an antistatic effect is provided, the dust attachment prevention effect can be further improved. FIG. 7 is a sectional view of an X-ray mask structure of this embodiment. An X-ray mask structure was fabricated following substantially the same procedure as in the fifth embodiment, except that pressure adjustment holes 53 and 54 were formed not on a frame member 50 but on a reinforcing member 44, a holding frame 41, and a membrane 42 on the mask side, and an adhesive 45 was applied not to close the holes. Since the space between the membrane 42 and a front-side thin film 47 is very narrow, the arrangement of this embodiment is more effective in pressure adjustment. FIG. 8 is a sectional view of an X-ray mask structure of this embodiment. The X-ray mask structure is made up of a 2-mm thick Si holding frame 41, a 2.0-xcexcm thick SiN X-ray transparent membrane 42 formed by CVD, and a W X-ray absorber 43. Steps used for attaching/detaching a thin film were worked on the holding frame 41 with high precision. This work can be attained by anisotropic etching using a strong alkali which is normally used upon forming the holding frame. Thin films on both surfaces were mounted with high precision as in the fifth embodiment. Pressure adjustment holes 54 were formed on the holding frame 41, as shown in FIG. 8. These holes may be formed on a frame member 46. Even a simple X-ray mask structure having no reinforcing member 44 like in this embodiment could prevent attachment of dust or the like as in the fifth and sixth embodiments. FIG. 9 is a sectional view of an X-ray mask structure of this embodiment. The X-ray mask structure is made up of a 2-mm thick Si holding frame 41, a 2.0-xcexcm thick SiN X-ray transparent membrane 42 formed by CVD, a Ta X-ray absorber 43 formed by sputtering, and a pyrex reinforcing member 44 anodically bonded to the holding frame 41. A 0.4-xcexcm thick DLC (Diamond-like Carbon) front-side thin film 47 formed on an Si frame 46 by CVD was mounted on the reinforcing member 44 by an easily detachable adhesive 49 to have an interval of 10 xcexcm from the membrane 42. The flatness of the thin film 47 was controlled to 1 xcexcm or less. Pressure adjustment holes 54 were formed on the reinforcing member 44 on the mask side, as shown in FIG. 9. These holes may be formed on the frame member 46, as in the fifth embodiment. Filters for preventing entrance of dust were attached to these holes. Also, a rear-side thin film 51 was formed of 0.4-xcexcm thick DLC on an Si frame member 50, and was mounted on the rear surface of the reinforcing member 44 by an easily detachable adhesive. The interval between the rear-side thin film 51 and the membrane 42 was set at 5 mm. Since the DLC thin films have higher radiation resistance and conductivity than those of an organic film, dust-proof films which have long-term stability and also serve as antistatic films can be provided. FIG. 10 is a sectional view of an X-ray mask structure of this embodiment. An X-ray mask structure was fabricated following substantially the same procedure as in the ninth embodiment, except that a front-side thin film 47 used polyphenylene sulfite (thickness=0.8 xcexcm) having high radiation resistance and conductivity, and the shape of a frame member was changed. FIG. 11 is a sectional view of an X-ray mask structure of this embodiment. The X-ray mask structure is made up of a 2-mm thick Si holding frame 41, a 2.0-xcexcm thick SiN X-ray transparent membrane 42 formed by CVD, a W X-ray absorber 43 formed by sputtering, and an SiC reinforcing member 44 directly bonded to the holding frame 41 by metal diffusion (metal diffused portions 55 of, e.g., Au, Cu, Si, or the like). A front-side thin film 47, which consisted of two layers, i.e., a 0.5-xcexcm thick polyimide film 47a and a 0.3-xcexcm thick ITO film 47b, and was formed on an SiC frame member 46, was mounted on the reinforcing member 44 by screws 56 that could be easily attached/detached, so as to have an interval of 8 xcexcm from the membrane 42. The flatness of the front-side thin film 47 was controlled to 1 xcexcm or less. Pressure adjustment holes 54 were formed on the reinforcing member 44, as shown in FIG. 11. These holes may be formed on the frame member 46. Filters for preventing entrance of dust were attached to these holes. A rear-side thin film 51 was also formed by a two-layered film (a polyimide film 51a and an ITO film 51b) as in the front-side thin film 47, and was mounted on the reinforcing member 44 by screws 57. Since each thin film has a two-layered structure in which the polyimide film having high tenacity but serving as an insulator is formed on the membrane side (47a, 51a), and the ITO film serving as a conductor is formed on the side (47b, 51b) opposite to the membrane side, it can serve as a dust-proof film, and can improve its functions of an antistatic film and a scattering prevention film. The ITO film as a conductor can serve as an antistatic film that can prevent attachment of dust, and the polyimide film having high tenacity and serving as an insulator can prevent scattering of the membrane if the membrane is damaged, so that the scattered pieces can be positively collected by static electricity. An X-ray exposure apparatus used in the manufacture of microdevices (semiconductor devices, thin film magnetic heads, micromachines, and the like) using a mask structure will be described below with reference to FIG. 12. FIG. 12 is a schematic view showing a principal part of an X-ray exposure apparatus comprising an X-ray mask structure of the present invention. Referring to FIG. 12, synchrotron radiation light 102 radiated by an SR radiation source 101 has a sheet beam shape whose light intensity spreads uniformly in the horizontal direction but spreads little in the vertical direction. The synchrotron radiation light is expanded in the vertical direction when it is reflected by a cylindrical mirror (convex mirror 103), so as to be converted into a beam having a nearly rectangular section, thus obtaining a rectangular exposure region. The expanded radiation light 102 is adjusted by a shutter 104 to have a uniform exposure amount in the irradiated region. The radiation light 102 that has passed through the shutter is guided to an X-ray mask structure 105. The X-ray mask structure is chucked on a mask stage 107, and is held at a position opposing a wafer 106 as the object to be exposed. The wafer is held by a wafer chuck 108. The wafer chuck is mounted on a wafer stage 109. By moving the wafer stage, the position of the wafer is determined. An alignment unit 110 has an optical system for detecting alignment marks formed on the X-ray mask structure 105 and the wafer 106, and an arithmetic unit for calculating the displacement between the two marks. When the X-ray mask structure 105 of the present invention is used, transmittances of 80% or higher (or less than the maximum valuexe2x80x945%) can be obtained at a plurality of wavelengths used in alignment (positioning), thus improving the S/N ratio of alignment light and allowing high-precision alignment. After the alignment, when a pattern formed on the X-ray mask structure is transferred onto the wafer 106 by step and repeat or scanning exposure, X-ray exposure can be precisely attained, and mass production can also be realized. The method of manufacturing a microdevice using the X-ray mask and the exposure apparatus will be explained below. The microdevice includes semiconductor chips such as ICs, LSIs, liquid crystal devices, micromachines, thin film magnetic heads, and the like. A method of manufacturing a semiconductor device will be exemplified below. FIG. 13 shows the overall flow in the manufacture of a semiconductor device. In step 1 (circuit design), the circuit design of a semiconductor device is made. In step 2 (fabricate mask), a mask formed with the designed circuit pattern is fabricated. On the other hand, in step 3 (fabricate wafer), a wafer is fabricated using a material such as silicon. Step 4 (wafer process) is also called a pre-process, and an actual circuit is formed on the wafer by photolithography using the prepared X-ray mask and wafer. The next step 5 (assembly) is also called a post-process, in which semiconductor chips are assembled using the wafer obtained in step 4, and includes an assembly process (dicing, bonding), a packaging process (encapsulating chips), and the like. In step 6 (inspection), inspections such as operation confirmation tests, durability tests, and the like of semiconductor devices assembled in step 5 are conducted. Semiconductor devices are completed via these processes, and are loaded (step 7). FIG. 14 shows the detailed flow of the wafer process. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), electrodes are formed by deposition on the wafer. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist process), a photosensitive agent is applied on the wafer. In step 16 (exposure), the circuit pattern on the mask is printed on the wafer by exposure using the above-mentioned exposure apparatus. In step 17 (development), the exposed wafer is developed. This step includes a PEB (Post Exposure Bake) process inherent to a chemical sensitization type resist. In step 18 (etching), a portion other than the developed resist image is removed by etching. In step 19 (remove resist), the resist film which becomes unnecessary after etching is removed. By repetitively executing these steps, multiple circuit patterns are formed on the wafer. According to the manufacturing method of this embodiment, a highly integrated semiconductor device which is not easy to manufacture by the conventional method can be manufactured.
	abstract	The exit thermocouples of a pressurized water reactor (PWR) are calibrated by recording the thermocouple temperature measurements periodically during power ascension of the reactor together with a predicted power at the corresponding locations at the same time determined by a three-dimensional analytical nodal model of the core at the same core average power. The temperature measurements are converted to local core power values which are then divided into the corresponding predicted powers for the corresponding locations to arrive at mixing factors which are fitted to a selected function of core power. These mixing factors are recorded and subsequently applied to local power values calculated from measured exit thermocouple temperatures to adjust the three-dimensional nodal model power. Periodically, the mixing factors are adjusted by using flux map data to update the three-dimensional analytical nodal model power to generate a reference power distribution, calculating updated mixing factors using the current thermocouple temperature measurement taken at the same time and therefore the same average core power, and the reference power distribution, and then shifting the mixing factor functions of core power accordingly to pass through the updated mixing factors.
	claims	1. A radiation protection system for shielding medical personnel from x-rays from an x-ray emitter while working on a patient, comprising: an x-ray table having a first side, a second side and a top surface, the top surface for supporting a patient; a radiation-shielding cubicle having an interior defining a medical personnel region, the cubicle having a ceiling, floor, a first wall for separating the medical personnel from an x-ray emitter disposed outside of the cubicle, a second wall extending from one end of said first wall adjacent to a first side of the x-ray table and a third wall extending from the first wall adjacent to a second side of the x-ray table, the first wall having an opening for locating a portion of the x-ray table into the interior of the cubicle; a radiation-shielding screen attached to the x-ray table for covering the portions of the patient and the top surface of the x-ray table located in the interior of the cubicle; a radiation-shielding flexible interface for joining the x-ray table to the cubicle, the flexible interface having a flexible radiation-resistant skirt sealing the opening; and an integrated procedural environment. 2. The system of claim 1 wherein said integrated procedural environment comprises a control module for controlling the x-ray table, x-ray emitter or environmental conditions. claim 1 3. The system of claim 1 wherein said integrated procedural environment comprises an operator""s chair positionable within the medical personnel region within the cubicle. claim 1 4. The system of claim 3 wherein said chair comprises a control module for controlling the x-ray table, x-ray emitter, or environmental conditions. claim 3 5. The system of claim 1 wherein said integrated procedural environment includes at least one fluoroscopic/cine screen mounted within the cubicle. claim 1 6. The system of claim 5 wherein said integrated procedural environment further comprises at least one physiological monitor mounted within the cubicle. claim 5 7. The system of claim 6 wherein said fluoroscopic screen and monitor are re-positionally mounted on the interior surface of the second wall of the cubicle. claim 6 8. The system of claim 1 wherein said integrated procedural environment comprises said radiation resistant screen having a vascular access drape, the drape having one or more ports for facilitating access to the patient. claim 1 9. The system of claim 8 wherein said drape comprises a circumferential pleated portion sealing said drape with said interface, x-ray table and cubicle. claim 8 10. The system of claim 8 wherein said drape further comprises one or more channels in continuity with said ports. claim 8 11. The system of claim 10 wherein said channels are formed by separating flaps of overlapping portions of drape material which, when closed, recomplete a radiation resistant seal over the channel. claim 10 12. The system of claim 8 further comprising one or more radiation-shielding cloaks sized for positioning a radiation-resistant seal over said one or more ports. claim 8 13. The system of claim 12 wherein at least one of said cloaks has a re-closable radial slit and central orifice for positioning over a port and around procedural equipment passing through said port to provide a radiation-resistant seal over said port while allowing said procedural equipment to pass through the orifice of said cloak. claim 12 14. The system of claim 1 wherein said environment includes conduit internal to said table into which leads, lines and other procedural equipment may be consolidated and orderly routed. claim 1 15. The system of claim 1 wherein said integrated procedural environment further includes at least one patient arm rest integral to said table. claim 1 16. The system of claim 15 wherein said arm rest comprises integrated restraints and physiological sensors. claim 15 17. The system of claim 1 wherein said environment comprises a platform disposed in or near the personnel region for holding procedural equipment. claim 1 18. The system of claim 1 wherein said environment comprises a radiation detector in operative connection to the interior of said cubicle and said x-ray emitter such that detection of excess radiation levels within said cubicle will shut down said x-ray emitter. claim 1 19. A radiation protection system for shielding medical personnel from x-rays from an x-ray emitter while working on a patient, comprising: an x-ray table having a first side, a second side and a top surface, the top surface for supporting a patient; a radiation-shielding cubicle having an interior defining a medical personnel region, the cubicle having a ceiling, floor, a first wall for separating the medical personnel from an x-ray emitter disposed outside of the cubicle, a second wall extending from one end of said first wall adjacent to a first side of the x-ray table and a third wall extending from the first wall adjacent to a second side of the x-ray table, the first wall having an opening for locating a portion of the x-ray table into the interior of the cubicle; a radiation-shielding screen attached to the x-ray table for covering the portions of the patient and the top surface of the x-ray table located in the interior of the cubicle; a radiation-shielding flexible interface for joining the x-ray table to the cubicle, the flexible interface having a flexible radiation-resistant skirt sealing the opening; and an integrated procedural environment comprising: a control module for controlling the x-ray table, x-ray emitter or environmental conditions; fluoroscopic/sine screens mounted within the cubicle; physiological monitors mounted within the cubicle; wherein said radiation resistant screen has a vascular access drape having one or more ports for facilitating access to the patient; wherein said drape comprises a circumferential pleated portion sealing said drape with said interface, table and cubicle; wherein said drape further comprises one or more channels in continuity with said ports; wherein said channels are formed by separating flaps of overlapping portions of drape material which, when closed, recomplete a radiation resistant seal over the channel; one or more radiation-closing cloaks sized for positioning a radiation-resistant seal over said one or more ports; wherein at least one of said cloaks has a re-closable radial slit and a central orifice for positioning over a port and around procedural equipment passing through said port to provide a substantially radiation-resistant seal over said port while allowing said procedural equipment to pass through the orifice of said cloak; conduit internal to said table into which leads, lines and other procedural equipment may be consolidated and orderly routed; at least one patient arm rest integral to said table comprising integrated restraints and physiological sensors; a platform disposed in or near the personnel region for holding procedural equipment; and a radiation detector and operative connection to the interior of said cubicle and said x-ray emitter such that detection of excess radiation levels within said cubicle will shut down said x-ray emitter. 20. The method of using a system of claim 19 comprising the steps of: claim 19 providing a sterilely prepared patient and x-ray table; extending the sterilized or sterilely covered screen from the foot of the x-ray table to approximately the patient""s knee area; positioning a sterilely prepared vascular access drape such that the ports are located over the right and left femoral vascular access regions of the patient; positioning the circumferential pleated portion of said drape such that it is in operative connection with said interface, table and cubicle to form a radiation-resistant seal; positioning a sterilely prepared cloak over any unused access port to create a radiation-resistant seal over the port; achieving vascular access into the patient through a port; and positioning a sterilely prepared cloak having a reclosable radial slit and central orifice such that a substantially radiation-resistant seal is created over said port and around said procedural equipment.
	summary
	description	The field relates generally to systems and methods for modulating an energy of a particle beam, such as a proton beam. Radiation therapy has been employed to treat tumorous tissue. In radiation therapy, a high energy beam is applied from an external source towards the patient. The external source produces a collimated beam of radiation that is directed into the patient to the target site. The dose and placement of the dose must be accurately controlled to ensure that the tumor receives sufficient radiation, and that damage to the surrounding healthy tissue is minimized. Existing radiotherapy systems use x-ray as the radiation beam. In such systems, the ability to control the dose placement is limited by the physics of the beam, which necessarily irradiates healthy tissue on the near-side and far-side of a target region as it passes through the patient. Thus, it may be desirable to use protons as the source of the radiation. By controlling the energy of the protons, the protons will stop at a precise location within the patient. In this way, tissue on the far-side of the target region does not receive any radiation dose. Further, because the dose provided by a proton is concentrated at a “Bragg peak” around the area where the proton stops, the dose to healthy tissue on the near-side of the target region may also be reduced. Sometimes, it may be desirable to selectively modulate an energy of the proton beam such that the Bragg peak can hit target regions that are located at different depths in the patient. Also, if proton technique is to be used to implement arc therapy, in which the beam source is rotated about the target region, it may also be desirable to selectively modulate the energy of the proton beam dynamically during the treatment procedure. This is especially the case if the target region is closer to one side of the patient than others. In this case, the proton beam may need to penetrate less tissue to reach the target region at certain gantry angle, and more tissue at other gantry angles. However, existing proton systems do not allow an energy of the beam to be modulated accurately, reliably, and effectively during a treatment procedure. In accordance with some embodiments, an energy modulator for use with a particle source that provides a beam of particles includes a first block moveable between a first position and a second position, wherein when the first block is at the second position, it is in a path of the beam, and a second block moveable relative to the first block, wherein the second block and the first block are offset from each other in a direction of the beam, wherein the first block has a first energy absorption characteristic, and the second block has a second energy absorption characteristic that is different from the first energy absorption characteristic. In accordance with other embodiments, an energy modulator for use with a particle source that provides a beam of particles includes a first block moveable between a first position and a second position, wherein when the first block is at the second position, it is in a path of the beam, and a second block moveable relative to the first block, wherein the second block and the first block are offset from each other in a direction of the beam, wherein the first block and the second block are at least partially transparent to the particle beam, the first block having a surface that is perpendicular to the beam. In accordance with other embodiments, an energy modulator for use with a particle source that provides a beam of particles includes a first block moveable between a first position and a second position, wherein when the first block is at the second position, it is in a path of the beam, and a second block moveable relative to the first block, wherein the second block and the first block are offset from each other in a direction of the beam, wherein the first block and the second block are at least partially transparent to the particle beam, and wherein the first block is made from a first material, the second block is made from a second material that is different from the first material. In accordance with other embodiments, a method for modulating an energy of a particle beam includes determining information regarding a desired particle beam energy, determining a combination of blocks to be placed in a path of a beam based on the determined information, wherein the blocks are offset from each other in a direction of the beam, and positioning the blocks such that they are in the path of the beam. In accordance with other embodiments, a method for modulating an energy of a particle beam includes providing a first modulator that is located closer to a particle source than a nozzle, providing a second modulator that is located closer to the nozzle than the particle source, operating the first modulator when an energy of the beam is desired to be decreased, and operating the second modulator when the energy of the beam is desired to be increased. Other and further aspects and features will be evident from reading the following detailed description of the embodiments, which are intended to illustrate, not limit, the invention. Various embodiments are described hereinafter with reference to the figures. It should be noted that the figures are not drawn to scale and that elements of similar structures or functions are represented by like reference numerals throughout the figures. It should also be noted that the figures are only intended to facilitate the description of the embodiments. They are not intended as an exhaustive description of the invention or as a limitation on the scope of the invention. In addition, an illustrated embodiment needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced in any other embodiments even if not so illustrated. Referring now to the drawings, in which similar or corresponding parts are identified with the same reference numeral, FIG. 1 illustrates a proton system 10, in accordance with some embodiments. The proton system 10 includes a proton generator 12, an energy modulator 14, a beam transport system 16, and a nozzle 18. The proton generator 12 is for providing accelerated protons, which may be transported to a target by the beam transport system 16. The beam transport system 16 also includes a plurality of magnets for steering the proton beam to a desired location, e.g., a particular treatment room. The accelerator may be a cyclotron, which provides a fixed energy, or alternatively, a synchrotron, which provides variable energy. Typically, the beam transport system 16 may be used for guiding the beam to more than one treatment rooms. The nozzle 18 is mounted on a gantry (e.g., a rotatable gantry) or a fixed beam port. The nozzle 18 is for adjusting the proton beam so that the beam 20 has a certain desired characteristic for treating a target region 23 within the patient 22 who is supported on a patient support 24. The nozzle 18 includes a collimator 19, which is for blocking at least some of the beam so that the resulting beam conforms to a shape of a target region. In the illustrated embodiments, the collimator 19 comprises a multi-leaf collimator, and includes a plurality of leafs or fingers that are slidable relative to each other. During use, the leafs are positioned to thereby form a desired shape of an opening for allowing the beam to pass through the collimator 19. In other embodiments, the collimator 19 may be a single block having an opening that is predetermined. The collimator 19 may be made from brass or other materials. The energy modulator 14 is shown as a separate component as the proton generator 12 and the beam transport system 16, but may be integrated with the proton generator 12 (in which case, the energy modulator 14 will be a part of the proton generator 12) or with the beam transport system 16 (in which case, the energy modulator 14 will be a part of the beam transport system 16). The system 10 also includes a processor 54, which may be used to control an operation of the proton source 12, the energy modulator 14, and/or an operation of the nozzle 18. In some cases, the processor 54 may also be used to obtain data regarding an operation of the proton machine, perform analysis and calculation on dose, and other functions, such as those described herein. The system 10 may also include an user interface 56 having a monitor and an input device (e.g., keyboard, mouse, etc.) for allowing a user to input and receive data. FIG. 2 illustrates the energy modulator 14 in accordance with some embodiments. The energy modulator 14 includes a plurality of blocks 200. In the illustrated embodiments, the energy modulator 14 includes eight blocks 200a-200h. In other embodiments, the energy modulator 14 may have other number of blocks, e.g., as many as 100 blocks or more. The blocks 200a-200h have respective thicknesses 202a-202h, wherein thickness 202h is two times the thickness 202g, thickness 202g is two times the thickness 202f, thickness 202f is two times the thickness 202e, thickness 202e is two times the thickness 202d, thickness 202d is two times the thickness 202c, thickness 202c is two times the thickness 202b, and thickness 202b is two times the thickness 202a. Thus, the blocks 200 have respective thicknesses 202h that collectively form a logarithmic pattern. Each of the blocks 200 may be individually moved between a first position and a second position, wherein when the block 200 is in the first position, the block 200 is not in a path of a beam 280, and when the block 200 is in the second position, it is in the path of the beam 280. Such binary configuration provides 2N variations of energy modulation, wherein N equals to the total number of blocks 200. In the example shown in the figure, there are eight blocks 200 (i.e., with N=8), providing 28=256 variations of energy modulation for the beam 280. In the illustrated embodiments, the blocks 200 are offset from each other in a direction of the beam 280. This configuration allows different blocks 200 to enter into the beam path at different locations along the beam line. As used in this specification, the term “offset” refers to any spacing between a reference point on one block 200 and a reference point on another block 200. The energy modulator 14 also includes a mounting structure 204 to which the blocks 200 are moveably mounted, and a positioning system 206 for moving the blocks 200. The positioning system 206 includes a plurality of arms 208 that are coupled to respective blocks 200. The positioning system 206 may include a plurality of pistons for moving the arms 208. The pistons may be driven by hydraulics, electric motors, piezoelectric motors, or other devices known in the art. If a motor is used, the motor may be a linear-type motor or a rotating-type motor. In other embodiments, the pistons may be driven pneumatically (e.g., by a pneumatic mechanism). In the illustrated embodiments, the arms 208 are located on a same side of the energy modulator 14. In other embodiments, the arms 208 may be located on different sides of the energy modulator 14. Such configuration provides more space to accommodate the arms 208 and other associated components for the blocks 200. The blocks 200 have different respective energy absorption characteristics. Each of the blocks 200 is made from a material that allows at least part of the proton beam to be transmitted therethrough while slowing down the protons. By means of non-limiting examples, the blocks 200 may be made from plastic(s), metal(s), graphite(s), other composite materials, or other suitable materials. In some cases, the relatively larger block(s) may be made from any conductive material(s). In some embodiments, all of the blocks 200 are made from the same material. In other embodiments, one or more of the blocks 200 may be made from a material that is different from the material of other block(s) 200. For example, in some embodiments, the thicker block(s) may be made from a first material with a Z value that is less than a Z value of a second material for the thinner block(s) 200. In such cases, the thicknesses and the materials of the blocks 200 are selected such that the change of energies affected by the respective blocks 200 form a logarithmic pattern. For example, in other embodiments, block 200h may have the same thickness as that of block 200g. However, the materials for blocks 200h and 200g may be different (e.g., the material for block 200h may have a lower Z value than that of the material for block 200g), such that the change of energy (ΔEh) affected by block 200h is twice as that of the change of energy (ΔEg) affected by block 200g. Similarly, the material and the thickness of block 200f may be selected such that the energy (ΔEg) affected by block 200g is twice as that of the change of energy (ΔEf) affected by block 200f, and so forth for the remaining blocks 200. Thus, the energy absorption characteristic for each of the blocks 200 may be accomplished by thickness selection, material selection, or both. In some embodiments, the material(s) and thickness(s) for the blocks 200 are selected such that the set of blocks 200 provide for the beam a total range of energy modulation ΔETotal that is between 40 kV and 600 MeV for protons, and between 40 kV and 1 GeV power nucleons for other ions (e.g., Carbon). Thus, if the beam has an initial energy Einitial, the use of the energy modulator 14 (i.e., to place the block(s) 200 in, or to remove the block(s) from, the beam path) may create a beam with energy Emodulated=Einitial±ΔETotal. For example, placing only the thinnest block 200a into the path of the beam would allow the energy of the beam to be decreased by as little as 5 kV, while placing all of the blocks 200 into the beam path would allow the energy of the beam to be decreased by as much as 200 MeV. Similarly, in another example, removing only the thinnest block 200a from the path of the beam would allow the energy of the beam to be increased by as little as 5 kV, while removing all of the blocks 200 from the beam path would allow the energy of the beam to be increased by as much as 200 MeV. In some cases, the thinnest block 200a may have a thickness that is less than 10 cm, e.g., less than 1 cm. In some embodiments, the use of the energy modulator 14 provides a beam at the nozzle 18 having an energy that is between 70 MeV and 250 MeV, which corresponds to tissue penetration that is between 4 cm and 38 cm. In the above embodiments, the blocks 200 are arranged such that the block 200h with the largest thickness 202h is closest to the particle source 12, with the remaining blocks 200a-200g being arranged further away from the particle source 12 in accordance with their decreasing thicknesses. In other embodiments, the blocks 200 may be arranged differently. For example, in other embodiments, the blocks 200 may be arranged in increasing thicknesses as they are placed further away from the particle source 12. Also, in other embodiments, the blocks 200 may not be arranged in increasing or decreasing thicknesses. Further, in other embodiments, the blocks 200 need not abut against one another as that shown in the figure, and may be spaced away from each other. In such cases, the gap (e.g., 0.5 mm to 20 cm) between the blocks 200 may allow at least some of the blocks 200 to be cooled by convection more efficiently. Spacing the blocks 200 away from each other also has the benefit of allowing components (e.g., positioner, arm 206, electronics, cooling mechanism for the block, etc.) to be accommodated within a limited space. In some cases, spacing the blocks 200 away from each other also facilitates cooling of the blocks via radiation convection. FIG. 3A illustrates a perspective view of one of the blocks 200 in accordance with some embodiments. As shown in the figure, the block 200 is a rectangular block with a rectangular cross section in the direction of the beam. The block 200 has a surface 300 that is substantially perpendicular (e.g., 90°±5°) to the beam. The surface 300 is substantially parallel to an opposite surface. Such configuration is beneficial in that it allows the beam to be filtered through the block 200 without steering effect (which may result if a wedge-like block is used). In other embodiments, the block 200 can have other shapes. For example, in other embodiments, the block 200 may have a circular cross section in the direction of the beam (FIG. 3B). In this embodiment, the block 200 also has a surface 300 that is substantially perpendicular to the beam. It should be noted that any of the blocks 200 needs not have a block-like configuration, and that it may have a non-block-like configuration, such as a structure with a thin profile. Thus, the term “block” should not be limited to structures having a block-like configuration, and may include structures having a thin or low profile such that a dimension on one side of the structure is substantially less than the dimension on another side. For example, block 200a in FIG. 2 may have a low profile because its thickness 202a is very small. In some cases, the energy modulator 14 may further include a frame 400 to which the block 200a (or another block with a thin profile) may be mounted (FIG. 4). The frame 400 provides structural integrity for the block 200a so that the block 200a does not bend or deform during use. The frame 400 includes a firs side 402, a second side 404, and a bottom side 406. In some embodiments, the frame 400 may not include the bottom side 406. Returning to FIG. 2, the energy modulator 14 further includes a cooling system 220 for cooling some or all of the blocks 200. The cooling system 220 includes a fluid source 222 for delivering cooling fluid to channel(s) 224 within each of the blocks 200 via pipe(s) 226. In some embodiments, two or more blocks 200 may share the fluid source 222. In other embodiments, any one of the blocks 200 may have its own fluid source 222. For blocks 200 that may be too thin to incorporate cooling channel(s), the cooling system 220 may include a fan system 240 for delivering cooling air to cool the blocks 220 using convection. In other embodiments, the cooling of the entire set of blocks 200 may be performed using convection, in which case, the cooling system 220 does not include the fluid source 222 and the pipes 226, and includes only the fan system 240. In further embodiments, the cooling of any of the blocks 200 may be performed using radiation convection. A method of using the system 10 that includes the energy modulator 14 will now be described. First information regarding a desired energy level for a proton beam is obtained. In some embodiments, such information may be a value of the desired energy level that is inputted into the processor 54 as a part of a treatment plan. In other embodiments, actual beam energy may be measured near the nozzle (e.g., via a chamber that measures monitor units), and the measured energy is compared with a desired level of energy to obtain a difference. In such case, the information regarding the desired energy level for a proton beam may be the difference value. Next, if a proton beam has not been generated, the proton generator 12 generates protons and delivers a proton beam 280 towards the energy modulator 14. Based on the information regarding the desired energy level (which is associated with a level of energy for the beam that is desired to be provided downstream from the energy modulator 14), the processor 54 transmits signal(s) to the energy modulator 14 to cause one or more blocks 200 to be moved (via the positioning system 206) into, or away from, the path of the beam 280. In some embodiments, the energy modulator 14 may employ a lookup table for determining which block(s) 200 to use based on the amount of energy that is desired to be adjusted for the beam. In such cases, the lookup table has a first column containing values of different amount of energy that is adjustable by different combination of the block(s) 200. The lookup table also includes a second column containing identifier of block(s) 200 that correspond to each of the energy values in the first column. Examples of some of the entries for such lookup table are illustrated below: Amount of energydesired to be adjustedIndex(ΔE)Block(s) to be positioned11.5 MeV Block 2214 MeVBlocks 2, 5, 7360 MeVBlocks 4, 20Thus, if the amount of energy ΔE desired to be adjusted is approximately 14 MeV, the processor 54 will determine from the lookup table that blocks with identifiers 2, 5, and 7 are to be positioned to provide such amount of energy modulation. The processor 54 then sends signal(s) to the positioner 206 to thereby position these blocks. In particular, the blocks will be removed from the path of the beam line if the amount of energy is to be incremented for the beam. Alternatively, the blocks will be placed into the beam path if the amount of energy is to be decreased for the beam. In other embodiments, instead of using a look-up table, the selection of the blocks may be determined using direction calculation technique. In the example shown in the figure, block 200e and block 200g are moved down into the path of the beam 280 (see dashed lines of blocks 200e, 200g). Thus, the beam 280 is being modulated by the block 200e and block 200g in the example to achieve a desired level of energy. In some cases, the positioning system 206 is configured to position selected ones of the blocks 200 simultaneously, thereby allowing the energy of the beam to be adjusted efficiently. Alternatively, a subset of one or more of the blocks 200 may be positioned sequentially after another subset of block(s) 200 has been positioned. Such configuration allows energy of the beam at downstream to be measured after a first subset of block(s) 200 has been positioned. The measured energy may then be used as feedback, based upon which, the processor 54 may determine which block(s) in the second subset are to be positioned. The above described method is performed when the nozzle 18 is at a certain position. If the nozzle 18 is mounted on a rotatable gantry, the above described method may be performed when the nozzle 18 is at a certain gantry angle, and may be repeated when the nozzle 18 is rotated to other gantry angles. In such cases, the operation of the energy modulator 14 is synchronized with the rotation of the nozzle 18. For example, when the nozzle 18 is at a certain gantry angle (at P1) at which the target region 23 is located deeper in the patient (t1 at FIG. 9), the energy modulator 14 is operated to increase the energy of the beam such that the Bragg peak will be located deeper within the patient at the target region 23. On the other hand, when the nozzle 18 is at another gantry angle (at P2) at which the target region 23 is closer to the surface of the patient (t2 at FIG. 9), the energy modulator 14 is accordingly operated to decrease the energy of the beam such that the Bragg peak will be located at the target region 23. In other embodiments, instead of rotating the nozzle 18 around the patient, the patient may be rotated relative to the nozzle 18 that is stationary. During use of the energy modulator 14, the collimator 19 may be used to change the shape of the cross-section of the beam so that the beam conforms to the shape of the target region 23. In such cases, the nozzle 18 may further include a scatterer for spreading the proton beam before it reaches the collimator 19. The operation of the collimator 19 may be synchronized with the rotation of the gantry, thereby conforming the beam to the shape of the target region 23 from different gantry angles. In some embodiments, the operation of the collimator and the rotation of the nozzle 18 may be slaved to monitor units. In other embodiments, the system 10 may be configured to deliver pencil proton beam, in which case, the scatterer and the collimator may not be needed. FIG. 5 illustrates an effect of using the block(s) 200 to modulate the beam energy. When a proton beam is delivered into matter, it results in a single Bragg peak curve 500. As illustrated by the Bragg peak curve 500, the energy is concentrated approximately at a location at which the beam ends. In accordance with embodiments described herein, when one or more of the blocks 200 are placed in the path of the beam, the block(s) 200 reduce the beam energy, thereby shifting the Bragg peak curve to a new position 510 (towards the left). On the other hand, when one or more of the blocks 200 are removed from the path of the beam, the beam energy increases, thereby allowing the beam to penetrate deeper, and shifting the Bragg peak curve to position 512 (towards the right). During use of the energy modulator 14, the interaction between the beam 280 and the block(s) 200 may cause the block(s) 200 to heat up. The cooling system 220 is used to providing cooling for the block(s) 200—e.g., through the use of cooling fluid, and/or convection using the fan system 240. In some cases, the interaction between the beam 280 and the block(s) 200 may create a scattering effect, thereby causing the beam exiting the block(s) 200 to diverge. In such cases, the energy modulator 14 may further include an emitance filter 282 having an opening 284. The emitance filter 282 is made from a material that blocks part of the diverged beam to thereby prevent the diverged beam from being transmitted downstream. The opening 284 at the emitance filter 282 allows part of the beam to be transmitted therethrough to the downstream direction. As illustrated in the embodiments, the energy modulator 14 is advantageous because the logarithmic pattern of the blocks' thicknesses allows the energy of the beam to be modulated quickly. In particular, if an energy of the beam is desired to be adjusted (e.g., increased or decreased) by a relatively large increment, then blocks 200 with larger thicknesses may be used. On the other hand, if the amount of energy desired to be adjusted is small, then smaller blocks 200 may be used. Also, the energy modulator 14 allows the energy of the beam to be selectively and dynamically modulated during the treatment session. Further, the energy modulator 14 is advantageous because the blocks 200 do not need to be calibrated. FIG. 6 illustrates a set 600 of blocks 200 that may be used for the energy modulator 14 in accordance with other embodiments. The set 600 of blocks 200 is similar to that shown previously in that the blocks have thicknesses that form a logarithmic pattern. However, in the illustrated embodiments, the total number of blocks are twice as much as the embodiment of FIG. 2. In particular, there are two blocks 200 for each of the thicknesses. Such configuration is advantageous in that it provides more combination of the blocks 200, which in turn, more variations of the amount of energy modulation. In other embodiments, more than two blocks 200 may have the same thickness. In the above embodiments, the thicknesses of the blocks 200 measured in the direction of the beam form a logarithmic pattern in which at least some of the blocks 200 are two times in thickness of another block. However, in other embodiments, the thicknesses of the blocks 200 may have other patterns. FIG. 7 illustrates a set 700 of blocks 200 in accordance with other embodiments. The set 700 includes three subsets 702, 704, 706 of blocks 200. The first subset 702 includes three blocks 200a-200c, the second subset 704 includes four blocks 200d-200g, and the third subset 706 includes five blocks 200h-200l. In the illustrated embodiments, the blocks 200h-200l in the third subset 706 have the same thickness, and collectively have a combined thickness that is equal to the thickness of a block (e.g., block 200d) in the second subset 704. Also, the blocks 200d-200g in the second subset 704 have the same thickness, and collectively have a combined thickness that is equal to the thickness of a block (e.g., block 200a) in the first subset 702. Such configuration is advantageous in that it allows an energy of the beam to be modulated by a constant increment of energy within a range. The increment can be made more refined, e.g., by providing a group of blocks 200 having a smaller thickness in the direction of the beam. In other embodiments, the energy modulator 14 may have other number of subsets of blocks 200. Also, in other embodiments, each of the subsets 702, 704, 706 may have numbers of blocks that are different from the example shown. Also, in other embodiments, the blocks 200 in any of the subsets 702, 704, 706 may have different thicknesses within the subset. In further embodiments, the blocks 200 in each subset need not be arranged in a group, and may be commingled with blocks 200 in other subset(s). For example, the smaller blocks may be placed in between larger blocks, thereby allowing more room to accommodate the components (e.g., positioner, arm, etc.) associated with the smaller blocks. In the above embodiments, the proton system 10 has one energy modulator 14. However, in other embodiments, the proton system 10 may have a plurality of energy modulators 14. FIG. 8 illustrates a variation of the proton system 10 that includes two energy modulators 14a, 14b. As shown in the figure, the first energy modulator 14a is located at a position that is closer to the proton generator 12 than the nozzle 18, and the second energy modulator 14b is located at a position that is closer to the nozzle 18 than the proton generator 12. The proton system 10 may further include a shield 800 located near the nozzle 18. The shield 800 is for protecting the patient from neutrons that may be created as a result of the proton beam interacting with the blocks 200. Alternatively, the housing of the energy modulator 14b itself made be made from a material that functions as the shield. In other embodiments, the system 10 may include more than two energy modulators 14. For example, in other embodiments, the system 10 may include an energy modulator 14 anywhere along the beam transport system 16. During use of the system 10 of FIG. 8, the nozzle 18 is rotated about the patient 22 to deliver proton beam towards the target region 23 from a plurality of gantry angles (FIG. 9). Because the target region 23 is offset from the center of the patient 22, the proton beam at different gantry angles needs to penetrate different amount of tissue before reaching the target region 23. For example, the proton beam at one gantry angle (i.e., when the nozzle 18 is at position P1) needs to penetrate tissue of thickness=t1, while at another gantry angle (i.e., when the nozzle 18 is at position P2), needs to penetrate tissue of thickness=t2 which is thinner than t1. In the illustrated embodiments, when the nozzle 12 is rotated from P1 to P2, the first energy modulator 14a may be used to decrease the energy of the beam by placing one or more blocks 200 in the first energy modulator 14a into the beam path. The operation of the first energy modulator 14a is similar to that described previously. When the nozzle 18 is rotated from P2 to P3, the amount of beam penetration needs to be increased to address the fact that there is an increasing amount of tissue that the beam needs to go through to reach the target region 23. In such cases, the second energy modulator 14b may be used to increase the energy of the beam by removing one or more blocks 200 in the second energy modulator 14b from the beam path. The operation of the second energy modulator 14b is also similar to that described previously. Sometimes, the magnetic components along the beam transport system 16, while allowing a beam with lower energy to be transported in a predictable manner, may not allow a beam with higher energy to be transported in a predictable manner. This is due to the hysteresis effect of the magnetic materials of the magnets that are in the beam transport system 16. As a result, without the second energy modulator 14b, in order to increase the beam transport to higher energy predictably, the energy acceptance of the magnet will need to be increased to a level that is higher than a desired level, and then the field must be adjusted downward to reach the magnetic field level for the desired beam energy. The use of the second energy modulator 14b obviates such need because the reduction of the beam energy is controlled by the second energy modulator 14b, which accounts for the hysteresis effect in the magnets of the beam transport system 16. Thus, the above technique is advantageous in that it allows an energy of the beam to be increased quickly and predictably. In other embodiments, instead of rotating the nozzle 18 around the patient, the patient may be rotated relative to the nozzle 18 that is stationary. In other embodiments, instead of having two energy modulators 14a, 14b, the modulator 14a may be omitted- In such cases, the system 10 includes the modulator 14b at the distal end only. In any of the embodiments described herein, the nozzle 18 may include additional components for altering the characteristic of the proton beam. For example, in some embodiments, the nozzle 18 may include a first scatterer for scattering the beam. Alternatively, instead of being part of the nozzle 18, the first scatterer may be upstream from the nozzle 18. In other embodiments, the nozzle 18 may include a second scatterer for further scattering the beam. In some cases, the nozzle 18 may include a range modulator configured to spread the concentration of energy associated with the Bragg peak. For example, the range modulator may include a disk and a positioner for rotating the disk, wherein the disk has a step configuration such that different portions of the disk have different respective thicknesses. Alternatively, the range modulator may be a ridge filter. During use, the positioner places different portions of the disk (e.g., by rotating the disk) in front of the beam such that the beam is filtered by different portions of the disk that have different thicknesses. The thicker portions reduce the energy of the proton beam more than the relatively thinner portions. FIG. 10 illustrates an effect of using the block(s) 200 to modulate beam energy in a system that includes a range modulator. When a proton beam is delivered into matter, it results in a single Bragg peak curve 1000. As illustrated by the Bragg peak curve 1000, the energy is concentrated approximately at a location at which the beam ends. As a result of using the range modulator (which is pre-configured for spreading concentration of energy using all portions of the rotating disk), the beam has a spread out Bragg peak (SOBP) 1002. In accordance with embodiments described herein, when one or more of the blocks 200 are placed in the path of the beam, the block(s) 200 reduce the beam energy, thereby shifting the SOBP 1002 to the new position 1004 (towards the left). On the other hand, when one or more of the blocks 200 are removed from the path of the beam, the beam energy is increased, thereby shifting the SOBP 1002 to position 1006 (towards the right). Also, in some embodiments, the system 10 may include a plurality of magnets for moving the proton beam. For example, in some embodiments, the system 10 may include two sets of orthogonal magnets for moving the proton beam, to thereby provide a scanning feature. The scanning may be done continuously or in a step-and-shoot manner. Computer System Architecture FIG. 11 is a block diagram that illustrates an embodiment of a computer system 1100 upon which an embodiment of the invention may be implemented. Computer system 1100 includes a bus 1102 or other communication mechanism for communicating information, and a processor 1104 coupled with the bus 1102 for processing information. The processor 1104 may be an example of the processor 54 of FIG. 1, or another processor that is used to perform various functions described herein. In some cases, the computer system 1100 may be used to implement the processor 54. The computer system 1100 also includes a main memory 1106, such as a random access memory (RAM) or other dynamic storage device, coupled to the bus 1102 for storing information and instructions to be executed by the processor 1104. The main memory 1106 also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor 1104. The computer system 1100 further includes a read only memory (ROM) 1108 or other static storage device coupled to the bus 1102 for storing static information and instructions for the processor 1104. A data storage device 1110, such as a magnetic disk or optical disk, is provided and coupled to the bus 1102 for storing information and instructions. The computer system 1100 may be coupled via the bus 1102 to a display 1112, such as a cathode ray tube (CRT) or a plat panel, for displaying information to a user. An input device 1114, including alphanumeric and other keys, is coupled to the bus 1102 for communicating information and command selections to processor 1104. Another type of user input device is cursor control 1116, such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processor 1104 and for controlling cursor movement on display 1112. This input device typically has two degrees of freedom in two axes, a first axis (e.g., x) and a second axis (e.g., y), that allows the device to specify positions in a plane. The computer system 1100 may be used for performing various functions (e.g., calculation) in accordance with the embodiments described herein. According to one embodiment, such use is provided by computer system 1100 in response to processor 1104 executing one or more sequences of one or more instructions contained in the main memory 1106. Such instructions may be read into the main memory 1106 from another computer-readable medium, such as storage device 1110. Execution of the sequences of instructions contained in the main memory 1106 causes the processor 1104 to perform the process steps described herein. One or more processors in a multi-processing arrangement may also be employed to execute the sequences of instructions contained in the main memory 1106. In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions to implement the invention. Thus, embodiments of the invention are not limited to any specific combination of hardware circuitry and software. The term “computer-readable medium” as used herein refers to any medium that participates in providing instructions to the processor 1104 for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media includes, for example, optical or magnetic disks, such as the storage device 1110. Volatile media includes dynamic memory, such as the main memory 1106. Transmission media includes coaxial cables, copper wire and fiber optics, including the wires that comprise the bus 1102. Transmission media can also take the form of acoustic or light waves, such as those generated during radio wave and infrared data communications. Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, or any other magnetic medium, a CD-ROM, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave as described hereinafter, or any other medium from which a computer can read. Various forms of computer-readable media may be involved in carrying one or more sequences of one or more instructions to the processor 1104 for execution. For example, the instructions may initially be carried on a magnetic disk of a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to the computer system 1100 can receive the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal. An infrared detector coupled to the bus 1102 can receive the data carried in the infrared signal and place the data on the bus 1102. The bus 1102 carries the data to the main memory 1106, from which the processor 1104 retrieves and executes the instructions. The instructions received by the main memory 1106 may optionally be stored on the storage device 1110 either before or after execution by the processor 1104. The computer system 1100 also includes a communication interface 1118 coupled to the bus 1102. The communication interface 1118 provides a two-way data communication coupling to a network link 1120 that is connected to a local network 1122. For example, the communication interface 1118 may be an integrated services digital network (ISDN) card or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, the communication interface 1118 may be a local area network (LAN) card to provide a data communication connection to a compatible LAN. Wireless links may also be implemented. In any such implementation, the communication interface 1118 sends and receives electrical, electromagnetic or optical signals that carry data streams representing various types of information. The network link 1120 typically provides data communication through one or more networks to other devices. For example, the network link 1120 may provide a connection through local network 1122 to a host computer 1124 or to equipment 1126 such as a radiation beam source or a switch operatively coupled to a radiation beam source. The data streams transported over the network link 1120 can comprise electrical, electromagnetic or optical signals. The signals through the various networks and the signals on the network link 1120 and through the communication interface 1118, which carry data to and from the computer system 1100, are exemplary forms of carrier waves transporting the information. The computer system 1100 can send messages and receive data, including program code, through the network(s), the network link 1120, and the communication interface 1118. Although particular embodiments of the present inventions have been shown and described, it will be understood that it is not intended to limit the present inventions to the preferred embodiments, and it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present inventions. For example, in other embodiments, any of the embodiments of the energy modulator described herein may be used with a Linac. Also, in other embodiments, the system 10 needs not be a proton system, and may be other particle systems, e.g., systems that provide electron beams, neutron beams, or other particle beams. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense. The present inventions are intended to cover alternatives, modifications, and equivalents, which may be included within the spirit and scope of the present inventions as defined by the claims.
	description	The present application is (a) a reissue of U.S. patent application Ser. No. 10/381,626, filed on Aug. 20, 2003, now U.S. Pat. No. 6,947,120, which is a U.S. national stage entry of International Application No. PCT/EP01/11233 , and (b) a continuation-in part of U.S. patent application Ser. No. 10/201,652. The PCT/EP01/11233 application was filed Sep. 28, 2001, and claims priority of U.S. patent application Ser. No. 09/679,718. The 10/201,652 application was filed Jul. 22, 2002, and is (a) a continuation-in part of U.S. patent application Ser. No. 10/150,650, and (b) a continuation-in part of the 09/679,718 application. The 10/150,650 application was filed May 17, 2002, and , filed Sep. 28, 2001, which is a continuation-in-part of the U.S. patent application Ser. No. 09/679,718 application. The 09/679,718 application was filed Sep. 29, 2000, issued as U.S. Pat. No. 6,438,199, and is a continuation-in part of U.S. patent application Ser. No. 09/305,017. The 09/305,017 application was filed May 4, 1999, and issued as U.S. Pat. No. 6,198,793. The present application is also claiming priority of (a) International Application No. PCT/EP00/07258, filed Jul. 28, 2000, (b) German Patent Application No. 299 02 108, filed Feb. 8, 1999, (c) German Patent Application No. 199 03 807, filed Feb. 2, 1999, and (d) German Patent Application No. 198 19 898, filed on May 5, 1998. (1) Field of the Invention The invention concerns an illumination system for wavelengths ≦193 nm as well as a projection exposure apparatus with such an illumination system. (2) Description of the Invention In order to be able to further reduce the structural widths of electronic components, particularly in the submicron range, it is necessary to reduce the wavelengths of the light utilized for microlithography. Lithography with very deep UV radiation, so called VUV (Very deep UV) lithography or with soft x-ray radiation, so-called EUV (extreme UV) lithography, is conceivable at wavelengths smaller than 193 nm, for example. An illumination system for a lithographic device, which uses EUV radiation, has been made known from U.S. Pat. No. 5,339,346. For uniform illumination in the reticle plane and filling of the pupil, U.S. Pat. No. 5,339,346 proposes a condenser, which is constructed as a collector lens and comprises at least 4 pairs of mirror facets, which are arranged symmetrically. A plasma light source is used as the light source. In U.S. Pat. No. 5,737,137, an illumination system with a plasma light source comprising a condenser mirror is shown, in which an illumination of a mask or a reticle to be illuminated is achieved by means of spherical mirrors. U.S. Pat. No. 5,361,292 shows an illumination system, in which a plasma light source is provided, and the point plasma light source is imaged in an annular illuminated surface by means of a condenser, which has five aspherical mirrors arranged off-center. From U.S. Pat. No. 5,581,605, an illumination system has been made known, in which a photon beam is split into a multiple number of secondary light sources by means of a plate with concave raster elements. In this way, a homogeneous or uniform illumination is achieved in the reticle plane. The imaging of the reticle on the wafer to be exposed is produced by means of a conventional reduction optics. EP-A-0 939 341 shows an illumination system and exposure apparatus for illuminating a surface over an illumination field having an arcuate shape with X-ray wavelength light. The illumination system comprises first and second optical integrators each with a plurality of reflecting elements. The first and second optical integrators being opposingly arranged such that a plurality of light source images are formed at the plurality of reflecting elements of the second optical integrator. To form an arcuate shaped illumination field in the field plane according to EP 0 939 341 A2 the reflecting elements of the first optical integrator have an arcuate shape similar to the arcuate illumination field. Such reflecting elements are complicate to manufacture. EP-A-1 026 547 also shows an illumination system with two optical integrators. Similar to the system of EP-A-0 939 341 the reflecting elements of the first optical integrator have an arcuate shape for forming an arcuate shaped illumination field in the field plane. In EP-A-0 955 641 a system with two optical integrators is shown. Each of said optical integrators comprises a plurality of raster elements. The raster elements of the first optical integrator are of rectangular shape. The arc shaped field in the field plane is formed by at least one grazing incidence field mirror. The content of the above mentioned patent-applications are incorporated by reference. All systems of the state of the art, e.g. the systems according EP-A-0 939 341 or EP-A-1 026 547 have the disadvantage that the track-length, of the illumination system is large. It is therefore an object of the invention to overcome the disadvantages of the illumination systems according to the state of the art and to provide on illumination system for microlithography that fulfills the requirements for advanced lithography with wavelength less or equal to 193 nm. The illumination system should be further compact in size and provide a plane in which devices could be placed to change the illumination mode or to filter the radiation of the beams. The system illuminates a structured reticle arranged in the image plane of the illumination system, which will be imaged by a projection objective onto a light sensitive substrate. In scanner-type lithography systems the reticle is illuminated with a rectangular or arc-shaped field, wherein a pregiven uniformity of the scanning energy distribution inside the field is required, for example better than ±5%. The scanning energy is defined as the line integral over the light intensity in the scanning direction. The shape of the field is dependent on the type of projection objective. All reflective projection objectives typically have an arc-shaped field, which is given by a segment of an annulus. A further requirement is the illumination of the exit pupil of the illumination system, which is located at the entrance pupil of the projection objective. A nearly field-independent illumination of the exit pupil is required. Typical light sources for wavelengths between 100 nm and 200 nm are excimer lasers, for example an ArF-Laser for 193 nm, an F2-Laser for 157 nm, an Ar2-Laser for 126 nm and an NeF-Laser for 109 nm. For systems in this wavelength region refractive components of SiO2, CaF2, BaF2 or other crystallites are used. Since the transmission of the optical materials deteriorates with decreasing wavelength, the illumination systems are designed with a combination of refractive and reflective components. For wavelengths in the EUV wavelength region, between 10 nm and 20 nm, the projection exposure apparatus is designed as all-reflective. A typical EUV light source is a Laser-Produced-Plasma-source, a Pinch-Plasma-Source, a Wiggler-Source or an Undulator-Source. The light of this primary light source is directed to a first optical element, wherein the first optical element is part of a first optical component. The first optical element is organized as a plurality of first raster elements and transforms the primary light source into a plurality of secondary light sources. Each first raster element corresponds to one secondary light source and focuses an incoming ray bundle, defined by all rays intersecting the first raster element, to the corresponding secondary light source. The secondary light sources are arranged in a pupil plane of the illumination system or nearby this plane. A second optical component is arranged between the pupil plane and the image plane of the illumination system to image the secondary light sources into an exit pupil of the illumination system, which corresponds to the entrance pupil of a following projection objective The first raster elements are imaged into the image plane, wherein their images are at least partially superimposed on a field that must be illuminated. Therefore, they are known as field raster elements or field honeycombs. All-reflective projection objectives used in the EUV wavelength region have typically an object field being a segment of an annulus. Therefore the field in the image plane of the illumination system in which the images of the field raster elements are at least partially superimposed has preferably the same shape. The shape of the illuminated field can be generated by the optical design of the components or by masking blades which have to be added nearby the image plane or in a plane conjugated to the image plane. According to the invention the second optical component of the illumination system comprises a first optical system comprising at least a third field mirror forming a plurality of the tertiary light sources in a plane conjugate to the exit pupil of the illumination system. The tertiary light sources are imaged by a second optical system comprising at least a second field mirror and a first field mirror into the exit pupil of the illumination system. The images of the tertiary light sources in the exit pupil of the illumination system are called quaternary light sources. The field raster elements are preferably rectangular. Rectangular field raster elements have the advantage that they can be arranged in rows being displaced against each other. Depending on the field to be illuminated they have a side aspect ratio in the range of 5:1 and 20:1. The length of the rectangular field raster elements is typically between 15 mm and 50 mm, the width is between 1 mm and 4 mm. To illuminate an arc-shaped field in the image plane with rectangular field raster elements the first field mirror of the second optical component preferably transforms the rectangular images of the rectangular field raster elements to arc-shaped images. The arc length is typically in the range of 80 mm to 105 mm, the radial width in the range of 5 mm to 9 mm. The transformation of the rectangular images of the rectangular field raster elements can be done by conical reflection with the first field mirror being a grazing incidence mirror with negative optical power. In other words, the imaging of the field raster elements is distorted to get the arc-shaped images, wherein the radius of the arc is determined by the shape of the object field of the projection objective. The first field mirror is preferably arranged in front of the image plane of the illumination system, wherein there should be a free working distance. For a configuration with a reflective reticle the free working distance has to be adapted to the fact that the rays traveling from the reticle to the projection objective are not vignetted by the first field mirror. The surface of the first field mirror is preferably an off-axis segment of a rotational symmetric reflective surface, which can be designed aspherical or spherical. The axis of symmetry of the supporting surface goes through the vertex of the surface. Therefore a segment around the vertex is called on-axis, wherein each segment of the surfaces which does not include the vertex is called off-axis. The supporting surface can be manufactured more easily due to the rotational symmetry. After producing the supporting surface the segment can be cut out with well-known techniques. The surface of the first field mirror can also be designed as an on-axis segment of a toroidal reflective surface. Therefore the surface has to be processed locally, but has the advantage that the surrounding shape can be produced before surface treatment. The incidence angles of the incoming rays with respect to the surface normals at the points of incidence of the incoming rays on the first field mirror are preferably greater than 70°, which results in a reflectivity of the first field mirror of more than 80%. The second field mirror with positive optical power is preferably an off-axis segment of a rotational symmetric reflective surface, which can he designed aspherical or spherical, or an on-axis segment of a toroidal reflective surface. The incidence angles of the incoming rays With respect to the surface normals at the points of incidence of the incoming rays on the second field mirror are preferably lower than 25°. Since the mirrors have to be coated with multilayers for the EUV wavelength region, the divergence and the incidence angles of the incoming rays are preferably as low as possible to increase the reflectivity, which should be better than 65%. With the second field mirror being arranged as a normal incidence mirror the beam path is folded and the illumination system can be made more compact. With the third field mirror of the second optical component the length of the illumination system can be reduced. The third field mirror is arranged between the plane with the secondary light sources and the second field mirror. The third field mirror has positive optical power to generate images of the secondary light sources in a plane between the third and second field mirror, forming the tertiary light sources. Since the plane with the tertiary light sources is arranged conjugated to the exit pupil, this plane can be used to arrange masking blades to change the illumination mode or to add transmission filters. This position in the beam path has the advantage to be freely accessible. To have not great distances between the second and third field mirror and to reduce the refractive power at least of the second and third mirror the conjugated planes to the image plane in the second optical component are virtual conjugated planes. This means that there is no accessible conjugated real image plane, in which the arc shaped field is formed in the second optical component. This is advantageous for a compact design: Furthermore field mirrors with low optical power are much easier to manufacture. The third field mirror is similar to the second field mirror preferably an off-axis segment of a relational symmetric reflective surface, which can be designed aspherical or spherical, or an on-axis segment of a toroidal reflective surface. The incidence angles of the incoming rays with respect to the surface normals at the points of incidence of the incoming rays on the third field mirror are preferably lower than 25°. With the third field mirror being arranged as a normal incidence mirror the beam path can be folded and therefore reduce the overall size of the illumination system. To avoid vignetting of the beam path the first, second and third field mirrors are preferably arranged in a non-centered system. There is no common axis of symmetry for the mirrors. An optical axis can be defined as a connecting line between the centers of the used areas on the field mirrors, wherein the optical axis is bent at the field mirrors depending on the tilt angles of the field mirrors. With the tilt angles of the reflective components of the illumination system the beam paths between the components can be bent. Therefore the orientation of the beam cone emitted by the source and the orientation of the image plane system can be arranged according to the requirements of the overall system. A preferable configuration has a source emitting a beam cone in one direction and an image plane having a surface normal which is oriented almost perpendicular to this direction. In one embodiment the source emits horizontally and the image plane has a vertical surface normal. Some light sources like undulator or wiggler sources emit only in the horizontal plane. On the other hand the reticle should be arranged horizontally for gravity reasons. The beam path therefore has to be bent between the light source and the image plane about almost 90°. Since mirrors with incidence angles between 30° and 60° lead to polarization effects and therefore to light losses, the beam bending has to be done only with grazing incidence or normal incidence mirrors. For efficiency reasons the number of mirrors has to be as small as possible. The illumination system preferably comprises a second optical element having a plurality of second raster elements. It is advantageous to insert a second optical element with second raster elements in the light path after the first optical element with first raster elements, wherein each of the first raster elements corresponds to one of the second raster elements. Therefore, the deflection angles of the first raster elements are designed to deflect the ray bundles impinging on the first raster elements to the corresponding second raster elements. The second raster elements are preferably arranged at the secondary light sources and are designed to image together with the second optical component the first raster elements or field raster elements into the image plane of the illumination system, wherein the images of the field raster elements are at least partially superimposed. The second raster elements are called pupil raster elements or pupil honeycombs. To avoid damaging the second raster elements due to the high intensity at the secondary light sources, the second raster elements are preferably arranged defocused of the secondary light sources, but in a range from 0 mm to 10% of the distance between the first and second raster elements. By definition all rays intersecting the field in the image plane have to go through the exit pupil of the illumination system. The position of the field and the position of the exit pupil are defined by the object field and the entrance pupil of the projection objective. For some projection objectives being centered systems the object field is arranged off-axis of an optical axis, wherein the entrance pupil is arranged on-axis in a finite distance to the object plane. For these projection objectives an angle between a straight line from the center of the object field to the center of the entrance pupil and the surface normal of the object plane can be defined. This angle is in the range of 3° to 10° for EUV projection objectives. Therefore the components of the illumination system have to be configured and arranged in such a way that all rays intersecting the object field of the projection objective are going through the entrance pupil of the projection objective being decentered to the object field. For projection exposure apparatus with a reflective reticle all rays intersecting the reticle needs to have incidence angles greater than 0° to avoid vignetting of the reflected rays at components of the illumination system. In the EUV wavelength region all components are reflective components, which are arranged preferably in such a way, that all incidence angles on the components are lower than 25° or greater than 65°. Therefore polarization effects arising for incidence angles around an angle of 45° are minimized. Since grazing incidence mirrors have a reflectivity greater than 80%, they are preferable in the optical design in comparison to normal incidence mirrors with a reflectivity greater than 65%. The illumination system is typically arranged in a mechanical box. By folding the beam path with mirrors the overall size of the box can be reduced. This box preferably does not interfere with the image plane, in which the reticle and the reticle supporting system are arranged. Therefore it is advantageous to arrange and tilt the reflective components in such a way that all components are completely arranged on one side of the reticle. This can be achieved if the field lens comprises only an even number of normal incidence mirrors. The illumination system as described before can be used preferably in a projection exposure apparatus comprising the illumination system, a reticle arranged in the image plane of the illumination system and a projection objective to image the reticle onto a wafer arranged in the image plane of the projection objective. Both, reticle and wafer are arranged on a support unit, which allows the exchange or scan of the reticle or wafer. The projection objective can be a catadioptric lens, as known from U.S. Pat. No. 5,402,267 for wavelengths in the range between 100 nm and 200 nm. These systems have typically a transmission reticle. For the EUV wavelength range the projection objectives are preferably all-reflective systems with four to eight mirrors as known for example from U.S. Ser. No. 09/503,640 showing a six mirror projection lens. These systems have typically a reflective reticle. For systems with a reflective reticle the illumination beam path between the light source and the reticle and the projection beam path between the reticle and the wafer preferably interfere only nearby the reticle, where the incoming and reflected rays for adjacent object points are traveling in the same region. If there are no further crossing of the illumination and projection beam path it is possible to separate the illumination system and the projection objective except for the reticle region. The projection objective has preferably a projection beam path between said reticle and the first imaging element which is tilted toward the optical axis of the projection objective. Especially for a projection exposure apparatus with a reflective reticle the separation of the illumination system and the projection objective is easier to achieve. FIG. 1 shows a schematic view of a purely reflective embodiment of the invention comprising a light source 8201, a collector mirror 8203, a plate with the field raster elements 8209, a plate with pupil raster elements 8215, a second optical component 8221, a image plane 8229 and a exit pupil 8235. The second optical component comprises a first optical system having a third field mirror 8225 and second optical system having a second field mirror 8223. The third field mirror 8225 as well as the second field mirror 8223 have positive optical power. Furthermore the second optical component comprises a first field mirror 8227. The first field mirror 8227 is a grazing-incidence mirror with negative optical power for field shaping. In the purely reflective embodiment shown in FIG. 1 the field mirror 8225 and the field mirror 8223 are both concave mirrors forming an off-axis Gregorian telescope configuration. The field mirror 8225 images the secondary light sources 8207 in the plane conjugate to the exit pupil between the field mirror 8225 and the field mirror 8223 forming tertiary light sources 8259. In FIG. 1 only the imaging of the central secondary light source 8207 is shown. At the plane with the tertiary light sources 8259 conjugate to the exit pupil a masking unit 8261 is arranged to change the illumination mode of the exit pupil 8233. With stop blades it is possible to mask the tertiary light sources 8259 and therefore to change the illumination of the exit pupil 8233 of the illumination system. Possible slop blades have circular shapes or for example two or four circular openings, e.g. for quadropolar illumination. Alternatively or in addition to stop blades also transmission filters can be arranged in or near the plane with tertiary light sources. The field mirror 8223 and the field mirror 8227 image the tertiary light sources 8259 into the exit pupil 8233 of the illumination system forming quaternary light sources 8235. The optical axis 8245 of the illumination system is not a straight line but is defined by the connection lines between the single components being intersected by the optical axis 8245 at the centers of the components. Therefore, the illumination system is a non-centered system having an optical axis 8245 being bent at each component to get a beam path free of vignetting. There is no common axis of symmetry for the optical components. Projection objectives for EUV exposure apparatus are typically centered systems with a straight optical axis and with an off-axis object field. The optical axis 8247 of the projection objective is shown as a dashed line. The distance between the center of the field 8231 and the optical axis 8247 of the projection objective is equal to the field radius Rfield. The field mirrors 8223, 8225 are designed as on-axis toroidal mirrors, which means that the optical axis 8245 paths through the vertices of the on-axis toroidal mirrors 8223, 8225 and 8227. The second and the third field mirror 8223 and 8225 are normal incidence mirrors, which means that the incidence angles of the incoming rays with respect to the surface normals at the points of incidence of the incoming rays on the second and the third mirror are preferably lower than 25°. The first field mirror 8227 is a grazing incidence mirror, which means that the incidence angles of the incoming rays with respect to the surface normal at the points of incidence of the incoming rays on the first mirror are preferably greater than 70°. In the embodiment depicted in FIG. 1 the second optical component comprising the first 8227, second 8223 and third field mirror 8225 has only virtual conjugate planes to the image plane 8229. This provides for a compact size of the second optical component with low refractive power for the field mirrors. FIG. 2 shows an EUV projection exposure apparatus in a detailed view. Corresponding elements have the same reference numbers as those in FIG. 1 increased by 200. Therefore, the description to these elements is found in the description to FIG. 1. The illumination system according to FIG. 2 comprises instead of the normal incidence collector 8203 a grazing incidence collector 8403 with a plurality of reflecting surfaces. Furthermore, for filtering the wavelength the illumination system comprises a grating element 8404 and a diaphragm 8406. An intermediate image 8408 of the primary light source 8401 lies at the diaphragm 8406. The system comprises as the system shown in FIG. 1 a first optical element with first raster elements 8409 and a second optical element with second raster element 8415 and a second optical component with a first field mirror 8427, a second field mirror 8423 and a third field mirror 8425. The second field mirror 8423 and the third field mirror 8425 are both concave mirrors. The field mirror 8425 images the secondary light sources in the plane conjugate to the exit pupil between the field mirror 8425 and the field mirror 8423 forming tertiary light sources. At the plane 8458 with the tertiary light sources conjugate to the exit pupil, a masking unit 8461 can be arranged to change the illumination mode of the exit pupil. The field mirror 8423 and the field mirror 8427 image the tertiary light sources into the exit pupil, not shown in FIG. 2, of the illumination system forming quaternary light sources. The data for the optical components of the system according to FIG. 2 are given in table 1. The components are shown in a y-z sectional view, wherein for each component the local co-ordinate system with the y- and z-axis is shown. For the field mirrors 8423, 8425 and 8427 the local co-ordinate systems are defined at the vertices of the mirrors. For the two plates with the raster elements the local co-ordinate systems are defined at the centers of the plates. In table 1 the local co-ordinate systems with respect to the local co-ordinate system of image plane is given. The tilt angle a about the x-axis of the local co-ordinate system results after the translation of the reference co-ordinate system in the image plane into the local co-ordinate system. All co-ordinate systems are right handed systems. TABLE 1Co-ordinate system of the optical componentsyzαRxRyKyIntermediate image 84041031.11−1064.5038.9Field raster elements 8409478.51−379.6532.75−833.27sphericalPupil raster elements 8415836.71−1094.97212.1−972.9sphericalThird field mirror 8425104.54−144.2230.6−264.68−268.67Conjugate plane to exit pupil164.59−281.68203.6Second field mirror 8423424.82−877.31208.9−831.34sphericalFirst field mirror 8427−219.99113.40−5.05−77.126hyperboloid−1.1479Image plane 8429000Exit pupil−125−1189.270 In the image plane 8429 of the illumination system the reticle 8467 is arranged. The reticle 8467 is positioned by a support system 8469. The projection objective 8471 having six mirrors images the reticle 8467 onto the wafer 8473 which is also positioned by a support system 8475. The mirrors of the projection objective 8471 are centered on a common straight optical axis 8447. The arc-shaped object field is arranged off-axis. The direction of the beam path between the reticle 8467 and the first mirror 8477 of the projection objective 8471 is tilted to the optical axis 8447 of the projection objective 8471. The angles of the chief rays 8479 with respect to the normal of the reticle 8467 are between 3° and 10°, preferably 5° and 7°. As shown in FIG. 1 the illumination system 8479 is well separated from the projection objective 8471. The illumination and the projection beam path interfere only nearby the reticle 8467.
	abstract	An x-ray beam conditioning system with a first diffractive element and a second diffractive element. The two diffractive elements are arranged in a sequential configuration, and one of the diffractive elements is a crystal. The other diffractive element may be a multilayer optic.
	description	A transportation cask according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings. As shown in FIG. 1, a transportation cask 11 according to the present embodiment comprises a substantially cylindrical body 10, formed of stainless steel, carbon steel, or some other metal, an outer tube 12 coaxial with the body 10 and constituting the outer surface of the cask, and a neutron shielding layer 14 of a high-molecular material that contains hydrogen, for example. The neutron shielding layer 14 is provided between the body 10 and the outer tube 12 and serves as a neutron shield. The body 10 has its upper end open and its lower end closed by means of a bottom wall 18 that is welded to it. Thus, a containing portion 17 is formed in the body 10. As shown in FIGS. 1 and 2, a canister 30 for use as a closed vessel is contained in the body 10 or the containing portion 17 of the transportation cask 11. Further, spent fuel assemblies as radioactive substances are contained in the canister 30. More specifically, as shown in FIGS. 1 to 3, the canister 30 comprises a substantially cylindrical vessel body 32 that is closed at the bottom and has a top opening 32a. The vessel body 32 is formed of a metal such as stainless steel. The vessel body 32 has an outside diameter a little smaller than the inside diameter of the body 10 of the transportation cask 11, and can be inserted into the body 10. A plurality of spent fuel assemblies 36 are sealed in the vessel body 32 in a manner such that they are supported by a basket 34. The basket 34 is formed of a composite material that combines boron and aluminum or SUS. The spent fuel assemblies 36 are formed of a spent fuel from a nuclear reactor, for example, and contain a radioactive substance that involves heat release attributable to decay heat and generation of radiation. The canister 30 has a weld-sealed structure to prevent the sealed radioactive substance from leaking out. Further, the vessel body 32 is filled with helium gas under a negative or positive pressure. A plurality of support blocks 38, e.g., four in number, are fixed on the inner peripheral surface of the upper end portion of the vessel body 32. The support blocks 38 are arranged at equal spaces in the circumferential direction. A disk-shaped shielding plate 40 overlies the support blocks 38 with a ring-shaped support plate between them, thereby closing the top opening of the vessel body 32. Further, a disc-shaped primary lid 42 is lapped on the shielding plate 40 in the top opening 32a of the vessel body 32, thereby closing the top opening of the vessel body. The topside part of the outer peripheral portion of the primary lid 42 is welded to the inner peripheral surface of the vessel body 32, covering the whole circumference. Furthermore, a disc-shaped secondary lid 44 is lapped on the primary lid 42 in the top opening 32a of the vessel body 32. The topside part of the outer peripheral portion of the secondary lid 44 is welded to the inner peripheral surface of the vessel body 32. A plurality of recesses 46 are formed on the inner surface of the secondary lid 44. The whole inner surface of the secondary lid 44 except the recesses 46 is in intimate contact with the upper surface of the primary lid 42. These recesses 46 define closed spaces that serve as inspection spaces for monitoring between the primary and secondary lids 42 and 44. The closed spaces are kept at a negative or positive pressure inside. Thus, a pressure barrier is defined between the inside and outside of the canister 30, so that the closed state can be monitored and the airtight leakage inspection can be carried out. As described above, the top opening 32a of the vessel body 32 is hermetically closed by means of the shielding plate 40, primary lid 42, and secondary lid 44. The shielding plate 40, primary lid 42, and secondary lid 44 are formed of a metal such as stainless steel. The canister 30 with the aforementioned construction is contained coaxially in the containing portion 17 of the body 10 of the transportation cask 11 and placed on the bottom wall 18. In this state, a narrow gap is formed between the outer peripheral surface of the canister 30 and the inner surface of the body 10. As shown in FIGS. 1 and 2, the inside diameter of the body 10 is a little greater than the outside diameter of the canister 30. The upper end portion of the containing portion 17 is formed having an inside diameter greater than that of the remaining portion, so that the containing portion 17 is stepped. Thus, an annular inspection space 16 for the insertion of a tester is formed in the upper end portion of the containing portion 17. The inspection space 16 is situated around the upper end portion of the canister 30, that is, outside the primary and secondary lids 42 and 44. A ring-shaped elastic tube 50 for use as a seal member is located in the inspection space 16. The elastic tube 50, which is formed of rubber, for example, can be inflated by being externally supplied with compressed air. The tube 50 is fixed to the inner peripheral surface of the body 10, and is liquid-tightly in contact with the inner peripheral surface of the body and the outer peripheral surface of the canister 30 in the inspection space 16. Thus, the elastic tube 50 seals the gap between the inner surface of the body 10 and the outer surface of the canister 30, thereby preventing a fluid from getting into the gap between the body 10 and the canister 30 through the top-opening side of the body. One or more supply holes 52 are formed penetrating the outer periphery of the upper end portion of the body 10, and open into a space that is sealed by means of the elastic tube 50. In the present embodiment, the supply holes 52 open into the inspection space 16 under the elastic tube 50. The fluid can be supplied from outside the body 10 to the space between the outer surface of the canister 30 and the inner surface of body 10, which is sealed by means of the elastic tube 50. Normally, each supply hole 52 is closed by a plug 54. As shown in FIGS. 1 and 2, the top opening of the body 10 of the transportation cask 11 is closed by means of a lid 20 that is formed of a metal such as stainless steel or carbon steel. The lid 20 is fastened to the upper end face of the body 10 by bolts 21. The inner surface of the lid 20 is intimately in contact with the outer surface of the secondary lid 44 of the canister 30. Further, the transportation cask 11 is provided with shock absorbers 22 and 24 that are attached to the upper and lower end portions of the body 10, respectively. The shock absorbers 22 and 24 are substantially disc-shaped members of wood, for example. The shock absorber 22 is fitted on and screwed to the upper end portion of the body 10 and covers the whole outer surface of the lid 20. On the other hand, the shock absorber 24 is fitted on and screwed to the lower end portion of the body 10 and covers the whole outer surface of the bottom wall 18. The following is a description of a method for setting the spent fuel assemblies 36 and the canister 30 in the transportation cask 11 constructed in this manner. In a decontamination pit 62, as shown in FIG. 4, the vessel body 32 of the canister 30 is put into the body 10 of the transportation cask 11 with its upper end open. In this stage, the shock absorbers 22 and 24 and the lid 20 are removed. Further, the basket 34 is placed in advance in the vessel body 32. Subsequently, the compressed air is supplied to the elastic tube 50 that is fixed to the inner surface of the upper end portion of the body 10. Thereupon, the tube 50 is inflated and brought intimately into contact with the inner surface of the body 10 and the outer periphery of the upper end portion of the vessel body 32 of the canister 30. By doing this, the gap between the inner surface of the body 10 and the outer surface of the canister 30 is sealed by the elastic tube 50. Thus, the fluid is prevented from getting into the gap between the body 10 and the canister 30 through the top-opening side of the body. Further, a gas such as uncontaminated air from outside the body 10 is filled into the space between the outer surface of the canister 30 and the inner surface of the body 10, which is sealed by the elastic tube 50, and each supply hole 52 is closed by the plug 54. Thus, the space that is sealed by the elastic tube 50 is filled with air, and the pressure in this space is kept at a level equal to or higher than external pressure, whereby penetration of the fluid can be prevented more securely. Thereupon, preparations for fuel loading are finished. The filled fluid is not limited to air, and may be any other gas or a liquid such as pure water. Subsequently, the body 10 of the transportation cask 11, containing the vessel body 32, is transferred to a cask loading pit 65 filled with cooling water 64 by means of an overhead traveling crane, and is immersed in the cooling water, as shown in FIGS. 4 and 5. Thereupon, the vessel body 32 and the upper end portion of the body 10 are filled with water. As this is done, there is no possibility of the contaminated cooling water 64 flowing into the gap between the body 10 and the vessel body 32 through the top opening of the body 10, since the space between the inner surface of the body 10 and the outer surface of the canister 30 is sealed by the elastic tube 50 and filled with air. In the cask loading pit 65, the spent fuel assemblies 36, having so far been contained in a spent fuel rack 60 in a spent fuel pit 66, are pulled out one after another by means of a pit crane 67 and loaded in succession into the basket 16 in the vessel body 32. After a given number of spent fuel assembly 36 are loaded into the vessel body 32, the support plate and the shielding plate 40 are fitted successively into the top opening 32a of the vessel body 32. Subsequently, the body 10 of the transportation cask 11 is pulled up from the cask loading pit 65 and transferred to the decontamination pit 62 by means of the overhead traveling crane. In the decontamination pit 62, a suitable quantity of cooling water is discharged from the vessel body 32 so that the surface of the cooling water 64 is situated slightly above the spent fuel assemblies 36. In this state, the primary lid 42 is set in the top opening 32a of the vessel body 32 of the canister 30, and the peripheral edge portion of the upper end of the primary lid 42 is welded to the inner surface of the vessel body 32, whereupon the top opening of the vessel body is closed. After the welding operation, the tester, e.g., an ultrasonic sensor 70, is inserted into the inspection space 16 through the top opening of the body 10 and located outside the welding portion of the primary lid 42. The sensor 70 is used to check the welding portion of the primary lid 42 for its welding state in a direction substantially perpendicular to the welding portion or the outer peripheral surface of the vessel body 32, from the outside of the vessel body 32. The tester is not limited to the ultrasonic sensor, and an electromagnet sensor or any other tester may be used for the purpose. Thereafter, complete dehydration of the interior of the vessel body 32, vacuum drying, inert gas replacement, sealing operation, welding portion inspection, and air leakage inspection are carried out. Then, the secondary lid 44 is set in the top opening 32a of the vessel body 32, and its outer peripheral edge portion is welded to the inner surface of the vessel body. Thereafter, the welding state of the secondary lid 44 is inspected by means of the ultrasonic sensor 70 in the same manner as aforesaid. Subsequently, inert gas replacement in the space between the primary and secondary lids 42 and 44, sealing operation, welding portion inspection, and air leakage inspection are carried out. Thus, seal-welding operation for the lids of the canister 30 is finished, whereupon the canister is completed contained the spent fuel. After the top opening of the body 10 of the transportation cask 11 is closed by the lid 20, the outer surface of the body 10 is washed. Further, the plug 54 is removed, and the air or pure water, having so far filled the aforesaid sealed space, is discharged. Finally, after the shock absorbers 22 and 24 are attached to the upper and lower ends of the body 10, respectively, a pre-transportation check is conducted, whereupon pre-shipment preparations are completed. Then, the transportation cask 11, thus containing the canister 30, is transported by truck or ship from a power plant to a containing facility. According to the transportation cask 11 constructed in this manner, the gap between the outer surface of the vessel body 32 of the canister 30 and the inner surface of the body 10 is sealed by means of the elastic tube 50 that is provided between those surfaces near the top opening of the body 10. By doing this, the fluid can be prevented from getting into the gap between the vessel body 32 and the inner surface of the body 10 through the top opening of the body 10. Thus, in immersing the body 10, containing the vessel body 32 of the canister 30, in the cooling water 64 to set the spent fuel assemblies 36 in position, the cooling water can be prevented from flowing into the gap between the vessel body 32 and the inner surface of the body 10 through the top opening of the body 10. In consequence, the outer surface of the vessel body 32 can be prevented from being contaminated with the cooling water. In immersing the body 10, containing the vessel body 32 of the canister 30, in the cooling water to set the radioactive substance in position, according to the transportation cask 11 with the aforementioned construction, moreover, a fluid such as air or pure water is injected in advance into the sealed space through the supply holes 52. By doing this, the contaminated cooling water can be prevented more securely from getting into the aforesaid space. Thus, there may be provided a transportation cask and a loading method such that loading operation can be easily performed without the necessity of pulling up the vessel body 32 from the body 10 and washing it after it is loaded with the spent fuel assemblies 36. The welding time can be shortened in a manner such that the welding portion is cooled with air supplied through the supply holes 52 as the primary and secondary lids are welded to the vessel body. Furthermore, the elastic tube 50 is fixed to the inner surface of the body 10 of the transportation cask 11. If the canister 30 falls as it is loaded into or pull up from the containing portion 17 of the body 10, therefore, its falling speed can be considerably lowered by the elastic tube 50. Thus, the canister 30 and the body 10 can be prevented from being damaged. According to the transportation cask 11 constructed in this manner, the annular inspection space 16 is defined between the upper end portion of the body 10 and the upper end portion of the vessel body 32 of the canister 30. Accordingly, the ultrasonic sensor 70 or some other tester can be inserted into the inspection space 16 to check the welding portions of the primary and secondary lids 42 and 44 of the canister 30 for the welding state in the direction perpendicular to the welding portions. Thus, the welding state of the primary and secondary lids 42 and 44 can be inspected securely, and the reliability of the welding can be improved. Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. For example, the ring-shaped seal member for preventing the penetration of the fluid is not limited to the elastic tube, and may alternatively be a solid member of an optional material that can be selected as required.
	claims	1. A reactor system, comprising:a first container defining a drywell therein;a second container defining a wetwell therein, the second container including an upper portion and a lower portion;a venting arrangement connecting the drywell to the wetwell, the venting arrangement including a proximal end extending into the drywell and a distal end extending into the upper portion of the wetwell;a suction structure extending into the lower portion of the wetwell; anda deflector disposed between the suction structure and the distal end of the venting arrangement within the second container, the deflector having a furrowed or concave side with perforations extending therethrough, the perforations being angled inward toward a furrow or concavity defined by the furrowed or concave side. 2. The reactor system of claim 1, wherein the second container is in a form of a torus. 3. The reactor system of claim 1, wherein the venting arrangement includes a vent pipe, a header connected to the vent pipe, and a downcomer connected to the header, the header and the downcomer being within the wetwell, the deflector being between the downcomer and the suction structure. 4. The reactor system of claim 1, wherein the deflector is secured to the second container such that the deflector does not directly contact the suction structure. 5. A method of reducing entrainment, comprising:discharging gases from a first container to a second container using a venting arrangement such that the gases are discharged into a liquid, the first container defining a drywell therein, the second container defining a wetwell therein, the second container including an upper portion and a lower portion, the venting arrangement connecting the drywell to the wetwell, the venting arrangement including a proximal end extending into the drywell and a distal end extending into the upper portion of the wetwell;alleviating an elevated level of the liquid resulting from condensing gases by performing an extraction of the liquid with a suction structure, the suction structure extending into the lower portion of the wetwell; andshielding the suction structure from the entrainment of uncondensed gases in the liquid with a deflector during the extraction of the liquid, the deflector disposed between the suction structure and the distal end of the venting arrangement within the second container, the deflector having a furrowed or concave side with perforations extending therethrough, the perforations being angled inward toward a furrow or concavity defined by the furrowed or concave side. 6. The method of claim 5, wherein the shielding includes redirecting the uncondensed gases away from the suction structure with the deflector. 7. The method of claim 5, wherein the shielding includes providing the perforations such that the perforations extend through the deflector at an angle toward the suction structure such that a Froude number (Fr) is less than 0.31 to allow a flow of the liquid through the perforations while hindering a passage of the uncondensed gases through the perforations, Fr = V L / g ⁡ ( ( ρ l - ρ G ) ρ l ) ⁢ D VL being a velocity of the liquid in the perforations, g being an acceleration due to gravity, ρt being a density of the liquid, ρG being a density of the gases, and D being a diameter of the perforations.
	abstract	A method of imaging an object by generating laser pulses with a short-pulse, high-power laser. When the laser pulse strikes a conductive target, bremsstrahlung radiation is generated such that hard ballistic high-energy electrons are formed to penetrate an object. A detector on the opposite side of the object detects these electrons. Since laser pulses are used to form the hard x-rays, multiple pulses can be used to image an object in motion, such as an exploding or compressing object, by using time gated detectors. Furthermore, the laser pulses can be directed down different tubes using mirrors and filters so that each laser pulse will image a different portion of the object.
