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abstract | Processes for the treatment of solutions used for the decontamination of radioactively contaminated surfaces wherein the solution contains radioactive metal ions and organic complexing agents are described herein. The processes include treating the solutions with a reagent suitable for the destruction of the complexing agent and contains a metal capable of existing in more than one oxidation state, and raising the pH of the resultant solution to a level at which the metal of the reagent precipitates or flocs out of the solution. Processes in which the contaminated solutions are treated with electromagnetic radiation, treated with UV or visible radiation, and treated at an ambient temperature are also described herein. |
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052020835 | summary | FIELD OF THE INVENTION The invention relates to a nuclear reactor with a primary cooling circuit for removing heat generated in the reactor core during normal operation and an additional means for dissipating decay heat, which is produced in the core of the nuclear reactor after the reactor has been shutdown, without short term reliance on electrical supplies, service water and operator action. BACKGROUND OF THE INVENTION An emergency or normal shutdown of any high-temperature nuclear reactor creates a need for a system to remove excessive decay heat. Nuclear reactors produce, during the course of their normal operation, radioactive materials which decay and produce heat for a period of time after the reactor is shutdown. Sufficient coolant must continue to circulate for a lengthy period of time to remove that heat to prevent damage to the reactor and associated systems. A power generating nuclear reactor, for instance, is generally provided with a steam generator which acts as a heat sink during normal operation. Therefore, a means must be present to provide an alternate heat sink when the steam generator is not available. U.S. Pat. No. 4,699,754 describes one system for removing decay heat from a reactor core which has a liquid metal coolant circulation system. Typical coolants for these type of reactors are sodium or potassium which, during operation, may reach temperatures in the order of 1200.degree. to 1500.degree. K. Previous reactors of this type have used an auxiliary Thermoelectric Electromagnetic Pump in an auxiliary flow path connected in parallel to a portion of the primary flow path. These previous reactors had a check valve in the primary flow path between the connections for the auxiliary path. During normal operation, a primary cooling pump flow holds that check valve open. However, the auxiliary Thermoelectric Electromagnetic Pump maintains a coolant flow through the auxiliary flow path with the check valve preventing back-flow if the primary cooling pump stops. U.S. Pat. No. 4,699,754 mentions that moving parts such as check valves are unreliable when subjected to high-temperatures and held in one position for long periods. In order to avoid the necessity for this check valve, U.S. Pat. No. 4,699,754 suggests using the Thermoelectric Electromagnetic Pump in the auxiliary flow path to re-inject a secondary stream of metal coolant into the main coolant stream. The re-injection acts as a drive fluid for a jet pump in the main flow path which, using the principal of momentum exchange, induces a circulation of the main fluid in the same direction as the normal primary coolant flow. This provides an auxiliary circulation system without any moving parts and which is self-regulating. The auxiliary Thermoelectric Electromagnetic Pump/jet pump combination operates during normal operation of the reactor but the flow in the auxiliary flow path is small compared to the main flow so that the systems efficiency is not greatly diminished. U.S. Pat. No. 4,689,194 shows another type of decay heat removal system which, in this case, is for a gas cooled reactor. Circulating blowers cause a cooling gas, such as helium, in this reactor to flow up through the reactor core and a central hot gas line down over principal heat exchangers, these may be steam generators, and decay heat exchangers back to the blowers. If the circulating blowers are not operational, decay heat from the core is removed by natural convection flow of the cooling gas in the same direction as the flow during normal operation of the reactor. The decay heat exchangers are each connected with an external re-cooling heat exchanger at a geodetically high location by means of two legs which form a water circulation loop. If the steam generators are no longer available for the removal of heat from the primary (helium) cooling path, they are traversed by hot gas which subsequently passes through the decay heat exchangers. This causes a rise in temperature at the inlet of the decay heat exchangers which leads to evaporation taking place in the water circulation loops whereby natural convection in these loops is enhanced and a sufficient amount of heat is removed from the primary loop through the decay heat exchangers. U.S. Pat. No. 4,312,703 describes another type of system for removing heat from a nuclear reactor employing liquid sodium as a primary cooling fluid along with means for dissipating the decay heat produced in the core of the nuclear reactor after it has been switched off. In this system, a pump draws the liquid sodium coolant from the reactor vessel and transports it to an integrated intermediate heat exchanger and decay heat cooler before the coolant is returned to the reactor vessel. A secondary coolant fluid, also liquid sodium, in the intermediate heat exchanger receives heat from the primary cooling fluid with the secondary cooling fluid being pumped to a steam generator and back to the intermediate heat exchanger during normal operation of the reactor. A separate or third cooling circuit is integrated into the intermediate heat exchanger and forms a decay heat cooler in which a third cooling fluid can flow to a cooler component (air cooler or steam generator), then to a pump which circulates the third cooling fluid back to the intermediate heat exchanger to remove decay heat generated when the reactor is shut down. This structure provides a very compact construction compared to previous systems wherein a decay heat cooler is incorporated as a separate heat exchanger in the primary circuit. SUMMARY OF THE INVENTION It is an object of the invention to provide an improved passive shutdown cooling system for a nuclear reactor without short term reliance on electrical supplies, service water and operator action by utilizing natural convection circulation of coolant. A nuclear reactor system, according to one preferred embodiment of the present invention, is provided with a main heat transport path containing a first heat removal component, a main coolant pump and coolant in the heat transport path; the coolant being pumped in the heat transport path by the main coolant pump through a core of the reactor to said heat removal component and back to the reactor core to transport heat generated in the reactor core to the heat removal component during normal operation of the reactor system; wherein a further decay heat removal path is connected in parallel with the heat removal component and main coolant pump, the further decay heat removal path including a heat exchange component located at an elevation such that a natural convection flow will occur in the decay heat removal path from a high temperature outlet for coolant from the reactor core to a low temperature inlet to the reactor core when said main coolant pump is shutdown; the further decay heat removal path includes a means to prevent flow in a direction opposite to the intended natural convection flow and a means to maintain a small flow of coolant from said outlet through the heat exchange component during normal operation of the main coolant pump. |
053135067 | claims | 1. An improved ferrule spacer for use with high density fuel rod arrays within boiling water reactor fuel bundles comprising in combination: a matrix of ferrules for surrounding fuel rods at selected elevations within said fuel bundle, said matrix of ferrules constructed from confronting first and second ferrules arrayed in discrete mating ferrule pairs, said first and second ferrules of said pair thereof extending along spaced parallel axes; each said first and second ferrule being divided into upper and lower ferrule halves with at least one ferrule half having a wall removed therefrom; the other ferrule half having ferrule complete walls present; each said ferrule half with wall removed being laterally juxtaposed to a ferrule half having said walls present whereby said ferrule pair at said respective ferrule halves together define solely a single wall between adjacent fuel rods along a line extending parallel to said axes and along a tangency between the ferrule pair; fuel rod stops carried by said ferrules; and means carried by said spacer for receiving and confining a spring for biasing fuel rods within said ferrules toward said stops. said spring generally having an "H" profile with first and second overlying leg member defining rod contacting portions for contacting fuel rods placed within said ferrules; and upper and lower spring loops fastened to the upper and lower ends of said spring legs for providing increased deflection to said spring whereby said spring can have a reduced vertical dimension between said loops. providing a matrix of ferrules for surrounding fuel rods at selected elevations within said fuel bundle, said matrix of ferrules constructed from adjacent first and second ferrules arrayed in discrete mating ferrule pairs; dividing each said first and second ferrules into upper and lower ferrule halves; removing from one said ferrule half at least one portion of a ferrule wall at a point of tangency to its adjacent ferrule of the ferrule pair; confronting said ferrule pairs with each complete ferrule wall being adjacent a ferrule half having said missing wall portion whereby said ferrule pair define a single wall between adjacent fuel rods at the point of tangency between ferrules of said ferrule pair; defining fuel rod stops configured with respect to said ferrule walls; and defining an aperture for receiving and confining a spring confined between the ferrules of said ferrule pair thereof with a first portion of said spring protruding into one of said ferrules of said ferrule pair and a second portion of said spring protruding into the second ferrule of said ferrule pair for biasing fuel rods within said ferrule pair into said stops; and confronting said ferrule pairs to form a matrix of ferrules each surrounding a fuel rod at a selected elevation within a fuel bundle. providing a generally "H" profiled spring having first and second overlying leg member defining rod contacting portions for contacting fuel rods placed within said ferrules; and providing upper and lower spring loops fastened to the upper and lower ends of said spring legs to afford increased deflection to said spring whereby said spring can have a reduced vertical dimension between said loops. a lower tie plate for supporting a plurality of upstanding fuel rods and permitting the entry of water coolant around said fuel rods; an upper tie plate for holding the upper end of at least some of said fuel rods and permitting the exit of water coolant and generated steam from said fuel bundle; a channel surrounding said fuel bundle including said lower tie plate, said fuel rods and said upper tie plate to define an isolated flow path through said fuel bundle; and at least one improved ferrule spacer for use with fuel rod arrays within boiling water reactor fuel bundles comprising in combination; a matrix of ferrules for surrounding fuel rods at selected elevations within said fuel bundle, said matrix of ferrules constructed from first and second ferrules arrayed in discrete mating ferrule pairs with said first and second ferrules of said pair thereof extending along spaced parallel axes; each said ferrule being divided into upper and lower ferrule halves with at least one ferrule half having walls removed therefrom; the other ferrule half having ferrule walls present; each said ferrule half with walls removed being laterally juxtaposed to a ferrule half having said walls present whereby said ferrule pair at said respective ferrule halves together define solely a single wall between adjacent fuel rods along a line extending parallel to said axis and along a tangency between the ferrule pair; fuel rod stops carried by said first and second ferrules; and means carried by said spacer for receiving and confining a spring for biasing fuel rods within said ferrules toward said stops. 