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	description	The present application is a U.S. National Stage of International Patent Application No. PCT/US2007/074647 filed Jul. 27, 2007 which published as WO 2008/091381 on Jul. 31, 2008, and claims the benefit of U.S. Provisional Patent Application No. 60/834,736, filed Aug. 1, 2006, the entire disclosure of each of these documents is expressly incorporated by reference in their entireties. 1. Field of the Invention The invention relates a system and method of equipping specific types of nuclear power plants with low cost storage that has a very high thermal efficiency. The invention also relates to systems and methods for operating nuclear reactors cost-effectively at maximum capacity so that nuclear plants will be able to compete with conventional fossil fueled power plants in their responsiveness to load changes over a wide range. The invention also relates to a storage system and method for a high-temperature gas-cooled nuclear reactor wherein the storage system or the method has a high efficiency (over 90%) and a low cost, allowing the nuclear reactor to always operate at maximum reactor power, while remaining capable of varying its electrical output as does a steam power plant. 2. Discussion of Background Information Nuclear reactors have a large thermal inertia, which slows their responsiveness to variations in the demand for power from the grid. Their potential to become the major source of electricity is seriously affected by this limitation. Additionally, the initial cost of investment in a nuclear power plant is high; therefore, they must be built to operate at full capacity as it is too costly to operate them at low loads. Commercial nuclear reactors are kept operating full time to ensure a profitable return on the original investment, therefore, most nuclear reactors are designed for base load. Operating them at or below half-capacity is not economically attractive since halving the load nearly doubles the cost per KWh. Another limitation on their functionality is that due to their thermal inertia, nuclear reactors can have a slow transient response. As currently designed, nuclear power plants are unable to follow the variable demands of the grid because they are expensive to operate at intermediate loads and unsuitable for rapid load following. Because they are used mostly for base power, the total contribution they can make to the grid is thereby limited. Sixty percent of the demand for electricity is for variable, controllable power. At present, this need is supplied by coal-fired steam and gas turbine power plants and to some extent by hydroelectric power. While coal-fired steam power plants can respond to load changes quickly and can operate well with a load of only 13% of design capacity, they are more expensive to use for generating electricity during periods of partial load as they must be designed for maximum capacity. Various energy storage devices have been proposed to solve this problem, but all of these proposals have limited efficiency (about 75%) and are expensive. Furthermore, while storage systems have been proposed for solar thermal power plants (see Sargent & Lundy, “Assessment of Parabolic Trough and Power Tower Solar Technology Cost and Performance Forecasts”, SL-5641, (2002), the disclosure of which is hereby expressly incorporated by reference in its entirety), they are based on liquid heat transfer fluids and molten salts, which may be unsuitable for nuclear reactors. Consider, for example, a high temperature nuclear reactor cooled by helium (He) or any intermediate heat transfer medium (see Baxi, C. B., et al.; “Evolution of the Power Conversion Unit Design of the GT-MHR”, presented at the International Congress on Advances in Nuclear Power Plants, (2006), the website en.wikipedia.org/wiki/Pebble_bed_reactor, and Penner, S. S.; Seiser, R. Schultz, K.; “Nuclear Energy for the Future”, Presented at the Meeting of the Doctors for Disaster Preparedness, Las Vegas Nev., 16-17 Jul. 2005, the disclosures of which are hereby expressly incorporated by reference in their entireties). The invention solves one or more of the problems associated with conventional nuclear power plants, is simple in design, is more robust, is cheaper and lacks one or more of the disadvantages of conventional nuclear power plants. The invention provides for a system and method for equipping specific types of nuclear power plants with low cost storage that has a very high thermal efficiency. As a result of the invention, nuclear reactors will be able to operate cost-effectively at maximum capacity and will be able to compete with conventional fossil fueled power plants in their responsiveness to load changes over a wide range. The system and method can utilize a high temperature heat transfer medium, e.g., hot helium (He), and can be used to provide heat for a steam power plant. A steam power plant can, in particular, be used as it has a high turndown ratio and provides a fast response. Of course, any device that can use heat to generate electricity may be substituted. To increase its suitability for variable operation, the size of the steam power plant can be enlarged to several times that of the nuclear reactor without increasing the size of the nuclear reactor itself. The invention also provides for a process for operating a nuclear reactor with a capability to store energy and deliver electricity when needed. The process comprises removing heat from a core of a nuclear reactor by a circulating liquid or gaseous heat transfer medium. The method also includes transferring the heat transfer medium at least one of directly to a power generating device capable of load following and to a storage system. Additionally, the process includes storing either the heat transfer medium or its heat in a storage system and delivering the either the stored heat transfer medium or its heat to the power-generating device when needed. The heat transfer medium may be a compressed gas. The compressed gas may be helium. The heat storage system may comprise a set of tanks or a set of pipes containing or filled with high temperature resistant solids through which hot gas from the nuclear reactor is passed in one direction heating up the filling and leaving a section of the end cooled such that the gas exits the tank at a low temperature to be recycled to the reactor core leaving a small section cold, and the storage circuit is either switched to another cold tank or stopped. The hot tank may remain hot as a storage medium until the heat is needed, wherein when the heat is needed, a second stream of the same compressed gas is passed in a counter current way to be heated in order to be fed to the power generating device and in a closed circuit recycled to the storage and back to the power generating device until only a small section remains hot to insure constant temperature of the hot gas delivered to the power generating device. The heat storage system may comprise a storage vessel configured such that heat is absorbed in a way that it spreads through the tank in a relatively sharp front, and preferably less wide than one tenth of the length of the vessel. The storage vessel may be similar to the design of a recuperative heat exchanger with the main difference being that in a recuperative heat exchanger the cycles are short and of similar duration and the counter current streams have similar velocities whereas when used for storage, whereby heating occurs whenever heat is available, and the heat recovery whenever needed to supply the variable load and the counter current streams may have totally different velocities. The power-generating device may be a steam power plant or a gas turbine. The heat transfer medium may be a liquid. The liquid may comprise one of a molten salt and a molten metal. The gas may be compressed and the heat exchanged with a gas of the same composition but at lower pressure, which is used in separate circuits to deposit the heat in the storage tank and to recover it when needed to the power-generating device. The lower pressure may comprise about 3 atm to about 30 atm. The process may further comprise storing hot liquid in one insulated tank, transferring it when not needed for power generation to a storage vessel, and when needed using it to provide heat to the power generating device preferably a steam power plant and the cooled liquid to a cold storage tank and when needed back to the reactor core. The process may be capable of providing fast load following whenever needed by using sufficient storage and a steam power plant is configured for a high turndown ratio and fast response. The power-generating device may be capable of meeting a maximum variable load expected even when the load is larger than the rated capacity of the nuclear power plant, whereby the nuclear power plant is able to achieve a large capacity for short times using the stored heat. The invention also provides for a system for storing heat in a nuclear power plant, wherein the system comprises at least one tank comprising solid media structured and arranged to store heat. The system is structured and arranged to pass a first fluid through at least one tank, transfer heat from the first fluid to the solid media, store the heat in the solid media, and transfer the heat from the solid media to a second fluid. The first fluid may comprise a compressed gas. The compressed gas may comprise helium. The second fluid may comprise a compressed gas. At least one of the first and second fluids may comprise a compressed gas having a high pressure. The first fluid may comprise a compressed gas moving a predetermined velocity. The first fluid may be higher in temperature than the second fluid. The first fluid may pass through at least one device heated by nuclear fission before entering the at least one tank. The second fluid may be used to produce steam in a power plant before entering the at least one tank. The first fluid may comprise a compressed gas passing through at least one nuclear reactor core. The second fluid may comprise a compressed gas passing through a power plant generating electrical power. The system may further comprise a control system controlling at least one of: when the first fluid is allowed to pass through the at least one tank and when the second fluid is allowed to pass through the at least one tank. The system may further comprise a control system controlling at least one of: when the first fluid is allowed to pass through the at least one tank, when the first fluid is allowed to bypass the at least one tank, when the second fluid is allowed to pass through the at least one tank, and when the second fluid is allowed to bypass the at least one tank. The solid media may comprise at least one of: alumina; silica; quartz; ceramic; pebbles made of at least one of alumina, silica, quartz, and ceramic; high conductivity and high temperature resistant particles; at least one packed bed of at least one of particles and pebbles; and at least one packed bed of solids. The system may be structured and arranged to move at least one of the first and second fluids through the at least one tank with at least one of uniform flow distribution and minimal pressure drops. The system may further comprise at least one nuclear reactor core heating the first fluid before the first fluid enters the at least one tank and a steam power plant receiving the heated fluid from the at least one nuclear reactor core under certain conditions and receiving the second fluid from the at least one tank under certain other conditions. The system may further comprise one or more valves controlling movement of the first and second fluids between the at least one nuclear reactor core, the at least one tank, and the steam power plant and one or more recycle compressors pressurizing the first and second fluids. The first and the second fluid may comprise helium. The first and second fluids may comprise portions of the same compressed gas flowing in a closed system, wherein the portions have different temperatures when entering the at least one tank. The first fluid may comprise a fluid heated by at least one reactor core before entering the at least one tank and the second fluid comprises a fluid exiting a power plant before entering the at least one tank. The system may have the following three cycles; a first cycle wherein the first fluid bypasses the at least one tank, flows to a power plant, and returns to at least one reactor core, a second cycle wherein at least a portion of the first fluid flows through the at least one tank and returns to the at least one reactor core, and a third cycle wherein the second fluid passes through the at least one tank, flows to a power plant, and returns to the at least one tank. The invention also provides for a system for producing electrical energy comprising at least one tank comprising solid media structured and arranged to store heat, at least one reactor core heating a first fluid before the first fluid enters the at least one tank, and a power plant receiving the heated fluid from the at least one reactor core under certain conditions and receiving a second fluid from the at least one tank under certain other conditions. The system is structured and arranged to pass the first fluid through the at least one tank, transfer heat from the first fluid to the solid media, store the heat in the solid media, and transfer the heat from the solid media to the second fluid. The system may further comprise one or more valves controlling movement of the first and second fluids between the at least one reactor core, the at least one tank, and the power plant, one or more recycle compressors pressurizing the first and second fluids, and a control system controlling at least one of: when the first fluid is allowed to pass through the at least one tank, when the first fluid is allowed to bypass the at least one tank and pass through the power plant, when the second fluid is allowed to pass through the at least one tank, and when the second fluid is allowed to bypass the at least one tank and enter the at least one reactor core. The system may have three cycles which include: a first cycle wherein the first fluid bypasses the at least one tank, flows to the power plant, and returns to the at least one reactor core, a second cycle wherein at least a portion of the first fluid flows through the at least one tank and returns to the at least one reactor core, and a third cycle wherein the second fluid passes through the at least one tank, flows to the power plant, and returns to the at least one tank. The invention also provides for a method of storing heat comprising moving a portion of heated fluid from at least one reactor core to at least one tank comprising solid media structured and arranged to store heat and transferring the stored heat from the solid media to a fluid that can be used by a power plant to generate electrical energy. The heated fluid and the fluid may comprise a compressed gas. The compressed gas may comprise helium. The method may further comprise pressurizing at least one of the heated fluid and the fluid to a high pressure. The invention also provides for a process for providing a nuclear reactor with a capability to store energy and deliver electricity when needed, wherein the process comprises removing heat from a core of a nuclear reactor by a circulating liquid or gaseous heat transfer medium, transferring the hot heat transfer medium when needed directly to a power generating device capable of load following, and when needed to a storage system, and storing either the heat transfer fluid or its heat in a storage system capable of storing either the heat transfer medium or its heat and capable of delivering the either the heat transfer medium or its heat to the power-generating device when needed. The heat transfer medium may be a compressed gas. The compressed gas may be helium. The heat storage system may comprise a set of tanks or a set of pipes containing or filled with high temperature resistant solids through which hot gas from the nuclear reactor is passed in one direction heating up the filling and leaving a section of the end cooled such that the gas exits the tank at a low temperature to be recycled to the reactor core leaving a small section cold, and the storage circuit is either switched to another cold tank or stopped. The hot tank may remain hot as a storage medium until the heat is needed, wherein when the heat is needed, a second stream of the same compressed gas is passed in a counter current way to be heated in order to be fed to the power generating device and in a closed circuit recycled to the storage and back to the power generating device until only a small section remains hot to insure constant temperature of the hot gas delivered to the power generating device. The heat storage system may comprise a storage vessel configured such that heat is absorbed in a way that it spreads through the tank in a relatively sharp front, and preferably less wide than one tenth of the length of the vessel. The storage vessel may be similar to the design of a recuperative heat exchanger with the main difference being that in a recuperative heat exchanger the cycles are short and of similar duration and the counter current streams have similar velocities whereas when used for storage, whereby heating occurs whenever heat is available, and the heat recovery whenever needed to supply the variable load and the counter current streams may have totally different velocities. The gas may be compressed and the heat exchanged with a gas of the same composition but at lower pressure, which is used in separate circuits to deposit the heat in the storage tank and to recover it when needed to the power-generating device. The lower pressure may comprise about 3 atm to about 30 atm. The power-generating device may be a steam power plant, or a gas turbine or, a combination of both. At least one power-producing device may comprise a gas turbine is utilized. The heat transfer medium may be a liquid. The liquid may comprise one of a molten salt and a molten metal. The process may further comprise storing hot metal in one insulated tank, transferring it when not needed for power generation to a storage vessel, and when needed using it to provide heat to the power generating device preferably a steam power plant and the cooled liquid to a cold storage tank and when needed back to the reactor core. The process may be capable of providing fast load following whenever needed by using sufficient storage and a steam power plant configured for a high turndown ratio and fast response. The power-generating device may be capable of meeting a maximum variable load expected even when the load is larger than the rated capacity of the nuclear power plant, whereby the nuclear power plant is able to achieve a large capacity for short times using the stored heat. The FIGURE provides a schematic of one non-limiting embodiment of the invention. The system utilizes a nuclear reactor or reactor core RC, a distribution valve system DV, a first helium compressor HC1, a steam power plant SPP, a heat storage system HSS, a helium tank HT, a second helium compressor HC2, as well as one or more valves V, and conduits, e.g., pipes, for moving the helium through the system. The solid-line (cycle 1) indicates a flow of He between the reactor core RC, distribution valve DV, the steam power plant SPP, the valve V and the first compressor HC1, and then back to the reactor core RC. The dotted-line (cycle 2) indicates a flow of He between the reactor core RC, through the distribution valve DV, through the heat storage system HSS, valve V, and compressor HC1, and then back to the reactor core RC. The dashed-line (cycle 3) indicates a flow of He from the steam power plant SPP, to the helium tank HT, through the second compressor HC2, to the heat storage system HSS, and then to the steam power plant SPP. As is apparent from the FIGURE, the invention provides for removing and storing the heat from hot He passing through one or more large storage tanks of the system HSS. The tanks can be filled with a suitable solid filling, which is resistant to (i.e., which can withstand) high temperature (e.g., pebbles or particles made from alumina, silica, quartz or ceramics) and preferably have a high heat capacity. Acceptable heat capacities (specific heat) are above 0.15 preferably above 0.2 and most preferably 0.25 and above. Heat conductivity should be above 2 W/m ° K. and preferably, above 5 W/m ° K. An example would be alumina balls (specific heat 0.27, conductivity 6-20 W/m ° K.). To minimize both the heating time of a particle and of the total pressure drop, their size should be preferably between 1 to 20 mm and most preferably between 3 to 10 mm to get acceptable heating times and pressure drop. While there may be other materials and other geometric shapes that may be preferable, the selection of appropriate materials and shapes are left to the artisan based upon the instant invention and cost considerations. In accordance with the features of the invention, the following example is provided to further facilitate understanding of the invention. When the full capacity of the nuclear power plant is used to meet the demand for electricity, all the He from the reactor core RC can be fed directly to the steam power plant SPP. When the demand for electricity is reduced or, when the plant SPP is to operate from storage HSS, the excess He not required in the steam plant SPP is directed or diverted to the storage tanks of the system HSS where its heat is deposited or transferred into the solid filling. Then, the cool He exits the system HSS and is fed back to the nuclear reactor RC. The storage system HSS is designed to allow the deposited heat to progress as a narrow front along the length of the tank(s). The tank(s) should be sufficiently oversized so that the cool end remains relatively cool at the end of the storage cycle. The same would apply when the flow is reversed. The hot end of the tank(s) would still stay hot until the end of the heat recovery cycle. The capacity of the tank(s) should be sufficient to accommodate the maximum volume of storage needed. When the stored heat of the system HSS is used to raise the temperature of the He (cycle 3), the flow through the system HSS is reversed and the cold He flowing into the system HSS from the second compressor HC2 is fed to the cold end of the system HSS and exits the system HSS hot. Due to the excellent heat transfer between the gas and the solid heat storing media, there is practically no energy loss in the heat transfer. The only loss of energy is due to pressure drops through the solid media bed, and the heat loss through the walls of the system HSS. Both of these losses, however, can be minimized by taking these into account in designing the system. Here, the aim is to make energy storage of the system HSS as efficient as possible, and to do so more so than by any other available method. When the power requirements of the system exceed normal capacity, all the He from the reactor core RC can be fed to the steam plant SPP. Additionally, pressurized He in the storage tank(s) of the system HSS is heated and also fed to the steam power plant SPP. This later flow represents a recycled counter flow through the storage tank(s) and then back to the steam plant SPP (cycle 3). The amount of gas in the He cycle 3 can be small, i.e., merely sufficient to compensate for the residence times in the reactor core RC, the power plant SPP, and the storage tank(s) of the system HSS. The arrangement described above can be likened to a steam power plant which uses stored hot He as a fuel and which stores a supply for one day of operation (or for whatever period is desired). The steam plant can be designed to meet almost any desired delivery schedule as long as the total output per day does not exceed the total output of the nuclear reactor. Thus, for intermediate loads, one can operate the plant at double the capacity of the nuclear reactor, e.g., twelve hours each day, and store the total output during the night (directing just enough He to keep the steam power plant hot). In this case, the capacity of the steam power plant would have to be doubled. The nuclear power plant could also be designed to supply instantaneously dispatchable electricity with a much larger electricity output than the capacity of the nuclear reactor itself for a limited period, i.e., based on demand. For example, by quadrupling the capacity of the steam power plant, one can supply instantaneously dispatchable electricity up to four times nominal capacity, as long as the total amount delivered does not reach the total capacity of the nuclear reactor for one day. To operate in variable mode, or to provide instantaneously available standby, however, the output of the steam power plant has to be kept above 13% of maximum capacity during this period. In this regard, the reactor can be shut down overnight and energy can be stored if enough heat is supplied to keep it warm. The invention or aspects thereof can be applied to any other power generating device that can convert the energy of the hot heat transfer medium to electricity. It can be assumed, for example, that a grid will be powered by differently designed reactors; some for base power, (40% of total power requirement of the grid) and others for intermediate load activity or load following. The invention or aspects thereof can also be applied to an HTR in which hot pressurized He (see Penner, S. S.; Seiser, R.; Schultz, K.; “Nuclear Energy for the Future”, Presented at the Meeting of the Doctors for Disaster Preparedness, Las Vegas Nev., 16-17 Jul. 2005, the disclosure of which is hereby expressly incorporated by reference in its entirety). Furthermore, the invention also contemplates using another pressurized gas which is expanded in a gas turbine to generate electricity and after cooling, is re-compressed and fed back to the reactor core. Such plants can be substituted for the steam power plant in the FIGURE. However, these other arrangements can limit the applicability of the invention to load following substantially. When used for intermediate loads, combined cycle gas turbine power plants are shut down at night and weekends and started up one hour before needed—so are the gas turbines. As should be apparent from the FIGURE, the invention can be used with combined cycle power plants or with any closed loop gas turbine (see, for example, “Small Nuclear Power Reactors”, UIC Nuclear Issues Briefing Paper #60, June 2006, the disclosure of which is hereby expressly incorporated by reference in its entirety). These can be used for intermediate power by doubling the capacity of the gas turbine and bypassing it when not in use, storing the heat in the same way as described in the example which follows. In this case, however, fast load following over large amplitudes is no longer feasible because efficiency drops severely when operation is below 80% capacity. The invention can be applied to any nuclear reactor in which the nuclear core is cooled by a circulating gas or liquid that can be used to heat or drive a power-generating device. A liquid heat transfer medium (of the type described in, for example, “Small Nuclear Power Reactors”, UIC Nuclear Issues Briefing Paper #60, June 2006) can also be used the same way in a tank filled with an appropriate temperature-resistant filling. Alternatively, one storage tank can be used for storing hot liquid and another for cold liquid. However, a much larger inventory of liquid is required when two empty tanks are used, therefore, the system described in the instant FIGURE is normally preferable. Consider a 250 MW high-temperature nuclear reactor in which the reactor core RC is cooled by circulating He under pressure. According to the invention, the hot He is used to raise or produce steam in a high-pressure, high-efficiency steam power plant SPP which has a fast response, a high turndown ratio and, can operate efficiently at 13% of capacity. Then, the gas is recycled cold to the reactor core RC. If the maximum capacity of the steam power plant SPP is increased four-fold to 1000 MW, 1000 MW can be delivered for short periods, even though the heat source is sufficient for only an average load of 250 MW. For load following, the output can be varied over the entire range, 150 to 1000 MW. For supplying intermediate power, the steam power plant SPP needs to be increased to 500 MW, operating 12-13 hours a day. In addition, it is assumed that 12 hours of storage might be optimal. Assuming also that a steam power plant SPP requires 8000 BTU/KWh, 12 times that amount or 96,000 BTU per KW capacity is required to provide 12 hours of storage; for the total plant, a storage capability of 24,000 MMBTU is required. Given that the heat resistant solid filling of the system HSS will have a specific heat Cp of 0.25 and that the temperature drop of the circulating He will be 1400° F., 0.125 tons of pebbles will be needed per KW installed or 31,200 tons of pebbles for the total plant, plus an excess of 15% to keep the two end sections at constant temperature, for a total of 36,000 tons. There are a significant number of suppliers for ceramic fillings in any desired shape, suitable alumina balls are made by MarkeTech (for example, grades P975 and P965). Special ceramic fillers can also be ordered. Another option would be to use ready made, e.g., 4-foot diameter steel pipes, and have them prepared in a shop to provide 50 to 100 foot sections coated in the inside with an insulating heat resistant layer, and designed for easy on-site assembly. The pipes can be provided already filled with the proper filling material. This is especially advisable if more than one plant is built. In this example, 700 such pipes, each 100 feet long, would be needed (or, 1200 section, each 60 feet long). In some high temperature nuclear reactors, the pressure of the helium can reach 70 to 100 atm. At this pressure, large tanks become expensive. A possible solution is to add a secondary circuit of helium at a lower pressure (2.0 to 50 atm, and preferably in the range of 20-35 atm) and heat exchange it with the primary circuit. The same applies to any other gaseous heat transfer medium used in the primary circuit. Later when needed, heat from the storage tank can be transferred to the power plant by the secondary circuit in the same manner as described above. This requires a vessel or tank volume of about 24,000 m3 or 0.1 m3/KW. It is preferable to use several tanks since a single tank of 24,000 m3 is likely too large and not optimal. The number and dimensions of the tanks used in the system HSS will depend on local conditions. While vertical tanks placed in the ground are acceptable when conditions permit, horizontal tanks in which the two end sections are easily available for maintenance may be preferable. Both ends require a distributor and an outlet collection system. There are many proven designs for distribution and collection developed for catalytic reactors which are well-known to those skilled in the art. High L/D ratios are preferable as they promote an even flow distribution, and a good plug flow. The example herein provides one possible embodiment. The desired volume of 20,000 m3 can be achieved by installing 17 tanks placed horizontally, each 8 meters in diameter and 30 meters long. Each tank will provide 14,750 KW capacity. The heat flowing through one storage tank is 111 million BTU/hr, the temperature drop is 1400° F., and the molar Cp of He is 5.0 moles. Thus, the total flow of He is 20,570 moles/hr or, 5.7 moles/second. In Table 1 we have estimates for a proposed design for this example using a pressure of 30 atm and a tank with a length of 100 feet. It should be noted that the linear velocities are small and the pressure drop and the required re-compression energy for the storage bed is quite small, and for maximum delivery during load following this pressure drop and the compression requirements are acceptable and the storage efficiency is still very high. Clearly, the total amount of electricity supplied per day cannot exceed 6 GWh/day, i.e., the capacity of the nuclear reactor in the instant example. With 12-hour storage, the maximum feasible output that can be supplied is 1 GW for 4 hours (of which 1 million KWh would come directly from the reactor RC and 3 million KWh from the storage HSS). An additional 2 GWh would have to be dispatched at the rate of 250 MW over a long time period. The foregoing is an extreme case. In practice, load following up to 500 MW for the entire time desired could be provided by one gigawatt output for shorter periods. With experience, a practical dispatching schedule that allows the system to be used for intermediate loads, peak loads and instantaneously dispatchable energy can be devised, and the system can be designed accordingly. The proposed system maximizes flexibility by using multiple tanks and by allowing for an increase in storage capacity. It should be apparent that there can be many potential variations in scheduling that fulfill the three constraints of the design: the capacity of the nuclear reactor, the storage supplied, and the size of the steam power plant. With the invention, the response to changes in demand can be as fast as with conventional steam power plants, and the nuclear reactors can always operate steadily at optimum conditions. Detailed cost estimates are not herein discussed, as they strongly depend on the location, timing and the desired load schedule. However, the following hypothetical example will illustrate the potential advantages of the invention. Consider a 250 MW high-temperature reactor RC cooled with pressurized He and designed with 12 hour heat storage in the system HSS. For simplicity, all costs are based on 1 KW capacity. We assume that the cost of the nuclear reactor complex itself without storage is $2500/KW capacity of which $350 goes for the steam power plants. To operate in intermediate mode, the capacity of the steam power plant SPP must be doubled and this adds $350/KW to the cost. When designed for load following mode, the steam power plant capacity must be increased four-fold, raising the base cost by $1050/KW. The cost of heat storage of the system HSS would be the same in each case. To store heat for 12 KWh, the storage system HSS need per KW capacity is 0.125 tons of solid media, which requires a storage vessel with a volume of 0.1 m3 per KW at a cost of less than $200. If another $100/KW is added for the cost of the rest of the storage system HSS, the total cost of the heat storage is $300 per KW. This brings the total cost to $3,250 for the total power plant. To increase the capacity four-fold, another $700 should be added for the steam plant SPP. This brings the total cost to $3950/KW of the base plant or about 60% above the cost of the base-load only cost. To supply 2 KW intermediate load from the same HTR without storage requires two 250 MW power plants. The incremental capital cost would be $2,500 compared to $750 for the storage case. Unlike the instant invention, which includes storage, however, this solution has very little load following capability. Where fast load following is required, however, the ability to produce up to 1 GW (as mentioned above) cannot be matched by any combination of HTRs without storage. Even if this were possible, the cost would be much higher. The invention described herein places high-temperature nuclear reactors at a substantial economic advantage. Today, their market is limited because they are more expensive to build and operate than water-cooled reactors and, their maximum size is small. In addition to increasing the cost-effectiveness of nuclear reactors for base load, the invention also makes them economically attractive for supplying the variable demands of the grid, which is the major part of the total market for electricity. It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to exemplary embodiments, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims. TABLE 1Nuclear Plant DesignParameterValueNuclear Plant Size (MW)250Steam Power Plant Size (MW)1000Heat Transfer FluidHePressure (atm)30TMax (° F.)1700Daily kWh via Storage/kW Installed12Power Plant Efficiency (%)42.6(1 kWh = 8000 Btu) TABLE 2Design of StorageParameterValueStorage: Number of Vessels17(Diameter × Length: m × m)(8 × 30)Solid Filling (mm)10Average Diameter Alumina ParticlesDensity (kg/m3)4000Bulk Density (kg/m3)2400Velocity in Storage Tank (m/sec)0.12Maximum Velocity in Storage Tank0.48During Load Following (m/sec)Single Pass Pressure Drops in Storage0.024Tank (atm)Maximum Single Pass Pressure Drops in0.45Storage Tank During Load Following (atm)kWh Compression per kWh Generated0.0006Maximum kWh Compression per kWh Generated0.011During Load Following
	summary
	claims	1. A surge protection apparatus comprising:a signal determination unit configured to generate a control signal by detecting a surge on a power line; anda switching unit connected between the power line and a ground terminal,wherein the switching unit is configured to comprise:a power transistor that is turned on in response to the control signal;a first diode connected between the power line and a collector of the power transistor; anda second diode connected between the ground terminal and the collector of the power transistor. 2. The surge protection apparatus of claim 1, wherein the power transistor is implemented as any one of an Insulated Gate Bipolar Transistor (IGBT), a Bipolar Junction Transistor (BJT), a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), a thyristor, and a Silicon carbide (SiC) transistor. 3. The surge protection apparatus of claim 1, wherein the signal determination unit comprises:a first capacitor connected to the power line;a first resistor connected between the first capacitor and a gate of the power transistor;a second resistor connected between the gate of the power transistor and the ground terminal; anda Zener diode connected between the ground terminal and the gate of the power transistor. 4. The surge protection apparatus of claim 1, further comprising a filter comprising:an inductor connected to the power line; anda capacitor connected between the inductor and the ground terminal. 5. The surge protection apparatus of claim 1, further comprising an overvoltage protection element comprising:an input inductor connected to the power line; anda Metal Oxide Varistor (MOV) connected between the input inductor and the ground terminal. 6. The surge protection apparatus of claim 3, further comprising a filter comprising:an inductor connected to the power line; anda capacitor connected between the inductor and the ground terminal. 7. The surge protection apparatus of claim 3, further comprising an overvoltage protection element comprising:an input inductor connected to the power line; anda Metal Oxide Varistor (MOV) connected between the input inductor and the ground terminal. 8. The surge protection apparatus of claim 4, further comprising an overvoltage protection element comprising:an input inductor connected to the power line; anda Metal Oxide Varistor (MOV) connected between the input inductor and the ground terminal. 9. A surge protection apparatus comprising:a signal determination unit configured to generate a control signal by detecting a surge on a power line; anda switching unit connected between the power line and a ground terminal and configured to comprise a power transistor that is turned on in response to the control signal,wherein the signal determination unit comprises:a first capacitor connected to the power line;a first resistor connected between the first capacitor and a gate of the power transistor;a second resistor connected between the gate of the power transistor and the ground terminal; anda Zener diode connected between the ground terminal and the gate of the power transistor. 10. The surge protection apparatus of claim 9, further comprising a filter comprising:an inductor connected to the power line; anda capacitor connected between the inductor and the ground terminal. 11. The surge protection apparatus of claim 9, further comprising an overvoltage protection element comprising:an input inductor connected to the power line; anda Metal Oxide Varistor (MOV) connected between the input inductor and the ground terminal. 12. The surge protection apparatus of claim 10, further comprising an overvoltage protection element comprising:an input inductor connected to the power line; anda Metal Oxide Varistor (MOV) connected between the input inductor and the ground terminal.
	summary
051942178	claims	1. An improved articulated sludge lance having a manipulator member, a plurality of block members attached to one end of the manipulator member and being actuatable to form an arc, and a fluid distribution member situated within the manipulator member for passing fluid therethrough, the improvement comprising: a flexible conduit constructed to extend out from an outer most end of the fluid distribution member; means for translating said flexible conduit from a first position where said flexible conduit is substantially situated inside the fluid distribution member for facilitating movement through a tube lane in a steam generator to a second position wherein said flexible conduit extends out of the fluid distribution member for cleaning; and means for positioning said flexible conduit in a preset direction for directing the fluid in close proximity to a support plate for cleaning the steam generator. 2. An improved articulated sludge lance as recited in claim 1, wherein said positioning means causes said flexible conduit to form an arc which is planar to the fluid distribution member. 3. An improved articulated sludge lance as recited in claim 1, further comprising a bumper member attached to said flexible conduit for interacting with tubes in a tube lane when the sludge lance is moved therethrough to effect a side-to-side motion of said flexible conduit. 4. An improved articulated sludge lance as recited in claim 1, wherein said positioning means comprises a cable connected to an outermost end of said flexible conduit, said cable passing through a passageway in the fluid distribution member, and being adapted to move said flexible conduit in a predetermined direction so as to place said flexible conduit into close proximity with a support plate. 5. An improved articulated sludge lance as recited in claim 4, further comprising a cam assembly attached to said cable and located on the manipulator member, said cam assembly including lever means for tensioning said cable to move said flexible conduit. 6. An improved articulated sludge lance as recited in claim 1, further comprising a nozzle positioned on an outer end of said flexible conduit. 7. An improved articulated sludge lance as recited in claim 6, further comprising a bumper member attached to said flexible conduit for interacting with tubes in a tube lane when the sludge lance is moved therethrough to effect a side-to-side motion of said flexible conduit. 8. An improved articulated sludge lance as recited in claim 6, wherein said positioning means comprises a cable connected to an outermost end of said flexible conduit, said cable passing through a passageway in the fluid distribution member, and being adapted to move said flexible conduit in a predetermined direction so as to place said flexible conduit into close proximity with a support plate. 9. An improved articulated sludge lance as recited in claim 6, wherein said nozzle comprises a plurality of orifices for directing fluid in several directions.
	description	1. Field of the Invention The invention relates to a charged particle lithography system for transferring a pattern onto the surface of a target. The invention further relates to a modulation device for use in a charged particle lithography system for patterning a plurality of charged particle beamlets in accordance with a pattern. Finally, the invention relates to a method of transferring a pattern on to a target surface using a charged particle lithography system. 2. Description of the Related Art Charged particle lithography systems are known in the art, for example from U.S. Pat. No. 6,958,804 in the name of the applicant. This lithography system uses a plurality of electron beamlets to transfer a pattern to the target surface. It operates with a continuous radiation source or with a source operating at constant frequency. The pattern data are herein sent to the modulation device, also referred to as a blanker arrangement and a beamlet blanker array. Herein, the beamlets are modulated by electrostatic deflection. The modulated beamlet is transferred to the target surface. In order to enable a high speed transfer of the pattern to the target surface, optical transmission of control signals from the control unit to the modulators is used. This transmission comprises conversion of the control signals into modulated light beams. The transmitted light beams are received by light sensitive elements and then converted to electric signals that go to one or more modulators. In order to enable the high speed e.g. high frequency modulation, the light sensitive elements are preferably located in the vicinity of the modulator it serves with control signals. The semiconductor industry requires lithography systems to be upgraded, i.e. smaller critical pattern dimensions with sufficiently high throughput. The manufacture and alignment becomes more difficult with an increase in the density of the modulation device. Such higher density is required for upgrading the lithography systems to smaller critical dimensions and higher throughput. The number of beams in a charged particle system suitable for smaller critical dimensions may be in the order of thousands or tens of thousands. For lithography purposes the area in which final projection occurs is typically limited to 27×27 mm. In a charged particle system where the electron beams remain substantially parallel this result in the area of the modulation device also being limited to 27×27 mm. Modulation of the substantially parallel electron beams requires a single modulator for each beam in the system. Therefore, increasing the number of modulators requires that the pitch of the modulators is decreased. In the known system this decrease in pitch is limited by the area that the combination of modulator, light sensitive element and wiring for the electrical signals requires thus ultimately limiting the performance of the system. In order to enable the high speed e.g. high frequency modulation, simply relocating the light sensitive elements at a relatively large distance to the modulators is not an option. Furthermore, to ensure correct functioning of the modulator components and/or the light sensitive elements, power losses over the wires should be limited as well. It is therefore an object of the invention to provide a charged particle lithography system which can reliably operate with a high density of components in the modulation device. For this purpose, an embodiment of the invention provides a charged particle lithography system for transferring a pattern onto the surface of a target, comprising: a beam generator for generating a plurality of charged particle beamlets, the plurality of beamlets defining a column; a beam stop array having a surface for blocking beamlets from reaching the target surface and an array of apertures in the surface for allowing the beamlets to reach the target surface; and a modulation device for modulating the beamlets to prevent one or more of the beamlets from reaching the target surface or allow one or more of the beamlets to reach the target surface, by deflecting or not deflecting the beamlets so that the beamlets are blocked or not blocked by the beam stop array, the modulation device comprising: a plurality of apertures arranged in arrays for letting the beamlets pass through the modulation device; a plurality of modulators associated with the plurality of apertures, each modulator being provided with electrodes extending on opposing sides of an associated aperture for generating an electric field across the aperture; and a plurality of light sensitive elements arranged in arrays, for receiving modulated light beams and converting the light beams into electric signals for actuating the modulators; wherein a surface area of the modulation device comprises an elongated beam area comprising an array of apertures and associated modulators, and a power interface area for accommodating a power arrangement for suitably powering elements within the modulation device, the power interface area being located alongside a long side of the elongated beam area and extending in a direction substantially parallel thereto. The power interface area may extend along the entire length of the long side of the elongated beam area. In this manner the power supply lines on the modulation device remain relatively short and consequently the power drop thereover remains limited. Such limited power drop may for example improve the transformation of light signals into an electric signal. Further limitation of the length of the power supply lines may be achieved by using a power interface area comprises a first portion positioned alongside a first long side of the elongated beam area and extending in a direction substantially parallel thereto, and a second portion alongside a second long side of the elongated beam area and extending in a direction substantially parallel thereto, the second long side being opposite to the first long side. Further improvement of light sensitive element performance, for example in view of reliable transformation of the light to an electric signal as mentioned above, may be achieved in a system where the surface area of the modulation device further comprises an optical interface area in which the light sensitive elements are placed, and the power arrangement is arranged for suitably powering the light sensitive elements. The optical interface area may have an elongated shape, and the optical interface area may then be located between the beam area and the power interface area. Modulated light beams may be guided towards the light sensitive elements via a plurality of optical fibers. The optical interface area may then be reserved for establishing an optical interface between the plurality of optical fibers and the light sensitive elements. Preferably, the power arrangement extends in a direction substantially perpendicular to, and away from the modulation device. In this way, limited surface area of the modulation device is covered by the power arrangement. The power arrangement may comprise a ribbon cable or a slab. The use of a slab enables an equal and stable distribution of an electric potential, which leads to an equal current supply through the long side of the beam area. In some embodiments of the invention, the surface area of the modulation device is subdivided into a plurality of alternating beam areas and non-beam areas, the modulators being located in the beam areas, and the light sensitive elements being located in the non-beam areas. The light sensitive elements in the non-beam areas are then communicatively coupled to the modulators in an adjacent beam area. The modulators in a beam area may be controllable by light sensitive elements arranged in non-beam areas located on more than one side of the beam area. Such arrangement may enable a further increase in modulator density. In some embodiments, the system further includes a shielding structure for shielding electric fields generated within the non-beam areas, for example in the vicinity of a light sensitive element. The use of such shielding structure may improve the reliability of the beamlet modulation. To enable reliable manufacturing with a high density of components, the modulators may be part of a CMOS (Complementary Metal Oxide Semiconductor) device. Electrodes of the modulators may then be part of the CMOS device, for example part of conductive layers therein. The invention further relates to a modulation device for use in a charged particle lithography system for patterning a plurality of charged particle beamlets in accordance with a pattern, the beamlets defining a column, the modulation device serving to modulate the beamlets to prevent one or more of the beamlets from reaching the target surface or allow one or more of the beamlets to reach the target surface, by deflecting or not deflecting the beamlets, the modulation device comprising: a plurality of apertures arranged in arrays for letting the beamlets pass through the modulation device and a plurality of modulators associated with the plurality of apertures, each modulator being provided with electrodes extending on opposing sides of an associated aperture for generating an electric field across the aperture; and a plurality of light sensitive elements arranged in arrays, for receiving modulated light beams and converting the light beams into electric signals for actuating the modulators; wherein a surface area of the modulation device comprises an elongated beam area comprising an array of apertures and associated modulators, and a power interface area for accommodating a power arrangement for suitably powering elements within the modulation device, the power interface area being located alongside a long side of the elongated beam area and extending in a direction substantially parallel thereto. Examples of further embodiments of the modulation device are already discussed with reference to abovementioned lithography apparatus. Finally, the invention relates to a method of transferring a pattern on to a target surface using a charged particle lithography system as described above. The method comprises the steps of: generating a plurality of beamlets defining a column; modulating the beamlets by deflecting or not deflecting the beamlets, for the purpose of completely or partly preventing the beamlets from reaching the target surface, under control of a control unit; transferring the passed beamlets to the target surface; wherein the modulating further comprises the steps of: optically transmitting data as modulated light beams carrying the pattern, to light sensitive elements; converting the modulated light beams received by the light sensitive elements into electric signals; actuating one or more modulators, on the basis of the electrical signals, to selectively deflect the beamlets for blocking or not blocking the beamlets from reaching the target surface, by means of deflection in an electric field. The figures are not drawn to scale and merely intended for illustrative purposes. Equal elements in different figures are referred to with same reference numerals. FIG. 1 shows a simplified schematic drawing of an embodiment of a charged particle multi-beamlet lithography system 1 based upon an electron beam optical system without a common cross-over of all the electron beamlets. Such lithography systems are described for example in U.S. Pat. Nos. 6,897,458 and 6,958,804 and 7,084,414 and 7,129,502, which are hereby incorporated by reference in their entirety, assigned to the owner if the present invention. Such a lithography system suitably comprises a beamlet generator generating a plurality of beamlets, a beamlet modulator patterning the beamlets into modulated beamlets, and a beamlet projector for projecting the beamlets onto a surface of a target. The beamlet generator typically comprises a source and at least one aperture array. The beamlet modulator is typically a beamlet blanker with a blanking deflector array and a beam stop array. The beamlet projector typically comprises a scanning deflector and a projection lens system. FIG. 1 does not show explicitly the positioning and support structure of the present invention. In the embodiment shown in FIG. 1, the lithography system comprises an electron source 3 for producing a homogeneous, expanding electron beam 4. Beam energy is preferably maintained relatively low in the range of about 1 to 10 keV. To achieve this, the acceleration voltage is preferably low, the electron source preferably kept at between about −1 to −10 kV with respect to the target at ground potential, although other settings may also be used. The electron beam 4 from the electron source 3 passes a double octopole and subsequently a collimator lens 5 for collimating the electron beam 4. As will be understood, the collimator lens 5 may be any type of collimating optical system. Subsequently, the electron beam 4 impinges on a beam splitter, which is in one suitable embodiment an aperture array 6. The aperture array 6 blocks part of the beam and allows a plurality of beamlets 7 to pass through the aperture array 6. The aperture array preferably comprises a plate having through-holes. Thus, a plurality of parallel electron beamlets 7 is produced. The system generates a large number of beamlets 7, preferably about 10,000 to 1,000,000 beamlets, although it is of course possible to use more or less beamlets. Note that other known methods may also be used to generate collimated beamlets. A second aperture array may be added in the system, so as to create subbeams from the electron beam 4 and to create electron beamlets 7 from the subbeam. This allows the manipulation of the subbeams, which turns out beneficial for the system operation, particularly when increasing the number of beamlets to 5,000 or more. Such manipulation is for instance carried out by a condenser lens, a collimator, a lens structure converging the subbeams to an optical axis, for instance in the plane of the projection lens. The plurality of electron beamlets 7 pass through a condenser lens array—not shown in the figure—which focuses each of the electron beamlets 7 in the plane of an array of modulators 9. The modulators 9 may be part of a CMOS (Complementary Metal Oxide Semiconductor) device. Electrodes of the modulators may then be part of the CMOS device, for example part of conductive layers therein. The array of modulators 9 is particularly an beamlet blanker array and comprises a plurality of blankers, which are each capable of deflecting one or more of the electron beamlets 7. The blankers are more specifically electrostatic deflectors provided with a first and a second electrode, the second electrode being a ground electrode. The beamlet blanker array 9 constitutes with a beam stop array 10 a modulating means 8. On the basis of input from a control unit 60, the modulating means 8 add a pattern to the electron beamlets 7. The pattern will be positioned on the target surface 13 by means of components present within an end module. In this embodiment, the beam stop array 10 comprises an array of apertures for allowing beamlets to pass through. The beam stop array, in its basic form, comprises a substrate provided with through-holes, typically round holes although other shapes may also be used. In one embodiment, the substrate of the beam stop array 8 is formed from a silicon wafer with a regularly spaced array of through-holes, and may be coated with a surface layer of a metal to prevent surface charging. In one embodiment, the metal is of a type that does not form a native-oxide skin. In some embodiments, the passages of the beam stop array 10 are aligned with the elements of the beamlet blanker array 9. The beamlet blanker array 9 and the beamlet stop array 10 operate together to block or let pass the beamlets 7. If beamlet blanker array 9 deflects a beamlet, it will not pass through the corresponding aperture in beamlet stop array 10, but instead will be blocked by the substrate of beamlet block array 10. But if beamlet blanker array 9 does not deflect a beamlet, then it will pass through the corresponding apertures in beamlet stop array 10 and will then be projected as a spot on a target surface 13 of the target 24. The target 24 is generally a substrate provided with a radiation-sensitive layer on top of its target surface 13. Examples of such substrate include, but are not limited to, a wafer and a mask. The lithography system furthermore comprises a control unit 60 comprising data storage 61, a read out unit 62 and data converter 63. The control unit 60 may be located remote from the rest of the system, for instance outside the inner part of a clean room. Using optical fibers 64, modulated light beams holding pattern data are transmitted to a projector 65 which projects the ends of the fibers (schematically depicted in plate 15) into the electron optical unit 18, here on to the modulation array 9. Modulated light beams from each optical fiber end are projected on a light sensitive element on the beamlet blanker array 9. Each light beam 14 holds a part of the pattern data for controlling one or more modulators coupled to the light sensitive element. Suitably, use is made of transmitting means 17 enabling that the projector 65 is appropriately aligned with the plate 15 at the ends of the fibers. A distance between the projector 65 and the light sensitive elements may vary. In one version, the projector 65 is located outside a virtual space column as defined by the distribution of the set of beamlets 7. This turns out suitable for minimizing disturbance of the beamlets 7. In order to project the light beam at the light sensitive element with a suitable incident angle, a mirror may be present between the projector 65 and the beamlet blanker array 9. In an alternative version, the projector may be present in the virtual space column near to the light sensitive elements 9. Such distance is suitably less than a cm, preferably in the order of mm or less. This prevents loss of light intensity while eliminating the need for assembly of the optical fibers to the light sensitive elements, and suitably thus the beamlet blanker array 9. Subsequently, the electron beamlets 7 enter the end module. Hereinafter, the term ‘beamlet’ is used to refer to a modulated beamlet. Such a modulated beamlet effectively comprises time-wise sequential portions. Some of these sequential portions may have a lower intensity and preferably have zero intensity—i.e. portions stopped at the beam stop. Some portions will have zero intensity in order to allow positioning of the beamlet to a starting position for a subsequent scanning period. In the shown embodiment, the end module comprises a beam stop array 10, a scanning deflector array 11, and a projection lens arrangement 12, although not all of these need be included in the end module and they may be arranged differently. The end module will, amongst other functions, provide a demagnification of about 100 to 500 times, preferably as large as possible, e.g. in the range 300 to 500 times. The end module preferably deflects the beamlets as described below. After leaving the end module, the beamlets 7 impinge on a target surface 13 positioned at a target plane. For lithography applications, the target usually comprises a wafer provided with a charged-particle sensitive layer or resist layer. After passing the beamlet stop array 10, the thus modulated beamlets 7 pass through a scanning deflector array 11 that provides for deflection of each beamlet 7 in the X- and/or Y-direction, substantially perpendicular to the direction of the undeflected beamlets 7. In this invention, the deflector array 11 is a scanning electrostatic deflector enabling the application of relatively small driving voltages, as will be explained hereinafter. Next, the beamlets 21 pass through projection lens arrangement 12 and are projected onto a target surface 13 of a target, typically a wafer, in a target plane. The projection lens arrangement 12 focuses the beamlet, preferably resulting in a geometric spot size of about 10 to 30 nanometers in diameter. The projection lens arrangement 12 in such a design preferably provides a demagnification of about 100 to 500 times. In this preferred embodiment, the projection lens arrangement 12 is advantageously located close to the target surface 13. In other embodiments, beam protector may be located between the target surface 13 and the focusing projection lens arrangement 12. The beam protector may be a foil or a plate, evidently provided with needed apertures, and are to absorb the released resist particles before they can reach any of the sensitive elements in the lithography system. Alternatively or additionally, the scanning deflection array 9 may be provided between the projection lens arrangement 12 and the target surface 13. Roughly speaking, the projection lens arrangement 12 focuses the beamlets 7 to the target surface 13. Therewith, it further ensures that the spot size of a single pixel is correct. The scanning deflector 11 deflects the beamlets 7 over the target surface 13. Therewith, it needs to ensure that the position of a pixel on the target surface 13 is correct on a microscale. Particularly, the operation of the scanning deflector 11 needs to ensure that a pixel fits well into a grid of pixels which ultimately constitutes the pattern on the target surface 13. It will be understood that the macroscale positioning of the pixel on the target surface is suitably enabled by wafer positioning means present below the target 13. Such high-quality projection is relevant to obtain a lithography system that provides a reproducible result. Commonly, the target surface 13 comprises a resist film on top of a substrate. Portions of the resist film will be chemically modified by application of the beamlets of charged particles, i.e. electrons. As a result thereof, the irradiated portion of the film will be more or less soluble in a developer, resulting in a resist pattern on a wafer. The resist pattern on the wafer can subsequently be transferred to an underlying layer, i.e. by implementation, etching and/or deposition steps as known in the art of semiconductor manufacturing. Evidently, if the irradiation is not uniform, the resist may not be developed in a uniform manner, leading to mistakes in the pattern. Moreover, many of such lithography systems make use of a plurality of beamlets. No difference in irradiation ought to result from deflection steps. FIG. 2 shows a simplified, schematic view of the beamlet blanker array 9. FIG. 2 effectively mere shows the key design features. FIGS. 7 and 8 show simplified top views of the beamlet blanker array 9 in different implementations. In these FIGS. 7 & 8, only a portion of the beamlet blanker array 9 is shown. FIG. 2 specifically shows the subdivision of the beamlet blanker array 9 into beam areas 51 and non-beam areas 52. Shown here is a representation for one subfield, that typically has a height h between 15 and 30 mm, for instance about 27 mm, and a width with corresponding dimensions. The width of a beam area 51 is for instance about 1.5 mm, but can be varied to any appropriate value, for instance in a range between 0.1 and 5 mm. FIG. 3A shows another simplified, schematic view of the beamlet blanker array in a different layout. Here again beamlet blanker array 9 is subdivided into areas 51 and non-beam areas 52. Shown again is a representation for one subfield, that typically has a height h between 15 and 30 mm, for instance approximately 27 mm. The width w2 of beam area 51 is now smaller than width w1 of non-beam area 52. Widths w1 and w2 can be varied to any appropriate value, for instance in a range between 0.1 mm and 5 mm, and may be chosen for resulting in an optimal distribution between beam and non-beam area. Preferably, width w1 of beam area 51 is approximately 2 mm and width w2 of non-beam area 52 is approximately 4 mm. In this embodiment, the wafer is mechanically scanned in a direction perpendicular to the main direction of the beam and non-beam areas. Also schematically shown in FIG. 3A is the projection area 20, which may have dimensions of up to 27 mm×27 mm but other arrangements are also possible. In FIG. 3A, the first non-beam area A is shown to be placed outside projection area 20. This allows for maximizing the space available for beam areas whilst at the same time realizing non-beam areas that are larger in area than the beam areas. FIG. 3B shows an advantageous variant of the previously shown layout. In this layout, each beam area 51 and non-beam area 52 are functionally divided into two halves. Here, a halve non-beam area is arranged to serve the adjacent beam area. An entire non-beam area will thus serve two separate halve beam areas, located on either side of the non-beam area. Thus, the modulators in the beam area are controlled by light sensitive elements in the non-beam areas located on more than one side. In FIG. 3B, the first non-beam area A and the last non-beam area B are also placed outside projection area 20. Again, this allows for maximizing the space available for beam areas. However, the entire array may also be placed inside projection area 20. FIG. 4 shows another simplified, schematic view of the beamlet blanker array in a different layout. Here again beamlet blanker array 9 is subdivided into areas 51 and non-beam areas 52. Shown again is a representation for one subfield, that typically has a height h between 15 and 30 mm, for instance approximately 27 mm. The width w2 of beam area 51 is again smaller than width w1 of non-beam area 52. For effectively an even greater reduction in pitch between the individual modulators in the beam area, the beam areas 51 and non-beam areas 52 are not placed exactly perpendicular to the mechanical scan direction but are rotated over a small angle α with regard to the mechanical scan direction. The rotation angle α can be small, suitably less than 5 degrees, more suitably less than 1 degree. From a side projection the modulators will appear to be closer together. This has the effect of reducing the pitch of the individual beams when projected on a target. In this embodiment, the wafer is again mechanically scanned in a direction perpendicular to the main direction of the beam and non-beam areas. In the mechanical scan direction the projection area (not shown in this figure) will still be completely covered in this layout and one non-beam area may still be placed largely outside the projection area. For allowing continuous projection of features, the beam and non-beam areas are placed in a stepped and configuration, allowing a feature to be written by beams from several beam 51 areas in succession, whilst assuring that no gaps in the pattern to be written occur. Also schematically shown in FIG. 4 is the projection area 20, which may have dimensions of up to 27 mm×27 mm but other arrangements are also possible. In FIG. 4, the first non-beam area A is shown to be partly placed outside projection area 20. A significant portion of the non-beam area A is placed outside projection area 20. This allows for maximizing the space available for beam areas whilst at the same time realizing non-beam areas that are larger in area than the beam areas. FIG. 4A schematically shows a top view of a more detailed lay-out of a portion of an embodiment of a beamlet blanker array, for example the beamlet blanker array 9 shown in FIG. 3A, 3B or 4. The blanker array portion includes a beam area 51 surrounded by an area reserved for a shielding structure 141. The beamlet blanker array further includes a non-beam area, which effectively is all the space that is not reserved for the beam area 51 and the shielding structure 141. The shielding structure 141 is arranged to substantially shield electric fields that are externally generated, for example in the proximity of light sensitive elements, such as photodiodes, within the non-beam areas. The shielding structure 141 can be described as comprising side walls forming an open-ended box-like structure. Note that the shielding structure 141 is not necessarily physically connected to the beamlet blanker array. If located within sufficiently close distance of the beamlet blanker array the shielding structure 141 can still sufficiently shield electric fields. Materials suitable for the shielding structure 141 are materials with sufficiently high electric conductivity. Additionally, the material should have sufficient strength and workability. An exemplary suitable material for use as main component of the shielding structure is titanium (Ti). Other exemplary materials that may be used include molybdenum (Mo) and aluminum (Al). In an exemplary embodiment, the shielding structure is made using Ti-plates coated with Mo. In another exemplary embodiment the shielding structure includes a stack of Mo sheets with Al spacers. The beamlet blanker array portion of FIG. 4A further includes an optical interface area 143 reserved for establishing an optical interface between a plurality of optical fibers and light sensitive elements within the beamlet blanker array. The optical fibers are arranged for guiding the modulated light beams towards the light sensitive elements within a non-beam area. The light sensitive elements, such as photodiodes, are thus placed within the optical interface area 143. The optical fibers may cover the entire optical interface area 143 or a portion thereof. The optical fibers are suitably arranged so that they do not physically block electron beamlets within the beam area 51 during use of the lithography system. Additionally, the non-beam area of the beamlet blanker array includes a power interface area 145. The power interface area 145 is arranged to accommodate a power arrangement for suitably powering the light sensitive elements, and optionally other components, within the optical interface area 143. The power arrangement 145 may extend in a direction substantially perpendicular to, and away from the blanker array. Such arrangement 145 may enable the spread of the power lines over a large surface area, which improves the efficiency and reduces losses, e.g. due to a reduced thermal resistance caused by an increased radiation surface area. An example of a power arrangement 145 is a slab, i.e. a structure which can be described as a flattened electric wire. The position of the power interface area 145 on the sides of the optical interface area 143 enables the use of relatively short power supply lines to the light sensitive elements. Consequently, the variation in voltage drop between different power lines, i.e. connections with nearby light sensitive elements versus connections with light sensitive elements further away, can be reduced. The power arrangement placed accommodated by the interface area 145 is arranged for connection with a power supply 151. Preferably, the power supply 151 is provided at or in proximity of a short end of the beam area 51. In case of a plurality of alternating beam areas 51 and non-beam areas, for example as shown in FIGS. 2, 3A, 3B and 4, the power supply 151 may extend along the short ends of these areas. The non-beam area may further include an additional interface area 147 to enable the accommodation of further circuitry, for example a clock and/or a control. The power arrangement within the power interface area 145 may also be arranged to provide sufficient power to the additional interface area 147. Although FIG. 4A schematically shows a very specific lay-out of the several areas, it will be understood that it is possible to have a different lay-out. Similarly, the size and shape of the different interface areas may vary in dependence of the specific application. FIG. 5 shows a schematic diagram of a blanker 8. It is more precisely a cross-sectional drawing in a vertical plane extending through the blanker. The blanker comprises a blanker array 9 with a plurality of apertures 35, and a beam stop array 10. For sake of reference the target 24 has also been indicated. The figure is not drawn to scale. For sake of clarity, only a section of the array 9 is indicated, including apertures 35 for beamlets 7a, 7b and 7c. These beamlets 7a, 7b, 7c form part of one group that may be generated from a beam from a single source or from a single subbeam. The present blanker 8 is designed for a system comprising a beamlet manipulator for converging groups of beamlets 7a, 7b, 7c towards a common point of convergence P for each group. This common point of convergence P is located on an optical axis O for the group of beamlets 7a, 7b, 7c. As a result of beam manipulating in the beam manipulator, the beamlets 7a, 7c are converging. These beamlets 7a, 7c have an incident angle α, γ extending between the beamlet ray and the optical axis O. The dashed lines 7a−, 7a+, 7b+, 7c− show orientations of the beamlets 7a, 7b, 7c, when these beamlets are deflected in the blanking deflectors of the blanking array 9. Beamlet 7c is herein deflected backwards into orientation 7c−; that is its incident angle γ is reduced by the operation of the blanking deflector 30. Beamlet 7b is effectively deflected forwards into direction 7b+. Therewith, beamlets 7b and 7c are deflected in mutually opposite directions, at least in the plane of this figure. For beamlet 7a, two deflection directions are shown, the backwards direction 7a− and the further forward direction 7a+. In this example, the further forward direction 7a+ would pass the beam stop array 10 and is therefore not appropriate. The backwards direction 7a− is therefore applied. FIG. 6 shows a first configuration of the deflector 30. The deflector 30 is preferably an electrostatic deflector with a first electrode 32 and a second electrode 34. This view shows an arrangement of the individual deflectors 30. FIG. 6 shows furthermore that the deflectors 30 comprise at least one concave electrode 32 or 34. Suitably, as in this embodiment, both electrodes 32, 34 have a concave shape. Apertures 35 extend through the blanker array 9 between the electrodes 32, 34. The concave shape results in the electrodes 32, 34 having a shape that is conformal to cylindrical apertures 35. This cylindrical aperture shape is in itself suitable for preventing the introduction of certain optical aberrations, such as astigmatism. By carefully choosing the layout and deflection direction the deflection of the beamlets can be spread out in all directions, preventing undesirable buildup of charge in specific locations. FIG. 7 shows a simplified top view of the beamlet blanker array 9 in one architecture of the present invention. The beamlet blanker array 9 comprises herein both individual blankers 30—also referred to as deflectors—and light sensitive elements 40. In this embodiment, the beamlet blanker array 9 is subdivided into beam areas 51 and non-beam areas 52. Both the beam areas 51 and the non-beam areas 52 are located within a virtual space column, e.g. the area defined by the distribution of the beamlets 7. The light sensitive elements 40 are located in the non-beam areas 52. Photodiodes and phototransistors are suitable examples of light sensitive elements 40. An optical waveguide may be present on top of the light sensitive elements to improve such incoupling of the light beams. Preferably, an antireflection coating is present on top of the light sensitive element 40. This at least substantially prevents reduction of light intensity due to reflections. In this embodiment, the number of light sensitive elements 40 is lower than the number of deflectors 30. Signals transmitted through the optical fibers are thereto first multiplexed, and again demultiplexed in a demultiplexer 41 after reception in the light sensitive elements 40. The demultiplexed signals are transmitted with interconnects 42 to the individual deflectors 30. These deflectors are thereto suitably arranged in an array of deflectors having columns and rows. Such array-wise addressing reduces the number of interconnects 42 extending from the demultiplexer 41 to the deflectors 30. While the current embodiment shows four deflectors 30 per light sensitive element 40, a ratio between deflectors 30 and light sensitive elements 40 may be increased up to 100 or even more, for instance 250. The need for reduction of interconnects 42 becomes then apparent. Additionally, the array-wise addressing particularly reduces area in the beam area 51 and/or mutual influencing of interconnects 42 to different deflectors 30. In order to ensure that such deflectors 30 deflect a passing beamlet 7 during a full deflection period, a memory element is preferably available. A control signal is then stored in the memory element for a period at least corresponding to the full deflection period. Thus, the control signal can be transmitted as short light pulses. An additional advantage of this arrangement is that the deflection step becomes time-wisely independent from the transmission of control signals. The transmission of control signals may thus be done sequentially, whereas the deflection of beamlets occurs simultaneously. The beam protector 55 of this embodiment may be embodied as a plate assembled substantially parallel to the substrate of the blanker array 9. Alternatively, it may be embodied as a side wall extending from the substrate. It is in both cases a structure extending, when viewed in a perpendicular projection of the beam protector 55 on the substrate, laterally around the one or one group of light sensitive elements 40. FIG. 7 shows the layout as shown previously in schematic form in FIGS. 3A, 3B, but the beam blanker array according to FIG. 7 may also be implemented in the rotated and stepped configuration of FIG. 4. FIG. 8 shows a simplified top view of the beamlet blanker array 9 comprising a plurality of beam areas 51 and non-beam areas 52. The present figure merely shows a portion of the array. The light sensitive elements 40 are here positioned in the non-beam area 52. Signals are transmitted from a light sensitive element 40 to a demultiplexer 41 via interconnect 42. Positioning of the demultiplexer 41 within the beam area 51 reduces the number of interconnects 42, particularly those with a relatively long extension from the non-beam area 52 into the beam area 51. The demultiplexer 41 is schematically shown here in the center of a 3×3 array of deflectors 30. That is a purely diagrammatical figure and is not intended to suggest that the center deflector 30 is replaced by the demultiplexer 41. In fact, it is more likely that the demultiplexer 41 is located between individual deflectors 30, at an edge of the 3×3 array or at any otherwise lost area. FIGS. 9A, 9B show examples of a power arrangement comprising a slab 201. The slab is made of an electrically conductive material, for example copper. The slab 201 in FIG. 9A takes the form of a flattened electrically conductive structure with a substantially rectangular shape. The slab 201 has a long side running parallel to the long direction of the power interface area. One of the long sides of the slab is connected to the power interface area. At least one of the short sides of the slab 201 may be connected to a power supply. The use of a slab 201 in this way provides a manner of supplying power in a well distributed manner. Instead of a rectangular structure, the slab may have a fixed width throughout the trajectory between the side at which connection is made with the power interface area 145 and the opposing side connected to the power supply. It can be readily understood, that instead of a slab 201, in this case a ribbon cable, i.e. a ribbon comprising a plurality of parallel electrically conducting cables, may be used as well. Preferably, the slab 201 has a height hslab that is equal to or greater than the long side of the beam area 51. Such height reduces impedance and reduces potential variations. The invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention, which is defined in the accompanying claims.