	description	A first invention relates to a treatment method and a treatment apparatus of an iron-group metal ion-containing liquid and, more particularly, relates to a method and an apparatus in which from a liquid containing iron-group metal ions of iron (Fe), cobalt (Co), nickel (Ni), and/or the like, the ions mentioned above are removed. In particular, the first invention is preferably used for treatment of a waste liquid containing iron-group metal ions generated from a nuclear power plant or the like, such as a decontamination waste liquid generated in a nuclear power plant or an eluent eluting iron-group metal ions from an ion exchange resin used in a nuclear power plant. A second invention relates to a method and an apparatus for electrodepositing Co and Fe and, more particularly, relates to a method and an apparatus in which from a liquid containing Co ions and Fe ions, those ions are simultaneously removed by electrodeposition. In particular, the second invention is preferably used for treatment of a waste liquid containing Co ions and Fe ions generated from a nuclear power plant or the like, such as a decontamination waste liquid generated in a nuclear power plant or a waste liquid eluting radioactive substances adsorbed to an ion exchange resin used in a nuclear power plant. A third invention relates to a decontamination method and a decontamination apparatus in which from a waste ion exchange resin which is used in a nuclear power plant or the like and which adsorbs radioactive substances and also contains a clad primarily formed of iron oxide, the radioactive substances are efficiently removed. In a nuclear power plant, when radioactive substances are chemically removed from apparatuses and pipes of a primary cooling system contaminated by radioactive substances and from surfaces of metal members of the system including those mentioned above, a large amount of decontamination waste liquids is generated. Those decontamination waste liquids contain iron-group metal ions of Fe, Co, or Ni and also contain a large amount of radioactive substances, such as Co-60 (cobalt 60) and Ni-63 (nickel 63). In general, a decontamination waste liquid is reused after ion components dissolved therein are removed by an ion exchange resin as a decontaminated liquid. Hence, there has been a problem in that a waste ion exchange resin containing a large amount of radioactive substances is generated. In a nuclear power plant and the like, since an ion exchange resin used for cleanup of a cooling water system, such as a reactor water cleanup system (CUW) or a fuel pool cooling cleanup system (FPC), which is directly brought into contact with a fuel rod and contains radioactive substances adsorbs a large amount of radioactive substances, as a high-dose rate waste, the above ion exchange resin is stored in a resin tank provide in the power plant. Those wastes containing radioactive substances are stabilized by kneading with a solid-forming auxiliary agent, such as cement, and finally, burial disposal thereof is performed. The cost for the burial disposal is changed depending on the amount of contained radioactive substances and is increased as the concentration thereof is increased. Hence, it is economical that after the volume of a high-dose rate waste is reduced as much as possible, a solid waste for burial disposal is formed. In particular, if the radioactive substances can be isolated in a solid form from the ion exchange resin and can be sealed in a shielding container, it is preferable in terms of the reduction in volume. Since a waste ion exchange resin from which the radioactive substances are removed is a low-dose rate waste which can be disposed at a low cost, if the radioactive substances can be removed therefrom to a level at which the waste ion exchange resin can be incinerated, a significant reduction in volume can be achieved by an incineration treatment. As a treatment method of a high-dose rate waste resin as described above, as proposed in Patent Literature 1 and Patent Literature 2, a Fenton method and a method for decomposing a waste resin by wet oxidation, such as supercritical water oxidation, have been known. When the methods as described above are used, in both the cases, a large amount of a high-dose rate waste liquid is generated. When this high-dose rate waste liquid is finally disposed, after evaporative concentration thereof is further performed, the concentrated liquid thus obtained is required to be stabilized in a solid form, for example, by a method for kneading the liquid with cement. In this case, since a solid-forming auxiliary agent, such as cement, is newly added, the volume of a high-dose rate waste to be finally disposed is increased by an amount corresponding to that of the agent, and as a result, a problem in that the reduction in volume of the waste cannot be achieved may arise. Patent Literature 3 has disclosed a technique in which after sulfuric acid is allowed to pass through a waste resin to elute ionic radioactive substances therefrom, the radioactive substances are isolated from the eluent by diffusion dialysis, and the sulfuric acid is recycled. Patent Literature 4 has disclosed a waste resin treatment method in which a waste resin is immersed in an oxalic acid aqueous solution to dissolve a metal clad on the surface of the resin, and in addition, metal ions adsorbed to the resin are also eluted into the oxalic acid aqueous solution. In the cases described above, although a waste liquid containing radioactive substances is produced, the solidification treatment thereof has not been sufficiently described. As a method for removing radioactive substances from a waste liquid containing ionic radioactive substances, Patent Literature 5 has disclosed a technique for regenerating and reusing a decontamination solution in which while a decontamination solution dissolving radioactive cations is allowed to pass through an electrodeposition cell, voltage application is performed thereon to deposit the radioactive cations on a cathode as radioactive metal grains. In this case, it has been described that a cathode liquid is pored over the entire cathode so that the radioactive metal grains are removed from the cathode on which the radioactive metal grains are deposited. In Patent Literature 5, while the decontamination solution dissolving radioactive cations is directly charged to a cathode side of the electrodeposition cell, by applying the voltage thereon, the radioactive cations are deposited on the cathode as the radioactive metal grains. In this method, since the cathode liquid properties are changed depending on the decontamination solution, the cathode liquid cannot be adjusted to have liquid properties suitable for electrodeposition. When the decontamination solution is an acidic waste liquid, since a radioactive metal component precipitated on the cathode surface is again dissolved in the acidic waste liquid, precipitation may not occur, or the precipitation rate may be seriously decreased. When the waste liquid is neutral or alkaline, a hydroxide deposit is formed in the vicinity of the cathode surface, and the recovery of the radioactive metal by electrodeposition thereof on the cathode surface becomes difficult. Hence, in order to efficiently recover radioactive substances from a waste liquid by an electrodeposition method, direct charge of a waste liquid into a cathode chamber is not preferable, and it is important to adjust the cathode liquid to have liquid properties suitable for electrodeposition. In addition, in order to efficiently recover radioactive substances from a waste liquid by an electrodeposition method, it is significantly important to appropriately select the liquid properties of a liquid into which the cathode is immersed. In a nuclear power plant, since an ion exchange resin used for cleanup of a cooling water system, such as a reactor water cleanup system (CUW) or a fuel pool cooling cleanup system (FPC), which is directly brought into contact with a fuel rod and contains radioactive substances adsorbs a large amount of radioactive substances, as a high-dose rate radioactive waste, the above ion exchange resin is stored in a resin tank provide in the power plant. In a nuclear power plant, when radioactive substances are removed by chemical cleaning from apparatuses and pipes of a primary cooling system contaminated by radioactive substances and from surfaces of metal members of the system including those mentioned above, an ion exchange resin is also used, and the ion exchange resin thus used is also stored in a resin tank as a high-dose rate radioactive waste. Those wastes containing radioactive substances are stabilized by kneading with a solid-forming auxiliary agent, such as cement, and finally, burial disposal thereof is performed. The cost for the burial disposal is changed depending on the amount of contained radioactive substances and is increased as the concentration thereof is increased. Hence, it is economical that after the volume of a high-dose rate waste is reduced as much as possible, a solid waste for burial disposal is formed. In particular, if the radioactive substances can be isolated in a solid form from the ion exchange resin and can be sealed in a shielding container, it is preferable in terms of the reduction in volume. Since a waste ion exchange resin from which the radioactive substances are removed is a low-dose rate waste which can be disposed at a low cost, if the radioactive substances can be removed therefrom to a level at which the waste ion exchange resin can be incinerated, a significant reduction in volume can be achieved by an incineration treatment. When a waste resin can be treated by incineration disposal, although a significant reduction in volume of radioactive wastes can be achieved, in this case, the radioactive substances are concentrated in incinerated ash, and hence, the incinerated ash becomes a high-dose rate material. If the radioactive substances can be completely removed from the waste resin, the incinerated ash can be prevented from becoming a high-dose rate material, and the reduction in volume can be performed by incineration; hence, various techniques for removing radioactive substances from a waste resin have been investigated. A high-dose rate waste resin used in a reactor water cleanup system or a fuel pool cooling cleanup system adsorbs ions of radioactive substances and also contains a clad primarily formed of iron oxide. Since the clad also contains radioactive substances, in order to completely remove radioactive substances from the waste resin, the clad is also required to be simultaneously removed from the waste resin. As the chemical form of the clad contained in the waste resin, magnetite (Fe3O4) and hematite (α-Fe2O3) are primarily present. As a technique for removing radioactive substances from a waste resin, in Patent Literature 6, a technique has been disclosed in which after sulfuric acid is allowed to pass through an eluting device in which a waste resin is packed to elute ionic radioactive substances therefrom, from the eluent, the radioactive substances are isolated by diffusion dialysis, and the sulfuric acid is recycled. As described above, in the method in which a room-temperature sulfuric acid which is not heated is allowed to pass through a waste resin, since poor soluble hematite (α-Fe2O3) is difficult to be dissolved, and the clad cannot be remove from the waste resin, a problem in that radioactive substances remain may arise in some cases. Patent Literature 1: Japanese Patent Publication S61-9599B Patent Literature 2: Japanese Patent 3657747B Patent Literature 3: Japanese Patent Publication 2004-28697A Patent Literature 4: Japanese Patent Publication 2013-44588A Patent Literature 5: Japanese Patent 4438988B Patent Literature 6: Japanese Patent Publication 2004-28697A A first invention aims to provide a treatment method and a treatment apparatus of an iron-group metal ion-containing liquid, in each of which in an electrodeposition treatment of an iron-group metal ion-containing liquid, iron-group metal ions are efficiently removed by precipitation without being influenced by the liquid properties of the iron-group metal ion-containing liquid. A second invention aims to provide an electrodeposition method and an apparatus therefor, in each of which in an electrodeposition treatment of a liquid containing Co ions and Fe ions, Co and Fe are efficiently removed from the liquid while the liquid properties thereof are set suitable for electrodeposition of Co and Fe. A third invention aims to provide a decontamination method and a decontamination apparatus, in each of which an ionic radioactive substance in a waste ion exchange resin is not only removed, but a clad is also removed by dissolution thereof, so that the radiation dose of the waste ion exchange resin is decreased to an ultra-low level. [First Invention] The present inventors found that in an electrodeposition bath in which an anode chamber provided with an anode and a cathode chamber provided with a cathode are separated from each other by a cation exchange membrane, when an iron-group metal ion-containing liquid is charged into the anode chamber, a cathode liquid is charged into the cathode chamber, and voltage application is performed between the anode and the cathode so as to precipitate an iron-group metal on the cathode by moving iron-group metal ions in the liquid in the anode chamber into the cathode liquid in the cathode chamber, without being influenced by the liquid properties of the iron-group metal ion-containing liquid, an iron-group metal can be removed by electrodeposition under appropriate electrodeposition conditions, and as a result, the first invention was completed. That is, the first invention is as described below. [1] A treatment method of an iron-group metal ion-containing liquid characterized in that an anode chamber provided with an anode and a cathode chamber provided with a cathode are separated from each other by a cation exchange membrane, an iron-group metal ion-containing liquid is charged into the anode chamber, a cathode liquid is charged into the cathode chamber, and a voltage is applied between the anode and the cathode, so that iron-group metal ions in the liquid in the anode chamber are moved into the liquid in the cathode chamber through the cation exchange membrane, and an iron-group metal is precipitated on the cathode. [2] The treatment method of an iron-group metal ion-containing liquid according to [1], wherein the iron-group metal is at least one selected from iron, cobalt, and nickel. [3] The treatment method of an iron-group metal ion-containing liquid according to [1] or [2], wherein the iron-group metal ion-containing liquid is an acidic waste liquid having a pH of less than 2. [4] The treatment method of an iron-group metal ion-containing liquid according to any one of [1] to [3], wherein the cathode liquid contains at least one additive selected from a dicarboxylic acid and a salt thereof and a tricarboxylic acid and a salt thereof. [5] A treatment apparatus of an iron-group metal ion-containing liquid, comprising: an electrodeposition bath which includes an anode chamber provided with an anode, a cathode chamber provided with a cathode, and a cation exchange membrane separating the anode chamber from the cathode chamber; a voltage applicater for applying a voltage between the anode and the cathode; a liquid passer for allowing an iron-group metal ion-containing liquid to pass through the anode chamber; and a liquid passer for allowing a cathode liquid to pass through the cathode chamber, wherein by applying the voltage between the anode and the cathode, iron-group metal ions in the liquid in the anode chamber are moved into the liquid in the cathode chamber through the cation exchange membrane, and an iron-group metal is precipitated on the cathode. [6] The treatment apparatus of an iron-group metal ion-containing liquid according to [5], wherein the iron-group metal is at least one selected from iron, cobalt, and nickel. [7] The treatment apparatus of an iron-group metal ion-containing liquid according to [5] or [6], wherein the iron-group metal ion-containing liquid is an acidic waste liquid having a pH of less than 2. [8] The treatment apparatus of an iron-group metal ion-containing liquid according to any one of [5] to [7], wherein the cathode liquid contains at least one additive selected from a dicarboxylic acid and a salt thereof and a tricarboxylic acid and a salt thereof. <Advantage of First Invention> According to the first invention, since the anode chamber into which the iron-group metal ion-containing liquid is charged and the cathode chamber in which the iron-group metal is precipitated are separated by the cation exchanged membrane, without being influenced by the liquid properties of the iron-group metal ion-containing liquid, the electrodeposition of the iron-group metal can be efficiently performed. In particular, when the iron-group metal ion-containing liquid is an acidic waste liquid, in a related method, the iron-group metal electrodeposited on the cathode may be dissolved, or the electrodeposition rate of the iron-group metal may be seriously decreased in some cases; however, according to the present invention, even if an acidic waste liquid is charged into the anode chamber, the cathode chamber can be placed under conditions suitable for electrodeposition. [Second Invention] The present inventors found that when at least one type of additive selected from a dicarboxylic acid and a salt thereof and a tricarboxylic acid and a salt thereof, each of which has a specific structure, is allowed to be present in an electrodeposition liquid system, the problem described above can be resolved, and as a result, the second invention was completed. That is, the second invention is as described below. [1] A method for electrodepositing Co and Fe characterized in that an anode and a cathode are immersed in a liquid containing Co ions and Fe ions and at least one additive selected from a dicarboxylic acid and a salt thereof and a tricarboxylic acid and a salt thereof, each of which is represented by the following formula (1), and by applying a voltage between the anode and the cathode, Co and Fe are precipitated on the cathode.M1OOC—(CHX1)a—(NH)b—(CX2X4)c—CX3X5—COOM2 (1) In the formula (1), X1, X2, and X3 each independently represent H or OH, X4 and X5 each independently represent H, OH, or COOM3, M1, M2, and M3 each independently represent H, a monovalent alkali metal, or an ammonium ion, and a, b, and c each independently represent an integer of 0 or 1. However, in the formula (1), X4 and X5 do not simultaneously represent COOM3. [2] A method for electrodepositing Co and Fe characterized in that an anode chamber provided with an anode is separated from a cathode chamber provided with a cathode by a cation exchange membrane, a liquid containing Co ions and Fe ions is charged into the anode chamber, a liquid containing at least one additive selected from a dicarboxylic acid and a salt thereof and a tricarboxylic acid and a salt thereof, each of which is represented by the following formula (1), is charged into the cathode chamber, and a voltage is applied between the anode and the cathode, so that Co ions and Fe ions in the liquid in the anode chamber are moved into the liquid in the cathode chamber through the cation exchange membrane, and Co and Fe are precipitated on the cathode.M1OOC—(CHX1)a—(NH)b—(CX2X4)c—CX3X5—COOM2 (1) In the formula (1), X1, X2, and X3 each independently represent H or OH, X4 and X5 each independently represent H, OH, or COOM3, M1, M2, and M3 each independently represent H, a monovalent alkali metal, or an ammonium ion, and a, b, and c each independently represent an integer of 0 or 1. However, in the formula (1), X4 and X5 do not simultaneously represent COOM3. [3] The method for electrodepositing Co and Fe according to [1] or [2], wherein the dicarboxylic acid is at least one selected from malonic acid, succinic acid, malic acid, tartaric acid, and iminodiacetic acid. [4] The method for electrodepositing Co and Fe according to any one of [1] to [3], wherein the tricarboxylic acid is citric acid. [5] The method for electrodepositing Co and Fe according to any one of [1] to [4], wherein the liquid containing an additive contains an ammonium salt. [6] The method for electrodepositing Co and Fe according to [5], wherein the ammonium salt is at least one selected from ammonium chloride, ammonium sulfate, and ammonium oxalate. [7] The method for electrodepositing Co and Fe according to [5], wherein the tricarboxylic acid is ammonium citrate. [8] An apparatus for electrodepositing Co and Fe, comprising: an electrodeposition bath holding a liquid which contains Co ions and Fe ions and at least one additive selected from a dicarboxylic acid and a salt thereof and a tricarboxylic acid and a salt thereof, each of which is represented by the following formula (1); an anode and a cathode provided in the liquid in the electrodeposition bath; and a voltage applicater for applying a voltage between the anode and the cathode, wherein by applying the voltage between the anode and the cathode, Co and Fe are precipitated on the cathode.M1OOC—(CHX1)a—(NH)b—(CX2X4)c—CX3X5—COOM2 (1) In the formula (1), X1, X2, and X3 each independently represent H or OH, X4 and X5 each independently represent H, OH, or COOM3, M1, M2, and M3 each independently represent H, a monovalent alkali metal, or an ammonium ion, and a, b, and c each independently represent an integer of 0 or 1. However, in the formula (1), X4 and X5 do not simultaneously represent COOM3. [9] An apparatus for electrodepositing Co and Fe, comprising: an electrodeposition bath which includes an anode chamber provided with an anode, a cathode chamber provided with a cathode, and a cation exchange membrane separating the anode chamber from the cathode chamber; a voltage applicater for applying a voltage between the anode and the cathode; a liquid passer for allowing a liquid containing Co ions and Fe ions to pass through the anode chamber; and a liquid passer for allowing a liquid containing at least one additive selected from a dicarboxylic acid and a salt thereof and a tricarboxylic acid and a salt thereof, each of which is represented by the following formula (1), wherein by applying a voltage between the anode and the cathode, Co ions and Fe ions in the liquid in the anode chamber are moved into the liquid in the cathode chamber through the cation exchange membrane, and Co and Fe are precipitated on the cathode.M1OOC—(CHX1)a—(NH)b—(CX2X4)c—CX3X5—COOM2 (1) In the formula (1), X1, X2, and X3 each independently represent H or OH, X4 and X5 each independently represent H, OH, or COOM3, M1, M2, and M3 each independently represent H, a monovalent alkali metal, or an ammonium ion, and a, b, and c each independently represent an integer of 0 or 1. However, in the formula (1), X4 and X5 do not simultaneously represent COOM3. [10] The apparatus for electrodepositing Co and Fe according to [8] or [9], wherein the dicarboxylic acid is at least one selected from malonic acid, succinic acid, malic acid, tartaric acid, and iminodiacetic acid. [11] The apparatus for electrodepositing Co and Fe according to any one of [8] to [10], wherein the tricarboxylic acid is citric acid. [12] The apparatus for electrodepositing Co and Fe according to any one of [8] to [11], wherein the liquid containing an additive contains an ammonium salt. [13] The apparatus for electrodepositing Co and Fe according to [12], wherein the ammonium salt is at least one selected from ammonium chloride, ammonium sulfate, and ammonium oxalate. [14] The apparatus for electrodepositing Co and Fe according to [12], wherein the tricarboxylic acid is ammonium citrate. <Advantage of Second Invention> According to the second invention, when Co and Fe are electrodeposited on the cathode by voltage application on the waste liquid containing Co ions and Fe ions, at least one type of additive selected from a dicarboxylic acid and a salt thereof and a tricarboxylic acid and a salt thereof, each of which has a specific structure, is allowed to be present in the liquid. Hence, the liquid properties can be made suitable for electrodeposition, and without causing a problem in that, for example, the voltage application treatment cannot be continued due to the generation of a suspended material having poor precipitation properties or due to the precipitation of a non-electrical conductive precipitate, Co and Fe can be simultaneously and efficiently removed by electrodeposition. [Third Invention] The present inventors found that by the use of an acid heated to a predetermined temperature, an ionic radioactive substance in a waste ion exchange resin can be not only removed by elution, but a clad can also be removed by dissolution, and that an acidic waste liquid obtained by this decontamination treatment can be recycled by an electrodeposition treatment, and as a result, the third invention was completed. That is, the third invention is as described below. [1] A decontamination method of a radioactive waste ion exchange resin, comprising a decontamination step in which an acid heated to 60° C. or more is brought into contact with a waste ion exchange resin which adsorbs a radioactive substance and simultaneously contains a clad primarily formed of iron oxide, so that an ionic radioactive substance in the waste ion exchange resin is removed by elution, and the clad is also removed by dissolution. [2] The decontamination method of a radioactive waste ion exchange resin according to [1], wherein the acid is sulfuric acid and/or oxalic acid. [3] The decontamination method of a radioactive waste ion exchange resin according to [1] or [2], wherein the acid is a sulfuric acid solution having a concentration of 5 to 40 percent by weight and/or an oxalic acid solution having a concentration of 0.1 to 40 percent by weight. [4] The decontamination method of a radioactive waste ion exchange resin according to any one of [1] to [3], wherein the radioactive substance contains cobalt-60. [5] The decontamination method of a radioactive waste ion exchange resin according to any one of [1] to [4], wherein the method comprises: an electrodeposition step in which an acidic waste liquid containing an ionic radioactive substance discharged from the decontamination step is charged into an electrodeposition bath including an anode and a cathode, and by applying the voltage between the anode and the cathode, the ionic radioactive substance in the acidic waste liquid is electrodeposited on the cathode, so that the ionic radioactive substance is removed from the acidic waste liquid; and a circulation step in which a treated liquid obtained by removing the ionic radioactive substance in the electrodeposition step is circulated to the decontamination step and is reused. [6] The decontamination method of a radioactive waste ion exchange resin according to [5], wherein in the electrodeposition bath, an anode chamber provided with an anode and a cathode chamber provided with a cathode are separated from each other by a cation exchange membrane, the acidic waste liquid is charged into the anode chamber, and by applying the voltage between the anode and the cathode, the ionic radioactive substance in the acidic waste liquid is moved into the cathode chamber through the cation exchange membrane and is electrodeposited on the cathode. [7] The decontamination method of a radioactive waste ion exchange resin according to [5] or [6], wherein on the cathode, cobalt-60 and iron which is a dissolved material of the clad are electrodeposited. [8] A decontamination apparatus of a radioactive waste ion exchange resin, comprising a decontaminater in which an acid heated to 60° C. or more is brought into contact with a waste ion exchange resin which adsorbs a radioactive substance and simultaneously contains a clad primarily formed of iron oxide, so that an ionic radioactive substance in the waste ion exchange resin is removed by elution, and the clad is also removed by dissolution, wherein the decontaminater includes a packed tower in which the waste ion exchange resin is packed, a charging pipe charging the heated acid into the packed tower, a heater provided for the charging pipe, and a discharging pipe discharging an acidic waste liquid containing an ionic radioactive substance from the packed tower. [9] The decontamination apparatus of a radioactive waste ion exchange resin according to [8], wherein the apparatus comprises an electrodeposition bath including an anode and a cathode, a voltage applier for applying a voltage between the anode and the cathode, a charger for charging the acidic waste liquid into the electrodeposition bath, and a circulater for circulating a treated liquid in the electrodeposition bath to an upstream side of the heating means, and by applying the voltage between the anode and the cathode, the ionic radioactive substance in the acidic waste liquid is electrodeposited on the cathode, so that the ionic radioactive substance is removed from the acidic waste liquid, and a treated liquid obtained by the removal of the ionic radioactive substance is reused in the decontamination means. [10] The decontamination apparatus of a radioactive waste ion exchange resin according to [9], wherein the electrodeposition bath includes an anode chamber provided with an anode, a cathode chamber provided with a cathode, and a cation exchange membrane separating the anode chamber from the cathode chamber, the acidic waste liquid is charged into the anode chamber, and by applying the voltage between the anode and the cathode, the ionic radioactive substance in the acidic waste liquid is moved into the cathode chamber through the cation exchange membrane and is electrodeposited on the cathode. [11] The decontamination apparatus of a radioactive waste ion exchange resin according to [9] or [10], wherein on the cathode, cobalt-60 and iron which is a dissolved material of the clad are electrodeposited. <Advantage of Third Invention> According to the third invention, since the acid heated to 60° C. or more is brought into contact with the waste ion exchange resin, radioactive metal ions adsorbed to a cationic exchange resin of the waste ion exchange resin can be removed by elution by ion exchange with H+ ions, and the clad containing hematite mixed in the waste ion exchange resin can be also efficiently removed by dissolution thereof. In addition, when an acidic waste liquid containing radioactive metal ions discharged by this decontamination treatment and iron ions which are dissolved materials of the clad is charged into the electrodeposition bath in which the anode and the cathode are provided, and when the voltage application is performed between the anode and the cathode, the radioactive metal ions and the iron ions can be simultaneously removed by electrodeposition thereof on the cathode, and the electrodeposition treated liquid can be reused for the decontamination treatment of the waste ion exchange resin. In addition, when electrodeposition is performed after the electrode used for the electrodeposition is changed or the electrodeposition layer on the electrode is removed, the decontamination of the waste ion exchange resin and the removal of radioactive substances from the acidic waste liquid can be continuously performed, and a large amount of waste ion exchange resins can be treated. According to the third invention, a waste ion exchange resin, the radioactive dose of which is decreased to an ultra-low level, can be obtained, and an incineration treatment of the treated waste ion exchange resin can be performed. In addition, when the waste ion exchange resin is incinerated to form incinerated ash, the volume can be reduced to 1/100 to 1/200. [Embodiment of First Invention] Hereinafter, with reference to the drawings, an embodiment of the first invention will be described in detail. FIG. 1 is a systematic diagram showing one example of an embodiment of a treatment apparatus of an iron-group metal ion-containing liquid according to the first invention. In an electrodeposition apparatus shown in FIG. 1, an anode chamber 2A provided with an anode 2 and a cathode chamber 3A provided with a cathode 3, each of which is placed in an electrodeposition bath 1, are separated from each other by a cation exchange membrane 5, an iron-group metal ion-containing liquid is allowed to pass through the anode chamber 2A, a cathode liquid is allowed to pass through the cathode chamber 3A, and voltage application is performed between the anode 2 and the cathode 3, so that iron-group metal ions in the liquid in the anode chamber 2A are moved into the liquid in the cathode chamber 3A through the cation exchange membrane 5, and an iron-group metal is precipitated on the cathode 3. In FIG. 1, reference numeral 10 indicates an iron-group metal ion-containing liquid bath, and a circulation system is formed so that the iron-group metal ion-containing liquid is charged into the anode chamber 2A by a pump P1 through a pipe 11, and a discharged liquid is returned to the iron-group metal ion-containing liquid bath 10 through a pipe 12. Reference numeral 20 indicates a cathode liquid storage bath, and a circulation system is formed so that the cathode liquid is charged into the cathode chamber 3A by a pump P2 through a pipe 21, and a discharged liquid is returned to the cathode liquid storage bath 20 through a pipe 22. If a waste liquid is directly charged into a bath in which the cathode is immersed without providing the cation exchange membrane, in the case in which the pH of the waste liquid is less than 2, and in particular, in the case in which the waste liquid is a strong-acid liquid having a pH of less than 1, unless otherwise the pH is appropriately adjusted using an alkali, a problem, such as re-dissolution of an iron-group metal electrodeposited on the cathode or no occurrence of the electrodeposition, may arise in some cases. On the other hand, in the apparatus in which the cation exchange membrane is provided as shown in FIG. 1, as long as the cathode liquid at the cathode side is placed under conditions suitable for electrodeposition, even if the waste liquid is a strong-acid liquid having the pH as described above, the iron-group metal can be preferably removed by electrodeposition. In the case in which a strong-acid waste liquid is reused after iron-group metal ions are removed therefrom, when a pH adjustment of the waste liquid is performed using an alkali, the waste liquid is difficult to be reused as a strong-acid liquid; however, in the apparatus shown in FIG. 1, without decreasing the acidity of the waste liquid, iron-group metal ions can be removed from the waste liquid through the cation exchange membrane, and a treated liquid thus obtained can be reused. In the first invention, as shown in FIG. 1, since the iron-group metal ions are moved into the cathode liquid through the cation exchange membrane, even if the concentration of the iron-group metal ions is low, such as 0.1 to 10,000 mg/L, and in particular, such as approximately 1 to 1,000 mg/L, the waste liquid can be efficiently treated. The pH of the cathode liquid used in the first invention is preferably set to 1 to 9, and more preferably set to 2 to 8. When the pH of the cathode liquid is excessively low, re-dissolution of an iron-group metal electrodeposited on the cathode may occur, and the electrodeposition rate may be decreased in some cases. When the pH of the cathode liquid is excessively high, a hydroxide of the iron-group metal is liable to be generated in the liquid as a suspended material. Hence, in the case in which the pH of the cathode liquid is out of the range described above, by using an alkali or an acid, an appropriate pH adjustment is preferably performed. In the first invention, a complexing agent (hereinafter, referred to as an additive in some cases) suitable for electrodeposition of iron-group metal ions is preferably added to the cathode liquid. As the additive, a compound selected from a dicarboxylic acid having 2 carboxylic groups in its molecule and a salt thereof (hereinafter, referred to as “dicarboxylic acid (salt)” in some cases) and a tricarboxylic acid having 3 carboxylic groups in its molecule and a salt thereof (hereinafter, referred to as “tricarboxylic acid (salt)” in some cases) is preferable. Those compounds may be used alone, or at least two types thereof may be used by mixing. The dicarboxylic acid (salt) and the tricarboxylic acid (salt) each suppress the generation of a suspended material during electrodeposition by its chelating effect, and as a result, an excellent effect of improving an electrodeposition effect can be obtained. On the other hand, since a monocarboxylic acid having 1 carboxylic group in its molecule has a weak bonding force to iron-group metal ions, problems in that a suspended material formed from a hydroxide of the iron-group metal is generated in the liquid and/or electrodeposition is not uniformly performed on the cathode may occur. When a carboxylic acid having at least 4 carboxylic groups in its molecule is used, since a bonding force to iron-group metal ions is excessively high, the iron-group metal is held in the liquid, and as a result, a problem in that the electrodeposition rate is seriously decreased may occur. As the dicarboxylic acid (salt) and the tricarboxylic acid (salt), a compound represented by the following formula (1) is particularly preferable since a suspended material is not likely to be generated, and electrodeposition is rapidly advanced. In the dicarboxylic acid (salt) and the tricarboxylic acid (salt) each represented by the following formula (1), 1 to 3 carbon atoms are present between the intramolecular carboxylic groups, and because of the shape thereof, it is estimated that an appropriate bonding force to the iron-group metal ions can be obtained.M1OOC—(CHX1)a—(NH)b—(CX2X4)c—CX3X5—COOM2 (1) In the formula (1), X1, X2, and X3 each independently represent H or OH, X4 and X5 each independently represent H, OH, or COOM3, M1, M2, and M3 each independently represent H, a monovalent alkali metal, or an ammonium ion, and a, b, and c each independently represent an integer of 0 or 1. However, in the formula (1), X4 and X5 do not simultaneously represent COOM3. As a dicarboxylic acid preferable for the first invention, although oxalic acid (ethane dicarboxylic acid, HOOC—COOH), malonic acid (propane dicarboxylic acid, HOOC—CH2—COOH), succinic acid (butane dicarboxylic acid, HOOC—CH2—CH2—COOH), glutaric acid (pentane dicarboxylic acid, HOOC—CH2—CH2—CH2—COOH), malic acid (2-hydroxybutane dicarboxylic acid, HOOC—CH2—CH(OH)—COOH), tartaric acid (2,3-dihydroxybutane dicarboxylic acid, HOOC—CH(OH)—CH(OH)—COOH), iminodiacetic acid (HOOC—CH2—NH—CH2—COOH), and the like may be mentioned, malonic acid, succinic acid, malic acid, tartaric acid, and iminodiacetic acid are particularly preferable. As the tricarboxylic acid, although citric acid (HOOC—CH2—COH(COOH)—CH2—COOH), 1,2,3-propane tricarboxylic acid, and the like may be mentioned, citric acid is particularly preferable. In addition, as the salts of those dicarboxylic acid and tricarboxylic acid, alkali meal salts, such as a sodium salt and a potassium salt, and ammonium salts may be mentioned. In the first invention, in the case in which the iron-group metal ion-containing liquid contains at least two types of iron-group metal ions, an ammonium salt is preferably present together with the dicarboxylic acid (salt) and/or the tricarboxylic acid (salt). For example, in the case in which an iron-group metal ion-containing liquid containing Co and Fe is treated by the present invention, when an ammonium salt is not added, the electrodeposition rate of Co is generally faster than that of Fe, and an electrodeposition layer of Fe is formed on an electrodeposition layer of Co; however, by the addition of an ammonium salt, the electrodeposition rates of Co and Fe become approximately equivalent to each other, and Co and Fe are electrodeposited so as to form an alloy. When the electrodeposition rates of Co and Fe are different from each other, and a Co layer and an Fe layer are separately electrodeposited, because of the difference in physical properties of Co and Fe, floating and/or peeling of an electrodeposition material is liable to occur, and a successive electrodeposition treatment may not be performed in some cases. As the ammonium salt, any salt generating ammonium ions may be used, and for example, ammonium chloride, ammonium sulfate, ammonium oxalate, and ammonium citrate are preferable. Those ammonium salts may be used alone, or at least two types thereof may be used by mixing. In particular, when an ammonium dicarboxylate, such as ammonium oxalate, or an ammonium tricarboxylate, such as ammonium citrate, is used, since the above compound may function as both the ammonium salt and the additive, an effect of suppressing the generation of a suspended material obtained by the chelating effect of the dicarboxylic acid or the tricarboxylic acid and an effect of adjusting the electrodeposition rates of Co and Fe can be simultaneously obtained by one chemical agent. Although the concentration of the additive in the cathode liquid is not particularly limited, with respect to the total molar concentration of iron-group metal ions in the iron-group metal ion-containing liquid charged into the anode chamber, the molar concentration of the additive in the cathode liquid charged into the cathode chamber is preferably 0.1 to 50 times, and particularly preferably 0.5 to 10 times, and as the cathode liquid, for example, an aqueous solution containing 0.01 to 20 percent by weight of the additive and preferably 0.1 to 5 percent by weight thereof and having a pH of 1 to 9 and preferably a pH of 2 to 8 is used. When the amount of the additive is excessively small, the effect of suppressing the generation of a suspended material obtained by addition of the additive cannot be sufficiently obtained, and when the amount of the additive is excessively large, the chelating effect is excessively enhanced, the electrodeposition rate is decreased. Although the additive described above is decomposed by oxidation when being brought into contact with the anode of the electrodeposition bath, in the electrodeposition bath described above, since the anode chamber is separated from the cathode chamber by the cation exchange membrane, the electrodeposition liquid in which the additive is contained is not directly brought into contact with the anode, and hence, the additive is not wastefully consumed by oxidation. Accordingly, the amount of the additive to be replenished into the cathode liquid may be small, and the amount of the chemical agent to be consumed can be decreased. In the case in which the ammonium salt is used, the ammonium salt is preferably used in an amount so that the concentration thereof in the cathode liquid is 0.01 to 20 percent by weight and preferably 0.1 to 5 percent by weight. When the concentration of the ammonium salt is excessively low, the effect described above by the use of the ammonium salt may not be sufficiently obtained, and when the concentration is excessively high, the effect cannot be improved, and the amount of the chemical agent to be consumed is increased. Although the electrodeposition conditions (such as the current, the current density, and the temperature) are not particularly limited, the current density is preferably set to 5 to 600 mA/cm2 with respect to the cathode area in terms of the electrodeposition efficiency. Although the iron-group metal ion-containing liquid is generally a liquid containing ions of at least one type of iron, manganese, cobalt, and nickel, and in particular, ions of at least one type of iron, cobalt, and nickel, even if a metal other than the iron-group metals is contained, no problems may arise. The first invention is preferable for treatment of a radioactive iron-group metal ion-containing waste liquid generated from a nuclear power plant or the like, such as a decontamination waste liquid generated in a nuclear power plant or an eluent eluting iron-group metal ions from an ion exchange resin used in a nuclear power plant, and in particular, is preferable for treatment of an acidic waste liquid having a pH of less than 2, and by efficiently removing the iron-group metal ions from those waste liquids, a treated liquid obtained thereby can be reused. Hereinafter, an example in which the first invention is applied to a decontamination step of a waste ion exchange resin used in a nuclear power plant will be described with reference to FIG. 2. In FIG. 2, a member having the same function as that of the member shown in FIG. 1 is designated by the same reference numeral as described above. An apparatus shown in FIG. 2 includes an eluent storage bath 30 storing an eluent eluting iron-group metal ions from a waste ion exchange resin, an eluting bath 8 which is a packed tower in which a waste ion exchange resin 40 is packed, an iron-group metal ion-containing liquid storage bath 10 which is an acidic waste liquid storage bath storing an acidic waste liquid discharged from the eluting bath 8, an electrodeposition bath 1 into which an acidic waste liquid from the iron-group metal ion-containing liquid storage bath (acidic waste liquid storage bath) 10 is charged, and a cathode liquid storage bath 20 storing a cathode liquid to be supplied to the electrodeposition bath 1. The electrodeposition bath 1 has the structure in which an anode chamber 2A including an anode 2 and a cathode chamber 3A including a cathode 3 are separated from each other by a cation exchange membrane 5, the acidic waste liquid from the iron-group metal ion-containing liquid storage bath (acidic waste liquid storage bath) 10 is allowed to pass through the anode chamber 2A, and the cathode liquid is allowed to pass through the cathode chamber 3A. Reference numerals 9A and 9B each indicate a heat exchanger. The eluent in the eluent storage bath 30 is heated by the heat exchanger 9A to 60° C. or more, preferably 70° C. to 120° C., and more preferably 80° C. to 100° C. while being transported to the eluting bath 8 by a pump P3 through a pipe 31 and is then allowed to pass through the eluting bath 8 in an upward flow. An outflow liquid (acidic waste liquid) is subsequently cooled by the heat exchanger 9B to a temperature of less than 60° C., such as 10° C. to less than 60° C., at which the cation exchange membrane 5 in the electrodeposition bath 4 is not so much degraded and is further transported to the iron-group metal ion-containing liquid storage bath (acidic waste liquid storage bath) 10 through a pipe 32. The acidic waste liquid in the iron-group metal ion-containing liquid storage bath (acidic waste liquid storage bath) 10 is charged into the anode chamber 2A of the electrodeposition bath 1 by a pump P1 through a pipe 11, and an electrodeposition treated liquid is circulated to the eluent storage bath 30 through a pipe 34 and is reused as the eluent. Into the cathode chamber 3A of the electrodeposition bath 1, the cathode liquid in the cathode liquid storage bath 20 is charged by a pump P2 through a pipe 21 and is then returned to the cathode liquid storage bath 20 through a pipe 22. An acid is appropriately replenished into the eluent storage bath 30 by a pipe 33, and into the cathode liquid storage bath 20, the cathode liquid is replenished by a pipe 23. In this apparatus, since the heated eluent is allowed to pass through the eluting bath 8 in which the waste ion exchange resin 40 is packed, ionic radioactive nuclear species adsorbed to the waste ion exchange resin 40 are removed by elution, and in addition, a clad mixed in the waste ion exchange resin 40 or incorporated in resin particles is also removed by dissolution. After being brought into contact with the waste ion exchange resin 40, the eluent (acidic waste liquid) containing ionic radioactive nuclear species and a dissolved material of the clad is charged into the anode chamber 2A of the electrodeposition bath 1 through the iron-group metal ion-containing liquid storage bath (acidic waste liquid storage bath) 10. When the voltage is applied between the anode 2 and the cathode 3 of the electrodeposition bath 1, iron-group metal ions, such as radioactive metal ions in the acidic waste liquid and iron ions derived from the clad, are moved into the cathode chamber 3A through the cation exchange membrane 5 and are electrodeposited on the cathode 3. A treated liquid of the acid waste liquid from which the iron-group metal ions are removed in the electrodeposition bath 1 is returned to the eluent storage bath 30 and is recycled. The cathode liquid in the cathode chamber 3A is circulated through the cathode liquid storage bath 20 by the pump P2 and is recycled while the cathode liquid in an amount corresponding to the decrease thereof is added to the cathode liquid storage bath 20. In the apparatus shown in FIG. 2, as the eluent used for decontamination of the waste ion exchange resin, an acidic eluent heated to 60° C. or more is preferably used. By the use of the heated acidic eluent, radioactive metal ions adsorbed to a cationic exchange resin of the waste ion exchange resin can be removed by elution through ion exchange with H+ ions, and in addition, the clad mixed in the waste ion exchange resin can be also efficiently removed by dissolution. As the acidic eluent, an inorganic acid, such as sulfuric acid, hydrochloric acid, or nitric acid, or an organic acid, such as formic acid, acetic acid, or oxalic acid, may be used. Those acids may be used alone, or at least two types thereof may be used by mixing. Sulfuric acid and/or oxalic acid, each of which is not likely to be volatilized during heating and is not categorized as a hazardous material, is preferably used. As for the acid concentration in the eluent, a preferable concentration is present in accordance with an acid to be used. The sulfuric acid concentration is preferably 5 to 40 percent by weight and more preferably 10 to 30 percent by weight. The oxalic acid concentration is preferably 0.1 to 40 percent by weight and more preferably 1 to 20 percent by weight. When the acid concentration is lower than the range described above, the dissolution efficiency of hematite (α-Fe2O3) which is a primary component of the clad is decreased. The clad is present so as to be mixed in the waste ion exchange resin or incorporated in the resin, and the primary component of the clad is poor soluble hematite, so that dissolution thereof is difficult by a low concentration acid. When the acid concentration in the eluent is high, the amount of hydrogen generated in the electrodeposition bath provided at a latter stage becomes excessive, and the electrodeposition efficiency is decreased. In the apparatus shown in FIG. 2, when a substance, such as Cobalt-60 or Nickel-63, which is contained in the radioactive waste ion exchange resin and which forms metal cations by dissolution is electrodeposited on the cathode, the radioactive substance can be highly concentrated. In addition, a waste ion exchange resin in which the radioactive dose is decreased to an ultra-low level can be obtained, and the waste ion exchange resin thus treated can be processed by an incineration treatment. When the waste ion exchange resin is formed into incinerated ash by incineration, the volume of the waste can be reduced to 1/100 to 1/200. FIGS. 1 and 2 each show one example of a treatment apparatus preferable for the embodiment of the first invention, and the treatment apparatus of the first invention is not limited at all to those shown in the drawings. In the apparatuses shown in FIGS. 1 and 2, although the electrodeposition bath 1 is a closed system, since a hydrogen gas is generated from the cathode, an open system in which an upper portion is opened is preferable. When a cathode on which a metal is electrodeposited is changed, the change thereof can be easily performed if the upper portion of the electrodeposition bath is opened. In FIG. 2, although being allowed to pass through the eluting bath 8 in an upward flow, the eluent may pass therethrough in a downward flow. When the waste ion exchange resin is a powder, the differential pressure is liable to increase when the liquid is allowed to pass therethrough, and hence the upward flow is preferable. In the electrodeposition bath 1, the acidic waste liquid and the cathode liquid may be allowed to pass in opposite directions with the cation exchange membrane 5 provided therebetween. Heat exchange can also be performed between the eluent charged into the eluting bath 8 and the acid waste liquid discharged therefrom. Hereinafter, with reference to examples, the first invention will be described in more detail. (1) Electrodeposition of Waste Sulfuric Acid Liquid Containing Iron-Group Metals (Fe, Co) 1) Test Conditions A simulated acidic waste liquid having properties shown in Table 1 was prepared by dissolving CoCl2, FeCl3, and sulfuric acid in water. A simulated electrodeposition liquid (cathode liquid) having properties shown in Table 1 was prepared by dissolving citric acid in water. By the use of the apparatus shown in FIG. 1, an electrodeposition test of Co and Fe was performed. The electrodeposition conditions are as shown in Table 1. A Pt-plated Ti plate was used as the anode, and a Cu plate was used as the cathode. Co and Fe in the simulated acidic waste liquid after a 6-hour voltage application were measured by an atomic absorption photometer. After 400 mL of a simulated acidic waste liquid having properties shown in Table 2 was prepared and then received in a 500-mL beaker, a cathode (Cu plate) and an anode (Pt-plated Ti plate) were inserted therein, and the voltage was applied therebetween. No cation exchange membrane was used. The electrodeposition conditions are as shown in Table 2. Co and Fe in the simulated acidic waste liquid after a voltage application for 6 hours were measured by an atomic absorption photometer. TABLE 1<Conditions of Example 1>Example 1Current [A]0.4Current Density [mA/cm2]47.6Electrode Area, Membrane Area [cm2−]8.4Anode Chamber Volume,10.1Cathode Chamber Volume [mL]Simulated AcidicCompositionSulfuric Acid: 10 wt %Waste LiquidCoCl2: 500 mg-Co/LFeCl3: 500 mg-Fe/LVolume [mL]100 mLpH<0Anode Chamber SV4[hr−1]SimulatedCompositionCitric Acid: 3.4 g/LElectrodepositionVolume [mL]500LiquidpH2.5Cathode Chamber SV30[hr−1]Voltage Application Time [hr]6 TABLE 2<Conditions of Comparative Examples 1 and 2>Comparative Example 1Comparative Example 2Current [A]1.0Current Density [mA/cm2]62.5Electrode Area [cm2−]16Simulated AcidicCompositionSulfuric Acid: 10 wt %Sulfuric Acid: 10 wt %Waste LiquidCoCl2: 100 mg-Co/LCitric Acid: 3.35 g/LFeCl3: 100 mg-Fe/LCoCl2: 100 mg-Co/LFeCl3: 100 mg-Fe/LVolume [mL]400 mLpH<0Voltage Application Time [hr]6 2) Results In Example 1, by the voltage application for 6 hours, 19% of Co and 10% of Fe in the simulated acidic waste liquid could be removed, and a black electrodeposition material was obtained on the cathode. In Comparative Examples 1 and 2, the removal rate of Co and Fe in the liquid was 0% even after the voltage application for 6 hours, and no electrodeposition material was observed on the cathode. From Example 1 and Comparative Examples 1 and 2, it is found that a method in which, without direct contact of the acidic waste liquid with the cathode, metal ions are moved into the cathode chamber through the cation exchange membrane and are electrodeposited is effective. (2) Electrodeposition of Co and Fe in Presence of Dicarboxylic Acid or Tricarboxylic Acid 1) Test Conditions By the use of CoCl2, FeCl3, and the additive shown in Table 3, liquids each in a volume of 400 mL having the compositions shown in Table 3 were prepared, and a liquid in which no suspended material was generated was subjected to an electrodeposition test similar to that of Comparative Example 1. The voltage application was performed for 8 hours. 2) Results In Table 3, the presence or the absence of the generation of a suspended material and the pH of the liquid before and after the voltage application are shown in Table 3. As for Reference Examples 1 to 7 and Comparative Reference Examples 2 and 6 in each of which no suspended material was generated both before and after the voltage application, the results of analysis of the change in concentration of Co and Fe in the liquid with time are shown in FIGS. 3 and 4. From the results obtained by the voltage application for 8 hours, it is found that in Reference Examples 1 to 7, Co and Fe can be simultaneously electrodeposited with time. TABLE 3<Electrodeposition Liquid Conditions and Confirmation Results of Suspended Material>Composition of Electrodeposition LiquidAdditiveBefore VoltageAfter 8-Hour VoltageAdditionApplicationApplicationAmountCoCl2FeCl3SuspendedSuspendedType[※][mg-Co/L][mg-Fe/L]pHMaterialpHMaterialComparativeNone—5005002.4∘None1.9xYesReference Example 1ComparativeSodium Ethylenediaminetetraacetate208.6∘None—∘NoneReference Example 2ComparativeOxalic Acid51.34xYes——Reference Example 3ComparativeEthylenediamine510.1xYes——Reference Example 4Reference Example 1DL-Malic Acid51.7∘None1.8∘NoneComparativeTannic Acid0.51.8∘None1.7xYesReference Example 5Reference Example 2Sodium Tartrate54.5∘None9.1∘NoneReference Example 3Iminodiacetic Acid51.9∘None1.9∘NoneComparativeAscorbic Acid51.9∘None1.4∘NoneReference Example 6Reference Example 4Succinic Acid51.7∘None1.6∘NoneReference Example 5Malonic Acid51.5∘None1.5∘NoneComparativeGallic Acid21.8xYes1.6xYesReference Example 7ComparativeGlycine52.9∘None2.2xYesReference Example 8Reference Example 6Citric Acid Monohydrate51.5∘None1.3∘NoneReference Example 7Citric Acid Monohydrate21.5∘None1.7∘None[※] Molar Amount Ratio (indicating the ratio of the molar amount to the total molar amount of Co and Fe.) (3) Continuous Electrodeposition Test If the electrodeposition can be successively performed, the electrodeposition amount per unit electrode area can be increased, and the reduction in amount of a waste can be performed. Hence, it was confirmed whether long-hour continuous electrodeposition could be performed or not while Co and Fe were replenished. 1) Test Method By the use of CoCl2, FeCl3, and citric acid, after 400 ml of a liquid containing 100 mg-Co/L, 100 mg-Fe/L, and 3,350 mg/L of citric acid (5 times in molar amount with respect to the total molar amount of Co and Fe) and having a pH of 2.2 was prepared in a 500-mL beaker, an electrodeposition test under conditions similar to those of Comparative Example 1 was started, and solid chlorides of Co and Fe in amounts each corresponding to 50 mg/L were additionally added every 2 hours, so that a long-hour electrodeposition test was performed. 2) Results and Discussion By the voltage application, a black electrodeposition material was adhered to the cathode. From FIG. 5 showing the change in voltage with time during the continuous test, it is found that although the voltage application is continued, the voltage is not increased, and the precipitate on the cathode is electrically conductive. By this test, it was found that an electrodeposition treatment could be stably performed for long hours. [Embodiment of Second Invention] Hereinafter, an embodiment of the second invention will be described in detail. In the second invention, at least one type of additive which is used to improve the electrodeposition efficiency and which is selected from a dicarboxylic acid and a salt thereof and a tricarboxylic acid and a salt thereof, each of which has a specific structure and, will be described. In the second invention, as the additive, a compound selected from a dicarboxylic acid having 2 carboxylic groups in its molecule and a salt thereof (hereinafter, referred to as “dicarboxylic acid (salt)” in some cases) and a tricarboxylic acid having 3 carboxylic groups in its molecule and a salt thereof (hereinafter, referred to as “tricarboxylic acid (salt)” in some cases) is used. Those compounds may be used alone, or at least two types thereof may be used by mixing. The dicarboxylic acid (salt) and the tricarboxylic acid (salt) each suppress the generation of a suspended material during an electrodeposition treatment by the chelating effect thereof and have an excellent effect of improving the electrodeposition effect. On the other hand, a monocarboxylic acid having 1 carboxylic group in its molecule has a weak bonding force to Co ions and Fe ions, and problems in that suspended materials formed from hydroxides of Co and Fe are generated in the liquid and/or electrodeposition is not uniformly performed on the cathode may occur. When a carboxylic acid having at least 4 carboxylic groups in its molecule is used, a bonding force to Co ions and Fe ions is excessively high, Co and Fe are held in the liquid, and a problem in that the electrodeposition rate is seriously decreased may arise. In the second invention, as the dicarboxylic acid (salt) or the tricarboxylic acid (salt), by the use of the compound having a specific structure represented by the above formula (1), a suspended material is not likely to be generated during the electrodeposition treatment, and in addition, the electrodeposition is rapidly advanced. In the dicarboxylic acid (salt) and the tricarboxylic acid (salt) each represented by the above formula (1), 1 to 3 carbon atoms are present between the intramolecular carboxyl groups which are most distant from each other, and because of the shape thereof, it is estimated that an appropriate bonding force to Co ions and Fe ions is obtained. The dicarboxylic acid (salt) and the tricarboxylic acid (salt) preferable for the second invention are the same as the dicarboxylic acid (salt) and the tricarboxylic acid (salt) preferable for the first invention. In the second invention, the dicarboxylic acid (salt) and/or the tricarboxylic acid (salt) is preferably present with an ammonium salt. In the case in which no ammonium salt is added, in general, the electrodeposition rate of Co is faster than that of Fe, and an Fe electrodeposition layer is formed on a Co electrodeposition layer; however, when the ammonium salt is added, the electrodeposition rate of Co becomes approximately equivalent to that of Fe, and Co and Fe are electrodeposited so as to form an alloy. When the electrodeposition rate of Co is different from that of Fe, and a Co layer and an Fe layer are separately electrodeposited, because of the difference in physical properties between Co and Fe, floating and/or peeling of an electrodeposition material is liable to occur, and as a result, a successive electrodeposition treatment may not be performed in some cases. A preferable ammonium salt is the same as the ammonium salt preferable in the first invention. An ammonium citrate includes monoammonium citrate, diammonium citrate, and triammonium citrate, and although all of them may be preferably used, since the amount of ammonium is large in the compound, triammonium citrate is preferably used. In order to perform electrodeposition by the second invention, for example, as shown in FIG. 6, after a waste liquid (Co, Fe-containing waste liquid) containing Co ions and Fe ions is charged into an electrodeposition bath 41, and at the same time, the additive described above is added with or without an ammonium salt to the waste liquid and is then mixed therewith, and the voltage is applied between an anode 42 and a cathode 43 inserted in the liquid by a power source 44, so that Co and Fe are simultaneously electrodeposited on the cathode 43. By the use of the above electrodeposition apparatus shown in FIG. 1 in which the cation exchange membrane is provided in the electrodeposition bath, a more preferable electrodeposition treatment can be performed. In the above electrodeposition apparatus shown in FIG. 1, the anode chamber 2A provided with the anode 2 of the electrodeposition bath 1 and the cathode chamber 3A provided with the cathode 3 thereof are separated from each other by the cation exchange membrane 5, the waste liquid (Co, Fe-containing waste liquid) containing Co ions and Fe ions is allowed to pass through the anode chamber 2A, an electrodeposition liquid containing the additive described above with or without an ammonium salt is allowed to pass through the cathode chamber 3A, and the voltage is applied between the anode 2 and the cathode 3, so that Co ions and Fe ions in the liquid in the anode chamber 2A are moved into the liquid in the cathode chamber 3A through the cation exchange membrane 5, and Co and Fe are precipitated on the cathode 3. In the case in which the electrodeposition apparatus shown in FIG. 1 is used for the second invention, reference numeral 10 indicates a Co, Fe-containing waste liquid storage bath, and a circulation system is formed so that the Co, Fe-containing waste liquid is charged into the anode chamber 2A by the pump P1 through the pipe 11, and the discharged liquid is returned to the Co, Fe-containing waste liquid storage bath 10 through the pipe 12. Reference numeral 20 indicates an electrodeposition liquid storage bath containing the additive described above with or without an ammonium salt, and a circulation system is formed so that the electrodeposition liquid is charged into the cathode chamber 3A by the pump P2 through the pipe 21, and the discharged liquid is returned to the electrodeposition liquid storage bath 20 through the pipe 22. In the second invention, the pH of the liquid into which the cathode is immersed is set to preferably 1 to 9 and more preferably 2 to 8.5. When the pH is excessively low, re-dissolution of Co and Fe electrodeposited on the cathode occurs, and the electrodeposition rate may be decreased in some cases. When the pH is excessively high, hydroxides of Co and Fe are liable to be generated as suspended materials in the liquid. When the pH is out of the range described above, an appropriate pH adjustment is preferably performed using an alkali or an acid. In the apparatus shown in FIG. 6, in the case in which the waste liquid is a strong-acid liquid having a pH of 1 or less, unless otherwise the pH is adjusted by addition of an alkali, a problem in that Co and Fe electrodeposited on the cathode 43 are re-dissolved, or no electrodeposition itself occurs may arise. On the other hand, in the apparatus shown in FIG. 1 in which the cation exchange membrane 5 is provided, as long as the electrodeposition liquid at the cathode 3 side is placed under conditions suitable for the electrodeposition, even if the waste liquid is a strong-acid liquid, Co and Fe can be removed by electrodeposition without causing any problems. In the case in which a strong-acid waste liquid is reused after Co ions and Fe ions are removed therefrom, when the pH adjustment is once performed with an alkali, the reuse as an strong-acid liquid becomes difficult; however, according to the apparatus shown in FIG. 1, without decreasing the acidity of the waste liquid, Co ions and Fe ions can be removed from the waste liquid through the cation exchange membrane, so that a treated liquid can be reused. Although the dicarboxylic acid (salt) and the tricarboxylic acid (salt), each of which functions as the additive, are each decomposed by an oxidation reaction at the anode when being brought into contact with the anode, in the apparatus shown in FIG. 1 in which the cation exchange membrane 5 is provided, since the electrodeposition liquid containing the dicarboxylic acid (salt) or the tricarboxylic acid (salt) at the cathode side is not brought into contact with the anode, the dicarboxylic acid (salt) and the tricarboxylic acid (salt) can be prevented from being consumed by oxidation. In the apparatus shown in FIG. 1, although the electrodeposition bath 1 is a closed system, an open system in which the upper portion is opened as shown in FIG. 6 may also be used. In the electrodeposition bath 1, since a hydrogen gas is generated from the cathode, an open system in which the upper portion is opened is preferable. When the cathode on which Co and Fe are electrodeposited is changed, the change thereof can be easily performed in the system in which the upper portion of the electrodeposition bath is opened. In both the electrodeposition apparatuses shown in FIGS. 6 and 1, in order to improve the electrodeposition efficiency, besides the use of an appropriate amount of the additive described above, furthermore, an ammonium salt is preferably used. In the apparatus shown in FIG. 6, with respect to the total molar amount of Co and Fe in the liquid in the electrodeposition bath at the start of the electrodeposition, the additive described above is preferably added so that the amount thereof is 0.1 to 50 molar times and particularly 0.5 to 10 molar times. In the case of the electrodeposition apparatus shown in FIG. 1, with respect to the total molar concentration of Co and Fe in the Co, Fe-containing waste liquid to be charged into the anode chamber, the molar concentration of the additive described above in the electrodeposition liquid to be charged into the cathode chamber is preferably 0.1 to 50 times and particularly preferably 0.5 to 10 times. As the electrodeposition liquid, for example, an aqueous solution containing 0.01 to 20 percent by weight of the above additive and preferably 0.1 to 5 percent by weight thereof and having a pH of 1 to 9 and preferably 2 to 8.5 is used. In both the cases described above, when the amount of the additive described above is excessively small, the effect of suppressing a suspended material obtained by the use of the additive cannot be sufficiently obtained, and when the amount is excessively large, since the chelating effect is excessively enhanced, the electrodeposition rate is decreased. In the case in which the ammonium salt is used, the ammonium salt is preferably used in an amount so that the concentration thereof in the liquid (electrodeposition liquid in the structure shown in FIG. 1) in the electrodeposition bath is 0.01 to 20 percent by weigh and preferably 0.1 to 5 percent by weight. When the concentration of the ammonium salt is excessively low, the above effect obtained by the use of the ammonium salt cannot be sufficiently obtained, and when the concentration is excessively high, the effect is not improved, and the consumption amount of the chemical agent is increased. In the case in which the additive described above and the ammonium salt are formed into one component type and then added, the addition may be performed so that a preferable addition amount range of the additive described above and a preferable addition amount range of the ammonium salt are simultaneously satisfied. Although the electrodeposition conditions (such as the current, the current density, and the temperature) are not particularly limited, the current density is preferably set to 5 to 600 mA/cm2 with respect to the cathode area in terms of the electrodeposition efficiency. The Co ion concentration and the Fe ion concentration in the liquid containing Co ions and Fe ions on which the electrodeposition treatment is performed in the second invention are not particularly limited. The second invention may be applied, for example, to a liquid containing Co ions at 0.1 to 5,000 mg-Co/L, Fe ions at 0.1 to 10,000 mg-Fe/L, and a total thereof at 0.2 to 15,000 mg/L. The second invention is preferably used for the treatment of a waste liquid containing radioactive Co ions and Fe ions generated from a nuclear power plant or the like, such as a decontamination waste liquid generated in a nuclear power plant or an eluent eluting metal ions from an ion exchange resin used in a nuclear power plant. Those waste liquids frequently contain metal ions, such as radioactive Ni ions, other than radioactive Co ions and Fe ions, and even in the case in which those metal ions are contained, an electrodeposition treatment can be performed together with Co and Fe. Hereinafter, with reference to examples, the second invention will be described in more detail. (1) Electrodeposition of Co and Fe in Presence of Dicarboxylic Acid or Tricarboxylic Acid 1) Test Conditions By the use of various types of additives, CoCl2, and FeCl3, electrodeposition liquids each in a volume of 400 mL having the compositions shown in Table 4 were prepared, and a liquid which generated no suspended materials was subjected to an electrodeposition test using the apparatus shown in FIG. 6. The voltage application was performed at 1 A (current density: 62.5 mA/cm2) for 8 hours. A Pt-plated Ti plate was used as the anode, and a Cu plate was used as the cathode. 2) Results The presence or the absence of the generation of a suspended material and the pH of the liquid before and after the voltage application are shown in Table 4. As for the electrodeposition liquids of Examples 2 to 8 and Comparative Examples 4 and 8 in each of which no suspended material was observed both before and after the voltage application, the results of analysis of the change in concentration of Co and Fe in the liquid with time are shown in FIGS. 7 and 8. From the results of the voltage application for 8 hours, in Examples 2 to 8, it is found that Co and Fe can be electrodeposited with time. TABLE 4<Electrodeposition Liquid Conditions and Confirmation Results of Suspended Material>Composition of Electrodeposition LiquidAdditiveBefore VoltageAfter 8-Hour VoltageAdditionApplicationApplicationAmountCoCl2FeCl3SuspendedSuspendedType[※][mg-Co/L][mg-Fe/L]pHMaterialpHMaterialComparativeNone—5005002.4∘None1.9xYesExample3ComparativeSodium Ethylenediaminetetraacetate208.6∘None—∘NoneExample4ComparativeOxalic Acid51.34xYes——Example5ComparativeEthylenediamine510.1xYes——Example6Example2DL-Malic Acid51.7∘None1.8∘NoneComparativeTannic Acid0.51.8∘None1.7xYesExample 7Example 3Sodium Tartrate54.5∘None9.1∘NoneExample 4Iminodiacetic Acid51.9∘None1.9∘NoneComparativeAscorbic Acid51.9∘None1.4∘NoneExample 8Example 5Succinic Acid51.7∘None1.6∘NoneExample 6Malonic Acid51.5∘None1.5∘NoneComparativeGallic Acid21.8xYes1.6xYesExample 9ComparativeGlycine52.9∘None2.2xYesExample 10Example 7Citric Acid Monohydrate51.5∘None1.3∘NoneExample 8Citric Acid Monohydrate21.5∘None1.7∘None[※] Molar Amount Ratio (indicating the ratio of the molar amount to the total molar amount of Co and Fe.) (2) Electrodeposition of Co and Fe with Citric Acid 1) Test Method By the use of the apparatus shown in FIG. 6, a voltage application test was performed under the conditions shown in Table 5. In a 500-mL beaker, the electrodeposition liquid was prepared in a volume of 400 mL using CoCl2, FeCl3, and citric acid so as to have the composition shown in Table 5. A Pt-plated Ti plate was used as the anode, and a Cu plate was used as the cathode. TABLE 5<Electrodeposition Test Conditions (Only Citric Acid))>Composition of Electrodeposition LiquidElectrodeposition ConditionsCitricCitricVoltageCurrentReachingCoCl2FeCl3AcidAcidApplicationCurrentDensityTemperature[mg-Co/L][mg-Fe/L][※][mg/L]pHTime [hr][A][mA/cm2]Heating[° C.]Example 910010053,3502.280.531.3None33Example 10162.5None42Example 111.593.8None60Example 12162.5Yes60[※] Molar Amount Ratio (indicating the ratio of the molar amount to the total molar amount of Co and Fe.)2) Results The electrodeposition results using only citric acid are shown in Table 6, and the change in concentration of Co and Fe in the liquid with time in the electrodeposition test is shown in FIG. 9. It is found that as for both Co and Fe, when the current density is increased, the electrodeposition rates of Co and Fe are increased. TABLE 6<Results of Electrodeposition Test (Only Citric Acid)>Concentration afterConcentration beforeVoltage ApplicationCurrentVoltage Application(after 8 Hours)Removal RateCurrentDensityCoFeCoFeCoFeTest No.[A][mA/cm2][mg/L][mg/L][mg/L][mg/L][%][%]Example 90.531.31011002.041.598.058.6Example 101.062.51041110.677.499.493.3Example 111.593.81031020.855.799.294.4Example 121.062.51021010.292.099.798.0 (3) Continuous Electrodeposition Test When the electrodeposition can be successively performed, the electrodeposition amount per electrode unit area can be increased, and the amount of wastes can be reduced. Hence, it was confirmed whether a long-hour continuous electrodeposition can be performed or not while Co and Fe are replenished. 1) Test Method The electrodeposition test was started under the same conditions as those of Example 10 shown in Table 5, and while Co and Fe, each of which was a solid chloride in an amount corresponding to 50 mg/L, were additionally added every 2 hours, a long-hour electrodeposition test was performed. The other conditions were the same as those of Example 10. 2) Results and Discussion By the voltage application, a black electrodeposition material was adhered to the cathode. From FIG. 10 showing the change in voltage with time during the continuous test, it is found that although the voltage application is continued, the voltage is not increased, and the precipitate on the cathode is electrically conductive. From this test, it was found that the electrodeposition treatment could be stably performed for long hours. (4) Electrodeposition Test Using Both Citric Acid and Ammonium Salt or Using Ammonium Citrate 1) Test Method By the use of the apparatus shown in FIG. 6, the electrodeposition test was performed under the conditions shown in Tables 7A and 7B. In Examples 13 to 17, by the use of CoCl2, FeCl3, and citric acid and/or an ammonium salt shown in FIG. 7A, 400 mL of an electrodeposition liquid was prepared in a 500-mL beaker, and a Pt-plated Ti plate and a Cu plate were used as the anode and the cathode, respectively. In Examples 18 to 21, by the use of CoSO4, Fe2(SO4)3, and ammonium citrate in the amounts shown in Table 7B, 400 mL of an electrodeposition liquid was prepared in a 500-mL beaker, and a Pt-plated Ti plate and a Cu plate were used as the anode and the cathode, respectively. For comparison, the electrodeposition conditions (Examples 10 and 11 shown in Table 5) using only citric acid are also shown in Table 7A. TABLE 7AConfirmation Test of Effect of Ammonium SaltComposition of Electrodeposition LiquidElectrodeposition ConditionsAmmonium SaltVoltageAdditionApplicationCurrentCoCl2FeCl3Citric AcidCitric AcidAmountTimeCurrentDensity[mg-Co/L][mg-Fe/L][※][mg/L]Type[g/L]pH[hr][A][mA/cm2]HeatingExample 1010010053,35002.28162.5NoneExample 111.593.8Example 1353,350Ammonium33.44.32125OxalateExample 14Ammonium32.01.9162.5Example 15Chloride2125Example 16Ammonium31.02.5162.5SulfateExample 1700Ammonium33.46.4162.5Oxalate[※] Molar Amount Ratio (indicating the ratio of the molar amount to the total molar amount of Co and Fe.) TABLE 7BConfirmation Test of Effect of Ammonium CitrateComposition of Electrodeposition LiquidElectrodeposition ConditionsAmmonium CitrateVoltageAdditionApplicationCurrentCoSO4Fe2(SO4)3AmountTimeCurrentDensity[mg-Co/L][mg-Fe/L]Type[g/L]pH[hr][A][mA/cm2]HeatingExample 18100100Diammonium Citrate7.94.786162.5NoneExample 19Triammonium Citrate8.56.44Example 206.412125Example 2117.06.46162.5 The results of the electrodeposition test using only citric acid (Examples 10 and 11) are shown in FIG. 11, the result of the electrodeposition using both citric acid and ammonium oxalate (Example 13) is shown in FIG. 12, the results of the electrodeposition using both citric acid and ammonium chloride (Examples 14 and 15) are shown in FIG. 13, and the results of the electrodeposition using both citric acid and ammonium sulfate (Example 16) are shown in FIG. 14. In FIG. 15, the results of the electrodeposition using only ammonium oxalate (Example 17) are shown. The results of the electrodeposition tests of Examples 18 to 21, in each of which ammonium citrate was used, are shown in FIGS. 16 to 19, respectively. In the drawings, “k” represents a reaction rate constant (proportional constant in the case in which the rate of decrease in concentration is proportional to the concentration), and a larger k represents a higher electrodeposition rate. From FIG. 11, it is found that when citric acid is only used, although the electrodeposition rate of Co is high, the electrodeposition of Fe is slow. Hence, in the electrodeposition using only citric acid, it is believed that an Fe electrodeposition material is generated on a Co electrodeposition material. In the systems in each of which the ammonium salt was added shown in FIGS. 12 to 15, it is found that electrodeposition of Co and that of Fe simultaneously occur. The reason for this is believed that since Co forms an ammine complex, the degree of stability of Co in the liquid is increased, and hence, Co is suppressed from being preferentially electrodeposited. in the electrodeposition test using only ammonium oxalate shown in FIG. 15, by oxalic acid, which is a dicarboxylic acid, and ammonium ions, Co and Fe can both be rapidly electrodeposited by one component agent. In the electrodeposition tests using only ammonium citrate shown in FIGS. 16 to 19, by citric acid, which is a tricarboxylic acid, and ammonium ions, Co and Fe can both be rapidly electrodeposited by one component agent. When the result obtained by diammonium citrate (FIG. 16) and the result obtained by triammonium citrate (FIG. 17) are compared to each other, it is found that the electrodeposition efficiency of Co and Fe using triammonium citrate, which has a larger ammonium amount, is higher. (5) Confirmation of Permeation of Co and Fe Through Cation Exchange Membrane In the case in which as the electrodeposition liquid, a citric acid aqueous solution was used, and as the eluent, a sulfuric acid aqueous solution was used, the permeation of Co and Fe through the cation exchange membrane by voltage application was confirmed. 1) Test Method By the use of the electrodeposition apparatus shown in FIG. 1 in which the cation exchange membrane was provided, a voltage application test was performed (Example 22 and Example 23). The test conditions are shown in Table 8. TABLE 8Example 22Example 23Current [A]0.410Current Density [mA/cm2]47.6125Electrode Area, Membrane Area [cm2]8.480Simulated EluentCompositionSulfuric Acid 10%Sulfuric Acid 5%(Co, Fe-ContainingCo: 500 mg/LCo: 3 mg/LWaste Liquid)Fe: 500 mg/LFe: 500 mg/LVolume [mL]100400SV [hr−1]433SimulatedComposition3.4 g/LCitric Acid17 g/LTriammonium CitrateElectrodepositionpH 2.5pH 6.4LiquidVolume [mL]500200SV [hr−1]3033Voltage Application Time [hr]17162) Results and Discussion In FIG. 20, the change in concentration of Co and Fe with time at the eluent side and that at the electrodeposition liquid side in Examples 22 are shown. The change in concentration of Co and Fe with time at the eluent side and that at the electrodeposition liquid side of Example 23 are shown in FIGS. 21 and 22, respectively. In both the cases, since the concentrations of Co and Fe are decreased at the eluent side and are increased at the electrodeposition liquid side, it is found that by the voltage application, Co ions and Fe ions permeate the cation exchange membrane. When the electrodeposition material on the cathode in each of Examples 22 and 23 was completely dissolved in a dissolution liquid in which a hydrochloric acid (mixture of 35% hydrochloric acid and purified water at a ratio of 1:1) and a nitric acid (mixture of 60% nitric acid and purified water at a ratio of 1:1) were mixed at a ratio of 2:3, and the electrodeposition amount was measured by an atomic absorption photometer, the measurement result coincided with the amount obtained by subtracting the increased amount of Co and Fe in the electrodeposition liquid from the decreased amount of Co and Fe in the eluent; hence, it was confirmed that Co ions and Fe ions in the eluent permeated the cation exchange membrane and were electrodeposited on the cathode. [Embodiment of Third Invention] Hereinafter, an embodiment of the third invention will be described in detail. In the third invention, an acid (hereinafter, referred to as an eluent in some cases) heated to 60° C. or more is brought into contact with a waste ion exchange resin which adsorbs radioactive substances and also contains a clad primarily formed of iron oxide, so that ionic radioactive substances in the waste ion exchange resin are removed by elution, and at the same time, the clad is also removed by dissolution. In the third invention, the radioactive waste ion exchange resin to be processed by a decontamination treatment adsorbs radioactive substances, such as radioactive metal components including cobalt-60 and nickel-63, which are formed into cations in the eluent, and also contains a clad primarily formed of iron oxide. In this case, “primarily formed of iron oxide” indicates that 50 percent by weight or more of iron oxide is contained in the clad. The adsorption amount of the radioactive substances and the content of the clad of the waste ion exchange resin are not particularly limited. As the eluent, an aqueous solution of an inorganic acid, such as sulfuric acid, hydrochloric acid, or nitric acid, or an organic acid, such as formic acid, acetic acid, or oxalic acid, may be used. Those acids may be used alone, or at least two types thereof may be used by mixing. Sulfuric acid and/or oxalic acid, each of which is not likely to be volatilized during heating at 60° C. or more and is not categorized as a hazardous material, is preferably used. As for the acid concentration in the eluent, a preferable concentration is present in accordance with an acid to be used. The sulfuric acid concentration is preferably 5 to 40 percent by weight and more preferably 10 to 30 percent by weight. The oxalic acid concentration is preferably 0.1 to 40 percent by weight and more preferably 1 to 20 percent by weight. When the acid concentration is lower than the range described above, the dissolution efficiency of hematite (α-Fe2O3) which is a primary component of the clad is decreased. That is, the clad is present so as to be mixed in the waste ion exchange resin or incorporated in the resin, and the primary component of the clad is poor soluble hematite, so that dissolution thereof is difficult by a low concentration acid. When the acid concentration in the eluent is high, the amount of hydrogen generated in the electrodeposition step performed at a latter stage becomes excessive, and the electrodeposition efficiency is decreased. In the third invention, the eluent is preferably used by heating to 60° C. or more, preferably 70° C. to 120° C., and more preferably 80° C. to 100° C. When this temperature is excessively low, the dissolution efficiency of the clad is low, and when this temperature is excessively high, since evaporation of water and volatilization of the acid become excessive, it is not preferable from a handling point of view. A contact method between the heated eluent and the waste ion exchange resin is not particularly limited, and there may be used either a batch method in which the waste ion exchange resin is charged into the eluent and stirred or a liquid flow method in which as shown in the above FIG. 2, the eluent is allowed to pass through the packed tower in which the waste ion exchange resin is packed. In the case of the batch method, the contact time between the eluent and the waste ion exchange resin is preferably set to approximately 0.5 to 24 hours and is particularly preferably set to approximately 2 to 12 hours. In the case of the liquid flow method, a liquid passage SV is preferably set to approximately 0.2 to 10 hour−1 with respect to the volume of the packed tower. It is preferable that after an eluent (hereinafter, referred to as acidic waste liquid in some cases) which elutes ionic radioactive substances adsorbed to the waste ion exchange resin and dissolves the clad mixed therein by contact with the waste ion exchange resin and which contains those materials mentioned above is charged into an electrodeposition bath including an anode and a cathode, by voltage application between the anode and the cathode of the electrodeposition bath, cationic radioactive substances in the acidic waste liquid and iron ions derived from the clad are removed by electrodeposition thereof on the cathode, and a treated liquid thus obtained is reused as the eluent. A preferable apparatus as an apparatus which performs a decontamination treatment of a waste ion exchange resin and an electrodeposition treatment of an acid waste liquid obtained by the decontamination treatment so as to reuse the acidic waste liquid is the above apparatus shown in FIG. 2. The apparatus shown in FIG. 2 includes the eluent storage bath 30 storing an eluent, the eluting bath 8 which is a packed tower in which the waste ion exchange resin 40 is packed, the acid waste liquid storage bath 10 storing an acidic waste liquid to be discharged from the eluting bath 8, the electrodeposition bath 1 into which the acidic waste liquid from the acidic waste liquid storage bath 10 is charged, and the bath 20 storing an electrodeposition liquid (cathode liquid) to be supplied to the electrodeposition bath 1. The electrodeposition bath 1 has the structure in which the anode chamber 2A including the anode 2 and the cathode chamber 3A including the cathode 3 are separated from each other by the cation exchange membrane 5, the acidic waste liquid is allowed to pass through the anode chamber 2A, and the electrodeposition liquid (cathode liquid) is allowed to pass through the cathode chamber 3A. Reference numerals 9A and 9B each represent a heat exchanger. As long as the heat exchanger 9A can perform heating, and the heat exchanger 9B can perform cooling, any means may be used, and as the heat exchanger 9A, an electric heater may also be used. The eluent in the eluent storage bath 30 is heated by the heat exchanger 9A to 60° C. or more while being transported to the eluting bath 8 by the pump P3 through the pipe 31 and is then allowed to pass through the eluting bath 8 in an upward flow. An outflow liquid (acidic waste liquid) is subsequently cooled by the heat exchanger 9B to a temperature of less than 60° C., such as 10° C. to less than 60° C., at which the cation exchange membrane 5 in the electrodeposition bath 1 is not so much degraded, and is further transported to the acidic waste liquid storage bath 10 through the pipe 32. The acidic waste liquid in the acidic waste liquid storage bath 10 is charged into the anode chamber 2A of the electrodeposition bath 1 by the pump P1 through the pipe 11, and an electrodeposition treated liquid is circulated to the eluent storage bath 30 through the pipe 34 and is reused as the eluent. In addition, into the cathode chamber 3A of the electrodeposition bath 1, the electrodeposition liquid (cathode liquid) in the storage bath 20 is charged by the pump P2 through the pipe 21 and is then returned to the storage bath 20 through the pipe 22. An acid is appropriately replenished into the eluent storage bath 30 by the pipe 33, and into the storage bath 20, the electrodeposition liquid (cathode liquid) is appropriately replenished by the pipe 23. In this apparatus, since the heated eluent is allowed to pass through the eluting bath 8 in which the waste ion exchange resin 40 is packed, ionic radioactive substances adsorbed to the waste ion exchange resin 40 are removed by elution, and in addition, the clad mixed in the waste ion exchange resin 40 or incorporated into resin particles is also removed by dissolution. After being brought into contact with the waste ion exchange resin 40, the eluent (acidic waste liquid) containing ionic radioactive substances and a dissolved material of the clad is charged into the anode chamber 2A of the electrodeposition bath (electrodeposition cell) 1 through the acidic waste liquid storage bath 10. When the voltage is applied between the anode 2 and the cathode 3 of the electrodeposition bath 1, radioactive metal ions and iron ions derived from the clad in the acidic waste liquid are moved into the cathode chamber 3A through the cation exchange membrane 5 and are then electrodeposited on the cathode 3. A treated liquid of the acid waste liquid from which the radioactive metal ions and the iron ions are removed in the electrodeposition bath 1 is returned to the eluent storage bath 30 and is recycled. The electrodeposition liquid in the cathode chamber 3A is circulated by the pump P2 through the storage bath 20 and is recycled while the electrodeposition liquid in an amount corresponding to the decrease thereof is added to the storage bath 20. As the electrodeposition liquid (cathode liquid), an aqueous solution containing at least one type of additive selected from a dicarboxylic acid having 2 carboxylic groups in its molecule and a salt thereof (hereinafter, referred to as “dicarboxylic acid (salt)” in some cases) and a tricarboxylic acid having 3 carboxylic groups in its molecule and a salt thereof (hereinafter, referred to as “tricarboxylic acid (salt)” in some cases) is preferably used. Those dicarboxylic acid (salt) and the tricarboxylic acid (salt) suppress the generation of a suspended material during electrodeposition by its chelating effect, and as a result, an effect of improving an electrodeposition effect can be obtained. On the other hand, since a monocarboxylic acid having 1 carboxylic group in its molecule has a weak bonding force to radioactive metal ions (the radioactive substance is not limited at all to Co-60, and hereinafter, Co-60 and a stable Co isotope are collectively referred to as Co), such as Co-60, and Fe ions derived from the clad, problems in that suspended substances formed of hydroxides of Co and Fe are generated in the liquid and/or electrodeposition is not uniformly performed on the cathode may occur. When a carboxylic acid having at least 4 carboxylic groups in its molecule is used, since a bonding force to Co ions and Fe ions is excessively high, Co and Fe are held in the liquid, and as a result, a problem in that the electrodeposition rate is seriously decreased may occur. As the dicarboxylic acid (salt) and the tricarboxylic acid (salt), a compound represented by the above formula (1) is preferable since a suspended material is not likely to be generated, and electrodeposition is rapidly advanced. In the dicarboxylic acid (salt) and the tricarboxylic acid (salt) each represented by the above formula (1), 1 to 3 carbon atoms are present between the intramolecular carboxylic groups, and because of the shape thereof, it is estimated that an appropriate bonding force to Co ions and Fe ions can be obtained. The dicarboxylic acid (salt) and the tricarboxylic acid (salt) preferable for the third invention are the same as the dicarboxylic acid (salt) and the tricarboxylic acid (salt) preferable for the first invention. In the electrodeposition liquid, the dicarboxylic acid (salt) and/or the tricarboxylic acid (salt) is preferably present with an ammonium salt. In the case in which the ammonium salt is not added, in general, the electrodeposition rate of Co is faster than that of Fe, and an Fe electrodeposition layer is formed on a Co electrodeposition layer; however, when the ammonium salt is added, the electrodeposition rate of Co becomes approximately equivalent to that of Fe, and Co and Fe are electrodeposited so as to form an alloy. When the electrodeposition rate of Co is different from that of Fe, and a Co layer and an Fe layer are separately electrodeposited, floating and/or peeling of an electrodeposition material is liable to occur, and as a result, a successive electrodeposition treatment may not be performed in some cases. A preferable ammonium salt is the same as the preferable ammonium salt in the first invention. The pH of the electrodeposition liquid is set to preferably 1 to 9 and more preferably 2 to 8.5. When the pH of the electrodeposition liquid is excessively low, re-dissolution of Co and Fe electrodeposited on the cathode occurs, and the electrodeposition rate may be decreased in some cases. When the pH of the electrodeposition liquid is excessively high, hydroxides of Co and Fe are liable to be generated as suspended materials in the liquid. When the pH of the electrodeposition liquid is out of the range described above, an appropriate pH adjustment is preferably performed using an alkali or an acid. As the acid to be used for the pH adjustment, the same dicarboxylic acid (salt) and/or tricarboxylic acid (salt) as the above additive in the electrodeposition liquid is preferably used. As the electrodeposition liquid, for example, an aqueous solution containing 0.01 to 20 percent by weight of the additive described above and preferably 0.1 to 5 percent by weight thereof and having a pH of 1 to 9 and preferably 2 to 8.5 is used. When the amount of the additive in the electrodeposition liquid is excessively small, the effect of suppressing a suspended material obtained by the use of the additive cannot be sufficiently obtained, and when the amount is excessively large, the chelating effect is excessively enhanced, and as a result, the electrodeposition rate is decreased. In the case in which the ammonium salt is used, a concentration of the ammonium salt in the electrodeposition liquid is preferably 0.01 to 20 percent by weight and preferably 0.1 to 5 percent by weight. When the concentration of the ammonium salt of the electrodeposition liquid is excessively low, the above effect obtained by the use of the ammonium salt cannot be sufficiently obtained, and when the concentration is excessively high, the effect is not improved, and the consumption amount of the chemical agent is wasteful. Although the electrodeposition conditions (such as the current, the current density, and the temperature) are not particularly limited, the current density is preferably set to 5 to 600 mA/cm2 with respect to the cathode area in terms of the electrodeposition efficiency. FIG. 2 shows one example of a decontamination apparatus preferable for the embodiment of the third invention, and the decontamination apparatus of the third invention is not limited at all to that shown in the drawing. In FIG. 2, although being allowed to pass through the eluting bath 8 in an upward flow, the eluent may also be allowed to pass therethrough in a downward flow. In the case in which the waste ion exchange resin is a powder, the differential pressure is liable to increase when the liquid is allowed to pass therethrough, and hence the upward flow is preferable. In the electrodeposition bath 1, the acidic waste liquid and the electrodeposition liquid may be allowed to pass in opposite directions with the cation exchange membrane 5 provided therebetween. Heat exchange may also be performed between the eluent charged into the eluting bath 8 and the acid waste liquid discharged therefrom. Although the electrodeposition bath 1 is a closed system, since a hydrogen gas is generated from the cathode, an open system in which an upper portion is opened is preferable. When a cathode on which a metal is electrodeposited is changed, the change thereof can be easily performed if the upper portion of the electrodeposition bath is opened. In a nuclear power plant, the third invention can be effectively applied to a waste ion exchange resin which adsorbs ionic radioactive substances and which also contains a clad primarily formed of iron oxide, the waste ion exchange resin including a waste ion exchange resin used for cleanup of a cooling water system, such as a reactor water cleanup system or a fuel pool cooling cleanup system, which is directly brought into contact with a fuel rod and a waste ion exchange resin used for a treatment of a decontamination waste liquid discharged when radioactive substances are chemically removed from apparatuses and pipes of a primary cooling system contaminated by radioactive substances and from surfaces of metal members of the system including those mentioned above. Hereinafter, with reference to experimental examples and examples, the third invention will be described in more detail. An eluent (aqueous solution) having the acid concentration and the pH shown in Table 9 was prepared in a volume of 500 mL, and 1 g of a simulated clad (manufactured by Kojundo Chemical Laboratory Co., Ltd., α-Fe2O3, diameter announced by the maker: 1 μm) was added into this eluent, so that a dissolution test was performed at the liquid temperature and for the dissolution time shown in Table 9. From the Fe concentration in the eluent, the dissolution rate of Fe (clad) was investigated, and the results are shown in Table 9. TABLE 9ResultsEluentDissolution ConditionsFeAcidDissolutionFe ConcentrationDissolutionConcentrationTemperatureTimein EluentRateNo.Type(wt %)pH(° C.)(hr)[mg/L][%]EvaluationNote1Sulfuric Acid5<0.59041,20085∘Example of210<0.52.51,400100∘Third Invention320<0.511,400100∘4Oxalic Acid90.600.51,400100∘5Sulfuric Acid + 5 + 0.9<0.521,400100∘Oxalic Acid6Sulfuric Acid + 5 + 0.09<0.531,400100∘Oxalic Acid7Sulfuric Acid1<1No Heating1890.6xComparative85<118634.5xExample910<118997.1x10Hydrochloric12 + 20<11880057ΔAcid + SulfuricAcid11Oxalic Acid90.604018110.8x12Hydrazine3.210.9401800x As apparent from Table 9, although the dissolution rate is low in Nos. 7 to 12 in which the dissolution test was performed at a low temperature, in Nos. 1 to 6 in which a sulfuric acid aqueous solution and/or an oxalic acid aqueous solution, each of which was heated to 90° C., was used, the clad can be efficiently dissolved. A mixed resin adsorbing Co was prepared in such a way that with an aqueous solution dissolving 96 mg of cobalt chloride (II) hexahydrate, 40.0 g of a powdered H-type cationic exchange resin (manufactured by Mitsubishi Chemical Co., Ltd., exchange capacity: 5.1 meq/g, grain size of 10 to 200 μm: 95%) and 40.0 g of a powdered OH-type anionic exchange resin (manufactured by Mitsubishi Chemical Co., Ltd., exchange capacity: 4.1 meq/g, grain size of 0 to 100 μm: 74%, 10 to 250 μm: 93%) were mixed and were then stirred for 12 hours. After 12 hours passed, since the result obtained by the measurement of the Co concentration in supernatant water using an atomic absorption photometer was the detection limit or less, it was confirmed that approximately all Co ions were adsorbed to the ion exchange resin. As a simulated clad, 4.0 g of an iron oxide (manufactured by Kojundo Chemical Laboratory Co., Ltd., α-Fe2O3, diameter announced by the maker: 1 μm) was added to and mixed with the mixed resin described above, so that a simulated waste resin was prepared. Subsequently, after this simulated waste resin was charged into 1.6 L of a sulfuric acid eluent (aqueous solution) at a concentration 10 percent by weight heated to 90° C., the temperature was maintained at 90° C. while heating and stirring were performed, and the dissolution behavior was confirmed. After the simulated waste resin was charged into the sulfuric acid eluent at a concentration of 10 percent by weight, several milliliters of the sulfuric acid eluent was sampled every predetermined time, so that Fe in the filtrated sample was analyzed by an atomic absorption photometer, and Co was also analyzed by ICP-MS. As a result, as for Fe, as shown in FIG. 23, it was found that approximately 100% of the Fe amount in the simulated clad thus added is dissolved in the sulfuric acid eluent, and that after the simulated clad is dissolved, no re-adsorption thereof to the cation exchange membrane occurs. The reason the dissolution rate after 2 hours or more is more that 100% is the evaporation of water in the eluent caused by heating. As for Co, it was confirmed that approximately 100% of the Co amount in cobalt chloride thus added is eluted, and that Co ions can be preferably eluted from the resin. After CoCl2, FeCl3, and sulfuric acid were dissolved in water so that a simulated waste liquid having properties shown in Table 10 was prepared, and citric acid was dissolved in water so that a simulated electrodeposition liquid (cathode liquid) having properties shown in Table 10 was prepared, by the use of the apparatus shown in FIG. 1, an electrodeposition test of Co and Fe was performed. In FIG. 1, reference numeral 12 indicates a pipe returning an electrodeposition treated liquid to the acidic waste liquid storage bath 10. The electrodeposition conditions are as shown in Table 10. A Pt-plated Ti plate and a Cu plate were used as the anode and the cathode, respectively. TABLE 10<Conditions of Experimental Example 2>Experimental Example 2Current [A]0.4Current Density [mA/cm2]47.6Electrode Area, Membrane Area [cm2−]8.4Anode Chamber Volume, Cathode Chamber10.1Volume [mL]Simulated AcidicCompositionSulfuric Acid: 10 wt %Waste LiquidCoCl2: 500 mg-Co/LFeCl3: 500 mg-Fe/LVolume [mL]100 mLpH<0Anode Chamber SV [hr−1]4SimulatedCompositionCitric Acid: 3.4 g/LElectrodepositionVolume [mL]500LiquidpH2.5Cathode Chamber SV [hr−1]30Voltage Application Time [hr]6 When Co and Fe in the simulated acidic waste liquid after 6-hour voltage application were measured by an atomic absorption photometer, by the voltage application for 6 hours, 19% of Co and 10% of Fe in the simulated acidic waste liquid could be removed, and a black electrodeposition material was obtained on the cathode. By this electrodeposition apparatus, without direct contact of a waste liquid having a strong acidity with the cathode, electrodeposition could be efficiently performed by moving metal ions into the cathode chamber through the cation exchange membrane. By the use of various types of additives, CoCl2, and FeCl3, electrodeposition liquids having the compositions shown in Table 11 were each prepared in a volume of 400 mL, and by the use of the apparatus shown in Table 6, the electrodeposition test was performed on electrodeposition liquids in each of which no suspended material was generated. The voltage application was performed at a current of 1 A (current density: 62.5 mA/cm2) for 8 hours. A Pt-plated Ti plate and a Cu plate were used as the anode and the cathode, respectively. In Table 11, the presence or the absence of the generation of a suspended material and the pH of the liquid before and after the voltage application are shown. As for the electrodeposition liquids of Experimental Examples 3 to 9 and Comparative Experimental Examples 2 and 6, in each of which no suspended material was present both before and after the voltage application, the results of analysis of the change in concentration of Co and Fe in the liquid with time are shown in FIGS. 24 and 25. From the result of the voltage application for 8 hours, it is found that in Experimental Examples 3 to 9, Co and Fe can be electrodeposited with time. TABLE 11<Electrodeposition Liquid Conditions and Confirmation Results of Suspended Material>Composition of Electrodeposition LiquidAdditiveBefore VoltageAfter 8-Hour VoltageAdditionApplicationApplicationAmountCoCl2FeCl3SuspendedSuspendedType[※][mg-Co/L][mg-Fe/L]pHMaterialpHMaterialComparativeNone—5005002.4∘None1.9xYesExperimentalExample 1ComparativeSodium Ethylenediaminetetraacetate208.6∘None—∘NoneExperimentalExample 2ComparativeOxalic Acid51.34xYes——ExperimentalExample 3ComparativeEthylenediamine510.1xYes——ExperimentalExample 4ExperimentalDL-Malic Acid51.7∘None1.8∘NoneExample 3ComparativeTannic Acid0.51.8∘None1.7xYesExperimentalExample 5ExperimentalSodium Tartrate54.5∘None9.1∘NoneExample 4ExperimentalIminodiacetic Acid51.9∘None1.9∘NoneExample 5ComparativeAscorbic Acid51.9∘None1.4∘NoneExperimentalExample 6ExperimentalSuccinic Acid51.7∘None1.6∘NoneExample 6ExperimentalMalonic Acid51.5∘None1.5∘NoneExample 7ComparativeGallic Acid21.8xYes1.6xYesExperimentalExample 7ComparativeGlycine52.9∘None2.2xYesExperimentalExample 8ExperimentalCitric Acid Monohydrate51.5∘None1.3∘NoneExample 8ExperimentalCitric Acid Monohydrate21.5∘None1.7∘NoneExample 9[※] Molar Amount Ratio (indicating the ratio of the molar amount to the total molar amount of Co and Fe.) Although the present invention has been described in detail with reference to the specific aspects, it is apparent to a person skilled in the art that various modifications may be performed without departing from the spirit and the scope of the present invention. This application claims the benefit of Japanese Patent Application No. 2013-221320 filed Oct. 24, 2013, No. 2013-221321 filed Oct. 24, 2013, No. 2013-221322 filed Oct. 24, 2013, and No. 2014-045235 filed Mar. 7, 2014, which are hereby incorporated by reference herein in their entirety.
	description	The fluid flow in a boiling water reactor will be generally described with reference to FIG. 2. Feed water is admitted into a reactor pressure vessel (RPV) 10 via a feed water inlet 12 and a feed water sparger 14, which is a ring-shaped pipe having suitable apertures for circumferentially distributing the feed water inside the RPV. A core spray inlet 11 supplies water to a core spray sparger 15 via core spray line 13. The feed water from feed water sparger 14 flows downwardly through the down corner annulus 16, which is an annular region between RPV 10 and core shroud 18. Core shroud 18 is a stainless steel cylinder, which surrounds the core 20 comprising numerous fuel assemblies 22 (only two 2xc3x972 arrays of which are depicted in FIG. 2). Each fuel assembly is supported at the top guide 19 and at the bottom by core plate 21. Water flowing through downcomer annulus 16 then flows to the reactor lower plenum 24. The water subsequently enters the fuel assemblies 22 disposed within core 20, wherein a boiling boundary layer (not shown) is established. A mixture of water and steam enters reactor upper plenum 26 under shroud head 28. Reactor upper plenum 26 provides standoff between the steam-water mixture exiting core 20 and entering vertical standpipe 30, which are disposed atop shroud head 28 and in fluid communication with reactor upper plenum 26. The steam-water mixture flows through standpipes 30 and enters steam separators 32, which are of the axial-flow centrifugal type. The separated liquid water then mixes with feed water in the mixing plenum 33, which mixture then returns to the core via the downcomer annulus and/or through jet pump assemblies. The steam passes through steam dryers 34 and enters steam dome 36. The steam is withdrawn from the RPV via steam outlet 38. The BWR also includes a coolant recirculation system, which provides the forced convection flow through the core necessary to attain the required power density. A portion of the water is sucked from the lower end of the downcomer annulus 16 via recirculation pump (not shown) into jet pump assemblies 42 (only one of which is shown) via recirculation water inlets 45. The BWR has two recirculation pumps, each of which provides the driving flow for a plurality of jet pump assemblies. The pressurized driving water is supplied to each jet pump nozzle 44 via an inlet riser 47, an elbow 48 and an inlet mixer 46 in flow sequence. A typical BWR has 16 to 24 inlet mixers. The present disclosure is directed to a method of reducing the electrochemical corrosion potential of a component (i.e., structural material) exposed to high temperature water in a hot water system, which includes providing a reducing species to the high temperature water, providing a plurality of catalytic and dielectric nanoparticles to the high temperature water, wherein the catalytic nanoparticles provide a catalytic surface on which the reducing species reacts with the at least one oxidizing species present in the high temperature water, and wherein the dielectric nanoparticles provide insulative protection to the surfaces, regardless of the water chemistry conditions, and correspondingly reducing the electrochemical corrosion potential of the component. The introduction of the catalytic and dielectric nanoparticles into the high temperature water of reactors, such as the BWR described above, advantageously protects the reactor components and reduces the oxidizing properties of the high temperature water. The nanoparticles comprise both dielectric nanoparticles and catalytic nanoparticles and/or nanoparticles having both dielectric and catalytic properties, i.e., each nanoparticle possesses both a catalytic functionality and a dielectric functionality. Although described with respect to a BWR, the present disclosure is not intended to be limited to use in BWRs and is applicable to the primary and secondary sides of PWRs. Other suitable structures include those structural components that are exposed to high temperature water environments. Such structures include pressurized water reactors, steam driven turbines, water deaerators, and the like. As used herein, the term high temperature water refers to water having a temperature between about 50xc2x0 C. and about 320xc2x0 C., and preferably, between about 50xc2x0 C. and about 290xc2x0 C. As used herein, the term xe2x80x9cnanoparticlesxe2x80x9d is defined as discrete particles with average diameters less than about 100 nanometers (nm). More preferably, the nanoparticles have diameters of about 1 nm to about 100 nm, and with about 5 nm to about 50 nm even more preferred. Due to the large fraction of atoms located at the surface, nanoparticles possess very unique electrical, magnetic, mechanical, and optical properties, such as, but not limited to, increased surface area and the ability to form colloidal suspensions. Particles having a diameter of about 9 nm, for example, may have a surface area of about 97 m2/g when fully dispersed. In the present disclosure, the nanoparticles preferably have a surface area of about 1 m2/g to about 300 m2/g, and more preferably, a surface area of about 10 m2/g to about 100 m2/g. The nanoparticles generally comprise both dielectric non-noble metal nanoparticles and a catalytic noble metal nanoparticles, and/or nanoparticles comprising a mixture of both catalytic noble metal and dielectric non-noble metals, i.e., each nanoparticle is comprised of both catalytic and dielectric functional materials. While not wanting to be bound by theory, it is believed that upon introduction of the nanoparticles in the high temperature water, the nanoparticles are colloidally dispersed in the water to provide protection to the reactor components from the detrimental effects of the high temperature water. In particular, the catalytic nanoparticles catalytically increase the efficiency of the recombination kinetics for hydrogen and oxygen to lower the electrochemical corrosion potential of the water. The dielectric nanoparticles provide insulative barrier protection properties to reactor surfaces proximate to or in contact therewith. Some of the nanoparticles, e.g., catalytic noble metal component and/or dielectric component, may also deposit onto surfaces of the components in contact with the high temperature water to provide continued protection. Once deposited onto the component surfaces, the nanoparticles may redeposit onto other component surfaces during operation or become colloidally dispersed in the high temperature water. Upon introduction of the nanoparticles to the reactor, the nanoparticles are colloidally dispersed throughout the water and are responsive to electrostatic forces in the water. As a result, redistribution of the nanoparticles can occur on various component surfaces of the reactor. In addition, it has been found that the catalytic efficiency is greatly improved due to the increased surface area provided by the use of nanoparticles, relative to coated articles. Thus, the presence of the catalytic nanoparticles and/or the dielectric nanoparticles can reduce the oxidizing power of the water and at the same time, can lead to the formation of an insulated and/or catalytic deposits on surfaces of the reactor components. In addition, such nanoparticles are capable of penetrating or diffusing into the existing crevice and thus inhibit further growing. Examples of suitable metals for forming the various reactor components to be protected are nickel based alloys, cobalt based alloys, titanium based alloys, copper based alloys, and ferrous and non-ferrous alloys. Carbon steels and low alloy steels are further examples. In a preferred embodiment, a mixture of nanoparticles including both dielectric nanoparticles and catalytic nanoparticles are introduced into the high temperature water. In another embodiment, each nanoparticle is fabricated as a mixture of both the dielectric component and the catalytic component, wherein all or a portion of the catalytic component contacts the high temperature water upon immersion therein. Advantageously, the use of the nanoparticles as disclosed herein reduces the electrochemical corrosion potential without the need to continuously monitor variables such as dissolved hydrogen/oxygen levels, flow rates, temperature gradients, radiation fluxes, and the like, which are generally difficult to accurately monitor in BWRs and other like reactors. The nanoparticles may have a variety of morphologies, including single-lobed such as spherical, substantially spherical, cigar-shaped, rod-shaped and moon-shaped, and multi-lobed such as tetrahedral, raspberry, acorn, dumb-bell, and the like. The size distribution of the nanoparticles may be monodisperse, bimodal, or polydisperse. In a preferred embodiment, the nanoparticles have an average diameter less than about 100 nanometers. The nanoparticles are formed using conventional techniques leading to a wide variation in the amount of agglomeration of particles. As those skilled in the art will appreciate, the stoichiometry of the metals (non-noble metals and noble metals) will establish the ratio of the metal in the final product Typically, nanoparticles need to be dispersed to take advantage of their unique properties. Particle dispersion can be divided into three stages: wetting; separation of particles; and stabilization. Once wetted, the breakdown of agglomerates is usually achieved by collision or attrition. Methods used to disperse the nanoparticles include ultrasonic energy, vigorous mixing, vigorous spraying, and the like. Nanoparticles, once dispersed, can remain in a colloidal suspension indefinitely due to Brownian motion. Oxidizing species present in the high temperature water include, but are not limited to, oxygen (O2), hydrogen peroxide (H2O2), and various radicals, such as OH-, and the like. Reducing species include, but are not limited to, hydrogen (H2), hydrazine (N2H2), ammonia (NH3), alcohols, and the like. In a preferred embodiment, a catalytic nanoparticle provides a catalytic surface upon which hydrogen reacts with oxygen and hydrogen peroxide to form water. The reductants may already be present in the high temperature reactor water in equilibrium concentrations. Alternatively, the reductants may be introduced into the high temperature water and dissolved therein. In one such embodiment, an amount of hydrogen gas is introduced into the high temperature water such that the ratio of H2O2in the high temperature water has a value determined by weight of about 1:8. The dielectric nanoparticles preferably comprise a non-noble metal material. Suitable dielectric materials for fabricating the nanoparticles include, but are not intended to be limited to, inorganic or organometallic compounds, metals, zeolites, metal oxides, and the like. Examples of non-noble metals include zirconium, hafnium, niobium, tantalum, yttrium, ytterbium, tungsten, vanadium, titanium, molybdenum, chromium, cerium, germanium, scandium, lanthanum, and nickel. It is also possible to use non-noble metals that possess conducting or semiconducting properties such as carbon, or silicon. The non-noble metal identified above can be used alone or in admixture with other non-noble metals or non-metals. The catalytic nanoparticles preferably comprise at least one of platinum, palladium, osmium, rhodium, ruthenium, iridium, oxides, nitrides, borides, phosphides and mixtures of these metals. Preferably, the plurality of catalytic nanoparticles comprises at least one of palladium, platinum, rhodium, and combinations thereof. Additionally, the plurality of catalytic nanoparticles may comprise other chemical compounds containing at least one of platinum, palladium, osmium, ruthenium, iridium, and rhodium. Such compounds include intermetallic compounds formed with other elements. The ratio of catalytic nanoparticles to dielectric nanoparticles will depend on the desired application and can vary widely as any ratio can be employed. Upon introduction into the reactor, the concentration of the catalytic nanoparticles is preferably less than about 100 parts per billion (ppb), preferably about 1 parts per trillion (ppt) to about 10 ppb, and even more preferably, about 10 ppt to about 1 ppb. The concentration of the dielectric nanoparticles is preferably less than about 100 ppb, preferably about 1 ppt to about 10 ppb, and even more preferably, about 10 ppt to about 1 ppb. In one embodiment of the present invention, the nanoparticles are deposited onto the component surfaces to provide a heterogeneous catalysis site and form a protective insulative layer. In another embodiment however, the plurality of nanoparticles are sufficiently buoyant to remain in a colloidal suspension in the high temperature water and act as homogenous catalysts for the reaction between oxidizing and reducing species within the high temperature water, and also provide insulative properties due to the proximity of the dielectric nanoparticles to the reactor surfaces. The presence of a colloidal suspension of nanoparticles having a high surface area in the BWR waterxe2x80x94when coupled with the presence of a stoichiometric excess of reductantxe2x80x94may cause an increase in radioactivity resulting from increased volatility of N-16 compounds that are produced by transmutation of O-16 to N-16 in the reactor core, otherwise known as xe2x80x9cturbine shine.xe2x80x9d This method of providing the nanoparticles to the high temperature water may require that injection of the reductant (e.g., H2) be temporarily suspended when the nanoparticles are initially introduced into the reactor to minimize the production of N-16 containing species. The electrochemical corrosion potential of the reaction components can be lowered in situ by providing the nanoparticles directly to the reactor feedwater, thus eliminating the need to remove the components for treatment with noble metal powders. The nanoparticles may be provided to the BWR feedwater during reactor operation, thus avoiding expensive and complicated BWR shutdowns. Alternatively, the nanoparticles may be added to the reactor feedwater during a scheduled reactor shutdown. Depending on the needs of the respective nuclear reactor, a predetermined amount of the nanoparticles can be introduced into the high temperature water in the reactor either continuously or incrementally at predetermined time intervals. Predetermined quantities of the catalytic nanoparticles can be introduced into the BWR to obtain a predetermined concentration of the catalytic nanoparticles in the high temperature reactor water. Several options are available for introducing the catalytic nanoparticles in situ into the thigh temperature water to reduce the electrochemical corrosion potential. The nanoparticles can be introduced homogeneously so as to create colloidal floaters within the BWR, wherein the nanoparticles remain in colloidal suspension indefinitely due to Brownian motion. Alternatively, the nanoparticles can be introduced heterogeneously such that the nanoparticles deposit on the BWR component surfaces. The nanoparticles may be provided to the high temperature water by first preparing a concentrated solution or suspension of the nanoparticles, using fluid media well known to those skilled in the art, and subsequently delivering the concentrated suspension to the reactor feedwater. Suitable media for forming such concentrated solutions or suspensions include, but are not limited to: water; alcohols such as methanol, ethanol, propanol, and n-butanol; and acids such as lower carboxylic acids, e.g. acetic acid, propionic acid, and butyric acid; or ketones such as acetone and acetylacetone; and combinations thereof. The nanoparticles may also be entrained in gaseous fluid media, such as air. Alternatively, the nanoparticles may be introduced in nondispersed metallic form into the reactor feedwater. The nanoparticles may be introduced into the high temperature water during various stages of operation of the reactor. The nanoparticles may be provided to the high temperature water in any of the embodiments described above during full power operation, cool down, outage, heat-up, hot standby, or low power operation of the reactor. Moreover, the nanoparticles may be introduced into the high temperature water at any location within the reactor structure where thorough mixing of the nanoparticles in the high temperature water can occur. The locations at which the nanoparticles may be introduced into the high temperature water include, but are not necessarily limited to, residual heat removal (RHR) piping, recirculation piping, feedwater lines, core delta P lines, jet pump instrumentation lines, control rod drive cooling water lines, water level control points, reactor water clean-up (RWCU) systems, and the like. The various lines may be either open or closed to the remainder of the coolant system during introduction of the catalytic nanoparticles. The temperature of the high temperature reactor water when the catalytic nanoparticles are introduced into to the reactor water is typically in the range between about 50xc2x0 C. and about 290xc2x0 C. for BWR reactors, and between about 50xc2x0 C. and about 320xc2x0 C. for PWR reactors. The temperature is generally in the range of 100-177xc2x0 C. and, most frequently, between about 170xc2x0 C. and about 185xc2x0 C. If the nanoparticle addition is performed at full power operation, the reactor water temperature is between about 270xc2x0 C. and about 290xc2x0 C. The following examples are provided to illustrate some embodiments of the present disclosure. They are not intended to limit the disclosure in any aspect. In this example, the catalytic effect of nanoparticle addition in a simulated BWR environment was studied by introducing the platinum nanoparticles into water held at 288xc2x0 C. and containing excess hydrogen. FIG. 3 graphically illustrates the corrosion potential behavior for Type 304 stainless steel electrodes as a function of immersion time in the 288xc2x0 C. high temperature water containing excess the hydrogen (molar ratio H/O=3.0). Prior to injection of 5 ppb of platinum nanoparticles, the corrosion potential was relatively constant at about xe2x88x9250 mV over a 5-day period. Upon addition of the catalytic nanoparticles, the corrosion potential steadily dropped over the next 20 days of monitoring indicating that the catalytic nanoparticles are highly effective in lowering electrochemical corrosion potential in a simulated BWR environment, i.e., a high efficiency of recombination kinetics for oxygen and hydrogen. Thus, the results indicate that the presence of the catalytic nanoparticles catalytically enhances the kinetics in the formation of water by oxygen and hydrogen present in the high temperature water, thereby reducing the electrochemical corrosion potential of the stainless steel electrodes. FIG. 4 is a scanning electron micrograph showing the size and distribution of the platinum nanoparticles on the Type 304 stainless steel oxide surface. The platinum nanoparticles were injected for 12 days to high temperature water at 288xc2x0 C. In this example, in situ deposition of a dielectric nanoparticle was conducted to study the effectiveness of longer in situ deposition times. Coupons of Type 304 stainless steel and alloy 600 were immersed in 288xc2x0 C. water containing 300 ppb of dissolved oxygen for a period of about 31 days. Test electrodes were first immersed in the 300 ppb dissolved oxygen water for a period of about 5 days. After about 5 days, 10 ppm ZrO(NO3)2 was continuously injected into the water for a period of about 14 days, wherein a dramatic initial reduction in ECP is observed for both specimens, as shown in FIG. 5. After about 22 days, the flow of 10 ppm ZrO(NO3)2 into the water was discontinued, wherein a marginal increase in electrochemical corrosion potential was observed. It is evident that the addition of ZrO(NO3)2 to 300 ppb dissolved oxygen water decreased ECP by 50 to 100 mV. Also, the presence of the high oxygen conditions may enhance formation of ZrO2.H2O on the surface of the specimens. Advantageously, the catalytic nanoparticles provide a high efficiency of recombination kinetics, while the dielectric nanoparticles restricts mass transport of oxidants through the oxide layer to the substrate. Moreover, the use of nanoparticles provides a colloidal behavior that permits redistribution to occur. Thus, the presence of the catalytic component on the surface of the dielectric component can reduce the oxidizing power of water, and simultaneously, provide an insulative layer onto surfaces of the reactor. While the disclosure has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this disclosure, but that the disclosure will include all embodiments falling within the scope of the appended claims.