2. The spacer according to claim 1 wherein said upper half of said first ferrule is identical in construction with said lower half of said second ferrule, the upper half of said second ferrule being identical in construction with said lower half of said first ferrule. 3. The spacer according to claim 1 wherein said ferrules are circular. 4. The spacer according to claim 1 wherein said ferrules are octagonal. 5. The spacer according to claim 1 wherein said ferrules define a circular surround for the fuel rods. 6. The spacer according to claim 1 wherein said ferrules define an octagon sectioned surround for the fuel rods. 7. The spacer according to claim 1 wherein said confronting ferrules of said ferrule pair define an aperture for capturing a spring therebetween. 8. The spacer according to claim 7 including said spring; 9. The spacer according to claim 1 wherein said one ferrule half having a removed wall defines a slot extending generally parallel to the axes of said ferrules opening through an end of said one ferrule half and terminating at an opposite end slightly beyond a media of the height of said spacer. 10. The spacer according to claim 9 wherein a portion of the walls present of said other ferrule extends within said slot to comprise said single wall between adjacent fuel rods. 11. A method for manufacturing an improved ferrule spacer for use with high density fuel rod arrays within boiling water nuclear reactor fuel bundles comprising in combination: 12. The method according to claim 11 wherein said step of providing said spring includes: 13. The method according to claim 11 wherein said removing step includes removing said ferrule walls on four sides of said one ferrule half. 14. In a fuel bundle including: |
summary | ||
claims | 1. An apparatus for the confinement of long-life waste actinide and beryllium mixture in a capsule placed within a neutron moderator material to accelerate the destruction or transmutation of the waste actinide to the stable nonradioactive states of the waste actinide decay series, and said capsule being a double shell, stainless steel vessel containing the waste actinide having a length of about 2.0 inches and a diameter of about 0.75 inches. 2. A method according to claim 1 wherein the waste actinide contents of the capsule may be a single isotope or a mixture of isotopes in a stable dry state, including isotopes mixtures stabilized by glass, resin, ceramic or polymer binders, mixed with beryllium in the appropriate atomic ratios. 3. A method according to claim 2 wherein the waste actinide and beryllium mixture is an alloy. 4. A method according to claim 2 wherein the waste actinide and beryllium mixture is formed as a block or sphere encased in a shell of beryllium. 5. A method according to claim 3 wherein a graphite disk is substantially encased in stainless steel or aluminum, having one or more wells to accept loaded capsules. 6. A method according to claim 3 wherein a graphite component may be a graphite block of regular or irregular shape. 7. A method according to claim 1 wherein one or more capsules containing the waste actinide/beryllium contents are placed within a graphite disk. 8. A method according to claim 7 wherein the graphite disk is sized to fit various DOE Standard Canisters for disposal, or other accepted long-term storage radioactive waste containers. 9. A method according to claim 8 wherein the stainless steel or aluminum encased the graphite is loaded with capsules closed by a welded cover. 10. A method according to claim 9 wherein the graphite disks may be stacked within a Canister or other acceptable container. 11. A method according to claim 9 wherein stacked graphite disks are separated by copper or aluminum disks of the same diameter to aid in heat transfer within the Canister or other acceptable container. 12. A method according to claim 7 wherein crumpled aluminum or other similar impact absorbing material is provided in each capsule well of the graphite disk to provide for axial support and transfer of decay heat. 13. A method according to claim 1 wherein the capsule may be a single shell or double shell configuration having a length and diameter to conform to the design requirements of a specific testing, long-term storage or disposal container. 14. A method according to claim 13 wherein a graphite or beryllium reflector/moderator is of a specified length and diameter to conform to the design of the confined alloy. 15. A preferred method of making an apparatus for passively accelerating the rate of radioactive decay of waste actinides, the method including the steps ofa. mixing a powder form of waste actinide and beryllium in an atomic weight ratio of 1:13 to form a uniform first mixture;b. loading the mixture into a beryllium oxide crucible and subsequently heating the mixture to 1375° F., under vacuum, to achieve a molten alloy;c. shaping the molten alloy in a suitable die forming an ingot;d. loading the ingot into a double shell capsule and closing the inner and outer capsules by welding, inspecting and testing wells to verify sealing;e. preparing a graphite disk to accept sealed capsules by encasing the bottom and sides of the graphite in stainless steel or aluminum, creating wells within the graphite, also lined with stainless steel or aluminum, to form a graphite assembly;f. loading sealed capsules in the wells of the graphite assembly, using crumpled aluminum or similar material as necessary to provide axial support or to improve heat transfer from the capsules to the graphite disk housing; andg. closing the graphite assembly by installing and welding in place a top closure plate. 16. An apparatus comprising long-life waste actinide and beryllium mixture in a capsule placed within a neutron moderator, reflector material incorporated into said capsule, said mixture comprising alpha particle radiation emitted in natural decay which undergoes a subcritical nuclear reaction with adjacent beryllium thereby releasing a fast neutron which is subsequently slowed down or thermalized, and said neutron being retained within the apparatus by said reflector material such that it is available to cause transmutation of other waste actinides within the apparatus and thereby accelerate the destruction or transmutation of the waste actinide to the stable nonradioactive states of the waste actinide decay series. |
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abstract | A passive safety system comprises a heat exchanger, a thermoelectric element, and a fan unit. The heat exchanger is located inside a containment. The heat exchanger allows for temperature of atmosphere in the containment to be reduced. The thermoelectric element is disposed within the heat exchanger. The thermoelectric element is configured to generate electricity due to a temperature difference. The fan unit receives electricity generated by the thermoelectric element. The fan unit is configured to increase flow rate of fluid inside the containment. A nuclear power plant can include the passive safety system. |
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claims | 1. A nuclear fuel assembly body including a lengthways axis and configured to receive nuclear fuel pins to form a nuclear fuel assembly, said body comprising:a frame made from a metal material, the frame being openworked;a first sleeve made from a metal material and connected to a first end of the frame;a second sleeve made from a metal material and connected to a second end of the frame opposite the first sleeve along the lengthways axis, anda ceramic tubular internal structure positioned inside the frame and along the lengthways axis between the first and second sleeves, wherein the ceramic tubular internal structure comprises a plurality of lengthways superimposed segments, includinga first segment positioned at a first end of the ceramic tubular internal structure and partially penetrating into the first sleeve, anda second segment positioned at a second end of the ceramic tubular internal structure, opposite the first end, and partially penetrating into the second sleeve,wherein joints between the segments comprise leakage zones. 2. The assembly body according to claim 1, wherein the ceramic tubular internal structure prevents leakage of the cooling fluid intended to traverse it. 3. The assembly body according to claim 1, wherein the segments are socketed into one another. 4. The assembly body according to claim 3, in which the lengthways ends of the socketed segments comprise, in the case of one, a groove and, in the case of the other, a rib of matching shape. 5. The assembly body according to claim 1, wherein the frame is formed by an assembly of struts defining windows. 6. The assembly body according to claim 5, wherein the frame comprises lengthways and transverse struts. 7. The assembly body according to claim 6, whereinthe transverse struts cover zones where the lengthways superimposed segments are connected. 8. The assembly body according to claim 5, in which the ceramic tubular internal structure is formed from plates attached to the frame so as to block the windows of said frame. 9. The assembly body according to claim 1, wherein the frame is attached to the first and second sleeves by welding. 10. The assembly body according to claim 1, wherein the frame is attached to the first and second sleeves by a mechanical assembly method. 11. The assembly body according to claim 10, wherein the mechanical assembly method is of the dovetail joint type. 12. The assembly body according to claim 1, wherein the frame is formed from a tube perforated with drill holes forming circular or oblong slots. 13. The assembly body according to claim 1, further comprising: a washer with undulations of amplitude 5 mm inserted between an end of an end section of the tubular internal structure and the second sleeve located in an upper part of the assembly. 14. The assembly body according to claim 1, having a regular hexagonal transverse section. 15. The assembly body according to claim 1, in which the ceramic tubular internal structure is made of SiC, fibre-reinforced SiC or MAX-phases of the Ti3SiC2 type. 16. The assembly body according to claim 1 for a sodium-cooled fast neutron reactor, wherein the sleeves and the frame are made from at least one of austenitic, ferritic, and ferritic/martensitic steels. 17. The assembly body according to claim 1 for a sodium-cooled fast neutron reactor, in which the first and second sleeves are made from 316 Ti standard austenitic steel and the frame from EM10. 18. The assembly body according to claim 1 for a gas-cooled fast neutron reactor, in which the first and second sleeves and the frame are made from refractory metals. 19. An assembly, comprising:a foot,the assembly body according to claim 1,nuclear fuel pins positioned in the assembly body, andan upper neutron protection,wherein the body is attached to the foot and to the upper neutron protection in the area of the first and second sleeves respectively by welding. |