042788900	summary	BACKGROUND OF THE INVENTION This invention relates to the bombardment of surfaces by beams of ions. Ion bombardment has been widely used in recent years as a method of implanting into a target and of sputtering a deposit of the material of the target onto a substrate. This is usually carried out under vacuum conditions and involves directing a stream of ions at the target. Collisions of the ions with atoms or molecules of the target during implantation impart enough energy to some of these atoms or molecules to free them from the body of the target. They are then directed or attracted to the substrate and deposited on the substrate. The flow of ions involves not only a transport of mass but also the flow of an electric current. The path of current in an apparatus for sputtering thus involves a complete circuit that includes the source of the beam of ions, the beam itself, the target, and a return through a power supply to the source. Such systems work very successfully when the target is an electrical conductor which thus supplies an equipotential surface upon which the beam of ions impinges. However, several disadvantages become apparent if it is desired to direct such a beam at an insulating target, either for sputtering of atoms or molecules of the insulator onto another surface or to implant ions from the beam into the insulator. An attempt to direct an ion beam onto the surface of an insulator causes a local buildup of charges that repel the beam from the surface of the insulator. Such a beam can be seen to wander about on the surface, resulting in uneven areal implantation of ions and uneven removal of material for sputtering. The wandering occurs because areas that are locally charged repel the beam, causing it to be directed to areas that have accumulated less charge. Sometimes the buildup of charge is sufficiently great to deflect the beam entirely from the target until the charge has leaked away. This results in unsatisfactory operation, either for ion implantation or for sputtering. It is an object of the present invention to provide a better method and means of sputtering insulating material from a target onto a substrate. It is a further object of the present invention to provide a better method and means of implanting ions into an insulator. Other objects will become apparent in the course of a detailed description of the invention. SUMMARY OF THE INVENTION Sputtering of an insulating material and implantation of ions into an insulating material from an ion beam are facilitated by directing a flow of electrons at the target in an amount sufficient to equal the current flow in the ion beam. Ions are thereby directed in a controlled uniform beam onto the target for uniform areal implantation. Both implantation into the target and sputtering of material from the target to a substrate are facilitated by the resulting electrical neutralization of the beam.
	summary
	claims	1. An insulated solution injector comprising:an outer tube having a first outer surface and a first inner surface;an inner tube arranged within the outer tube, the inner tube having a second outer surface and a second inner surface, the first inner surface of the outer tube and the second outer surface of the inner tube defining an annular space, the second inner surface of the inner tube defining a solution space;an inboard end section at a distal end of the outer tube and the inner tube, the inboard end section capping a distal end of the annular space, the inboard end section including a base portion and a shield portion extending longitudinally from a distal end of the base portion, the shield portion having a groove extending a length of the shield portion from the distal end of the base portion, the base portion having a hole extending therethrough, the hole being in fluidic communication with the solution space and the groove, the hole opening up to the groove to permit injection of solution along a length of the groove, the hole being between the solution space and the groove, a majority of the groove being downstream from the hole such that the groove and, the solution space do not overlap based on a flow direction of the solution; andan outboard end section at an opposing proximal end of the outer tube and the inner tube. 2. The insulated solution injector of claim 1, wherein the second outer surface of the inner tube is spaced apart from the first inner surface of the outer tube. 3. The insulated solution injector of claim 1, wherein the inner tube is concentrically arranged within the outer tube. 4. The insulated solution injector of claim 1, wherein the annular space is isolated from the solution space. 5. The insulated solution injector of claim 1, wherein the hole extending through the base portion has a diameter ranging from 0.1 to 0.3 inches. 6. The insulated solution injector of claim 1, wherein the groove of the shield portion exposes a wedge-shaped area of the base portion, the hole extending through the wedge-shaped area of the base portion. 7. The insulated solution injector of claim 1, further comprising:an insulating layer occupying the annular space between the outer tube and the inner tube. 8. The insulated solution injector of claim 7, wherein the insulating layer is a gas layer. 9. The insulated solution injector of claim 1, wherein the hole is not overlapped by the shield portion. 10. The insulated solution injector of claim 1, wherein the shield portion is a terminal part of the outer tube. 11. The insulated solution injector of claim 1, wherein the shield portion extends beyond the inner tube. 12. The insulated solution injector of claim 1, wherein the inboard end section is disposed directly at the distal end of the outer tube. 13. The insulated solution injector of claim 1, wherein the base portion is a planar structure that contacts the outer tube and the inner tube. 14. The insulated solution injector of claim 1, wherein the base portion is a planar structure that overlaps the annular space and the solution space. 15. The insulated solution injector of claim 1, wherein the outer tube and the inboard end section enclose the distal end of the inner tube. 16. The insulated solution injector of claim 1, wherein a longitudinal axis of the hole is aligned with a longitudinal axis of the solution space. 17. An insulated solution injector comprising:an outer tube having a first outer surface and a first inner surface;an inner tube arranged within the outer tube, the inner tube having a second outer surface and a second inner surface, the first inner surface of the outer tube and the second outer surface of the inner tube defining an annular space, the second inner surface of the inner tube defining a solution space;an inboard end section at a distal end of the outer tube and the inner tube, the inboard end section capping a distal end of the annular space, the inboard end section including a base portion and a shield portion extending longitudinally from a distal end of the base portion, the shield portion having a groove extending a length of the shield portion from the distal end of the base portion, the base portion having a hole extending therethrough, the hole being in fluidic communication with the solution space and the groove, the hole opening up to the groove to permit injection of solution along a length of the groove; andan outboard end section at an opposing proximal end of the outer tube and the inner tube, the outboard end section having an opening configured to allow atmospheric air to enter and circulate within the annular space by natural convection. 18. An injection system comprising:a pipe having an exterior surface and an interior surface, the interior surface defining a flow space; andan insulated solution injector penetrating the pipe, the insulated solution injector includingan outer tube having a first outer surface and a first inner surface;an inner tube arranged within the outer tube, the inner tube having a second outer surface and a second inner surface, the first inner surface of the outer tube and the second outer surface of the inner tube defining an annular space, the second inner surface of the inner tube defining a solution space;an inboard end section at a distal end of the outer tube and the inner tube, the inboard end section capping a distal end of the annular space, the inboard end section being within the flow space of the pipe, the inboard end section including a base portion and a shield portion extending longitudinally from a distal end of the base portion, the shield portion having a groove extending a length of the shield portion from the distal end of the base portion, the base portion having a hole extending therethrough, the flow space being in fluidic communication with the solution space via the hole, the hole opening up to the groove to permit injection of solution along a length of the groove, the groove facing a downstream side of the flow space in the pipe, the hole being between the solution space and the groove, a majority of the groove being downstream from the hole such that the groove and the solution space do not overlap based on a flow direction of the solution; andan outboard end section at an opposing proximal end of the outer tube and the inner tube. 19. The injection system of claim 18, wherein the insulated solution injector extends into the pipe about 5 to 15% of an inside diameter of the pipe. 20. The injection system of claim 18, wherein the insulated solution injector extends into the pipe about 1 to 2 inches beyond the interior surface of the pipe.
	description	The present invention provides a process for fabricating a robust x-ray mask tool. In particular, the present invention provides a process for fabricating an x-ray mask tool capable of providing a plurality of x-ray dose levels across the face of the mask. Such a mask would have great utility for providing molds for producing microparts which incorporate lei a wide variety of feature sizes and packing densities, i.e., part patterns and geometries which tend to be difficult to develop uniformly. Large widely spaced features tend to develop faster than small closely packed features at the same exposure dose since it is much more difficult for fresh developer to migrate to a reaction interface as the depth-to-width aspect ratio of a feature becomes large. By xe2x80x9cfeaturexe2x80x9d it is meant the volume within the substrate defined by a surrounding wall or channel that is created when the exposed substrate is chemically developed. By xe2x80x9cpacking densityxe2x80x9d it is meant the relative number of features per unit area or the relative proximity of a xe2x80x9cfeaturexe2x80x9d to an unexposed portion. This invention describes a lithographic mask having x-ray attenuating structures applied to one or both sides of an essentially x-ray transparent support media. Furthermore, the invention describes a lithographic mask having features which may be embedded into the thickness of the supporting substrate by a mask, etch, and plating process described in co-pending U.S. patent application Ser. No. 09/636,002, entitled xe2x80x9cX-ray Mask and Method for Providing Samexe2x80x9d filed on Aug. 9, 2000 and herein incorporated by reference. The process begins with a standard silicon wafer or disc. The two xe2x80x9cfacesxe2x80x9d of the substrate, i.e., each of the two large, flat surfaces of the wafer or similar article, are first xe2x80x9cmetallizedxe2x80x9d by depositing one or more metal layers onto the surfaces of the substrate. The metallizing layers are quite thinxe2x80x94typically a few hundred angstroms, and are used to provide a conductive deposition layer for subsequent processing. After metallizing the substrate a number of xe2x80x9cwitnessxe2x80x9d marks are applied onto one of the two plated surfaces. The marks are placed at several locations on one face of the substrate. The witness marks will be used, subsequently, as alignment aids for establishing pattern registration between the substrate top and bottom faces. A polymer photoresist is placed onto a top surface opposite the surface with the witness marks such that the layer is several microns thick. The method of application and composition of the resist is not critical: any technique for applying such layers may be used, including dipping, spraying, spinning or vapor depositing, and either organic or inorganic resists may be used. The resist layer is baked, or otherwise cured, and the desired image pattern rendered onto the top layer surface by using any conventional lithographic processes, e.g., by a direct contact transmission mask, by imaging the reflection of a non-contact mask through camera optics onto the resist surface, or by directly xe2x80x9cwritingxe2x80x9d the image by using a programmable e-beam writer. Each type of masking technique employs some method of pattern alignment registration such as a corresponding set of witness marks designed to complement those marks xe2x80x9cwrittenxe2x80x9d onto the metallized surface of the silicon substrate. Important to the proper operation of the invention is the ability to co-locate the position of the mask with respect to the witness marks on the underside of the substrate. After establishing the position of the mask with respect to the substrate, the image of the mask is rendered into the resist by well-known lithographic techniques. The resist layer is then chemically xe2x80x9cdevelopedxe2x80x9d and the exposed areas of the resist either removed or retained, depending upon the specific resist chemistry used. Following the development of the resist, the patterned substrate is coated with a xe2x80x9cthickxe2x80x9d layer of gold or some similar metal selected from the IUPAC group of Transition metals in new Groups 4-12, plus aluminum and tin. The term xe2x80x9cthickxe2x80x9d is used here in a relative sense to mean 1 to 3 orders of magnitude thicker then the initial several hundred angstrom thick metallize layer. Typically this layer would range from about 0.1 microns to about 5 microns in thickness depending upon the amount of x-ray attenuation desired. Coating is typically done by electroplating or by electroless deposition onto the metallize layer but may be done by any method providing the applied layer is uniform in composition and structure and provides a continuous, condensed layer. The thick x-ray attenuating layer may be laid down, for instance, by particle vapor deposition, chemical vapor deposition, plasma spraying, or epitaxy deposition. Time and cost, however, favor a plating process. Once plated, the incipient mask is planarized by lapping the top plated surface layer down to the resist layer and then chemically removing the remaining resist leaving only the patterned metal layer on the substrate surface. Finally, the foregoing process is repeated a second time to apply a second x-ray attenuating layer having a second pattern to the opposite surface of the substrate. This second pattern is designed to overlap various portions of the first pattern and thus provide an added thickness of attenuating material through which the radiation must pass. What is provided therefore, is a xe2x80x9csteppedxe2x80x9d, xe2x80x9cgradedxe2x80x9d mask pattern permitting reduced radiation exposure over specific regions on the mold. This second pattern layer is provided by inverting the coated and patterned substrate and once again aligning the image forming mask with the witness marks applied to the first surface of the substrate. As before, the substrate second surface is coated with a resist layer, imaged by means of a second, similar, imaging mask, the resist developed and the back surface (second) of the substrate, coated, as before, with gold or some similar metal selected from the aforementioned list of Transition metals. The second surface is then planarized and the remaining resist removed leaving a two sided x-ray mask. Alternately, the second surface pattern imaging step may be performed immediately after the first imaging step has been rendered but not developed. This has the advantage of requiring only one step to develop, and one step to plate (or deposit) rather than two, and thus avoiding potential damage to the mask due to handling. It should be noted that as a practical matter the silicon substrate comprises a disc, or xe2x80x9cwafer,xe2x80x9d which is thinned to adjust the wafer thickness to a useful point since the silicon itself can be used to attenuate radiation. Thinning, of course, must be done prior to second surface processing. Furthermore, depending on the desired final thickness of the substrate it may be necessary to provide the wafer with a series of internal xe2x80x9cribsxe2x80x9d criss-crossing the thinned surface to support and strengthen the finished mask. Unfortunately, such structures are potentially incompatible with a second surface mask pattern and an alternate embodiment is necessary to overcome this difficulty. In order to provide a mask comprising the benefit of the two surface mask patterns, while still allowing for the possibility of thinning the substrate, it is necessary to place both patterns on the same surface of the wafer. This may be done by embedding the first pattern into the thickness of the substrate, as taught by co-pending U.S. patent application Ser. No. 09/636,002, herein incorporated by reference, followed by a second pattern imaging and deposition process applied over the embedded pattern. Altemately, a second technique provides a two step pattern imaging and deposition process wherein a second pattern layer is placed directly on top of a first layer forming, thereby, a xe2x80x9csteppedxe2x80x9d mask. As required, detailed embodiments of the present invention are disclosed herein. However, it is to be understood that the disclosed embodiments are merely exemplary of the present invention which may be embodied in various systems. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to variously practice the present invention. Several embodiments are disclosed hereunder: embodiment 1 refers to a two surface mask wherein first and second imaging patterns are deposited on top and bottom surfaces of the silicon substrate wafer; embodiment 2 refers to a two layer mask comprising a first imaging layer embedded into a first surface and a second overlaying imaging layer; embodiment 3 refers to a two layer mask comprising a first imaging layer on a first surface and a second overlaying imaging layer deposited onto the first layer. One embodiment of the steps of the invention are described with reference to FIGS. 1 through 5. Referring to FIG. 1A, the process begins with a silicon substrate or wafer 10. This substrate can, generally, have any useful shape and thickness but should of necessity be a thin wafer having parallel top and bottom surfaces 11 and 12. In particular the present invention is most easily implemented by using an industry standard 100 mm Øxc3x970.67 mm thick wafer. However, because the standard wafer thickness is much too thick to allow standard fluxes of x-rays to penetrate, these wafers must be thinned first using a conventional blanket etch to reduce its thickness below about 100 microns. Etching is performed only in selective zones in order to leave sufficient structural support for further processing the wafer. All FIGURES shown for this embodiment, therefore, are intended to show only a limited cross section of wafer 10 in an area thinned by the blanket etching process. In FIG. 1B the process begins with xe2x80x9cfacesxe2x80x9d 11 and 12, of the substrate being xe2x80x9cmetallizedxe2x80x9d by depositing a first layer of chromium followed by a second layer of gold in order to provide first and second surfaces 13 and 14. By xe2x80x9cfacesxe2x80x9d it is meant each of the two large, flat surfaces of the wafer or similar article. First and second metallized layers 13 and 14 are quite thinxe2x80x94typically several hundred angstroms, respectively, and are used to provide a conductive deposition layer for subsequent processing. Metallization is performed by any known technique including but not limited to vapor phase deposition, particle deposition, or epitaxial deposition. After metallizing the substrate several xe2x80x9cwitnessxe2x80x9d marks 15 are applied onto one of the two metallized surfaces. This may be done by using any conventional lithographic technique or by xe2x80x9cwritingxe2x80x9d the pattern directly into the metallized coating by means of an electron beam or laser such that the xe2x80x9cwitnessxe2x80x9d marks in the metallized layer are removed. The marks are placed at several locations remote, possible peripheral, points on one xe2x80x9cfacexe2x80x9d of the substrate. The witness marks will be used, subsequently, as alignment aids for establishing mask pattern registration between the substrate top and bottom metallized surfaces 13 and 14. In FIG. 1D a liquid photoresist film 16 (herein Shipley SJR5740) is applied by spin coating to a thickness of less than about 50 microns, preferably from about 5 to 20 microns, and then baked at a temperature of 110xc2x0 C. for about 10 minutes in order to at least partially cure the resist layer. The particular resist thickness is chosen so as to provide a stencil form for a thick absorber layer while still providing for fully exposing the full thickness of the resist during the light exposure phase. In a next step, shown in FIG. 2A, a standard direct-contact lithographic mask 17, herein embodying a negative trace image of the desired pattern 18, is placed on the surface of resist layer 16. Alternately, it is known to those skilled in the art that proximity exposure is also effective as a means for providing the requisite trace image. Mask 17 is provided with corresponding witness marks 19 and aligned such that witness marks 19 on the mask and witness marks 15 the underside of the metallized substrate are brought into coincidence, as seen in FIG. 2A (mask 17 is shown above the surface of resist layer 16 for clarity sake only). This may be done by first fixing the position of the substrate and then moving the mask over the substrate by means of a standard x-y translatable stage driven by a pair of precision stepper motors (not shown). Mask 17 and substrate 10 are aligned by imaging the underside of the substrate, metallized surface 14, with its witness marks 15, using conventional microscopy and camera optics and combining this image with an image of the corresponding set of witness marks 19 in pattern-forming mask 17. By carefully adjusting the x-y stage the two sets of witness marks may be brought into coincidence or are otherwise uniquely arranged. Once the mask and substrate are properly aligned, the portions of the resist layer 16 exposed by the open areas of the mask are subjected to a source (not shown) of broadband light, 20, herein shown in FIG. 2B. The exposure source used herein was a high pressure mercury-vapor lamp emitting light over a spectral range of about 365 nm to 450 nm and providing a dose of approximately 1000 millijoules/cm2 measured at a wavelength of 365 nm. In the next step in the process, illustrated in FIG. 2C, the photoresist is chemically xe2x80x9cdevelopedxe2x80x9d and the exposed portions, 21a, of photoresist layer 16 are removed. What remains are the unexposed portions, 21b, of the resist in an inverse image of the mask pattern wherein this inverse image comprises xe2x80x9cclearxe2x80x9d areas 22 exposing portions of the underlying metallize layer 13. Again, this step is performed using standard and well-known lithographic processes. It should be noted that the choice of a positive or negative image mask depends largely on the nature of the photoresist used, i.e., depending upon whether or not the exposed portion of the photoresist is removed or left intact after the resist has been developed. Either approach is possible, although, depending on the nature of the desired pattern, one is usually more preferred than the other. After cleaning and drying the developed mask, those portions of the mask surface which have been uncovered during the photoresist development process (open areas 22) are subsequently covered with a thin, pin-hole free metal film 23, such as that shown in FIG. 2D. The chosen process for applying the coating of FIG. 2D is either electrochemically or electroless plated although any other coating process which would provide such a layer would be equally effective. Such methods could include, but are not limited to, thermal evaporation or particle vapor deposition (PVD) process, chemical vapor deposition (CVD), sputtering and spraying coating methods. As disclosed herein, the film 23 is rendered In gold and is as thick as the resist layer. Any similar metal or combination of metals would be equally useful including most of the metals in the Transition series of metal listed in New IUPAC Group Numbers 4xe2x88x9d12 of the Period Table of elements, alloys thereof, and certain of the metals of Groups 13 and 14, such as aluminum and tin providing that the thickness of the metal layer is adjusted to provide for attenuating radiation to a desired level. Following this step of depositing the x-ray absorbing layer 23, the mask assembly is planarized, as shown in FIG. 2D, to remove metal from across the top surface of the photoresist 22. Planarizing is typically performed by lapping the top surface to remove the xe2x80x9coverburdenxe2x80x9d metal layer and developing and removing the remaining photoresist layer. Close control of the final desired pattern thickness can be achieved by lapping, however, it is generally easier to simply time the plating process. To complete the variable dosing x-ray mask a second pattern layer 24 is now laid down on the wafer face opposite first pattern 18 by repeating the steps of FIGS. 1D through 2D in the same manner as discussed above. In FIG. 3A a second resist film 24 (Shipley SJR5740) is applied by spin coating to a thickness of less than about 50 microns, preferably from about 5 to 20 microns, and then baked at a temperature of 110xc2x0 C. for about 10 minutes in order to at least partially cure the resist layer. The particular resist thickness is again chosen so as to provide a stencil for a thick absorber layer while still providing for fully exposing the full thickness of the resist during the light exposure phase. Importantly, clear zones 24a are provided along the outside edge of substrate 10 by covering the substrate edge with a template or barrier prior to resist coating. This is done in order not to obstruct witness marks 15. In FIG. 3B, another direct-contact lithographic mask 25 again embodying a negative trace image of the desired second pattern 26, is placed over the surface of resist layer 24. Mask 25 is provided with a duplicate set of witness marks 19a and aligned such that marks 19a are brought into coincidence with marks 15 in the metallized substrate. As before, this may be done by fixing the position of the substrate and then moving mask 25 over the substrate by means of the x-y translatable stage (not shown). and imaging the substrate metallized surface 14 and its witness marks 15, using conventional microscopy and camera optics to combine this image with an image of the corresponding set of witness marks 19a. Once the mask and substrate are aligned, the portions of the resist layer 24 exposed by the open areas in the mask are subjected to a source (not shown) of broadband light, 20, herein shown in FIG. 3B. The exposure source used herein was a high pressure mercury-vapor lamp emitting light over a spectral range of about 365 nm to 450 nm and providing a dose of approximately 1,000 millijoules/cm2 measured at a wavelength of 365 nm. In FIG. 3C, the photoresist has been chemically xe2x80x9cdevelopedxe2x80x9d and the exposed portions of photoresist layer 24 are removed. What remains are the unexposed portions, 27, of the resist in an inverse image of the mask pattern wherein this inverse image comprises xe2x80x9cclearxe2x80x9d areas 28 exposing portions of the underlying metallize layer 14. Again, this step is performed using standard and well-known lithographic processes. After cleaning and drying the developed mask, those portions of the mask surface which have been uncovered during the photoresist development process (open areas 28) are subsequently covered with a thin, pin-hole free metal film 30, as shown in FIG. 3D. The chosen process for applying the coating of FIG. 3D may be either by means of electrochemical or electroless plating although any other coating process which would provide a continuous layer would be equally effective. Such methods could include, but are not limited to, thermal evaporation or particle vapor deposition (PVD) process, chemical vapor deposition (CVD), sputtering and spraying coating methods. As disclosed herein, the film 30 is rendered in gold and is as thick as the resist layer. Any similar metal or combination of metals would be equally useful including most of the metals in the Transition series of metal listed in New IUPAC Group Numbers 4-12 of the Period Table of elements, alloys thereof, and certain of the metals of Groups 13 and 14, such as aluminum and tin providing that the thickness of the metal layer is adjusted to provide for attenuating radiation to a desired level. Following this step of depositing the x-ray absorbing layer 30, the mask assembly is planarized, as shown in FIG. 4D, to remove metal from across the top surface of the photoresist 24. Planarizing is typically performed by lapping the top surface to remove the xe2x80x9coverburdenxe2x80x9d metal layer and developing and removing the remaining photoresist layer. The sole remaining issues are 1.) the registration of the second pattern with the first pattern in order that pattern features overlap within an achievable tolerance limit, and 2.) achieving a desired level of additional attenuation of the incoming radiation flux sufficient to slow development in selective areas in order that all areas develop at about the same rate. Accomplishing the first of these tasks is made somewhat easier since it is the larger open areas (areas to be removed during developing) surrounding isolated features in which the development reaction is desired to be slowed and therefore must be underexposed to the radiation. Since it is only necessary that most of this area be underexposed, it is not necessary that the patterns exactly match each other so long as the profile of one pattern does not extend over the profile of the other. The pattern dosest to the incoming beam of radiation may be used to establish the desired overall size and shape of the finished mold while the second, overlapping pattern may be laid down slightly smaller than the primary pattern such that its image does not overlap that of the primary pattem. This has the effect of slowing PMMA development over most of the larger portion to be removed while still providing proper definition for the final part without the need for the extremely precise registration necessary if a near zero stack-up tolerance is required between patterns. Accomplishing the second issue requires some experimentation in order to determine the desired reduction in mold dissolution rate since this factor will depend to a large extent on the geometry and packing density of the parts comprising the mold. In general, however, these effects have been addressed previously in an article by Griffiths, et al., entitled xe2x80x9cthe influence of feature sidewall tolerance on minimum absorber thickness for LIGA x-ray masks,xe2x80x9d published in J. Micromech. Microeng., vol. 9 (1999) pp. 353-361, herein incorporated by reference. This article provides numerical solution with which to estimate the total local dose rate of x-rays transmitted by a hypothetical x-ray mask. Operation of mask 100 is shown schematically in FIG. 5, wherein collimated x-ray radiation strikes the mask perpendicularly to surfaces 11 and 12. In those areas where the x-ray flux merely passes though the thinned silicon substrate the x-ray flux is D1. In those areas where the radiation is obstructed by pattern 18 or 26 the radiation flux D0 is attenuated to flux D2. Where the radiation is obstructed by both of patterns 18 and 26, the radiation flux is further attenuated to a flux D3. A second embodiment of the present invention follows many of the first steps developed in embodiment one, but adds several additional steps to provide the etched trench feature of this embodiment. These steps are described with reference to FIGS. 6 through 12. Referring to FIG. 6A, the process for embodiment 2 begins, as before, with silicon substrate or wafer 10. This substrate can, generally, have any useful shape and thickness but should of necessity be a thin wafer having parallel top and bottom surfaces 11 and 12. In particular, the present invention is most easily implemented by using an industry standard 100 mm Øxc3x970.67 mm thick wafer. Again, the thickness of a standard wafer is too great to allow transmission of standard fluxes of x-rays,i the wafer must be thinned. Unlike embodiment 1, however, because embodiment 2 applies the x-ray moderating layer only to one face of the substrate, the thinning step may be preformed as a final step. The FIGURES shown for this embodiment, therefore, are not necessarily intended to show only a cross section of wafer 10 in an area thinned by the blanket etching process. The process begins by xe2x80x9cmetallizingxe2x80x9d one of the two surfaces of the substrate wafer, FIG. 6B. Again, metallization is performed by depositing a layer of gold over a layer of chromium as in embodiment 1. Furthermore, like the first embodiment the function of the metallize layer is to provide a surface for xe2x80x9cwritingxe2x80x9d witness marks 15, shown in FIG. 6C, which are used to align first and second image patterns. Again, the metallization is performed by any known technique including but not limited to vapor phase deposition, particle deposition, or epitaxial deposition. In FIG. 6D a liquid photoresist film 16 (herein SRP 3612 Novolak) is applied by spin coating, in this case, to a thickness of less than about 2 microns, preferably from about 1 to 1.5 microns, and then baked at a temperature of 95xc2x0 C. for about 90 seconds in order to at least partially cure the resist layer. The particular resist thickness is chosen so as to balance the need for providing a thick enough layer to protect the unexposed portions of the silicon substrate from the effects of the latter ion etch phase against the desire to fully expose the full thickness of the resist during the light exposure phase. A standard direct-contact lithographic mask 17, herein embodying a negative trace image of the desired pattern 18, is placed on the surface of resist layer 16 and aligned such that witness marks 19 on contact mask 17 and witness marks 15 on metallized surface 14 are brought into coincidence as seen in FIG. 7A (FIG. 7A intentionally shows contact mask 17 above this surface for clarity sake only). This may be done by first fixing the position of substrate 10 and then moving the mask 17 over the substrate by means of a standard x-y translatable stage driven by a pair of precision stepper motors (not shown). Contact mask 17 and substrate 10 are aligned by imaging the underside of the substrate, metallize surface 14, with its witness marks 15, using conventional microscopy and camera optics and combining this image with an image of the corresponding witness marks 19 written into contact mask 17. (It is important, in this embodiment that witness marks 15 be placed on the substrate face opposite the subsequent embedded layer since, as will be seen, it will be necessary to planarize this surface after depositing the x-ray absorber material onto the first face of the substrate, inevitably removing the top surface metallize layer.) Once the mask and substrate are properly aligned the portions of the resist layer 16 exposed by the openings in contact mask 17 are subjected to a source (not shown) of broadband light, 20, herein shown in FIG. 7B. The exposure source used herein was a high pressure mercury-vapor lamp emitting light over a spectral range of about 365 nm to 450 nm and providing a dose of approximately 1000 millijoules/cm2 measured at a wavelength of 365 nm. In the next step in the process, illustrated in FIG. 7C, the photoresist is chemically xe2x80x9cdevelopedxe2x80x9d and the exposed portions, 21a, of photoresist layer 16 are removed. What remains are the unexposed portions, 21b, of the resist in an inverse image of the mask pattern (and thus a positive image of the desired mold part) and xe2x80x9cclearxe2x80x9d areas 22 of exposed silicon whose edges eventually define the walls of the mold structure. As will be seen in the next steps, clear areas 22 comprise regions of the substrate that will be removed by an etching process and later filled with an x-ray obstructing metal layer. After cleaning and drying, the patterned substrate 40 is subjected to a series of anisotropic reactive etching steps such as those set forth in the so-called BOSCH process described in U.S. Pat. No. 5,501,893, herein incorporated by reference in its entirety. FIG. 8A shows this step applied in the present invention. In this process pattern substrate 40 is subjected to a reactive ion plasma 45. The patterned top surface of the silicon substrate is protected from bombardment of the ion species by the retained resist layer 21b. This first etching step is followed by a first polymerization step (not shown) which coats the walls, edges and bases of the etched recesses in the silicon substrate and the process of FIG. 8A is repeated as many times as is necessary until a final depth d, shown in FIG. 8B, is achieved. Herein, the BOSCH technique (or any other similar etch-and-coat technique), etches the xe2x80x98clearxe2x80x99 areas 22xe2x80x2 of the patterned silicon substrate 40 to a depth d and is used primarily to provide a very straight wall edge for etched channels 44. As noted supra. the BOSCH process is a two step etch-and-coat process wherein the intervening coating step comprises coating the exposed silicon with a thin layer of a polymer film (not shown) which protects the walls 42 and bases 43 of etched channel 44 but is quickly destroyed on those surfaces which directly face the bombardment of the reactive plasma 45 shown in FIG. 8A. This action has the effect of etching regions in the exposed silicon which have a substantially uniform width and substantially parallel walls. The process continues until the desired etch depth d has been achieved. In the case of the present invention the desired depth was about 30 microns and is intended to attenuate transmission of x-ray flux having an incoming energy of about 10 KeV to near zero. The BOSCH pattern rendered in the silicon wafer is a print-negative image of the desired mold configuration to be produced by the x-ray mask. After etching patterned substrate 40 to the desired depth, the remaining resist layer 21b is removed, and the part cleaned, leaving a plurality of deeply etched channels across top surface 11 of the substrate as shown in FIG. 9A. Surface 11 of the patterned substrate 40 is subsequently covered with a thin electrically conductive metal film 46, as shown in FIG. 9B. Film 46 is necessary to enable adherence of a second, thicker metal layer 47 which is deposited in a subsequent step. The chosen process for applying the first thin coating is a thermal evaporation or particle vapor deposition (PVD) process, although any other coating process which would provide a thin, continuous layer of conductive material would be equally effective. However, any such processes must be able to coat both the walls 42 and the bases 43 of the etched channels 44. Such methods could include, but are not limited to, sputtering and chemical vapor deposition or spraying coating methods, and electrochemical and electroless plating methods, and only require that the coating process provide a continuous, adherent, and conductive layer. As disclosed herein, film 46 is about a 0.025 microns layer of chromium with an overlaying layer of about 0.08 microns of gold. Any similar metal or combination of metals would be useful including most of the metals in the Transition series of metal listed in New IUPAC Group Numbers 4-12 of the Period Table of elements, alloys thereof, and certain of the metals of Groups 13 and 14, such as aluminum and tin. As shown in FIG. 9C, thicker layer 47 is also chosen to be gold but ,as before, could be any similar metal selected from the list supplied above, providing that the etch depth d of the mask is adjusted to provide for a layer of sufficient thickness to eliminate most of the synchrotron radiation emanating from the light source used to illuminate the mask. Following the step of depositing second layer 47, the mask assembly is planarized to provide the structure shown in FIG. 10A. Unlike the step of planarizing in embodiment 1, however, the present step is performed to remove metal from across top surface 11 down to the surface of the substrate 10 to provide planarized surface 11a. This surface is intended to be as flat and smooth as possible since it is the surface which will lay against the surface of the material onto which the synchrotron radiation is to be illuminated. As before, planarizing is performed by lapping the top surface until the surface of the silicon is reached leaving only the portion 47a of layer 47 embedded into the thickness of substrate 10 exposed and exposed portions 47a provide an obstruction to the transmission of synchrotron radiation in those areas of the mask intended to form the exterior walls of the final structures in the PMMA mold. Portions 47a thus collectively comprise a negative image of the structures that are to be exposed to synchrotron radiation. After the planarizing step has been completed, the x-ray mask of embodiment 2 is prepared for a final finishing x-ray absorber layer by first applying a thin (a few hundred Angstroms) conductive metal layer 51 onto surface 11a by a particle or vapor deposition process, as shown in FIG. 10A This metal coating will eventually form the substrate for subsequent final overlaying metal layer across those areas of the mask in which some moderation of the full flux of the synchrotron radiation source is desired. These steps are shown in FIGS. 10B through 11C. The overlaying layer is applied by the same lithographic process illustrated in FIGS. 6 through 7. The metal coated silicon wafer of FIG. 1A is coated with a thick photoresist layer 48 and a second image forming contact mask 50 is placed over the surface of resist layer 48 and aligned as before. As before the image forming mask is aligned by first fixing the position of the substrate and then moving the mask over the substrate using a standard x-y translatable stage driven by precision stepper motors (not shown). Contact mask 50 and etched substrate 40a are aligned by again imaging the underside surface 14 of the substrate with its witness marks 15 using conventional microscopy and camera optics and combining this image with an Image of a corresponding set of witness marks 50a written onto contact mask 50. Again, by carefully adjusting the x-y stage the two sets of witness marks may be brought Into coincidence, or are otherwise uniquely arranged, as shown in FIG. 10C. In the case of embodiment 2, however, the positional tolerances of the second pattern vis-a-vis the first are far less critical since by carefully designing the pattern mask it is possible to avoid many of the critical alignment issues of the first embodiment. In particular, it is possible to prepare mask 50 such that it comprises xe2x80x9cwindowsxe2x80x9d roughly centered over the large open areas of the mask 48a which will form the desired mold structures in the PMMA substrate, regions that are intended to receive a lower x-ray dose such that once resist 48 is exposed and developed, as shown in FIG. 11A, x-ray moderating layer 52 may be deposited. Once the exposed resist material 48a is removed a portion of metal layer 51 is exposed, as shown in FIG. 11B, and it is this exposed substrate onto which the final x-ray moderating layer 52, shown in FIG. 11C, is applied. Because layer 52 is designed to reduce, but not totally eliminate the x-ray flux transmitted through the layer, it will cover those larger areas of substrate surface 11 in which a reduced x-ray flux is desired while embedded layer 47a provides a barrier to stop transmitted x-rays altogether and, therefore, provide an effective xe2x80x9cedgexe2x80x9d for establishing feature detail. Furthermore, layer 51 does not significantly add to the absorption of x-ray flux due to its very thin cross section. Thus when the patterned substrate is illuminated by x-ray radiation it will provide not only a sharp, positive image of the features to be replicated as mold recesses in PMMA but it will also provide for a means for reducing the PMMA development rate in those area where geometry factors favor such a reduction. A final thinning step, illustrated in FIG. 11D, may be performed at this stage if the substrate has not been previously thinned. Again, thinning is intended to reduce the thickness of silicon substrate 10 across an area beneath the embedded metal pattern 47a since the thickness of the standard wafer is too thick to allow transmission of conventional x-ray fluxes. Thinning is performed on substrate surface 12, opposite pattern 47a, using a standard blanket etching technique until the thickness of silicon everywhere underneath pattern 47a is reduced to a thickness below about 100 microns which is consistent with the desired level of x-ray attenuation since the silicon substrate itself absorbs some portion of the beam. Etching is performed only in selective zones beneath pattern 47a in order to leave sufficient structural support for further processing the wafer. As before, as similarly shown in FIG. 5, the operation of the variable dosing mask implemented as embodiment 2 is shown schematically in FIG. 12 and illustrates the attenuating effect in the incoming x-ray radiation Do by the stack layers of absorber material 47a, 51, and 52 providing attenuated x-ray fluxes D1 greater than D2. A third and final embodiment follows essentially all of the steps of embodiment one, but instead of inverting the wafer and placing a second absorbing pattern layer on the second face of the wafer, the second pattern is placed over the first layer. The first layer provides a layer for a moderate reduction in transmitted x-ray flux and is used to underexposed regions of a mold in which slower development is desired. The second layer, in combination with the first, is intended to be nearly opaque to x-rays and is used to establish an inside edge of a feature and thus provide the desired overall size and shape of that feature rendered into the finished mold. These steps are described with reference to FIGS. 13 through 16. In embodiment 3, therefore, each of the steps of embodiment 1 are duplicated up to the point at which the first image pattern is laid down. Instead of placing the x-ray limiting layers on opposite sides of the silicon wafer, as in embodiment 1, the present embodiment places these layers on the same side of the wafer substrate. As already noted, the first layer provides a substantially continuous x-ray attenuating layer which also contains a number of openings in which the image of a feature will be rendered which will have a large height-to-width aspect ratio and which will therefore require a higher relative x-ray dose in order that these features can be xe2x80x9cdevelopedxe2x80x9d in a timely manner. Once the first x-ray attenuating pattern has been created the second image forming pattern may be rendered over it. A thick layer of print-positive photoresist is applied over the first patterned layer and a second contact mask aligned with the witness marks applied to the opposite side of the substrate as before. The image described by the second contact mask is then rendered into the second photoresist layer using a high intensity source. The frequency of light used will depend upon the size of the smallest part (usually those which are to be exposed to the full x-ray dose) and the thickness of the resist layer. It is intended that the second resist layer be applied in a thick enough layer that the openings in the first x-ray attenuating layer do not impart a substantial edge effect at the surface of the second resist layer. As described, in this configuration, is the second overlapping pattern which is used to establish the desired overall size and shape of the features rendered into the finished mold. By carefully designing the mask of the present invention such that those features known, as a consequence of their size and shape, to be difficult to develop in PMMA are located in zones over those open areas in the first layer, it is possible to obtain the benefits Referring now to FIG. 13A, the process begins with a silicon substrate or wafer 10. This substrate can, generally, have any useful shape and thickness but should of necessity be a thin wafer having parallel top and bottom surfaces 11 and 12. In particular the present invention is most easily implemented by using an industry standard 100 mm Øxc3x970.67 mm thick wafer. Once again, the thickness of a standard wafer is too great to allow transmission of standard fluxes of x-rays. However, because embodiment 3, like embodiment 2, applies the x-ray moderating layer only to one face of the substrate, the thinning step can be preformed as a final processing step. The FIGURES shown for this embodiment, therefore, are not necessarily intended to show only a cross section of wafer in an area thinned by the blanket etching process. As before, the process begins with the two xe2x80x9cfaces,xe2x80x9d 13 and 14, of the substrate being xe2x80x9cmetallizedxe2x80x9d, as illustrated in FIG. 13B, by depositing a first layer of chromium followed by a second layer of gold. By xe2x80x9cfacesxe2x80x9d it is meant each of the two large, flat surfaces of the wafer or similar article. The first and second metallizing layers are quite thinxe2x80x94typically about one hundred to several hundred angstroms, respectively, and are used to provide a conductive deposition layer for subsequent processing. Metallization is performed by any known technique including but not limited to vapor phase deposition, particle deposition, or epitaxial deposition. After metallizing the substrate several xe2x80x9cwitnessxe2x80x9d marks 15 are applied onto one of the two plated surfaces, as shown in FIG. 13C. This is done by using any conventional lithographic technique or by xe2x80x9cwritingxe2x80x9d the pattern directly into the metallized coating by means of an electron beam or laser such that the metallized layer is removed. The marks are placed at several locations remote, possible peripheral, points on one xe2x80x9cfacexe2x80x9d of the substrate. The witness marks will be used, subsequently, as alignment aids for establishing pattern registration between the substrate top and bottom faces. In FIG. 13D a liquid photoresist film 16xe2x80x2 (herein Shipley 5740) comprises a print-positive resist and is applied by spin coating to a thickness of less than about 50 microns, preferably from about 5 to 20 microns, and then baked at a temperature of 110xc2x0 C. for about 10 minutes in order to at least partially cure the resist layer. The particular resist thickness is chosen so as to provide a stencil form for a thick absorber layer while still providing for fully exposing the full thickness of the resist during the light exposure phase. In a next step, shown in FIG. 14A, a standard direct-contact lithographic mask 17xe2x80x2 herein embodying a negative trace image of the desired pattern 18xe2x80x2 is placed on the surface of the of resist layer 16xe2x80x2. Mask 17xe2x80x2 is provided with corresponding witness marks 19 and aligned such that witness marks 19 on the mask and witness marks 15 the underside of the metallized substrate are brought into coincidence, as seen in FIG. 14A (mask 17xe2x80x2 is shown above the surface of resist layer 16xe2x80x2 for clarity sake only). This may be done by first fixing the position of the substrate and then moving the mask over the substrate by means of a standard x-y translatable stage driven by a pair of precision stepper motors (not shown). Mask 17xe2x80x2 and substrate 10 are aligned by imaging the underside of the substrate metallized surface 14, with its witness marks 15, using conventional microscopy and camera optics and combining this image with an image of the corresponding set of witness marks 19 in contact mask 17xe2x80x2. By carefully adjusting the x-y stage the two sets of witness marks may be brought into coincidence or are otherwise uniquely arranged. Once the mask and substrate are properly aligned, the portions of the resist layer 16xe2x80x2 exposed by openings in mask 17xe2x80x2 are subjected to a source (not shown) of broadband light, 20 herein shown in FIG. 14B. The exposure source used herein was a high pressure mercury-vapor lamp emitting light over a spectral range of about 365 nm to 450 nm and providing a dose of approximately 1000 millijoules/cm2 measured at a wavelength of 365 nm. In the next step in the process, illustrated in FIG. 14C the photoresist is chemically xe2x80x9cdevelopedxe2x80x9d and the unexposed portions, 21xe2x80x2, of photoresist layer 16xe2x80x2 are removed. What remains are the exposed portions, 21axe2x80x2, of the resist in an Inverse image of mask pattern 18xe2x80x2 wherein this inverse image comprises xe2x80x9cClearxe2x80x9d areas 21bxe2x80x2 of substrate metallize surface 13. Again, this step is performed using standard and well-known lithographic processes. After cleaning and drying the developed mask, the entire surface of the mask is subsequently covered with thick metal film 23, as shown in FIG. 14D. The chosen process for applying the coating is typically a plating method although any other coating process which would provide a continuous layer would be equally effective. Such methods could include, but are not limited to, thermal evaporation or particle vapor deposition (PVD) process, chemical vapor deposition (CVD), sputtering and spraying coating methods. As disclosed herein, the film 23 is rendered in gold and is as thick as the resist layer. Any similar metal or combination of metals would be equally useful including most of the metals in the Transition series of metal listed in New IUPAC Group Numbers 4-12 of the Period Table of elements, alloys thereof, and certain of the metals of Groups 13 and 14, such as aluminum and tin providing that the thickness of the metal layer is adjusted to provide for attenuating radiation to a desired level. Following the final step of depositing the x-ray absorbing layer 23, the mask assembly is planarized and the remaining, exposed resist 21axe2x80x2 is removed. The process is now repeated to apply the image forming layer onto the first x-ray moderating layer. In FIG. 15A a liquid photoresist film 24 (herein Shipley 5740) is applied by spin coating to a thickness of less than about 50 microns, preferably from about 5 to 15 microns, and then baked at a temperature of 110xc2x0 C. for about 10 minutes in order to at least partially cure the resist layer. The particular resist thickness is chosen so as to provide a stencil form for a thick absorber layer while still providing for fully exposing the full thickness of the resist during the light exposure phase. In a next step, shown in FIG. 15B, lithographic mask 25xe2x80x2, embodying a negative trace image of the desired pattern 26xe2x80x2, is placed on the surface of resist layer 24xe2x80x2. Mask 25xe2x80x2 is provided with corresponding witness marks 19 and aligned such that witness marks 19 on the mask and witness marks 15 the underside of the metallized substrate are brought into coincidence, as seen in FIG. 15B. This may be done by first fixing the position of the substrate and then moving the mask over the substrate by means of a standard x-y translatable stage driven by a pair of precision stepper motors (not shown). Mask 25xe2x80x2 and substrate 10 are aligned by imaging the underside of the substrate metallized surface 14, with its witness marks 15, using conventional microscopy and camera optics and combining this image with an image of the corresponding set of witness marks 19 in contact mask 25xe2x80x2. By carefully adjusting the x-y stage the two sets of witness marks may be brought into coincidence or are otherwise uniquely arranged. Once the mask and substrate are properly aligned, the portions of the resist layer 24xe2x80x2 exposed by openings in mask 25xe2x80x2 are subjected to a source (not shown) of broadband light, 20, herein shown in FIG. 15B. The exposure source used herein was a high pressure mercury-vapor lamp emitting light over a spectral range of about 365nm to 450 nm and providing a dose of approximately 1000 millijoules/cm2 measured at a wavelength of 365 nm. FIG. 15C shows the areas 24axe2x80x2 of the resist that have been exposed to light source 20 and areas 24bxe2x80x2 that have been covered by opaque areas of the mask. In the next step in the process, illustrated in FIG. 15D, the photoresist is chemically xe2x80x9cdevelopedxe2x80x9d in order to remove exposed areas, 24axe2x80x2, of the resist layer. Unexposed portions 24bxe2x80x2 remain, and are used as a blocking template to create zones within which deposition of a second metal absorber layer is prevented. After cleaning and drying the developed mask, those portions of the mask surface which have been uncovered during the photoresist development process (open areas corresponding to removed resist portion 24axe2x80x2) are subsequently covered with thick metal film 30xe2x80x2, as shown in FIG. 16A. The chosen process for applying the coating is typically a plating method although any other coating process which would provide a continuous layer would be equally effective. Such methods could include, but are not limited to, thermal evaporation or particle vapor deposition (PVD) process, chemical vapor deposition (CVD), sputtering and spraying coating methods. As disclosed herein, the film 30xe2x80x2 is rendered in gold and is as thick as the resist layer. Any similar metal or combination of metals would be equally useful including most of the metals in the Transition series of metal listed in New IUPAC Group Numbers 4-12 of the Period Table of elements, alloys thereof, and certain of the metals of Groups 13 and 14, such as aluminum and tin providing that the thickness of the metal layer is adjusted to provide for attenuating radiation to a desired level. Following the final step of depositing the x-ray absorbing layer 30xe2x80x2, the mask assembly is planarized and the remaining, exposed resist 24bxe2x80x2 is removed. A final thinning step, illustrated In FIG. 16B, is intended to reduce the thickness of silicon substrate 10 across a region beneath the embedded metal pattern. As shown in FIG. 16B, thinning is performed on the back side 12 of wafer 10 using a standard blanket etching technique until the thickness of silicon beneath metal patterns 33xe2x80x2 is reduced to a thickness which is consistent with the desired level of x-ray attenuation since the silicon substrate itself absorbs some portion of the beam, especially at wafer thicknesses above 100 microns. The operation of the third embodiment of the variable dosing mask is schematically illustrated, as before with embodiments 1 and 2, in FIG. 17 and illustrates the attenuating effect in the incoming x-ray radiation D0 by the stack layers of absorber material 13, 23xe2x80x2, and 30xe2x80x2 providing attenuated x-ray fluxes D1 greater than D2 greater than D3. At this point, the x-ray mask is complete. By implementing these steps, a mask having x-ray attenuating structures which allow varying the x-ray exposure dose from point to point across the surface of the mask. The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best use the invention in various embodiments and with various modifications suited to the particular use contemplated. The scope of the invention is to be defined by the following claims.
039881539	abstract	A method of forming an iris diaphragm for use in a corpuscular beam apparatus and having a thin metal layer with at least one opening and an integral reinforcing portion of the same metal which is set back from each of the openings characterized by providing a substrate with the first mask leaving an unexposed surface of the configuration of the thin metal layer, applying a thin metal layer on the exposed surface, forming a second mask having configuration of the reinforcing portion of the iris diaphragm and including a portion covering the thin metal layer adjacent each opening, applying a second thicker layer of the same metal to form a reinforcing portion and subsequently removing the iris diaphragm from the surface of the substrate. Preferably, each of the masks are formed by a photo development process and the metal layers are applied by electro-depositing.
	claims	1. An articulated arm ( 11 ) to be put through an opening ( 4 ) of a slab ( 5 ) acting as cover for a tank ( 2 ), comprising an upper section ( 12 ) and a lower section ( 13 ) linked together by an articulation ( 14 ), a bearing placed around the opening and comprising a fixed ring ( 19 ), integral with the slab, and a turning ring ( 21 ), integral with the upper section ( 12 ), means ( 26 , 27 , 28 ) of control of the rotation of the turning ring, a tool ( 1 ) suspended from the lower section by a cable ( 6 ) of variable length, which extends above the slab and the arm and over a suspension pulley ( 15 ) to a free end of the lower section ( 13 ), a return pulley ( 16 ) set at the articulation of the sections, the cable passes under the return pulley ( 16 ) wherein the lower section is formed of two articulated parts ( 41 , 42 ) and there are means of control ( 29 to 32 ) of an angle formed by the sections, the lower section is pivotable in vertical planes either in a back direction, or in a front direction in which the suspension pulley intercepts and catches the cable, and the lower section comprising girders ( 17 ) leaving a cross-section for passage of the tool when the lower section is pivoted in the back direction. 2. An articulated arm according to claim 1 , characterized in that the parts of the lower section are articulated by an axle ( 43 ) situated on the front edges ( 44 ) in a pivoting direction of the lower section ( 13 ) relative to the upper section, and the parts of the lower section comprise locking means on their rear edges. claim 1 3. An articulated arm according to claim 1 , characterized in that the means of control for rotating the turning ring comprise a gear with drive pinion ( 26 ) and toothed crown ( 28 ), the pinion and the crown being integral with one, respectively, of the rings. claim 1 4. An articulated arm according to claim 1 , characterized in that the upper section ( 12 ) comprises a support structure ( 22 ) which can be screwed to the turning ring. claim 1 5. An articulated arm according to claim 1 , characterized in that it comprises a plug ( 33 ), mounted on the turning ring and closing the opening, provided with a detachable part ( 34 ) for passage of the upper section. claim 1 6. An articulated arm according to claim 1 , characterized in that it comprises a sealing joint composed of a continuous skirt ( 35 ) under the fixed ring ( 19 ) with its lower edge dipping into liquid filling a groove ( 36 ) surrounding the opening. claim 1 7. An articulated arm ( 11 ) to be put through an opening ( 4 ) of a slab ( 5 ) acting as cover for a tank ( 2 ), comprising an upper section ( 12 ) and a lower section ( 13 ) linked together by an articulation ( 14 ), a bearing placed around the opening and comprising a fixed ring ( 19 ), integral with the slab, and a turning ring ( 21 ), integral with the upper section ( 12 ), means ( 26 , 27 , 28 ) of control of the rotation of the turning ring, a tool ( 1 ) suspended from the lower section by a cable ( 6 ) of variable length, which extends above the slab and the arm and over a suspension pulley ( 15 ) to a free end of the lower section ( 13 ), a return pulley ( 16 ) set at the articulation of the sections, the cable passes under the return pulley ( 16 ) wherein there are means of control ( 29 to 32 ) of an angle formed by the sections, the lower section is pivotable in vertical planes either in a back direction, either in a front direction in which the suspension pulley intercepts and catches the cable, and the lower section comprising girders ( 17 ) leaving a cross-section for passage of the tool when the lower section is pivoted in the back direction. 8. An articulated arm according to claim 7 , characterized in that the means of control for rotating the turning ring comprise a gear with drive pinion ( 26 ) and toothed crown ( 28 ), the pinion and the crown being integral with one, respectively, of the rings. claim 7 9. An articulated arm according to claim 7 , characterized in that the upper section ( 12 ) comprises a support structure ( 22 ) which can be screwed to the turning ring. claim 7 10. An articulated arm according to claim 7 , characterized in that it comprises a plug ( 33 ), mounted on the turning ring and closing the opening, provided with a detachable part ( 34 ) for passage of the upper section. claim 7 11. An articulated arm according to claim 7 , characterized in that it comprises a sealing joint composed of a continuous skirt ( 35 ) under the fixed ring ( 19 ) with its lower edge dipping into liquid filling a groove ( 36 ) surrounding the opening. claim 7
	description	The present disclosure relates to a safety system shutdown including a passive electrical component that senses a system parameter and becomes tripped if a predetermined set point is reached so that a signal is sent to take an action in the system. The passive electrical component makes use of Gauss' Law. This section provides background information related to the present disclosure which is not necessarily prior art. Modern nuclear reactors use a variety of digital systems for both control and safety, referred to as a Distributed Control and Information System (DCIS). These systems must be redundant, diverse, fault tolerant, and have extensive self-diagnosis while the system is in operation. Meanwhile, the nuclear digital industry is concerned with common cause software failure. Even more damaging is a cyberattack to, or through, the system safety systems. In the digital industry, the desire to increase computational power while decreasing component size results in a very small digital device with embedded software. It is very difficult to convince a regulatory body that these systems cannot have a common cause failure. Even more damaging operations can occur when this compact digital system is subjected to a cyberattack. These extreme unknown conditions of a nuclear power plant safety system lead to the cause for redundancy, independence, and determinacy, all of which contribute to significant added cost. FIG. 6 schematically shows a conventional distributed control and information system (DCIS) 200 with both a safety portion 202 and non-safety portion 204 that are interfaced by a control panel 203. The present disclosure is directed to the safety portion 202 of the DCIS 200 which is shown in FIG. 7. The safety portion 202 of the DCIS 200 includes four independently designed divisions 202A-202D which each receive measured system signals that are collected and sent from a remote multiplexer unit RMU 205 which provides output to the digital trip module DTM 206 which each provide outputs to the trip logic units TLU 208 which each provide an output signal to the output logic unit OLU 210. The conventional safety portions 202 use a voting logic of at least 2 out of 4 of the different divisions 202A-202d receiving like signals in order to determine a fault (i.e. pressures and temperatures are not compared against each other). It becomes more difficult for the nuclear power plant control system designer, purchaser, installer, and operator to establish and trace the essential safety signals to ensure the system is performing as designed. A device and method are needed on a scale that humans can vary “signal flow” or “trace the flow of electrons/data so that the system is immune from cyber-attack. This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. The present disclosure provides electro-technical devices that, coupled to control systems, can provide passive system safety shutdown or other emergency operation using Gauss' Law. These devices will solve the issue of common cause software failure or cyber security attacks that are inherent limitations of digital safety systems. The Gauss Law contactor provides an electro-technical device that can be set up to protect a nuclear power plant, or another sensitive infrastructure. The Gauss Law contactor of the present disclosure can be produced using metallic and plastic 3-D printing machines that can be utilized to ensure consistent manufacture of the device for which the manufacturing data can be captured and stored for utilization in confirming the devices consistent operational characteristics. The Gauss Law contactor uses a simple pass/fail or go/no-go check to convey to an electrical safety system to change state to safe shutdown. The printed device is placed into the safety system to perform 3 basic tasks: sense a system parameter (e.g. temperature, flow, pressure, power or rate of change), if the predetermined set point is reached—result in a “tripped” state, and lastly, if the safety system logic is met—send a signal to take an action in the system, such as shutdown. In the event of normal power supply loss, the Gauss Law contactor can either fail as is or fail in a safe state, depending on user requirements. The system prevents any loss of the safety function of the digital device due to power outage. The device also eliminates failures due to software or digital cyber attacks. An electro-technical device according to the principles of the present disclosure includes a point source supplied with an input signal. A first housing portion is electrically isolated from a second housing portion with the point source being disposed within the first housing portion. A movable conductor is connected to the first portion and is responsive to an electric field generated by the point source to cause the movable conductor to contact the second housing portion to complete a circuit and send out a control signal. According to a further aspect of the present disclosure, an electro-technical device is provided for detecting a fault state in a nuclear system. The electro-technical device includes a first housing portion electrically isolated from a second housing portion and a plurality of point sources being spaced from one another and disposed within the first housing portion, each of the point sources being supplied with an input signal. A movable conductor is connected to the first housing portion and is responsive to an electric filed generated by the plurality of point sources to contact the second portion to complete a circuit for sending out a control signal when at least two of the point sources receive an input signal indicative of a fault state. According to a further aspect of the present disclosure, a method of making an electro-technical device includes digitally printing a first housing portion with a movable conductor connected to the first housing portion and a point source within the first housing portion and spaced from the movable conductor. Connecting the point source with an input signal. Digitally printing a second housing portion opposite to and electrically isolated from the first housing portion, wherein the movable conductor is responsive to an electric field generated by the point source to contact the second housing portion to complete a circuit and send out a control signal. Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. With reference to FIGS. 1 and 2, a Gauss Law contactor 10 according to the principles of the present disclosure will now be described. As shown in FIG. 1, the Gauss law contactor 10 includes a lower housing portion 12 and an upper housing portion 14 that are electrically separated from one another by an insulated joint 16. A point source 18 is connected to an input signal 20 and is disposed in the lower housing portion 12. A movable conductor 22 is connected to the lower housing portion 12 and is spaced from the point source 18. The electrical separation between the lower housing portion 12 and the upper housing portion 14 results in an open control circuit 24 for the Gauss Law contactor 10. As shown in FIG. 2, the point source 18 is supplied with an increased input signal 20′ indicative of an increased sensor voltage representing a safety condition. The safety condition can include an increase in temperature, pressure, fluid flow or other monitored condition. The increased input signal 20′ results in an increased charge point source 18′ which creates more divergence in the electrical field. The increased divergence of the electrical field around point source 18′ causes the movable conductor 22 to move away from the charged point source 18′ and into contact with the upper housing portion 14 of the Gauss Law contactor 10, resulting in the closing of the contactor 24′. The closed contactor 24′ results in a safety control signal or action 26 to be taken. As an alternative, the reverse circuit can be set up to open (rather than close) the contactor 24 to de-energize a system for a protective feature. With reference to FIGS. 3-5, a Gauss Law contactor 30 is illustrated in a nuclear safety system 31 to provide a logic device without software. As shown in FIG. 3, the Gauss law contactor 30 includes a lower housing portion 32 and an upper housing portion 34 that are electrically separated from one another by an insulated joint 36. Four independent point sources 38a-38d are connected to separate input signals 40a-40d from sensors 41a-41d from the nuclear safety system 31 and are disposed in the lower housing portion 32. A movable conductor 42 is connected to the lower housing portion 32 and is spaced from the point sources 38a-38d. The electrical separation between the lower housing portion 32 and the upper housing portion 34 results in an open control circuit 44 for the Gauss Law contactor 30. As shown in FIG. 4, one of the point sources 38a′ is supplied with an increased input signal 40a′ from the sensor 41a′ of the nuclear safety system 31 indicative of a safety condition. The safety condition can include an increase in temperature, pressure, fluid flow or other monitored condition as detected by a sensor 41a-41d of the nuclear safety system 31. The increased input signal 40a′ results in an increased charge point source 38a′ which creates more divergence in the electrical field. The increased divergence of the electrical field around point source 38a′ causes the movable conductor 42 to move away from the charged point source 38a′ which however, is insufficient to cause the movable conductor 42 to contact with the upper housing portion 34 of the Gauss contactor 30 so that the control circuit 44 remains open. As shown in FIG. 5, multiple ones of the point sources 38a′, 38b′ are supplied with an increased input signal 40a′, 40b′ each indicative of a safety condition. The increased input signals 40a′, 40b′ result in an increased charge point source 38a′ and 38b′ which creates more divergence in the electrical field. The increased divergence of the electrical field around point sources 38a′ and 38b′ cause the movable conductor 42 to move away from the charged point sources 38a′ and 38b′ and into contact with the upper portion 34 of the Gauss Law contactor 30, resulting in the closing of the control circuit 44′ to provide a safety control signal 46 to be sent so that a shutdown action or other security operation can be performed. As an alternative, the reverse circuit can be set up to open (rather than close) the contactor 24 to deenergize a system for a protective feature. The Gauss Law contactor 30 can replace the digital trip module DTM 206, trip logic unit TLU 208, and the output logic unit OLU 210 previously described in prior art FIGS. 6 and 7. The Gauss Law contactor 10/30 can be manufactured by digital printing some or all of the components to insure consistent operation and response. By way of example, the upper and lower housings 12, 14/32, 34, the point sources 18/38a-38d and the movable conductor 22/42 can all be made by digital printing from the same or different materials. The movable conductor 22/42 can be formed as a thin metal film and can include folds, undulations or a bellows shape to allow for uninhibited movement in response to an increased electrical field emanating from the point sources 18/38a-38d. Digital printing results in highly accurate and consistent production of component parts and can have a digital record for the accurate manufacture of each component. The digital record can be utilized to certify the accurate production of the Gauss Law contactor 10/30. The present disclosure envisions the use of the Gauss Law contactor provided in this application according to the following operating modes. During steady-state operation of the Gauss Law contactor 10/30, a baseline voltage can be supplied to the contactor. If the voltage to the device 10 or two out of four voltages for the device 30 exceeds the device baseline, the circuit 24/44 is closed and a safety system response 26/46 is actuated. For some devices the response is a once-in-a-lifetime component accusation, (the fuse) whereas some of the embodiments described can be physically reset by the operator. If there is a loss of primary power, and uninterruptible power supplies used to maintain a constant voltage level within the circuitry. The electricity from this secondary supply will also be fed to the safety measuring devices, and the loss results in the safe shutdown of the system. In the event of a loss of all power, then the system either fails as is or to a safety state, depending on how the device is placed into an architecture by the circuit designer. The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
	description	This application is the national phase under 35 U.S.C. § 371 of PCT International Application No. PCT/EP2016/074007 which has an International filing date of Oct. 7, 2016, which designated the United States of America and which claims priority to German patent application number DE 10 2015 222 268.3 filed Nov. 11, 2015, the entire contents of which are hereby incorporated herein by reference. An embodiment of the invention generally relates to a detector element for detecting incident x-ray radiation, the detector element including a scintillation layer for converting the x-ray radiation into scintillation light and a photoactive element for converting the scintillation light into an electrical signal. Imaging x-ray detectors are employed for the spatially resolved detection of x-ray radiation in materials analysis, in security checks and quality assurance inspections, as well as in the medical technology field. An x-ray detector of the type typically comprises a number of pixel-like detector elements which are arranged for example as a two-dimensional detector array. There are direct-converting detector elements and indirect-converting detector elements. Whereas a direct-converting detector element converts the impinging x-ray radiation directly into an electrical signal, in the case of an indirect-converting detector element the x-ray radiation is initially converted into low-energy (in comparison with x-ray radiation) electromagnetic radiation in the visible, infrared or ultraviolet spectral range (light). For this purpose, an indirect-converting detector element comprises a layer composed of scintillating material which absorbs incident x-ray beams and emits (scintillation) light. The scintillation light is detected by means of a photoactive element, such as a photodiode, for example, and converted into an electrical signal. Organic photodiodes are used increasingly as photoactive elements owing to the fact that the organic semiconductor materials utilized for this purpose absorb the scintillation light better than inorganic semiconductor materials. An organic photodiode of the aforesaid type typically comprises a photoactive organic absorption layer which is arranged between an electrode and a counter electrode. WO 2012/062625 A2 discloses a hybrid structure for a detector element in which the scintillation layer and the photoactive layer are combined to form a common hybrid layer. The hybrid layer arranged between an electrode and a counter electrode is formed from a photoactive absorption layer composed of organic semiconductor material in which a plurality of scintillator particles are embedded. However, experience shows that in order to achieve an adequate degree of x-ray absorption, the hybrid layer of such detector elements must have a minimum thickness of typically about 100 μm. The inventors have discovered that such a thick absorption layer proves problematic in organic semiconductor materials due to the typically low charge carrier mobility, especially because in general the charge carriers as a result can only be extracted effectively in the boundary regions of the absorption layer. This causes depletion zones to develop during the operation of detector elements of the type, which depletion zones at least partially shield off the electrical field between the electrode and the counter electrode. The response time of the photoactive element deteriorates proportionately, which has a disadvantageous impact on the competitiveness of hybrid detector elements of the type in comparison with conventional (inorganic) detector elements. At least one embodiment of the invention discloses a detector element that is particularly suitable for detecting x-ray radiation. A corresponding x-ray detector is to be disclosed in addition. A further embodiment of the invention discloses a method for producing a detector element of the type. Embodiments of the invention are directed to a detector element, an x-ray detector, and a method for producing a detector element of the type. Advantageous embodiments and developments are set forth in the claims and the following description. The detector element according to at least one embodiment of the invention comprises a scintillation layer for converting incident x-ray radiation into scintillation light (i.e. into low-energy electromagnetic radiation in the visible, infrared or ultraviolet spectral range). The detector element further comprises a photoactive element for converting the scintillation light into an electrical signal. The photoactive element has a first photoactive absorption layer contacted by an electrode, and a second photoactive absorption layer contacted by a counter electrode. The scintillation layer is in this case arranged between the first photoactive absorption layer and the second photoactive absorption layer. The x-ray detector according to at least one embodiment of the invention comprises a plurality of detector elements of at least one embodiment of the invention. In order to produce the detector element according to an embodiment, a method is provided. According to at least one embodiment of the method, the scintillation layer is produced from a liquid dispersion or suspension of scintillator particles and a polymer material. This enables the scintillation layer to be processed out from the liquid dispersion and thereafter dried or cured (hardened). A method according to an embodiment of the invention is for producing a detector element of at least one embodiment, in which the scintillation layer is produced from a liquid dispersion of scintillator particles and a polymer material, and in which the photoactive absorption layers are deposited out of a solution directly onto opposite plane faces of the scintillation layer. In the figures, parts and sizes corresponding to one another are consistently labeled with the same reference signs. The detector element according to at least one embodiment of the invention comprises a scintillation layer for converting incident x-ray radiation into scintillation light (i.e. into low-energy electromagnetic radiation in the visible, infrared or ultraviolet spectral range). The detector element further comprises a photoactive element for converting the scintillation light into an electrical signal. The photoactive element has a first photoactive absorption layer contacted by an electrode, and a second photoactive absorption layer contacted by a counter electrode. The scintillation layer is in this case arranged between the first photoactive absorption layer and the second photoactive absorption layer. The sandwich-like arrangement of the scintillation layer between the two absorption layers enables a comparatively thin embodiment of the absorption layers to be realized, as a result of which a particularly good quantum yield and a particularly good signal-to-noise ratio are achieved in the detection of the scintillation light. By arranging the absorption layers on the opposite plane faces of the scintillation layer, a doubling of the detection surface area for the scintillation light is achieved in this case—in comparison with conventional detector elements having only one photoactive layer—and consequently a doubling of the quantum yield is realized. A further contributory factor to the improvement in the quantum yield and the signal-to-noise ratio is that small layer thicknesses enable particularly close inspection of the microstructure of the absorption layer in the course of process control, with the result that particularly high-quality surfaces having defined boundary layers can be produced. The thin absorption layers are furthermore favorable to a lower bias or forward voltage between the electrode and the counter electrode during the operation of the detector element, thereby reducing the occurring dark current. In particular, it also becomes possible to operate the detector element in a photovoltaic mode in which no bias or forward voltage is applied. The signal-to-noise ratio of the detector element is improved further as a result. In a beneficial embodiment, the preferably semiconductor-like absorption layers are adapted in terms of their absorption spectrum to match the emission spectrum of the scintillation layer, i.e. they are selected such that they absorb the scintillation light as completely as possible, electrical charges in the form of electron-hole pairs being created in the process in the absorption layers. During the operation of the detection element, an electrical voltage is usually applied to the electrode and the counter electrode, the electrical voltages accelerating the created electrons and holes toward the electrode and counter electrode, respectively. The electrical (current) signal generated as a result represents a measure for the intensity of the x-ray radiation striking the detector element and is suitable to be used for generating digital image data, for example. In a particularly preferred embodiment of the invention, at least one of the absorption layers is produced from organic semiconductor material. Within the scope of the invention, the absorption layer is fabricated in particular from a purely organic material. It is, however, equally conceivable within the scope of embodiments of the invention also for at least one of the absorption layers to be embodied as a hybrid layer (i.e. as an absorption layer in which additional scintillator particles are embedded) or as an organometallic perovskite material. The term perovskite material designates a substance whose chemical structure typically takes the form ABX3, where A is an organic residue or counterion, B is a metal and X is an anion from the group comprising the halogenides iodine, bromine and chlorine. For example, methylammonium lead trihalide (CH3NH3PbX3) is employed as a perovskite material, with iodine (I—), bromine (Br—) or chlorine (Cl—) as the halogenide anion X. The absorption layers are in this case formed in particular from an organic semiconductor material which is also suitable for organic photovoltaics. Organic semiconductors typically have absorption coefficients in the range of 105 or 104 cm−1. Thus, even very thin absorption layers which, in the case of the x-ray detector according to embodiments of the invention, lie in the order of magnitude of approx. 300 nm, for example, are adequate for absorbing a sufficient amount of light. Such a layer thickness permits an efficient extraction of charge carriers, even given comparatively low charge carrier mobility. In order to achieve the best possible signal-to-noise ratio, the x-ray detector provided with such thin absorption layers is preferably operated in the so-called “photovoltaic mode”, i.e. without electrical bias voltage, as a result of which a particularly low dark current or leakage current is achieved. Alternatively, however, the x-ray detector may also be operated within the scope of the invention with electrical bias voltage in order to achieve particularly fast signal responses. In this case the absorption layers are preferably embodied as having a greater thickness, in particular having a layer thickness in the range of a few micrometers. The susceptibility to defects in the absorption layer is reduced by this means, since such defects would otherwise allow a strong increase in dark current. On the other hand, the absorption layers formed from organic semiconductor materials exhibit only an extremely low level of x-ray absorption. The absorption layers are therefore substantially transparent to the incident x-ray radiation, as a result of which the x-ray radiation is able to penetrate virtually unattenuated into the scintillation layer. For the same purpose, the electrode and/or the counter electrode are preferably produced from x-ray transparent material, for example indium tin oxide (ITO), an electrically conductive polymer (e.g. PEDOT-PSS) or very thin metallic contacts (e.g. having layer thicknesses in the range of a few hundred nanometers). In an advantageous embodiment of the invention, the absorption layers are implemented as bulk heterojunctions (BHJs). By bulk heterojunction is understood a heterogeneous mixture or “blend” between at least one organic acceptor material and at least one organic donor material, in which case boundary layers or heterojunctions are formed between the phases of the acceptor and donor materials within the complete layer volume (“bulk”) or at least a large portion of the same. A particularly large (inner) boundary layer between the acceptor and donor materials is provided as a result. The separation of the charge carriers (electron-hole pairs) taking place at the boundary layer is consequently particularly efficient in the absorption layers embodied as BHJ layers, which in turn favors a particularly flat embodiment of the absorption layers. In an advantageous embodiment of the invention, a first electrically conductive intermediate layer is arranged between the first absorption layer and the electrode, while a second electrically conductive intermediate layer is inserted between the second absorption layer and the counter electrode. The first and the second intermediate layer are in this case in particular selectively electrically conductive for charge carriers of different electrical charge polarity (in particular electrons and holes). The intermediate layers produced in a suitable embodiment from highly doped inorganic semiconductor material are in particular selectively electron-conducting or selectively hole-conducting, and consequently prevent an injection of the respective minority charge carriers from the absorption layers into the electrode or counter electrode. The leakage current (dark current) occurring during the operation of the detector element is reduced as such. In an advantageous embodiment, the scintillation layer is formed by a matrix which is optically transparent to the scintillation light and in which a plurality of scintillator particles are embedded. On the one hand, a high effective absorption cross-section for the incident x-ray radiation is achieved by way of the scintillator particles. On the other hand, however, the emitted scintillation light is attenuated only to a negligible extent in the scintillation layer, which further promotes the quantum yield of the detector element. In addition, due to the scintillator particles embedded therein, the transparent matrix has numerous scatter centers for the emitted scintillation light. A lateral spreading of the scintillation light within the scintillation layer is inhibited by this. This is advantageous in particular in the case of an x-ray detector having a plurality of adjacently arranged detector elements, since the optical crosstalk between the neighboring detector elements is minimized as a result. In a beneficial development of at least one embodiment, the matrix has an optical refractive index which is matched to the wavelength of the scintillation light. The refractive indices of the matrix material and of the material of the scintillator particles are in this case aligned as closely as possible with one another. The extraction of the scintillation light from the scintillator particles into the matrix is improved as a result, which is conducive to the sensitivity of the detector element. In order to match the refractive index of the matrix material to the wavelength of the scintillation light, the matrix material is provided for example with nanoscopic particles from a metal oxide, titanium oxide, for example. What are understood as nanoscopic particles in this context are particles having typical particle diameters in the nanometer range, which are therefore small compared to the wavelength of the emitted scintillation light, and which consequently produce no scattering of the scintillation light. A terbium-doped gadolinium oxysulfide which has an emission maximum in the green spectral range is used for example as the scintillator material. PMMA, an epoxy resin or silicone, for example, is used as the matrix material in this case, because these substances exhibit a comparatively low level of absorption in the cited spectral range. The layer thickness of the scintillation layer is beneficially chosen such that sufficiently good values are yielded both for the x-ray absorption and for the light extraction, as well as, where applicable, for the conductivity of the matrix. Typically, the scintillation layer in this case has a layer thickness in the range of several micrometers. In a particularly advantageous development, the matrix is electrically conductive in an ambipolar manner. In this development, the detector element with its sandwich-like structure acts like two photodiodes connected in series. By virtue of the electrical conductivity of the matrix, a capacitive charging of the detector element during its operation and a slowdown of the detector response caused thereby are avoided. The matrix material in this case acts as a recombination layer for the non-extracted charge carriers. A permanently efficient extraction of charge carriers during the operation of the detector element is possible as a result, even under continuous bombardment by x-ray radiation. Alternatively hereto once again, the matrix is embodied as photoconducting. In the unirradiated state, the matrix in this case is electrically insulating, so only a small or even vanishing dark current flows. The matrix material only becomes electrically conductive (preferably in an ambipolar manner) when exposed to x-ray irradiation and thus enables the charge carrier recombination from the two photoactive elements. Furthermore, further charge carriers are generated in the matrix in this process, and under certain conditions these can also contribute to the measured signal of the x-ray detector. Thus, a particularly good signal-to-noise ratio of the x-ray detector is achieved thanks to the photoconducting embodiment of the matrix. A plurality of detector elements of the above-described type are fixed in a predefined geometric arrangement in relation to one another in order to form the x-ray detector according to an example embodiment of the invention. The individual detector elements or detector pixels are arranged in this case, in particular for the purpose of forming an x-ray detector detecting in a spatially resolved manner in a one-dimensional detector row or a two-dimensional detector array. Within the scope of the x-ray detector, the individual detector elements are preferably coupled to one another for signal processing purposes. In particular, the electrical signals of a plurality of or all the detector elements of the x-ray detector are processed and controlled by a common control or evaluation unit. The x-ray detector is used for example in the medical technology field, in particular as part of a computed tomography system. Furthermore, such an x-ray detector is also used for example as a radiation monitor, i.e. as a measuring instrument for measuring the x-ray dose rate and therefore the radiation burden for a patient exposed to the x-ray radiation. The use of the x-ray detector provided with organic absorption layers of the detector pixels as a radiation monitor is particularly advantageous in this instance, since owing to the (in this case x-ray transparent) absorption layers, the radiation burden for the patient can be monitored at a high resolution without unwanted shadowing effects occurring on the actual x-ray image in the process. For the application as radiation monitor, the fill level of the scintillation layer (that is to say, the number and density of the scintillator particles within the matrix) is preferably chosen sufficiently large to ensure that the detector pixels of the radiation monitor reliably generate a sufficiently high and low-noise signal even at a low x-ray dose. Conversely, the fill level is preferably chosen sufficiently small to ensure that no (x-ray) shadows are generated due to the detector elements of the radiation monitor on a downstream-connected imaging detector, and consequently on the x-ray image. In order to produce the detector element according to an embodiment of the invention, it is provided according to the method that the scintillation layer is produced from a liquid dispersion or suspension of scintillator particles and a polymer material. This enables the scintillation layer to be processed out from the liquid dispersion and thereafter dried or cured (hardened). In a preferred development of an embodiment of the method, the photoactive absorption layers are deposited out of a solution directly onto opposite plane faces of the scintillation layer. By processing the absorption layers directly out of a solution, a particularly effective and surface-covering optical coupling is ensured between the matrix and the material of the absorption layers. The detector element 2 shown in FIG. 1 is particularly suited to and equipped for an indirect x-ray detection of incident x-ray radiation. To that end, the detector element 2 comprises a scintillation layer 4 for converting the x-ray radiation into scintillation light having a wavelength in the visible, infrared or ultraviolet spectral range. In addition, the detector element 2 comprises a photoactive element 6 by means of which the scintillation light is subsequently absorbed for conversion into an electrical signal. The photoactive element 6 is formed by two photodiodes 6a, 6b. One of the two photodiodes 6a, 6b in each case is arranged therein on one of the two plane faces of the scintillation layer 4 for the purpose of detecting the generated scintillation light, with the result that the scintillation layer 4 is accommodated in a sandwich-like manner between the two photodiodes 6a, 6b. Each of the two photodiodes 6a, 6b comprises an absorption layer 8a and 8b, respectively, in which the scintillation light can be absorbed, with electron-hole pairs being formed in the process. Adjoining each of the absorption layers 8a, 8b on the outside face in each case is an intermediate layer 10a and 10b, respectively, by means of which the respective absorption layer 8a, 8b is coupled in an electrically conductive manner to an electrode 12 and a counter electrode 14, respectively. The photodiode 6a is accordingly formed from the absorption layer 8a, the intermediate layer 10a and the electrode 12, whereas the photodiode 6b is formed from the absorption layer 8b, the intermediate layer 10b and the counter electrode 14. The scintillation layer 4 is formed by a matrix 16 composed of a polymer, in which matrix 16 a plurality of scintillator particles 18 are embedded. The scintillator particles 18 absorb incident x-ray radiation and convert the same into the scintillation light. The matrix 16 is transparent to the incident x-ray radiation as well as to the emitted scintillation light. With regard to the optical refractive index, the matrix 16 is furthermore adapted to match the scintillator particles 18, such that a particularly effective optical extraction of the scintillation light into the matrix 16 is realized. The matrix 16 is furthermore electrically conducting in an ambipolar manner. In an alternative example embodiment, the matrix 16 is photoconductive. In this case the matrix 16 is electrically conductive only in the presence of scintillation light, whereas it is electrically nonconductive in the absence of scintillation light, and the absorption layers 8a, 8b are therefore insulated from one another. The scintillator particles 18 preferably have a diameter in the range of the wavelength of the scintillation light. This causes the scintillator particles 18 to act as scatter centers for the scintillation light, as a result of which the lateral transmission of the scintillation light within the scintillation layer 4 is inhibited. The scintillation light is therefore coupled into the photodiodes 6a and 6b primarily via the plane faces of the scintillation layer 4. The scintillation layer 4 is produced from a liquid dispersion of the scintillator particles 18 and the matrix polymer by drying and curing. The absorption layers 8a, 8b are subsequently deposited out from a liquid directly onto the scintillation layer 4. A particularly effective optical coupling between the scintillation layer 4 and the absorption layers 8a and 8b is achieved as a result. The absorption layers 8a and 8b are composed of a photoactive organic semiconductor material. The absorption layers 8a and 8b are in this case embodied as bulk heterojunctions. The intermediate layers 10a, 10b are fabricated from highly doped semiconductor material. The doping of the intermediate layers 10a, 10b is in this case chosen such that the intermediate layer 10a is electrically selectively conductive for electrons, whereas the intermediate layer 10b is electrically selectively conductive for holes. As a result, the absorption layers 8a and 8b are contacted by the electrode and the counter electrode 14, respectively, in a complementary selective manner in relation to the charge polarity. During the operation of the detector element 2, an electrical voltage is applied between the electrode 12 and the counter electrode 14, the electrode 12 being connected in particular to a positive terminal of a voltage source, and the counter electrode 14 being connected in particular to a negative terminal of the voltage source. Incident x-ray radiation induces the scintillation light within the scintillation layer 4, which scintillation light is absorbed by the absorption layers 8a and 8b, with charge carriers (electron-hole pairs) being formed in the process. The created charge carriers are separated by the electrical field between the electrode 12 and the counter electrode 14. Owing to the intermediate layers 10a and 10b, electrons are accelerated toward the electrode 12 and holes are accelerated toward the counter electrode 14 and are extracted there. In this case the respective minority charge carriers, i.e. holes in respect of the photodiode 6a and electrons in respect of the photodiode 6b, remain behind in the absorption layers 8a and 8b. The minority charge carriers can be recombined with one another through charge exchange via the electrically conductive matrix 16. A capacitive charging of the detector element 2 is prevented as a result, thereby enabling a continuous extraction of the charge carriers during exposure to x-ray irradiation. FIG. 2 shows the detector element 2 in a further embodiment variant. In this case, unless described otherwise in the following, the detector element 2 according to FIG. 2 corresponds to the embodiment variant described hereinabove. In contrast to the latter, however, two further intermediate layers 20a and 20b are present, each of which is immediately adjacent to the scintillation layer 4. The intermediate layer 20a is thus arranged between the scintillation layer 4 and the absorption layer 8a, while the intermediate layer 20b is arranged between the scintillation layer 4 and the absorption layer 8b. The intermediate layers 20a and 20b are semiconductor layers which, in terms of their selective conductivity, are complementary to the respective associated intermediate layers 10a and 10b. Compared to the embodiment variant according to FIG. 1, the electrical connection to the scintillation layer 4 is improved as a result of the additional intermediate layers 20a, 20b. Furthermore, sites of unevenness at the surface of the scintillation layer 4 are leveled out by the additional intermediate layers 20a, 20b. The mode of operation of the detector element 2 is otherwise not affected by the intermediate layers 20a and 20b, so that in this regard reference is made to the aforementioned embodiments described with reference to FIG. 1. All of the layers of the detector element 2 according to FIG. 1 or 2 are preferably produced from a solution, suspension or paste, in particular by means of screen printing, doctor blading or a spray coating technique. Care should be taken in this case to ensure that the solvent of the currently produced layer does not disperse or dissolve the layer beneath. In a beneficial embodiment of the production method, the process is started with a glass substrate that has already been sputtered with a layer composed of ITO acting as the counter electrode 14. On this, the first three layers are applied by means of a doctor blade or slot-die coater, in the following order: as intermediate layer 10b, a hole-conducting layer composed of PEDOT having a layer thickness between 30 nm and 100 nm, as absorption layer 8b, a photoactive layer (BHJ) composed of poly(3-hexyl)thiophene (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) or pure perovskite having a layer thickness between 100 nm and 1000 nm, and optionally, as intermediate layer 20b, an electron-conducting layer composed of zinc oxide nanoparticles having a layer thickness <50 nm. The scintillation layer 4 having a layer thickness between 2 μm and 6 μm is deposited on these layers, likewise by doctor blading, for example. The scintillation layer 4 is subsequently dried or cured (preferably by means of a UV-activated curing process). In an alternative method variant, the scintillation layer 4 is laminated on as a finished layer. The following layers are deposited onto the layer stack, likewise by means of a doctor blade or a slot-die coater: optionally, as intermediate layer 20a, a hole-conducting layer composed of PEDOT having a layer thickness <50 nm, as absorption layer 8a, a further photoactive layer composed of P3HT:PCBM having a layer thickness <1000 nm, preferably between 100 nm and 300 nm, and as intermediate layer 10a, an electron-conducting layer composed of ZnO nanoparticles having a layer thickness <50 nm. As the final electrode (12), a metal layer (Al or Ag) having a layer thickness of approx. 100 nm is applied by thermal vapor deposition. Alternatively hereto, the electrode (12) is produced from a layer composed of silver nanowires which are deposited out of an ink. A small number of monolayers (in particular approx. 2 to 5) are preferably applied in this case. The invention is not limited to the example embodiments described in the foregoing. Rather, other variants of the invention may also be derived herefrom by the person skilled in the art without departing from the subject matter of the invention.