041586395	claims	1. A method of storing gas by high temperature and pressure absorption, adsorption or reaction with a bed of capturing solids comprising the steps for (a) placing the capturing solids in a relatively thin-walled container having an opening therein connectable to a conduit, (b) placing the thin-walled container in a pressurizable autoclave, (c) bringing the opening in the thin-walled container into communication with a conduit extending through the walls of the autoclave and communicating with the source of gas to be stored, (d) heating and simultaneously pressurizing the autoclave and the interior of the thin-walled vessel by pumping gas to be stored into the thin-walled vessel as gas is absorbed, adsorbed or reacted with the bed of solids, (e) cooling and thereafter depressurizing the autoclave and the thin-walled vessel and its contents, and (f) opening the autoclave, sealing said vessel, disconnecting the conduit from the thin-walled vessel and removing a substantially non-pressurized container loaded with absorbed, adsorbed or reacted gases. (a) placing the capturing zeolites in a relatively thin-walled container having an opening therein connectable to a conduit, (b) placing the thin-walled container in a pressurizable autoclave, (c) bringing the opening in the thin-walled container into communication with a conduit extending through the walls of the autoclave and communicating with the source of krypton, (d) heating and simultaneously pressurizing the autoclave and the interior of the thin-walled vessel by pumping krypton to be stored into the thin-walled vessel as gas is absorbed by the bed of zeolite, (e) cooling and thereafter depressurizing the autoclave and the thin-walled vessel and its contents, and (f) opening the autoclave, sealing said vessel, disconnecting the conduit from the thin-walled vessel, and removing a substantially non-pressurized container loaded with absorbed radioactive krypton. 2. A method of storing radioactive krypton or the like by high temperature and pressure absorption with a bed of capturing zeolites comprising the steps for 3. A method according to claim 2 wherein in step (d) the contents of the autoclave are heated to a temperature in excess of 500.degree. C. and the pressure in the autoclave is raised to at least 15,000 psi.
	abstract	A system and method for detection of special nuclear materials within a larger space is disclosed and claimed. Gamma rays emitted from special nuclear materials upon neutron interrogation detected. An associated-particle neutron generator provides interrogation neutrons.
	summary
	summary
	abstract	A closed drift ion source is provided, having an anode that serves as both the center magnetic pole and as the electrical anode. The anode has an insulating material cap that produces a closed drift region to further increase the electrical impedance of the source. The ion source can be configured as a round, conventional ion source for space thruster applications or as a long, linear ion source for uniformly treating large area substrates. A particularly useful implementation uses the present invention as an anode for a magnetron sputter process.
	claims	1. A method of optimizing a model of a pipe network with respect to a predetermined criteria, the method comprising modifying a starting proposal for a list of pipes within the network model which may be modified by performing the following operations: i) selecting a first pipe from the pipe list which may be considered for modification; ii) proposing a modification to the selected pipe which provides an incremental improvement in said criteria; iii) performing a network analysis of at least one predetermined operating parameter of the network to predict whether a predefined operating limit of said operating parameter will be violated as a result of the modification; iv) if said network analysis predicts a violation of said predefined operating limit, then rejecting the proposed modification and removing the respective pipe from consideration for any further modification; v) selecting a next pipe from the pipe list which may be considered for modification and performing operations (ii) to (iv) on the selected pipe; vi) repeating operation (v) until all pipes which may be considered for modification have been selected; and vii) repeating operations (i) and (vi) until no pipes of the pipe list remain to be considered for further modification. 2. A method according to claim 1 , wherein said at least one predetermined operating parameter is the peak flow rate any particular pipe must be able to provide, said peak flow rate for said any particular pipe determined by: claim 1 a) totaling the peak flow for the whole network and distributing this across the network to give a network peak flow demand on said any particular pipe; b) deriving a local peak flow demand representative of the localized demand on said any particular pipe of the network; and c) combining the network peak flow demand with the local peak flow demand to arrive at a peak flow rate demand for said any particular pipe in the network. 3. A method according to claim 2 , wherein the determination of the local peak demand flow comprises: claim 2 a) performing a network analysis on the network model at the peak flow time to determine the network peak flow pattern; b) identifying each source or pseudo-source within the network model. c) identifying each node which receives convergent in flows from two or more pipes within the network model; d) treating each source and/or node identified above as the origin of a pipe tree having one or more branches each comprising one or more pipes, each branch terminating at a downstream convergent node or terminal node; e) estimating the local demand on each pipe tree branch and assuming this estimate to be the local peak flow demand for said any particular pipe in the respective branch. 4. A method according to claims 3 , wherein the network peak flow demand is determined by estimating the through flow through each pipe tree branch required to meet network demand downstream of the branch, giving a branch through flow demand, and for each pipe summing the branch through flow demand for each branch of which that pipe is a part to arrive at the network peak demand for that pipe. 5. A method according to claim 4 , wherein the branch through flow is taken to be the contribution made by the flow through that branch to the network flow immediately downstream of the node at which the branch terminates. claim 4 6. A method according to claim 5 , wherein said contribution is obtained as the ratio of the flow through the downstream pipe of the branch to the total network flow converging at the node at which the downstream pipe of the branch terminates, multiplied by the total network flow immediately downstream of the node. claim 5 7. A method according to claim 3 , wherein the local peak demand for said any particular pipe is estimated by determining the relative demand of the users supplied by each pipe in a pipe tree branch, and estimating the required flow through each pipe in the pipe tree branch required to meet the local demand on the pipe tree branch. claim 3 8. A method according to claim 7 , wherein said estimating comprises combining the direct local peak demand on each pipe in a pipe tree branch with an indirect local demand on each pipe which is the contribution made by flow through the respective pipe to the direct local demand on each downstream pipe in the same pipe tree branch. claim 7 9. A method according to claim 1 , wherein the starting proposal is selected as the proposal offering the greatest optimization of said predetermined criteria from a database of possible proposals available for consideration. claim 1 10. A method according to claim 9 , wherein said starting proposal is taken as an initial starting proposal and further comprising the operations of: claim 9 a) performing a first revision of the initial starting proposal to revise the proposal for at least some of the pipes in the pipe list to a proposal less likely to result in a violation of said predefined operating limit; b) performing a network analysis of said at least one predetermined operating parameter of the network to predict whether the predefined operating limit will be violated on the basis of said first revision; c) if said network analysis predicts a violation of said predefined operating limit, then performing a second revision of the starting proposal for each pipe in the list, said second revision comprising adopting a proposal for each pipe which is least likely to produce a violation in said predefined operating limit from the possible proposals available for consideration. 11. A method according to claim 10 , wherein in performing said first revision the proposal for each of the pipes in the pipe list is revised by proposing an increased size for each pipe compared to the size proposed for the initial starting proposal. claim 10 12. A method according to claim 11 , wherein in performing the first revision the proposal for a selection of the most hydraulically significant pipes is increased in size by a greater magnitude than the proposal for pipes of lesser hydraulic significance. claim 11 13. A method according to claim 10 , wherein the pipe list comprises existing pipes selected for rehabilitation within the pipe network and further comprising the following operations: claim 10 d) performing a network analysis to determine whether the second revision of the starting proposal is predicted to result in a violation of said at least one predefined operating limit; e) if no operating limit violation is predicted, adopting said second revision as the starting proposal, otherwise performing a third revision of the starting proposal corresponding to the existing pipes in the network; f) performing a network analysis to determine whether the existing network is predicted as producing a violation of said at least one predefined operating limit; and g) if the network analysis predicts a violation then adopting the second revision as the starting proposal, otherwise increasing the size of each pipe proposal above the size of the corresponding existing pipe by a single size step. 14. A method according to claim 1 , wherein the modification of operation (ii) is selected from a database of possible modifications. claim 1 15. A method according to claim 14 , wherein the possible modifications are ordered in said database by reference to the magnitude of the improvement they provide in said criteria. claim 14 16. A method according to claim 15 , wherein the modification operation (ii) comprises selecting from the database of possible modifications the modification which provides the smallest improvement in said criteria. claim 15 17. A method to claim 14 , wherein the criteria is cost and the modification operation (ii) proposes a modification selected from a database of possible modifications and their associated costs, wherein the selected modification is the modification providing the smallest decrease in costs from the current proposal. claim 14 18. A method according to claim 1 , wherein the list of pipes comprises a selection of pipes from the network model. claim 1 19. A method according to claim 18 , wherein the pipe list comprises a selection of pipes to be rehabilitated within the model of a pipe network modeled by the network model. claim 18 20. A method according to claim 18 , wherein the pipe list is compiled by performing a filter operation on the full pipe list to select pipes satisfying specified filter conditions. claim 18 21. A method according to claim 1 , wherein the pipes are selected for modification in an order based on the hydraulic significance of each pipe within the network model. claim 1 22. A method according to claim 21 , wherein the pipe ordering is the reverse of their hydraulic significance. claim 21 23. A method according to claim 1 , wherein the model of a pipe network modeled is a water supply and/or distribution network. claim 1 24. A method according to claim 23 , wherein the network is a model of a predefined metering district of a water supply and/or distribution network. claim 23 25. A method according to claim 1 , wherein said at least one predetermined operating parameter includes one or more of a maximum acceptable hydraulic gradient, minimum and maximum permissible pressures specified for elements of the network, minimum and maximum flow rates through particular elements of the network, minimum tank levels and minimum and maximum permissible pipe sizes. claim 1 26. A method according to claim 1 , wherein the list of pipes comprises every pipe in the network model. claim 1 27. A method according to claim 1 , wherein said network model is a part of a larger network or network model. claim 1 28. A method according to claim 1 , wherein said predetermined criteria is the cost of installing or rehabilitating pipes within the network, or of operating the network. claim 1 29. A computer program comprising computer readable program code for executing a method according claim 1 . claim 1 30. A program storage device readable by a machine and encoding a program of instructions for executing the method according to claim 1 . claim 1 31. A computer system comprising means for operating a method according to claim 1 . claim 1 32. A method of determining peak flow rate demands on pipes within a model of a pipe network, the method comprising: a) totaling the peak flow rate demands for the whole network and distributing this across the network to give a network peak flow demand on each pipe; b) deriving a local peak flow demand representative of the localized demand on each pipe of the network; and c) combining the network peak flow demand with the local peak flow demand to arrive at a peak flow rate demand for each pipe in the network. 33. A method according to claim 32 , wherein the derivation of the local peak flow demand comprises: claim 32 a) performing a network analysis on the network model at the time of peak flow to determine the network peak flow pattern; b) identifying each source or pseudo-source within the network model; c) identifying each node which receives convergent in flows from two or more pipes within the network model; d) treating each source and/or node identified above as the origin of a pipe tree having one or more branches each comprising one or more pipes, each branch terminating at a downstream convergent node or terminal node; e) estimating a local demand on each pipe tree branch and assuming this estimate to be the local peak flow demand for each pipe in the respective branch. 34. A method according to claim 30 , wherein the network peak flow demand is determined by: claim 30 i) estimating the through flow through each pipe tree branch required to meet network demand downstream of each said pipe tree branch to derive a branch through flow demand for each said pipe tree branch; and ii) for each pipe, summing the branch through flow demand of each said pipe tree branch that includes the said each pipe to arrive at the network peak demand for the said pipe. 35. A method according to claim 34 , wherein the branch through flow is taken to be the contribution made by the flow through that branch to the network flow immediately downstream of the node at which the branch terminates. claim 34 36. A method according to claim 35 , wherein said contribution is obtained as the ratio of the flow through the downstream pipe of the branch to the total network flow converging at the node at which the downstream pipe of the branch terminates, multiplied by the total network flow immediately downstream of the node. claim 35 37. A method according to claim 33 , wherein the local peak demand for each pipe is estimated by determining a relative demand of the users supplied by each pipe in a pipe tree branch, and estimating the required flow through each pipe in the pipe tree branch required to meet the local demand on the pipe tree branch. claim 33 38. A method according to claim 37 , wherein said estimating comprises combining a direct local peak demand on each pipe in a pipe tree branch with an indirect local demand on each pipe which is the contribution made by flow through the respective pipe to the direct local demand on each downstream pipe in the same pipe tree branch. claim 37 39. A computer program comprising computer readable program code for executing a method according claim 32 . claim 32 40. A program storage device readable by a machine and encoding a program of instructions for executing the method according to claim 32 . claim 32 41. A computer system comprising means for operating a method according to claim 32 . claim 32 42. A method of determining the hydraulic significance of each of a list of pipes within a model of a pipe network, the method comprising: i) performing a network analysis on the network model to determine the flow patterns through the network at a given time; ii) counting the number of instances of each pipe occurring in a flow path between a source node defined by the network model and the boundary of the network model, and using the instance count for each pipe as the indication of the hydraulic significance of that pipe within the network, such that pipes with a higher instance count are considered to be more hydraulically significant than pipes with a lower instance count. 43. A method according to claim 42 , wherein operations (i) and (ii) are performed for a number of different times over a predetermined time period and the instance count of each pipe determined at each time is summed to give a total instance count for each pipe which is used as an indication of a hydraulic significance of that pipe within the network. claim 42 44. A method according to claim 43 , wherein the times are 30 minute intervals over a 24 hour period modeled by the network. claim 43 45. A method according to claim 42 wherein the instance count is made by considering each node defined by the network model in turn and the pipe or pipes which converge or terminate at each node, and increasing the instance count for each pipe occurring at least once in a flow path to that node through the or each pipe terminating or converging at that node. claim 42 46. A method according to claim 42 , wherein the instance count is made by considering each pipe in turn and implementing the instance count for each pipe occurring at least once in a flow path through the selected pipe. claim 42 47. A computer program comprising computer readable program code for executing a method according claim 42 . claim 42 48. A program storage device readable by a machine and encoding a program of instructions for executing the method according to claim 42 . claim 42 49. A computer system comprising means for operating a method according to claim 42 . claim 42 50. A method of according to claim 21 , wherein the hydraulic significance of each pipe of the pipe list is determined by: claim 21 i) performing a network analysis on the network model to determine the flow patterns through the network at a given time; ii) counting the number of instances of said each pipe occurring in a flow path between a source node defined by the network model and the boundary of the network model, and using the instance count for each pipe as the indication of the hydraulic significance of said each pipe within the network, such that pipes with a higher instance count are considered to be more hydraulically significant than pipes with a lower instance count. 51. A method according to claim 50 , wherein operations (i) and (ii) are performed for a number of different times over a predetermined time period and the instance count of said each pipe determined at each time is summed to give a total instance count for said each pipe which is used as an indication of a hydraulic significance of said each pipe within the network. claim 50 52. A method according to claim 51 , wherein the times are 30 minute intervals over a 24 hour period modeled by the network. claim 51 53. A method according to claim 50 , wherein the instance count is made by considering each node defined by the network model in turn and the pipe or pipes which converge or terminate at each node, and increasing the instance count for each pipe occurring at least once in a flow path to that node through said each pipe terminating or converging at that node. claim 50 54. A method according to claim 50 , wherein the instance count is made by considering said each pipe in return and implementing the instance count for each said pipe occurring at least once in a flow path through the selected pipe. claim 50
	description	1. Field of the Invention The present invention relates to an ex-core nuclear instrumentation system that monitors neutron flux outside a reactor vessel and, more particularly, relates to an ex-core nuclear instrumentation panel that constitutes the ex-core nuclear instrumentation system. 2. Description of the Related Art An ex-core nuclear instrumentation system continuously monitors a neutron flux outside a reactor vessel of a pressurized water reactor (PWR) and accordingly the state of the reactor at start and in operation is monitored; and when an abnormality is detected in the condition of the neutron flux, the ex-core nuclear instrumentation system outputs an alarm signal and a signal for emergency shutdown of the reactor and accordingly the reactor is protected. The ex-core nuclear instrumentation system mainly includes a neutron detector that measures the neutron flux and converts the neutron flux into a current value and an ex-core nuclear instrumentation panel that performs arithmetic processing of the converted current value to convert into the signals. Generally, a neutron measurement range of the ex-core nuclear instrumentation system is divided into a neutron source range, an intermediate range, and an output range (operation range) depending on the level of neutron flux from a stopped state to output operation of the reactor. The structure and function of the neutron detector and the ex-core nuclear instrumentation panel is different for each range, and a detector signal processing circuit (I/E amplifier, that is, current/voltage amplifier) is used for performing arithmetic processing of the output range. An ex-core nuclear instrumentation system includes a neutron detector and an ex-core nuclear instrumentation panel as above-mentioned. A plurality of the neutron detector is located around outside a reactor vessel to be provided inside a reactor containment vessel. The neutron detector measures neutron flux leaked from the reactor vessel and converts the neutron flux into a current value. The current value is inputted to a detector signal processing circuit of the ex-core nuclear instrumentation panel and is converted into an output voltage corresponding to a reactor power level. Then, the output voltage of the detector signal processing circuit is inputted to a signal processing card. The signal processing card performs analog/digital (A/D) conversion and engineering value conversion, and outputs various signals to an operation panel and an input and output card in a reactor protection based system. Further, the measured data which is converted into digital data is stored in an electrically rewritable storage device such as EEPROM (Electronically Erasable and Programmable Read Only Memory) (registered trademark). Here, in order to correct the aged deterioration of a neutron detector itself, an amplifier of a detector signal processing circuit, etc., calibration work is required (For example, Japanese Unexamined Patent Publication No. 2000-266884). The calibration work is performed via an operation panel by an operator. In performing the calibration work, in some cases, work of rewriting the data stored in the storage device is generated. Regarding conventional ex-core nuclear instrumentation systems, FIG. 4 is a block diagram showing an example of a memory access structure for rewriting the data which is stored in a storage device. The memory access structure includes a signal processing card 111, on which a CPU 220, a FPGA (Field Programmable Gate Array) 230 and an electrically rewritable nonvolatile memory 240 such as an EEPROM (registered trademark) are equipped, and an operation panel 120 which is operated by a human being from outside. The operation panel 120 is provided at an electronic substrate 310 which is separated from the signal processing card 111. The CPU 220 mainly performs control of signal processing or performs arithmetic processing. The data is inputted from the operation panel 120 by communicating with the FPGA230. When the data is inputted, a write signal which is transmitted from the CPU is processed by a software with FPGA 230, and the FPGA230 directly rewrites the data which is stored in the nonvolatile memory 240. Memory access of rewriting data in conventional ex-core nuclear instrumentation systems are configured as above-mentioned. It is configured such that when the data is rewritten by inputting the data from an operation panel, the operation is performed via software processing with FPGA, therefore the operation is not performed by directly accessing to memory from CPU. In a case of memory access via FPGA, there is a problem such that the processing inside the FPGA is a black box, therefore operation can not be understood only by a circuit diagram. Further, there also other problems such that a nonvolatile memory does not have a reset function, therefore, at the start of power supply, etc, false writing into the memory might be generated, or in a case where erroneous operation of operation panel is performed, the data in the memory might be rewritten. In order to solve the above-mentioned problems, this invention was made. An objective of this invention is to provide an ex-core nuclear instrumentation system in which false writing into a memory can be prevented under various kinds of situation so as to secure more safety. An ex-core nuclear instrumentation system according to this invention includes neutron detectors which measure neutron flux leaked from a reactor vessel and convert the neutron flux into a current value, a detector signal processing circuit which converts the converted current value into a voltage value, a signal processing card which performs arithmetic processing using a voltage value which is converted in the detector signal processing circuit so as to input the state of neutron flux during the operation of the reactor, and an operation panel having a man machine interface, wherein the signal processing card includes a CPU, a FPGA, an electrically rewritable nonvolatile memory and a key hole, it is configured such that in the state where a key lock switch is inserted into the key hole, by a general-purpose logic, writing to the electrically rewritable nonvolatile memory is made valid, and when writing to the electrically rewritable nonvolatile memory is in valid and the operation panel and the FPGA perform a serial communication and in a case where the data order of the serial communication is the predetermined data order, the CPU controls the electrically rewritable nonvolatile memory, and rewrite data, which is outputted from the operation panel, to the electrically rewritable nonvolatile memory is transmitted from the FPGA to the electrically rewritable nonvolatile memory so as to rewrite the data in the electrically rewritable nonvolatile memory. According to this invention, a reliable ex-core nuclear instrumentation system in which false writing to a memory can be prevented under various kinds of situations can be provided. Embodiment 1 FIG. 2 is a configuration diagram showing a general configuration of an ex-core nuclear instrumentation system. In FIG. 2, a neutron detector 3 of an ex-core nuclear instrumentation system 14 is provided around outside a reactor vessel 16 which is located in a reactor containment vessel 15. The neutron detector 3 is one in which an upper detector 4 and a lower detector 5 are integrated. The upper detector 4 detects neutron flux leaked from an upper part of the reactor vessel 16 and converts the neutron flux into a current value; and the lower detector 5 detects a neutron flux leaked from a lower part of the reactor vessel 16 and converts the neutron flux into a current value. The current value converted by the upper detector 4 is inputted to a detector signal processing circuit 8 located in an ex-core nuclear instrumentation panel 1 of the ex-core nuclear instrumentation system 14 via an upper detector cable 6, the ex-core nuclear instrumentation panel 1 being usually located outside the reactor containment vessel 15. The current value converted by the lower detector 5 is also similarly inputted to the detector signal processing circuit 8 via a lower detector cable 7. The detector signal processing circuit 8 has a circuit corresponding to the upper detector 4 and a circuit corresponding to the lower detector 5, respectively; and, by the detector signal processing circuit 8, the current values are converted into an output voltage signal for the upper detector 9 and an output voltage signal for the lower detector 10. Both of the output voltage signals 9 and 10 are inputted to a signal processing card 11 in the ex-core nuclear instrumentation panel 1. The signal processing card 11 performs analog/digital (A/D) conversion and engineering value conversion, and data communication of various kinds of signals is performed by serial communication with an operation panel 12 which is provided at an electronic substrate 31 which separates from the signal processing card 11 or with a reactor protection board 18. The details of the signal processing card 11 according to embodiment of this invention are shown in FIG. 1. The output voltage signal for the upper detector 9 and the output voltage signal for the lower detector 10 which are transmitted from the detector signal processing circuit 8 are inputted to an A/D converter 110 so as to be converted into a digital signal, and then is inputted to a first FPGA (Field Programmable Gate Array) 231. Further, the detector signal processing circuit 8 has a man machine interface such as an indicator 83, an input key 82, etc. in a front operation panel 80. From the front operation panel 80, for example, the gain of an amplifier in the detector signal processing circuit 8 can be set. The gain value is inputted also to the first FPGA 231 via a serial communication line 84. The indicator 83 indicates the gain when the gain is set or indicates an engineering value or a trip set value. On the other hand, an operation panel 12 also has a man machine interface such as an indicator 123, an input key 122, etc. From the operation panel, a trip set value is changed or a gain is set. Further, from the operation panel 12, for periodical adjustment, or calibration work, a test signal is transmitted to the detector signal processing circuit 8 via a card for test calibration 17 so as to perform adjustment and calibration work. Further, from the front operation panel 80 in the detector signal processing circuit 8, as above-mentioned, a gain of an amplifier in the detector signal processing circuit 8, etc. is set. On the other hand, from the operation panel 12, when the sensitivity of the neutron detector 3 itself such as the upper detector 4 or the lower detector 5 is changed due to its aged deterioration, a correction coefficient as the amount of variation is set. From the operation panel 12, in a case where abnormalities exceeding a predetermined level or fault are generated, a trip set value is set so as to change a neutron flux high trip (high set) value for making an emergency stop. The operation panel 12 performs serial communication with a second FPGA 232 via a serial communication line 124 so as to write again value, which is set by the operation panel 12, in an electrically rewritable nonvolatile memory 24 from the second FPGA 232. As above-mentioned, in the electrically rewritable nonvolatile memory 24, in addition to set value data which is transmitted from the detector signal processing circuit 8, set value data which is transmitted from the operation panel 12, an invariable value such as device numbers which are determined by signal processing card unit or a device numbers of a reactor protection board 18 which is a communication connecting party is stored. Here, memory access structure will be described. Data to the electrically rewritable nonvolatile memory 24 is transmitted from the first FPGA 231 and the second FPGA 232. Memory access control is performed by a CPU 22. However, in a case where writing data to the electrically rewritable nonvolatile memory 24 is always capable, there is the risk such that false writing is made. Therefore, in the signal processing card 11, a key hole 25 for physically limiting memory access is provided. The key hole 25 outputs a signal for limiting the access to the electrically rewritable nonvolatile memory 24 via a general-purpose logic 27. When the key hole 25 is not opened, a write signal which is transmitted from the CPU 22 via the first FPGA 231 is made invalid by the general-purpose logic 27, therefore an access of the electrically rewritable nonvolatile memory 24 is limited by the general-purpose logic 27. When the key hole 25 is opened by a key lock switch 26, a write signal which is transmitted from the CPU 22 via the first FPGA 231 is made valid by the general-purpose logic 27. Consequently, data which is stored in the electrically rewritable nonvolatile memory 24 can be rewritten. Further, in a case where the keyhole 25 is not opened by the key lock switch 26, a write protect (WP) lump 81 in the front operation panel 80 in the detector signal processing circuit 8 or a write protect lump 121 in the operation panel 12 is lighted up, and it indicates the state in which data including the change of a set value can not be rewritten to the electrically rewritable nonvolatile memory 24. Further, by providing a write protect lump 251 in the signal processing card 11, the state of memory access limitation can be recognized more accurately. The configuration of the CPU 22, the first FPGA 231, the second FPGA 232 and the electrically rewritable nonvolatile memory 24 shown in FIG. 1 are different from those of CPU 220, FPGA 230, and the electrically rewritable nonvolatile memory 240 shown in FIG. 4, respectively. That is, as the state of the key hole 25 controls the write signal (WR) of the electrically rewritable nonvolatile memory 24 via the general-purpose logic 27, the state of write protect is the configuration which can be recognized by means of a circuit. Operation will be described with reference to FIGS. 1, 2 and 3. The CPU 22 mainly performs control or arithmetic processing of signal processing so as to process a signal of the neutron detector 3 which is inputted from the detector signal processing circuit 8. On the other hand, output from the operation panel 12 is inputted to the second FPGA 232 by performing serial communication with the second FPGA 232 which is connected with the operation panel 12 with a serial communication line. As an example of inputting data from the operation panel 12, in a case where the sensitivity of the neutron detector 3 is changed, in order to correct the set value data, which is stored in the electrically rewritable nonvolatile memory 24, such as magnification of arithmetic, (correction coefficient), there is an operation for rewriting the set value data which is stored in the electrically rewritable nonvolatile memory 24 by inputting new set value data. The above-mentioned state, in which the data in the electrically rewritable nonvolatile memory 24 is required to rewrite, does not occur so often. Then, it is configured such that the operation of rewriting the data can be executed only after the key hole 25 is opened by the key lock switch 26. In performing an operation other than the operation of rewriting the data which is stored in the electrically rewritable nonvolatile memory 24, there is a case in which an operator inputs the data from the operation panel 12. That is, a signal which is outputted from the operation panel 12 includes a signal other than a signal to the electrically rewritable nonvolatile memory 24. For example, there is a following example. In FIG. 2, the detector signal processing circuit 8 includes a current/voltage conversion amplifier, and a card for test calibration 17 is provided so as to calibrate the current voltage conversion amplifier. In a case where a current voltage conversion amplifier is calibrated, a signal for calibrating is outputted from the card for test calibration 17 so as to calibrate the current voltage conversion amplifier. Ina case where a test calibration is executed, the operation panel 12 is operated by an operator, and a command is transmitted from the operation panel 12 to the card for test calibration 17. In this time, operation for rewriting the data in the electrically rewritable nonvolatile memory 24 is not executed. However, in some cases, an operator may perform the operation for rewriting the data by mistake. In the configuration of FIG. 1, as long as the key hole 25 is not opened by the key lock switch 26, data in an electrically rewritable nonvolatile memory can not be rewritten. As above-mentioned, only in the case of operation for rewriting the data which is stored in the electrically rewritable nonvolatile memory 24, after the key hole 25 is opened by an operator with the key lock switch 26, operation for rewriting the data is executed from the operation panel 12 or the front operation panel 80. When the key hole 25 is opened, the general-purpose logic 27 makes an access to the electrically rewritable nonvolatile memory 24 valid. Under the above-mentioned state, for example, when data is transmitted from the operation panel 12 to the second FPGA 232, the CPU 22 transmits a write signal to the electrically rewritable nonvolatile memory 24 via the first FPGA 231 and the general-purpose logic 27. Consequently, the data to be rewritten which is transmitted from the second FPGA 232 can be received by the electrically rewritable nonvolatile memory 24. Further, the electrically rewritable nonvolatile memory 24 has a reset function. Upon starting up a power source, in an inner circuit in the electrically rewritable nonvolatile memory 24 and an external circuit thereof, a power source is started up by passing through a low voltage region in which the voltage is unstable. Therefore, it is configured such that, by providing a power supply monitoring circuit 28, an internal part of the electrically rewritable nonvolatile memory 24 is completely reset until a power supply starts normally so as to start up. As above-mentioned, as the memory access is limited by physical access limitation of the key hole 25, only when the data in the electrically rewritable nonvolatile memory 24 is rewritten, the data is securely rewritten. In performing operation other than operation of rewriting data, access limitation to the electrically rewritable nonvolatile memory 24 is executed by the key hole 25. Consequently, the data in the electrically rewritable nonvolatile memory 24 can not be rewritten. For example, false writing in starting up of an electric power can be prevented. Further, in performing operation, other than rewriting the data in the electrically rewritable nonvolatile memory 24, which is executed by the operation panel 12 or the front operation panel 80, rewriting the data in the electrically rewritable nonvolatile memory 24 by mistake can be prevented. Operation of rewriting the data will be concretely explained by flow chart shown in FIG. 3. In the state where the key hole 25 is closed, rewriting the data in the electrically rewritable nonvolatile memory 24 is prohibited. Therefore, a WP (write protect) lump 121 of the operation panel 12 is lighted up so as to inform an operator of the above-mentioned state. When the operator intends to execute the operation of data rewriting, the operator is supposed to check whether the WP lump 121 of the operation panel 12 is lighted up or not (ST1). When the operator checks such that the WP lump 121 is lighted up, the key lock switch 26 is inserted into the keyhole 25 so as to unlock the keyhole 25 (ST2). When the key hole 25 is unlocked, the WP lump 121 of the operation panel 12 is turned off (ST3) so as to inform the operator of the state in which the lock is unlocked. In the step ST1, in a case where the WP lump 121 of the operation panel 12 is not lighted up, the lock of the key hole has been already unlocked; therefore, it is not necessary to perform the operation of unlocking the key by the key lock switch 26. When it is checked such that the WP lump of the operation panel is turned off, write data is set from the operation panel (ST4). When it is checked such that the set value is correct, an EN(set) key of the operation panel is pressed down (ST5), set value data is inputted from the operation panel 12 to the second FPGA 232, and operation of writing data in the electrically rewritable nonvolatile memory 24 is executed (ST6). After the execution of operation of writing data is completed, by pulling the key lock switch 26 from the key hole 25, the key hole 25 is locked (ST7), the WP lump of the operation panel is lighted up (ST8), and it is informed to the operator such that data can not be rewritten. As above-mentioned, the ex-core nuclear instrumentation system according to the present invention is configured such that in the state where the key lock switch 26 is inserted into the key hole 25, via the general-purpose logic 27, data can be rewritten in the electrically rewritable nonvolatile memory 24. In addition to that, the ex-core nuclear instrumentation system according to the present invention is configured such that when data can be rewritten in the electrically rewritable nonvolatile memory 24, the operation panel 12 and the second FPGA 232 perform serial communication, and in a case where the order of the data of the serial communication is a predetermined order of the data, the electrically rewritable nonvolatile memory 24 is controlled by the CPU 22. Consequently, it is configured such that rewriting data, which is outputted from the operation panel 12, to the electrically rewritable nonvolatile memory 24 is transmitted from the second FPGA 232 to the electrically rewritable nonvolatile memory 24 so as to rewrite the data in the electrically rewritable nonvolatile memory 24. As above-mentioned, rewriting data to the electrically rewritable nonvolatile memory 24 from the operation panel 12 was explained. In rewriting data to the electrically rewritable nonvolatile memory 24 from the front operation panel 80, such as gain set which is set from the front operation panel 80 in the detector signal processing circuit 8, data is transferred via a serial communication line 84 between the front operation panel 80 and the first FPGA 231. In this time, as clear from the configuration of FIG. 1, in the same way as that of rewriting the data to the electrically rewritable nonvolatile memory 24 from the operation panel 12, access limit which is made by the key hole 25 and the key lock switch 26 is valid. As above-mentioned, in the embodiment of the present invention, it is configured such that only when the key hole 25 is opened by the key lock switch 26, the data which is stored in the electrically rewritable nonvolatile memory 24 can be rewritten, and when the key hole 25 is not opened by the key lock switch 26, rewriting the data in the electrically rewritable nonvolatile memory 24 is not permitted. Further, reset function is added to the electrically rewritable nonvolatile memory 24, it is configured such that the reset function works in the unstable state when a power supply starts. Therefore, there is not any risk such that the data in the electrically rewritable nonvolatile memory 24 is rewritten by false operation of operator or when a power supply starts up.
043022847	abstract	A toroidal plasma device has a toroidal confinement vessel defining a toroidal space and confining ionized gas therein. A solenoid which links the toroidal space induces a toroidal electric field therein to produce plasma current. A plurality of first windings are wound substantially helically around the vessel substantially equally spaced around its minor circumference. A plurality of second windings are wound substantially helically around the vessel substantially midway between successive first windings. Direct current is passed through the respective first and second windings in opposite directions with the current in the respective first and second windings equal or slightly unbalanced. The currents in the first and second windings produce a helical magnetic field. The combination of the poloidal magnetic field from the plasma current with this helical magnetic field produces a separatrix in the toroidal space, this separatrix defining a closed surface which limits and encloses a region within which closed and nested magnetic flux surfaces exist. The sense of rotation of the first and second windings and the direction of the plasma current produces a variation in the safety fractor q with minor radius at any poloidal angle, whereby the sign of q reverses near the outer edge of the plasma, q being an average over a flux surface of the number of transit made around the torus in the toroidal direction by a magnetic flux line in making a single transit in the poloidal direction. The sign of q is determined by the sense of the direction in which the toroidal transit is made.
056299648	description	DETAILED DESCRIPTION OF THE INVENTION To provide a concise and appropriate description, alternative terminology may be employed depending on the context. In particular, a neutron absorbing plate may be alternatively referred to as neutron absorber, or simply as absorber. The perspective view of a preferred embodiment of the invention for use with BWR fuel assemblies illustrated in FIG. 1A shows the invention to comprise a neutron absorber plate 1, a right lower fuel assembly clip 6A, a left lower fuel assembly clip 6B, a mounting plate 15 with a plurality of flow holes, such as hole 15A, an aperture 16, and a latch 17. The neutron absorber plates are typically 13 to 14 feet in length, but only 5 inches in width. To conveniently illustrate these plates in FIG. 1A, their midsection has ben shown as broken away along the lines at drawing numeral 4. For this configuration, the neutron absorber plate 1 has been folded to form two plates a right plate 2 and a left plate 3. These plates are positioned generally orthogonal to one another to fit about two sides of the generally rectangular fuel assemblies. The upper ends of these plates are connected to two adjacent outer edges of the mounting plate, while the right and left clips, 6A and 6B are connected to lower ends of the right and left absorber plates respectively. These clips extend outward from the the absorber plates to grip the lower end of the fuel assembly. The neutron absorber plate is formed of thee layers, a backing plate 25, a neutron absorbing sheet, such as sheet 26B, and a cover plate, such as 27B. There is usually a separation 25A on the backing plate between the mounting plate 15 and the top of a cover plate, such as cover plate 27A. There is no need to extend the neutron absorbing sheet 26B to the top of the backing plate because there is no fuel in the fuel assembly in this area. The fabrication and assembly of the invention are described in greater detail in the description of FIG. 6. As has been noted, the configuration of the invention shown in FIG. 1A is referred to as the chevron configuration because of the orthogonal positioning of the absorber plate which has been designed to fit about a generally rectangular fuel assembly, such as the fuel assembly 7 shown in FIG. 2. The BWR fuel assembly shown in FIG. 2 can be seen to comprise a flow channel 8, an upper fuel tie plate 9 with a plurality of apertures such as 9A and 9B which are designed to accept the upper end of fuel rods, such as fuel rod 9C, a fuel rod interim spacer 11, a lower fuel rod tie plate 13, a bail 14, and a flow channel corner plate 10. Since this fuel assembly has an aspect ratio similar to that of the neutron absorber plate shown in FIG. 1, the midsection of the fuel assembly in FIG. 2 has been shown as broken away at drawing numeral 12 for convenience of illustration. The basic function of the fuel assembly is to provide a means of conveniently handling a plurality of fuel rods while maintaining a prescribed spacing between the rods. Typically, the fuel rods are oriented parallel to one another and are spaced apart by a distance of approximately 3/8 of an inch. This is accomplished by fastening the rods in apertures, such as 9A and 9B, in the upper tie plate and in similar apertures in the lower tie plate. The bail, which is mounted on the upper surface of the upper tie plate, is used as the principal means of lifting and transporting the fuel assembly about a power station. It is particularly useful in raising and lowering the fuel assembly in and out of the fuel storage rack. The flow channel, which is secured to both the upper an lower tie plates, is used to aid in directing the flow of water about the fuel rods while the fuel assembly is in the reactor core. The flow channel includes two spacer buttons 55 whose purpose is to provide the proper spacing between adjacent fuel assemblies in the reactor core. These buttons extend generally 0.316 inch outwardly from two sides of the flow channel as can be seen in FIG. 2. The outward extension of these buttons make it difficult to closely fit neutron absorbers about all four sides of the fuel assembly because of the mechanical interference which would occur on the two sides of the fuel assembly containing these spacer buttons. This is a problem with prior art neutron absorber that attempt to cover all four sides without making provision for these buttons. However, the chevron configuration of the present invention shown in FIG. 1A and 1B covers only two sides of the fuel assembly and can easily accommodate these buttons. The orthogonal cross section of the absorber plate in the chevron configuration can be seen in FIG. 1B. This Figure is a plan view of the present invention with the upper section removed to clearly show the orthogonal orientation of the right and left absorber plates. This cross sectional view shows the location of the neutron absorber sheets 26A and 26B, covering plates 27A and 27B, and backing plate 25. This Figure also shows lower end mounting clips 6A and 6B located at the lower end of the absorber plate. When the invention is in place about a fuel assembly, these clips extend about the lower end of the flow channel to hold the lower end of the invention to the fuel assembly. The upper end of the invention for BWR fuel assemblies is secured to the fuel assembly by means of the latch 17 which can be seen in FIG. 1A secured to the upper surface of the mounting plate. The latch is shown in greater detail in FIGS. 3 and 4A. FIG. 3 is a plan view of the mounting plate 15, showing the latch 17 and its principal components, a captured screw 24, a hinge 19 and a tongue 20. The hinge rotatably connects the tongue to the mounting plate. The hinge includes trunnions 19A and 19B. The point of rotation is shown more clearly in the side view of the latch provided by FIG. 4A. In this Figure, the latch tongue is cross hatched from upper left to lower right to distinguish it from the mounting plate, which is cross hatched in the opposite direction, upper right to lower left. The tongue passes through an aperture 15B in the mounting plate where the hinge connects the tongue to the cover plate. FIG. 4A shows the details of one embodiment of the hinge. In this embodiment, the hinge comprises a cylindrical port 19C passing through the tongue to accept the two trunnions 19A and 19B, only one of which, 19A, is shown in this Figure. The trunnions are disposed on either side of the tongue and are attached to the mounting plate 15. Cylindrical projections on the trunnions extend into the cylindrical port in the tongue, rotatably supporting it and providing it with the ability to rotate with respect to the mounting plate. The tongue's cross section is in the form of a reversed "S" which allows the upper portion of the tongue 20A to be located above the mounting plate, while the lower portion 20B is located below the mounting plate. The lower portion of the tongue, when in its latched position as shown in FIG. 4A, extends beneath the corner plate 10 of the flow channel, securing the invention to the fuel assembly. The tongue is maintained in its latching position by means of a captured screw 24 and a nut 18. The captured screw 24 is attached to the upper portion of the tongue 20A, while the nut 18 is attached to the bottom of the mounting plate in a position to receive screw 24. The screw 24 is threaded into the nut, enabling it to hold the upper portion of the tongue down on the mounting plate and thereby preventing the lower portion of the tongue from releasing the corner plate. The lower tip 24A of screw 24 is conical to aid in guiding it into the nut 18. The head of the screw 24B is also conical to aid in guiding a socket wrench on to the screw head. Typically, a socket wrench attached to a long shaft is guided onto the screw head and the screw is tightened down onto the cover plate manually from the top of the storage pool. The use of specialized personnel or tools is completely avoided. Prior to lowering the the invention down onto a fuel assembly, the tongue must be oriented generally vertically to enable it to later close on the corner plate. The tongue is maintained in this vertical position by means of a slight compression occurring between the tongue and the edge of aperture 15, as indicated by path of rotation 20C of the lower portion 20B of the tongue. This path results in a slight interference fit for the tongue as it rotates to a vertical position through aperture 15B. Once the invention is in position on the fuel assembly, the socket wrench can be moved manually by way of the attached shaft to tap the latch past this interference point and into position where the captured screw may be tightened down, forcing the tongue down flush onto the mounting plate. A captured lock washer 24C is located just below the screw head and above the upper portion of the tongue. As the screw is tightened down, it is locked in place by this washer. There is rarely any vibration occurring in the storage pools, but this feature is an added safety factor designed to provide an extra margin of safety to protect against such event, even though they may be rare. The configuration of a PWR fuel assembly differs from that of a BWR fuel assembly and accordingly requires a different embodiment of the present invention to provide a convenient means of attachment to the PWR fuel assembly. The differences in the two types of fuel assemblies lies primarily in the components forming their upper and lower end fittings and the absence of a flow channel in the PWR fuel assembly. A PWR fuel assembly 49 is shown in FIG. 4B. Since the means for attachment of the invention describe herein is made to the upper end of the PWR fuel assembly, only the the upper end of the PWR fuel assembly is shown in this Figure. The lower portion of this fuel assembly is deleted below point 50. The primary components of the upper end of the PRW fuel assembly comprise a flow nozzle 47, a plurality of fuel rods, such as rod 9D, a plurality of guide tubes, such as guide tube 54, and spacer grids, such as spacer grid 53. The guide tubes are attached to the nozzle 47 and also attached to the spacer grid 53. The connection between the spacer grid and the guide tubes occurs within the fuel assembly. The spacer grid extends inward from the periphery of the fuel assembly where it is shown in FIG. 4B, passing about the fuel rods to reach the guide tubes. The fuel rods are connected to and supported in position by the spacer grid. The nozzle 47, which is located on the top of the fuel assembly, has a rectangular outer perimeter, conforming generally to the outer perimeter of the fuel assembly. This nozzle also includes a rectangular inner aperture 51, which is centrally located and is symmetrically positioned with respect to the outer perimeter. This aperture produces a nozzle that is in the form of a rectangular wall which is approximately one-half inch thick. The means for attachment to the PWR fuel assembly is illustrated in the embodiment of the invention shown in the upper portion of FIG. 4B. This embodiment comprises an absorber plate 1, a rectangular sleeve 43, and four upper attachment clips 44. The sleeve is formed about a rectangular aperture 52 which is sufficiently wide to fit closely about the fuel assembly nozzle 47. The upper attachment clips are shown in detail in FIG. 4C. These clips comprise arms 45 and retaining tips 46. The arms are connected to the top of the sleeve and extend over the top of the nozzle and then downward inside the aperture 51 to a depth where the nozzle contains a recess 48. At this depth, the arms of the clips terminate in the retaining tips 46. As can be seen in FIG. 4C, the retaining tips have a triangular cross section, with one of the orthogonal sides aligned with the clip arm and the other extending beneath the collar recess to secure the invention to the fuel assembly. This means of attachment can also be applied while the fuel assembly is in storage. As the invention is lowered about the fuel assembly, the hypotenuse of the retaining clips acts as a cam to force the arms of the clips sufficiently towards the center of aperture 52 to allow the the clips to pass down into the aperture 51 until the recess 48 has been reached. The arms of the clips 44 are resilient and cause the tips to extend under the recess once they have reach the depth of the recess. The clips may be released by use of a special tool to force them back into the aperture and out from under the recess. As shown in FIG. 7, a fuel assembly 7 with the invention attached is typically stored in a storage rack 37 that is normally located in a 40 foot deep pool. The fuel storage rack consists of a generally rectangular outer wall 32 within which the internal volume is divided into a series of small rectangular cells such as cells 33. When placing a fuel assembly into storage, the fuel assembly, such as assembly 7 is lowered down into a cell such as 33A to occupy the volume in the fuel rack showed by projection lines 38. In FIG. 7, the fuel assembly 7 has been foreshortened for illustrative purposes. The height of the fuel assembly is approximately the same as that of the fuel rack. The fuel assembly essentially occupies the total volume of the cell, with the exception of a clearance space between the fuel assembly and the cell walls which is used to to permit the insertion of the present invention about the fuel assembly while it remains in storage in a fuel rack. In most currently used fuel racks, all four walls of the fuel cell contained neutron absorber plates. FIG. 8 shows a plan view representation of the cells in a fuel rack 37. This rack consists of the outer wall 32, a plurality of cells 33 with all four walls of the cells containing absorber plates. For illustrative purposes, the location of the absorber plates in the cell walls is shown in this Figure by the darkened peripheral area in cell 34. These are the absorber plates that are now corroding and are losing their effectiveness as neutron absorbers, requiring replacement by means such as the present invention. Cell 34 is shown more clearly in the larger drawing of this cell presented in FIG. 8B. This cell is formed of four walls, such as wall 34A, containing the existing, but often depleted neutron absorbing material. This cell also includes a cross sectional view of the chevron configuration of the invention, 34B as it would normally to positioned in such a cell. The chevron configuration of the present invention, which ordinarily protect only two sides of the fuel assembly, can be oriented to protect all four sides of the fuel assembly by using the proper orientation of the absorber plates in the fuel rack. This orientation is illustrated in FIG. 9 where a fuel storage rack 37 is shown holding a number of fuel assemblies with the present invention secured to each fuel assembly. The orientation and general location of the absorber plates of the invention is represented by a chevron, such as chevron 35. A chevron is drawn in each cell containing the invention. In this Figure, each chevron is oriented to protect the upper and the left wall of its respective cell. Three contiguous cells containing three chevron configured absorber plates 35A, 35B, and 35C with the same orientation, completely protect all four sides of the cell containing absorber plates 35A. The upper and left wall of the cell containing absorber plates 35A are protected by absorber plates 35A. The left plate from chevron plates 35B protects the right wall of the cell containing 35A and the upper plates from chevron plates 35C protects the lower wall of this cell. Continuing the same orientation through out the entire fuel rack will provide protection of all four wall of all cells with the exception of the the right and lower outside walls of the fuel storage rack. Neutron absorber plates can be generally omitted from these walls because they face open water which is itself a neutron absorber. However, if additional protection is desired, additional neutron absorbing plates can be added to these outside walls in several ways. A first way is to add a series of absorber plates along the outside wall such as plates 36 which are shown positioned along the right outside wall in FIG. 9. A second way is to add a single, large absorber plate, such as plate 40, to protect one or two walls of the storage rack. A third way is to use two of the chevron absorber plates per fuel cell to protect all four walls within a cell as shown in cell 39. This arrangement may be applied to any cell as necessary to increase neutron absorption, but in most instances it can be restricted to use only along the right and lower wall in FIG. 8 for cost savings purposes. The relatively thin wall of the present invention makes this more feasible than is possible with prior art thick wall absorbers. In order to describe other alternate ways of providing neutron absorber protection that can be use along the outside wall of the fuel rack, it is necessary to briefly consider alternative configurations of the invention. Although the chevron configuration is the preferred configuration of the present invention, as will be shown in greater detail below, the invention may be fabricated as a single plate absorber, such as shown in FIG. 5B, as a double plate absorber, such as shown in FIG. 6, as a triple plate absorber, such as shown in cell 41 of FIG. 9, as a quadruple plate absorber, such as shown in cell 42, and as a large plate absorber such as plate 40 of FIG. 9. These various configurations of the invention may be applied in different ways to achieve additional neutron absorber protection for the outside walls of the fuel rack. For example, further cost savings may be obtained by using a fourth way of protecting this wall in which the single absorber plate form of the present invention is attached to the fuel assembly and positioned within a cell against an outside wall as shown by the location of the single plate absorber 36A in FIG. 9. The addition of a single plate to the chevron configuration in effect produces a triple plate absorber. A triple plate absorber may be fabricated directly and installed as shown in cell 41 of FIG. 9 to produce the same results. In cell 42 of FIG. 9 outside protection of all four walls of the cell is required if in addition to the upper and left walls both the right and lower outside walls of the fuel rack are to be protected. If the protection is to be obtained from absorber plates within the cell, either the quadruple plate configuration shown in this cell or a combination of the previously described plate configurations can be used. An advantage of using absorber plates within the cell is they are relatively easily installed. These plates can be secured to the mounting plate of the invention in any desired configuration and installed in the same manner as previously described for the chevron configuration. Applying absorber plates to the outside of fuel storage racks can be somewhat more difficult than installing plates within the cell as described above, but it is feasible and constitutes a fifth way to protect the fuel rack wall. This way is feasible because the outside walls are relatively accessible. They face open water within the storage pool, providing ample room to maneuver absorber plates and tools required for the installation of the absorber plates. The absorber plates may be installed on a fuel storage rack without removal of either the fuel assemblies or the fuel storage rack. The edges of these absorber plates incorporate projections that are designed to grip the the walls of the fuel storage rack, as shown in FIG. 9 by edge projection 40A on plate 40. This edge projection extends about the corner contour of the fuel rack to provide a lip that grips the fuel rack. Such edge projections reduce the required number of conventional securing means, such as screws and tapped holes, that are required to be placed in the fuel rack, thereby reducing the amount of under water machining operations. The internal features of the absorber plates used in the present invention are shown in FIG. 5A. In this Figure, the plates are shown as being flat because they are initially fabricated from flat plate material which is later folded into the chevron configuration shown in FIG. 6. In FIG. 5A, an absorber plate assembly 23A comprises a backing plate 25, a first neutron absorbing sheet 26A, a second neutron absorbing sheet 26B, a first cover plate 27A, and a second cover plate 27B. The backing and cover plates are made of a material such as stainless steel or aluminum having a thickness ranging between 0.020 and 0.050 inches. These materials are selected to prevent corrosion of the neutron absorbing sheet which would otherwise occur because of contact with the water in the storage pool The neutron absorbing sheet is made of a neutron absorbing material such as cadmium having a thickness ranging between 0.004 and 0.040 inches. The cover plates are separated from each other to expose an area located generally in the middle of the backing plate about dashed line 31 along which the backing plate is later folded into the chevron configuration shown in FIG. 6. Cadmium is the preferred material for the neutron absorbing sheet because it provides a high level of neutron absorption even when used in sheets that are only 0.004 to 0.040 inch thick. However, the invention is not limited to the use of cadmium. Other materials such as borated stainless steel and boron in a ceramic matrix may serve as the neutron absorbing material in this invention. The first and second neutron absorbing sheets are smaller than the cover plates an are positioned so that they are centered beneath the first and second cover plates, respectively. This positioning of the neutron absorbing sheets provides an area along the edges of the cover plates, indicated by dashed line 29, for sealing the neutron absorbing sheets between the cover plates and the backing plate. Along these edges, the cover plates lie directly over the backing plate without an intervening neutron absorbing sheet. The cover plates are joined to the backing plate in this area by means of a process, such as seam welding, which provides a seal that protects the neutron absorber sheets from the corrosive action of the water in the storage pool. As shown in FIG. 5A there are two distinct absorber plates spaced apart and supported in this position by a single backing plate which is folded after seam welding of the cover plates to form the chevron configuration. Typically, there is a space 25A between the top of the cover plate and the top of the backing plate because there is no fuel in this area of the fuel assembly. There are a number of distinct advantages to this method of fabrication. The first advantage is this method avoids a major problem encountered with prior art processes where there is no area free of a cover late or neutron absorber sheet. Unless special, costly precautions are taken, the folding of the backing plate in the area where it is not free of a cover plate would cause buckling and possibly cracks which would in turn leave the absorber sheet exposed. In the present invention, there is no cover plate nor neutron absorber sheet in the area in which the backing plate is folded, permitting the backing plate to be folded easily without concern for damaging the seal about the neutron absorber sheet. This feature provides a significant cost saving during fabrication and increases the reliability of the neutron absorber plate. Another significant cost saving advantage is gained by this method of fabrication because a fast, low cost process such as seam welding can be used for sealing the neutron absorber sheet. The invention is first fabricated using readily available flat sheet material. While the invention is still in flat form it is seam welded at low cost with standard, readily available equipment. It is then folded without damage, again by means of standard low cost readily available equipment. In some previously used processes, tubes with circular cross sections or rectangular cross sections were required to be welded. Such cross sections made it difficult or impossible to use low cost processes such as seam welding. FIG. 5B shows a single plate absorber 28B in accordance with the present invention. This absorber plate is fabricated in the same way as the invention shown in FIG. 5A with the exception that it is designed to cover only one side of a fuel assembly. This absorber plate can be used in such applications as the single plate absorber 36A shown in FIG. 9 or wherever additional neutron absorption is required, such as on the side of a fuel assembly. The absorber plate shown in FIG. 5B has two additional features, not shown in FIG. 5A. The first is the neutron absorber sheet is divided into two or more segments such as segments 26C and 26D as in the cover plate, such as segments 27C and 27D. There is space between these segments that exposes the backing plate 25. The segments of the cover plate are sealed to protect the corresponding segments of the neutron absorbing. The segmenting and individual sealing of the segmented portions of the neutron absorbing sheet in this way permits the absorbing sheet to be cut between the welded seals of the individual segments to provide various lengths of absorber plate in the field. The second feature is the angled lower end of the absorber plate leading to a tip 28. Although there is usually room to fit within a cell of a fuel storage rack the present invention attached to a fuel assembly, there are occasions when the fuel assembly may be warped. A single absorber plate can be maneuvered more easily than a two plate assembly and may be able to be pressed by a tight fitting area with the aid of the angled lower end. As noted above, it is usually possible to provide protection in four radial directions with the chevron configuration and it is also possible in most instances to insert the chevron configuration into a cell of a fuel storage rack while attached to a fuel assembly. This is possible because the chevron configuration covers only two sides of the fuel assembly, leaving ample room for insertion by avoiding the use of all the clearance space on all four sides of the fuel assembly. These important advantages make the chevron configuration the preferred embodiment of the present invention. Although the three plate or four plate configurations may on occasion be more difficult to insert into a fuel storage cell, they can be employed to serve as necessary in the special applications noted above. Three and four plate absorber can be fabricated using the same process described above. The number of sides dictates the width of the backing plate, the number of absorber sheets and the number of cover plates. Once sealed by welding or other appropriate means, the flat plate is folded in three to form a three sided or "U" cross section or into four to form a rectangular cross section, as required to produce the desired cross section. Prior art absorber plates in many instances tried to completely encircle the fuel assembly with the absorber medium because it was not known what discontinuities in the coverage of the absorber medium could be tolerated and still avoid criticallity. Computers with large storage capacities are more readily available now and have been used to determine this information. It has been determined that the small discontinuities in the absorber plates at the fold in the backing plate and at the outside edges of the right and left absorber plates can be easily tolerated, permitting the use of the present invention to provide the desired neutron absorption protection as shown and described. A special configuration of the present invention that essentially eliminates any loss of nuclear absorber coverage at the fold in the backing plate, and at the same time simplifies the fabrication process is shown in FIGS. 10A, 10B, 11, 12A and 12B. In this embodiment of the invention, a special backing plate made of borated aluminum or borated stainless steel replaces the aluminum or stainless steel backing plate of the embodiments described herein previously. This special backing plate is itself a nuclear absorber and needs no additional absorber added to provide sufficient nuclear absorption of this application. Borated aluminum or borated stainless steel contains natural or enriched boron. The enriched boron contains more Boron--10 atoms than natural Boron. As can be seen in FIGS. 12A and 12B, which are front and top views of this special configuration of the present invention, it has not been necessary to include a neutron absorbing sheet, such as sheet 26B or a cover plate, such as plate 27B, that are contained in the configuration shown in FIG. 1A and 1B. Virtually all the drawing numerals in FIGS. 12A and 12B are the same as were used in FIGS. 1A and 1B and refer to the same elements. In addition to the special backing plate and the absence of the cover plate and the neutron absorbing sheet, there are two additional minor differences between FIGS. 1A and 1B and FIGS. 12A and 12B. The first of these two minor differences is the two plates forming the chevron configuration in FIGS. 12A and 12B are welded together at their juncture, 64, whereas the plates forming the chevron configuration in FIGS. 1A and 1B are simply folded at their juncture. The second minor difference is the special backing plates in FIGS. 12A and 12B extend all the way upward to the mounting plate 15. Therefore, there is no omission of the neutron absorber such as there is in the area designated by drawing numeral 25A in FIG. 1A. FIGS. 10A, 10B and 11 are similar to FIGS. 5A, 5B and 6, with the exception that the multiplicity of drawing numerals in 5A, 5B and 6 necessary to identify the cover plates and neutron absorber sheets are absent in FIGS. 10A, 10B and 11. These drawing numbers can be eliminated because the cover plates and neutron absorber sheets are no longer necessary for the special configuration. FIG. 10 is a view of two separate borated backing plates, 60 and 61, used to provide the chevron formation for the special configuration. Unlike FIG. 5A, where one backing plate is folded to form the two plates of the chevron formation of FIG. 6, two individual backing plates are used instead. The two individual plates are necessary because the borated backing plates cannot be folded, but must welded. In FIG. 11, the two borated backing plates of FIG. 10A are welded together along seam 64 to provide the chevron formation necessary to produce plates 2 and 3 of the complete invention, shown in FIG. 12A. FIG. 10B shows a single plate absorber 62 using the special configuration and having a pointed tip 28 similar to the single plate absorber 28B of FIG. 5B. Again, the multiplicity of drawing numerals in FIG. 5B are absent in FIG. 10B because the cover plate and absorber sheet are no longer necessary for the special configuration. The single plate absorber of FIG. 10B can be cut as necessary at any point to fit a specific requirement at the storage site. The single blade absorber of FIG. 10B has all the advantages of the blade shown in FIG. 5B with less complication in manufacturer and in use in the field. The embodiment of the invention shown in FIG. 12A is designed to be used with a BWR fuel assembly. This special configuration is equally applicable to a PWR fuel assembly. For use with a PWR fuel assembly, the special backing plates are simply connected to the attachment means for a PWR shown in FIG. 4B.
	summary
051376814	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In the schematic illustration of an electrical power generation system according to the present invention, as depicted in FIG. 1, an electrical power generating system 10 utilizes high pressure steam from a thermal steam generator 12. Various types of such steam generators are well known, and the particular type is not significant to the invention. The steam generator 12 exchanges heat to condensate and fresh feed water to produce dry high pressure steam, typically in the ranges of 900.degree.-1000.degree. F. at 1,000 psi. In the depicted system, the high pressure steam is routed via appropriate control valves to a steam jet ejector 14, where it is mixed with re-compressed turbine exhaust steam, as more fully described hereafter. The mixed steam is regulated at a steady pressure by a servo-pressure control valve device 16. Such devices are well known to those skilled in the art. The regulated mixed steam is then routed to the turbine inlet of a coaxial dual shaft compresser-turbine 18. The compresser-turbine 18 is more fully depicted in FIG. 2, but as shown schematically in FIG. 1, comprises a turbine section 20, a compressor section 22, and a dual shaft 24 which couples the turbine section 20 to the compressor section 22. A power output shaft 26 transmits rotational energy from the turbine section 20 to an electrical generator 28. Exhaust steam from the turbine section 20 is routed to a dryer 30, which is more fully depicted in FIG. 3. The dryer 30 removes moisture from the turbine exhaust and passes the dried exhaust steam to the inlet of the compressor section 22. The hot water extracted from the dryer 30 is withdrawn through pump 32 and routed back to the steam generator 12 as system condensate. The dry exhaust steam from the dryer 30 is compressed by compressor 22, is extracted from the compressor 22 and passed to a steam jet ejector 14, where it is mixed with fresh steam from steam generator 12. The steam jet ejector 14 is more fully described in FIG. 4. Turning now to FIG. 2, the turbo-compressor 18 is more fully illustrated. The shaft 24 coupling the turbine section 20 to the compressor section 22 is a coaxial dual shaft, comprising a high pressure shaft 34 disposed concentrically around an intermediate section of a low pressure shaft 36, allowing the two shafts to rotate at different speeds. Mixed steam is inlet to the turbine section 20 at the turbine inlet 38, and passes first through a high pressure turbine blade wheel 40, which extracts thermal energy and converts it to rotational mechanical energy transmitted to the high pressure shaft 34. Although a single high pressure turbine wheel 40 is depicted, there may be one or more such high pressure turbine wheels connected to the high pressure shaft 34, as is well known to those in the art. Additionally, there will be stator blades (not depicted) interspersed between the rotating turbine wheels, as well known in the art. After passing through the high pressure turbine wheel 40, the mixed steam is passed through a series of low pressure turbine wheels 42. Four such low pressure wheels 42 are depicted in FIG. 2, although the number of low pressure wheels is not critical to the invention and, as well known to those in the art, a different number of wheels may be utilized. The low pressure wheels 42 are mounted on the low pressure shaft 36, and extract thermal energy from the steam and convert the same to rotating mechanical energy. Low pressure shaft 36 is connected to output shaft 26 by an appropriate coupling 44, and provides the motive power for generator 28. Exhaust steam is extracted from the turbine section 20 at the turbine exhaust duct 46, and routed to dryer 30 as previously described. The dry exhaust steam from dryer 30 is then routed to the compressor section 22 at its inlet 48, and passes initially through low pressure compressor blades 50. Low pressure blades 50 are blade wheels mounted on the low pressure shaft 36, and thereby received motive power from turbine wheels 42 through shaft 36. The compressed steam is then passed through high pressure compressor blade wheels 52, which are mounted on shaft 34 and receive power from turbine wheel 40 through shaft 34. Stator blades (not depicted) are interspersed between the compressor blade wheels. The sequential compressor stages of wheels 50 and 52 progressively compress the dried exhaust steam, and discharge it as high pressure steam from the compressor discharge duct 54. As shown in FIG. 3, dryer 30 comprises a labrynth of metal vanes 56 enclosed in a dryer hood 58. The exhaust steam is passed through the vanes 56, which collect moisture from the steam and allow it to drip as hot condensate into a collecting trough 60 beneath the vanes. The exhaust steam emerges from the vanes in a dry condition, while the hot condensate is extracted from the collecting trough 60 and pumped back to the steam generator 12 as condensate, as previously described. As shown in FIG. 4, the steam jet ejector 14 receives fresh steam from the steam generator 12 at inlet 62 and passes it through a nozzle 64 to increase its velocity. Dry exhaust steam is input to the ejector at inlet 66 and enters a low pressure manifold 68 which encloses the nozzle 64. The venturi effect of the nozzle 64 and manifold 68 pumps the dry exhaust steam through the air ejector discharge 68, and mixes both fresh steam and recycled exhaust steam at an equilibrium pressure, which is regulated by servo-pressure control valve 16, to be used by the turbine section of the turbo-compressor.
	abstract	An integral collimator for an extra-oral imaging system that includes a lead plate surrounding an elongated fixed slot aperture and includes a unitary body in substantially continuous contact with an outer surface of the elongated lead plate. The unitary body can include a lower portion surrounding the elongated lead plate and an upper portion, where the upper portion includes a protrusion configured to engage a transport mechanism for translation in a direction orthogonal to a path of the x-ray.
	description	The present application is a continuation of and claims the priority of U.S. application Ser. No. 12/788,789, filed May 27, 2010, which is incorporated herein by reference in its entirety. The present disclosure relates to semiconductor fabrication generally and more specifically to double patterning. In semiconductor fabrication processes, the photo resolution of a photoresist pattern begins to blur at about 45 nanometer (nm) half pitch. As feature sizes decrease to 20/22 nm and beyond, various methods are used to address the resolution issue. Particularly, double exposure techniques may be used to maintain resolution using two masks. Double exposure involves forming patterns on a single layer of a substrate using two different masks in succession. As a result, line spacing in the combined pattern can be reduced while maintaining good resolution. In a method referred to as double dipole lithography (DDL), the patterns to be formed on the layer are decomposed and formed on a first mask having only horizontal lines, and on a second mask having only vertical lines. The first and second masks are said to have 1-dimensional (1-D) patterns, which can be printed with existing lithographic tools. Another form of double exposure is referred to as double patterning technology (DPT). Unlike the 1-D approach of DDL, DPT in some cases allows a vertex (angle) to be formed of a vertical segment and a horizontal segment on the same mask. Thus, DPT generally allows for greater reduction in overall IC layout than DDL does. DPT is a layout splitting method analogous to a two coloring problem for layout splitting in graph theory. In its simplest form, the two coloring problem is a way of coloring the vertices (or edge or face) of a graph such that no two adjacent vertices share the same color. Two adjacent vertices connected with an edge should be assigned different colors. Only two “color types” can be assigned. If a 2 color solution exists, the graph is said to be 2-colorable. An IC layout includes multiple patterns on many layers. The distance between adjacent elements may be too small to be on the same mask, referred to herein as G0-space, but not so small to be beyond the capability of the technology node. Each pattern on a layer is assigned a first or second “color”; the patterns of the first color are formed by a first mask, and the patterns of the second color are formed by a second mask. DPT is computationally intensive because IC layouts have many solutions having different costs, which are evaluated separately. However, many layouts cannot be simply resolved into two masks, i.e. 2-colorable. FIGS. 1A and 1B show two examples of pattern layouts that present situations that are not 2-colorable. In FIGS. 1A and 1B, the line width is labeled W, the minimum space between lines is labeled S, and the center-to-center pitch between lines is labeled P. The minimum spacing S is a parameter of a particular process technology node; smaller S corresponds to more advanced technology nodes. In FIG. 1A, the segments 50, 52, and 54 form a first pattern 49 with nearby additional patterns 56 and 58. There are three spatial relationships (indicated by dashed lines), which would violate DPT constraints if put in the same mask. Example DPT constraints may include spacing rules, for example, edge of runs must be a further than a certain distance apart, and shape rules, for example, a pattern cannot violate a spacing rule with itself. Spatial relationships that violate DPT constraints when put into the same mask are called G0-space. In FIG. 1A, patterns 49 and 56 are too close to be put in the same mask, because segment 50 and pattern 56 are too close, violating a spacing rule and forming a G0-space. Thus pattern 49 must be assigned to a different mask from pattern 56. Assigning pattern 49 to mask A, the first mask, and pattern 56 to mask, B, it is noted that patterns 49 and 58 are also too close to be put in the same mask because segment 54 and pattern 58 form another G0-space. Because pattern 49 is already assigned to mask A, then pattern 58 must be assigned to mask B, the second mask. However, patterns 56 and 58 are similarly too close to each other to be put in the same mask, but both are already assigned to the same mask B. Thus, there is no way to distribute the first pattern 49 and the two additional patterns 56 and 58 between two masks A and B without violating a DPT constraint. In terms of graph theory, when the total number of relationships between patterns that violate the minimum spacing for a single mask is odd, an odd cycle is present, and DPT cannot be used without changing the layout. FIG. 1B shows a similar odd cycle situation. Segments 60, 62 and 64 form a first pattern 59. The patterns 59, 70, 72, 74 and 76 have five relationships (shown by dashed lines) that violate minimum spacing constraints for being formed in the same mask with each other. Because the number of relationships violating the minimum spacing requirements is an odd number, an odd cycle is present, and DPT cannot be used without changing the layout. Design Rule Checker (DRC) software can systematically check design rules by showing all G0-spaces in a layout design. A designer would enter the necessary design rules, referred to as a deck, into the DRC using its design rule language, such as Standard Verification Rule Format (SVRF) or a software specific Tool Command Language (TCL). The design rules would specify the criteria for a particular spatial relationship to be a G0-space, such as corner-to-corner distance, end-to-end distance, or run-to-end distance. The DRC software would then take the layout input in a standard format, such as Graphic Data System II (GDSII), and produce an output that shows all the spatial relationships that are G0-spaces. Commonly used DRC software includes Calibre® by Mentor Graphics; Hercules™ by Synopsys; Diva®, Dracula®, Assura®, and PVS by Cadence Design Systems. If a layout cannot be separated into two masks, the problem can be addressed by changing the layout design. The layout design is usually changed manually by a designer reviewing the G0-space output from a DRC software. Changing a layout design is time-consuming, because a designer aims to minimize the total volume of a design and a change often affects structures in other layers. A designer must evaluate many alternate fixes before selecting on the best solution. Additionally, some fixes does not necessarily resolve certain loop combinations. Therefore, improved methods for efficiently resolving DPT constraint violations are desired. This description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” 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. FIG. 2 shows a system 100 having an electronic design automation (EDA) tool 110 such as “IC COMPILER”™, sold by Synopsis, Inc. of Mountain View, Calif., including a router 120 such as “ZROUTE” ™, also sold by Synopsis. Other EDA tools 110 may be used, such as the “VIRTUOSO” custom design platform or the Cadence “ENCOUNTER”® digital IC design platform may be used, along with the “VIRTUOSO” chip assembly router 120, all sold by Cadence Design Systems, Inc. of San Jose, Calif. The EDA tool 110 is a special purpose computer formed by retrieving stored program instructions from a computer readable storage medium 112 and executing the instructions on a processor 111. One or more computer readable storage media 112 and/or 130 are provided to store input data used by the EDA tool 110. The storage medium 130 and/or the storage medium 112 may include one or more of dynamic random access memory (RAM), SDRAM, a read only memory (ROM), EEPROM, a hard disk drive (HDD), an optical disk drive (CD-ROM, DVD-ROM or BD-ROM), or a flash memory, or the like. The input data may include an identification of a plurality of cells to be included in an integrated circuit (IC) layout, including a list of pairs of cells within the plurality of cells to be connected to each other and other design information. The input data may also include design rules. Design rules may include default rules applicable to all designs or rules specific to a particular kind of design or the instant design. A computer readable storage medium 140 is provided, for outputting an IC layout 142. The medium 140 may be a separate storage device, or a portion of the same storage medium 130 described above. The medium 140 may be any of the types of storage media described above with respect to medium 130. The IC layout 142 is then checked for DPT compliance by the Design Rule Checker (DRC) software 150 for G0-space. The G0-space information is outputted in 160 to various output devices such as a printer, a screen, a graphic display device, or the like. Commonly, G0-spaces are simply highlighted in a layout diagram as shown in FIG. 3. FIG. 3 shows a layout 200 for a particular layer in an integrated circuit. The layout includes various features such as 201, 203, 207, and 209. The features may be portions of interconnects in a particular metal layer. G0-spaces are highlighted, in some embodiments, using a line between the violating elements, shown as 205, 211, 213, and 215. Among all G0-spaces shown, a designer must select a number of G0-spaces to fix. A G0-space may be fixed by changing a pattern dimension or moving patterns. Fixing a G0-space usually takes time, because changing the layout in one layer affects layout in other layers. The fix also can increase the total space of the layout, such as when the fix is accomplished by moving patterns further apart. Such fixes can increase device size and possibly affecting the total number of die that can fit on one wafer. In order to minimize the time spent and size of the layout, it is desirable to reduce the number of G0-space fixes. Further, the selection of G0-space to fix has different effectiveness in achieving a 2-colorable layout. Fixing some G0-spaces can even have the opposite effect of increasing the total number of fixes to achieve a 2-colorable layout. The present disclosure describes methods and systems to effectively select a number of G0-spaces to achieve a 2-colorable layout. In one aspect, some embodiments of the present invention provides a method to produce a 2-colorable layout using a minimum number of G0-space fixes, which can correspond to the layout that uses the least space. FIGS. 4A-4C define a set of G0 rules for determining whether a given set of patterns can be used in a DPT compliant routing pattern according to some embodiments. The parameter G0 is derived as a function of the minimum line spacing. FIGS. 4A to 4C show an example of a set of definitions of relevant line spacing criteria, given a minimum line spacing S defined by the routing grid. The minimum spacing S is a parameter of a particular process technology node. Criteria are applied to determine whether a given spatial relationship between two of the patterns in a routing layout would create a G0-space. For a region of the layout surrounded by a plurality of patterns, DPT may be possible if the number of G0 spaces surrounding the region of the layout is an even number. On the other hand, a 2-colorable layout is not achieved if the number of G0 spaces surrounding the region of the layout is an odd number. In FIG. 4A, the G0-rule for end-end or end-run space is shown. A “G0 space” is formed in an area 302, for which the end-end or end-run distance is less than a parameter X times a minimum spacing S, or XS. For example, if the distance is greater than 2.1S (X=2.1), then these two patterns do not form a G0 space between them. If the distance is between S and 2.1S, then a G0 space 302 is formed as shown in FIG. 4A. Note that the multiplier X may be different depending on a number of variables, for example, the wavelength of the lithographic radiation, the type of mask, etc. An even number of G0 spaces around a given region of the layout can nevertheless result in a 2-colorable layout. Thus a G0 space is formed when an end-to-end distance between two of the plurality of segments which are aligned with each other, or between two of the additional patterns which are aligned with each other, or between one of the plurality of segments and one of the additional patterns aligned therewith, to at least X times a minimum line spacing used between pairs of adjacent lines. Also, a G0 space is formed when an end-to-run distance between two of the plurality of segments which are unconnected and perpendicular to each other, or between two of the additional patterns which are unconnected and perpendicular to each other, or between one of the plurality of segments and one of the additional patterns which are unconnected and perpendicular to each other, to at least X times a minimum line spacing used between pairs of adjacent lines. FIG. 4B shows the G0-rule for run-run space. A “G0 space” is formed in an area 306, for which the run-run distance is less than a parameter Y times a minimum spacing S, or YS. If the distance is greater than 1.6S (Y=1.6), then these two patterns do not form a G0 space between them. If the distance is between S and 1.6S, then an even number of G0 spaces around a given region of the layout can nevertheless result in a 2-colorable layout. Thus, a G0 space is formed if a run-to-run distance between two of the plurality of segments which are parallel to each other, or between two of the additional patterns which are parallel to each other, or between one of the plurality of segments and one of the additional patterns which are parallel to each other and extend, to at least Y times a minimum line spacing used between pairs of adjacent lines. FIG. 4C shows the G0-rule for corner-corner space. A “G0 space” is formed in an area 308, for which the corner-corner distance is less than a parameter Z times a minimum spacing S, or ZS. If the distance is greater than 1.6S (Z=1.6), then these two patterns do not form a G0 space between them. If the distance is between S and 1.6S, then an even number of G0 spaces around a given region of the layout can nevertheless result in a 2-colorable layout. Thus, a G0 space is formed when a corner-to-corner distance between two of the plurality of segments which are unconnected and perpendicular to each other, or between two of the additional patterns which are unconnected and perpendicular to each other, or between one of the plurality of segments and one of the additional patterns which are unconnected and perpendicular to each other, to at least Z times a minimum line spacing used between pairs of adjacent lines. The descriptions of FIGS. 4A-4C above are non-limiting examples. Different technologies may use different threshold values for identifying a G0-space, including different S values and multipliers X, Y, and Z. That is, in other embodiments, the threshold distance may differ from 1.6S or 2.1S (e.g., 1.8S, 2.4S, or the like). In some embodiments, the G0 threshold may be a constant number regardless of the minimum spacing S. In other embodiments, the G0 threshold may use the same multiple of S (e.g., 2.1S) for all types of spacing. In still other embodiments, alternate or additional examples of G0-space may be identified, such where a layout includes lines that are not either perpendicular or parallel to each other. As discussed, an odd-cycle loop is not 2-colorable, but an even-cycle loop is. A loop is where the G0-spaces among polygons form a cyclic sequence. As described above, patterns across a G0-space should be split into different masks. Because the odd-cycle loop has a number of polygons that cannot be split into two masks, it has a native conflict, or a G0-rule violation. FIG. 5 shows a four-pattern loop. The patterns are 511, 512, 513, and 514 through four G0-spaces 515, 516, 517, and 518. Working though the loop clock wise, patterns 511 and 512 should be separated into two masks because they have G0-space 515 between them. For example, pattern 511 is assigned to mask A (hatch pattern) and pattern 512 assigned to mask B (vertical pattern). Similarly, patterns 512 and 513 should be separated into two masks because they have G0-space 516 between them. Because pattern 512 is assigned to mask B, then 513 should be assigned to mask A. Again, patterns 513 and 514 should be separated into two masks because they have G0-space 517 between them. Because pattern 513 is already assigned to mask A, then 514 should be assigned to mask B. Lastly, patterns 514 and 511 should be separated into two masks because they have G0-space 518 between them. Because pattern 514 is assigned to mask B, then 511 should be assigned to mask A, which it already is. Thus, the loop as shown in FIG. 5 is 2-colorable, or separable into two masks. FIG. 5 includes four patterns, forming an even-loop. Whenever G0-spaces form an even loop, the patterns can be separated into two masks and is 2-colorable. In some cases, the relations of G0-spaces do not form a cyclic sequence. The arrangement of patterns is referred to as a non-loop, as shown in FIG. 6. FIG. 6 shows patterns 611, 612, 613, and 614 with G0-spaces 615, 617, and 618. The space 616 between patterns 612 and 613 is not a G0-space because the distance between the patterns exceeds X*S, as described above in relation to FIG. 4A. The patterns and G0-spaces in FIG. 6 do not form a cyclic sequence because not all legs of the imaginary polygon are G0-spaces. Thus, the patterns form a non-loop. Non-loops are not G0-rule violations no matter how many legs they have because they can always be separated into two masks. FIGS. 7A-7D show two different methods to resolve, or fix, a G0-rule violation involving double odd-loops. FIG. 7A shows four patterns 701, 703, 705, and 707 forming two three-loops 709 and 711. The odd-loop 709 is formed by patterns 701, 703, and 707. The odd-loop 711 is formed by patterns 701, 705, and 707. Between each consecutive pattern in the loop is at least one G0-space. FIGS. 7B and 7C show one way to fix the odd-loops of FIG. 7A. In FIG. 7B, the G0-space between 701 and 705 of FIG. 7A is fixed by removing a portion 713 of the pattern 705, forming 705A, which has a reduced area. While this fix made the odd-loop 711 into a non-loop as shown in FIG. 7B, the odd-loop 709 remains. The odd-loops 709 and 711 completely resolved in FIG. 7C when a portion 715 of pattern 703 is removed to increase the distance between 703 and 707, removing the G0-space between 703A and 707 as a result. Thus, the two odd-loops 709 and 711 of FIG. 7A becomes a non-loop of FIG. 7C, which is easily separated into two masks. A different way to fix the G0-rule violation of FIG. 7A involves removing a portion 719 of pattern 707 as shown in FIG. 7D. Instead of making a non-loop as in FIG. 7C, an even-loop 717 is created by removing the G0-space between 701 and 707. As discussed above, an even-loop is also easily separated into two masks. By focusing the fix on a different pattern, the technique of FIG. 7D resolved the G0-rule violation by changing one pattern instead of two patterns as shown in FIGS. 7B and 7C. Because its fixing resolved the G0-rule violation, the G0-space between 701 and 707 is identified as a critical G0-space in accordance with some embodiments of the present invention. Identifying the critical G0-space to a designer for fixing reduces the total number of fixes required to resolve a 2 odd-loops layout. FIGS. 8A-8D show two different methods to resolve, or fix, a G0-rule violation involving an odd-loop and an even-loop. FIG. 8A shows four patterns 801, 803, 805, 806, and 807 forming two loops, an even-loop 809 and an odd-loop 811. The odd-loop 811 is formed by patterns 801, 805, and 806. The even-loop 809 is formed by patterns 801, 803, 807, and 806. Between each consecutive pattern in the loop is at least one G0-space. FIGS. 8B and 8C show one way to fix the loops of FIG. 8A. In FIG. 8B, the G0-space between 801 and 806 of FIG. 8A is fixed by removing a portion 813 of the pattern 806, forming 806A, which has a reduced area. While this fix removed the odd-loop 811, it created an even larger odd loop 810 having 5 patterns. The odd-loop 810 resolves by removing a portion 815 of the pattern 807, forming 807A, as shown in FIG. 8C. Finally, the even and odd loops of FIG. 8A are resolved into a non-loop, which is easily separated into two masks. Note that although the odd-loop is resolved by reducing the dimensions of pattern 807, changing the dimensions of any of the patterns of loop 810 to remove any G0-space would resolve the loop 810. A different way to fix the G0-rule violation of FIG. 8A involves removing a portion 819 of pattern 805 as shown in FIG. 8D. Instead of making a non-loop as in FIG. 8C, an even-loop 817 plus a non-loop segment is created by removing the G0-space between 801 and 805. As discussed above, an even-loop is easily separated into two masks. By focusing the fix on a different pattern (805, instead of 806 and then 807), the technique of FIG. 8D resolved the G0-rule violation by changing one pattern instead of two patterns as shown in FIGS. 8B and 8C. Because its resolution fixed the G0-rule violation, the G0-space between 801 and 805 is identified as a critical G0-space in accordance with some embodiments of the present invention. Note that in the case of an odd-loop and an even-loop layout, fixing the G0-space between the loops does not resolve the layout. Thus the identification of a critical G0-space depends on the type of loops surrounding the G0-space. Fixing such critical G0-space reduces the total number of fixes required to solve such layout involving an odd-loop and an even-loop. FIG. 9 is a flow chart of a circuit layout method in accordance with some embodiments. In operation 902, layout data representing a plurality of patterns is received. The layout data includes information about each pattern such as runs, ends, and corners locations and sizes. The layout data may include a number of layers having different patterns that may be connected through the layers. The layout data may be generated by an electronic design automation (EDA) tool such as Synphony from Synopsis, Virtuoso from Cadence Systems, and IC Station from Mentor Graphics. The layout data may be provided using a computer readable medium using a standard layout format such as GDSII. The layout data may also be provided directly through software interface when the method is executed by an EDA system. In operation 904, the G0-spaces in the layout are determined. Various distances between pattern elements of adjacent patterns are compared to specified G0-space rules. The specified G0-space rules may be entered in the form of a DRC deck with the layout data. In addition to G0-space rules, the DRC deck may include special instructions on how to represent data, special rules, specific calculations, and warnings. For example, the distance between a run of one pattern and a run of an adjacent pattern may be 60 nm, but the G0-space rule may specify less than 65 nm for G0-space. Then the run-run space between these two patterns is a G0-space. In some embodiments, the G0-space rules include run-run/run-end, end-end, and corner-corner. The G0-space rules may also include other spatial relationships defined as being a G0-space. As disclosed above, the G0 distances specified may be different or same of each type of distance. Once all the G0-spaces are identified, then the G0-rule violations are determined for the identified G0-spaces in operation 906. According to some embodiments, the G0-rule violation is an odd-loop, a contiguous group of G0-spaces forming a polygon across an odd number of patterns. However, other G0-rule violation may be defined. An example may be when G0-spaces overlap, i.e., a corner-corner G0-space crossing over another corner-corner G0-space. In operation 908, critical G0-spaces are determined from the G0-spaces forming the G0-rule violations. Critical G0-spaces includes G0-spaces between two odd-loops, or between two G0-rule violations. Critical G0-spaces may also include G0-spaces between an odd loop and a non-loop. For an odd-loop that does not have an adjacent odd-loop, but does have an adjacent even-loop, the critical G0-space may be a G0-space that is not shared with the even-loop. As discussed above, critical G0-spaces are those whose fixing would aid in the resolution of the layout pattern to be 2-colorable. A designer may spend a lot of time fixing G0-spaces only to realize that they are not critical because odd-loops still exist. By determining the critical G0-space to fix using the methodology disclosed, the design rule checker (DRC) presents the designer with a mapping of effective fixes. In operation 910, a representation of G0-rule violations and critical G0-spaces is outputted to an output device. FIG. 11A is an example of such an output in accordance with some embodiments. FIG. 11A shows the circuit layout having G0-rule violations and critical G0-spaces. The G0-rule violations are highlighted by a polygon next to patterns and pattern elements forming G0-spaces, such as G0-rule violations 1105, 1113, 1107, and 1111. The G0-rule violations may include odd-loops having a few or many patterns: the G0-rule violation 1107 is an odd-loop of three patterns 1102, 1104, and 1106, but the G0-rule violation 1105 is an odd-loop of thirteen patterns. FIG. 11A also shows critical G0-spaces as a line between the pattern elements meeting the G0-space criteria. Examples include 1101, a corner to corner G0-space, 1103, a run-run G0-space, and 1109, an end-end G0-space. The representations may be sent to a machine-readable storage medium, i.e., memory, such as a memory chip, a disk and/or a drive or to a display device, such as a monitor or a printer. Although FIG. 11A shows a particular way of highlighting G0-rule violations and critical G0-spaces on a layout diagram, other techniques to highlight G0-rule violations and critical G0-spaces may be used. For example, the patterns belonging to a G0-rule violation may be highlighted. Further, other types of representation may be used, including non-graphical representations listing the G0-rule violations and critical G0-spaces. Using the output, a designer can decide which critical G0-spaces to fix. FIGS. 11A and 11B show an example of the before and after output of one such fix. A designer may choose to fix G0-space 1112 between G0-rule violations 1111 and 1113. FIG. 11B shows the result of fixing the G0-space 1112 by reducing the area of pattern 1114. After the G0-space is fixed, the G0-rule violations 1111 and 1113 disappear. When more than one G0-space can be critical G0-spaces between the two G0-rule violations, both may be represented in the output. For example, two odd-loops may share two G0-spaces. Both of the shared G0-spaces may be indicated as critical G0-spaces. A designer can then choose which one to fix depending on the layout constraints. One G0-space may be easier than another to fix if the associated pattern does not reach many adjacent layers or if space around it is available to move into. In this situation only one critical G0-space need be fixed. Referring back to FIG. 9, the designer may optionally enter an adjustment to the layout data for one or more patterns in operation 912. The adjustment corresponds to the G0-space fix or fixes. The adjustment may be received by the DRC in the form of typed entry, mouse click, or changed memory. The DRC then determines whether a distance between an adjusted pattern and an adjacent pattern is a G0-space in operation 914. If not, then operations 906 to 910 repeat to determine what the new G0-rule violations and G0-spaces are and to output the result representation. The process may repeat until no G0-rule violation is determined. According to certain embodiments, when an adjustment is entered for a pattern that affects patterns in other layers, the DRC may propagate the adjustment to adjacent layers until all affected layers are adjusted. For example, a designer may choose to reduce a pattern area and enters this adjustment on one layer. However, the pattern is a trench that is physically connected to vias in adjacent layers. Then the vias should be moved or removed and any further interconnect that the vias connect to must also be moved or reshaped. In other embodiments, the DRC would rely on the designer to manually enter adjustments for all affected layers. The DRC may also issue warnings that the adjustment causes a misalignment of other patterns on other layers and highlight those. FIG. 10 shows a process flow for a method in accordance with some embodiments. Similar to the process in FIG. 9, layout data representing a plurality of patterns, each pattern having a plurality of runs, ends, and corners is received, in operation 1002. The DRC then finds all the G0-spaces between the pattern elements by comparing the layout with specified values, in operation 1004. Then the G0-spaces are analyzed to determine the G0-rule violations, in operation 1006. Using the G0-rule violations, critical G0-spaces are found in operation 1008. The DRC then determines a potential fix for at least one critical G0-space in operation 1010. The potential fix may include moving one or more patterns or reducing an area of a pattern. If reducing an area of a pattern affects layout of patterns on adjacent layers, the change to patterns on other layers should be included. In operation 1012, a representation comprising G0-rule violations, critical G0-spaces and potential fixes is outputted to an output device, for example, a monitor. The output may resemble that of FIG. 11A, except that when a critical G0-space is selected, for example, by a mouse click, a potential fix listing would appear requesting a selection. A designer may choose to apply a potential fix from the list. When the designer chooses a potential fix, the DRC receives an adjustment to the layout data for one or more patterns or a selection of a potential fix, as shown in operation 1014. This selection is then used to re-determine the G0-spaces, G0-rule violations, and critical G0-spaces in operations 1004, 1006, and 1008. The process would iterate until all critical G0-spaces are fixed and no G0-rule violation is found. FIGS. 12A to 12D shows some example iterations of the method in accordance with some embodiments. FIG. 12A is a layout diagram showing various G0-rule violations, for example, 1213 and 1215, and critical G0-spaces, for example, 1201-1211. In order to resolve G0-rule violations 1213 and 1215, critical G0-space 1201 may be fixed, by reducing the area of pattern 1225. After critical G0-space 1201 is fixed, G0-rule violations 1213 and 1215 disappear when the layout is checked again, as shown in FIG. 12B. FIG. 12B includes G0-rule violations 1217 and 1219 with critical G0-space 1203 between them. FIG. 12C depicts the results when G0-space 1203 is fixed by reducing the area of 1227. Note that although these examples involve fixing the critical G0-spaces by reducing pattern area for one pattern, in practice other methods may be used. Other methods may include moving one or more patterns and changing the shape of one or more patterns. FIG. 12C includes G0-rule violations 1221 and 1223 with critical G0-space 1205 between them. FIG. 12D depicts the results when G0-space 1205 is fixed by reducing the area of 1229. In FIG. 12D, the entire right side of the layout is clear of G0-rule violations and critical G0-spaces after resolving three critical G0-spaces 1201, 1203, and 1205. Note that FIG. 12A showed other critical G0-spaces 1207, 1209, and 1211 that disappeared as the critical G0-spaces 1201, 1203, and 1205 are fixed. Critical G0-spaces 1207, 1209, and 1211 may be considered as alternatives to critical G0-spaces 1201, 1203, and 1205 because only one set of critical G0-spaces need be fixed. A designer can choose to fix one set of critical G0-spaces over another set of critical G0-spaces depending on difficulty. The methods and systems disclosed herein allow a designer to have flexibility in choosing how to fix a number of G0-rule violations among efficient alternatives. In one aspect according to some embodiments, the present disclosure pertains to a system for checking design rules. The system includes a computer readable storage medium, a processor coupled to read the storage medium, and an output device. The processor may be part of a special purpose computer for design rule checking configured to perform various methods as disclosed herein. The computer readable storage medium may include one or more of dynamic random access memory (RAM), SDRAM, a read only memory (ROM), EEPROM, a hard disk drive (HDD), an optical disk drive (CD-ROM, DVD-ROM or BD-ROM), or a flash memory, or the like. The output device may be a display, a printer, or the computer storage medium. The system may further include an input device for entering the layout data and/or adjustment to the layout data during one or more iterative resolution of the layout. Using the system, a designer may inputting layout data representing a plurality of patterns, each pattern having a plurality of runs, ends, and corners, specify a plurality of G0-space distance criteria corresponding to a distance between run and run of pattern pairs, run and end of pattern pairs, end and end of pattern pairs, and corner and corner of pattern pairs, review a representation of G0-space and G0 rule violations; and, input an adjustment to the layout data. One aspect of this description relates to a circuit layout method of forming two masks for a plurality of patterns. The method includes receiving layout data representing the plurality of patterns, the layout data including a plurality of layers and identifying spaces between adjacent patterns in at least one layer of the plurality of layers which violate a G0-rule, by a processor of a computer system. The method further includes determining whether each identified space is a critical G0-space, by the processor, wherein the identified space is determined to be the critical G0-space if removal of a portion of at least one of pattern merges two adjacent odd-loops of G0-spaces into a single even-loop of G0-spaces or converts one odd-loop of G0-spaces to a non-loop of G0-spaces. The method further includes receiving a modification of the at least one pattern and updating a spacing of a layer adjacent to the at least one layer based on the received modification, by the processor. Another aspect of this description relates to a circuit layout method of forming two masks for a plurality of patterns. The method includes receiving layout data representing the plurality of patterns of at least one layer of the circuit layout and determining whether a distance between the pair of adjacent patterns is a G0-space for each pair of adjacent patterns, by a processor of a computer system. The method further includes determining whether a G0-rule violation exists for the G0-space, by the processor. The method further includes determining whether the G0-space violating the G0-rule is a critical G0-space based on whether the pair of adjacent patterns are separable into different masks, by the processor. The method further includes outputting a representation comprising the G0-rule violation and the critical G0-space. Still another aspect of this description relates to a system. The system includes a computer readable storage medium containing data representing an integrated circuit (IC) layout, said IC layout comprising a plurality of patterns. The system further includes a processor coupled to the computer readable storage medium. The processor configured for receiving layout data representing the plurality of patterns, the layout data including a plurality of layers and identifying spaces between adjacent patterns in at least one layer of the plurality of layers which violate a G0-rule. The processor further configured for determining whether each identified space is a critical G0-space, wherein the identified space is determined to be the critical G0-space if removal of a portion of at least one of pattern merges two adjacent odd-loops of G0-spaces into a single even-loop of G0-spaces or converts one odd-loop of G0-spaces to a non-loop of G0-spaces. The processor further configured for receiving a modification of the at least one pattern and updating a spacing of a layer adjacent to the at least one layer based on the received modification. Although the embodiments and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, and composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
052979172	abstract	A method of remote control of a mobile carriage including at least one transmit and receive antenna for movement into an underground gallery connected to the surface by a shaft provided with an elevator for effecting deep storage of radioactive wastes. The method involves fitting the site with a plurality of waveguides from a control station which includes a signal generator and a signal receiver and being situated on the surface. The plurality of waveguides are disposed with at least one first waveguide at the surface extending from the control station to the entrance to the shaft. At least one second waveguide is disposed along the shaft and connected at its top end to the first waveguide. At least one third waveguide is disposed along the gallery and connected to the second waveguide in the vicinity of the entrance to the gallery. The waveguides are designed for remote tracking of the robot carriage and for controlling the elevator and at least one robot carriage carried by the elevator during vertical descent and ascent of the elevator within the shaft, and for controlling lateral movement of the robot carriage from the elevator into and within the gallery.
	description	This application claims priority to Provisional Application Ser. No. 61/537,702, entitled “Method of Segmenting Irradiated Boiling Water Reactor Control Rod Blades,” filed Sep. 22, 2011 and is related to U.S. patent application Ser. No. 13/612,982, entitled “Apparatus For Vertically Segmenting A Boiling Water Reactor Control Rod Blade,” filed concurrently herewith. 1. Field This invention relates generally to the storage, transportation and/or disposal of highly radioactive components, and more particularly, to a method of reducing the volume of radioactive boiling water reactor control rods for long term storage. 2. Related Art One type of commonly used boiling water nuclear reactor employs a nuclear fuel assembly comprised of fuel rods surrounded by a fuel channel. Each fuel channel of a boiling water reactor fuel assembly typically consists of a hollow, linear, elongated, four-sided channel of integral construction, which, except for its rounded corner edges, has a substantially square cross section. Commonly, each channel is roughly 14 feet (4.27 m) long by five inches (12.7 cm) square and laterally encloses a plurality of elongated fuel elements. The fuel elements are arranged to allow for the insertion of a cruciform-shaped control rod, which, during reactor operation, is movable vertically to control the nuclear reaction. As is generally known, the control rods include an upper portion having a handle and four upper ball rollers for guiding the control rod as it moves vertically and a lower portion comprising a lower casting and lower ball rollers. The main body structure includes four blades or panels which extend radially from a central spline. Preferably, the blades extend longitudinally to a height that substantially equals the height of the fuel elements, which is approximately 12 feet (3.66 m). The width of the control rods at the blade section is approximately twice the width of the panels, which is in the order of 10 inches (25.4 cms.) and the blades are approximately 2.8 in. (7 mm.) thick. Following functional service, boiling water reactor control rod blades are difficult to store and dispose of because of their size, configuration, embrittled condition, and radiological activity. Heretofore within the United States, in-pool storage of control rod blades has been extremely space inefficient and dry cask storage is not readily available. Control rod blades and other irradiated hardware are typically Class C, low level radioactive waste as defined and determined pursuant to 10 CFR 61 and related regulatory guidance, e.g., NRC's Branch Technical Position on Concentration Averaging and Encapsulation. Since Jul. 1, 2008, low level radioactive waste generators within the United States that are located outside of the Atlantic Compact (Connecticut, New Jersey and South Carolina) have not had access to Class B or Class C, low level radioactive waste disposal capacity. Lack of disposal capacity has caused boiling water reactor operators considerable spent fuel pool overcrowding. Though currently very uncertain and subject to numerous regulatory and commercial challenges, Class B and Class C low level radioactive waste disposal capacity for the remainder of the United States low level radioactive waste generators is anticipated in the relatively near future. One technique for reducing the volume of boiling water reactor control rods for spent fuel pool storage has been to sever the upper and lower portions of the control rods from the control rods' blades. In the remaining main blade structure, the individual blade sections have been removed from the central spline by longitudinal cuts and the severed parts are then stacked for storage or burial as described in U.S. Pat. No. 4,507,840. An alternate approach has been taken in U.S. Pat. No. 5,055,236, which suggests that the vertical cut be made along the center line of the spline to divide the control rod blades into two chevrons. The chevrons can then be closely stacked for storage. Each of the approaches yields twelve-foot (3.66 m) long segments that are costly to shield and transport. U.S. Pat. No. 4,507,840 recognizes that since the blades enclose neutron absorber rods which contain radioactive gas, the vertical cuts must be made quite near the central spline to avoid releasing the radioactive gases. Thus, horizontal segmentation of the blades, which would cut across the sealed rods that contain the neutron absorber material and the radioactive gases, is problematic. Therefore, for safe shipment, a new method is desired for reducing the storage volume of a boiling water reactor control rod. Furthermore, such a method is desired that will reduce the length and width of the segments to be transported so that they will fit in existing, standard, licensed transport casks. Additionally, such a method is desired that will minimize the release of radioactive debris. These and other objects are achieved by a method of reducing the storage volume of a boiling water reactor control rod having a main control element with four panels radially extending along an elongated length of a central spline at four 90° locations around a circumference of the spline, in a cruciform shape. The method includes a step of separating the spline along its elongated length into four substantially equal longitudinal sections with each longitudinal section including one of the panels. The method then identifies at least one elevation along a longitudinal length of each longitudinal section along which the longitudinal section is to be separated into lateral sections. Then a sleeve is wrapped laterally around the longitudinal section at the identified elevation, with the sleeve extending an incremental distance on either side of the elevation. The method then laterally shears at least one of the longitudinal sections at the elevation and substantially simultaneously seals the sleeve against an opposite side of the sleeve as it is sheared. Preferably, the sleeve extends substantially between one and four inches (2.54 and 10.16 cm) on either side of the elevation and more preferably between two and three inches (5.08 and 7.62 cm). Desirably, the sleeve thickness is approximately one-eighth of an inch (0.32 cm) and the sleeve is made out of a malleable metal such as stainless steel or copper. In one embodiment, the step of separating the central spline is achieved by making two cuts along the elongated length and 90° apart around the circumference of the spline with the two cuts preferably being made substantially at the same time. Desirably, the sealing step is achieved by crimping a sheared end of the sleeve to the opposite side of the sleeve. In one preferred embodiment, the crimping step and the shearing step occur substantially simultaneously. FIG. 1 shows a boiling water reactor control rod blade of the type to which the present invention is applicable. As such, the control rod blade comprises an upper portion 11 having an upper handle 10 and four upper ball rollers 12; a lower portion 14 having a lower casting 15 and lower rollers 17; and a main blade structure 16 therebetween. The main blade structure 16 includes four panels or blades 18 arranged in a cruciform shape about a central spline 20. According to one embodiment of the invention, lower portion 14 is removed by cutting approximately in the plane defined by lines m and n, and the upper portion 11 is removed by cutting in a transverse plane defined by lines j and k. Another alternative is to just cut around the rollers to remove them or to leave the handle 10 in place. Although it is possible to practice the invention without removing even the rollers, it is desirable to do so since they typically contain cobalt and are radioactively much hotter than the other portions of the control rod blade. For the general purposes of this description, the principal components of a control rod blade are the lifting handle 10, the stellite roller bearings 12 and 17, the lower portion 14 containing the velocity limiter 19 and the cruciform shape main body 16 including the blades or panels 18 and the central spline 20. To consolidate the control rod blade section 16 the upper portion 11 and the lower portion 14 are first removed in a manner consistent with existing art as part of a control rod blade volume reduction process. The cruciform shaped main body 16 is comprised of four sheathed metallic “panels” 18 of metallic tubes containing powdered boron carbide or other neutron absorbing material that are welded together and to the central spline 20 lengthwise at opposing angles to form the cruciform shape. Because of the radioactive nature of the control rod, it is necessary for the volume reduction process to be performed under water, most preferably in the spent fuel pool. To separate the control rod into practically transportable segments it will be necessary to laterally segment the main body portion 16. However, under water lateral segmentation of the panels 16 will rupture both the sheathing and the tubes contained within the sheathing of the panels 16 thereby exposing the spent fuel pool to unwanted debris in the form of sheathing material, tubes and boron carbide. Embrittlement of the control rod blades caused by the extended neutron exposure that they will have experienced within the reactor compounds the difficulty of lateral segmentation. One prior art method employed to reduce the volume of the control rod blades for storage includes the mechanical longitudinal segmentation of the control rod blade cruciform shaped main body 16 through the center spline 13 resulting in two chevron-shaped sections as is described in U.S. Pat. No. 5,055,236. Segmentation in this fashion substantially improves the in-pool storage efficiency, but does not lend the chevrons to a practical form for transportation to a remote site for storage or for lateral segmentation. One aspect of the method described herein is to further longitudinally segment each chevron along the remaining portion of the spline 13 thereby resulting in four separate and detached panels 18. This subsequent segmentation will improve in-pool storage efficiency, and substantially facilitate the lateral panel segmentation process that will facilitate containerization and optimal radiological characterization for purposes of shipment and disposal. Both physical and radiological criterion will dictate the optimal location along the length of a panel 18 at which lateral segmentation is desired. In other words, the configurations of the transport casks, the intended placement of a separated segment of a panel within the transport cask and the radiation intensity of the segment will all contribute to determine at what elevation along the panel 18 the lateral segmentation should be made. Once the desired point of lateral segmentation of the panel is determined, a preformed band of malleable metal will be slid along the length of the panel to that location or wrapped around the panel at that location. Two such bands 21 are shown in FIG. 2, however, it should be appreciated that the upper panel segment 22, middle panel segment 23 and lower panel segment 24 may or may not be of equal length and the number of panel segments and the number of bands employed will vary depending upon the foregoing dictates. As an example, the bands 21 may be formed from 303 stainless steel or copper and extend one to four inches (2.54-10.16 cm) on either side of the line of demarcation and be approximately ⅛ inch (0.32 cm) thick. Preferably, the bands 21 will extend between two and three inches (5.08-7.62 cm) on either side of the line of demarcation. The panel 18 with the band 21 positioned as described is crimped at the desired point of lateral segmentation and several inches to either side thereof to seal off both segments being separated at the point of demarcation. Lateral segmentation of both the crimped panel and band will be achieved by a hydraulic shear figuratively illustrated by reference character 25. The crimped band 21 is intended to limit or eliminate panel sheathing spring back, and to capture shattered sheathing and the neutron absorbing material within the tubes within the sheathing that has been embrittled by neutron exposure. Once sheared, the panel sections 22, 23 and 24 may be handled and packaged in a manner that optimizes physical and radiological efficiency. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.
	summary
	abstract	A process for gasifying hydrocarbon-containing materials and separating the resultant stream into hydrogen gas and other useful products.