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050200844 | description | In FIGS. 1a and 1b the vertical axis represents the count of photons and the horizontal axis the energy of the exciting X-rays; this illustrates the spectrum of the X-rays bombarding the sample in the method and apparatus according to the invention. FIG. 1a shows, at 1, the broad bremsstrahlung peak emitted by an X-ray tube with a tungsten anode operated at 130 kV. It will be seen that there is a broad maximum at photon energy about 65 keV. According to the invention this broad maximum is reduced by filtration through metallic tin to give a reduced maximum for irradiation of the sample. This reduced maximum is shown on a larger scale in FIG. 1b, from which it will be seen that there is a peak at 115 keV with a Gaussian fall-off in number of counts on either side. A typical ore containing gold, lead and uranium, after bombardment with incident X-rays having the spectrum shown in FIG. 1b, emits at 90.degree. fluorescence radiation having the spectrum illustrated in FIG. 2 in which the axes represent the same parameters. This Figure illustrates the characteristic peaks of gold, lead and uranium, those of particular significance for the invention being the gold K.alpha..sub.1 peak at 68.8 keV and the gold K.alpha..sub.2 peak at 67.0 keV. The maximum of the overall bremsstrahlung peak is shifted from about 115 to about 100 keV. At the concentrations with which the invention is primarily concerned, (i.e. up to 10 ppm of ore) the gold peaks in the spectrum shown in FIG. 2 cannot be measured accurately with a time span convenient for industrial application by even the most sensitive means presently known. The maximum count-rate which each detector and associated electronics channel can handle is an inherently limiting factor. With known pulse-shaping techniques, as are envisaged for use in the invention, there is a trade-off between count-rate and detector resolution. At the detector resolution required for the analysis of the ores and other materials in which we are interested, the maximum input counting-rate is about 150,000 counts per second. In the context of analysis for gold and uranium, however, only the fairly narrow energy bands around the gold K.alpha. (and uranium K.beta.) peaks are of interest. An ideal detector would respond only to these. Unfortunately the detector response (illustrated diagrammatically in FIG. 5, see below) can only be partially optimized by careful selection of the detector thickness (in the range of 2-4 mm) and the photons in the large bremsstrahlung peak, which are of no interest, use up a large proportion of the detector live time. This difficulty is overcome according to the invention by the use of an iridium or platinum filter, the characteristic absorbtion spectra of which are illustrated in FIG. 3 in which the vertical axis represents absorbtion and the horizontal axis the energy of the incident radiation. When X-rays emitted by fluorescence from a sample in the apparatus according to the invention are passed through such a filter before detection the absorbtion spectrum of the filter is effectively superimposed upon the peak shown in FIG. 2 with result that the gold K.alpha..sub.1 and K.alpha..sub.2 peaks are much more readily detectable for the same total detector count rate, because there are more counts in the energy region of interest and statistical errors are reduced. In other words, the iridium and platinum filters used according to the invention preferentially attenuate the higher energy radiations in which we are not interested. For example, a 0.125 mm thick iridium filter will transmit about 40% of the photons in the regions of interest (i.e. channels 0-5 in FIG. 6), but will transmit only about 20% of photons in the range 80-120 keV (the bremsstrahlung peak). As this latter peak comprises most of the photons, when we use the iridium filter we require about 5 times more power from the X-ray source to get the count-rate back to the maximum which the detectors can handle. However, the use of an iridium (for example) filter converts the spectrum shown in FIG. 2 to that shown in FIG. 4, and the proportion of photons in the region of interest, relative to the total count-rate, has increased by a factor of 0.4.times.5 i.e. doubled. Thus the use of the iridium filter has the same effect as doubling the number of detectors, and the statistical error in the result is reduced by about 2. A thicker filter would give more improvement. This selectivity is enhanced according to the invention by the use of germanium detectors, the efficiency curve of which is illustrated in FIG. 5 in which detection efficiency (%) assuming photoelectric cross-section only is plotted against excitation energy (keV) for various detector active thicknesses. The efficiency falls assymptotically away from 100% with increasing exciting energy, being about 90% for a 4 mm thick detector at the crucial energy of 68.8 keV (the energy of the gold K.alpha..sub.1 band). With increasing energy the efficiency falls off more rapidly to about 50% at 110 keV. It will be seen that a thickness of 2-4 mm gives a curve corresponding most closely to that of FIG. 4, and a detector thickness within this range is therefore preferred according to the invention for use in gold analysis. The spectrum resulting from the combined use of an iridium filter and germanium detectors in the apparatus according to the invention gives a spectrum as shown in FIG. 6 which corresponds generally to FIG. 4 but shows the gold K.alpha..sub.1 and K.alpha..sub.2 bands on a greatly enlarged scale. The associated electronic instrumentation is programmed in known manner to measure the number of impacts in selected band widths (or channels) such as those shown in FIG. 6. The instrumentation is programmed to compare the total signal plus background from the bands numbered 2 and 3 with the total background signal from the bands 1 and 4. The measurement of the gold content of the ore is therefore based not on an absolute measurement but on comparative measurements, thus eliminating uncertainties and inaccuracies inherent in the measurement of absolute values (e.g. the variations in excitation voltage or current in the X-ray source). For gold measurement, bands 1-4 are used. Each band has a nominal width of 600 eV, but in practice these widths may be altered to suit detector resolution, for example bands 1 and 4 may be 500 eV wide, and bands 2 and 3 may be 700 eV wide, or vice versa. Bands 0 and 5 are used for diagnostic purposes. The symmetry of the curve around the K.alpha..sub.1 peak is important. In a diagnostic routine, a solid gold check source is used to determine the proportion of gold counts falling into each of channels 1-4. The spectrum from a solid gold source does not contain much scattered radiation (which originates predominantly from low atomic number material) and is shown in FIG. 8. The count in channel 2 is compared with the count in channel 3, and if these are unequal by more than a predetermined amount, the mid-point position between channels 2 and 3 is altered electronically, until symmetry is restored. Thus the fraction X of counts in channels (2+3) over channels (1+2+3+4) is measured and stored, and this indicates what fraction of the signal representing the gold K.alpha..sub.1 band, which is nominally in channels 2 and 3, is spilling over into channels 1 and 4. As will be mentioned in more detail below, the use of a check source of the metal being analysed is an important technique in practising the invention. When a series of samples are being analysed, as will normally happen, the check source is interposed between samples at intervals of, say, 4 or 5 samples, to determine and correct for any instrument drift due for example to temperature changes. This process for gold is given by the algorithm: ##EQU1## where G=gold concentration in suitable units (e.g. g/tonne) S=a normalized sensitivity factor (corrected for sample density and predetermined with calibration samples as described in more detail below) K=a background factor (predetermined and corrected for sample density with calibration samples) PA1 T.sub.1 =counts in channels (2+3) PA1 T.sub.2 =counts in channels (1+4) PA1 X=fraction of total signal counts in channels (2+3) (predetermined) PA1 Y=fraction of total signal counts in channels (1+4) PA1 (The total number of signal counts being the numbers in channels (1+2+3+4), so that Y=(1-X)) Ideally, with no spillover of gold signal into channels 1 and 4, X=1 and Y=0, and ##EQU2## The preferred normalizing technique according to the invention for the factor S is as follows. The counts from the sample depend both on the sample density and on the number of photons exciting the sample. Variations due to the latter (e.g. due to changes in the X-ray generator current and high voltage) can be minimised by reference to the counts (H) obtained recently from a standard scatterer, which can be a solid gold check source or an aluminium background standard. The assumption is made that the instrument has remained stable since the last reading of the standard, which is reasonable. Thus, the variation in counts from the sample can be normalised to a standard excitation intensity, and the remaining variations are due to sample density alone, which is corrected for as described below. It is within the scope of the invention to use a separate detector or detectors to check dynamically the excitation intensity and so remove the remaining uncertainty due to the time delay. It has been found that, as sample density increases, the counts B in the background channels (corrected for overlap of signal) also increase, due both to more primary scattering and to more multiple scattering. The increase is partially offset by more attenuation and absorption. At the same time the signal counts per ppm also increase, due to the increased number of interactions, but not so fast as B. It has been determined, with a high correlation coefficient, that this process can be described by the equation: ##EQU3## where M and N are constants determined by regression analysis from a set of values of S and B obtained from known high value ore samples, having a range of densities. Even single samples can be prepared with a range of densities, by a combination of compression and grinding to different grain sizes. B should ideally be corrected for system deadtime, but in most practical cases the latter is largely compensated for in the actual measurement of M and N for similar photon energy spectrums. Variable lead peaks can cause a slight error, as they vary system deadtime. The ratio T1/T2 in the gold equation given above is independent of system deadtime. Other techniques for refining the density correction will readily be apparent, for example by consideration of higher energy sections of the photon energy spectrum which are less affected by multiple scattering. However, a particular advantage of basing the density correction on background channels on both sides of the signal channels is that primary attenuation and absorption effects are matched for both signal and background. The values of M and N determined also compensate for counts due to the sample container itself, and other scattered radiation not originating from