	claims	1. A method of inspecting a sample, comprising:directing a primary electron beam containing a first group of electrons to be incident on an area of said sample including a plurality of pixels such that electrons are simultaneously emitted from each of the plurality of pixels; employing charge control means on said area of said sample such that said first group of electrons and said charge control means act together to maintain a stable electrostatic charge on said sample; and using a sensor to detect any emitted electrons by simultaneously imaging said emitted electrons from said area of said sample. 2. The method according to claim 1, wherein said primary electron beam has a width greater than about 0.1 millimeters. 3. The method according to claim 1, wherein said sensor is operated in time delay integration mode. 4. The method of claim 1, wherein at least one of said first group of electrons or said charge control means acts on an area larger than a portion of said area which is imaged. 5. A method of inspecting objects, comprising:providing a sample; directing an electron beam containing a first group of electrons to be incident on a multi-pixel imaging region of said sample; employing charge control means on said sample, wherein said first group of electrons and said charge control means act together to maintain a stable electrostatic charge on said sample; and simultaneously detecting electrons emitted from said multi-pixel imaging region. 6. A system for inspecting a reticle, comprising:an electron beam source configured to emit a primary electron beam along a primary beam path, the primary electron beam being simultaneously incident on a multi-pixel imaging region of the reticle to provide electrons along a detected beam path; and a sensor positioned and configured to detect electrons from the multi-pixel imaging region of the reticle. 7. The system of claim 6 wherein the sensor is a detector array. 8. The system of claim 7 wherein the detector array images about 500,000 to 1,000,000 pixels in parallel. 9. The system of claim 6 wherein the emitted electrons are focused onto the sensor by a projection electron lens. 10. The system of claim 6 wherein the sensor is a time delay integration sensor. 11. The system of claim 10 wherein the time delay integration sensor is implemented by focusing a moving image onto a two-dimensional charge coupled device sensing array. 12. The system of claim 6 wherein the emitted electrons are converted into a light beam and detected with a time delay integration optical detector. 13. The system of claim 6 wherein the primary electron multi-pixel beam is operated near a stable E2 energy point of the reticle. 14. The system of claim 6 wherein a collimated width of the primary electron beam incident on the reticle is larger than an image plane located in proximity to the sensor. 15. The system of claim 14 wherein the collimated width is about one to two millimeters. 16. A system for inspecting a reticle, comprising:a means for directing a beam along a primary beam path, the beam configured to be simultaneously incident on an area of the reticle comprising a plurality of pixels; and a means for simultaneously detecting electrons emitted from the area of the reticle. 17. A method for inspecting a reticle, comprising:directing a primary electron beam to be simultaneously incident on an area of the reticle comprising a plurality of pixels; and simultaneously detecting electrons from the area of the reticle. 18. An inspection system, comprising:an electron beam source configured to emit a primary electron beam along a primary beam path, the primary electron beam configured to be simultaneously incident on a multi-pixel imaging region of a sample to cause the sample to emit electrons along a secondary electron beam path; and a sensor positioned in the secondary electron beam path, the sensor configured to simultaneously detect the electrons emitted from the multi-pixel imaging region of the sample. 19. The system of claim 18 wherein the sample comprises a semiconductor wafer. 20. The system of claim 18 wherein the sample comprises a semiconductor die. 21. The system of claim 18 wherein the sample comprises a flat panel display. 22. The system of claim 18 wherein the sample comprises a thin film magnetic head. 23. An inspection system, comprising:an electron beam source configured to emit a primary electron beam along a primary beam path, the primary electron beam configured to be incident on a multi-pixel imaging region of a sample to cause the sample to emit electrons along a secondary electron beam path, wherein the inspection system does not comprise an electron beam deflection system; and a sensor positioned in the secondary electron beam path, the sensor configured to simultaneously detect the electrons emitted from the multi-pixel imaging region of the sample.
	claims	1. A sample processing apparatus comprising:a probe;probe moving means for moving the probe such that the probe is brought into contact with a part of a sample;adhering means for adhering the probe to the part of the sample;ion beam generation means for irradiating the sample with an ion beam to separate the part of the sample from a remaining body of the sample;detection means for detecting a signal emitted from the sample in response to irradiation with an ion beam generated by the ion beam generation means; andtemperature controlling means for controlling temperatures of the probe and the sample individually to prevent a temperature change of the part of the sample when the probe is bought into contact with the part of the sample and when the sample is irradiated with an ion beam by the ion beam generation means,wherein the emitted signal is secondary electrons or secondary ions, and the detection means includes a first detector for detecting the secondary electrons and a second detector for detecting the secondary ions. 2. A sample processing apparatus according to claim 1, wherein the ion beam generation means generates a focused ion beam for processing the sample to almost separate the part of the sample from the remaining body of the sample before the probe is brought into contact with the part of the sample and completely separate the part of the sample after the probe is adhered to the sample. 3. A sample processing apparatus according to claim 1, wherein the temperature of the sample is regulated at a temperature where water present in the sample is solidified. 4. A sample processing apparatus according to claim 1, wherein the ion beam generation means, the detection means and the probe are provided in a chamber with a controllable atmosphere. 5. A sample processing apparatus comprising:a probe;probe moving means for moving the probe such that the probe is brought into contact with a part of a sample;adhering means for adhering the probe to the part of the sample;ion beam generation means for irradiating the sample with an ion beam to separate the part of the sample from a remaining body of the sample;detection means for detecting a signal emitted from the sample in response to irradiation with an ion beam generated by the ion beam generation means;temperature controlling means for controlling temperatures of the probe and the sample individually to prevent a temperature change of the part of the sample when the probe is bought into contact with the part of the sample and when the sample is irradiated with an ion beam by the ion beam generation means; anddetection means for detecting a signal emitted from the sample in response to irradiation with an ion beam generated by the ion beam generation means,wherein the detection means includes a first detector for detecting secondary electrons and a second detector for detecting secondary ions.
047088451	claims	1. In a fuel assembly having a bundle of elongated fuel rods disposed in side-by-side relationship so as to form an array of spaced fuel rods, an outer tubular flow channel surrounding said fuel rods so as to direct flow of coolant/moderator fluid along said fuel rods, a hollow water cross extending centrally through and interconnected with said outer flow channel so as to divide said channel into separate compartments and said bundle of fuel rods into a plurality of mini-bundles thereof being disposed in said compartments, and a plurality of spacers axially displaced along said fuel rods in each of said mini-bundles thereof, each spacer being composed of inner and outer means which together define spacer cells at corner, side and interior locations of said spacer and have respective protrusions formed thereon which extend into cells so as to maintain said fuel rods received through said spacer cells in laterally spaced relationships, the improvement which comprises: (a) a generally uniform poison coating within at least a majority of said fuel rods; (b) a predetermined pattern of fuel enrichment with respect to said fuel rods of each mini-bundle thereof which together with said uniform poison coating within said fuel rods ensures that the packing powers of the fuel rods in said corner and side cells of said spacers are less than the peaking power of a leading one of said fuel rods in said interior cells of said spacers; and (c) each of said fuel rods being received through said cells of said each spacer having a diametric size smaller than that of each of said fuel rods received through said side and interior cells of said each spacer, said diametric sizes of each of said fuel rods received through said side and interior cells of each spacer being generally equal. each of said fuel rods includes an outer tubular member having an inner clad surface and a plurality of fuel pellets contained within said tubular member; and said uniform poison coating is applied to one of said fuel pellets and said inner clad surface of said tubular member. each of said protrusions in said corner cells extending a greater distance into said corner cells than the distance through which said protrusions in said side and interior cells extend into said side and interior cells, whereby increased coolant flow space is provided through said corner cells as compared to said side and interior cells so as to increase heat transfer from said corner fuel rods to the coolant. perforations formed in said outer spacer means at the locations of said corner and side cells of said spacer for reducing the amount of area of spacer material adjacent said fuel rods received in said corner and side cells and thereby increasing coolant flow to said corner and side fuel rods. (a) each of said fuel rods received through said corner cells of said each spacer having a diametric size smaller than that of each of said fuel rods received through said side and interior cells of said each spacer, said diametric sizes of each of said fuel rods received through said side and interior cells of each spacer being generally equal; (b) each of said protrusions in said corner cells extending a greater distance into said corner cells than the distance through which said protrusions in said side and interior cells extend into said side and interior cells, whereby increased coolant flow space is provided through said corner cells as compared to said side and interior cells so as to increase heat transfer from said corner fuel rods to the coolant; (c) perforations formed in said outer strap at the locations of said corner and side cells of said each spacer for reducing the amount of strap area adjacent said fuel rods received in said corner and side cells and thereby increasing coolant flow to said corner and side fuel rods; (d) a generally uniform poison coating within at least a majority of said fuel rods, said uniform poison coating being applied to one of said fuel pellets and said inner clad surface of said tubular member of said each fuel rod in said majority thereof; and (e) a predetermined pattern of fuel enrichment with respect to said fuel rods of each mini-bundle thereof which together with said uniform poison coatings within said fuel rods ensures that the peaking powers of fuel rods in said corner and side cells of said spacers are less than the peaking power of a leading one of said fuel rods in said interior cells of said spacers. 2. The fuel assembly as recited in claim 1, wherein said uniform poison is boron. 3. The fuel assembly as recited in claim 1, wherein: 4. The fuel assembly as recited in claim 1, further comprising: 5. The fuel assembly as recited in claim 1, further comprising: 6. In a fuel assembly having a bundle of elongated fuel rods disposed in side-by-side relationship so as to form an array of spaced fuel rods, an outer tubular flow channel surrounding said fuel rods so as to direct flow of coolant/moderator fluid along said fuel rods, a hollow water cross extending centrally through and interconnected with said outer flow channel so as to divide said channel into separate compartments and said bundle of fuel rods into a plurality of mini-bundles thereof being disposed in said respective compartments, and a plurality of spacers axially displaced along said fuel rods in each of said mini-bundles thereof, each of said fuel rods including an outer tubular member having an inner clad surface and a plurality of fuel pellets contained within said tubular member, each spacer being composed of a plurality of interleaved inner straps and an outer strap encompassing said inner straps, said interleaved inner straps and said outer strap having respective protrusions formed thereon and together defining spacer cells into which said respective protrusions extend to maintain said fuel rods received through said spacer cells in laterally spaced relationships in respective corner and side cells defined by said interleaved inner straps together with said outer straps and in respective interior cells defined by said interleaved inner straps along, the improvement which comprises: 7. The fuel assembly as recited in claim 6, wherein said uniform poison is boron.
	abstract	A method for recognizing the step movement sequence of a control rod drive mechanism of a nuclear reactor, which withdraws and inserts a control rod of a nuclear reactor, includes the steps of: measuring current and voltage flowing through an electromagnetic coil used in the control rod drive mechanism of the nuclear reactor; calculating inductance of the coil by using the measured current and voltage; calculating a distance between a rotor and a stator of the control rod drive mechanism on the basis of the calculated inductance; and recognizing the step movement sequence of the control rod drive mechanism on the basis of the calculated distance. This method ensures good reliability in determining the step movement sequence, allows easy implementation using a digital signal processor, and is hardly affected by external factors such as noise.
040381358	claims	1. A plate-type nuclear fuel element comprising a core having a base of ceramic fuel material enclosed between two metallic cladding plates, wherein the fuel core is constituted by the juxtaposed array of a plurality of thin wafers of a ceramic fuel material, said wafers each having a geometric shape such that their planar juxtaposed assembly serves to form said plate-type nuclear fuel element which does not have any vacant spaces, at least a number of said wafers being provided with an individual metallic protection constituted by covering at least the lateral perimeters of said wafers with a thin metallic covering prior to assembly of said wafers to form said plate-type nuclear fuel element, said thin metallic covering having a contributory function in the assembly of cladding the wafers and dividing said plate-type nuclear fuel element into compartments. 2. A fuel element according to claim 1, wherein the protection of each wafer of ceramic fuel material is provided laterally by means of a thin metallic strip. 3. A fuel element according to claim 2, wherein the thin metallic strip has a thickness within the range of 0.1 to 0.5 mm. 4. A fuel element according to claim 2, wherein the thin metallic strip is constituted by two strip components bent in the shape of a U, said components being fitted one inside the other along the sides of the wafer and secured by spot welds. 5. A fuel element according to claim 2, wherein the thin metallic strip is formed by winding at least one turn of metallic ribbon around the lateral perimeter of each wafer, said metallic ribbon being of small thickness within the range of 0.05 to 0.2 mm. 6. A fuel element according to claim 1, wherein the individual protection of each wafer is provided by means of a sheet of thin metallic foil which completely surrounds said wafer. 7. A nuclear fuel element according to claim 6, wherein metallic partition-strips are interposed between the protected fuel wafers in such a manner as to ensure that two adjacent fuel wafers are separated by the whole or a part of a metallic partition-strip. 8. A nuclear fuel element according to claim 6, wherein any two adjacent rows of protected fuel wafers are separated by a metallic partition-strip which extends along the entire length of said element. 9. A fuel element according to claim 1, wherein the framed wafers of fuel material are aligned in a single row so as to form a narrow plate unit of substantial length between two top and bottom metallic cladding plates. 10. A fuel element according to claim 1, wherein the material constituting the independent and individual covering of each wafer is selected from the group comprising zirconium and the zirconium alloys. 11. A nuclear fuel element according to claim 1, wherein the ceramic fuel material is uranium dioxide. 12. A fuel element according to claim 1, wherein the ceramic fuel material is loaded with a burnable neutron poison. 13. A fuel element according to claim 1, wherein the cladding material is selected from the group comprising zirconium and the zirconium alloys. 14. A fuel element according to claim 7, wherein the metallic partition-strips are formed of material which is identical with that of the fuel element cladding.
054810612	claims	1. A method for solidifying a radioactive waste with cement as a main solidifying material to produce a solidified radioactive waste, comprising: mixing water, a hydrophilic polymer emulsion and cement to form a first mixture, said cement having a coefficient of linear expansion of 0.1 to 0.5% with respect to volume change upon hardening and containing an expanding agent selected from the group consisting of calcium sulfate, calcium sulfoaluminate and calcium oxide; adding radioactive waste to said first mixture and kneading the radioactive waste and first mixture to form a kneaded mixture, said radioactive waste being a water-absorptive; and packing the kneaded mixture into a solidifying container. 2. A method for solidifying a radioactive waste according to claim 1, wherein the step of mixing said water, said hydrophilic polymer emulsion and said cement to form said first mixture is accomplished in a first mixer and wherein the steps of adding the radioactive waste to said first mixture and kneading the radioactive waste and first mixture to form said kneaded mixture is accomplished in a second mixer. 3. A method for solidifying a radioactive waste according to claim 1, wherein a mixing ratio of water to cement is 0.15 to 0.45. 4. A method for solidifying a radioactive waste according to claim 1, wherein said hydrophilic polymer emulsion is latex emulsion. 5. A method for solidifying a radioactive waste according to claim 1, wherein said radioactive waste is a concentrated liquid radioactive waste containing sodium sulfate and i wherein said method further comprises drying the concentrated liquid radioactive waste to obtain dried sodium sulfate powder and remaining concentrated radioactive liquid waste, and wherein the dried sodium sulfate and the remaining concentrated liquid radioactive waste are separately added to said first mixture.
043022952	abstract	A fuel element contains a tag gas serving to detect breakage of a cladding tube. Pellets of a fuel material and a metal foil having a tag gas implanted thereinto by ion implantation method are loaded in a cladding tube.
052375994	abstract	In order to perform stereoradiography, an X-ray apparatus utilizes an X-ray tube having a pair of X-ray focal points. The X-ray beams are alternately irradiated from the focal points toward an image intensifier through a patient and are limited by an X-ray beam limiting device. The device shapes the irradiated X-ray beams onto a circular detection surface of the image intensifier into a polygon such as octagon. The X-ray irradiation field on the detection surface can be circumscribed to a circular input window (i.e. effective input area), preventing the field from going beyond the detection surface. Thus, direct X-ray leaking over the image intensifier is avoidable.
048329002	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS The test tool of the present invention provides for simulation of all the level monitoring signals encountered in Westinghouse Electric Corporation pressurized water nuclear reactors, including resistance temperature detector signals, pump status and hydraulic isolator overrange limit signals, reactor coolant outlet temperature sensor signals, differential pressure cell signals and reactor coolant inlet pressure sensor signals. The test tools for both the 8-bit 9RVLIS) and 16-bit (RVLIS-86) reactor vessel level instrumentation system are designed to accommodate the maximum number of sensors that will be encountered in the field. Whenever a sensor is not present on site, the simulator or testing signal generator circuit associated with that sensor need not be corrected. FIG. 2 illustrates a test tool 40 connected to an 8-bit microprocessor based RVLIS 10. The test tool 40 includes a resistance temperature detector simulator 41 comprising 500 ohm potentiometers 42-48 for simulating temperature measured by resistance temperature detectors 17-23 (FIG. 1). Seven potentiometers 42-48 are provided because seven is the maximum number of resistance temperature detectors which will be encountered in the field. The potentiometers 42-48 need not be precision potentiometers, but must have the ability to handle up to 1 volt and 1 milliamp of current, and must be lockable so that a set value will not drift. The potentiometers 42-48 are connected to the appropriate terminals T1-T39 of the associated terminal block 49 in the instrumentation system 10 as shown in FIG. 2. The particular terminal block 49 in the 8-bit RVLIS is terminal block 105 and care must be taken that the wiper arms of the potentiometers are not connected to the negative terminals (-). During operation, the negative terminal (-) of each terminal pair provides a 1 milliamp current to the associated potentiometer supplied by an operational amplifier in the instrumentation system 10. As the potentiometer is adjusted, the voltage will vary between 0 and 0.5 volts. A twenty-eight wire cable connects the simulator 41 to a terminal block 49 and should have spade lug connectors on the RVLIS side for ease of connection. The cable need not be of a special type, but the wire should be at least 22 gauge. A military lockable connector can be used on the test tool 40 side. FIG. 3 illustrates a pump status simulator 50 of the test tool 40 connected to the RVLIS 10. The pump status simulator comprises pump status switches 51-54. Four pump status switches 51-54 are provided since this is the maximum number of reactor coolant pumps that will be encountered in the field. The switches can be any type of single-pole, single-throw switch capable of transmitting a +5 volt signal. The pump status switches 51-54 are connected to terminals T1-T11 of the associated terminal block 55 in the instrumentation system 10, as shown in FIG. 3. When the pump status simulator 50 is operated, a five volt signal supplied by a positive terminal (+) is returned to the instrumentation system 10 through the negative terminal (-). The presence of a 5 volt detection signal on the negative terminal simulates a run or on status of a corresponding reactor coolant pump as produced by pump status monitors 24. FIG. 3 also illustrates an isolator overrange limit simulator 56 which simulates overrange limit signals produced by hydraulic isolators 14-16 (FIG. 1) and which comprises ordinary single-pole, single-throw switches 57-59. The switches 57-59 are connected to terminal points T13-T20 of terminal block 55, as shown in FIG. 3. The terminal block 55 in the 8-bit RVLIS is designated as terminal block 101. During operation, the limit switches 57-59, when closed, return a +5 volt detection signal to the RVLIS which simulates liquid pressure exceeding the associated hydraulic isolator's range. A fourteen conductor wire cable with spade lug connectors on the RVLIS 10 side should be provided for connecting the pump status simulator 50 and isolator limit overrange limit simulator 56 to the instrumentation system 10. A military lockable connector can be used on the test tool 40 side. FIG. 4 illustrates a temperature hot sensor simulator 60 connected to the instrumentation system 10 and which simulates coolant outlet temperature sensors 26. The temperature hot simulator is connected to a five volt power supply 61 which can be an off-the-shelf power supply as long as it has a ten percent voltage accuracy and will supply 250 milliamps of current. The power supply is connected to 200 ohm resistors 62 and 63 within the temperature hot simulator 60. The 200 ohm resistors are connected to 1 kilo ohm potentiometers 64 and 65 which are connected to the instrumentation system 10. The resistors 62 and 63 and potentiometers 64 and 65 need not be precision; however, the potentiometers need to be the lockable type so that the a value will not change. The temperature hot sensor simulator 60 is connected to terminals T1-T9 of the associated thermal block 66 in the instrumentation system 10. Care must be taken to ensure that the wiper arm of each potentiometer is connected to the positive terminal (+). During operation, as the potentiometers 64 and 65 are operated, the simulator 60 will provide a signal with a range of either 1-5 volts or 0.2-1 volt, depending upon whether the termination within the RVLIS 10 is a 50 or 250 ohm termination. The test tool 40 operator need not be concerned with the termination resistance, only with the possible range of the produced signals. FIG. 4 also illustrates a differential pressure cell simulator 67 which simulates variations in differential pressure detected by cells 11-13 (FIG. 1) and which includes 10 kilo ohm potentiometers 68-70 which should also be lockable. Between the wiper arm of the potentiometers 68-70 and the terminal block 66 are 1.2 kilo ohm resistors 71-73. The potentiometers 68-70 and resistors 71-73 need not be precision components. Three resistor/potentiometer pairs are provided in the simulator 67 because three is the maximum number of differential pressure cells which will be encountered in the field. The differential pressure simulator 67 is connected to terminals T25-T37 of terminal block 66. During operation, as the potentiometers 68-70 are adjusted, the RVLIS produces thirty volts and the current is varied between 2 and 23 milliamps by the potentiometers 68-70. FIG. 4 additionally illustrates a pressure wide range sensor simulator 74 connected to the power supply 61 and which simulates the wide range pressure sensor 25 (FIG. 1). The pressure wide sensor simulator includes a 200 ohm resistor 75 connected to the power supply 61 and a 1 kilo ohm lockable potentiometer 76 connected between the 200 ohm resistor and the terminal block 66 in the instrumentation system 10. The connection of the simulator 74 to the terminal T40-T42 includes a connection to the shield terminal(s) of the terminal block 66 and care must be taken to connect the wiper arm of potentiometer 76 to the positive terminal (+). The terminal block 66 in the 8-bit microprocessor based Westinghouse RVLIS is terminal block 106. During operation, as the potentiometer 76 is adjusted, a signal similar to the signals produced by the temperature hot simulator 60 will be produced. A nineteen conductor wire cable including spade lug connectors on the RVLIS 10 side is used to connect the temperature hot simulator 60, differential pressure cell simulator 67 and pressure wide range sensor simulator 74 to the instrumentation system 10. A military lockable connector can be used on the test tool 40 side. FIGS. 5-7 illustrate how a meter 77 is connected to the different simulators to allow visual verification of the value of the signal being input into the instrumentation system 10. The meter must always be connected between the positive (+) and negative (-) conductors. Between the meter and the various simulators, a 13 position selectable switch can be provided for connecting the meter 77 to the appropriate simulator. As an alternative, banana plugs could be used to connect the meter 77 to the appropriate simulator. The meter 77 can be a standard off-the-shelf meter capable of measuring milliamp currents, resistances varying between zero and approximately 15 kilo ohms and voltages varying from zero to fifteen volts. Two volt meters 77 should be provided so that at least two signals can be monitored at the same time. FIG. 8 illustrates the resistance temperature detector simulator portion of the test tool 40 for the 16 bit microprocessor based instrumentation system RVLIS-86. The potentiometers 42-48 are the same as depicted in FIG. 2. However, the potentiometers 42-48 are connected to terminal blocks 112 and 113 within the RVLIS-86. FIG. 9 illustrates the connections of the pump status simulator switches 51-54 and the isolator overrange limit switches 57-59 to terminals T2-T23 on terminal block 118 of the RVLIS-86. FIG. 10 illustrates the power supply 61, resistors 62, 63 and 75 and potentiometers 64, 65 and 76 which simulate the temperature hot sensors and pressure wide range sensor as they are connected to terminals T2-T9 on terminal block 111 of the RVLIS-86. FIG. 11 illustrates the potentiometers 68-70 and resistors 71-72 for simulating the differential pressure cells and how they are connected to the terminals T2-T9 on terminal block 110 of the RVLIS-86. As discussed with respect to the 8-bit RVLIS, the connections of the potentiometer wiper arm conductors of the RVLIS-86 test tool to the proper terminals must correct to ensure proper operation of the test tool. When visual verification of the output of the RVLIS-86 test tool 40 is required, a meter 77 would be connected to the various potentiometers in the same manner as illustrated in FIGS. 5-7. The resistors and potentiometers in the RVLIS-86 test tool need not be precision components and all the wiring terminations at the instrumentation system side should be spade lug connections for ease of use while a military connector can be used on the test tool side. As illustrated in the various figures, the test tool will allow all of the input signals to a light water pressurized reactor vessel level instrumentation system to be simulated throughout their ranges and, thus, allow a technician to test the system or allow training of operators. In connecting the test tool to the RVLIS, the RVLIS equipment must be de-energized. To replace the field wiring to the RVLIS with the test tool inputs, the test tool operator must first identify the terminal boards shown in the test tool in the connecting wiring diagrams of the associated figures. The associated terminal blocks are located in the rear of the local display cabinet. The appropriate field wiring connections are removed from the terminal boards and the test tool is connected to the designated terminals. Once the terminal connections are verified, the power supply in the test tool is plugged in and energized. During operation, the technician should be able to see the associated measured values change on the local display 31 as the input values change along with the corresponding changes in vessel level associated with the input value change. When the technician wants to verify the value of the output signal, meter 77 can be connected to the appropriate simulator circuit. For example, when a resistance temperature simulated value is changed, this change should show up on a local display. However, the display associated with actual reactor vessel fluid level should not change. If a hydraulic isolator overrange limit signal is simulated, an alarm should appear on both the local display 31 and the remote display 30. Whenever a differential pressure cell is simulated, the local display should show the change in the value of the pressure cell signal as well as a change in reactor fluid level and the remote display 30 should only show a change in reactor fluid level. If the technician wants to verify proper operation of the remote display 30, a spare remote display can be jumpered at the instrumentation system cabinet. The many features and advantages of the invention are apparent from the detailed specification and, thus, it is intended by the appended claims to over all such features and advantages of the test tool which fall within the true spirit and scope of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and, accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
	summary
	claims	1. An apparatus that provides an absolute nuclear material assay of an unknown source that emits neutrons, comprising:a multigate neutron multiplicity counter detecting neutrons emitted from the source and grouped with respect to time, and collecting a number of neutrons within a defined time window to derive neutron multiplet count data, the multigate counter further measuring the multiplet count in a measurement as a function of lifetime and neutron number;a processor of a plurality of processors coupled to the multiplicity counter and executing code to iteratively solve a plurality of coupled algebraic equations for five unknown parameters of the source using the first three moments of a fission chain distribution, wherein the parameters comprise mass, multiplication, alpha ratio, detector efficiency, and time constant (lambda), and wherein the first three moments are corrected with respect to the impact of instrument dead time on the count distributions of the emitted neutrons;another processor of the plurality of processors coupled to the multiplicity counter executing code that fits the time constant parameter to the actual time dependence of the moments to reduce the unknown parameters to four parameters of mass, multiplication, alpha ratio, and detector efficiency; andyet another processor of the plurality of processors coupled to the multiplicity counter that executes code that compares truncated data moments with untruncated and truncated theoretical moments to provide an estimation of a parameter of the four parameters and to allow for solution of the remaining three parameters using the first three moments. 2. The apparatus of claim 1 wherein the correction of the first three moments with respect to dead time is performed by time-tagging the neutron count events as seen during a measurement and creating a fitting algorithm that preferentially weights longer time gates so that short mode effects minimally alter a resulting asymptote of the count distribution. 3. The apparatus of claim 2 wherein the first moment is a dead-time reduced count rate correction, and a first iteration produces a first estimate of the true count rate and the second and third moments. 4. The apparatus of claim 3 wherein the first estimate of the true count rate and the second and third moments is used to create an estimate of the fourth moment that is used to refine the estimate of the true count rate and second and third moments in subsequent iterative steps until no change is found, at which time the four parameters are determined.
	abstract	A system and method for automatic production of astatine-211 labeled molecules is described. The invention represents a significant advantage in the preparation of At-211 radiopharmaceuticals including better reproducibility, reduced production time and increased radiation safety. The invention also enables routine automatic synthesis of radiopharmaceuticals in a clinical setting, in conjunction or at short distance from a cyclotron unit capable of producing the radionuclide.
052788768	summary	The present invention relates generally to boiling water nuclear reactors, and, more specifically, to a removable reactor pressure vessel head. BACKGROUND OF THE INVENTION A boiling water nuclear reactor (BWR) includes a pressure vessel containing a nuclear reactor core and water which is boiled thereby for generating steam for producing power such as by driving a turbine-generator for producing electrical power. The pressure vessel typically includes a cylindrical shell having a removable head at the top, and an integral head at the bottom thereof. The top head typically includes an arcuate dome having an integral mounting flange which mates with a complementary supporting flange on the shell. A plurality of circumferentially spaced apart bolts extend through the head flange into the shell supporting flange for bolting the upper head to the shell to form a pressure vessel capable of withstanding the relatively high pressures generated within the pressure vessel during operation of the reactor core. The upper head typically includes an integral nozzle at the top center thereof which is conventionally joined to a vent line, or a spray line, or both. The vent line communicates with the head nozzle for releasing or venting non-condensable gases such as nitrogen before startup of the reactor core, for example. And, the spray line communicates with the nozzle for injecting or spraying water therein for cooling purposes, for example. In both configurations, the vent and spray lines must be disconnected from the upper head prior to removing the upper head from the shell during a maintenance operation. This increases the complexity and time for accomplishing routine maintenance and increases the duration of radiation exposure to maintenance personnel. SUMMARY OF THE INVENTION A head for closing a nuclear reactor pressure vessel shell includes an arcuate dome having an integral head flange which includes a mating surface for sealingly mating with the shell upon assembly therewith. The head flange includes an internal passage extending therethrough with a first port being disposed on the head mating surface. A vent line includes a proximal end disposed in flow communication with the head internal passage, and a distal end disposed in flow communication with the inside of the dome for channeling a fluid therethrough. The vent line is fixedly joined to the dome and is carried therewith when the head is assembled to and disassembled from the shell.
	summary
051484650	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows an X-ray examination apparatus including an X-ray source 1 for transmitting a beam of X-rays 3. The beam of X-rays 3 impinges upon an input screen 5 of an X-ray image intensifier tube 7. The input screen 5 has a phosphor layer located behind a glass or aluminium envelope and in which the X-ray beam 3 effects luminescence. With the aid of a photocathode the light quanta emitted by the phosphor are captured and electrons are released which are accelerated to, for example, 20 keV and are displayed on an output screen 9. Via a twin optical system 11 the luminous image from the output screen is displayed on an input screen of a television pick-up device 13. A partially transmitting mirror 17 which projects the luminous image originating from the output screen onto a photographic film in a film camera 19 is between the lenses of the twin optical system 11. The television pick-up device 13 generates a video signal which is proportional to the light intensity detected at its input screen. The video signal is applied to a television monitor 15 and to a control device 25. Arranged between the X-ray source 1 and the X-ray image intensifier tube 7 is an adjustable filter 21 which via a fluid pump 23 is adjustable by the control device 25 in dependence on the video signal. Then, fluid is supplied to or withdrawn from the filter by the pump 23 until on uniform irradiation of the input screen 5 the video signal for edges of an X-ray image is equal to the video signal for center portions of the X-ray image. FIG. 2 shows schematically how an object 27 extending in an x-direction located transversely of the optical axis 29 is displayed by a lens 31. An apertured diaphragm 30 is between the object 27 and the lens 31. When the object 27 is a uniform line source, then the flux passing through the aperture of the diaphragm 30 varies proportionally to (cos .theta.).sup.4, wherin .theta. is the angle of the radius between the portion of the object emitting the flux and the center of the aperture to the optical axis 29. For Gaussian systems, in which a distance in the x-direction is small compared to the dimensions of the system along the optical axis 29, the following approximation can be made for an object located at a distance L from the diaphragm 30: ##EQU1## An image 27' of the object 27 has, because of the bounding diaphragm 30 an intensity variation which quadratically decreases relative to the optical axis 29. For a length L of 5 cms. and a distance x to the optical axis of 1 cm this approximation is accurate to within 0.5%. FIG. 3 shows how a beam of X-rays impinging from the X-ray focus 33 onto the input screen 5 of the X-ray image intensifier tube has on the input screen a higher intensity than an X-ray beam 35 incident on the input screen 5 at an angle .alpha. relative to the optical axis. The intensity on the input screen varies as (cos .alpha.).sup.3, which for small distances of x with respect to Z can be approximated by: ##EQU2## Herein Z is the spacing between the X-ray focus 33 and the input screen 5. For a value of 1 meter for Z this approximation is accurate to within 0.02%. Both vignetting due to bounding apertures in the optical system of the X-ray imaging system and the decrease in intensity due to the geometry of the input screen of the X-ray image intensifier tube can be compensated for by the filter 21 between the X-ray source 1 and the X-ray image intensifier tube 7. For water, an attenuation length amounts to approximately 3 cm. for X-rays generated in an X-ray tube at approximately 80 kV. For a maximum filter thickness of 0.5 cm (in the center of the filter) the attenuation is linear within a margin of 0.5%. A layer of water having a thickness which decreases quadratically, provided between the source 1 and the X-ray image intensifier tube 7 can compensate for vignetting. Since vignetting varies versus the distance Z between the X-ray source 1 and the X-ray image intensifier tube 7, it is advantageous for the filter thickness to be variable. FIG. 4 shows a filter 21, two flexible X-ray radiation transparent walls 37 and 39 being clamped between two anular clamping members 40 and 41. The walls 37 and 39 may be rubber or thermoplastic, for example. FIG. 5 shows an X-ray radiation transparent filter 21, a flexible wall 43 being clamped between a rigid wall 45 of, for example, Perspex, an X-ray transparent thermoplastic material, and an anular clamping member 47. In this situation the filter has, for example, a diameter D of 10 cm. and a maximum height H of 2.5 cm. The filter is connected to the fluid pump 23, not shown, via a supply line 49. For an adequate form-retaining capacity of the flexible wall 43, not disturbed by force of gravity effects, the overpressure in the filter preferably exceeds 0.5 atmosphere. The walls curve in a lens-like arrangement in which the central region has the greatest spacing between the filter walls and the spacing decreases to the wall edges in a curve-like manner to a minimum similar to an optical lens.
	claims	1. A container for holding radioactive waste, the container comprising:a side wall;a floor connected to a lower end of the side wall;a cover;a set of side-wall formations at an upper end of the side wall and on an inner surface of the side wall; anda set of cover-edge formations distributed around an outer edge of the cover and fittable with the side-wall formations such that, as a result of the interfitting of cover-edge formations with the side-wall formations, the formations of one of the sets being L-shaped radially open grooves that each have two portions extending perpendicular or substantially perpendicular to one another such that the cover can be or is fixedly connected to the side wall without welds. 2. The container defined in claim 1, further comprising:a support basket inside the container for holding spent fuel elements constituting the radioactive waste. 3. The container defined in claim 1, wherein the floor and the side wall are integrally connected to one another. 4. The container defined in claim 1, wherein there are at least three of the side-wall formations distributed around the inner surface of the side wall. 5. The container defined in claim 1, wherein there are at least three cover-edge formations distributed around the outer edge of the cover. 6. The container defined in claim 1, wherein the formations of the other of the sets are radial projections fittable in the grooves. 7. The container defined in claim 1, wherein the side wall is substantially cylindrical and centered on an axis, one of the portions of each groove extending tangentially and the other of the portions of each groove extending axially. 8. The container defined in claim 7, wherein, in a locking position with the cover axially secured by the formations to the side wall, the formations of the other set each bear upward on a downwardly directed upper face of the one portion of the respective groove. 9. The container defined in claim 8, wherein an upwardly directed lower face of each of the other portions of each groove is angled downward and toward the floor, and lower downwardly directed faces of the formations of the other set are complementarily angled, whereby an upward force on the cover pulls the upper edge of the side wall radially inward. 10. The container defined in claim 1, wherein the cover and side wall form an upwardly open sealing groove, the container further comprising:an annular seal fitted in the groove. 11. The container defined in claim 10, wherein the seal is a metal or elastomeric seal. 12. The container defined in claim 10, further comprising:a compression ring releasably secured atop the cover and formed with an axially downwardly projecting ridge engaging in the groove and pressing the seal against an upper face of the sealing groove and the inner surface of the side wall. 13. The container defined in claim 12, wherein the ridge has a frustoconical lower face facing radially outward and downward and the sealing groove has a frustoconical upper face facing radially outward and upward, whereby the ridge presses the seal radially outward against the inner surface of the side wall when axially squeezing the seal between the lower and upper faces. 14. The container defined in claim 1, wherein the container is a transport or storage container, the cover is a primary cover of the transport or storage container, the container further comprising:a secondary cover fixed to the container above the primary cover seals. 15. A container assembly, comprising a container according to claim 14, wherein the container is a canister loaded with spent fuel elements and received in a transport or storage container that can be or is sealed with the secondary cover over the primary cover.
	summary
041644794	claims	1. In the method of solidifying aqueous nuclear fuel reprocessing waste solutions containing zirconium, fluoride and chloride for long-term storage by adding calcium nitrate to the solution in an amount sufficient to establish a calcium to fluoride mole ratio of at least 0.55, and heating the resulting solution to calcining temperature, thereby calcining the waste solution to form a calcine, the calcium nitrate being present to suppress the volatility of the fluoride during calcination, the improvement wherein aluminum is added to the waste solution before the addition of calcium nitrate, the aluminum being added as a soluble, compatible compound in an amount sufficient to establish an aluminum to fluoride mole ratio of from 0.27 to 0.40 whereby the aluminum reduces the amount of gelatinous solid formed in the solution due to the presence of calcium nitrate and suppresses the volatility of the chloride during calcination of the waste solution. 2. The method of claim 1 wherein the aluminum is added as aluminum nitrate. 3. The method of claim 2 wherein the aluminum to fluoride mole ratio is 0.27. 4. The method of claim 1 wherein the waste solution containing zirconium, fluoride and chloride is a zirconium-fluoride waste solution and is present in a blend in a ratio of 3 parts zirconium-fluoride waste solution with 1 part second cycle waste, the calcium nitrate added to the blend is an amount sufficient to establish a calcium to fluoride mole ratio of from 0.6 to 0.7 and the aluminum is added in an amount sufficient to establish an aluminum to fluoride mole ratio of from 0.32 to 0.4. 5. The method of claim 4 wherein the aluminum is added as aluminum nitrate. 6. The method of claim 5 wherein the aluminum to fluoride mole ratio is 0.32.
	summary
	abstract	Systems and methods for obtaining and displaying a collimated X-ray image are described. The methods can include providing an X-ray device having an X-ray source, a square or rectangular X-ray detector, and a collimator. The collimator can be sized and shaped to collimate an X-ray beam from the X-ray source that exposes a receptor region on the detector. The collimator can allow the X-ray image received by the X-ray detector to have any suitable shape that allows a relatively large view of the image to be displayed and rotated on the display device without changing the shape or size of the image as it rotated. In some instances, the collimator provides the image with superellipse shapes or cornerless shapes having four substantially straight edges with a 90 degree corner missing between at least two edges that run substantially perpendicular to each other. Other embodiments are described.
	abstract	Ion implant apparatus using a drum-type scan wheel holds wafers with a total cone angle less than 60°. A collimated scanned beam of ions, for example H+, is directed along a final beam path which is at an angle of at least 45° to the axis of rotation of the scan wheel. Ions are extracted from a source and accelerated along a linear acceleration path to a high implant energy (more than 500 keV) before scanning or mass analysis. The mass analyzer may be located near the axis of rotation and unwanted ions are directed to an annular beam dump which may be mounted on the scan wheel.
053295633	abstract	A latch tool features two elongate arms which extend down along either side of a control rod. Rotatable actuating rods are mounted on the arms. The upper ends of the actuating rods are provided with cranks which engage in slots formed in an actuating disc. As the disc is rotated, the cranks rotate the actuating rods and swing cam-like members, which are fixed to the rods, into position under an unlatching handle. In the preferred embodiments, the actuating disc is threaded onto the exterior of a rotatable input member, so that after the cam-like members are swung into position, the actuating disc threads its way up the input member in a manner which pulls the cam-like members upwardly and pulls the unlatching handle. In addition to the cam-like members which actuate the unlatching handle, lifting cam-like members may additionally be provided to fit in under a lifting handle of the control rod, and facilitate lifting of the control rod out of its position.
	summary
	abstract	A universal control and diagnostic system for a transformer that may be retrofit with existing control and tap-changer equipment, the system providing for remote monitoring and control of the equipment and for measuring various criteria associated with the tap-changer to substantially minimize damage to the equipment during a maneuver and for substantially avoiding carbonization of a connected contact.