043326404	description	DETAILED DESCRIPTION OF THE INVENTION The invention involves a refueling method and apparatus for the removal of spent fuel assemblies from a reactor core by applying axial force and vibration to the spent fuel assemblies to overcome weight and frictional loads without exceeding the allowable axial force limit that can be safely applied to a fuel assembly without damage thereto or to adjacent assemblies. Vibration reduces the effective coefficient of friction created between adjacent fuel assemblies as they undergo irradiation within a reactor core which results in swelling and creep behavior. By the addition of vibrational action to the axial force applied to a spent fuel assembly undergoing removal, the withdrawal capability is greatly increased without exceeding the allowable axial force limit. Vibration is produced by incorporating into the fuel grapple mechanism a pneumatic vibrator involving a steel ball pneumatically driven around a track by a gas, such as argon used as the reactor cover gas, such that the centrifugal force created by the ball is transmitted through the grapple to the fuel assembly handling socket which in turn applies a vibration to the fuel assembly being removed. The gas utilized to drive the ball may be argon reactor cover gas. Referring now to the drawings, the fuel grapple assembly generally indicated at 10 is shown extending through a hold down tube 11 into a fuel assembly 12. Fuel grapple 10 includes a casing or housing 13 composed of interconnecting sections 13a, 13b and 13c which is provided at its outer end (section 13c) with a grapple latch mechanism generally indicated at 14 and provided with a plurality of latches 15 (only one shown) adapted to engage with an annular notch 16 in a fuel handling socket or tube 17 of fuel assembly 12. As shown in FIG. 2, hold down tube 11 rests against adjacent fuel assemblies surrounding the one to which the grapple is engaged. Latch mechanism 14 is controlled by a push-pull latch actuator 18 such that movement of actuator 18 as indicated by the arrows moves collars 19 and 20 secured thereto to force latch 15 into engagement with notch 16, as shown for removal of the fuel assembly from a reactor core, not shown, or to disengage the latch 15, as conventionally known in the art. Fuel grapple 10 is also provided with a pneumatic vibrator mechanism generally indicated at 21 and located within casing 13 adjacent latch mechanism 14, with latch actuator 18 extending therethrough. As seen in FIGS. 1 and 2, pneumatic vibrator mechanism 21 includes a collar-shaped housing 22, secured intermediate casing sections 13b and 13c, having an annular groove 23 extending around its periphery and defining an annular, tapered raceway or track 24 on the interior surface thereof. The track 24 includes a centrally located annular groove 25 with a plurality of tangentially directed gas passageways 26 (two shown) extending between grooves 23 and 25 (see FIG. 2). A plurality of gas passageways 28 extend between groove 23 and an exterior surface 29 of housing 22 which are in communication with an annular chamber or groove 30 in casing section 13b which in turn is connected to a gas passage 31-32 having a fitting 33 secured thereto to which is connected a gas (such as argon or other cover gas, for example) inlet tube or line 34. A rotating ball 35 (constructed of steel for example) is rotatably positioned within track or raceway 24 and a seal assembly 36 is mounted in casing section 13c about latch actuator 18 to prevent leakage of the gas from the pneumatic vibrator mechanism 21 into the latch mechanism area of the grapple and the associated coolant (liquid sodium) about fuel assembly 12. Coolant vent passageways 37 and cooperating vent holes, 38 are located in grapple casing section 3c and hold down tube 11 to prevent entrapment of liquid sodium, for example, therein. In operation, with the fuel grapple assembly inserted such that the latch mechanism 14 is engaged with fuel handling tube 17 of the fuel assembly 12 to be removed, and with the hold down tube 11 positioned against the outer surface of the adjacent fuel assemblies, as known in the art, the pneumatic vibrator mechanism 21 is activated by directing gas under pressure, such as argon, from a source, not shown, into tube 34, as indicated by the legend and arrow. The gas flows from tube 34 and fitting 33 through passages 32-31, chamber 30, passages 28, groove 23, tangential passages 26 and is directed against rotating ball 35 which drives the ball around track 24 as indicated by the arrows in FIG. 2. The gas is exhausted, as indicated by legend and arrow, through a chamber 40 defined within casing sections 13b and 13a and passes through a plurality of openings 41 in casing section 13a into the reactor cover gas, as indicated by legend and arrow. Centrifugal force created by rotating ball 35 being driven around track 24 produces a vibrating which is transmitted through the grapple assembly to the fuel assembly handling socket or tube 17. The vibration, as pointed out above, reduces the effective coefficient of friction between the fuel assemblies thereby reducing the friction load, thus enabling additional withdrawal capability without exceeding the allowable axial force limit applied to the fuel assembly being removed. It has thus been shown that the present invention provides a refueling method an improved refueling fuel grapple mechanism for use in removing fuel assemblies from a reactor core which have swelled due to exposure to radiation, and thus difficult to remove due to friction loading, without exceeding the allowable safe axial force limit. This is accomplished by the incorporation of a pneumatic vibrator mechanism into the grapple wherein a rotating ball is driven around a track by means of a gas, the centrifugal force created thereby producing vibration in the grapple mechanism which is transmitted to the fuel assembly attached to the grapple. While a particular embodiment of the invention has been illustrated and described, modifications will become apparent to those skilled in the art, and it is intended to cover in the appended claims all such modifications as come within the spirit and scope of the invention.
	claims	1. A computer-implemented method for calibrating leaves of a multi-leaf collimator of a radiotherapy device, the leaves comprising imaging markers and configured to shape a radiation beam emitted by the radiotherapy device by blocking radiation, wherein the radiotherapy device includes an imaging device configured to image the leaves, the imaging device including a lens, wherein the method comprises:receiving, from the imaging device, a plurality of images of the leaves, wherein the leaves are in a first position in at least a first image and in a second position in at least a second image;generating, based at least in part on the first image and the second image, initial position estimates of the leaves in the first position and in the second position, wherein the initial position estimates of the leaves are generated with respect to a predetermined coordinate space associated with the multi-leaf collimator;determining, based at least in part on the initial position estimates of the leaves in the first position and in the second position, offsets for the leaves, the offsets reflecting differences between imaging marker positions of the leaves and positions of tips of the leaves;identifying first position coordinates, with respect to the predetermined coordinate space, for the leaves based upon the offsets of the leaves and the initial position estimates of the leaves;calculating a distortion coefficient of the lens based upon the first position coordinates for the leaves and the offsets of the leaves, the distortion coefficient representing an optical distortion effect associated with the lens;determining corrected position coordinates, with respect to the predetermined coordinate space, for the leaves based on the distortion coefficient and the first position coordinates for the leaves;correcting the offsets for the leaves based on the corrected position coordinates for the leaves; andcalibrating the multi-leaf collimator based on the corrected offsets, wherein at least one leaf of the multi-leaf collimator is controlled based on the calibration. 2. The method of claim 1, wherein the multi-leaf collimator includes two banks of leaves which are captured in the images and wherein two opposing leaves constitute a leaf pair. 3. The method of claim 2, wherein the first position is a retracted position of the leaves and the second position is an extended position of the leaves. 4. The method of claim 2, wherein:a first bank of leaves moves into the retracted position in the first image and the extended position in the second image; anda second bank of leaves moves into the extended position in the first image and the retracted position in the second image. 5. The method of claim 2, wherein calculating the distortion coefficient comprises identifying, in the predetermined coordinate space, a lens x-coordinate and a lens y-coordinate associated with a centre of the lens. 6. The method of claim 5, wherein identifying the lens x-coordinate comprises:for each leaf pair, generating a function based on the first position coordinates of the two opposing leaves in the first position and in the second position;identifying one of a maximum or a minimum of each function;determining an x-coordinate, relative to the predetermined coordinate space, of each maximum or minimum; andaveraging the x-coordinates of the maximums and minimums. 7. The method of claim 6, wherein the function of each leaf pair is a second-order polynomial. 8. The method of claim 5, wherein identifying the lens y-coordinate comprises:for each bank of leaves in each of the first and second positions, generating a function based on the first position coordinates of the leaves;identifying a turning point for each function; andaveraging the turning points. 9. The method of claim 8, wherein the function for each bank of leaves in each of the first and second positions is a second-order polynomial. 10. The method of claim 2, wherein calculating of the distortion coefficient of the lens comprises:generating a function based on the first position coordinates and offsets of a selected one of the banks of leaves in one of the images;calculating a provisional distortion coefficient of the lens based on the function;determining an error value of the provisional distortion coefficient;if the error value is above a predetermined threshold, regenerating the function using the error value, recalculating the provisional distortion coefficient of the lens based on the regenerated function, and determining the error value of the recalculated provisional distortion coefficient until the error value is below the predetermined threshold; andwhen the error value is below the predetermined threshold, setting the distortion coefficient of the lens to be equal to the provisional distortion coefficient. 11. The method of claim 10, wherein the function is generated using a root mean square technique. 12. The method of claim 10, wherein calculating the provisional distortion coefficient comprises:determining undistorted position coordinates, with respect to the predetermined coordinate space, for each leaf in the selected bank of leaves by minimizing, with the generated function, optical distortion associated with the lens;calculating a distortion coefficient of each leaf in the selected bank of leaves based on the undistorted position coordinates; andgenerating the provisional distortion coefficient of the lens by averaging the distortion coefficients of the leaves. 13. The method of claim 1, further comprising identifying the imaging marker positions of the leaves utilizing a predetermined conversion factor relating numbers of pixels and distance. 14. The method of claim 1, wherein determining the offsets for the leaves comprises:identifying the imaging marker positions of the leaves, wherein each leaf is associated with at least two identified imaging marker positions;averaging, for each leaf, the imaging marker positions;identifying a reference leaf based on the average imaging marker positions;determining differences between the average imaging marker positions of the leaves and the average imaging marker position of the reference leaf; andcalculating the offsets based on the determined differences. 15. A computer-implemented method for use in a radiotherapy device that emits a radiation beam to treat a target tumour of a patient, wherein the radiotherapy device comprises a multi-leaf collimator having a plurality of leaves, the leaves comprising imaging markers and configured to shape the radiation beam emitted by the radiotherapy device by blocking radiation, wherein the radiotherapy device includes an imaging device configured to image the leaves, the imaging device including a lens, wherein the method comprises:receiving a treatment plan for treating the target tumour with radiation, wherein the treatment plan includes a therapeutic radiation beam shape for irradiating the target tumour;identifying radiotherapy position coordinates, with respect to a predetermined coordinate space associated with the multi-leaf collimator, for the leaves of the multi-leaf collimator, wherein the leaves form the therapeutic radiation beam shape by blocking radiation when they are positioned at the radiotherapy position coordinates;receiving offsets for the leaves, the offsets reflecting differences between imaging marker positions of the leaves and positions of tips of the leaves;receiving calibration coefficients based on leaf position data from multiple multi-leaf collimators;generating a position error function based on the calibration coefficients, wherein the position error function indicates a leaf position error associated with an optical distortion effect of the lens; andcontrolling the leaves to move to the radiotherapy position coordinates based on the offsets and the position error function. 16. The method of claim 15, wherein the multi-leaf collimator includes two opposing banks of leaves and wherein generating the position error function comprises:generating position error polynomials for the banks of leaves, wherein each position error polynomial is based on different calibration coefficients;receiving, from the imaging device, an image of the leaves;identifying distorted position coordinates, with respect to the predetermined coordinate space, for the leaves based upon positions of the imaging markers of the leaves in the image; andgenerating the position error function based on the position error polynomials and the distorted position coordinates of the leaves. 17. The method of claim 16, wherein each bank of leaves is associated with three position error polynomials, and each position error polynomial is based on four calibration coefficients. 18. The method of claim 15, wherein the offsets of the leaves are determined, at least in part, from leaf position data obtained when the leaves are in a first position and upon leaf position data obtained when the leaves are in a second position. 19. The method of claim 15, wherein the position error function indicates a leaf position error of each leaf. 20. The method of claim 15, further comprising:calculating corrected calibration coefficients to accommodate an adjustment of the multi-leaf collimator; andgenerating a corrected position error function based on the corrected calibration coefficients.
	description	The following are descriptions on a reactor nuclear instrumentation system and a reactor power distribution monitor system including the reactor nuclear instrumentation system according to the present invention. Embodiments will be described hereunder with reference to the accompanying drawings. FIG. 1 is a block diagram schematically showing a configuration of a reactor power distribution monitor system according to one embodiment of the present invention. The reactor power distribution monitor system is applied to a boiling water reactor (BWR) and includes a reactor nuclear instrumentation system 30 comprising a detector and a signal processing device and a reactor power distribution computing device 31 for computing a power distribution of a reactor core. The reactor power distribution computing device 31 is a part of a process control computer and monitors a reactor core performance. In the boiling water reactor, a reactor pressure vessel 2 is housed in a reactor container 1, and a reactor core 3 is housed in the reactor pressure vessel 2. The reactor core 3 is cooled by a coolant combining a moderator. The reactor core 3 is mounted with many fuel assemblies 4 as shown in FIG. 2 and FIG. 3. In these many fuel assemblies 4, four fuels assemblies constitutes one set, and a control rod 5 having a shape of cross in its cross section is mounted between one set of fuel assemblies 4 so as to be freely take in and out from a lower portion. The reactor core 3 is constructed so that a plurality of sets of four fuel assemblies 4 are mounted therein. Further, the reactor core 3 is provided with a plurality of incore nuclear instrumented fuel assemblies 32 constituting a detector of the reactor nuclear instrumentation system. The incore nuclear instrumented fuel assemblies 32 are arranged at a position different from a position where the control rod 5 is arranged. Further, the incore nuclear instrumented fuel assembly 32 is arranged at a corner water gap G formed between four fuel assemblies 4, as shown in FIG. 2 and FIG. 3. Further, the incore nuclear instrumented fuel assembly 32 includes a thin and long tube-shaped nuclear instrumentation tube 33. The nuclear instrumentation tube 33 is dispersively provided with a plurality of neutron detectors 34 which function as a fixed type (stationary or immovable) neutron detecting means and a xcex3-ray heat detectors 35 which function as a fixed type xcex3-ray detecting means in an axial direction thereof. In the nuclear instrumentation tube 33, a plurality of fixed type neutron detectors 34 are dispersively arranged as an LPRM detector at equal intervals in a core axial direction, and in this manner, a neutron detector assembly 37 is constructed. In a boiling water reactor, usually, four fixed type neutron detectors 34 are dispersively arranged at equal intervals in the core axial direction. Further, each of the neutron detectors 34 is electrically connected to a signal processing device 40 by means of a signal cable 38 penetrating through a penetration portion 39, and in this manner, a power range neutron flux measurement system 41 is constructed. Further, in the nuclear instrumentation tube 33, a plurality of fixed type xcex3-ray heat detectors 35 are dispersively arranged in the core axial direction as a gamma thermometer in an arrangement of assembly (called merely gamma thermometer herein) and measures a gamma ray heat. The xcex3-ray heat detectors 35 has the same numbers as the fixed type neutron detectors 34 arranged in the core axial direction or more, for example, 8 in the core axial direction, and in this manner, a xcex3-ray heat detector assembly 44 is constructed as a gamma thermometer 44. Each of the xcex3-ray heat detectors 35 of the gamma thermometer 44 is electrically connected to a gamma thermometer signal processing device 48 by means of a signal cable 45 penetrating through a penetration portion 46, and in this manner, a gamma thermometer power distribution measurement system 50 is constructed. The reactor nuclear instrumentation system 30 is composed of the power distribution neutron measurement system 41 and the gamma thermometer power distribution measurement system 50. A detector group of the reactor nuclear instrumentation system 30 is housed in the incore nuclear instrumentation assembly 32. The incore nuclear instrumentation assembly 32 measures a neutron flux and a xcex3-ray heat at a predetermined measuring point in the reactor core 3. In the reactor nuclear instrumentation system 30, the movable neutron detector and the xcex3-ray detector are unnecessary, so that a mechanical drive device included in the conventional reactor nuclear instrumentation system can be omitted. Therefore, it is possible to simplify a structure of the reactor nuclear instrumentation system 30, and a driving part is dispensed in the reactor nuclear instrumentation system 30, so that maintenance free can be achieved, and also, an exposure work of a worker can be dispensed or greatly reduced. The reactor pressure vessel 2 or a primary pipe system (not shown) is provided with a reactor core condition (present) data measuring device 52 which measures core process data such as a coolant core flow rate (or an approximate re-circulation flow rate), a core pressure and a coolant inlet temperature, a control rod position in a control rod drive device and the like. Although the reactor core operating status (present) data measuring device 52 is simply illustrated as one measuring device in FIG. 1, actually, it is reactor core operating status data measuring means which is composed of a plurality of measuring equipments for measuring or monitoring various reactor core process data. The reactor core operating status data measuring device 52 is connected to a condition data processing device 55 via a signal cable 54 penetrating through a penetration portion 53, and in this manner, a process data measurement system 56 is constructed. The condition data processing device 55 of the process data measurement system 56 is not a exclusively independent device, but may be constructed as a process control computer or a part thereof. Thus, the process data measurement system 56 is included in the process control computer constituting the reactor core power distribution computing device 31. Further, the process data measurement system 56 may be constructed as a part of the reactor nuclear instrumentation system 30 in the light of a concept of a detector and a signal processing device. Moreover, the process data measurement system 56, the power range neutron flux measurement system 41 and the gamma thermometer power distribution measurement 50 are electrically connected to the reactor power distribution computing device 31. Then, a signal processed by respective signal processing devices 40, 48 and 55 is inputted to a power distribution computing module 58 of the reactor power distribution computing device 31. The reactor power distribution computing device 31 is composed of: a power distribution computing module 58 which computes a neutron flux distribution, a power distribution, a margin of a thermal operation limit value or the like in a reactor core 3; a power distribution learning module 59 which is inputted with and corrects the computed result from the power distribution computing module and obtains a reactor core power distribution reflecting an actually measured process data; and an input-output device 60 including a display device. The following signals are inputted to the reactor power distribution computing device 31. That is, the input signals includes a detection signal (xcex3-ray heat measurement signal) S1 from the xcex3-ray heat detector 35 functioning as a gamma thermometer, a neutron flux detection signal S2 from the neutron detector 34, and a reactor core present data detection signal S3 from the reactor core present data measuring device 52. The power distribution computing module 58 of the reactor power distribution computing device 31 processes the inputted reactor core present data detection signal S3 according to a three-dimensional nuclear thermal-hydraulics computing code with the use of a physical model stored in the process control computer, and then, computes a neutron flux distribution, a power distribution, a margin of a thermal operation limit value or the like in a reactor core 3. The physical model is a spacer model taking an influence on an node power by the fuel spacer into consideration. A computation result computed by using the physical model is inputted to the power distribution adaption (learning) module 59 which functions as a power distribution correction module. The power distribution learning module 59 corrects a power distribution computation result based on the physical model with reference to the xcex3-ray heat measurement signal S1, and then, returns it to the power distribution computing module 58. Subsequently, the module 58 makes an evaluation with respect to a reactor power distribution reflecting actually measured data and having high reliability and a thermal limit value. By the way, as shown in FIG. 1 to FIG. 3, the incore nuclear instrumentation assembly 32 constitutes the reactor nuclear instrumentation system 30. The incore nuclear instrumentation assembly 32 is integrally arranged in the nuclear instrumentation tube 33 in a manner of combining a local power range monitor system (LPRM) 37 which is a neutron detector assembly functioning as a fixed type fission chamber (neutron detecting means), and the gamma thermometer 44 which is a xcex3-ray heat detector assembly functioning as a fixed type gamma ray detecting means. Further, the nuclear instrumentation tube 33 is arranged in a state of vertically extending in the core 3 of the reactor. The LPRM 37 includes N (number, integer) (Nxe2x89xa74), for example, four fixed type neutron detectors 34 which are dispersively arranged at equal intervals in an axial direction, and the gamma thermometer 44 includes 8 or 9 gamma (xcex3) ray heat detectors 35 which are dispersively arranged in an axial direction. The neutron detectors 34 of the LPRM 37 and the gamma ray heat detectors 35 of the gamma thermometer 44 are housed in the nuclear instrumentation tube 33 while a coolant being guided so as to flow upwardly in the nuclear instrumentation tube 33. In FIG. 2 and FIG. 3, there is shown an example of the gamma thermometer 44 which is constructed in a manner that eight xcex3-ray heat detectors 35 are arranged in a fuel effective portion H of the core axial direction. An arrangement interval of each xcex3-ray heat detector 35 in the core axial direction is determined taking an arrangement interval of each neutron detector 34 of the LPRM 37 in the core axial direction into consideration. More specifically, if an axial distance between neutron detectors 34 of the LPRM 37 is set as L, in the gamma thermometer 44, four of the eight xcex3-ray heat detectors 35 are arranged at the same axial position as the fixed type neutron detector 34, three of them are arranged at an intermediate position of the neutron detector 34 at an interval L/2, and the lowest xcex3-ray heat detector 35 is arranged at a distance L/4 to L/2 below the lowest neutron detector 34 and in the fuel effective portion of 15 cm or more from the lower end of the fuel effective portion, and axial centers of these detectors are aligned with each other. In the case of locating the xcex3-ray heat detectors 35 above the uppermost neutron detector 34, the uppermost xcex3-ray heat detector 35 is arranged so as to be situated at a distance L/4 to L/2 above the lowest neutron detector 34 and in the fuel effective portion of 15 cm or more from the lower end of the fuel effective portion. The lowest xcex3-ray heat detector 35 is arranged at a position near the lower end of the fuel effective portion as much as possible in a fuel effective length. In the case where the fuel effective length (371 cm at present) is divided into 24 nodes in a core axial direction, preferably, the xcex3-ray heat detector 35 is arranged so that its center is aligned with the axial center of the second core axial direction node from the bottom. When such an arrangement is made, in the xcex3-ray heat detector 35 of the gamma thermometer 44, it is possible to detect a xcex3-ray heat on a lower end side of the reactor core, and to measure the xcex3-ray heat on the lower end over a wider range of the fuel effective length in the core axial direction. This is because of preventing the following matter. That is, a power of the node on the lowest end is originally low due to a neutron leakage, and a sensitivity by the xcex3-ray heat detector 35 is low, and further, a contributing range of gamma ray to the xcex3-ray heat detector 35 is 15 cm or more as described later. For this reason, unless the xcex3-ray heat detector 35 is separated 15 cm or more from the lower end of the fuel effective length, other xcex3-ray heat detector 35 arranged at a core axial direction position measures a heating effect of xcex3-ray from the vertical direction in the axial direction. On the contrary, the lowest xcex3-ray heat detector 35 detects only xcex3-ray heat contribution from above. As a result, a correlation equation of power measurement is different. In an axial directional design of a recent fuel assembly 4, there are many cases where a natural uranium blanket is used as the node on the lowest end. For this reason, even if the natural uranium blanket portion of a low power (output) is measured, the output signal of the gamma thermometer 44 is very low. Therefore, there is no means of interpolating and extrapolating a power distribution at a position below the lowest neutron detector 34. The gamma thermometer 44 has a long rod-shaped structure as shown in FIG. 4 and FIG. 5. The gamma thermometer 44 is a thin and long rod-shaped assembly having a diameter of e.g., about 8 mm xcex8, and has a length of substantially covering a fuel effective length in a core axial direction. In the gamma thermometer 44, a cover tube 62 formed of stainless steel is used as a metallic jacket, and a metallic long rod-shaped core tube 63 is housed in the cover tube 62. Further, the cover tube 62 and the core tube 63 are fastened, and then, are fixed to each other by means of shrinkage fit, cooling fit or the like. A sleeve or annular space portion 64 constituting an adiabatic portion is formed between the cover tube 62 and the core tube 63. A plurality of e.g., 8 or 9 annular space portions 64 are dispersively arranged at intervals in an axial direction. The annular space portion 64 is formed by cutting an outer surface of the core tube 63 along a circumferential direction. Then, a gas having a low heat conductivity, for example, an argon Ar gas is encapsulated in the annular space portion 64. The annular space portion 64 may be formed on the cover tube 62 side which is a jacket tube. The xcex3-ray heat detector 35 is provided at a position where the annular space portion 64 is formed, and thus, a sensor section of the gamma thermometer 44 is constructed. The core tube 63 has an internal hole 65 which extends to an axial direction along the center thereof. In the internal hole 65, a mineral insulated (MI) cable sensor assembly 65 is fixed by means of brazing, caulking or the like. The cable sensor assembly 66 is provided with a built-in heater 67 which functions as a correction rod-shaped exothermic body of the gamma thermometer 44 at the center thereof, and a differential type thermocouple 68 which functions a plurality of temperature sensors. The built-in heater 67 and the thermocouple 68 are hardened by an electric insulating layer or a metal/metal alloy filler 69, and then, are integrally housed in a metallic cladding tube 70. The metallic cladding tube 70 is closely abutted against others at both outer and inner surfaces thereof. The built-in heater 67 comprises a sheath heater and is integrally constructed in a manner that a heater wire 72 is coated with a metallic cladding tube 74 via an electric insulating layer 73. Further, the thermocouple 68 is integrally constructed in a manner that a thermocouple single wire 75 is coated with a metallic cladding tube 77 via an electric insulating layer 76. The differential type thermocouple 68 located in the internal hold 65 of the core tube 63 is arranged so as to correspond to the annular space portion 64, and thus, the xcex3-ray heat detector 35 is constructed. As shown in FIG. 5, each thermocouple 68 is set in a manner that a high temperature side contact 78a is situated on the sensor section formed in the annular space portion 64, that is, on the center of the adiabatic portion in the axial direction, and a low temperature side contact 78b is situated at a downward position slightly separating from the adiabatic portion (the low temperature side contact 78b may be situated at an upward position slightly separating from the adiabatic portion). The thermocouple 68 is coaxially inserted around the built-in heater 67 by the same number as the xcex3-ray heat detector 35. The gamma thermometer 44 is an incore power distribution detector (xcex3-ray heat detector) assembly, and the incore power distribution measuring principle is shown in FIG. 6A and FIG. 6B. In a reactor such as a boiling water reactor or the like, a xcex3-ray is generated proportional to a fission yield of a nuclear fuel mounted in the reactor core 3 housed in the reactor pressure vessel 2. The generated xcex3-ray flux heats a structural element of the gamma thermometer 44, for example, the core tube 63. The heat energy is proportional to a xcex3-ray flux, and then, the xcex3-ray flux is proportional to a fission yield. In the annular space portion 64 of each xcex3-ray heat detector 35 which is a sensor section of the gamma thermometer 44, a performance of eliminating a heat by a diametrical coolant is worse due to a heat resistance of the annular space portion 64. For this reason, there is generated a heat flux as shown by an arrow A, which makes a detour in an axial direction, and as a result, a temperature difference is caused. So, the high temperature side contact 78a and the low temperature side contact 78b of the differential type thermocouple 68 are arranged as shown in FIG. 5, and it is possible to detect the temperature difference by a voltage signal. The temperature difference is proportional to the xcex3-ray heat, and therefore, it is possible to obtain a xcex3-ray heat which is proportional to a local fission yield from the voltage signal of the differential type thermocouple 68. This is the measuring principle of the gamma thermometer 44. On the other hand, in the fuel assembly 4, as shown in FIG. 2, a fuel bundle (not shown) bundling up many fuel rods (not shown) is housed in a rectangular and cylindrical channel box 80. The fuel bundle is constructed in a manner that many fuel rods are bundled by a fuel spacer 81 (see SP position of FIG. 7) so as to provide a square lattice arrangement. The fuel spacer 81 holds a clearance between fuel rods. For example, seven fuel spacers 81 is dispersively arranged in the channel box 80 along an axial direction of the fuel bundle. The fuel assembly 4 is mounted in the reactor core 3 in a state that its upper and lower ends are tightly fixed by an upper tie-plate and a lower tie-plate, respectively. Each fuel rod housed in the fuel assembly 4 is fixed in a manner that a fuel sintering pellet is filled in a fuel cladding tube made of a zirconium alloy, and upper and lower ends of the fuel cladding tube are deposited by an end plug. For example, an uranium oxide fuel or a uranium/plutonium mixed oxide (MOX) fuel is used as the fuel sintering pellet. In a boiling water reactor, a great many of fuel assemblies 4 are mounted in the reactor core 3, and each fuel assembly 4 is formed with a coolant passage outside and inside the channel box 80. Many fuel assemblies 4 are mounted in the reactor core 3 in a state of standing together in the large number, and a computation of power distribution of the reactor core is carried out by means of the reactor power distribution computing device 31 according to a three-dimensional nuclear thermal-hydraulics simulation computation (three-dimensional nuclear hydrothermal computing code) stored in the process control computer. The three-dimensional nuclear thermal-hydraulics computing code has a spacer model. The reactor power distribution computing device 31 is also called as a reactor core power distribution computing device or as a reactor core performance monitor and is one of functions stored in the process control computer of the reactor. In the reactor power distribution computing device 31, the following information is inputted to the power distribution computing module 58. That is, the information includes a control rod pattern obtained from the reactor core present data measuring device 52, a core flow rate, a reactor doom pressure (internal pressure of reactor pressure vessel), and various parameters such as a reactor heat power and a detection signal of a core inlet coolant temperature obtained from the reactor core condition (present) data. In concrete, the reactor core present data signal S3 from the condition data processing device 55, the neutron flux signal S2 from the signal processing device 40 and the xcex3-ray heat signal S1 from the gamma thermometer signal processing device 48 are respectively inputted to the power distribution computing module 58 as a measured data. Meanwhile, the power distribution computing module 58 of the reactor power distribution computing device 31 has a built-in three-dimensional nuclear thermal-hydraulics computing code which is a physical model. Then, an input signal is computed and processed with the use of the three-dimensional nuclear thermal-hydraulics computing code, and thus, an incore power distribution is obtained by computation (calculation). In such three-dimensional nuclear thermal-hydraulics computing code, an influence on an node power by the fuel spacer 81 is previously evaluated and is stored in the process control computer as a spacer model. In the fuel assembly 4, the fuel rods are bundled up, and then, 7 to 8 fuel spacers 81 are dispersively arranged in an axial direction so as to keep predetermined interval between fuel rods. The arrangement effect of the fuel spacers 81 has not been considered in the conventional three-dimensional nuclear thermal-hydraulics computing code. The fuel spacer 81 is mainly made of a zirconium alloy having a low neutron absorption. It is found that a cooling water which is a moderator is locally reduced due to an existence of the fuel spacer 81, and for this reason, a thermal neutron flux is decreased. Also, the fuel spacer 81 has an effect of absorbing a neutron although the effect is slight, and therefore, this effect should not be disregarded. Incidentally, in the case of computing a power distribution of the fuel assembly 4, frequently, the computation is carried out after the conventional fuel assembly is divided into 24 nodes in the axial direction. Although it is general that the number of nodes thus divided is 24, the fuel assembly may be divided into any of a range from 12 nodes to 26 nodes in accordance with a size of a reactor core. A node power is lowered due to an existence of the fuel spacer as described above, and it is found that there is an error of about 0.05 (i.e., 5% of node average power) at the maximum in a state standardized so that an average power of each node in the axial direction of the reactor core 3 becomes 1.0, depending upon an axial direction position and a diametrical direction in the reactor core 3. However, in the conventional movable neutron flux measuring device (TIP), all of power distribution of 24 nodes in the core axial direction is read, and then, the whole node power is computed as a reference measurement signal according to the three-dimensional nuclear thermal-hydraulics computing code of the reactor power distribution computing device 31. Then, in the power distribution learning module which corrects the computed result, a node power including the fuel spacer is corrected, and as a result, the fuel spacer effect in the axial direction is accurately read (captured). A power distribution of an axial direction of the reactor core 3 is computed according to the three-dimensional nuclear hydrothermal computing code on the basis of all nodes, for example, an axial measurement data less than 24 nodes and not the whole core axial direction node, and then, the computed result is learnt and corrected. In this case, however, if a gamma ray heat of the xcex3-ray heat detector portion corresponding to each position of the nuclear instrumentation tube 33 is computed on the basis of the power distribution result computed according to the three-dimensional nuclear thermal-hydraulics computing code having no spacer model, a learning error is caused in the node having the spacer, and then, the influence is given to other nodes. Next, to give an example of a physical model of a three-dimensional nuclear thermal-hydraulics simulation computing code which is employed in a boiling water reactor, a reactor power computation will be explained with reference to a flowchart shown in FIG. 11. In this case, a three-dimensional nuclear thermal-hydraulics computing code is generally called as correction group will be explained below. [A] Input Data Reading: Data required for computation, that is, the whole reactor core coolant flow rate, a control rod pattern, the whole reactor core generated power level, a power distribution (primary approximation) of the previous computation, a combustion distribution, LPRM and GT actually measured values, are inputted to the three-dimensional nuclear thermal-hydraulics computing code. The coolant flow rate is a reactor core operating status (present) data, and for this reason, some of process data are obtained from the operating status data measuring device 52, and then, are computed by means of the process data measurement system 56. The LPRM and GT actually measured values are inputted from each neutron detector 34 of the LPRM 37 and the xcex3-ray heat detector 35 of the gamma thermometer (GT) 44. The power distribution (primary approximation) of the previous computation and a combustion distribution are previous data stored in the reactor power distribution computing device. [B] Supposition of the initial value of incore power distribution Pijk: Usually, an incore (in-channel) power distribution or the like is supposed as the initial value required for a repeating computation called as Void Iteration, and then, the supposed value is set as a temporary incore power distribution Pijk for the following computation to advance the following computation. In this case, subscripts i and j are indicative of fuel assembly 4 position in the reactor core 3 and the subscript k is indicative of a reactor core axial position. [C] Computation of Incore Void Distribution: In order to compute an incore void axial distribution VFijk of each fuel assembly 4 in the reactor core 3 and a reactor core average void axial distribution VFBk of a bypass range, required for an effective multiplication factor (constant) and an incore power distribution computation which will be described in the next item [D], the incore void axial distribution VFijk of each fuel assembly 4 and the reactor core average void axial distribution VFBk are computed according to the following procedures. (1) Computation of Each Fuel Assembly In-Channel Flow Rate Wij: A coolant flowing into the reactor core 3 is divided into an in-channel (incore) flow flowing in each fuel assembly 4 and a bypass range flow in each fuel assembly 4 at a the reactor core bottom portion, and then, these in-channel flow and bypass range flow again join together at a reactor core top portion outlet. Therefore, a distribution computation need to be carried out so that each pressure loss of the in-channel flow rate Wij and the bypass range flow rate BPF of each fuel assembly 4 becomes equal when these flows pass through respective channels in the reactor core 3. Moreover, there are a kind of fuel assembly 4 (e.g., 8xc3x978 fuel or 9xc3x979 fuel) and a kind of an orifice (e.g., peripheral orifice and center orifice) as a factor of giving a great influence to the distribution of the incore flow rate. For this reason, a coefficient of pressure loss for each axial portion of a hydrothermal characteristic representative fuel assembly channel and fuel assembly 4 is inputted every kind of the fuel assembly in the reactor core 3 and every kind of the orifice. The coefficient of pressure loss uses the result previously computed according to a reactor core hydrothermal analysis code every kind of the fuel assembly in the reactor core 3 and every kind of the orifice. The computation of the in-channel flow rate distribution is carried out according to a repeating computation because a pressure loss of each fuel assembly 4 depends upon a power distribution and a void distribution. In this case, the void distribution in fuel channel (channel box) gives a great influence to the computation of pressure loss. A pressure loss of the fuel assembly is classified into four, that is, a friction pressure loss, a local pressure loss, a position pressure loss and an acceleration pressure loss. In order to compute the pressure loss, a known two-phase flow pressure loss equation is used such that an equation used in a usual single-phase flow is multiplied by a two-phase flow friction resistance magnification. (2) Computation of Each Fuel Assembly Incore Enthalpy Axial Distribution Hijk and Bypass Range Core Average Enthalpy Axial Distribution HBk: In this enthalpy axial distribution computation, each fuel assembly incore (in-channel) enthalpy axial distribution Hijk and the bypass range core average enthalpy axial distribution HBk are computed by using the temporary incore power distribution Pijk used as the initial value, the in-channel flow rate Wij of each fuel assembly 4 computed in the following item [D], and the inputted bypass range flow rate BPF. There is already a heat generated by a nuclear fission in the fuel rod as a factor of increasing an enthalpy of each fuel assembly in-channel node, and besides, there are gamma heat in the fuel rod, a neutron moderation of the coolant, gamma heat, and a heat transfer effect to the bypass range via a fuel channel. Considering these factors, an enthalpy of each fuel assembly In-channel node is computed. The enthalpy computation is carried out for each fuel assembly channel with the use of an inputted core inlet coolant enthalpy, an incore power distribution Pijk and the in-channel flow rate Wij successively over a range from the bottom to the top portion of the reactor core. Supposed that a bypass flow is sufficiently and uniformly mixed in the bottom portion of the reactor core, in the bypass range enthalpy axial distribution, an average distribution of the reactor core is used. The factors of increasing an enthalpy of each bypass range node include a heat generated by a nuclear fission in the fuel rod, and besides, gamma heat in the fuel rod, a coolant in the bypass range, contribution by a neutron moderation-absorption of the control rod and gamma heat, and a heat transfer effect to the bypass range from a fuel channel, and a heat transfer effect from the bypass range to the outside of the reactor core. Considering these factors, an enthalpy of the bypass range core average enthalpy axial distribution HBk is computed. The computation is carried out successively over a range from the bottom portion to the top portion of the reactor core with the use of the following mathematical equation as the inputted reactor core inlet coolant enthalpy, the bypass flow rate BPF and the reactor core axial power distribution Pk. [Mathematical Expression 1] ( ∑ i ⁢ ∑ j ⁢ P ijk ) (3) Computation of Each Fuel Assembly In-Channel Void Rate Axial Distribution VFijk and Reactor Core Average Void Axial Distribution VFBk of Bypass Range: Based on each fuel assembly in-channel (incore) enthalpy axial distribution Hijk and the bypass range core average enthalpy axial distribution HBk computed in the above item [C], the fuel assembly in-channel void axial distribution VFijk and the reactor core average void axial distribution VFBk of a bypass range are computed. In order to compute a void content (amount or rate) from a coolant enthalpy, there is the following equation (1) as a method of computing a void content of a sub-cool range. [Mathematical Expression 2] Quality: Xijk=(Hijkxe2x88x92hsat)/(hgxe2x88x92hsat)xe2x80x83xe2x80x83(1) In place of the above equation (1), the following equation (3) is computed on the basis of a liquid enthalpy HLijk. [Mathematical Expression 3] Flow Quality: XFijk=(Hijkxe2x88x92HLijk)/(hgxe2x88x92HLijk)xe2x80x83xe2x80x83(2) Then, a flow quality XFijk is computed with the use of an equation in which a drift flux model is applied to an expression of relation of the flow quality XFijk and the void content. In this case, hgat represents an enthalpy of saturated water, and hg represents an enthalpy of saturated steam. The reactor core average void rate axial distribution VFBk of a bypass range and an outlet void content VFBex are computed from the bypass range core average enthalpy axial distribution HBk, and the computing method is the same as the In-channel case. [D] Computation of Effective Multiplication Factor and Incore Power Distribution: This item [D] is a so-called nuclear computation section, and a nuclear constant of each node of the reactor core 3 is computed with the use of the incore in-channel void rate axial distribution VFijk, and the bypass range void axial distribution VFBk computed in the above item [C], and then, an effective multiplication factor keff and an incore power distribution Pijk are computed. A power Pijk of each node is computed according to a nuclear fission by a neutron in each node. Therefore, in order to compute the incore power distribution Pijk, a neutron flux distribution xcfx86ijk in the reactor core 3 must be computed. Now, assuming that the neutron flux xcfx86 is divided into three groups, that is, a fast neutron flux xcfx861, an intermediate neutron flux xcfx862 and a thermal neutron flux xcfx863 according to an energy of neutron flux xcfx86, these three groups, that is, neutron flux xcfx861, xcfx862 and xcfx863 are obtained by solving the following diffusion equations (3), (4) and (5). [Mathematical Expression 4] - D 1 ⁢ ∇ 2 ⁢ φ 1 + Σ 1 ⁢ φ 1 = 1 k eff ⁢ ( v 1 ⁢ Σ f1 ⁢ φ 1 + v 2 ⁢ Σ f2 ⁢ φ 2 + v 3 ⁢ Σ f3 ⁢ φ 3 ) ( 3 ) xe2x88x92D2∇2xcfx862+xcexa32xcfx862=xcexa3sl1xcfx861xe2x80x83xe2x80x83(4) xe2x88x92D3∇2xcfx863+xcexa33xcfx863=xcexa3sl2xcfx862xe2x80x83xe2x80x83(5) where, Dg: diffusion coefficient of energy g-group xcexa3g: eliminated cross section xcexa3slg: moderating cross section xcexa3fg: fission cross section xcexdg: number of neutrons generated per fission In this case, g is a suffix of 1, 2 and 3 In order to solve the above diffusion equation, assuming that a buckling (see the following mathematical expression 5) of neutron flux of each energy group is equal, the above equations of energy three-group such as fast, intermediate and slow neutron fluxes are summarized to the diffusion equation of the fast neutron group, and then, only fast neutron flux distribution xcfx861ijk is computed. [Mathematical Expression 5] B g 2 ⁡ ( = - ∇ 2 ⁢ φ g φ g ) xe2x80x83 The incore power distribution Pijk is computed by adding an effect by the intermediate neutron flux xcfx862 and the thermal neutron flux xcfx863 to a nuclear fission by the fast neutron flux distribution xcfx861ijk thus obtained. (1) Computation of Effective Multiplication Factor keff and incore fast neutron flux distribution xcfx861ijk: Assuming that a buckling B2g, of neutron flux of each energy group is equal, the fast neutron flux xcfx861 is distributed in the reactor core according to the following equations (6) and (7) which modifies the diffusion equations [Mathematical Expression 6] ∇2xcfx861+B2xcfx861=0xe2x80x83xe2x80x83(6) where, [Mathematical Expression 7] B 2 = ( k ∞ / k eff ) - 1 M 2 - A ∞ / K eff ( 7 ) k∞: infinite multiplication factor of each point of reactor core M2: neutron migration area A∞: correction term for diffusion of fast neutron and thermal neutron In order to solve a numerical value of the above equation, the above equation is transformed into the following difference equation (8). [Mathematical Expression 8] 1 Δ ⁢ xe2x80x83 ⁢ X 2 ⁢ { φ i + 1 , j , k + φ i - 1 , j , k + φ i , j + 1 , k + φ i , j - 1 , k - 4 ⁢ φ i , j , k } + 1 Δ ⁢ xe2x80x83 ⁢ Z 2 ⁢ { φ i , j , K + 1 + φ i , j , k - 1 - 2 ⁢ φ i , j , k } + B i , j , k 2 ⁢ φ i , j , k = 0 ( 8 ) where, xcex94X: length (about 15 cm) of X direction and Y direction of each node xcex94Z: length (about 15 cm) of Z direction, that is, axial direction of each node [Mathematical Expression 9] B ijk 2 = ( k ijk ∞ / k eff ) - 1 M ijk 2 - A ij1k ∞ / K eff . ( 9 ) In the above equation (9), for simplification, the fast neutron flux xcfx861ijk of node (i, j, k) is represented as xcfx86ijk The above difference equation is prepared for each node of the reactor core 3, and then, is transformed into a simultaneous equation, and thus, the equation is solved so as to obtain a fast neutron flux distribution xcfx86ijk of each node of the reactor core. The fast neutron flux distribution xcfx86ijk is obtained by carrying out a repetition computation and making a numerical solution. The repetition computation is carried out at the same time with repetition computation of the fast neutron flux and the effective multiplication factor Keff, and is called as Source Iteration. The solution of the difference equation is as described above. Before obtaining the solution of the difference equation, there is a need of computing nuclear constants k∞ijk, M∞ijk, and A∞ijk of each node included in the difference equation and a boundary conditions contacting with an outer surface of the reactor core. In particular, the nuclear constant greatly varies due to a void content in the node and the boundary, and for this reason, the nuclear constant is newly computed every Void Iteration. A channel void content of each fuel assembly is computed with the use of the In-channel void content (In-channel void rate axial distribution VFijk and the bypass range void (void rate axial distribution) VFBk computed in the above item [C](3). A moderator relative history density Uijk defined in the following equation (10) is computed, and then, nuclear constants k∞ijk, M∞ijk, and A∞ijk of each node are computed by a fitting equation using these as parameters. [Mathematical Expression 10] U ijk = 1 - [ FwVF ijk + ( 1 - Fw ) ⁢ VFB k ] · ( 1 - ρ g ρ sat ) ( 10 ) where, Fw: ratio of In-channel active coolant channel area to the whole coolant channel area In the case of computing nuclear constants k∞ijk, M2ijk and A∞ijk of each node, in addition to the moderator relative history density Uijk, a moderator relative history density UHijk, a burn-up Eijk, a presence of control rod Cijk and the like are used as parameters, and then, these effects are taken into consideration as the necessity arises. A great influence is given to the nuclear constant depending upon condition that the moderator is burnt up to the burn-up Eijk how void history, and for this reason, the moderator relative history density UHijk is defined by the following equation (11) using introduced parameters. [Mathematical Expression 11] UH ijk = ∫ 0 E ijk ⁢ U ijk ⁡ ( E ) ⁢ ⅆ E / ∫ 0 E ijk ⁢ ⅆ E ( 11 ) In this case, the power Pijk supposed in the above item [B] is used in the computation of the nuclear constant k∞ijk so as to make a Doppler correction, and also, an average xenon of the node is computed so as to make a xenoncorrection. A coefficient required for the computation of the above fitting equation is inputted as a library data with the use of the result computed every kind of fuel assembly and every parameter according to the fuel assembly nuclear hydrothermal computing code. (2) Computation of Reactor Core Power Distribution Pijk: A power distribution Pijk is computed with the use of the incore fast neutron flux distribution xcfx86ijk computed in the above item [D](1). By using the conditions supposed in the above item [D](1), a power Pijk of each node (i, j, k) is expressed by the following equation (12). [Mathematical Expression 12] P ijk = k ijk ∞ ⁢ ∑ 1 ⁢ ijk ⁢ φ ijk v _ ijk ( 12 ) where, xcexa31ijk: eliminated cross section of fast neutron flux group {overscore (xcexd)}ijk: number of average neutron generated per fission of the whole neutron group [External character 1] xcexa31ijk and {overscore (xcexd)}ijk are computed by a fitting equation using the moderate relative density Uijk and by a fitting equation using the burn-up Eijk as parameter, respectively. A coefficient used in these fitting equations is computed in the same manner as the nuclear constant computed in the above item [D](1). Therefore, first, xcexa31ijk and {overscore (xcexd)}ijk required for computing the incore power distribution Pijk are computed by the fitting equation, and then, the incore power distribution Pijk is computed by the above equation (12) with the use of k∞ijk and xcfx86ijk computed in the above item [D](1). [E] Void Repetition Computation Convergence Criterion and Power Distribution Learning: This item [E] is a so-called Void iteration convergence criterion. More specifically, a comparison is made between the incore power distribution Pijk supposed in the above item [B] and the power distribution Pijk computed in the above item [D](2). The comparison is carried out with respect to all nodes in the reactor core, and if the comparative result is coincident, the Void Iteration converges. If the comparative result is not coincident, the computation sequence returns to the above item [B], and then, the power distribution Pijk is again supposed and corrected, and thus, the computation stated in the items [B] to [E] is repeated until the comparative result is coincident. In the convergence criterion, a comparison of effective multiplication factor of the whole reactor core is carried out at the same time with the comparison of power distribution. By the way, in the case of learning a power distribution, in the Void Iteration, further, a comparison is carried out between a xcex3-ray heat (actually measured heating value) from the gamma thermometer (GT) 44 and a xcex3-ray heat (computed heating value) from the computed power distribution Pijk, and then, the difference between heating value is computed as a ratio. The difference of ratio is interpolated and extrapolated with respect to the axial node having no GT detector 35, and then, is computed as a difference data (actually measured value)/(computed value) between a reactor core coordinate position having each GT 44 and 24 axial modes for a xcex3-ray heat computation of GT 44 of a nuclear instrumentation coordinate to which the actually measured value is applicable on the basis of a symmetry of the reactor core although there is no GT 44. The difference data is BCFijk shown in FIG. 10. A computation value of the node power distribution around the GT 44 is corrected so as to be adapted to the BCFijk, and Void Iteration is repeated so that the xcex3-ray computed heating value of GT 44 is coincident with the actually measured value. In the case where the Void Iteration converges, and the xcex3-ray computed heating value of GT 44 is coincident with the actually measured value, and further, the computed power distribution Pijk is coincident with the previous repeated power distribution, the computation sequence proceeds to a computation of a thermal margin value in the reactor core 3 which will be described in the following item [F]. If coincidence is not obtained, the computation sequence returns to the item [B], and then, the power distribution Pijk is again supposed and corrected, and thus, the computation stated in the items [B] to [E] is repeated until the comparative result is coincident. [F] Computation of Thermal Margin Value In the item [F], a thermal margin value of each node of the reactor core 3 is computed with the use of the numerical solution converged in the Void Iteration. However, the solution obtained from the Void Iteration is an average value of each node. In the case of computing a thermal margin value, there is a need of carrying out a computation relative to the maximum generating power fuel rod. Then, the power Pijk of each node computed in the above item [D](2) is divided by the number of fuel rods of node, and then, is multiplied by a local power keeping coefficient, and thus, a power of the maximum power generating fuel rod of each node is first computed. The following computation of thermal margin value is carried out with respect to the fuel rod generating the maximum power. The void content and burn-up of the node gives a great influence to the local power keeping coefficient required for the computation of the thermal margin value, in addition to the presence of a control rod inserted adjacent to or in the vicinity of the node. In the present computing code, these three variables are used as a parameter, and the local power keeping coefficient is computed by a fitting equation for each node. A coefficient required for the fitting equation is computed with the use of the result previously computed every fuel assembly 4 and every each parameter according to the fuel assembly nuclear characteristic computing code, and thus, is inputted to the present computing code as a library data. (1) Computation of Maximum Linear Heating Generation Ratio LHGRijk: The maximum linear heat generation ratio LHGRijk of each node (i, j, k) is obtained by dividing it by an axial unit node length xcex94Z because a power of the maximum power generation fuel rod of each node has been already computed. The maximum linear heat generation ratio of the whole node of the reactor core is set as the whole reactor core maximum linear heat generation ratio MLHGR. (2) Computation of minimum critical power ratio MCPR: A critical power ratio CPR is defined by the following equation (13). [Mathematical Expression 13] CPR=CP/ABPxe2x80x83xe2x80x83(13) where, CP: critical power ABP: actual power of fuel assembly A critical power CP is a power which is anticipated that the fuel assembly 4 of a computing target generates transition boiling, and is obtained from a GEXL correlation equation based on an experiment simulating a shape of an actual fuel rod. A critical power ratio CPR is an index indicative of a thermal freedom until the fuel assembly 4 of a computing target generates transition boiling. In the present (condition) computing code, the critical power ratio CPR is computed for each fuel assembly 4, and the minimum of the computed ratios is set as a minimum critical power ration MCPR. [G] Output of Computed Result: In this item [G], the computed result is outputted as the necessity arises. By carrying out the repetition computation as described above, an axial power distribution of each fuel assembly is obtained. This is a typical method for obtaining the axial power distribution of each fuel assembly. In fact, a secondary correction model is introduced into the method, and it is general that a design is made in order to improve an accuracy of the power distribution and the effective multiplication factor. However, the explanation is not a subject matter of the present invention and it is hence omitted. A reactor power distribution computing method is applicable to the method mentioned hereinbefore, and has the following features as described below. More specifically, a fuel spacer effect should be taken into consideration in parameters of nuclear constants k∞ijk, M2ijk and A∞ijk of core axial node having the fuel spacer 85. For example, in a state that the control rod is not inserted, k∞ijk is obtained by the following equation (14). [Mathematical Expression 14] k ijk , UN ∞ = xe2x80x83 ⁢ [ 1 + f ⁡ ( IFT , Exp . , UH ) + Δ ⁢ xe2x80x83 ⁢ f1 ⁡ ( IFT , Exp . , U , UH ) ] xe2x80x83 ⁢ [ 1 + Δ ⁢ xe2x80x83 ⁢ f2 ⁡ ( IFT , Exp . , UH , P ) ] * xe2x80x83 ⁢ [ 1 + Δ ⁢ xe2x80x83 ⁢ f3 ⁡ ( IFT , Exp . , UH , P ) ] ( 14 ) where, IFT: type of design of fuel cross section Exp: node burn-up UH: node history relative water density U: node instantaneous relative water density P: node power f (IFT, Exp, UH): (infinite multiplication factor having Xe to base power)xe2x88x921.0 xcex94f1 (IFT, Exp, UH): effect by difference between node history relative water density UH and instantaneous relative water density U xcex94f2 (IFT, Exp, UH): Doppler effect correction by difference from temperature in base output xcex94f3 (IFT, Exp, UH): effect by Xe, Sm Thus, the infinite multiplication factor is obtained. However, in this case, conventionally, the effect by the fuel spacer 81 has not been taken into consideration with respect to values of the node history relative water density UH and the instantaneous relative water density U. On the other hand, the moderator relative density Uijk is defined by the following equation (10). [Mathematical Expression 15] U ijk = 1 - [ FwVF ijk + ( 1 - Fw ) ⁢ VFB k ] · ( 1 - ρ g ρ sat ) ( 10 ) In each fuel spacer 81, a spacer portion is additionally computed from the In-channel passage void VFijk in the case of disregarding the fuel spacer, and then, a new moderator relative density Uijk,sp is computed by the following equation (10A). [Mathematical Expression 16] U ijk , sp = xe2x80x83 ⁢ 1 - Fw * S sp + Fw * s sp ⁢ ρ sp ρ sat - [ Fw ⁡ ( 1 - S sp ) ⁢ VF ijk + xe2x80x83 ⁢ ( 1 - Fw ) ⁢ VFB k ] · ( 1 - ρ g ρ sat ) (10A) where, Ssp: spacer occupied area ratio of in-channel (active coolant) passage xcfx81sp: equivalent water density of fuel spacer The moderator (water) relative density Uijk,sp defined in the above equation (10A) is stored as a history relative water density UH for each spacer position of each fuel assembly 4, and an infinite multiplication factor of the node having the fuel spacer 81 is computed in the following manner. For example, in a state that the control rod 5 is not inserted into the reactor core 3, an average infinite multiplication factor k∞ijk of the node having the fuel spacer shown in the above equation (14) is expressed as below by a load average of k∞jk, UN in the case of disregarding the spacer into consideration and the infinite multiplication factor k∞ijk,UN,SP (however, U and UH is replaced with USP and UHSP taking the fuel spacer into consideration) taking a fuel spacer defined in the same manner into consideration, and adjustment factors (C0+C1 U+C2U2). In this case, C0, C1 and C2 are each a constant different from a fuel type. Namely, the above equation (14) is rewritten into the following equation (14A). [Mathematical Expression 17] [(1xe2x88x92VS)k∞ijk,UN+VSk∞ijk,UN,sp][C0=C1U+C2U2]xe2x80x83xe2x80x83(14A) where, Vs: weight coefficient taking an axial volume rate of the node having the fuel spacer 81 into consideration In the same manner, infinite multiplication factors M2ijk and A∞ijk of the node having the fuel spacer are respectively defined by the following load average of the moderator relative density Uijk in the case of disregarding the fuel spacer and the moderator relative density Uijk,sp in the case of taking the fuel spacer into consideration. [Mathematical Expression 18] (1xe2x88x92VS)M2ijk,UN+VSM2ijk,UN,spxe2x80x83xe2x80x83(15) (1xe2x88x92VS)A∞ijk,UN+VSA∞ijk,UN,spxe2x80x83xe2x80x83(16) The state that the control rod 5 is inserted into the reactor core 3 is a method for preparing a data library used conventionally, and the method is readily carried out by using a ratio to a state that the control rod 5 is not inserted. By defining in the manner as described above, it is possible to correct a library data such as the infinite multiplication factor of the node having the fuel spacer 81, migration area or the like, and a neutron flux can be accurately computed in the node having the fuel spacer 81. According to this definition, a node power is obtained by the same equation as the above equation (12) with respect to the node having the fuel spacer 81. [Mathematical Expression 19] P ijk , = k * ∞ ijk ⁢ ∑ * 1 ⁢ ijk ⁢ φ ijk v * _ ijk (12A) In this case, in order to take the spacer effect into consideration, a symbol, to which a mark * is given as an additional character, is indicative that the parameter in the case of having a spacer is obtained by being subjected to a load average process to compute a node average parameter. The computing method is the same as the equations (14A), (15) and (16). According to the above explanation, the correction first group diffusion equation is obtained on the assumption that buckling of neutron flux xcfx861, xcfx862 and xcfx863 of each energy group is equal. Even in the case of considering an influence caused by the fact that the thermal neutron distribution of the core axial node diverges from a basic mode by a spectrum mismatch effect between the node and the node adjacent thereto, the aforesaid concept for obtaining the diffusion equation may be adaptable. Further, without using the correction first group diffusion equation, in the case of using a three-group diffusion equation, each of the constants Dg, xcexa3g, xcexdg xcexa3fg, and xcexa3slg can be generally expressed as shown below by a load average of a value in the case of taking the fuel spacer into consideration and a value which does not take it into consideration, and by adjustment factors (14B) and (14C). In this case, there is shown an example of a nuclear constant in the case where the control rod is not inserted. [Mathematical Expression 20] X gijk , UN * = xe2x80x83 ⁢ [ ( 1 - V sxg ) * x gijk , UN + V sxg ⁢ X gijk , UN ] * xe2x80x83 ⁢ [ C 0 ⁢ xg + C 1 ⁢ xg ⁢ U + c 2 ⁢ xg ⁢ U 2 ] (14B) [Mathematical Expression 21] x gijk , UN = xe2x80x83 ⁢ f xg ⁡ ( IFT , EXP . , UH ) + Δ ⁢ xe2x80x83 ⁢ f 1 ⁢ xg ⁡ ( IFT , EXP . , U , UH ) + xe2x80x83 ⁢ Δ ⁢ xe2x80x83 ⁢ f 2 ⁢ xg ⁡ ( IFT , EXP . , UH , P ) + Δ ⁢ xe2x80x83 ⁢ f 3 ⁢ xg ⁡ ( IFT , EXP . , U , UH , P ) (14C) where, Xg: nuclear constant X of g-group (one of Dg, xcexa3g, xcexdg xcexa3fg, and xcexa3slg) Xg: node average nuclear constant in the case of considering effect by a g-group spacer fxg(IFT, EXP, UH): equilibrium Xe to base power, value of nuclear constant Xg xcex94f1xg (IFT, EXP, U, UH): effect by difference between history relative water density and instantaneous relative water density xcex94f2xg (IFT, EXP, UH, P): Doppler effect correction by difference from temperature in base power xcex94f3xg (IFT, EXP, U, UH, P): effect by Xe, Sn Vsxg: weight coefficient taking an axial volume rate in the node having the spacer of g-group nuclear constant X into consideration C0xg, C1xg, C2xg: adjustment factor of g-group nuclear constant determined every fuel type Therefore, this spacer model is generally applicable in addition to a correction first group code. Next, the following is a description on an operation by the neutron flux distribution monitor system and reactor core power distribution computing method. According to the above first embodiment, in the reactor power distribution computing device 31, various core present data such as control rod pattern obtained from the present data measuring device 52 of the reactor core 3, core flow rate, reactor doom pressure, core inlet coolant temperature are collected to the present (condition) data processing device (including the process control computer) 55, and then, a reactor thermal power (output) or the like is computed. The reactor core present (operating status) data measuring device 52 is actually composed of a plurality of monitor equipments and is the general term of a device for collecting process data of various operation parameter of the reactor and is expressed as one measuring equipment for simplification. Further. The process data processed by the present data processing device 55 is transferred to the three-dimensional nuclear thermal-hydraulics computing code of the reactor core powerdistribution computing device 31 (used as part of the process control computer or as an exclusive computer independently located) as various required data. The three-dimensional nuclear thermal-hydraulics computing code computes an incore power distribution with the use of these process data and the reactor core nuclear instrumentation data S1 and S2. In the reactor core power distribution computation, a correction spacer nuclear constant parameter is held with respect to a node having the fuel spacer 81, in addition to the nuclear constant parameter which does not take the fuel spacer 81 into consideration as conventionally. Further, in the history relative water density of the fuel spacer portion, the equation (10A) is integrated as the equation (11) so that the moderator relative history density UHijk,sp is held. For example, as shown in the above equations (14A), (15) and (16), in the node having the fuel spacer 81, the effect by the fuel spacer 81 is taken into consideration, and then, in accordance with the necessity, a parameter reflecting as a function of a burn-up, history relative water density and instantaneous relative water density is subjected to a load average process so as to obtain a node average value. Whereby a solution of correction first group difference equation is obtained, and in first group node average neutron flux computing process, an effect of lowering first group neutron flux by the fuel spacer effect is reflected. Further, in order to obtain a node average power from first group neutron flux xcfx861, contribution by second and third group neutron fluxes xcfx862 and xcfx863 need to be reflected. In this case, also, in the node having the fuel spacer 81, the equation (12A) is used in place of the equation (12), and therefore, in the effect by the spacer 81 to the first group neutron flux xcfx861, a diffusion coefficient is large in the first group. Because of this reason, the contribution by the spacer effect is not so large. The effect obtained by the fact that the third group neutron flux xcfx863, of the energy group lowers is taken into consideration. Furthermore, in the equation (12A), xcexa3iijk includes the spacer effect by the fuel spacer 81 by load average, but may be used as xcexa3ijk which does not take the spacer effect into consideration for simplification. As a result, it is possible to accurately reflect node power lowering on the spacer portion which has not been taken into consideration in the conventional power distribution computing method, with respect to the node having the fuel spacer 81. Moreover, in this first embodiment, it is possible to learn and correct the axial power distribution with the use of the LPRM detectors which are less then 24, four or more measurement data, and the three-dimensional nuclear thermal-hydraulics computing code evaluating an influence on the node power by the fuel spacer. The actual thermocouple output signal S1 of the gamma thermometer 44 is converted from a voltage into a gamma ray heating value by means of the gamma thermometer signal processing device 48, and then, is inputted to the reactor power distribution computing device 31. In the reactor power distribution computing device 31, a correction in difference between a simulation computation value of the xcex3-ray heating value obtained from the reactor core power distribution computed by the three-dimensional nuclear thermal-hydraulics computing module 58 and the actually measured xcex3-ray heating value is computed as a ratio by means of the power distribution correcting (learning) module 59. Further, in the power distribution learning (adaption) module 59, a numerical difference ratio limited to the axial direction, that is, a ratio of the computed xcex3-ray heating value and the actually measured xcex3-ray heating value is set as a correction data of the xcex3-ray heating value difference correction of the total core axial node by interpolating and extrapolating the ratio data to each axial node by a straight line or a quadratic curve. Moreover, a learning correction of the power distribution learning module 59 of the reactor power distribution computing device 31 will be described below with reference to a flowchart of FIG. 10. The power distribution computing module 58 of the reactor power distribution computing device 31 is built in the process computer and computes an incore power distribution according to the aforesaid method with the use of the three-dimensional nuclear thermal-hydraulics computing code which takes an influence on the node power by the fuel spacer into consideration. A xcex3-ray heat computation value Wck,m on the xcex3-ray heat detector 35 position is computed by the following equation (17) on the basis of a power of a node corresponding to a height position of the xcex3-ray heat detector of four fuel assemblies 4 located around the xcex3-ray heat detector 35 and a power of a vertical node adjacent to the node. [Mathematical Expression 22] w Ck , m = xe2x80x83 ⁢ 1 4 xc3x97 ∑ n = 1 4 ⁢ { c k - 1 → k , m , n ⁢ Δ ⁢ xe2x80x83 ⁢ P k - 1 , m , n + xe2x80x83 ⁢ c k , m , n ⁢ P k , m , n + c k + 1 → k , m , n ⁢ Δ ⁢ xe2x80x83 ⁢ P k + 1 , m , n } ( 17 ) where, Wck,m: computation value of xcex3-ray heating value (read value) of the GT sensor located on the axial center of k node situated at the nuclear instrumentation tube position m Pk,m,n: axial k node average power of the fuel assembly n in four fuel assemblies around the nuclear instrumentation tube position m xcex94Pkxe2x88x921: Pkxe2x88x921xe2x88x92Pk xcex94Pk+1: Pk+1xe2x88x92Pk c: correlation function from node power to xcex3-ray heating value m: nuclear instrumentation tube position n: four assemblies located around the nuclear instrumentation tube An actually measured value of the xcex3-ray heating value Wmk,m at xcex3-ray heating value measurement points k and m is inputted to the power distribution learning module 59, and then, the above xcex3-ray heating value Wck,m is compared with a xcex3-ray heating value measurement value Wmk,m, and thus, a correction coefficient BCFk,m is computed by the following equation (18). [Mathematical Expression 23] BCFk,m=Wmk,m/Wck,mxe2x80x83xe2x80x83(18) A xcex3-ray heating value correction coefficient BCFk,m is an index indicative of a difference (error) between the actually measured value of the xcex3-ray heating value and the xcex3-ray heat computation value according to the physical model. The xcex3-ray heating value is proportional to a power of fuels around the xcex3-ray heat detector 35, and for this reason, a power distribution computation value Pk,m,n is corrected by the following equation (19) with the use of the correction coefficient BCFk,m, whereby it becomes possible to obtain a power distribution which eliminates an error by the physical model and has high reliability. In this case, Pak,m,n shows a node power at the corrected xcex3-ray heating value measurement points k and m. [Mathematical Expression 24] Pak,m,n=BCFk,mxc3x97Pk,m,nxe2x80x83xe2x80x83(19) By the way, the xcex3-ray heat detector 35 of thegamma thermometer 44 is located continuously in only core axial direction, and at the node position having no xcex3-ray heat detector 35, it is impossible to compute the correction coefficient BCFk,m. For this reason, in other core axial nodes, the correction coefficient BCFk,m obtained at measurement points k and m is computed by interpolating and extrapolating it to a straight line or a quadratic curve, and then, the total node power Pak,m,n of axial direction is computed with the use of the correction coefficient BCFk,m. Moreover, the fuel assembly having the gamma thermometer 44 in the core diametrical direction position is learned and corrected with the use of a signal from the gamma thermometer 44 on the identical position on the basis of symmetry of the reactor core. In this case, a subscript k shows a core axial node, and subscripts m and n merely show a coordinate of reactor core based on the relationship between the fuel assembly 4 and nuclear instrumentation tube. The coordinate makes it possible to replace with the coordinate i and j of reactor core of the fuel assembly 4 used in the above equations (1) to (16). Furthermore, there is the following method as a method for correcting the power distribution computed by the physical model which refers to the actually measured value of the xcex3-ray heating value. The neutron flux xcfx86k,m,n obtained via the void repetition computation of the equation (8) is corrected with the use of the correction coefficient BCFk,m, and then, a correction neutron flux xcfx86ak,m,n is computed by the following equation (20). [Mathematical Expression 25] xcfx86ak,m,n=BCFk,mxc3x97GFk,mxc2x7xcfx86k,m,nxe2x80x83xe2x80x83(20) In this case, GFk,m is previously computed according to a lattice computation in an equation of transformation from the xcex3-ray heating value into a neutron flux. In the case of substituting the correction neutron flux xcfx86k,m,n for the equation (8), it is a matter of course that the above equation (8) is not satisfied. Then, in the following equation (8A) and the equation (8), (B2i.j.k+xcex94B2i,j,k) is obtained by correcting buckling B2i,j,k of neutron flux of each energy group and satisfying the equation (8). In this case, xcex94B2i,j,k is indicative of a correction of buckling B2i,j,k of neutron flux when the correction neutron flux xcfx86ai,j,k satisfies the equation (8). [Mathematical Expression 26] 1 Δ ⁢ xe2x80x83 ⁢ X 2 ⁢ { φ i + 1 , j , k + φ i - 1 , j , k + φ i , j + 1 , k + φ i , j - 1 , k - 4 ⁢ φ i , j , k } + 1 Δ ⁢ xe2x80x83 ⁢ Z 2 ⁢ { φ i , j , K + 1 + φ i , j , k - 1 - 2 ⁢ φ i , j , k } + ( B i , j , k 2 + Δ ⁢ xe2x80x83 ⁢ B i , j , k 2 ) ⁢ φ i , j , k = 0 ⁢ (8A) In the axial position having no xcex3-ray heat detector 35, it is possible to obtain the correction neutron flux xcfx86ak,m,n of the total reactor core axial node, that is, the incore neutron flux distribution the correction neutron flux xcfx86i,j,k computed with the use of the correction coefficient BCFk,m obtained by interpolating and extrapolating it with a straight line or a quadratic curve in the axial direction. Thus, in the core diametrical direction, it is possible to compute a correction of buckling xcex94B2i,j,k with respect to all of core axial nodes based on symmetry of the reactor core. The power distribution computed in the above manner is displayed by means of a display device of the input/output device 60 as shown in FIG. 1. As described above, in the power distribution computing module 58 including the three-dimensional nuclear thermal-hydraulics computing code as the physical model, in order that the power of each core axial node of four assemblies 4 around the nuclear instrumentation tube 33 is adapt to the node power correction previously computed, the correction is distributed to the peripheral nodes on the basis of the computed result at the same proportional distribution, and then, the corresponding power adjustment factors or first group neutron flux adjustment factors of each of nodes are anticipated, and thus, returned to the power distribution computing module 58 including the three-dimensional nuclear hydrothermal computing code. The three-dimensional nuclear thermal-hydraulics repetition computation and repetition computation of learning correction are carried out, and finally, if the difference between the previous (nxe2x88x921) node power Pnxe2x88x921 of each core axial node and the node power Pn of the present (n) computed is smaller than a fixed value, the repetition computation converges. Then, a computation of operation limit value is carried out, and the computation is completed. The flow is shown in FIG. 10. In FIG. 7, a curved line a (shown by a mark ▴) is a power distribution computed result of the fuel assembly 4 in the case of taking a local distortion of neutron flux due to the fuel spacer portion into consideration in the three-dimensional nuclear thermal-hydraulics simulation computing code. A curved line b (shown by a mark ▪) is a power distribution computed result of the fuel assembly 4 in the case where a local distortion of neutron flux due to the fuel spacer 81 is not taken into consideration. In FIG. 7, these curved lines a and b shows a corrected result so that a position where the GT signal is obtained is coincident with the GT signal. A portion A of FIG. 7 is enlarged in FIG. 8, and is shown by a broken line b. On the other hand, in FIG. 8, there is shown a true value by a solid curved line c based on measurement point data of the gamma thermometer (GT). A broken line d of FIG. 8 shows a node power curve before correction. The node power curve d before correction has been computed according to the three-dimensional nuclear thermal-hydraulics computing code which does not take the fuel spacer into consideration. Then, when the node power curve d before correction is corrected on the basis of the GT measurement point data, in the case where there is the output signal of the gamma thermometer (GT) 44 in the node having the fuel spacer SP, the power is corrected to a minus side larger than the case where the neutron flux distortion at the GT position of the node power curve d before correction is not taken into consideration, and then, a power of up and down (vertical) nodes adjacent to the node is corrected to a minus side with the same proportional distribution. The node power correction is made with the proportional distribution between nodes around the nuclear instrumentation tube, a learning correction xcex94S is large. In the case where there is a power peak between GT positions, the node having no fuel spacer SP has no GT measurement data at the peal position although the node power is high, and for this reason, the peak position become an maximum correction xcex94Ma. Therefore, the node power after correction is shown by the curved line d, and then, there is a problem that the node power peak value is evaluated smaller. On the other hand, as shown in a portion B of FIG. 7, in the case where there is a measurement data of the gamma thermometer (GT) 44 in the core axial node having no fuel spacer SP and there is no measurement data of the gamma thermometer (GT) 44 in the core axial node having the fuel spacer SP, the learning correction is small, and the power of the node having the fuel spacer SP is excessively evaluated because a local distortion of neutron flux is not taken into consideration. On the contrary, in the case where the three-dimensional nuclear thermal-hydraulics computing code evaluates an influence on the node power by the fuel spacer SP, like the present invention, as shown by the curved line a of FIG. 7, the power distribution by the fuel spacer SP has a concave and convex portion in the axial direction from first. Therefore, no excessive correction is made even if the correction is interpolated and extrapolated in the axial direction. That is, as shown in FIG. 7, the xcex3-ray heating value of the GT detector 35 at the nuclear instrumentation tube position is coincident with a node power around the GT detector 35 converted by a correlation relation (in this case, its details are omitted) between a xcex3-ray heating value and a node power. As seen from the core power distribution learned and computed by the three-dimensional nuclear thermal-hydraulics computing code and from the effect described in FIG. 7 to FIG. 9, in the power distribution computing method of taking the fuel spacer 81 into consideration, it is possible to make a learning correction with high precision on the basis of the measurement data of each GT detector 35 of the less axial GT 44, and it is found that the reactor power distribution can be effectively obtained with high precision. Next, the following is a description on a reactor nuclear instrumentation system according to a second embodiment of the present invention. In the reactor nuclear instrumentation system according to this second embodiment, the reactor core 3 is provided with a plurality of incore nuclear instrumentation assemblies 32 which constitute a reactor power detecting device in a core diametrical direction. As shown in FIG. 12 and FIG. 13, the incore nuclear instrumentation assembly 32 includes a nuclear instrumentation tube 33 mounted between four fuel assemblies 4. The nuclear instrumentation tube 33 is provided integrally with a neutron detector assembly 37 which functions as a fixed type LPRM, and a fixed type gamma thermometer 44. In the neutron detector assembly (LPRM) 37, N (number, integer) fixed type (stationary or immovable) neutron detectors 34 are dispersively arranged at equal intervals in a core axial direction. The fixed type neutron detector 35, for example, four are arranged. On the other hand, in the gamma thermometer 44, a plurality of fixed type xcex3-ray heat detectors 34, and N xcex3-ray heat detectors 34, for example, four are arranged in the same axial direction as the fixed type neutron detector 35. FIG. 12 and FIG. 13 show an arrangement such that the xcex3-ray heat detectors 35 of the gamma thermometer 44 are dispersively arranged in the same axial direction as the fixed type neutron detector 34 of the N fixed type LPRM 37. In the incore nuclear instrumentation assembly 32, gain adjustment of the neutron flux detector 34 of the fixed type LPRM 37 is directly compared and corrected with the use of a measurement value of the xcex3-ray heat detectors 35 of the gamma thermometer 44 which are arranged in the same axial direction so as to correspond to a reactor nuclear instrumentation system 30. The reactor nuclear instrumentation system 30 and the reactor power distribution computing device 31 has the same configuration as the reactor power distribution monitor system shown in FIG. 1, and therefore, the explanation of the overlapping portion is omitted. In the incore nuclear instrumentation assembly which is a detector of the reactor nuclear instrumentation system shown in FIG. 12 and FIG. 13, the number (N: integer) of xcex3-ray heat detectors 34 of the gamma thermometer 44 in the core axial direction is the same number (N) as the fixed type neutron detector 34 located in the core axial direction, and is arranged in the same core axial direction. As shown in FIG. 1, the LPRM detection signal S2 of the fixed type neutron detector (LPRM detector) 34 is processed by means of the power range detector signal processing device 40. The signal processing device 40 includes a pre-amplifier, a high pressure source, a pulse height discrimination circuit, a gain adjuster circuit or the like, and their details are omitted. In the power range detector signal processing device 40, a plurality of LPRM detection signals S2 is made average so as to prepare a power range average output signal (APRM signal). If the APRM signal level exceeds a predetermined value, a trip signal for scramming the reactor is supplied to a logic circuit of a safety guard system. The safety guard system makes a decision whether a state when the plurality of APRM output the trip signal is an operating state required for scramming, according to a predetermined logical decision, and then, scrams the reactor. The power range neutron detector (LPRM detector) 34 of the reactor core 3 is an ionization chamber type detector, and a fission material (uranium) is applied to an inner surface of an outer wall of the neutron detector 34. A high voltage is applied between the outer wall and the central electrode. In the neutron detector 34, an inert gas Ar is encapsulated as an ionization gas. In the ionization chamber type neutron detector 34, succeeding electron circuits such as an amplifier, a pulse height discriminator filter vary in its characteristic with time, and a so-called drift phenomenon happens. Further, detection sensitivity varies depending upon a change of uranium U-235 applied onto the inner surface of the outer wall of the neutron detector 34. Taking these factors into consideration, the LPRM signal used as the APRM signal need to be used as the APRM signal after being properly corrected. On the other hand, a measurement signal (mV signal) S1 of a differential type thermocouple 68 constituting the xcex3-ray heat detectors 35 of the gamma thermometer 44 is converted from an analog signal into a digital signal by means of an A/D converter processor (not shown), and thereafter, is amplified in digital form. For this reason, the output signal S1 of the differential type thermocouple 68 has no change in a heat field, and then, almost no drift phenomenon happens. In the reactor nuclear instrumentation system, the xcex3-ray heat detectors 35 of the gamma thermometer 44, that is, a gamma thermometer (GT) detecting portion is located on the same position as the neutron detector 34 of the fixed type LPRM 37. Thus, there is no need of obtaining a signal of the LPRM detector position by moving it like the movable type neutron detector (TIP). In the reactor nuclear instrumentation system of this second embodiment, a calibration of the signal output of the fixed type neutron detector 34 is directly carried out with the use of the xcex3-ray heating value computed from the detection signal from the xcex3-ray heat detector 35 situated at the same level in the axial direction, whereby it becomes possible to make a calibration at a high speed and with high reliability without using the power distribution computing device which is mounted with the three-dimensional nuclear hydrothermal simulation computing code. In the incore nuclear instrumentation assembly 32, the GT detecting portion signal S1 located at the same position as the LPRM detector 34 is directly and electronically retrieved, and thereby, it is possible to measure a xcex3-ray heating value by electronic data reading and conversion to xcex3-ray heating value. Therefore, it is possible to carry out a calibration of the LPRM detector 34 for a very short time (e.g., 5 to 10 minutes), and at one time per day or one time per time. In this case, when the signal level S2 of the LPRM detector is calibrated as a xcex3-ray heating value of the gamma thermometer (GT) 44, the LPRM input signal of the APRM is proportional to a local power, and it is possible to provide an excellent local average power which does not depend upon the result computed by the physical model of the three-dimensional nuclear thermal-hydraulics simulation computing code included in the process control computer. The xcex3-ray heating value of the gamma thermometer (GT) 44 is substantially proportional to a node average power around the GT, and a local power distribution of the fuel assembly corner fuel rod on the nuclear instrumentation 33 side does not so depend upon the computed result as compared with the case of the LPRM detector 34. In the case of calibrating the LPRM signal at short intervals, a change in an uranium isotope of the LPRM detector 34 and in a local power distribution of a cross section of the fuel assembly 4 is supposed as zero. Further, the LPRM detection signal level is calibrated to a value approximate to the node average power around the LPRM detector 34. Thus, even if the signal level generated by the LPRM detector 34 contains a weight of the local power of the fuel assembly cross section, when the node power varies, the LPRM signal is proportional to the change, and then, changes. Therefore, as compared with the case of calibrating the LPRM signal via a predictive LPRM signal based on the computed result by the three-dimensional nuclear hydrothermal simulation model as the conventional reactor nuclear instrumentation system, reliability is high, and it is possible to readily calibrate the LPRM detector signal S2 even when the reactor power distribution computing device 31 is temporarily fault or is during maintenance. In particular, the power range detector processing device 40 is a device constituting the safety guard system, and also, the gamma thermometer signal processing device 48 is composed of a digital circuit which has a simple software and includes a microprocessor having a reliability more than a process computer. Therefore, the present invention has a higher reliability as compared with the case of depending upon the computed result of the reactor power distribution computing device 31 which has a physical model and repeats convergence computation with the use of many stored data. In the reactor nuclear instrumentation system, the GT 44 is fixed and arranged in the reactor core 3. A part of the GT detectors has the same number as the LPRM detector 34 in the core axial direction and is arranged in the identical core axial direction. Thus, in order to calibrate the LPRM detector 34, the GT detector is a GT measurement system which is composed of the minimum numbers. The three-dimensional nuclear thermal-hydraulics simulation computing code has an efficient accuracy. Even if the GT detector portion is a little in the core axial direction and learning (adaption) data point is a little, if the spacer model is sufficiently taken into consideration in the three-dimensional nuclear thermal-hydraulics simulation, it is possible to dispense the number of the GT detector portion, that is, the number of the located xcex3-ray heat detectors 35 as the reactor nuclear instrumentation system. By the reactor nuclear instrumentation system, no mechanical movement as the TIP need to be carried out in order to scan all GT detector 35 of the reactor core 3, so that a xcex3-ray heating value approximate to the node power in the vicinity of the LPRM detector position can be computed for a very short time (about 5 to 10 minutes). In the case of carrying out a power level adjustment (gain adjustment) of the fixed type neutron detector 34 by a reading value of the xcex3-ray heat detector 35 having no drift, the adjustment is made without using the core axial power distribution computed result by the process control computer. Thus, it is possible to calibrate a change in sensitivity due to drift of each power range local power detector (LPRM detector) constituting a part of the safety guard system with high reliability. Therefore, it is possible to dispense the movable neutron flux measuring device or a xcex3-ray flux measuring device which has been conventionally required for calibrating the LPRM detector. The gamma thermometer 44 is a fixed type, and the number of xcex3-ray heat detectors 35 is the same as the number of LPRM detectors 34, and thus, the GT measurement system can be composed of the minimum components. In the reactor nuclear instrumentation system of this second embodiment, the xcex3-ray heat detectors 35 has the same number as the fixed type neutron detector 34 in the axial direction and is arranged in the identical axial direction. In the case of carrying out a power level adjustment (gain adjustment) of the fixed type neutron detector 34 by a reading value of the xcex3-ray heat detector 35 having no drift, when the LPRM detector 34 is shifted from the node center axial directional position, the adjustment is made without using axial interpolation and extrapolation by a straight line or a quadratic line of the core axial power distribution computed result by the process control computer. Thus, it is possible to calibrate a change in sensitivity due to drift of each power range local power detector (LPRM detector) constituting a part of the safety guard system with high reliability. Usually, an ionization chamber type detector is used as the power range neutron detector (LPRM detector) 34 of the reactor core 3, and a fission material (uranium) is applied to an inner surface of an outer wall of the neutron detector 34. A high voltage is applied between the outer wall and the central electrode. In the neutron detector 34, an inert gas Ar is encapsulated as an ionization gas. In the ionization chamber type neutron detector 34, succeeding electron circuits such as an amplifier, a pulse height discriminator filter vary in its characteristic with time, and a so-called drift phenomenon happens. Further, detection sensitivity varies depending upon a change of uranium U-235 applied onto the inner surface of the outer wall of the neutron detector 34. In order to correct a change in neutron detection sensitivity, the change has been conventionally calibrated by means of the TIP device. However, the TIP device requires a mechanical drive mechanism for moving the movable type neutron detector to a core axial direction. On the contrary, in the present second embodiment, the TIP device is unnecessary, and the fixed GT detector 35 is arranged at the same position as the LPRM detector 34. Thus, it is possible to directly obtain a signal at the axial direction position of the LPRM detector 34 without interpolation and extrapolation. The output signal of the LPRM detector 34 is mainly a detection signal in accordance with a thermal neutron flux in a corner gap of the fuel assembly 4. Thus, the signal level relates not only to the average node power of four fuel assemblies 4 around the node, but also to local power peaking of the corner fuel rod of the fuel assembly on the corner gap side of the nuclear instrumentation tube 33 which strongly contributes to a thermal neutron flux level of the corner gap. The local power peaking varies with the combustion of fuel, and in the case of calibrating the LPRM detector 34 by means of the conventional TIP device, the calibration is carried out at a rate of one time for one month, and correction is made taking a deterioration (change) of the neutron detector 34 into consideration. The fixed type gamma thermometer (GT) 44 is fixed in the reactor core, no mechanical movement as the TIP need to be carried out in order to scan all GT detector 35 of the reactor core 3 (requiring about one hour to two hours), and thereby, it is possible to measure a xcex3-ray heating value by electronic data reading and conversion to xcex3-ray heating value. Therefore, it is possible to carry out a calibration of the LPRM detector 34 for a very short time (e.g., 5 to 10 minutes), and at one time per day or one time per time. In the case of calibrating the LPRM detector 34, when converting the signal level of the LPRM detector 34 into a xcex3-ray heating value of the GT 44, an input signal of the safety guard system of the reactor is proportional to a local power, and it is possible to provide an excellent local average power which does not depend upon the result computed by the physical model of the three-dimensional nuclear thermal-hydraulics simulation computing code included in the process control computer. In this case, the xcex3-ray heating value of the fixed type gamma thermometer (GT) 44 is substantially proportional to a node average power around the GT, and a local power distribution of the fuel assembly corner fuel rod on the nuclear instrumentation 33 side does not so depend upon the computed result as compared with the case of the LPRM detector 34. Thus, it is possible to carry out calibration in proportion to the local power of the fuel assembly 4 around the GT 44 with high precision. FIG. 14 and FIG. 15 show a reactor nuclear instrumentation system and a reactor power distribution monitor system including the same system according to a third embodiment of the present invention. The reactor power distribution monitor system of this third embodiment has the same configuration as the reactor power distribution monitor system shown in FIG. 1 and includes a reactor nuclear instrumentation system 30 and a reactor power distribution computing device 31. The reactor power distribution monitor system of this embodiment relates to an improvement in the incore nuclear instrumentation assembly 32 which functions as a reactor power detecting device constituting the reactor nuclear instrumentation system 30. The incore nuclear instrumentation assembly 32 is composed of a plurality of fixed type neutron detector assemblies (LPRM) 37 and fixed type gamma thermometers 44 which are mounted in the reactor core 3 and is housed in a nuclear instrumentation tube 33. The fixed type neutron detector assembly (LPRM) 37 is constructed in a manner that N (number, integer) (Nxe2x89xa74) fixed type neutron detectors 34 are dispersively arranged at a predetermined distance L in a core axial direction. On the other hand, the fixed type gamma thermometer 44 is constructed in a manner that (2Nxe2x88x921) fixed type xcex3-ray heat detectors 35 are arranged in the core axial direction. N (number, integer) detectors of the xcex3-ray heat detectors 35 are arranged in the same core axial direction as the fixed type neutron detector 34, and the remainder (Nxe2x88x921) are arranged with a distance L/2 at the intermediate position in the core axial direction of the fixed type neutron detector 34. The reactor nuclear instrumentation system shown in FIG. 14 and FIG. 15 shows the case where a locating number of the fixed type neutron detector 35 constituting the fixed type LPRM 37 is four. For example, in a boiling water reactor mainly used nowadays, an effective length of a core axial direction is about 146 inches (3708 mm). The reactor core is divided into 8 equal parts, and the LPRM detector 34 and the xcex3-ray heat detector 35 are arranged. In this case, a distance L/2 of the core axial direction is about 18 inches (457 mm). In the above manner, the xcex3-ray heat detector 35 which is a GT detector portion, is arranged at equal intervals L/2, and the xcex3-ray heat detectors 35 covers a lower end to an upper end of the effective length of the core axial direction, whereby it becomes possible to secure a computing precision of the three-dimensional nuclear thermal-hydraulics simulation computing code by making a learning correction over the whole core axial direction. Therefore, it is possible to finely make a learning correction in the core axial direction as compared with the case of the above second embodiment, so that a computing precision of the three-dimensional nuclear thermal-hydraulics simulation computing code can be secured. In the reactor nuclear instrumentation system of this third embodiment, the fixed type xcex3-ray heat detector 35 has the same number as the fixed type neutron detector 34, and is arranged in the same axial direction as the fixed type neutron detector 34. Further, (Nxe2x88x921) fixed type xcex3-ray heat detector 35 is arranged at the intermediate position of the N fixed type neutron detector 34, and thereby, many xcex3-ray heat detectors 35 are arranged in the core axial direction so as to obtain the GT detector signal. Therefore, it is possible to improve an axial power distribution measurement precision as compared with the reactor nuclear instrumentation system shown in the second embodiment. FIG. 16 and FIG. 17 show a reactor power distribution monitor system according to a fourth embodiment of the present invention. The reactor power distribution monitor system of this fourth embodiment has the same configuration as the reactor power distribution monitor system shown in FIG. 1 and includes a reactor nuclear instrumentation system 30 and a reactor power distribution computing device 31. The reactor power distribution monitor system relates to an improvement in the incore nuclearinstrumentation assembly 32 which functions as a reactorpower detecting device constituting the reactor nuclear instrumentation system 30. In the incore nuclear instrumentation assembly 32, a fixed type neutron detector assemblies (LPRM) 37 and a fixed type gamma thermometers 44 are housed in a nuclear instrumentation tube 33, and are formed into a rod-like structure. The neutron detector assembly 32 is constructed in a manner that N (Nxe2x89xa74) fixed type neutron detectors (LPRM detector) 34 are dispersively arranged at a predetermined distance L in a core axial direction. On the other hand, the fixed type gamma thermometer 44 is constructed in a manner that N detector of 2N fixed type xcex3-ray heat detectors 35 are arranged in the core axial direction. N detectors of the xcex3-ray heat detectors 35 are arranged in the same core axial direction as the fixed type neutron detector 34, and the remainder (Nxe2x88x921) are arranged with a distance L/2 at the intermediate position in the core axial direction of the fixed type neutron detector 34. The last one of detectors is arranged at a position separating from a distance L/2 to L/4 below the lowest position of the fixed type neutron detector 34. The lowest xcex3-ray heat detectors 35 is arranged in the fuel effective length in the core axial direction. The reactor nuclear instrumentation system shown in FIG. 16 and FIG. 17 shows the case where a locating number of the fixed type neutron detector 35 constituting the fixed type LPRM 37 is four. In a boiling water type reactor (BWR) mainly used nowadays, the reactor core 3 is divided into 8 equal parts, and the LPRM detector 34 and the xcex3-ray heat detector 35 are arranged. In this case, a distance L/2 of the core axial direction is about 18 inches (457 mm). According to the correction first group three-dimensional nuclear thermal-hydraulics simulation computing code in the process control computer using a diffusion equation, a computing precision of the nodes on the uppermost and lower ends in the core axial direction is liable to become worse due to an influence by neutron leakage. For this reason, in the core lower end side, computation must be carried out with high precision even if there is the possibility of an error of computation. However, in the BWR, a void is not so generated in the core lower end side, and the reactor power is easy to become high in its characteristic. Therefore, in the core lower portion, the fixed type xcex3-ray heat detector 35 is actually interpolated rather than by extrapolating the difference between the GT measurement signal and the detection signal, and therefore, excellent learning is carried out with high precision. Thus, as described in this fourth embodiment, it is preferable that in the core lower end side, the fixed type xcex3-ray heat detector 35 is arranged further below the lowest neutron detector 34 in a range from L/4 to L/2. The position where the fixed type xcex3-ray heat detector 35 is located on the lowest end, that is, a distance below the fixed type neutron detector 34, is natural uranium blanket range per up and down (vertical) nodes (occasionally, 2 nodes on the upper end side) in a design of an axial direction of the latest BWR fuel assembly. Thus, the reactor power on upper and lower ends is low, and there is no need of measuring the upper and lower ends in its precision. For this reason, it is preferable that the axial center of the fixed type xcex3-ray heat detector (GT detector) 35 is set above 1 node (about 15 cm) or more from the lower end of the fuel effective length. Moreover, it is found that the GT detector 35 responses an average power in a vertical range of 15 cm in the core axial direction. In the case where the locating number N of the fixed type xcex3-ray heat detectors 35 is N=4, it is preferable that the lowest GT detector 35 is located at the intermediate point L/4 (about 9 inches) between the lowest neutron detector 34 and the lower end of the fuel effective length. If the GT detector 35 is located within 15 cm from the lower end of the fuel effective length in the axial direction, a correlation equation between the GT detector and the node power around the GT as GT reading value must be prepared, or the following matter must be accepted. That is, a slightly measurement error is caused between the computation result of the GT reading value and the GT measurement signal from the lowest GT detector 35. In the reactor nuclear instrumentation system of this fourth embodiment, in addition to an axial arrangement of the xcex3-ray heat detector 35 of the reactor nuclear instrumentation system of the third embodiment, the xcex3-ray heat detector 35 is arranged below the lowest neutron detector 34. Thus, the fixed type xcex3-ray heat detectors 35 is arranged so as to substantially equally cover the fuel effective length, so that the extrapolation can be reduced. Therefore, it is possible to compute a node power in the vicinity of the lower end higher than the upper end of the fuel effective length from the measurement result of the reactor core power distribution with high precision. FIG. 18 and FIG. 19 show a reactor power distribution monitor system according to a fifth embodiment of the present invention. The reactor power distribution monitor system of this fifth embodiment has the same configuration as the reactor power distribution monitor system shown in FIG. 1, and includes a reactor nuclear instrumentation system 30 and a reactor power distribution computing device 31. The reactor power distribution monitor system relates to an improvement in the incore nuclear instrumentation assembly 32 which functions as a reactor power detecting device constituting the reactor nuclear instrumentation system 30. In the incore nuclear instrumentation assembly 32 is formed into a long rod-shaped structure, and a fixed type neutron detector assemblies (LPRM) 37 and a fixed type gamma thermometers 44 are integrally housed in a nuclear instrumentation tube 33. The fixed type neutron detector assembly (LPRM) 37 is constructed in a manner that N (Nxe2x89xa74) fixed type neutron detectors (LPRM detector) 34 are dispersively arranged at a predetermined distance L in a core axial direction of the nuclear instrumentation tube 33. On the other hand, the fixed type gamma thermometer 44 is constructed in a manner that (2N+1) fixed type xcex3-ray heat detectors 35 are arranged in the core axial direction. N detectors of the (2N+1) xcex3-ray heat detectors 35 are arranged in the same core axial direction as the fixed type neutron detector 34, and the remainder (Nxe2x88x921) are arranged at the axial intermediate position. Further, the remainder, that is, two detectors are arranged below and above the lowest and uppermost fixed type neutron detectors 34. The lowest fixed type xcex3-ray heat detector 35 is arranged below a distance L/4 to L/2 from the lowest neutron detector 34 in the fuel effective length of the core axial direction, and on the other hand, the uppermost fixed type xcex3-ray heat detector 35 is arranged above a predetermined distance, that is, a distance L/4 from the uppermost neutron detector 34 in the fuel effective length of the core axial direction. The reactor nuclear instrumentation system shown in FIG. 18 and FIG. 19 shows the case where the locating number N of the fixed type neutron detector 34 is four. In this case, a distance L/2 of the reactor core axial direction is about 18 inches (457 mm), for example. In the reactor nuclear instrumentation system, further, one fixed type xcex3-ray heat detectors 35 is added to the case where the locating number 2N of the fixed type xcex3-ray heat detectors 35 in the reactor nuclear instrumentation system of the fourth embodiment. The added fixed type xcex3-ray heat detector 35 is arranged at a position further above the lowest fixed type neutron detector 34 in the axial direction within the fuel effective length. As described above, the fixed type xcex3-ray heat detectors 35 is arranged at a position further above the lowest fixed type neutron detector 34 in the axial direction within the fuel effective length, and thus, it is possible to reduce an extrapolation of an error between the core axial power distribution measurement value and the computed value by the simulation (process control computer) in the vicinity of the uppermost end of the fuel effective length, so that a precision of the axial power distribution on the upper end portion of the reactor core can be improved. In the conventional neutron detector which measures a thermal neutron flux, the upper end of the nuclear instrumentation tube 33 has a plunger structure which is inserted into a hole portion formed on the lower surface of the upper lattice plate. The plunger structure is different from most of parts of the nuclear instrumentation tube 33 of the reactor core. For this reason, in the xcex3-ray heat detector 35, a xcex3-ray transmission is great although having thermal neutron distortion and is hard to be affected by a structure of the nuclear instrumentation tube. Therefore, the xcex3-ray heat detectors 35 is arranged at a position further above the lowest fixed type neutron detector 34 in the axial direction within the fuel effective length, and thereby, it is possible to preferably measure the core axial power distribution in detail and to improve a learning precision of the three-dimensional nuclear thermal-hydraulics simulator in the process control computer. Furthermore, it is preferable that the position for locating the uppermost xcex3-ray heat detectors 35 is below 15 cm or more from the upper end of the fuel effective length on the basis of the same reason as mentioned above. In the reactor nuclear instrumentation system of this embodiment, in addition to the axial arrangement of the xcex3-ray heat detectors 35 of the reactor nuclear instrumentation system of the third embodiment, the xcex3-ray heat detectors 35 is arranged above the uppermost fixed type neutron detector 34 and below the lowest fixed type neutron detector 34. Thus, the fixed type xcex3-ray heat detectors 35 is arranged so as to substantially equally cover the fuel effective length, so that the extrapolation can be reduced. Therefore, it is possible to compute a node power in the vicinity of the lower end higher than the upper end of the fuel effective length from the measurement result of the reactor core power distribution with high precision. FIG. 20 and FIG. 21 show a reactor power distribution monitor system according to a sixth embodiment of the present invention. The reactor power distribution monitor system of this sixth embodiment has the same configuration as the reactor power distribution monitor system shown in FIG. 1, and includes a reactor nuclear instrumentation system 30 and a reactor power distribution computing device 31. The reactor power distribution monitor system relates to an improvement in the incore nuclear instrumentation assembly 32 which functions as a reactor power detecting device constituting the reactor nuclear instrumentation system 30. In the incore nuclear instrumentation assembly 32 is formed into a rod-shaped structure, and a fixed type neutron detector assemblies (LPRM) 37 and a fixed type gamma thermometers 44 are integrally housed in a nuclear instrumentation tube 33. In the incore nuclear instrumentation assembly 32 constituting the reactor nuclear instrumentation system 30, the fixed type xcex3-ray heat detector (GT detector) 35, which is arranged above the lowest fixed type neutron detector 34 at a distance L/4, is added to the incore nuclear instrumentation assembly of the third to fifth embodiments. In this case, the distance L is an interval in the axial direction of the fixed type neutron detector 34. FIG. 20 and FIG. 21 show the case where the locating number N of the fixed type neutron detector 34 is four. In a boiling water type reactor (BWR), it is general that the core has an effective length of 144 or 146 inches in a core axial direction. In the case, of dividing the core axial direction length into 24 node equal parts, a node, in which the maximum linear heat generation ratio is easy to be generated during an operation in the axial power distribution of the fuel assembly 4, is 4 nodes to 6 nodes from the bottom. In particular, in the first half of reactor operating cycle, a lower power peak operation is allowed within a range of operating limit value of the maximum linear heat generation ratio as much as possible, and in the end of operating cycle, the core axial or upper peak power distribution is made. In a core reaction effective operating method (BSO operation), the maximum linear heat generation ration is easy to be generated in the 4 nodes to 6 nodes from the bottom at the initial period to the intermediate period of operating cycle. In order to precisely evaluate a degree of freedom with respect to the maximum linear heat generation ration, the xcex3-ray heat detectors 35 is arranged in the vicinity of the node, and thereby, it is possible to make a learning correction on the basis of the measurement value at the vicinity of the maximum peak portion of the core axial power distribution, and to improve measurement precision. In the reactor nuclear instrumentation system of this sixth embodiment, a plurality of fixed type xcex3-ray heat detectors 35 in the incore nuclear instrumentation assembly 32 are additionally arranged above the lowest fixed type neutron detector 34 at a distance L/4, in addition to the locating position of the fixed type xcex3-ray heat detectors 35 included in the reactor nuclear instrumentation system shown in the third to fifth embodiments. The position where the added fixed type xcex3-ray heat detector 35 is arranged is a position where the maximum peaking is easy to be generated in the core axial direction in the latest high burnup (combustion) 8xc3x978 fuel or high burnup 9xc3x979 fuel core. Therefore, it is possible to precisely monitor a power distribution at a core position where the maximum linear heat generation ratio is easy to be generated and to improve a measurement precision. In particular, in the fixed type gamma thermometer 44, in the case where the locating number of the gamma ray heat detector in the core axial direction is limited in a mechanical design, it is possible to improve a precision in the limited number, thus being optimal. Next, the following is a description on a reactor power distribution monitor system according to a seventh embodiment of the present invention. The reactor power distribution monitor system of this seventh embodiment relates to improvement of an arrangement of a fixed type neutron detector and a fixed type xcex3-ray heat detector in the incore nuclear instrumentation assembly 32 constituting the reactor nuclear instrumentation system. The reactor power distribution monitor system has the same configuration as the reactor power distribution monitor system shown in FIG. 1 and its details are omitted herein. The reactor power distribution monitor system has the same configuration as that of each former embodiment, that is, the fixed type neutron detector assembly (LPRM) 37 and the fixed type gamma thermometer 44 are integrally housed in the incore nuclear instrumentation assembly 32 constituting the reactor nuclear instrumentation system. The core axial position of the fixed type neutron detector 35 of the neutron detector assembly (LPRM) 37 is coincident with the center of the nodes divided in the fuel axial direction, which is used in the reactor power distribution computing device 31, and further, the core axial position of the xcex3-ray heat detector 35 is also coincident with the center of node. In the reactor nuclear instrumentation system of this seventh embodiment, in the case where the power distribution computing device 31 computes a response of the xcex3-ray heat detector, a consideration is taken such that a range of gamma ray is longer a thermal neutron. Further, by taking not only the axial node having the xcex3-ray heat detector 35 but also contribution by a xcex3-ray heating value of up and down nodes adjacent to each other into consideration, it is possible to improve a precision of power distribution by the minimum computation. A xcex3-ray generated by a fission reaction has a range longer than a thermal neutron, and for this reason, the xcex3-ray heat detector 35 need to be arranged in a fuel effective length of the core axial direction and at a position separating from the fuel effective end with 15 cm in the core axial direction. Referring now to FIG. 22, FIG. 22 is a chart showing a distribution of detected sensitivity in the case where the origin takes a surface xcex3-ray source (xcex3-ray surface source) which distributes in the fuel cross section, and a xcex3-ray heat detector is located in an axial direction (X-axis) of the nuclear instrumentation tube 33. As seen from the detected sensitivity distribution result, the xcex3-ray heating value is reduced in accordance with an axial distance from the xcex3-ray surface source. However, the xcex3-ray heat contributes to the fixed type gamma thermometer (GT) 44 by 6 inches (15 cm) or more in the axial distance, and for this reason, in order to improve a computation precision of the GT 44 reading value, there is a need of taking a power distribution within 23 cm in axial distance into consideration. Therefore, in the case where there is a difference in power between the node having the xcex3-ray heat detector 35 and the adjacent axial nodes, it is found that an influence is given to a reading value of the xcex3-ray heat detector 35. Taking a change in the core axial power distribution into consideration, a xcex3-ray heating value is integrated in the core axial direction as the following equation (21), and then, is obtained therefrom. [Mathematical Expression 27] W ⁡ ( z ) = ∫ 0 Zmax ⁢ ⅆ z xe2x80x2 ⁢ R ⁡ ( z xe2x80x2 ) ⁢ P ⁡ ( z xe2x80x2 ) ⁢ ⅇ - "LeftBracketingBar" z - z xe2x80x2 "RightBracketingBar" / λ 2 ⁢ λ ( 21 ) where, W(z): xcex3-ray heating value at a z position in anaxial direction P(z): node core power density R(z): correlation equation from power density to xcex3-ray heating value xcex: xcex3-ray transport mean free path of core axial direction (obtained by gamma ray Monte Calro computation as shown in FIG. 22) In this case, a computation of an actual xcex3-ray heating value to the fixed type gamma thermometer (GT) 44 is carried out by a fuel assembly nuclear characteristic computing code and a xcex3-ray transport computation. The xcex3-ray heating value is computed by supposing a uniform xcex3-ray source distribution in the core axial direction, that is, a uniform axial power distribution, and based on this, when the above equation (21) is again defined, the xcex3-ray heating value is expressed by the following equation (22). [Mathematical Expression 28] W ⁡ ( z ) = R * ⁡ ( z ) ⁢ P ⁡ ( z ) + ∫ 0 Zmax ⁢ ⅆ z xe2x80x2 ⁢ R ⁡ ( z xe2x80x2 ) ⁢ xe2x80x83 ⁢ ( P ⁡ ( z xe2x80x2 ) - P ⁡ ( z ) ) ⁢ ⅇ - "LeftBracketingBar" z - z xe2x80x2 "RightBracketingBar" / λ 2 ⁢ λ ⁢ ⁢ R * ⁡ ( z ) = ∫ 0 zmax ⁢ ⅆ z xe2x80x2 ⁢ R ⁡ ( z xe2x80x2 ) ⁢ ⅇ - "LeftBracketingBar" z - z xe2x80x2 "RightBracketingBar" / λ 2 ⁢ λ ( 22 ) As seen from FIG. 22, the xcex3-ray heating value may disregard the contribution from about 23 cm or more in the core axial direction. In a general BWR, the reactor core 3 is divided into, for example, 24 nodes, and one node is substantially 6 inches (15 cm). Thus, in order to detect a xcex3-ray heating value, it is sufficient to considering nodes directly adjacent to each other and adjacent nodes far from one adjacent node. If the fixed type xcex3-ray heat detector 35 is situated at the center of the axial node of the reactor core 3, as shown in FIG. 23, the axial node having the xcex3-ray heat detector 35 of the GT sensor portion and upper and lower (vertical) nodes adjacent to each other merely be taken into consideration, and an integration range is made to have the same length, and thus, a relative equation becomes simple. The above equation (17) is an example of this case. On the contrary, in the case where the fixed type xcex3-ray heat detector (GT detector) 35 which is a GT sensor portion of the fixed type gamma thermometer (GT) 44, is not situated at the center of the axial node of the reactor core 3, as shown in FIG. 24, an influence of xcex3-ray heating value W other than adjacent nodes is given to the xcex3-ray heat detector 35. Therefore, as shown in FIG. 25, a sensor reading value on the center of the axial node is temporarily computed, and then, is interpolated to an actual sensor position reading value. By making a comparison, when the xcex3-ray heat detector 35 is situated at the center of the axial node, it is possible to readily calculate the xcex3-ray heating value. According to this seventh embodiment, the core axial position of the xcex3-ray heat detector 35 (GT sensor portion) of the fixed type gamma thermometer 44 is coincident with the center of the axial node, and thereby, it is possible to make a simple polynomial of the node having the xcex3-ray detector 35 and a node mean power of upper and lower nodes adjacent to each other. [Mathematical Expression 29] Wc k , m = xe2x80x83 ⁢ 1 4 xc3x97 ∑ n = 1 4 ⁢ { R k , m , n ⁢ P k , m , n + ∑ k xe2x80x2 = k - 1 k + 1 ⁢ R k xe2x80x2 , m , n ( P k xe2x80x2 , m , n - xe2x80x83 ⁢ P k , m , n ) ⁢ ∫ Zk xe2x80x2 - 1 Zk xe2x80x2 ⁢ ⅆ z xe2x80x2 ⁢ ⅇ - "LeftBracketingBar" z - z xe2x80x2 "RightBracketingBar" / λ 2 ⁢ λ } = xe2x80x83 ⁢ 1 4 xc3x97 ∑ n = 1 4 ⁢ { c k - 1 → k , m , n ⁢ Δ ⁢ xe2x80x83 ⁢ P k - 1 , m , n + c k , m , n ⁢ P k , m , n + xe2x80x83 ⁢ c k + 1 → k , m , n ⁢ Δ ⁢ xe2x80x83 ⁢ P k + 1 , m , n } ( 17 ) where, Wck,m: computation value of xcex3-ray heating value (read value) of the GT sensor located on the axial center of k node situated at the nuclear instrumentation tube position m Pk,m,n: axial k node average power of the fuel assembly n in four fuel assemblies around the nuclear instrumentation tube position m xcex94Pkxe2x88x921: Pkxe2x88x921xe2x88x92Pk xcex94Pk+1: Pk+1xe2x88x92Pk c: correlation function from node power to xcex3-ray heating value m: nuclear instrumentation tube position n: number of four assemblies located around nuclear instrumentation tube In the case where the core axial position of the fuel spacer is coincident with the center of the axial node, a concave portion of the core axial neutron flux by the fuel spacer affects only the computed result of the node average neutron flux and the node average power distribution. Therefore, it is very convenient because there is no need of preparing an influence to adjacent nodes as a correlation equation used in the three-dimensional BWR simulation computing code. In the reactor power distribution monitor system of this seventh embodiment, the fixed type neutron detector 34 and the xcex3-ray heat detector 35 of the incore nuclear instrumentation assembly 32 constituting the reactor nuclear instrumentation system are situated at the center of the node divided in the fuel axial direction. In the case where the fixed type neutron detector 34 is not situated at the center of node, a correction is made by interpolating the axial distribution of the read calculation value of the fixed type neutron detector of the core axial adjacent node, thus being very troublesome. Moreover, the xcex3-ray heat detector 35 is a xcex3-ray source contributing to the detector position, that is, the power distribution advantageously contributes within a range of 15 cm. Thus, even if the xcex3-ray heat detector 35 is situated on the center of the axial node with a height of 15 cm, the xcex3-ray heat detector 35 receives the influence of power distribution of the up and down (vertical) adjacent nodes. The influence of powerdistribution from the adjacent nodes is attenuated in series by a function near to an exponential of the locating position z from the xcex3-ray heat detector 35. Therefore, in the case where the xcex3-ray heat detector 35 is not situated at the center of the axial node, there is a need of computing a reading value by an axial non-symmetrical weight distribution of the axial power distribution in the node having the xcex3-ray heat detector 35 and the adjacent nodes. Conversely, in the case of converting the reading value of the xcex3-ray heat detector 35 into a peripheral power distribution, interpolation or extrapolation is made in the axial direction so as to make the computation easy, and thus, the read value need to be computed. In the reactor nuclear instrumentation system of this seventh embodiment, the xcex3-ray heat detector 35 is coincident with the center of the axial node, and thereby, the same weight of the adjacent node is used in the correlation equation with respect to locating positions of all xcex3-ray heat detectors 35, so that the computation can be made simple, and also, a precision can be improved. Further, the axial position of the fuel spacer is coincident with the center of the axial node, and hence, an axial distortion of the neutron flux in the three-dimensional nuclear hydrothermal simulation computing model becomes maximum at the node center. By only converting the node into a substantially average node data, it is possible to consider the axial effect of the fuel spacer, so that a computation precision can be improved in the axial distortion of the neutron flux of the three-dimensional nuclear thermal-hydraulics simulation computing model. It is finally to be noted that the present invention is not limited to the described embodiments and many other changes and modifications may be made without departing from the scopes of the appended claims.