the sample. The software can be made slightly easier by redefining the signal counts simply as those appearing in channels (2+3), in which case X=1. Then the equation becomes: ##EQU4## This is not different, but the same process in slightly different format. FIG. 9 illustrates schematically the geometry of excitation and detection according to the invention. As mentioned above, an important feature of the invention is that it provides a geometry for the apparatus which exploits the polarization of X-rays emitted from a source with a thick target. In FIG. 9, the X-ray source is indicated generally at 91 and comprises an X-ray tube 92, with tungsten cathode at 93 and tungsten anode at 94. The exciting radiation 90 from the anode 94 emerges through a lead collimator 95 and a tin filter 96 to strike a sample 97. Scattered and fluorescent radiation 102 from the sample emitted at about 90.degree. to the incident exciting radiation passes through an aperture in a tin collimator 98 and an iridium or platinum filter 99 to the germanium detector array 100. This array may consist for example of two vertical rows of 8 detectors each. These are preferably circular and may for example be about 8 mm in diameter and about 2-4 mm thick. The tolerance in thickness is about 15% owing to limitations in the reproducibility of the lithium-diffused contact. Square cross-sectioned detectors would be preferable but currently available detectors are not suitable at high-count rates due to insufficient field strength in the rear corners resulting in low-energy tailing. A second filter and detector array (similar to that already described) may be provided at 101. Radiation 103 scattered from the tin filter 96 is stopped by the collimator 98. The preferred use according to the invention of a scattering angle of about 90.degree. is of especial significance for the measurement of uranium because the X-rays emitted from a thick target are often partially polarized. It is therefore important that, as shown in FIG. 9, the sample should be positioned so as to intercept X-rays emerging frOm the tube at 90.degree. to the electron beam passing from cathode 93 to anode 94 in the tube. This polarization phenomenon can, according to a preferred feature of the invention, be applied advantageously to the simultaneous analysis of gold and uranium. This is illustrated in FIG. 7(a), in which, as in previous figures, number of photon impacts is plotted vertically and photon energy in keV horizontally. The curve illustrated is that containing the uranium K bands on the high-energy side of the energy peak in FIG. 4. Broken curve (a) in FIG. 7(a) illustrates the curve obtained without the advantage of the reduction of background radiation obtained using the polarization technique described above. Curve (b) is obtained using the polarization technique, and illustrates the reduction in background counts. The channels 0-5 illustrated in FIG. 7 are counted and compared in a manner generally similar to that described above with reference to FIG. 6. In FIG. 7(a), the signal channels are channels 1, 2 and 4 and the background channels 0, 3 and 5. The edge of the uranium K-band is at 115.6 keV, thus if we are operating at 125-130 keV, reasonable excitation and polarization effects are obtained. This technique for measuring uranium could suffer from interference by a thorium peak which occurs in channel 0 as shown in FIG. 7(a). In FIG. 7(b) is illustrated a method according to the invention of reducing or eliminating this interference. In FIG. 7(b) the channel numbers and energies have been shifted to lower energies and part of channel 0 re-allocated to provide an additional channel for thorium. The principal uranium K.beta..sub.1 and K.beta..sub.3 peaks then appearin channels (2+3) and the background measurement is determined from channels (0+4). The thorium K.beta..sub.2 peak appears in channel 1. This not only reduces or eliminates thorium interference where uranium is being determined but also provides a method of determining thorium concentration. A further application of the selection and allocation of channels according to preferred embodiments of the invention to reduce or eliminate interference from unwanted elements or even to determine the concentration of the same elements is illustrated in FIGS. 7(c) and 7(d). A preferred feature of the invention is the use of an analysis board with six channels, which not only facilitates the determination of certain elements as described below, and is the number required for uranium determination but also simplifies electronic design. FIGS. 7(c) and 7(d), which have been separated for clarity, illustrate the simultaneous detection of interference from mercury and tungsten in analysis for gold. As shown in FIG. 7(c) the mercury K.alpha..sub.2 peak overlaps the gold K.alpha..sub.1 peak. The presence of mercury is detected via its K.alpha..sub.1 peak in channel 5. This enables the gold result to be questioned or corrected. In most gold mining areas, the ratio of mercury to gold is very low, and in practice mercury in ore samples is not expected to present a problem. In processed material, however, the mercury may be concentrated relative to the gold. The K.alpha..sub.2 peak of thallium overlaps the mercury K.alpha..sub.1 peak and can give a false mercury indication. In practice, the occurrence of thallium is rare, and the indication of possible interference is fail-safe. FIG. 7(d) illustrates the application of this technique to tungsten, the K.beta. peaks of which occur at virtually the same energy as the gold peaks but are differently proportioned as regards amplitude. The tungsten K.beta..sub.2 peak occurs at a slightly higher energy than the gold K.alpha..sub.1 peak, and most of it falls in the signal channels (2+3) with a small amount in channel 4. Part of the tungsten K.beta..sub.1 peaks fall in channel 1. The tungsten signal appearing in channel 0 is much greater than the signal appearing in channels (2+3), which contrasts with the gold signal, which is higher in channels (2+3) than in channel 0. Thus the ratio of the total signal in channels (2+3) to the total signal in channel 0 provides an indication of whether or not tungsten is present. The platinum K.alpha..sub.1 peak and the tantalum K.beta..sub.2 peaks also appear in channel 0, and can give false indications of tungsten. However, in practice, the occurrence of these elements in ore bodies when gold is the major mineral is rare. The indication of possible interference is fail-safe. FIG. 10 is a schematic block diagram showing the method and apparatus according to the invention in use. The apparatus consists essentially of a source of high energy X-rays (photons) 201 arranged to bombard a sample in a cylindrical container 202 as described above and below through a collimator 203. Interposed between the X-ray source and the sample 202 is a metallic tin filter 204. The fluorescence photons emitted at right angles to the bombarding rays pass through an iridium filter 205 before collimation to a detector 206 comprising a regular array of germanium detector elements with axes parallel to the incident radiation, each with its own pre-amplification and signal conditioning circuitry. In FIG. 10, 209 represents a check source, consisting for example of a piece of gold foil in a sample container which is interposed between every, say 4 or 5 ore samples during readings. The sample container 202 is preferably a cylindrical thin walled container of plastic material such as acetal plastic. A thin container is necessary so that counts due to the sample container are very much less than the counts due to the sample. We have found that generally a diameter in the range of 10-30 mm gives satisfactory results depending on the considerations set forth below, while a wall thickness of 0.35 to 0.5 mm typically about 0.4 mm provides sufficient rigidity, can be made reproducibly, and complies with the above requirement. The diameter of the sample container can be varied to suit the application and ore bodies. For inhomogenous ore bodies, when sampling error is high, it is desirable to maximise the mass of sample irradiated, and an internal diameter of typically about 18.7 mm is a good compromise between the conflicting requirements of sensitivity and sampling error. However, the smaller the diameter of the sample container, the higher the sensitivity will be, as there will be less attenuation or absorption of the signal, and less multiple scattering. However, if the sample container is made too small, the effect of counts from its wall will become more noticeable, and also the power of the X-ray generator will have to be greatly increased to provide the high count rate necessary for minimisation of errors due to counting statistics. The sample size will be smaller, and may cause sampling errors. However, for the homogeneous ore bodies, as occur in several parts of the world, the sampling error is low, and a good compromise is a tube having an internal diameter of about 12.7 mm. The invention is not, however, limited to the use of cylindrical containers with the above dimensions. It is also possible to use differently shaped sample containers with, for example, rectangular cross sections in which the long axis of the rectangular cross section is angled at about 45.degree. to both the exciting beam and the detected beam, so that the desired scattering angle, as described above, is still in the order of 90.degree.. A further precaution by which inaccuracies due to non-uniform particle size or packing in the sample can be reduced is to shift the sample container, for example along its longitudinal axis, and to measure the scattered radiation in two or more positions of the containers; alternatively the zone of the sample scanned (with the preferred containers of the dimensions mentioned above this is generally about 7 cm long) may be moved along the sample. The apparatus shown schematically is FIG. 10 employs an automatic sample changer to achieve a continuous throughput of, for example, one sample per 100 seconds. Such rapid throughput is as described above essential in mining applications where continuous analysis of a succession of samples must continue at all times. It is within the scope of the invention to irradiate the sample with a second beam of exciting X-radiation from a source diametrically opposite to the first source. This technique reduces the gradient of the exciting photons throughout the thickness of the irradiated sample and may also be applied to the use of other types of irradiation source such as special X-ray tubes and radioisotopes; the use of radiootopes source is not however within the scope of the present invention. |