	description	This application is a division of U.S. patent application Ser. No. 13/758,813, filed Feb. 4, 2013, now U.S. Pat. No. 9,724,790, which claims the benefit of U.S. Provisional Application No. 61/663,427, filed Jun. 22, 2012, all the disclosures of which are expressly incorporated by reference herein in their entirety. With the prospect of radioactive material remaining in storage at reactor sites longer than was originally anticipated, there is a need to verify the condition of the canister shell, which forms the primary boundary for confinement of radioactive materials in ventilated canister storage systems. The need for inspection is particularly important at coastal storage facilities, where stress corrosion cracking of stainless steel canisters may be a concern. Depending on the results of the inspection, maintenance may also be necessary. Therefore, there exists a need for delivering various non-destructive examination and maintenance tools, which can be mounted between the storage module and the transfer cask in a storage system. This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key 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. In accordance with one embodiment of the present disclosure, a travel system for a canister storage, transfer, or transport system is provided. The travel system generally includes a support structure, at least one traveling device for preparing, inspecting, and/or repairing the canister, and a base ring for supporting the traveling device and providing for rotational movement of the traveling device relative to the support structure. In accordance with another embodiment of the present disclosure, a travel system for a canister storage, transfer, or transport system is provided. The travel system generally includes a support structure couplable to the canister storage, transfer, or transport system, at least one traveling device selected from the group consisting of a sensing device, a preparation device, and a repair device, and a base ring for supporting the at least one traveling device and providing for rotational movement of the traveling device relative to the support structure. In accordance with another embodiment of the present disclosure, a method of preparing, inspecting, and/or repairing a canister in a canister storage, transfer, or transport system is provided. The method generally includes mounting a travel system on a canister storage, transfer, or transport system, wherein the travel system includes a support structure, at least one traveling device, and a base ring for supporting the traveling device and providing for rotational movement of the traveling device relative to the support structure. The method further includes rotating the base ring and the traveling device relative to the support structure or moving the canister relative to a fixed base ring and traveling device. The detailed description set forth below in connection with the appended drawings where like numerals reference like elements is intended as a description of various embodiments of the disclosed subject matter and is not intended to represent the only embodiments. Each embodiment described in this disclosure is provided merely as an example or illustration and should not be construed as preferred or advantageous over other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Similarly, any steps described herein may be interchangeable with other steps, or combinations of steps, in order to achieve the same or substantially similar result. In the following description, numerous specific details are set forth in order to provide a thorough understanding of exemplary embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that many embodiments of the present disclosure may be practiced without some or all of the specific details. In some instances, well-known process steps have not been described in detail in order not to unnecessarily obscure various aspects of the present disclosure. Further, it will be appreciated that embodiments of the present disclosure may employ any combination of features described herein. Embodiments of the present disclosure are generally directed to systems, devices, and methods for inspecting canisters designed for containing radioactive material for abnormalities, for example, for stress corrosion cracking, and for providing maintenance where needed. Referring to FIG. 1, a horizontal dry storage module M for a canister C is shown that has its front door removed so that the canister C may be moved in and out of the module M. A travel system 20 is attached to the module M and is designed for traveling along external surfaces of the canister C for preparation, inspection, and/or repair of the external surfaces that cannot be manually affected because of the canister's radiation field. The travel system 20 may be configured to prepare, examine, and/or repair any of the external surfaces of the canister C, but also may have a particular focus on welds and other surfaces subject to degradation. Preparation, examination, and maintenance of a canister C using the travel system 20 can prepare the canister C for transport, for example, after an extended period of storage, or for extended storage. Although shown in FIGS. 1-8 as being used on a horizontal storage module M, it should be appreciated that canister travel systems 20 may also be used in vertical storage systems, for example, including vertical storage silos. As described in detail below, FIGS. 9-12 represent one embodiment of a vertical storage system. The travel system 20 may be mounted between a storage over pack (for example, a horizontal storage module M, as can be seen in FIG. 1, or a vertical storage silo S, as can be seen in FIG. 9) and a cask (for example, a transfer cask or a transportation cask, not shown). In that regard, the external surfaces of the canister C may be prepared, examined, and/or repaired during the canister C transfer process, for example, as the canister is withdrawn from the over pack into the cask, as it is being inserted into the over pack from the cask, or both. Returning to FIG. 1, the travel system 20 generally includes a support structure 22, at least one traveling device (for example, a sensing device 24), and a base ring 26 for supporting the sensing device 24 relative to the support structure 22. It should be appreciated, however, that the travel system 20 may also be designed to support preparation and maintenance tools, in addition to sensing tools. As described in greater detail below, the travel system 20 may move relative to the canister C (see e.g., FIG. 8), or in the alternative, the canister C may move relative to the travel system 20 (see e.g., FIG. 5). Comparing FIGS. 2 and 3, the support structure 22 may be attached to the entry point of the module M by using the same embedments 30 that are used for door installation. In that regard, fasteners may be used to couple with embedments 30 that are provided for door attachment. The support structure 22 is therefore designed for repeatable and precise installation on the module M. In addition, the support structure 22 is easy to attach to and remove from the module M and is configured to operate in the limiting space of opening between the module M and the transfer equipment (not shown). Arms 32 extending outwardly from the support structure 22 can be used to support control and power cables 42 (see FIG. 1). Referring to FIGS. 3 and 4, the components of the travel system 20 will now be described in greater detail. The base ring 26 is coupled to the support structure 22 and as shown in the illustrated embodiment, may be configured for rotational movement relative to the support structure 22. Referring to FIG. 3, the base ring 26 is rotatably mountable on the support structure 22 to align and be concentric with an opening O into the module M, in which the canister C is inserted and contained. The base ring 26 may be configured to rotate either clockwise or counterclockwise, or both (e.g., to oscillate between clockwise and counterclockwise). The base ring 26 may be actuatable for precise and repeatable movements relative to the support structure 22. In the illustrated embodiment of FIG. 3, an actuation assembly 36 includes a precision timing belt 38, which may be driven by a stepper motor 40. The advantage of using a timing belt 38 and stepper motor 40 for actuation is that locations of, for example, defects, can be pinpointed using software coordinates. It should be appreciated, however, that other actuation assemblies are also within the scope of the present disclosure. For example, transmissions for rotation may include one or more gears, sprockets, chains, or one or more timing belts (for example, one timing belt used as a gear and one to transmit motion). Actuation assemblies in accordance with embodiments of the present disclosure may be designed to prevent slippage. A bearing system 44 allows the base ring 26 to move relative to the support structure 22. In the illustrated embodiment, the base ring 26 of the illustrated embodiment has a channel 78, which is shown in the cross-sectional view of FIG. 4 as a cup-shaped design. The channel 78 is configured to interface with the bearing assembly 44 and the support structure 22. In that regard, the bearing assembly 44 allows the base ring 26 to rotate without constraint relative to the support structure 22 while carrying the load of the base ring 26 itself and prevent radial or linear movement of the base ring 26 relative to the support structure 22. Referring to FIGS. 3 and 4, the bearing assembly 44 includes a guide ring 80 extending from the support structure 22, an external bearing ring 82 that is positioned external to the guide ring 80, and an internal bearing ring assembly 84 to interface with the guide ring 80. As can be seen in the cross-sectional view of FIG. 4, the guide ring 80 extending from the support structure 22 has a first end 86 coupled to the support structure 22 and a second end 88 distal from the support structure 22. From the first end 86 to the second end 88, the cross-sectional shape of the guide ring 80 expands such that it has a larger width as the second end 88 than at the first end 86. The external bearing ring assembly 82 includes outer and inner components 82a and 82b that are designed to interface as bearing surfaces between the surfaces of the guide ring 80 and the surfaces of the base ring channel 78. In that regard, the outer and inner components 82a and 82b have trapezoidal cross-sectional shapes to interface with the cross-sectional shape of the guide ring 80. The internal bearing ring 84 provides a bearing surface between the second end 88 of the guide ring 80 and the inner surface of the channel 78. The bearing surfaces of the external bearing ring assembly 82 (82a and 82b) and the internal bearing ring 84 allow the base ring 26 to rotate relative to the support structure 22. In addition, in this horizontal orientation, the external bearing ring assembly 82 (82a and 82b) carries the load of the base ring 26 itself. The fit of the bearing assembly 44 components allows for rotation movement of the base ring 26 relative to the support structure 22, but prevents radial or linear movement of the base ring 26 relative to the support structure 22. Referring to FIG. 5, the base ring 26 is configured to have “pockets” or specific mounting positions 46 for its payloads, which may include one or more sensing devices 24 or preparation devices 48. As a non-limiting example, the mounting positions 46 may be rigidly attached to the base ring 26 to receive either rigidly mountable or removable sensors. In the illustrated embodiment of FIG. 4, the mounting positions 46 are radially spaced from one another along the base ring 26 and include a receiving portion for receiving any number of inspection, preparation, and maintenance tools necessary for a particular operation, for example, a mountable sensing device 24 or a preparation device 48. The mounting positions 46 can also be configured to hold other mountable devices, including, but not limited to, grinders, welding heads, peening nozzles, abrasive blast nozzles, surface coating spray nozzles, surface cleaning spray nozzles, or other devices needed to repair surface defects, to clean the surface, or to provide preventative maintenance such as surface coating for extended storage. Mounting positions 46 may be located at multiple positions along the base ring 26. For example, in one embodiment of the present disclosure, the base ring 26 may include mounting positions 46 at two sides of the base ring 26 so that 180 degree rotation of the base ring 26 can be configured to provide 360 degrees of surface coverage. Reducing the degrees of rotation required for the base ring 26 to cover the entire surface may provide advantages in terms of management of cables, to the travel system 20, such as power, controls, compressed gas, etc. In the illustrated embodiment of FIG. 5, a sensing device 24 is mounted between two preparation devices 48 to allow for two-way scanning, for example, in either of the clockwise and counterclockwise directions. The preparation devices 48 may be used to either clean the surface before inspection or apply a solution needed for inspection (for example, in ultrasonic and penetration testing). By mounting a single sensing device 24 between two preparation devices 48, preparation may be achieved before sensing if the base ring 26 is moving in either a clockwise or counterclockwise direction. Moreover, by mounting a single sensing device 24 between two preparation devices 48, the first device 48 can be used to apply a solution needed for inspection, and the second device 48 can be used to remove the solution after testing. Referring to FIG. 6, an exemplary preparation device 48 is provided. The preparation device 48 includes a body 50 having first and second main rollers 52 and 54 and a tape 56 that travels between the first and second main rollers 52 and 54. The preparation device 48 may further include one or more smaller return rollers 58 that are configured to tension the tape 56, taking up any slack in the tape 56 on its return. In another configuration, however, the preparation device 48 may not include return rollers; rather, the first main roller 52 may be a supply roller and the second main roller may be a take-up roller, similar to an audio cassette tape. In the illustrated embodiment, the plurality of return rollers are included to allow for a long tape 56, so as to minimize tape changes in the process, as well as any take up problems in the device 48. One or both of the main rollers 52 and 54 may be driven, for example, by a drive roller 64, an air motor having a gear head, or by any other suitable driving mechanism. If the preparation device 48 is being used as a cleaning device, the tape 56 may be any type of cleaning media, for example, including but not limited to cloth, abrasive pads, felt, etc., and may depend on the required cleaning application. The spread of the first and second main rollers 52 and 54 shall be sufficient to allow the span of tape 56 between the rollers 52 and 54 to cover a flat surface on the canister C, but also to conform to the curvature of the canister C, for example, when running over either a front or back end welding seam. It should be appreciated, however, that other preparation and cleaning devices besides use of a tape and roller mechanism are also within the scope of the present disclosure. If the preparation device 48 is being used as a solution delivery system, the tape 56 may be any suitable media for delivering solution. The preparation device 48 may also include a delivery nozzle 60, which may be configured to deliver a solution to the surface of the canister C, and a suction nozzle 62 to provide evacuation of the delivered solution. The sensing device 24 may be mounted to the base ring 26 with multiple degrees of movement freedom to achieve an optimal sensing position. Referring to FIG. 7, an exemplary sensing device 24 is mounted on a tool arm assembly 70. The sensing device 24 may be mounted to have multiple degrees of freedom relative to the canister C surface that it is sensing. For example, the arm 72 is slidable within an arm casing 74 to allow the sensing device to move forward and back relative to the base ring 26 and the canister C surface. Moreover, the sensing device 24 is mounted on a moveable neck 76 that is capable of radial rotation relative to the arm 72. The preparation device 48 may be mounted on a similar arm assembly. Further, the arm casing 74 is pivotably mounted to the pockets 46 (see FIG. 5 to provide for pivotal rotation relative to the pocket 46). The purpose of the sensing device 24 is to inspect canisters welds and surfaces, for example, during transition of the canister C between its storage over pack module M and a transfer cask or a transportation cask (not shown). This extraction could occur at any time during the storage, transfer, or transportation of the canister C. Examination or sensing methods are primarily aimed at examining canisters to discover imperfections in the outer canister wall, including, but not limited to, pitting corrosion, rust discoloration, and/or stress corrosion cracking in weld and heat-affected zones. Suitable sensing devices may include non-destructive testing devices, such as dye penetrant sensors, ultrasonic examination sensors, eddy current examination sensors, laser ultrasonic examination sensors, and/or visual inspection sensors. The sensing devices used may vary depending on the quality and quantity of sediments on the surfaces of the canisters C, and the size and orientation of imperfections. In the case of ultrasonic and penetration testing, solutions may need to be applied before the testing and evacuated after the testing. Therefore, embodiments of the present disclosure further include cleaning heads that can be used to clean and/or apply and evacuate solutions. Eddy current examination uses eddy currents, which are electric currents induced in conductors when a conductor is exposed to a changing magnetic field due to variations of the field with time. The changing magnetic field can cause a circulating flow of electrons, or current, within the body of the conductor. Eddy current sensors are generally capable of discovering stress corrosion cracking on smooth surfaces, such as mill-finish plate or flush-ground welds. The eddy current testing generally includes tools for visual inspection, surface cleaning, and manipulation of the eddy current probe. Dye penetrant testing uses a penetrant and developer solution to penetrate cracks and highlight surface defects. Penetrant testing is generally capable of discovering stress corrosion cracking. The procedure is typically performed as a manual procedure; however, it can be automated using spray nozzles, wipers, and/or fiber optics to clean the surface, apply the penetrant, wipe off excess penetrant, apply the developer, and visually inspect the surface. In that regard, dye penetrant testing generally includes a camera or fiber optic probe with lighting for visual inspection, surface cleaning, application of penetrant, and application of developer. In ultrasonic examination, very short ultrasonic pulse-waves with center frequencies ranging from 0.1-15 MHz and occasionally up to 50 MHz are launched into the canister wall or weld to detect internal flaws or to characterize materials. The technique is also commonly used to determine the thickness of the test object, for example, to monitor pipe work corrosion. Ultrasonic testing is often performed on steel and other metals and alloys, though it can also be used on concrete, wood and composites, albeit with less resolution. In ultrasonic testing, an ultrasound transducer connected to a diagnostic machine is passed over the object being inspected. The transducer is typically separated from the test object by a couplant (such as oil) or by water, as in immersion testing. Ultrasonic examination techniques are specifically designed to locate and size near-side defects. Ultrasonic examination generally includes tools for visual inspection, surface cleaning, application of couplant, and manipulation of the ultrasonic probe. Laser-ultrasonic examination uses lasers to generate and detect ultrasonic waves. It is a non-contact technique used to measure materials thickness, detect flaws and materials characterization. The basic components of a laser-ultrasonic system are a generation laser, a detection laser and a detector. Laser ultrasonic examination generally includes tools for visual inspection, surface cleaning, and manipulation of the laser ultrasonic probe. Visual inspection generally includes using special illumination and magnification techniques generally capable of discovering pitting and rusting that are precursors to stress corrosion cracking. Visual inspection may also include surface cleaning and/or testing. Suitable maintenance devices may include surface cleaning, for example, by dry ice blasting, repairing cracked welds, and applications of protective coatings. A dry ice blasting process may include spray nozzles to apply dry ice and filtered waste evacuation to collect material removed from the canister C surface. A repair for cracked welds process may include a grinding head, weld heat, and one or more visual inspection tools. An application of protective coatings process may include one or more spray nozzles and visual inspection tools. Returning now to FIGS. 1 and 5, a front weld inspection will be described in greater detail. The front weld F is the circular weld between the front closure portion of the container C and the cylindrical sidewall of the container C. The front weld F can be inspected by pulling the canister C slightly forward in the module M (for example, using grappler ring 66) such that the travel system 20 is generally aligned with the canister C front weld F, as can be confirmed by operator visual inspection or by a sensing device. After canister C adjustment, the sensing device 24 and preparation devices 48 can be finely articulated and adjusted to meet the front weld F on the canister C using, for example, articulation controls. After adjustment, the actuation assembly 36 can be used to rotate the base ring 26 (on which the exemplary sensing device 24 and preparation devices 48 are mounted) relative to the canister C around the entirety of the front weld F. Depending on the sensor used by the sensing device 24, the preparation devices 48 may clean the front weld F surface before sensing or they may apply and remove a solution necessary for inspection. As discussed above, the travel system 20 may also support repair tools, in addition to preparation and examination tools, for the front weld F in any suitable combination. Referring now to FIG. 5, a longitudinal weld inspection will be described. The longitudinal weld L is the straight weld between the front closure portion of the container C and the back closure portion of the container C. The longitudinal weld L can be inspected by pulling the canister C slightly forward in the module M such that the travel system 20 is generally aligned with the canister C longitudinal weld L, as can be confirmed by operator visual inspection or by a sensing device. After canister C adjustment, the sensing device 24 and preparation devices 48 can be finely articulated and adjusted to meet the longitudinal weld L on the canister C using, for example, articulation controls. In the illustrated embodiment of FIG. 5, a preparation device 48 has been adjusted to meet the longitudinal weld L on the canister C. The canister C can be pulled forward (for example, using grappler ring 66) from the module M as the sensing device 24 or preparation device 48 runs along the length of the longitudinal weld L. It should also be appreciated that the canister C may also be moved relative to the travel system 20 in the reverse direction. This action can be repeated as needed for further sensing, preparation, or clean-up, for example, to remove a solution necessary for inspection. As discussed above, the travel system 20 may also support repair tools, in addition to preparation and examination tools, for the longitudinal weld L in any suitable combination. Referring now to FIG. 8, a back weld inspection will be described. The back weld B is the circular weld between the back closure portion of the container C and the cylindrical sidewall of the container C. The back weld B can be inspected by pulling the canister C completely forward in the module M such that the travel system 20 is generally aligned with the canister C back weld B, as can be confirmed by operator visual inspection or by a sensing device. After canister C adjustment, the sensing device 24 and preparation devices 48 can be finely articulated and adjusted to meet the back weld B on the canister C using, for example, articulation controls. After adjustment, the actuation assembly 36 can be used to rotate the base ring 26 (on which the exemplary sensing device 24 and preparation devices 48 are mounted) relative to the canister C around the entirety of the back weld B. Depending on the sensor used by the sensing device 24, the preparation devices 48 may clean the back weld B surface before sensing or they may apply and remove a solution necessary for inspection. As discussed above, the travel system 20 may also support repair tools, in addition to preparation and examination tools, for the back weld B in any suitable combination. Referring now to FIGS. 9-12, another embodiment of the present disclosure will now be described. The embodiment shown in FIGS. 9-12 is substantially similar to the embodiment of FIGS. 1-8, except for differences regarding the vertical orientation of the canister C and the storage silo S. Like parts in FIGS. 9-12 use like numerals as used in FIGS. 1-8 in the 100 series. In the illustrated embodiment of FIGS. 9-12, the storage silo S is a vertical storage silo. Therefore, the travel system 120 is attached to the top entry point of the module S using embedments 130 that are provided for top plate attachment. The travel system 120 further includes a cage 128 for protecting components of the system 120 from damage and also may be used for supporting control and power cables 142. Vertical storage systems typically include a gate or mating mechanism located between the vertical silo and the transfer cask. It should be appreciated that the travel system may be placed either below or above a mating mechanism, and that the cage 128 may be interrupted to clear the mating mechanism. In addition, the travel system 120 includes an adaptor 190 such that support structure 122 is attachable to embedments 130 on silo S. Similar to the embodiment of FIGS. 1-8, the travel system 120 shown in FIGS. 9-12 is designed to prepare, inspect, and repair canisters C, which may be subject to front, longitudinal, and back weld review (see, for example, FIGS. 11 and 12). However, with the embodiment of FIGS. 9-12, the canister C is lifted from the vertical module S using hooks 134, instead of being move horizontally as shown in the embodiment of FIGS. 1-8. While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the disclosure.
	abstract	An active zone includes a homogeneous uranium-plutonium nitride fuel, the mass fraction of which is a minimum 0.305, and consists of central, intermediate and peripheral parts which form fuel assemblies comprising fuel elements with geometrically identical shells but differing heights. The radial distribution of the fuel across the volume of the active zone has a stepped shape. The radius of the central part is from 0.4 to 0.5 of the effective active zone radius, while the height of the fuel column in the fuel elements in the central part is from 0.5 to 0.8 of the height of the fuel column in the peripheral part. The heights of the fuel columns forming a stepped intermediate part for diameters ranging from 0.5 to 0.85 of the effective active zone diameter are within the range from 0.55 to 0.9 of the height of the fuel column in the peripheral part.
	abstract	The present invention relates to a method for treating tritium water-containing raw water, the method including supplying a part of raw water containing tritium water and alkali water to a circulation tank, mixing the raw water with alkali water in the circulation tank to obtain an electrolyte adjusted so as to have a desired alkali concentration, and continuously electrolyzing the electrolyte while circulating the electrolyte, thereby subjecting the raw water stored in the storage tank to alkali water electrolysis and thus gasifying the raw water.
	abstract	The invention relates to a container (1) for radioactive materials comprising a main hollow body (2) as well as a cover (6) made of at least one first metallic material, the cover being capable of being fixed on the main hollow body by means of sealing means (26) made of a second metallic material poured into a groove (24) defined by the cover and the main hollow body of the container. According to the invention, the cover (6) and the main hollow body (2) are made solid with the sealing means (26) by means of a bonding zone (28), formed by chemical reaction between the first and second metallic materials.
	abstract	An improved, accident tolerant fuel for use in light water and lead fast reactors is described. The fuel includes a ceramic cladding, such as a multi-layered silicon carbide cladding, and fuel pellets formed from U15N and from 100 to 10000 ppm of a boron-containing integral fuel burnable absorber, such as UB2 or ZrB2.
047541474	abstract	A variable collimator 10 for shaping the cross-section of the beam 100 is described. The collimator relies upon rods 16 which are positioned around the beam axis a-a with the rod 16 axis b-b perpendicular to the beam axis. The rods are shaped by shaping member 24 which is cut to the shape of an area of a patient or other surface to be irradiated.
052563383	abstract	According to the present invention, a fibrous material having a property to adsorb radioactive nuclides in the form of ion or molecule onto its surface is added to a cement type hydraulic solidifying material used for a solidifying material, a waste container, a structure in disposal site and a back-filling material used for production of a waste form of radioactive wastes, whereby improvement of long-term endurance of the waste form, the structure and the like and diminishment of leaching of radioactivity from the waste form and the like can be simultaneously attained.
	abstract	The invention relates to a container system for the transport and storage of highly reactive materials, which comprises an outer container (1) that encompasses at least one inner container (2) in which the radioactive material is disposed. The inner container (2) is resiliently received in the inner container so as to absorb shocks. The outer container (1) comprises a cylinder (4) whose jacket (5) consists of prestressed reinforced concrete molded by centrifugal action and is provided with a lid (6) and a bottom pate (7) that consist of reinforced concrete. Like the outer container (1), an intermediate container may consist of prestressed reinforced concrete molded by centrifugal action and may encompass the inner container (2). Preferably, the concrete parts of the outer container (1) and the intermediate container (3) are provided with, e.g., boroxyde as an additional neutron absorber. The resilient mounting of the inner container (3) or the intermediate container (3) consists of a plurality of spring elements (10, 11) that encompass, side by side, in the longitudinal direction of the jacket (5) and on all sides thereof, the intermediate container (3) or the inner container (2). The spring elements (10, 11) for their part are provided with shock absorbers.
	description	FIG. 1 shows the vessel 1 of a pressurized-water nuclear reactor which contains the reactor core 2 and which is closed in its upper part by a closure head 1a of approximately hemispherical shape. The nuclear reactor core 2 consists of fuel assemblies which are placed vertically in adjacent arrangement and which comprise means for guiding control rod neutron absorbers which are moved vertically inside the nuclear reactor core 2 in order to adjust the reactivity of the core. FIG. 1 shows schematically two systems 3 for guiding neutron absorbers of two nuclear reactor core assemblies inside each of which a neutron absorber rod cluster 4 moves, the latter being shown conventionally in the form of a solid unit. In fact, the neutron absorber rod cluster 4 consists of a number of parallel absorber rods and the guiding system 3 consists of a set of guide tubes for the fuel assembly in which the neutron absorber rod cluster moves, each of the neutron absorbers of the rod cluster being guided inside the fuel assembly by a guide tube. Each of the neutron absorber rod clusters 4 is connected in its upper part to a drive shaft 6 placed in the axial extension of the rod cluster 4. The system consisting of the neutron absorber rod cluster and the drive shaft 6 constitutes a control rod 5 for controlling the reactivity in the nuclear reactor core. FIG. 1 shows one of the neutron absorber rod clusters 4 in the low position, fully inserted into the core, and the second neutron absorber rod cluster 4 in the high position, fully extracted from the core 2. As will be explained below, the drive shafts 6 are splined shafts, the splining of which defines a toothing over the entire length of the drive shaft. The drive shafts 6 of the control rods 5 move, between the fully extracted high position of the control rod and the fully inserted low position, inside tubular enclosures 7 which are fastened vertically above the vessel closure head 1a plumb with the rod cluster guide tube and in the upper part of the nuclear reactor vessel. Each of the tubular enclosures 7 has a mechanism 8 for moving the corresponding control rod 5 via its splined drive shaft 6. The mechanisms 8 are latch-arm mechanisms which engage with the toothing of the splined drive shaft 6 in order to move the drive shaft step by step inside the tubular enclosure 7 and move the control rod cluster 4 inside the nuclear reactor core 2 in order to adjust the reactivity of the core. The mechanisms 8 comprise latch arms for movement of the control rods and latch arms for retention of the control rods by means of the drive shafts, the opening of the retention latch arms allowing release of the drive shaft and of the control rod from a high position, the control rod then being able to drop back into the position of maximum insertion in the nuclear reactor core under the effect of gravity. As indicated above, it is important, before starting up or restarting a nuclear reactor, to determine the drop time of the control rods which constitute safety elements of the nuclear reactor. Placed around the tubular enclosures 7 for moving the drive shafts 6 of the control rods 5, over a substantial part of the length of the tubular enclosure in the axial direction, above the mechanisms 8, are means 9 for measuring the position of the drive shaft inside the tubular enclosure 7 and therefore the position of the neutron absorber rod cluster of the control rod 5 inside the nuclear reactor core. FIG. 2 shows a tubular enclosure 7 in which a splined drive shaft 6 moves, a control rod cluster being fastened to its lower end (not shown). The tubular enclosure 7 is fastened in the axial extension of a tubular element 7a which is fastened to the vessel closure head 1a and ensures penetration of the drive shaft 6, to which closure head the mechanisms 8 for moving the control rod, via the splined shaft 6, are fastened. The latch arms for retaining and for moving the mechanisms 8 of the control rod engage, inside the tubular parts 7a of the enclosure 7, with the toothing 6a of the splined drive shaft 6. FIG. 2 shows in solid lines the shaft 6 in its low position corresponding to the position in which the neutron absorber rod cluster is fully inserted into the nuclear reactor core and shows in broken lines the drive shaft 6 in the high position inside the upper part of the tubular enclosure 7. The upper part of the tubular enclosure 7 allows the drive shaft 6 to move over a length equal to the total height of the core, that is to say over a length of the order of four to five meters. The device 9 for measuring the position of the control rod is placed around the upper part of the tubular assembly 7 and approximately over the entire length of this upper part, above the mechanisms 8. As can be seen in FIG. 3, the device 9 for measuring the position of the control rods is placed around the tubular enclosure 7 to which it is fastened by means of upper and lower clamps. The measurement device 9 is placed inside a casing of tubular overall shape bounded by two coaxial cylindrical shells in a coaxial arrangement with respect to the tubular enclosure 7 in which the drive shaft 6 of the control rod moves in the axial direction 10. The measurement device 9 has the overall form of a differential transformer comprising a primary winding 11 extending approximately over the entire length of the measurement device, that is to say approximately over the entire axial length of the tubular enclosure, and secondary windings 12 distributed in the axial direction 10 of the measurement device, with a constant spacing. The primary winding 11 and the secondary windings 12 together with auxiliary end windings 13, located at the axial ends of the device 9, are placed in annular cavities of a support 14 placed in a coaxial arrangement with respect to the tubular enclosure 7. The various windings are connected to supply and measurement lines via a connection box 15. The primary winding 11 is supplied with AC current at a frequency of 50 Hz, it being possible in addition for the voltage in the winding to be picked up via a pick-up cable connected to the connection device 15. Each of the secondary windings 12 and of the auxiliary windings 13 is also connected to a cable for picking up the voltage at the terminals of the winding whose connection is provided inside the connection device 15. Measuring the voltages induced by the primary winding in each of the secondary windings, or in the secondary windings placed in series, makes it possible to determine the position of the drive shaft 6 inside the tubular enclosure 7 and therefore the position of the control rod in the nuclear reactor core, the presence of the drive shaft 6 facing a secondary winding 12 modifying the reluctance of the secondary winding and therefore the coupling between the primary winding and the secondary winding. In addition, the drop of a control rod from its high position to its low position in the nuclear reactor core results in a movement of the drive shaft 6 inside the enclosure 7 in the axial direction 10, that is to say in the axial direction of the primary winding 11. This results in an induced voltage which, when recorded over time, allows the drop time of the control rod to be determined. FIG. 4 shows the cross section of the core 2 of a pressurized-water nuclear reactor, which comprises four quadrants 2a, 2b, 2c, 2d separated from one another by two vertical planes of symmetry indicated by the lines 16a and 16 in FIG. 4, which are mutually perpendicular and pass through the axis of the core 2. Eighteen neutron absorber rod clusters of eighteen control rods for controlling the core reactivity are moved inside the fuel assemblies located in the quadrants 2a, 2b and 2c, the fuel assemblies in which the neutron absorber rod clusters are moved being distributed over the area of the quadrants. Nineteen neutron absorber rod clusters of nineteen control rods are moved, in the fourth quadrant 2d, in fuel assemblies distributed over the cross section of the quadrant 2d. The nuclear reactor is therefore controlled by means of seventy-three control rod clusters distributed in three subassemblies of eighteen rod clusters and one subassembly of nineteen rod clusters. Each subassembly of control rods and of neutron absorber rod clusters has its own means for collecting the measurements on the position of the control rods of the subassembly and for processing these measurements in order to protect the nuclear reactor during its operation. All the means for collecting the position measurements and the means for protecting the core are placed in protection rooms 17 lying around the nuclear reactor vessel containing the core 2. The protection rooms 17 contain, for each of the control rod subassemblies associated with one quadrant of the core 2, means 18 for collecting the measurements carried out on the eighteen or nineteen control rods of the subassembly. The means 18 for collecting the measurements of the position of the control rods of a subassembly are called IPB cabinets, these cabinets containing rod position instrumentation (IPB) sensors. The means for measuring each of the control rods are connected by measurement cables to the corresponding IPB cabinet in which measurement sensors 18a transfer the measurement signals to a data acquisition and processing unit 19, called UATP cabinet, for protecting the nuclear reactor. Among the signals transmitted to the IPB cabinet are the voltage signals from the primary windings of the position measurement means of each of the tubular enclosures for moving a control rod drive shaft. The position measurements carried out on the control rods are also used in a room 20 from which the movement of the control rods is controlled, and in which are placed, in particular, nineteen cabinets 21 called EEC1 . . . EEC19 cabinets which contain an electronic device for controlling the movements of the control rods. These devices are units of the system for controlling the movement of the control rods which deliver currents to the actuators of the mechanisms for moving the control rods, according to the orders received by the control units. Also placed inside the room 20 is a unit for controlling the power generator sets and a unit for controlling the shutdown generator sets and the temperature in the nuclear reactor core. This unit 22 for controlling the movement of the control rod clusters coordinates the operation of the electronic control devices (EECs) 21. When it is desired to carry out a measurement of the drop time of the control rod clusters, it is necessary, within each of the IPB cabinets 18 of each of the control rod subassemblies, to connect a cable for measuring the voltage at the terminals of a primary winding of a means for measuring the movement of a control rod. It is thus possible to carry out, simultaneously, a measurement of the drop time of four control rods each belonging to one subassembly. It is therefore necessary to carry out measurement cable connections and the control rod drop test operations nineteen times, the last operation being carried out on a single control rod of the last subassembly located in the quadrant 2d. As indicated above, this procedure is lengthy and requires a connection to be made before the measurement and then a return of the connections to their initial state in the IPB cabinet. Furthermore, it is not possible to make the connections and therefore to carry out the tests while the nuclear reactor is operating. Should a control rod accidentally drop while the nuclear reactor is operating, there is no means for measuring the drop time of the control rod. FIG. 5 shows a measurement device according to the invention which makes it possible to overcome the drawbacks of the measurement operations carried out according to the prior art. The device according to the invention has been shown in FIG. 5 which depicts the protection rooms 17 and the control rooms 20 from which the movement of the control rods is controlled, the corresponding elements in FIGS. 4 and 5 being denoted by the same reference numbers. The measurement device according to the invention comprises, in each of the IPB cabinets for each of the control rod subassemblies receiving the control rod measurement signals, a system of connection means 23 each produced in the form of an interface box receiving, via measurement cables for each of the control rods of the subassembly, the measurement signals and in particular the voltage signals from the primary windings of the control rod position measurement means. The interface boxes 23 permanently connected to the measurement cables for the control rods of the subassembly make it possible to extract, without making a connection, the voltage signals from the primary windings of the control rod position measurement means in order to carry out measurements of the drop time of the control rods as a whole. Each of the interface boxes 23 of an IPB cabinet 18 of a control rod subassembly is connected, via an isolating box 24, to a system 25 for the real-time acquisition of the voltage measurement signals from the primary windings, this acquisition system 25 being placed in the room 20 from which the movement of the control rods is controlled. In this way, the real-time measurement-signal acquisition system 25 can simultaneously receive the voltage signals from all the primary windings of the means for measuring the movement of all the control rods, for example during a test for measuring the control rod drop time. Only one control rod drop and release operation is thus carried out, it being possible for the voltages at the primary windings to be picked up simultaneously and stored in memory in the acquisition system 25. Each IPB cabinet 18 therefore has an interface box 23 for each of the pick-up and measurement cables coming from each of the means for measuring the movement of a control rod. Each interface box 23 is connected to the acquisition system 25 via an isolating box 24. FIG. 6 shows the rack of the IPB cabinet 18 to which each of the measurement cables 29 associated with the means for measuring the movement of a control rod is connected via the interface boxes 23. A cable 30 can be used to pick up the voltage signals coming from the primary windings of the measurement means and transmit them to the real-time acquisition system via an isolating box 24. Each of the interface boxes 23 includes an attenuator making it possible to adapt the level of the signal transmitted to the electronics carrying out the DC isolating of the signals in the isolating box 24 and to protect the primary winding circuit from any risk of short circuit. The DC isolation box 24 contains two isolation cards each having ten channels and withstands an isolation of 500 volts rms, the output voltage being 10 volts. The isolating boxes 24 associated with each of the control rods subassemblies make it possible to clearly separate the protection function from the control function, thus preventing any electrical interference coming from components which are not classified for nuclear reactor safety. There is no risk of the measurements taken by the interface boxes 23 in the IPB cabinets 18 disturbing the operation of the processing units 19 for protecting the nuclear reactor. In its entirety, the IPB interface, which incorporates the measurement device according to the invention, comprises in total seventy-three interface boxes equipped with attenuators, eight electronic isolation cards and four isolation boxes. A second part of the measurement device according to the invention is placed inside the room 20 from which the movement of the control rods is controlled. From this room, or RGL (full-length rod control system) room, the movement of the full length control rods is controlled, that is to say the raising and lowering of the rod clusters from and into the nuclear reactor is controlled. The measurement device according to the invention includes, inside the RGL room, the real-time measurement-signal acquisition system 25 which is connected, on the one hand, via four isolation boxes 24, to the four IPB cabinets 18 and, on the other hand, inside the RGL room 20, to each of the EEC cabinets, that is to say the cabinets for the electronic devices for controlling the movement of the rod clusters. In addition, the acquisition system 25 receives a signal 28 for automatically shutting down the reactor by dropping the control rods, this signal being taken off a free contact of the nuclear reactor control unit. A DC isolation of 500 volts rms is achieved by standard modules inserted into a rack of the data acquisition system 25 in order to effectively isolate the acquisition system from the units for controlling the movement of the rod clusters from the RGL room. All the measurement signals from the primary windings are combined in the real-time acquisition system 25 which delivers, for each of the control rods, at the moment when the control rod drops, a curve giving the voltage induced in the primary winding as a function of time, this curve making it possible to determine the duration of the voltage signal and from it deduce the drop time of the control rod. The data is processed by a microcomputer 26 which is used to determine the control rod drop times and to store these drop times in its memory. The input data and the data provided by the microcomputer 26 relating to the drop time can be printed on a printer 27. The microcomputer 26 and the printer 27 therefore constitute means for displaying and printing the results relating to the control rod drop time. FIG. 7 shows, in a diagram giving the voltage as a function of time, the curve of the voltage induced in a primary winding of a tubular enclosure for a control rod, during the drop of the control rod. The movement of the drive shaft inside the tubular enclosure and inside the primary winding produces a dynamic change in the reluctance of the winding and therefore an induced voltage at the terminals of the primary winding. The signal representative of this induced voltage varies as a function of time during the drop of the control rod, this variation being shown by curve 31 in FIG. 7. In FIG. 7, the times t0, t1, t2 and t3 are plotted on the x-axis. The time t0 corresponds to the time origin of the drop time measurement. This time t0 can be determined in different ways. Firstly, the time t0 can be determined from the nuclear reactor emergency shutdown signal 28 which is transmitted to the acquisition system 25. The time t0 can also be determined from the current signals 32 which are transmitted by the cabinets 21 in the RGL room to the acquisition system 25. These signals 32 correspond to the current supplied to the stationary grippers of the mechanisms for moving the control rods, these grippers ensuring retention of the drive shafts and of the control rods. The moment when the current supply to the stationary gripper becomes zero corresponds to the moment that the control rod is released. Finally, the start of the drop of the control rod can equally be determined purely graphically, from the shape of the induced voltage curve 31 as a function of time. Up to the time t1, that is for a very short period T4 from t0 to t1, the voltage induced in the primary winding remains virtually constant, which corresponds to the inertia of the system at the moment when the control rod is released. After the time t1 and up to the time t2, the induced voltage increases and stabilizes over a period T5 extending from the time t1 to the time t2. This phase in the drop of the control rod corresponds to the acceleration of the drive shaft and its exit from the tubular enclosure and from the primary winding, these two phenomena being counterbalanced in order to stabilize the induced voltage at a high level. Thereafter, from the time t2 to the time t3 during a period T6, the induced voltage decreases and returns to a level approximately equal to the starting level, with a certain amount of instability. The drop is regarded as being complete when the induced voltage returns to the initial level for the first time. This phase, during which the induced voltage is decreasing, corresponds to the exit of the drive shaft from the tubular enclosure and from the primary winding. The drop time is determined by adding the times T4, T5 and T6 together. The primary winding is generally supplied with AC current at a frequency of 50 Hz and at a voltage of 50 to 70 V. The induced voltage is a signal at a very low frequency (xcx9c10 Hz) and with an amplitude of a very few volts depending on the initial position of the control rod at the moment of its release. To obtain the induced voltage curve (like the one shown in FIG. 7), it is necessary to filter the voltage picked up, in order to overcome the problem of the supply voltage. If the primary winding is not powered, the induced voltage is picked up directly at the terminals of the primary winding. The device according to the invention allows the control rod drop time to be measured accurately, with a very small number of measurements, for example one or two measurements, it being possible for the signals relating to all of the rods to be recorded in a single operation and then processed after they have been stored. The method according to the invention has the advantage of avoiding any operation of connecting and disconnecting measurement lines, before and after the drop time measurements. The device according to the invention also has the advantage of being able to carry out measurements while the nuclear reactor is operating and in the event of the accidental dropping of a control rod, the induced voltage signal then being automatically recorded by the real-time signal acquisition system. The invention is not limited to the embodiment which has been described. Thus, the various connections of the measurement device according to the invention to units used for protecting or controlling the nuclear reactor may be different from those described. The invention applies in the case of any nuclear reactor having control rods consisting of control rod clusters which are moved vertically in the core of a nuclear reactor by means of drive shafts.
	claims	1. A medical imaging method, comprising:generating an electron beam at one of a first energy level and a second energy level by an electron source, the second energy level being different from the first energy level;emitting radiation from a target through a patient and towards a detector upon receiving the electron beam at the target; andblocking or diverting the electron beam prior to reaching the target during at least one intermediate phase during which the electron source switches in a transient way from one of the first energy level and the second energy level to the other of the first energy level and the second energy level,wherein:the electron source comprises a deflection system and an electron collector positioned between the electron source and the target,the electron collector defines an aperture through which the electron beam passes, and comprises an inner surface, wherein at least a portion of the inner surface is tilted so that the cross section of the aperture changes along a path of the electron beam, andthe step of blocking or diverting the electron beam comprises deflecting the electron beam toward the inner surface of the electron collector. 2. The method according to claim 1, further comprising:modulating the duration of the at least one intermediate phase during which the electron beam is blocked or diverted depending on a dose level per image to which a patient may be subjected. 3. The method according to claim 1, wherein the electron source comprises:a source of electrons configured to emit a flux of electrons; andthe target comprising a first focal area, through which the radiation is emitted when the first focal area is exposed to the flux of electrons, the flux of electrons being diverted relative to the first focal area during the at least one intermediate phase. 4. The method according to claim 3, wherein the flux of electrons is blocked or diverted by magnetic deflection or electrostatic deflection. 5. A medical imaging device, comprising:an electron source;an X-ray detector;the electron source being controlled by a control module to generate an electron beam at one of a first energy level, and a second energy level different from the first energy level, and to emit the electron beam towards the X-ray detector, the electron source generating an electron beam of variable energy over time during an intermediate phase during which the electron source switches in a transient way from the first energy level to the second energy level or vice versa; a target comprising a focal area adapted to emit X-rays towards the detector through a patient upon receiving the electron beam;the electron source further comprising:a deflection system positioned between the electron source and the target, adapted so as to modify the trajectory of the electron beam during the intermediate phasean electron collector positioned between the deflection system and the target, the electron collector defining an aperture through which the electron beam passes, and comprising an inner surface, wherein at least a portion of the inner surface is tilted so that the cross section of the aperture changes along a path of the electron beam, andthe deflection system configured to divert the electron beam towards the inner surface of the electron collector during the intermediate phase. 6. The medical imaging device according to claim 5, wherein said electron collector is adapted for absorbing the electron beam. 7. The medical imaging device according to claim 5, wherein the target further comprises at least one second focal area through which X-rays are not emitted when the at least one second focal area is exposed to a flux of electrons, and wherein the flux of electrons is diverted by the deflection system towards the at least one second focal area during the at least one intermediate phase. 8. The medical imaging device according to claim 7, wherein the at least one second focal area is configured to absorb the flux of electrons. 9. The medical imaging device according to claim 5, wherein the target further comprises at least one second focal area through which radiations are emitted towards a direction distinct from a direction of emission of the first focal area, the medical imaging device further comprising a collimator positioned between the target and the detector, wherein the collimator is configured to block the radiations emitted from the at least one second focal area. 10. The medical imaging device according to claim 8, wherein the target is an axisymmetrical solid centered on an axis, wherein the target rotates around the axis, and wherein the first focal area and the at least one second focal area are concentric rings distinct from each other. 11. The medical imaging device according to claim 10, wherein the at least one second focal area is a groove in the target, wherein the electron beam emitted towards the at least one second focal area is blocked by a wall of the groove. 12. The medical imaging device according to claim 5, further comprising a processing unit configured to process images obtained by the detector. 13. The medical imaging device according to claim 7, wherein the at least one second focal area is on the inner surface. 14. The medical imaging device according to claim 8, wherein the at least one second focal area is on the inner surface.
	abstract	One embodiment relates to an apparatus for inspecting a substrate using charged particles. The apparatus includes an illumination subsystem, an objective subsystem, a projection subsystem, and a beam separator interconnecting those subsystems. The apparatus further includes a detection system which includes a scintillating screen, a detector array, and an optical coupling apparatus positioned therebetween. The optical coupling apparatus includes both refractive and reflective elements. Other embodiments and features are also disclosed.
	summary
	abstract	The invention provides a reactor containment vessel vent system capable of continuously releasing steam generated in a reactor containment vessel to the atmosphere even when a power supply is lost. In the reactor containment vessel vent system (15), the noble gas filter (23) that allows steam to pass through but does not allow radioactive noble gases to pass through among vent gas discharged from the reactor containment vessel (1) is provided at a most downstream portion of the vent line. An immediate upstream portion of the noble gas filter (23) and the reactor containment vessel (1) are connected to each other by the return pipe (24a, 24b) via the intermediate vessel (100). Further, when the radioactive noble gases having pressure equal to or higher than predetermined pressure stays in the immediate upstream portion of the noble gas filter (23), the staying radioactive noble gases flows into the intermediate vessel (100) by the relief valve (25). Thus, the noble gas filter (23) does not lose steam permeability, and the reactor containment vessel vent system (15) can continuously release the steam to the atmosphere.
	claims	1. A shield cover for a radiation source machine, wherein, comprising:a frame body provided with a receiving chamber for receiving the radiation source machine, an end opening and an ray exit through which rays are emitted out from the radiation source machine;an end cover disposed at the end opening of the frame body and provided with a sealed chamber communicating with the receiving chamber; anda connecting member disposed between the end cover and the frame body and provided with an opening for communicating the sealed chamber of the end cover with the receiving chamber of the frame body, and the end cover being movably connected to the frame body by the connecting member such that a distance of the end cover from the end opening of the frame body is adjustable. 2. The shield cover for a radiation source machine of claim 1, wherein, the connecting member comprises a first connecting member and a second connecting member, a side of the first connecting member is fixedly connected to the end cover and the other side of the first connecting member is movably connected to the frame body, and a side of the second connecting member is fixedly connected to the end cover and the other side of the second connecting member is movably connected to the frame body, wherein the first connecting member and the second connecting member are arranged to mate with each other to form the opening. 3. The shield cover for a radiation source machine of claim 2, wherein,the first connecting member and the frame body are respectively provided with a first hole and a second hole corresponding with each other, wherein at least one of the first hole and the second hole is formed into a strip-shaped hole, and a first connector is disposed within the first hole and the second hole to movably connect the first connecting member to the frame body, andthe second connecting member and the frame body are respectively provided with a third hole and a fourth hole corresponding with each other, wherein at least one of the third hole and the fourth hole is formed into a strip-shaped hole, and a second connector is disposed within the third hole and the fourth hole to movably connect the second connecting member to the frame body. 4. The shield cover for a radiation source machine of claim 1, wherein, the connecting member is provided with an enclosing member surrounding the opening and extending into the receiving chamber, and an outer wall surface of the enclosing member and an inner wall surface of the receiving chamber are kept overlapping with each other with a gap remained therebetween. 5. The shield cover for a radiation source machine of claim 4, wherein, the frame body, the end cover, and the enclosing member are provided with anti-radiation plates on their respective wall surfaces. 6. The shield cover for a radiation source machine of claim 5, wherein, the anti-radiation plates are provided on respective inner wall surfaces of the frame body, the end cover and the enclosing member, and two adjacent ends of two adjacent anti-radiation plates are in an overlapping connection with each other. 7. The shield cover for a radiation source machine of claim 6, wherein, one of the two adjacent ends is formed with a stepped portion, and the other of the two adjacent ends is formed to mate with the stepped portion such that the two adjacent ends are in the overlapping connection with each other. 8. The shield cover for a radiation source machine of claim 1, wherein, the frame body is formed into a separated structure and includes a top cover and a bottom cover in connection with each other. 9. The shield cover for a radiation source machine of claim 1, wherein, the end cover is provided with an auxiliary positioning member, an end of which is formed to extend into the sealed chamber so as to be capable of abutting the radiation source machine and limiting a horizontal play of the radiation source machine. 10. The shield cover for a radiation source machine of claim 9, wherein, the auxiliary positioning member is formed as a rod threadedly connected to the end cover. 11. A security inspection apparatus, wherein, comprising:a shield cover for a radiation source machine, comprising:a frame body provided with a receiving chamber for receiving the radiation source machine, an end opening and an ray exit through which rays are emitted out from the radiation source machine;an end cover disposed at the end opening of the frame body and provided with a sealed chamber communicating with the receiving chamber; anda connecting member disposed between the end cover and the frame body and provided with an opening for communicating the sealed chamber of the end cover with the receiving chamber of the frame body, and the end cover being movably connected to the frame body by the connecting member such that a distance of the end cover from the end opening of the frame body is adjustable,the radiation source machine disposed in the receiving chamber; anda U-shaped arm provided on an outside of the frame body and connected to the radiation source machine to make the radiation source machine in a suspended state in the receiving chamber. 12. The security inspection apparatus of claim 11, wherein, the U-shaped arm is engaged with the frame body with the frame body received in an U-shaped opening of the U-shaped arm, and the frame body is provided with a fixing seat at a position corresponding to the U-shaped arm, through which the U-shaped arm is connected to the frame body, wherein an adjusting pad is provided between a bottom of the U-shaped arm and the fixing seat. 13. The security inspection apparatus of claim 11, wherein, the connecting member comprises a first connecting member and a second connecting member, a side of the first connecting member is fixedly connected to the end cover and the other side of the first connecting member is movably connected to the frame body, and a side of the second connecting member is fixedly connected to the end cover and the other side of the second connecting member is movably connected to the frame body, wherein the first connecting member and the second connecting member are arranged to mate with each other to form the opening. 14. The security inspection apparatus of claim 13, wherein,the first connecting member and the frame body are respectively provided with a first hole and a second hole corresponding with each other, wherein at least one of the first hole and the second hole is formed into a strip-shaped hole, and a first connector is disposed within the first hole and the second hole to movably connect the first connecting member to the frame body, andthe second connecting member and the frame body are respectively provided with a third hole and a fourth hole corresponding with each other, wherein at least one of the third hole and the fourth hole is formed into a strip-shaped hole, and a second connector is disposed within the third hole and the fourth hole to movably connect the second connecting member to the frame body. 15. The security inspection apparatus of claim 11, wherein, the connecting member is provided with an enclosing member surrounding the opening and extending into the receiving chamber, and an outer wall surface of the enclosing member and an inner wall surface of the receiving chamber are kept overlapping with each other with a gap remained therebetween. 16. The security inspection apparatus of claim 15, wherein, the frame body, the end cover, and the enclosing member are provided with anti-radiation plates on their respective wall surfaces. 17. The security inspection apparatus of claim 16, wherein, the anti-radiation plates are provided on respective inner wall surfaces of the frame body, the end cover and the enclosing member, and two adjacent ends of two adjacent anti-radiation plates are in an overlapping connection with each other. 18. The security inspection apparatus of claim 17, wherein, one of the two adjacent ends is formed with a stepped portion, and the other of the two adjacent ends is formed to mate with the stepped portion such that the two adjacent ends are in the overlapping connection with each other. 19. A method of radiating an object, comprising:placing an object within a radiation source machine; the radiation source machine have a shield cover comprising:a frame body provided with a receiving chamber for receiving the radiation source machine, an end opening and an ray exit through which rays are emitted out from the radiation source machine;an end cover disposed at the end opening of the frame body and provided with a sealed chamber communicating with the receiving chamber; anda connecting member disposed between the end cover and the frame body and provided with an opening for communicating the sealed chamber of the end cover with the receiving chamber of the frame body, and the end cover being movably connected to the frame body by the connecting member such that a distance of the end cover from the end opening of the frame body is adjustable, andirradiating the object. 20. The method of claim 19, further comprising receiving radiation that passed through the object.
	abstract	A nozzle repair method and a nuclear reactor vessel include: removing a trepanning portion (208) as a connection portion with respect to an in-core instrumentation cylinder (204) in a groove-welding portion (206); removing the in-core instrumentation cylinder (204) from a lower end plate (66); forming a plug attachment opening (211) by removing the groove-welding portion (206); applying a pressing load to the lower end plate (66) by attaching a plug (212) to the plug attachment opening (211); and welding and fixing the plug (212) attached to the plug attachment opening (211). Accordingly, since a repair is easily performed, it is possible to improve the workability and to decrease a repair cost.
	summary
	abstract	A decontamination formulation is provided which is effective against a broad spectrum of chemical and biological warfare agents and radioactive dusts, comprising an active decontamination agent, a co-solvent, a buffer system to optimize the initial reaction pH above 8.5 and more preferably in the range of 10 to 11 for favoring oxidation of VX and HD and hydrolysis of G agents, and a surfactant similar to fire-fighting foaming agent. Formulations comprise, in water by weight, 1% to 15% of a hydrated chloroisocyanuric acid salt, 1% to 10% of a polypropylene glycol co-solvent, 1% to 15% surfactant and a buffer system to initially maintain said formulation at a pH from about 11 to about 8.5 for sufficient duration to effect decontamination. The formulation can be provided in kit form or concentrate form, be prepared, in part, in advance or on site, and be dispensed in foam form which aids in coating and adhering of the decontamination formulation to contaminated surfaces. All ingredients can be pumped through a foam nozzle or water, co-solvent and surfactant can be pumped to the nozzle with solutions of buffer and of active ingredient being introduced at the nozzle for minimizing pump exposure.
	description	The disclosed concept pertains generally to nuclear power equipment and, more particularly, to a sensor system usable with a fuel rod of a fuel assembly of a nuclear reactor. Nuclear reactor systems include many types of sensors for monitoring various characteristics of the system. One type of sensor is designed to monitor centerline fuel temperature, fuel pellet stack elongation, and internal fuel rod pressure. FIG. 1 is a schematic diagram of a sensor designed to monitor centerline fuel temperature, fuel pellet stack elongation, and internal fuel rod temperature. The sensor includes a passive sensor component 10 located within a fuel rod 2 of a nuclear reactor and a wireless interrogator 20 located within an instrument thimble 4 of the nuclear reactor. The passive component 10 includes an inductor 12 and a capacitor 14 which together form a resonant circuit. The wireless interrogator 20 includes a transmitter 22 and a receiver 24 and is electrically connected to an electronic apparatus 30 outside the nuclear reactor core. The sensor operates by passing current through the transmitter 22, which causes it to generate an interrogation signal that is received by and excites the passive component 10. In response, the passive component 10 generates a response signal that is received by the receiver 24. The response signal includes characteristics indicative of centerline fuel temperature, fuel pellet stack elongation, and internal fuel rod temperature. These characteristics change the inductance of the inductor 12 and are reflected in the response signal, for example by changes in the frequency of the response signal. In some methodologies, a ferrite core coupled to a stack of fuel pellets is passed through the inductor 12, which results in changes in the inductance of the inductor 12 as the stack of fuel pellets elongates. The sensitivity of the sensor of FIG. 1 is limited. Thus, there is room for improvement in sensors within fuel rods. Embodiments of the disclosed concept provide an improved sensor for monitoring centerline fuel temperature, fuel pellet stack elongation, and/or internal fuel rod pressure. As one aspect of the disclosed concept, a sensor system for a fuel rod including a fuel pellet stack comprises: a wireless interrogator disposed outside the fuel rod, the wireless interrogator comprising: a transmitter structured to wirelessly output an interrogation signal; a reference receiver; and a sensing receiver; a passive sensor component disposed within the fuel rod, the passive sensor component comprising: a receiver structured to receive the interrogation signal and output an excitation signal in response to receiving the interrogation signal; a reference transmitter structured to output a reference signal to the reference receiver in response to the excitation signal; a sensing transmitter structured to output a sensing signal to the sensing receiver in response to the excitation signal, wherein the receiver, the reference transmitter, and the sensing transmitter are electrically connected in series; and a core at least partially disposed within the sensing transmitter and coupled to move in conjunction with expansion or contraction of the fuel pellet stack, to move based on changes in pressure within the fuel rod, or to change temperature based on temperature changes within the fuel rod. As one aspect of the disclosed concept, a sensor system for a fuel rod including a fuel pellet stack comprises: a wireless interrogator disposed outside the fuel rod, the wireless interrogator comprising: a primary transmitter structured to wirelessly output an interrogation signal; and a secondary receiver; a passive sensor component disposed within the fuel rod, the passive sensor comprising: a primary receiver structured to receive the interrogation signal and output an excitation signal in response to receiving the interrogation signal; a linear differential variable transformer (LVDT) including a core coupled to move in conjunction with expansion or contraction of the fuel pellet stack, to move based on changes in pressure within the fuel rod, or to change temperature based on temperature changes within the fuel rod, wherein the LVDT is structured to receive the excitation signal and to output an output signal indicative of a position or a temperature of the core; and a secondary transmitter structured to receive the output signal from the LVDT and to output a response signal proportional to the output signal to the secondary receiver. As another aspect of the disclosed concept, a system comprises: at least one fuel rod including a fuel pellet stack; and at least one sensor system comprising: a wireless interrogator disposed outside the fuel rod, the wireless interrogator comprising: a primary transmitter structured to wirelessly output an interrogation signal; and a secondary receiver; a passive sensor component disposed within the fuel rod, the passive sensor comprising: a primary receiver structured to receive the interrogation signal and output an excitation signal in response to receiving the interrogation signal; a linear differential variable transformer (LVDT) including a core coupled to move in conjunction with expansion or contraction of the fuel pellet stack, to move based on changes in pressure within the fuel rod, or to change temperature based on temperature changes within the fuel rod, wherein the LVDT is structured to receive the excitation signal and to output an output signal indicative of a position or a temperature of the core; and a secondary transmitter structured to receive the output signal from the LVDT and to output a response signal proportional to the output signal to the secondary receiver. As another aspect of the disclosed concept, a method of sensing fuel rod characteristics in a fuel rod including a fuel pellet stack comprises: providing a wireless interrogator disposed outside the fuel rod; providing a passive sensor component disposed within the fuel rod, the passive sensor including a linear differential variable transformer (LVDT) including a core coupled to move in conjunction with expansion or contraction of the fuel pellet stack, to move based on changes in pressure within the fuel rod, or to change temperature based on temperature changes within the fuel rod, wherein the LVDT is structured to receive the excitation signal and to output an output signal indicative of a position or a temperature of the core; wirelessly outputting an interrogation signal from the wireless interrogator to the passive sensor component; providing an excitation signal to the LVDT in response to receiving the wireless interrogation signal; outputting an output signal indicative of a position or a temperature of the core from the LVDT; and wirelessly outputting a response signal proportional to the output signal from the passive sensor component to the wireless interrogator. FIG. 2 is a schematic diagram of a sensor system in accordance with an example embodiment of the disclosed concept. The sensor system is suitable for monitoring a centerline fuel temperature, fuel pellet stack elongation, and/or internal fuel rod pressure in a nuclear reactor system. The sensor system includes a passive component 60 and a wireless interrogator 50. The passive component 60 is disposed within a fuel rod 2 of the nuclear reactor and the wireless interrogator 50 is disposed within an instrument thimble of the nuclear reactor. The wireless interrogator 50 is coupled to an electronic processing apparatus 200 located outside the nuclear reactor core. The fuel rod 2 is entirely enclosed while the instrument thimble 4 includes a penetration through which electrical conductors can pass such as electrical conductors between the wireless interrogator 50 and the electronic processing apparatus 200. It will also be appreciated that the wireless interrogator 50 may be disposed in a region adjacent to the fuel rod 2. For example, the wireless interrogation 50 may be disposed in a different enclosure than the instrument thimble 4 without departing from the scope of the disclosed concept. The wireless interrogator 50 includes a transmitter 52, a reference receiver 54, and a sensing receiver 56. The transmitter 52, the reference receiver 54, and the sensing receiver 56 may be inductors (also referred to as coils). The passive component 60 includes a receiver 62, a reference transmitter 64 and a sensing transmitter 66 electrically connected in series. The receiver 62, the reference transmitter 64, and the sensing transmitter 66 may be inductors (also referred to as coils). The passive component 60 also includes a core 130. The core 130 is disposed at least partially within the sensing transmitter 66. The transmitter 52 is structured to generate an interrogation signal. For example, the electronic processing apparatus 200 may generate and provide a signal to the transmitter 52 which energizes the transmitter 52 and causes it to generate the interrogation signal. The interrogation signal may be a continuous sinusoid wave or pulsed wave that is received by and excites the receiver 62. For example, the interrogation signal may be a time varying magnetic field generated by the transmitter 52 which produces an electromotive force on the receiver 62, causing current to flow through the receiver 62, and in turn through the reference transmitter 64 and the sensing transmitter 66. The current through the reference transmitter 64 and the and the sensing transmitter 66 causes them to generate a reference signal and a sensing signal, respectively, that are received by the reference receiver 54 and the sensing receiver, respectively. For example, the reference signal and the sensing signal may be time varying magnetic fields generated by the reference transmitter 64 and the sensing transmitter 66 in response to current flowing through them, which in turn produces electromagnetic forces in the reference receiver 54 and the sensing receiver 56. The core 130 is physically coupled to a fuel pellet stack within the fuel rod 2. In some example embodiments, the core 130 is coupled such that the core 130 moves rectilinearly with the fuel pellet stack. For example, as the fuel pellet stack swells or expands, the core 130 will move upward through the sensing transmitter 66 the same distance that the fuel pellet stack has elongated. In this manner, the physical displacement of the core 130 within the sensing transmitter 66 will change the voltage across the sensing transmitter 66, thus changing the sensing signal, which is in turn received by the sensing receiver 56 and can be used to determine fuel pellet stack elongation. In some example embodiments, the core 130 is coupled such that changes in temperature of the fuel pellet stack change the temperature of the core 130. The change in temperature of the core 130 changes magnetic permeability resulting in a change in voltage across the sensing transmitter 66. This results in a change in the sensing signal which is received by the sensing receiver 56 and can be used to determine centerline fuel temperature. In some example embodiments, the core 130 is coupled such that changes in pressure within the fuel rod cause the core 130 to move with changes in temperature. For example, the core 130 may be coupled to bellows within the fuel rod 2 such that increases in pressure cause the bellows to expand and move the core 130 further within the sensing transmitter 66. The physical displacement of the core 130 within the sensing transmitter 66 will change the voltage across the sensing transmitter 66, thus changing the sensing signal, which is in turn received by the sensing receiver 56 and can be used to determine pressure within the fuel rod 2. In these example embodiment, the centerline fuel temperature, fuel pellet stack elongation, and fuel pressure are considered the sensed parameters and their values affect the sensing signal. However, their values have little effect on the reference signal output by the reference transmitter 64. The sensing signal and the reference signal are received by the sensing receiver 56 and reference receiver 54, respectively. The difference between these two signals may be used to determine the sensed parameter, as the difference between the sensing signal and the reference signal cancels out any drift due to temperature or other effects common to the reference transmitter 64, the sensing transmitter 66, and other components. FIG. 3 is a schematic diagram of a sensor in accordance with an example embodiment of the disclosed concept. The sensor is suitable for monitoring centerline fuel temperature, fuel pellet stack elongation, and internal fuel rod pressure in a nuclear reactor system. The sensor includes a passive component 110 and a wireless interrogator 140. The passive component 110 is disposed within a fuel rod 2 of the nuclear reactor and the wireless interrogator 140 is disposed within an instrument thimble 4 of the nuclear reactor. The wireless interrogator 140 is coupled to an electronic processing apparatus 200 located outside the nuclear reactor core. The wireless interrogator 140 includes a primary transmitter 142 and a secondary receiver 144. The passive component 110 includes a primary receiver 112 that corresponds to the primary transmitter 142 of the wireless interrogator 140 and a secondary transmitter 114 that corresponds to the secondary receiver 144 of the wireless interrogator 140. For example, the primary transmitter 142 is structured to output an interrogation signal and the primary receiver 112 is structured to receive the interrogation signal. Also, the secondary transmitter 114 is structured to output a response signal and the secondary receiver 144 is structured to receive the response signal. It is to be understood that the interrogation signal, response signal, or any other signals exchanged between the wireless interrogator 140 and the passive component 110 are wireless signals as the passive component 110 is fully enclosed within the fuel rod 2 and does not have a wired connection to any components outside the fuel rod 2. The passive component 110 also includes a linear variable differential transformer (LVDT) 120. The LVDT 120 is structured to sense rectilinear motion of a core 130 included with the LVDT 120 within the fuel rod. In some example embodiments, the core 130 is coupled such that it moves rectilinearly with the fuel pellet stack in order to sense fuel pellet stack elongation. In some example embodiments, the core 130 is coupled such that it move rectilinearly based on pressure within the fuel rod 2, for example, by using bellows as previously described, to sense fuel pressure. In some example embodiments, the core 130 is coupled such that it is static and its temperature changed with centerline fuel temperature. For example, to measure centerline fuel temperature, the core 130 may be static in that it does not move and have varying permeability along its length. Heat will travel from the fuel pellet stack up the core 130 such that the bottom of the core 130 will be hotter than the top of the core 130. The different temperatures will result in different voltages being output by coils of the LVDT 120 resulting in an output of the LVDT 120 that is similar to if the core 130 had moved in the LVDT 120. The centerline temperature of the fuel can be determined from this output. In some example embodiments of the disclosed concept the core 130 is composed of ferrite material. However, it will be appreciated that the core 130 may be composed of other suitable materials without departing from the scope of the disclosed concept. The LVDT 120 is electrically connected to the primary receiver 112 and the secondary transmitter 114. The LVDT 120 is structured to receive an excitation signal from the primary receiver 112. To generate the excitation signal, the electronic processing apparatus 200 provides a signal to the primary transmitter 142, causing the primary transmitter 142 to output the interrogation signal. The primary receiver 112 receives the interrogation signal, which excites the primary receiver 112 and causes the primary receiver 112 to output the excitation signal to the LVDT 120. The excitation signal causes the LVDT 120 to generate an output signal that is indicative of the position of the core 130. For example, at a null position, where the core 130 is centered within the LVDT 120, the output signal of the LVDT 120 will be about 0 V. As the core 130 moves from the null position, the voltage of the output signal will increase linearly. A phase angle of the output signal is indicative of which direction the core 130 has moved with respect to the null position. The LVDT 120 is structured to provide the output signal to the secondary transmitter 114. Receiving the output signal from the LVDT 120 causes the secondary transmitter 114 to output the response signal, which is in turn received by the secondary receiver 144 and provided to the electronic processing apparatus 200. The response signal is proportional to the output signal of the LVDT 120. Thus, any increases or decreases in the voltage of the output signal of the LVDT 120 are reflected in the response signal. Similarly, the phase angle of the output signal of the LVDT 120 is reflected in the response signal. From the response signal, the electronic processing apparatus 200 is able to determine the position of the core 130 within the LVDT 120. The LVDT 120 is able to more accurately sense the rectilinear motion and position of the core 130. In some example embodiments, the LVDT 120 can monitor the position of the core 130 within ±2 μm. While the example embodiment of FIG. 3 illustrates the wireless interrogator 140 as being within the instrument thimble 4, it will be appreciated that the wireless interrogator 140 can be disposed at other location outside the fuel rod 2 without departing from the scope of the disclosed concept. FIG. 4 is a schematic diagram of a sensor in accordance with an example embodiment of the disclosed concept. The sensor of FIG. 4 operates similar to the sensor of FIG. 3. However, FIG. 4 illustrates an example embodiment of the LVDT 120 in more detail. For example, in the example embodiment of FIG. 4, the LVDT 120 includes a primary coil 122, a first secondary coil 124, and a second secondary coil 126. The primary coil 122 is disposed between the first secondary coil 124 and the second secondary coil 126. The primary coil 122, the first secondary coil 124, and the second secondary coil 126 are aligned such that the core 130 is able to pass through all of them. In FIG. 3, the core 130 is disposed in the null position where it is centered in the LVDT 120. That is, the center of the core 130 is aligned with the center of the primary coil 122 and equal lengths of the core 130 extend into the first secondary coil 124 and the second secondary coil 126. The first secondary coil 124 and the second secondary coil 126 are equally spaced from the primary coil 122. For example, an end of the first secondary coil 124 is spaced equally from the center of the primary coil 122 as an end of the second secondary coil 126. The primary coil 122 is electrically connected to the output of the primary receiver 112 such that the primary coil 122 is structured to receive the excitation signal from the primary receiver 112. In an example embodiment, the first and second secondary coils 124,126 each have a first end closest to the primary coil 122 and a second end furthest from the primary coil 122. The first end of the first secondary coil 124 is electrically connected to an output of the LVDT 120 and the second end of the first secondary coil 124 is electrically connected to the first end of the second secondary coil 126. The second end of the second secondary coil 126 is electrically connected to the output of the LVDT 120. However, it will be appreciated that the positions of the first and second secondary coils 124,126 can be swapped without departing from the scope of the disclosed concept. When the primary coil 122 receives the excitation signal, the primary coil 122 induces a current in the core 130, which is then sensed by the first and second secondary coils 124,126. When the core 130 is in the null position, as shown in FIG. 3, the outputs of the first and second secondary coils 124,126 cancel each other, resulting in the output signal of the LVDT 120 being 0 V. As the core 130 moves from the null position, more of the core 130 will be disposed within one of the first or second secondary coils 124,126 than the other. This results in the output of one of the first or second secondary coils 124,126 being greater than the output of the other because the greater length of core 130 in one of the first and second secondary coils 124,126 will result in a greater output in that coil compared to the other. As a result, the output of the LVDT 120 will linearly increase as the core 130 moves further into one of the first and second secondary coils 124,126. Also, when the core 130 is moved in one direction from the null position, the output of the LVDT 120 will have a first phase angle and when the core 130 moves in the other direction from the null position, the output of the LVDT 120 will have a second phase angle. Thus, the magnitude of the output signal of the LVDT 120 provides an indication of the distance the core 130 has moved from the null position and the phase angle of the output signal of the LVDT 120 provides an indication of the direction that the core 130 has moved. Taking these together, the output signal of the LVDT 120 provides an accurate indication of the position of the core 130. As in the embodiment shown in FIG. 3, the output signal of the LVDT 120 is provided to the secondary transmitter 114. Receiving the output signal of the LVDT 120 causes the secondary transmitter 114 to output the response signal, which is proportional to the output signal of the LVDT 120. The response signal is received by the secondary receiver 144 and is provided to the electronic processing apparatus 200. The electronic processing apparatus 200 is structured to interpret the response signal to determine the position of the core 130. In some example embodiments of the disclosed concept, the first and second secondary coils 124,126 are substantially similar. That is, they have a substantially similar length and number of windings and are composed of substantially similar materials. When the first and second secondary coils 124,126 are substantially similar, their outputs will cancel each other out when the core 130 is in the null position and the output of the LVDT 120 will linearly increase as the core 130 moves from the null position. The primary coil 122 may or may not be substantially similar to the first and second secondary coils 124,126 without departing from the scope of the disclosed concept. In some example embodiments of the disclosed concept, the primary transmitter 142, the primary receiver 112, the secondary transmitter 114, and the secondary receiver 144 are coils. However, it will be appreciated that other components capable of wirelessly transmitting or receiving signals may be employed without departing from the scope of the disclosed concept. FIG. 5A is a top view of the LVDT 120 in accordance with an example embodiment of the disclosed concept and FIG. 5B is a cross-sectional side view of the LVDT 120 in accordance with an example embodiment of the disclosed concept. In some example embodiments of the disclosed concept, the LVDT 120 may have a cylindrical shape. However, it will be appreciated that the LVDT 120 may have different shapes without departing from the scope of the disclosed concept. The LVDT 120 may include a housing 128 as shown in FIGS. 5A and 5B. The housing 127 has a hollow center through which the ore 130 may pass. The housing 128 may include interior compartments respectively containing the primary coil 122, the first secondary coil 124, and the second secondary coil 126. As has been previously described, the primary coil 122 is disposed between the first and second secondary coils 124,126. FIG. 6 is a simplified cross-sectional view of the fuel rod 2 including the LVDT 120 in accordance with an example embodiment of the disclosed concept. As shown in FIG. 6, the core 130 passes through the LVDT 120. The fuel pellets 150 in the fuel pellet stack are physically coupled to the core 130 via an elongated member 152 such as a plunger. In this manner, the core 130 moves within the LVDT 120 in conjunction with expansion or contraction of the fuel pellet stack. FIG. 7 is a simplified cross-sectional view of the fuel rod 2 including the LVDT 120 in accordance with an example embodiment of the disclosed concept. As shown in FIG. 7, the core 130 passes through the LVDT 120. The core 130 is coupled to a bellows 154 either directly, or via an intermediate member 156. The bellows 154 is structured to expand in response to increasing pressure within the fuel rod 2 and to contract in response to decreasing pressure within the fuel rod 2. In this manner, the core 130 moves within the LVDT 120 in conjunction with changes in pressure within the fuel rod 2. It will be appreciated that the arrangements shown in FIGS. 6 and 7 may also be employed in conjunction with the sensor system described with respect to FIG. 2 without departing from the scope of the disclosed concept. FIG. 8 is a schematic diagram of a system including multiple sensors in accordance with an example embodiment of the disclosed concept. In the example embodiment of FIG. 8, multiple sensors are disposed within close proximity. For example, multiple wireless interrogators 140 are disposed in close proximity to multiple passive components 110. In some example embodiments, the wireless interrogators 140 may output interrogation signals having unique frequencies. That is, one wireless interrogator 140 may output an interrogation signal having a first frequency and another wireless interrogator 140 may output an interrogation signal having a second frequency. The wireless interrogators 140 may each correspond to a respective passive component 110. Due to the close proximity, a wireless interrogator 140 may receive a response signal from a passive component 110 that it does not correspond to. By interrogating signals with unique frequencies, the response signal from the passive component 110 corresponding to the wireless interrogator 140 will have the same unique frequency as the interrogation signal. The electronic processing apparatus 200 may have a frequency filtering function such that it may filter for the unique frequency of the interrogation signal. Thus, even if a wireless interrogator 140 receives response signals from passive components 110 it does not correspond to, those response signals may be filtered out due to their different frequencies. FIG. 9 is a flowchart of a method of sensing fuel rod characteristics in accordance with an example embodiment of the disclosed concept. The method of FIG. 9 may be employed in conjunction with the embodiments of the disclosed concept described herein or in other similar applications. The method begins at 300 by providing a wireless interrogator disposed outside the fuel rod. The wireless interrogator may be the wireless interrogator 140 described in conjunction with embodiments of the disclosed concept. The method continues at 302 by providing a passive sensor component disposed within the fuel rod. The passive sensor component includes an LVDT including a core coupled to the fuel pellet stack such that the core moves in conjunction with expansion or contraction of the fuel pellet stack. The passive sensor component may be the passive sensor component 110 described in conjunction with embodiments of the disclosed concept. The method continues at 304 with wirelessly outputting an interrogation signal from the wireless interrogator to the passive sensor component. The interrogation signal may be output for example by a primary transmitter of the wireless interrogator and received for example by a primary receiver of the passive sensor component. The method continues at 306 with providing an excitation signal to the LVDT in response to receiving the interrogation signal. The excitation signal may be provided for example by the primary receiver of the passive sensor component. The method continues at 308 with outputting an output signal indicative of a position of the core from the LVDT. Finally, at 310, the method continues with wirelessly outputting a response signal proportional to the output signal from the passive sensor component to the wireless interrogator. It will be appreciated that the method may include additional steps, the steps of the method may be modified, or the steps of the method may be rearranged without departing from the scope of the disclosed concept. FIG. 10 is a flowchart of a method of sensing fuel rod characteristics in accordance with an example embodiment of the disclosed concept. The method of FIG. 10 may be employed in conjunction with the embodiments of the disclosed concept described herein or in other similar applications. The method begins at 400 by providing a wireless interrogator disposed outside the fuel rod. The wireless interrogator may be the wireless interrogator 50 described in conjunction with embodiments of the disclosed concept. The method continues at 402 by providing a passive sensor component disposed within the fuel rod. The passive sensor component may be the passive sensor component 40 described in conjunction with embodiments of the disclosed concept and may include a sensing transmitter whose output is affected by the sensed parameter and a reference transmitter whose output is not affected by the sensed parameter. The method continues at 404 with wirelessly outputting an interrogation signal from the wireless interrogator to the passive sensor component. The method continues at 406 with receiving a reference signal from the passive sensor component and continues at 408 with receiving a sensing signal from the passive sensor component. The sensing signal is affected by the sensed parameter while the reference signal is not. The method then continues at 410 with subtracting the reference signal from the sensing signal. The subtracting cancels out temperature drift and other factors that affect all components within the system. It will be appreciated that the method may include additional steps, the steps of the method may be modified, or the steps of the method may be rearranged without departing from the scope of the disclosed concept. 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 and that selected elements of one or more of the example embodiments may be combined with one or more elements from other embodiments without varying from the scope of the disclosed concepts. 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.