	abstract	In the present invention, a reactor power control apparatus of a natural circulation reactor comprises a reactor pressure vessel which circulates cooling water using the density difference of the coolant inside, a feed water pipe which is connected to the reactor pressure vessel and supplies cooling water, a power control section which controls the reactor power using a control rod. The feed water pipe has an ultrasonic thermometer sensor. Driving of the control rod is controlled by the power control section based on the feed water temperature detected by the feed water thermometer. The reactor power control apparatus can detect the temperature of the feed water and perform drive control of the control rod preferentially, and obtain stable reactor power.
	description	This application claims the benefit of and is a U.S. National Phase filing of PCT Application PCT/US2016/066246 filed Dec. 13, 2016 entitled “VOLUMETRIC IMAGING SYSTEM FOR HEALTH SCREENING”, in the name of Simon et al., which claims benefit of U.S. Provisional application Ser. No. 62/267,427, provisionally filed on Dec. 15, 2015, entitled “VOLUMETRIC IMAGING SYSTEM FOR LUNG HEALTH SCREENING”, in the name of Simon et al., all of which are hereby incorporated by reference herein in their entirety. This disclosure relates generally to the field of radiographic imaging, in particular, to radiographic volume imaging and to apparatuses and methods for acquiring projection images of a patient such as for chest x-ray screenings. There is a need for a low cost, portable radiographic imaging device that may be used in remote areas for patient-accessible low-dose screening, such as for lung cancer and other conditions. In particular, it would be advantageous to be able to provide the benefits of volume imaging, wherein a three-dimensional (3-D) image of a subject, such as the chest of a patient, may be obtained at any of a broad range of possible remote sites, including in areas not typically provided with radiographic imaging facilities, and without requiring the high overhead of a full-scale radiography facility or the high cost of attending staff for screening functions. In order to allow more widespread use of the benefits of 3-D imaging for screening, design of a volume imaging apparatus is constrained by cost, usability, and dimensional factors, as well as radiation management factors associated with radiographic imaging equipment. There have been a number of solutions proposed to meet the need for portable volume imaging apparatuses, including those described in U.S. Pat. No. 7,003,070 to Chen et al.; U.S. Pat. No. 6,735,274 to Zahavi et al.; and U.S. Pat. No. 7,224,764 to Sukovic et al. Some drawbacks of proposed solutions include high cost, mechanical complexity, and lack of flexibility for handling different types of screening and for adapting to differences between individuals in the patient population. Proposed solutions do not provide sufficient shielding for stand-alone use of the system outside the confines of a shielded radiographic facility and thus would not be appropriate for broader clinical use or for access outside a fully featured radiography site that is designed with integrated shielding. Thus, it may be seen that there would be advantages in providing a volume imaging apparatus that would allow more widespread access to high-volume screening in a clinical environment as well as in other environments not typically associated with conventional radiography equipment. The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. An apparatus having an x-ray source and an x-ray detector is configured to be rotated about a standing patient to capture and store a plurality of radiographic images of the patient during the rotation. A portable enclosure surrounds the source, the detector and the patient. An advantage that may be realized in the practice of some disclosed embodiments of the apparatus is to provide imaging availability at locations remote from standard medical facilities. In one embodiment, an apparatus includes an x-ray source assembly and a detector assembly configured to rotate about a central axis to capture and store a plurality of radiographic images of a patient positioned at the central axis. An x-ray shielded enclosure is attached to the x-ray source assembly and the x-ray detector assembly, and is configured to entirely enclose the source assembly, the detector assembly and the patient, and is transportable as a unit. In one embodiment, an x-ray source is positioned on one side of a central axis, an x-ray detector is positioned on a second side of the central axis opposite the x-ray source. The detector is configured to capture and store a plurality of radiographic images of a patient standing at the central axis. A platform is configured to support the patient standing thereon and to rotate the standing patient at the central axis between the source and detector. An x-ray shielded portable enclosure surrounds the source, the detector and the patient. In one embodiment, an apparatus having a stationary x-ray detector and a movable x-ray source rotates the x-ray source as it moves to continuously aim the source at the detector. The source is configured to emit x-rays at predetermined times during its movement so that the detector captures radiographic images of a patient standing therebetween. An x-ray shielded enclosure attached to the x-ray source and the x-ray detector entirely enclosed the source, the detector and the patient during imaging, and is transportable as a unitary integrated whole. According to one aspect of the present invention, there is disclosed an apparatus comprising an x-ray source, an x-ray detector, a mechanism attached to the source and the detector to rotate the source and detector about a standing person. The source and detector may be configured to capture and store a plurality of radiographic images of the person while being rotated. An x-ray shielded portable enclosure to enclose the source, the detector, the mechanism, and the standing person. According to one aspect of the present invention, there is disclosed an apparatus comprising an x-ray source, an x-ray detector, and a platform to support a person standing thereon. The platform may be configured to rotate the standing person between the source and detector while the source and detector capture and store a plurality of radiographic images of the person during rotation. An x-ray shielded portable enclosure surrounds the source, the detector and the standing person. According to another aspect of the present invention, there is disclosed an apparatus comprising an x-ray source, an x-ray detector, and a mechanism attached to the source which moves the source relative to a person standing between the source and the detector. The detector captures and stores a plurality of radiographic images of the person while the source is moved. An x-ray shielded portable enclosure completely encloses the source, the detector, the mechanism, and the standing person. An object of the present disclosure is to address the need for improved volume image acquisition apparatus for low dose screening and related projection and volume imaging applications. Embodiments of the present disclosure provide a portable volume imaging apparatus that allows a high-degree of operation and allow patient imaging with minimal or no technician assistance. These objects are given only by way of illustrative example, and such objects may be exemplary of one or more embodiments of the invention. Other desirable objectives and advantages inherently achieved may occur or become apparent to those skilled in the art. The invention is defined by the appended claims. This brief description of the invention is intended only to provide a brief overview of subject matter disclosed herein according to one or more illustrative embodiments, and does not serve as a guide to interpreting the claims or to define or limit the scope of the invention, which is defined only by the appended claims. This brief description is provided to introduce an illustrative selection of concepts in a simplified form that are further described below in the detailed description. This brief description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background. This application claims priority to U.S. Patent Application Ser. No. 62/267,427, filed Dec. 15, 2015, in the name of Simon et al., and entitled VOLUMETRIC IMAGING SYSTEM FOR LUNG HEALTH SCREENING, which is hereby incorporated by reference in its entirety. The following is a detailed description of the preferred embodiments, reference being made to the drawings in which the same reference numerals identify the same elements of structure in each of the several figures. Where they are used herein, the terms “first”, “second”, and so on, do not necessarily denote any ordinal, sequential, or priority relation, but are simply used to more clearly distinguish one element or set of elements from another, unless specified otherwise. In the context of the present disclosure, the terms “viewer”, “operator”, “viewing practitioner”, “observer”, and “user” are considered to be equivalent and refer to the viewing practitioner or other person who views and manipulates an x-ray image on a display monitor or other viewing apparatus. As used herein, the term “energizable” relates to a device or set of components that perform an indicated function upon receiving power and, optionally, upon receiving an enabling signal. The term “actuable” has its conventional meaning, relating to a device or component that is capable of effecting an action in response to a stimulus, such as in response to an electrical signal, for example. The term “modality” is a term of art that refers to types of imaging. Modalities for an imaging system may be conventional x-ray radiography, fluoroscopy or pulsed radiography, tomosynthesis, tomography, ultrasound, magnetic resonance imaging (MRI), or other types of imaging. The term “subject” refers to the patient who is being imaged and, in optical terms, may be considered equivalent to the “object” of the corresponding imaging system. The term “set”, as used herein, refers to a non-empty set, as the concept of a collection of elements or members of a set is widely understood in elementary mathematics. The terms “subset” or “partial subset”, unless otherwise explicitly stated, are used herein to refer to a non-empty proper subset, that is, to a subset of the larger set, having one or more members. For a set S, a subset may comprise the complete set S. A “proper subset” of set S, however, is strictly contained in set S and excludes at least one member of set S. A “partition of a set” is a grouping of the set's elements into non-empty subsets so that every element is included in one and only one of the subsets. Two sets are “disjoint” when they have no element in common. The terms “image” and “image data” may be used interchangeably in the context of the present disclosure. A digital image that is captured by a digital imaging apparatus may be processed, displayed, transmitted, and/or stored as image data. For the image processing steps described herein, the term “image pixels” is used to refer to image data elements, conventionally used with respect to 2-D imaging and image display, and “voxels” is used for volume image data elements, often used with respect to 3-D imaging, and may be used interchangeably. It should be noted that the 3-D tomosynthesis image may itself be synthesized from 2-D image data obtained as image pixels on a 2-D sensor array and displays as a 2-D image from one angle of view. Thus, 2-D image processing and image analysis techniques may be applied to the 3-D volume image data. In the description that follows, image processing techniques described as operating upon pixels may alternately be described as operating upon the 3-D voxel data that is stored and represented in the form of 2-D pixel data for display. In the same way, techniques that operate upon voxel data may also be described as operating upon pixels. With respect to an image detector, the term “imaging pixel” refers to a picture element unit cell containing a photosensitive element and related circuitry for converting incident electromagnetic radiation to an electrical signal. In the context of the present disclosure, “tomographic imaging apparatus” include various types of imaging systems that scan the subject patient to acquire a number of 2-D radiographic projection images using radiant energy that is directed toward the patient from a range of different positions, then process the 2-D projection images to reconstruct a 3-D image of the subject. For the sake of description, the present disclosure primarily discloses a cone-beam computed tomography (CBCT) imaging modality. However, other types of tomographic imaging apparatus may be used, including generalized computed tomography (CT) systems such as those using fan beam radiant energy or tomosynthesis imaging systems that scan over a limited angular range, i.e., less than 360° or less than 180°. These systems may also be individually referred to as a “radiographic volume imaging apparatus” in the present disclosure. The schematic diagram of FIG. 1 shows an imaging system 10 that may be used to acquire projection images of a subject 14. The projection images may be used for generating volume images of a subject 14 using a cone-beam computed tomography (CBCT) imaging apparatus 40. The imaging apparatus 40 has a protective shell or enclosure 16, that houses internal components including an x-ray radiation source 12 and a digital detector 20 that captures digital radiographic images of the subject 14, and also provides sufficient levels of radiation shielding to minimize or prevent x-rays emitted by the source 12 from exiting the enclosure 16. For volume imaging, source 12 and detector 20 are both moved into diametrically opposed positions, relative to imaging central axis 13, at different angular locations along the source/detector path 15 to acquire a number of 2-D projection images of the subject 14, each image acquired at one of the different angular locations. The acquired projection image data may then be stored in an electronic memory of the detector 20, transmitted by the detector 20 over a wide area network (WAN) 22 to a remote site 24 for processing, viewing, assessment, and storage of the image data. At remote site 24, a computer system or other processing system 30 may be in signal communication with the components of the imaging apparatus 40 to receive the digital images captured and transmitted by the detector 20 or the imaging apparatus 40. Computer system 30 may execute programs to reconstruct a digital volume image of the subject 14 using the received radiographic projection images. The digital volume image may be presented on a display 32 for viewing and assessment. The volume image may also be transmitted over the WAN 22 to other suitable networked computers (not shown) and to a digital image storage device located in database 26. It may be appreciated that the embodiment shown in FIG. 1 allows imaging apparatus 40 to be easily transported to, and used at, a remote site for capturing and supplying projection images of a subject 14. A hospital or radiology practice may communicate over the WAN 22 and utilize satellite volume imaging stations comprising the imaging apparatus 40 that are remotely installed to provide a needed portable facility for obtaining patient image data, such as for screening or other procedures, without requiring the patient to travel to a central hospital or radiology facility. It should be noted that imaging apparatus 40 may also be used for tomosynthesis imaging, with appropriate modifications as described in more detail herein. To support the requirements of volume radiographic imaging, which utilizes multiple 2-D images, each taken at a different rotational angle about subject 14, and the programmed algorithms that reconstruct a 3-D image volume, CBCT imaging apparatus 40 may provide image capturing scanning movements in a number of ways. By way of example, FIG. 2A illustrates revolution of a radiographic energy source 12 and a digital detector 20 about a radial path 15, wherein the focal spot of the source 12 orbits the patient 14 while remaining in the plane of the radial path 15 at every image capture position in the scan. The orbital path of FIG. 2A may be most useful when the imaging region of interest of the subject 14 is positioned at or proximate the imaging central axis 13 (FIG. 1) of the radial path 15. FIG. 2B illustrates an alternate helical scan path 19 that may be used to generate a larger image volume. Other exemplary scan patterns that may be effective include reverse helical scan patterns that effect downward movement over one part of the scan and upward movement over another part of the scan, while the source and detector revolve about an imaging axis. Other scan patterns, including sinusoidal scanning, wherein the source and detector are continuously moving upward and downward parallel to an imaging axis while revolving about the imaging axis, may alternately be used. An elliptical scan may be of value, particularly for low-dose chest imaging, since an elliptical pattern may be compatible with the overall shape of the chest. It should also be noted that a partial revolution about the subject may be sufficient, depending on the amount of depth data that may be required for a particular case. Tomosynthesis imaging may also be provided with a stationary detector 20 and source 12 that is moved over an arc, for example, or with a stationary detector 20 and stationary source 12 and a moving patient 14. Tomosynthesis may also employ a linear scan, such as a scan wherein source 12 is moved vertically through a range of height positions, or along an arc less than 180° (FIGS. 3D-3E), while directing radiation energy through the subject 14 toward the detector 20. Scanning movements as illustrated in FIGS. 2A and 2B, or other scan patterns, may be effected by any of a number of mechanisms, such as by revolving source 12 and detector 20 about a stationary subject 14. According to an alternate embodiment, scanning may be effected by rotating the patient while the source and detector remain stationary, such as by rotating a platform on which the patient is standing, for example. According to an alternate embodiment of the present disclosure, as shown schematically in FIG. 2C, an array 70 of multiple x-ray sources 12 arranged in an arc may be provided for obtaining projection images. For CT or CBCT imaging, the individual sources 12 may be energized in a timed sequence, corresponding with a complementary movement of detector 20 about the subject 14. In one tomosynthesis imaging embodiment, detector 20 may be stationary as a plurality of sources 12 is energized in a timed programmed sequence. The sources 12 in array 70 may include distributed carbon nanotube (CNT) emissive devices, for example, configured to be individually energized, or fired, for providing x-ray radiation in a predetermined timed sequence. Relative rotation between the subject 14 and the radiation imaging components may be provided in any of a number of ways. FIGS. 3A, 3B, and 3C show, from a top view, scanner movement for an embodiment in which the subject 14 is standing in a stationary position while source 12 and detector 20 revolve about a central axis 15 at or near the patient's position. Subject 14 may be standing on a stationary platform 18 while source 12 and detector 20 are attached to a cylindrical shell or enclosure 16 that rotates about the patient 14 positioned at or near the central axis 15 while platform 18 remains still. The source and detector travel paths may be defined using one or more rigid tracks that guide the paths of source 12 and detector 20 within the enclosure as an imaging session proceeds. The use of tracks or other guidance may help to provide an elliptical scan pattern or other suitable scan trajectory, for example. In one embodiment, both CBCT and tomosynthesis imaging may be performed using one imaging apparatus 40. One mechanism may be used to revolve source 12 about the patient who is positioned at or near the central axis 15, while a separate mechanism may be used to revolve the detector 20. For CBCT operation, the two mechanisms are linked so that source 12 and detector 20 both simultaneously and synchronously revolve about the subject 14 positioned at or near at central axis 15. In the embodiment shown in FIGS. 3D and 3E, a tomosynthesis imaging mechanism may include separable assemblies allowing the detector 20 to be fixed in position so that only source 12 moves along an arc of revolution about central axis 15, as shown. In the embodiment of FIGS. 3D and 3E, source 12 may be coupled to rotatable gantry 17 and detector 20 may be coupled to a stationary shell 16. Source 12 itself may be rotated during its revolving movement around central axis 15 so that it is aimed at the detector 20 such that a central ray 21 emitted by the source 12 is directed substantially toward a center of detector 20. It can readily be appreciated that a number of different mechanical arrangements may be used for coupled or de-coupled orbital movement of source 12 and detector 20 about the patient. FIGS. 4A, 4B, and 4C show top views of a scanning procedure using imaging apparatus 40 in an embodiment in which the standing subject 14 rotates while maintaining at least a portion of the subject's body, such as a torso, proximate to or at the central imaging axis 15, while source 12 and detector 20 remain stationary. Subject 14 is standing on a rotating platform 18 while source 12 and detector 20 are attached to a cylindrical enclosure 16 that remains in a stationary position. Belts, straps, and/or a support attached to the platform 18 and extending upward to support the patient 14, and/or other supporting features may be provided to secure the patient 14 in a position oriented for optimal radiographic imaging within the enclosure 16. Additional support features may include a headrest secured in an appropriate position to support the head of the patient 14, and/or hand grips to assure that the patient's hands and arms are appropriately positioned. The imaging apparatus 40 may include a voltage supply (not shown) electrically connected to the x-ray source to provide adjustable x-ray energy levels. Chest imaging, for example, may require increased x-ray energy for obtaining images of the patient from a lateral view, since there may be more patient mass between the source and detector in that direction; and less energy could be used for the posterior-anterior (PA) image. X-ray energy levels may be accordingly varied at different imaging positions during the scan. A plurality of detectors 20 having different sizes and relative dimensions may be provided to address the particular requirements of the imaging apparatus 40 and the patient. For example, a detector 20 width may be selected to be larger than the width of the patient's lungs. Detector 20 height may be selected relative to average lung size for a local patient population. FIGS. 5A, 5B, 6, and 7 show lateral views of the patient 14 within an enclosure 16 provided by imaging apparatus 40. Various components and configurations are illustrated for positioning and supporting the patient 14 within the enclosure 16 during the scanning procedure. Considerations for patient positioning include positioning the patient's arms up and away from the chest area during scanning. As illustrated in FIGS. 5A and 5B, handles or a handle bar 42 or other device may be attached to the shell 16 for grasping by the patient. An adjustable platform, or backrest, 46 may be attached to the imaging apparatus 40 to provide support for the patient 14 while the patient 14 leans against it and may be particularly useful where obtaining images of the patient 14 may require that the patient not be positioned in a vertical orientation. Backrest 46 may be adjustable for angle, such as by including an adjustable support member 34, and for patient height. Backrest 46 can support the person during image capture and may be vertical or obliquely disposed at an angle away from vertical, such as an angle between about 5 degrees and about 15 degrees away from a vertical position, for example. Patient support components that work with backrest 46 may include handle bar 42 devices, straps that extend around a torso of patient 14, suction devices, releasable fasteners such as hook-and-loop fasteners, or other mechanisms for temporarily securing the patient in position and for holding the patient's arms comfortably in place, either in an upward position, away from the chest, as shown in FIGS. 5A-5B or in other suitable positions. The backrest 46 support may be positioned vertically or at a slight slant angle when the enclosure shell 16 is unoccupied, and may be designed to tilt the patient into a suitable position for imaging while the patient is leaning against it. FIG. 6 shows the subject 14 in a non-vertical position but leaning backward against backrest 46, obliquely disposed in a tilted position within imaging apparatus 40. FIG. 7 shows an alternate embodiment with subject 14 leaning forward against backrest 46. In this configuration, the subject 14 also has arms raised above the chest area. FIG. 7 also shows a configuration that uses a radiopaque sliding door 48 that may be closed to provide shielding during the imaging session as well as a rotatable door 49. In addition to patient 14 support and stabilization, there are a number of other features that may be provided for x-ray shielding and enclosure. The extent of the shielding above and below the patient depends, in part, on measured exposure levels. In an alternate embodiment, the enclosure 16 may include a variable height that may be changed based on factors such as the examination type and patient height, for example. Where the enclosure fully encloses the subject 14 during imaging, one or more windows may be provided to allow light to enter the enclosure from the surrounding environment and, optionally, visibility of the surrounding environment for the enclosed patient. According to one embodiment shown in FIG. 8, a leaded glass window 92 may be provided along the top of the enclosure, with one or more additional windows (not shown) provided in lower portions of the enclosure. The material used for windows may be radiopaque, in order to block radiographic energy, but is transparent to visible light. This may provide a more comfortable and less confining environment for the subject 14 being imaged. FIG. 8 is a schematic diagram that shows control features and supporting components that allow CBCT imaging apparatus 40 to be used in clinical applications and at sites that do not have a trained technician to assist in setting up and running the imaging exam. As part of imaging apparatus 40 a controller 60, which may include a programmable processor, provides control functions and monitoring of apparatus operation and also provides the needed WAN interface for communication of control signals and transfer of acquired image data. Patient access to the imaging area inside enclosure 16 may be provided via a sliding or hinged door 48, which may be lockable using a locking mechanism controlled by an access controller 54. Digital access control may be provided by a number of mechanisms. For example, access controller 54 may be programmed to unlock the locking mechanism for the door 48 in response to receiving an access code that is read from an encoded token or encoded ID card containing an authorized digital access code as a type of electronic identification, which token or ID card may be provided to the patient data by a doctor or by a medical facility. A reader 68 may be connected to access controller 54 which reader 68 may include a magnetic reader for detecting magnetically detectable digital access data, such as provided on a magnetic strip on an ID card, for entry and use of the imaging apparatus 40; a laser reader for detecting 1D or 2D bar codes; other biomarker detectors such as fingerprint readers; as well as audio detectors; an optical reader for reading optically detectable access data; or a combination thereof. Access controller 54 may be electrically connected to a digital camera 56 that is configured to detect and verify patient ID using iris scanning or facial recognition, for example, to capture and record patient identification or exam documentation, or a combination thereof. Alternately, for digital access control, the patient 14 may be provided with a code for keypad entry in order to use the imaging apparatus 40. Using such identification features may allow imaging apparatus 40 to be installed at an unattended site, such as in a public area, shopping mall, or other public or private facility for use only by authorized patients. An interlock apparatus 64 may be provided, including both hardware and software components and sensors for preventing operation where door 48 is not properly closed or the patient is not detected in a correct position for the required imaging procedure. A speaker 50 may be provided within the enclosure 16 in order to provide digitally prerecorded or live audio instructional messages to the patient immediately prior to and during an imaging procedure. These may include messages automatically responsive to sensors within the enclosure 16 detecting a proper or improper position of the patient 14 within the imaging apparatus 40 before and during execution of the imaging procedure. The speaker 50 may also be used to play music, such as might be useful for assisting relaxation. A display monitor 52 may be provided within the enclosure 16 for displaying instructional text and videos, which text and videos may correspond in time to the audio messages described herein. The monitor 52 may also be used to display still and moving images to complement the playback of relaxation music. In one embodiment, the camera 56 may be used to detect a height of the subject 14 and transmit detected height data to controller 60, wherein the controller 60, in turn, may signal a mechanism to adjust a height of the radial travel path 15 (FIG. 2A) above the platform 18, for the source 12 and detector 20. A WAN-connected microphone 66, video camera 56, and speaker 50 may be provided to allow patient 14 to communicate with remote personnel in the event that live audio and/or video network streaming instruction and response is desired. Controller 60 may also be electrically connected to a motorized mechanism for controlling movement of a transport apparatus 62 that provides the orbital movement to x-ray source 12 and detector 20 for x-ray scanning. Additional actuators of transport apparatus 62 may also be provided to change a height of the radial scan path 15, helical pitch for a helical scan path 19, and other variables related to the scan procedure. Enclosure 16 may be formed from any of a number of materials that provide a sufficient measure of absorption of x-ray radiation to meet regulatory requirements. Enclosure 16 may be formed from lead or other radiopaque material. Alternately, enclosure 16 may be covered or coated with a radiopaque material. External and internal dimensions of enclosure 16 should allow for sufficient shielding of the standing patient and proper spacing of patient 14, and source 12 and detector 20 assembly components. In one embodiment, a circular enclosure 16 may include an interior diameter configured to be between about 28 inches and 38 inches, which may result in providing a usable floor or platform 18 area between about 600 square inches and 1200 square inches. In one embodiment, a height of enclosure 16 extends from about 4 feet to about 9 feet, allowing configurations that enclose only a part of the patient 14 anatomy within the enclosure 16 or the entirety of patient 14. In one such embodiment, the interior volume of enclosure 16 may range between about 17 cubic feet and about 71 cubic feet. The interior volume allows patient movement therein such as for assuming a proper imaging position, and otherwise adjusting body position for radiographic imaging. Thus, the size of imaging apparatus 40 is consistent with embodiments thereof that are portable or transportable easily to locations remote from large centralized medical imaging facilities. With respect to the logic flow diagram of FIG. 9, a method is disclosed for automatically obtaining multiple 2-D radiographic images of a subject using imaging apparatus 40 without requiring on-site personal technician assistance according to an embodiment of the present disclosure. In a patient access step S900, the patient 14 is permitted to enter the imaging apparatus 40. An electronically controlled lock connected to the controller 60 releases the door to be opened upon receiving an unlock command from controller 60, thereby allowing the patient to open the door 48 and enter the imaging apparatus 40 alone after a proper access ID procedure is followed. A proper access procedure for allowing patient access into enclosure 16 may be accomplished in any of a number of ways, such as by providing the patient with an encoded ID card, or ID token from a doctor or medical facility, which is detected and recognized by a reading apparatus 68 electrically connected to the imaging apparatus 40. An identification card or other permission document may alternately be used or may be required to verify patient identity. In an exam determination step S910, the controller 60, electrically connected to the imaging apparatus 40 and to a WAN 22 determines the type of exam prescribed for the identified patient 14. This may have been provided on access documentation carried by the patient and communicated to the imaging apparatus 40, or it may be accessed and downloaded from WAN connected database 26, for example, by automatically communicating the recognized patient ID to the database 26 which uses the ID as an index into the database 26 to retrieve and return the prescribed exam type. In a patient instruction step S920, the patient 14 may be provided with instructions for proper positioning to allow the image acquisition procedure. This may include pre-recorded audio played back over the speaker 50, text messages displayed on a monitor 52, or recorded video instructions played back using both the speaker 50 and monitor 52, or even live streamed video via the connected WAN 22 from a technician or practitioner who may communicate with and view the patient 14 over the same two-way video stream using the camera 56 within imaging apparatus 40. Audio and/or visual feedback may be provided to the patient 14 to indicate successful positioning and equipment setup. An imaging verification step S930 then executes, in which the imaging apparatus and/or the remote technician checks that the required imaging conditions are met. These may include hardware conditions such as, for example, proper closing of doors 48, 49 for radiation shielding, etc. If the imaging conditions are not met at step S930, imaging is inhibited at step S932 and the method returns to step S920 for additional patient instruction as described above. If the imaging conditions are met at step S930, a scout image acquisition step S940 may be performed to obtain and analyze at least one low-dose scout image of patient 14 as a prelude to subsequent volume imaging activity. The scout image allows a quick check of calibration, equipment settings, and patient position, to verify that equipment and patient setup are acceptable. The scout image may also be used to verify that power levels are acceptable for subsequent imaging. For some imaging cases, a two-view scout image may be obtained, such as one lateral view and one PA view. A position detecting step S950 is then executed, in which the imaging apparatus checks for proper patient positioning for the selected examination. In addition to using image results from the scout image, this step may use recorded information from camera 56, live video information transmitted from camera 56 to a remote technician, and information from one or more sensors that are in signal communication with controller 60. A laser source and detector, for example, may be placed within enclosure 16 to verify the position of patient 14. If patient positioning conditions are unsatisfactory at step S950, an inhibit step S932 prevents imaging from proceeding, and the method returns to step S920 to activate additional instructions as described herein, additional review of proper setup and patient positioning procedures, and to communicate any other additional audio and/or visual instructions. If proper positioning is verified at step S950, a scan step S960 is then performed according to a programmed imaging sequence associated with the required exam type. For example, the scan step may include moving and activating the (source and detector) imaging components and acquiring 2-D projection images for the associated exam type. An image upload step S970 then uploads the acquired projection images to a central processor 30 (FIG. 1) over WAN 22, or other suitable location. A processing and reconstruction step S980 is then executed at the central processor 30 for reconstructing the volume image using an appropriate 3-D reconstruction algorithm. The reconstructed image may be transmitted to a local or network connected facility for viewing by medical personnel, or the reconstructed image may be stored for later transmission and/or viewing as part of processing step S980. Alternative embodiments consistent with the disclosure hereinabove may include an apparatus for imaging a subject, wherein the apparatus comprises a plurality of x-ray sources, such as carbon nanotube sources, in an x-ray assembly that are electrically connected to be controllably individually fired. An x-ray detector may be positioned to capture radiographic images of a patient positioned between the source and detector. A controller may be configured to selectively fire two or more of the sources in a predetermined sequence and a predetermined timing, wherein the plurality of sources and the detector are configured to capture and store a plurality of radiographic images of the subject while sequentially firing the sources. A transport mechanism may be provided to move the detector, with respect to a standing subject, to respective positions corresponding to the positions of each of the plurality of x-ray sources. A portable x-ray shielded enclosure surrounds the source, the detector, the transport mechanism, and the subject to be imaged. In another alternative embodiment, a method for acquiring a volume image of a subject includes unlocking an entry to an imaging enclosure in response to receiving an access code associated with the subject. Corresponding hardware assemblies within the enclosure automatically provide audio and visual instructions to the subject for positioning himself or herself within the imaging enclosure. Corresponding visual cues or indicators may be provided on interior surfaces of the enclosure, such as floors, walls, and ceilings. Handles and other body supports may be provided to support the subject in a correct orientation with respect to imaging components such as an x-ray source and detector. After verifying correct positioning, a scout image may be obtained to further verify correct subject positioning for a predetermined exam type to be performed. The subject may be radiographically imaged from a plurality of source and/or detector positions, and the captured images of the subject may be uploaded. The uploaded projection images may be processed in the usual course, such as reconstructing a volume image based on the uploaded images. Any, or both, of the captured and reconstructed images may be displayed, stored, or otherwise transmitted to remote computer systems. In another alternative embodiment, an apparatus for obtaining a sequence of radiographic images of a subject includes a portable radiation shielded enclosure having sufficient interior room to surround a subject to be imaged between an x-ray source and an x-ray detector. The source and detector may be configured to acquire a plurality of radiographic images of the subject at different angles. A patient support may be provided to support the subject in a suitable position on a platform within the enclosure for image acquisition. A motor controlled mechanism incrementally moves the source or both the source and detector for repeated image acquisition at different angles. The plurality of images so obtained may include a radial scan, or a helical scan, for example. For exemplary functions described herein and/or performed as described with reference to the figures, the system processor, host computer or the radiographic imaging system/unit may be implemented, for example, but not limited to using one or more of a conventional general purpose processor, digital computer, microprocessor, microcontroller, RISC (reduced instruction set computer) processor, CISC (complex instruction set computer) processor, SIMD (single instruction multiple data) processor, signal processor, CPU (central processing unit), ALU (arithmetic logic unit), GPU (graphics processing unit), VDSP (video digital signal processor) and/or similar computational machines, programmed according to the teachings of the present specification, as will be apparent to those skilled in the relevant art(s). Appropriate software, firmware, coding, routines, instructions, opcodes, microcode, and/or program modules may readily be prepared by skilled programmers based on the teachings of the present disclosure, as will also be apparent to those skilled in the relevant art(s). The software may be generally executed from a medium or several media by one or more of the processors of the machine implementation. Consistent with one embodiment, the present invention utilizes a computer program with stored instructions that control system functions for image acquisition and image data processing for image data that may be stored and accessed from an electronic memory. As may be appreciated by those skilled in the image processing arts, a computer program of an embodiment of the present invention may be utilized by a suitable, general-purpose computer system, such as a personal computer or workstation that acts as an image processor. However, many other types of computer systems may be used to execute the computer program of the present invention, including an arrangement of networked processors, for example. The computer program for performing the method of the present invention may be stored in a computer readable storage medium. This medium may comprise, for example; magnetic storage media such as a magnetic disk such as a hard drive or removable device or magnetic tape; optical storage media such as an optical disc, optical tape, or machine readable optical encoding; solid state electronic storage devices such as random access memory (RAM), or read only memory (ROM); or any other physical device or medium employed to store a computer program. The computer program for performing the method of the present invention may also be stored on computer readable storage medium that may be connected to the image processor by way of the internet or other network or communication medium. Those skilled in the art will further readily recognize that the equivalent of such a computer program product may also be constructed in hardware. It is noted that the term “memory”, equivalent to “computer-accessible memory” in the context of the present disclosure, may refer to any type of temporary or more enduring data storage workspace used for storing and operating upon image data and accessible to a computer system, including a database. The memory could be non-volatile, using, for example, a long-term storage medium such as magnetic or optical storage. Alternately, the memory could be of a more volatile nature, using an electronic circuit, such as random-access memory (RAM) that may be used as a temporary buffer or workspace by a microprocessor or other control logic processor device. Display data, for example, is typically stored in a temporary storage buffer that may be directly associated with a display device and may be periodically refreshed as needed in order to provide displayed data. This temporary storage buffer may also be considered to be a memory, as the term may be used in the present disclosure. Memory may be also used as the data workspace for executing and storing intermediate and final results of calculations and other processing. Computer-accessible memory may be volatile, non-volatile, or a hybrid combination of volatile and non-volatile types. It is understood that the computer program product of the present invention may make use of various image manipulation algorithms and processes that are well known. It will be further understood that the computer program product embodiment of the present invention may embody algorithms and processes not specifically shown or described herein that are useful for implementation. Such algorithms and processes may include conventional utilities that are within the ordinary skill of the image processing arts. Additional aspects of such algorithms and systems, and hardware and/or software for producing and otherwise processing the images or co-operating with the computer program product of the present invention, are not specifically shown or described herein and may be selected from such algorithms, systems, hardware, components and elements known in the art. As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method, or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.), or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “service,” “circuit,” “circuitry,” “module,” and/or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon. Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that may contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. Program code and/or executable instructions embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user's computer (device), partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer program instructions may also be stored in a computer readable medium that may direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks. The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
	description	The present invention generally relates to the field of application of radiation engineering, and particularly, to a non-destructive inspection device and a method thereof, and more particularly, to a scanning device using radiation beam for backscatter imaging and a method thereof. In the application of non-destructive inspection and human body inspection, two types of technologies are generally utilized: an imaging technology using radiation beam for transmission and an imaging technology using radiation beam for backscattering. Where backscatter imaging is employed, a subject to be inspected is scanned by radiation beam, i.e. a pencil beam, simultaneously the detector receives signal representative of radiation scattered back from the subject. A scatter image can be reconstructed or obtained based on the detected signals which are correlated with scanned positions or portions of the subject to be inspected. Conventional flying-spot scanning mechanism implements a first dimension scanning by rotation motion of the rotary shield body with multiple collimation holes within a ray scanning sector while carrying out a second dimension scanning by swing or translating the ray scanning sector. However, in the arrangement of the above-mentioned rotary shield body with multiple collimation holes, a relatively complex flying-spot formation mechanism is used and it has disadvantage on shielding of the X-ray and the leakage of the X-ray is hazardous to human body. Further, when implementing the first dimension scanning, the scanning device carries out a non-uniform scanning on the subject in a vertical plane. More specifically, the scanning ray accelerates at the starting and ending of one single pencil beam scanning operation. As a result, the scanning spot will be further enlarged longitudinally at the starting and ending points of one single pencil beam scanning operation where geometric deformation of the scanning spot occurs. Accordingly, a longitudinal compression deformation due to variation of the scanning velocity of the scanning takes place in addition to the geometric deformation of the resultant image. Furthermore, for the operation of the second dimension scanning, if a translational movement of the ray scanning sector is performed, the ray generator, the rotary shield body, and so on is required to translate in the second dimension, this renders the mechanical configuration of this device rather complicate; and if a rotation motion of the ray scanning sector is performed, rotational inertia of the ray generator and the rotary shield body should be overcome. This gives rise to a problem concerning wear and tear or breakdown of bearings of the rotating driver and the rotating ray generator and the rotary shield body. In addition, in the prior art, the radiation source, for example the X-ray tube, is generally disposed inside the rotary radiation body, so it is difficult to match interface of the scanning mechanism with that of the conventional X-ray tube. Consequently, it necessitates redesigning the shield body of the X-ray tube so as to achieve matching the same with the interface of a conventional X-ray tube, which in turn increases the cost of the scanning device for backscatter imaging. The present invention has been made to overcome or alleviate at least one aspect of the above mentioned disadvantages or problems existing in the prior art. Accordingly, it is an object of the present invention to provide a scanning device using radiation beam for backscatter imaging and a method thereof, which adopts a novel “flying-spot” formation mechanism so as to achieve the radiation beam scanning for backscattering. Accordingly, it is another object of the present invention to provide radiation beam scanning device and method in which a linear moving flying-spot is achieved. Accordingly, it is still another object of the present invention to provide a scanning device and scanning method for controlling sectional shape of the radiation beam passing through the scanning collimation holes and irradiating on the subject to be scanned by constraining shapes of the scanning collimation holes at different positions. According to one aspect of the present invention, there is provided a scanning device using radiation beam for backscatter imaging, the scanning device comprising: a radiation source; and a stationary shield plate and a rotary shield body positioned respectively between the radiation source and a subject to be scanned, wherein the stationary shield plate is fixed relative to the radiation source, and the rotary shield body is rotatable relative to the stationary shield plate; wherein: a ray passing area permitting the radiation beams from the radiation source to pass through the stationary shield plate is provided on the stationary shield plate; and a ray incidence area and a ray exit area are respectively provided on the rotary shield body; during the process of the rotating and scanning of the rotary shield body, the ray passing area of the stationary shield plate intersects consecutively the ray incidence area and the ray exit area of the rotary shield body to form scanning collimation holes. According to one preferred embodiment of the present invention, the ray passing area of the stationary shield plate is a linear slit; the rotary shield body is a cylinder, and the ray incidence area and the ray exit area are spiral slits. When the rotary shield body rotates in a uniform velocity, the scanning collimation holes consecutively move along the linear slit. According to one preferred embodiment of the present invention, the stationary shield plate is provided between the radiation source and the rotary shield body. Preferably, the scanning device using radiation beam for backscatter imaging further comprises: a control unit which controls scanning velocity of the radiation beam by controlling rotary velocity of the rotary shield body and acquires exit direction of the radiation beam by detecting rotary angle of the rotary shield body. According to one preferred embodiment of the present invention, by controlling widths of the spiral slits of the rotary shield body at different positions, shapes of the scanning collimation holes at different positions are controlled such that sectional shape of the radiation beam passing through the scanning collimation holes and irradiating on the subject to be scanned is controlled. Moreover, the scanning device further comprises: a drive unit adapted for driving the rotary shield body to rotate; wherein the rotary shield body is a hollow cylinder or a solid cylinder. Specifically, rotary axis of the rotary shield body is located on a coplanar plane which is defined by the radiation source and the linear slit of the stationary shield plate. According to another aspect of the present invention, there is provided a scanning method using radiation beam for backscatter imaging, the scanning method comprising the steps of: providing a radiation source which emits radiation beam; providing a stationary shield plate and a rotary shield body positioned respectively between the radiation source and a subject to be scanned, wherein the stationary shield plate is fixed relative to the radiation source, and the rotary shield body is rotatable relative to the stationary shield plate; wherein a ray passing area permitting the radiation beams from the radiation source to pass through the stationary shield plate is provided on the stationary shield plate, and, a ray incidence area and a ray exit area are respectively provided on the rotary shield body; and rotating the rotary shield body such that the ray passing area of the stationary shield plate intersects consecutively the ray incidence area and the ray exit area of the rotary shield body to form scanning collimation holes. Preferably, the ray passing area of the stationary shield plate is a linear slit; the rotary shield body is a cylinder, and the ray incidence area and the ray exit area are spiral slits. When the rotary shield body rotates in a uniform velocity, the scanning collimation holes consecutively move along the linear slit. According to one preferred embodiment of the present invention, the scanning method further comprises the steps of: detecting positions of the scanning collimation holes; and, controlling exit direction of the radiation beam based on detection of positions of the scanning collimation holes. Preferably, the scanning method further comprises the steps of: arranging the scanning collimation holes in a manner such that these holes have predetermined shapes relative to the radiation source, as a result, sectional shape of the radiation beam passing through the scanning collimation holes and irradiating on the subject to be scanned has a predetermined shape. As apparent from the above-mentioned unspecified embodiments, the present invention at least has the one or more following advantages and effects: 1. The present invention provides scanning device and method with novel “flying-spot” formation mechanism, which adopts a simplified scanning mechanism for backscatter imaging and achieves good effect for shielding radiation. 2. According to one preferred embodiment of the present invention, the scanning device and method may enable a controllable scanning for the subject to be scanned and a convenient sampling for the subject to be scanned in accordance with the predetermined mode, thereby backscatter image data as desired can be obtained. For example, the scanning device and method of the present invention may perform scanning on the subject to be scanned in a uniform velocity, which brings conveniently the uniform sampling for the subject to be scanned and avoids longitudinal compression deformation in the obtained backscatter image. 3. In accordance with different application needs, different rotary shield bodies with different spiral lines or with different slits may be manufactured, the rotary shield body of the scanning mechanism according to the present invention is replaceable to meet different application needs. 4. According to the present invention, during the operation of the second dimension scanning in which swing movement of the ray scanning sector is to be carried out, since the ray scanning sector and the rotary shield body perform rotation movement in the same plane, direction of angular momentum of the rotary shield body will not change by the rotary ray scanning on the ray scanning sector. As such, it is not required to overcome rotational inertia of the rotary shield body when the ray scanning sector is to be swung, and, the operation of the second dimension scanning may be easily done by swinging the ray scanning sector. 5. In accordance with the present invention, as radiation source is not disposed inside the rotary shield body, scanning mechanism may be equipped with mechanical interface that matches that of conventional X-ray tube, without redesigning the shield body for the X-ray tube. Accordingly, a compact structure is achieved while the cost may be greatly reduced. Exemplary embodiments of the present disclosure will be described hereinafter in detail with reference to the attached FIGS. 1-3, wherein the like reference numerals refer to the like elements. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein; rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the concept of the disclosure to those skilled in the art. Referring to FIGS. 1-3 of the drawings, a scanning device using radiation beam for backscatter imaging according to a preferred embodiment of the present invention is illustrated. The scanning device comprises: a radiation source 13 (for example, an X-ray tube), a stationary shield plate 5 and a rotary shield body 1 positioned respectively between the radiation source 13 and a subject to be scanned (no shown, for example at the left side of FIG. 2). The stationary shield plate 4 is fixed relative to the radiation source 13, and the rotary shield body 1 is rotatable relative to the stationary shield plate 4. Further, a ray passing area permitting the radiation beams from the radiation source 13 to pass through the stationary shield plate 4 (for example the longitudinal slit 5 of FIGS. 1-3) is provided on the stationary shield plate 4. A ray incidence area (for example the slit 3 of FIGS. 1-3) and a ray exit area (for example the slit 2 of FIGS. 1-3) are respectively provided on the rotary shield body 1; during the process of the rotating and scanning of the rotary shield body 1, the ray passing area 5 of the stationary shield plate 4 intersects consecutively with the ray incidence area 3 and the ray exit area 2 of the rotary shield body 1 to form scanning collimation holes. In the above-mentioned embodiment, the stationary shield plate 4 is provided between the radiation source 13 and the rotary shield body 1. In the above embodiment of the present invention, a ray generator, such as an X-ray tube, includes a ray generator housing 11 and the radiation source 13 accommodated in the ray generator housing 11. In the above-mentioned arrangement, the radiation source 13 may be a X-ray tube, y-ray source or, isotopic source, etc. As shown in FIGS. 1 and 3, in one preferred embodiment, the ray generator housing 11 has a substantially rectangular case shape, and a collimation slit 31 is provided on the ray generator housing 11 such that the radiation ray emitted from the radiation source 13 exits through the collimation slit 31 of the ray generator housing 11. Radiation beam 14 emitted from a target point P of the radiation source 13 passes through the collimation slit 31 to form a ray sector, and then goes through the ray passing area (for example the longitudinal slit 5 of FIGS. 1-3) through the stationary shield plate 4, the ray incidence area (for example the slit 3 of FIGS. 1-3), and the ray exit area (for example the slit 2 of FIGS. 1-3). By provision of the longitudinal slit 5 of the stationary shield plate 4, the relative position relationship between the slits 3 and 2 is made such that during the process of the rotating and scanning of the rotary shield body 1, the ray passing area 5 of the stationary shield plate 4 intersects consecutively with the ray incidence area 3 and the ray exit area 2 of the rotary shield body 1 to form scanning collimation holes. In other words, the ray incidence spiral slit 3 and the ray exit spiral slit 2 of the rotary shield body 1 and the longitudinal slit 5 of the stationary shield plate 4 together constitute a radiation beam collimation hole. As shown in FIGS. 1-3, the ray passing area 5 of the stationary shield plate 4 is a linear slit, the rotary shield body 1 is a cylinder, and the ray incidence area 3 and the ray exit area 2 are spiral slits. Referring to FIG. 2, specifically, any point at the ray incidence area 3, and the ray exit area 2, for example, point A and point B, run in a uniform circular motion along the cylindrical face of the rotary shield body 1, and simultaneously, run in a linear motion in accordance with certain velocity distribution as required along the radial direction of the rotary shield body 1, so as to form a certain cylindrically spiral line. In one preferred embodiment, any point at the ray incidence area 3 and the ray exit area 2, for example, point A and point B, may run in a uniform circular motion along the cylindrical face of the rotary shield body 1, and simultaneously, run in a linear motion at a uniform velocity along the radial direction of the rotary shield body 1, so as to form a uniform speed cylindrically spiral line. Referring to FIG. 2, after determination of the target point P of the radiation source 13 and the point A of the ray incidence area 3, by linking the target point P of the radiation source 13 with the point A of the ray incidence area 3 to form a radiation beam 14 in a linear direction, the point B of the ray exit area 2 can be determined. Since the ray incidence area 3 and the ray exit area 2 are configured to be the uniform speed cylindrically spiral line slits, when the rotary shield body 1 rotates in a uniform velocity, positions of the scanning collimation holes move with rotation of the rotary shield body 1, Accordingly the exit radiation beam 14 move, such that the scanning collimation holes consecutively and uniformly move along the linear slit 5. Although the ray incidence area 3 and the ray exit area 2 are configured to be the uniform speed cylindrically spiral line slits in the above-mentioned embodiments, they are not limited to this according to the present invention. For example, the ray incidence area 3 and the ray exit area 2 may be configured to be the spiral lines with the above certain form, that is, any point at the ray incidence area 3 and the ray exit area 2 may run in a uniform circular motion along the cylindrical face of the rotary shield body 1, and simultaneously, run in a linear motion in accordance with certain velocity distribution along the radial direction of the rotary shield body 1, so as to form a certain cylindrically spiral line. As a result, when the rotary shield body 1 rotates in a uniform velocity, positions of the scanning collimation holes move with rotation of the rotary shield body 1. Accordingly the exit radiation beam 14 move, such that the scanning collimation holes move along the linear slit 5 in accordance with the predetermined velocity distribution. Accordingly, the scanning device according to the present invention may enable a controllable scanning for the subject to be scanned and a convenient sampling for the subject to be scanned in accordance with the predetermined mode, thereby backscatter image data as desired can be obtained. As a result, qualities and resolutions of the backscatter images are improved, and precision and efficiency of the backscatter detection are advanced, thus satisfying different application demands. Moreover, the scanning device may further includes a drive unit 6 adapted for driving rotation of the rotary shield body 1, for example, speed-regulating motor and so on. In order to reduce rotary inertia of the rotary shield body 1, according to one preferred embodiment, the rotary shield body 1 is embodied in a hollow cylindrical form. However, according to the present invention, it is not limited to this. For example, the rotary shield body 1 may also be embodied as a solid cylinder. Particularly, in the above-mentioned embodiment, referring to FIG. 1, the scanning device may further includes rotary coded disk readout unit 7 adapted for detecting rotation position of the rotary shield body 1, and a coded disk readout signal line 8 adapted for inputting information relating to rotation position of the rotary shield body 1 into a control unit 10. Since positions of the scanning collimation holes are determined by the rotational position of the rotary shield body 1. With the above arrangement, positions where the scanning collimation holes are formed can be detected. As shown in FIG. 1, the control unit 10 is also connected with the drive motor 6 via motor drive line 9, so as to further control rotation of the rotary shield body 1. By controlling rotary speed of the rotary shield body 1, scanning speed of the radiation beam may be controlled, and, by detecting rotation angle of the rotary shield body 1, exit direction of the radiation beam can be acquired. Referring to FIG. 2, in one preferred embodiment, rotary axis L of the rotary shield body 1 may be located on a coplanar plane which is defined in common by the radiation source 13 and the linear slit 5 of the stationary shield plate 4. As described above, the rotary shield body 1 may be embodied as a solid cylinder, or else, a hollow cylinder with certain thickness. By constraining widths of the spiral slits of the rotary shield body at different positions, shapes of the scanning collimation holes at different positions are controlled such that sectional shape of the radiation beam passing through the scanning collimation holes and irradiating on the subject to be scanned is controlled. For example, the widths of the spiral slits 2 and 3 at both longitudinal ends of the rotary shield body 1 may be narrower than that of the slit at the longitudinally center position, and, the scanning collimation holes at the spiral slits 2 and 3 at both longitudinal ends of the rotary shield body 1 can be formed with a certain angle relative to these at the longitudinal middle part. By adopting the above-mentioned arrangement, it ensures that the scanning collimation holes always aim at the target point from the radiation source and an unblocked passage for the radiation beam is formed therein. Further, sectional shapes of the radiation beams passing through the scanning collimation holes and irradiating on the subject to be scanned, at different positions, for example radiation beams emitting from both ends and the middle portions of the rotary shield body 1, are maintained constant and uniform. However, according to the present invention, it is not limited to this. For example, by limiting widths of the spiral slits of the rotary shield body at different positions, shapes of the scanning collimation holes at different positions are controlled, as a result, sectional shapes of the radiation beam passing through the scanning collimation holes and irradiating on the subject to be scanned are controlled to meet different scanning demands. Referring to FIG. 3, the ray generator housing 11 may further be connected with the stationary shield plate 4 through a shield sleeve 12, so as to ensure the ray shielding effect. It can be seen from the above-mentioned arrangement, the radiation source 13 is disposed inside the ray generator housing 11, instead of inside the rotary shield body 1. The scanning mechanism may be equipped with a shield sleeve 12 with a mechanical interface that matches with that of conventional X-ray tube, without redesigning the shield body for the X-ray tube. As such, the scanning mechanism of the present invention has a compact structure, and the cost is greatly reduced. With reference to the accompanying drawings, a scanning method using radiation beam for backscatter imaging according to the present invention will be described hereinafter Referring to FIGS. 1-3, the scanning method using radiation beam for backscatter imaging according to one preferred embodiment of the present invention, comprises the steps of: providing a radiation source 13 which emits radiation beam 14; providing a stationary shield plate 4 and a rotary shield body 1 positioned respectively between the radiation source 13 and a subject to be scanned, wherein the stationary shield plate 4 is fixed relative to the radiation source, and the rotary shield body 1 is rotatable relative to the stationary shield plate 4; wherein a ray passing area permitting the radiation beams 14 from the radiation source 13 to pass through the stationary shield plate 4 is provided on the stationary shield plate 4, and, a ray incidence area 3 and a ray exit area 2 are respectively provided on the rotary shield body 4; and, rotating the rotary shield body 4 such that the ray passing area 5 of the stationary shield plate 4 intersects consecutively with the ray incidence area 3 and the ray exit area 2 of the rotary shield body 4 to form scanning collimation holes. In the above-mentioned scanning device, the ray passing area 5 of the stationary shield plate 4 is a linear slit; the rotary shield body 1 is a cylinder, and the ray incidence area 3 and the ray exit area 2 are spiral slits; and when the rotary shield body 1 rotates in a uniform velocity, the scanning collimation holes consecutively move along the linear slit 5 at a controllable speed. Referring to FIG. 1, during the process of the scanning, by rotary coded disk readout unit 7 and coded disk readout signal line 8, control unit 10 may read out current state of the rotary shield body 1, accordingly the current positions of the scanning collimation holes are determined. Based on detection of positions of the scanning collimation holes, exit direction of the radiation beam can be further acquired. Furthermore, by arranging the scanning collimation holes in a manner such that these holes have predetermined shapes relative to the radiation source 13, as a result, sectional shape of the radiation beam 14 passing through the scanning collimation holes and irradiating on the subject to be scanned may be kept in a predetermined shape, so as to satisfy various demands for different scanning operation. Although several exemplary embodiments have been shown and described, it would be appreciated by those skilled in the art that various changes or modifications may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents.
054066093	abstract	An X-ray analysis apparatus including an artificial multi-layered grating for rendering X-ray beams to be monochromatic before they are incident on a specimen to be analyzed. This artificial multi-layered grating operates to diffract the X-ray beam, generated from an X-ray radiation source and subsequently impinging on a reflective surface of the artificial multi-layered grating, at a predetermined angle of diffraction to provide the monochromatic X-ray beams. The periodicity of the spacing of lattice planes of the artificial multi-layered grating is so chosen as to be of a value progressively varying along the reflective surface thereof with an increase in distance from the X-ray radiation source. The X-ray analysis apparatus herein disclosed is designed to avoid any possible reduction of the intensity of the X-ray beams which would occur when they are rendered to be monochromatic, and to increase the intensity of the X-ray beams to ensure an improved accuracy in spectroscopic analysis.
051014203	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The X-ray mask support film of the present invention comprises a support frame and a support film, and is characterized in that both the support frame and support film comprise a material having a thermal expansion coefficient of not more than 1.times.10.sup.-5 K.sup.-1 or a material such that the thermal expansion coefficient of said support film does not exceed the thermal expansion coefficient of said support frame. The present invention will be described below in detail. In the present invention, the material that has a thermal expansion coefficient of not more than 1.times.10.sup.-1 and a Young's modulus of not less than 10 GPa may typically include ceramics. They include, for example, ceramics such as silicon nitride, silicon carbide, sialon (Si, Al, O, N) in which part of the silicon of silicon nitride has been substituted with aluminum and part of the nitrogen thereof has been substituted with oxygen, and carbon or graphite. Of the above materials, particularly preferably used in the present invention are silicon nitride and silicon carbide. The feature that the thermal expansion coefficient is not more than 1.times.10.sup.-5 K.sup.-1 requires that, assuming a mask pattern on a support member to be 1 cm, the elongation caused by a temperature change of 1.degree. C. is not more than 10.sup.-7. To retain the submicron patterns, the thermal expansion coefficient must be not more than 1.times.10.sup.-5 K.sup.-1. The feature that the thermal expansion coefficient of the support film is smaller than that of the support frame is advantageous for retaining the state that the film is stretched, since the frame undergoes a larger thermal expansion than the film when exposed to heat. The above ceramics have differences in particle diameter, particle size distribution, or crystal form including three types of a cubic system (.beta.), a hexagonal system (.alpha.) and amorphous in case of Silicon carbide, and also three types of a hexagonal system (.alpha.), trigonal (.beta.) and amorphous in the case of silicon nitride. These structural differences result in differences in values of physical properties, based on differences in preparation methods. Accordingly, the thermal expansion coefficient of the support frame can be readily set so as not to exceed that of the support film. In the case of carbon or graphite, when it is obtained by sintering a pitch, the above setting can be easily carried out by controlling the degree of graphite formation and the layer structure. The film is subjected to a constant stress to maintain the flatness, where its elongation must be very small, and hence the film is required to be stretched with a tension of from 10 to 100 MPa. What is required in the submicron processing is to withstand the stress to give no elongation, and this is preferred for the reason that the dimensional precision can be retained. It is also preferred for the support film to have a thermal conductivity of not less than 4 W/m.multidot.K, for the reason that the local distortion produced by the temperature rise caused by irradiation with X-rays can be suppressed owing to heat conduction. In the present invention, an organosilicon polymer may be used. The organosilicon polymer includes, for example, a polymer generically termed as polysilane represented by the general formula: ##STR1## wherein R' is methyl; R" is methyl, ethyl, cyclohexyl, phenyl, phenetyl, or tolyl; and n is not less than 100, more preferably not less than 200. It may specifically include poly(dimethylsilane-methylphenylsilane), poly((dimethylsilane-methylcyclohexylsilane) and poly(methylphenetylsilane-methylphenethylsilane). Readily available is poly(dimethylsilane-methylphenylsilane). Another example of the organosilicon polymer is a polymer generically termed as polysilazane represented by the general formula: ##STR2## wherein R is hydrogen, C.sub.1 to C.sub.8 alkyl, or aryl such as phenyl, benzyl or phenetyl, n is not less than 100, preferably not less than 200. It specifically includes poly(methylsilazane), poly(ethylsilazane) and poly(phenylsilazane). In the case of carbon, petroleum pitch commonly used in formation of carbon fiber may be molded according to a molding method such as press molding, injection molding or cast molding in a mold previously prepared, since it has melt properties similar to organic polymers. Of the materials described above, preferably used in the present invention are particularly polysilane and polysilazane. Employment of these materials as described above and the preparation method as described below makes it possible to well satisfy the preferable conditions as required herein. Hitherto, well known methods of preparing silicon carbide include a method in which silica is carbonized by reduction using carbon, and a method in which metal silicon, silicon monoxide or silicon dioxide is reacted with carbon. In the case of silicon nitride, known are methods which are direct-nitriding of metal silicon, silica reduction, imide nitride thermal decomposition, etc. The above polymers have recently been found, which are polymers for use in silicon carbide or silicon nitride, comprising silicon as a polymer backbone and called ceramics precursor polymers to which usual molding methods for thermoplastic resins can be applied, and have been used in preparation of ceramics. Also, in the case of carbon, carbon materials synthesized from petroleum pitch have become available on the market. Typical processes for preparing the mask support frame of the present invention include the following (1), (2) and (3). PROCESS (1) Polysilane, polysilazane or petroleum pitch is molded by a usual thermoplastic resin molding method (such as compression or injection) at temperatures higher than its melting point, using a mold capable of intergrally molding the support frame and support film (FIG. 1). It is preferred to bring a molded product to have no edge as shown in FIG. 2, thereby making it possible to effect mold release with ease. Next, the resulting molded product is sintered in an inert gas atmosphere to make an X-ray mask support. Typical conditions for the sintering are as follows: In the instance where the material comprises polysilane, the sintering may be carried out at temperatures raised up to 1,400.degree. C. in one stage, or preferably used is the two-stage sintering such that the sintering is carried out at 400.degree. to 600.degree. C. for a given time and thereafter, the temperature is raised to carry out the sintering at 1,100.degree. to 1,400.degree. C. for a given time. In the instance where the material comprises polysilazane, the sintering may be carried out according to the two-stage sintering such that the temperature is raised up to 500.degree. C., which is maintained for several to several tens of hours, and then raised to 1,000.degree. C. Such sintering brings polysilane finally into an SiC sinter from SiC-SiH.sub.2 ; and petroleum pitch is brought into graphite. Even if no complete SiC formation, SiN formation or carbon formation is effected, in other words, even if SiC-SiH.sub.2 or the like remains, the previously described properties, required for the X-ray mask support film of the present invention, can be sufficiently exhibited. PROCESS (2) The support frame alone is first prepared by molding and sintering. There can be utilized known methods of sinter-molding of SiC, SiN or carbon. Methods of preparing silicon carbide include a method in which silica is carbonized by reduction using carbon, and a method in which metal silicon, silicon monoxide or silicon dioxide is reacted with carbon. In the case of silicon nitride, known are methods which are direct-nitriding of metal silicon, reduction of silica, and thermal decomposition of imide nitride, etc. In the case of carbon, known is a method in which petroleum pitch is fomed into graphite by sintering. Next, a thin film (support film) comprising the organosilicon polymer is formed on a substrate. For that purpose, for example, the organosilicon polymer may be dissolved in a solvent, and the resulting solution may be coated on the substrate by use of a coating method such as dipping, casting or spin coating, optionally followed by drying. The solvent to dissolve the organosilicon polymer may typically include aromatic hydrocarbons such as benzene and toluene, saturated hydrocarbons such as hexane and octane, halogen derivatives, and cyclic ethers such as tetrahydrofuran. Suitable values of concentration of the organosilicon polymer solution used for the purpose of coating the polymer may vary depending on the conditions for film formation, but may be selected from the range of from 3% by weight to 60% by weight. In forming the thin film on the substrate, employment of the soulution used as described above may be replaced with employment of a melt of the organosilicon polymer or the like. More specifically, the organosilicon polymer can be synthesized usually so as to have a molecular weight of from several thousand to about 1,000,000, and its melting point falls within the range of from 70.degree. to 200.degree. C. depending on its average molecular weight. Accordingly, the above film formation can be carried out by melting the organosilicon polymer (for example, at a temperature several tens of degrees higher than its melting point), followed by a commonly available polymer film formation method such as pressing, laminating or T-die extrusion. In the case of carbon, the same method as in the case of the polymer may be employed to form a film on a suitable substrate by dissolving pitch in a suitable diluent as exemplified by quinoline so that the viscosity of pitch may fall within the range of from 10.degree.to 10,000 cp, or heating the pitch. In any film formation method of the above, the thin film formation is required to be made so that the thin film formed may have a uniform thickness over the whole. On the thin film formed in the above manner and comprising the organosilicon polymer or pitch, a support frame previously prepared may be placed, and they may be sintered under the conditions as explained below, so that an X-ray surpport having sufficiently satisfied the properties previously mentioned can be obtained. The support film may preferably have a film thickness of from 1 to 5 .mu.m, particularly preferably from 2 to 4 .mu.m, in view of the strength and X-ray transmission. In the above thin film comprising the organosilicon polymer or pitch, a known sintering aid may also be added in a trace amount (not more than 2 or 3%). The sintering aid includes, for example, A1.sub.2 0.sub.3 BN and BeO. In the above film of the organosilicon polymer or pitch, fibers and/or fine particles of ceramics or carbon may be contained, there by making it easy to make crystal control since the fibers or fine particles serve as crystal nuclei at the time of sintering, so that a film having much better tensile strength or impact strength can be obtained and the sintering time can also be shortened. Further, in view of the X-ray transmitting properties of the support film, it is preferred that ceramics are used. Regarding the ceramics used in the above embodiment, there may be used ceramics whose main component unit comprises silicon carbide in the instance when a silicon carbide polymer such as polysilane is used as the organosilicon polymer, and there may be used ceramics whose main component unit comprises silicon nitride in the instance when a silicon nitride polymer such as polysilazane is used. Alternatively, there may be used sialon in which part of silicon in silicon nitride has been substituted with aluminum. An additive may also be added to these ceramics. Such an additive may include, for example, a sintering aid, boron nitride, alumina and yttrium oxide. As to the size of the ceramics, the fineness of the ceramic fibers and particle diameter of the ceramic fine particles may preferably be 3 .mu.m or less since the preferred thickness of the X-ray support film is 3 .mu.m or less. Further, the fineness of the ceramic fibers may more preferably be in the range of from 0.05 to 1.5 .mu.m. With regard to the particle diameter of the ceramic fine particles, there is no particular limitation in the lower limit for a preferred range so long as it is not more than 0.3 .mu.m. The particle size distribution thereof may also be broad without any disadvantage. Formed is a film containing the above described organosilicon polymer and ceramics in a suitable proportion. The proportion may be selected to find a suitable value depending on the type and molecular weight of the silicon polymer and on, when a solvent is mixed in the polymer, the type of the solvent, the type of ceramics, and so forth. There is no limitation in the film formation method so long as the film can be formed to have a desired structure so that the film having been subjected to sintering may exhibit good properties as the X-ray mask support film, but usable is, for example, a method comprising laying up the ceramic fibers and/or fine particles on a substrate, impregnating the resulting layup with the organosilicon polymer to have the desired composition, and forming the layup into a film. Methods for laying-up may include, for example, a method in which the ceramic fibers and/or fine particles are laid up by allowing them to fall in the air, a method in which they are laid up by allowing them to settle in a liquid, a method in which they are allowed to float in a liquid and a layup layer is obtained by a papermaking method, and a method in which a ceramic nonwoven fabric or woven fabric is merely used as the above layup. Also, the laying-up may preferably be carried out by wetting the ceramic fibers and/or fine particles with a low-melting organic solvent, thereby preventing them from being electrically charged, so that the layup can be obtained in a good state. Methods of impregnating the layup obtained according to such methods with the organosilicon polymer may include a method in which the layup is merely impregnated with a solution or melt of the above organosilicon polymer, and a method in which the surface of the layup is covered with solid powder of the organosilicon polymer and then the surface is pressed and heated, thus impregnating the former with the latter. Also, part of the above thin film of the organosilicon polymer may be previously formed of a silicon carbide material, so that the X-ray mask support film comprises a silicon carbide film having a surface roughness of 10 mn r.m.s. or less. More specifically, silicon carbide is first formed into a film on a substrate typified by a silicon wafer. For this purpose, a process can be utilized, for example. In ths instance, SiH.sub.4 and CH.sub.4 are used as raw material gases, and the substrate is heated to temperatures of from about 600.degree. to 800.degree. C. The CVD process carried out under such conditions brings about polycrystalline silicon carbide, thus obtaining a film having a high modulus of elasticity. The film thickness may desirably be selected so as to be from about 1 to 3 .mu.m so that X-rays can be sufficiently transmitted. The silicon carbide film thus formed has a surface roughness of about 0.5 .mu.m. The substrate having the above SiC film may be prepared, not only by the CVD process, but also by other processes such as gaseous phase formation or sintering of fine particles. On the silicon carbide film formed on the substrate according to the above method, the thin film comprising the organosilicon polymer may be formed according to the method previously described, so that the organosilicon polymer film whose part has been formed of silicon carbide or silicon nitride can be formed on the substrate. Here, when there is no particular limitation in materials for the substrate used in the present invention, and substrates made of various materials can be used, so long as the substrate can meet the conditions such that, when it is a substrate to be removed before the sintering step as described below and when the substrate peeling method as describe below is employed as the method for removing it, it exhibits a peel readiness in such a degree that th substrate and the film can be separated in a good state, and, when a solvent is mixed in the organosilicon polymer at the time of coating, it has sufficient solvent resistance to that solvent. Usable methods of peeling from a substrate, the film formed on the substrate, include a method in which it is mechanically peeled, a method in which it is mechanically peeled by sticking a pressure-sensitive adhesive, a bonding adhesive or the like, a method in which it is peeled by immersing it in a solvent insoluble or poorly soluble to the organosilicon polymer, as exemplified by water and alcohol, and a method in which the substrate is removed by dissolution when the substrate is soluble to a solvent that may not act on the organosilicon polymer. Examples of the method in which the substrate is removed by dissolution include a method in which a PVA film or an NaCl sheet is used as the substrate and the substrate is removed by dissolution using water, etc., and a method in which a polymethyl methacrylate sheet is used as the substrate and is similary removed by dissolution using acetone or the like. The organosilicon polymer of the present invention is known to undergo cross-linking when irradiatd with light having a wavelength shorter than 350 nm (Lactualite Chimique, page 64, 1986, R. West). Accordingly, in instances in which light-irradiation is effected upon forming the film of the organosilicon polymer, there may be conducted irradiation with light having a wavelength region corresponding thereto, or light having a wavelength region of at least from 300 to 350 nm. Specifically, it is possible to use a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a xenon lamp, etc. The radiation heat that generates at the time of the above light-irradiation in the present invention may not particularly be removed. In instances in which the sintering described below is applied to a film brought to have its own form without the use of a substrate as in the present invention or, at the time of peeling, the peeling can not be well carried out because of lack of strength of the film, a preferred method is to improve the film strength by applying light-irradiation and thereafter carrying out peeling. Embodiments of typical methods for the light-irradiation for that purpose will be discribed below with reference to the drawings. FIG. 3 is a cross section illustrating an embodiment of the light-irradiation methods in the present invention. This embodiment is concerned with a method in which uniform light-irradiation is applied to the whole surface of an organosilicon polymer 1 from the upper part of the polymer laminated or coated on a substrate 2. Employment of this embodiment makes it possible to use as the substrate, various substrates such as a light-reflective substrate, light-transmissive substrate and light-absorptive substrate so long as they have sufficient peel readiness and solvent resistance as previously mentioned. FIG. 4 is a cross section illustrating another embodiment of the light-irradiation in the present invention. Used as the substrate in this embodiment is a light-transmissive substrate 2a that does not absorb light having wavelengths shorter than 350 nm, and simultaneous irradiation of light on both the surfaces of the organosilicon polymer 1 enables more uniform cross-linking of the whole polymer 1. The light-transmissive substrate 2a used in this embodiment may specifically include glass having no absorption band at a wavelength region of 290 nm or more. FIG. 5 is a cross section illustrating still another embodiment of the light-irradiation in the present invention. This embodiment is concerned with a method in which two sheets of the above light-transmissive substrate 2a are used and the organosilicon polymer 1 is held between them and light-irradiation is effected from both surfaces thereof. Employment of this embodiment makes it possible to prevent surface irregularities owing to the evaporation of the solvent contained in the polymer 1 to form a smoother film. In the present invention, the substrate that can be used when the substrate and film are sintered together may be satisfactory if it is a heat-resistant substrate that can endure sintering up to the stage at which the organosilicon polymer has cured by sintering and its flatness has not been substantially lost. Acocrdingly, it is also possible to use as the heat-resistant substrate those which may disappear in the course of sintering. However, it is preferred that the heat-resistant substrate may not disappear or deform, from the viewpoint of the flatness of the X-ray mask suppout film formed thereon, etc. Such a heat-resistant substrate may be satisfactory if it comprises a material stable to a high temperature of at least 1,400.degree. C., preferably 1,500.degree. C. or more. It may specifically include ceramics as exemplified by alumina and magnesium oxide, and graphite. In instances in which materials like metal silicon are utilized as the substrate, the substrate can be removed from the support film by ion etching in a gaseous phase, or by dissolution acid or alkali after sintering. On the other hand, the heat-resistant substrate that disappears in the course of the sintering may include substrates made of a resin or metal having thermal resistance up to about 300.degree. to 400.degree. C. Such disappearance of the heat-resistant substrate results from decomposition, melting etc. occurring at 500.degree. to 600.degree. C. As the above resin, suitably usable are the so-called engineering plastics as exemplified by polyoxymethylene, polyethersulfon, polyethe ether ketone and polybutylene terephthalate, and as the metal, suitably usable are tin, lead, zinc and aluminum. It is also preferred from the viewpoint of the surface smoothness of the resulting support film that the root-mean-square roughness of the heat-resistant substrate has a precision of not more than 10 nm. Preparing the support film by using the above substrate makes it possible to obtain an X-ray mask support film having a surface roughness of not more than 10 nm r.m.s. The surface roughness at this time may preferably be measured by a measurement method that employs a non-contact optical roughness meter and can measure the roughness without giving any stress at the time of measurement, and it may be measured, for example, with a digital optical linear profiler TOPO.TM.-2D (Wyko Corporation). The surface roughness as defined in the present invention can be conveniently measured using the above surface roughness meter. The sintering step in the process of the present invention comprises, when the film is prepared according to the film formation method using a solution and when polysilane is employed as the organosilicon polymer, heating first the film for a given time, raising the temperature to 500.degree. to 600.degree. C., maintaining this temperature for a given time, thereafter, further raising the temperature to 1,100.degree. to 1,400.degree. C., and maintaining this temperature for a given time or gradually raising the temperature from 1,100.degree. C. up to about 1,400.degree. C., thus making a film having SiC crystals in a sintered state. When polysilazan is employed as the organosilicon polymer, the step comprises raising first the temperature to 500.degree. C., and thereafter, raising it to from 1,000.degree. to 1,200.degree. C. to carry out two-stage sintering, or gradually raising the temperature from 1,000.degree. to about 1,400.degree. C. Typical examples for the heating rate or heating retention time in the sintering are set out later in Examples, but sintering conditions may be appropriately selected so that the Young's modulus and thermal expansion coefficient previously described may be set at the intended values. The sintering is carried out in an atmosphere of inert gas, but the sintering may be carried out using other gases if such sintering is carried out at a stage in which the formation of SiC as the X-ray mask support film may not substantially be hindered. PROCESS (3) Prepared first are structures of a support frame and a support film each having the same form. The structures may comprise sintered products made of SiC, SiN or carbon, or products obtained by sintering the organosilicon polymer at about several hundred degrees Celsius, or molded products having plasticity. The sintered products or the like can be prepared by employing the same methods as described in Processes (1) and (2). Next, on the structures of the support frame and support film each having the same form, a solution of the organosilicon polymer used in Process (2) is coated or a melt of the organosilicon polymer heated to a temperature higher than the melting point is coated, and thereafter, both structures (i.e., a support frame structure 4 and a support film structure 5) are fixed utilizing the adhesive force of an adhesive layer 3 comprising the organosilicon polymer or the like. To increase the adhesive force, a rougher adhering surface is preferred. Thereafter, sintering is carried out in the same manner as in Process (1), thus making an X-ray mask support. For the solution or melt for use in provisionally adhering both the above structures, it is necessary to use the one that may form by sintering a sintered product having substantially the same composition as that of either the support frame or support film. The X-ray mask support prepared in the above manner can be made free from the very cumbersome operation of particularly applying stress to the support film to fix it uniformly, because stress is necessarily applied to the support film owing to the contraction that takes place on sintering. This also makes it ready to prepare a homogeneous support film. As described above, since no gaseous phase film formation may be utilized in the present invention, preparation conditions can be set relatively with ease, and mass production becomes possible. Also, since a high yield can be achieved, X-ray mask support films can be prepared at a low cost. It also has become possible to provide X-ray mask supports that may cause substantially no elongation of adhesives, deformation of frame members and sag or distortion of support films even by heat generated by X-ray irradiation or the like, and also can have a high mechanical strength. Moreover, since the surface of the support film is so flat that preparing X-ray masks by using the same can bring about the effect such that; (1) scattering of the visible light or infrared light for making alignment is small with high transmittance, resulting in improvement of the S/N ratio of the alignment light signal; PA1 (2) non-uniformity in the strength of transmitting X-rays becomes very small; and PA1 (3) precision in forming fine patterns and adhesion of the X-ray opaque or absorbing material are improved, resulting in almost no non-uniformity in thickness of the X-ray opaque or absorbing material. The present invention will be described below in greater detail by giving specific Examples. EXAMPLE 1 Polysilastyrene (trade name: S-400, available from NIPPON SODA CO., LTD.) was dissolved in toluene to prepare a 10 wt/v % solution. A surface-polished Al.sub.2 O.sub.3 substrate having a surface roughness of 9 nm r.m.s. was set on a spinner (Mikasa Spinner 1H-2) and rotated at 400 rpm, on which the above solution was dropped, thus preparing a film of 31 .mu.m thick. Next, this film was placed in a sintering furnace together with the substrate, and, under dry nitrogen, heated at 200.degree. C. for 1 hour and further raised up to 1,200.degree. C. at a rate of 10.degree. C./min. The furnace was maintained at this temperature for 1 hour, followed by cooling to obtain a silicon carbide film having a thickness of 2.9 .mu.m and a surface roughness of 8 nm. The silicon carbide film was cut into a strip of 10.times.50 mm.sup.2, and its Young's modulus measured using a tensile tester was found to be 200 GPa. Thermal expansion coefficient was 7.times.10.sup.-6 K.sup.-1. The above polysilastyrene solution was coated by brushing on a silicon carbide support frame (having the shape of a ring of 75 mm in inner diameter, 90 mm in outer diameter and 5 mm in thickness) obtained by a reactive sintering process, and the above silicon carbide film was fixed thereon, followed by sintering under the same condition as above to obtain an X-ray mask support. EXAMPLE 2 A silicon carbide support frame similar to the one used in Example 1 was placed on a carbon substrate, and a polysilastyrene solution in a concentration of 10 wt/v % was flowed thereon, followed by drying to form a polysilastyrene film. This was sintered in the same manner as in Example 1. As a result, there was obtained an X-ray mask support comprising the support frame and a silicon carbide film fixed on the support frame. EXAMPLE 3 The inside of a 1 liter autoclave made of glass was replaced with dry nitrogen, and charged therein was 0.4 g of KH (100 mmol; 3.9 mol % based on CH.sub.3 SiHNH). Tetrahydrofuran (300 ml) was dropwise added with a syringe in flask having a three-way cock, and the mixture was stirred to disperse KH. Next, using a syringe filled with nitrogen, 15.271 g (0.258 mol) of (CH.sub.3 SiHNH).sub.3 was slowly added to the stirred KH slurry over a period of 15 minutes. After stirring at room temperature for 90 minutes, generation of gas stopped, and a transparent and homogeneous solution remained. Addition thereto of 2.28 g (16.1 mmol) of methyl iodide immediately resulted in formation of a white precipitate of KI. This reaction mixture was further stirred for 30 minutes. Next, most of the THF solution was removed under reduced pressure, and 80 ml of hexane was added to the remaining white slurry. The resulting mixture was subjected to centrifugal separation to separate supernatant liquid from a white solid. This solution was subjected to a trap-to-trap distillation, so that 15.1 g (99% by weight) of a white precipitate remained. This was dissolved in toluene and spin-coated on a carbon substrate having a surface roughness of 10 nm. Placed thereon was a silicon nitride ring having the same size as used in Example 1, which was heated in a sintering furnace to 1,300.degree. C., and thereafter, the furnace was maintained at this temperature for 4 hours, followed by cooling to obtain an X-ray mask support having a support film of 2.2 .mu.m in thickness and 9.5 nm in surface roughness. EXAMPLE 4 A mold 6 as shown in FIG. 7 was placed on a heater, which was kept heated to 200.degree. C., and a melt flow indexer was connected to a hole provided on the mold. Nozzle temperature was kept to 250.degree. C., and polysilastyrene was introduced. A weight (22.125 g) was placed on the upper part and the polysilastyrene was flowed in the mold until it flowed out from another hole. Thereafter, this was subjected to press molding at 300.degree. C. under a pressure of 150 kg/cm.sup.2. After being cooled, the molded product was heated to 600.degree. C. at a rate of 5.degree. C./min and kept at this temperature for 1 hour. Thereafter, after being taken off from the mold, the product was again heated to 1,350.degree. C. and kept at that temperature for 1 hour, followed by cooling. There was obtained an integral type mask support comprising silicon carbide. EXAMPLE 5 X-Ray Mask Support Film (A) Polysilastyrene (trade name: S-400, available from NIPPON SODA CO., LTD.) was dissolved in toluene to prepare a 10 wt/v % solution. A surface-polished carbon substrate (10 mm thick) having a surface roughness of 7.5 nm when measured with the surface roughness meter TOPO.TM.-2D previously described was set on a spinner (Mikasa Spinner 1H-2) and rotated at 500 rpm, on which the above solution was dropped, thus obtaining a film of 28 .mu.m thick. A carbon substrate polished similarly to the above was laid overlapping, and the film was laminated by pressing under a pressure of 10 kgf/cm.sup.2 and at a temperature of 180.degree. C. In a sintering furnace whose inside was replaced with dry nitrogen, the film was heated at 200.degree. C. for 1 hour and then raised up to 1,350.degree. C. at a rate of 10.degree. C./min. The furnace was maintained in this state for 1 hour, followed by cooling. The carbon substrate was taken off, and the surface roughness of the film was measured, which was found to be 9.0 nm. Film thickness was 2.6 .mu.m and thermal expansion coefficient was 5.times.10.sup.-5 K.sup.-1. X-Ray Mask Support Film (B) On a carbon substrate made ready for use in the same manner as in the support film (A), a toluene solution of 10 wt/v % polysilastyrene was spin-coated with a spinner. Revolution number was set to 400 rpm, and spin time to 30 seconds, thus obtaining a film of 3.2 .mu.m thick. A carbon substrate finished similarly to the above substrate was laid overlapping, and the film was laminated in the same manner as in Example 1 by pressing under a pressure of 10 kgf/cm.sup.2 and at a temperature of 180.degree. C. In a sintering furnace whose inside was replaced with dry argon, the film was heated at 500.degree. C. for 1 hour, and further raised up to 1,400.degree. C. at a rate of 10.degree. C./min. The furnace was maintained in this state for 2 hours, and then left to cool. The carbon substrate was taken off, and then the surface roughness of the film was measured, which was found to be 8.0 nm. Film thickness was 2.9 .mu.m and thermal expansion coefficient was 5.times.10.sup.-5 K.sup.-1. The film (A) and film (B) were adhered on a circular frame, made of e.g., stainless steel, having a larger thermal expansion coefficient (thermal expansion coefficient: 2.times.10.sup.-5 K.sup.-1) than that of the films of the above (A) and (B), while applying tension. The film tension at this time was 70 MPa. On the film, an absorber (X-ray intercepting material) comprising gold was formed according to a usual mask preparation process. As a result, the lowering of yield because of defects such as peeling-off of the absorber was remarkably suppressed as compared with an instance in which the absorber comprising gold was formed similarly on an SiC film formed according to the CVD process commonly practiced and having a root-mean-square surface roughness of 50 nm. Also, the film was sagged upon X-ray irradiation in the case of a support in which a support frame (thermal expansion coefficient: 0.4.times.10.sup.-6 K.sup.-1) made of quartz glass and having a smaller thermal expansion coefficient was used in place of the above support frame. For evaluation of performances, Young's modulus of the above film was measured according to a static pressure balloon method. As a result, there was obtained a value of 200 GPa. EXAMPLE 6 Polysilastyrene (trade name: S-400, available from NIPPON SODA CO., LTD.) was dissolved in toluene to prepare a 10 wt/v % solution. A surface-polished Al.sub.2 O.sub.3 substrate having a surface roughness of 9 nm was set on a spinner (Mikasa Spinner 1H-2) and rotated at 1,000 rpm, on which the above solution was dropped, thus preparing a film of 31 .mu.m thick. Put thereon was a silicon carbide support frame (having the shape of a ring of 75 mm in inner diameter, 90 mm in outer diameter and 5 mm in thickness) obtained according to a reactive sintering process, and the film was heated in an atmosphere of nitrogen at 200.degree. C. for 1 hour, and further raised up to 500.degree. C. at a rate of 10.degree. C./min. The film was kept in this state for 1 hour, and further heated up to 1,300.degree. C. at a rate of 5.degree. C./min, which was maintained for two hours, followed by cooling to obtain an X-ray mask support having a silicon carbide film of 2.9 .mu.m in thickness and 8 nm in surface roughness. EXAMPLE 7 An X-ray mask support film comprising a silicon carbide film was obtained in the same manner as in Example 6 except that a polyether ether ketone sheet was used as a substrate. The resulting film showed the same properties as in Example 6, and there was seen no difference considered to be caused by the influence of the decomposition of substrate polymer. EXAMPLE 8 X-Ray Mask Support Film (C) On a silicon wafer (100) substrate of 0.5 mm in thickness and 2.0 nm in surface roughness, an SiC film was formed using a plasma CVD apparatus to have a thickness of 2.0 .mu.m. Used as raw material gases were SiH.sub.4 and CH.sub.4, and the component ratio was kept at 1:10, pressure at 10 to 50 Torr, and substrate temperature at 800.degree. C. Thus, a film having a surface roughness of 0.5 .mu.m was obtained. Next, this substrate was set on a spinner (Mikasa Spinner 1H-2), and a solution obtained by dissolving polysilastyrene (trade name: S-400, available from NIPPON SODA CO., LTD.) in toluene to give a concentration of 10 wt/v % was dropped on the spinner which was rotated at 1,000 rpm, thus obtaining a film of 7.2 .mu.m thick. Next, this film was placed in a sintering furnace in which Ar gas was flowed, and the temperature was raised from room temperature up to 650.degree. C. at a rate of 10.degree. C./hr, which was maintained for 40 hours. Thereafter, the furnace was allowed to cool to room temperature, and subsequently, the temperature was raised up to 1,000.degree. C. at a rate of 100.degree. C./hr, which was maintained for 30 hours. Thereafter, the furnace was allowed to cool. Finally, the Si wafer was anisotropically etched from the back surface with use of an aqueous KOH solution, and removed. In this manner, there was obtained an X-ray mask support film comprising a self-supporting SiC film of 3.2 .mu.m thick. This has a surface roughness of 2.0 nm on the surface that had been in contact with the Si wafer and 8.0 nm on the opposite surface. X-Ray Mask Support Film (D) On a silicon wafer (100) substrate of 0.5 mm in thickness, 76 mm in diameter and 2.0 nm in surface roughness, an SiC film and a polysilastyrene film were formed in the same manner as in support film (C). They had a film thickness of 1.8 .mu.m and 5.1 .mu.m, respectively. The SiC film had a surface roughness of 11 nm. In a sintering furnace whose inside was replaced with dry nitrogen, the product was sintered at 700.degree. C. for 30 hours and at 1,050.degree. C. for 20 hours, followed by slow cooling to room temperature. Next, the silicon wafer was anisotropically etched from the back surface with use of an aqueous KOH solution, and removed. Thus, there was obtained an X-ray mask support film. The silicon carbide frame, the same as in Example 1 was provided on each of these films (C) and (D) in the same manner as in Example 1 to obtain X-ray mask supports. On each of these X-ray mask supports, an X-ray absorber made of gold was formed according to a usual mask preparation process. As a result, in each film, the defects such as peeling-off of the absorber was remarkably decreased as compared with an instance in which the absorber comprising gold was formed similarly on an SiC film formed only according to the CVD process commonly practiced and having a surface roughness of 0.4 .mu.m. Accordingly, the lowering of yield was remarkably suppressed even when a large number of X-ray masks were prepared. Also, the transmittance of the visible light for alignment was improved by 10% or more. EXAMPLE 9 Polysilastyrene (trade name: S-400, available from NIPPON SODA CO., LTD.) was dissolved in toluene to prepare a 10 wt/v % solution. A surface-polished Al.sub.2 O.sub.3 substrate having a surface roughness of 9 nm was set on a spinner (Mikasa Spinner 1H-2) and rotated at 400 rpm, on which the above solution was dropped, thus preparing a film of 31 .mu.m thick. Subsequently, using a high-pressure mercury lamp (USH-250), light irradiation was carried out on the film for 20 minutes, which film was then immersed in a mixed solvent of water: methanol=1:1 for 1 hour to peel the polysilastyrene film from the substrate. Next, the resulting polysilastyrene film was placed alone in a sintering furnace, and the temperature was raised from room temperature to 600.degree. C. at the rate of 5.degree. C./min. The furnace was maintained in this state for 1 hour, and thereafter, the temperature was raised up to 1,300.degree. C. at the rate of 5.degree. C./min. The furnace was maintained in this state for 1 hour, followed by cooling to obtain a silicon carbide film of 2.9 .mu.m in thickness and 8 nm in surface roughness. The silicon carbide film was cut into a strip of 10.times.50 mm.sup.2, and its Young's modulus measured using a tensile tester was found to be 200 GPa. EXAMPLE 10 A silicon carbide whisker (available from Tateho Chemical Industries, Ltd.) of from 0.5 to 1.5 .mu.m in fineness and from 5 to 200 .mu.m in length was wetted with ethanol, and laid up on a graphite sheet having a surface roughness of 11 nm, followed by pressing under a pressure of 10 kg/cm.sup.2 to prepare a layup with a thickness of 2 .mu.m. Subsequently, ethanol in the layup was evaporated, and the resulting layup was spray-coated with a viscous solution obtained by dissolving polysilastyrene (trade name: S-400, available from NIPPON SODA CO., LTD.) in toluene to give a concentration of 40% by weight, followed by evaporation of toluene. Next, on the resulting film, a silicon carbide support frame (having the shape of a ring of 75 mm in inner diameter, 90 mm in outer diameter and 5 mm in thickness) was put and pressed under a pressure of 5 kg/cm.sup.2, and then placed in a sintering furnace filled with dry nitrogen. Subsequently, the temperature inside the furnace was maintained at 200.degree. C. for 1 hour, and then raised to 1,400.degree. C. at a rate of 10.degree. C./min. The furnace was maintained at this temperature for 1 hour, and then cooled to obtain an X-ray mask support having a silicon carbide support film of 2.1 .mu.m in thickness and 9 nm in surface roughness. The silicon carbide film in the X-ray mask support prepared in the above manner according to the process of the present invention was cut into a strip of 10.times.50 mm.sup.2, and its Young's modulus was measured using a tensile tester. The Young's modulus was found to be 250 GPa, which was a value enough for the X-ray mask support film. EXAMPLE 11 Inside of a 1 liter autoclave made of glass was replaced with dry nitrogen, and charged therein was 0.40 g of KH (100 mmol; 3.9 mol % based on CH.sub.3 SiNHN). Tetrahydrofuran (300 ml) was dropwise added the use of a syringe to the inside of the above autoclave, and the mixture was stirred to disperse KH. Next, using a syringe filled with nitrogen, 15.271 g (0.258 mol) of (CH.sub.3 SiHNH).sub.3 was slowly added to the stirred KH slurry over a period of 15 minutes. After stirring at room temperature for 90 minutes, generation of gas stopped, and a transparent and homogeneous solution remained. Addition thereto of 2.28 (16.1 mmol) g of methyl iodide immediately resulted in the formation of a white precipitate of KI. This reaction mixture was further stirred for 30 minutes. Next, most of the THF was removed under reduced pressure, and 80 ml of hexane was added to the remaining white slurry. The resulting mixture was subjected to centrifugal separation to separate supernatant liquid from a white solid. This solution was subjected to trap-to-trap distillation, so that 15.1 g (99% by weight) of white powdery polymethylsilazane was obtained. A silicon nitride whisker (trade name: SNW, available from Tateho Chemical Industries, Ltd.) of from 0.1 to 1.5 .mu.m in fineness and from 5 to 200 .mu.m in length was laid up in the same manner as in Example 10. Subsequently, the resulting layup was spray-coated in the same manner as in Example 10, with a solution obtained by dissolving in toluene 40% by weight of the polymethylsilazane synthesized as described above, thus obtaining a film. Next, on the resulting film, a silicon carbide support frame having the shape as the frame of Example 10 was put and pressed under a pressure of 5 kg/cm.sup.2, which was placed in a sintering furnace filled with dry nitrogen. Subsequently, the temperature inside the furnace was raised to 1,300.degree. C. at a rate of 5.degree. C./min. The furnace was maintained at this temperature for 4 hours, and then cooled to obtain an X-ray mask support having a silicon carbide support film of 2.9 .mu.m in thickness and 8 nm in surface roughness. Young's modulus of the silicon carbide film in the X-ray mask support prepared in the above manner according to the process of the present invention was measured in the same manner as in Example 10. The Young's modulus was found to be 220 GPa, which was a value sufficient for the X-ray mask support film. EXAMPLE 12 An X-ray mask support was obtained in the same manner as in Example 10 except that silicon carbide particles having an average particle diameter of 0.45 .mu.m (grade: DUA-1, available from Showa Denko KK) were used in place of the silicon carbide whisker. A support film in the resulting support showed good properties like the support film obtained in Example 10. EXAMPLE 13 An X-ray mask support was obtained in the same manner as in Example 11 except that silicon nitride particles having an average particle diameter of 0.2 .mu.m (grade: SNE-10, available from Ube Industries, Ltd.) were used in place of the silicon nitride whisker. A support film in the resulting support showed good properties like the support film obtained in Example 11. REFERENCE EXAMPLE 1 Polysilastyrene (trade name: S-400, available from NIPPON SODA193 toluene to prepare a solution of 10 wt/v % in concentration. A surface-polished carbon substrate was set on a spinner (Mikasa Spinner 1H-2) and rotated at 400 rpm, on which the above solution was dropped, thus preparing a film of 31 .mu.m thick. Next, the resulting film was sintered in the same manner as in Example 10 to obtain an X-ray mask support film. Young's modulus of the film was measured in the same manner as in Example 10. The Young's modulus was found to be 200 GPa, which is a value lower than that of the films obtained in Examples of the present invention. Young's moduli of the support films in the X-ray mask supports prepared in the above Examples were 200 GPa to 250 GPa (in SiC) and 200 GPa to 220 GPa (in SiN); thermal expansion coefficients of the support films and support frames were 4.times.10.sup.-6 to 1.times.10.sup.-5 K.sup.-1 (in SiC) and 3.times.10.sup.-6 to 1.times.10.sup.-5 K.sup.-1 (in SiN); and thermal conductivities were 80 W/m.multidot.K (in the case of SiC) and 20 W/m.multidot.K (in the case of SiN).