claims | 1. An X-ray microscopic inspection apparatus having X-ray generating means for generating an X-ray by allowing an electron beam from an electron source to impinge on a target for X-ray generation, for inspecting an object by utilizing said X-ray, said X-ray microscopic inspection apparatus comprising:a field emission electron gun having an ultra-high vacuum electron gun chamber, an anode and an electron generating portion, wherein the electron generating portion is adapted to generate electrons and said anode is adapted to generate an electric field to accelerate said electrons;said field emission electron gun further comprising a magnetic superposition lens including a magnetic circuit and a magnetic field generating portion, wherein said magnetic field generating portion is disposed separately from said ultra-high vacuum electron gun chamber and said magnetic superposition lens is adapted to generate a magnetic field,wherein said electron generating portion is disposed in said magnetic field and said magnetic field is superposed to said electric field thereby reducing the loss amount of said electron beams from said electron source by focusing the accelerated electrons prior to being impinged on said target for X-ray generation. 2. The X-ray microscopic inspection apparatus according to claim 1, wherein the electron source is a liquid metal electron source utilizing liquid metal. 3. The X-ray microscopic inspection apparatus according to claim 1, wherein the electron source is a thermal field emission electron source. 4. The X-ray microscopic inspection apparatus according to claim 1, wherein the target for X-ray generation is a target with a heat sink using thin CVD diamond plate as the heat sink. 5. The X-ray microscopic inspection apparatus according to claim 1, wherein the electron gun chamber of ultra-high vacuum is covered by the magnetic circuit. 6. The X-ray microscopic inspection apparatus according to claim 1, wherein the electron gun chamber is formed in the convex form, a section of the magnetic body of the magnetic generation portion is formed in a concaved form, and the electron generating portion of the electron gun is disposed in said concaved portion to that said electron generating portion and said magnetic generating portion become more close. 7. The X-ray microscopic inspection apparatus according to claim 1, wherein an accelerating voltage applied to the electron gun is within the range of 10 to 20 kV, and the focused electron beam is impinged to the target for the X-ray generation composed of germanium or chromium so that a characteristic X-ray having a wavelength of 0.2 to 3 nm. 8. The X-ray microscopic inspection apparatus according to claim 1, further comprising an electron lens disposed between the magnetic superposition lens and the target so that the electron beam is focused by two stages through said magnetic superposition lens and said electron lens. |
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summary | ||
abstract | Embodiments herein disclose a shielding curtain that is configured to block electromagnetic radiation from passing through it. The shielding curtain may be a flap portion of a larger shielding curtain or a single, unitary body that includes a single mounting bead and a plurality of flaps. The shielding curtain is formed of a polymer material that has a uniformly dispersed particulate material. Electromagnetic radiation emitted by an inspection system is blocked by the uniformly dispersed particulate material. |
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claims | 1. A method of creating a topography at a surface of a specimen, the method comprising:providing desired surface height values for one or more locations at the surface of the specimen;providing,an energetic particle column comprising a source of energetic particles, the energetic particle column operatively arranged to form the energetic particles into a beam,a controller connected to the energetic particle column, the controller and the energetic particle column operatively arranged to direct the beam of energetic particles to the one or more locations and to provide doses of energetic particles to the one or more locations and,an interferometer integrated with the energetic particle column, the interferometer comprising a light source and a reference mirror, the interferometer connected to the controller, the interferometer operatively arranged with respect to the energetic particle column to illuminate an area at the surface of the specimen comprising at least a part of the one or more locations with a first portion of light from the light source and, to illuminate the reference mirror with a second portion of light from the light source;exposing to first doses of energetic particles, the one or more locations;measuring current surface height values at the one or more locations by interferometrically combining a reflected first portion of light from the illuminated area, with a reflected second portion of light from the reference mirror;comparing the desired surface height values to the current surface height values to determine a difference and, calculating second doses of energetic particles for the one or more locations, based upon the difference; and,exposing to second doses of energetic particles, the one or more locations. 2. The method of claim 1 wherein the energetic particles comprise one or more particles selected from the group consisting of ions, electrons, photons and accelerated neutrals. 3. The method of claim 1 wherein the steps of exposing to first doses and exposing to second doses, cause one or more actions selected from the group consisting of adding material to the surface of the specimen and, removing material from the surface of the specimen. 4. The method of claim 1 wherein the step of measuring current surface height values is performed simultaneously with one or more steps selected from the group consisting of exposing to first doses and, exposing to second doses. 5. The method of claim 1 wherein the step of measuring current surface height values is performed sequentially with one or more steps selected from the group consisting of exposing to first doses and, exposing to second doses. 6. The method of claim 5 comprising one or more steps selected from the group consisting of directing the beam of energetic particles away from the surface of the specimen and, turning off the source of energetic particles, prior to the step of measuring current surface height values. 7. The method of claim 1 wherein the surface of the specimen comprises one or more features selected from the group consisting of a planar surface, a multi-planar surface, a faceted surface, a curved surface, and a blind hole. 8. The method of claim 1 wherein the step of measuring current surface height values comprises translating one or more constituents selected from the group consisting of the specimen, a mirror disposed on an optical path and, the reference mirror. 9. The method of claim 1 wherein the reference mirror comprises a reference area at the surface of the specimen, the reference area comprising unexposed locations at the surface of the specimen, the unexposed locations not exposed to the beam of energetic particles. 10. The method of claim 1 wherein at least one step selected from the group consisting of exposing to first doses and, exposing to second doses, comprises exposing the one or more locations to the beam of energetic particles for one or more beam dwell times. 11. The method of claim 1 comprising the step of measuring surface height values at one or more unexposed locations at the surface of the specimen, the one or more unexposed locations not exposed to the beam of energetic particles. 12. The method of claim 1 wherein at least one step selected from the group consisting of exposing to first doses and, exposing to second doses, comprises rastering the beam of energetic particles over the surface of the specimen. 13. The method of claim 12 comprising the step of partitioning one or more doses selected from the group consisting of the first doses and, the second doses, over multiple raster scans. 14. A method of creating a topography at a surface of a specimen, the method comprising:providing,initial and desired surface height values for one or more locations at the surface of the specimen;providing,an energetic particle column comprising a source of energetic particles, the energetic particle column operatively arranged to form the energetic particles into a beam,a controller connected to the energetic particle column, the controller and the energetic particle column operatively arranged to direct the beam of energetic particles to the one or more locations and to provide doses of energetic particles to the one or more locations and,an interferometer integrated with the energetic particle column, the interferometer comprising a light source and a reference mirror, the interferometer connected to the controller, the interferometer operatively arranged with respect to the energetic particle column to illuminate an area comprising at least a part of the one or more locations with a first portion of light from the light source and, to illuminate the reference mirror with a second portion of light from the light source;comparing the initial surface height values to the desired surface height values to determine a first difference and calculating first doses of energetic particles for the one or more locations based upon the first difference;exposing to the first doses of energetic particles, the one or more locations;measuring current surface height values at the one or more locations by interferometrically combining a reflected first portion of light from the illuminated area, with a reflected second portion of light from the reference mirror;comparing the desired surface height values to the current surface height values to determine a second difference and, calculating second doses of energetic particles for the one or more locations based upon the second difference; and,exposing to the second doses of energetic particles, the one or more locations. 15. The method of claim 14 wherein the energetic particles comprise one or more particles selected from the group consisting of ions, electrons, photons and accelerated neutrals. 16. The method of claim 14 wherein the step of providing initial surface height values comprises interferometrically measuring the initial surface height values at the one or more locations. 17. The method of claim 14 wherein the step of providing initial surface height values comprises providing coordinates for the one or more locations and predetermined surface height values for the one or more locations. 18. The method of claim 14 wherein at least one step selected from the group consisting of exposing to first doses and, exposing to second doses, comprises rastering the beam of energetic particles over the surface of the specimen. 19. The method of claim 18 comprising the step of partitioning one or more doses selected from the group consisting of the first doses and, the second doses, over multiple raster scans. 20. An apparatus for creating a topography at a surface of a specimen, the apparatus comprising:an energetic particle column comprising a source of energetic particles, the energetic particle column operatively arranged to form the energetic particles into a beam;a controller connected to the energetic particle column, the controller and the energetic particle column operatively arranged to direct the beam of energetic particles to one or more locations at the surface of the specimen and to provide doses of energetic particles to the one or more locations;an interferometer integrated with the energetic particle column, the interferometer comprising a light source and a reference mirror, the interferometer connected to the controller, the interferometer operatively arranged with respect to the energetic particle column to illuminate an area comprising at least a part of the one or more locations with a first portion of light from the light source and, to illuminate the reference mirror with a second portion of light from the light source, the interferometer comprising at least one objective lens having a working distance equal to or greater than about 32 mm. 21. The apparatus of claim 20 wherein the at least one objective lens comprises a charge dissipative coating. 22. The apparatus of claim 20 wherein the light from the light source comprises a wavelength of from about 510 nm to about 550 nm. 23. An apparatus for creating a topography at a surface of a specimen, the apparatus comprising:an energetic particle column comprising a source of energetic particles, the energetic particle column operatively arranged to form the energetic particles into a beam;a controller connected to the energetic particle column, the controller and the energetic particle column operatively arranged to direct the beam of energetic particles to one or more locations at the surface of the specimen and to provide doses of energetic particles to the one or more locations;an interferometer integrated with the energetic particle column, the interferometer comprising a light source and a reference mirror, the interferometer connected to the controller, the interferometer operatively arranged with respect to the energetic particle column to illuminate an area comprising at least a part of the one or more locations with a first portion of light from the light source and, to illuminate the reference mirror with a second portion of light from the light source, the interferometer comprising an objective mirror having an aperture there through, the objective mirror located between the energetic particle column and the specimen, the objective mirror external of the energetic particle column and, the objective mirror operatively arranged to allow the beam of energetic particles to pass through the aperture and onto the one or more locations at the surface of the specimen. 24. The apparatus of claim 23 wherein the energetic particle column comprises an ion beam column including an ion source. |