042241073	summary	This invention relates to nuclear reactor fuel assemblies each constituted by a cluster of parallel fuel pins of substantial length and small cross-sectional area each containing a stack of nuclear fuel pellets within a metal can. This fuel cluster is associated along the length of the fuel pins with spacer grids placed at uniform intervals so as to permit suitable bracing of the fuel pins with respect to each other while preventing vibrations of these latter and deformation of the initial geometry of the cluster under the action of the stresses to which the fuel assembly is subjected during operation within the reactor core. In a fuel assembly of this type which is usually intended to be employed in a light-water reactor, the invention is more particularly applicable to an improvement in the construction of the spacer grids of the fuel-pin cluster. It is known that a spacer grid of the type mentioned above is usually constituted by an open structure formed by two sets of sheet metal members which are parallel to each other but oriented in two perpendicular directions in each set. Said sheet metal members are intended to interengage in slits formed lengthwise in these latter and thus constitute a series of compartments having a generally square cross-section through which the fuel pins are intended pass in a direction parallel to the plane of said sheet metal members. A number of different solutions have already been proposed in order to ensure correct positioning of said fuel pins within each compartment of the spacer grid and especially in order to ensure suitable stress distribution on the fuel-pin cans at the level of each spacer grid. In particular,* the sheet metal members of the grid are provided with wide openings separated by narrow corrugated strips forming springs and projecting either inwardly or outwardly from the compartments so as to provide, in conjunction with other corrugated strips or with bosses formed in the solid portions of the sheet metal members, a series of bearing points for each fuel pin at the location corresponding to the passage of said pin through each compartment. Each fuel pin is thus maintained in two different directions at four points spaced at uniform intervals at its periphery and also at a number of points in the longitudinal direction by means of as many spacer grids as the total number provided for the fuel assembly. By making use of narrow corrugated strips for separating open portions having appreciable dimensions, the coolant fluid which circulates in contact with the fuel assembly ensures efficacious cooling of the fuel pins; furthermore, the shape and arrangement of the corrugated strips and of the bearing bosses makes it possible to ensure efficacious absorption of vibrations and expansions during operation. FNT * in the U.S. Pat. No. 3,674,687 of June 20, 1969 In a practical design of this type, the corrugated strips which form springs must maintain the fuel pins with a sufficient bearing force against the fixed bosses of the sheet metal members, especially in order to prevent wear as a result of impact of the fuel-pin cans against said bosses under the action of vibrations produced by the flow of the coolant fluid. On the other hand, the clamping action thus produced on the fuel pins must not be too powerful in order to prevent collapse of the fuel cans. However, the springs constituted by the corrugated strips must provide adequate compensation for manufacturing tolerances allowed on the diameters of the fuel pins and on the dimensions of the spacer grid compartments. In consequence, the curve representing the force applied by the spring formed by each corrugated strip as a function of its deflection must be as flat as possible within the operating range corresponding to a bearing pressure which varies only to a slight extent in respect of a range of deflection which can on the contrary vary to an appreciable extent; it is therefore found necessary to increase the flexibility of the spring without thereby permitting the possibility of modifying the spacing of the sheet metal members of the grid. The present invention is directed to an improvement which is made in spacer grids of the type referred-to in the foregoing and which meets this requirement. To this end, the invention is characterized in that the sheet metal members are joined to the corrugated strips by means of a zone which has lower mechanical strength and increased flexibility and increases the deflection due to increased flexibility of each strip in respect of the same applied force.
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	claims	1. A method for irradiating in an irradiation chamber products being stored in the form of pallets or in the form of bulk material in containers with a high energy x-ray beam source, the method comprising:placing the products onto two different levels of products, so that a first set of products is placed on an upper level and a second set of products is placed on a lower level;irradiating both sets of products during a first period of time by directing the x-ray beam source to the products from about mid-height of the products on the lower level to about mid-height of the products on the upper level;switching the products placed on the two levels to make a new arrangement so that the set of products irradiated on the upper level during the first time period are placed on the lower level and the set of products irradiated on the lower level during the first time period are placed on the upper level; andirradiating during a second period of time the new arrangement formed of the two switched sets of products by directing the x-ray beam source to the products from about mid-height of the products on the lower level to about mid-height of the products on the upper level. 2. The method according to claim 1, wherein the two different levels are two superposed vertical levels. 3. The method according to claim 1 wherein the total period of irradiation comprises the first period of time and the second period of time and the switching of the two levels occurs in the middle of the total period of irradiation of the products. 4. The method according to claim 1, wherein the products are conveyed before the source with a translation conveyor device. 5. The method according to claim 4, wherein the translation conveyor device comprises two independent parallel sub-devices conveying the products on the two different levels. 6. The method according to claim 1, wherein the products are conveyed before the source with a rotating conveyor device. 7. The method according to claim 6, wherein the rotating conveyor device comprises two independent parallel sub-devices conveying the products on the two different levels. 8. The method according to claim 1, wherein the set of products present on each level comprises one pallet or one container. 9. The method according to claim 1, wherein the set of products present on each level is in the form of a stack of at least several contiguous pallets or containers placed in the same plane. 10. The method according to claim 9, wherein the plane is essentially a horizontal plane. 11. The method according to claim 1, wherein the high energy x-rays are obtained by scanning an electron beam along a conversion target on a height essentially corresponding to a distance comprised between substantially mid-height of the lower level up to substantially mid-height of the upper level. 12. An apparatus for irradiating in an irradiation chamber products being stored in the form of pallets or in the form of bulk material in containers, the apparatus comprising:a high energy photon source;a conveying device configured to convey the products in front of the photon source and arrange the products in two sets of products, each being placed on a different level, the different levels comprising an upper level and a lower level;a transposition device configured to switch the sets of products arranged on each level so that the set of products irradiated on the upper level during the first time period are placed on the lower level and the set of products irradiated on the lower level during the first time period are placed on the upper level, anda directing device configured to direct the high energy photon source to the products from about mid-height of the products on the lower level to about mid-height of the products on the upper level. 13. The apparatus according to claim 12, further comprising a directing device configured to direct a photon beam along a height essentially corresponding to a distance comprised between substantially mid-height of the lower level products up to substantially mid-height of the upper level products. 14. A method for irradiating in an irradiation chamber products being stored in the form of pallets or in the form of bulk material in containers with a high energy x-ray beam source, the method comprising:placing the products onto two different levels of products so that a first set of products is placed on an upper level on a first horizontal plane and a second set of products is placed on a lower level on a second horizontal plane;irradiating both sets of products during a first period of time by directing the x-ray beam source to the products from about mid-height of the products on the lower level to about mid-height of the products on the upper level and holding the first and second horizontal planes stationary during the first time period;switching the products arranged on the two levels to make a new arrangement so that the set of products irradiated on the upper level during the first time period are placed on the lower level on the second horizontal plane and the set of products irradiated on the lower level during the first time period are placed on the upper level on the first horizontal plane; andirradiating during a second period of time the new arrangement formed of the two switched sets of products by directing the x-ray beam source to the products from about mid-height of the products on the lower level to about mid-height of the products on the upper level and the first and second horizontal planes are held stationary during the second time period,wherein the total period of irradiation comprises the first period of time and the second period of time and provides a dose uniformity ratio less than 2.5. 15. The method according to claim 14, wherein the two different levels are two superposed vertical levels. 16. The method according to claim 14, wherein the switching of the two levels occurs in the middle of the total period of irradiation of the products. 17. The method according to claim 14, wherein the products are conveyed before the source with a translation conveyor device comprising two independent parallel sub-devices conveying the products on the two different levels. 18. The method according to claim 14, wherein the products are conveyed before the source with a rotating conveyor device comprising two independent parallel sub-devices conveying the products on the two different levels. 19. The method according to claim 14, wherein the dose uniformity ratio is about 1. 20. The method according to claim 14, wherein the high energy x-rays are obtained by scanning an electron beam along a conversion target on a height essentially corresponding to a distance comprised between substantially mid-height of the lower level up to substantially mid-height of the upper level.
	claims	1. A Y-shaped carbon nanotube atomic force microscope probe tip comprising:a shaft portion;a pair of angled arms extending from a same end of said shaft portion,wherein said shaft portion and said pair of angled arms comprise a chemically modified carbon nanotube, andwherein said chemically modified carbon nanotube is modified with any of an amine, carboxyl, fluorine, and metallic component. 2. The probe tip of claim 1, all the limitations of which are incorporated herein by reference, wherein each of said pair of angled arms comprise a length of at least 200 nm. 3. The probe tip of claim 1, all the limitations of which are incorporated herein by reference, wherein each of said pair of angled arms comprise a diameter between 10 and 200 nm. 4. The probe tip of claim 1, all the limitations of which are incorporated herein by reference, wherein said chemically modified carbon nanotube is adapted to allow differentiation between substrate materials to be probed. 5. The probe tip of claim 1, all the limitations of which are incorporated herein by reference, wherein said chemically modified carbon nanotube is adapted to allow fluorine gas to flow through said chemically modified carbon nanotube onto a substrate to be characterized. 6. The probe tip of claim 1, all the limitations of which are incorporated herein by reference, wherein said chemically modified carbon nanotube is adapted to chemically react with a substrate surface to be characterized. 7. A method of forming a Y-shaped carbon nanotube atomic force microscope probe tip, said method comprising:forming a shaft portion of said probe tip;extending a pair of angled arms from a same end of said shaft portion, wherein said shaft portion and said pair of angled arms comprise a carbon nanotube; andchemically modifying said carbon nanotube with any of an amine, carboxyl, fluorine, and metallic component. 8. The method of claim 7, all the limitations of which are incorporated herein by reference, further comprising configuring each of said pair of angled arms at a length of at least 200 nm. 9. The method of claim 7, all the limitations of which are incorporated herein by reference, further comprising configuring each of said pair of angled arms at a diameter between 10 and 200 nm. 10. The method of claim 7, all the limitations of which are incorporated herein by reference, wherein said chemically modified carbon nanotube is adapted to allow differentiation between substrate materials to be probed. 11. The method of claim 7, all the limitations of which are incorporated herein by reference, wherein said chemically modified carbon nanotube is adapted to allow fluorine gas to flow through said chemically modified carbon nanotube onto a substrate to be characterized. 12. The method of claim 7, all the limitations of which are incorporated herein by reference, wherein said chemically modified carbon nanotube is adapted to chemically react with a substrate surface to be characterized. 13. A method of performing atomic force microscopy, said method comprising:attaching a carbon nanotube to an atomic force microscope probe to form a probe tip, wherein said carbon nanotube is configured into a Y shape;chemically modifying the carbon nanotube probe tip with any of an amine, carboxyl, fluorine, and metallic component; andanalyzing a surface of a substrate using the chemically modified Y-shaped carbon nanotube probe tip. 14. The method of claim 13, all the limitations of which are incorporated herein by reference, further comprising configuring said carbon nanotube probe tip with a shaft portion and a pair of angled arms extending from a same end of said shaft portion. 15. The method of claim 14, all the limitations of which are incorporated herein by reference, further comprising configuring each of said pair of angled arms at a length of at least 200 nm. 16. The method of claim 14, all the limitations of which are incorporated herein by reference, further comprising configuring each of said pair of angled arms at a diameter between 10 and 200 nm. 17. The method of claim 13, all the limitations of which are incorporated herein by reference, wherein said chemically modified Y-shaped carbon nanotube is adapted to allow differentiation between substrate materials to be probed. 18. The method of claim 13, all the limitations of which are incorporated herein by reference, wherein said chemically modified Y-shaped carbon nanotube is adapted to allow fluorine gas to flow through said chemically modified carbon nanotube onto a substrate to be characterized. 19. The method of claim 13, all the limitations of which are incorporated herein by reference, wherein said chemically modified Y-shaped carbon nanotube is adapted to chemically react with a substrate surface to be characterized. 20. The method of claim 14, wherein said chemically modified Y-shaped carbon nanotube is attached at a confluence point between said pair of angled arms extending to a probe arm of said atomic force microscope.
	abstract	A system to control an ion beam in an ion implanter includes a detector to perform a plurality of beam current measurements of the ion beam along a first direction perpendicular to a direction of propagation of the ion beam. The system also includes an analysis component to determine a beam current profile based upon the plurality of beam current measurements, the beam current profile comprising a variation of beam current along the first direction; and an adjustment component to adjust a height of the ion beam along the first direction when the beam current profile indicates the beam height is below a threshold.
053923260	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a boiling water reactor according to the present invention will be described hereunder in conjunction with FIGS. 1 to 17. Referring to FIG. 1, a reactor pressure vessel 20 is installed in a vertical fashion and a core 21 is arranged at a lower portion in the pressure vessel 20. In the core 21, a plurality of fuel assemblies 22 are arranged in lattice so that control rods 23 are inserted into or withdrawn from the core between the respective fuel assemblies 22. The outer periphery of the fuel assemblies 22 in the lattice arrangement are surrounded by a shroud 24 having an upper opening to which a shroud head 25 is mounted. The shroud 24 supports a core support plate 26 and an upper grid plate 27 and surrounds the entire structure of the fuel assemblies 22 to constitute the core 21. The core support plate 26 supports the lower end of the entire structure of the fuel assemblies 22 and the upper grid plate 27 supports the upper end thereof. A plurality of stand pipes 28 stand upward from the shroud head 25 and a plurality of separators 29 are connected to the stand pipes 28. A pedestal 31 for fixing the control rod driving mechanism is disposed above the separators 29 through a support member 32 and the fixing pedestal 31 is provided with a number of steam passing holes 30. The support member 32 is welded to an inner wall surface of the reactor pressure vessel 20. An upper control rod driving mechanism 33 for driving the control rods 23 from the upper side is mounted on the control rod driving mechanism fixing pedestal 31, and an annular drier means 34 is mounted on the fixing pedestal along its outer periphery along the inner wall surface of the reactor pressure vessel 20. The drier means 34 comprises a plurality of drier elements 51, each in shape of a short strip, which are annularly arranged along the inner wall surface of the reactor pressure vessel 20. The reactor pressure vessel 20 has an upper opening closed pressure-tightly by an upper flange 35. A plurality of jet pumps 36 are arranged between the shroud 24 and a lower inner wall surface of the reactor pressure vessel 20 and the jet pumps 36 are connected to coolant supply pipes 37 mounted to the side of the reactor pressure vessel 20. A plurality of water supply pipes adapted to control the water level in the core are also mounted to the side of the reactor pressure vessel in parallel with the coolant supply pipes 37. Main steam pipes 39 are connected to the upper side wall of the reactor pressure vessel 20 for feeding the steam dried by the annular drier means 34 to the steam turbine. The reactor pressure vessel 20 of the characters or structure described above is accommodated in a predetermined position of a reactor containment vessel 40. In FIG. 1, reference numerals 41, 42 and 43 denote support legs supporting the reactor pressure vessel 20 at its bottom portion, a drywell cooling device and a pressure suppression pool, respectively. FIG. 2 is a perspective view as viewed from an arrowed direction II in FIG. 1 and only a quarter thereof is shown. It is apparent from FIG. 2, though not shown in FIG. 1, that one cable protecting tube 50 is air-tightly attached to substantially the central portion of the upper cover 35 and four cable protecting tubes 50 are also air-tightly attached to the outer portions thereof. These cable protecting tubes 50 are utilized for accommodating several tens of cables, in several bundles, through which current is conducted to the upper control rod driving mechanism 33 and for accommodating cables for incore neutron dectectors. These cables are for wires for electric power or electric signals, and a plurality of wires in a bundle are accommodated in each of the cable protecting tubes 50. These tubes 50 penetrate vertically and air-tightly the upper cover 35 of the reactor pressure vessel 20 and the extreme outer ends thereof extend outside the reactor pressure vessel 20. FIG. 3 is a cross sectional view taken along the line III--III in FIG. 1, but merely a quarter thereof is shown for the sake of convenience. Referring to FIG. 3, an angle of attachment of the main steam pipe 39 is 18.degree. with respect to the center of the axial center of the reactor pressure vessel 20. The annular drier means 34, which is composed of a plurality of drier elements 51 each in a short strip shape, and arranged annularly along the inner wall surface of the reactor pressure vessel 31, is mounted on the control rod driving mechanism fixing pedestal 31. It will be apparent from FIG. 3 that the upper control rod driving mechanism 33 and the separators 29 are alternately arranged in lattice structures on the fixing pedestal 31. The detailed structure of the drier means 34 is shown in FIG. 10, which will be described hereinlater. FIG. 4 is a cross sectional view taken along the line IV--IV in FIG. 1, but merely a quarter thereof is shown for the sake of convenience. As shown in FIG. 4, the coolant supply pipe 37 is attached to the reactor pressure vessel 20 with an angle of 30.degree. with respect to the horizontal direction, and the control rods 23 are arranged between the separators 29, which will be described hereinlater with reference to FIG. 12. FIG. 5A is a cross sectional view taken along the line V--V in FIG. 1, but merely a quarter thereof is shown for the sake of convenience and FIG. 5B is one section of FIG. 5A in an enlarged scale. From FIGS. 5A and 5B the arrangement of the fuel assemblies 22 in the core 21 is apparent, and also apparent is an inserted condition of a guide pad 63 inserted into a space between adjacent two fuel assemblies 22 for maintaining a space between a channel box and the control rod 23. The control rods 23, each being enlarged, are utilized for the purpose of reducing numbers of the control rod driving mechanisms and the amount of fuel because short and enlarged fuel assemblies 22 have been developed. That is, in comparison of a large-sized T-shape lattice core 21 having each side a length twice that of a conventional fuel rod with a conventional C-shape lattice core 2 of FIG. 20, the numbers of the fuel rods and the control rod driving mechanisms are reduced in proportion to the provision of the large-sized fuel rods, thus reducing the processes needed for the periodical inspection of the reactor and hence being advantageous for the operators or workers who work in the reactor. It is of course noted that the present invention is not limited to the T-shape lattice core and applicable to the conventional core or to the fuel rods having other sizes. FIG. 6 is a cross sectional view taken along the line VI--VI in FIG. 1, but merely a quarter thereof is shown for the sake of convenience. It is apparant from FIG. 6 that twenty-four jet pumps 36 are regularly arranged with angles of 15.degree. in the reactor pressure vessel 20 along the inner peripheral wall thereof. Each of the jet pumps 36 includes a two-staged driving water nozzle for making the flow rate ratio of the driving water with respect to a driven water greater than 6. The detail of the jet pump 36 is shown in FIG. 15. These jet pumps 36 are driven by a plurality of jet pump driving pumps or steam injectors. FIG. 7 is a cross sectional view taken along the line VII--VII, but merely a quarter thereof is shown, and shows an arrangement of the jet pumps 36, the shroud 24 and the core 21. FIG. 8 shows a cross section of one example of a fuel assembly 22, utilized for the core 21, having short length and large size, and it is a matter of natural course that the present invention is not limited to the fuel assembly 22 of FIG. 8 and other large-sized fuel assemblies may be utilized. Referring to FIG. 8, the fuel assembly 22 is composed of four fuel assembly sections 46 in a 2-row.times.2-line, each being composed of a plurality of fuel rods 44 in lattice arrangement of 9-row.times.9-line and a water rod 45 arranged centrally of the fuel assembly section 46. The entire structure of the fuel assembly 22 is composed of the four fuel assembly sections 46 and is surrounded by a large-sized channel box 47. These four fuel assembly sections 46 are arranged with a cross-shaped space between them, in which a large-sized cross-shape water rod 48 is inserted. The large-sized cross-shape water rod 48 acts in some ways as a channel box disposed inside the respective fuel assembly sections 46 for mutually partitioning the respective sections 46. The inside of the large water rod 48 forms a non-boiling water area 49, and the location of such non-boiling water area 49 makes small thermal neutron diffusion between the fuel assembly sections 46 and reduces an influence of the control rod 23 to the sections 46 with respect to the control rods 23. FIG. 9 is an elevational view for explaining an allowable range of the water level change in the reactor pressure vessel 20, and as is apparent from FIG. 9, according to the present invention, a space for locating the separators 29 each having a long length above the core 21 can be ensured because the core 21 is positioned at a portion lower than the location of the core in the conventional arrangement. Accordingly, the allowable range of the water level change can be made large along the entire vertical length of the separator 29. FIG. 10 is a partial sectional view of the thin annular drier means 34 shown in FIG. 1, and the drier means 34 comprises a plurality of drier elements 51, a drain receiving vessel 52 disposed below the drier elements 51 and drain tubes 53 extending downward from the drain receiving vessel 52. An area of the thin annular drier means 34 through which the steam passes is designed so as to have a height higher by 1.7 times than that of the conventional rectangular flat type drier 8 of FIG. 8 so that the area is substantially equal to 6 times of the drier 8. The drier elements are formed by a punched metal plate provided with a number of punched holes 51a for protecting the drier elements 51 from colliding with machineries during the periodical inspection. FIG. 11 is a schematic view of the upper control rod driving mechanism 33, shown in FIG. 1 and in FIG. 11. Coils operating in a steam atmosphere are accommodated in pressure proof vessels 54 made of steel to thereby prevent moisture content from invading. The upper control rod driving mechanism 33 is mounted on the control rod driving mechanism fixing pedestal 31, and in the periodical inspection, the mechanism 33 can be entirely withdrawn outside the core by a suitable handling machine. The control rod driving mechanism fixing pedestal 31 is formed with steam passing holes 30 attaining a rectifying function of the steam directing to the annular drier means 34. The upper control rod driving mechanism 33 includes control rod driving shafts 55 extending vertically and a magnet coupling 56 is mounted on the way of each of the control rod driving shafts 56 for separating it at that portion in the periodical inspection time or at any accident of the control rod driving mechanism 33. Lead wires of electromagnetic coils 57 of the upper control rod driving mechanism 33 are formed as MI (metal insulated) cables 58 effected with metal coating ceramics insulation and the MI cables 58 extends externally of the core through cable protection tubes 50. An electromagnetic motor may be utilized for the electromagnetic coils 57, but in both uses, it is necessary for these elements to be composed as a high temperature sealed structure. Since the upper control rod driving mechanism 33 is mounted on the control rod driving mechanism fixing pedestal 31 formed with a plurality of steam passing holes 30, these members 33 and 30 can be entirely taken out of the core at the time of the periodical inspection. FIG. 12 is a perspective view showing the separators 29 each having a vertical long length and formed integrally with the control rod guide tube shown in FIG. 1. The separator 29 comprises cylindrical separator bodies 59 standing from the shroud head 25, cross-shaped control rod guide tubes 60 and the separator supporting plate 61. A labyrinth 62 is provided for the penetrating portion of the control rod driving shaft 55 above the cross-shaped control rod guide tube 60 for preventing the water coolant from rising upward. Further, it is to be noted that the core shown in FIG. 12 at the lower portion therein represents another embodiment of the present invention and shows a case of the application of the present invention to the conventional core, and the cross-shaped control rod guide tube is inserted into a central space between four adjacent fuel assemblies. An example of a large-sized T-shape lattice core will be shown in FIG. 14. FIG. 13 is an elevational section for showing axial dimensions of the respective members or elements disposed in the reactor pressure vessel 20 shown in FIG. 1. In FIG. 13, the longitudinal lengths L1, L2 and L3 of the core 21, the control rod 23 and the control rod driving shaft 55 are made approximately equal to each other, so that when the length of the core 21 is shortened by a length of X, the entire length of the reactor pressure vessel 20 is made shortened by the length of 3X. Namely, the vertical length, i.e. height, of the reactor pressure vessel 20 and, hence, the reactor building, can be shortened by three times by shortening the length of the core 21. FIG. 14 is a perspective view for showing a state in which the control rod 23 inserted between the fuel assemblies 22 in the large-sized T-shape lattice core 21 is withdrawn upwardly by some extent. In FIG. 14, the cross-shaped guide pads 63 and flat plate-like guide pads 63a shown in FIG. 5 are fixed to the longitudinal side surfaces of the large-sized channel box 47 in which the fuel rods are accommodated. The control rod 23 has an upper portion to which are formed coupling grooves 64 to which the control rod driving shaft 65 is mounted. The control rod 23 has blade portions 65 in a comb shape extending downward from the cross-shaped base portion 23a. Each of the blade portions 65 has a cluster structure to be inserted between a slender gap 66 between the cross-shaped guide pad 63 and the flat plate-like guide pad 63a. The control rod 23 is mounted or dismounted through the gaps 66 positioned to the outer sides of the channel box 47 as guide grooves. FIG. 15 is a perspective view of one jet pump 36 shown in FIG. 1. The jet pump 36 has a two staged structure (multi-nozzle structure) having a first stage nozzle 67 and a second stage nozzle 68 for obtaining a high flow magnification ratio (M ratio). In FIG. 15, reference numeral 69 denotes a first stage throat, 70 is a second stage throat and 71 is a diffuser connected to the second stage throat. FIG. 16 is a system diagram of a supply water driving jet pump system 72 utilizing the jet pump 36 of FIG. 15. The system 72 is composed of a low pressure condensate pump 73, a condensate desalting filter 74, a high pressure condensate pump 75, a supply water heater 76, supply water pump chamber 77, a jet pump driving pump 78 and the jet pump 36. The water level in the reactor pressure vessel 20 is adjusted to a predetermined level by controlling, by means of a water level control valve 79, a flow rate of the water to be supplied to a supply water sparger 80 for controlling the water level. A check valve 81 is provided for the supply water system in consideration of an accidental pump trip. FIG. 17 is a system diagram showing a system including a steam injector driving jet pump system 82 and a high pressure water supply system 83. The steam injector driving jet pump system 72 is a system in which a recirculation steam injector 84 is substituted for the jet pump driving pump 78 in the supply water jet pump system 72 of FIG. 16. The recirculation steam injector 84 is operated by a discharge water from the high pressure condensate pump 75 and a steam 85 for driving the steam injector extracted from the main steam tube or high pressure stage of a main turbine. At the operation start time, an overflow water is discharged to a drain tube 87 through a start escape valve 86. The water supply to the recirculation steam injector 84 is performed on an upstream side of the supply water heater 76 because the recirculation steam injector 84 is itself provided with a function of the supply water heater 76. While, the steam injector high pressure water supply system 83 is operated in the use of the high pressure supply water injector 88 by a supply water from a condensate storage tank 89 and the steam 85 extracted from the main steam tube or high pressure stage of the main turbine. The steam injector high pressure water supply system 83 is operated as reactor core isolation cooling (RCIC) system at a time of a trip or isolation of the reactor and also operated as an emergency core cooling system (ECCS) at a time of loss of coolant accident (LOCA). The steam injectors 84 and 88 are not equipped with any movable portions therein and hence are kinds of stationary type fluid pumps having an extremely compact structure. Furthermore, these steam injectors 84 and 88 do not require an AC power source for driving and an emergency diesel generator at the operation period thereof, thus being advantageous when applied to a reactor power plant. The steam injector high pressure supply water system is operated by a pool, as a water source, inside or outside the reactor containment vessel. FIG. 18 is a block diagram showing that actual equipments and machineries such as various kinds of system and incore assemblies arranged in the boiling water reactor are selected from the basic design concept of "Gentle For Worker" through design objectives. From this block, diagram it will be apparent that these equipments and machineries are selected remarkably in view of the concept of "Gentle For Worker" with respect to the workers for the periodical inspections, operators of a reactor, power supply firms, residents, environment and etc. In this block, the abbreviations PCV, RPV, DG, MSIV, JP, SI, CRD, RCIC, ECCS and RIP denote a reactor containment vessel, a reactor pressure vessel, an emergency deasel generator, a main steam isolation valve, a jet pump, a steam injector, a control rod driving mechanism, a reactor core isolation cooling system, an emergency core cooling system and internal pump, respectively. FIG. 19 is an elevational view of a reactor for comparison having a right half representing the structure according to the present invention and a left half representing a conventional structure with a chain and dot line .PHI. being the center line. In the right half structure, the control rod driving mechanism is not disposed below the reactor pressure vessel 20, so that the height of the reactor building can be reduced by an amount of, about 10 m, shown with a large arrow, corresponding to a height of the control rod driving mechanism handling machine 17 in the conventional structure of the left half. Furthermore, according to the structure of the present invention, since no duct or machinery penetrating the bottom of the reactor pressure vessel 20 exists, it is not necessary for the workers or operators to perform the removal or inspection of the machineries at a portion below the reactor pressure vessel for maintenace, thus being advantageous as "Gentle For Worker". Still furthermore, the reactor core 21 according to the structure of the present invention is positioned at a portion lower than that 2 in the conventional structure, so that the space for arranging machineries such as separators 29 above the core 21 can be ensured, whereby the separators having relatively long lengths can be disposed, thus realizing a reactor having wide allowance range with respect to the water level change in the core.
044951450	abstract	A feeding apparatus for the loading of the spherical nuclear fuel into a fuel rod. The apparatus feeds fuel of three different diameters into a fuel rod so that the three different sized spheres are appropriately packed to achieve sufficient density of fuel to be used in a nuclear reactor.
056125437	summary	BACKGROUND OF THE INVENTION 1. Field of Invention This invention relates to shipping baskets and casks for storing and transporting spent nuclear waste materials, and particularly to multi-purpose baskets and casks for transporting, storing, and disposal of boiling water reactor (BWR) plants waste spent fuel and other waste materials. 2. Description of the Related Art Various baskets and casks have been proposed and implemented for transporting, storing, and disposal of nuclear waste material. However, previous baskets and casks have been limited by durability, cost, and failure to meet stringent regulatory criteria. The present invention overcomes all such limitations by providing a multi-purpose basket which is a separate component of and not integral with a cask which is typically used to encompasses a fuel basket. A nuclear reactor operates by initiating, maintaining and controlling fission chain reactions. These reactions occur within fissionable material such as Uranium 235 placed within the core of the reactor. In commercial type reactors, nuclear fuel is most often configured in the form of fuel assemblies, which are approximately 12-15 feet long and have a square cross section. Nuclear fuel is both loaded into and removed from the nuclear reactor one assembly at a time. Since the nuclear reactor operates generating fission chain reactions, the nuclear fuel within a fuel assembly gradually becomes depleted and fission product contaminants build up until it reaches the point that it is no longer capable of maintaining the chain reactions necessary for operation of the reactor. When this occurs, the fuel assembly is removed from the reactor and replaced by a new fuel assembly. The depleted or spent fuel assembly, although incapable of maintaining the fission chain reaction in the reactor, is still highly radioactive and generates a significant amount of heat. Typically, a spent fuel assembly is stored in a pool of water called a spent fuel pool for a period of time after it is removed from the reactor, until temperatures and radioactivity levels have decreased enough to make it safe to move to another form of storage, or transport to a facility for reprocessing or disposal of the spent material. After a spent fuel assembly has cooled sufficiently to permit its transfer, one of several alternative events may occur. The fuel assembly may be packaged and moved to another location on the reactor site for interim storage, or it may be packaged and transported to a remote site, sometimes at a long distance from the reactor site, for reprocessing, storage, or disposal. One type of nuclear power plant is a plant which allows water in the reactor to boil to produce steam which drives a turbine generator to produce electricity. This type of plant is referred to as a boiling water reactor (BWR) plant. The fuel assemblies used within BWR reactors have particular characteristics such as size and composition that make them unique with respect to fuel assemblies from other types of nuclear reactors. Although prior baskets and containers have been proposed and developed to store or transport nuclear fuels all suffer significant limitations and disadvantages. For example, U.S. Pat. No. 4,827,139 issued to Wells et al. discloses a cylindrical cask which contains a fuel basket composed of independent tubes. Such basket is integral with the cask, i.e. the basket is not a separate component, it is not separately sealed, and it cannot be removed from the cask after fuel has been loaded into it. The basket of Wells et al., for example, is capable of containing 31 fuel assembles of an unnamed type, while the basket of the present invention may hold 61 boiling water reactor fuel assemblies. Moreover, the present invention comprises a multi-purpose basket which is a separate component not integral with a cask. After fuel assemblies have been loaded into the basket of the present invention, the basket is sealed and may be placed within and removed from various types of casks, such as storage casks, transportation casks, or transfer casks, thereby enabling the basket to be used for many different applications. While other baskets have been proposed and configured to act as a separate and removable component of casks all differ significantly from the present invention by using a different basket structure than the sleeve type structure disclosed herein and are restricted to accommodating fewer fuel assemblies. The present invention encompasses a multi-purpose, sealed, fuel basket which secures and contains boiling water reactor type fuel assemblies. The basket of the present invention may be used for various applications including: 1. Storage of contained fuel assemblies inside of a storage cask for storage either at the reactor site of at a remote site. 2. Transporting of contained fuel assemblies from one location to another inside a transportation cask over public or private transportation routes. 3. Transfer means for transferring the contained fuel assemblies inside of a transfer cask between the spent fuel pool, a storage cask, and a transportation cask. 4. Disposal means for the disposal of spent nuclear fuel used in a facility or facilities constructed for the disposal of spent nuclear fuel. The basket of the present invention provides a means to meet the very stringent set of criteria that has been established by regulatory authorities in order to ensure safety during the transportation and storage of nuclear fuel assemblies. The basket is specifically designed and constructed to ensure that the nuclear chain reaction is maintained below critical limits, and harmful radiation does not escape. The basket configuration assures that these conditions are maintained even under extreme circumstances such as accidents, geologic stress, pressure, and the like. Accordingly, it is the primary object of this invention to provide a basket for the containment of nuclear waste from nuclear reactors which is extremely durable, resilient, easy to use, store, transport, and contain, and which is adaptable to a wide variety of storage casks, transportation casks, transfer casks, and contained fuel assemblies. Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentality's and combinations particularly pointed out in the appended claims. SUMMARY OF THE INVENTION To achieve the foregoing objects, and in accordance with the purpose of the invention as embodied and broadly described herein, a basket for transporting, storing, and containing nuclear fuel assemblies is provided having an assembly of sleeves with a plurality of sleeves arranged in a uniform pattern and secured within a cylindrical shell. Each of the plurality of independent sleeves being sized to secure and contain a fuel assembly. A plurality of alternating sleeves of the plurality of independent sleeves are configured to include an angular shaped separator element secured to each corner of each of the plurality of alternating sleeves. A sheet of neutron absorbing material is positioned between each of the plurality of alternating sleeves for maintaining fission reactions within the basket below a critical level necessary to sustain a fission reaction. A support element for positioning and securing the plurality of independent sleeves is secured within the cylindrical shell. A bottom plate is secured to the bottom of the cylindrical shell providing vertical support for the plurality of independent sleeves. A shield lid is secured to the cylindrical shell and includes a plurality of disc elements and an access port for selective entry into the basket and a lid element is secured to the shield lid and to the cylindrical shell. The lid element includes an access port for selective entry into the basket. There is also provided, in accordance with the invention a basket for a cask for transporting, storing, and containing nuclear fuel assemblies, comprising: an assembly of sleeves having a plurality of sleeves arranged in a uniform pattern and secured within a cylindrical shell. Each of the plurality of independent sleeves being sized to secure and contain a fuel assembly; a plurality of alternating sleeves of the plurality of independent sleeves each being configured to include an angular shaped separator element secured to each corner of each of the plurality of alternating sleeves. A neutron absorbing means for absorbing neutrons is positioned between each of the plurality of alternating sleeves for maintaining fission reactions within the basket below a critical level necessary to sustain a fission reaction. Support element means are provided for positioning and securing the plurality of independent sleeves. A bottom plate secured to the cylindrical shell providing vertical support means for the plurality of independent sleeves. Shield means for providing a shield element for the cylindrical shell are provided and secured to the cylindrical shell including a plurality of disc elements and access means for selective entry into the basket. Lid means for providing a lid element are secured to the shield means and to the cylindrical shell. The lid element including access means for selective entry into the basket.
	summary
	description	The present invention relates to the field of radioisotopes production, and more particularly to an apparatus and a method for the production of Molybdenum-99 and other radioisotopes. During the last years, the world of Nuclear Medicine has experienced a number of times severe shortages of radioisotopes for different diagnostic procedures. The most prominent of these radioisotopes is Molybdenum-99 (Mo-99) which is used as a precursor for Tc-99m. This latter isotope is used in more than 80% of nuclear imaging tests for detecting cancer, heart disease and other medical conditions. Each day, hospitals and clinics around the world use Mo-99/Tc-99m in more than 60,000 diagnostic procedures. As for now, the state-of-the-art technology for producing the most important radioisotopes for nuclear medicine (such as Mo-99, I-131, I-125, Xe-133) is based on irradiation of highly enriched uranium (HEU) targets in dedicated nuclear reactors. More than 95% of the present world production of Mo-99 employs neutron fission (n,f) process. It uses an intense thermal neutron beam from a nuclear reactor irradiating a HEU (U-235) target thus producing Mo-99 in 6.161% of all fission events according to the following reaction:U-235+n=Mo-99+Sn13x+νn (Eq. 1) The irradiation of 1 g of U-235 target for 7 days in a typical thermal neutron flux of 71013 n/cm2/s results in approximately 140 Ci of Mo-99 with very high specific activity of more than 104 Ci/g Mo. However, it should be pointed out that the Mo-99 production from the neutron fission (n,f) of U-235 requires very elaborate and very expensive processing facilities. In addition, extreme precautions must be taken to avoid contamination of the Mo-99 with highly toxic fission products and transuranics. This results in high capital investment and running costs, which, in turn, yields in the high cost of producing 1 Ci (n,f) fission Mo-99 being more than four times higher than the cost of 1 Ci of Mo-99 by other methods. In addition, this approach suffers from two main global problems. The first is that all such five nuclear reactors (one in Canada, three in Europe, and one in South Africa) producing together roughly 90% of the global Mo-99 requirements are very old (“geriatric”) reactors with an average age of 47 years. As a result, these reactors are frequently shut down for unscheduled and time-consuming repair and routine maintenance and, in any case, all of them are close to total decommissioning. The second problem is that the US administration recently began to oppose vigorously the use of HEU for production of radioisotopes because its use endangers the Nuclear Non-Proliferation Treaty (NPT) and nuclear safety in general. As of now, there is no generally accepted scientific and technological strategy to exit this crisis. One of the proposals mentioned recently is to check the possibility of using a photo-fission (γ,f) reaction by means of a high-power electron linear accelerator instead of thermal neutron fission in a nuclear reactor. In other words, this method relates to electron accelerator production of Mo-99 via the (γ,f) reaction on uranium target instead of the (n,f) reaction in nuclear reactors. In the case of photo-fission, there is no need in HEU since the natural or, at the most, low enriched uranium (LEU) can be used for this purpose. The Mo-99 producing reaction, in this case, can be summarized by the reaction below:U-238+γ=Mo-99+Sn13x+ν*n (Eq. 2) The other possibility is based on the photo-neutron, i.e. (γ,n), process in which the heaviest stable isotope of molybdenum, Mo-100 (isotopic abundance of 9.63%), has been irradiated by bremsstrahlung photons from an electron linear accelerator target. The Mo-99 producing reaction, in this case, can be summarized by the reaction belowMo-100+γ=Mo-99+n (Eq. 3) Both in the case of the (γ,f) and (γ,n) reactions, the source of gamma radiation is a linear accelerator of electrons with an energy up to 50 MeV and an electron beam power up to 500 kW. The target of such accelerator, which converts the kinetic energy of an accelerated electron beam into bremsstrahlung (braking radiation) should be chosen from the high atomic number (Z) metals such as 73Ta, 74W, depleted U, in order to maximize the bremsstrahlung yield. In such a case, a target to be irradiated, the isotope Mo-100 (for production of radioisotope Mo-99/Tc-99m) has to be attached to the source of the bremsstrahlung target (converter) assembly as close as possible. However, because of the low efficiency of bremsstrahlung production and because of the considerable self absorption of the produced bremsstrahlung radiation in high-Z body of the bremsstrahlung target, this target must effectively be cooled down by distilled water under pressure. All this does increase the distance between the bremsstrahlung source and the sample to be irradiated (Mo-100) and significantly decreases the yield of Mo-99 production. Techniques and apparatus for the production of radioisotopes can be found for instance in the following publications: U.S. Pat. No. 5,784,423 relates to the production of radioisotopes by exposing a targeted isotope in a target material to a high energy photon beam to isotopically convert the targeted isotope. In particular, the invention is used to produce Mo-99 from Mo-100. U.S. Pat. No. 5,802,439 relates to the production of 99mTc compositions from 99Mo-containing materials. The art has so far failed to provide an efficient method and system to overcome the aforementioned drawbacks of the prior art. It is therefore an object of the present invention to provide an apparatus for producing Mo-99 radioisotope. It is a further object of the invention to provide a method for the production of Mo-99 radioisotope. These and other objects of the invention will become apparent as the description proceeds. In one aspect the invention is directed to a method for producing molybdenum-99 comprising: i) providing an electron accelerator; ii) providing a molybdenum converter/target unit (Mo-CTU) comprising one or more metallic components, wherein each one of these metallic components is made of a material selected from the group consisting of natural molybdenum, molybdenum-100, molybdenum-98, and mixtures thereof; iii) directing an electron beam generated via said electron accelerator onto said Mo-CTU to produce a braking radiation (bremsstrahlung); iv) employing said bremsstrahlung onto said Mo-CTU to produce molybdenum-99 and neutrons via a photo-neutron reaction; v) slowing down the neutrons produced in step iv) with a low atomic liquid, e.g. distilled water; and optionally vi) employing the neutrons produced in step iv) to produce a complementary amount of molybdenum-99 via a neutron capture reaction on said Mo-CTU. Typically, production and accumulation of the isotope Mo-99 is carried out in the Mo-CTU itself located inside the target assembly of the linear accelerator. In one embodiment of the invention the high fluxes of high energy bremsstrahlung photons and neutrons that are found around the target assembly outside the accelerator are used to produce other radioactive isotopes via the (γ,n) and (n,γ) reactions on the appropriate target materials placed outside the accelerator target assembly and adjacent to it. For instance, an external target of the stable isotope Xe-124 can be used to produce simultaneously the primary radioisotope Mo-99 inside the accelerator Mo-CTU and two radioisotopes of iodine: I-123 via the (γ,n) reaction and I-125 via the (n,γ) reaction. Furthermore, the short-lived radioisotopes F-18, O-15, N-13, and C-11 (which are used for instance in Positron Emission Tomography or PET) can be produced by placing an external target of the appropriate stable isotope adjacent to the accelerator target assembly. In a further embodiment of the invention the high flux of high energy bremsstrahlung photons exiting the accelerator target assembly is used for photo-fission (γ,f) of LEU samples placed outside the accelerator target assembly and adjacent to it. In another aspect the invention is directed to apparatus for producing molybdenum-99, comprising: a) an electron accelerator; b) a molybdenum converter/target unit (Mo-CTU) comprising one or more metallic components, wherein each one of these metallic components is made of a material selected from the group consisting of natural molybdenum, molybdenum-100, molybdenum-98, and mixtures thereof; c) means for directing an electron beam generated via said electron accelerator onto said Mo-CTU to produce a braking radiation (bremsstrahlung); d) means for directing said bremsstrahlung onto said Mo-CTU to produce molybdenum-99 and neutrons via a photo-neutron reaction; and e) a low atomic number liquid, e.g. distilled water, for slowing down the neutrons produced in step d). Reference is made to FIG. 1. To overcome the drawbacks of the prior art, the present invention employs a bremsstrahlung producing converter/target unit made from molybdenum (Mo-CTU). In this way, the molybdenum target to be irradiated with the bremsstrahlung is ideally located in the bremsstrahlung radiation focus, thus maximizing the production of Mo-99 via the (γ,n) reaction. In addition, the use of molybdenum directly as a bremsstrahlung converter/target unit enables using the neutrons produced by the reactions (γ,n), (γ,2n), (γ, pn), and so on, for the complementary production of Mo-99 via the (n,γ) reaction on the isotope Mo-98 (when present in the Mo-CTU, for instance in natural molybdenum or in pure form Mo-98):Mo-98+n=Mo-99+γ (Eq. 4) Isotopic abundance of the isotope Mo-98 in natural molybdenum is 2.5 times higher than that of Mo-100 and amounts to 24.13%. It means that in such a case, Mo-99 will be produced simultaneously from the two stable isotopes of molybdenum: both from Mo-100 (9.63%) via the (γ,n) reaction and from Mo-98 (24.13%) via the (n,γ) reaction. It should be pointed out that in order to maximize the second channel for the Mo-99 production via the (n,γ) reaction, the neutrons from the first (neutron producing) channel should be slowed down to the epithermal/thermal energy interval. For this purpose, a low atomic number liquid, e.g. distilled water, which was intended primarily for cooling down of the target assembly of the electron linear accelerator can be used for neutron slowing down too. In the method of the invention, production and accumulation of the isotope Mo-99 has been carried out in the Mo-CTU itself located inside the target assembly of the linear accelerator. Therefore, high fluxes of high energy bremsstrahlung photons and neutrons (many MeV's energy range) are found around the target assembly outside the accelerator. These high energy bremsstrahlung photons can be used to produce some other very important radioactive isotopes via the (γ,n) reaction on the appropriate target materials placed outside the accelerator target assembly and adjacent to it. For example, placing an external target of the stable isotope Xe-124, enables the simultaneous production of the primary radioisotope Mo-99 (inside the accelerator Mo-CTU) and of two important radioisotopes of iodine: I-123 via the (γ,n) reaction and I-125 via the (n,γ) reaction. Moreover, short-lived radioisotopes like F-18, O-15, N-13, and C-11 for use in Positron Emission Tomography (PET) can be also produced in this way by placing an external target from an appropriate stable isotope adjacent to the accelerator target assembly. All this occurs simultaneously with the production and accumulation of the primary radioisotope Mo-99 in the Mo-CTU inside the linear accelerator. In addition, the high flux of high energy bremsstrahlung photons exiting the accelerator target assembly can be used for photo- fission (γ,f) of LEU samples placed outside the accelerator target assembly and adjacent to it. It should be pointed out that the photonuclear accelerator-based technique in general has several advantages: 1) natural or depleted uranium (U-238) target can be used, thereby obviating problems of security and NPT; 2) the electron accelerator can be turned on and off at will; 3) an electron accelerator is inexpensive to decommission at end-of-life; 4) the electron accelerator-based technology promises to be scalable. All the above description has been provided for the purpose of illustration and is not intended to limit the invention in any way. As will be apparent to the skilled person the invention allows exploiting different products of the reaction, and to use different targets, all of which results in a flexible, safe and economic method and system.
	description	The drive assembly of the present invention provides several advantages over prior art drive mechanisms. By combining the driving mechanism with the slide or shaft on which a driven member travels, one can eliminate relative movement between the driver and the driven member. This arrangement reduces the number of independently mounted parts which must be independently secured and provides a more smooth movement of the driven member. Such a drive assembly is particularly useful in precision drive mechanisms, including the drive mechanisms used in imaging equipment in which beam collimation is carried out by movement of a slit plate relative to an x-ray beam. Movement of the slit plate must be accurate, repeatable and precise throughout all operating speeds and temperatures of the imaging equipment. FIG. 1 illustrates a collimator assembly 10 of an x-ray imaging apparatus which includes a drive assembly 12 according to the invention. The assembly includes a base 14, which is typically made of cast and machined aluminum or brass. The base includes an aperture 16 for admission of a radiation beam from a focal spot of an x-ray source (not shown). A first shaft. 18 is secured to blocks or pads 20 at one side of the aperture on the base with screws or like fasteners 22. A driver 24, shown in FIG. 1 as a stepper motor 24a with associated controller circuitry 24b, is also mounted to the base. The driver is rotatably coupled to a second shaft 26 which is substantially parallel to the first shaft 18. A carrier 28 extends between the shafts and is disposed over the aperture 16 in the base. The carrier is adapted to slide along the shafts 18, 26 in the direction of z axis 30 and is preferably made of cast aluminum or brass. According to the invention, the second shaft 26 is coupled to the driver 24 via a backlash-resistant nut assembly 32. As shown in FIG. 2, the second shaft 26 includes a nonthreaded portion 34 and a threaded portion 36. The non-threaded portion 34 of the shaft 26 is adapted for sliding engagement with the carrier, whereas the threaded portion 36 engages with the nut assembly 32, which is fixed to the carrier 28. The nut assembly 32 is shown in FIG. 3 and includes a first nut portion 38, a second nut portion 40, and a wave washer.42 disposed between them. The first-nut portion 38 has a threaded bore 44 which engages with the threaded portion 36 on the second shaft 26. The second nut portion 40 also has a threaded bore 41 which engages with the threaded portion 36 of the second shaft. The assembly also includes fasteners 46, such as dowel pins, which fit into holes 48 in the first nut portion and slots 50 in the second nut portion. The fasteners join the nut portions together around the wave washer 42, which biases the first and second nut portions away from each other. Means for biasing the nut portions apart other than a wave washer can be used, such as a coiled compression spring. The combined tension and compression of the nut assembly which is created by the counteracting forces of the wave washer 42 and the joined first and second nut portions 38, 40 eliminates substantially all play between the threads of the nut assembly and the threaded portion 36 of the second shaft and prevents any backlash in the movement of the nut over the threaded portion of the shaft 26. The first nut portion 38 includes counterbored holes 52 for receiving fasteners or screws for joining the nut assembly to the carrier, as shown in FIG. 1. The first and second nut portions of the assembly are preferably made of an easily machinable metal, such as brass or phosphor bronze. To reduce friction and facilitate smooth movement of the carrier over the shafts, a ball bearing sleeve 54 may be disposed over each of the shafts. A typical ball bearing sleeve is illustrated in FIG. 4 and in phantom on the shaft of FIG. 2. The ball bearing sleeve 54 includes several apertures extending through the wall of the sleeve. A ball bearing is disposed in each aperture and is movable therein without becoming disengaged from the aperture, so that the ball bearing seems to float within the apertures. The ball bearings provide rolling contact between the shaft inside the sleeve and the carrier outside of the sleeve and substantially reduce the friction between these components. The collimator assembly 10 includes a slit plate 56 which is disposed in the carrier 28 so as to be positioned over the beam aperture in the base. The slit plate 56 includes multiple slits 57 having different widths, for defining beams of different thicknesses in the z direction. The carrier and slit plate move along z axis 30 in response to travel of the nut assembly 32 over the second shaft 26. A mask plate 58 is fixed to the base beneath the carrier 28 and is disposed over the aperture 16 in the base. The mask plate includes a single slit 60. In operation, the carrier 28 is moved in the z axis direction by operation of the motor 24a so that one of the slits 57 in the slit plate 56 is aligned with the slit 60 in the mask plate, thereby allowing a collimated beam of radiation to pass through the aperture in the base to an object to be scanned and to a detector bank (not shown) beyond the object to be scanned. The motor 24a preferably comprises a stepping motor controlled by a controller 24b having a counter for calculating which of the plurality of slits 57 of the collimator 56 is aligned with the slit 60 of the mask plate 58 based upon the stepped rotation of the motor. A suitable controller and counter combination is shown, for example, in U.S. Pat. No. 5,550,886 to Dobbs et al. entitled xe2x80x9cX-ray Focal Spot Movement Compensation Systemxe2x80x9d, which is assigned to the assignee of the present disclosure and which is incorporated herein by reference in its entirety. Referring now to FIGS. 5 through 8, an alternative carrier 70 and drive shaft assembly 72 for use with the collimator assembly of FIG. 1 is shown. Referring to FIG. 5, the carrier 70 is preferably made of cast aluminum or brass and includes a first support member 74 having a bore 75 for slidingly receiving the ball bearing sleeve 54 of the first shaft 18. The carrier 70 also includes second and third spaced-apart support members 76, 78 having bores 77, 79, respectively, for slidingly receiving linear-rotary bearings 80 of the drive shaft assembly 72 of FIG. 7. The second and third support members 76, 78 are each relatively-wide, and provide additional stability for the carrier 70 as the carrier slides on the drive shaft assembly 72. The second support member 76 includes an annular recess 82 and fasteners holes 84.for receipt of the backlash resistant nut assembly 32. As shown, the annular recess 82 faces the third support member 78 such that, when assembled, the nut assembly 32 is positioned between the support members 76, 78 to provide further stability. Referring to FIG. 7, the drive shaft assembly 72 includes a second shaft 86, which is similar to the second shaft 26 of FIGS. 1 and 2, for supporting the carrier 70 on the base 14 of the collimator assembly 10. The second shaft 86 includes a first end 88 that is formed to be coupled to the driver 24 for turning the shaft. The shaft 86 also includes journals 90 adjacent opposite ends of the shaft, a centrally located threaded portion 92, and non-threaded portions 94 between the threaded portion and the journals. As shown in FIG. 7, each of the non-threaded-portions 94 of the shaft 86 slidingly and rotatingly receive the linear-rotary bearing 80, which are in turn for being received in the bores of the support members 76, 78 of the carrier 70. The threaded portion 92 of the shaft 86 engages with the backlash resistant nut assembly 32, which is in turn for-being fixed to the annular recess 82 of the third support member 78 of the carrier 70. Each linear-rotary bearing 80 includes an inner ball bearing sleeve 54 received on the shaft 86, and an outer sleeve 96 received on the inner ball bearing sleeve, as also shown in FIG. 8. The linear-rotary bearings 80 allow the shaft 86 to rotate with respect to the support members 76, 78 of the carrier 70 as the motor 24 turns the shaft 86. The linear-rotary bearings 80 also allow the support members 76, 78 of the carrier 70 to linearly slide with respect to the shaft 86 as the backlash resistant nut assembly 32 moves along the threaded portion 92 of the shaft 86. Preferred linear-rotary bearings are available, for example, from Berg Manufacturing of East Rockaway, NY (http://www.wmberg.com). Referring again to FIG. 7, the drive shaft assembly also includes rotary bearings 100, and a thrust bearing 102 received on the journals 90 of the second shaft 86 for rotatably mounting the drive shaft assembly 72 on the base 14 of the collimator assembly 10. Because certain changes may be made in the above apparatus without departing from the scope of the invention herein disclosed, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted in an illustrative and not a limiting sense.