060581530	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a preventive maintenance apparatus for structural members inside a reactor pressure vessel (hereinafter, simply referred to as "preventive maintenance apparatus for structural members") in accordance with the present invention will be described below, referring to FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6 and FIG. 7. A boiling water reactor (BWR) comprises a reactor pressure vessel 2, a core shroud 3 installed inside the reactor pressure vessel 2, an upper core grid plate 82 and a lower core support plate 121 installed inside the core shroud 3, and jet pumps 123 arranged in a ring-shaped space 122 formed between the reactor pressure vessel 2 and the core shroud 3. The preventive maintenance apparatus for structural members in accordance with the present invention comprises a guide rail 5, a turntable 6, a control board 18, a crud collecting apparatus 41, discharging nozzle moving apparatuses 124 and 124C, and a discharged water supply apparatus 125. Preventive maintenance work to structural members inside the reactor pressure vessel 2 using the preventive maintenance apparatus for structural members is performed while operation of the BWR is stopped. After stopping the operation of the BWR, a top head of a reactor container (dry-well) and a upper vessel head of the reactor pressure vessel 2, not shown, are removed. A steam dryer assembly and a steam separator assembly installed inside the reactor pressure vessel 2 are also detached and removed out of the reactor pressure vessel 2. A well 126 above the reactor pressure vessel 2 is filled with water. Before filling the well with water, in order to prevent water from entering into main steam pipes 129, openings of the main steam pipes 129 to the reactor pressure vessel are sealed with main steam line plugs 130 as shown in FIG. 1. All fuel assemblies, not shown, supported in the core by the upper core grid plate 82 and the lower core support plate 121 are removed out of the reactor pressure vessel 2 and temporarily stored inside a fuel storage pool 46. In a state that the guide rail 5 mounts the turntable 6 mounting the discharging nozzle moving apparatuses 124 and 124C, the guide rail 5 is suspended by a ceiling crane, not shown, installed above an operating floor 21 inside the reactor building, and then placed on an upper flange 4 of the core shroud 3. The guide rail 5 has a fixing lug 12 in an outer peripheral surface. The lug 12 is detachably fixed to a lug 13 for fixing a shroud head, not shown, attached to the outer peripheral surface of the upper flange 4 with a bolt 14. The turntable 6 is placed so as to be rotated on the guide rail 5. The turntable 6 has a box 53 as shown in FIG. 3. A drive mechanism for rotating the turntable 6 is installed inside the box 53. The drive mechanism comprises a motor 54, gears 55A, 55B attached to a shaft 57 and a gear 56. The gear 55A is engaged with a gear 55C attached to a rotating shaft of the motor 54. The gear 55B is engaged with the gear 56. The gear 56 is attached to a shaft 58 of a wheel 16 rotatably attached to the turntable 6. The wheel 16 runs on a rail 15 installed on an upper surface of the guide rail 5. Since both of projecting portions 16A provided in the inner side and the outer side of the wheel 16 interpose the rail 15, the wheel 16 does not run off the rail 15 during rotating the turntable 6. The guide rail 5 has three bent members 59A, 59B and 59C, as shown in FIG. 4. The three bent members 59A, 59B and 59C are assembled into a ring shape in the operating floor 21. The three bent members 59A, 59B and 59C are arranged in a ring shape by engaging an engaging portion 61A and an engaging portion 61B of the bent members different to each other. The engaging portion 61A and the engaging portion 61B adjacent to each other are joined together with a pin 111. A lug 62A is attached to a side surface in the outer side of the bent member 59A. A lug 62B is attached to a side surface in the outer side of the bent member 59C. Each of the lugs 62A, 62B has a cut portion 60. The discharging nozzle moving apparatus 124 comprises an apparatus main body 1 attached to the turntable 6, an arm member 8 attached to the apparatus main body 1 movable in the horizontal direction, a pole member 9 attached to the arm member 8 and a discharging nozzle 10 provided in a vertically moving body 7 vertically movable along the pole member 9. The structure of the arm member 8 and the driving mechanism for driving the arm member 8 in the horizontal direction will be described below, referring to FIG. 5 and FIG. 6. The arm member 8 is constructed by connecting both ends of four circular rods 8A with connecting members 8B, 8C, and penetrates through a casing 128 of the apparatus main body 1. Both end portions of a pole screw 67 are supported by the connecting members 8B, 8C. The drive mechanism installed in the casing 128 has a motor 68, and gears 69A and 69B. The gear 69A is attached to a rotating shaft of the motor 68. The gear 69B is rotatably attached to the casing 128. The outer surface of the gear 69B is engaged with the gear 69A, and the inner surface of the gear 69B is engaged with the pole screw 67. A rotating force of the motor 68 is transmitted to the pole screw 67 through the gear 69A and the gear 69B to horizontally move the arm member 8 in one direction. By reversely rotating the motor 68, the arm member 8 is moved in the opposite direction. Instead of using the motor 68, the gear 69A and the gear 69B, it is possible that a cylinder may be provided in the casing 128 and the arm member 8 is moved in the horizontal direction. A motor 120 attached to the pole member 9 rotates a pole screw, not shown, attached to the pole member 9 to vertically move the vertically moving body 7 engaging with the pole screw along the pole member 9. The discharging nozzle 10 can be operated in such actions as to be moved forward and backward to a surface of a structural member on which preventive maintenance is to be performed, rotated in the horizontal direction, and swung in the vertical direction. In order to perform the three actions described above, the discharging nozzle drive mechanism comprises dedicated motors for the individual actions. The discharging nozzle 10 may be fixed to the vertically moving body 7 so as to have a certain angle. The discharging nozzle moving apparatus 124C comprises an apparatus main body 1 and an arm member 8, similarly to the discharging nozzle moving apparatus 124. The discharging nozzle moving apparatus 124C further comprises a pole member 9A inserted into a through hole (similar to a through hole 131 in FIG. 8) provided in a top end portion 8D of the arm member 8, a multi-joint arm portion 78 and a discharging nozzle 10B. The pole member 9A has a rack 77 on a side surface. A motor 71 as a drive unit for vertically moving the pole member 9A, a gear 75 and a pinion 76 engaging with the rack 77 are provided in the top end portion 8D, as shown in FIG. 8, though these are not shown in FIG. 7. The multi-joint arm portion 78 is attached to a bottom end portion of the pole member 9A with a rotating shaft 80. The multi-joint arm portion 78 is formed by jointing a plurality of arm portions 79 with the rotating shafts 80. The discharging nozzle 10B is attached to a bottom end portion of the multi-joint arm portion 78 with the rotating shaft 80. A monitoring camera, not shown, for taking a picture of preventive maintenance work is provided in the discharging nozzle 10B. Each of the arm portions 79 and the discharging nozzle 10B contains a motor, not shown, for applying a rotating force to the corresponding arm portion 79 or the corresponding discharging nozzle 10B in respect to each of the rotating shafts 80 as a center. The discharging nozzle moving apparatuses 124 and 124C are installed on the turntable 6 in the both end portions of the turntable 6. The discharged water supply apparatus 125 as shown in FIG. 1 comprises a high pressure pump 30, a filter 37, a recirculation pump 38, a hose 36 and high pressure hoses 19A and 19B. One end of the hose 36 is immersed into the reactor water 20 inside the well 126. The hose 36 connects the filter 37 and the recirculation pump 38 and is connected to the high pressure pump 30. The high pressure hose 19A connected to the high pressure pump 30 is once attached to the casing 128 of the apparatus main body 1 and the arm member 8, and is connected to the discharging nozzle 10. The other high pressure hose 19B connected to the high pressure pump 30 is once attached to the pole member 9A, and is connected to the discharging nozzle 10B. The filter 37 removes crud contained in the reactor water 20. The high pressure pump 30 is installed on the operating floor 21. A low pressure hose 35 connected to another water source is also connected to the high pressure pump 30. The high pressure pump 30 pumps up water supplied from either the hose 36 or the low pressure hose 35 by switching to supply the discharging nozzles 10 and 10B as the high pressure water. The crud collecting apparatus 41 is constructed by connecting a sucking port 40, a crud transferring pump 43 and a filter 44 using a crud transfer hose 42. The control board 18 installed on the operating floor 21 is connected to control cable 31 for transmitting and receiving electric signals by which the preventive maintenance apparatus for structural members is remotely operated, an air hose 32 for supplying air by which the preventive maintenance apparatus for structural members is remotely operated, a control cable 33 for transmitting and receiving electric signals by which the high pressure pump is remotely operated and so on. Based on the control signals transmitted through the control cables 31 and 33, the corresponding apparatuses or units are remotely controlled. These remote controls can be performed selectively by manual mode or automatic mode. The preventive maintenance work is basically performed by the automatic mode. In addition to this, the control board 18 adjusts the speed of each of the actions such as forward and backward movements, rotation and swinging of the discharging nozzle 10, and vertical movement of the vertically moving body 7. The operating air for remotely operating the preventive maintenance apparatus for structural materials is conducted to the control board 18 from an air supply source, not shown, through an air hose 34 to control a valve inside the control board 18. By doing so, the preventive maintenance apparatus for structural materials can be remotely operated. It is also possible to operate the preventive maintenance apparatus for structural materials by supplying air to the air hose 34 from another compressor different from the air supply source described above. Each of the motors for performing each of actions of the turntable 6, the vertically moving body 7, the arm member 8, the discharging nozzles 10, 10A and the arm members 79, and each of detectors, not shown, for detecting a rotating position and detecting a rotating speed such as potentiometers are arranged in appropriate positions in the preventive maintenance apparatus for structural materials. Measured signals of these detectors are transmitted to the control board 18 through the control cable 17. During preventive maintenance work, a computer, not shown, incorporated in the control board 18 calculates an optimum condition to a traveling speed of the discharging nozzle 10 and a discharging position (vertical position, rotating position, swinging angle), and transmits each of the control signals to each of the corresponding motors through the control cables 31 and 33. The computer also calculates an optimum condition to a traveling speed of the discharging nozzle 10B and a discharging position (vertical position, rotating position, swinging angle), and transmits each of the control signals to each of the corresponding motors through the control cables 31 and 33. When preventive maintenance work is performed to the core shroud 3, the preventive maintenance apparatus for structural materials is set onto the upper flange 4. This setting work will be described below. The guide rail 5 is assembled into a ring shape on the operating floor 21. The turntable 6 is set on the guide rail 5, and the discharging nozzle moving apparatuses 124 and 124C are mounted on the turntable 6. After assembling the guide rail 5, the turntable 6 and the discharging nozzles 124 and 124C in a unit, the guide rail 5 is hung down inside the reactor pressure vessel 2 using the ceiling crane described above. As shown in FIG. 4, the two guide rods 63 are set to the inner surface of the reactor pressure vessel 2 by supporting members 112 spaced apart by 180.degree.. The cut portion 60 of the lug 62A provided on the guide rail 5 is engaged with the guide rod 63. The cut portion 60 of the lug 628 is engaged with the other one of the guide rods 63 not shown in the figure. The guide rail 5 is lowered on the upper flange 4 along the two guide rods 63. After that, the guide rail 5 is detachably attached to the upper flange 4 with bolts 14. Since the guide rail 5 is lowered on the upper flange 4 along the two guide rods 63, the guide rail 5 can be lowered without interference with the main steam line plugs 130. The work of setting the guide rail 5 on the upper flange 4 is performed by picture-taking using the monitoring camera 24 attached to the vertically moving body 7 and a monitoring camera 25 hung inside the reactor pressure vessel 2 by the cables 28, 29, and monitoring the pictures displayed on a monitor 27 placed in the control board 18. The images taken by the monitoring camera 25 is transmitted to the monitor 27 through the cable 26. The work setting the guide rail 5 and the turntable 6 onto the upper flange 4 is monitored by the picture from the monitoring camera 25. Moving of the monitoring camera 25 is performed by a worker from a refueling machine 22. The worker moves the monitoring camera 25 by operating cables 28, 29. Description will be made below in a case where preventive maintenance work is performed to welded portions in the outer surface and the inner surface of the core shroud 3. The pole member 9 of the discharging nozzle moving apparatus 124 is inserted into the ring-shaped space 122. The vertically moving body 7 is moved by driving of the motor 120. The discharging nozzle 10 is positioned to a welded portion or which preventive maintenance work is to be performed from the outside of the core shroud 3. On the other hand, the discharge nozzle 10B is inserted into the narrow portion between the core shroud 3 and the upper core grid plate 82 by lowering of the pole member 9A and rotation of each of the arm portions 79 around the rotating shaft 80 as a center by driving of each of the motors contained in each of the arm portions 79. By driving the recirculation pump 38, the reactor water 20 is cleaned by the filter 37, and then transferred to the high pressure pump 30. The high pressure water pressurized by the high pressure pump 30 and sent through the high pressure hose 19A is discharged out of the discharging nozzle 10 from the outside of the core shroud 3 to a welded portion on which preventive maintenance work is to be performed. Cavitation bubbles are generated by a pressure difference and a shear action between the discharged water flow from the discharging nozzle 10 and the environmental reactor water 20. The cavitation bubbles move toward the welded portion together with the discharged water flow. The cavitation bubbles are collapsed on the surface of the welded portion and the surrounding vicinity. The impulsive pressures generated by the collapse of the cavitation bubbles reach the surface of the welded portion to convert the tensile remaining stress in the surface to a compressive remaining stress. Since the compressive remaining stress is added to the outside surface of the welded portion, it is possible to prevent occurrence of stress corrosion cracks in the welded portion. The discharging nozzle 10 discharges the discharged water flow while being moved zigzag near the welded portion over all the circumference of the welded portion in the circumferential direction by vertical movement of the vertically moving body 7 by the driving of the motor 120 and rotation of the turntable 6. Therefore, the compressive remaining stress is added over all the circumference of the outside surface portion of the welded portion, and it is possible to prevent occurrence of stress corrosion crack in the welded portion. Similarly, the high pressure water conducted through the high pressure hose 19B is discharged out of the discharging nozzle 10B from the inside of the core shroud 3 to the welded portion on which preventive maintenance work is to be performed. The compressive remaining stress is added over the inside surface portion of the welded portion by the collapse of the cavitation bubbles. By vertical movement of the pole member 9A and rotation of the turntable 6, the compressive remaining stress is added over all the circumference of the inside surface portion of the welded portion. In this embodiment, since the discharging nozzles 10 and 10B are used, the compressive remaining stress can be added to the welded portion from the inside and the outside of the core shroud 3 at the same time. Therefore, the preventive maintenance work to the core shroud 3 can be completed in a short time. In a case where the preventive maintenance work from either the inside surface or the outside surface is not required, one of the valve 83A arranged in the high pressure hose 19A or the valve 83A arranged in the high pressure hose 19B (FIG. 1) not corresponding to the surface to be performed with the preventive maintenance work is closed to stop supplying of high pressure water to one of the discharging nozzles. The discharging nozzle moving apparatus 124 in this embodiment may be constructed in such a structure that the pole member 9 is vertically moved by providing a motor 71, a gear 75, a pinion 76 and a rack 77, as shown in FIG. 8 to be described later. The arm member 8 has a through hole into which the pole member 9 is to be inserted. The motor 71 is operated when the pole member 9 is lowered inside the ring-shaped space 122 after the discharging nozzle moving apparatus 124 is set in the turntable 6. Vertical movement of the discharging nozzle 10 near the welded portion during the preventive maintenance work is performed by vertical movement of the vertically moving body 7 using the motor 120. By the action of the impulsive pressure generated at collapsing of the cavitation bubbles, crud (the main component is radioactivated iron oxide) attached near the welded portion is peeled off and suspended in the reactor water 20. A crud transfer pump 43 is operated during the preventive maintenance work. A sucking port 40 is arranged at a place performing the preventive maintenance work. The reactor water 20 containing the crud is sucked through the sucking port 40, and transferred to the filter 44 through the crud transfer hose 42. The crud is removed by the filter 44, and the cleaned reactor water 20 is discharged into the fuel storage tank 46 out of the hose 45. Crud is settled out and accumulated mainly in a core shroud flange portion 39. This crud is sucked through the sucking port 40 and removed by the filter 44 before initiating the preventive maintenance work. Since the accumulated crud and the crud peeled off during the preventive maintenance work can be removed from the reactor water 20 by the crud collecting apparatus 41, problems in the visibility of the monitoring cameras 24, 25 caused by suspending crud can be solved. Therefore, progress of the preventive maintenance work can be monitored under a good condition based on the pictures from the monitoring cameras 24, 25. In addition to this, since diffusion of the crud can be suppressed, radiation exposure To during the preventive maintenance work can be reduced. Radioactive contamination of the reactor water can be also suppressed. The filter 44 having captured the crud is enclosed in a drum having a radiation shield or the like as a high level radioactive waste to be stored in a nuclear power plant site. Part of the cavitation bubbles rise up to the water surface 47 without collapsing. These bubbles contain radioactivated crud. When these bubbles collapse on the reactor water surface 47, the crud is dispersed and accordingly there is a possibility to expand a radioactive contamination area. In order to prevent expansion of the radioactive contamination area, the reactor water surface 47 is covered with an air collecting cover 48. The bubbles having risen up to the reactor water surface 47 are collected by the air collecting cover 48, and transferred to a filter 50 through a transfer hose 49. The filter captures dust and mist. The gas cleaned by the filter 50 is exhausted to a ventilating and air conditioning exhaust duct 51 existing in the reactor building. The filter 52 having captured the dust and the mist is enclosed in a drum having a radiation shield or the like as a high level radioactive waste to be stored in a nuclear power plant site. By setting the air collecting cover 48, it is possible to suppress dispersion of radioactive substances to the zone above the operating floor 21. Therefore, it is possible to reduce radiation exposure to workers in the operating floor 21. When it is required to exchange the discharging nozzle 10 of the discharging nozzle moving apparatus 124 or the discharging nozzle 10B of the discharging nozzle moving apparatus 124C, the discharging nozzle moving apparatus 124 or the discharging nozzle moving apparatus 124C is detached from the turntable 6 using a tong from the operating floor 21. The detached discharging nozzle moving apparatus is hung by a wire loop 23 and lifted up to the operating floor 21 using a hoist crane 11 of the refueling machine 22. The discharging nozzle moving apparatus after having exchanged the discharging nozzle is hung and lowered using the hoist crane 11 to be set on the turntable 6. In the present embodiment, since the discharging nozzle 10 can be continuously moved around the core shroud 3 by rotating the turntable 6, it is unnecessary to dismount and mount the discharging nozzle moving apparatuses 124 and 124C when the discharging nozzle 10 can be moved around the core shroud 3. Therefore, the time required to perform the preventive maintenance work using the discharge nozzle 10 can be shortened. Further, since the discharging nozzle moving apparatus 124 is set on the upper flange 4 through the guide rail 5 and the turntable 6, the length of the pole member 9 can be shortened. Therefore, the discharging nozzle moving apparatus 124 becomes easy to be handled when it is set onto the turntable 6, and the pole member 9 can be easily inserted inside the narrow ring-shaped space 122. Since the discharging nozzle moving apparatus 124C in this embodiment has the multi-joint arm portion 78, the discharging nozzle 10B can be easily inserted into the narrow portion between the core shroud 3 and the upper core grid plate 82. Therefore, it is possible to easily perform the preventive maintenance work to the inside of the welding portion of the core shroud 3 in the narrow portion. In this embodiment, since the turntable 6, is not moved directly on the upper flange 4 but on the guide rail 5 arranged on the upper flange 4, the upper flange 4 cannot be damaged by moving of the turntable 6. Further, the guide rail 5, the turntable 6 and the discharging nozzle moving apparatuses 124 and 124C are integrated into a unit in which the discharging nozzle moving apparatuses 124 and 124C are in a state of being mounted on the turntable 6, and then the unit is lowered onto the upper flange. Therefore, the discharging nozzle moving apparatuses 124 and 124C can be set on the upper flange at the same time. Compared to a case where the discharging nozzle moving apparatuses 124 and 124C are separately set onto the turntable 6 placed in the reactor pressure vessel 2, the guide rail 5, the turntable 6 and the discharging nozzle moving apparatuses 124 and 124C can be set onto the upper flange 4 in a shorter time. The structure of the pole member 9 and the vertically moving body 7 in the discharging nozzle moving apparatus 124 of the preventive maintenance apparatus for structural members in the embodiment described above may be modified as shown in FIG. 8. This structure will be described below. An arm member 8A penetrating a casing 128 has a through hole 131 in the top end portion. A pole member 9A extending in the vertical direction is vertically moved in the through hole 131. A mounting plate 72 is attached to the arm member 8A with bolts and nuts 74. A motor 71 is attached to the mounting plate 72 with bolts and nuts 73. A pinion 76 is also rotatably attached to the mounting plate 72. A gear 75 attached to a rotating shaft of the motor 71 is engaged with the pinion 76. The pinion 76 is engaged with a rack 77 provided in the pole member 9A. A discharging nozzle 10 and a monitoring camera 24 are arranged on a bottom end portion of the pole member 9A. A rotating force of the motor 71 is transmitted to the pinion 76 to vertically move the pole member 9A. In the structure of FIG. 8, the discharging nozzle 10 is vertically moved by the motor 71 during preventive maintenance work. Another embodiment of a preventive maintenance apparatus for structural members in accordance with the present invention will be described below, referring to FIG. 9. The preventive maintenance apparatus for structural members of this embodiment comprises a guide rail 5, a turntable 6, a control board 18, a crud collecting apparatus 41, and discharging nozzle moving apparatuses 124 and 124A. The same components in this embodiment as in the embodiment of FIG. 1 are indicated by the same reference characters. This embodiment has the discharging nozzle moving apparatus 124A instead of the discharging nozzle moving apparatus 124C in the embodiment of FIG. 1. The discharging nozzle moving apparatus 124A has the same construction as the discharging nozzle moving apparatus 124C. The discharging nozzle moving apparatuses 124 and 124A are set onto the turntable 6 on both end portions of the turntable 6. Each of the pole members 9 of the discharging nozzle moving apparatuses 124 and 124A is inserted into the ring-shaped space 122. In this embodiment, by arranging the discharging nozzle moving apparatuses 124 and 124A on both end portions of the turntable 6, the preventive maintenance work to the outside surface of the core shroud 3 using the discharging nozzle moving apparatus 124 described in the embodiment of FIG. 1 can be performed at two positions on the core shroud 3 spaced apart by 180.degree. at the same time also using the discharging nozzle 10 of the discharging nozzle moving apparatus 124A. In this embodiment, when the preventive maintenance work is performed to the inside surface of the core shroud 3 in the narrow portion between the core shroud 3 and the upper core grid plate 82, the discharging nozzle moving apparatuses 124 and 124A are detached from the turntable 6 using the tong, as described above. Then, the discharging nozzle moving apparatuses are successively lifted up to the operating floor 21 using the hoist crane 11. Instead, two discharging nozzle moving apparatuses 124C are lowered and set on the turntable 6. Each of the discharging nozzles 10B of the discharging nozzle moving apparatuses 124C is inserted into the narrow portion by operating the pole member 9A and the multi-joint arm portion 78. By using the two discharging nozzle moving apparatuses 124C, the preventive maintenance work to the inside surface of the core shroud 3 using the discharging nozzle moving apparatus 124C described in the embodiment of FIG. 1 can be performed at two positions on the core shroud 3 spaced apart by 180.degree. at a time. This embodiment can attain the same effect as that attained in the embodiment of FIG. 1. However, compared to the embodiment of FIG. 1, this embodiment needs to additionally prepare the discharging nozzle moving apparatus 124 and the discharging nozzle moving apparatus 124C by one more each. Further, this embodiment requires work to exchange between the discharging nozzle moving apparatuses 124 and the discharging nozzle moving apparatuses 124C. A further embodiment of a preventive maintenance apparatus for structural members in accordance with the present invention will be described below, referring to FIG. 10. The preventive maintenance apparatus for structural members of this embodiment is different from the embodiment of FIG. 1 in that a discharging nozzle moving apparatus 124B is provided instead of the discharging nozzle moving apparatus 124. The other constructions of this embodiment are the same as those in the embodiment of FIG. 1. The discharging nozzle moving apparatus 124B is constructed by further adding a vertically moving body 7A, a pole member 9B, a discharging nozzle 10A and a motor 120A to the construction of the discharging nozzle moving apparatus 124. The pole member 9B is installed in the arm member 8 so as to be in parallel to the pole member 9. The vertically moving body 7A is vertically moved by the motor 120A similarly to the vertically moving body 7. The discharging nozzle 10A is fixed to the vertically moving body 7A at a preset angle so as to be directed upward. In this embodiment, the discharging nozzle 10 is fixed to the vertically moving body 7 at a preset angle so as to be directed downward. In this embodiment, the preventive maintenance work is performed using the discharging nozzles 10, 10A. At that time, the discharging nozzles 10 and 10A perform the preventive maintenance work to different positions in the vertical direction of the core shroud 3. Since this embodiment can perform the preventive maintenance work to a plurality of positions at the same time, the time required for the work can be shortened. A still further embodiment of a preventive maintenance apparatus for structural members in accordance with the present invention will be described below, referring to FIG. 11. The preventive maintenance apparatus for structural members of this embodiment is different from the embodiment of FIG. 1 in that a discharging nozzle moving apparatus 124D is provided instead of the discharging nozzle moving apparatus 124. The other constructions of this embodiment are the same as those in the embodiment of FIG. 1. Spray headers 83A, 83B of a core spray system are installed in the inside surface of the core shroud 3 under the upper flange 4. The discharging nozzle moving apparatus 124D comprises a horizontal arm 90, a box 91 and a rotating cover 93 instead of the multi-arm portion 78 in the discharging nozzle moving apparatus 124C. The horizontal arm 90 is attached to a bottom end portion of the pole member 9A. The box 91 is attached to the horizontal arm 90. The rotating cover 93 is rotatably attached to the box 91. The discharging nozzle 10B is attached to the top end portion of the rotating cover 93. When a motor 92 provided in the horizontal arm 90 is operated, a gear, not shown, is rotated to move the rotating cover 93 in directions indicated by an arrow 94. By lowering the pole member 9A and rotating the rotating cover 93 toward the left hand side in FIG. 11, the discharging nozzle 10B is inserted into the narrow portion between the core shroud 3 and the upper core grid plate 82. The preventive maintenance work to the inside surface of the core shroud 3 can be performed by discharging high pressure water out of the discharging nozzle 10B. As described above, the preventive maintenance work to the inside surface of the core shroud 3 can be performed from a portion above the upper core grid plate 82. In this embodiment, the preventive maintenance work to the inside surface of the core shroud 3 can be also performed from a portion below the upper core grid plate 82. The pole member 9A is lowered in the upper core grid plate 82. When the horizontal arm 90 reaches the bottom end portion of the upper core grid plate 82, lowering of the pole member 9A is stopped. The box 91 is rotated by a motor, not shown, so that the discharging nozzle 10B is directed upward. By rotating the rotating cover 93, the discharging nozzle 10B is inserted into the narrow portion from an opening 84 formed in the bottom end portion of the upper core grid plate 82. Under this state, high pressure water hits onto the inside surface of the core shroud 3 from the lower side. This embodiment can attain the same effect as that attained in the embodiment of FIG. 1. Further, the present embodiment can also perform preventive maintenance work to the inside surface of the core shroud 3 from the bottom end portion in the narrow portion. A further embodiment of a preventive maintenance apparatus for structural members in accordance with the present invention will be described below, referring to FIG. 12. This embodiment is constructed by further adding a rotating apparatus 101 to the construction of the embodiment of FIG. 1. The rotating apparatus 101 comprises a table 103 for rotation, a ring 107 and a fixing metal fitting 108. The table 103 for rotation is set on a bulk head plate 106 in the reactor well 126 through legs 104. The ring 107 is mounted on the table 103 for rotation through roller bearings. The ring 107 is rotatable on the table 103 for rotation. The fixing metal fitting 108 is composed of two half-divided parts which are joined together and attached to the ring 107. The fixing metal fitting 108 bundles the high pressure hoses 19A, 19B connected to the discharging nozzle moving apparatuses 124 and 124C and the various kinds of cables such as the control cable 31 and so on. When the turntable 6 is rotated during preventive maintenance work using the discharging nozzle moving apparatuses 124 and 124C, the ring 107 is also rotated in the same direction together with the rotation of the turntable 6. This embodiment can attain the same effect as that attained in the embodiment of FIG. 1. Further, since the fixing metal fitting 108 bundles the hoses and the control cable and is rotated in the same direction as the rotation of the turntable 6, it is possible to prevent the hoses and the cables from being intertwined by performing the preventive maintenance work. A still further embodiment of a preventive maintenance apparatus for structural members in accordance with the present invention will be described below, referring to FIG. 13. In this embodiment, two discharging nozzle moving apparatuses 124E are mounted in both end portions of the turntable 6 instead of the discharging nozzle moving apparatuses 124 and 124C in the embodiment of FIG. 1. In the discharging nozzle moving apparatus 124E, two pole members 9A are attached to a top end portion 8E of the arm member 8 in such a manner as to be slidable in the vertical direction. One of the pole members 9A is inserted into the ring-shaped space 122. Similar to the discharging nozzle moving apparatus 124, a vertically moving body 7 having a discharging nozzle 10 is attached to the pole member 9A in such a manner as to be movable in the vertical direction. A multi-joint arm 78 similar to that in the discharging nozzle moving apparatus 124C is attached to the other pole member 9A with a rotating shaft 80. A discharging nozzle 10B is provided in a top end portion of the multi-joint arm 78. This embodiment can attain the same effect as that attained in the embodiment of FIG. 1. Further, the present embodiment can perform preventive maintenance work to both the inside surface and the outside surface of the core shroud 3 at the same time by the one discharging nozzle moving apparatus 124E. Since this embodiment comprises two sets of such discharging nozzle moving apparatuses 124E, the time required for the preventive maintenance work to the core shroud 3 can be shortened compared to that in the embodiment of FIG. 1.
	summary
	claims	1. An attenuator, comprising:a grating element having i) grating grooves that produce a grating period (p), and ii) a grating plane,wherein said grating period (p) is at least about 150 times greater than said used wavelength,wherein said grating element attenuates electromagnetic radiation of wavelengths unequal to said used wavelength,wherein said grating element is a binary grating and said grating grooves have a first height (H1) and a second height (H2) in a direction perpendicular to said binary grating,wherein said first height (H1) and said second height (H2) have a difference between them that defines a grating depth h,wherein said grating depth h is defined by the following equation: λ min 4 ⁢ ⁢ cos ⁢ ⁢ α < h < ( n + 1 2 ) ⁢ λ max 2 ⁢ ⁢ cos ⁢ ⁢ α , ⁢ andwherein λmin is a shortest wavelength of wavelengths to be attenuated by said attenuator, λmax is a longest wavelength of said wavelengths to be attenuated by said attenuator, α is an incidence angle of a ray relative to a normal line of a surface of said grating element, and n is an integer number ≧0. 2. An illumination system for wavelengths <100 nn, comprising:a first attenuator having:a grating element having i) grating grooves that produce a grating period (p), and ii) a grating plane,wherein said grating period (p) is at least about 150 times greater than said used wavelength, andwherein said grating element attenuates electromagnetic radiation of wavelengths unequal to said used wavelengtha second attenuator situated downstream from said first attenuator;a diaphragm in a diaphragm plane,wherein said diaphragm is situated downstream from said first attenuator in a path of rays from an object plane to a field plane, andwherein said diaphragm includes an opening at a location of a 0th diffraction order of said at least one grating element; anda light source from which rays of a beam bundle pass through to said field plane,wherein said rays impinge upon said first attenuator at an angle >70° to a normal line of a surface of said first attenuator, andwherein said rays impinge upon said second attenuator at an angle <20° to a normal line of a surface of said second attenuator. 3. An illumination system comprising:an object plane;an image plane;a light source emitting radiation of a used wavelength ≦100 nm and long-wavelength radiation of a wavelength >100 nm, the radiation propagating in a path of rays from the object to the image plane;at least one attenuator with at least one grating element having grating grooves with a grating depth h;at least one physical diaphragm in a diaphragm plane, which is situated downstream to the attenuator in the path of rays from the object plane to the image plane;the physical diaphragm comprising an opening at a location of a 0th diffraction order of the at least one grating element;wherein the at least one grating element is arranged in the path of rays from the object plane to the image plane such that the 0th diffraction order is passed through the diaphragm and long-wavelength radiation is diffracted at least partially to orders other than the 0th order;wherein said grating depth h is chosen to diffract the long-wavelength radiation with an optimal efficiency into orders other than the 0th diffraction order; andwherein the opening has a size and is chosen in such a way that the long-wavelength radiation of a wavelength larger than 10 times the used wavelength, which is diffracted at least partially by the at least one grating element of the attenuator into orders other than the 0th order is blocked substantially completely by the diaphragm. 4. The illumination system of claim 3, wherein the diffraction into diffraction orders other than the 0th order of the long wavelength radiation is wavelength dependent. 5. The illumination system of claim 4, wherein the diffraction of the long wavelength radiation in orders other than the 0th order is characterized by a wavelength region and a mean diffraction efficiency calculated by averaging the diffraction efficiencies over the wavelength region. 6. The illumination system of claim 5, wherein the wavelength region is from 130 nm to 330 nm and the mean diffraction efficiency is in a range between 13% and 34%. 7. The illumination system of claim 5, wherein the wavelength region is from 130 nm to 600 nm and the mean diffraction efficiency is in a range between 8% and 29%. 8. The illumination system of claim 3, wherein the size of the opening of the physical diaphragm is chosen in such a way that also the radiation of the used wavelength which is diffracted by the at least one grating element of the attenuator into orders other than the 0th diffraction passes through the diaphragm. 9. The illumination system of claim 3,wherein the grating grooves produce at least one grating periodicity (p) and a grating plane, andwherein the at least one grating periodicity (p) is at least 150 times greater than the used wavelength. 10. The illumination system of claim 3, wherein the grating element is a binary grating and the grating grooves have a different height in a direction perpendicular to the grating, with the grating grooves having a first height and a second height. 11. The illumination system of claim 10, wherein the difference between the first and second height defines the grating depth h and the grating depth is λ min 4 ⁢ cos ⁢ ⁢ α < h < ( n + 1 2 ) ⁢ λ max 2 ⁢ cos ⁢ ⁢ α withh being the grating depth,λmin being the shortest of the wavelengths to be attenuated by the attenuator,λmax being the longest of the wavelengths to be attenuated by the attenuator,α being the incidence angle of a ray relative to the normal line of the surface, andn being an integer number ≧0. 12. The illumination system of claim 3, wherein the rays of a beam bundle impinge on the grating element at an angle <30° relative to a normal line of a surface which stands perpendicular to a grating plane. 13. The illumination system of claim 3, wherein the rays impinge on the grating element at an angle >70° relative to a normal line of a surface which stands perpendicular to a grating plane of the grating element. 14. The illumination system of claim 13, wherein the rays and the normal line of the surface define an incidence plane and a grating vector stands perpendicular to the incidence plane of the grating element, so that the grating grooves of the grating plane extend in a direction parallel to the direction of the rays impinging onto the grating element. 15. The illumination system of claim 3, wherein the grating element comprises a plurality of individual grating elements. 16. The illumination system of claim 15, wherein the individual grating elements comprise grating grooves of different grating depths. 17. The illumination system of claim 15, wherein said attenuator is a first attenuator, and said illumination system further comprises a second attenuator in said path, downstream of said first attenuator. 18. The illumination system of claim 17, wherein the rays of a beam bundle which propagate through the illumination system from the light source to the field plane impinge under an angle >70° to a normal line of the surface of the first attenuator, and the rays of a beam bundle which passes through the illumination system from the light source to the field plane impinge under an angle <20° to the normal line of the surface of at least one grating element of the second attenuator upon the second attenuator. 19. The illumination system as claimed in claim 3, further comprising a collector, wherein the attenuator is the first optical element in the path of rays from the light source to the field plane which is situated downstream the light source and the collector. 20. The illumination system of claim 3, further comprising a mixing unit with a first optical element with first facets, and a second optical element with second facets, wherein at least one of the two facets is arranged as an attenuator. 21. The illumination system of claim 20, further comprising further diaphragms downstream of the attenuator in the path of the rays from the light source to the field plane, wherein said further diaphragms include an opening at the location of the 0th diffraction order of the at least one grating element of the attenuator. 22. A projection exposure system for producing microelectronic components, comprising:the illumination system of claim 3;a structure-bearing mask;a projection lens; anda light-sensitive object, wherein the structure-bearing mask is projected onto the light-sensitive object. 23. A method comprising: employing a projection exposure system to produce a microelectronic component, wherein said projection exposure system includes:(A) an illumination system having:an object plane;an image plane;a light source emitting radiation of a used wavelength 100 nm and long-wavelength radiation of a wavelength >100 nm, the radiation propagating in a path of rays from the object to the image plane;at least one attenuator with at least one grating element having grating grooves with a grating depth h;at least one physical diaphragm in a diaphragm plane, which is situated downstream to the attenuator in the path of rays from the object plane to the image plane;the physical diaphragm comprising an opening at a location of a 0thdiffraction order of the at least one grating element;wherein the at least one grating element is arranged in the path of rays from the object plane to the image plane such that the 0th diffraction order is passed through the diaphragm and long-wavelength radiation is diffracted at least partially to orders other than the 0thorderwherein said grating depth h is chosen to diffract the long-wavelength radiation with an optimal efficiency into orders other than the 0thdiffraction order; andwherein the opening has a size and is chosen in such a way that the long-wavelength radiation of a wavelength larger than 10 times the used wavelength, which is diffracted at least partially by the at least one grating element of the attenuator into orders other than the 0th order is blocked substantially completely by the diaphragm;(B) a structure-bearing mask;(C) a projection lens; and(D) a light-sensitive object, wherein the structure-bearing mask is projected onto the light-sensitive object.
	claims	1. A system, comprising:an optical element configured to be a component of an EUV microlithography tool;a cooling element disposed away from the optical element, the cooling element being configured to cool the optical element via radiation heat transfer;a shielding configured to prevent the cooling element from absorbing heat from a component of the system other than the optical element; anda controller configured to control a temperature of the cooling element,wherein the system is configured to control a temperature of the optical element when the optical element is in a vacuum atmosphere. 2. The system of claim 1, further comprising a light source configured so that light emitted from the light source impinges on the optical element during use of the system, wherein:the controller is configured to control the light source; andthe controller is configured to stabilize the temperature of the optical element by controlling light from the light source that impinges on the optical element and by controlling cooling of the optical element via the cooling element. 3. The system of claim 1, further comprising a heating device configured to heat the optical element. 4. The system of claim 3, further comprising a light source configured so that light emitted from the light source impinges on the optical element during use of the system, wherein:the controller is configured to control the light source; andthe controller is configured to stabilize the temperature of the optical element by controlling light from the light source that impinges on the optical element, by heating the optical element via the heating device, and by cooling the optical element via the cooling element. 5. The system of claim 1, wherein the controller is configured to control heating of the optical element by the heating device. 6. The system of claim 1, wherein the optical element comprises a mirror. 7. The system of claim 6, further comprising a light source configured so that light emitted from the light source impinges on the mirror during use of the system, wherein:the controller is configured to control the light source; andthe controller is configured to stabilize the temperature of the mirror by controlling light from the light source that impinges on the mirror and by controlling cooling of the mirror via the cooling element. 8. The system of claim 6, further comprising a heating device configured to heat the mirror. 9. The system of claim 8, further comprising a light source configured so that light emitted from the light source impinges on the mirror during use of the system, wherein:the controller is configured to control the light source; andthe controller is configured to stabilize the temperature of the mirror by controlling light from the light source that impinges on the mirror, by heating the mirror via the heating device, and by cooling the mirror via the cooling element. 10. The system of claim 6, wherein the controller is configured to control heating of the mirror by the heating device. 11. An EUV microlithography tool comprising the system of claim 6. 12. An EUV microlithography tool comprising the system of claim 1. 13. A system, comprising:an optical element configured to be a component of an EUV microlithography tool;a heating device configured to heat the optical element;a shielding configured to prevent components of the system neighboring the optical element from absorbing heat from the heating device; anda controller configured to control a temperature of the heating device and/or to control a temperature of the shielding,wherein the system is configured to control a temperature of the optical element when the optical element is in a vacuum atmosphere. 14. The system of claim 13, further comprising a cooling element disposed away from an optical element, wherein the cooling element is configured to cool the optical element via radiation heat transfer. 15. The system of claim 14, further comprising a light source configured so that light emitted from the light source impinges on the optical element during use of the system, wherein:the controller is configured to control the light source; andthe controller is configured to stabilize the temperature of the optical element by controlling light from the light source that impinges on the optical element, by heating the optical element via the heating device, and by cooling the optical element via the cooling element. 16. The system of claim 13, wherein the optical element comprises a mirror. 17. The system of claim 16, further comprising a cooling element disposed away from an mirror, wherein the cooling element is configured to cool the mirror via radiation heat transfer. 18. The system of claim 17, further comprising a light source configured so that light emitted from the light source impinges on the mirror during use of the system, wherein:the controller is configured to control the light source; andthe controller is configured to stabilize the temperature of the mirror by controlling light from the light source that impinges on the mirror, by heating the optical element via the heating device, and by cooling the mirror via the cooling element. 19. An EUV microlithography tool comprising the system of claim 16. 20. An EUV microlithography tool comprising the system of claim 13.
051184672	claims	1. Fuel assembly for a boiling water reactor, comprising an elongated fuel assembly case having an interior, mutually parallel fuel rods having longitudinal axes and being disposed in said case, and inner walls disposed in said fuel assembly case and extending longitudinally through the interior of said case and having lateral surfaces facing toward said fuel rods, at least some of said internal surfaces having grooves formed therein extending perpendicular to the longitudinal axes of said fuel rods. 2. Fuel assembly according to claim 1, wherein said inner walls form at least one water channel for non-boiling water being laterally closed off from said fuel rods. 3. Fuel assembly according to claim 2, wherein said grooves extend continuously around the outside of said water channel. 4. Fuel assembly according to claim 2, wherein said lateral surfaces with said grooves are planar outer surfaces of said water channel. 5. Fuel assembly according to claim 1, wherein said case has mutually opposite walls, a plurality of said inner walls interconnect at least two of said mutually opposite walls, and said inner walls each have two of said lateral surfaces in which said grooves are formed. 6. Fuel assembly according to claim 5, wherein said inner walls have sides being parallel to the longitudinal axes of said fuel rods, and said grooves formed in one of said lateral surfaces each extend as far as said sides of said inner walls. 7. Fuel assembly according to claim 5, wherein said inner walls have sides being parallel to the longitudinal axes of said fuel rods, and said grooves formed in one of said inner walls end in a rounded portion at a distance from said sides of said inner walls. 8. Fuel assembly according to claim 1, wherein said case has a polygonal cross section and oppositely disposed side walls, a plurality of said inner walls are parallel to said oppositely disposed side walls of said case, each of said inner walls interconnect two respective oppositely disposed side walls of said case, and said grooves are formed in all of said lateral surfaces facing toward said fuel rods. 9. Fuel assembly according to claim 8, wherein said polygonal cross section is a square cross section. 10. Fuel assembly according to claim 1, wherein said case has a regular polygonal cross section and side walls, said inner walls include a first group of inner walls forming a water channel for non-boiling water extending at least approximately centrally in said case and being laterally closed off from said fuel rods, and a second group of inner walls connecting each of said side walls of said case to said water channel, and at least said second group of inner walls has said grooves formed in all of said surfaces facing toward said fuel rods. 11. Fuel assembly according to claim 10, wherein said regular polygonal cross section is a square cross section. 12. Fuel assembly according to claim 1, wherein said grooves have narrow sides perpendicular to the longitudinal axes of said fuel rods. 13. Fuel assembly according to claim 1, wherein said case has a lower end with a base having inlet openings for boiling water, an upper portion with a top part having outlet openings for boiling water, and a plurality of spacers being longitudinally spaced apart from one another and having ribs between said fuel rods extending transversely to the longitudinal axes of said fuel rods, said grooves being formed only said upper portion and each of said grooves being upstream of a respective one of said spacers, as seen in flow direction of boiling water. 14. Fuel assembly according to claim 1, wherein said inner walls extend longitudinally between said fuel rods. 15. Boiling water reactor, comprising a boiling water circuit having a pressure vessel and a steam turbine, and a plurality of mutually parallel fuel assemblies disposed in said pressure vessel, each of said fuel assemblies including an elongated fuel assembly case, mutually parallel fuel rods having longitudinal axes and being disposed in said case, and longitudinally extending inner walls having lateral surfaces facing toward said fuel rods, at least some of said lateral surfaces having grooves formed therein extending perpendicular to the longitudinal axes of said fuel rods, and said fuel rods being bathed by boiling water flowing around them in the longitudinal direction of said fuel rods.
	description	The present invention relates to a laminated X-ray or radiation protection material and in particular to a radiation protection material provided with a secondary radiation layer with a low Z radiation protection material and a barrier layer with a high Z radiation protection material. Radiation protection materials provided with a secondary radiation layer with a low Z radiation protection material and a barrier layer with a high Z radiation protection material are known from WO 20051024846 A1, WO 2005/023116 A1 and DE 1 010 666 A1 but are not yet used in practical applications. Radiation protection materials are used in medical technology to protect the attending physicians, but also to protect those parts of the patient's body which should not be subjected to radiation. A typical example of such an application are protective aprons which are predominantly worn by the physicians and medical personnel, as well as partial body protection gear such as a for example gloves, head gear, thyroid gland protection, gonad protection, ovary protection. The latter three in particular are intended to protect those parts of the body of the patient to be X-rayed which should not be exposed to radiation. In addition, there are stationary protection devices located in the immediate vicinity of the patient or the medical professional, such as radiation protection curtains and shields on X-ray machines. Conventional radiation protection clothing in the medical field usually contains lead or lead oxide as protective material. The use of lead is disadvantageous due to the environmental pollution resulting from its toxicity and due to its relatively high weight. Therefore, more and more efforts have been made recently to provide lead-free radiation protection material and thus lead-free radiation protection clothing. Such radiation protection materials should have sufficient absorption properties in the energy range of an X-ray tube having a voltage of from 60 to 125 kV. The absorption properties of the radiation protection material are expressed by an attenuation value, or attenuation factor, e.g. in the form of the lead attenuation value (in short: lead equivalent) (International Standard IEC 61331-1, protective devices against diagnostic medical X-radiation). Some of the elements used in the lead-free radiation protection materials exhibit a dependence of the absorption on the radiation energy which significantly differs from that of lead. In addition, while some of the elements used for absorption purposes show sufficient absorption in the relevant energy range, a part of the absorbed energy is re-emitted from the lead-free radiation protection material in the form of X-ray fluorescence radiation in a spatially distributed manner. Together, the X-ray fluorescence radiation, the classic scattered radiation, and the Compton scattering are referred to as secondary radiation. The X-ray fluorescence radiation accounts for a significant portion of the secondary radiation. In order to shield from secondary radiation, combinations of different elements are frequently used to mimic the absorption behavior of lead. As has been shown, the lead-free radiation protection materials which are currently commercially available show hardly any advantage compared to lead in terms of weight. A lower weight in combination with the same attenuation effect is only achieved with a structure comprising a secondary radiation layer and a barrier layer wherein the secondary radiation, which mainly consists of X-ray fluorescence radiation (characteristic X-ray radiation), is effectively shielded by the barrier layer so that it cannot escape from the radiation protection material. Only under this condition is it possible to gain a weight advantage of maximum about 20% compared to lead. In particular, the barrier layer serves to absorb the secondary radiation, especially the high content of X-ray fluorescence radiation, which is generated in the secondary radiation layer during the absorption of low-energy X-ray radiation. Since secondary radiation or fluorescence radiation is essentially radiated evenly in all directions by the secondary radiation layer, the barrier layer in radiation protection clothing is provided close to the body while the secondary radiation layer is provided away from the body. Depending on the type of application, X-ray or radiation protection clothing is generally offered at different protection levels, e.g. 0.25 mm, 0.35 mm, 0.50, 1.0 mm nominal Pb value, whereby it has been suggested to create a radiation protection material with all of these different protection levels by combining individual layers in order to facilitate the production process. A problem that has been largely ignored so far is the fact that in a radiation protection material with a barrier layer close to the body and a secondary radiation layer away from the body only the secondary radiation aimed at the body of the medical professional is absorbed by the barrier layer. This is sufficient for common X-ray examinations since in those cases the patient is usually alone during imaging. However, it is more problematic for example during surgery if the patient is regularly or continuously X-rayed while the surgeon and/or additional medical personnel remain in close proximity to the patient. The medical staff is protected relatively well by the X-ray protection aprons they all wear. However, the situation is different for the patient who, in addition to the normal X-ray radiation, is also exposed to the added dose of secondary radiation emitting from the radiation protection clothing of the medical staff. So far, this problem has been paid little or no attention. It is therefore the object of the present invention to provide a radiation protection material with protection at different levels, e.g. 0.25 mm, 0.35 mm, 0.50, 1.0 mm nominal Pb value, which can be manufactured relatively easily and which absorbs the secondary radiation emitting to both sides—both to the medical professional and the patient—to a large degree. According to the present invention, this object is achieved by a multi-layer, lead-free radiation protection material comprising at least two individual composite layers, wherein each individual composite layer comprises a secondary radiation layer with a low Z radiation protection material and a barrier layer with a high Z radiation protection material and wherein the individual composite layers are arranged such in the radiation protection material that a barrier layer is provided on each surface of the radiation protection material and the respective secondary radiation layer is provided away form the surface. In other words, the secondary radiation layers are located inside of the radiation protection material while the barrier layers are provided on the surfaces, or face the surfaces. In such a material, the X-ray radiation entering the protective material is absorbed particularly effectively by the secondary radiation layer provided inside the lead-free radiation protection material. However, the secondary radiation forming during this absorption cannot escape from the radiation protection material since a barrier layer is provided on each of the two surfaces. The structure according to the present invention comprising at least two individual composite layers offers some considerable advantages in manufacturing. In particular, one single such individual composite layer material can be used to produce a radiation protection material with the desired protection values since two such layers result in a radiation protection material with 0.25 mm nominal Pb value, three such individual composite layers result in a radiation protection material with 0.35 mm nominal Pb value and four individual composite layers result in a radiation protection material with 0.50 mm nominal Pb value. The individual composite layers can be processed to form the radiation protection material with the desired protection value immediately during manufacture, for example by folding and/or gluing. Alternatively, the sequence of individual composite layers can be produced during the manufacture of the radiation protection clothing. The sequence of layers can be connected by gluing. It is also possible to sew the individual layers together. Another way to connect the layers is to provide them in a joint shell. It is for example possible to provide a “bag” made from a suitable material, for example a textile material or PVC, and to “lower” the layers into this bag. The individual layers then hang in the bag like a curtain. Such an arrangement has the advantage that the layers do not have to be glued together but rather hang together loosely, which leads to a markedly lower stiffness than if the layers were glued together. The bag and/or the individual layers can be sewn together, for example they can be sewn along their edges. It is also possible to seal the individual layers. Here as well, they can be sealed along their edges. Instead of a bag which is essentially completely closed except for one opening, an inner and an outer cover layer can be provided which are connected with the individual intermediate layers, for example by sewing or sealing. Other bonding methods can be applied as well. One disadvantage of the radiation protection material structure in the form of loosely stacked individual layers is their proneness to mechanical damage. For instance, it has been found that in the case of aprons, the radiation protection material is worn down at folds or typical points of contact, where the user rubs for example against edges of a table. This is particularly true for the structure consisting of several individual layers, but also for radiation protection materials which are produced from one single thick layer. It is therefore preferred to provide a sliding layer on at least one side of a radiation protection material layer. The sliding layer can be provided as a separate layer. The sliding layer can also be formed integrally with the radiation protection material layer. For instance, in that case, a thin Teflon coating can be provided on the radiation protection material layer. In the case of several individual layers, it is particularly advantageous to provide slide-promoting intermediate layers between the individual layers. These intermediate layers made from the above-mentioned Teflon can either be provided separately or, as described above, in the form of an additional layer on the lead-free material. On the other hand, a fibrous material, for example glass silk, which is available in wafer-thin layers, can be used as a slide-promoting intermediate layer. In particular in the case of the above-described production in a “bag”, it is relatively simple to incorporate such intermediate layers. It is also possible to provide a double intermediate layer in which case an intermediate layer rubs against an intermediate layer between two individual layers which translates into a particularly low coefficient of friction. It is furthermore possible to produce the “bag” from a slide-promoting material or to provide a sliding layer on its interior. It is pointed out that this feature of a sliding layer in itself is considered inventive, in particular without all or only some of the features of claim 1. As regards the provision of a sliding layer or several sliding layers in the radiation protection material, additional explanations will be given in the paragraphs below: In the radiation protection material it is advantageous to provide sliding layers in those areas where there are no adjacent components connected via their surfaces in order to reduce friction, counteract wear and damage, and avoid a decrease in flexibility due to friction. This applies to adjacent radiation protection components (in particular in the case of secondary radiation layer against secondary radiation layer, or barrier layer against barrier layer, or secondary radiation layer against barrier layer, whereby the mentioned layers are part of an individual composite layer or not part of an individual composite layer) but also to a radiation protection component (in particular in the case of a secondary radiation layer or a barrier layer, each of which is part of an individual composite layer or not part of an individual composite layer) adjacent to a cover layer (which, in turn, has a single-layer or a multi-layer structure) of the radiation protection material, Sliding layers can be provided in all of the structures discussed above, alternatively only in what is considered an important portion of such adjacent components or, at the very least, only in one such situation of adjacent components. Each of the sliding layers can be its own layer, e.g. polytetrafluoroethylene film or a—preferably light and pliant—fabric of polyamide or polyester or other plastic fibers or glass fibers. The sliding layer can be a punched part, punched in the desired outline. The following methods are preferred for connecting the sliding layer to the radiation protection materials Connection only at the upper edge of the sliding layer and/or at the two side edges or additionally also at the lower edge. Sewing and gluing are the preferred connection methods. Alternatively, the sliding layer can be connected with a radiation protection component via a large surface area or the entire surface area, preferably by laminating or in the form of a fabric connected to a radiation protection material layer. A polytetrafluoroethylene film and a—preferably light and pliant—fabric of polyamide or polyester or other plastic fibers or glass fibers are preferred. The methods described above do not have to be applied in the same manner in all the sliding layers of the radiation protection material. Variations are possible for every sliding layer within the radiation protection material. If it is connected to the radiation protection layer via a large surface area or the entire surface area, the sliding layer can also serve as a reinforcing layer or carrier layer, or constitute the only reinforcing layer or carrier layer of this radiation protection material layer. It is possible to provide an adhesive layer between the sliding layer and the other radiation protection material layer in order to perfect the bonding. It is explicitly emphasized that the radiation protection material with at least one sliding layer as described above constitutes its own invention and is realized in an advantageous manner even without the features of claim 1 and even in the case of lead-containing radiation protection materials and/or in the case of radiation protection materials which do not have a structure comprising secondary radiation layer(s) and barrier layer(s). On the other hand, all the features disclosed in this application can be realized alone or in combination as preferred features together with the sliding layer. Preferably, an individual composite layer has a protection value of about 0.25 mm, 0.20 mm, 0.175 mm or about 0.125 mm nominal Pb value. For instance, an individual composite layer which can be used to build the common protection values can have a protection value of between 0.05 mm to 0.15 mm nominal Pb value. The smaller the protection value, the thinner and the more easily the individual composite layers can be produced, and the lighter and more elastic the resulting piece of radiation protection clothing will be since the individual layers each have a low degree of stiffness. In the radiation protection material, the individual composite layers can be essentially identical. A single type of individual composite layer is enough to produce the desired radiation protection material. A protective apron with 0.5 mm nominal Pb can be constructed from 5 identical individual composite layers with a nominal value of 0.100 mm each in order to achieve a high level of comfort for the wearer (flexibility). Also, individual composite layers with different nominal Pb values, e.g. 0.125 and 0.100 mm, can be combined to arrive at a certain total nominal value of the protective clothing. For example, a protection layer with a protection value of 0.25 mm nominal Pb value can be produced from two individual layers with about 0.125 mm nominal Pb value. However, one could also conceive of e.g. three individual composite layers with a protection value of slightly less than 0.1 mm nominal Pb value. It is also possible to combine two individual composite layers with a protection value of about 0.1 mm nominal Pb value with another layer with 0.05 mm nominal Pb value. Accordingly, a radiation protection material with a protection value of about 0.35 mm nominal Pb value could for example be produced from two individual composite layers with 0.175 mm nominal Pb value each or from three individual composite layers with 0.125 mm nominal Pb value each, Accordingly, a radiation protection material with a protection value of about 0.5 mm nominal Pb value could for example be produced from four individual composite layers with 0.125 mm nominal Pb value each or from two individual composite layers with 0.25 mm nominal Pb value each. Other combinations, such as for example one 0.25 nominal Pb value and two 0.125 mm nominal Pb value are possible as well. It is also conceivable to only provide individual composite layers with barrier layer and secondary radiation layer on the outside of the radiation protection material and to arrange one or more individual layers between those two layers, e.g. those of low Z material or layers mainly comprising low Z materials, with or without barrier layer. A cover layer, e.g. a textile cover or PVC, is incorporated for example into radiation protection clothing at the outer surface and/or the inner surface of the radiation protection material. The cover layer can be coated with a high Z material, in particular on the inner surface. In addition, it can be coated with a secondary radiation layer further inside than the barrier layer made from high Z material. The subsequent secondary radiation layer can also be provided separately from the coated cover layer and can comprise its own reinforcing layer. Several such secondary radiation layers can follow either separately or integrally formed. In such a layer sequence, one or more individual composite layer(s) can be provided, but it is not obligatory. A cover layer, optionally coated, can be provided on the opposite surface. Preferably, the individual composite layer comprises a reinforcing layer. The reinforcing layer can be provided between the barrier layer and the secondary radiation layer. Alternatively, it can also be provided on one side of the barrier layer and secondary radiation layer. The reinforcing layer should be relatively tear-resistant in its layer plane and not stretch easily in order to avoid that, upon corresponding tensile stress, the relatively thin secondary radiation layer and particularly the even thinner barrier layer expand locally and become even thinner or, in an extreme case, even rupture. A film material can be used as a reinforcing layer, The reinforcing layer can comprise a thin, tear-resistant fabric. The reinforcing layer can comprise an aramide or a glass fiber material. Alternatively, other fibrous materials such as for example plastic, carbon or ceramic fibers or metal filaments, e.g. copper or tungsten filaments, can be used, Fabrics can be produced from all these fibers or filaments, A material which is especially suitable for absorbing X-rays, such as for example copper or in particular tungsten material, offers the additional advantage that it increases the absorption effect while at the same time providing stiffness. The metal filaments and especially fabrics made from metal filaments have the advantage that they provide particularly high stability but also the advantage that they possess a certain inherent stability which is especially important for applications where the radiation protection material has to be brought into a certain shape and should remain in that shape during use, for instance gonad protection, etc. Another extremely important field of application for such formable radiation protection materials is the use as overhand protection. Such overhand protection is used when very difficult operations have to be performed which are impeded by the use of radiation protection gloves. In such cases, what is referred to as an overhand protection is used which is attached for example to the arm of the surgeon or to the patient, and which the surgeon is able to manipulate during the operation such that his unprotected hands underneath are sufficiently protected. It is also possible to introduce the above-mentioned fibrous materials or filaments into the matrix of the barrier layer and/or the matrix of the secondary radiation layer and to embed them therein. The reinforcing layer can also be provided on the outside surface of an individual composite layer, or a reinforcing layer can be provided on each outside surface of an individual composite layer. It is also possible to form the reinforcing layer as the slide-promoting layer at the same time. The low Z material of the secondary radiation layer is preferably selected such that it exhibits as even and as high an absorption as possible throughout the desired energy range of 60 to 125 kV, in particular together with the barrier layer, whereby the selection can be made independently of the generation of secondary radiation. In particular in the case of radiation protection material which is only intended for use in specific applications having a somewhat limited energy range, the selection can also be optimized with respect to that limited energy range. Optimally, the high Z material of the secondary radiation layer is selected such that it provides maximum absorption, if possible, for the typical secondary radiation of the secondary radiation layer whose energy is essentially composed of the X-ray emission spectra of the elements of the secondary radiation layer. Both in the selection of the material of the secondary radiation layer and the selection of the material of the barrier layer, the weight per unit area of the material at which the desired absorption coefficient is reached is taken into consideration as well, in addition to the absorption properties. At the same time, aspects like producibility, miscibility with the matrix material, etc. can also be taken into account. The boundary between low Z material and high Z material approximately lies with elements with an atomic number Z of 60, wherein the low Z material has an atomic number of about 39 to 60 and the high Z material has an atomic number higher than 60 and preferably higher than 70. Even if the two ranges overlap for the atomic number 60, the high Z material is always different from the low Z material in order to do justice to the different absorption requirements. The individual elements of the low Z material or the high Z material, respectively, can be provided in the radiation protection material in the form of a thin film. However, they are typically dispersed in powder form in a matrix material. Examples of matrix materials include rubber, latex, synthetic, flexible or solid polymers or silicone materials. The low Z material can comprise at least one of the following elements: tin, antimony, iodine, caesium, barium, lanthanum, cerium, praseodymium and neodymium. One or more of these elements can additionally be mixed with elements not from this group; elements suitable for use in such a mixture include for example rare-earth elements with Z=60 to 70, preferably samarium, gadolinium, terbium and/or erbium and/or ytterbium. The high Z material of the barrier layer can comprise at least one of the following materials: tantalum, tungsten, bismuth. In a preferred embodiment, the barrier layer comprises bismuth, and the secondary radiation layer comprises tin as well as at least one of the elements lanthanum, cerium or gadolinium. Preferably, the radiation protection material with 0.25 mm nominal Pb value consists of two individual composite layers, while the radiation protection material with 0.35 mm nominal Pb value consists of three individual composite layers. The individual layers can be provided directly next to each other, e.g. in contact with each other or connected. It is also possible to separate the individual layers for example by means of an air gap, a fabric or another intermediate layer. This applies in general and independently of the nominal Pb value. The radiation protection material comprising three individual composite layers has an asymmetric structure with two barrier layers on the outside and one on the inside. Consequently, it has a surface which is closer to the inside barrier layer than the second surface. In the case of a sequence of barrier layers, the next inside barrier layer also contributes to the absorption of secondary radiation from the secondary radiation layers deeper inside. The surface closest to the inside barrier layer can be used as the layer closest to the body of the user in radiation protection clothing. It can therefore be planned to mark three-layer radiation protection material and radiation protection material in order to guarantee correct incorporation into the radiation protection clothing. The same generally applies to radiation protection material with an uneven number of layers and radiation protection material with an even number of layers but an asymmetrical structure. The marking can e.g. be a color mark or writing. The present invention furthermore relates to radiation protection clothing comprising a radiation protection material according to the present invention and in particular radiation protection clothing wherein in the case of an asymmetrical structure of the radiation protection material the surface with most barrier layers in its vicinity is provided closest to the body to be protected. FIG. 1 shows the structure of an individual composite layer 2 comprising a barrier layer 4, a reinforcing layer 6 and a secondary radiation layer 8. In particular, the barrier layer comprises a layer of 0.5 kg/m2 bismuth including the appropriate elastomer matrix, and the secondary radiation layer comprises a layer of 0.9 kg/m2 of a tin/gadolinium filling including an elastomer matrix. The weight per unit area of tin is 0.7 kg/m2 , and the weight per unit area of gadolinium is 0.2 kg/m2, which results in the total weight per unit area of the secondary radiation layer of about 0.9 kg/m2. The pure matrix weight accounts for 10 to 20%, preferably 12 to 15% of the total weight per unit area. The thickness of an individual composite layer with about 0.125 mm nominal Pb value is between about 0.3 to 0.6 mm, more precisely about 0.40 mm. With 4 individual composite layers with a thickness of 0.40 mm each, a protective apron with a nominal Pb value of 0.50 mm can be created which offers the same attenuation as a corresponding lead apron. The lead-free apron with 0.5 mm nominal Pb value thus weighs 5.6 kg/m2. The corresponding lead apron has a pure lead weight of 5.7 kg/m2. To this are added the weight of the oxygen in the case of lead oxide, and the weight of the matrix. Lead aprons with 0.5 mm nominal Pb value therefore usually weigh 7 kg/m2. Thus, the lead-free apron weighs 20% less than a lead apron. Between the two layers of the individual composite layer 2, the reinforcing layer is provided which according to the embodiment is manufactured from a very thin tear-resistant fabric, e.g. glass fibers or aramide. Thus, the weight per unit area of a glass filament fabric is about 25 g/m2 and is therefore negligible as far as increasing the weight of the apron is concerned. The entire individual composite layer 2 can therefore be designed to be relatively thin and very light. It has a weight per unit area of about 1.4 kg/m2. The three layers of an individual composite layer 2 are connected during the manufacturing process. For example, in a first step, the secondary radiation layer 8 can be applied onto the reinforcing layer 6, and in a second step, the barrier layer 4 can be applied on the other side of the reinforcing layer 6. The individual composite layer itself exhibits a relatively high degree of flexibility. The selection of the matrix material essentially determines the flexibility of the individual barrier layer. The material of the reinforcing layer as well influences the flexibility/stiffness of an individual composite layer. For instance, glass fiber material is especially suitable due to its high degree of flexibility. In addition, it is chemically safe. A conceivable alternative to glass fibers would be an aramide material. It has a slightly higher stiffness, which can be disadvantageous especially for the use as radiation protection clothing. In order to manufacture rigid construction elements such as plates and supports, carbon fibers can be used in the reinforcing layer. The carbon fibers can be additionally or exclusively embedded in the matrix material. FIG. 2 shows different radiation protection materials 10, 12 and 14. The topmost radiation protection material 10 comprises two individual composite layers. Similar to FIG. 1, the layer structure of the two layer sequences comprises the barrier layer 4, reinforcing layer 6 and secondary radiation layer 8. The radiation protection material 10 comprising two individual composite layers 2 has a symmetrical structure. The gap 16 shown between the two secondary radiation layers 8 indicates that the two individual composite layers do not necessarily have to be connected via their surface. It can also be inferred from FIG. 1 that each of the two surfaces 18, 20 of the dual-layer radiation protection material 10 is formed by a barrier layer 4. A three-layer radiation protection material is shown with the reference number 12. Essentially, the statements made with respect to the dual-layer radiation protection material 10 apply here as well. It can be inferred that compared to the dual-layer radiation protection material 10 a third individual composite layer has been added from below, so that a second barrier layer 8′, provided inside of the radiation protection material 12, is closer to the lower surface 20 than to the upper surface 18. In this asymmetrical structure it is preferred that the lower surface 20 be provided closer to the skin. A four-layer radiation protection material 14 is shown as well. Compared to the three-layer radiation protection material 12, another individual composite layer 2 has been added on top of the three-layer layer sequence. Thus, it is possible in practice to manufacture radiation protection material with different protection values at a relatively low expense by using a single individual composite layer 2 as a starting material for radiation protection material with different protection values, In particular, dual-layer radiation protection material 10 with a nominal value of 0.25 mm Pb, three-layer radiation protection material 12 with a nominal value of 35 mm Pb and four-layer radiation protection material 14 with a nominal value of 0.50 mm Pb (according to DIN IN 61331-3) can be produced by multiple layering. Such radiation protection material is suitable for the applications mentioned above. In particular, it can be used to produce radiation protection clothing, especially aprons, gloves, thyroid gland protection, gonad protection, ovary protection, etc., but also eye protection, protective shields, etc. Flexible protective curtains low in secondary radiation can also be produced as stationary protection devices for X-ray machines. Such protective curtains can be used with stationary machines or on movable or mobile frames. FIG. 3 shows a schematic view of the individual X-ray portion and the effect of radiation protection clothing comprising the radiation protection material 10 according to the present invention. Such a situation arises if the medical professional is in close proximity to the patient, which is for example common in minimally invasive surgeries as well as in catheter examinations in angiography. The radiation 24 primarily emitting from the X-rayed patient 22 hits the radiation protection clothing 26, typically the radiation protection apron of the medial professional 28, and excites fluorescence or secondary radiation, part of which, see arrow 30, is scattered back towards the patient. On the side of the medical professional 28, number 32 indicates the primary radiation portion and number 34 denotes the secondary radiation from the side of the medial professional. It can also be inferred from the schematic dimensions (which are not true to scale) that the primary radiation, but also the secondary radiation, is not completely absorbed by the radiation protection material but it is merely reduced significantly. Equating the fluorescence radiation and the secondary radiation of the secondary radiation layer 8, as was done above, is not completely correct in terms of physics. Rather, the secondary radiation 30, 34 from the secondary radiation layer 8 comprises different portions, for example the classic scattering radiation, Compton scattering and fluorescence radiation. However, fluorescence radiation accounts for most of this secondary radiation. For the tin used in the secondary radiation layer 8, the energy of the fluorescence radiation (K radiation) is 26 keV. This low-energy X-ray radiation mainly affects the skin and organs close to the skin. In this connection, female mammary gland tissue becomes the focus of attention, which is relatively radiosensitive, as are male testicles and the thyroid gland. According to recent scientific findings, this low-energy radiation is much more effective biologically than higher energy X-rays. The high Z radiation protection material of barrier layer 4 on the other hand only develops relatively little fluorescence radiation or secondary radiation since its K absorption edge falls within a high energy range, typically at 70 to 90 keV and consequently no or only little excitement takes place in the usual application range of 60 to 125 kV tube voltage of the X-ray source. Thus, the two outside barrier layers 4 create an effective shield against the secondary radiation also towards the body of the patient 22. The effect described above could be confirmed by measurements as shown in the schematic illustration of FIG. 4. In particular, FIG. 4 shows the X-ray tube with the reference number 36 and the shield 38. From there, the X-ray extends in the direction of the body of the medical professional represented by a water phantom 40. Reference number 42 denotes a measuring chamber which is positioned at a distance a from the radiation protection clothing 26. Number 4 again represents the barrier layers facing the patient and the medical professional, respectively, wherein the secondary radiation layer is marked 8. The water phantom 40 with a water content of 25×25×15 cm3 mimics the scattering properties of the medical professional's body. The secondary radiation layer of the radiation protection clothing 26 was formed from lead-free material, in particular tin with a weight per unit area of 2.0 kg/m2. The dosage was measured with an air kerma measuring chamber 42, at distances of 0 (bodily contact), 5, 10, 20 and 30 cm from the radiation protection clothing 26, with a barrier layer of 0.7 kg/m2 bismuth, once on the side of the patient and once on the side of the medical professional. The difference between these two measured values corresponds to the increase in dosage due to the secondary radiation generated in the material (e.g. tin K radiation). The patient would be exposed to this additional radiation if the surface of his body were located at the measuring chamber 42. The measuring results show that the portion of secondary radiation at the location of the patient can be reduced to one third if the barrier layer is located at the side of the patient. The reduction in secondary radiation at the patient is most significant when the medical professional 40 stands directly by the patient. In a second round, a measuring location between the radiation protection clothing 26 and the water phantom 40 (which corresponds to the body of the medical professional) was selected since the medical professional wears the apron directly on the surface of his body. The barrier layer of 0.7 kg m2 bismuth is again provided once on the side of the patient and once on the side of the medical professional. The difference between the two measured values corresponds to the relative decrease in dosage due to the secondary radiation. Accordingly, by providing a barrier layer on the side of the medical professional—just as on the side of the patient—the secondary radiation can be reduced to one third. The provision of a double-sided barrier layer as in the radiation protection material 10, 12, 14 according to the present invention combines these two attenuation effects and leads to a marked reduction in the secondary radiation both on the side of the medical professional and the side of the patient. The results of the measurements are summarized in Tables 1 and 2 below: TABLE 1Portion of secondary radiation on thepatient's body surface tube voltage 70 kVWithoutWithFluorescenceDistance medicalbarrier layerbarrier layerportion shielded byprofessional/patienton patienton patientbarrier layer0 cm (bodily contact)33.6%10.6% 23%10 cm12.1%4.7%7.4%20 cm5.4%2.2%3.2%30 cm1.5%0.4%1.1% TABLE 2Portion of secondary radiation on themedical professional's body surfaceWithout barrierWith barrier layerFluorescencelayer on medicalon medicalportion shielded byTube voltageprofessionalprofessionalbarrier layer 70 kV241%77%164% 100 kV155%74%81%125 kV139%81%58% In general, and in particular in the example above, the radiation protection clothing 26 usually contains the radiation protection material in the form of a powder. If only the elements are mentioned in connection with the embodiment, this particularly refers to the powder form or compounds of the element or elements in powder form. Radiation protection material with a sliding layer or several sliding layers is explained in more detail based on the examples according to FIGS. 5, 6 and 7. The radiation protection material 2 depicted in FIG. 5 comprises three radiation protection components or individual radiation protection layers, namely a barrier layer 4 on the left side of FIG. 5 facing the patient, a secondary radiation layer 8 in the middle, and a barrier layer 4 on the right side of FIG. 5 closer to the medical professional. Each of the layers 4 and 8 comprises a reinforcing layer 6 which can be provided somewhere in the middle area of the layer, or also in the surface area of the layer. Furthermore, FIG. 5 shows a cover layer 50 on the left and a cover layer 52 on the right, The cover layer 50 on the left is preferably formed from a strong plastic fiber fabric with a coating on its left surface, preferably a polyurethane coating, in order to protect the fabric from splattered liquid. The cover layer 52 on the right is preferably also provided with a strong plastic fiber fabric wherein in this case a coating, preferably of polyurethane, can be provided either on the left side of cover layer 52 or on the right side of cover layer 52 as depicted in FIG. 5. Between the left cover layer 50 and the left barrier layer 4, there is a sliding layer 54, as is the case between the left barrier layer 4 and the secondary radiation layer 8, between the secondary radiation layer 8 and the right barrier layer 4, and between the right barrier layer 4 and the right cover layer 52. The thicknesses of the individual layers and the distances between the layers, where the sliding layers 54 are positioned, are depicted at an exaggerated scale for the purpose of clarity. In reality, these distances are small in relation to the layer thicknesses so that the various sliding layers 54 are more or less completely in physical contact with their two neighboring layers. The sliding layers 54 are only sewn or glued together with the other radiation protection material in the area of their top edge, Additional bonding along the two side edges, i.e. behind the drawing plane and in front of the drawing plane and/or in the area of the lower edge is optionally possible. It is also possible to laminate each sliding layer 54 onto one of the two neighboring layers. It is emphasized that the reinforcing layers 6 are optional and do not have to necessarily be present. It is furthermore emphasized that there are embodiments of the radiation protection material 2 wherein the left barrier layer 4 is not present. Moreover, it is emphasized that alternatively the left barrier layer 4 and the secondary radiation layer 8 can be combined to form an individual composite layer, preferably in a structure as described in the present application. A structure comprising several such individual composite layers as described in the present application can be used as well. As another alternative, two secondary radiation layers 8 can be provided instead of the single secondary radiation layer 8 depicted in the drawing. Not all four sliding layers 54 have to be present. In particular between the right barrier layer 4 and the right cover layer 52, a sliding layer 54 is non-essential if the right cover layer 52 is coated on its left side. FIG. 6 illustrates that—optionally in some or all of the situations of adjacent components—the sliding layer 54, if a sliding layer 54 is even provided, can be realized in the form of a layer which is connected to a component of the radiation protection material 2 via a large surface area or the entire surface area. Compared to the embodiment according to FIG. 5, the left barrier layer 4 is now provided with a sliding layer 54 on its left side, the secondary radiation layer 8 is provided with a sliding layer 54 on its right side, and the right barrier layer 4 is provided with a sliding layer on its right side. There is a “free” sliding layer 54 between the left barrier layer 4 and the secondary radiation layer 87 as in the example according to FIG. 5. In this case, the sliding layers 54 connected with the radiation protection components via a large surface area or the entire surface area are preferably formed from a light, pliant fabric, preferably polyamide fabric or polyester fabric. Such fabrics are available with a weight per unit area of about 30 g/m2 and above. During the production of the layers 4 and 8, a viscous material, e.g. a mixture of matrix material (in particular polyurethane or rubber) and a low Z material or a high Z material, respectively, was applied onto the fabric and then reached a ready-for-use state due to a chemical reaction in the matrix material. The example according to FIG. 7 differs from the example according to FIG. 6 in that the secondary radiation layer 8 and the right barrier layer each have their directly assigned sliding layer 54 on the left side in FIG. 7 (instead of on the right side), and that the “free” sliding layer 54 of FIG. 6 is not present. As regards the exaggerated distances, the number of sliding layers, the number of radiation protection components and other possible embodiments, the statements made in connection with the example according to FIG. 5 analogously also apply to the embodiment according to FIG. 6.
039649695	summary	Liquid metal cooled, fast breeder reactors (LMFBR) designed for commercial power generation or as large test reactors have several unique characteristics associated with the reactor core. As a result, special attention must be given to the structure that supports and retains the core components. For example, one problem is the material swelling and creep induced by the high fluence (neutron flux .times. time) associated with economically acceptable fuel burnup. This swelling and creep results in the deformation of fuel assemblies and the introduction of restraint loads necessary to maintain fuel assembly lateral positioning. The positioning is very important since a characteristic of large fast reactor cores is the sensitivity of nuclear reactivity to small geometric changes in core configuration (typically $4 reactivity increase for a 1 inch radius reduction). This results in the necessity for tight geometric control of core configuration and yet be able to accommodate irradiation induced swelling in addition to the normal thermal expansion. Several basic concepts can be envisioned that could perform this function. In general, these concepts involve constraint mechanisms and some form of compliance or flexibility to accommodate normal distortions without excessive restraint on the components. One of these concepts consists of a fixed external boundary located at several elevations near the core and the use of an internal tightening device, located at a number of the core flow channels, that removes the clearance necessary in the refueling process. Compliance can be provided by spring devices located on the periphery of the core and blanket assemblies and within the fixed boundaries. Alternately, compliance can be provided locally on each of the tightener assemblies located throughout the core and blanket. The use of internal tightener compliance has an advantage in that the accidental release of possible core disarrangement caused by ratcheting of the channels at the clamping planes will not cause a decrease in core radius and thus will not introduce positive reactivity. This is a potential safety feature in the use of internal compliance. SUMMARY OF THE INVENTION The present invention is directed to an apparatus that provides the basic function of internal tightening and provides for local compliance. The primary features of the apparatus include large contact areas to transmit loads during reactor operation, actuation cam surfaces loaded only during clamping and unclamping operations, and preloaded pads with compliant travel at each face of the hexagonal assembly at each clamping plane to accommodate thermal expansion and irradiation induced swelling. Therefore, it is an object of the invention to provide a device that accomplishes the basic function of internal tightening and provides for local compliance in the core of a liquid metal cooled, fast breeder reactor. A further object of the invention is to provide an internal core tightener for an LMFBR which is a linear actuated expanding device using a minimum of moving parts to perform the lateral tightening function. Another object of the invention is to provide an internal core tightener for an LMFBR which utilizes large contact areas to transmit loads, actuation cam surfaces loading only during certain operations, and preloaded pads with compliant travel to accommodate thermal expansion and irradiation induced swelling.
050287966	summary	BACKGROUND OF THE INVENTION It is well-known in the art to provide protective garments tO personnel working in or near a radioactive environment, for example, to health care workers operating x-ray equipment or working in radiology laboratories. Generally, such radiation shield garments are extremely heavy because they include one or more layers of lead sheet material to provide the desired protection. Prior art protective garments were designed and worn in such a way that most of the weight of the garment was supported by the wearer's shoulders and upper back leading to discomfort and excessive fatigue. One example of such a garment is shown in U.S. Pat. No. 4,441,025 to McCoy. This disadvantage of prior art protective garments led to efforts to shift the weight load to other parts of the wearer's body. Based on the technology of backpacks for hikers, which are designed to shift at least a portion of the weight to the user's waist and hips, Cusick et al. developed the idea for an elasticized support belt to be used in conjunction with protective garments, as described in U.S. Pat. No. 4,766,608. The aforementioned patents and the references cited therein are incorporated herein by reference. As shown in FIGS. 1-5 of the Cusick et al. patent, the support belt is an integral part of and permanently attached to the protective garment (col.3, lines 37-39). Similarly, as shown in FIGS. 6-8, the Cusick et al. support belt is integral with the protective garment (col.4, lines 48-50). As shown in FIGS. 9 and 10, however, the Cusick et al. support belt is detachably attached to the protective garment by snap buttons or, alternatively, "can be fixed to the garment by velcro, rivets, stitching etc." (col. 5, lines 13-17). The patent further teaches that: "Indeed, the belt need not be attached to the garment at all, but only fixed to itself when worn around the waist of the garment," (col. 5, lines 18-21). But, the Cusick et al. patent does not teach how a separate, independent support belt that is not in some way attached to the protective garment during use could supply the necessary support to significantly reduce the weight load carried on the user's shoulders and upper back. It must be kept in mind that the function of the belt in Cusick et al. is not just to close the front of the garment and gather it about the waist, but rather to effectively shift a significant share of the weight of the garment to the wearer's waist and hips. As shown and described in Cusick et al., this weight shifting occurs because, when the belt is fastened around the user's waist substantially all of the weight of the garment below the user's waist is supported by the user's hips, and a substantial proportion of the weight of the garment above the waist is also supported by the user's hips. This support occurs, according to Cusick et al., precisely because of "the action of the belt in holding the garment firmly against the body" (col. 2, lines 19-24 ). In other words, it is at the point of physical attachment between the belt and the garment that the bulk of the garment's weight is transferred from the user's shoulders to his waist. If the belt in the Cusick et al. invention is not physically attached in some way to the garment while in use, the garment would have a tendency by action of gravity to slide downward, slipping underneath the belt, until the bulk of the garment's weight was again being carried on the user's shoulders and back. Even if the belt of the Cusick et al. invention were tightened to the point of extreme user discomfort, there would still be a tendency for slippage with every user movement, especially during bending movements. Accordingly, Cusick et al. does not teach any way to actually carry out the concept of a separate, independent support belt that does not need to be physically attached to the protective garment while in use. Furthermore, the elasticized belt described in Cusick et al. can be uncomfortable and unduly restrictive in use. The need to attach the belt to the garment requires attachment means on both the belt and the garment which increases manufacturing costs and prevents interchangeable use of the belt with other protective garments. The need for attachment means also increases the time required to put on and remove the support belt. These and other drawbacks of the prior art are overcome with the present invention. OBJECTIVES OF THE INVENTION It is a principal object of this invention to provide a support belt for radiation shield garments that is completely independent of said garments. It is also an object of this invention to provide a support belt for radiation shield garments that shifts a substantial portion of the garment's weight from the user's shoulders and upper back to his waist and hips without any physical attachment between the support belt and the garment. A further object of this invention is to provide a support belt that can be used interchangeably with a variety of radiation shield garments without special adaptation. Still another object of this invention is to provide a comfortable, light-weight and less restrictive support belt that can quickly be put on and removed. These and other objects and advantages of this invention will be apparent from the following description.
047818824	claims	1. An apparatus for loading or unloading a fuel assembly in a nuclear reactor comprising: means for positioning a fuel assembly above the reactor; a housing on said positioning means; a pair of concentric inner and outer masts carried by said housing; said inner mast having means thereon for gripping a fuel assembly; means for vertically axially moving said inner mast relative to said outer mast; and guide means on said inner and outer masts to align the inner mast centrally within the outer mast during vertical axially moving the inner mast relative to the outer mast, said guide means including a plurality of inner members disposed on the inner mast and complementary shaped outer members vertically spaced on the outer mast which cooperate with said inner members, means for supporting said outer members on said outer mast, means for pivoting said outer members relative to said support means towards and away from said inner members, and means for vertically aligning the position of said outer member. a plurality of inner members disposed on the inner mast; a plurality of complementary shaped outer members vertically spaced on the outer mast which cooperate with said inner members; means for supporting said outer members on said outer mast; means for pivoting said outer members relative to said support means towards and away from said inner members; and means for precisely vertically aligning the position of said outer members. 2. The apparatus for loading or unloading a fuel assembly in a nuclear reactor as defined in claim 1 wherein said outer members on said outer mast comprise rollers. 3. The apparatus for loading or unloading a fuel assembly in a nuclear reactor as defined in claim 2 wherein said rollers have a concave groove therein and said inner members have a convex surface thereon cooperating with said groove. 4. The apparatus for loading or unloading a fuel assembly in a nuclear reactor as defined in claim 1 wherein said means for supporting said outer members on said outer mast comprises a framework about an opening in the wall of the outer mast and said outer members are rollers disposed on a shaft, and said shaft extends between two spaced side bars mounted for pivoted movement relative to said framework. 5. The apparatus for loading or unloading a fuel assembly in a nuclear reactor as defined in claim 4 wherein said framework comprises a top wall above said opening, a bottom wall below said opening and a plate extending between said top and bottom walls, said bottom wall comprises a block with a bore therethrough, and said side bars are secured to a pivot pin disposed in said bore for said pivotal movement. 6. The apparatus for loading or unloading a fuel assembly in a nuclear reactor as defined in claim 5 wherein said framework includes an aperture through said bottom wall and a cooperating aperture through said plate, with a bolt passing therethrough and threadedly engaged in the wall of the outer mast, and a groove is provided in the lower face of said top wall and a cooperating aperture through said plate, with a bolt passing therethrough threadedly engaged in the wall of the outer mast. 7. The apparatus for loading or unloading a fuel assembly in a nuclear reactor as defined in claim 4 wherein said alignment means comprises an alignment beam adjacent to and extending between the upper ends of the side bars, an alignment pin extending from one end of the alignment beam for vertically aligning the position of said rollers, and an adjustable device which contacts the alignment beam. 8. The apparatus for loading or unloading a fuel assembly in a nuclear reactor as defined in claim 7 wherein said adjustable device comprises a sleeve enclosing said alignment beam, a threaded shaft co-acting with said sleeve and extending from said sleeve outwardly through an opening in said plate, a hollow stud having threads on the internal and external wall thereof about said threaded shaft in the opening of said plate, having a shoulder thereon, for abutting the inside of said plate and a lock nut engageable with the threads of said threaded shaft, for abutting the outside of said plate. 9. A guide means for use in centrally aligning inner and outer masts of an apparatus including means for vertically axially moving said inner mast relative to said outer mast, said guide means comprising: 10. The guide means as defined in claim 9 wherein said means for supporting said outer members on said outer mast comprises a framework about an opening in the wall of the outer mast and said outer members are rollers disposed on a shaft, and said shaft extends between two spaced side bars mounted for pivoted movement relative to said framework. 11. The guide means as defined in claim 10 wherein said framework comprises a top wall above said opening, a bottom wall below said opening and a plate extending between said top and bottom walls, said bottom wall comprises a block with a bore therethrough, and said side bars are secured to a pivot pin disposed in said bore for said pivotal movement. 12. The guide means as defined in claim 11 wherein said framework includes an aperture through said bottom wall and a cooperating aperture through said plate, with a bolt passing therethrough and threadedly engaged in the wall of the outer mast, and a groove is provided in the lower face of said top wall and a cooperating aperture through said plate, with a bolt passing therethrough threadedly engaged in the wall of the outer mast. 13. The guide means as defined in claim 11 wherein said alignment means comprises an alignment beam adjacent to and extending between the upper ends of the side bars, an alignment pin extending from one end of the alignment beam for vertically aligning the position of said rollers, and an adjustable device which contacts the alignment beam. 14. The guide means as defined in claim 13 wherein said adjustable device comprises a sleeve enclosing said alignment beam, a threaded shaft co-acting with said sleeve and extending from said sleeve outwardly through an opening in said plate, a hollow stud having threads on the internal and external wall thereof about said threaded shaft in the opening of said plate, having a shoulder thereon, for abutting the inside of said plate and a lock nut engageable with the threads of said threaded shaft, for abutting the outside of said plate.
	description	The present invention relates to accelerated hydriding of metallic substrates to evaluate the effects of hydrogen adsorption on substrate performance, and in particular, as cladding materials for handling, storage and transfer of nuclear fuels. Zirconium alloys have been used as nuclear fuel cladding material in fuel assemblies for nuclear power reactors due to their relatively low neutron cross section and high corrosion resistance. Two zirconium alloy groups, including the traditional Zircaloy-2™ in boiling water reactors and Zircaloy-4™ in pressurized water reactors (PWR) have been used as cladding material. Newer materials, such as ZIRLO™ (Zr-1Nb-1Sn-0.1Fe in wt %) and M5® (Zr-1Nb-0.04Fe in wt %) have also been evaluated. During reactor operations, the cladding typically undergoes outer surface corrosion as high temperature water reacts with the cladding producing hydrogen. A fraction of this hydrogen is then absorbed by the cladding. The total hydrogen concentration generally depends on temperature, fuel burn-up, and material type. The hydrogen concentration could be up to 600 ppm. J. P. Mardon et al, Update on the Development of Advanced Zirconium Alloys for PWR Fuel Rod Claddings, Proceedings of the 1997 International Topical Meeting on LWR Fuel Performance, Portland Oreg., La Grange Park, Ill.: American Nuclear Society, pp. 405-412. During extended dry storage, cladding plays an important role in safely handling, storing, and transferring spent nuclear fuel. As the cladding cools with time during extended storage, the hydrogen inside the cladding may precipitate as hydrides because the solubility of hydrogen in zirconium decreases with temperature. Furthermore, both existing and newly formed hydrides may reorient. Depending on size, distribution, and orientation, these hydrides may induce premature fracture as a result of hydride embrittlement or delayed hydride cracking. Hydride embrittlement and reorientation of spent nuclear fuel cladding is therefore a potentially significant operational and safety concern. As the industry has considered extended dry storage as an alternative approach to manage the spent nuclear fuel and the amount of high burn-up fuel is increasing as a result of changes in plant operating conditions, there is a need to evaluate the effects of hydriding on metallic substrate materials. See, e.g., R. L. Sindelar et al, Materials Aging Issues and Aging Management for Extended Storage and Transportation of Spent Nuclear Fuels, NUREG/CR-7116; SRNL-STI-2011-00005, Washington D.C. Traditional methods of hydriding using electrochemical charging followed by annealing and charging in hydrogen gas are relatively time-consuming involving multiple steps where several days are required and the hydrides must be processed at high temperature (e.g., 300° C.). Accelerated hydriding methods that can be operated at relatively lower temperature would be very important for selection and evaluation of metallic materials for cladding applications. In addition, hydriding at relatively lower temperatures could be extended to other applications such as evaluating hydrogen embrittlement of oil and gas pipeline materials. A method for accelerated hydriding of a metallic substrate comprising supplying a metallic substrate wherein said metal substrate has an activation energy for hydrogen adsorption (Easubstrate). This may then be followed by cleaning the substrate surface by etching with an acid and then coating at least a portion of the substrate surface with a metal having an activation energy for hydrogen adsorption (Eametal) that is lower than Easubstrate. This is then followed by hydriding the substrate at a temperature of less than or equal 500° C. and for a period of less than or equal to 24 hours wherein the hydriding occurs in the metallic substrate. The present invention relates to accelerated hydriding of metallic substrate materials. The metallic substrate materials may therefore include any metal capable of hydrogen absorption wherein the influence of hydrogen absorption is to be evaluated. Metal substrates may therefore include transition metals such as Ag, Au, Co, Cr, Cu, Fe, Ir, Mo, Nb, Ni, Os, Pd, Pt, Re, Rh, Su, Sc, Ta, Ti, V, W Y and Zr. Alloys of all such metals are also contemplated. Preferred metal substrates include Zr, Ti, Ni, Ta and alloys thereof. Particularly preferred herein for accelerated hydriding are Zr type alloys, such as Zircaloy-2™ and Zircaloy-4™. Zircaloy-2™ typically contains about 1.4 wt. % tin, 0.15 wt. % iron, 0.1 wt. % chromium and 0.06 wt. % nickel, 1,000 ppm oxygen and the balance zirconium. Zircaloy-4™ typically contains about 1.4 wt. % tin, 0.21 wt. % iron, 0.11 wt. % chromium, 30 ppm nickel, 1,200 ppm oxygen and the balance zirconium. FIG. 1 compares the activation energies for hydrogen adsorption in electron volts (eV) for the identified metals. As can be observed, the activation energy barrier for hydrogen adsorption on Zr is relatively higher than that of metals such as Co, Cu, Ni, Pd or Pt. Accordingly, deposition of any one of these metals on Zr or a Zr alloy will now uniquely provide for acceleration of hydrogen adsorption on the Zr or Zr based alloy to facilitate the ability to evaluate the effects of hydrogen adsorption on Zr or Zr based alloys in a much more efficient manner. In such regard, it may now be appreciated that one may now identify a substrate containing a metallic alloy (two or more metals) and then identify the activation energies for hydrogen adsorption for each of the metals within such alloy. Then, one may select for surface treatment a metal that has a relatively lower activation energy for hydrogen adsorption than any one of the metals of the substrate alloy. In this manner, accelerated hydrogen adsorption can be achieved and the evaluation of the effects of such hydrogen adsorption on the substrate alloy is more readily available. In addition, in that situation where the underlying metal substrate contains or consists of only one single metal, activation of the surface for hydriding comprises the selection of a metal that has an activation energy for hydrogen adsorption that is lower than such single metal based substrate material. It is useful to note that the activation energies (Ea) that one may utilize and compare may be activation energies that are either measured or calculated for a given metal. In addition, the activation energies that one may consider herein may include activation energies for hydrogen diffusion from the surface to a subsurface or the activation energy from a 1st to 2nd subsurface of the metal at issue. See, e.g., Hydrogen Adsorption, Absorption and Diffusion On and In Transition Metal Surfaces, Ferrin et al, Surface Science 606 (2012) 679-689; A Systematic DFT Study of Hydrogen Diffusion on Transition Metal Surfaces, Kristinsdóttir et al, Surface Science 606 (2012) 1400-1404. For the purpose of the present disclosure, when considering activation energies of either the substrate or the activating metal layer, one should be consistent in the selection criterion (e.g. compare activation energies of hydrogen diffusion for the surface to a subsurface for a given metal substrate and given surface activating metal or compare activation energies of hydrogen diffusion from a 1st subsurface to a 2nd subsurface for a given substrate and activating metal to be applied thereto). The present invention therefore discloses and identifies a method for reducing the time and temperature that is necessary for hydriding of a selected metal substrate. Without being bound by any particular theory, attention is directed to FIG. 2 which identifies what is believed to reflect one potential model of hydrogen storage, migration and diffusion into a given substrate surface, in connection with the observed accelerated hydriding disclosed herein. As can be seen, one may partially coat the substrate surface. For example, one may partially coat 1-90% of the available substrate surface. More preferably, one may coat 1-80%, 1-70%, 1-60%, 1-50%, 1-40%, or 1-30% of said substrate surface. Accordingly, one may therefore now coat only 50% or less of the substrate surface with an activating metal and still provide herein a useful procedure to more effectively evaluate the effect of hydrogen adsorption on the underlying substrate by triggering hydrogen adsorption at temperatures and times that are less than what would be otherwise necessary to hydrate a given substrate. As illustrated in FIG. 2, the hydrogen that is adsorbed on the surface of the accelerating metal deposited on the substrate surface may then migrate to the substrate surface for ensuing hydrogen adsorption. However, in the broad context of the present invention, one may also activate the surface herein by fully coating (100%) the substrate surface with a metal with the relatively lower activation energy (Ea) for hydrogen absorption. Preferably, the thickness of the metal layer applied to the substrate for surface activation for hydrogen adsorption, whether a partial or full coating, falls in the range of 5.0-100 nm. In particular, it has now been observed that by activation of the surface of a metal substrate to hydriding herein, hydrogen adsorption may now proceed at temperatures in the range of 50° C. to 500° C. More preferably, hydriding can now be made to occur for a selected metal substrate at temperatures of 50° C. to 300° C. In addition, the time period to effect hydriding of the underlying substrate is now reduced to a period of up to 24 hours, preferably within a period of 2-12 hours. Attention is next directed to FIG. 3 which outlines a preferred procedure for accelerated hydriding of a metal substrate. Initially, for a selected cladding substrate (metal substrate that is used, e.g., as a liner for a nuclear power reactor) one initially removes any oil residues by treatment with organic solvent. This is then followed by removal of any oxide layer which preferably can be achieved by treatment with inorganic acids, such as nitric acid (HNO3) or hydrofluoric acid (HF) or a mixture thereof where each inorganic acid present at 20 wt. % in aqueous solution. The substrate surface is then washed with deionized water and surface treatment (surface activation for hydriding) is then applied. Surface treatment may be achieved by any one of the following three preferred steps. First, one can expose the substrate to a solution of an inorganic metal salt. In this situation, as noted herein, the metal component of the metal salt is one that has a relatively lower activation energy for hydrogen adsorption than the substrate surface which will be activated. Examples of suitable salts include nickel chloride (NiCl2), cobalt nitrate [Co(NO3)2], copper chloride (CuCl2), palladium chloride (PdCl2)and organometallic salts such as 1,5-cyclooctadiene platinum II. It also should be noted that one of the advantages of surface treatment with metal salts is that after treatment and surface activation, upon exposure to hydrogen, the metal salts themselves are reduced to metal elements which facilitates hydrogen adsorption and diffusion to the substrate surface. A second procedure for surface activation for hydriding includes electroless deposition of a layer of the metal having the lower relative activation energy for hydrogen adsorption. Electroless deposition is reference to the use of a redox reaction to deposit the selected metal without the passage of an electric current. For example, Ag may be deposited according to the following reaction:R—CHO+2[Ag(NH3)2]OH→2Ag(s)+RCOONH4+H2O+3NH3 Accordingly, electroless plating may be conveniently employed herein to deposit metals as copper, nickel, silver, gold, or palladium on the substrate surface by means of a reducing chemical bath. This may then be followed by accelerated hydriding and evaluation of the hydriding on the underlying substrate. A third method for activation of a substrate surface for hydriding involves treatment of the substrate surface with a solution of a metal β-diketonate complex (metal acetylacetonate): It may be appreciated that M in the above formula may comprise transition metal identified in FIG. 1 wherein as noted above, the metal selected is one that has a relatively lower activation for hydrogen adsorption than the particular metal substrate at issue. Or, in the case, of a metal substrate that is of alloy composition (mixture of metals), M in the above is selected from a transition metal that has a lower activation energy for hydrogen adsorption than any one of the metals present in the substrate alloy. The value of n in the above formula is typically 3. One may therefore preferably employ iron acetylacetonates, nickel acetylacetonate, copper acetylacetonate or cobalt acetylacetonates. More specifically, one may preferably employ (1,5-cyclooctadiene) dimethyl platinum (II) or bis(1,5-cyclooctadiene) nickel (0). A Zircaloy-2™ alloy was selected as the substrate material and for comparison purposes. An electrochemical method was employed wherein the alloy was hydrided by cathodic charging followed by diffusion annealing. The annealing took place at a temperature of 400° C. for a period of two hours. FIG. 4 is a cross-section of the Zircaloy-2™ alloy after etching to highlight the hydride formation. A Zircaloy-2™ alloy was employed as the substrate. After the oxide layer was removed by acid etching as noted herein the clean Zircaloy-2 surface was activated by treatment of the substrate surface with a solution of a metal β-diketonate complex (metal acetylacetonate), as noted above. After hydriding at noted above, the surface layers were removed by polishing. Test samples were cut into shapes approximately 4 mm square and 0.5 mm thick, weighing about 40-50 mg. For characterization purposes, it is noted that differential scanning calorimetry (DSC) has been previously used to measure what it understood as the terminal solid solubility (TSS) of hydrogen over the temperature range of 50° C.-600° C. The TSS dissolution curve defines the temperature (TSSD) and hydrogen concentration condition for dissolution of hydrides on warmup. The precipitation curve defines the temperature (TSSP) and hydrogen concentration conditions for hydride precipitation on cooldown. See, The Terminal Solid Solubility Of Hydrogen in Irradiated Zircaloy-2 and Microscopic Modeling of Hydride Behavior, Une et al, Journal of Nuclear Materials 389 (2009) 127-136. FIG. 5 shows the DSC results for a blank Zircaloy-2 (no surface activation and no hydriding). FIG. 6 shows the results the Zircaloy-2 alloy treated with a nickel β-diketonate complex. An endothermic peak is observed at 279.4° C. which is assigned as the TSSP temperature. As an additional characterization procedure, one may employ weight loss by thermogravimetric analysis (TGA). Test specimens were run from room temperature to 1000° C. at 20° C./minute with a 100 ml/min nitrogen purge gas. FIG. 7 provides the results of TGA testing of a hydrided Zircoloy-2 alloy employing nickel as the activating metal. Hydriding was achieved by charging the surface with pure hydrogen in a pressurized tubular reactor for 3 minutes and then pressurized to 200 psig and heated to 300° C. for 12 hours. In FIG. 7, from 580 to 770° C., the weight loss was 0.08578%, or 857.8 ppm; from 750 to 1000° C., the weight loss was 0.06996%, or 699.6 ppm. In FIG. 8, hydriding initially took place in supercritical water in a pressurized tubular reaction pressurized to 200 psig and heated to 300 C for 12 hours. During the ensuing TGA analysis a weight loss was 0.5% was observed at the temperature range of 570-650° C. Weight losses at these ranges of temperatures are believed to be indicative of hydriding. Hydrogen analysis was next conducted along with one sample without surface activation. The results are summarized below for treatment of a Zircaloy-2 alloy: Measured Hydrogen Content Of Activated & Non-ActivatedZircaloy-2 ™ AlloysSurface Activation of Zircaloy-2 ™ AlloyHydrogen Content (ppm)Activation by dimethyl 1,5-cyclooctadiene476platinum (II) (CODPtMe2)Activated by PdCl235No Activation21 As can be seen from the above table, surface activation of the Zircaloy-2™ alloy by treatment of CODPtMe2 provided for relatively high hydrogen concentration after hydriding. Activation with PdCl2 was relatively lower, but still provided a higher hydrogen concentration of the non-activated Zircaloy-2™ alloy surface. The penetration of hydrogen into the bulk of a metal alloy causing embrittlement is an important metallurgical condition that is important to monitor and evaluation. The present invention confirms that in the case of an underlying metallic substrate, such as an alloy employed in as a cladding material in a nuclear power reactor, one may now accelerate the hydriding of such cladding at relatively low temperatures and at periods of less than or equal to a maximum of 24 hours in order to more effectively evaluate the effects of hydriding on cladding performance. As noted, since hydriding will tend to cause fracture and embrittlement, the present invention provides for the ability to more efficiently evaluate the operational performance of a given cladding material and provide for a more reliable prediction of expected cladding lifetime.