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claims | 1. A fuel element for a nuclear reactor, comprising:a fuel rod bundle, at least one spacer formed with cells that are bounded by at least one web portion consisting of a first material, and a plurality of guide tubes each passing through a respective cell and being axially fixed to said cell and consisting of a second material having a different thermal expansion from the first material;an assembly for connecting a respective said guide tube and said spacer, said assembly including:first projections directly or indirectly fixed to said guide tube in a first axial position thereof and second projections directly or indirectly fixed to said guide tube in a second axial position thereof; andsaid first and second projections each engaging in a respective aperture formed in a respective said web portion, so as to form an axial support;wherein, on occasion of a higher degree of thermal expansion of said guide tube than said web portion, said projections having sides facing away from one another cooperate in each case with an abutment region of said apertures and, on occasion of a higher degree of thermal expansion of said web portion than said guide tube, said projections having sides facing one another cooperate in each case with an abutment region of said apertures; andwherein said abutment region of said apertures is formed with at least one oblique edge running obliquely with respect to a longitudinal direction of said spacer or of said guide tube and, together with a projection, forming a push-and-wedge connection, and said abutment regions corresponding to said first projections and said abutment regions corresponding to said second projections being disposed spaced apart from one another in an axial direction of said guide tube. 2. The fuel element according to claim 1, wherein a respective one of said projections has an oblique surface cooperating with said oblique edge. 3. The fuel element according to claim 2, wherein said oblique surface has an additional obliquity in a radial direction and engages behind said oblique edge in a circumferential direction, such that, during a relative movement between said web portion and said guide tube, said web portion is acted upon by a radially acting force component. 4. The fuel element according to claim 1, wherein said guide tube is surrounded, fixed axially, in a region of said spacer by an upper and a lower sleeve, said upper sleeve carrying said first projections and said lower sleeve carrying said second projections. 5. The fuel element according to claim 4, which comprises a plurality of arms extending axially away from an end face of one of said sleeves facing said spacer, wherein said first and second projections are disposed on the outsides of said arms. 6. The fuel element according to claim 5, wherein an inside of said arms bears against a circumferential surface of said guide tube. 7. The fuel element according to claim 5, wherein said spacer has rectangular cells each formed by four web portions, and four arms each oriented centrally with respect to a web portion are present on a sleeve, said web portions having a radially widened reception region extending axially away from an upper margin of said web portions and a radially widened reception region extending axially away from a lower margin of said web portions, and wherein a respective said arm assigned to one of said reception regions extends axially and radially and engages with said projection into an aperture. 8. The fuel element according to claim 5, wherein said spacer has rectangular cells each formed by four web portions, and four arms each oriented toward corner regions of said cells are present on a sleeve, and wherein an upper and a lower aperture are provided in the cell corner region of each web portion, and said projection of an arm engaging simultaneously into two upper and two lower apertures of a cell corner region. 9. The fuel element according to claim 1, wherein said first projections and said second projections are circumferentially aligned with one another on said guide tube. |
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abstract | Certain embodiments of the present invention provide an antiscatter grid including an electromagnetic coil array integrated with the antiscatter grid. The electromagnetic coil array is registered with the antiscatter grid. The electromagnetic coil array is configured to detect an electromagnetic field at the antiscatter grid. In an embodiment, the electromagnetic coil array may be positioned in front of the antiscatter grid. In an embodiment, the electromagnetic coil array may be positioned behind the antiscatter grid. In an embodiment, the electromagnetic coil array may be attached to the antiscatter grid. In an embodiment, a portion of the electromagnetic coil array may be transparent to x-rays. In an embodiment, the electromagnetic coil array may include one or more electromagnetic coils. In an embodiment, the electromagnetic coil array may be a printed circuit board (PCB) electromagnetic coil array. |
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053713630 | description | DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring now in detail to the drawings and, in particular, to FIG. 1, there is shown a radiation sensing device 10 having three carriages or crawlers 11a, 11b and 11c which are coupled together by rods 12a and 12b. Connected to the rear of carriage 11a is a cable 13a and connected to the front of carriage 11c is a cable 13b. A central axis extends through device 10 along cables 13a and 13b and rods 12a and 12b. Radiation sensors 14a, 15a and 16a are mounted on carriage 11a equiangularly about the carriage's central axis. Similarly, radiation sensors 14b, 15b and 16b are mounted equiangularly about carriage 11b and radiation sensors 14c, 15c and 16c are mounted equiangularly about carriage 11c. Looking from the rear of device 10 along cable 13a toward cable 13b, radiation sensor 15a is located at an initial position of 0.degree. . Radiation sensor 15b is rotated 40.degree. counter-clockwise from radiation sensor 15a and radiation sensor 15c is rotated another 40.degree. counter-clockwise from radiation sensor 15b. As was mentioned earlier, radiation sensors 14, 15 and 16 are each mounted equiangularly on their respective carriage 11. Thus, radiation sensor 16a is disposed 120.degree. counter-clockwise from radiation sensor 15a and counter-clockwise from radiation sensor 15c. Radiation sensor 16b is rotated 40.degree. counter-clockwise from sensor 16a and sensor 16c is further rotated 40.degree. counter-clockwise from sensor 16b. Sensors 14a, 14b, and 14c are each rotated an additional 40.degree. counter-clockwise so that sensor 14c is 40.degree. away from sensor 15a. Thus, the nine sensors are positioned at 40.degree. intervals around the central axis of device 10. The number of carriages and number of sensors is selected so that adjacent sensors overlap slightly to completely cover the entire inner circumference of the pipe. As will be understood by those skilled in the art, depending on the size of the pipe, fewer or additional carriages may be required with fewer or additional sensors to provide complete and slightly overlapping coverage. For example, the smallest diameter pipes require a device having two carriages with two sensors on each carriage. The sensors on each carriage face 180.degree. away from each other. The sensors on the first carriage are rotated 90.degree. from the sensors on the second carriage, so that the four sensors are positioned at 90.degree. intervals. For slightly larger pipes, the device is equipped with two carriages each having three sensors. The sensors on each carriage face 120.degree. away from each other, with the six sensors being positioned at 60.degree. intervals. Each radiation sensor is equipped with one or more wheels, designated generally as wheels 17. Since the sensors are mounted equiangularly about each carriage, the radial distance between wheels 17 and the inner surface of the pipe can be closely adjusted so that each carriage fits snugly within the pipe. In this manner, the sensors can be located very close to the inner pipe surface, for example, within one-half-inch, which is critical for obtaining accurate measurements. However, the sensors are kept a slight distance away from the pipe to avoid contacting the pipe and contaminating the sensors. Since the sensors must be placed close to the pipe's inner surface without rotating about the device's central axis, device 10 is specifically designed for one size of pipe. For example, one embodiment of device 10 is designed to fit snugly within a 4" schedule 40 pipe while an alternate embodiment would be designed to fit snugly within a 4" schedule 80 pipe. Wheels 17 are mounted on wheel axles, that are flexibly mounted to the radiation sensors, so that the wheel axles are capable of flexing to overcome weld build-up between sections of pipe or other obstacles within the pipe. Optionally, the entire sensor/wheel assembly is spring loaded on the carriage, for example, with a pin/coil spring assembly. In this manner, the sensor/wheel assemblies can be compressed together against the biasing force of the coil spring to place the device into a 4" diameter pipe. The nine sensors provide approximately 150% coverage inside the 4" diameter pipe. The device can be pulled into a 6" pipe with the sensor/wheel assemblies springing open to provide 100% coverage along the 6" pipe. Such an embodiment allows a single device to survey two diameters of pipe in a single pass. After device 10 is placed into the pipe, cables 13a and 13b are used to advance device 10 through the pipe in a push-pull arrangement. Rods 12a and 12b between carriages 11a, 11b and 11c, allow movement of the carriages with respect to each other, so that device 10 can negotiate curves. However, rods 12a and 12b prevent rotation of the carriages with respect to each other so that even around tight curves, the sensors maintain their phase relationship with each other. As device 10 moves through the pipe, sensor data is transmitted along wires, designated generally as wires 18. Each sensor