053923235	abstract	The reactor pressure vessel comprises a pipe socket (2) connected to a feed-water supply line (3), in which is disposed a coaxial protective sleeve (5) (thermal sleeve) which expands with changes in temperature. With its outer end the protective sleeve (5) slidably abuts the pipe socket (2) and with its inner end it is connected to a feed-water distributing ring situated in the vessel. A pipe section (10), in which bellows (15) are disposed, is inserted between the outer end of the pipe socket (2) and the feed-water supply line (3). With one end the bellows (15) are tightly connected to the outer end of the protective sleeve (5) and with their other end they are tightly connected to the pipe section (10).
	description	This application is a 35 U.S.C. §371 national stage application of International Application No. PCT/US2012/027525, filed Mar. 2, 2012, the entire contents of which is incorporated herein by reference. In a nuclear reactor, a core of nuclear material is confined to a small volume internal to the reactor so that a reaction may occur. In many instances, a controlled nuclear reaction may persist for an extended period of time, such as several years or even longer, before refueling of the nuclear core is required. Accordingly, when used as a source of heat for converting quantities of water into steam, a properly designed nuclear reactor may provide a long-lasting, carbon-free, and highly reliable source of energy. Relatively small, modular or standalone nuclear reactors may be built in a manufacturing environment and transported to a reactor bay at a power generating facility that is far removed from the manufacturing location. A group of modular nuclear reactors of the same design may be aggregated at the power generating facility to provide a multiple of the power output of a single, standalone reactor module. This allows additional modules to be placed into service over time so that the output of a power generating station may be incrementally increased to keep pace with a growing demand for electrical power. For example, a power generating station that initially employs two nuclear reactor modules servicing a small town may incorporate additional modules in several increments as the town increases in size and the demand for electrical power increases correspondingly. When refueling a nuclear reactor module, a servicing crew may disassemble various reactor components so that spent fuel can be removed and stored in a spent fuel pool. In addition to loading fresh fuel into the reactor, the servicing crew may be required to perform additional maintenance operations. These operations may include inspecting the reactor module components for excessive wear, leak testing of components that operate under pressure, and inspecting structural and load-bearing components for stress cracks. In some instances, it may be useful to perform such servicing at a location separate from the reactor's normal operating bay. In a general embodiment, a method of servicing a nuclear reactor module includes decoupling one or more sensors of the nuclear reactor module from a first sensor receiver, followed by coupling the one or more sensors of the nuclear reactor module to a second sensor receiver, and moving the nuclear reactor module from a first location, such as a reactor bay, to a second location, such as a servicing area. A first aspect combinable with the general embodiment includes displaying a representation of at least one signal from the one or more sensors of the nuclear reactor module on a display located within a servicing area. In a second aspect combinable with any of the previous aspects, the representation of the at least one signal from the one or more sensors of the nuclear reactor module may be displayed on a display located in a reactor operator area. In a third aspect combinable with any of the previous aspects, the coupling may further include transmitting signals from the one or more sensors of the nuclear reactor module through a conduit located on a crane coupled to the nuclear reactor module to the second receiver. In an aspect, which may be combinable with any previous aspect, the decoupling and coupling occur in a sensor-by-sensor manner wherein a first sensor of two or more sensors of the nuclear reactor module is decoupled from the first sensor receiver and coupled to the second sensor receiver prior to a second sensor of the two or more sensors of the nuclear reactor module being decoupled from the first sensor receiver. In an aspect of an embodiment, the method may further include comparing a signal level from the first sensor received by the first sensor receiver with a signal level from the first sensor received by the second sensor receiver. Wherein, in an aspect that may be combinable with any previous aspect, if the signal level from the first sensor received by the first sensor receiver approximates the signal level from the first sensor received by the second sensor receiver, the method may include decoupling a second sensor from the first sensor receiver. In an aspect, which may be combinable with any previous aspect, the method may further include approximately continuously monitoring the nuclear reactor module during the moving using the second sensor receiver. In another embodiment, a system for servicing a nuclear reactor module includes a crane operable to couple to the nuclear reactor module, wherein the crane includes a conduit for routing signals from one or more sensors of the nuclear reactor module to one or more sensor receivers. In an aspect, which may be combinable with any previous aspect, the crane may include a drive mechanism operable to move the nuclear reactor module from a reactor bay to a servicing area. In an aspect, which may be combinable with any previous aspect, the drive mechanism may move the nuclear reactor module in a first direction and a second direction approximately orthogonal to the first direction. In an aspect, which may be combinable with any previous aspect, the crane may further include at least one support bracket for mounting one or more sensor signal receivers operable to receive signals from one or more sensors within the nuclear reactor module. In an aspect, which may be combinable with any previous aspect, the system may further include a display operable to display representations of signals from the one or more sensors of the nuclear reactor module in a servicing area and may further include a display operable to display representations of signals from the one or more sensors of the nuclear reactor module in an operator area. In another general embodiment, an apparatus includes a fastener operable to couple to a nuclear reactor module, an interface panel for accepting one or more signals from the nuclear reactor module, and a device operable to move the nuclear reactor module in a lateral direction. In a first aspect combinable with the general embodiment, the device is operable to move the nuclear reactor module in the lateral direction operates to move the nuclear reactor module in a first direction and a second direction approximately orthogonal to the first direction. A second aspect combinable with any of the previous aspects includes a track for maintaining a minimum bend radius of at least one conductor conveying the one or more signal. A third aspect, which may be combinable with any of the previous aspects, includes a controller for assisting and relocating a nuclear reactor module to a lower containment vessel removal fixture located in a servicing area. A fourth aspect, which may be combinable with any of the previous aspects, includes a conduit operable to hold a receiver that receives signals from one or more sensors located within the nuclear reactor module. Methods, apparatuses, and systems for servicing a nuclear reactor module are described. In one implementation, pressure, temperature, source range neutron count, and other operating parameters of the nuclear reactor module may be monitored while the module is in operation. In preparation for a refueling or other servicing operation, a first sensor receiver located outside of the nuclear reactor module may be decoupled from sensors located within the reactor module. The sensors within the nuclear reactor module may then be coupled to a second sensor receiver by way of an electrical, fiber-optic, or other type of bundle routed along a routing path that is attached to, or included within, an overhead crane. Upon coupling of the sensors within the nuclear reactor module to the second sensor receiver, the overhead crane may be activated to move the module from an operating bay to a servicing area. In another implementation, decoupling and coupling of sensors within the nuclear reactor module may occur in a sensor-by-sensor manner in which an output signal level from a first sensor located within a nuclear reactor module may be recorded prior to decoupling the first sensor from a first sensor receiver. The first sensor may then be coupled to a second sensor receiver. The output signal level recorded by the first sensor receiver may then be compared with the output signal level recorded by the second sensor receiver to determine if an error condition in the first or the second sensor receiver is present. An error condition may also result from a defect in wire or fiber optic cable bundle used to couple a sensor to a sensor receiver. In the event that an error condition is not present, the comparison process may be repeated for a second sensor located within a reactor module beginning with recording an output signal level from the second sensor, decoupling the second sensor from a first sensor receiver, and comparing the output signal level received by the first sensor receiver with the output signal level received by the second sensor receiver to determine if an error condition is present. In an implementation, an overhead crane may include an interface panel that receives output signals from two or more sensors within the nuclear reactor module prior to movement of the module. In this implementation, an operator may decouple the two or more sensors, as a group, from a first sensor receiver and couple the group of one or more sensors to a second sensor receiver by way of the interface panel. This allows the group of two or more sensors to be decoupled nearly simultaneously from a first sensor receiver and quickly coupled to a second sensor receiver. As used herein and as described in greater detail in subsequent sections, embodiments of the invention may include various nuclear reactor technologies. Thus, some implementations may include reactor technologies that employ pressurized water, which may include boron and/or other chemicals or compounds in addition to water, liquid metal cooling, gas cooling, molten salt cooling, and/or other cooling methods. Implementations may also include nuclear reactors that employ uranium oxides, uranium hydrides, uranium nitrides, uranium carbides, mixed oxides, and/or other types of radioactive fuel. It should be noted that embodiments are not limited to any particular type of reactor cooling mechanism, nor to any particular type of fuel employed to produce heat within or associated with a nuclear reaction. FIG. 1 shows a crane (110) fastened to a nuclear reactor module according to an implementation. In FIG. 1, reactor core 20 is positioned at a bottom portion of a cylinder-shaped or capsule-shaped reactor vessel 70. Reactor core 20 comprises a quantity of fissile material that produces a controlled reaction that may occur over a period of perhaps several years or longer. Although not shown explicitly in FIG. 1, control rods may be employed to control the rate of fission within reactor core 20. Control rods may comprise silver, indium, cadmium, boron, cobalt, hafnium, dysprosium, gadolinium, samarium, erbium, and europium, or their alloys and compounds. However, these are merely a few of many possible control rod materials. In implementations, a cylinder-shaped or capsule-shaped containment vessel 10 surrounds reactor vessel 70 and is partially or completely submerged in a reactor pool, such as below waterline 90, within reactor bay 5. The volume between reactor vessel 70 and containment vessel 10 may be partially or completely evacuated to reduce heat transfer from reactor vessel 70 to the reactor pool. However, in other embodiments, the volume between reactor vessel 70 and containment vessel 10 may be at least partially filled with a gas and/or a liquid that increases heat transfer between the reactor and containment vessels. Containment vessel 10 rests on skirt 100 at the base of reactor bay 5. In a particular implementation, reactor core 20 is submerged within a liquid, such as water, which may include boron or other additive, which rises into channel 30 after making contact with a surface of the reactor core. In FIG. 1, the upward motion of heated coolant is represented by arrows 40 within channel 30. The coolant travels over the top of heat exchangers 50 and 60 and is drawn downward by way of convection along the inner walls of reactor vessel 70 thus allowing the coolant to impart heat to heat exchangers 50 and 60. After reaching a bottom portion of the reactor vessel, contact with reactor core 20 results in heating the coolant, which again rises through channel 30. Although heat exchangers 50 and 60 are shown as two distinct elements in FIG. 1, heat exchangers 50 and 60 may represent any number of helical coils that wrap around at least a portion of channel 30. In another implementation, a different number of helical coils may wrap around channel 30 in an opposite direction, in which, for example, a first helical coil wraps helically in a counterclockwise direction, while a second helical coil wraps helically in a clockwise direction. However, nothing prevents the use of differently-configured and/or differently-oriented heat exchangers and embodiments are not limited in this regard. Further, although water line 80 is shown as being positioned just above upper portions of heat exchangers 50 and 60, in other implementations, reactor vessel 70 may include lesser or greater amounts of water. In FIG. 1, normal operation of the nuclear reactor module proceeds in a manner wherein heated coolant rises through channel 30 and makes contact with heat exchangers 50 and 60. After contacting heat exchangers 50 and 60, the coolant sinks towards the bottom of reactor vessel 70 in a manner that induces a thermal siphoning process. In the example of FIG. 1, coolant within reactor vessel 70 remains at a pressure above atmospheric pressure, thus allowing the coolant to maintain a high temperature without vaporizing (i.e. boiling). As coolant within heat exchangers 50 and 60 increases in temperature, the coolant may begin to boil. As the coolant within heat exchangers 50 and 60 boils, vaporized coolant, such as steam moving upward as indicated by arrows 51 and 61, may be used to drive one or more turbines that convert the thermal potential energy of steam into electrical energy. After condensing, coolant is returned to locations near the base of heat exchangers 50 and 60 as shown by arrows 52 and 62. During normal operation of the reactor module of FIG. 1, various performance parameters of the reactor may be monitored by way of sensors positioned at various locations within the module. In the example of FIG. 1, sensors within the reactor module may measure reactor system temperatures, reactor system pressures, containment vessel pressure, reactor primary and/or secondary coolant levels, reactor core neutron flux, and/or reactor core neutron fluence. Signals that represent these measurements may be reported external to the reactor module by way of bundle 120 to reactor bay interface panel 130. In one implementation, bundle 120 represents a multi-conductor cable. In another implementation, bundle 120 may represent a single- or multi-fiber optical transmission medium. In the implementation of FIG. 1, crane 110 is shown as being positioned above reactor bay 5. Crane 110 includes a cable or other device that fastens to attachment 105, which may include a lifting lug, eyelet, or other device that couples an upper portion of containment vessel 10 to crane 110. Thus, crane 110 operates to lift and suspend the nuclear reactor module of FIG. 1 in reactor bay 5. In implementations, crane 110 includes a motor or other drive mechanism that enables the crane to move laterally so as to allow the nuclear reactor module to be repositioned. Prior to the upward or lateral movement of the nuclear reactor module of FIG. 1, a connector at an end of bundle 120 may be detached from reactor bay interface panel 130, thereby decoupling one or more sensors operating within the reactor module from a first sensor receiver. In an implementation, bundle 120 may be attached to crane interface panel 135, thereby coupling the one or more sensors operating within the reactor module to a second sensor receiver by way of crane interface panel 135. In FIG. 1, crane 110 includes provisions for routing bundle 140 through, for example, conduit 137, along an outside surface of at least a portion of the crane, or within the structure of crane 110 for connection to receptacle 115. In an implementation, crane 110 includes a track for maintaining a minimum bend radius of bundle 140 while crane 110 moves from side to side. However, in other implementations, crane 110 may include a rack for festooning or hanging portions of bundle 140 from a surface. In an implementation, crane interface panel 135 may include, for example, at least one set of brackets or a conduit that holds one or more signal conditioning units or other sensor receivers that function to convert electrical and/or optical signals from sensors located within the reactor module of FIG. 1. In one possible example, bundle 120 may carry low-voltage signals from a thermocouple located within reactor vessel 70. Accordingly, crane interface panel 135 may include one or more of an amplifier, an analog to digital converter, and a multiplexer that converts and electrical signal conveyed on a conductor to an optical signal transmitted along a single-fiber or multi-fiber optical transmission medium represented by bundle 140. FIG. 2 is a top view showing 12 nuclear reactor modules that may be moved within a power generating station using an overhead crane according to an implementation. In FIG. 2, containment vessel 10 of a nuclear reactor module is shown within reactor bay 5. Crane 110 moves in both an X and Y direction along track 150, wherein X and Y represent orthogonal directions in a Cartesian coordinate system. In this manner, crane 110 may include a control capable of relocating or assisting in relocating a nuclear reactor module from reactor bay 5, along track 150, to servicing area 160 where the nuclear reactor module may be placed on or proximate with a lower containment vessel removal fixture. Prior to movement of a nuclear reactor module, sensors located within a reactor module may be decoupled from a first sensor receiver to a second sensor receiver by way of detaching a connector from a reactor bay interface panel to a crane interface panel, such as crane interface panel 135 of FIG. 1. FIG. 3 is a diagram of a nuclear reactor module coupled to sensor receivers and displays according to an implementation. In FIG. 3, sensors from nuclear reactor module 200 have been decoupled from sensor receiver 220 and operator display 230. In an implementation, operator display 230 represents one or more displays located in a reactor operator area. After such decoupling, sensors located within nuclear reactor module 200 are coupled to a second sensor receiver (240) by way of interface panel 235 of crane 210. After nuclear reactor module 200 has been coupled to sensor receiver 240, module 200 may then be relocated from, for example, a reactor operating bay to a servicing area. While module 200 is in transit from the reactor bay to the servicing area, sensors monitoring various parameters may continue to provide output signals representing the conditions within the module. Representations of these parameters may be displayed on servicing area display 240, thus providing real-time monitoring of conditions within reactor module 200 to a servicing crew. Additionally, representations of output signals reflecting the conditions within reactor module 200 may be displayed on operator display 230 These representations on operator display 230 may be accompanied by an identifier indicating that the module is “in transit” between and operating bay to a servicing area. FIG. 4 is a flowchart for a method for servicing a nuclear reactor module according to an implementation. The device of FIG. 3 may be suitable for performing the method of FIG. 4, although nothing prevents performing the method of FIG. 4 using alternate arrangements of components in other embodiments. Implementations may include blocks in addition to those shown and/or described in FIG. 4, fewer blocks, blocks occurring in an order different from FIG. 4, or any combination thereof. In the method described in FIG. 4, sensors are coupled from a first receiver to a second receiver in a sensor-by-sensor manner as described below. In an implementation, at least a portion of the method of FIG. 4 may be performed by a controller or other hardware or software based processing resource. FIG. 4 begins at block 300, which includes recording a signal level from a first sensor of a nuclear reactor module received by a first sensor receiver. At 310, the first sensor may be decoupled from the first sensor receiver. At 320, the first sensor may be coupled to a second sensor receiver. At 330, a signal level from the first sensor as received by the first sensor receiver is compared with the signal level from the first sensor has received by the second sensor. At 340, signal levels as received by first and second sensor receiver modules are compared. In the event that the comparison of block 340 indicates that the signal levels are within a limit, block 350 is performed in which a signal output from the next sensor received by a first sensor receiver module may be recorded. In the event that the comparison of block 340 indicates that the signal levels are outside of a limit, block 360 may be performed in which a troubleshooting routine may be performed. While several examples have been illustrated and described, it will be understood by those skilled in the art that various other modifications may be made, and equivalents may be substituted, without departing from the scope of the following claims.
	summary
054886341	summary	TECHNICAL FIELD The present invention relates to a lower tie plate grid for a nuclear reactor fuel bundle and particularly relates to a unitary one-piece lower tie plate grid forming part of a lower tie plate assembly, the grid having a lower portion with a plurality of small openings for separating debris from the flow of water coolant through the tie plate, and an upper portion which, in conjunction with the lower portion, support the fuel bundle. The grid is constructed to afford a minimum pressure loss for the water coolant flow through the tie plate grid into the region downstream of the tie plate assembly. BACKGROUND Boiling water nuclear reactors have been in operation for many years. Commencing with their initial construction and throughout their service lives, these reactors may accumulate debris in their closed circulation moderator systems. This debris can become an operating hazard if the debris is allowed to enter into the fuel bundle core region containing the heat generating fuel rods. In order to understand this problem, a summary of reactor construction as it relates to the accumulation of debris in the core needs first to be given. Thereafter, fuel bundle construction will be set forth. Emphasis will be given to the need to preserve substantially unchanged the regions of pressure drop within the fuel bundles. Thereafter, the effects caused by debris entering into the fuel rod region of the fuel bundles will be summarized. In boiling water nuclear reactor construction, the reactor is provided with a large, central core. Liquid water coolant/moderator flow enters the core from the bottom and exits the core as a water steam mixture from the top. The core includes many side-by-side fuel bundles, each containing a plurality of fuel rods. Water is introduced into each fuel bundle through a fuel bundle support casting from a high pressure plenum situated below the core. Water passes in a distributed flow through the individual fuel bundles and about the fuel rods, is heated to generate steam, and exits the upper portion of the core as a two-phase water steam mixture from which the steam is extracted for the generation of energy. The core support castings and fuel bundles are a source of pressure loss in the circulation of water through the core. By properly controlling such pressure losses substantially even distribution of flow across the individual fuel bundles of the reactor core is achieved. When it is remembered that there are as many as 750 individual fuel bundles in a reactor core, it can be appreciated that assurance of the uniformity of flow distribution is important. To interfere with the pressure drop within the fuel bundles could affect the overall distribution of coolant/moderator within the fuel bundles of the reactor core. The fuel bundles for a boiling water nuclear reactor include a fuel rod supporting lower tie plate assembly. Typically, this is a one-piece cast structure including an upper grid, a lower inlet nozzle and a structure providing a transition region from the inlet to the grid. The inlet nozzle provides for coolant entry to an enlarged flow volume within the flow transition region of the lower tie plate assembly. At the upper end of the flow volume, there is located a tie plate grid defining with the nozzle a flow volume. The tie plate grid has two purposes. First, it provides the mechanical support connection for the weight of the individual fuel rods to be transmitted through the entire lower tie plate assembly to the fuel support casting. Secondly, the tie plate grid provides a path for liquid water moderator to flow into the fuel bundle for passage between the side-by-side supported fuel rods. Above the lower tie plate grid, each fuel bundle includes a matrix of upstanding fuel rods--sealed tubes each containing fissionable material which when undergoing nuclear reaction transfers energy to the flowing water to produce the power generating steam. The matrix of upstanding fuel rods includes at its upper end an upper tie plate assembly. This upper tie plate assembly holds at least some of the fuel rods in vertical side-by-side alignment. Some of the fuel rods are attached to both the upper and lower tie plate assemblies. Usually, water rods are also included between the upper and lower tie plate assemblies for improvement of the water moderator to fuel ratio, particularly in the upper region of the fuel bundle. Fuel bundles also include a number of fuel rod spacers at varying elevations along the length of the fuel bundle. These spacers are required because the fuel rods are long (about 160 inches) and slender (about 0.4 to 0.5 inches in diameter), and would come into abrading contact under the dynamics of fluid flow and nuclear power generation within the fuel bundles. The spacers provide appropriate lateral restraints for each fuel rod at their respective elevations and thus prevent abrading contact between the fuel rods and maintain the fuel rods at uniform spacing relative to one another along the length of the fuel bundle for optimum performance. It will be appreciated that these spacers are sites where debris can be trapped and damage the fuel rods. Each fuel bundle is surrounded by a channel. This channel causes water flowing between the upper and lower tie plate assemblies to be restricted to only one bundle in an isolated flow path between the tie plate assemblies. The channel also serves to separate the steam generating flow path through the fuel bundles from the surrounding core bypass region, this region being utilized for the penetration of the control rods. The water in the bypass region also provides neutron moderation. In the operation of a boiling water nuclear reactor, maintenance of the originally designed flow distribution is very important. Specifically, from the lower (high pressure) plenum inlet to the core to the outlet from the core of the steam and water mixture through the upper tie plate assemblies of the fuel bundles, about 20 pounds per square inch (psi) of the pressure drop is encountered at typical flow operating conditions. About 7 to 8 psi of this pressure drop occurs through the fuel support casting. This pressure drop is mainly to assure the uniform distribution of coolant/moderator flow through the many fuel bundles making up the core of the reactor and is related to the prevention of operating instabilities within the reactor at certain power rates. At the lower tie plate assembly of each fuel bundle, from the inlet nozzle into the flow volume and through the tie plate grid, about 1 to 11/2 psi pressure drop occurs which contributes to establishing flow distribution between the individual fuel rods of each fuel bundle. Finally, through the fuel bundle itself--from the exit of the lower tie plate assembly to the exit at the upper tie plate assembly--about 11 psi of pressure drop usually occurs. When new fuel bundles are introduced into a reactor core, these pressure drops must be preserved. Otherwise, the coolant/moderator flow distribution could be compromised. With respect to the tie plate grid of the lower tie plate assembly, a matrix of cylindrical bosses and webs generally form the grid. The bosses are sized to receive the fuel rod end plugs. The spacing and thickness of the bosses and webs are primary factors in controlling pressure drop resulting from water flow through the grid. In early grid constructions, since the fuel rods had greater cross-sectional diameters, the bosses were large. In more recent grid constructions, since the fuel rods have smaller cross-sectional diameters, the bosses are smaller. Also, in early constructions, fewer fuel rods formed a fuel bundle than in recent constructions. Even with all of these changes in grid and bundle construction, however, it is necessary to avoid significantly altering pressure drop. For example, a core may be composed of older (8.times.8) bundles and newer (11.times.11) bundles, and the pressure drop through each bundle preferably is uniform. One challenge with new fuel bundle constructions, and particularly, lower tie plate grid constructions, is to accommodate more fuel rods and perform debris catching functions yet maintain a pressure drop equivalent to the pressure drop resulting from older bundle constructions. Typically, debris within boiling water nuclear reactors can include extraneous materials left over from reactor construction, debris liberated from corrosion during the reactor lifetime, and during the numerous outages and repairs, further debris accumulates. Because nuclear reactors constitute closed circulation systems, it will be appreciated that debris will essentially accumulate with increasing age and use of the reactor. A particularly vexing and usual place for the accumulation of debris is in the fuel bundles between the fuel rods, particularly in the vicinity of the fuel rod spacers. It will be recalled that each fuel rod is surrounded by a spacer at the particular elevation of the spacer. Debris particles tend to lodge between the spacer structure and the fuel rods and often dynamically vibrate with the coolant/moderator flow in abrading contact to the sealed cladding of the fuel rods. SUMMARY OF THE INVENTION The present invention provides a lower tie plate assembly including a debris catcher forming part of a grid. The grid has lower and upper portions, the lower portion serving to catch debris above a predetermined size, while simultaneously providing minimal pressure drop of water coolant through the grid. The grid also supports the fuel rods in a manner enabling a smooth, substantially uniform expansion of the flow into the fuel bundle. To accomplish the latter, a plurality of laterally spaced, generally cylindrical bosses, defining through openings, extend between upper and lower surfaces of the lower tie plate grid and receive lower ends of the fuel rods. Webs also extend between those surfaces and interconnect the bosses. The bosses and webs include respective portions thereof which extend upwardly from the lower portion of the grid and lie coextensively with the upper portion of the grid to define in the upper grid portion a plurality of flow spaces. The bosses are arranged on vertical centerlines arranged at the corners of square matrices, with the webs extending linearly between the bosses along the sides of the square matrices. Convex portions of the cylindrical bosses extend between the right angularly related webs of each matrix. Thus, the webs and the convex portions of the bosses of the upper portion of the lower tie plate grid define the flow spaces. This lower grid portion has a plurality of openings extending therethrough and which open into the flow spaces. These lower grid portion openings separate debris above a certain size from the water flowing through those openings into the flow spaces between the boss and web portions in the upper grid portion. In a preferred embodiment of the present invention, a plurality of openings extend through the lower grid portion and open into each of the flow spaces. In order to minimize the pressure loss and maximize the debris catching function, the openings are specifically oriented, shaped and dimensioned. For example, given the shape of certain of the flow spaces defined by the web and boss portions, a first array of generally square openings with linear sides and radiussed corners are located in the lower grid portion such that vertical centerlines through these square openings intersect a diagonal of a square matrix and which diagonal passes through the vertical centerlines of the cylindrical bosses. A second array of openings having a plurality of sides in excess of four sides, preferably five generally linear sides, with adjacent sides having a radius therebetween, is oriented such that each opening of the second array has a side oriented generally parallel to a web. Preferably, each opening in the lower grid portion has an optimal minimum area, e.g., a throat area, serving to catch debris larger than the minimum area and prevent it from passing through the grid. The openings in the lower portion transition from the minimum or throat areas into the flow spaces and preferably have walls laterally divergent in a direction toward the upper surface of the lower tie plate grid such that each opening defines a venturi in a direction toward the associated flow space. Consequently, the flow pattern for each opening obtains a substantially uniform velocity over its cross-section and which flow pattern flares as it transitions from the lower portion and enters the associated flow space in the upper grid portion to reduce the pressure loss and enable the flow to expand smoothly into the flow spaces. To further facilitate the debris catching function with minimum pressure drop, the lower grid portion has a thickness in the direction of flow less than about 25% of the overall thickness of the tie plate. Preferably, the ratio of the overall thickness of the tie plate grid to the thickness of the lower grid portion is within a range of 5-7 to 1. Additionally, the thickness of the lower grid portion is preferably less than about two times the shortest hole size dimension. In a preferred embodiment according to the present invention, there is provided in a nuclear fuel assembly, a unitary one-piece lower tie plate grid comprising a lower grid portion and an upper grid portion, means for supporting fuel rods above the lower tie plate grid including the upper and lower grid portions, the supporting means comprising a plurality of laterally spaced bosses having portions extending upwardly from the lower grid portion, with the bosses being sized for receiving lower ends of the fuel rods. The supporting means further include web portions extending upwardly from the lower grid portion and interconnecting the boss portions to define with the boss portions a plurality of flow spaces in the upper grid portion extending from the lower grid portion and opening through an upper surface of the lower tie plate grid, the lower grid portion of the lower tie plate grid including a plurality of openings extending therethrough and opening into the flow spaces for separating debris from a coolant flowing through the lower grid portion into the flow spaces between the boss and the web portions. In a further preferred embodiment according to the present invention, there is provided in a nuclear fuel assembly, a fuel rod support structure, comprising a lower tie plate assembly including an inlet nozzle, a unitary one-piece lower tie plate grid and a transition structure defining a flow volume for receiving coolant entering the nozzle and flowing coolant to the lower tie plate grid, the unitary one-piece lower tie plate grid having a lower grid portion and an upper grid portion. The lower tie plate grid comprises a plurality of laterally spaced bosses having portions extending upwardly from the lower grid portion, the bosses being sized for receiving lower ends of the fuel rods, the lower tie plate grid further including web portions extending upwardly from the lower grid portion and interconnecting the boss portions to define with the boss portions a plurality of flow spaces in the upper grid portion extending from the lower grid portion and opening through an upper surface of the lower tie plate grid, the lower grid portion of the lower tie plate grid including a plurality of openings extending therethrough and opening into the flow spaces for receiving the coolant from the flow volume and flowing the coolant through the lower grid portion into the flow spaces between the boss and the web portions. In a further preferred embodiment according to the present invention, there is provided a nuclear fuel bundle and support therefor comprising upper and lower tie plate assemblies, a nuclear fuel bundle between the upper and lower tie plate assemblies and including a plurality of fuel rods, the lower tie plate assembly including means for supporting the nuclear fuel bundles, the lower tie plate assembly further including a lower tie plate grid having a lower grid portion and an upper grid portion. The lower tie plate grid comprises a plurality of laterally spaced bosses having portions extending upwardly from the lower grid portion, the bosses being sized for receiving lower ends of the fuel rods, the supporting means further including web portions extending upwardly from the lower grid portion and interconnecting the boss portions to define with the boss portions a plurality of flow spaces in the upper grid portion extending from the lower grid portion and opening through an upper surface of the lower tie plate grid. The lower grid portion of the lower tie plate grid includes a plurality of openings extending therethrough and opening into the flow spaces for flowing a coolant flowing through the lower grid portion into the flow spaces between the boss and the web portions. Accordingly, it is a primary object of the present invention to provide a novel and improved unitary one-piece lower tie plate grid for supporting a nuclear fuel bundle and having a lower portion for limiting the passage of debris in the moderator flow through the tie plate grid with minimal pressure drop.
	description	The embodiments described below accomplish several difficult design goals for multi-column FIB systems. The optical elements are sufficiently electrically isolated to maintain the required high operating voltages. In some embodiments, the number of high voltage power supplies is reduced from the number that would be required in multiple independent columns. The voltage level of the high voltage power supplies are also reduced from that of conventional FIB systems. In addition, the difficulties of keeping multiple LMIS""s (Liquid Metal Ion Sources) operating and maintained with minimum down time is addressed by using a vacuum sealable, multiple gun chamber as described below. FIGS. 1, 2A, and 2B show a multi-column FIB array using LMIS""s. FIG. 1 shows a multi-column FIB system 108 that includes a gun vacuum chamber 110 and a primary vacuum chamber 112. Gun chamber 110 is a single, sealable vacuum chamber that includes a set of ion guns 114. Gun chamber 110 can be replaced as a unit and has its own vacuum pump, preferably an ion pump (not shown). When one of the guns 114 in gun chamber 110 fails, the entire gun chamber 110 can be replaced with another gun chamber 110 that is already evacuated to an ultra high vacuum and ready to begin operation. Thus, multi-column system 108 does not need to remain out of production while the gun chamber is being evacuated. Each ion gun 114 includes an emitter 120, a suppressor 122, an extractor 124, an acceleration lens 126, a deceleration lens 128 and a ground element 169. The four elements 124, 126, 128 and 169 of each column together are referred as the xe2x80x9clens 1xe2x80x9d of the column. Although FIG. 1 shows a lens 1 comprising four lens elements, other lens designs can be used for lens1. Also, some or all of the elements of lens 1 could alternatively be positioned in primary vacuum chamber 112. Each ion gun 114 forms part of an ion optical column 136 that also includes an aperture 152, a steering element 154, a blanking element and Faraday cup 156, dual deflection elements 160 and 161, second lens elements 163, 162 and 165 (referred to collectively as the xe2x80x9clens 2xe2x80x9d), and a detector 164. At the bottom of each column is a work piece or target 170, such as a semiconductor wafer. An isolation valve 150 at the bottom of each gun 114 selectively closes a beam hole 168, thereby vacuum isolating gun chamber 110. The isolation valves 150 of the column in a gun chamber 110 are preferably xe2x80x9cganged,xe2x80x9d that is, connected in a manner so that all valves are opened or closed together. The detectors 164 for the columns 136 are also preferably ganged, that is, physically and electrically connected, but constructed so that each column""s secondary electrons are independently detected. The aperture 152 preferably comprises an automatic variable aperture. Such apertures are known and details are not shown in FIG. 1. A gas injection can optionally be used with apparatus of FIG. 1 to inject a gas for ion beam assisted deposition or for enhanced etching. The construction and operation of such systems are known and are described, for example, in U.S. Pat. No. 5,435,850 to Rasmussen. The gun elements, that is, emitters 120, suppressors 122, extractors 124, acceleration lenses 126, deceleration lenses 128, and ground element 169 are preferably contained in gun chamber 110. The number of guns in gun chamber 110 is preferably limited to about five. If one of the emitters 120 fails, then the exchange of a five-gun set is easier and less costly than replacing a larger number of guns, such as ten or more guns. Moreover, the restarting of five emitters in parallel is also much less prone to failure than restarting a larger number simultaneously. The set of ganged isolation valves 150 for the set of guns simultaneously isolates the beam holes 168 in the ion beam paths at the bottom of gun chamber 110 from the primary vacuum chamber 112. Valves 150 are preferably formed by a bar 172 that moves relative to bottom portion 174 of gun chamber 110. When valves 150 are open, the openings in bar 172 line up with the openings 169 in bottom portion 174. To seal gun chamber 110, bar 172 is shifted so that the holes in bar 172 are offset from the holes in bottom portion 174, and O-rings 176 form a seal between a solid portion of bar 172 and bottom portion 174. Before shifting bar 172, it is preferably lowered away from O-rings 176 to prevent damage to the O-rings that can create contamination and vacuum leakage. After bar 172 is shifted, it is raised again into contact with O-rings 176 to create a vacuum seal to isolate gun chamber 110. Primary chamber 112 can be exposed to air when gun chamber 110 is removed or alternatively, primary chamber 112 can be made sealable by using a second set of valves (not shown). Details of the mounting of gun chamber 110 to primary chamber 112 are conventional and not shown. A multiple ion column system could use a single gun chamber 110 or multiple gun chambers. FIG. 2A shows a top view of an arrangement of multiple linear gun chambers 110 grouped to form a two-dimensional array of fifteen guns. The number of guns per gun chamber can be varied, as well as the number of gun chambers to produce a system having the desired number of FIB columns for a particular application. FIG. 2A shows an outlet 210 from each gun chamber 110 to an associated ion pump. FIG. 2B is a side view of the multiple gun chamber system of FIG. 2A. FIG. 2B shows also a location for high voltage feed-throughs 212, a flange 214 at the top of a gun chamber 110, and an actuator 216 for ganged gate valves 150. The construction of the optical elements, such as extractors 124, acceleration lenses 126, and deceleration lenses 128 in gun chamber 110, can be simplified by using flat bars with holes to form lens elements. This construction technique can also be used to construct optical elements in the primary vacuum chamber. Using a single bar to form corresponding lens elements in different columns with a gun chamber can reduce the number of high voltage power supplies required. FIG. 3 is a cross-sectional view of a gun chamber 110 showing bars 310 used to form optical elements. Bars 310 form suppressors 122, extractors 124, acceleration lenses 126, and deceleration lenses 128. Bars 310 are electrically isolated from each other and from the chamber itself using HV (High Voltage) insulator disks 312 composed preferably of a ceramic material. Other means, such as dielectric balls, can be used to isolate the gun HV elements. The assembly may be glued together using a suitable epoxy or other means known in the art. After the bars and insulators are installed in the casing of gun chamber 110, the assembly can optionally be machined to provide additional accuracy in shaping and aligning the lens elements. The optical elements can be formed directly by the holes in a conductive bar, as shown with regard to acceleration lenses 126. A common voltage is thus applied to all lenses formed by the bar, reducing the number of high voltage power supplies required for the multi-column system. The number of high voltage power supplies can be further reduced by using a common high voltage supply for corresponding bars in multiple gun chambers. Conductive bars are typically made of a titanium alloy having a low thermal coefficient of expansion. Optical elements can also be formed by inserts placed into holes in a bar. For example, FIG. 1 shows the use of lens inserts 178 in the bar 310 forming deceleration lenses 128. The bar in which lenses 128 are formed is constructed from an insulating material, for example, a ceramic material such as alumina, and the lens inserts are composed of a conductive material, preferably a titanium alloy which has is low thermal coefficient of expansion that is similar to that of the alumina bar. The alumina bar provides high voltage isolation to the individual lenses 128 with respect to the bars 310. Voltage is applied to the individual lenses by wires connected to the lenses in a conventional manner, such as conductive silver epoxy or using connector pins. Alternatively, metal films can be placed upon the insulator bar to replace the wires. Another method of providing high voltage insulation to lenses 128 entails using a conductive bar 310, with an insulating insert placed in a hole in the bar, and then a conductive lens placed in the insulating insert. Such inserts can be glued into insulator material, which can then be glued into the bars. Lenses formed by inserts can also be post machined, that is, machined after assembly, for additional accuracy in shape and alignment. These construction methods that individually isolate lenses can be particularly useful for suppressor lenses 122, extractor lenses 124, or individual elements of lens 1 or lens 2. FIG. 1 shows inserts used only on the deceleration lens 128. Deceleration lens 128 can be operated near ground potential, which simplifies the power supply requirements for lens 1. Isolating lens elements allows the voltages in individual columns to be controlled. For example, the voltage on one of extractor lenses 124 can be individually boosted about 2 kV above the common extractor voltage to start or restart the individual emitter in the corresponding column. The extractor lens 124 can then return to or near the common extractor voltage for normal operation. Optical elements that are isolated can still use the common high voltage supply, but isolated elements can also be floated at a voltage above or below the common voltage, thereby reducing the number of high voltage power supplies required. Charged particle signal detection capability for imaging can be accomplished by a traditional side mounted electron multiplier or scintillator means, or by two other novel methods described below. For many nanofabrication applications, the beam current can be greater than a nanoampere. At this level of current, an amplifier or amplifiers can be attached directly to detector plate 164 below lens 2. Separate detector plates for each column could also be used. Alternatively, through-the-lens (TTL) electron detection can be used. Through-the-lens electron detection is known and described, for example, incorporated into an electron column in PCT Publication WO 99/34397 of Krans et al. In the Krans et al. design, the lens 2 center element and upper element (and optionally the lower element) are biased to positive potentials to draw the electrons from the sample up and above the lens, where they are detected by a channel plate electron multiplier, which is placed roughly perpendicular to the ion column axis, and has a hole in its center to pass the primary beam. FIG. 4 shows a TTL detection system for an ion column 410 in which low energy secondary electrons from the sample, having energies of about 5 eV (electron volts), are accelerated up through the lens 412 by positive potentials on the elements of lens 412, the deflector plates 432 and magnetic deflector 414. The TTL system in FIG. 4 utilizes a magnetic deflector 414 to deflect the secondary electrons 418 off to the side while allowing the high mass-to-charge ratio primary ions 420 to pass nearly straight through column 410. Alternatively, a Wien filter or an electrostatic deflection device could be used. An electron detector 424, such as a scintillator, continuous dynode multiplier, or channel plate, is then placed to the side for collecting and amplifying the electron signal for processing by standard FIB video electronics. In the embodiment of FIG. 4, a sample 426 and a lower lens element 428 are maintained at approximately ground potential. An upper lens element 430 is biased to between about +500 and +5000 volts with respect to ground to continue the secondary electron velocities upward beyond the lens 412. Similarly, electrostatic deflector plates 432 and deflector 414 are biased to between about +500 and +5000 volts to continue this upward velocity of secondary electrons 418 towards electron detector 424, the input of which must be similarly biased. The approximately 5 eV secondary electrons are accelerated rapidly by the lens element 440, which is at high positive potential, such as about 20,000 Volts. These electrons are decelerated as they pass through the lens element 430 and the deflection electrodes 432, but the secondary electrons still maintain trajectories that remain relatively close to the column axis. Magnetic deflector 414 or other separation device then directs the electrons toward the detector 424. FIG. 6 is an electron optics computer simulation of the secondary electrons 610 traveling from a sample 612 back through optical elements 616, 618, 620, and 622, with element 616 having a potential relative to sample 612. FIG. 5 shows an alternate ion column 508 design using a TTL secondary electron detector. A sample 510 and a lower final lens element 512 are each biased about xe2x88x922000 V negative to propel the electrons back through the lens. If it is desired to collect secondary positive ions instead of electrons, sample 510 and lower final lens element 512 can be biased to about +2000 V. Center lens element 514 is biased to approximately +20,000 V. Lens element 516, electrostatic deflector elements 520 and deflector 414 need not be positively biased, which simplifies the electronics and the optics construction. If the ion beam systems include other devices, such as gas injectors, these devices must also be biased to the same potential as the sample. The apparatus in FIG. 4 also may be used to detect secondary positive ions from the sample. To collect secondary positive ions, the lens 2 element 440 is biased to a negative potential. (Lens 2 is then an acceleration lens). In addition, electrostatic deflector 432, the deflector 414 and the input of particle detector 424 are negatively biased. Similarly, the potentials in FIG. 5 may be changed to collect and detect positive secondary ions. A quadrupole or other mass spectrometer can also be placed in the position of detector 424 to perform Secondary Ion Mass Spectrometry. The appropriate biasing of the column and detector may be employed to detect either positive or negative ions. For thin film head trimming or other applications, the ion beams must be tilted about +/xe2x88x923 degrees with respect to the normal to the sample surface. This beam tilting is to achieve undercutting or to yield cuts to the sides of the head with walls more normal to the head surface. This +/xe2x88x923 degree tilt can be achieved, for example, by tilting every other mw of columns by about +/xe2x88x923 degrees with respect to the normal to the sample surface. In other words, in a multi-chamber system, the ion guns in one chamber can be tilted at an angle of about 3 degrees from a normal to the sample surface and the ion suns in the next chamber are tilted at an angle of about three degrees from a normal to the sample surface in an opposite direction. The inventions described above can be embodied in a variety of systems, and the advantages delineated below can be provided in many or all of the embodiments. Because the embodiments will vary with the goals of a particular application, not all advantages will be provided, or need to be provided, in all embodiments. An advantage of the invention is an increase in the processing speed by providing a system including multiple ion guns capable of operating simultaneously on one or more targets. Another advantage of the invention is that it provides a system in which the multiple ion guns operate on one or more targets in a single primary vacuum chamber. Another advantage of the invention is that it provides a system in which the multiple ion guns are in a gun chamber capable of being vacuum isolated from the main chamber, that is, the gun chamber is capable of being evacuated or exposed to atmosphere independently, without disrupting the vacuum in the main chamber. Another advantage of the invention is that it provides a system in which the multiple ion guns are positioned in multiple gun chambers, each gun chamber containing one or more ion guns and each gun chamber capable of being vacuum isolated from the main chamber and from each other. Another advantage of the invention is that it provides a multiple ion gun system in which a portion of the ion column elements are in the primary vacuum chamber. Another advantage of the invention is that it provides a system in which an ion gun or set of ion guns in one chamber can be replaced while maintaining a vacuum in the main chamber and in other gun chambers. Another advantage of the invention is that it provides a system that uses multiple ion guns and provides the capability to detect secondary particles emitted from a sample at the target point of each of the multiple guns. Another advantage of the invention is that it provides charged particle optical elements in parallel for multiple columns and a method of efficiently manufacturing such elements. Another advantage of the invention is that it provides such charged particle optical elements with at least one of the optical elements being individually controllable. Another advantage of the invention is that it provides an electrode design for a multiple column focused ion beam system that reduces the number of high voltage power supplies required for the system. Another advantage of the invention is that it provides a multiple column focused ion beam system using fewer high voltage power supplies than the number of columns. Another advantage of the invention is that it provides an electrode design and voltage application scheme that reduces the voltage requirement of the high voltage power supply. Another advantage of the invention is that it reduces the cost of processing multiple targets simultaneously from the cost of using multiple, single beam focused ion beam systems. Another advantage of the invention is that individual emitters can be restarted by individually increasing the extraction voltage of that particular gun and not disturb the other gun voltages. This can be achieved either by increasing the extractor voltage with respect to the emitter/suppressor elements by using isolated extractor elements, or by increasing the emitter/suppressor voltage with respect to the common extractor voltage for that particular gun. Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made to the embodiments described 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, 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.
041359712	summary	BACKGROUND OF THE INVENTION This invention relates to nuclear reactors and in particular to an apparatus for holding down fuel assemblies within the reactor core. In pressurized water reactors the coolant flow rate and fuel assembly flow resistance are such that the hydraulic uplift force is of sufficient magnitude to cause the assemblies to jitter and even lift off the core support structure. Various approaches have been used to eliminate this detrimental movement. One suggested solution involves the use of a lock down device which attaches the lower end of the fuel assemblies to the core support structure. While this device will function properly, it does introduce mechanical complexity since the device must not only lock and unlock remotely, but it must release reliably after a year of operation in the reactor environment. Another approach has been to use springs located above each fuel assembly which bear against an upper alignment plate, thereby urging the fuel assemblies down. As reactors have been designed with increasingly large hydraulic uplift forces the spring force has become very large. The springs themselves have become so large that an excessively large plenum is required between the alignment plate and the upper end fitting of the fuel assembly. The springs at this location produce an undesirable flow pattern and an excessively high pressure drop through the plenum. They are also potentially subject to flow induced vibration since the total reactor coolant passes over these springs. SUMMARY OF THE INVENTION It is an object of the invention to hold-down fuel assemblies in a simple uncomplicated manner which will eliminate or reduce the need for spring hold-down forces. It is a further object to introduce these forces in a manner which will compensate for variations in primary flow through the reactor. These and other objects are achieved in the invention by attaching to the fuel assembly, at either end, a pressure plate. The pressure plate is horizontally coextensive with the fuel assembly and has the side of the plate adjacent the fuel assembly exposed to the reactor fluid pressure existing in that area. The other side of the pressure plate is exposed to a pressure from another location in the reactor vessel. The pressure are selected so that the higher pressure is always above the pressure plate, thereby resulting in a downward force on the fuel assembly. Where the pressure plate is located above the fuel assembly the high pressure is preferably obtained from a location where the coolant enters the reactor vessel. Alternately this pressure may be obtained from a location at the bottom of the core. Where the pressure plate is located below the fuel assembly the low pressure is obtained by connecting this area to a portion of the fluid flow path near the outlet from the reactor. A pressurizable plenum is formed on the side of the sealing plate away from the fuel assemblies by providing a sealing arrangement between extensions on the sealing plate and a support plate or alignment plate which is adjacent thereto. Spring means to supplement the hold-down force may be used since they are compatible with the hydraulic structure and they may be of lesser magnitude than the prior art structure where the spring means supplied the entire hold-down force. Various other objects and advantages will appear from the following description of the embodiments of the invention, and the novel features will be particularly pointed out in connection with the appended claims.
	claims	1. An apparatus for retrofitting an intraoral radiology positioning device comprised of an aiming ring, a bite block and a sensor basket attached to a guide arm, comprising:a near side cover;a far side cover; anda first collimation plate with a first collimation aperture;wherein the near side cover and the far side cover are adapted so as to releasably attach together about the aiming ring so as to hold the first collimation plate and position the first collimation plate so that the first collimation aperture restricts the size of an X-ray beam traveling through the aiming ring;wherein the near side cover is adapted to be positioned adjacent to a near side surface of the aiming ring while the far side cover is adapted to be positioned adjacent to a far side surface of the aiming ring so that the aiming ring is positioned between the near side cover and the far side cover and neither the near side cover nor the far side cover is mechanically secured by itself to the aiming ring. 2. The apparatus of claim 1, wherein the first collimation plate is removable from the near and far side covers. 3. The apparatus of claim 2, further comprising a second collimation plate adapted to be held by the near and far side covers, said second collimation plate having a second collimation aperture of a different size than that of the first collimation aperture. 4. The apparatus of claim 1, wherein the first collimation plate is a single plate held by one of the near side cover and the far side cover. 5. The apparatus of claim 4, wherein the first collimation plate is releasably held by one of the near side cover and the far side cover. 6. The apparatus of claim 1, wherein the first collimation plate is adjustable between a first aperture size and a second aperture size. 7. The apparatus of claim 1, wherein the near side cover and the far side cover are held together by a snap fit. 8. An apparatus, comprising:an intraoral radiology positioning device comprised of an aiming ring, a bite block and a sensor basket attached to a guide arm;a near side cover;a far side cover; anda first collimation plate with a first collimation aperture;a second collimation plate with a first collimation aperture of a different size that that of the first collimation aperture;wherein the near side cover and the far side cover are adapted so as to releasably attach together about the aiming ring so as to hold the first collimation plate and the second collimation plate and position the first collimation plate and the second collimation plate so that the first collimation aperture and the second collimation aperture restrict the size of an X-ray beam traveling through the aiming ring;wherein the near side cover is adapted to be positioned adjacent to a near side surface of the aiming ring while the far side cover is adapted to be positioned adjacent to a far side surface of the aiming ring so that the aiming ring is positioned between the near side cover and the far side cover and neither the near side cover nor the far side cover is mechanically secured by itself to the aiming ring; andwherein at least one of the first and the second collimation plates is removable from the near and far side covers. 9. The apparatus of claim 8, wherein both the first collimation plate and the second collimation plate are removable from the near and far side covers. 10. A method for retrofitting an intraoral radiology positioning device comprised of an aiming ring, a bite block and a sensor basket attached to a guide arm, comprising the steps of:releasably attaching a near side cover and a far side cover together about the aiming ring so as to hold a collimation plate and position the collimation plate so that the collimation aperture restricts the size of an X-ray beam traveling through the aiming ring wherein the near side cover is positioned adjacent to a near side surface of the aiming ring while the far side cover is positioned adjacent to a far side surface of the aiming ring so that the aiming ring is positioned between the near side cover and the far side cover and neither the near side cover nor the far side cover is mechanically secured by itself to the aiming ring. 11. The method of claim 10, comprising the further step of adjusting the size of the collimation aperture between a first aperture size and a second aperture size. 12. The method of claim 11, wherein the size of the collimation aperture is adjusted by substituting a second collimation plate for the collimation plate. 13. An apparatus for retrofitting an intraoral radiology positioning device comprised of an aiming ring, a bite block and a sensor basket attached to a guide arm, comprising:a near side cover;a far side cover; anda collimation plate with a collimation aperture;wherein the near side cover and the far side cover are adapted so as to releasably attach together about the aiming ring so as to hold the collimation plate and position the collimation plate so that the collimation aperture restricts the size of an X-ray beam traveling through the aiming ring;wherein the collimation plate is comprised of a near side collimation plate held by the near side cover and a far side collimation plate held by the far side collimation plate. 14. The apparatus of claim 13, wherein the near side collimation plate is releasably held by the near side cover and the far side collimation plate is releasably held by the far side cover. 15. The apparatus of claim 6, wherein the first collimation plate is adjustable between the first aperture size and the second aperture size by use of at least one sliding shutter that can be moved between two or more positions.
052757897	summary	FIELD OF THE INVENTION The present invention relates to the preparation and use of molecules carrying attached thereon radiolabeled species. DESCRIPTION OF THE PRIOR ART The use of radiolabeled therapeutic and diagnostic agents has recently received renewed interest. The development of monoclonal antibodies of high avidity and specificity has encouraged the development of new agents for diagnostic and therapeutic treatment of cancer. These radiolabeled monoclonal antibodies, ligands, unsaturated fatty acids and other compounds are finding clinical applications both in vitro (for example in radioimmunoassay systems) and in vivo (for example in diagnostic imaging, radiotherapy and other novel techniques such as radioimmunoguided surgery). Bifunctional chelates are being utilized to radiolabel the above mentioned biomolecules, e.g., antibodies and other agents with Y.sup.90, In.sup.111 , Re.sup.186, Ga.sup.67 etc., for diagnostic and therapeutic purpose, however, I.sup.125, I.sup.131 and I.sup.123 remain the radioisotopes of choice for use with the method and apparatus of this invention. Several remote or semiautomatic radiolabelling, specifically radioiodination, systems have been described (see for example, Ferens J. M., Krohn K. A., Beaumier P. L. et al., High-level iodination of monoclonal antibody fragments for radiotherapy. J Nucl Med 1984;25:367-70; or James S. F. W., Fairweather D. S. L. , Bradwell A. R., A shielded sterile apparatus for iodinating proteins, Med Lab Sci 1983;40:67-8; or Henville A. Jenkin G., A simple and cheap remotely operated system for the iodination of proteins, Anal Biochem 1973;52:336-41). These systems are dependent on gel filtration columns to separate bound from free isotope and in line pumps to propel reagents from one vessel to another. Such systems are prone to leakage, difficult to shield, and require decontamination after use. Other shieldable, disposable and relatively cheap systems are reported (see for example, Weadock K. S., Anderson L. L. , Kassis A. I., A simple remote system for the high-level radioiodination of monoclonal antibodies; J Nuc Med All Sci 1989;33:37-41, or James Watson S. F., Fairweather D. S. , Bradwell A. R., A shielded, sterile apparatus for iodinating proteins, Med Lab Sci 1983;40:67-68.) but these systems are complex to use requiring manipulation of valves and positioning of needles. These systems are inherently less reliable for iodinating since the result will depend on the mechanics of vial coating and the timing of the iodination and purification reactions. These systems are also more difficult to shield than the present invention because there are multiple vials to shield (apparatus is spread out) and a lead wall is also required. Another technique is the `single vial technique` described in U.S. Pat. No. 4,775,638. This technique, although simple looking, requires manipulations of reagents with a syringe, and the timing of incubations. The mechanics of vial coating with the iodination reagent, manipulation of reagents and timing of the reaction, contribute to reduced consistency of results. Also, it would be difficult to safely shield the user from the radiation field emanating from the syringe utilized in this method, especially when preparing therapeutic doses of I.sup.131 labeled agents. A similar technique to the `single vial technique` described above is the Iodo-Bead.TM. method of Pierce Chemical. This method is essentially identical to the `single vial technique` except that instead of coating the reaction vial with oxidant, one or more Iodo-Beads.TM. are added to the reaction vial. The same concerns for reagent manipulation, timing of incubation and shielding apply to this technique. In addition, the Iodo-Bead.TM. has a polystyrene base which will absorb oxidized iodine from the reaction mixture and thus reduce the percent incorporation of iodine into the agent of interest. Radioiodinated monoclonal antibodies and other radiolabelled compounds may soon serve as standard diagnostic and therapeutic tools in clinical oncology. When preparing these agents, the integrity of the agent must be maintained while minimizing personnel exposure to radioactivity, including direct exposure to radiation and internal exposure to the thyroid. Thyroid uptake of radioiodine can easily result if elemental radioiodine generated in the labeling process is not contained. The ability to prepare these agents in a consistent manner, including specific activity, yield and purity will be useful in evaluating potential therapies. Simplification of the radiolabeling process will allow widespread use of the new therapies as they become available. SUMMARY OF THE INVENTION Many of the disadvantages of the prior art methods and apparatus are alleviated by this invention. According to the invention, a method of labelling materials with a radioisotope comprises the steps of providing a sealed column having an inlet end and an outlet end, the column being packed with sequential stages of (a) beads coated with an oxidizing reagent for coupling the radioisotopes to the biomolecule, (b) an anion exchange resin, and (c) a material for trapping elemental radioisotope, and flowing a mixture of the radioisotope and a solution of the material to be labelled through the column, and collecting the purified product at the effluent side of the device. The radiolabeling reaction (incorporation of radiolabel into the functional material) and the purification reaction (removal of unincorporated radiolabel from the radiolabeled material) occur as the reaction mixture flows through the column. In addition, all unincorporated radiolabel is contained and trapped within the column, thus, reducing the quantity of radioactive waste generated and eliminating the need to handle this waste. In a preferred embodiment of the invention, the mixture is flowed through a device, typically a column, as described. This method is particularly suited for labeling monoclonal and polyclonal antibodies for use in radioimmunoguided surgery, radiotherapy and diagnostic imaging. Consistent radiolabeled antibody yields and purity are obtained when utilizing this method without releasing volatile radioiodine. Higher yields of radiolabeled antibody are obtained when using the device compared to other methods. The apparatus used in the method is easily shielded and can be operated remotely if a pump such as a peristaltic pump is utilized to flow the reaction mixture through the column. Radiolabeling by this method is rapid and easy and does not generate radioactive waste except for that contained within the device itself. The invention also includes an apparatus for labelling materials with a radioisotope comprising a sealed column having an inlet and an outlet, the column being packed with, in the order named, (a) beads coated with an oxidizing reagent for coupling the radioisotope to the material, (b) an anion resin, and (c) a material for trapping elemental radioisotope, whereby when a radioisotope and a buffer solution of the material are passed through the column, the radioisotope becomes reactively coupled to the material. In a preferred embodiment of the invention, the beads of (a) are coated with an iodination reagent. Further the material for trapping elemental radioisotope is chloromethylated styrene resin. Additional material for trapping elemental isotope may be placed at the inlet end of the column. Finally, filters may be placed at the inlet ends and outlet ends of the column between beads (a) and (b). This particular apparatus has many advantages over similar devices of the prior art. For one, the higher surface area of the glass beads coated with an oxidizing agent enhances the reaction kinetics of the operation. The apparatus permits a more efficient conversion of the radiolabel to labelled materials. Virtually all the radioactivity is contained in one vessel and requires no valves or connectors. After use, the ends of the apparatus can be sealed and its entire contents remain self-contained for safe disposal. Exposure of the operator's hands to the radioactivity is not significant. The approaches of the prior art require significant hand manipulation of syringes or bottles thus making the possibility of radiation exposure to the hand a real concern. Finally, the apparatus of the invention permits higher specific activity of the labelled materials.
	abstract	A beam forming system includes one or more beam forming elements that are arranged to provide a non-planar doubly ruled radiation surface. The surface is defined by two families of rulings such that the length of the rulings within each family are configured to provide a radiation surface with substantially straight boundary edges, and the beam forming system is arranged to form acoustic beams.
053496256	claims	1. An x-ray diagnostics installation for peripheral angiography comprising: an x-ray exposure means for generating an x-ray beam and for detecting said x-ray beam after passage through a patient to obtain an x-ray exposure of said subject, said x-ray exposure unit including diaphragm means for selectively gating said x-ray beam; a support unit for receiving a patient to be examined using said x-ray exposure means, said support unit and said x-ray exposure means being relatively movable through a plurality of steps each having a step length with an exposure of said patient being obtained by said x-ray exposure means at each of said steps to obtain a plurality of successive exposures; and control means connected to said x-ray exposure means and to said support unit for controlling operation of said x-ray exposure means and said support unit, including controlling said diaphragm means, said control means including arithmetic means for calculating values for pre-setting one or more of said plurality of successive exposures, said step length and said plurality of steps matched to said patient based on subject-related data including the size, weight and physique of said patient. 2. An x-ray diagnostics installation as claimed in claim 1 wherein said x-ray exposure means includes an x-ray radiator having a focus, and a radiation receiver, and wherein said arithmetic means comprises means for employing a focus-to-patient distance and a focus-to-radiation receiver distance in calculating said values for pre-setting by said control means in combination with said subject-related data. 3. An x-ray diagnostics installation as claimed in claim 1 wherein said control means includes display means for displaying a contour of said patient in a patient plane, a setting of said diaphragm means and a setting of the radiation field of said x-ray exposure unit with reference to said patient for each exposure position in said plurality of successive exposures. 4. An x-ray diagnostics installation as claimed in claim 3 wherein said display means is a video monitor. 5. An x-ray diagnostics installation as claimed in claim 3 wherein said display means is a printer. 6. An x-ray diagnostics installation as claimed in claim 3 wherein said control means includes an operating unit and wherein said display means is a display field of said operating unit. 7. An x-ray diagnostics installation as claimed in claim 1 wherein said installation has system-related distance parameters, and wherein said control means includes a memory, connected to said arithmetic means, in which said distance parameters, said step length, said plurality of steps, and standard settings for said diaphragm means are stored for use by said arithmetic means. 8. An x-ray diagnostics installation as claimed in claim 1 further comprising video chain means for generating and processing a digital image of said patient, for obtaining and supplying said patient-related data to said arithmetic means. 9. An x-ray diagnostics installation as claimed in claim 1 wherein said exposures in said plurality of exposures have an overlap and said installation further comprising means for supplying data corresponding to a selected overlap to said arithmetic means for use in calculating said values for pre-setting by said control means. 10. An x-ray diagnostics installation as claimed in claim 1 wherein said exposures in said plurality of exposures have a section with said installation further comprising means for supplying data corresponding to a selected section with said arithmetic means for use in calculating said values for pre-setting by said control means. 11. An x-ray diagnostics installation as claimed in claim 1 further comprising memory means for storing data for a specified patient and pre-settings associated with said specified patient for re-use in subsequent examinations of said specified patient. 12. An x-ray diagnostics installation as claimed in claim 1 wherein said x-ray exposure means and said patient support define an examination region, and further comprising means for supplying data corresponding to a selected examination region to said arithmetic means for use in calculating said values for pre-setting by said control means.
	abstract	A detector module is disclosed including a plurality of directly converting detector submodules, each with a back contact, and a scattered radiation collimator spanning the detector submodules. For contacting the back contacts, a contacting unit is provided in at least one embodiment and designed so that a contact connection is established between the contacting unit and the counter-electrodes by way of assembly-related proximity of the scattered radiation collimator and the counter-electrodes.
	description	The present invention concerns a fuel assembly for a nuclear power boiling water reactor. In a fuel assembly for a nuclear boiling water reactor, there are a number of fuel rods, which comprise a nuclear fuel material. When the fuel assembly is in operation in a nuclear reactor, a cooling medium, usually water, flows up through the fuel assembly. This water fulfills several functions. It functions as a cooling medium for cooling the fuel rods such that they will not be overheated. The water also serves as a neutron moderator, i.e. the water slows down the neutrons to a lower speed. Thereby, the reactivity of the reactor is increased. Since the water flows upwards through the fuel assembly, in the upper part of the fuel assembly, the water has been heated to a larger extent. This has as a consequence that the portion of steam is larger in the upper part of the fuel assembly than in the lower part. Since steam has a relatively low density, the steam in the upper part of the fuel assembly is a poorer moderator than the water in the lower part of the fuel assembly. Furthermore, cold water is a better moderator than warm water. This means that the largest moderation is obtained when the reactor is out of operation, i.e. when it is cool. The reactivity of a reactor depends on the amount of nuclear fuel material and on the amount of moderator. The reactivity in a cool reactor is thereby higher than the reactivity in a warm reactor. To enable safe shutdown, there are requirements on a highest allowed reactivity when the reactor is out of operation. An aim is thus that the reactor has a reactivity as high as possible when the reactor is in operation at the same time as the reactivity may not be too high when the reactor is out of operation. It should be mentioned that the water does not only have a moderating function. The water functions in fact also as a neutron absorber. In this context, the expression over-moderation is often used. Thereby is meant that the absorbing function of the water dominates over its moderating function. Such an over-moderation thus leads to a lowered reactivity. This means that the requirement on a highest allowed reactivity when the reactor is out of operation is more easily fulfilled if the amount of water leads to over-moderation. Another requirement is that the cooling of the fuel rods is sufficient such that a so-called dry-out does not occur. Dry-out means that the water film which exists on the surface of the fuel rods disappears or is broken in limited areas. This leads to a locally deteriorated heat transfer between the fuel rod and the water flowing through the fuel assembly. This leads in its turn to an increased wall temperature of the fuel rods. The increased wall temperature may lead to serious damage on the fuel rod. It is desired to achieve a distribution of fission power over the cross-section of the fuel assembly which is more uniform such that the so-called radial peaking factor will be reduced. This means that the assembly can be operated to a higher total power before any individual fuel rod reaches its limits in terms of dry-out margin and other safety related parameters. In order to fulfill the different safety requirements, to obtain a sufficient cooling of the fuel rods, and, at the same time, to obtain a high reactivity during operation, a large number of different technical solutions have been proposed. Examples of different designs of fuel assemblies for a nuclear boiling water reactor can be seen in EP 1551034 A2, U.S. Pat. No. 5,068,082 and U.S. Pat. No. 4,968,479. An object of the present invention is to provide a fuel assembly for a nuclear boiling water reactor with an improved cold shut-down margin, i.e. the reactivity should be sufficiently low when the nuclear reactor is shut down (cold condition). A further object is to provide such a fuel assembly which has a high reactivity when the nuclear reactor is in operation (hot condition). A further object is to provide such a fuel assembly which has a fission power distributed evenly over the cross-section of the fuel assembly. A further object is to provide such a fuel assembly which has a reduced pressure drop in the upper two-phase flow region, in order to improve thermal-hydraulic stability. Another object is to provide such a fuel assembly in which the risk to cause damage to spacer grids positioned at higher levels in the fuel assembly (above shorter fuel rods) is low. Still another object is to provide such a fuel assembly which has an advantageous nuclear performance. The above objects are achieved by a fuel assembly as defined in a fuel assembly for a nuclear power boiling water reactor, comprising: a fuel channel extending in and defining a length direction of the fuel assembly and defining a central fuel channel axis extending in said length direction, fuel rods positioned such that they are surrounded by said fuel channel, each fuel rod having a central fuel rod axis extending substantially in said length direction, water channels positioned such that they are surrounded by said fuel channel, the water channels being configured and positioned for, during operation, allowing non-boiling water to flow through the water channels, each water channel having a central water channel axis extending substantially in said length direction, wherein said fuel rods comprise a first group of fuel rods and a second group of fuel rods, wherein each fuel rod in said first group is a so-called full length fuel rod which extends from a lower part of the fuel assembly to an upper part of the fuel assembly, wherein each fuel rod in said second group extends from said lower part of the fuel assembly and upwards, but does not reach as high up as said full length fuel rods, wherein the fuel assembly comprises at least 3 water channels, each of which has a cross-sectional area which is at least twice as large as the cross-sectional area of each one of said fuel rods, or, in case the fuel assembly has fuel rods of different cross-sectional areas, at least twice as large as the average cross-sectional area of the fuel rods, wherein said at least 3 water channels are positioned such that there is no further water channel, the central water channel axis of which is closer to the central fuel channel axis than the central water channel axis of each of said at least 3 water channels, characterized in that the fuel assembly comprises 3 or 4, but not more than 4, fuel rods which belong to said second group and which are positioned such that the central fuel rod axis of each of these 3 or 4 fuel rods is closer to the central fuel channel axis than any of the water channel axes of the water channels. Since the fuel assembly comprises a relatively large number of shorter fuel rods in a central position of the fuel assembly, together with at least three, relatively large, water channels, which are positioned “outside” of the central short fuel rods, a large volume of water is created in the central upper region of the fuel assembly, when the nuclear reactor is in the cold condition. This region is then overmoderated and the cold reactivity is reduced. Therefore, an improved shut-down margin is obtained. Furthermore, since at least three, relatively large, water channels are used, and since these water channels are “spread out” in the fuel assembly (since they are positioned further out from the central fuel channel axis than the defined 3 or 4 central shorter fuel rods), these water channels will be located near many of the fuel rods arranged in the fuel assembly. Therefore a good moderation is obtained in the hot condition, which means that the reactivity of the nuclear reactor will be high. Moreover, because the reactivity is more evenly spread out to more fuel rods, the distribution of fission power over the cross-section of the fuel assembly will be more uniform. Also, because of the relatively large number of central shorter fuel rods, a larger volume without any fuel rods is created in the upper part of the fuel assembly. This means that the pressure drop will be relatively low in the upper part of the fuel assembly as desired. The fact that there are not more than four short central fuel rods, which fulfill the definition in claim 1, means that the flow velocity of the steam and water in the central opening above these fuel rods will not be very high. A too high flow velocity in this region could increase the corrosion and erosion of the spacer material positioned at higher levels in the fuel assembly. Loss of spacer material by erosion can harm the spacer integrity. This elevated erosion risk can be handled by removing the empty spacer cells above the short central fuel rods. However, this weakens the mechanical strength of the spacer grids in the central region when exposed to external loads, e.g., during transport or in an earthquake event. The present invention allows keeping the empty spacer cells, which increases the structural strength of the spacer grids, while maintaining a low risk of erosion. Furthermore, by having not more than four central short fuel rods of the kind described above, the nuclear performance is more optimized; for example the so-called void reactivity coefficient is thereby improved to minimize the severity of certain anticipated events, such as pressure transients, and the shut down margin is well optimized, in particular relating to the lower part of the fuel assembly. In an operating boiling water reactor the moderation changes up through the reactor due to the formation of steam and hence the reduced density. This gives a higher conversion in the upper part, i.e. more production of Pu-239 from U-238, with higher reactivity at cold condition as a result. This problem has in the prior art been solved by use of shorter fuel rods. Since the shorter rods have negative side effects, their numbers, lengths and positions are crucial. The relatively large open region above the 3 or 4 central shorter fuel rods also enhances natural steam separation which reduces the average steam volume and hence increases moderation at hot conditions. A separation of steam and water where the steam travels upwards through the assembly at a higher speed reduces the average steam volume. This process requires larger open areas than the empty positions above single shorter fuel rods. The following may be noted concerning the expressions used in the claims. A fuel channel can also be called for example a box wall or channel wall. The fuel channel is normally quite long (for example about 4 m) compared to its width (for example about 1.5 dm). It therefore has a length direction. In use in a nuclear reactor, the fuel assembly, and the fuel channel, preferably extend mainly in the vertical direction. The length direction is thus, in use, the vertical direction. The lower and upper parts of the fuel assembly therefore refer to the fuel assembly as seen in the intended use position. The fuel rods could be slightly tilted. Hence, it is specified that the fuel rod axis extends substantially in the length direction. However, preferably the fuel rods are not tilted and therefore the fuel rod axis extends only in the length direction. Preferably the fuel rods are straight. However, the fuel rods may also be somewhat bent. The defined central fuel rod axis would in that case follow the bent shape of the fuel rod, i.e. also the central fuel rod axis would in that case be bent. Similarly for the water channels. The water channels could be slightly tilted. Hence it is specified that the water channel axis extends substantially in the length direction. However, preferably the water channels are not tilted and therefore the water channel axis extends only in the length direction. Also, preferably the water channels are straight. However, the water channels could also be bent. The defined central water channel axis would in that case follow the bent shape of the water channel, i.e. also the central water channel axis would in that case be bent. A water channel in this application thus means an enclosure (for example of a tubular shape) which is positioned in the fuel assembly and which is arranged for allowing non-boiling water to flow therethrough. Furthermore, preferably the water channel has a constant cross-sectional area over at least 80% of its length, preferably over its whole length (the cross-sectional area could change somewhat close to the end(s) of the water channel). However, according to an alternative embodiment, the cross-sectional area of the water channel may vary along its length. For example, the cross-sectional area may become larger at a level above the mentioned 3 or 4 shorter central fuel rods. When the cross-sectional area of the water channels and the fuel rods are compared with each other, this comparison concerns the same level in the fuel assembly (in case the water channels or, possibly, the fuel rods would have a varying cross-sectional area). In particular, the comparison applies to the lower part of fuel assembly, where the shorter fuel rods are positioned. The cross-sectional area relates to the area defined by the outer periphery of the water channels or the fuel rods. The nuclear reactor is preferably a light water reactor. According to one embodiment of a fuel assembly according to the invention, there is no full length fuel rod, the central fuel rod axis of which is positioned closer to the central fuel channel axis than the central fuel rod axis of any of said 3 or 4 fuel rods. This fact ensures that there will be a relatively large region above the mentioned centrally located shorter fuel rods. Consequently, a space is provided above these shorter rods for a relatively large volume of water, which will improve the shut-down margin. According to another embodiment of a fuel assembly according to the invention, the fuel assembly comprises 4 fuel rods which belong to said second group and which are positioned such that the central fuel rod axis of each of these 4 fuel rods is closer to the central fuel channel axis than any of the water channel axes of the water channels. With 4 such fuel rods, a larger central space is created, which means a further improved shut-down margin. According to another embodiment of a fuel assembly according to the invention, the fuel assembly comprises a set of 6-12, preferably 6-10, fuel rods, wherein said set includes said 3 or 4 fuel rods, wherein each fuel rod in said set has a length which is less than 0.80 times the length of said full length fuel rods, wherein the fuel rods in said set are grouped together such that each fuel rod in said set is positioned next to at least one other fuel rod belonging to said set. According to this embodiment, there are thus a relatively large number of centrally located shorter fuel rods. This ensures a quite large space for water above these fuel rods. This space, together with the space inside the water channels, ensure a good shut-down margin. According to another embodiment of a fuel assembly according to the invention, each of said 3 or 4 fuel rods has a length that is less than 0.50 times the length of said full length fuel rods. Since the fuel rods are that short, it is ensured that there is a large space for water above the fuel rods. According to a preferred embodiment, each of said 3 or 4 fuel rods has a length that is between 0.25 and 0.45 times the length of said full length fuel rods. With such short fuel rods an even larger volume for water is created. According to another embodiment, there is no fuel rod which is such that it is longer than 0.50 times the length of said full length fuel rods and has a central fuel rod axis which is positioned closer to the central fuel channel axis than the central fuel rod axis of any of said 3 or 4 fuel rods. Similarly to the above explanation, by ensuring that there are no longer fuel rods among the mentioned central shorter fuel rods, a large, undisturbed, space for water is created. According to another embodiment, the fuel assembly comprises no more than 3 of said at least 3 water channels. It has been found that the use of three such, relatively large, water channels is optimal for achieving good moderation in the hot condition, at the same time as there is still sufficient space in the fuel assembly for a relatively large number of fuel rods. According to a preferred embodiment, the fuel assembly does not comprise any other water channels either (i.e. also no water channel with a cross-sectional area which is less than twice as large as the cross-sectional area of each one of said fuel rods, or, in case the fuel assembly has fuel rods of different cross-sectional areas, less than twice as large as the average cross-sectional area of the fuel rods). According to another embodiment, each one of said at least 3 water channels has a cross-sectional area which is between 3.0 and 10.0, preferably between 4.0 and 8.0, times the cross-sectional area of each one of said fuel rods, or, in case the fuel assembly has fuel rods of different cross-sectional areas, between 3.0 and 10.0, preferably between 4.0 and 8.0, times the average cross-sectional area of the fuel rods. With such relatively large water channels, a sufficiently high amount of non-boiling water will flow through the fuel assembly. This ensures a good moderation, i.e. a high reactivity. According to another embodiment, each of said at least 3 water channels has a circular cross-section, at least in the portion of the water channel that is located at the level of said 3 or 4 fuel rods. From a flow dynamic point of view, it is advantageous to use round water channels. Furthermore, it is easy to manufacture and position such round water channels in the fuel assembly. According to another embodiment, the fuel assembly comprises no more than 12 fuel rods, preferably no more than 8 fuel rods, more preferred no more than 6 fuel rods, each of which fulfills the following criterion: the distance between the central fuel rod axis and the central fuel channel axis is less than the distance between the central water channel axis of at least one of said at least 3 water channels and the central fuel channel axis. It is thereby ensured that the water channels are not positioned too far towards the periphery of the fuel assembly. This means that a good moderation, and a high reactivity, for many fuel rods is achieved, and consequently also an evenly distributed fission power. According to a preferred embodiment, the fuel assembly comprises 6 fuel rods which fulfill the mentioned criterion. This has appeared to ensure an optimal positioning of the water channels. This means that the water channels are positioned near the central short fuel rods. Preferably, each of the water channels is positioned next to at least two of said 3 or 4 fuel rods, such that there is no further fuel rod positioned between the respective water channel and said 3 or 4 central short fuel rods. According to another embodiment, the fuel assembly comprises a substantially regular pattern of fuel rod positions, wherein each one of said at least 3 water channels is positioned such that it replaces 4 fuel rods in this substantially regular pattern. Such a design is quite easy to implement in a fuel assembly. The concept “substantially regular pattern” is used, since some fuel rods may be slightly displaced from the absolutely regular pattern. Preferably the regular pattern is in the form of rows and columns (when a cross-section of the fuel assembly is viewed). According to another embodiment, the fuel assembly comprises 65-160, preferably 100-120, more preferred 105-113, most preferred 109 fuel rods. Such a relatively high number of fuel rods ensures that the fuel assembly can achieve an efficient heat transfer to the coolant, and because of the arrangement of the fuel rods and the water channels, a good moderation is obtained. According to another embodiment, the fuel assembly comprises 2-10, preferably 6-8 fuel rods, each of which has a length of between 0.59 and 0.79 times the length of said full length fuel rods. The arrangement of such fuel rods contributes to the shut-down margin and to a reduction of the pressure drop in the upper part of the fuel assembly. According to one embodiment, the fuel assembly comprises 8-16, preferably 10-12 fuel rods, each of which has a length that is between 0.25 and 0.45 times the length of said full length fuel rods. With this number of such short fuel rods, the shut-down margin is improved. According to another embodiment, the fuel assembly comprises at least 70, preferably at least 80, or at least 90 full length fuel rods. An efficient heat transfer is obtained by using many full length fuel rods. According to one embodiment, the fuel assembly comprises 5-20, preferably 10-15 fuel rods, each of which has a length of between 0.80 and 0.95 times the length of said full length fuel rods. The arrangement of such fuel rods will reduce the pressure drop in the upper part of the fuel assembly, near the outlet for the water/steam. According to another embodiment, the fuel assembly comprises: a lower tie plate, positioned below the fuel rods, wherein a lower end of each of said at least 3 water channels is attached to said tie plate, an upper lifting device, positioned above the fuel rods, including a handle for gripping and lifting a bundle of fuel rods, a plurality of spacer grids for holding the fuel rods, at least most of the spacer grids being attached to said at least 3 water channels, attachment rods, attached at a lower end to the upper part of said at least 3 water channels and at an upper end attached to said upper lifting device. Such a design will make it easier to handle the bundle of fuel rods. Since the upper handle and lifting device is attached to the attachment rods, which are attached to the water channels, which are attached to the lower tie plate, and since the spacer grids hold the fuel rods and since at least most of the spacer grids are attached to the water channels, it is possible to lift the whole bundle of fuel rods by gripping and lifting the handle. According to one design principle, the fuel channel is permanently fixed to a bottom transition piece, which includes a debris filter, and the whole fuel bundle as described above (including upper handle and lifting device, attachments rods, water channels, lower tie plate, and spacer grids) is lowered into the fuel channel and is resting freely on top of the transition piece. According to an alternative design principle, the whole fuel bundle as described above (including upper handle and lifting device, attachments rods, water channels, lower tie plate, and spacer grids) is permanently fixed to the transition piece, which includes a debris filter, and the fuel channel is placed over the fuel bundle and resting on the upper lifting device or handle. A first embodiment of the invention will now be described with reference to FIG. 1 and FIG. 2. FIG. 1 shows schematically a side view of a fuel assembly 4 according to an embodiment of the invention. The fuel assembly 4 comprises a number of fuel rods 10 and water channels 14. A lower tie plate 20 is arranged below the fuel rods 10. A lower end of the water channels 14 is attached to the tie plate 20. Above the fuel rods 10 an upper lifting device 22 is arranged. The upper lifting device 22 has a handle 24 for gripping and lifting a bundle of fuel rods 10. The fuel rods 10 are held by a plurality of spacer grids 26. It should be noted that FIG. 1 schematically shows only an upper and lower part of the fuel assembly 4. According to an embodiment, the fuel assembly 4 comprises ten spacer grids 26. The fuel assembly 4 also comprises attachment rods 28, which at a lower end are attached to the upper part of the water channels 14 and which at an upper end are attached to the upper lifting device 22. All spacer grids 26, with one exception, are attached to the water channels 14. The upper spacer grid 26 is positioned at the level of the attachment rods 28. The whole bundle of fuel rods 10 is thus held together with the help of the water channels 14, lower tie plate 20, attachment rods 28, upper lifting device 22 and spacer grids 26. It is therefore possible to lift the whole bundle of fuel rods 10 by gripping and lifting at the handle 24. With reference also to FIG. 2 the fuel assembly 4 will now be described in more detail. The fuel assembly 4 comprises a fuel channel 6 which surrounds the bundle of fuel rods 10. In FIG. 1 the fuel channel 6 has been removed in the viewing direction in order to make it possible to see the components arranged inside the fuel channel 6. Also, two water channels 14 are shown in FIG. 1, although they in a side view would be partly hidden behind fuel rods 10. The fuel channel 6 extends in a length direction L. The length direction L is normally, when the fuel assembly 4 is in use in a nuclear reactor, the vertical direction. The fuel channel 6 has a central fuel channel axis 8 in said length direction L. In FIG. 2, all the small circles refer to fuel rods 10. Each fuel rod 10 has a central fuel rod axis 12 (shown only for one fuel rod 10), which extends substantially in the length direction L. The larger circles in FIG. 2 show the water channels 14. The water channels 14 are configured and positioned for allowing non-boiling water to flow through the water channels 14, when the fuel assembly 4 is in use in a nuclear reactor. Each water channel 14 has a central water channel axis 16 (shown only for one water channel 14 in FIG. 2), which extends substantially in the length direction L. The fuel assembly comprises a first group of full length fuel rods 10. The full length fuel rods are not marked in FIG. 2 (i.e. they are shown by empty circles). The full length fuel rods 10 extend from a lower part of the fuel assembly 4 to an upper part of the fuel assembly 4, preferably through all the spacer grids 26. It can be noted that in FIG. 1 only full length fuel rods 10 are shown. The fuel assembly 4 also comprises a second group of fuel rods 10. The second group of fuel rods 10 extend from the lower part of the fuel assembly (like the full length fuel rods) but do not reach as high up as the full length fuel rods. The fuel rods 10 in said second group can have different lengths. In the shown embodiment, some fuel rods 10 are marked with one stroke. These fuel rods have a length of about 9/10 of the length of the full length fuel rods. In the shown embodiment, there are ten such fuel rods. When placing these 9/10 fuel rods, the most reactive positions next to non-boiling water inside the water channels and outside the fuel channel are avoided. This is to minimize the negative impacts of having 1/10 less uranium in these rods, while serving their purpose of reducing pressure drop near the assembly outlet. The fuel rods 10 marked with two strokes (a cross) have a length of about ⅔ of the length of the full length fuel rods. In the shown embodiment there are six such fuel rods. These ⅔ fuel rods are positioned about halfway between the corner rods in the outer rows and columns of the 11×11 fuel rod array. This is to reduce cold reactivity in the upper part of the fuel bundle which improves the shutdown margin late in the fuel cycle when the power distribution has moved towards the top. The fuel rods 10 marked with three strokes (a star) have a length of about ⅓ of the length of the full length fuel rods. In the shown embodiment there are twelve such fuel rods. As shown in FIG. 2, the fuel assembly 4 according to this embodiment has three water channels 14. Each water channel 14 has a cross-sectional area which is about 5.5 times the cross-sectional area of each one of the fuel rods 10 (or, in case the fuel assembly 4 would have fuel rods 10 of different cross-sectional areas, about 5.5 times the average cross-sectional area of the fuel rods 10). In the shown embodiment, there are only three water channels 14, i.e. no further water channels. As shown in FIG. 2, there are eight centrally located fuel rods 10 of the shortest kind, i.e. eight central short fuel rods, which are grouped together and form a set of fuel rods, such that each fuel rod in this set is positioned next to at least one other fuel rod belonging to this set. Of these eight central short fuel rods 10, four are positioned such that for each of these four fuel rods 10 it is the case that the distance between the fuel rod axis 12 and the central fuel channel axis 8 is shorter than the distance between any of the water channel axes 16 of the water channels 14 and the fuel channel axis 8. These four short central fuel rod are thus (with reference to FIG. 2) the central fuel rod positioned on the fuel channel axis 8, the fuel rod positioned just below the central fuel rod, the fuel rod positioned just to the right of the central fuel rod and the fuel rod positioned next to the central fuel rod, one column to the left and one row up. It should be noted that FIG. 2 shows a schematic cross-section of the fuel assembly 4 in the lower part of the fuel assembly (where also all the shorter fuel rods 10 are present). There is no longer fuel rod 10 (no ⅔ fuel rod or 9/10 fuel rod or full length fuel rod) which is positioned closer to the central fuel channel axis 8 than the central fuel rod axis 12 of any of the four central short fuel rods 10 which fulfill the above definition. Above the four short central fuel rods 10, there is thus an empty space for water in the fuel assembly 4. In fact, there is an empty space for water above all the mentioned eight centrally located short fuel rods 10. In addition to the eight centrally located short ⅓ fuel rods, there are a further four such short fuel rods 10 located in the corners of the fuel assembly 4. Each of the water channels 14 has a circular cross-section, at least in the lower part of the fuel assembly 4 where the shorter central fuel rods 10 are arranged. In addition to the mentioned four defined central short fuel rods 10, the fuel assembly 4 comprises a further two fuel rods, each of which fulfills the following criterion. The distance between the central fuel rod axis 12 and the central fuel channel axis 8 is less than the distance between the central water channel axis 16 of at least one of the three water channels 14 and the central fuel channel axis 8. In the shown embodiment, there are thus six fuel rods 10 that fulfill the mentioned criterion. These fuel rods 10 are located inside the dashed lines in FIG. 2. Each water channel 14 is positioned next to at least two of the four defined centrally located short fuel rods 10. As can be seen in FIG. 2, the fuel assembly 4 comprises a substantially regular pattern of fuel rod positions. Each one of the water channels 14 is positioned such that it replaces four fuel rods 10 in this regular pattern. In the shown embodiment, the fuel assembly 4 thus comprises 81 full length fuel rods 10, ten 9/10 length fuel rods, six ⅔ length fuel rods and twelve ⅓ length fuel rods. Further embodiments of the present invention are shown in FIGS. 3, 4 and 5. In these figures, the same markings and the same reference numbers are used as in FIG. 2. It will therefore now only be described how these embodiments differ from the embodiment shown in FIG. 2. FIG. 3 shows an embodiment which differs from the embodiment in FIG. 2 in that the fuel rods 10 that have a length of about ⅔ of the length of the full length fuel rods are not positioned next to the periphery of the fuel assembly 4, but instead are positioned further inside the fuel assembly 4. In the embodiment of FIG. 2, the full length fuel rods which are positioned in the outer rows and columns next to the fuel rods of ⅔ length are highly moderated in the upper region (since there is a large space for water next to these full length fuel rods). This means that the local effect in the higher part of these full length fuel rods is quite high. With the embodiment of FIG. 3, this local high effect is avoided. FIG. 4 shows an embodiment which differs from the embodiment in FIG. 2 in that two of the centrally located eight ⅓ short fuel rods 10 have been replaced by full length fuel rods. Furthermore, in the embodiment of FIG. 4 there are eight (instead of six as in FIG. 2) fuel rods of the length ⅔ arranged in the outer rows and columns. Since there are only six central short ⅓ fuel rods in the embodiment of FIG. 4, the flow velocity in the central upper region is reduced. Furthermore, with the arrangement of FIG. 4, there is a more even distribution of the nuclear fuel in the upper part of the fuel assembly as compared to the embodiment of FIG. 2. FIG. 5 shows an embodiment which differs from the embodiment in FIG. 2 in that two of the centrally located eight ⅓ short fuel rods 10 have been replaced by ⅔ length fuel rods. Furthermore, in the embodiment of FIG. 5 there are only four ⅔ length fuel rods which are positioned in the outer rows and columns. Instead, there are two ⅔ length fuel rods which are positioned next to the centrally located ⅓ length fuel rods (one ⅔ length fuel rod positioned in the third row from above and the fifth column from the left and one ⅔ length fuel rod positioned in the fifth row from above and the third column from the left). In the embodiment of FIG. 5, there are thus six centrally located ⅓ length fuel rods and also four ⅔ length fuel rods, i.e. together 10 fuel rods shorter than 0.80 of the length of the full length fuel rods, which are grouped together such that they form a set such that each fuel rod in the set is positioned next to at least one other fuel rod belonging to the set. This embodiment has appeared to bring about a good compromise of the advantages described in connection with the previous embodiments. The shown embodiments provide advantageous fuel assemblies with which the above described objects and advantages of the invention are achieved. Many variations of the illustrated embodiments are possible within the scope of the present invention. For example, the number of fuel rods may vary and the number of fuel rods of the different lengths may vary. For example, there may be fewer, or more, or no at all, fuel rods which have the length 9/10. The present invention is thus not limited to the examples described herein, but can be varied and modified within the scope of the following claims.