050646028	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with the present invention, flux-trap control rod 100 comprises four wings 102, two of which are shown in FIG. 1. Control rod 100 is accessed from above via handle 104, and is coupled from below to a hydraulic control rod drive with coupling socket 106, which may be released with coupling release handle 108. The hydraulic control rod drive raises, or lowers, control rod 100 to control the reactivity of the reactor core. Each wing 102 comprises an outer stainless steel sheath 110 with openings 112 that correspond to the openings in the hollow absorber tubes inside the sheath. When control rod 100 is in place in the reactor, water along its length is exchanged between the outside of the control rod and the inside of the absorber tubes. Openings 114 allow water to enter the bottom and leave the top of the absorber tubes through sheath 110. The flux-trap control rod 100 of the present invention has a cruciform configuration (looks like a "plus" sign (+) from above), as can be seen from FIG. 2. Each wing 102 contains three absorber tubes 200. These define four quadrants where fuel assemblies are located, indicated by dotted lines 202. A neutron-absorber tube 200 has water inlets 300, flux-trap control rod flow diverters 302, and an attachment portion 304, as shown in FIG. 3. The flow diverters 302 are made by cutting tabs out of absorber tube 200 while leaving integral attachment portions 304. The tabs are bent inwards until they touch the opposite wall of absorber tube 200, thus forming flow diverters 302, as well as inlets 300. In a preferred embodiment of the present invention, the absorber tube 200 is made of hafnium, and the inlets 300 and flow diverters 302 are rectangular. The size of the inlets 300 and flow diverters 302 may be varied to divert any, or virtually all of the water flowing up absorber tube 200. Neutron absorber tube 200 has outlets 400, as shown in FIG. 4. The outlets 400 oppose inlets 300, and are located directly beneath the point where flow diverters 302 touch the inner wall of absorber tube 200. The spacing and size of flow diverters 302 are such that the water flowing through absorber tube 200 is diverted through outlets 400 before it has a chance to boil. In a preferred embodiment of the present invention, the outlets 400 are circular. At least a portion of the water traveling up absorber tube 200 is diverted through outlets 400 by flow diverters 302. Inlets 300 are about the same size as outlets 400, which reduces pressure gradients. Control rod 100 has hafnium absorber tubes 200 with flat opposing sides and rounded ends as shown in FIGS. 3 and 4. The tubes are about 12' long, and made in two 6' sections with an expansion joint in between to accomodate temperature changes. The hafnium in the top section is 0.07" thick. In the bottom section it is half as thick, 0.035". Both sections have the same outer dimensions. The absorber tube 200 has a width of 1.35", and a thickness of 0.22". The radius of curvature at each of the corners is about 0.11". Inlets 300 are rectangular with widths of 0.4", and heights of 0.5" in the bottom section and 0.6" in the top section. Flow diverters 302 are 0.4" wide and 0.5" high in both sections. The inlets 300 in the top section are slightly larger than the flow diverters 302 because the hafnium is thicker than in the bottom section, and doesn't leave as large of an opening when bent to the opposite wall. Outlets 400 are circular with a 0.4" diameter. Inlets 300 and outlets 400 are spaced at 6 inch intervals along the length of the absorber tube 200, with the top of the outlets 400 located at the same spot the tab diverters 302 touch when bent. Rectanglular inlets 300 are preferred because the resultant flow diverters 302 remain flush with the opposite wall in an absorber tube 200, shaped as shown in FIGS. 3 and 4. Circular outlets 400 are preferred because they have the most area for a given perimeter, leaving absorber tube 200 more intact. FIG. 5 shows a cross-section of a single wing 102 of control rod 100 when operational, i.e., inside the reactor core, with the resultant water flow. Sheath openings 112 coincide with, and are slightly larger than, inlets 300 and outlets 400 in absorber tube 200. The difference in size is shown by the overlap portion 500 of absorber tube 200, and is there to take into account the difference in thermal expansion between hafnium and stainless steel. A small gap 504 also separates sheath 110 and absorber tubes 200 for this same reason. Water flow, indicated by arrows 502, is essentially parallel to flux-trap control rod 100. External water between control rod 100 and the fuel assemblies (located at dotted line 202) enters control rod 100 through inlet openings 300, and flows up absorber tube 200 to the next flow diverter 302, where it is at least partially diverted back outside through outlet openings 400. The active divergence of the water to the exterior of control rod 100 through outlets 400 causes more water to be drawn through the corresponding inlets 300. This is where the improvement lies when compared to the prior art passive exchange of water through simple openings. As can be seen in FIG. 5, flow diverters 302 are bent inwards until they touch the opposing wall of absorber tube 200 while remaining attached at attachment portion 304. Since the internal water is substantially replenished with external water at every flow diverter 302 as it travels up the flux-trap control rod 100, it does not reach saturation and boil. Thus its effectiveness as a neutron moderator is assured. In turn, absorber tube 200 has increased effectiveness as a neutron absorber, and the flux-trap control rods 100 of the present invention work reliably with a constant efficiency in a boiling water reactor operating at full power. FIG. 6 provides a general overview of the waterflow in a reactor pressure vessel equipped with control rods of the present invention. Inside pressure vessel 600 is reactor core 602. Waterflow 604 travels up through core 602 (using pumps, which are not shown) where it is partially converted to steam 606. Steam 606 goes through outlet 608, and is used to turn turbines which turns a generator to produce electricity. The steam is passed through a cooler, or "heat exchanger", to condense it to water, which enters pressure vessel 600 through inlet 610, where it rejoins reactor water 604. The reactor water that was not vaporized travels down the outside periphery of core 602 after it has emerged from the top, and repeats the cycle. Regions 612 in core 602 depict two control rod configurations (not to scale), each consisting of a control rod and its four associated fuel assemblies. Extensions 614 below pressure vessel 600 house the hydraulic drives that raise and lower the control rods. Diagonals 616 represent the locations of each set of twelve flow diverters along the length of each control rod configuration 612. The waterflow at the inlets and outlets associated with flow diverters 616 is shown respectively by arrows 618 and 620. Water 622 entering the bottom of control rod configurations 612 is continually exchanged between the interior and exterior of the twelve absorber tubes in each configuration 612 as it flows upwards, and boiling inside the absorber tubes is prevented. Although inlets and outlets are shown as rectangular and circular, respectively, other shapes can be employed. Moreover, rectangular flow diverters can have rounded vertical sides so the shape of flow diverters more closely approximates the internal cross-section of the absorber tube. Such an arrangement forces the exchange of more hot internal water for cooler external water at each of the intervals where inlets and outlets are located. Inlets can be trapezoidal, with a wide attachment portion to strengthen the flow diverters. Inlets and outlets with circular or oblong shapes tend to maximize area while minimizing perimeter, and thus tend to leave the absorber tube more intact for a given surface area. One advantage of the present invention is the amount of latitude there is in fitting the flux-trap control rod to the specific engineering and environmental constraints it may be exposed to inside the BWR. To avoid internal boiling under a given set of circumstances, the flow diverters may be made larger, relative to the internal cross-sectional area of the absorber tubes, and spaced further apart. Alternatively, the flow diverters can be smaller or spaced closer together. The ease with which the flow diverter configuration can be made to fit individual situations is inherent in the design of the present invention. An additional advantage of the present invention is the facility with which one can modify the flow diverters to accomodate variations in the internal and external water temperatures along the length of the absorber tubes. The spacing, shape, and/or size of the flow diverters can be varied along the length of each tube individually. The flow diverters may also be utilized with hafnium absorber tubes that have varying thicknesses along the length of the tubes, of the type mentioned in U.S. Pat. No. 4,882,123, and described above. The present invention thus provides a flux-trap design control rod for a boiling water reactor that is both effective in preventing internal boiling, and adaptable to external conditions. Flow diverters may also be utilized with absorber tubes that have various internal cross-sectional shapes. The present invention also provides for a range of embodiments not described above. The neutron absorbing material need not be hafnium, but can be any other suitable material. Likewise, moderators other than water are used in alternative embodiments. Flux-trap control rods of the present invention can be made with any combination of a liquid moderating material and bendable absorbing material. These and other modifications to and variations upon the described embodiments are provided for by the present invention, the scope of which is limited only by the following claims.
	description	The present application is a National Stage Application of International Application No. PCT/EP2009/067899 entitled “Method For Processing A Nitrous Aqueous Liquid Effluent By Calcination And Vitrification” filed Dec. 23, 2009, which claims priority of French Patent Application No. 08 59134, filed Dec. 30, 2008, the contents of which are incorporated herein by reference in their entirety. The invention relates to a method for treating a nitric aqueous liquid effluent generally containing in majority sodium nitrate with nitrates of metals or metalloids, which comprises a calcination step generally followed by a step for vitrification of the calcinate, calcine, obtained during said calcination step. The technical field of the invention may generally be defined as that of the calcination of liquid effluents, more particularly the technical field of the invention may be defined as that of the calcination of radio-active liquid effluents with view to their vitrification. The French method for vitrification of radio-active liquid effluents includes two steps. The first step is a step for calcination of the effluent during which drying and then denitration of a portion of the nitrates occurs, the second step is a vitrification step by dissolution in a confinement, containment, isolation glass of the calcinate produced during the calcination step. The calcination step is generally carried out in a rotating tube heated up to 400° C. by an electric oven. The solid calcinate is milled by a loose bar placed inside the rotating tube. During the calcination of certain solutions, in particular solutions rich in sodium nitrate, in other words solutions with a high sodium content in a nitric medium, adhesion of the calcinate on the walls of the rotating tube may be observed which may lead to total clogging of the tube of the calciner. The answer to this consisted of adding to the effluent a compound notoriously known to be non-tacky, aluminium nitrate, in order to allow their calcination while avoiding clogging of the calciner. But this aluminium nitrate added to the effluent increases the amount of glass to be produced. Indeed, the presence of alumina in the glass increases its elaboration temperature and leads to limiting the load level of the waste, effluent in the glass, so as not to degrade the confinement, containment properties of this glass. The aluminium content in the glass should therefore not be too high and is generally limited to about 15% by mass expressed as Al2O3. The amount of aluminium nitrate to be added is moreover difficult to optimize, thus for each new effluent, several tests are necessary for determining the operating calcination conditions in the heated rotating tube with which tube cloggings may be avoided. Especially, the heating of the calcination oven and the amounts of calcination adjuvant which is different from the dilution adjuvant and which is very often sugar, have to be adjusted. Therefore, considering the foregoing, there exists a need for a method for treating by calcination a nitric aqueous effluent containing compounds, such as nitrates of metals or metalloids and other compounds, which may form tacky oxides during their calcination, which gives the possibility of avoiding adhesion of the calcinate, calcine, on the walls of the calcination tube and clogging of this calcination tube and which simultaneously limits the increase in the amount of confinement, containment glass to be produced during the vitrification of the calcinate. More particularly, there exists a need for a method for treating effluents which may cause adhesion during, upon, their calcination, applying a dilution adjuvant, which while avoiding the adhesion of the calcinate on the walls of the calcination apparatus and clogging of the latter, in at least one way as efficient as with aluminium nitrate, does not increase like the latter, the amount of glass to be produced, and does not limit the waste load level of the glass. There especially exists a need for a method for treating effluents containing compounds, such as nitrates of metals or metalloids and other compounds, generating tacky oxides during, upon, their calcination, in particular solutions with a high sodium nitrate content, which avoids clogging of the calcination tube and decreases the requirements, constraints imposed on the glass-making formulation, these requirements, constraints being due to the provision of aluminium in the form of aluminium nitrate in the calcination adjuvant. The goal of the present invention is to provide a method for treating a nitric aqueous liquid effluent containing metal or metalloid nitrates, this method comprising a step for calcination of the effluent in order to convert the metal or metalloid nitrates into their oxides which i.a. meet the needs mentioned above. The goal of the present invention is further to provide such a method which does not have the drawbacks, limitations, defects and disadvantages of the methods of the prior art and which solves the problems of the methods of the prior art, especially of the methods using aluminium nitrate as a dilution adjuvant. This goal, and further other ones are achieved, according to the invention with a method for treating a nitric aqueous liquid effluent containing nitrates of metals or metalloids, comprising a step for calcination of the effluent in order to convert the nitrates of metals or metalloids into oxides of said metals or metalloids, at least one compound selected from the nitrates of metals or metalloids and the other compounds of the effluent leading upon, during, calcination to a tacky oxide, and a dilution adjuvant leading upon, during, calcination to a non-tacky oxide, being added to the effluent prior to the calcination step, a method wherein the dilution adjuvant comprises aluminium nitrate and at least one nitrate selected from iron nitrate and rare earth nitrates. Advantageously, the dilution adjuvant consists of aluminium nitrate and of at least one other nitrate selected from iron nitrate and rare earth nitrates. The method according to the invention is fundamentally characterized by the application, use, during, upon, calcination, of a particular dilution adjuvant which comprises in addition to aluminium nitrate, at least one specific nitrate selected from iron nitrate and rare earth nitrates. The use of iron nitrate or of a rare earth nitrate in a dilution adjuvant added to a nitric aqueous liquid effluent prior to the calcination of this effluent has hitherto never been mentioned nor brought up. Surprisingly it was found that iron nitrate and rare earth nitrates had properties for limiting the adhesion of the calcinate, close to those of aluminium nitrate, but that the oxides derived from said specific nitrates, which are so-called “non-tacky”oxides may also be dissolved into the final glass produced during the subsequent vitrification step. The application of a dilution adjuvant comprising a nitrate selected from iron nitrate and rare earth nitrates as a substitution for a portion of the aluminium nitrate therefore gives the possibility of avoiding clogging of the tube of the calcination apparatus during, upon the calcination of effluents generating very tacky oxides, such as solutions with a high sodium content, while minimizing the increase in the amount of confinement, containment glass to be produced during the vitrification step which generally follows calcination. It may be stated that, surprisingly, iron nitrate and rare earth nitrates all have the excellent properties of aluminium nitrate as to its capability of limiting adhesion of the calcinate, and therefore as regards avoiding clogging of the calcination tube, and have an advantage as regards the reduction in the amount of glass to be produced and the increase in the load level of waste incorporated into the glass. The constraints, requirements imposed on the glass-making formulation by the dilution adjuvants according to the invention comprising, as a substitution for a portion of the aluminium nitrate, at least one specific nitrate selected from iron nitrate and rare earth nitrates, are significantly reduced with respect to the dilution adjuvants only consisting of aluminium nitrate because of the lower or even zero provision of aluminium. The rare earth nitrates are generally to be selected from lanthanum nitrate, cerium nitrate, praseodymium nitrate, and neodymium nitrate; and therefore the dilution adjuvant may advantageously comprise aluminium nitrate and at least one other nitrate selected from iron nitrate, lanthanum nitrate, cerium nitrate, praseodymium nitrate and neodymium nitrate. Still advantageously, the dilution adjuvant consists of aluminium nitrate and of at least one other nitrate selected from iron nitrate, lanthanum nitrate, cerium nitrate, praseodymium nitrate and neodymium nitrate. A more preferred dilution adjuvant according to the invention consists of aluminium nitrate and iron nitrate. Another more preferred dilution adjuvant according to the invention consists of aluminium nitrate, lanthanum nitrate, neodymium nitrate, cerium nitrate and praseodymium nitrate. The respective amounts of each of the aluminium, iron and rare earth nitrates are free from the point of view of their efficiency for preventing adhesion of the calcinate in the tube and may therefore be adjusted according to their impact on the properties of the confinement, containment glass prepared in a subsequent vitrification step. The amount of dilution adjuvant added to the liquid effluent depends on the tacky compounds contents of the liquid effluent (nitrates and/or other compounds), expressed in terms of oxides, on the total mass of the nitrates (or possibly, more specifically, of the total mass of the salts), also expressed in terms of oxides, contained in the effluent. Generally the effluent mainly consists of a mixture of nitrates of metals and metalloids with a majority of sodium nitrate and may also contain an amount of aluminium, iron and rare earth nitrates in insufficient levels for avoiding clogging of the tube during, upon, the calcination step. The effluent may also contain “tacky”or “non-tacky”compounds which are not nitrates, generally present as salts, such as phosphomolybdic acid which is a so-called “tacky”compound. The method according to the invention because of the application of the specific dilution adjuvant mentioned above allows calcination without clogging of all kinds of effluents, regardless of their nature and of the nature of the nitrates and tacky nitrates which are contained therein. The liquid effluent treated by the method according to the invention contains at least one compound such as a metal or metalloid nitrate leading upon, during calcination to a so-called “tacky”oxide, such as sodium nitrate, and/or another compound (which is not a nitrate) leading during calcination to a so-called “tacky”oxide. In the present description, the terms of “tacky compounds”, “tacky oxides”or else “tacky nitrates”are used. By “tacky compounds”, “tacky nitrates”or “tacky oxides”are meant compounds, oxides, nitrates known for adhering to the walls of calcination apparatuses, “calciner”, and inducing clogging phenomena of these calciners. The terms of “tacky compounds”, “tacky oxide”, “tacky nitrate”are terms currently used in this technical field, which have a well established meaning, which are known to the man skilled in the art and have no ambiguity for him. Thus, the compound(s), such as nitrate(s) and/or other compound(s), which, upon, during calcination lead(s) to tacky oxide(s) may be selected from sodium nitrate, phosphomolybdic acid, boron nitrate and mixtures thereof. The content of compound(s), such as this(these) nitrate(s) and other compound(s) leading during calcination to “tacky”oxide(s), in the effluent, expressed as oxide, based on the total mass of the salts, including the nitrates, contained in the effluent, also expressed as oxides, is generally greater than 35% by mass. Indeed the method according to the invention in particular, gives the possibility of calcination of effluents having a high content of nitrates and other compounds, so-called “tacky compounds”, i.e. greater than 35% by mass expressed as oxides. In a particularly advantageous way, the method according to the invention allows calcination of solutions with a high sodium content, which are highly tacky. By “high content”of sodium, more specifically of sodium nitrate, is generally meant that the effluent has a sodium nitrate content expressed as a sodium oxide Na2O, based on the total mass of the salts, including the nitrates, contained in the effluent, expressed as oxides, greater than 30% by mass, preferably greater than 50% by mass. The conditions of the calcination step are known to the man skilled in the art in this technical field and may easily be adapted depending on the nature of the treated effluents. The conditions of this calcination, except for the notable fact that any clogging is avoided, are not fundamentally modified by applying the specific calcination adjuvant according to the invention. The conditions of the calcination are generally the following: temperature reached by the calcinate of about 400° C., speed of rotation of the tube 10 to 40 rpm, addition of a calcination adjuvant for example of the sugar type. This calcination step is generally carried out in a heated rotating tube, for example a rotating tube heated by an electric oven with several independent heating areas. Some heating areas are more particularly dedicated to evaporation and other ones to calcination. The calcination areas allow the calcinate to be heated to a temperature of about 400° C. The speed of rotation of the tube, the addition of the calcination adjuvant and the presence of a loose bar allow the solid calcinate to be split up so that the latter may react under good conditions in the vitrification unit. The treatment method according to the invention generally comprises after the calcination step, a step for vitrification of the calcinate obtained during this calcination step. This vitrification step consists in a reaction between the calcinate and a glass frit (preformed glass) in order to obtain a confinement, containment glass. In other words, after the calcination step, a vitrification step is carried out which consists of elaborating a confinement glass from the melting of the calcinate produced during the calcination step with a glass frit. As this was already specified above, the application in the dilution adjuvant of specific nitrates of iron and of rare earths gives the possibility of relaxing the constraints, requirements, as to the formulation of the glass. In particular, it is possible to incorporate a greater proportion of effluent into the glass when the calcinate was obtained by using the dilution adjuvant according to the invention in the place of and instead of a dilution adjuvant only consisting of aluminium nitrate. In other words, the restricting limit on the incorporation level of effluents in the glass, due to aluminium nitrate, is suppressed and the incorporation level is significantly increased and for example passes from 13% by mass of oxides to 18% by mass of oxides, based on the total mass of the glass. Further, the significant provision of aluminium in the case of a dilution adjuvant only consisting of aluminium nitrate tends to harden the calcinate and has the consequence of causing lowering of the reactivity between the calcinate and the glass frit in the vitrification oven. On the contrary, addition of iron makes the calcinate more friable and therefore more easy to vitrify. The vitrification consists in a melting reaction between the calcinate and the glass frit in order to form a confinement, containment, glass. It is carried out in two types of oven: indirect induction ovens which consist of heating with four inductors a metal pot, can, into which the frit/calcinate mixture is fed, and direct induction ovens which consist of heating the glass with an inductor through a cooled structure (cold crucible) which lets through a portion of the electromagnetic field and into which the frit/calcinate mixture is fed continuously. The invention will now be described with reference to the following examples given as an illustration and not as a limitation. In this example, vitrification of the calcinate obtained in the comparative example 1 is carried out. Let us recall that this calcinate was prepared by using an adjuvant (“adjuvant No. 1”) only consisting of aluminium nitrate. The elaboration of a glass from the calcinate and from a glass frit containing 1% by mass of alumina, the proportion of frit in the glass being of 77.43%, leads to a 11.6% maximum incorporation level of the initial waste into the glass by the following calculation ((100−51,27))*(13−1)/(51,27−1)). In this example, the calcination of the same effluent as the one in Example 1 and described in Table 1 is carried out. An adjuvant (adjuvant 2) according to the invention which consists of 75% by mass of aluminium nitrate expressed as oxide Al2O3 and of 25% by mass of iron nitrate expressed as oxide Fe2O3 is added to this effluent. The conditions of this calcination are the same as those of example 1. TABLE 1WasteAdjuvant 1Adjuvant 2Compound(mass %)(mass %)(mass %)Al2O3100.0075.00BaO2.98Na2O56.43Cr2O30.56NiO0.48Fe2O31.6325.00MnO21.61La2O30.44Nd2O33.45Ce2O36.24ZrO28.23MoO35.71P2O53.49RuO21.00B2O36.13SO31.61100.00 In this example, it is proceeded with vitrification of the calcinate obtained in Example 2 according to the invention. Let us recall that this calcinate was prepared by using an adjuvant (“adjuvant No. 2”) consisting of 75% by mass of aluminium salt and of 25% by mass of iron salt. It was determined that the maximum incorporation level of the initial waste (therefore before mixing) is limited to 11.6% of the mass of the glass in the comparative example 3, while in Example 4, the maximum incorporation level is 15.6%. Further, the substantial provision of aluminium by the adjuvant No. 1 tends to harden the calcinate and has the consequence of causing a slight lowering of reactivity between the calcinate and the glass frit in the vitrification oven. On the contrary, providing iron with the adjuvant No. 2 according to the invention, makes the calcinate more friable and therefore more easy to vitrify. In this example, the calcination of an effluent is described, consisting of 100% sodium nitrate as described in Table 2. In a first experiment, an adjuvant (adjuvant 1) of the prior art which consists of 100% by mass of aluminium nitrate expressed as oxide Al2O3 is added to this effluent. In a second experiment, the calcination of the sodium nitrate was carried out with an adjuvant (adjuvant 3) according to the invention in which a portion of the aluminium nitrate was replaced with a mixture of lanthanum, cerium, neodymium and praseodymium nitrates. For both cases, the sodium nitrate content expressed as a total mass of oxide represents 30% in the mixture of the effluent with the dilution adjuvant. The calcination conditions are the following: Calciner with two independent heating areas, the temperature reached by the calcinate is about 350° C., the speed of rotation of the rotating tube containing the loose bar is 35 rpm, the calcination adjuvant content is 20 g/L of the mixture of the effluent with the dilution adjuvant. TABLE 2EffluentAdjuvant 1Adjuvant 3(%)(%)(%)Na2O100Al2O310038.05La2O38.65Nd2O328.56Ce2O316.78Pr2O37.95
	summary
	summary
	description	This disclosure relates to a nuclear fuel composition for rendering the fuel inherently subcritical. Compact nuclear reactors may be used in vehicles, such as aerospace vehicles, as a power plant to propel the vehicle and/or to run the vehicle operating systems. In the event of a vehicle accident, the reactor may lose coolant and become exposed to foreign materials, such as water, sand, or other substances. Under such conditions, current nuclear fissile fuels for thermal and epithermal reactors would be expected to reach nuclear criticality. The use of thermal and epithermal nuclear reactors in vehicles is therefore limited. An example nuclear fuel composition includes a nuclear fissile material and a neutron-absorption material that adjoins the nuclear fissile material. The nuclear fuel composition may be used in a nuclear reactor, such as a thermal reactor. An exemplary method of rendering a nuclear fuel inherently subcritical includes forming the nuclear fuel from a nuclear fissile material and a neutron-absorption material that adjoins the nuclear fissile material. The neutron-absorption material has a neutron absorption energy range that overlaps a thermal energy range of neutrons from the nuclear fissile material to render the nuclear fuel inherently subcritical. FIG. 1A schematically illustrates an example nuclear fuel 20 that may be used in a nuclear reactor, such as a compact epithermal or thermal reactor, for vehicles, aerospace applications, or other uses. As will be described, the composition of the nuclear fuel 20 renders the fuel inherently subcritical, such that if there is an incident that exposes the core of the reactor to outside substances, such as water and sand, the fuel remains subcritical. As an example, the current U.S. aerospace nuclear safety posture requires reactors to remain subcritical in accidents, which has been achieved for fast reactors but not thermal or epithermal reactors. The composition of the nuclear fuel 20 includes a nuclear fissile material 22 and a neutron-absorption material 24 that adjoins the nuclear fissile material 22 to render the fuel inherently subcritical. That is, the neutron-absorption material 24 is in contact with or directly contiguous with the nuclear fissile material 22, which facilitates absorption of neutrons from the nuclear fissile material 22. The nuclear fissile material 22 may be any of a variety of different types of fissile material. For instance, the nuclear fissile material 22 may be a uranium-based material, such as a uranium hydride or uranium oxide. In one example, the nuclear fissile material 22 is uranium-zirconium-hrdride (UZrHx) and it is used in combination with a sodium-potassium coolant (e.g., NaK-78). In this case, the neutron-absorption material 24 may also be a hydride. The composition of the nuclear fuel 20 may include only a small, effective amount of the neutron-absorption material 24, to avoid poisoning the reactivity of the nuclear fissile material 22. For instance, based on the total combined weight of the neutron-absorption material 24 and the nuclear fissile material 22, the nuclear fuel 20 may include ≦0.5 wt % of the neutron-absorption material 24. In some examples, ≦0.1 wt % of the neutron-absorption material 24 is effective to achieve inherent subcriticality and in further examples ≦0.05 wt % of the neutron-absorption material 24 is needed to achieve inherent subcriticality. For uranium hydride type nuclear fissile materials, the amount ≦0.05 wt % may be effective. The neutron-absorption material 24 may be a composite of several elements. For instance, the neutron-absorption material 24 may include samarium and a rare earth element, such as gadolinium. The samarium and gadolinium function as neutron absorbers. However, in high amounts, gadolinium destroys the negative temperature coefficient of reactivity of the nuclear fissile material 22. Thus, samarium serves as a substitute for a portion of the gadolinium. That is, samarium has a neutron-absorption energy peak (cross-section) that at least partially overlaps the thermal energy range of the neutrons (e.g., in the range of approximately 0.025 eV) from the nuclear fissile material 22 (e.g., see FIG. 1B). Thus, the samarium functions as an effective neutron absorber in addition to the gadolinium, while avoiding destroying the negative temperature coefficient of reactivity of the nuclear fissile material 22. The composition of the neutron-absorption material 24 may include 25 wt %-75 wt % of samarium and a remainder of the rare earth element. Although gadolinium is disclosed, it is contemplated that other rare earth elements may also be useful. In further examples, the composition of the neutron-absorption material 24 may include 30 wt %-40 wt % of the samarium and a remainder of gadolinium, or even 35 wt %-38 wt % of the samarium and a remainder of gadolinium. The amount 35 wt %-38 wt % of samarium provides a desirable balance of the neutron-absorbing properties of samarium without high levels of gadolinium that can destroy fissile reactivity. In the illustrated example, the neutron-absorption material 24 is mixed with the nuclear fissile material 22 to form a composite as the nuclear fuel 20. In this case, the neutron-absorption material 24 is relatively uniformly dispersed through the nuclear fissile material 22. The neutron-absorption material 24 may be mixed with the nuclear fissile material 22 using the same techniques that are used to mix other additives with fissile materials, such as moderators. The nuclear fuel 20 may then be provided in a known manner in the form of a pellet for use in a nuclear reactor. FIG. 2 illustrates a modified example of a nuclear fuel 120. In this disclosure, like reference numerals designate like elements where appropriate and reference numerals with the addition of one-hundred or multiples thereof designate modified elements that are understood to incorporate the same features and benefits as the corresponding original elements. In this case, the neutron-absorption material 124 is provided as a coating on the nuclear fissile material 122. For instance, the nuclear fissile material 122 may be a pellet that is coated on a portion or all of its peripheral surfaces with the neutron-absorption material 124. The neutron-absorption material 124 may be deposited by vapor deposition or other suitable method. Additionally, the thickness of the coating of neutron-absorption material 124 may be controlled such that on a weight percentage basis, the nuclear fuel 120 includes an amount of the neutron-absorption material 124 as described above with reference to FIG. 1. FIG. 3 illustrates another example nuclear fuel 220 that is somewhat similar to the example of FIG. 2. In this case, the nuclear fissile material 222 is contained within a hollow cladding 226. The neutron-absorption material 224 is disposed on an inner surface 228 of the hollow cladding 226 such that the neutron-absorption material 224 adjoins the outer peripheral surfaces of the nuclear fissile material 222, which may be provided as pellets within the hollow cladding 226. As an example, the neutron-absorption material 224 may be deposited by vapor deposition onto the inner surface 228 of the hollow cladding 226 or “painted” on in mixture with a carrier solvent that evaporates to leave the neutron-absorption material 224. FIG. 4 illustrates an example nuclear reactor 340 that may employ the nuclear fuel 20, 120 or 220. The nuclear reactor 340 is shown with the nuclear fuel 20. However, it is to be understood that the nuclear fuel 120 or 220 may alternatively be used. The nuclear reactor 340 is a thermal reactor for use in an aerospace vehicle, for example. The nuclear fuel 20 is located within a moderator 342. The nuclear fuel 20 and moderator 342 are contained within a vessel 344 that may prevent the escape of radiation. A coolant system 346 circulates a coolant, such as water or NaK-78, through the core in vessel 344 to heat the coolant for a downstream use, such as power generation. Control rods 348 may be used to moderate the power output in a known manner. Additionally, other components, such as reflectors, etc., may also be used, depending upon the particular implementation. Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments. The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.
	abstract	A container for the consolidation of waste materials including radioactive containing waste, and a method of consolidating such materials. The container comprises an outer cylinder and an inner cylinder comprising internal compression plates that are designed to resist collapse during consolidation, and therefore control the size of the consolidated container to a predictable shape and dimension. The container is sufficient to hold a variety of materials, including hazardous, toxic, or radioactive waste, and the container is configured to hold such waste without releasing it to the environment.
060350113	claims	1. A reactor core for a boiling water nuclear reactor which includes four vertical fuel assemblies positioned around a control rod having arms that provide said control rod with a cruciform cross section, each of said four fuel assemblies being surrounded by a first and a second pair of gaps arranged transversely to and adjacent each other, which during reactor operation are filled with water, said first pair of gaps being adapted to encase two arms of said control rod, each fuel assembly containing a plurality of fuel rods containing enriched nuclear fuel material, said fuel rods being arranged between a bottom tie plate and a top tie plate, wherein at least one fuel assembly comprises a substantially pentagonally formed fuel channel with, in a cross section, four relatively long side portions and one relatively short side portion, said short side portion facing said second pair of gaps where they transversely communicate with each other. 2. A reactor core according to claim 1, wherein at least one of said four fuel assemblies comprises an integrally arranged channel in the form of a hollow tubular member connected to said top and bottom tie plates for conducting water in a vertical direction from the bottom tie plate upwards through the core. 3. A reactor core according to claim 2, wherein said internally arranged channel is a sub-channel-forming support member of cruciform cross-section spacing apart four sub-bundles of fuel rods within said one fuel assembly from each other, said cruciform support member constituting a central water passage in the space defined by removing one fuel rod from each of the corner portions of said sub-bundles directed towards the centre of a fuel channel box. 4. A reactor core according to claim 1, wherein said first pair of gaps are wider than said second pair of gaps and encase said two arms of a control rod. 5. A reactor core according to claim 1, wherein enrichment contents A in a fuel rod arranged adjacent to a centre of said control rod and the enrichment content B in the fuel rods arranged adjacent to said short side portion of the fuel channel is in accordance with the formula B=A.times.Fk(Fs(a/b-1)+1), where 0.72.ltoreq.Fk.ltoreq.0.92, Fs=0.72, a is a gap width of said first pair of gaps, and b is a width of said second pair of gaps. 6. In a boiling water nuclear reactor which includes a reactor core containing a plurality of vertical fuel assemblies, each fuel assembly including a bottom tie plate, a top tie plate, an outer channel, and a plurality of fuel rods within the outer channel and extending between said bottom and top tie plates, each fuel assembly being surrounded by first and second pairs of gaps arranged transversely to and adjacent each other, said gaps being filled with water when said reactor is operating, and a control rod having a cruciform cross section, two arms of which are located in said first pair of gaps, the improvement wherein the outer channel of one of said fuel assemblies has five sides, four of said five sides having a greater width than a fifth of said five sides, said fifth side facing said second pair of gaps where said second pair of gaps transversely communicate with each other.
056489951	abstract	The method serves to manufacture tubes for constituting sheaths for nuclear fuel rods. A bar is made out of a zirconium-based alloy containing 50 ppm to 250 ppm iron, 0.8% to 1.3% by weight niobium, less than 1600 ppm oxygen, less than 200 ppm carbon, and less than 120 ppm silicon. The bar is heated to a temperature in the range 1000.degree. C. to 1200.degree. C. and is quenched in water. A blank is extruded after heating to a temperature in the range 600.degree. C. to 800.degree. C. and cold-rolled in at least four passes in order to obtain a tube, with intermediate heat treatment being performed between passes at temperatures in the range 560.degree. C. to 620.degree. C. A final heat treatment is performed at a temperature in the range 560.degree. C. to 620.degree. C., all of the heat treatments being performed under an inert atmosphere or a vacuum.
	abstract	A ratio of the number of fuel assemblies loaded on a core to the number of control rod drive mechanisms is 3 or more. The fuel assembly itself contains mixed oxides of a low enrichment concentration uranium oxide containing 3 to 8 wt % in the average enrichment concentration of the fuel assembly, or mixed oxide containing not less than 2 wt %, but less than 6 wt % in the average enrichment concentration of fissile plutonium of. In the burner type BWR core on which the fuel assemblies are loaded, an average weight density of uranium, plutonium and minor actinides is 2.1 to 3.4 kg/L as a conversion at the value of unburned state.
	summary
	description	This invention was made with government support under Management and Operating Contract No. DE-AC05-06OR23177 awarded by the Department of Energy. The United States Government has certain rights in the invention. The present invention relates to radiation collimators and gamma and x-ray photon systems as applied to medical radiology and nuclear medicine. In radiation imaging, collimators are used to limit the passage of radiation beams to a specific angle in order to minimize detection of beams of scattered or secondary radiation. Single angle collimation provides 2-dimensional (2D) projection of radiation sources on an imager while the combining of multi angle projections provides 3-dimensional (3D) position of radiation sources by image reconstruction techniques. Hence, it is more desirable to achieve 3D images particularly in clinical nuclear imaging. Devices have been proposed for multi angle projection imagers using multiple detectors at different positions, or by moving the position of a single detector, or by fixing the location of a detector and using multiple collimators each of which has a different collimation angle. It is not always feasible to combine aspects of these methods due to physical interference with the imaging target. Previously proposed multi angle collimators typically include either variable angle slant hole (VASH) collimators or multi-view collimators. Although the VASH provides an adjustable angle of collimation, the reported alignment mechanism of the multiple leaves clearly does not provide accurate alignment of each leaf, thereby resulting in a reduced size of the openings and an inaccurate collimation angle that reduces the output image quality. Accordingly, it would be desirable to provide a multiple leaf collimator in which the openings are accurately aligned, that maintains a constant collimation angle, and thus achieves high output image quality. It is therefore an object of the present invention to provide a variable angle slant hole (VASH) collimator that enables accurate tomographic acquisition by multiple angle projection while the detector remains stationary. A second object is to provide a multiple leaf collimator that provides multiple views through the breast, thyroid, heart, or similar body part. A further object of the invention is to provide an improved VASH actuation device that eliminates mechanisms adjacent the patient. The compact nature of the multi-leaf collimator collimator and the fact that the mechanism can be positioned under covers on the side of the detector, away from the patient, makes it inherently safer to operate. This contributes greatly to the physical and emotional comfort of the patient. This is a significant improvement over prior mechanisms that use knife edge actuators, such as in breast imaging, in which the breast must be positioned between two knife blades. A further object of the invention is to provide a multi-leaf collimator in which the openings can be maintained at a constant collimation angle and thus achieves high output image quality. A further object of the invention is to provide a multi-leaf collimator that eliminates the need to rotate the detector. A further object of the invention is to provide a multi-leaf collimator that can be adjusted to various viewing angles very quickly and with a high degree of precision. A further object of the invention is to provide a multi-leaf collimator in which the aperture alignment is maintained and the motor doesn't strain when the collimator stack is turned vertically. A further object of the invention is to provide a collimator in which the viewing angle can be changed very quickly to limit the radiation dose to the patient while acquiring the data for tomographic imaging. A further object of the invention is to minimize the amount of time for acquiring multiple angle views of a patient that has been administered a radioisotope. A further object of the invention is to provide a variable angle slant hole collimator that is compact in size to enable easy handling and turning to different orientations with respect to the patient. A variable angle slant hole (VASH) collimator provides collimation of high energy photon such as gamma ray used for radiological imaging of human. The VASH collimator is consist of multiple collimator leaves and alignment of each leave can provide various projection angles. Rather than rotate the detector around the subject, the VASH collimator allows tomographic acquisition while the detector remains stationary by multiple angle projection. An accurate alignment of leaves is required to provide maximum collimation efficiency. Individual leaf has own angled cut on each side and face matching wedge blocks driven by two actuators with twin-lead screws is providing an accurate position of each leaf resulting target collimation angle. Continuous collimation angle can be achieved by position control of wedge block. With reference to FIG. 1, the present invention is a compact and efficient multi-leaf variable angle slant hole (VASH) collimator 10 in which the viewing angle of the apertures can be rapidly and accurately changed to provide various projection angles for 2-dimensional (2D) and 3-dimensional (3D) image reconstruction techniques. The VASH collimator 10 includes a frame 12 with opposing sides 14, opposing ends 16, and a front panel 18 with an opening 20 therein. A means 22 for positioning a plurality of collimator leaves (not shown) includes two motors 24 coupled by a gearbox 26 to a lead screw 28 at each end of the frame 12. Two stack alignment rails 30, which will serve as guides for a stack of collimator leaves, extend along each side 14 of the frame. Two end bearings 32 positioned in each end of the rails 30 form paired end bearings that are axially aligned and enable rotation of the lead screws 28 with respect to the rails and frame. Two wedge blocks 34 are positioned on each lead screw 28 at the two ends 16 of the frame 12. The wedge blocks 34 include an inner end 36 and an outer end 38. A drive nut 40 is embedded in each wedge block to accommodate the screw threads of the lead screws 28. The outer end 38 of each wedge block 34 includes set screws 42 for locking each wedge block to its respective drive nut 40. A pillow block 44 supports each lead screw approximately mid-way between the two end bearings 32. Each wedge block 34 includes a clearance notch 46 for accommodating the pillow blocks 44 at full inward travel of the wedge blocks. A side mount 48 extends from one side 14 of the frame 12 and includes two bores 50 therein to accommodate attachments for imaging specific body parts, such as compression paddles (not shown) for breast imaging. One of the rails 30 includes two brackets 52 for mounting of the gearboxes 26 and motors 24 thereto. Referring to FIG. 2, a coupler 54 including one or more screws 56 secures each motor 24 and gearbox 26 to their respective lead screw 28. A plurality of substantially planar leaves, of which the top leaf 58 having a face 60 is visible, are stacked against the front panel 18 to form a stack 61 of leaves. An array 62 of apertures 64 are arranged in an identical pattern in each of the leaves 58, with the leaves capable of alignment in an initial position wherein the apertures 64 in the leaves are axially aligned with one another and at 90° with respect to the face 60 of the top leaf. Each leaf 58 includes sides 66 and ends 68. The rails 30 maintain the contact with the sides 66 of the leaves 58 thus keeping the stack of leaves in alignment. The ends 68 of each leaf 58 include an angled cut 70 that is unique to that leaf. Most preferably the angled cut 70 on the ends of the leaves includes a substantially central apex 72 and two angled surfaces 74 extending to the sides 66 of each leaf. The bottom leaf (not shown) is preferably not angled, but includes ends that are at 90° with respect to its sides. A computer interface 76 may be used for controlling and synchronizing the direction of rotation of each of the motors 24 to change the position of the leaves 58 and thus the alignment of the apertures 64 to a desired slant angle. A stack cover plate 77 extends from each wedge block 34 and maintains the stack 61 of leaves 58 in place on the frame 12. Preferably, with reference to FIG. 3, a reverse thread is included on the shaft of the lead screws 28 on opposing sides of the pillow block 44, such as the screw threads on one half of the lead screws are right-hand threaded 78a and the screw threads on the opposing half of the lead screws are left-hand threaded 78b. Referring to FIGS. 4 and 5, each wedge block 34 includes a wedge body 80 having a flat bottom surface 82, two sides 84, a top 86, and a first end 88 second end 90. The bottom surface 92 is at 90 degrees with respect to the sides 84 and the first end 88 is cut with a desired angle. A stepped edge 92 is provided on the first end 88 of the wedge block. Preferably, the length L of each step 94 in the stepped edge matches the thickness of a corresponding leaf in the stack of leaves held by the frame 12. The wedge block 34 further includes a side bore 96 for accommodating the drive nut 40 and two apertures 98 for screw attachment of the cover plate 77 (see FIG. 2). FIGS. 6-8 depict the actuation mechanism of the VASH collimator 10 including movement of the top leaf (FIG. 6), movement of the middle leaf (FIG. 7), and a side view of multi-leaf motion (FIG. 8). The top leaf 58 and middle leaf 101 have different side profiles, with the top leaf 58 including a length d and the middle leaf 101 including a length d/2, resulting in a displacement of x and x/2 for the two leaves, respectively. A continuous slant angle can be achieved by positioning of the four wedge blocks 34. The bottom leaf with a straight side does not move. The other leaves have an angled cut and the tangent value of each angle is a linear step to make the stepped displacement linear. The sliding wedge blocks 34 each include a stepped profile with each step being the same thickness as a corresponding leaf so that there is no gap between the sliding wedge 34 and the side of each leaf as shown in FIG. 8. This will provide a maximum efficiency for wedging motion. The desired angle of the slant hole collimation is selected by moving the four sliding wedges 34, such that the motion moves each leaf in one direction with a different displacement. As shown in FIG. 1, the two wedge blocks 34 on each end 16 are moving in opposite directions of each other by the rotation of the twin-lead screw 28. At the same time, the two wedge blocks 34 on the opposing end 16 are moving in the opposite direction of those on the first end in order to compensate leaf motion. There is a pillow block 44 at the middle of each twin-lead screw to prevent bending of the lead screws 28. Each wedge block 34 has a cover plate 77 to ensure all leaves are stacked at the same height as the wedge blocks 34. Accurate motion and counter motion of the wedge blocks 34 at each end 16 of the VASH collimator provides an exact amount of space for each leaf resulting in an accurate positioning and setting of the collimation angle for all the apertures in the leaves. The range of slant angles is determined by the cut profile of opposing sides of each leaf, the matching profile for the sliding wedge block 34, and by the sliding/travel range of the wedge blocks. Since the displacement by wedge motion of each leaf is continuous, the collimation angle can be set continuously within a pre-defined range. On one end 16 of the leaves, the two wedges 34 are moving in opposite direction of those on the opposing end of the leaves to balance the force. Actuators for the twin-lead screws 28 are driven by a motor 24 with a high ratio gear box 26. The present invention further includes a method for aligning a collimator, the method including: a. providing a frame including side rails, and two ends; b. providing twin lead screws, two wedge blocks on each lead screw, coupling nuts, and a plurality of leaves with an array of apertures therein; c. moving the wedge blocks and coupling nuts to the side rails of the frame; d. fixing the wedge blocks to the coupling nuts; e. stacking the leaves in the frame to form a multi-leaf stack; f. adjusting the position of two wedge blocks on a first end of the frame toward each other until they are in contact with each other; and g. moving the four wedge blocks in the desired direction with the desired distance, at the same speed, for setting the slant angle of the multi-leaf stack. Preferably the leaves 58 and the frame 12 are constructed of tungsten primarily for its ability to stop radiation penetration, and also for non-dulling properties, abrasion resistance, and mechanical strength. Preferably the apertures 64 are photo-etched square holes, but may be hexagonal or circular shaped. The size of the apertures can be selected for the desired levels of sensitivity and resolution, with larger apertures leading to higher sensitivity but lowering the resolution. The thickness of the leaves may also be selected for the application, with thicker leaves leading to lower resolution. The energy of the radioactive tracer determines the number of leaves required, with a taller stack leading to higher resolution and a shorter stack leading to higher sensitivity. Although the disclosure herein depicts the apertures parallel to one another, it is within the scope of the invention to provide apertures at various angles, such as sloping the apertures higher toward the edge of each leaf. The theoretical analysis of VASH is as follows: (a) The maximum travel range of wedge motion is limited by following equationTw=0.5Wc−Wb where Tw is the travel range of wedge block, Wc is the width of collimator leaf, and Wb is the width of wedge block. (b) The profile of the top leaf is defined by P which is the half of the difference between the longest length of leaf and the shortest length of leaf. (d in FIG. 6). (c) Movement of each leaf from the zero degree (perpendicular to the detector) collimation to the maximum angle, M, is defined by followingM=PTw/Wc (d) The maximum collimation angle A is defined byA=tan−1(M/((N−1)*T)) where N is the number of the leaf and T is the thickness of a single leaf. As an example, a VASH collimator constructed for breast imaging included 50 leaves that were each 0.25 mm in thickness for a total stack height of 12.5 mm. A tungsten frame held the leaves. Two lead screws, each being ½ right-hand threaded and ½ being left-hand threaded, were driven by a motor and gearbox to change the viewing angle +/−28 degrees. There are two end bearings per end, one supporting each end of each screw. A pillow block supported each screw in the center. A drive nut was embedded in each wedge block to accommodate the screw threads of the lead screws. Each wedge included a clearance notch for pillow block clearance. A gamma transparent cover was used to cover the collimator stack, both for keeping the apertures clear and shielding the patient from moving parts of the collimator. A brushless motor available from Micromo of Clearwater, Fla., was used to power the lead screws and wedge blocks. The gearing ratio of the motor and gearbox was 134:1. The motion of the wedges was limited at each end of the lead screws by high current. Driving the motors required 100 mA for the first motor and 150 mA the second motor. The end pushing the wedge blocks to the center was the drive motor. The drive switches end-to-end to change the direction of leaves and thus the viewing angle. In the preferred embodiment, an elapsed time of one minute was required to move the viewing angle from +28 to −28. If preferred, by changing the gearbox, the elapsed time can be reduced to 20 seconds. Four (2×2) apertures were provided to each scintillator element. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiments herein were chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.
	claims	1. An ion therapy machine for treatment of a patient comprising:a treatment head positionable about a patient support for directing a beam of ions toward the patient over a range of angles; anda magnet system providing at least two quadrupole magnets within the treatment head receiving a pencil beam of ions and spreading them into a fan beam by magnetic deflection, the quadrupole magnets positioned successively along an axis of the pencil beam and aligned to provide divergence of the pencil beam along a common divergence plane;whereby the production of excess neutrons from a beam spreading foil is avoided. 2. The ion therapy machine of claim 1 wherein the fan beam has a cross-sectional width at least 5 times that of its cross-sectional thickness. 3. The ion therapy machine of claim 2 including a modulator receiving the fan beam to separately modulate beamlets, the beamlets being adjacent sectors of the fan beam. 4. The ion therapy machine of claim 1 wherein the quadrupole magnets each comprises two pairs of magnets, with the magnets of each pair opposed along a magnet axis perpendicular to the axis of the pencil beam of ions, with the magnet axes perpendicular to each other, and with one pair having opposed north poles and the other pair having opposed south poles. 5. The heavy ion therapy machine of claim 1 further including an adjustment mechanism to adjust a separation the at least two quadrupole magnets to change at least one of a width and thickness of a cross-section of the fan beam during treatment of a patient. 6. An ion therapy machine for treatment of a patient comprising:a treatment head positionable about a patient support for directing a beam of ions toward the patient over a range of angles; anda magnet system within the treatment head receiving a pencil beam of ions and spreading them into a fan beam by magnetic deflection, wherein the magnet system comprises at least at least two quadrupole magnets positioned successively along an axis of the pencil beam of ions with two quadrupole magnets having substantially aligned magnetic axes; anda means for adjusting a separation of the pair of quadrupole magnets along the axis to change a cross-sectional dimension of the fan beam;whereby the production of excess neutrons from beam spreading foils is avoided. 7. A method of treating a patient with a beam of ions comprising:(a) generating a pencil beam of ions;(b) receiving the beam of ions with at least two quadrupole magnets aligned to each spread the pencil beam into a fan beam by magnetic deflection in a common plane, the fan beam's largest cross-sectional axis extending along a plane; and(c) directing the fan beam at a patient at a variety of angles within the plane about the patient. 8. The method of claim 7 wherein the at least two quadrupole magnets are configured to spread the beam into a fan beam having a cross-sectional width at least 5 times that of its cross-sectional thickness. 9. The method of claim 7 further including the step of separately modulating the ions in beamlets being adjacent sectors of the fan beam. 10. A method of treating a patient with a beam of ions comprising:(a) generating a pencil beam of ions;(b) receiving the beam of ions with a magnet system to spread the pencil beam into a fan beam by magnetic deflection, the fan beam's largest cross-sectional axis extending along a plane; wherein the magnet system comprises a pair of quadrupole magnets positioned successively along an axis of the pencil beam of ions with each quadrupole magnet rotated 0° about the axis with respect to the others and further including the step of dynamically changing a separation of the quadrupole magnets to change the cross-section of the fan beam during treatment; and(c) directing the fan beam at a patient at a variety of angles within the plane about the patient.
040244024	summary	Our invention relates to specimen cartridges for particle beam devices, such as electron microscopes or the like. To bring specimens into the interior of a particle beam device, specimen cartridges are used. Specimen cartridges include a conical member with which the specimen cartridge is insertable into the specimen table of the microscope in a direction parallel to the axis of the particle beam. The specimen table is transversely adjustable in the interior of the electron microscope relative to a table carrier, to permit various surface regions of the inserted specimen to be investigated. The table carrier can, for example,s be made from the pole shoe to the magnetic objective lens of an electron beam microscope. The specimen cartridge often includes a specimen holder for receiving the specimen to be investigated. This specimen received by the specimen holder is readily exchangeable for other specimens. Each specimen to be investigated is first secured by means of the specimen holder and then, with the conical member, is placed into the microscope through an air lock, the microscope being connected with an operating pump. After this preparatory step, the specimen regions of interest are investigated. In many cases, it is desired to compare the specimen under investigation with other specimens. In this connection, difficulties arise because of the necessary preparation associated with insertion of the specimen or comparison specimens into the microscope. It is an object of our invention to provide a specimen cartridge for a particle beam apparatus, such as an electron microscope or the like. Subsidiary to this object, it is an object of our invention to provide a specimen cartridge which is insertable into a transversely adjustable specimen table along an axis parallel to the beam axis. The specimen cartridge of the invention includes a cartridge cone or conical member, as well as a specimen holder connected to the latter. In this connection, it becomes a further object of our invention to provide a specimen cartridge which permits and facilitates the simultaneous insertion of a plurality of specimens into the interior of the electron microscope, thereby preventing the above-mentioned difficulties. According to a feature of the invention, the specimen holder of the specimen cartridge is provided with a plurality of openings for receiving specimens and, according to a further feature, the specimen holder is secured to the conical member and is rotatable about an axis of rotation extending eccentric to the longitudinal axis of the conical member. In applying the specimen cartridge of the invention, it is possible to bring a plurality of specimens simultaneously into the interior of an electron microscope and to place the specimens individually by means of a rotation of the specimen holder into the path of the particle beam. According to a preferred embodiment of the invention, the specimen holder is configured so as to be in the form of a circular disk. According to another embodiment of the invention, the openings of the circular shaped disk are configured for receiving special specimen carriers. These object carriers are tightly held in place by means of a plate which is tensioned against the disk. These specimen carriers are for example, formed from ring apertures receiving the specimens and have a centric bore for leaving the specimen surfaces to be investigated free. In an alternate embodiment of the invention, the openings are configured as slits extending concentric to the rotating axis of the disk. With this embodiment, investigations of large surface areas of the specimens is possible. In an advantageous embodiment of the invention, the specimen holder is joined with a gear wheel via a shaft. The gear wheel is rotatably borne on, the end face of the cartridge cone. by means of the arrangement of the shaft, the specimen holder is directed at a distance from the end face of the cartridge cone. To insure a precise positioning of the specimen holder free of tipping, the gear wheel has a radius which extends beyond the longitudinal axis of the cone, whereby the gear wheel is provided with pass-through openings for the electron beam which correspond to the openings of the circular shaped disk. This embodiment affords the additional advantage that the gear wheel has a correspondingly large diameter to accommodate a large drive arrangement. The gear wheel is advantageously joined with a pinion positioned on a drive shaft which is directed in the cartridge cone parallel to the longitudinal axis of the cone. This drive shaft has a toothed drive wheel which has a diameter extending beyond the periphery of the cartridge cone. The toothed drive wheel meshes with a corresponding toothed wheel borne in the specimen table. The toothed wheel in the specimen table is driven from outside the electron microscope by means of appropriate linkages. By adjusting these linkages, the specimen holder is turned about an axis extending eccentric to the longitudinal axis of the cartridge cone, thereby permitting the specimens to be sequentially placed in the path of the electron beam.
049884743	claims	1. A method for repairing a nuclear reactor fuel assembly damaged at the periphery of an interim spacer support, the fuel assembly comprised of a bundle of longitudinally extended fuel rods held in position by several grid-shaped spacer supports axially distanced from one another whereby each fuel rod passes through and is elastically supported in a cell of the spacer support which is formed by intersecting metal crosspieces arranged at the edge, the method comprising: a. removing the damaged portion of a cell of a spacer support; and b. installing a holding component which contacts the fuel rod and is attached to a remaining portion of the cell. a. removing the damaged portion of a cell of a spacer support; and b. installing a holding component which contacts the fuel rod and is attached to a remaining portion of the cell by an elastically formed projection on each of its free ends which engages in a slot in the metal crosspiece. a. removing the damaged portion of a cell of a spacer support; b. replacing the fuel rod with a dummy fuel rod that does not contain nuclear fuel; and c. installing a holding component which contacts the dummy fuel rod and is attached to a remaining portion of the cell. a. said dummy fuel rod is provided with a radial bore; and b. said holding component is provided with projections in the form of a split pin that passes through the radial bore in said dummy fuel rod. 2. The method of claim 1, wherein the holding component is provided with a projection on each of its free ends which engages in a slot in the metal crosspiece. 3. The method of claim 1, wherein the holding component is provided with at least one elastic projection that engages over the metal crosspiece. 4. The method of claim 1, wherein the holding component is provided with a jut-out piece directed toward the fuel rod. 5. The method of claim 4, wherein the jut-out piece provided is formed elastically. 6. A method for repairing a nuclear reactor fuel assembly damaged at the periphery of an interim spacer support, the fuel assembly comprised of a bundle of longitudinally extended fuel rods held in position by several grid-shaped spacer supports axially distanced from one another whereby each fuel rod passes through and is elastically supported in a cell of the spacer support which is formed by intersecting metal crosspieces arranged at the edge, the method comprising: 7. The method of claim 6, wherein the holding component is provided with a jut-out piece directed toward the fuel rod. 8. A method for repairing a nuclear reactor fuel assembly damaged at the periphery of an interim spacer support, the fuel assembly comprised of a bundle of longitudinally extended fuel rods held in position by several grid-shaped spacer supports axially distanced from one another whereby each fuel rod passes through and is elastically supported in a cell of the spacer support which is formed by intersecting metal crosspieces arranged at the edge, the method comprising: 9. The method of claim 8, wherein:
	claims	1. A method of decontaminating a boiling water nuclear reactor having a plurality of reactor recirculation loops hydraulically connected in parallel with a reactor pressure vessel, the reactor pressure vessel having (i) a central core region, (ii) an annulus region surrounding the central core region and in hydraulic communication with the reactor recirculation loops and (iii) a lower internals region in hydraulic communication with the central core region, comprising the step of: circulating a decontamination solution through at least one of the reactor recirculation loops and the annulus region of the pressure vessel without circulating the decontamination solution through the central core region. 2. The method of claim 1 , including the step of: claim 1 providing flow passageways between the annulus region and the lower internals region by opening annulus manholes or cutting openings in internal members separating the annulus region and the lower internal region; and then circulating the decontamination solution from the lower internals region through the provided flow passageways into the annulus region while circulating the decontamination solution between the annulus region and the reactor recirculation loop without circulating the decontamination solution through the core region. 3. A method of decontaminating a boiling water nuclear reactor having a plurality of reactor recirculation loops hydraulically connected in parallel with a reactor pressure vessel, the reactor pressure vessel having: a central core region; an annulus region surrounding the central core region and in hydraulic communication with the reactor recirculation loops; a lower internals region in hydraulic communication with the central core region; and a plurality of jet pump assemblies disposed in the annulus region; each jet pump assembly including (i) inlet piping with a jet pump nozzle in fluid flow communication with one of the reactor recirculation loops, (ii) a mixing assembly having a suction inlet end in fluid flow communication with the annulus region spaced from the jet pump nozzle and (iii) a diffuser assembly having an outlet end in fluid flow communication with the lower internals region; the method comprising the steps of: removing at least part of one jet pump assembly from the reactor pressure vessel; capping the part of the jet pump assembly remaining in the reactor pressure vessel which is in fluid flow communication with the lower internals region for at least restricting fluid flow between the annulus region and the lower internals region; and then circulating a decontamination solution through at least one of the reactor recirculation loops and the annulus region of the pressure vessel without circulating the decontamination solution through the central core region. 4. The method of claim 3 , wherein the flow of the decontamination solution between the annulus region and the lower internals region is prevented while circulating the decontamination solution through the reactor recirculation loop and the annulus region without circulating the decontamination solution through the core region. claim 3 5. The method of claim 3 , wherein the suction inlet end of the mixing assembly is removed from the reactor vessel while retaining a portion of the mixing assembly and the diffuser assembly in the reactor pressure vessel. claim 3 6. The method of claim 3 , wherein the mixing assembly is removed from the reactor vessel while retaining the diffuser assembly in the reactor pressure vessel. claim 3 7. The method of claim 3 , wherein a part of the diffuser assembly is removed from the reactor pressure vessel. claim 3 8. The method of claim 3 , wherein a decontamination solution is circulated through all of the reactor recirculation loops and the annulus region of the pressure vessel without circulating the decontamination solution through the core region. claim 3 9. The method of claim 8 , wherein the decontamination solution is circulated from the lower internals region to the annulus region. claim 8 10. A method of decontaminating a boiling water nuclear reactor having a plurality of reactor recirculation loops hydraulically connected in parallel with a reactor pressure vessel, the reactor pressure vessel having: a central core region; an annulus region surrounding the central core region and in hydraulic communication with the reactor recirculation loops; a lower internals region in hydraulic communication with the central core region; a plurality of jet pump assemblies disposed in the annulus region; each jet pump assembly including (i) inlet piping with a jet pump nozzle in fluid flow communication with one of the reactor recirculation loops, (ii) a mixing assembly having a suction inlet end in fluid flow communication with the annulus region spaced from the jet pump nozzle and (iii) a diffuser assembly having an outlet end in fluid flow communication with the lower internals region; the method comprising the steps of: removing at least part of one jet pump assembly from the reactor pressure vessel while retaining at least one other jet pump assembly in the reactor pressure vessel; and then circulating a decontamination solution through at least one of the reactor recirculation loops and the annulus region of the pressure vessel without circulating the decontamination solution through the central core region; and circulating decontamination solution from the lower internals region into the annulus region while circulating the decontamination solution between the annulus region and the reactor recirculation loop without circulating the decontamination solution through the core region. 11. A method of decontaminating a boiling water nuclear reactor having a plurality of reactor recirculation loops hydraulically connected in parallel with a reactor pressure vessel, the reactor pressure vessel having (i) a central core region, (ii) an annulus region surrounding the central core region and containing inlet piping and jet pump nozzles in hydraulic communication with the reactor recirculation loops and (iii) a lower internals region in hydraulic communication with the central core region, comprising the step of: connecting a jumper pipe or hose between the inlet piping or jet pump nozzle of one reactor recirculation loop with the inlet piping or jet pump nozzle of another reactor recirculation loop; and then circulating a decontamination solution through the jumper pipe or hose from the one recirculation loop into the other recirculation loop while circulating the decontamination solution through the annulus region without circulating the decontamination solution through the core region.
059303158	description	DETAILED DESCRIPTION OF PREFERRED EMBODIMENT The present invention is adapted for use with and receives inputs from a fault detection and diagnosis system for an operating system such as a nuclear power plant, a chemical processing plant or a fuel fabrication plant. The present invention responds to the outputs of the fault detection and diagnosis system and will operate with virtually any type of fault detection and diagnosis system. One such type of system with which the present invention has been combined is the PRODIAG system developed at Argonne National Laboratory and described in U.S. Pat. Nos. 5,265,035 and 5,442,555. The detection and diagnosis system identifies a failed component type (mass, momentum, energy, e.g., pump, valve, heat exchanger) and its location in the plant system. Rather than rely on a definition of systems and subsystems and the creation of a System Classification Dictionary, the loop-component search approach of the present invention is based on a component search through a set of connected loops whose components are characterized in a Component Classification Dictionary (CCD). Using a modular interface to the process plant schematics, the structure of the loop with the failed component is defined by an ordered list of its components. The loops may be closed or open, and connect to other loops at junctions or tanks. Using the loop structure, the transient management module of the present invention searches for replacement components of the same function type within the affected loop. If a replacement component is identified, the program calculates (using a database or simulation routine) the capacity of the reconfigured loop to determine if it matches the thermal-hydraulic parameters of the original loop. If no replacement component is found in the affected loop, the program begins a forward search for important components serviced by the affected loop; starting at the failure site (or the boundary of the failure region, to the extent that the fault detection and diagnosis system has localized it) and working downstream within the loop and all connected loops. As used herein, the term "upstream" means in a direction counter to the direction of flow of the material being processed or controlled, while the term "downstream" means in the direction of flow of the material being processed or controlled. In addition, while the process transient management module of the present invention may be used with virtually any fault detection and diagnosis system, the following description relates to use of the present invention with the PRODIAG process transient diagnostic module developed at Argonne National Laboratory. The process transient management module of the present invention is known as PROMANA. Once all important components have been identified, the program begins a reverse search (upstream) starting at the inlet of each of the important components, one at a time. All possible loops with the potential to provide a replacement for the failed component loop are constructed. Once a connected loop has been identified, it is searched for a suitable replacement component. If one is found, the characteristics of the reconfigured loop are evaluated to ensure that the requirements of all high-level system functions and important components are satisfied. If any requirement is not satisfied, the search continues through other connected loops until a suitable replacement is identified, or until the search fails. This approach eliminates the necessity of creating a System Classification Dictionary. It also eliminates the need for a priori definitions of systems and subsystems based on plant functions. With some modifications, the Component Classification Dictionary structure developed for PRODIAG was used to define the components and their relationships in the plant loops for use with the present invention. The loop decomposition with component search approach was selected to be developed into the transient management system of the present invention. FIGS. 1 and 2 are flowcharts illustrating the sequence of steps taken upon receipt of a signal from PRODIAG that a fault has occurred in the process system being monitored. A description of the logical path through the flowcharts is provided. These flowcharts are representative of the general search engine, and minor modifications may be made as necessary for malfunctions of each of the three functional component types (mass, momentum, energy). In the flowcharts, a square or rectangle represents the carrying out of an operation or task, a diamond represents a decision point based upon the comparison of measured or designated system parameters, and a circle represents a system safety check. The steps carried out in the process implemented in the main module of the transient management system of the present invention will now be described with reference to FIG. 1. 1. A malfunction is signaled at step 20 by PRODIAG, or the fault detection diagnosis system, which identifies it by function type (mass, momentum or energy), loop location and, if possible, a specific component (or list of possible fault components). 2. Using the interface to the process plant Piping and Instrumentation Diagram (PID), the structure of the malfunctioning loop is retrieved at step 22. The loop structure consists of an ordered list of components arranged in the direction of normal flow. Loops can be closed (i.e. same first and last component) or open (first and last components or junctions or tanks). Except for common junctions or tanks, no component is contained in more than one loop. The Component Classification Dictionary is used to assign one of the three basic function types to each component. 3. The loop component list is searched at step 24 for other components of the same function type (designated as Q-COMP components in FIG. 1) as the faulty component. 4. If a component of the same type is found at step 26, the program branches to Subroutine A at step 28 to check the parameters of the loop with the replacement component. Subroutine A is described in detail below with reference to FIG. 2. If any of the tests in Subroutine A fail, control is returned to the main module shown in FIG. 1. 5. If there are more components in the faulty loop, the search continues at step 30, repeatedly calling Subroutine A when a component of the same function type is found. This continues until a satisfactory replacement component is found, or until no more components of that type remain in the affected loop. 6. If no suitable replacement component is found in the affected loop, the program uses the loop structure to generate an ordered list of connected loops at step 32 by searching in the forward mode (downstream) for important components, starting at the failure location and then searching upstream to conduct the connected loops. 7. Starting with the first loop in the list at step 34, the loop identification is used at step 36 to get the connected loop structure, component list and component functions. 8. At this point, the program performs a search at step 38 for components of the same function type carried out in steps 40, 42 and 44, similar to previously described steps 26, 28 and 30. 9. If the end of the connected loop is reached and no suitable replacement component has been found, the program continues to the next connected loop at step 46 and repeats steps 34 and 36. This is a reentrant section of the transient management module, since each connected loop will normally have connections of its own to follow. 10. If all connected loops have been searched and no suitable component has been found, the transient management module solution is to shut down the plant (which was assumed to be in a normal, full-power operating mode before the fault was detected) at step 48. A safety function check may also be required at this point. If a suitable replacement component was found, the program exits from Subroutine A with the solution. The steps carried out in Subroutine A shown in FIG. 2 are described in detail in the following paragraphs. A1. As shown in FIG. 2, Subroutine A is initiated at step 50 and performs several functions. First, at step 52 it generates a modified loop structure with the new component in place to replace the faulty component (or set of components identified by PRODIAG). Eventually, this step will include modifications that locate valves to isolate failed components. A2. Subroutine A then checks at step 54 to see if the reconstructed loop provides the target function (mass, momentum or energy) to all important components serviced by the original loop. Important components are defined by their function, and are typically energy and mass components. If any requirement of any important component is not satisfied, Subroutine A returns control to the main module at step 56 and the search continues. A3. The transient management module then calculates at step 58 the thermal-hydraulic parameters of the reconfigured loop and compares the results to those of the original loop configuration. This calculation will use either simple thermal-hydraulic models, a list of previously calculated values, or a plant simulator. A decision is made that the modified loop can provide full, partial or no replacement capacity, based on the result of the calculation. A4. If the modified loop provides none of the original loop capacity, Subroutine A returns control to the main program at step 60 to continue the search. A5a. If the modified loop provides a fraction of the original loop capacity, Subroutine A at step 70 checks to see if using the new component entails any other criteria that must be met, such as tank or sump capacity. If any auxiliary criteria exist and are not met, Subroutine A returns control to the main program at step 72 to continue the search. A6a. If there are no other criteria, or if the other criteria are met, a potential solution at reduced power is found at step 74. The program then resets the plant state to conform to the new loop configuration at step 76 and then proceeds to do a safety function check at step 78. A5b. If the modified loop provides the full capacity of the original loop, Subroutine A program checks at step 62 to see if using the new component entails any other criteria as in step 70. If any auxiliary criteria exist and are not met, the subroutine returns control to the main program at step 64 to continue the search. A6b. If there are no other criteria, or if the other criteria are met, a full power solution is found at step 66. The program resets the plant state to conform to the new loop configuration at step 68 and then proceeds to do a safety function check at step 78. Once a new plant state has been reached due to component replacement and loop reconfiguration, Subroutine A checks at step 78 to ensure that all safety function requirements are still met. These functions in a nuclear power station would include keeping the core covered, maintaining core temperature within limits, etc. The safety function check consists of retrieving a preprogrammed set of high-level safety functions, then deciding if the modified loop has any potential impact on those functions. If the modified loop might have an effect, a calculation is performed to verify that the safety functions are still maintained within prescribed limits. The safety function check routine at step 78 returns control to the transient management system main module shown in FIG. 1 to continue the search for a workable solution. Each potential solution is stored so that a prioritized list of recommendations can be presented to the plant operator. Prioritization may be done according to a set of criteria added to the program, some form of probabilistic risk assessment or a faster-than-real-time simulator. Several examples have been used to test and verify the logic of the inventive transient management module. The responses of the transient management module to various hypothesized faults in the Chemical Volume and Control System (CVCS) of the Braidwood nuclear power plant in Braidwood, Ill. are discussed in the following paragraphs. Four sample faults have been processed according to the logic of the module described above, using a subset of a typical CVCS system from a nuclear power plant. FIG. 3 shows a partial diagram of the CVCS. Diagnostic Results Usage Once PRODIAG, the process transient diagnostic module, performs the diagnostics for the thermal-hydraulic system transient initiator and identifies the malfunctioning component, the operator advisor provides assistance in recommending sequences of operator actions which would aid in managing the thermal hydraulic (T-H) system response to the transient. This assistance is provided by the process transient management module of the present invention. The process transient management module uses knowledge of the malfunctioning component identified by PRODIAG and provides possible sequences of operator actions which would continue to meet process specifications and maximize reliability and minimize risk in response to the transient initiator. This may be in the form of actions to compensate for the loss of the malfunctioning component and keep the plant operating or actions to optimally bring the plant to other operating states. In the following paragraphs, the knowledge-base structuring concepts along the lines of the three databases, the PRD (Physical Rules Databases), CCD (Component Classification Dictionary), and PID (Piping and Instrumentation Diagram), utilized in the inventive process transient management module are described. The knowledge-base structuring of the inventive process transient management module is at a very basic level, component-level structuring, and not at a higher level, system-level structuring. This necessitates the usage of the generic component-level classification dictionary, the CCD, and obviates the usage of the generic system-level classification dictionary, the SCD. This basic level classification is required because a system could have more than one of the three T-H functions, Q.sub.mass (mass), Q.sub.mom (momentum), or Q.sub.eng (energy) In contrast, it is easier to classify the T-H function on a component level. Using the CCD concept places the inventive process transient management module on the same footing as PRODIAG. Similarly to PRODIAG, in addition to T-H function, the invention also uses T-H characteristics (attributes both qualitative and quantitative). There are, however, differences in that the T-H attributes useful for transient management are not exactly the same as those useful for T-H diagnostics. But in general, both the inventive process transient management module and PRODIAG use the first principles T-H function/T-H characteristics approach derived by Argonne National Laboratory for the knowledge-base structuring. The major difference between the invention and PRODIAG in the knowledge-base structuring has been in the loop decomposition of the T-H system. The decomposition of the T-H system into a number of interfacing loops was carried out in PRODIAG manually. This process has been automated in the present invention. In the present invention, the T-H system has been broken down by the junctions (intersections of piping) and then PRD rules have been developed to connect the junctions into T-H loops. This is described below. This is necessary at the basic level in the search for alternative T-H pathways which are then translated into a set of suggested operator actions on individual components. In a sense, this particular part of the inventive process transient management module can be used as a complement to PRODIAG to automatically generate the T-H loops required for the PRODIAG diagnostics. This development contributes to the generic portability of the PRODIAG/PROMANA package which was one of the initial criteria specified for the development of the knowledge-base structure. It can also be used if the PRODIAG/PROMANA package is utilized off-line to generate higher-level expert system rules or expert systems (ESs), presumably computationally faster, for on-line transient diagnostic and management using the higher level SCD. The CCD is a generic grouping of generic component types. It is a classification of components by T-H function/attributes. FIGS. 4 and 5 show an integration of these two perspectives for the CCD used in the present invention. FIG. 4 is a classification by T-H function/attribute. FIG. 5 is an overlay of groups of generic components on the FIG. 4 T-H function/attributes. We concentrate on FIG. 4 first. At the top level the T-H function classification is, as in PRODIAG, by Q.sub.mass, Q.sub.mom and Q.sub.eng. Under the T-H function of Q.sub.mom it can be seen that the momentum attributes which are important to process transient management are not those which are important, or at least of different priority, to process transient diagnostics. In terms of attribute groups, the important attributes are those which are relevant to the driving force, the controllability, the direction of the momentum and finally the magnitude of the momentum. Passive momentum components require an active momentum component to provide the driving force. Non T-H signals such as electric current to a valve positioner or a motor can provide controllability not dependent upon the thermal hydraulic variables of flow, pressure, temperature and level. But there is a class of components which can not be controlled by these non T-H signals. Some of these do, however, respond to the T-H signals such as a change in pressure level without having to convert to an electric signal during a mechanical actuation of some kind. The next component attribute which is important in the management of momentum are those which contribute to the management of the momentum direction. There is a group of components which block the momentum (or flow), and there is a group of components which do not block the momentum. Within these groups the blocking can be independent of momentum direction or the blocking can be dependent upon the momentum direction. After this attribute group important for momentum direction, the next important attribute is whether the management of momentum direction can be only done for one direction/dimension or for a multiple of directions/dimensions. The next large class of attributes belong to those which are important for the management of the magnitude of the momentum (flow). At this point the attributes become less qualitative and more quantitative in nature. These attributes may more appropriately belong to a PID supplement rather than to the CCD. Specific valve characteristics are definitely more useful to a quantitative simulation calculation rather than a qualitative momentum direction analysis. The PID as envisioned only contains the geometrical configuration information. The plant specific topology is stored in the PID. In our approach to date, the PRD and CCD are not changed as the process transient management module is ported from T-H system to T-H system and from plant to plant. However, management of momentum so that technical criteria such as capacity specifications are met would also require management of momentum magnitude. The PID supplement if chosen as the solution, would be required to contain the quantitative momentum characteristics required to perform the quantitative calculations. In the context of FIG. 4, the required momentum characteristics (attributes) can be classified by the type of detail/sophistication of the calculation which needs to be performed. The first differentiation is to be made between semi-quantitative and quantitative characteristics. Semi-quantitative characteristics such as the sign of the gradient of a head vs. flow curve would be used in semi-quantitative trend analysis for the T-H variables. The quantitative characteristics can be clarified according to the temporal frequency band of the T-H response analysis; static, quasi-static or full transient solution. Further classification can then be made at the level of one-dimensional or multi-dimensional momentum characteristics. It can be seen that in this attribute classification scheme every component has all these momentum characteristics. It, therefore, does not aid in the differentiation between the components if generic components are added to the CCD with this classification scheme. Utilizing a PID supplement appears to be more appropriate. FIG. 5 shows the grouping of generic components by the attributes of FIG. 4. The components at the lower levels of the tree inherit all the attributes of the parent components above it. For example, the component "closed 3-way MOV" has the multi-D attribute, the independent of flow direction blocking attributes, the non-TH signal controllability, the passive attribute and the Q.sub.mom T-H function of the generic components above it. As we ascend the tree, attributes and in this case descriptors are dropped from the component labeling. That this CCD classification scheme is an advantage in the portability of the inventive process transient management module is best illustrated by using the PORV. The PORV is a pressure operated relief valve. The labeling "pressure operated" points to the lowest level attribute in FIG. 4 where it can be seen that the PORV requires .DELTA.p>0. The label "relief" gives it the flow direction dependence non-controllability and blocking attribute while the "valve" label gives it the passive attribute and the Q.sub.mom function. Furthermore, in both the case of the PORV and the case of the closed 3-way MOV, the PID blueprint will show a unique generic symbol. So a generic classification in the CCD is convenient and appropriate. All this attribute information is directly available from the PID blueprint. Interfacing with the PID electronic database provided by CAD (Computed Aided Design) tools should provide this information. With this classification of generic components by T-H attributes available in the CCD, the PRD first principle rules for momentum management can be couched in generic T-H system and plant-independent rules. These rules are used in the following algorithm which achieves the transient management goal of compensating for the T-H function imbalance. We illustrate here with regard to the subgoal of "search loop for other Q-comp components." Bypass and isolation can also be treated by the same process. (1) PRODIAG passes to the process transient management module the location and identity of the malfunctioning Q.sub.mom component which caused the transient upset. PA1 (2) Starting at the downstream junction closest to the malfunctioning Q.sub.mom component a forward search is made in the direction of the momentum, junction by junction, for the list of components serviced by this Q.sub.mom component until the closest junctions upstream of the malfunction component or a boundary condition is reached. PA1 (3) During the forward search once a component that is blocked to momentum (flow) is encountered the search will look for an alternative path at the closest upstream junction. The generic first principle rule is PA1 (4) Once the list of components serviced by the malfunctioning Q.sub.mom is available, it is prioritized by the importance of the T-H function of the components; Q.sub.eng components are the most important components. PA1 (5) A backward search then proceeds to find an alternative Q.sub.mom component to service the Q.sub.eng component. The backward search starts at the upstream junction closest to the Q.sub.eng component. It searches in the direction opposite to the steady-state flow direction (upstream) until either a boundary condition or the downstream junction closest to the Q.sub.eng is reached. If no alternative Q.sub.mom component with the desired attributes is found in this path, the path is discarded. Otherwise, it is retained in the list of possibilities. Additional criteria have to be developed to prioritize the acceptability of each alternate path. One of those criteria can be potential capacity (momentum magnitude). Alternatively, a probabilistic risk assessment or simulator program could be used for the prioritization. Additional algorithm development will be required if the path terminates in a boundary condition. A complementary alternate path will have to be found to match this path and complete an open loop. PA1 (6) During the backward search paths are now allowed through blocked components if operator action can be taken to unblock them. This would then determine the list of operator actions required to realign and actuate an alternative to the malfunctioning component. The generic first principle rule is IF (component has block attribute) THEN start in another direction at closest upstream junction (A.1). PA2 IF (component has block attribute and controllability attribute) THEN continue path search (B.1). This search is basically a search in the direction of the steady-state flow pattern (down the pressure gradient) existing at the normal operating condition. Other generic rules have been developed similar in form to rule (A.1) which are used in the forward search. Other generic rules have been developed similar in form to rule (B.1) which are used in the backward search. Attributes such as dependency upon direction (check valve) are used in these rules to help better limit the search with physical laws of T-H response. This illustrates the conceptual framework for the search algorithm which has been developed. It can be seen that while the steady-state momentum (flow) direction is required in search steps (3) and (5), this momentum direction can be determined a priori by modifying the forward search step (3). Starting at an active Q.sub.mom component in the predefined direction of the momentum at that component or at an inlet boundary condition in the predefined direction of the momentum at that boundary condition, the search proceeds from junction to junction with the stipulation that the path not include the same junction twice and that the search stops at the other end of the active Q.sub.mom component or at an outlet boundary condition. With this algorithm the momentum direction throughout the T-H system can be determined with only the predefined momentum direction at the active Q.sub.mom components and the boundary conditions. The present approach to the automated construction of alternate flow paths is based on the premise that any system can be described by a series of interconnected segments, each defined by one inlet and one outlet junction. Each junction can have up to a maximum of three segments attached to it (a current limit imposed for development purposes). The relationships between the junctions and segments are stored in one of several files in the PID database used by the search program. When a given component is identified as faulted, the segment containing that component is identified from the database. The search program is invoked in a forward-search mode, starting at the outlet junction of the failed segment. Following normal flow paths, all loops (open and closed) that are serviced (i.e., receive flow from) by the failed segment are tracked and stored in a table. Each of these loops is examined to see if it contains any important components. Important components are defined as those whose function is critical and must be maintained if the process or plant is to remain on-line, or whose function is necessary for the safety of the system. Starting from the inlet junction of any segment containing an important component, the search program is then run in backward-search mode to construct either (a) all loops than can deliver flow to the important component or (b) all loops that can function as a bypass around the failed segment. During this search, normally closed valves may be opened and segments whose flow may be reversed are included in potential paths. The parameters associated with the components of each new loop are examined to see if they match or exceed those necessary to meet the requirements of the important component. If the new loop meets those requirements, it is added to a table of recommended alternate paths. Currently, the search code results are presented using a stand-alone graphical interface. In its final form, the code will not only present the graphical solution, but create a list of instructions (e.g., close Valve A, open Valve B) for the operator. All of the code modules developed to this point for the inventive process transient management module are written in the Fortran 90 language, developed on an IBM-compatible personal computer and compiled with the Lahey Fortran LF90 compiler. Table I shows an overall view of the steps required to generate a system database, search for new paths and display the results. Included in Table I are the names of files that are created or used by the various modules in the system. In order to create alternate flow loops and evaluate their thermal-hydraulic capacities, detailed information about segment interconnections, component properties and system requirements must be tabulated in a searchable database. A large fraction of the preparation work for the inventive process transient management module was centered on the development of this database, which consists of several computer files. The first section of Table I shows the steps used in the development of a single system database. In general, the final database will be a representation of the Component Classification Dictionary (CCD) used by PRODIAG. This CCD is based on the premise that each component can be assigned to one of three basic classes: energy, mass or momentum. Each of these basic categories contains many generic components such as heaters and heat exchangers in the energy category. Each of these generic component classes is then subdivided further into specific component types. For example, heat exchangers may be regenerative or non-regenerative. The CCD up to this point is completely general, and the properties of each type of component are not system dependent. The final subdivision of the CCD incorporates the data from the system PID to assign each specific component in the PID to one of the CCD component types. This invention relates to an expert system involving the management of process component malfunctions. Conventional expert system methods for management of process component malfunctions are based upon heuristically derived operator procedures translated into computerized format. Predetermined sequences of recommended operator actions for responding to a predetermined set of malfunctions are coded into the databases of these expert systems. In contrast, this new expert system method for the management of process component malfunctions is based upon generic thermal-hydraulic (T-H) first principles. The automated reasoning inference engine of the expert system is used to operate upon these fundamental physical principles coded into the knowledge base to produce recommended sequences of operator actions in response to each diagnosed component malfunction. Unlike the conventional expert systems, unanticipated component malfunctions can be accommodated by this method. The knowledge base of this method is structured at the thermal-hydraulic process component level and not at the thermal-hydraulic process system level. Each specific component is classified by its thermal-hydraulic function, the generic qualitative physical rules for that function, and the generic and specific component characteristics for that function. Generic classes of components are defined in the knowledge base according to the three T-H functions of mass, momentum and energy transfer. This is the Component Classification Dictionary (CCD). This knowledge base is then used to produce possible realignments of component configurations in the process system to respond to the T-H function imbalance caused by the malfunctioning component. Using the junction connectivity information in the system Piping and Instrumentation Diagram (PID) database, a component-to-component linkage search is performed using the CCD component attributes and process objectives as constraints to produce the possible component realignments. The search algorithm is governed by the IF-THEN rules of the Physical Rules Database (PRD), which is based upon first principles conservation of mass, momentum and energy so that qualitatively T-H fundamental principles are satisfied for the new system configurations. Each realignment to a new configuration produces the accompanying sequence of recommended operator actions. This qualitative, physics-based search algorithm generically applies for the possible process system objectives of remaining at full capacity, reduction to partial capacity and safe shutdown of the process system. The algorithm is generally comprised of a forward search and a backward search. The forward search is summarized as follows: given the T-H function and location of the malfunctioning component, follow the momentum flow paths, segment by segment, applying conservation of momentum and the component momentum attributes from the CCD to construct all possible flow loops (both open and closed) which contain the malfunctioning component; then prioritize all the important components in these loop(s) according to T-H function class. The backward search then follows the procedure of the forward search but is looking for all loops which run through the important components on the priority list and also through the possible replacement components in the same T-H function class as the malfunctioning component. In the backward search, operator control of components is permitted and this search then produces the realigned configurations and the sequences of operator actions. After these sets of operator actions are determined, quantitative technical specifications such as system capacity are employed to further narrow the possible set of operator action sequences with the aid of a systems simulator. An additional interface to a PRA (probabilistic risk assessment) package could further filter the possible set of operator action sequences by adding probabilistic criteria such as minimum risk or maximum reliability to select an optimum sequence of operator actions. TABLE I ______________________________________ PROMANA System Code Module Sequence Input Files Code Modules Output Files ______________________________________ Database Development Text Editor junction.dat segments.dat junction.dat SEGTEST4 jcnsort.dat segments.dat segments.dat MAKECOMP comps.dat Text Editor comps.dat CVTCOMP comps.bin system.tif PTIMAGE system.pti system.pti READPTI plotsegs.dat Text Editor plotsegs.dat PLTCONVT plotsegs.bin Path Search segments.dat SEARCH9 allpaths.nnn jcnsort.dat comps.bin Path Display allpaths.nnn MAKEGRAF graph.sub.-- n plotsegs.bin Database Development system.tif PTIMAGE system.pti graph.sub.-- n ______________________________________ While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects. Therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.
	abstract	The invention relates to a production process of a composite material composed of aggregates of a blend of UO2 and of PuO2 dispersed in a UO2 matrix comprising the steps of dry co-grinding of a UO2 powder and of a PuO2 powder in order to obtain a homogenous primary blend, of consolidating the primary blend in order to obtain cohesive aggregates, of sieving the aggregates in a range of 20 to 350 μm, of diluting the sieved aggregates in a UO2 matrix in order to obtain a powder blend, of pelletising the powder blend and of sintering the pellets obtained in order to obtain the composite.
	summary
060410914	abstract	A control rod for a nuclear reactor is composed of a center structural member, a plurality of wings each composed of a sheath member of long plate structure having a U-shaped cross section and secured to the center structural member, a front end structural member secured to a front end side of the wing in a wing inserting direction in a reactor core, a terminal end structural member secured to a terminal end side of the wing, a plurality of integral type neutron absorbing elements each having a plate structure accommodated in each of the sheaths in a row in a longitudinal direction thereof and each being formed in plate shape by integrating one or more neutron absorbing plates, and a plurality of load supporting members for supporting weights of the integral type neutron absorbing elements. A length in the sheath longitudinal direction of at least one set of the integral type neutron absorbing elements accommodated in the wing is reduced, and the reduced integral type neutron absorbing elements are supported to the U-shaped sheath by the load supporting members to thereby reduce a local load applied to the U-shaped sheath.
	summary
047132094	abstract	A drain recovery system for the condensate feedwater system of a nuclear power plant having condensate pumps for boosting the condensate from a condenser, and feedwater heaters for heating the condensate from the condensate pumps. The drain recovery system is provided with drain pumping-up recovery having a drain tank for storing a feedwater heater drain, and drain pumps connected to the drain tank for pumping up the drain therein to inject it into said condensate feedwater system at a predetermined portion thereof, and drain level control device having a conduit connected between a portion of the drain pumping-up recovery system upstream of the drain pumps and a portion of the condensate feedwater system upstream of the condensate pumps for causing the drain in the drain tank to be returned to the portion upstream of the condensate pumps by a pressure differential therebetween so as to maintain a drain level in the drain tank at a predetermined position when the plant operates at a low load level or the drain pumps malfunction.
047284889	abstract	Slender water displacer rods for use in water reactors are provided with rings of a wear resistant coating spaced along the length of the rod. Each coating contains Cr.sub.2 C.sub.3 and is metallurgically applied and bonded to the zirconium base alloy forming the outer portion of the rod by electrospark-deposition (ESD) technique.
	summary
	summary
	claims	1. A solidification method of radioactive waste, comprising:preparing an inorganic adsorbent absorbed with a radionuclide;kneading a binder and the inorganic adsorbent absorbed with the radionuclide to obtain a kneaded object;extruding the kneaded object to obtain an extruded material object;cutting the extruded material object to obtain at least one extruded material block; andfiring the at least one extruded material block to solidify the at least one extruded material block. 2. The solidification method of radioactive waste according to claim 1, wherein the binder contains clayey mineral. 3. The solidification method of radioactive waste according to claim 2, wherein the clayey mineral is composed primarily of bentonite or kaolin. 4. The solidification method of radioactive waste according to claim 1, wherein the binder is added to the inorganic adsorbent in an amount of 4%˜60% of the inorganic adsorbent. 5. The solidification method of radioactive waste according to claim 1, wherein the inorganic adsorbent includes chabazite or crystalline silico titanate. 6. The solidification method of radioactive waste according to claim 1, wherein the at least one extruded material block is fired during the firing at temperature set in a range of 700-900 degrees Celsius in an ambient atmosphere.
	claims	1. An optical device comprising:a laser source;a telescope collimator in an optical path immediately following the laser source to form a collimated coherent light beam having an axially symmetrical distribution of intensity thereof;an optical divergence controller in an optical path immediately following the telescope collimator to provide a capability to control divergence of the collimated coherent light beam; anda glass prism including a planar shape onto which a pyramidal structure is formed, the glass prism being positioned in an optical path immediately following the optical divergence controller such that an output of the optical divergence controller is incident on one of a planar surface of the planar shape and the pyramidal structure,wherein at least one of: controlling the divergence of the collimated coherent light beam through the optical divergence controller and varying a distance between the optical divergence controller and the glass prism enables controlling a distance between maxima of an output light field of the glass prism and intensity thereof,wherein the output light field of the glass prism is configured to be utilized in controlling microparticles in one of a microtechnology and a nanotechnology application, the microparticles being configured to be placed as part of a sample within a sample holder in an optical path immediately following the glass prism. 2. The optical device of claim 1, wherein the optical divergence controller is a spherical lens with varying focal distance. 3. The optical device of claim 1, further comprising at least one of a microscope and a CCD camera to at least one of observe, register and investigate the output light field of the glass prism. 4. The optical device of claim 1, wherein the output light field of the glass prism is configured to be utilized to allow for dosated laser influence on ensembles of the microparticles. 5. An optical system comprising:a laser source;a telescope collimator in an optical path immediately following the laser source to form a collimated coherent light beam having an axially symmetrical distribution of intensity thereof;an optical divergence controller in an optical path immediately following the telescope collimator to provide a capability to control divergence of the collimated coherent light beam;a glass prism including a planar shape onto which a pyramidal structure is formed, the glass prism being positioned in an optical path immediately following the optical divergence controller such that an output of the optical divergence controller is incident on one of a planar surface of the planar shape and the pyramidal structure; andan ensemble of microparticles as part of a sample within a sample holder in an optical path immediately following the glass prism,wherein at least one of: controlling the divergence of the collimated coherent light beam through the optical divergence controller and varying a distance between the optical divergence controller and the glass prism enables controlling a distance between maxima of an output light field of the glass prism and intensity thereof, andwherein the output light field of the glass prism is configured to be utilized in controlling the ensemble of microparticles. 6. The optical system of claim 5, wherein the optical divergence controller is a spherical lens with varying focal distance. 7. The optical system of claim 5, further comprising at least one of a microscope and a CCD camera to at least one of observe, register and investigate the output light field of the glass prism.
	description	This application is a continuation of, and claims priority under 35 U.S.C. § 120 to, U.S. patent application Ser. No. 16/419,866, filed on May 22, 2019, which is a continuation of, and claims priority to, U.S. patent application Ser. No. 15/997,819, filed on Jun. 5, 2018, now U.S. Pat. No. 10,300,512, 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 the previous applications 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.
	abstract	A gravitational wave generating device comprising an energizing means which act upon energizable elements such as molecules, atoms, nuclei or nuclear particles in order to create nuclear reactions or collisions, the products of which can move in a single preferred direction with an attendant impulse (jerk or harmonic oscillation) of an ensemble of target nuclei or other energizable elements over a very brief time period. The target nuclei or energizable elements acting in concert generate a gravitational wave. A preferred embodiment involves the use of a pulsed particle beam moving at the local gravitational wave speed in a target mass, which is comprised of target nuclei, to trigger a nuclear reaction and build up a coherent gravitational wave as the particles of the beam move through the target mass and impact target nuclei over very short time spans. An information-processing device connected to a computer, controls the particle beam""s high-frequency, (GHz to THz) pulse rate and the number of particles in each bunch comprising the pulse in order to produce modulated gravitational waves that can carry information. A gravitational wave generation device that exhibits directivity. A gravitational wave detection device that exhibits directivity and can be tuned. The utilization of a medium in which the gravitational wave speed is reduced in order to effect refraction of the gravitational wave.
042474957	description	DETAILED DESCRIPTION OF THE INVENTION The starting materials with their chemical formulas are indicated on the first line of the drawing. On the left-hand side of the drawing are shown the process steps (a), (b) and (c). These result in an intermediate product which is stored. The further processing of the intermediate product by pressing and sintering leads to Product I, shown in the lower left-hand corner of the drawing, which has the highest PuO.sub.2 content. A mixture of the intermediate product from process step (c) with UO.sub.2 granuleate, i.e. granules, is effected in process step (d). Two different mixing ratios of intermediate product to UO.sub.2 granules of 90% intermediate product to 10% UO.sub.2 granules and 10% intermediate to 90% UO.sub.2 granules are given in the drawing. This is to show that by means of process steps (c) and (d) practically any desired fuel specification can be realized as far as plutonium content is concerned, quickly and with a minimum of technical means. Products II and III, shown to the right of Product I in the drawing, are then generated, corresponding to the different mixing ratios. The process steps of milling, pressing and sintering under the designation Part 1 of the drawing are known and correspond to the state of the art as shown by German Published Prosecuted Application No. 1 571 343. However, one of the problems with which the invention is particularly concerned, namely substantially complete solubility in nitric acid suitable for reprocessing, is not mentioned in the German Publication. The following Comparative Example 1 shows that the solubility of the plutonium content attainable with these process steps of the prior art which is the problem to which this invention is addressed, is not satisfactory. COMPARATIVE EXAMPLE 1 Uranium oxide (UO.sub.2+x) with a percentage of about 75% and Pu dioxide with a percentage of about 25% were mixed in a mixer and subsequently milled together in a ball mill. The percentages are by weight based on the mixture. After a milling period of four hours, the powder was taken out of the mill and subsequently pressed without particular attention as to the form of the pressed powder or the density of the material, to obtain a readily transportable material with intimate contact of the different grains of UO.sub.2 and PuO.sub.2. Usual values of density were scattered between 5.0 and 6.0 g/cm.sup.3, but depending on the type of powder, other density values can also be obtained. These pellets and also fragments thereof were sintered in a sintering furnace in a reducing atmosphere (mixture of inert gas and hydrogen) at a temperature of 1700.degree. C. The holding time at sintering temperature was about four hours. The date, attainable with this procedure, regarding stoichiometry-oxygen content, O.sub.2+x, density in g/cm.sup.3 and solubility in nitric acid of the plutonium content are listed in the following Table I: TABLE I ______________________________________ Milling 1 Pressing 1 Sintering 1 ______________________________________ Stoichiometry 2.12 -- 1.97 Density -- 5.9 10.2 g/cm.sup.3 Solubility of the 2.6% -- 97.1% Pu Content ______________________________________ As is seen therefrom, the solubility of the plutonium content is only 97.1%. The process of the present invention starts with the sintered product of the prior art and subjects it to treatment as explained hereinafter to obtain the improved results. After the mentioned sintering process, the annealed material was comminuted down to a grain size of less than 1 mm. The comminuted material was placed in a ball mill and again milled for six hours down to a primary grain size of less than 2 .mu.m. After the milling, the powder was pre-compacted in a press. Contrary to the first-mentioned pressing, careful pressing for blank or pellet densities as uniform as possible is desirable here. The pressed blanks or pellets were subsequently comminuted to form a highly flowable granulate, i.e. free-flowing granules which readily pour, similar to fluid. This highly flowable granulate was subsequently formed into the nuclear fuel pellets to meet the requirements such as density of the pellets, height, special shapes (for instance, dishing at the two end faces). The so-called blanks were subsequently sintered in a second sintering processin an atmosphere of an inert gas/hydrogen mixture, in which again 1700.degree. C. was prescribed as the maximum temperature with a holding time of four hours. The results of this further treatment in the method in accordance with the invention are listed in the following Table II: TABLE II: ______________________________________ Milling 2 Pressing 2 Sintering 2 ______________________________________ Stoichiometry 2.06 -- 1.96 Density -- 7.9 10.6 g/cm.sup.3 Solubility of the 97.1 -- 99.8% Pu Content ______________________________________ It can be seen therefrom that now the solubility of the plutonium content is 99.8%. This procedure corresponds to that producing Product I as shown in the left-hand side of the drawing. In the process mentioned in German Published Prosecuted Application No. 1 571 343, in which, without reference to the tests performed here on the solubility of the plutonium dioxide component, renewed milling and sintering of already milled and sintered powder mixtures are carried out, so-called virgin powder U.sub.3 O.sub.x and PuO.sub.2 is added. No statement is made regarding the solubility of the nuclear fuel prepared by this method; however, the solubility must be less than that resulting from the process according to the present invention because of the admixture of virgin powders (raw powders) required by the German process. Our own tests have shown that in a nuclear fuel, of which about 40% consisted of already sintered and milled material and 42% of virgin UO.sub.2+x and approximately 18% of virgin PuO.sub.2, a maximum solubility of only about 72% could be achieved, referred to the total plutonium content present in the nuclear fuel. The method according to the invention, in contrast, offers not only the advantage of practically complete solubility of the plutonium content, but also that of uncomplicated production of practically any nuclear fuel specification by means of storing the intermediate product prepared in the process step (c). This will be illustrated by the following Example 2: EXAMPLE 2 Uranium dioxide and plutonium oxide were mixed, milled, pressed, sintered, milled again, pre-compacted and granulted in the same manner and in the same ratios as in Example 1. The granulate i.e. granules was homogenized in one lot and put into storage. Analyses were performed on representative samples for the purpose of determining all data required for the further processing, such as the plutonium isotope vector, the plutonium content, the uranium isotope vector, the uranium content, the bulk density, the sinterability, etc. At the same time, a UO.sub.2 granulate, i.e. granules, with specified powder date such as density of the granulate, grain shape of the granulate, sinterability of the granulate, uranium content and the isotope vector of the uranium, was produced in a UO.sub.2 processing plant and delivered. The specifications for the granulate depend in essence on the specifications required for the UO.sub.2 /PuO.sub.2 granulate. It was ensured thereby that the two granulates are compatible, i.e. pressed and sintered well. For manufacturing a mixed-oxide fuel, for instance, for thermal nuclear power plants, 17.5% of the UO.sub.2 PuO.sub.2 granulate and 82.5% of the UO.sub.2 granulate were weighted and mixed together. After mixing, the predetermined and adjusted Pu/U+Pu fission material content was checked once more. Thereupon the blanks of specified shape and dimensions were pressed and sintered. The measured product data are listed in the following Table III: TABLE III ______________________________________ UO.sub.2 /PuO.sub.2 Granulate as per process Nuclear Fuel UO.sub.2 Granulate step c Pellets ______________________________________ Density 6.5 7.0 10.4 g/cm.sup.3 Pu Content -- 22.0 3.9% by wt. U Content 87.8 66.0 84.3% by wt. Stoichiometry 2.05 2.10 1.98 Av.Granule Size - x.sub.50 = 180 .mu.m - x.sub.50 = 180 .mu.m -- Solubility 100 97.1 99.8% ______________________________________ The end product, which according to the flow sheet in the attached drawing falls in the product group II/III, therefore likewise exhibits a solubility of the plutonium content in nitric acid of 99.8%. The two examples mentioned are given only for better illustration; the data given therein such as sintering temperature, holding time at the sintering temperature, percent Pu content, etc. are not limiting. Thus, temperatures other than 1700.degree. C. are also possible, but a lower temperature than 1400.degree. C. is not desirable, as then the diffusion processes proceed too slowly. A temperature of 1800.degree. C. represents at present an upper limit due to the technical limitations in furnace design. Gas mxitures other than inert gas/hydrogen mixtures are also conceivable as the sintering atmosphere, but according to the present state of the art, the latter is preferable since furnaces of larger size for temperatures of 1700.degree. C. are usually laid out so that they can be operated only in a reducing atmosphere. For safety reasons (oxygen-hydrogen gas explosion), the hydrogen usually provided for reduction purposes must be diluted with the inert gas. In this connection, it should further be pointed out that the maximum plutonium content in the intermediate product of the process stage (c) should be smaller than 50%, as otherwise the risk of local plutonium enrichment due to the demixing processes i.e. separating effect of uranium and plutonium mentioned at the outset and thus, partial insolubility of the plutonium can occur in the reprocessing. Important advantages of the method according to the invention are: Simple procedure, because the specified fission material content is adjusted only shortly prior to the pressing of the nuclear fuel pellets by weighing the contents, calculated in advance, of the intermediate product after step (c) and UO.sub.2 granulate. From this it further follows that no special measures for cleaning the mills are required when the specified fission material is changed. The processing of the starting materials is uniform for the mixed-oxide nuclear fuel, for thermal nuclear power plants as well as for mixed-oxide nuclear fuels for fast reactors, particularly fast breeders. Substantial parts of the total process, namely, the process steps (a), (b) and (c), need not be carried out with the entire quantity of mixed-oxide nuclear fuel, so that only that part need to be processed under glove box conditions. If, for instance, a nuclear fuel for thermal nuclear power plants is to be manufactured, this corresponds only to about 10 to 15% of the total quantity of fuel. Reprocesing of the nuclear fuel is simplified, because in addition to uranium content, the plutonium content is also practically completely soluble in nitric acid without the use of additives.