is connected to its own separate wire. Wires 18 are strapped to cable 13a and extend along the length of cable 13a out of the pipe to monitoring and recording equipment. As can be seen in FIG. 2, wires 18 extend from the back of device 10 and are coupled to a radiation monitor 19 for monitoring and recording the sensor readings. Referring now to FIG. 3, there is shown an alternate embodiment of a radiation sensing device 20 including two sets of spring loaded wheel assemblies 21a and 21b. Each set of wheels includes three wheels mounted equiangularly about the central axle or axis 25 of device 20. Wheel assembly 21b is freely rotatable about axle 25 to help the device through turns. As device 20 is placed into the pipe, wheel support members 22 are forced radially into collars 23 against the biasing force of a coil spring, for example. The radially outward biasing force of the springs presses the wheels firmly against the pipe interior and prevent axial rotation of device 20 while allowing longitudinal movement along the pipe. Between wheels 21a and 21b there are three sets of sensors 24a and 24b, the third set not being visible in the drawing, rotatably mounted about central axle 25 of device 20. Each set of sensors is attached to a piston 26a, 26b and 26c, respectively, of which only 26a and 26b are visible in the drawing. Pistons 26 move sensors 24 radially between an extended position where sensors 24 are in close proximity or in contact with the interior pipe surface, and a retracted position where sensors 24 are spaced from the interior pipe surface retracted sufficiently for turning and rotating. Pistons 26 are extended and retracted hydraulically or pneumatically through control lines 27a and 27b. Since pistons 26 are intended to extend and retract synchronously, a single pair of hydraulic or pneumatic lines 27a and 27b is sufficient to drive all pistons. Hydraulic or pneumatic lines 27a and 27b extend rearwardly from device 20 out of the pipe. Sensors 24a, 24b and 24c are each located 120.degree. from each other. An indexer 30, fixed to wheel assembly 21a, rotates sensors 24 about axle 25. Indexer 30 is controlled by hydraulic lines or pneumatic 31a and 31b which extend out of the pipe. With sensors 24 in the retracted position, indexer 30 rotates the sensor 60.degree.0 or one-half the distance between adjacent sensors. Following rotation by indexer 30, pistons 26 are extended to place sensors 24 in contact with the interior pipe surface. After the reading is taken, pistons 26 retract and cables 13a and 13b advance device 20 slightly forward in a push-pull arrangement. Pistons 26 are extended to take a sensor reading and then retracted. Indexer 30 then rotates sensors 24 which are subsequently extended for reading and then retracted. In this manner, device 20 moves along the pipe interior while completely covering axially located circumferential strips. Device 20 is suited for pipes having a diameter of approximately 8", for example. The overall length of device 20 is sufficiently short so that device 20 can negotiate curves within 8" piping. As can be seen in FIG. 2, piston hydraulic lines 27 extend from device 20 to a hydraulic or pneumatic control 28a. Hydraulic or pneumatic lines 31 extend from indexer 30 to indexing control 32. Hydraulic or pneumatic control 28, indexing control 32 and radiation monitor 19 sequentially extend sensors 24 to obtain readings and retract sensors 24 for indexing and advancement of device 20 through the pipe. As can be seen in FIG. 4, sensors 24a, 24b and 24c are shown in solid line in the retracted position. Indexer 30 rotates sensors 24 into the positions shown in dotted line. As can be appreciated, the solid line positions and dotted line positions overlap to completely cover a circumferential strip of the pipe interior. In order to take a reading, pistons 26 extend to place sensors 24 directly against the interior pipe surface. The sensors are subsequently retracted by pistons 26 and either indexed or moved longitudinally through the pipe before being subsequently extended for the next reading. In between sensor readings, the pistons are alternately indexed and moved longitudinally along the pipe. FIG. 5 shows a further embodiment of the radiation sensing device 40 designed for even larger pipes. Device 40 includes a lead carriage 46 designed to assist device 40 in negotiating tight curves. Each embodiment is ideally provided with a lead carriage. Device 40 includes an indexer 41, which may be a double barreled indexer capable of rotating the larger sensors 42a, 42b, 42c and 42d. Each sensor is mounted on a piston 43a, 43b, 43c and 43d, respectively. The sensors and pistons are supported between sets of wheels 44a and 44b, which keep the sensors centered within the pipe. Device 40 is suitable for use in 10" to 12" diameter pipes. For larger pipes up to 24" the device may be equipped with eight sensors arranged equiangularly about the central axis of the device to form a hexagon. Since each of the eight sensors is disposed at an angle of 45.degree. with respect to the adjacent sensor, the indexing would only rotate the sensors 221/2.degree.. FIG. 6 shows indexer 30 coupled to hydraulic or pneumatic lines 31a and 31b. A gear 32 is concentrically mounted on the back end of axle 25. A rack 33 is correspondingly configured to engage the teeth of gear 32. Rack 33 is shown in its left most terminal position, but may be moved along direction 34 to a right most terminal position. By injecting pressurized fluid through hydraulic line 31a into cylinder 35a, a piston coupled to the left side of rack 33, is moved to the right in direction 34. This causes a counter-clockwise rotation of gear 32 which rotates sensors 24. The width of housing 36 as well as the selection of the pitch of the teeth on gear 32 and rack 33, determine through what angle gear 32 will rotate during movement of rack 33. Fluid can be alternately pumped through lines 31a and 31b to move rack 33 between its two terminal positions. Pressure is maintained in one of the lines during operation of the sensors to insure that the sensors are properly indexed. Rack 33 is equipped with adjusting screws to limit and/or adjust its travel to obtain precise rotation of gear 32 and axle 25. Optionally, a sensor may be mounted within housing 36 to positively determine when rack 33 has reached its terminal position. Once rack 33 is in the terminal position, a locking pin may also be actuated to hold rack 33 in its terminal position until the sensor reading is complete. Subsequently, the pistons can be retracted and the pin can be removed and rack 33 moved. Sensors 14, 15, 16, 24 and 42 may be any type of sensors to perform characterization and determine contamination level of a surface. The sensors may be used to detect alpha, beta or gamma radiation. For example, Geiger Muller pancake detectors may be used to detect beta particles while scintillators or sodium iodide scintillators may be used to detect gamma radiation. While several embodiments of the present invention have been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention as defined in the appended claims. |
summary | ||
description | This application is a continuation application claiming priority under 35 U.S.C. § 120 to U.S. patent application Ser. No. 15/799,111, filed Oct. 31, 2017 entitled APPARATUS FOR USE IN THE INSPECTION OF A TOP GRID GUIDE OF BOILING WATER REACTOR, the entire disclosure of which is hereby incorporated by reference herein. The disclosed and claimed concept relates generally to testing equipment and, more particularly, to an apparatus for the inspection of the top guide of a boiling water reactor. Numerous types of nuclear reactors are known to exist in the relevant art. One type of nuclear reactor is a Boiling Water Reactor (BWR) that boils water to form steam to generate electrical power. Such BWRs and other reactors must be periodically inspected in order to ensure that they maintain structural integrity, and such inspections typically are performed during refueling operations on the reactor. In a BWR, the fissile material typically is configured in fuel bundles that are supported in the BWR on a core plate at the lower end thereof and are supported at the top end thereof by a top guide. The top guide typically includes a plurality of beams that are arranged in a grid pattern to form a plurality of receptacles that are defined by and are situated adjacent corresponding segments of the grids, and typically four fuel bundles are received in each such receptacle. In the past, when the top guide 8 has been the subject of an inspection operation such as an ultrasonic testing operation or other such operation, most if not all of the fuel bundles typically had been required to be removed from the receptacles. In removing such fuel bundles from a receptacle, the typical practice has been to remove a pair of fuel bundles from diagonally opposed positions within the receptacle and to then position in their place in the receptacle a dummy pair of space holders that are of an elongated rectangular shape and that are approximately of the same size and shape as the pair of removed fuel bundles. Such reception of the dummy pair into the empty spaces vacated by the removed fuel bundles avoids the two remaining fuel bundles in receptacle from falling out of position. The space holders typically are connected together with a bail to enable the removal of the dummy pair after the two remaining fuel bundles are removed from the receptacle. Further regarding past inspection methodologies, once the fuel bundles and dummy pairs have been removed from the receptacles, the previous inspection methodology for the top guide have involved receiving a large inspection machine down onto the top guide that would occupy a large portion if not the entirety of the top guide. Such inspection devices were costly, difficult to maneuver, and interrupted other operations that might have been performed on the BWR. Improvements thus would be desirable. Accordingly, an improved apparatus for use in performing an inspection on the beams of the top guide of a BWR includes a housing, an alignment assembly, and an inspection system. The housing is receivable atop the upper edges of a first pair of beams adjacent a receptacle of the top guide. The reception of the housing atop the upper edges of the first pair of beams is facilitated by the alignment assembly which includes a plurality of legs that are simultaneously moved between a retracted position wherein one or more of the legs is disengaged from the beams within the receptacle and an extended position wherein all of the legs are engaged with the beams of the top guide within the receptacle. The inspection system includes a pair of inspection elements that are translated above a second pair of beams that are adjacent the receptacle and that do not have the housing received on the upper edges thereof. After the inspection of the second pair of the beams adjacent the receptacle, the alignment assembly can be moved to the retracted position. The apparatus can then be rotated ninety degrees and the alignment assembly can be returned to the extended position, which permits the housing to be received on the second pair of beams, i.e., whose segments adjacent the receptacle have just been inspected. The inspection system can then be operated to inspect the upper edges of the first pair of beams that are adjacent the receptacle. The apparatus is usable to perform such an inspection without any need to remove the fuel bundles or the dummy pair from a receptacle, although the apparatus is still usable to inspect the beam segments adjacent a receptacle