	abstract	A nuclear reactor vibration surveillance system has a first ultrasonic transducer for transmission, an ultrasonic transmitter, a second ultrasonic transducer for reception, an ultrasonic receiver, a signal processor, and a display unit. The first ultrasonic transducer for transmission is arranged on the outer surface of a reactor pressure vessel and is configured to convert a transmission signal into an ultrasonic pulse signal and allow the ultrasonic pulse to be transmitted to a reactor internal component. The second ultrasonic transducer for reception is arranged on the outer surface of the reactor pressure vessel and is configured to receive a reflected ultrasonic pulse reflected by the reactor internal component and convert the received reflected ultrasonic pulse into a reception signal.
	summary
	claims	1. A method of hermetically sealing at least one end cap to a nuclear reactor fuel rod cladding tube, the tube being formed from a ceramic composite comprising:(1) providing a tube formed from a ceramic composite, the tube having tube walls, at least one open end, and a circumferential axis, and providing at least one end cap, the end cap having an exterior side and an interior side;(2) applying the at least one end cap to the at least one open end of the tube to define an interface between a portion of the end cap and the tube, wherein the at least one end cap is made from a material selected from the group consisting of multiple layers of a SiC—SiC ceramic composite, a ternary carbide, and a ternary nitride;(3) applying at least one primary electrode to the exterior side of the at least one end cap;(4) applying current to the at least one electrode using a spark plasma sintering means to supply a rapid temperature rise in the interface applied for 0.01 to 6.0 minutes at a rate of 200° C./min up to 1,500° C./min. where the temperatures at the interface are from ambient to 2,500° C. 2. The method of claim 1, wherein the at least one end cap is based on SiC. 3. The method of claim 1, wherein after step (1), the portion of the end cap and tube defining the interface are polished. 4. The method of claim 1, further comprising applying in step (3) a secondary electrode to the exterior side of the tube. 5. A method of hermetically sealing at least one end cap to a nuclear reactor fuel rod cladding tube, the tube being formed from a ceramic composite, comprising:(1) providing a tube formed from a ceramic composite, the tube having tube walls, at least one end, and a circumferential axis;(2) applying at least one end cap to the at least one end of the tube to define an interface between a portion of the end cap and the tube, the end cap being formed from a composition selected from the group consisting of a ceramic composition or a precursor to a ceramic composition, and having an exterior and interior side and;(3) applying at least one primary electrode to the exterior side of the at least one end cap;(4) applying current to the at least one electrode using a spark plasma sintering means (SPS) for 0.01 to 6.0 minutes to supply a rapid temperature rise in the interface at a rate of 200° C./min. up to 1,500° C./min. where temperatures at the interface are from ambient to 2,500° C., and holding a peak temperature for 5 to 60 minutes at pressures from 0.001 MPa to 50 MPa to hermetically seal the tube to the at least one end cap. 6. The method of claim 5, wherein the at least one ceramic end cap is formed from the same composition as the composition forming the tube. 7. The method of claim 5, wherein the operating parameters of the SPS process are applying the rapid temperature rise at a rate of 1000° C./min. up to 1,500° C./min. to raise the interface temperature up to 2,500° C. in 1.0 to 5.0 minutes and the pressures are 0.001 to 10 MPa. 8. The method of claim 5, wherein the tube and the at least one end cap are made of SiC. 9. The method of claim 5, wherein after step (1), the interface of the at least one end cap and tube are polished. 10. The method of claim 5, wherein the tube and end cap are made from a SiC composite comprising monolithic SiC-based layer or multi-layers on the inside and at least one outer layer of SiC-based fibers in a SiC-based matrix. 11. The method of claim 5, wherein the tube is from 2 feet to 18 feet long. 12. The method of claim 5, wherein after step (1), the interface of the end caps and tube are polished. 13. The method of claim 5, wherein a bonding pressure of 4 to 20 MPa is applied after step (3), with a hold time of 5 minutes to 60 minutes applied after step (4). 14. The method of claim 5, wherein an inert gas is inserted into the tube after step (1) or step (2), at a back pressure of 50 psi to 500 psi. 15. The method of claim 14, wherein the inert gas is helium. 16. The method of claim 5, wherein at least step 4 of the method is carried out in a furnace having a temperature of from about 50° C. to 1,500° C. 17. A tubular ceramic composite made by the method of claim 5. 18. The method of claim 5, wherein the method further comprises applying a secondary electrode to the exterior side of the tube and in step (4) applying current to the secondary electrode for 0.01 to 6.0 minutes using the spark plasma sintering means (SPS). 19. The method of claim 1, wherein current is applied to the at least one electrode at a rate of about 1000° C./min to 1500° C./min. for 1.0 to 5.0 minutes at a pressure of 0.001 to 10 MPa.
	claims	1. A filled composition for radiation shielding, comprising:at least one polymer ingredient selected from the group consisting of a polyolefin elastomer, a polyolefin co-polymer, a polyolefin ter-polymer, and a combination thereof, wherein the polyolefin elastomer, the polyolefin co-polymer, or the polyolefin ter-polymer comprises monomer units derived from ethylene and at least one vinyl monomer being butene or an alkene having at least five carbon atoms; andat least 60 weight percent of at least one metal-containing filler other than BaSO4 the at least one metal-containing filler comprising a metal having an atomic number greater than 50. 2. The filled composition of claim 1, whereinthe at least one vinyl monomer has from five to ten carbon atoms. 3. The filled composition of claim 1, whereinthe at least one polymer ingredient comprises a polyolefin elastomer (POE). 4. The filled composition of claim 1, whereinthe at least one polymer ingredient comprises a polyolefin elastomer (POE), and the POE is a copolymer of ethylene and at least one vinyl monomer selected from the group consisting of butene, pentene, hexene, heptene, octene and a combination thereof. 5. The filled composition of claim 1, whereinthe at least one polymer ingredient comprises a polyolefin elastomer (POE) comprising a copolymer of ethylene and octene. 6. The filled composition of claim 1, whereinthe at least one polymer ingredient comprises an olefin block copolymer (OBC) having alternating blocks of rigid and elastomeric segments. 7. The filled composition of claim 1, whereinthe at least one polymer ingredient comprises an olefin block copolymer (OBC) of ethylene and at least one vinyl monomer selected from the group consisting of butene, pentene, hexene, heptene, octene and a combination thereof. 8. The filled composition of claim 1, whereinthe at least one polymer ingredient comprises an olefin block copolymer (OBC) of ethylene and octene. 9. The filled composition of claim 1, whereinthe at least one metal-containing filler comprises Sb, W, Pb, Bi, an alloy thereof, an oxide thereof, a salt thereof, or a combination thereof. 10. The filled composition of claim 1, whereinthe at least one metal-containing filler is substantially free of Pb, and comprises a filler selected from Sb, W, Bi, or a combination thereof; and optionally the filled composition further comprises BaSO4. 11. The filled composition of claim 1, further comprising:an additive package comprising an additive selected from the group consisting of a paraffinic oil, an aromatic oil, an antioxidant, a compatibilizer, an adhesion promoter, a processing aid, and a combination thereof. 12. The filled composition of claim 11, whereinthe filled composition is cross-linkable, and the additive package further comprises an additive selected from the group consisting of an initiator, a curing agent, an accelerator, and a combination thereof. 13. The filled composition of claim 11, whereinthe at least one polymer ingredient constitutes from about 0.4 weight percent (wt. %) to about 35 wt. % of the filled composition. 14. The filled composition of claim 11, whereinthe at least one polymer ingredient constitutes from about 1 wt. % to about 25 wt. % of the filled composition;the at least one metal-containing filler constitutes from 60 wt. % to about 95 wt. % of the filled composition; andthe additive package constitutes from about 4 wt. % to about 15 wt. % of the filled composition. 15. The filled composition of claim 11, wherein the filled composition includes:the at least one polymer ingredient in the range of from about 10 wt. % to about 15 wt. %;the at least one metal-containing filler in the range of from about 75 wt. % to about 85 wt. %; andthe additive package in the range of from about 5 wt. % to about 10 wt. %. 16. The filled composition of claim 11, whereinthe additive package comprises a paraffinic oil in the range of from about 5 wt. % to about 9 wt. %. 17. A filled sheet for radiation shielding, comprising:from about 0.4 wt. % to about 25 wt. % of at least one polymer ingredient selected from the group consisting of a polyolefin elastomer, a polyolefin co-polymer, a polyolefin ter-polymer, and a combination thereof, wherein the polyolefin elastomer, the polyolefin co-polymer, or the polyolefin ter-polymer comprises monomer units derived from ethylene and at least one vinyl monomer being butene or an alkene having at least five carbon atoms;from about 60 wt. % to 95.5 wt. % of at least one metal-containing filler other than BaSO4, the at least one metal-containing filler comprising a metal having an atomic number greater than 50; andfrom about 0.1 wt. % to about 15 wt. % of an additive package comprising an additive selected from the group consisting of a paraffinic oil, an aromatic oil, an antioxidant, a compatibilizer, an adhesion promoter, a processing aid, and a combination thereof. 18. The filled sheet of claim 17, whereinthe at least one polymer ingredient comprises a polyolefin elastomer (POE), which is a copolymer of ethylene and at least one vinyl monomer selected from the group consisting of butene, pentene, hexene, heptene, octene and a combination thereof. 19. The filled sheet of claim 17, whereinthe at least one polymer ingredient comprises an olefin block copolymer (OBC) of ethylene and at least one vinyl monomer selected from the group consisting of butene, pentene, hexene, heptene, octene and a combination thereof. 20. The filled sheet of claim 17, whereinthe at least one metal-containing filler comprises Sb, W, Pb, Bi, an alloy thereof, an oxide thereof, a salt thereof, or a combination thereof. 21. A protective garment for radiation shielding, comprising a filled composition comprising:from about 0.4 wt. % to about 35 wt. % of at least one polymer ingredient selected from the group consisting of a polyolefin elastomer, a polyolefin co-polymer, a polyolefin ter-polymer, and a combination thereof, wherein the polyolefin elastomer, the polyolefin co-polymer, or the polyolefin ter-polymer comprises monomer units derived from ethylene and at least one vinyl monomer being butene or an alkene having at least five carbon atoms;from about 50 wt. % to 95.5 wt. % of at least one metal-containing filler comprising a metal having an atomic number greater than 50;from about 0.1 wt. % to about 15 wt. % of an additive package comprising an additive selected from the group consisting of a paraffinic oil, an aromatic oil, an antioxidant, a compatibilizer, an adhesion promoter, a processing aid, and a combination thereof; andat least one layer of fabric. 22. The protective garment of claim 21, wherein in the filled compositionthe at least one polymer ingredient comprises a polyolefin elastomer (POE), which is a copolymer of ethylene and at least one vinyl monomer selected from the group consisting of butene, pentene, hexene, heptene, octene and a combination thereof. 23. The protective garment of claim 21, wherein in the filled compositionthe at least one polymer ingredient comprises an olefin block copolymer (OBC) of ethylene and at least one vinyl monomer selected from the group consisting of butene, pentene, hexene, heptene, octene and a combination thereof. 24. The protective garment of claim 21, wherein in the filled compositionthe at least one metal-containing filler comprises Sb, W, Ba, Pb, Bi, an alloy thereof, an oxide thereof, a salt thereof, or a combination thereof. 25. The protective garment of claim 21, wherein the protective garment is in a design selected from the group consisting of a vest-skirt apron, a frontal apron, a thyroid collar, a gonad shield, and a dental apron. 26. The protective garment of claim 21, wherein the filled composition is uncrosslinked. 27. The protective garment of claim 21, wherein the filled composition is crosslinked.
	abstract	Infrared marking devices and methods for marking an object, such as a door, inside a structure, such as a smoke-filled or burning structure. The infrared marking device comprises a ring-shaped, elasticized outer sleeve having a tubular sidewall and an amount of a self-heating material confined inside the tubular sidewall of the outer sleeve. The self-heating material emits infrared radiation when activated to initiate an exothermic chemical reaction. The infrared radiation is visible in a thermal imaging camera. The method comprises activating a self-heating material confined inside a marking device to initiate an exothermic reaction that emits infrared radiation and applying the marking device to an object inside the structure.
	summary
	description	The present invention relates to ballistic protective apparel in general, and more particularly to undergarments for use with ballistic armor. Persons exposed to projectile threats, such as police officers and soldiers, may seek a certain level of protection by wearing armored clothing. Low velocity projectiles such as handgun rounds, fragmentation rounds from a grenade or mortar, and miscellaneous shrapnel may be countered by so-called “soft armor.” Soft armor is worn in the form of jackets, vests, etc. which are composed of assemblies of ballistic fabric such as those formed from DuPont Kevlar® fibers. In a more serious threat situations, where higher velocity rifle rounds must be countered, soft armor has typically been supplemented with hard armor. The hard armor is fabricated of rigid plates of ceramic, polymer, or metal. A common approach to mounting the plates to the wearer is to secure them within exterior pockets fabricated on a soft armor jacket or vest. Conventionally, the armor jacket or vest will be worn over a durable shirt, such as a battle dress uniform blouse. The durable fabric protects the wearer from sun, dust, and minor abrasions. By wearing a conventional blouse, a soldier can remove his armor while still maintaining required uniform standards. Yet the heavy soft armor, possibly supplemented by hard armor, does not require a durable fabric beneath it, and the less breathable durable fabric can contribute to heat build-up in the wearer. Higher metabolic activities encountered under combat conditions can result in greater perspiration. It is important that this moisture be able to evaporate away from the wearer's skin, and that heat loads be dissipated. An early combat shirt developed for the U.S. Army employs a lightweight wicking fabric in the torso, while the sleeves of the garment, which may not be covered by the armor, are composed of a durable, less open, fabric. The torso fabric may be similar to that used in UNDER ARMOUR® undershirts marketed by Under Armour, Inc. of Baltimore, Md. By forming the combat shirt from materials with differing properties, the wearer's arms are protected, while heat dispersion is facilitated. However, the wicking material is also more elastic or stretchable than the durable fabric, with the result that the shirt tends to lose its shape, with the durable sleeves pulling down the resilient torso material at the shoulders. What is needed is a combat shirt having desirable protective and wicking abilities, yet which at the same time satisfactorily retains its shape on the wearer. A protective body armor system for protection against ballistic threats of this invention has an armored element such as a vest with front and rear ballistic armor. A long-sleeved shirt is worn beneath the ballistic armor which has a wicking, lightweight, low thermal insulation torso element. Two long sleeves are connected to and extend from the torso element. The shirt has a durable collar connected to the torso element and to the two sleeves. The collar extends upwardly from the armored element. The collar is less stretchy than the torso element, and serves to connect the two sleeves and to restrain the garment from undesired distortion. The torso element is substantially overlain by portions of the armored element, while the collar and portions of the sleeve extend beyond the armored element. The collar and sleeves are formed of a more durable material than the torso element. It is an object of this invention to provide a body armor system having a base layer shirt which has different wicking and durability properties under armored and unarmored regions, and which resists undesired distortion. Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings. Referring more particularly to FIGS. 1-3, wherein like numbers refer to similar parts, a body armor system 20 of this invention is shown in relation to a wearer 22 in FIG. 1. The wearer 22 will typically be a soldier or police officer performing duties which present a risk of encountering gunfire. Such duties not infrequently call for high levels of exertion while carrying equipment. The armor system 20 is comprised of a shirt 24 worn with an armored element 26. The armored element 26 may be a ballistic vest such as is disclosed in our U.S. Pat. No. 6,892,392, the disclosure of which is incorporated by reference herein, or it may be any conventional ballistic vest, for example the U.S. Military Interceptor Multi-Threat Body Armor System, or its predecessor the Personnel Armor System for Ground Troops (PASGT) vest. The vest may have soft armor 30 or plate armor 32 inserts. The vest has a front section 56 with the armor 32, and a rear section 58 with the armor 30. The shirt 24 is fabricated of different fabrics to provide different functions at different locations. As shown in FIG. 1, the shirt 24 is worn directly against the body of the wearer 22 without any underlying garment. The shirt 24 has a torso element 28. A left sleeve 34 and a right sleeve 36 are sewn to the torso element 28. The sleeves are connected to each other by an upwardly extending collar 38. The collar 38 may be formed of a single strip of fabric, and serves as a connecting strip between the sleeves, which prevents distortion of the torso element 28 causing the sleeves to be excessively displaced from one another. The sleeves 34, 36 may be raglan sleeves which extend in one piece from the arm to the collar 38, to avoid the need to place a seam on the shoulder of the wearer. Both sleeves 34, 36 have lateral portions 54 extending toward the collar 28 which do not conform to the arms. Under arm panels 40 are preferably provided which extend from the torso element 28 to each sleeve 34, 36, beneath the sleeves. The under arm panels 40 are preferably fabricated of the same material as the torso element 28. The sleeves and collar are fabricated of a durable material, as they will be exposed to the environment, and can encounter dirt, impact, and abrasion. The durability of a material may be measured, for example, by its performance in the Modified Wyzenbeek abrasion test, or by ASTM D 4157 Standard Test Method for Abrasion Resistance of Textile Fabrics (Oscillatory Cylinder Method), or by any abrasion test measured in cycles. A higher number indicates that the fabric survived a greater number of abrasion cycles, and is hence of greater durability or abrasion resistance. The sleeves and collar are fabricated of a material which is substantially more durable/abrasion resistant than the material of the torso element, preferably having a modified Wyzenbeek abrasion test score which is at least 50 percent greater. The collar and sleeves may be formed of material which is of greater weight than the material of the torso element. Weight is a conventional measure of fabric properties, and is usually presented in terms of ounces of weight per square yard of material. Typically, the sleeves and collar will be fabricated of material having a weight of from about 6 to about 8 oz/yard2, while the torso material will have a weight of about 3 to 5 oz/yard2, although with appropriately durable lightweight material, and heavier wicking material, in some situations the weights may be the same, or the torso element material may have a greater weight than the sleeve or collar material. The material of which the torso element is fabricated is a stretchable fabric, for example having a stretch of 60 to 100 percent, while the material of which the collar is fabricated is a very low stretch fabric, preferably having approximately no stretch. A level of stretch may be defined as the amount a given sample of material will stretch in response to a given applied tension in a particular direction. The torso element material may be cotton, wool, polyester, nylon, or a blend thereof. A preferred embodiment is a polyester, Lycra® brand synthetic polyurethane-based elastane textile blend, which is stretchy and form fitting. A cotton material may be used where flame retarding properties are required. Cotton will usually not wick as well, but also resists melting better for environments likely to encounter flame and melting temperatures. The torso element 28 is preferably formed of a knit material, for example microfiber polyester. The material may be a tubular knit which is a continuous tube of material, or a warp knit which results in seams running up and down the sides of the torso. The torso element material has a low clo value, and also serves to wick away perspiration from the wearer's body. However, this knit material is also more resilient, and is sized to cling or conform to the wearer's torso. As a result, the torso element is readily deformed and distorted. While the strands in woven fabrics extend straight horizontally and vertically, knit threads follow a loopy path as they extend in rows, with the result that a knit fabric piece will be stretchy in all directions. The stretchy torso element material's stretchiness permits it to cling tightly or very tightly to the wearer. This clinging helps to keep the torso element material from bunching up beneath the armor and forming folds under the armor that can be uncomfortable. The sleeves 34, 36 are terminated with cuffs 42 which may be tightened with overlapping strips 44 provided with hook and loop fastener such as VELCRO® material of Velcro Industries B.V. Ltd Liab. Co., of the Netherlands. As best shown in FIG. 3, the sleeves may have closable pockets 46 above the elbows. Each sleeve may also have a pad pocket 48 positioned to receive an elbow pad or elbow protector, not shown. The collar 38 extends upwardly from a neck hole 50 defined by the two sleeves and the torso element. To permit the wearer's head to pass through the collar 38, the collar is provided with a closure 52 such as a zipper closure. The zipper extends from the torso element 28 through the collar 38 at the front of the shirt 24. When the closure 52 is unzipped, the shirt 24 may be passed over the wearer's head. The thermal insulation value of clothing is measured in clo. 1 clo=1.55 m2° C./W. The clo unit relates to the quantity of clothing required on a subject at rest at room temperature to be comfortable. A higher clo value provides higher insulation. The sleeves 34, 36 and the collar 38 are fabricated from a material which is more dimensionally stable than the torso element material, i.e., which is less resilient, and less given to distortion when subjected to tension. This material is preferably a woven fabric, woven of a cotton polyester blend fiber. The collar and sleeve material is more durable than the torso element material, and also has a higher clo value. Although the collar, by extending upwardly from the torso element 28, serves to protect the wearer's neck, the function of connecting the sleeves and maintaining the shape of the garment may be formed by a connecting strip between the sleeves which lies flat as it encircles the neck hole 50, and which does not protrude upwardly from the garment shoulders. The shirt 24 preferably has two types of elements, the torso element which is an element which conforms to the body of the wearer, and the sleeves and collar which do not conform to the body of the wearer. By “conforming” is meant an element having sufficient elasticity to be placed over a body portion which is of greater circumferential size than the element so that substantially all the material making up the element is brought into compressive intimate contact by reason of the elasticity of the element. By “nonconforming” is meant an element having in itself not a significant cause of compressive intimate contact by reason of its lack of significant elasticity. It is understood that the invention is not limited to the particular construction and arrangement of parts herein illustrated and described, but embraces all such modified forms thereof as come within the scope of the following claims.
051857758	description	DETAILED DESCRIPTION OF THE INVENTION A radiological apparatus 10 for angiographic examination schematically comprises (FIG. 1) a table 11 having a base 12 with a sliding panel 13 mounted thereon to support a patient 14. The patient 14 is irradiated by a beam 19 of X-rays which is emitted by a radiation source 15 having a focus F and an aperture 34. After being absorbed to a greater or lesser extent by the patient's body, the X-rays are detected by a receiver 16 which may be any conventional receiver such as photographic film, a screen in combination with photographic film, or an image intensifier. If an image intensifier is used, then the light signals delivered by the image intensifier are processed in conventional manner in order to obtain images suitable for tracking the progress of the contrast substance. In order to track the progress of the contrast substance, the X-ray beam 19 needs to be displaced relative to the patient 14, either by displacing the source 15 as shown in FIG. 1, or else by sliding the panel 13. In this figure, means for controlling the displacement of the source 15 and of the receiver 16 are represented by a device 36. This device 36 is a computer which receives position data relating to the source 15 and to the table 11 and which issues instructions for displacing the source 15 and the table 11, both of which are fitted with motorized horizontal displacement means (not shown in FIG. 1). As shown in FIGS. 2 and 3, the X-rays are subject to very different degrees of attenuation since they go through portions of the patient's body having a wide range of thicknesses and/or having different absorption coefficients. Thus, the abdomen attenuates X-rays more than do the legs because of the difference in thickness, but even so the bones in the legs also attenuate strongly because they have a higher coefficient of absorption than do the tissues of the abdomen. In addition, between the legs and around the margins of the legs and the abdomen, the X-rays are not attenuated. These phenomena lead to images having very high degrees of contrast, making them difficult to analyze or else obliging the practitioner to change the exposure parameters. In order to mitigate these drawbacks, the invention proposes interposing a "homogenizing" filter between the X-ray source and the receiver, and preferably between the source and the patient and in the proximity of the source. The filter 20 is constituted by a plate 27 which is made of an X-ray absorbent material and which is of varying thickness so as to attenuate each X-ray path in such a manner that the total attenuation to which the said X-rays are subjected over their entire path all the way to the receiver is substantially the same for all paths in the X-ray beam. As a result, maximum attenuation is inserted between the legs and minimum attenuation is inserted for the abdomen zone, and the attenuation in other zones has intermediate values. An image is then obtained in which the exposure is homogenized. Perfect compensation would lead to an image that was uniformly gray on which only the contrast substance conveyed by the blood vessels would appear. The geometrical diagrams of FIGS. 2 and 3 serve to explain how the thickness of the filter is determined for each X-ray path, taking account of the respective positions of the filter 20 and of the patient 14 relative to the focus F of the X-ray source 15, which positions define a scale factor. This scale factor is used for calculating the lateral and transverse dimensions of the filter, and the nearer the filter is to the focus F, the smaller these dimensions. In FIG. 2, which corresponds to a section through the knees of the patient, the rays 26 and 26' determine the limits of the gap between the legs and define the high attenuation (or high thickness) central zone 28 of the filter. The rays 25 and 25' determine the side edges of the patient and define the outer high attenuation (or thickness) zones 29 and 30 of the filter. Finally, all of the rays such as 24 and 24' are attenuated by respective ones of the legs 22 and 23 of the patient and define zones 31 and 32 of varying attenuation (or thickness). In general, the thickness of the plate 27 is selected so as to impart attenuation on the path of each X-ray such that the total attenuation to which the X-ray is subjected on its path all the way to the receiver 16 is substantially the same for all of the paths in the beam. In FIGS. 3a and 3b, which are schematic sections through the apparatus of FIG. 1 at respective positions A and B of the source and receiver pair (the receiver not being shown), the filter is shown having the shape that it would have were it to be placed level with the patient: i.e. a half-mold 33 of the lower limbs of the patient. According to the invention, the filter is placed close to the focus F at the outlet from the source 15, thereby, as shown in FIG. 3, defining a scale factor of five between the lateral and transverse dimensions of the half-mold 33 and the corresponding dimensions of the filter 20. The thickness of the filter does not depend on the scale factor, but on the attenuation to which the X-rays are subjected passing through the patient and on the attenuation coefficient of the material used for making the filter. Since the radiological apparatus 10 is designed to take several pictures of the lower limbs, with each picture corresponding to a different zone, the filter 20 must be capable of being displaced horizontally relative to the X-ray source 15 in order to ensure that corresponding zones of the filter and of the patient lie on the paths of the X-rays. To this end, the filter 20 is carried by the X-ray source 15 in such a manner as to be capable of sliding relative to the aperture 34 through the diaphragm of the source. In FIG. 1, the device for horizontally displacing the filter 20 is not shown, but it is clear that it can be implemented in various different ways without requiring invention. Thus, the filter may be motorized and controlled synchronously with the horizontal displacement of the source-receiver pair or of the panel 13 if the radiological apparatus is of the type in which the patient is displaced. In FIG. 1, the means for controlling horizontal displacement of the filter constitute a portion of the device 36, but the motorized displacement means are not shown. According to the invention, the device 36 is also provided to control vertical displacement of the filter 20 and/or of the source 15 and/or of the panel 13 in such a manner as to vary the scale factor K=(a+b)/a, thereby adapting the filter to the size of the patient. These vertical displacement means are not shown in FIG. 1. In addition, the device 36 is designed to adapt the horizontal displacement of the filter as a function of the scale factor K and of the ratio K'=H/h between the size H of the patient and the length h of the filter. It should be observed that K=K' for a filter designed to correspond to the standard patient, and the filter is displaced by h/K between taking two pictures so as to obtain a displacement of H/K at the patient. If, in order to match the filter to the size H1 of the patient, K is changed to become K1, then it is necessary also to change the length of the horizontal displacement of the filter before taking two pictures so as to maintain correspondence in each picture between corresponding portions of the filter and of the patient. This change in displacement is determined by the device 36. The filter must match the morphology of the patient, and according to the invention it is proposed that a plurality of filters should be made depending on whether the patient is male or female, and depending on whether the patient is large, medium, or small in size, or possibly depending on the weight of the patient. The practitioner will thus have a set of filters available from which the filter most closely matching the patient to be examined will be selected. The filter of the invention thus makes it possible to homogenize image exposure, and consequently to distinguish the contrast substance more clearly. In addition, there is no need to change exposure parameters from one image to the next. Finally, the dynamic range of such a homogenized image is reduced, thereby making digital encoding possible without losing information. This gives rise to better digital processing of the image. The invention has been described with the filter placed at the outlet from the X-ray source, however it would be preferable to integrate the filter in the assembly constituted by the X-ray tube and the collimator including an iris and/or flaps. The material from which the filter of the invention is made may be an acrylic resin, for example, having a lead filler, e.g. the substance sold under the name "Kyowa Glass". The varying attenuation of the filter is obtained by the varying thickness of the plate 27, but it would also be possible to vary attenuation by varying the composition of the plate materiel, e.g. by adding more highly absorbent particles, particularly for the paths between the legs and for the outside margins. The horizontal and vertical displacement means for the source 15, the filter 20, and the table 11 are not shown in FIG. 1 so as to avoid overcrowding the figure. In any case, these means are known to the person skilled in the art and may be implemented without requiring any invention.
	abstract	The invention comprises a system for controlling a charged particle beam shape and direction relative to a controlled and dynamically positioned patient and/or an imaging surface, such as a scintillation plate of a tomography system and/or a first two-dimensional imaging system coupled to a second two-dimensional imaging system. Multiple interlinked beam/patient/imaging control stations allow safe zone operation and clear interaction with the charged particle beam system and the patient. Both treatment and imaging are facilitated using automated sequences controlled with a work-flow control system.
	description
	abstract	An x-ray focusing device generally includes a slide pivotable about a pivot point defined at a forward end thereof, a rail unit fixed with respect to the pivotable slide, a forward crystal for focusing x-rays disposed at the forward end of the pivotable slide and a rearward crystal for focusing x-rays movably coupled to the pivotable slide and the fixed rail unit at a distance rearward from the forward crystal. The forward and rearward crystals define reciprocal angles of incidence with respect to the pivot point, wherein pivoting of the slide about the pivot point changes the incidence angles of the forward and rearward crystals while simultaneously changing the distance between the forward and rearward crystals.
	description	This application is a divisional application and claims priority to application Ser. No. 13/957,919, filed Aug. 2, 2013, which application claims priority to U.S. Provisional Application No. 61/678,702, filed Aug. 2, 2012, which is hereby incorporated by reference herein in its entirety. Nuclear fuel assemblies for powering nuclear reactors generally comprise large numbers of fuel rods that are contained in discrete fuel rod assemblies. These assemblies typically comprise a bottom end fitting or nozzle, a plurality of fuel rods extending upwardly therefrom and spaced from each other in a square or triangular pitch configuration, spacer grids situated periodically along the length of the assembly for support and orientation of the fuel rods, a plurality of control guide tubes interspersed throughout the assembly, and a top end fitting or cap. Once assembled, the fuel rod assembly can be installed within and removed from the reactor as a unit. When the nuclear fuel rods have expended a large amount of their available energy, they are considered to be “spent,” and the fuel rod assembly is removed from the reactor and temporarily stored in an adjacent pool until they can be transported to an interim storage facility, reprocessing center, or to a permanent storage facility or repository. Even though the rods are considered to be spent, they are still highly radioactive and hazardous both to people and property. There are a number of options available for storing and disposing of the radioactive spent fuel rods. In one such option, the fuel rod assemblies are contained within a dry storage system that can be transported offsite to another facility. In such systems, the fuel rod assemblies are typically placed, without water, within cylindrical canisters, which are then placed within transport casks. Transportable canister-based dry spent fuel storage systems must comply with multiple federal regulatory requirements, including both storage and transport requirements. Systems that are licensed for storage must meet safety design conditions imposed by 10 CFR Part 72, while systems that are licensed for transport must meet more challenging safety design conditions that are imposed by 10 CFR Part 71 (Part 71 hereafter). These parts are the sections of the Code of Federal Regulations that stipulate the requirements that must be complied with to obtain U.S. Nuclear Regulatory Commission (NRC) certification for the storage and transport of spent fuel. In order to achieve NRC certification under Part 71 for transport of a dry storage system for spent fuel, the storage system must be designed such that nuclear criticality cannot be achieved under normal operations and postulated accident conditions. Nuclear criticality is a condition in which the effective neutron multiplication factor of the fuel array, keff, is greater than or equal to 1.0 and a nuclear chain reaction becomes self-sustaining. According to the requirements, nuclear criticality must not be achieved even if the storage system is flooded with a neutron moderator, like water, in an optimal condition that enhances the potential for criticality. Notably, no regulatory credit is given for designing the system to ensure that water intrusion is not realistically possible. The requirement to prevent criticality even in the presence of a neutron moderator typically forces dry storage and transport system designers to produce systems that incorporate expensive neutron absorber material in the spaces between the fuel rod assemblies. The neutron absorber material ensures that, even with a neutron moderator present, keff remains less than or equal to 0.95 and the system is not able to sustain a nuclear chain reaction. Unfortunately, such designs have relatively low fuel storage capacity and are expensive because of the need for the neutron absorber material. Furthermore, these systems are not perfectly suitable to be placed in a permanent repository because of exceedingly large dimensions, typical neutron absorber degradation uncertainties, and other canister material degradation concerns under long-term disposal conditions. The net result is that the cost per spent fuel assembly stored, transported, and disposed of is greatly increased. From the above discussion, it can be appreciated that it would be desirable to have a transportable dry storage system and method that have higher spent fuel storage capacity and/or that remove the need for expensive neutron absorber material. As described above, it would be desirable to have a transportable dry storage system and method that have higher spent fuel storage capacity and/or that remove the need for expensive neutron absorber materials. Examples of such systems and methods are described in the following disclosure. In some embodiments, spent fuel rods are separated from their fuel rod assemblies and the freed rods are placed within a dry storage canister that, for example, can be placed in a storage or transport cask or in a repository. Because the fuel rods are separated from the fuel rod assembly, the rods can be placed within the storage canister with a much higher packing density. As a consequence, there is less space between the rods and, therefore, less danger of the system reaching nuclear criticality if a neutron moderator such as water were to enter the canister. Because of this, there is no need to provide expensive neutron absorber material within the canister. Furthermore, because of the limited open spacing, there is minimal risk for the rods to become geometrically reconfigured within the canister, a desirable feature when analyzing transport accident conditions to meet regulatory requirements. In the following disclosure, various specific embodiments are described. It is to be understood that those embodiments are example implementations of the disclosed inventions and that alternative embodiments are possible. All such embodiments are intended to fall within the scope of this disclosure. As described above, in order to satisfy federal safety requirements, fuel rod assemblies are typically placed within cylindrical canisters along with expensive neutron absorber material, resulting in low spent fuel storage capacity and high costs. An alternative way to satisfy such requirements is to package spent fuel in a manner in which there are few voids between the rods that a neutron moderator material, such as water, can fill so as to reduce the potential for nuclear criticality. Accordingly, neutron absorber material is unnecessary. In addition to increasing spent fuel storage capacity and removing the need for expensive neutron absorber material, such a design may enable credits to be awarded for the effects of burnup on the nuclear fuel to decrease criticality. As nuclear fuel is used, it builds up fission products that reduce its capability to support a self-sustaining chain reaction. This process is referred to as “burnup” and it is measured in terms of megawatt days per ton. Once burnup is sufficient to prevent further power development, the fuel is typically termed “spent fuel.” Possible credits could include (a) a reasonable credit for reduction in the amount of effective fissile material content of the fuel, resulting from that material being consumed by protracted fissioning during power operations, (b) a reasonable credit for effective neutron absorption by the actinides that are present in the spent fuel, and (c) a reasonable credit for effective neutron absorption by the fission products that are present in the spent fuel. One way of achieving the above-described goals is to remove spent fuel rods from their fuel rod assemblies and place the freed rods within a dry storage canister with very little space between the rods. Doing this provides several benefits. First, the spent fuel rods will have a higher packing density within the canister and therefore a higher storage capacity can be obtained. In addition, because there is very little space between the rods, the risks associated with ingress of water or another neutron moderator are reduced and no expensive neutron absorber material is required. Furthermore, because there is less risk associated with nuclear criticality in the event of compromise of the canister, the canister can be made of relatively inexpensive materials. When increasing the packing density in this manner, steps can be taken to ensure that the heat generated by the spent fuel rods is dissipated, especially from the center of the canister, which is farthest from the canister walls. FIGS. 1-8 illustrate various canister designs that can be used to achieve both high rod packing density as well as desirable heat dissipation. FIGS. 1 and 2 illustrate a first embodiment of a dry storage canister 10 in which free spent fuel rods (i.e., rods separated from their fuel rod assemblies) can be stored in a dry condition (i.e., without the presence of water). As shown in FIG. 1, the canister 10 generally comprises an elongated outer housing 12 in which is provided an internal basket 14 that is adapted to receive spent fuel rods and dissipate their heat. The shape and dimensions of the outer housing 12 can depend upon the size and nature of the rods it is to store and/or the size and nature of a container (e.g., cask) in which the canister is to be placed. In some embodiments, however, the outer housing 12 is cylindrical, approximately 165 to 210 inches long, and has a diameter of approximately 12 to 24 inches. The walls of the outer housing 12 can be made of a strong metal material, such as stainless steel, and can be approximately ¼ to ½ inches thick. As shown in FIG. 1, the internal basket 14 divides the interior space of the outer housing 12 into multiple storage compartments or cells 16 in which spent fuel rods, such as rods 18, can be provided. As is apparent from FIG. 1, the cells 16 extend along the length direction of the housing 12 from one end of the housing to the other. FIG. 2 shows the configuration of the basket 14 more clearly. In the example shown in FIG. 2, the basket 14 comprises a central tube 20 from which radially extend multiple divider walls 22 that create a “pie piece” configuration for the cells 16. The divider walls 22 extend to the housing 12. Between the distal ends of the divider walls 22 extend end walls 24. With such a configuration, each cell 16 of the basket 14 is generally triangular and is defined by the central tube 20, two divider walls 22, and an end wall 24. The various components of the internal basket 14, including the central tube 20, the divider walls 22, and the end walls 24, can be made of a metal or alloy materials having high thermal conductivity (e.g., 200 to 380 W/(m·k)). Example materials include aluminum alloys and copper. When the spent fuel has aged for many years and has lower residual heat, the basket 14 can be made of materials with lower thermal conductivity and higher strength, such as steel, to further increase packing density. The thickness and materials of these components can be selected based upon the strength that is needed as well as the amount of heat dissipation that is required. In some embodiments, however, the walls of the basket 14 are approximately ¼ to ⅝ inches thick. The number of divider walls 22 that the basket 14 includes can be varied based upon the size and number of cells 16 that are desired. In the illustrated example, however, the basket 14 comprises eight divider walls 22 that form eight separate cells 16. In FIG. 2, only one of the storage cells 16 is shown filled with spent fuel rods 18. As is clear from the figure, the rods 18 are tightly packed within the cell 16 such that there is very little space between them. In some embodiments, the rods 18 contact each other along much of or all of their lengths. By way of example, a packing density of approximately 5 to 6 spent fuel rods per squared inch can be achieved within each cell 16 for rods of typical dimensions (e.g., 0.382 to 0.45 inches in diameter). In the illustrated example, 271 rods 18 are shown contained within the filled cell 16, in which case the canister 10, with an approximate radius of 12 inches would be able to store 2,168 such rods in total. The internal basket 14 is configured to not only provide structural support to the spent fuel rods 18 but also to dissipate heat generated by the rods, particularly in the center of the canister, which is farthest from the walls of the outer housing 12. The basket 14 achieves this with the dividing walls 22, which transfer heat from the center of the canister 10 to the outer housing 12, which acts like a heat sink. The pie-piece configuration of the cells 16 increases this heat transfer by increasing the amount of basket material in the center of the canister 10 while simultaneously reducing the concentration of rods 18 in that location. In other words, the ratio of the mass of the heat-dissipating basket material to the mass of the fuel rod material increases as the canister 10 is traversed from the walls of the outer housing 12 to the center of the canister. The central tube 20 also reduces the density of the spent fuel rod material near the center of the canister 10. In addition, the central tube 20 acts as a load distribution cell that spreads loads imposed upon the canister 10, for example, if the canister is impacted because of an accident. In addition, the central tube 20 can provide space for a drain tube (not shown) that is used to drain residual water that drips down to the bottom of the canister from the fuel rods during a draining and drying process performed prior to sealing of the canister 10. FIG. 3 illustrates an alternative dry storage canister 30 that is similar in many ways to the canister 10 shown in FIGS. 1 and 2. The canister 30 also generally comprises an elongated outer housing 32 and an internal basket 34 that defines multiple storage cells 36 having a pie-piece configuration. In the embodiment of FIG. 3, however, each cell 36 is provided with corrugated dividers 38 that further dissipate heat generated by the spent fuel rods 18. The dividers 38 can therefore also be made of a material having high thermal conductivity, such as aluminum alloys or copper. If the spent fuel has lower residual heat, lower thermal conductivity and higher strength materials, such as steel, can be used. As is apparent in FIG. 3, the corrugated dividers 38 separate the spent fuel rods 18 into multiple discrete rows of rods that are generally perpendicular to the radial direction of the canister 10. With such a configuration, the dividers 38 separate the rods 18 of one row from the rods of adjacent rows. In addition, because each divider 38 is corrugated, each rod 18 within each row can be, if desired, separated from adjacent rods within its own row depending upon the configurations of the corrugations. In addition to dissipating heat from the rods 18, the dividers 38 can facilitate packing of the free fuel rods 18 into their cells 36. For example, the rods 18 and dividers 38 can be combined together separate from the canister 30 and later placed together as a preformed unit into a cell 36 of the canister. Alternatively, the dividers 38 can be positioned within the cell 36 and can be used to guide the various free rods 18 into their respective positions within the cell 36. FIGS. 4 and 5 illustrate a third embodiment of a dry storage canister 40. As shown in FIG. 4, the canister 40 generally comprises an elongated outer housing 42 in which is provided an internal basket 44 that is adapted to receive spent fuel rods 18. In some embodiments, the shape, dimensions, and material of the outer housing 42 can be similar to those described above in relation to the outer housing 12 shown in FIGS. 1 and 2. The internal basket 44 forms multiple cylindrical storage cells 46. As is apparent from FIG. 4, the cells 46 generally extend along the length direction of the outer housing 42 from one end of the housing to the other. FIG. 5 shows the configuration of the basket 44 more clearly. In the example shown in FIG. 5, the basket 44 comprises twelve storage cells 46 each formed by a cylindrical tube 48 of the basket. Although twelve cells 46 are shown in FIG. 5, it is noted that a larger or smaller number of cells could be used. By way of example, the tubes 48 can have a diameter of approximately 4 to 6 inches and also can be made of metal materials that have high thermal conductivity. Example materials include, aluminum alloys and copper. Again, if the spent fuel has lower residual heat, lower thermal conductivity and higher strength materials, such as steel, can be used. The thickness of the walls and materials of the cylindrical tubes 48 can be selected based upon the strength that is needed as well as the amount of heat dissipation that is required. In some embodiments, however, the walls of the tubes 48 are approximately ⅛ to ¼ inches thick. In FIG. 5, nine of the storage cells 46 are shown filled with spent fuel rods 18. As is clear from the figure, the rods 18 are tightly packed within the cells 46 such that there is very little space between the rods. In some embodiments, the rods 18 contact each other along much of or all of their lengths. By way of example, a packing density of approximately 4 to 5 spent fuel rods per square inch can be achieved within each cell 46. In the illustrated example, 108 rods are shown contained within the filled cells 46, in which case the canister 40 would be able to store 1,296 such rods in total. Spacing between the cylindrical tubes 48 is maintained by one or more spacer disks 50 that extend between the outer surfaces of the tubes. In some embodiments, one such spacer disk 50 can be positioned at least at each end of the canister 40. The spacer disks 50 can, for example, be made of the same thermally-conductive material from which the tubes 48 are made. As is further shown in FIG. 5, the internal basket 44 can further comprise elongated peripheral plates 52 that are positioned at the edges of the spacer disks 50 and extend along the length direction of the canister 40. When provided, the plates 52 provide further structural integrity to the basket 44. It is also noted that, instead of basket 44, solid aluminum cylinders having bored cylindrical channels to receive cylindrical tubes 48 could be used to separate the tubes and provide for increased heat dissipation. Although corrugated dividers similar to those described above can be provided within the storage cells 46, if desired, it is noted that they are not likely required because the distance from the outer wall of the cylindrical tubes 48 to the centers of the tubes is not great. FIGS. 6 and 7 illustrate a third embodiment of a dry storage canister 60. As shown in FIG. 6, the canister 60 generally comprises an elongated outer housing 62 in which is provided an internal basket 64 that is adapted to receive spent fuel rods 18. In some embodiments, the shape, dimensions, and material of the outer housing 62 can be similar to those described above in relation to the outer housing 12 shown in FIGS. 1 and 2. The internal basket 64 defines multiple rectangular storage cells 66. As is apparent from FIG. 6, the cells 66 generally extend along the length direction of the outer housing 62 from one end of the housing to the other. FIG. 7 shows the configuration of the basket 64 more clearly. In the example shown in FIG. 7, the basket 64 comprises seven storage cells 66 each formed by a rectangular (e.g., square) tube 68 of the basket. Although seven cells 66 are shown in FIG. 7, it is noted that a larger or smaller number of cells could be used. By way of example, the tubes 68 can have cross-sectional (height and width) dimensions of approximately 4 to 6 inches and also can also be made of metal material that have high thermal conductivity. Example materials include aluminum alloys and copper. If the spent fuel has a lower residual heat, lower thermal conductivity and higher strength materials, such as steel, can be used. The thickness of the walls of the tubes 68 can be selected based upon the strength that is needed as well as the amount of heat dissipation that is required. In some embodiments, however, the walls of the tubes 68 are approximately ¼ to ⅜ inches thick. In FIG. 7, one of the storage cells 66 is shown filled with spent fuel rods 18. As is clear from the figure, the rods 18 are tightly packed within the cells 66 such that there is very little space between the rods. In some embodiments, the rods 18 contact each other along much of or all of their lengths. By way of example, a packing density of approximately 4 to 5 rods of spent fuel per square inch can be achieved within each cell 66. In the illustrated example, 225 rods 18 are shown contained within the filled cells 66, in which case the canister 60 would be able to store 1,575 such rods in total. Spacing between the rectangular tubes 68 is maintained by one or more spacer disks 70 that extend between the outer surfaces of the tubes. In some embodiments, one such spacer disk 70 can be positioned at least at each end of the canister 60. In some embodiments, the spacer disks 70 can be made of the same thermally-conductive material from which the tubes 68 are made. It is also noted that, instead of spacer disks 70, the basket 64 could comprise a solid cylindrical member having drilled rectangular channels adapted to receive tubes 68 could be used to separate the tubes and provide for increased heat dissipation. FIG. 8 illustrates a further dry storage canister 80 that is similar in many ways to the canister 60 shown in FIGS. 6 and 7. Accordingly, the canister 80 generally comprises an elongated outer housing 82 and an internal basket 84 that defines multiple storage cells 86. In the embodiment of FIG. 8, however, each cell 86 is provided with corrugated dividers 88 that further dissipate heat generated by the spent fuel rods 18. The dividers 88 can therefore also be made of a material having high thermal conductivity, such as aluminum alloys or copper. If the spent fuel has lower residual heat, lower thermal conductivity and higher strength materials, such as steel, can be used. As is apparent in FIG. 8, the corrugated dividers 88 separate the spent fuel rods 18 into multiple discrete rows of rods. With such a configuration, the dividers 88 separate the rods 18 of one row from the rods of adjacent rows. In addition, because each divider 88 is corrugated, each rod 18 within each row can be, if desired, separated from adjacent rods within its own row. Aside from dissipating heat from the rods 18, the dividers 88 facilitate packing of the free rods into their cell 86. For example, the rods 18 and dividers 88 can be combined together separate from the canister 80 and later placed together as a preformed unit into a cell 86 of the canister. Alternatively, the dividers 88 can be positioned within the cell 86 and can be used to guide the various free rods 18 into their respective positions within the cell 86. Irrespective to the nature of the canisters that are used to store the spent fuel rods 18, the canisters can be placed in a storage or transport cask. FIG. 9 illustrates an example storage cask 90 in which multiple canisters 92 have been provided. In this example, the walls of the cask 90 are made of concrete. In other cases, such as when the cask is a transport cask, the walls of the cask can be made of other materials, such as stainless steel and/or lead. The dry storage systems described in this disclosure provide numerous advantages over conventional storage systems. As noted above, much higher packaging density can be achieved and a large amount of void space is removed to limit the amount of neutron moderator (e.g., water) that can intrude, and reconfiguration of the fuel within the canister under transport and long-term disposal conditions. This eliminates need for expensive neutron absorber material. Because of the design of the canister baskets, improved heat removal can be achieved providing for a more uniform heat profile for the canisters in a geologic repository. Because of the high packing density, better shielding can be achieved with the outer rods shielding the inner rods, especially if the inner rods are hotter, high burnup fuel rods. In addition, the canister designs are relatively simple, which provides advantages in terms of structural analysis and ease of implementation. Furthermore, higher safety margins of storage can be achieved while simultaneously reducing costs. Additionally, damaged fuel rods can be managed more easily. Finally, the designs present a configuration strategy that supports efficient spent fuel packaging, fuel reprocessing, transport, and disposal, as well as standardization of storage, transport, and disposal systems.
	claims	1. A charged particle beam device for scanning a sample using a charged particle beam to inspect the sample, the sample placed on a sample stage and having a plurality of pattern-regions each where a predetermined pattern is formed, wherein:the device is configured to scan the sample using the charged particle beam in a direction intersecting a sample stage-movement direction and capture an image based on signals obtained by detecting a secondary electron or a reflection electron generated on the sample by the scanning;the device is configured to inspect the sample using the captured image,the device includes a charged particle column including a scanning deflector for controlling the scanning direction of the charged particle beam, and a control section for controlling a movement velocity of the sample stage,the device is configured to set a plurality of scan regions arranged intermittently in an inspection stripe extended on the sample in a movement direction of the sample stage, the plurality of scan regions which are to be scanned by the charged particle beam for the captured image,the device is configured to set a plurality of partial inspection regions in each of the scan regions through a screen of a console, wherein each of the partial inspection regions includes edges to be inspected partially in each of ions on the sample, andthe device is configured to sample the plurality of partial inspection regions including the edges from each of the scan regions by the scanning while the stage is being moved to capture the inspection image from the partial inspection regions. 2. The charged particle beam device according to claim 1,wherein the device is further configured to select the partial inspection regions including a first scan region and a second scan region, the first scan region from which a first image is captured by the scanning, and the second scan region from which a second image is captured later than the first image; andwherein the control section is configured to set the sample stage-movement velocity so that a scan ending edge of the first scan region and a scan beginning edge of the second scan region fall within a visual field in which aberrations and distortions of the scan ending edge and the scan beginning edge are regarded as the same respectively in a range of the charged particle beam scanning in the sample stage-movement direction. 3. The charged particle beam device according to claim 1,wherein the device is configured to set a scan skip region between the partial inspection regions, the scan skip region where the scanning is not executed by a skip. 4. The charged particle beam device according to claim 1,wherein the charged particle column is configured to execute the scanning while deflecting the charged particle beam in the same direction as the sample stage-movement direction to irradiate the inspection region selected by the sampling with the charged particle beam. 5. The charged particle beam device according to claim 1, further comprising:a screen display section for displaying a region setting screen for the sampling. 6. The charged particle beam device according to claim 1,wherein the sample stage is configured to place a semiconductor wafer on which a plurality of memory mats are formed, each memory mat being composed of a plurality of memory cells. 7. The charged particle beam device according to claim 6, further comprising:a display section for displaying a region setting screen for the sampling, the region setting screen being equipped with a display window on which one memory mat out of the plurality of memory mats is displayed,wherein the inspection region to be sampled set on the displayed memory mat is developed to another memory mat based on the regularity of arrangement of the memory cell to sample the plural inspection regions. 8. A charged particle beam device for scanning a sample using a charged particle beam to inspect the sample, the sample placed on a sample stage and having a plurality of pattern-regions each where a predetermined pattern is formed, wherein:the device is configured to scan the sample using the charged particle beam in a direction intersecting a sample stage-movement direction and capture an image based on signals obtained by detecting a secondary electron or a reflection electron generated on the sample by the scanning;the device configured to inspect the sample using the captured image;the device includes a control section for controlling a movement velocity of the sample stage;the device is configured to set a first scan region, a second scan region and a scan skip region in each of the pattern-regions, the first and second scan regions each where a plurality of scanning lines with the beam run sequentially for the scanning and the scan skip region where the scanning is not executed by a skip, wherein the scan skip region is arranged between the first and second scan regions; andthe control section is configured to set the sample stage-movement velocity so that a scan ending edge of the first scan region and a scan beginning edge of the second scan region fall within a visual field in which aberrations and distortions of the scan ending edge and the scan beginning edge are regarded as the same respectively in a range of the charged particle beam scanning in the sample stage-movement direction. 9. The charged particle beam device according to claim 8,wherein the control section is configured to control the sample stage-movement velocity so that a width of each of the partial inspection regions in the sample-stage movement direction falls within the visual field. 10. A charged particle beam device for scanning a sample using a charged particle beam to inspect the sample, the sample placed on a sample stage and having a plurality of pattern-regions each where a predetermined pattern is formed wherein:the device is configured to scan the sample using the charged particle beam in a direction intersecting a sample stage-movement direction and capture an image based on signals obtained by detecting a secondary electron or a reflection electron generated on the sample by the scanning;the device is configured to inspect the sample using the captured image;the device includes a control section for controlling a movement velocity of the sample stage;the device is configured to set a scan region and a scan skip region in each pattern-region, the scan region where plural scanning lines with the beam run sequentially for the scanning and the scan skip region where the scanning is not executed by a skip; andthe control section is configured to set the sample stage-movement velocity in accordance with a ratio of a width of the scan region to a width of the scan skip region in the sample stage-movement direction.