048636800	summary	The present application claims priority of Japanese Patent Application No. 62-82124 filed on Apr. 2, and No. 62-187295, No. 62-187296 and No. 62-187297 filed on July 27, 1987, respectively. FIELD OF THE INVENTION AND RELATED ART STATEMENT This invention relates to a fuel assembly for use in a light-water nuclear rector. In recent years, the trend of light-water nuclear reactors toward increase in power generation capacity has been urging an exacting demand for improvement of the fuel cycle cost of power generation. Various improvements, therefore, have been given to fuel assemblies. Since an extension of fuel burnup is an effective approach to the improvement of the fuel cycle cost of power generation, the desirability of improving the fuel for the purpose of alleviating a possible effect of an elevated fuel burnup upon the core operation characteristic has been finding approval. The fuel assembly heretofore used in the boiling-water reactor (BWR) is constructed by arranging cylindrical fuel rods each containing fuel pellets in a sealed state in the pattern of an 8-row 8-column tetragonal lattice within a channel box and disposing two water rods in the central part of the horizontal cross section of the interior of the channel box. In the core of the BWR, the adjacent channel boxes are spaced with a water gap of a width approximately in the range of 10 to 20 mm and cruciform control rods are inserted therein. In the BWR, the light water which flows inside the channel boxes boiled and forms a two-phase flow containing an average of about 40% by volume of steam while the reactor is in operation. In contrast, the light water flowing through the water-gap region outside the channel boxes does not boil even while the reactor is in operation. Owing to the effect manifested in moderating neutrons by the light water present in the water-gap region, the thermal neutron flux distribution in the horizontal direction in the fuel assembly tends to increase towards the periphery and decrease towards the center. The fuel assembly, therefore, is provided near the center thereof with two water rods adapted to pass non-boiling water through the interior thereof. The water rods, owing to the effect manifested in moderating neutrons by the water passed therethrough, serve the role of enhancing the thermal neutron utilization factor of thermal by moderating the depress of the thermal neutron flux in the central part, diminishing the output peaking, and heightening the thermal neutron flux inside the bundle. The effective multiplication factor of the core of a thermal reactor can be expressed with the four-factor formula as follows: EQU K.sub.eff =.epsilon..times.f.times.p.times.p.sub.L wherein K.sub.eff =effective multiplication factor, .epsilon.=fast fission factor, .eta.=regeneration factor, f=thermal utilization factor. p=resonance escape probability, and p.sub.L =ratio of neutrons leaking from core. The water rods mentioned above are intended to increase the effective multiplication factor by heightening the thermal neutron utilization factor, f. An effort to heighten the burnup for the purpose of improving the reduction of the fuel cycle cost, however, entails aggravation of the power mismatch among fuel assemblies and consequent rigidification of such thermal restrictions as the maximum linear power density and the minimum critical power ratio. The feasibility of a fuel assembly using an increased number, 9 (row).times.9 (column), or fuel rods as a countermeasure is being considered. The increase in the number of fuel rods, however, entails a decrease in the outside diameter of component fuel rods an increase in the resonance escape probability and cancels the effect brought about in the enhancement of thermal utilization factor by the aforementioned incorporation of water rods. For successful production of a fuel which permits extension of burnup and, at the same time, excels in economy, the enhance of thermal neutron utilization factor and the increase of resonance escape probability must be simultaneously satisfied. The attainment of an extension of the burnup requires an increase of the initial concentration of fissionable isotopes (enrichment of uranium-235 and fissionable plutonium isotopes) in the fuel and, therefore, brings about various effects on the core characteristic of a reactor. In all the effects, the decrease of the subcriticality (shut down margin) during the period of cold state and the increase of the change of core reactivity (void reactivity coefficient and moderator temperature reactivity coefficient) due to the change in the density of moderator constitute the hardest problems from the standpoint of design. One possible way of overcoming these problems may reside in increasing the water-to-fuel. An increase in the volume of the light-water region, however, entails an addition to the core volume and an increase in the construction cost of the reactor. A decrease in the amount of fuel material results in an increase in the number of fuel assemblies to be replaced per cycle and a decline of the economy of fuel. For successful production of a fuel assembly meeting the requirement for extension of burnup and excelling in core characteristic, therefore, it is further necessary to increase the shut down margin and lower the moderator density reactivity coefficient without entailing an increase in the volume of light water or a decrease in the amount of fuel material. Some of the boiling-water reactor have a core of the construction called D-lattice core. In this core, wide gaps of large width permitting insertion of control rods and narrow gaps of small width not permitting insertion of any control rod are formed outside a channel box. The width of the wide gaps is roughly twice that of the narrow gaps. In the D-lattice core, therefore, the power issues more readily from the wide gap side corners than from the narrow gap side corners. The power also issues more readily from the fuel rods facing on these gaps than from those not bordering on the gaps. Adjustment of the power, therefore, is accomplished by disposing a plurality of types of uranium rods differing in enrichment. For the increase of the average enrichment in the fuel assembly of this nature, it is necessary not only to add water rods and gadolinia rods but also to increase the number of types of uranium rods differing in enrichment (hereinafter referred to as "split number"). The addition of gadolinia rods and the increase in the number of splits, however, are nothing desirable from the standpoint of lowering the fuel cycle cost. OBJECT AND SUMMARY OF THE INVENTION As object of this invention, therefore, is to provide a fuel assembly which excels in reduction of the fuel cycle cost because of an increased multiplication factor during the course of operation as compared with the conventional fuel assembly, possesses a shut down margin enough to meet the requirement for extension of burnup and permits an effective improvement of the moderator density reactivity coefficient, and ensures a generous thermal margin during the operation. Another object of this invention is to provide a fuel assembly which minimizes the addition of gadolinia rods and obviates the necessity for increasing the number of splits in the improvement of the average enrichment of fuel assembly and, as compared with the conventional fuel assembly of equal average degree of concentration and equal water-to-fuel volumetric ratio, exhibits a high reactivity during the output operation, a small local power peaking, and a small difference of reactivity during the power operation and during the period of cold state. To be specific, the fuel assembly of this invention is constructed by preparing small units each having a small number of fuel rods bundled as spaced with a fixed intercentral distance, arranging a plurality of such small units in such a manner that the intercentral distance between the component fuel rods forming mutually juxtaposed sides of the adjacent small units is larger than the intercentral distance between the adjacent fuel rods within the small units, and disposing a water rod near the center of a cluster of the plurality of small units. Owing to this construction, the fuel assembly enjoys outstanding fuel economy, ensures an ample shut down margin even when the fuel to be used has a high enrichment, and permits a decrease in the moderator density reactivity coefficient.
	summary
	abstract	The invention is related to the systems of so-called “security entrance” and, in particular, to the systems for preventing the entry of forbidden articles and/or substances from an unprotected area to a protected one. The simplicity, efficiency and secrecy of examination in a security system for preventing the entry of forbidden articles and/or substances from a surrounding area to a protected one, said system comprised of a partitioning separating a protected area from an unprotected one, at least, one walk-gate made in said partitioning, an information control-and-processing device and a detector of forbidden articles and/or substances is achieved due to said detector of forbidden articles and/or substances made an X-ray kind to provide secret examination of every person passing through said walk-gate.
	description	The present invention relates to a sample repairing apparatus and a sample repairing method for repairing a defect with high accuracy in a sample, such as a mask, used in the production of a device or the like having a line width equal to or less than 0.1 μm, and further to a device manufacturing method using such a sample repairing method. There has been a known method in the prior art, in which a sample, such as a mask, is irradiated with a finely focused electron beam and then a reactive gas is blown to the irradiated region thereof with a nozzle so as to carry out the etching of the sample. When the mask subject to the repairing has the minimum line width as narrow as about 90 nm, the edge roughness in the repaired pattern should be controlled to be of the order of some ten nm or less, which in turn requires to focus the beam to be half a size of the required roughness or smaller than that. On the other hand, from the reason that the electron beam, if having a higher landing energy, could cause a back scattering after an incidence upon the sample and the reflected beam thereof could emit secondary electrons to contribute to the etching, there is another problem that a precision of processing would be not greater than that limited by the extent of the back scattered electrons. Besides, it has been a main stream to use an ion beam for repairing the mask in the prior art. The repairing apparatus employing the focused ion beam has a problem that an ion implantation to a mask substrate or a damage from an irradiation beam could deteriorate a transmittance in a silica substrate, substantially inhibiting the repair of opaque defect from being carried out, which is considered to be a serious problem especially in the F2 lithography. REFERENCE [Non-Patent Document] A set of advance copies from the NEXT GENERATION LITHOGRAPHY WORKSHOP (NGL2003), Jul. 10 and 11, 2003, National Museum of Emerging Science and Innovation, “Next generation Electron Beam mask repair tool”, Dr. Jayant Neogi, Johannes Bihr and Klaus Edinger, hosted by: Silicon Technology Subcommittee, Next Generation Lithography Technology Workshop, Japan Society of Applied Physics, co-hosted by: No. 132 committee, “Industrial Application of Charged Particle Beam”, Japan Society of the Promotion of Science. The present invention has been made in the light of the above-pointed problems pertaining to the prior art, and an object thereof is to provide a sample repairing apparatus, a sample repairing method and a device manufacturing method using the same method, which can reduce an edge roughness in a repaired pattern and also can repair a sample by applying an electron beam-assisted etching or an electron beam-assisted deposition. The present invention provides a sample repairing method, comprising: (a) a step of focusing an electron beam by an objective lens to irradiate a sample; (b) a step of supplying a reactive gas onto an electron beam irradiated surface of said sample; (c) a step of selectively scanning a pattern to be repaired on said sample with the electron beam so as to repair said pattern by applying an etching or a deposition; and (d) a step of providing a continuous exhausting operation by means of a differential exhaust system arranged in said objective lens so as to prevent the reactive gas supplied onto said electron beam irradiated surface from flowing toward an electron gun side. Further, it is more preferred that said sample may be applied with a negative voltage. Further, preferably a landing energy of the electron beam may be equal to or less than 3 keV. Further, said focused electron beam may define a shaped beam that has been shaped into a rectangle having parallel sides in the x-direction and in the y-direction, or a shaped beam that has been shaped into a rectangle having sides inclined at predetermined angles (e.g., 45 degrees) relative to the x-direction and the y-direction. The present invention provides another sample repairing method, comprising: (a) a step of transmitting an electron beam emitted from an electron gun through an objective lens to irradiate a sample; (b) a step of obtaining an image of said sample surface; (c) a step of searching for a region to be repaired on said sample from said image of said sample surface and scanning said region to be repaired by the electron beam: (d) a step of increasing a pressure of a reactive gas in said region on said sample subject to the scanning with the electron beam; and (e) a step of confirming the completion of said repairing of said sample, wherein a small aperture for limiting the pressure is disposed between said sample and said objective lens. Further, more preferably said electron gun has a ZrO/W Schottky cathode or a TaC cathode, and an electron beam emitted in the direction having a certain angle with respect to an optical axis is used. Further, It is more preferred that said objective lens for focusing said electron beam to be finer comprises a magnetic lens having a magnetic gap formed in the sample side thereof and an axially symmetric electrode disposed in the sample side of said magnetic lens and having a potential higher than that of the sample. Yet further, an E×B separator may be provided in the electron gun side of said objective lens or inside said objective lens, and said step of obtaining the image of said sample surface may include a step of deflecting secondary electrons emitted from said sample, by said E×B separator and detecting said secondary electrons by a detector to thereby obtain the image of said sample surface. Further, the present invention provides a device manufacturing method for carrying out a lithography by using a mask which has been repaired in accordance with the sample repairing method defined in any one of claim 1 through 8. The present invention provides a sample repairing apparatus for repairing a sample, comprising: an objective lens for focusing an electron beam to Irradiate a sample; a gas supply for supplying a reactive gas onto an electron beam irradiated surface of said sample: and a differential exhaust system disposed in said objective lens and operative to keep exhausting the reactive gas so as to inhibit the reactive gas supplied onto said electron beam irradiated surface by said gas supply from flowing toward an electron gun side, wherein a pattern to be repaired on said sample is selectively scanned with an electron beam so as to repair said pattern by applying an etching or a deposition. Further, it is more preferred that said sample may be applied with a negative voltage. Further, preferably a landing energy of said electron beam may be equal to or less than 3 keV. In addition, the apparatus may further comprise a condenser lens located downstream to the electron gun and a shaping aperture plate located upstream or downstream to said condenser lens, in which said shaping aperture plate comprises: a first shaping aperture for shaping said electron beam that has been focused by said condenser lens into a rectangle having parallel sides in the x-direction and in the y-direction; and a second shaping aperture for shaping said electron beam that has been focused by said condenser lens into a rectangle having sides inclined at predetermined angles (e.g., 45 degrees) relative to the x-direction and the y-direction, wherein said first shaping aperture and said second shaping aperture are switchable from each other. The present invention provides another sample repairing apparatus for repairing a sample, comprising: an electron gun for emitting an electron beam; an objective lens for focusing said electron beam emitted from said electron gun to irradiate a sample; an image obtaining means for obtaining an Image of said sample surface: a gas supply for supplying a reactive gas onto an electron beam irradiated surface of said sample so as to increase a pressure of the reactive gas in the electron beam scanning region on said sample: and a small aperture disposed between said sample and said objective lens for limiting the pressure of said reactive gas, wherein a region to be repaired of said sample is searched for from said image of said sample surface, which has been obtained by said image obtaining means, and then said region to be repaired is scanned with the electron beam to repair it by applying an etching or a deposition. Further, preferably said electron gun has a ZrO/W Schottky cathode or a TaC cathode, and an electron beam emitted in the direction having a certain angle relative to the optical axis is used. Further, it is more preferred that said objective lens for focusing said electron beam to be finer comprises: a magnetic lens having a magnetic gap formed in a sample side thereof; and an axially symmetric electrode disposed in the sample side of said magnetic lens and having a potential higher than that of the sample. Furthermore, an E×B separator may be provided in the electron gun side of said objective lens or inside said objective lens, and said image obtaining means for obtaining the image of said sample surface obtains the image of the sample surface through the steps of deflecting secondary electrons emitted from said sample, by said E×B separator and detecting said secondary electrons by a detector. According to the invention as defined In claim 1 or claim 10, the edge roughness in the repaired pattern can be reduced. Further, owing to the objective lens with a structure for the differential exhaust system, an amount of a reactive gas flowing into the electron gun side is reduced, thus reducing the number of cleaning operations of the optical column. According to the invention as defined in claim 5 or claim 14, the repairing of the sample, such as a mask, can be carried out successfully by applying an electron beam-assisted etching or an electron beam-assisted deposition. Further, since the beam can be focused to be finer even during use (introduction) of the reactive gas, a fine-controlled repairing can be achieved. Components in the attached drawings are designated as follows: 1 Zr-W tip 2 Schottky shield 3 Tip heating W filament 4 Condenser lens 5 Shaping aperture plate 6 Rectangular aperture 7 Rectangular aperture 8 NA aperture 9 Reduction lens 10 Objective lens system 11 High vacuum exhaust pipe 12 Low vacuum exhaust pipe 13 Gas Injection tube 14 Low vacuum exhaust pipe 15 Negative power supply 16 Mask 17 Cooling gas 18 B×B separator 19 Secondary electron detector (SE detector) 20 Deflector 21 Cr pattern 22 Opaque defect 23 Shaped beam 23 Shaped beam 26 Clear defect 31 Cathode 32 Wehnelt or Schottky shield 33 Anode 34 Condenser lens 35 Shaping aperture plate 36 Reduction lens 37 Electrostatic deflector 38 E×B separating and scanning electrostatic deflector 39 E×B separating deflector (electromagnetic deflector) 40 Objective lens 41 O ring 42 Magnetic gap 43 Small aperture 44 Axially symmetric electrode 45 Pressure wall 46 Pressure bulkhead 47 Mask 48 Guard ring 49 Exhaust pipe 50 Gas introducing tube 51 Locus 52 Secondary electron locus 53 Secondary electron detector (SE detector) 54 Pivot deflection 56 Aperture A best mode for carrying out a sample repairing apparatus, a sample repairing method and a device manufacturing method using the same method according to the present invention will now be described with reference to the attached drawings. FIG. 1 shows schematically an electron beam apparatus (i.e., an electron beam optical column) used in a repairing method of a sample, such as a mask and the like, according to the present invention. As illustrated, an electron gun comprises a Zr-W tip 1, a Schottky shield 2 and a tip heating W filament 3, taking advantage of Schottky emission. An electron beam emitted from this electron gun is focused with a condenser lens 4 to form a crossover image in an NA aperture 8. A shaping aperture plate 5 serving as a shaping aperture Is disposed in a sample (mask) side of a condenser lens 4. The shaping aperture plate 5 includes a rectangular aperture (a first shaping aperture) having sides extending in parallel in the x-direction and the y-direction and another rectangular aperture (a second shaping aperture) 7 having sides angled at a predetermined angle of 45 degrees relative to the x-direction and the y-direction, each formed through the plate 5, in which the rectangular aperture 6 and the rectangular aperture 7 are adapted to be switched from each other by sliding and thereby moving the shaping aperture plate 5 or by deflecting the irradiating beam. Thus, the electron beam that has passed through the rectangular aperture 6 of the shaping aperture plate 5 forms a rectangular-shaped beam having its sides extending in parallel in the x-direction and the y-direction, while on the other hand, the electron beam that has passed through the rectangular aperture 7 having its sides angled at 45 degrees relative to the x-direction and the y-direction forms a rectangular-shaped beam having its sides angled at 45 degrees relative to the x-direction and the y-direction. It is to be noted that the illustrated embodiment represents a case of the electron beam passing through the rectangular aperture 6. Although the rectangular aperture 7 is shown to be angled at 45 degrees relative to the x-direction and the y-direction, the sides are not necessarily angled at 45 degrees but it may have the sides angled at certain degrees proximal to the angles in conformity with patterned sides, for example, 30 or 60 degrees. The electron beam, once having passed through the rectangular aperture 6 or the rectangular aperture 7 to be shaped into a rectangular shape, is then reduced with a reduction lens 9 and an objective lens system 10 into an image on a mask 16 (A step of focusing the electron beam by the objective lens to irradiate the sample). The objective lens system 10 defines an uni-potential lens system having three electrodes designed to have a particularly small bore and a particularly large lens gap. Onto a back surface of the sample or the mask 16 has been blown a cooling gas 17 to prevent a temperature rise. Further, the mask 16 is applied with a negative voltage by a negative power supply 15. Since the cathode of the electron gun has a voltage of 4500V and the mask 16 is being applied with a voltage of −4000V, the sample is resultantly irradiated with 500 eV of energy. With 500 eV of energy, the extent of back scattered electrons in Cr of a light absorbing material of the mask 16 is limited to 50 nm or shorter, which allows a sufficiently precise processing of the mask to be carried out. The voltage of the cathode of the electron gun (acceleration voltage for the electron beam) is in a range of 0.5 to 10 kV, and the potential of the wafer could be variable in a range of 0 to −5 kV. An etching gas represented by halogen gases, such as chlorine or fluorine gases, is injected onto an electron beam Irradiated surface of the sample from a gas injection tube 13 serving as a gas supply (A step of supplying the reactive gas onto the electron beam irradiated surface of the sample). The gas used herein is not limited, but any types of gas may be used so far as it can provide etching process with the aid of the EB irradiation, including hydrogen and oxygen. A low vacuum exhaust pipe 12 is coupled to a vacuum pump (not shown) for low vacuum operation, which serves as an exhaust system, while on the other hand, a high vacuum exhaust pipe 11 is coupled to a turbo-molecular pump (not shown), so that a differential exhaust system can prevent the reactive gas filling up over the electron beam irradiated surface from flowing toward the electron gun side (A step of providing a continuous exhausting operation by means of a differential exhaust system arranged in the objective lens so as to prevent the reactive gas supplied onto the electron beam irradiated surface from flowing toward the electron gun side). The objective lens system 10, that has been designed to have the particularly small bore diameter and the particularly large lens gap as mentioned above, can provide for an effective differential exhausting operation. The low vacuum exhaust pipe 14 is also coupled to the exhaust system. Besides, in order to prevent the primary beam from being blurred and the beam current contained in the beam having fine beam diameter from being reduced, a pressure of the gas over the sample surface is controlled to be a certain pressure level which is just sufficient to meet a pressure requirement for the etching. It is to be noted that the differential exhaust system is provided in the objective lens system in the illustrated embodiment, but it may be provided at any locations in the vicinity of the sample so far as the reactive gas supplied onto the sample surface can be exhausted effectively. A deflector 20 and an E×B separator 18 allow scanning with the electron beam in any desired directions on the sample surface for providing the etching, and occasional SEM scanning can be applied to detect an end point of the etching (A step of selectively scanning the pattern to be repaired on the sample with the electron beam so as to repair the pattern by applying an etching or a deposition). At this time, the secondary electrons emanated from the sample surface pass through the objective lens system 10, deflected (toward the left in FIG. 1) by the E×B separator 18 and finally detected by a secondary electron detector 19 (SE detector). In this way, a SEM image can be obtained, and thus obtained SEM image can be monitored to see whether or not the Cr has been left in a region of the opaque defect. Further, upon detecting the end point of the etching, the gas supply from the gas injection tube 13 can be suspended immediately to thereby reduce the gas pressure in a short time to the pressure level for preventing the further etching process. Furthermore, the voltage applied to each of the electrodes of the objective lens system 10 is limited to a value of voltage that would not induce an electric discharge. Further, from the fact that the break down voltage depends on a surface condition of the electrode, the respective electrodes of the objective lens 10 have been coated with gold or platinum. FIG. 2 shows, by way of example, how to repair an opaque defect and a clear defect. FIG. 2(A) shows a case of an opaque defect 22 adhering to a Cr pattern 21 extending along the x-direction. In this case, the scanning operation is performed with such a shaped beam 23 having a size about one half of a minimum line width, which has been shaped through the rectangular aperture 6 of the shaping aperture plate 5 into a rectangle having the sides extending in parallel in the x-direction and the y-direction, to be driven In the x-direction (the direction designated by reference numeral 24 in FIG. 2(A)) so as to apply the etching to peel away (repair) the opaque defect 22. FIG. 2(B) shows a case containing an opaque defect 22 adhering to a pattern 21 extending along the y-direction. In this case also, the scanning operation is performed with such a shaped beam 23 having a size about one half of a minimum line width, which has been shaped through the rectangular aperture 6 of the shaping aperture plate 5 into a rectangle having the sides extending in parallel in the x-direction and the y-direction, to be driven in the y-direction (the direction designated by reference numeral 24′ in FIG. 2(B)) so as to apply the etching to peel away (repair) the opaque defect 22. FIG. 2(C) shows a case containing an opaque defect 22 adhering to a pattern 21 extending along the directions angled at 45 degrees relative to the x-direction and the y-direction. In this case, the scanning operation is performed with such a shaped beam 23′, which has been shaped through the rectangular aperture 7 of the shaping aperture plate 5 into a rectangle having the sides angled at 45 degrees relative to the x-direction and the y-direction, to be driven in the directions angled at 45 degrees relative to the x-direction and the y-direction (the directions designated by reference numeral 25 in FIG. 2(C)) so as to apply the etching to peel away (repair) the opaque defect 22. FIG. 2(D) shows, by way of example, a case for repairing a clear defect 26 in a pattern 21 extending along the x-direction, and in this case, the etching gas of halogens may be replaced with a gas capable of providing a deposition of tungsten metal. This gas may be such a gas that contains a metal and Is decomposed by the electron beam to form a deposition of metal, including carbonyls and methyls of metal, and the metal may be tungsten, copper, noble metals such as silver, aluminum or chrome. In case of FIG. 2(D), the scanning operation is performed with such a shaped beam 23, which has been shaped through the rectangular aperture 6 of the shaping aperture plate 5 into a rectangle having the parallel sides in the x-direction and the y-direction, to be driven in the x-direction (the direction designated by reference numeral 24 in FIG. 2(D)) so as to repair a clear defect 26. FIG. 2(E) shows a case for repairing a clear defect 26 in a pattern extending along the y-direction. In this case also, the scanning operation is performed with such a shaped beam 23, which has been shaped through the rectangular aperture 6 of the shaping aperture plate 5 into a rectangle having the sides extending in parallel in the x-direction and the y-direction, to be driven in the y-direction (the direction designated by reference numeral 24′ in FIG. 2(E)) so as to repair the clear defect 26. FIG. 2(F) shows a case for repairing a clear defect 26 in a pattern 21 extending along the directions angled at 45 degrees relative to the x-direction and the y-direction. In this case, the scanning operation is performed with such a beam 23′, which has been shaped through the rectangular aperture 7 of the shaping aperture plate 5 into a rectangle having the sides angled at 45 degrees relative to the x-direction and the y-direction, to be driven in the direction angled at 45 degrees relative to the x-direction and the y-direction (the direction designated by reference numeral 25 in FIG. 2(F)) so as to repair the clear defect 26. Another embodiment of a sample repairing method according to the present invention will now be described. FIG. 3 shows schematically an electron beam apparatus (electron beam optical column) used in the repairing method for repairing defects in a mask, in which an electron beam that has been focused to be finer by an objective lens is irradiated onto the mask so as to repair the defect therein. A cathode 31 has employed a Schottky cathode of Zr/O-W or a thermal field emission cathode of TaC. Reference numeral 32 designates a Wehnelt or Schottky shield, and reference numeral 33 designates an anode. An electron gun comprises the cathode 31, the Wehnelt or Schottky shield 32 and the anode 33, and is configured for emitting electron beams from the Z-W Schottky cathode or the TaC cathode 31 to the directions away from the optical axis, for example, in four directions away from the optical axis, in which those electron beams emitted from the electron gun are focused by the condenser lens 34. This condenser lens 34 is made of electromagnetic lens which is capable of not only focusing the electron beams but also adjusting a rotational displacement of each electron beam in the azimuthal direction. A shaping aperture plate 35 is disposed in the sample (mask) side of the condenser lens 34. An aperture 56 is formed In the shaping aperture plate 35. As shown in FIG. 4, at least one aperture 56 is formed in the shaping aperture plate 35 in a location offset from the optical axis so as to permit one of four beam 55 that have been emitted from the electron gun in four different directions away from the optical axis to pass through the aperture 56. Accordingly, an ion beam along the optical axis, which otherwise Is to flow toward the electron gun, can be blocked. The beam passes through either one of the apertures 56 in the shaping aperture plate 35 and is reduced by means of a reduction lens 36 and an objective lens (an electromagnetic lens for an objective lens) 40, and thereby the beam is irradiated onto the mask 47 (sample to be repaired) as a beam of small-diameter in the order of about 50 nm. That is, the electron beam that has been focused to be finer by the objective lens 40 is irradiated onto the mask 47 (A step of focusing the electron beam emitted from the electron gun to be finer by means of at least the objective lens to irradiate the sample). Using a two-stage deflector system including an electrostatic deflector 37 and an E×B separating and scanning electrostatic deflector 38 disposed on the objective lens 40 defined in the electron gun side, the mask 47 is scanned in the two-dimensional manner to allow the secondary electrons emanating from the mask 47 surface (sample) to pass through a small aperture 43, then to be deflected toward the direction of the secondary electron locus 52 by the E×B separating and scanning electrostatic deflector 38 and the E×B separating deflector (electromagnetic deflector) 39 and finally to be detected by the secondary electron detector (SE detector) 53. Through those steps, a SEM image can be obtained (A step of obtaining the SEM image of the sample) and the obtained SEM image can be monitored to search for a region to be repaired. If the region to be repaired is located, the scanning is applied only to that region (A step of searching for the region to be repaired on the sample from the SEM image of the sample and scanning the region to be repaired by the electron beam) and an reactive gas is introduced from a gas introduction tube 50 serving as a gas supply (A step of increasing a pressure of the reactive gas in the region on the sample subject to the scanning with the electron beam) to apply an etching (electron beam-assisted etching) or a deposition (electron beam-assisted deposition) thereto. Further, after the repairing operation has been completed, the SEM image is obtained again and the checking operation Is performed over the SEM image to see whether or not the repairing has been accurately completed (A step of confirming the completion of the repairing of the sample). Since a small aperture (an aperture for NA and for limiting a pressure) 43 is disposed between the mask 47 and the objective lens and so the region defined in the electron gun side is kept in high vacuum with the aid of the small aperture 43, even when the gas is introduced, therefore the beam would not be blurred but can be focused to be finer, thereby providing a precise repairing. Further, since a distance between the small aperture 43 and the mask 47 is short, a magnitude of blur of the beam, if any, could be limited to an extremely minute magnitude. The objective lens 40 for focusing said electron beam to be finer comprises a magnetic lens (electromagnetic lens) 40 including a magnetic gap 42 formed therein defined in the mask 47 side and an axially symmetric electrode 44 disposed in the mask 47 side with respect to the magnetic lens 40 and having a potential higher than that of the mask 47. Since the negative voltage in the order of −4000V is applied to the mask 47 and the positive high voltage is applied to the electrode 44, therefore even with the landing energy not higher than 1 keV, it will be still possible to focus the beam to be sufficiently finer. Further, since a locus 51 during the scanning defines a pivot point 54 of deflection in the electron gun side with respect to the small aperture 43, an aberration during the deflection can be reduced. A pressure wall 45 and a pressure bulkhead 46 define a partition wall for separating an exhaust pipe 49 coupled to a vacuum pump (not shown) and a gas introduction tube 50 from each other and are made of insulating material. A guard ring 48 is disposed below the pressure bulkhead 46 to reduce a space with respect to the pressure bulkhead 46, which also helps prevent a large amount of gas from flowing into a region defined in a sample chamber side. Further, an O-ring 41 is provided to separate a coil of the magnetic lens 40 from the vacuum environment. Since the system uses only one of four beams emitted from the Zr/O-W Schottky cathode of the electron gun in four different directions angled with respect to the optical axis is used, the beam of high intensity can be used, which means that even with the beam that has been focused to 50 nm, a beam current equal to or more than 500 nA can be still obtained. Accordingly, the repairing operation can be carried out with high throughput, and also the observation of the SEM image can be carried out with good S/N ratio even with the beam focused for detecting the end-point. Since it is not known that in which direction of the azimuthal angles θ of the beams emitted from the Zr-W Schottky cathode of the electron gun in four directions away from the optical axis the stronger beam 55 is shot, a plurality of apertures 56 (two in the illustrated embodiment) of the shaping aperture plate 35 can be disposed in the direction of the azimuthal angles θ of the beam, which are spaced from each other by a distance corresponding to a diameter of the beam on the shaping aperture plate 35, as shown in FIG. 4. With this arrangement, a rotational amount to be adjusted by the condenser lens (magnetic lens) 34 can be reduced, It is to be noted that although the Illustrated embodiment shows an example using an inspection apparatus of the SEM type (scanning electron microscope), the present invention is not limited thereto but is applicable to the inspection apparatus of projecting optical system using the principle of parallel image-taking and to the inspection apparatus by ion beam using ions (referred to as a charged particle beam including an electron beam) or by light beam using light. It is to be noted that although the description has been directed to the repairing operation applied to the mask in the above-Illustrated embodiments, the present invention is not limited to this but is applicable to a wafer in the course of fabrication of an advanced device (GaAs wafer in the course of fabrication of a discrete device). By using the mask repaired by the above-described sample repairing method, a well-performed lithography can be carried out in the device manufacturing method. With reference to FIGS. 5 and 6, the description will now be directed to an embodiment for carrying out a method for manufacturing a semiconductor device by using a mask repaired by the above-described sample repairing method. FIG. 5 is a flow chart showing an embodiment of a manufacturing method of a semiconductor device according to the present invention. The manufacturing process in this embodiment includes the following main processes. (1) A wafer manufacturing process for manufacturing a wafer (or wafer preparing process for preparing a wafer). (Step 100) (2) A mask manufacturing process for fabricating a mask to be used in the exposure (or a mask preparing process for preparing a mask). (Step 101) (3) A wafer processing process for performing any processing treatments necessary for the wafer. (Step 102) (4) A chip assembling process for cutting out those chips formed on the wafer one by one to make them operative. (Step 103) (5) A chip inspection process for inspecting an assembled chip. (Step 104) It is to be appreciated that each of those main processes further comprises several sub-processes. Among those main processes, one that gives a critical affection to the performance of the semiconductor device is (3) the wafer processing process. In this wafer processing process, the designed circuit patterns are deposited on the wafer one on another, thus to form many chips, which will function as memories or MPUs. This wafer processing process includes the following sub-processes. (A) A thin film deposition process for forming a dielectric thin film to be used as an insulation layer, a metallic thin film to be formed into a wiring section or an electrode section, and the like (by using the CVD process or the sputtering). (B) An oxidizing process for oxidizing the wafer substrate, which is another means to form those thin films. (C) A lithography process for forming a resist pattern by using a mask (reticule) in order to selectively process the thin film layers and/or the wafer substrate. (D) An etching process for processing the thin film layer and/or the wafer substrate in conformity to the resist pattern (by using, for example, the dry etching technology). (E) An ions/impurities implant and diffusion process. (F) A resist stripping process. (G) An inspection process for inspecting the processed wafer. It is to be noted that the wafer processing process must be performed repeatedly as desired depending on the number of layers contained in the wafer, thus to manufacture the device that will be able to operate as designed. A flow chart of FIG. 6 shows the lithography process included as a core process in said wafer processing process. The lithography process comprises the respective processes as described below. (a) A resist coating process for coating the wafer having a circuit pattern formed thereon in the preceding stage with the resist. (Step 200) (b). An exposing process for exposing the resist. (Step 201) (c) A developing process for developing the exposed resist to obtain the pattern of the resist. (Step 202) (d) An annealing process for stabilizing the developed pattern. (Step 203) All of the semiconductor device manufacturing process, the wafer processing process, and the lithography process described above are well-known, and so any further description on them should not be necessary. When a defect inspection method and a defect inspection apparatus according to the present invention is used in the above-described inspection process of (G), any defects can be detected with high throughput even on a semiconductor device having a fine pattern, enabling the 100-percent inspection and thus the improvement in yield of the products as well as the avoidance of shipping of any defective products to be achieved.
053393422	claims	1. A fuel assembly for a boiling water reactor, comprising: a) approximately mutually parallel fuel rods in a bundle having upper and lower ends; b) a skeleton holding said bundle and having a handle, an upper tie plate retained on said handle at said upper end of said bundle, a lower tie plate at said lower end of said bundle, and at least one support element joining together said lower tie plate and said upper tie plate; c) a fuel assembly case in which said skeleton and said bundle are inserted; and d) redundant support means holding said lower tie plate, said fuel assembly case and said upper tie plate together independently of said skeleton, when said handle is lifted. a) a bundle of approximately mutually parallel fuel rods; b) a lower end having a base part and a lower tie plate forming a lower stop for said fuel rods; c) an upper end having an upper tie plate forming an upper stop for said fuel rods, having a laterally protruding distance piece, and having a handle connected to said upper tie plate and to said distance piece; d) spacers for laterally fixing said fuel rods in place; e) a fuel assembly case laterally surrounding said bundle with said spacers, said lower tie plate and said upper tie plate; f) means for retaining said lower end at said fuel assembly case; and g) a locking spring being retained by said upper end and having a locking element reaching through a window formed in said fuel assembly case. 2. The fuel assembly according to claim 1, including a base part secured to said fuel assembly case, said lower tie plate being inserted into said base part, and said redundant support means including a releasable upper stop engaging said fuel assembly case and one of said upper tie plate and said handle. 3. The fuel assembly according to claim 1, wherein said fuel assembly case has a lower part disposed at said lower tie plate, and said redundant support means include an upper stop engaging said fuel assembly case and one of said upper tie plate and said handle, said upper stop defining a maximum distance between said handle and said lower part of said fuel assembly case, at least when said handle is lifted. 4. The fuel assembly according to claim 1, including a base plate carrying said lower tie plate, said fuel assembly case having an upper part disposed at said upper tie plate, said redundant support means including a releasable lower stop engaging said fuel assembly case and at least one of said lower tie plate and said base plate, and said lower stop defining a maximum distance between said lower tie plate and said upper part of said fuel assembly case, at least when said fuel assembly case is lifted. 5. The fuel assembly according to claim 3, wherein said fuel assembly case has a recess formed therein, said skeleton has a stop surface opposite said recess, said stop is retained in said recess and on said stop surface in an installed state of the fuel assembly, and said stop is movable by a tool far enough to displace said fuel assembly case relative to said skeleton for disassembly of the fuel assembly. 6. The fuel assembly according to claim 4, wherein said fuel assembly case has a recess formed therein, said skeleton has a stop surface opposite said recess, said stop is retained in said recess and on said stop surface in an installed state of the fuel assembly, and said stop is movable by a tool far enough to displace said fuel assembly case relative to said skeleton for disassembly of the fuel assembly. 7. The fuel assembly according to claim 4, wherein said lower stop is a screw passing through said fuel assembly case and said base part transversely to the axis of the fuel assembly, said screw having a head being countersunk in said fuel assembly case from the outside and a bore formed in said screw being accessible from inside said base part and facing toward said head, said bore being flared open after said screw has been screwed into said base part. 8. The fuel assembly according to claim 3, wherein said upper stop is resiliently retained on said skeleton and reaches through a window 16 formed in said fuel assembly case in a direction transverse to the axis of the fuel assembly. 9. A fuel assembly installed in a boiling water reactor, comprising: 10. The fuel assembly according to claim 9, including a tension spring, said locking spring and said tension spring having restoring forces, said upper end being displaceable toward said lower end counter to the restoring force of said tension spring, and said locking element being movable out of said window counter to the restoring force of said locking spring, with said upper end displaced. 11. The fuel assembly according to claim 9, wherein said fuel assembly case has an upper part, said locking spring has a spring element resting flatly on said upper part of said fuel assembly case in the direction of said lower end, said spring element is secured to said upper end and has a lower end engaging said window from above in hook-like fashion. 12. The fuel assembly according to claim 11, wherein said locking spring has an engagement surface, and said upper end has a disassembly bore formed therein leading to said engagement surface from above. 13. The fuel assembly according to claim 9, wherein said locking element is a locking bar being held by said upper end, being displaceable counter to the restoring force of said locking spring, and protruding into said window. 14. The fuel assembly according to claim 13, wherein in another window formed in said upper end said locking spring and said locking bar are supported in another window formed in said upper end, and said locking bar has an end being supported in said recess and pressed outward. 15. The fuel assembly according to claim 9, wherein said locking element is a latch being held by said upper end and pivotable approximately at right angles to the axis of the fuel assembly counter to the restoring force of said locking spring. 16. The fuel assembly according to claim 15, wherein said fuel assembly case has corners, said pivotable latch has a joint part, said upper end has a frame part resting inside one of said corners of said fuel assembly case, said frame part has a recess formed therein, and said locking spring and said joint part are supported in said recess. 17. The fuel assembly according to claim 16, wherein said recess forms a joint socket, said joint part and said joint socket have corresponding approximately hemispherical shapes, and said joint part rolls on said joint socket. 18. The fuel assembly according to claim 16, wherein said recess forms a joint socket, said joint part and said joint socket have corresponding approximately cylindrical shapes, and said joint part rolls on said joint socket. 19. The fuel assembly according to claim 16, wherein said corner of said fuel assembly case is formed by two adjacent walls toward which said recess is open, and said latch is laterally introduced into said recess, has play in all directions in said recess and is retained by said locking spring. 20. The fuel assembly according to claim 19, wherein said locking element has a forked tongue engaging corresponding windows formed in said walls of said fuel assembly case meeting one another in said corner of said fuel assembly case.
052609847	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS An x-ray diagnostics installation constructed in accordance with the principles of the present invention is shown in FIG. 1, which includes an x-ray tube 2 fed by a high-voltage generator 1. The x-ray tube 2 is provided with a primary radiation diaphragm 3, for example, a heart contour diaphragm. The x-ray tube 2 generates an x-ray beam which is limited by the primary radiation diaphragm 3 (i.e., by the beam-interacting elements thereof). The x-ray beam as limited by the primary radiation diaphragm 3 penetrates a patient 4, and the attenuated radiation is incident on an input screen of an x-ray image intensifier 5. The incident radiation image is intensified and is reproduced on the output screen of the x-ray image intensifier 5, from which it is imaged on the target of a video camera 8 by means of optics 6 having an iris diaphragm 7. A processing circuit 9 is connected to the video camera 8, the processing circuit 9 being connected to a monitor 10 for displaying the x-ray image in visible form. The processing circuit 9 may include a transducer, an image store and calculating units operating in a known manner. Synchronization of the various components of the installation of FIG. 1 is undertaken by a central control unit 11. A diaphragm positioning control unit 12 having a setting element 13 (shown in greater detail in FIG. 2) is connected to the primary radiation diaphragm 3. The control unit 12 consists of a control box to which an operating lever 14 provided with a cap 15 is attached, the operating lever 14 and the cap 15 being in the shape of a mushroom knob. In the manner of a joystick, the operating lever 14 can be pivoted in all directions, and it can be rotated by its cap 15. Additionally, the operating lever 14 can be pressed or pulled by grasping the cap 15, as described below. The monitor 10 on which the image of a heart 16 is schematically portrayed is shown in FIG. 3. A diaphragm plate 17 of the primary radiation diaphragm 3 is also seen in the image. The setting element 13 is schematically shown in FIG. 4. When the setting element 13 is moved or pivoted in one of the directions of the double arrow 18, the diaphragm plate 17 is moved in a corresponding direction, as indicated by the double arrow 19. When the operating lever 14, for example, is pivoted toward the bottom left in the direction of the double arrow 18, this results in the primary radiation diaphragm 3 becoming more closed, because the diaphragm plate 17 moves toward the contour of the heart 16 toward the bottom left in the direction of the double arrow 19. If pivoting of the primary radiation diaphragm is required, this is undertaken buy a rotational motion of the setting element 13 in the direction of the double arrow 20, which causes a rotation of the primary radiation diaphragm 3, and thus of the diaphragm plate 17 in the direction of the double arrow 21. A further example is shown in a similar manner in FIGS. 5 and 6. The diaphragm plate 17 in this example is situated in the upper region of the video image. For example, this could be effected by moving the diaphragm plate from the position shown in FIG. 3 by turning the setting element 13 toward the left. Pivoting of the setting element 13 in the direction of the double arrow 22 then causes the primary radiation diaphragm 3 to open or close, by moving the diaphragm plate 17 in a corresponding direction of the double arrow 23. Rotational motion according to the double arrow 24 causes the primary radiation diaphragm 3 to execute a rotational motion conforming to the double arrow 25. It is thus insured that the alignment of the primary radiation diaphragm 3 and the video image thereof on the monitor 10 will agree during setting of the primary radiation diaphragm 3, so that the attending personnel can identify by visual contact the direction in which the primary radiation diaphragm 3 is to be moved, and can implement a corresponding operation via the setting element 13. As shown in FIG. 1, the control unit 12 can also be connected to the high-voltage generator 1. Each actuation of the setting element 13 supplies a control signal to the high-voltage generator 1, which reduces the radiation dose in the transillumination mode in response thereto, so the patient 4 receives a lower radiation load during the setting of, for example, the heart contour diaphragm as the primary radiation diaphragm 3. Such setting can be undertaken with a reduced does because high-quality x-ray images are not required during setting, since no diagnosis is undertaken. The control unit 12 can also be connected, for example, to the processing circuit 9, causing a line representing the edge of the diaphragm plate 17 to be mixed into the video image. Actuation of the setting element 13 may also initiate an automatic gain control so that, for example, the brightness of the video image remains the same given the reduced dose. The control unit 12 can also be connected to the iris diaphragm 7 disposed in the optics 6. Operation of the iris diaphragm 7 can be undertaken by pressing and pulling the setting element 13. For example, pressing on the operating lever 14 can close the iris diaphragm 7, and pulling on the cap 15 can open iris diaphragm 7. Instead of only one operating lever 14 having a plurality of functions, a plurality of operating levers can alternatively be provided as the setting element, with the respective functions being divided among these operating levers. Thus, a first operating lever, by its pivot motion, can move the diaphragm plate 17 to open and close the diaphragm 3, with a second operating lever effecting rotation of the diaphragm plate 17 in the direction of the double arrows 21 or 25 by rotating such a second lever toward the right or the left against a detent. Even more functions can be integrated in the operating lever 14. For example, pivoting of the setting element 13 in a direction substantially perpendicular to the double arrows 22, i.e., toward the right for example, can cause a rotary motion of the diaphragm plate 17 in the direction of the double arrows 25 toward the left, until the edge of the diaphragm plate 17 is disposed perpendicularly relative to the direction of the pivoting of the setting element 13. Closing or opening of the diaphragm 3 by means of moving the diaphragm plate 17 can be subsequently undertaken by another actuation of the setting element in the desired direction. The control of the diaphragm plate 17 from the position shown in FIG. 5, however, can also be achieved by pivoting the setting element in a desired direction of the double arrow 22 takes place first up to a detent, with the setting element being subsequently pivoted in the direction of the double arrow 24. A rotation in the direction of the double arrow 25 and a subsequent closing of the diaphragm plate 17 will then occur. The x-ray diagnostics installation disclosed herein provides an ergonometric operation of the primary radiation diaphragm which is based on operating possibilities which unambiguously correspond to the displayed image. A rotary motion of the setting element 13 in the form of a mushroom knob is implemented for rotating the primary radiation diaphragm 3 and a tilting or pivoting motion of the setting element 13 in the desired direction is implemented for introduction and withdrawal of the diaphragm plates in directions perpendicular to an axis through the center of the image. Regardless of the individual geometrical conditions of the x-ray apparatus, the video image, from the standpoint of the operator, is the only reference point which must be observed in order to correctly and accurately position the elements of the primary radiation diaphragm 3. Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of his contribution to the art.
	description	This application claims the benefit of U.S. Provisional Patent Application No. 61/051,887, filed May 9, 2008, and is a continuation-in-part of U.S. patent application Ser. No. 12/426,515, filed Apr. 20, 2009, which claims the benefit of U.S. Provisional Application Nos. 61/046,126, filed Apr. 18, 2008, 61/046,132, filed Apr. 18, 2008 and 61/051,887, filed May 9, 2008, the entireties of which are incorporated herein by reference. The research leading to the present invention was supported, in part by the Department of Defense's Technical Service Work Group (TSWG) through a contract (N41756-04C-4163) and by the U.S. Army through a contract (DAAE3003D1015-18). Accordingly, the United States Government may have certain rights in the invention. This invention relates to methods of rapid phase modulation of terahertz (THz) radiation and devices and systems employing same for high-speed THz imaging, spectroscopy and wireless communications. There has been a rapid expansion in the area of terahertz technology, apparatus and components using THz technology. The feasibility of various THz applications has been greatly expanded due to the development of spectroscopy and imaging methods such as THz time-domain spectroscopy (THz TDS) and continuous wave (CW) THz imaging. One of the limitations in applying THz TDS to imaging has been the requirement for a scanning method that records the entire THz time-domain waveform. Most time-domain THz systems use slow mechanical scanning delay lines, or mirror shakers (15-300 Hz repetition rate)(Chan et al., “Imaging with terahertz radiation”, Rep. Prog. Phys. 70, 1325-1379 (2007)) to detect the THz waveform on a point by point basis. Improvements to the mechanical scanning method have included piezo-electric delay lines, which are reasonably fast (kHz) but are limited to a 10 ps scanning range, as well as a rotating scanning stage. J. Xu and X.-C. Zhang, “Circular involute stage”, Opt. Lett. 29 2082 (2004). For the CW photomixing configuration, two laser sources are typically multiplied or mixed in a device such as a photoconductive antenna structure. THz radiation is generated at the difference frequency of the two laser sources. Some groups have used Golay cells, bolometers (J.-Y. Lu et al., “Optoelectronic-based high-efficiency quasi-CW terahertz imaging”, IEEE Photon. Tech. Letters 17, 2406 (2005)), or other power detection devices. Since the THz power, not electric field, is detected in these devices, the THz phase information is lost. However, no scanning of the THz waveform is required. For the coherent detection approach, the THz waveform is scanned by varying the phase (or arrival) of the THz waveform relative to the phase of the mixed laser beams. Following the example of THz TDS, a mechanically scanning delay rail (A. Nahata et al., “Free-space electro-optic detection of continuous-wave terahertz radiation”, Appl. Phys. Lett. 75, 2524 (1999); K. J. Siebert et al., “Continuous-wave all-optoelectronic terahertz imaging”, Appl. Phys. Lett. 80, 3003 (2002); N. Karpowicz et al., “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging”, Semicond. Sci. Technol. 20, 293 (2005)) typically is used to vary the optical path of the two infrared laser beams after the beams have been combined. These delay rails are typically slow, not because a long waveform is recorded as is the case of the THz TDS systems, but rather because the delay induced by the scanning rail must be comparable in distance to the wavelength of the THz radiation (˜300 μm for 1THz). Consequently there is the need for faster THz methods and devices and systems employing same. The present inventors have found that faster THz methods and devices can be achieved in accordance with various aspects of the present invention. In accordance with one aspect of the present invention, the inventors have found that the rate of scanning can increased because the initial phase of the THz wave in the photomixing process is determined by the phase difference of the two lasers. In accordance with one embodiment of the present invention, a system is provided in which one of the infrared lasers is directly modulated using a Lithium Niobate phase modulator. Since the speed of Lithium Niobate modulators can be as high as the gigahertz range, the speed limitations due to mechanical scanning in acquiring a THz waveform in prior art methods and systems are essentially eliminated. The present invention provides methods of rapid phase modulation of terahertz (THz) radiation for high-speed THz imaging, spectroscopy and communications. Terahertz (THz) radiation has shown potential in a wide variety of applications including detection of concealed weapons and explosives (J. F. Federici et al., “Detection of Explosives by Terahertz Imaging”, in Counter-Terrorism Detection Techniques of Explosives Jehuda Yinon Ed. (Elsevier 2007); T. Löffler, et al., “Continuous-wave terahertz imaging with a hybrid system”, Appl. Phys. Lett. 90, 091111 (2007)); chemical detection and spectroscopy (A. I. Meshkov and F. C. DeLucia, “Broadband absolute absorption measurements of atmospheric continua with millimeter wave cavity ringdown spectroscopy”, Rev. Sci. Instrum. 76, 083103 (2005)); and imaging (W. L. Chan et al., “Imaging with terahertz radiation”, Rep. Prog. Phys. 70, 1325-1379 (2007)). The disclosed methods can be employed in a wide variety of devices and systems including but not limited to stand-off detection of explosives, biological and chemical weapons; concealed weapon detection, drug detection, hand-held scanners, imaging and non-destructive testing and wireless communications. It should be noted that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be construed as limiting of its scope, for the invention may admit to other equally effective embodiments. Where possible, identical reference numerals have been inserted in the figures to denote identical elements. In the following description, for purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one having ordinary skill in the art that the invention may be practiced without these specific details. In some instances, well-known features may be omitted or simplified so as not to obscure the present invention. Furthermore, reference in the specification to phrases such as “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of phrases such as “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment. Now referring to FIG. 1 in one embodiment a schematic of a rapid continuous wave CW detection apparatus for detecting THz phase and amplitude is shown. The apparatus 10 includes lasers 12 and 14, beam splitters 20, a phase modulator 30, optical fibers 40, transmitter 50, receiver 60, lenses 70 and mirrors 80. Lasers 12 and 14 may be external cavity diode lasers such as are commercially available from Sacher Lasertechnik of Marburg Germany. Phase modulator 30 is preferably a Lithium Niobate phase modulator, commercially available for example from New Focus Corp. of San Jose, Calif. Suitable examples include the New Focus models 4002, 4441 or the like. In one embodiment THz radiation is generated at the beating frequency of two Littman external cavity diode lasers 12 and 14 (Sacher Lion TEC520) operating near 0.78 μm. For purposes of the disclosed examples, the lasers 12 and 14 are detuned by 0.6 nm which corresponds to 0.3THz. The output of each laser 12 and 14 is evenly split using a first pair of beam splitters 20. A phase modulator 30, for example a MgO:LiNbO3 modulator such as a New Focus 4002, is inserted into the path of a beam from laser 12. After splitting and passing one beam through the modulator 30, the light from the lasers 12 and 14 are combined with another pair of beam splitters 20. The combined laser light is coupled into polarization-maintaining optical fibers 40 and delivered to both the THz transmitter 50 and receiver 60. Now referring to FIG. 1A, the transmitter 50 and receiver 60 in the present example may be Low-Temperature-Grown GaAs bowtie-type photo-conductive dipole antennae (PDA) 66. The total optical power on both channels is ˜12 mW. A bias of 20 V DC is applied to power the THz transmitter 50. For the portion of the system 10 that operates in free space (˜47 cm), beam walk of the lasers 12 and 14 does not appear to play a major role. As the wavelength of either laser 12 or 14 is piezo-tuned, <3% fluctuation in the polarized optical power that emerges from the optical fibers 40 is observed. THz radiation is generated by photomixing of the laser beams in the THz transmitter 50. The generated THz wave can be presented as a product of electric fields, ETHz˜E1□E2˜E1E2[cos(Δωt+Δφo)] where Δω=ω1−ω2, Δωo=φ1−φ2, E1 and E2 are the amplitudes of infrared EDCL electric fields at the frequencies ω1 and ω2, and phases φ1 and φ2, respectively. The electro-optic phase modulator 30, which is inserted into the optical path of the beam of laser 12 that will drive the THz transmitter 50, is oriented so that the applied voltage induces a change in refractive index along the polarization axis of the infrared laser beam. By varying the applied voltage to the phase modulator 30, the optical path length experienced by the propagating laser beam varies proportionally. Adding the additional phase shift φm(t) induced by the modulator 30 gives ETHz(t)˜E1E2[cos(Δωt+Δφo+φm(t))] where the time-dependent phase shift can be expressed as φm(t)=CoV(t) in which Co is a constant and V(t) is the applied voltage. Since the phase shift is proportional to the applied voltage, a linear phase shift requires a linear increase in voltage. After passing through free space to the THz receiver 60, the THz beam acquires a phase shift φp. The detected THz signal is determined by mixing (multiplying) the incoming THz radiation with the two infrared laser signals present at the THz receiver 60:Edet(t)˜E12E22 cos(φm(t)+φp). The output of the THz receiver 60 can be recorded with a digital lock-in amplifier 100 that locks to the ramp modulation frequency. However, if the voltage swing corresponds to a phase shift that were either smaller than or larger than 2π, the output voltage from the THz receiver 60 would not be perfectly sinusoidal. The preference for a complete 2π phase shift in the modulator 30 is illustrated in FIGS. 2(a) and 2(b). Referring to FIG. 2(a), for voltages below the equivalent of 2π phase shift, the output waveforms are not complete sinusoids. Now referring to FIG. 2(b), for voltages that are too large, a waveform swing larger than one cycle is observed. The infrared wavelength of laser 12 in FIG. 1 is kept fixed while the wavelength of laser 14 is tuned to vary the THz wavelength. In the present example, the required voltage for a 2π phase shift should remain fixed. When an object is inserted between the THz transmitter 50 and receiver 60 which modifies the phase shift of the propagating THz beam φp, the measured phase of the receiver 60 waveform shifts as well. Now referring to FIG. 1, to illustrate this effect, a thin business card was inserted between the THz transmitter 50 and receiver 60. When the phase modulator 30 voltage is set correctly, the phase of the THz receiver 60 waveform shifts by 1.6 μs corresponding to a 0.32π phase shift of the THz wave. Neglecting any birefringence, the measured phase shift for the 0.34 mm thick card corresponds to a 1.47 index of refraction. The kinks in the waveforms at 0, 10, 20, 30, and 40 ps correspond to the ramp voltage resetting from a 2π to 0π phase shift. With the card present the kink occurs almost at the peak of the waveform, while the kink occurs about half-way up the waveform when the card is removed. To demonstrate the utility of the method for fast spectral scanning, the piezo tuning capabilities on laser 14 are used to sweep the THz frequency. FIG. 3 illustrates the measured THz amplitude and phase as measured with a digital lock-in amplifier using a time constant of 640 μs. In this example, for this measurement the total tuning range of 1V corresponds to a tuning of the THz frequency by ˜3 GHz. Over this range of tuning the laser 14 does not exhibit any mode hops. The THz is scanned at 3 MHz per data point, which roughly corresponds to the spectral width of the laser. The acquisition time for the 1000 data point scan of FIG. 3 is completed in only a few seconds. In FIG. 3 the inset shows the measured change in phase during tuning. Ideally, referring to FIG. 1, if the optical path lengths for the beam from laser 14 through the optical components and fiber-optical cables 40 to the transmitter 50 and receiver 60 were identical, there would be no observed change in phase with frequency. Based on the measured 2π phase shift over 1.43 GHz, a path difference of roughly 21 cm is estimated. This distance roughly corresponds to the expected optical path length delay due to mismatched optical fiber lengths in the apparatus 10 of this embodiment. In regard to CW THz systems with mechanical scanning of the THz waveform, the 100 kHz repetition rate is roughly three orders of magnitude faster. The maximum scanning speed of the system 10 in this embodiment is limited due to the electronic bandwidth (roughly 420 kHz) of the THz receiver 60. In a classic THz imaging configuration in which the object's position is scanned between a single THz transmitter and receiver, the rapid scanning system operating at 100 kHz enables an averaging of 100 oscillations of the THz waveform with roughly 1000 pixels imaged per second. In another embodiment, using synthetic aperture imaging methods as disclosed in A. Bandyopadhyay, A. Stepanov, B. Schulkin, M. D. Federici, A. Sengupta, D. Gary, J. F. Federici, R. Barat, Z.-H. Michalopoulou and D. Zimdars, “Terahertz interferometric and synthetic aperture imaging”, J. Opt. Soc. Am. A 23, 1168 (2006), video-rate imaging may be attained. In applying THz spectroscopy to the gas phase chemical detection, it has been recognized that the spectral width of the absorption lines of low pressure gases is about 1 MHz in the THz range. THz spectroscopy instrumentation for gas analysis includes a fast scanning cavity ringdown approach, as disclosed in A. I. Meshkov and F. C. De Lucia, “Broadband absolute absorption measurements of atmospheric continua with millimeter wave cavity ringdown spectroscopy”, Rev. Sci. Instrum. 76, 083103 (2005), that enables the measurement of 6000 different THz frequencies at a rate of ˜2000 data points per second. The data shown in FIG. 3 were acquired at a rate of ˜1000 data points per second with a time constant of ˜640 μs per data point. The specification of the laser for the maximum rate of piezo-actuated frequency tuning is 12 kHz. Consequently, the rapid phase modulation system of the present invention may enable a data rate of ˜12 k data points per second with a time constant of ˜0.08 ms. Using THz time-domain systems, the maximum measured data rate for THz wireless communication has been reported to be 1Mbit/s. Möller, L.; Federici, J.; Sinyukov, A; Xie, C.; Lim, H.; Giles, R., “Data encoding on terahertz signals for communication and sensing”, Optics Letters, 33:4, 393-395 (2008). Data is encoded on the THz pulse train by modulating the bias voltage applied to the THz transmitter. There are two limitations to this data rate: the first limitation is the electronic bandwidth (420 kHz) of the THz receivers, the second is the repetition rate (˜80 MHz) of the Ti:Sapphire laser that is used to generate and detect the THz. Using the present methods, increasing the bandwidth of the THz receivers beyond 80 MHz, the data rate of the fast phase modulation system exceeds that of a time-domain system. As noted the opto-electronic methods disclosed herein are roughly 3 orders of magnitude faster than mechanical scanning methods. Utilizing the rapid phase modulation method enables MHz data rates for THz communication and can be applied for phase modulation in accordance with the present invention. In one embodiment phase modulation can be achieved using a Lithium Niobate phase modulator which can operate in the GHz range. The phase of the THz radiation can be directly modulated through a 2π phase shift. By varying the applied voltage to the modulator 50, the optical path length experienced by the propagating laser beam varies proportionally. The speed of a Lithium Niobate phase modulator can be optimized in a communications system with a function generator 110 in the hundreds of MHz range and a THz receiver having a large bandwidth response, preferably greater than 420 kHz and more preferably 80 MHz or greater. The present inventions can be employed as wireless communication devices, and applied in any environment where deployment of same would be necessary or desirable, including but not limited to airports, military installations, mobile military units, vehicles and the like. Applicants have attempted to disclose all embodiments and applications of the described subject matter that could be reasonably foreseen. However, there may be unforeseeable, insubstantial modifications that remain as equivalents. While the present invention has been described in conjunction with specific, exemplary embodiments thereof, it is evident that many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description without departing from the spirit or scope of the present disclosure. Accordingly, the present disclosure is intended to embrace all such alterations, modifications, and variations of the above detailed description. All references cited herein are incorporated fully by reference.
055704689	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method and an apparatus for decontaminating substances contaminated with radioactivity that are to be used in a nuclear power station or the like for the purpose of decontaminating such contaminated substances. 2. Description of the Prior Art Heretofore, in a nuclear power station or the like, various parts contaminated with radioactivity are produced in the power generating equipment, the attendant equipment thereof, etc., as a result of a long-term operation. To decontaminate such parts, a shot blasting method is generally employed. As a result, a great amount of shot blasting grit contaminated with radioactivity is produced. The amount of such contaminated grit, which is usually stored in metal drums, is enormous, so that a vast storage place is required. However, an attempt to expand the storage place will meet with objections from the inhabitants of the area, thereby causing a social problem. It is accordingly an object of the present invention to provide a method and an apparatus for decontaminating substances contaminated with radioactivity which help to decontaminate grit contaminated with radioactivity to thereby make it possible to reduce the requisite area for storing the grit. While in this invention the object of decontamination is mainly shot blasting grit contaminated with radioactivity, as stated above, the method and the apparatus of this invention are not restricted to the decontamination of such grit, but are also applicable to the decontamination of other substances contaminated with radioactivity. In such a decontaminating apparatus, a problem generally experienced is the necessity to move the contaminated substance from one place to another for each decontamination process. That is, the contaminated substance is first decontaminated by using a liquid, rinsed in the same liquid, and then dried. Then, the substance is decontaminated with another liquid, rinsed in the same liquid, dried, and so on. Thus, the contaminated substance must be moved from one decontaminating apparatus to another. As a result, great space is required for installing these apparatuses. Further, it is necessary to provide a step and a device for performing the bothersome operation of moving the substance from one decontaminating apparatus to another and for mechanically and reliably grasping and releasing the substance each time it is moved. It is an object of this invention to provide a method and an apparatus for decontaminating substances contaminated with radioactivity which require no such large space, do not necessitate any movement of the contaminated substance for each decontaminating step, and do not require any complicated apparatus for mechanically grasping and releasing the contaminated substance, whereby all of the decontamination processes can be performed in a single apparatus. In some cases, for convenience sake, a plurality of apparatuses according to the present invention may be provided, the contaminated substance being moved between these apparatuses. Such arrangement is also included in the scope of this invention for the purpose of achieving an improvement in operational efficiency, without any difference to the fact that a single apparatus can perform all the decontaminating processes. Another object of this invention is to provide a method and an apparatus for decontaminating substances contaminated with radioactivity which make it possible to decontaminate the contaminated substances effectively and to a sufficient degree. BRIEF SUMMARY OF THE INVENTION To achieve the above objects, this invention provides a method for decontaminating substances contaminated with radioactivity, comprising the steps of: decontaminating a substance contaminated with radioactivity by using a chelate liquid, removing the chelate liquid from the contaminated substance, drying and heating the contaminated substance by hot air at a temperature not lower than the boiling point of a solvent, adding the above-mentioned solvent to the contaminated substance to rapidly vaporize the solvent to thereby separate the remaining chelate liquid from the contaminated substance, and removing the thus separated chelate liquid from the contaminated substance together with the solvent. There is also provided an aspect of the method for decontaminating substances contaminated with radioactivity, wherein methylene chloride is used as a solvent. There is further provided another aspect of the method for decontaminating substances contaminated with radioactivity, wherein the substance contaminated with radioactivity is shot blasting grit. In accordance with this method, constructed as described above, the remaining chelate liquid adhering to the contaminated substance and containing contaminated metal ions is separated from the contaminated substance by the rapid vaporization of the solvent, and then drained along with the solvent subsequently fed. Thus, the remaining chelate can be removed effectively to thereby effect decontamination. Further, the draining of the solvent immediately results in the substance being brought to a dried state, so that there is no need to perform the bothersome operation of removing the chelate liquid by drying. This can be executed very effectively when the solvent is methylene chloride. Further, when the contaminated substance is shot blasting grit, which consists of fine particles, it is possible to effectively perform the difficult separation and removal of the remaining and adhering chelate liquid, bringing the grit in a dried state. This invention also provides an apparatus for decontaminating substances contaminated with radioactivity, comprising: a washing device including a spray device for ejecting liquid, a solvent filtering device, and a chelate liquid filtering device; a solvent supply device communicating with the spray device and the solvent filtering device and provided in such a way as to allow circulation of liquid; a rinse solvent supply device connected to the solvent supply device through the intermediation of a solvent purifying device and communicating with the spray device; a chelate liquid supply device provided in such a way as to allow circulation successively through the spray device, and the chelate liquid filtering device; an electrolytic processing device communicating with the chelate liquid supply device and adapted to electrolyze the chelate liquid; a precipitation device for supplying a precipitant to the chelate liquid which has lost its chelating property by being electrolyzed by the electrolytic device, to thereby form floes i n the liquid; a filtering device communicating with an ion exchange device and adapted to filter the flocs; a chelating agent supply device communicating with the ion exchange device and adapted to supply chelating agent to water; and a hot air supply device and a gas recovery device which communicate with the washing device. There is also provided an aspect of the apparatus for decontaminating substances contaminated with radioactivity, wherein the washing device comprises a main vessel provided to a frame and having an opening and a lid; a decontamination vessel rotatably provided in the main vessel and having a large number of pores in its outer periphery, an opening and an opening/closing lid; and a driving device connected with the decontaminating vessel and adapted to rotate the decontaminating vessel. There is provided another aspect of the apparatus for decontaminating substances contaminated with radioactivity, wherein the pores have a width or size that is smaller than that of the shot blasting grit, so that the shot blasting grit cannot pass therethrough. There is provided still another aspect of the apparatus for decontaminating substances contaminated with radioactivity, wherein the decontamination vessel has a polishing-cleaning material combined with the decontamination vessel. There is provided yet another aspect of the apparatus for decontaminating substances contaminated with radioactivity, wherein the decontamination vessel is detachably formed with respect to the main vessel, and a plurality of decontamination vessels and a plurality of main vessels are formed. Next, the operation of the apparatus will be described. In the apparatus of this invention, constructed as described above, a single apparatus can perform all of the following processes: decontamination using a solvent and decontamination using a chelate liquid; rinsing using a solvent, and separation of the remaining chelate liquid rapidly resulting from the rinsing; drying of a contaminated substance, and so on. Further, the chelate liquid can be reproduced and recycled through the steps of: electrolysis in a electrolytic device, addition of a precipitant in a precipitation device to form and precipitate flocs, filtration, processing in an ion exchange device to make clean water, and supplying thereto of a chelating agent from a chelating agent supply device. Also the pores of the decontamination vessel having a size or width that is smaller than that of the grit enable the grit to be effectively decontaminated. Further, since the decontamination vessel has a polishing-cleaning material, decontamination is performed effectively by joint use of polishing and cleaning during the so-called running-liquid washing using the solvent and the chelate liquid. Further, in an aspect where the decontamination vessel is detachably formed with respect to the main vessel, and a plurality of main vessels and a plurarity of decontamination vessels are formed, a time-consuming process and a non-time consuming process can be conducted separately, thereby achieving an improvement in operational efficiency.
	summary
	abstract	Provided is a radiation detector, including: a two-dimensional light receiving element including a plurality of pixels; and a scintillator layer having multiple scintillator crystals two-dimensionally arranged on a light receiving surface of the two-dimensional light receiving element, in which: the scintillator crystal includes two crystal phases, which are a first crystal phase including a material including a plurality of columnar crystals extending in a direction perpendicular to the light receiving surface of the two-dimensional light receiving element and having a refractive index n1, and a second crystal phase including a material existing between the plurality of columnar crystals and having a refractive index n2; and a material having a refractive index n3 is placed between adjacent scintillator crystals, the refractive index n3 satisfying a relationship of one of n1≦n3≦n2 and n2≦n3≦n1.
047599049	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the pressure vessel of a pressurized water reactor system of an advanced design and, more particularly, to an improved calandria assembly within the pressure vessel which provides requisite mechanical support functions, taking into account acceptable stress conditions and vibration problems to which the calandria assembly is subjected, while affording enhanced flow conditions. 2. State of the Relevant Art As is well known in the art, conventional pressurized water reactors employ a number of control rods which are mounted within the reactor vessel, generally in parallel axial relationship, for axial translational movement in telescoping relationship with the fuel rod assemblies. The control rods contain materials which absorb neutrons and thereby lower the neutron flux level within the core. Adjusting the positions of the control rods relative to the respectively associated fuel rod assemblies thereby controls and regulates the reactivity and correspondingly the power output level of the reactor. Typically, the control rods, or rodlets, are arranged in clusters, and the rods of each cluster are mounted to a common, respectively associated spider. Each spider, in turn, is connected to a respectively associated adjustment mechanism for raising or lowering the associated rod cluster. In certain advanced designs of such pressurized water reactors, there are employed both control rod clusters (RCC) and water displacer rod clusters (WDRC), and also so-called gray rod clusters which, to the extent here relevant, are structurally identical to the RCC's and therefore both are referred to collectively hereinafter as RCC's. In one such reactor design, a total of over 2800 reactor control rods and water displacer rods are arranged in 185 clusters, each of the rod clusters having a respectively corresponding spider to which the rods of the cluster are individually mounted. In the exemplary such advanced design pressurized water reactor, there are provided, at successsively higher, axially aligned elevations within the reactor vessel, a lower barrel assembly, an inner barrel assembly, and a calandria, each of generally cylindrical configuration, and an upper closure dome. The lower barrel assembly has mounted therein, in parallel axial relationship, a plurality of fuel rod assemblies comprising the reactor core, and which are supported at the lower and upper ends thereof, respectively, by corresponding lower and upper core plates, the latter being welded to the bottom edges of the cylindrical sidewall of the inner barrel assembly. Within the inner barrel assembly there are mounted a large number of rod guides disposed in closely spaced relationship, in an array extending substantially throughout the cross-sectional area of the inner barrel assembly. The rod guides are of first and second types, respectively housing therewithin reactor control rod clusters (RCC) and water displacer rod clusters (WDRC); these clusters, as received in telescoping relationship within their respectively associated guides, generally are aligned with respectively associated fuel rod assemblies. One of the main objectives of the advanced design, pressurized water reactors to which the present invention is directed, is to achieve a significant improvement in the fuel utilization efficiency, resulting in lower, overall fuel costs. Consistent with this objective, the water displacement rodlet clusters (WDRC's) function as a mechanical moderator control, all of the WDRC's being fully inserted into association with the fuel rod assemblies, and thus into the reactor core, when initiating a new fuel cycle. Typically, a fuel cycle is of approximately 18 months, following which the fuel must be replaced. As the excess reactivity level diminishes over the cycle, the WDRC's are progressively, in groups, withdrawn from the core so as to enable the reactor to maintain the same reactivity level, even though the reactivity level of the fuel rod assemblies is reducing due to dissipation over time. Conversely, the control rod clusters are moved, again in axial translation and thus telescoping relationship relatively to the respectively associated fuel rod assemblies, for control of the reactivity and correspondingly the power output level of the reactor on a continuing basis, for example in response to load demands, in a manner analogous to conventional reactor control operations. The WDRC's provide a mechanical means for spectral shift control of a reactor and a reactor incorporating same is disclosed in the copending application Ser. No. 946,112, filed Dec. 24, 1986 a continuation of application Ser. No. 217,503, filed Dec. 16, 1980 and entitled MECHANICAL SPECTERAL SHIFT REACTOR and applications cited therein; a system and method for achieving the adjustment of both the RCC's and WDRC's are disclosed in the copending application of Altman et al., Ser. No. 806,719, filed Sept. 12, 1985, and entitled "DISPLACER ROD DRIVE MECHANISM VENT SYSTEM." Each of the foregoing applications is assigned to the common assignee hereof and is incorporated herein by reference. A critical design criterion of such advanced design reactors is to minimize vibration of the reactor internals structures, as may be induced by the core outlet flow as it passes therethrough. A significant factor for achieving that criterion is to maintain the core outlet flow in an axial direction throughout the inner barrel assembly of the pressure vessel and thus in parallel axial relationship relative to the rod clusters and associated rod guides. The significance of maintaining the axial flow condition is to minimize the exposure of the rod clusters to crossflow, a particularly important objective due to the large number of rods and the type of material required for the WDRC's which creates a significant wear potential. This is accomplished by increasing the vessel length sufficiently so as to locate the rods below the vessel outlet nozzles, whereby the rods are subjected only to axial flow. The calandria then is provided as an additional structure, disposed above the inner barrel assembly and thus above the level of the rods. The calandria receives the axial core outlet flow, and turns the flow through 90.degree. to a radial direction for exiting from the radially oriented outlet nozzles of the vessel. The calandria thus must withstand the crossflow generated as the coolant turns from the axial to the radial directions, and must provide for shielding and flow distribution in the upper internals of the vessel. Advanced design pressurized water reactors of the type here considered incorporating such calandria structures are disclosed in the copending application Ser. No. 490,101 to James E. Kimbrell et al., for "NUCLEAR REACTOR"; application Ser. No. 490,059 to Luciano C. Veronesi for "CALANDRIA"; and application Ser. No. 490,099, "NUCLEAR REACTOR" all thereof concurrently filed on Apr. 29, 1983 and incorporated herein by reference. Additionally, structural elements known as formers are included within the vessel to assist in maintaining the desired axial flow condition within the inner barrel, assembly; modular such formers are disclosed in the copending application Ser. No. 798,195, filed Nov. 14, 1985, and entitled "MODULAR FORMER FOR INNER BARREL ASSEMBLY OF PRESSURIZED WATER REACTOR," having a common coinventor herewith and assigned to the common assignee hereof. In general, the calandria includes a lower calandria plate and an upper calandria plate. The rod guides are secured in position at the lower and upper ends thereof, respectively, to the upper core plate and the lower calandria plate. Within the calandria and extending between aligned apertures in the lower and upper plates thereof is mounted a plurality of calandria tubes in parallel axial relationship, respectively aligned with the rod guides. A number of flow holes are provided in the lower calandria plates, at positions displaced from the apertures associated with the calandria tubes, through which the reactor core outlet flow passes as it exits from its upward passage through the inner barrel assembly. The core outlet flow or a major portion thereof, as received in the calandria, turns from the axial flow direction to a radial direction for passage through radially outwardly oriented outlet nozzles which are in fluid communication with the calandria. In similar parallel axial and aligned relationship, the calandria tubes are joined to corresponding flow shrouds which extend to a predetermined elevation within the dome, and which in turn are in alignment with and in close proximity to corresponding head extensions which pass through the structural wall of the dome and carry, on their free ends at the exterior of and vertically above the dome, corresponding adjustment mechanisms, as above noted. The adjustment mechanisms have corresponding drive rods which extend through the respective head extensions, flow shrouds, and calandria tubes and are connected to the respectively associated spiders to which the clusters of RCC rods and WDRC rods are mounted, and serve to adjust their elevational positions within the inner barrel assembly and, correspondingly, the level to which the rods are lowered into the lower barrel assembly and thus into association with the fuel rod assemblies therein, thereby to control the reactivity within the core. The calandria, as before noted, performs the important function of shielding the drive rods and performing flow distribution in the upper internals. Since the radial flow, or crossflow, velocities are the range of 40 feet per second, it must be robust and able to withstand the vibrational loading imposed thereon by such crossflow. Further, the vessel provides a flow path for the coolant to enter the head region directly, for cooling the adjustment mechanisms mounted on the head assembly and vessel dome, and a downcomer flow path through which the head coolant normally passes from the head region to mix with the core outlet flow and exit from the vessel through the outlet nozzles. The head region also serves as a reservoir of low temperature coolant which passes through the downcomer flow path and ultimately into the lower internals, to cool the core in the event of a LOCA (loss of coolant accident). The calandria thus is an interface between the high temperature core outlet flow and the low temperature coolant of the head region, and accordingly is subjected to the significant temperature differential which exists therebetween, and must be flexible in order to limit the magnitude of the resulting thermal stresses. Conventional reactor internals have no structural analogy to the calandria assembly of such advanced design reactors, and thus there are no known solutions for satisfying the requirements of such a calandria assembly as above set forth and to which the present invention relates. SUMMARY OF THE INVENTION As before noted, a pressurized water nuclear reactor incorporating a calandria assembly, and particularly the improved calandria assembly of the present invention, employs a large number of control rods, or rodlets, typically arranged in what are termed reactor control rod clusters (RCC) and, additionally, a large number of water displacer rods, or rodlets, similarly arranged in water displacer rod clusters (WDRC), an array of 185 such clusters containing a total of 2800 rodlets (i.e., the total of reactor control rods and water displacer rods) being mounted in respective, corresponding rod guides and in parallel axial relationship within the inner barrel assembly of the reactor vessel. More specifically, the rods of each cluster are mounted at their upper ends to a corresponding spider, and the spider-mounted cluster is received in telescoping relationship within the corresponding rod guide. The spider is connected through a drive rod to a corresponding adjustment mechanism disposed on the exterior of the head assembly of the vessel, which provides for selectively raising or lowering the rod cluster relatively to an associated group of fuel rod assemblies, to control the reactivity, and thus the power output level of the reactor, as before described. The basic calandria structure comprises an annular, flanged cylinder, the flange of which is received on a supporting ledge of the vessel and the lower end of the cylinder being connected to the periphery of a main structural support plate, termed the upper calandria plate, of corresponding, generally circular configuration. A connecting cylinder is connected at its upper end to the periphery of, and depends from, the main structural support plate and is connected at its lower end to the perimeter of a generally circular, lower calandria plate which is much thinner than the upper calandria plate. Hollow tubes of generally circular cross-section, termed calandria tubes, extend in a parallel axial direction between the upper and lower calandria plates and are aligned with corresponding holes provided therefor in those plates. As before noted, the drive rods for the rod clusters are received through the calandria tubes and are shielded thereby from the crossflow within the calandria. The present invention provides for welded connections between the calandria tubes and the upper and lower calandria plates, which eliminate the potential of loosening, due to flow induced vibration, of mechanical connections which potentially could be employed for this purpose, and afford the further advantage of requiring less space than a mechanical connection requires. The resulting construction is quite stiff, consistent with the support requirements of the calandria, but introduces the potential of being susceptible to developing significant thermal stresses due to the differences in the material structure and geometry, and particularly the redundant structure between the lower and upper calandria plates, as presented by the calandria tubes and the connecting cylinder, or skirt, in view of the temperatures to which they are subjected. Further, whereas the upper calandria plate is relatively massive and stable, temperature differentials or gradients to which it is subjected may cause it to bend; the connecting cylinder, or skirt, is likewise very stiff, but is much thinner than the upper calandria plate and therefor exhibits a different thermal response. Thus, there is a critical requirement to relieve or limit the levels of thermal stress which can develop in the calandria assembly. In accordance with the present invention, the potentially significant thermal stresses are limited and relieved by controlling the stiffness of the lower calandria plate, in the axial direction, achieved in accordance with the proper selection of plate thickness and flow hole pattern therein, and the provision of flexible weld joints between the plate and the calandria tubes. Specifically, the lower calandria plate is selected to be of a thickness of approximately 1.5 inches and the flow hole pattern comprises a substantially symmetrical distribution of flow holes about each of the mounting holes associated with the calandria tubes; further, flexible welds are formed between the calandria tubes and the lower calandria plate, achieved in the embodiment disclosed herein by counterbored annular weld interfaces of a "J-shaped" configuration. These combined features afford the requisite stiffness for affording the requisite structural support and withstanding vibration, while relieving thermal stresses. As before noted, flow shrouds are provided in the head assembly to protect the drive lines, or drive rods, from direct exposure to the head coolant flow which, if it contacted the drive rods directly, could cause unacceptable levels of drive rod vibration due to the long, unsupported lengths of the drive rods. The flow shrouds, however, if implemented as simple cylinders surrounding the drive rods, would preclude the blowdown flow of a large portion of the coolant in the head assembly, as is relied upon for cooling the core in the event of a LOCA. Particularly, the coolant flow path from the head region to the core during blowdown is through the inside annuli intermediate the outer diameter of the drive rods and the inner diameter of the corresponding calandria tubes. Thus, once the head region drains to the tops of the flow shrouds, the remaining coolant is trapped within the head above the upper calandria plate and can no longer pass through the flow shrouds/calandria tube annuli and drain into the core. To solve this problem, the present invention introduces flow holes at the base of the flow shrouds and above the top surface of the upper calandria plate, and a flow diverter which is disposed coaxially within each flow shroud and in surrounding, shielding relationship with respect to the drive rod at the vicinity of the flow holes. The flow holes thus permit drainage of the complete head cooling region during blowdown, while the flow diverter protects the drive rod from exposure to jetting of the head coolant flow in its passage through the flow holes, the latter presenting an undesirable condition which can result in increased drive rod lateral motion and corresponding wear. The flow diverter, moreover, incorporates a flow restrictor on its interior portion contiguous the drive rod therein and disposed above the flow holes, to prevent flashing of steam from blocking the flow of coolant through the flow holes during blowdown. Such blockage potentially can occur when the liquid level within the head reaches the top of the flow shroud during blowdown, if the flow path from the top of the flow shrouds to the flow holes is not restricted. The flow restrictor more particularly provides sufficient flow resistance, such that the head coolant will continue to enter the flow holes at the base of the flow shroud without being choked by steam entering the top of the flow shroud. Accordingly, the calandria and the associated shrouds and flowhole/diverter structures afford complete shielding of the drive rods from the reactor cooant crossflow throughout the entire extent of the drive rods from the head region to the top of the rod guides, without impairment of and, indeed, while assuring the requisite head coolant flow to the core during blowdown. These and other advantages of the present invention will become more apparent from the following detailed description, taken with reference to the enclosed Figures, in which like reference numerals and letters refer to like parts throughout.
	abstract	A method and system detects failures in nuclear fuel assemblies (600). A water treatment device degasses/removes fission gases from water used in the canister (500) of a vacuum sipping device (30). A sipping procedure then detects a failure in a fuel assembly in the canister. The degassing improves a signal-to-noise ratio of the detector used during the sipping process, and improves the failure detection sensitivity of the system. Additionally and/or alternatively, gas may be recirculated through the canister water before the vacuum is applied so that fission gas concentration in the recirculating gas reaches a baseline equilibrium with the canister water. The vacuum is thereafter applied and the sipping procedure proceeds such that an increase in detected radioactivity over the baseline equilibrium indicates a leak in the fuel assembly.
	claims	1. A particle irradiation system for repeating an operation of moving an incident particle beam along a first axis and for making the incident particle beam dwell so as to irradiate the particle beam onto a target, comprising:a first deflector having a maximum deflection amount which enables the first deflector to move the particle beam along the first axis to a maximum width of the target;a second deflector having a maximum deflection amount which enables the second deflector to move the particle beam along the first axis, the maximum deflection amount by the second deflector being less than the maximum deflection amount by the first deflector; anda scanning control apparatus which controls the first deflector and the second deflector,wherein the scanning control apparatus is configured to (i) perform a control in which the particle beam is moved by increasing at least a deflection amount by the second deflector when the particle beam is moved, and (ii) subsequently perform a deflection substitution control in which a deflection by the second deflector is substituted by a deflection by the first deflector by decreasing the deflection amount by the second deflector and changing a deflection amount by the first deflector so as to make a position of the particle beam in the target dwell. 2. The particle irradiation system according to claim 1, wherein the scanning control apparatus is configured to control a rate of change of deflection amount by the second deflector, which increases the deflection amount when the particle beam moves, to be faster than a rate of change of deflection amount by the first deflector which changes the deflection amount when the particle beam dwells. 3. The particle irradiation system according to claim 1, wherein the first deflector deflects the particle beam by an electromagnet. 4. The particle irradiation system according to claim 3, wherein the second deflector deflects the particle beam by an electromagnet. 5. The particle irradiation system according to claim 2, wherein the second deflector deflects the particle beam by an electric field. 6. The particle irradiation system according to claim 1, further comprising:a beam position monitor which obtains an information of a position of the particle beam which is scanned, wherein a feedback control is added to the control, in which the deflection amount by the second deflector is decreased, by the information from the beam position monitor when the particle beam dwells. 7. The particle irradiation system according to claim 4, wherein the first deflector comprises an excitation coil of an electromagnet and a first power source which supplies a current to the excitation coil and the second deflector comprises the excitation coil of the electromagnet and a second power source which supplies a current to the excitation coil. 8. The particle irradiation system according to claim 4, whereinan electromagnet comprises a first excitation coil and a second excitation coil on the same iron core;the first deflector comprises the first excitation coil and a first power source which supplies a current to the first excitation coil; andthe second deflector comprises the second excitation coil and a second power source which supplies a current to the second excitation coil. 9. The particle irradiation system according to claim 3, wherein the second deflector is disposed at a position which is a particle beam incident side of a deflection electromagnet which deflects a main direction of particle beam traveling so as to guide the particle beam to the target. 10. The particle irradiation system according to claim 3, wherein (i) the system has the configuration of a rotating gantry and (ii) the second deflector is disposed at a particle beam incident side of a deflection electromagnet which is disposed at a most downstream side of a particle beam traveling the rotating gantry. 11. A particle beam irradiation method in which a target is irradiated by repeating an operation of moving the particle beam along a first axis and making the particle beam dwell so as to scan by a first deflector having a maximum deflection amount which enables the first deflector to move an incident particle beam along the first axis to a maximum width of the target and a second deflector having a maximum deflection amount, which enables the second deflector to move the particle beam along the first axis, and is less than the maximum deflection amount by the first deflector, the method comprising:increasing at least a deflection amount by the second deflector so as to move the particle beam in the target when the particle beam moves; andonce the particle beam is moved within the target, decreasing the deflection amount by the second deflector; andchanging a deflection amount by the first deflector in such a manner that a deflection by the second deflector is gradually substituted by a deflection by the first deflector so as to make a position of the particle beam in the target dwell. 12. The particle beam irradiation method according to claim 11, wherein a rate of change of deflection amount by the second deflector, which increases the deflection amount when a particle beam moves, is faster than a rate of change of deflection by the first deflector, which changes the deflection amount when the particle beam dwells.
040081710	summary	BACKGROUND OF THE INVENTION Ion exchange resins are conventionally used in various nuclear reactor collant, water make-up and other systems for removing mineral, metallic and other impurities from water circulated through the reactor and its associated components. Contrary to practices followed in commercial and domestic ion exchange systems used for conditioning water, the radioactive resins in the reactor systems usually are not regenerated, and once spent, must be disposed of as radioactive waste. Various methods have been developed for disposing of the radioactive water and resins. Currently, the spent resins are separated from a resin-water mixture by utilizing a centrifuge which isolates the resins to eventually form a radioactive paste or cake which is disposed of in suitable containers. In those cases where disposal of the water does not take place, it is recycled to the waste process system for further use. In other system, the resin-water slurry is mixed with a fixing agent and discharged to an appropriate disposal package. In still other systems, the resin-water slurry above is discharged into an evacuated drum filled with dry cement and equipped with a screen cage insert. The slurry fills the cage and water seeps through the screen into the cement lining the cage thereby encapsulating the resin in a lining of solidified concrete. All of these and other disposal methods are expensive because the large volume of radioactive resin and water must be contained in an appropriate receptacle to eliminate the possibility of later escape to the environment in which the receptacles are buried or stored. Moreover, substanial effort in terms of time and labor costs, and material costs, is required to carry out the processing and encapsulation of the radioactive waste products in order to comply with prevailing rules and regulations governing their disposal. SUMMARY OF THE INVENTION Briefly stated, the above disadvantages are eliminated by the present invention by providing a process which substantially reduces the volume of radioactive resins required to be encapsulated for disposition by removing all of the slurry water as well as the intrinsic water from the resins. The resins are subjected to a vacuum filtration process which removes the free water and the remaining wet resins are then exposed to a vacuum environment, where superheated steam injected into the evacuated resin container acts to remove the intrinsic water. Since the removed radioactive free water is sufficiently pure to permit recycling in a hold-up tank while the dried resin which shrinks about 50% during treatment, is discharged to a steel or other drum suitable for burial according to conventional practices. An object of the invention therefore is to provide a process for reducing the volume of spent radioactive resins by subjecting a water-resin slurry to vacuum filtration to remove free water followed by vacuum dehydration to remove intrinsic water from the resins. Another object of the invention is to provide a process for reducing the volume of spent radioactive resins by utilizing superheated steam or other fluids as a fluidizing medium thereby minimizing release of radioactive particles to the environment. Another object of the invention is to provide a process for reducing the volume of spent radioactive resins by utilizing a superheated fluid which dries the resins and further serves to transport the resins through the volume reduction system. Still another object of the invention is to provide a process for reducing the volume of spent radioactive resins by vacuum drying the resins to permit efficient packaging at low cost while returning water from the treatment process to systems associated with a nuclear reactor.
050948083	description	BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT The challenge of oxygen activation is to measure activation counts which are moving in the channel behind the casing before those counts diminish to an energy and population level where they cannot be detected. With various injection rates and channel volumes, water will move within a channel at varying fluid velocities. In channel constrictions, water velocity will increase given a constant flow rate. Conversely, in a washout or large channel, the fluid velocity will decrease. It can be seen that the distance the counts will travel before decaying to zero will be changing while logging, although the distance the detectors are spaced from the neutron source will remain fixed. Whenever the fluid velocity does not coincide with the spacing of the detectors, the count rates received by those detectors will be near zero. To solve this detection problem, according to the invention, several detectors are spaced so that for various fluid velocities, one can acquire gamma ray counts before they decay below a given threshold percentage of their original population, ranging from 3% to 10%, and preferably approximating 6.25%. To maintain high count rates, a tool T, with three, and preferably four, gamma detectors 10, 12, 14 and 16, at the proposed spacings shown below, is adapted to be suspended in and moved through the casing 20 by an armored cable. The gamma ray detectors are known per se, and may be, e.g., of the NaI T1 or BGO type. By placing four detectors at these preferred longitudinal spacings from a neutron source 18, the number of counts received under a wide range of fluid velocities can be maximized. The source 18 is, e.g., an electronic generator of the type which generates discrete pulses of fast neutrons (14 MeV), and may be of the type described in U.S. Pat. Nos. 2,991,364 or 3,596,572, which are herein incorporated by reference. A chart of the theoretical count-rate response of these detector spacings is included as FIG. 2. The detector spacings for a prior art tool are also shown. ______________________________________ DETECTOR SPACINGS PRIOR ART PREFERRED EMBODIMENT DETECTOR SPACINGS ______________________________________ D.sub.1 - 14.75" D.sub.1 - 27" D.sub.2 - 24.6" D.sub.2 - 42.75" D.sub.3 - 44" D.sub.4 - 56.5" ______________________________________ The preferred spacings can vary by about .+-.15 percent, without departing from the spirit of the invention. When measuring these count rates, it must be ensured that the count rates that are acquired are strictly from the effect of oxygen activation and not from other sources of gamma ray emission. Other sources of gamma ray emission include steel activation, NaI detector activation, as well as formation or background radiation. Steel activation occurs in the well while logging and emits 1.8 MeV gamma rays while decaying with a 2.5-hour half-life. NaI detector activation occurs in the detectors, and this reaction gives off a 2.2 MeV Beta decay with a 25-minute half-life. Detector activation is more of a problem in detectors which are spaced close to the neutron source. A discriminator is used at the output of the detectors to discriminate all counts of gamma rays which have an energy less than 2.5-3 MeV. This eliminates all counts from the three sources mentioned above. This procedure eliminates a large portion of the counts which were emitted through oxygen activation, but have low energy levels when they reach the detector due to the collisions with other formation elements prior to reaching the detector. This factor puts added emphasis on ensuring that count rates are maximized in every other way to offset this necessary discrimination procedure. The oxygen activation counts looked for must also be distinguished from gamma rays of capture within the formation. To perform this function, a time delay circuit is engaged to avoid any readings until a period in time from 3000 microseconds to 4500 microseconds after the burst ceases. This should ensure that any capture gamma ray activity is not measured. Due to the long half-life of the oxygen activation counts compared to the half-life of the formation's capture gamma ray activity, the readings obtained should contain only formation background counts and oxygen activation counts. The formation background counts should be relatively small because most background radiation counts will be discriminated out by the 3 MeV discriminator. With this configuration, oxygen activation counts will be measured about 30% of the time that the neutron source is being cycled. The prior art measures oxygen activation counts only 17.9% of the time. The above-mentioned prior art tool is configured so that it predominantly measures formation effects. It operates on approximately 28 short cycles of one millisecond each, followed by a long seven-millisecond cycle. During the short cycles, the effects of oxygen activation and background are not measured. The background and oxygen activation levels are measured during the seven-millisecond cycle. The net result is that only about 17 percent of the time are there any measurements of oxygen activation or background in the above-mentioned tool. The apparatus and method of the present invention employ cycles which are longer than the prior art cycles; e.g., several millisecond cycles, and, more particularly, five-millisecond cycles. Due to these longer cycles, the background is more frequently and efficiently measured. The use of the four detectors aids in maximizing total count rates of oxygen activation and the background, thereby statistically diminishing the effectiveness of the background as a percentage of the total measurement. Additionally, the longer cycles allow the background itself to be more accurately measured. When the four detectors are combined with the use of gates, statistical variations in the background itself are made less meaningful in view of the fact that the total number of counts measured is enhanced and the background measurement is also improved due to the longer cycle time. Typically, readings from the background occur due to the presence of uranium salts or thorium or potassium found in shales. Readings from the formation typically come from the presence of chlorides found in salt water. The advantage of this design is the increased count rates obtained due to the multiple detectors that are employed. The prior art devices' count rates are very low and yield very high statistics under many conditions. With higher count rates and lower statistics, interpretation of the data will become much more precise. The four-detector arrangement gives answers over a wider span of fluid velocities than the prior art. This would be especially advantageous when evaluating producing wells. The advantage of the apparatus of the present invention is seen in that it provides a greater span of distances between detectors and the neutron source, which makes it more adept at measuring higher water velocities than the embodiments known in the prior art. Additionally, this same feature enables the apparatus of the present invention to better measure background conditions before any neutron sources are activated, with smaller statistical errors than with the prior art devices. There are various variables that could affect the accuracy of background statistics. These include cement voids and cement thickness variations, as well as how well the cement has bonded to the formation. The apparatus of the present invention, by providing a very short spacing as well as a long spacing, provides flexibility to measure at the shorter detector spacing, which is more sensitive at low flow velocities. The use of the additional detectors in the apparatus of the present invention allows higher velocity water intrusions to be seen, where with prior art devices there would have been an indication of no water flow at all. This occurred due to high velocity of water sweeping activated oxygen beyond the detectors too quickly for the prior art devices to obtain a measurement. The apparatus and method of the present invention seek to optimize the accuracy of oxygen activation measurements. Two important variables in making accurate oxygen activation measurements are the spacing of the detectors and the frequency of measurement. In the preferred embodiment, these variables are optimized by using the four detectors in the approximate spacing hereinabove indicated. The use of the detectors in this spacing allows for an apparatus and method which can accurately detect water flow rates somewhere in the range of about 11/2 to 50 ft/min. The tool further optimizes the oxygen activation measurements by employing time gates included in the electronic circuitry 22 for processing the counts, and by cycling the neutron source 18. The rest of the circuitry 22 is known per se and may be of the type described in U.S. Pat. No. 3,603,795. The time gates are designated time delays which control the length of time the detectors can measure gamma radiation within the wellbore. The above-mentioned prior art tool is set up for a series of approximately twenty-eight short cycles of about one millisecond each, followed by one long cycle of about seven millisecond. It is only during the long cycle that meaningful background measurements can be obtained. The reason for this is that short-measurement durations do not allow for accurate measurement of the total gamma rays in the well due to background as well as oxygen activation. The background gamma ray level can vary somewhat in different portions of the well. It becomes important to measure as many counts as possible, especially in low-velocity waterflow situations where fewer counts are generated. The fewer the counts generated due to oxygen activation, the more statistically significant are the background levels of counts. The apparatus of the present invention seeks to reduce the significance of the effect of the statistical variation of the background counts by longer measurement times which promote higher count rates by optimizing detector spacing to diminish the effect of the background level of gamma rays found in the wellbore. The level of background radiation can vary within a statistical field. For example, background gamma radiation could result in a measurement of four or five counts. In low-velocity waterflow situations where the number of total counts measured is, in itself, low, the effect of the background level of radiation and its own variability become much more statistically significant. However, if the number of counts measured is increased due to the use of four detectors and long measurement cycles, raising the total counts measured decreases the statistical importance of the background level of radiation. Longer measurement cycles yield more repeatable results and their use with four detectors improves the ability to measure more counts, thereby obtaining more statistically meaningful results in low-velocity waterflow situations a greater percentage of the time than prior art tools. The apparatus and method of the present invention employs longer cycles of detector measurement (5 millisecond) through the use of gates so that, in each time cycle of source activation, oxygen activation readings are obtained. The detectors continue to sense gamma rays in an effort to more continuously determine the background level of gamma radiation in the wellbore. The combination of the four detectors, along with judicious use of the gates, permits the apparatus and method of the present invention to obtain meaningful statistical data about the background level of gamma radiation approximately 30% of the time, as opposed to only about 18% of the time for the tool of the prior art. This is particularly important since there can occur changes in the background level of gamma radiation along the depth of the well. The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.
	summary
053655575	description	Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there are seen four fuel rods 1, 2, 3, 4 that define a flow channel 6, and a lengthwise web 8 extending between them, to which further lengthwise webs 9 and 10 are parallel. Lateral protrusions in the form of bent-out sheet--metal strips 12, on which the fuel rods 1 and 2 are supported, are formed from the sheet metal of the web. In order to support the fuel rods 3 and 4, the lengthwise web has one spring 14 each. Reference numeral 16 indicates a lengthwise axis of the flow channel, which at the same time forms the center axis of a twisted tab having parts located on either side of the center axis that are indicated by reference numerals 19 and 20. As FIG. 2 shows, the lengthwise web is stamped from a metal sheet and has tabs 24 on an upper edge 22 thereof that taper toward their end. Web parts 25, 26 are formed onto this tapered end. The tabs are then twisted relative to the plane of the web in such a way that their ends are at right angles to the web, as is seen in FIG. 3. A sharp bend at an upper edge 28 of the web is avoided. Instead, the web in this case merges steadily and slowly with the tab. The angle of twisting of the tab relative to the web increases out of proportion to the distance from the upper edge of the web. This continuously more-severe twisting is shown quite clearly in FIGS. 4 and 5, in each of which planes are shown at which a twisting of 90.degree., 180.degree., and 270.degree. is attained. Arrows 32 and 34 shown in FIG. 1 indicate the direction of rotation of the twisting. It can be assumed that the fuel rods are disposed in square holes in an imaginary grid and that the tabs are disposed at intersections of the grid. At adjacent intersections carrying the tabs, the tabs of these two intersections are twisted in mirror fashion relative to one another, as is indicated by the arrows 32, 34. Reference numerals 38, 39 indicate weld seams, with which the web parts of the tabs that are perpendicular to the lengthwise webs are connected to the corresponding web parts on the tabs of adjacent lengthwise webs. In the embodiment shown in FIG. 1, only the maximum twisting angle of 90.degree. shown in FIG. 3 has been made. A contour of side edges 40, 42 of the tabs is selected in such a way that after the twisting, a practically constant spacing relative to the fuel rods results. FIG. 6 shows a part of a web 56 before its twisting, having tab parts 50 which merge with web parts 52, that are located in a plane in which twisting through 90.degree. relative to the web 56 is attained. The web parts 52 are welded together with the web parts 54 of the tabs of adjacent webs to make a crosswise web, as is seen in FIG. 7. The tabs of the webs 56 still have free ends 58, which extend into a plane in which the twisting amounts to 180.degree.. The contour of the tabs is selected in such a way that after the twisting, an annular space of constant width is produced between the tabs and the fuel rods. FIG. 8 shows tabs with a twisting of 360.degree.. In this case two helical windings of the twisted tab face one another in each quadrant of the flow channel, but their inclination decreases continuously, because of the increasing twisting toward the tab ends. The contour of the tab is selected in such a way that the lower winding leaves a narrower annular space free around the fuel rods, while the upper winding leaves a broader annular space free around these rods. The invention accordingly imposes an intensive spin upon a coolant flow in the various flow channels. In the process, however, the liquid is forced into the region adjacent the fuel rods, where it is needed to cool the fuel rods, and is made only slightly turbulent. There, only a slight tangential speed occurs with only slight flow resistance. However, the steam flows, virtually decoupled from the liquid flow, with a tolerable pressure loss through the center of the flow channel. Since the steam can attain high speeds and is removed quickly, the volumetric proportion of the liquid increases, and therefore the moderation of the neutrons increases as well. As a result, with pronounced cooling, good utilization of the fuel is achieved.

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