	summary
	claims	1. An ion implantation apparatus including a beam line arranged to implant an ion to a wafer by irradiating an ion beam, the ion beam arranged to be extracted from an ion source and running over the beam line and being passed through a mass analysis magnet apparatus and a mass analysis slit to the wafer on the beam line, and after passing the mass analysis slit on the beam line, the ion beam being arranged to reciprocally scanned by a beam scanner,wherein the ion implantation apparatus further includes:an injector flag Faraday cup arranged on the beam line after passing a second quadrupole vertically focusing electromagnet and before incidence of the beam scanner, the Faraday cup being adapted to detect a full beam current by measuring a total beam amount of the ion beam to be able to be brought in and out thereto and therefrom, the Faraday cup that shuts off the ion beam as necessary, entering or leaving against the beam line before incidence of the beam scanner on the beam line, and then the ion beam full stopping, receiving, measuring or full passing on the beam line just before the beam scanning, anda scanner housing that contains the beam scanner and the Faraday cup,the Faraday cup being arranged immediately after an ion beam inlet at the scanner housing and the beam scanner being arranged immediately after the Faraday cup, the Faraday cup being provided with an incident beam receiving area in correspondence with a sectional shape of the ion beam which is constituted by an elliptical or a flat shape having a long axis in a lateral direction by shaping with the second quadrupole vertically focusing electromagnet,the incident beam receiving area of the Faraday cup being constituted by a rectangular shape slightly larger than a sectional shape of the ion beam. 2. The ion implantation apparatus according to claim 1, wherein a shape of a beam incident portion at the Faraday cup is constituted by a rectangular shape to be able to deal with an ion beam having a section in an elliptical shape having a long axis in a lateral direction or a longitudinal direction. 3. The ion implantation apparatus according to claim 1, wherein a drive mechanism that brings in and out the Faraday cup to and from the beam line is installed at outside of the scanner housing and the Faraday cup is attached to a drive shaft of the drive mechanism introduced into the scanner housing by penetrating an wall of the scanner housing. 4. The ion implantation apparatus according to claim 1, further including a beam dump arranged at a most downstream position of the beam line and having a beam current detecting function, wherein a beam transporting efficiency is made to be able to be calculated by comparing a detected value of the Faraday cup and a detected value of the beam dump. 5. The ion implantation apparatus according to claim 1, further including a profile monitor arranged to measure a current density distribution of a section of the ion beam, wherein the profile monitor is arranged at a immediate vicinity on an upstream side or an immediate vicinity on a downstream side of the Faraday cup at inside of the scanner housing. 6. The ion implantation apparatus according to claim 1, further including:dose amount measurement means arranged at a vicinity of the wafer;resolving means that determines whether the measured dose amount is not less than a predetermined value;a deflecting apparatus arranged at a section of the beam line from an outlet of the mass analysis magnet apparatus to a front side of the mass analysis slit for deflecting the ion beam in a predetermined direction deviated from the beam trajectory line and maintaining the deflection; andcontrol means that carries out temporal evacuating of the ion beam by the deflecting apparatus when the dose amount measured in implanting the ion is determined to be less than the predetermined value by the resolving means;wherein the control means recovers the ion beam to the beam trajectory line by stopping the temporal evacuating of the ion beam when a predetermined time period has elapsed since the dose amount has been determined to be less than the predetermined value; andwherein when the dose amount remeasured by the dose amount measurement means is determined to be less than the predetermined value again, the control means inserts the Faraday cup to the beam line and releases the temporal evacuating of the ion beam.
	summary
	description	The present invention relates to a heel effect compensation filter, an X-ray irradiator and an X-ray CT scanner, which adjust a nonuniform X-ray intensity angular distribution of an X-ray flux due to a heel effect to become uniform when the X-ray flux is irradiated on a subject. The present invention also relates to a heel effect compensation filter, an X-ray irradiator, an X-ray CT scanner and an X-ray CT imaging method, with which image quality of image data obtained with the X-ray CT scanner is made uniform and improved in a body axis direction. An X-ray generator in general is a device which irradiates a thermoelectron beam flux from a cathode to an anode, and generates an X-ray flux at the anode. The X-ray flux generated by the X-ray generator is irradiated on a subject, and the X-ray flux transmitted through the subject is detected by a predetermined detection means, to thereby obtain information of a part through which the X-ray flux has transmitted, as a slice image. A tomograph is a device which irradiates an X-ray flux from an X-ray generator on a subject, detects the X-ray flux transmitted through the subject by detection means arranged in a plane, and obtains slice data based on the detected information, which data is used for diagnosing a state of the slice. As one of the most typical devices using an X-ray irradiator, an X-ray CT scanner (hereinbelow, referred to as “CT (Computed Tomography)”) has been known. The CT is, for example, composed of an X-ray irradiator and a detection means which is a combination of a scintillator and a semiconductor device. However, for the CT, any device can be used in combination with the X-ray irradiator, as long as the device can detect an X-ray. The X-ray CT scanner is an X-ray diagnostic apparatus in which a large number of detectors each composed of a combination of the scintillator and the semiconductor device revolve around a body axis of a subject, while the X-ray irradiator and the detectors keep a flanking position relative to the subject, and slice images in a body width direction are continuously obtained in a body axis direction. It should be noted that the body axis direction and the body width direction are orthogonal to each other, and an irradiation axis of the X-ray flux is orthogonal to both the body axis direction and the body width direction. The CT is provided with a gantry and a platform. The gantry is formed in a shape of a thin-walled cylinder, and a central axis in a hollow part of the gantry is oriented so as to be included in a plane (hereinbelow, referred to as “axial plane”) containing an incoming axis of the thermoelectron ray and an irradiation axis of the X-ray flux. The platform is placed to be movable backward and forward in the hollow part of the gantry in such a manner that the body axis of the subject to be subjected to the X-ray flux irradiation coincides with the central axis of the gantry. Further, the gantry has an X-ray tube and detectors at an opposed position to a position of the X-ray tube across the hollow part. As the X-ray tube and the detectors revolve around the body axis of the subject lying on the platform in the hollow part, the platform moves forward/backward. During this movement, the X-ray flux irradiated from the X-ray tube and transmitted through the subject is detected by the detectors to thereby obtain slice data along a predetermined length of the subject in the body axis direction. The slice data are subjected to computer analysis and a number of slice image data are created, which are then used for diagnosis of an inside of the subject. Accordingly, based on differences in intensity of the incoming X-ray flux that has transmitted through the subject into respective detectors, a state of a slice part through which the X-ray has transmitted can be determined. In order to reduce exposure of the subject, it is preferred that an X-ray intensity angular distribution of the X-ray flux be made to fall in the lowest range that can be detected by the detectors, and at the same time, difference range of the X-ray flux intensity be made as small as possible. The term “slice data” used herein means electrically generated data of a state of a slice part of the subject, based on the differences in intensity of the incoming X-ray flux that has transmitted through the subject into respective detectors. The term “image data” used herein means data visually represented as an image based on the slice data. In order to reduce the exposure of the subject as much as possible, the CT has the following means. For example, in a case where the subject is a human being (hereinbelow, frequently referred to as “examinee”), when the examinee at the irradiation position is seen in the body axis direction, a center of the examinee is the thickest and both ends in the body width direction are the thinnest. Therefore, during the X-ray flux irradiation, an absorption amount of the X-ray by the examinee body becomes largest at the central part of the body, and becomes smaller towards the both ends of the body. Attempts have been made to adjust such a difference in absorption of an X-ray flux in the body width direction due to the thickness of the examinee to fall in the lowest range that can be detected by the detectors (hereinbelow, referred to as “appropriate range”), by disposing a wedge filter between the X-ray tube and the examinee. The wedge filter is made of aluminum or the like, and a transmissive surface thereof is a cylindrical concave surface formed in such a manner that a vertical section seen in the body axis direction is in a shape of a concave lens which is axisymmetrical relative to the irradiation axis. With this configuration, a relatively strong X-ray that has transmitted through a central thinner part of the cylindrical concave wedge filter reaches the central part of the body, while a relatively weak X-ray that has transmitted through thicker lateral parts of the cylindrical concave wedge filter reaches thinner parts of the body. In this manner, the intensity of the X-ray flux is adjusted by the difference in the filter thickness so as to correspond the difference in body thickness while the X-ray flux transmits through the wedge filter. It should be noted that, since the wedge filter revolves uniformly with the x-ray detector and the detectors, the filter in practice is designed based on a cross section of the examinee as a perfect circle. On the other hand, in a case of X-ray flux irradiation in the body axis direction of the examinee, when the X-ray flux is irradiated by the X-ray generator, a phenomenon called “heel effect” occurs, in which an X-ray intensity angular distribution on an axis orthogonal to the irradiation axis at a predetermined distance from the anode becomes a shape with a cone angle (a shape of an approximate sector), on the axial plane containing the beam irradiation axis of the thermoelectron beam flux and the irradiation axis of the X-ray flux. Due to this heel effect, when the X-ray flux is irradiated on the examinee, the X-ray intensity angular distribution in the body axis direction becomes nonuniform. In other words, when obtaining slice data along the body axis, the thickness of the examinee body is considered to be even in the body axis direction, and an irradiation amount in this direction is kept uniform. As a result, at a portion with a strong X-ray irradiation intensity, the irradiation amount becomes excessively high, and the body part of the examinee is overexposed. However, the overexposure due to this heel effect has not been taken into account, and a part of the slice data obtained by detecting the transmitted X-ray flux by the detector becomes blurry. For obtaining clear slice data, the heel effect has been cancelled merely by adjusting the obtained slice data themselves. For example, a proposal has been made in which an intensity distribution of various parts in the irradiation space of the X-ray flux is measured in advance by a sensor and the like without the examinee on the platform; data prepared in advance are referred to every time X-ray image is obtained; and the intensity distribution is adjusted by a computer program so that variation in the intensity distribution is cancelled (see, for example, Patent Document 1). Recently, there has been disclosed an X-ray irradiator which uniformly irradiates X-ray by use of a metallic filter (see, for example, Patent Document 2). Specifically, the invention disclosed in Patent Document 2 provides an X-ray irradiator having: an X-ray tube which outputs X-ray generated by irradiation of an electron beam on a target from an X-ray irradiation opening to outside; and a metallic filter which is attached to the X-ray irradiation opening of the X-ray tube and configured in such a manner that a portion of the filter exposed to a larger irradiation dosage is made thicker, based on the measurement of an X-ray dose distribution output from the X-ray irradiation opening of the X-ray tube. In addition, there is a problem of artifacts (obstructive shadow) which are always present in X-ray CT imaging. An artifact is a phenomenon in which a virtual image is included in slice image data due to various factors, such as a failure of a device, defects in an image reconstruction system and scanning conditions. For example, it is considered that a ring-shaped artifact results from a failure of a detector, and that a beam hardening artifact results from a difference in energy of an outgoing X-ray due to energy absorption during transmission of an X-ray flux through a subject. Generation of artifacts lowers accuracy of diagnosis or the like on a subject based on slice image data. In order to reduce generation of the artifacts, attempts has been made in which an image is first obtained and a cause is specified from a type and shape of the artifact and then removed; or in which image data are adjusted by a computer program (see, for example, Non-patent Document 1). (Patent Document 1) Japanese Unexamined Patent Publication Kokai No. 2000-079114 (paragraphs 0008-0029 and FIG. 2) (Patent Document 2) Japanese Unexamined Patent Publication Kokai No. 2004-214130 (claim 1) (Non-Patent Document 1) Katsumi Tsujioka, “Mechanical Engineering of X-ray CT scanner (5)-Artifact-” (PDF file), p 737, 6. Artifact Due to Cone-Angle of Multi-Slice CT, (online), Fujita Health University School of Health Sciences, (searched on Mar. 16, 2005), internet (URL: http://www.fujita-hu.ac.jp/˜tsujioka/education.html) Problem to be Solved by the Invention Under the current situation as mentioned above with respect to the X-ray flux irradiation, a predominant type of the detector of the most recent CT has 16 arrays (arranged in the hollow part of the gantry in the axis direction). With a progress of accuracy and the like in adjustment of an X-ray image by a computer program, and an introduction of a larger number of arrays, such as 32 or more (e.g. 32, 40, 64, 124) arrays, various advantages are expected, such as speed-up of measurement time, high accuracy of an image, and three-dimensional imaging. At the same time, an irradiation width in the body axis direction of the subject is becoming larger. Consequently, unnecessary exposure due to the heel effect is anticipated to increase, with respect to a subject (for example, a patient at hospital) irradiated with an X-ray flux using an X-ray generator, such as a tomograph. A large amount of the X-ray flux irradiation will render the subject a heavy load, and if the X-ray flux is repeatedly irradiated, undesired disorder (including cancer development and other diseases) may be initiated in the examinee. Under the current situation as mentioned above with respect to the X-ray CT scanner, there are problems in that CT imaging and data processing are time consuming and laborsome, for identifying and removing a cause of the artifact generation, and for adjusting image data by a computer program. Especially, in a case of the X-ray CT scanner having 32 arrays or more of detectors, the problem of the artifact becomes notable as in Non-Patent Document 1. Therefore, in development of the X-ray CT scanner having 32 arrays or more of detectors, it would be desirable to provide a method which reduces generation of artifacts when obtaining an X-ray CT image, not only when the image is processed after the X-ray CT imaging. The present invention is made with the view toward solving the above-mentioned problems, and it is an object of the present invention to provide a heel effect compensation filter, an X-ray irradiator and an X-ray CT scanner, which uniform the X-ray intensity angular distribution of the X-ray flux that is nonuniform due to the heel effect, to thereby prevent the subject from being unnecessarily exposed to the X-ray. It is another object to provide a heel effect compensation filter, an X-ray irradiator, an X-ray CT scanner and an X-ray CT imaging method, with which an image quality of image data obtained with an X-ray CT scanner, especially an X-ray CT scanner having 32 arrays or more of detectors, is made uniform and improved in the body axis direction. In order to solve the above-mentioned problems, a heel effect compensation filter according to the present invention as set forth in claim 1 is configured to have a thickness distribution that uniforms an X-ray intensity angular distribution that is nonuniform in a body axis direction of a subject in an X-ray flux irradiated space, the space being formed by an X-ray flux diverging from an anode in a body width direction of the subject and diverging in a shape of an approximate sector in the body axis direction orthogonal to the body width direction due to the X-ray intensity angular distribution affected by the heel effect, when the X-ray flux generated on the anode by irradiating a thermoelectron beam flux from a cathode to the anode is irradiated on the subject through a wedge filter configured to have a cylindrical concave surface with a curve being formed in the body width direction of the subject, wherein the thickness distribution is defined by Formula 1: ( y ′ z ′ ) = ( L ⁡ ( θ ) ⁢ cos ⁢ ⁢ θ FFD FCD ⁢ ( FCD ⁢ ⁢ tan ⁢ ⁢ θ - L ⁡ ( θ ) ⁢ sin ⁢ ⁢ θ ) ) ⁢ ⁢ ( θ ≤  cone ⁢ ⁢ angle  ) ( Formula ⁢ ⁢ 1 ) where, on a plane containing an irradiation axis of the X-ray flux and a beam irradiation axis of the thermoelectron beam flux, the irradiation axis of the X-ray flux is defined as a Y-axis, and an axis orthogonal to the Y-axis at a distance FCD along the Y-axis in a direction of X-ray flux irradiation is defined as a Z-axis; z′ and y′ represent positions in corresponding axial directions with the proviso that an intersection point of the Z-axis and the Y-axis is defined as an origin point; FFD is defined as a predetermined distance along the Y-axis from a position of the anode; θ is defined as a predetermined angle within a range of a cone angle symmetrically diverging from the position of the anode relative to the irradiation axis of X-ray flux; and La (θ) is defined as a length in a y′ direction at the angle θ. In accordance with the thickness distribution of the heel effect compensation filter obtained by the formula 1, the heel effect is adjusted so that the X-ray intensity angular distribution of the X-ray flux becomes uniform. In addition, by obtaining the thickness distribution not based on a measured value of the X-ray angular distribution but by the formula, the filter can be easily designed. Further, by obtaining the thickness distribution of the heel effect compensation filter by Formula 1, effective energy on an axis orthogonal to the irradiation axis at a predetermined distance from the anode can be made high and uniform on an axial plane containing the beam irradiation axis of the thermoelectron beam flux and the irradiation axis of the X-ray flux. When the effective energy of the incoming X-ray into the subject is high, energy absorption becomes poor during the transmission through the subject, and thus a difference in the effective energy of the outgoing X-ray from the subject becomes small. When such a heel effect compensation filter is employed in an X-ray CT scanner and the like, the generation of artifacts, such as a beam hardening artifact, is reduced, and image quality of image data is made uniform and improved in the body axis direction. The heel effect compensation filter according to the present invention as set forth in claim 2 is the heel effect compensation filter of claim 1, wherein the heel effect compensation filter is separable into pieces and a distance in the heel effect compensation filter through which the X-ray flux transmits during usage is equal to the thickness distribution. By defining the thickness distribution of the heel effect compensation filter based on the distance through which the X-ray flux transmits, the filter can be made in various shapes while retaining the above-mentioned predetermined effects. The heel effect compensation filter according to the present invention as set forth in claim 3 is the heel effect compensation filter of claim 1 or 2, wherein either of an X-ray flux-incoming side transmissive surface and an X-ray flux-outgoing side transmissive surface may be configured as a cylindrical convex surface with a curve being formed in the body axis direction of the subject and the other may be configured as a flat surface. By forming either of the X-ray flux-incoming side transmissive surface and the X-ray flux-outgoing side transmissive surface of the heel effect compensation filter as a curved surface and the other surface as a flat surface, the heel effect compensation filter can be easily designed, and processing cost can be suppressed. The heel effect compensation filter according to the present invention as set forth in claim 4 is the heel effect compensation filter of claim 1 or 2, wherein either of an X-ray flux-incoming side transmissive surface and an X-ray flux-outgoing side transmissive surface may be configured as a cylindrical convex surface with a curve being formed in the body axis direction and the other may be configured as a cylindrical concave surface with a curve being formed in the body width direction orthogonal to the body axis direction. Since single heel effect compensation filter has functions of a heel effect compensation filter and a wedge filter, an X-ray irradiator having the heel effect compensation filter can be made compact. The heel effect compensation filter according to the present invention as set forth in claim 5 is the heel effect compensation filter of any one of claims 1-4, which may be employed in an X-ray CT scanner having 32 arrays or more of X-ray detectors. By employing such a heel effect compensation filter in an X-ray CT scanner having 32 arrays or more of detectors, an X-ray intensity angular distribution of the X-ray flux becomes uniform, and therefore, unnecessary X-ray flux irradiation on the subject can be prevented. By using such an X-ray irradiator, artifacts, such as a beam hardening artifact, can be reduced, and image quality of image data can be made uniform in the body axis direction. For example, especially in a case of the X-ray CT scanner having 32 arrays of detectors, artifacts are easily generated since effective energy of the X-ray flux is likely to become nonuniform. However, by using such a heel effect compensation filter, generation of the artifacts can be effectively reduced. An X-ray irradiator according to the present invention as set forth in claim 6, in which a thermoelectron beam flux is irradiated from a cathode to an anode and an X-ray flux generated on the anode is irradiated on a subject, is characterized in that the heel effect compensation filter of any one of claims 1-5 is disposed between the anode and the subject at a predetermined distance, the filter being configured to adjust the X-ray intensity angular distribution of the X-ray flux to become uniform that is nonuniform in a body axis direction of the subject in an X-ray flux irradiated space, the space being formed by the X-ray flux diverging from the anode in a body width direction of the subject and diverging in a shape of an approximate sector in the body axis direction orthogonal to the body width direction due to the heel effect. In this manner, by disposing the heel effect compensation filter between the anode and the subject at a predetermined distance, the X-ray intensity angular distribution of the X-ray flux becomes uniform, and therefore, unnecessary X-ray irradiation on the subject can be prevented. In addition, by disposing the heel effect compensation filter between the anode and the subject at a predetermined distance, effective energy on an axis orthogonal to the irradiation axis at a predetermined distance from the anode can be made high and uniform on an axial plane containing the beam irradiation axis of the thermoelectron beam flux and the irradiation axis of the X-ray flux. An X-ray CT scanner according to the present invention as set forth in claim 7 is characterized in that the scanner has the X-ray irradiator of claim 6. Since the X-ray CT scanner of the present invention has an X-ray irradiator having a heel effect compensation filter, the X-ray intensity angular distribution of the X-ray flux transmitted through the heel effect compensation filter becomes uniform on an axial plane and a plane parallel to the axial plane. Therefore, unnecessary X-ray irradiation on the subject can be prevented. In addition, since the X-ray CT scanner of the present invention has an X-ray irradiator having a heel effect compensation filter, the effective energy of the X-ray flux transmitted through the heel effect compensation filter becomes high and uniform in a predetermined direction. At the same time the artifacts, especially a beam hardening artifact, can be reduced, and image quality of image data can be made uniform in the body axis direction. A method for X-ray CT imaging according to the present invention as set forth in claim 8 is characterized in that, for reducing an artifact of image data obtained by an X-ray CT scanner, the method employs the heel effect compensation filter of any one of claims 1-5 in the X-ray CT scanner and reduces a difference in CT value of the image data obtained along a body axis direction. Since, in the X-ray CT imaging method of the present invention, a heel effect compensation filter is employed in the X-ray CT scanner, the effective energy becomes high and uniform in a predetermined direction, after the X-ray flux that has been irradiated from the anode of the X-ray CT scanner transmitted through the heel effect compensation filter. At the same time the artifacts, especially a beam hardening artifact, can be reduced, and image quality of image data obtained with an X-ray CT scanner can be made uniform and improved in the body axis direction. Effect of the Invention According to the heel effect compensation filter, the X-ray intensity angular distribution of the X-ray flux which is nonuniform due to the heel effect can be made uniform. In addition, according to the heel effect compensation filter, the effective energy can be made high and uniform in a predetermined direction. According to the X-ray irradiator, the X-ray intensity angular distribution of the X-ray flux which is nonuniform due to the heel effect can be made uniform, and therefore, unnecessary exposure of the subject can be reduced. In addition, according to the X-ray irradiator, the effective energy can be made high and uniform in a predetermined direction. According to the X-ray CT scanner, the X-ray intensity angular distribution of the X-ray flux which is nonuniform due to the heel effect can be made uniform, and therefore, unnecessary exposure of the subject can be reduced. In addition, according to the X-ray CT scanner, the effective energy can be made high and uniform in a predetermined direction. At the same time, the artifacts, especially a beam hardening artifact, can be reduced, and image quality of image data can be made uniform in the body axis direction. According to the X-ray CT imaging method, the effective energy can be made high and uniform in a predetermined direction, at the same time, the artifacts, especially a beam hardening artifact, can be reduced, and image quality of image data can be made uniform in the body axis direction. 1 X-ray CT scanner 10 X-ray irradiator 11a anode (X-ray source) 11b cathode 13 wedge filter 13a curved surface 14a, 15a curved surface 13b, 14b flat surface 14, 15 heel effect compensation filter 14c, 15c crest part 15b curved surface 20 detection means XR X-ray flux S irradiation axis H examinee (subject) B platform The best mode for carrying out the present invention will be described in detail below with reference to the drawings. In each embodiment, descriptions are made by assuming that the subject is a patient treated at a hospital (hereinbelow, also referred to as “examinee”). Also descriptions are made for a case where the heel effect compensation filter and the X-ray irradiator of the present invention are used in an X-ray CT scanner. A direction of X-ray flux irradiation is defined as a direction orthogonal to a both body width direction and a body axis direction relative to an examinee H, which directions are also orthogonal to each other. FIG. 1 is a plan view diagrammatically showing one example of X-ray irradiator according to a first embodiment of the present invention. FIG. 2 is a diagram showing one example of an X-ray flux irradiated space of the irradiated X-ray flux. FIG. 3(a) is a perspective view showing one example of a heel effect compensation filter, and (b) is a perspective view showing one example of a wedge filter. FIG. 4(a) is a diagram showing a case where a heel effect compensation filter is not used, (b) is an X-ray intensity map showing a case where the heel effect compensation filter is not used, (c) is a diagram showing a case where the heel effect compensation filter is used, and (d) is a graph of an X-ray intensity angular distribution showing a case where the heel effect compensation filter is used. FIG. 5 is a diagram showing a positional relationship of signs to be used in a formula. FIG. 6(a) is a diagram showing a maximum value and a minimum value of an X-ray intensity, and (b) is a diagram showing a condition where the X-ray intensity is uniform at a minimum value. FIG. 7 is a graph showing a thickness distribution of a heel effect compensation filter. An X-ray CT scanner 1 according to a first embodiment of the present invention includes an X-ray irradiator 10, a detection means 20, a platform B and a gantry (not shown). The X-ray irradiator 10 irradiates an X-ray flux on an examinee H lying on the platform B as the X-ray irradiator 10 revolves around the body axis of the subject, while the platform B moves forward and backward. During this movement, the detection means 20 captures the X-ray flux that has transmitted through the examinee and produces slice data, which is then subjected to image processing by a computer (not shown) and converted into image data. The image data of a predetermined length in the body axis direction of the examinee H is displayed on a monitor or printed on a film, which is utilized in diagnosis on the examinee H. The gantry is configured to have a cylindrical shape, and on an inner periphery thereof, the X-ray irradiator 10 and the detection means 20 composed of a number of detectors are placed in such a manner that the X-ray irradiator 10 and the detection means 20 are opposed to each other by sandwiching a hollow space of the gantry therebetween. The detectors are arranged on an arc having a center on the anode. In the hollow space of the gantry, the platform B is disposed to be movable forward and backward. For example, the body axis direction of the examinee H is in parallel with a moving direction of the platform B, and the body width direction of the examinee H is in parallel with the width direction of the platform B. For the detection means 20, any conventional detection means can be used. As mentioned above, the detection means 20 is configured to detect an X-ray flux XR transmitted through the examinee H lying on the platform B disposed between the X-ray irradiator 10 and the detection means 20, and to generate slice data from the X-ray flux XR after detecting the X-ray flux XR transmitted through the examinee H. The detection means 20 is arranged, in the body width direction, on an arc having a radius R which has an origin point on the anode 11a so that a distance from the anode 11a to the detection means 20 becomes a predetermined constant distance R. The X-ray irradiator 10 is disposed in the gantry (not shown), and as shown in FIG. 1, irradiates the X-ray flux XR from the anode (hereinbelow, referred to as “X-ray source”) 11a in such a manner that the X-ray intensity angular distribution of the X-ray flux XR transmitted through the examinee H becomes uniform on a platform B-side surface of the detection means 20. The X-ray irradiator 10 includes a cathode 11b, the X-ray source 11a, a collimator 12, a wedge filter 13 having a cylindrical concave surface 13a, and a heel effect compensation filter 14 having a cylindrical convex surface 14a. In this X-ray irradiator 10, the X-ray flux XR passes through the heel effect compensation filter 14 which will be described below, and therefore the X-ray intensity angular distribution of the X-ray flux XR in the body axis direction of the examinee H becomes uniform. First, a mechanism of X-ray flux XR irradiation will be described. A thermoelectron beam flux, irradiated from the cathode 11b and accelerated by an electric field, collides with a rotating X-ray source 11a in a form of a disk (not shown), and an impact of the collision generates an X-ray flux XR which is then irradiated in a constant direction forming a predetermined angle α (not shown) together with the thermoelectron beam. In general, the cathode 11b and the X-ray source 11a are sealed in an X-ray tube casing (not shown) with insulating oil, for the purpose of stabilizing an irradiation direction. In the cathode 11b, there is provided a linear filament (not shown) to release thermoelectrons by heating. On the other hand, although not shown, the rotating disk-shaped X-ray source 11a as a whole is made of tungsten, and has a face piece, called “target”, against which the thermoelectrons collide, provided with an inclination in order to irradiate the X-ray flux XR in a constant direction. As a result of the impact by collision of the thermoelectrons against the inclined target surface, the X-ray flux XR is irradiated from the target in a constant direction. In contrast, an X-ray intensity angular distribution on an axial plane becomes a shape of an approximate sector. This is what is called “heel effect” described above. Referring to FIG. 2, the X-ray flux XR diverges from the X-ray source 11a in the body width direction of the examinee H and, due to the heel effect, diverges in a shape of an approximate sector in the body axis direction of the examinee H orthogonal to the body width direction, to thereby form an X-ray flux irradiated space V. The X-ray flux irradiated space V reaches the detection means 20, which is in a shape of an arc in the body width direction and has a center on the X-ray source 11a. In this case, for example, along a line A1-A2 orthogonal to the body width direction and to an irradiation axis S of the X-ray flux XR, the X-ray intensity angular distribution of the X-ray flux XR becomes uniform. Also along lines A3-A4 and A5-A6 on the detection means 20, the X-ray intensity angular distribution of the X-ray flux XR becomes uniform. In this manner, the X-ray intensity angular distribution of the X-ray flux XR also becomes uniform, on the surface areas in the body axis direction of the detection means 20 which is in a shape of an arc in the body width direction. It should be noted that, in the present embodiment, the term “array” used in description of configurations of an X-ray CT scanner is a general term to be used for describing configurations of X-ray CT scanners, and referring to FIG. 2, the term means a number of rows of the scintillators to be used in the detection means 20 for detecting irradiation, along the body axis direction, such as lines A1-A2, A3-A4 and A5-A6. Next, positional relationships of components will be described. As shown in FIG. 1, the irradiation axis S of the X-ray flux XR forms a predetermined angle together with the beam irradiation axis from the cathode 11b, and is set in a direction to transmit through the examinee H lying on the platform B. The heel effect compensation filter 14 is disposed at a predetermined distance FFD from the X-ray source 11a so as to intersect the irradiation axis S of the X-ray flux XR. In addition, the collimator 12 is disposed between the X-ray source 11a and the heel effect compensation filter 14, and a wedge filter 13 is disposed between the X-ray source 11a and the collimator 12. Each component will be described in detail below. The X-ray source 11a irradiates the examinee H with the X-ray flux XR. During irradiation, the X-ray flux XR is irradiated in such a manner that the irradiation space diverges from the X-ray source 11a as an origin point with an angle θ relative to the irradiation axis S, as the X-ray flux XR approaches the examinee H. The collimator 12 is a plate member having an opening 12a at the center of the surface thereof. The collimator 12 is disposed between the X-ray source 11a and the examinee H, and only the X-ray flux XR that has passed the opening 12a is irradiated on the examinee H. The heel effect compensation filter 14 is made of aluminum, and as shown in FIGS. 1 and 3(a), an X-ray flux XR-incoming side transmissive surface is formed as a cylindrical convex (approximately hog-backed) surface 14a extending in a direction orthogonal to an axial plane, and a transmissive surface on an examinee H side, i.e. an X-ray flux-outgoing side opposite to the cylindrical convex surface 14a is formed as a flat surface 14b. The heel effect compensation filter 14 has a function of adjusting an X-ray intensity angular distribution of the X-ray flux XR irradiated from the X-ray source 11a to become uniform in the body axis direction. The cylindrical convex surface 14a of the heel effect compensation filter 14 is formed in such a manner that a distance relative to the flat surface 14b changes in the body axis direction. With this configuration, when the X-ray flux XR transmits through the heel effect compensation filter 14, the X-ray intensity angular distribution of the X-ray flux XR in the X-ray flux irradiated space V becomes continuously uniform in the body axis direction. Since the subject is considered to have the same thickness in the body axis direction, the X-ray intensity angular distribution becomes uniform in the body axis direction after the X-ray flux XR transmitted through the subject. In FIG. 1, the heel effect compensation filter 14 is disposed between the collimator 12 and the examinee H at a position proximate to the collimator 12. In addition, the heel effect compensation filter 14 is positioned so that a minimum distance between the X-ray source 11a and an axis which is orthogonal to the irradiation axis S and passes through the crest part 14c of a cylindrical convex surface 14a of the heel effect compensation filter 14 becomes a predetermined distance FFD. By positioning the heel effect compensation filter 14 in this manner, a predetermined distance FCD from the X-ray source 11a matches with the position of the detection means 20, and the X-ray intensity angular distribution of the X-ray flux XR becomes uniform along the detection means 20. It should be noted that a value of the predetermined distance FCD is larger than that of the predetermined distance FFD. A thickness distribution of the heel effect compensation filter 14 is configured in such a manner that, as shown in FIG. 7, in the body axis direction of the examinee H, the thickness gradually increases from one end of the heel effect compensation filter 14, the thickness becomes maximum at a position away from the irradiation axis S of the X-ray flux XR to form the crest part 14c, and the thickness decreases towards the other end. The reason for this thickness distribution of the heel effect compensation filter 14 is as follows. Suppose there is a predetermined vertical line, which is in parallel with the body axis direction of the examinee H and is orthogonal to an irradiation axis S of the X-ray flux XR (for example, an X-ray intensity Imin shown in FIG. 6(a)) and crosses the X-ray intensity angular distribution. Provided that the X-ray intensity angular distribution of the X-ray flux XR at an intersection of the vertical line with the X-ray intensity angular distribution is a standard (base), an intensity of the X-ray flux XR becomes maximum at a position away from the irradiation axis S, and the intensity of the X-ray flux XR gradually decreases from that position towards the intersection of the vertical line with the X-ray intensity angular distribution, since the X-ray intensity angular distribution of the X-ray flux XR diverges in a shape of an approximate sector due to the heel effect. In order to deal with this intensity, the filter is made thicker at the position where an X-ray intensity is stronger, while the filter is made thinner at the position where the X-ray intensity is weaker. It should be noted that a minimum value of the X-ray intensity Imin, which is a criterion for calculating a thickness distribution of the heel effect compensation filter 14, can be selected depending on a configuration of the X-ray irradiator 10 used. FIG. 14 shows X-ray intensity maps in different X-ray irradiators. (a) is an X-ray intensity angular map in a case where an X-ray flux is irradiated through a collimator which regulates a shape of an X-ray flux irradiated space, (c) is an X-ray intensity angular map in a case where an X-ray flux is irradiated without regulation of a shape of an X-ray flux irradiated space by, especially collimator or the like. (b) and (d) show intensity maps for an X-ray flux XR in cases where appropriate heel effect compensation filters 14 are used in (a) and (c), respectively. In FIG. 14(a), of the X-ray flux irradiated space, an A′ space on a cathode 11b side and a B′ space on an anode 11a side are regulated by the collimator 12. In FIG. 14(a), a boundary point a′ between the A′ space and the X-ray irradiated space V indicates a minimum X-ray intensity (Imin) in the X-ray irradiated space V. Accordingly, the thickness distribution of the heel effect compensation filter 14 can be made such that the intensity distribution of the X-ray flux XR becomes uniform at Imin. In a case where such a heel effect compensation filter 14 is employed in the X-ray irradiator 10 shown in FIG. 14(a), an X-ray intensity distribution as shown in FIG. 14(b) is obtained. In FIG. 14(c), the X-ray flux irradiated space V is not regulated specifically by the collimator 12 or the like. As shown in FIG. 14(c), the X-ray intensity angular distribution typically contains: a maximum point K at a predetermined distance from the irradiation axis S where the X-ray intensity becomes maximum; a first inclination K1 in which the X-ray intensity decreases from the maximum point K to the cathode 11b side; and a second inclination K2 which is continuous with the first inclination, in which the X-ray intensity decreases with a larger inclination than the first inclination. An X-ray intensity at a boundary point a′ between the first inclination K1 and the second inclination K2 is set to Imin, and the thickness distribution of the heel effect compensation filter 14 can be made such that the intensity distribution of the X-ray flux XR becomes uniform at Imin. In a case where such a heel effect compensation filter is employed in the X-ray irradiator shown in FIG. 14(c), an X-ray intensity distribution as shown in FIG. 14(d) is obtained. By using the minimum value of the X-ray intensity Imin obtained in such a manner, the thickness distribution of the heel effect compensation filter 14 can be obtained in the following manner. In the case where the heel effect compensation filter 14 is not used like FIG. 4(a), the intensity of the X-ray flux XR that has passed through the opening 12a of the collimator 12 becomes maximum at a position away from the irradiation axis S and gradually decreases at a position further away from that point as shown in FIG. 4(b). In order to convert a nonuniform X-ray intensity angular distribution into a uniform one, the cylindrical convex surface 14a is formed as described above. Therefore, as shown in FIG. 4(c), in the case where the heel effect compensation filter 14 is used, as shown in FIG. 4(d), at the position where the intensity of the incoming X-ray flux XR into the heel effect compensation filter 14 is maximum, the heel effect compensation filter 14 is made thickest while at the position where the intensity of the X-ray flux XR is weaker, the heel effect compensation filter 14 is made thinner. Therefore, the X-ray intensity angular distribution of the X-ray flux XR becomes uniform in the body axis direction of the examinee H, at a predetermined distance FCD from the X-ray source 11a. It should be noted that the thickness distribution of the heel effect compensation filter 14 can be also obtained from the following Formula 1. ( y ′ z ′ ) = ( L ⁡ ( θ ) ⁢ cos ⁢ ⁢ θ FFD FCD ⁢ ( FCD ⁢ ⁢ tan ⁢ ⁢ θ - L ⁡ ( θ ) ⁢ sin ⁢ ⁢ θ ) ) ⁢ ⁢ ( θ ≤  cone ⁢ ⁢ angle  ) ( Formula ⁢ ⁢ 1 ) In short, on a plane containing the irradiation axis S of the X-ray flux XR and the beam irradiation axis of the thermoelectron beam flux, as shown in FIG. 5, the irradiation axis S of the X-ray flux XR is defined as a Y-axis, and a position at a distance FCD away from the focal point on the Y-axis (i.e. X-ray source 11a) is defined as an origin point of the coordinate axes (Y-Z). An axis passing the origin point and being orthogonal to the Y-axis, and in parallel with the body axis direction of the examinee H is defined as a Z-axis. The distance FCD is a distance from the X-ray source 11a to the isocenter, i.e. a distance to the platform B side detection means 20. In addition, with respect to a divergence angle θ of the X-ray flux XR relative to the irradiation axis S of the X-ray flux XR, an intensity of the X-ray flux XR before transmitting through the heel effect compensation filter 14 is defined as I0(θ), while an intensity of the X-ray flux XR after transmitting through the heel effect compensation filter 14 is defined as I(θ). An apparent thickness of the heel effect compensation filter 14 for an angle θ is defined as L(θ). The θ is a predetermined angle within a range of cone angle formed by symmetrically diverging from the X-ray source 11a with the irradiation axis of the X-ray flux as an axis of symmetry. The letters “z” and “y” in the formula represent positions in respective axial directions with an intersection of the Z-axis and the Y-axis as an origin point, and “FFD” represents a predetermined distance from the X-ray source 11a along the Y-axis. In this case, when the X-ray flux XR transmits through the heel effect compensation filter 14 at an angle θ, the apparent thickness L(θ) is expressed as an inclined distance, which is then converted into a length in a Y-axis direction (thickness) La(θ). Subsequently, within a range where the X-ray intensity angular distribution is adjusted as shown in FIG. 6(a), a fitting function which will be described below is assigned. Upon assigning, the maximum value and the minimum value of the X-ray intensity and the X-ray intensity at an angle θ are represented as Imax, Imin and I (θ), respectively. An attenuation coefficient is represented as μ. In addition, as shown in FIG. 6(b), in order to convert I (θ) to Imin, a required apparent thickness L(θ) is obtained by the following Formula 2:I(θ)=I0(θ)EXP(−μx) (Formula 2) where x is an apparent thickness. By assigning L(θ) to x and Imin to I0(θ) and rewriting the formula for L(θ), the formula above is expressed as the following Formula 3:L(θ)=1/μ×ln(I(θ)/Imin) (Formula 3) In order to obtain an actual thickness La(θ), the above formula is resolved into y and z components as shown in the following Formula 4: ( y z ) = ( L ⁡ ( θ ) ⁢ cos ⁢ ⁢ θ FCD ⁢ ⁢ tan ⁢ ⁢ θ - L ⁡ ( θ ) ⁢ sin ⁢ ⁢ θ ) ( Formula ⁢ ⁢ 4 ) Provided that the heel effect compensation filter 14 is installed at a distance FFD away from the focal point, Formula 4 can be expressed as Formula 1 shown below. In the formula, y′ and z′ mean a thickness relative to a position in the body axis direction and a position in the body axis direction, respectively. ( y ′ z ′ ) = ( L ⁡ ( θ ) ⁢ cos ⁢ ⁢ θ FFD FCD ⁢ ( FCD ⁢ ⁢ tan ⁢ ⁢ θ - L ⁡ ( θ ) ⁢ sin ⁢ ⁢ θ ) ) ⁢ ⁢ ( θ ≤  cone ⁢ ⁢ angle  ) ( Formula ⁢ ⁢ 1 ) By eliminating a trigonometric function from this formula, the following Formula 5 is obtained. z ′ = FFD FCD ⁢ ( FCD y ′ - 1 ) ⁢ L ⁡ ( θ ) 2 - y ′ 2 ( Formula ⁢ ⁢ 5 ) By solving this Formula 5 for y′, the thickness of the heel effect compensation filter 14 La(θ) can be obtained. With respect to the heel effect compensation filter 14 formed according to this Formula 1, the cylindrical convex surface 14a may be oriented either to an examinee H side or to an X-ray source 11a side. In this embodiment, the heel effect compensation filter 14 is formed as a single sheet. However, the filter may be formed of a plurality of separate sheets, as long as a distance in the filter through which the X-ray flux transmits is equal to the thickness distribution of the filter 14. As shown in FIG. 3(b), in the wedge filter 13, the examinee H-side transmissive surface is configured as a cylindrical concave surface extending in the body axis direction and an X-ray source 11a side transmissive surface is configured as a flat surface 13b. The wedge filter 13 has a function of adjusting the intensity of the X-ray flux XR around a torso of the examinee H, and is disposed between the X-ray source 11a and the collimator 12 at a position proximate to the collimator 12. It should be noted that the wedge filter 13 may be disposed between the collimator 12 and the examinee H, or between the collimator 12 and the heel effect compensation filter 14. (Usage) Usage of the X-ray CT scanner 1 of the present invention will be described in reference to FIG. 1. First, an examinee H is laid on the horizontal platform B positioned below the X-ray source 11a of the X-ray irradiator 10. When the X-ray flux XR is irradiated from the X-ray source 11a under this condition, the X-ray flux XR transmits through the wedge filter 13 while adjusted so that the X-ray intensity angular distribution becomes uniform in the body width direction, then reaches the collimator 12. The X-ray flux XR that has been limited the irradiation area thereof by the opening 12a of the collimator 12 transmits through the heel effect compensation filter 14, while the X-ray intensity angular distribution is adjusted to become uniform in the body axis direction, then reaches the examinee H. The X-ray flux XR that has transmitted through the examinee H reaches a large number of the detection means 20, while the X-ray intensity angular distribution in the body axis direction is kept uniform. Since the heel effect compensation filter 14 has such a configuration, the X-ray intensity angular distribution under the influence of the heel effect of the X-ray flux XR can be made uniform in the body axis direction after the X-ray flux XR transmitted through the heel effect compensation filter 14. Since the X-ray irradiator 10 has such a configuration, the examinee H is prevented from being unnecessarily exposed. In addition, since the X-ray CT scanner 1 has such a configuration, the X-ray intensity angular distribution of the X-ray flux XR can be made uniform at a predetermined distance FCD from the X-ray source 11a, and the examinee H is prevented from being unnecessarily exposed. An X-ray CT scanner according to a second embodiment of the present invention is different from the first embodiment in that, with respect to the X-ray irradiator 10a, a flat surface 14b of the heel effect compensation filter 14 as an X-ray flux XR-incoming side transmissive surface is formed on an X-ray source 11a side, and that a cylindrical convex surface 14a as an X-ray flux XR-outgoing side transmissive surface is formed on an examinee H-side, as shown in FIG. 8(a). When a flat surface 14b of the heel effect compensation filter 14 is disposed between the collimator 12 and the examinee H at a position proximate to the collimator 12 and at a predetermined distance FFD away from the X-ray source 11a, the X-ray intensity angular distribution of the X-ray flux XR becomes uniform at a predetermined distance FCD away from the X-ray source 11a, continuously along a body axis direction in the X-ray flux irradiated space V. Even when the heel effect compensation filter 14 is placed as explained above, like the first embodiment, as shown in FIG. 8(b), at a predetermined distance FCD from the X-ray source 11a (by the detection means 20), the X-ray intensity angular distribution of the X-ray flux XR can be made uniform, and the examinee H is prevented from being unnecessarily exposed. An X-ray CT scanner according to a third embodiment of the present invention is different from the first embodiment in that, with respect to the X-ray irradiator 10b, a flat surface 14b of the heel effect compensation filter 14 as an X-ray flux XR-incoming side transmissive surface is formed on an X-ray source 11a side, and that a cylindrical convex surface 14a as an X-ray flux XR-outgoing side transmissive surface is formed on an examinee H-side, and that the heel effect compensation filter 14 is disposed between the wedge filter 13 positioned on an X-ray source 11a side and the collimator 12, as shown in FIG. 8(c). Even when the heel effect compensation filter 14 is placed as explained above, like the first embodiment, as shown in FIG. 8(d), at a predetermined distance FCD from the X-ray source 11a (by the detection means 20), the X-ray intensity angular distribution of the X-ray flux XR can be made uniform, and the examinee H is prevented from being unnecessarily exposed. An X-ray CT scanner according to a fourth embodiment of the present invention is different from the first embodiment in that, with respect to the X-ray irradiator 10c, a cylindrical convex surface 14a of the heel effect compensation filter 14 as an X-ray flux XR-incoming side transmissive surface is formed on an X-ray source 11a side, that a flat surface 14b as an X-ray flux XR-outgoing side transmissive surface is formed on an examinee H side, and that the heel effect compensation filter 14 is disposed between the wedge filter 13 positioned on an X-ray source 11a side and the X-ray source 11a, as shown in FIG. 8(e). Even when the heel effect compensation filter 14 is placed as explained above, like the first embodiment, as shown in FIG. 8(f), at a predetermined distance FCD from the X-ray source 11a (by the detection means 20), the X-ray intensity angular distribution of the X-ray flux XR can be made uniform, and the examinee H is prevented from being unnecessarily exposed. An X-ray CT scanner according to a fifth embodiment of the present invention is different from the first embodiment in that, with respect to the X-ray irradiator, a heel effect compensation filter 15 shown in FIG. 9 has a cylindrical convex surface 15a with a curve being formed in the body axis direction of the examinee H and a cylindrical concave surface 15b with a curve being formed in the body width direction on the opposite side to the cylindrical convex surface 15a. The heel effect compensation filter 15 has a cylindrical convex surface 15a with a curve being formed in the body axis direction of the examinee H and a cylindrical concave surface 15b with a curve being formed in the body width direction on the opposite side to the cylindrical convex surface 15a. On the cylindrical convex surface 15a, a crest part 15c is formed at a position away from the irradiation axis S of the X-ray flux XR. In other words, the heel effect compensation filter 15 has a shape obtained by adjoining the flat surface 14b of the heel effect compensation filter 14 used in the first embodiment to the flat surface 13b of the wedge filter 13 of the first embodiment. Preferably, the heel effect compensation filter 14 and the wedge filter 13 used in the first embodiment are integrally formed. When the X-ray flux XR transmits through the heel effect compensation filter 15, at a predetermined distance FCD from the X-ray source 11a (the detection means 20), the X-ray intensity angular distribution of the X-ray flux XR can be made uniform along the body axis direction of the examinee H perpendicular to the irradiation axis S of the X-ray flux XR. In addition, the intensity of the X-ray flux XR can be adjusted in the body width direction of the examinee H in accordance with a difference in a thickness of the examinee H. Therefore, while preventing the examinee H from being unnecessarily exposed, clear slice data can be obtained. As shown above, according to the heel effect compensation filters 14 and 15 of the present invention, when irradiating the X-ray flux XR on the subject H, a nonuniform X-ray intensity angular distribution due to the heel effect of the X-ray flux XR can be adjusted to become uniform in the body axis direction. Further, the prevent inventors made intensive and extensive studies from detailed technical viewpoints with respect to the heel effect compensation filters 14 and 15 of the present invention. As a result, novel functions, effects and applications were found which had not been speculated from the conventional knowledge of heel effect. Herein, the novel functions, effects and applications of the heel effect compensation filters 14 and 15 of the present invention will be described. The X-ray flux XR irradiated from the X-ray source 11a of the X-ray CT scanner 1 is typically a continuous X-ray composed of a broad energy spectrum, and for evaluating irradiation quality, effective energy is generally used. The effective energy is an energy value of a monochromatic X-ray that gives a half-value layer equivalent to that of the X-ray flux XR, and can be easily calculated by a conventional method from the half-value layer of the irradiated X-ray flux XR. The half-value layer is represented by a thickness of a filter that halves an amount of outgoing X-ray relative to an amount of incoming X-ray. The present inventor has studied and found that, in an X-ray irradiator using solely a conventional wedge filter, effective energy of the X-ray flux transmitted through the wedge filter becomes nonuniform in a predetermined direction. Conventionally, in an X-ray irradiator, only dose distribution is taken into account and effective energy distribution has not drawn attention, and disadvantages of nonuniform effective energy of the X-ray flux irradiated on the subject had not even been come to an issue. As shown in FIG. 1, the X-ray irradiator 10 according to the present embodiment irradiates the X-ray flux XR from the anode (X-ray source) 11a in such a manner that the X-ray intensity angular distribution of the X-ray flux XR transmitted through the examinee H becomes uniform on the platform B-side surface of the detection means 20. The X-ray irradiator 10 includes the cathode 11b, the X-ray source 11a, the collimator 12, the wedge filter 13 having the cylindrical concave surface 13a, and the heel effect compensation filter 14 having the cylindrical convex surface 14a. In this X-ray irradiator 10, the X-ray flux XR passes through the heel effect compensation filter 14, and therefore the effective energy of the X-ray flux XR in a predetermined direction of the examinee H becomes high and uniform. The heel effect compensation filter 14 of the present embodiment has a function of adjusting the effective energy of the X-ray flux XR irradiated from the X-ray source 11a to become uniform in a predetermined direction, after the X-ray flux XR transmitted through the heel effect compensation filter 14. Specifically, the heel effect compensation filter 14 is made thicker at positions where the effective energy of the X-ray flux XR that has transmitted through the wedge filter 13 is low, and thinner at positions where the effective energy of the X-ray flux XR that has transmitted through the wedge filter 13 is high. Therefore, on the axial plane containing the beam irradiation axis of the thermoelectron beam flux and the irradiation axis S of the X-ray flux, the effective energy on an axis orthogonal to the irradiation axis S at a predetermined distance from the anode 11a can be made high and uniform. The reason for obtaining high effective energy is considered that, due to a predetermined thickness distribution of the heel effect compensation filter 14, a low-energy X-ray contained in the X-ray flux XR is absorbed when the X-ray flux XR transmits through the heel effect compensation filter 14, resulting in a shift of energy distribution of the X-ray flux XR to a high-energy side. When the effective energy of the incoming X-ray into the subject H is high, energy absorption becomes poor during the transmission through the subject H, and thus a difference in the effective energy of the outgoing X-ray from the subject becomes small. When such a heel effect compensation filter 14 is employed in the X-ray CT scanner 1 and the like, generation of artifacts, such as a beam hardening artifact, is reduced, and image quality of image data is made uniform and improved in the body axis direction. Further, as a formula for calculating a thickness distribution of the heel effect compensation filter 14 that makes the effective energy uniform in a predetermined direction, the above-mentioned Formula 1 may be used. In this embodiment, the heel effect compensation filter 14 is formed as a single sheet. However, the filter may be formed of a plurality of separate sheets, as long as a distance in the filter through which the X-ray flux transmits is equal to the thickness distribution of the filter 14. In addition, also in a case where the heel effect compensation filter is used for making the effective energy uniform in a predetermined direction, the heel effect compensation filter may be disposed in various ways as shown in the first to fifth embodiments. It should be noted that the artifact that can be reduced by introducing such a heel effect compensation filter 14 to the X-ray CT scanner 1 and the like is not limited to the beam hardening artifact. For example, a ring-shaped artifact is an artifact of a ring shape generated in image data due to failures of detectors. In general, a computer program is used for detecting and adjusting such a ring-shaped artifact of the image data. However, when a beam hardening artifact is present in the image data together with a ring-shaped artifact, the computer program may not properly detect and adjust the ring-shaped artifact. Therefore, the heel effect compensation filter 14 of the present embodiment can reduce not only a beam hardening artifact in image data, but also other artifacts, such as a ring-shaped artifact. Referring to FIG. 1, a description will be made below regarding the X-ray CT imaging method which uses a heel effect compensation filter providing a novel function and application in which the effective energy is made high and uniform and artifacts are reduced. As shown in FIG. 1, an X-ray CT scanner 11 to be used for the X-ray CT imaging method according to the present embodiment includes an X-ray irradiator 10 provided with such a heel effect compensation filter 14, a detection means 20, a platform B and a gantry (not shown). The X-ray flux XR is irradiated on the examinee H lying on the platform B as the X-ray irradiator 10 revolves around the body axis of the subject, while the platform B moves forward and backward. During this movement, the detection means 20 captures the X-ray flux that has transmitted through the examinee and produces slice data, which is then subjected to image processing by a computer (not shown) and converted into image data. Since a structure of the X-ray CT scanner 1 is the same as that described above, the description is omitted. The X-ray CT imaging method according to the present embodiment is performed in the following manner: first, an examinee H is laid on the horizontal platform B positioned below the X-ray source 11a of the X-ray irradiator 10. When the X-ray flux XR is irradiated from the X-ray source 11a under this condition, the X-ray flux XR transmits through the wedge filter 13, then reaches the collimator 12. The X-ray flux XR that has been limited the irradiation area thereof by the opening 12a of the collimator 12 transmits through the heel effect compensation filter 14, while on the axial plane containing the beam irradiation axis of the thermoelectron beam flux and the irradiation axis of the X-ray flux XR, the effective energy on an axis orthogonal to the irradiation axis at a predetermined distance from the X-ray source 11a is adjusted to become high and uniform, then reaches the examinee H. With such an X-ray flux XR that has transmitted through the heel effect compensation filter 14, energy absorption becomes poor during transmission through the examinee H, and thus a difference in the effective energy of the outgoing X-ray from the subject H becomes small. The X-ray flux XR that has transmitted through the examinee H reaches a large number of the detection means 20, while maintaining the effective energy. The detection means 20 captures the X-ray flux and produces slice data, which is then subjected to image processing by a computer (not shown) to be converted into image data. According to the X-ray CT imaging method using such a heel effect compensation filter 14, generation of artifacts, especially a beam hardening artifact, can be reduced and quality of image data can be made uniform in the body axis direction and excellent. The embodiments of the present invention have been described above. However, the present invention is not limited to the embodiments above. For example, the direction of the X-ray flux irradiation may be vertical, horizontal, oblique or the like. The subject is not limited to a human being, and may be an animal or a plant in general, or structures, such as buildings and machines. In each embodiment, the wedge filter 13 is present when the X-ray flux XR is irradiated. However, the X-ray flux XR may be irradiated without the wedge filter 13. In addition, use of the X-ray irradiator 10 of the present invention is not limited to CT, and the X-ray irradiator 10 may be employed in a clinical X-ray device, digital radiography (DR), or other general devices in which the X-ray flux is irradiated. The angle θ can be appropriately used, even when the width of the opening 12a of the collimator 12 is not evenly placed relative to the irradiation axis S of the X-ray flux XR. The present invention will be explained further in detail below with reference to Examples, though the present invention should not be construed to be limited by the following Examples. A thickness distribution of the heel effect compensation filter 14 used in the first embodiment is calculated from Formula 1. In the present example, a scanner with a 256-array CT, 120 kv and a wedge for head was used for the X-ray CT scanner 1, and a beam with a width of 138 mm was irradiated in order to obtain a distinct X-ray intensity angular distribution. The following Formula 6, which is a quadratic expression of a fitting function, was used for fitting.I(θ)=−10.8 tan2θ+0.9 tan θ+0.97(−6.560≦θ≦5.426, θ: degree)I(θ)=2124 tan2θ+3990 tan θ+17.56(5.426≦θ≦5.899, θ: degree) (Formula 6) Here, Imax and Imin of the X-ray intensity were set to 100% and 74%, respectively. Under this condition, calculation was made so that the X-ray intensity as a whole becomes 74% when the heel effect compensation filter 14 was used. Measurement was also made regarding a thickness and an X-ray transmissivity of the heel effect compensation filter 14, and results are shown in FIG. 10. The relationship is represented by the following Formula 7:I=EXP(−0.13×) (Formula 7)where I is an X-ray intensity after transmission and x is a thickness of the heel effect compensation filter 14. Using this Formula 7, an apparent thickness L(θ) was calculated which is necessary for making the X-ray intensity to Imin.L(θ)=7.67n(I(θ)/74) (Formula 8) With Formula 1, a cone angle was taken into account, and an actual thickness La(O) of the heel effect compensation filter 14 is calculated, where FCD=600 mm and FFD=40 mm. The resultant thickness La(θ) of the heel effect compensation filter 14 is shown in FIG. 7. In the present Example, a heel effect compensation filter actually produced was employed in the X-ray CT scanner 1, and effect thereof was demonstrated. In the present Example, a heel effect compensation filter with a shape which was used in the fifth embodiment was used. Specifically, the heel effect compensation filter has, as shown in FIG. 9, a cylindrical convex surface 15a with a curve being formed in the body axis direction and a cylindrical concave surface 15b with a curve being formed in the body width direction on the opposite side to the cylindrical convex surface 15a. On the cylindrical convex surface 15a, a crest part 15c is formed at a position away from the irradiation axis S of the X-ray flux XR. In other words, the heel effect compensation filter 15 used in the present Example has a shape obtained by adjoining the flat surface 14b of the heel effect compensation filter 14 used in the first embodiment to the flat surface 13b of the wedge filter 13 used in the first embodiment. For Comparative Example, measurement was made without the heel effect compensation filter but only with the wedge filter 13 used in the first embodiment. It should be noted that, the heel effect compensation filter 15 used in the present Example and the wedge filter 13 used in Comparative Example are made of the same aluminum material. Each of the heel effect compensation filters 15 obtained in the present Example and the wedge filter 13 of Comparative Example were installed in the X-ray CT scanner 1 shown in FIG. 1 and were evaluated in the following manner. [Dose Distribution] For evaluation of a dose distribution, a 256-array CT was used as an X-ray CT scanner 1. An X-ray was irradiated from a fixed X-ray tube in a vertical downward direction with a tube voltage of 120 kV and a tube current of 200 mA. X-ray intensity was measured with a plurality of detectors set along the body axis direction. For the detector, an Si PIN photodiode dosimeter (S2506-04 by Hamamatsu Photonics K.K) having a detection sensitivity of 2.8 mm (body width direction)×2.8 mm (body axis direction)×2.7 mm (thickness direction) was used. For each of Example and Comparative Example, the dose distribution in the body axis direction was evaluated. [Effective Energy] As described above, the effective energy is an energy value of a monochromatic X-ray that gives a half-value layer equivalent to that of the X-ray flux XR, and can be easily calculated by a conventional method from the half-value layer of the irradiated X-ray flux XR. The half-value layer is represented by a thickness of a filter that halves an amount of outgoing X-ray relative to an amount of incoming X-ray. Specifically, a fixed X-ray tube was covered with aluminum filters of various thicknesses, an X-ray is irradiated from the X-ray tube in a vertical downward direction, and X-ray intensity was detected with an ionization chamber-type irradiation dosimeter to obtain an irradiation absorption curve. Based on the irradiation absorption curve, the half-value layer was calculated. In the present Example, the ionization chamber-type irradiation dosimeter having a volume of 0.6 ml (C-110 by Applied Engineering Inc.) was used. For each of Example and Comparative Example, evaluation was made with respect to the effective energy distribution on a plane containing the body axis direction and the body width direction orthogonal to the body axis direction. [Image Data] For evaluation of image data, a 256-array CT was used as an X-ray CT scanner 1. Images of the CT phantom placed on the platform B were obtained under the following conditions: a tube voltage of 120 kV, a tube current of 200 mA, an irradiation time of 1 second, a gantry revolution time of 1 second and a slice thickness of 1 mm. For the CT phantom to be used for imaging, a phantom for low contrast evaluation (Calphan 500 by The Phantom Laboratory) was used. For each of Example and Comparative Example, evaluation was made using image data captured at positions of −40 mm, 0 mm and 40 mm in the body axis direction. Results of the evaluation will be explained below with reference to the drawings. FIG. 11 is a graph showing a result of a dose distribution measurement. In FIG. 11, a vertical axis represents X-ray intensity and a horizontal axis represents a position in the body axis direction (a cathode side is represented by “−” and an anode side is represented by “+”, relative to an intersection of the irradiation axis and the body axis). In FIG. 11, a broken line represents a dose distribution in a case where the heel effect compensation filter 15 of the present Example is employed (in the drawing, indicated with “HEC Wedge”), while a solid line represents a dose distribution in a case where solely the wedge filter of Comparative Example is employed (in the drawing, indicated with “Conventional Wedge”). It should be noted that, in FIG. 11, the X-ray intensity on the vertical axis is represented by a relative value in which the maximum X-ray intensity in Comparative Example is taken as 1.0. As shown in FIG. 11, the present Example shows a low and uniform X-ray intensity distribution along the body axis direction, as compared with Comparative Example having a maximum value. Moreover, as a result of the low and uniform X-ray intensity distribution in the present Example, an integral dose of the present Example was reduced by 20% as compared with Comparative Example (in FIG. 11, corresponding to area ratio). Therefore, according to the present Example, exposure of the examinee H can be significantly reduced during imaging with the X-ray CT scanner 1. Though the dose distribution was measured using a dosimeter in the present Example, methods for measuring the dose distribution is not limited to this. For example, in a case where an X-ray tube revolves in the X-ray CT scanner, the X-ray tube can be fixed, the X-ray flux can be irradiated in a vertical downward direction and measured using a predetermined film placed along the body axis direction. A degree of blackness of the film exposed to the X-ray is measured by a densitometer and the like to thereby obtain the dose distribution. FIG. 12 is a graph showing a result of effective energy measurement. (a) shows a case in which a wedge filter of Comparative Example is used and (b) shows a case in which a heel effect compensation filter of the present Example is used. In FIG. 12, a vertical axis and a horizontal axis are for showing coordinates on the plane containing the body axis direction and the body width direction, where the vertical axis represents a position in the body axis direction (a cathode side is represented by “−” and an anode side is represented by “+”, relative to an intersection of the irradiation axis and the body axis), and the horizontal axis represents a position in the body width direction (one side is represented by “−” and the other side as “+”, relative to an intersection of the irradiation axis and the body width line). In FIG. 12, coordinates having the same effective energy are connected to one another as an equi-energy line. An area with a deeper color indicates lower effective energy and an area with a lighter color indicates higher effective energy. As shown in FIG. 12, Comparative Example showed a nonuniform distribution with the cathode side being low and the anode side being high in the body axis direction, while the present Example showed a uniform distribution from the cathode side to the anode side in the body axis direction. FIG. 13 is image data of a CT phantom, which is imaged. As shown in FIG. 13, in Comparative Example, a ring-shaped black artifact appears at the center of the phantom as the position approaches the anode side. On the other hand, in the present Example, regardless of the position in the body axis direction, artifacts were not observed and the image quality of the image data was uniform. In addition, uniformity of image quality of the image data affected by the generation of the artifact can be evaluated using CT value. The CT value can be represented by the following Formula 9. CT ⁢ ⁢ value = μ - μ water μ water × 1000 ⁡ [ HU ] ( Formula ⁢ ⁢ 9 ) In Formula 9, μ represents a ray attenuation coefficient of the subject of interest, μwater represents a ray attenuation coefficient of water. The CT value of water is defined as 0, of air is defined as −1000. The unit to be used is HU (Hounsfield unit). When comparison is made between the positions of −40 mm and 40 mm in the body axis direction in Comparative Example, a difference in the CT value of the center part of the image data was 2-3%. On the other hand, when a comparison is made between the positions of −40 mm and 40 mm in the body axis direction in the present Example, a difference in the CT value of the center part of the image data was 0.3%. In short, in the present invention, the difference in the CT value depending on positions in the body axis direction can be reduced as compared with Comparative Example. By reducing the difference in the CT value in this manner, the artifacts can be reduced. Therefore, excellent image data can be obtained in a body part where a low contrast is important factor upon diagnosis, such as a liver, especially in a case where imaging is made with respect to a minute tumor or blood vessel It should be noted that, in the present Example, an effective energy of the X-ray flux was 55 keV. However, this value is merely an example of the effective energy when the artifacts were reduced in the image data, and this should not be construed to limit the present invention. Though results of the measurement are not shown in the drawing, even when the phantom as an imaging subject is replaced with other kind of phantom, artifacts were observed on the anode side in Comparative Example, while no artifact appeared in image data of the present Example. According to the present invention, regardless of an imaging subject, the artifacts can be reduced and image quality in the body axis direction of the image data can be made uniform. As shown above, according to the heel effect compensation filter of the present invention, an X-ray CT scanner having 256 arrays of detectors can also reduce the artifacts. In other words, the heel effect compensation filter according to the present invention can be suitably used in an X-ray CT scanner having, for example, 32 arrays or more (such as 32, 40, 64, 124 arrays) of detectors, as a filter which exhibits the following effects: lowering exposure to a subject by making the X-ray angular distribution uniform in a predetermined direction of the X-ray flux irradiated on an examinee; reducing artifacts, especially a beam hardening artifact, by making the effective energy high and uniform in a predetermined direction; and making image quality of image data uniform and improved in the body axis direction.
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