even if the fuel has been removed from the receptacle. The apparatus requires very little space above the top guide, thus permitting operations to be performed on other parts of the BWR while the apparatus is inspecting various segments of the beams of a given receptacle. Accordingly, an aspect of the disclosed and claimed concept is to provide an apparatus that can perform an inspection operation, such as an ultrasonic (UT) inspection operation of other such operation, on the beams of a top guide of a BWR. Another aspect of the disclosed and claimed concept is to provide such an apparatus that can be received on the upper edges of the segments of the beams that are adjacent a receptacle in the top guide and that employs an alignment assembly to enable such reception of the apparatus on the upper edges of the beams. Another aspect of the disclosed and claimed concept is to provide such an apparatus that occupies relatively little space in the region above the top guide of the BWR. Another aspect of the disclosed and claimed concept is to provide such an inspection apparatus that can be easily deployed and operated to perform an inspection operation on the top guide of a BWR. These aspects and others are provided by an improved apparatus structured to be received into a boiling water reactor (BWR) and to be usable to inspect at least a portion of a top guide of the BWR, the top guide having a plurality of beams arranged in a grid pattern, the top guide further having a number of receptacles, a receptacle of the number of receptacles being defined by and situated adjacent a subset of beams of the plurality of beams that can be generally stated as including a first pair of beams of the plurality of beams and a second pair of beams of the plurality of beams, each beam of the plurality of beams having an upper edge. The apparatus can be generally stated as including a housing that can be generally stated as including a base and a pair of supports, the pair of supports being situated on the base, each support of the pair of supports having an engagement edge, the engagement edges being structured to be received atop the upper edges of one of the first pair of beams and the second pair of beams, an alignment assembly situated on the base and which can be generally stated as including a plurality of legs and an actuator, the actuator being operable to simultaneously move the plurality of legs between a retracted position wherein at least one of the legs of the plurality of legs is structured to be disengaged from the subset of beams and an extended position wherein all of the legs of the plurality of legs are structured to be engaged with the subset of beams, and an inspection system situated on the base and that can be generally stated as including at least a first inspection device that is structured to be situated in proximity to the upper edge of a beam of the other of the first pair of beams and the second pair of beams when the legs are in the extended position and the engagement edges are received atop the upper edges of the one of the first pair of beams and the second pair of beams. Other aspects of the disclosed and claimed concept are provided by an improved apparatus structured to be received into a boiling water reactor (BWR) and to be usable to inspect at least a portion of a top guide of the BWR, the top guide having a plurality of beams arranged in a grid pattern, the top guide further having a number of receptacles, a receptacle of the number of receptacles being defined by and situated adjacent a subset of beams of the plurality of beams that can be generally stated as including a first pair of beams of the plurality of beams and a second pair of beams of the plurality of beams, each beam of the plurality of beams having an upper edge. The apparatus can be generally stated as including a housing that can be generally stated as including a base and a pair of supports, the pair of supports being situated on the base, each support of the pair of supports having an engagement edge, the engagement edges being structured to be received atop the upper edges of one of the first pair of beams and the second pair of beams, an alignment assembly situated on the base and can be generally stated as including a plurality of legs that are structured to be engaged with the subset of beams, an inspection system situated on the base and that can be generally stated as including at least a first inspection device that is structured to be situated in proximity to the upper edge of a beam of the other of the first pair of beams and the second pair of beams when the engagement edges are received atop the upper edges of the one of the first pair of beams and the second pair of beams, and the inspection system further can be generally stated as including a drive apparatus that is situated on the base, the at least first inspection device being situated on the drive apparatus, the drive apparatus being operable to translate the at least first inspection device along an inspection path between a first location adjacent a first support of the pair of supports and a second location adjacent a second support of the pair of supports. Similar numerals refer to similar parts throughout the specification. An improved apparatus 4 in accordance with the disclosed and claimed concept is depicted in FIGS. 1-7 and is depicted in section in FIGS. 8-12. The apparatus 4 is an inspection apparatus that is usable in performing an inspection operation on a Boiling Water Reactor (BWR) 6 such as is depicted generally in FIG. 5. More particularly, the apparatus 4 is configured to perform an inspection operation such as an ultrasonic (UT) inspection operation on a top guide 8 (FIGS. 5 and 7) of the boiling water reactor 6. As can be understood from FIGS. 5 and 7, the top guide 8 includes a plurality of beams that are arranged in a grid pattern. The beams are indicated at the numerals 10A, 10B, 10C, 10D, 10E, and 10F, which may be collectively or individually referred to herein with the numeral 10. It is noted that the numeral 10 refers to other beams of the top guide 8 that are not otherwise specifically enumerated herein. The beams 10 each have an upper edge 12 upon which the apparatus 4 is receivable, as will be set forth in greater detail below. The top guide 8 further includes a plurality of receptacles, two of which are indicated at the numerals 14A and 14B, and which may be collectively or individually referred to herein with the numeral 14. It is noted that other receptacles are likewise indicated at the numeral 14 if they are expressly enumerated otherwise herein. As can be understood from FIGS. 6 and 7, the receptacle 14A is situated adjacent the beams 10A, 10B, 10C, and 10D and, more specifically, is defined by and is situated adjacent segments of those four beams. The beams 10A and 10B are parallel one another and can be said to form a first pair of beams, and the beams 10C and 10D are likewise parallel with one another and can likewise be said to form a second pair of beams. The receptacle 14A is thus defined and is situated adjacent the segments of the first and second pairs of beams 10A, 10B, 10C, and 10D. In a similar fashion, the receptacle 14B is defined by and is situated adjacent segments of the beams 10B, 10E, 10D, and 10F. The segments of the beams 10B and 10E form another first pair of beams, and the segments of the beams 10D and 10F form another second pair of beams which together define and are situated adjacent the receptacle 14B. It can further be seen that the receptacles 14A and 14B can be said to be situated diagonally adjacent one another within the grid that is formed by the beams 10. FIG. 6 depicts the receptacle 14A as having a pair of fuel bundles 13 situated therein and as further having a dummy pair 15 situated therein in place of a diagonally opposed pair of other fuel bundles that have already been removed. As noted elsewhere herein, the apparatus 4 is usable on any receptacle 14 whether or not some or all of the fuel bundles have been removed from the receptacle and regardless of whether any such fuel bundles may have been replaced with dummy fuel structures. This is highly advantageous since it does not require the removal of the fuel bundles and likewise does not require that the fuel bundles be removed and stored elsewhere in an appropriate location, thus saving time, effort, and money. The apparatus 4 can be broadly construed as including a housing 16, an alignment assembly 20 situated on the housing 16, and an inspection system 22 that is likewise situated on the housing. The housing 16 itself can be said to include a base 26 and a pair of supports that are indicated at the numerals 28A and 28B, and which may be collectively or individually referred to herein with the numeral 28. The supports 28 are situated on the base 26 and extend away from the base 26 in a first direction 30. The supports 28 each include an engagement edge 32 at an end thereof opposite the base 26. As will be set forth in greater detail below, the engagement edges 32 are receivable on the upper edges 12 of a pair of beams 10 and, more specifically, are receivable atop the upper edges 12 of a pair of segments of an pair of parallel and adjacent beams 10 that are situated adjacent and that define one of the receptacles 14. The alignment assembly 20 can be said to include four legs that are indicated at the numerals 34A, 34B, 34C, and 34D, and which may be collectively or individually referred to herein with the numeral 34. The legs are each of an approximately L-shaped configuration as can be seen in the accompanying drawings. The alignment assembly 30 further includes an actuator 38 (such as is depicted in FIGS. 8-12) that is situated on the base 26. More specifically, the actuator 38 can be said to include a stationary portion 40 that is affixed to the base 26 and a follower 44 that is movable with respect to the stationary portion 40 and which is connected with the legs 34, as will be set forth in greater detail below. The actuator 38 can be any of a wide variety of mechanical actuator devices and may be, for example, of a pneumatic configuration or a hydraulic or electric configuration or the like, without limitation. The alignment assembly 20 further includes a hub 46 such as is depicted generally in FIG. 2 and which is affixed to an underside of the base 26. The legs 34 are each pivotably connected with the hub 46. More particularly, the legs 34 each include a first portion 50 that is pivotably connected with the hub 46 and which can be said to extend in a direction generally away from the hub 46. The legs 34 each further include a second portion 52 that is connected with the first portion 50 and which extends in the first direction 30 generally away from the corresponding first portion 50. As can be understood in the accompanying drawings, the first portions 50 of the legs 34A and 34B can be said to extend away from the hub 46 and toward the supports 28. The second portions 52 of the legs 34A and 34B can be said to extend along and adjacent the supports 28. The first portions 50 of the legs 34C and 34D extend away from the hub 46 but are situated approximately midway between the supports 28, and the second portions 52 of the legs 34C and 34D likewise extend in the first direction 30 away from the first portions 50 but are situated approximately midway between the supports 28. The alignment system 20 further includes four links that are indicated at the numerals 56A, 56B, 56C, and 56D, and which extend between the legs 34A, 34B, 34C, and 34D, respectively, and a connector 48 that is affixed to the follower 44. The links 56A, 56B, 56C, and 56D may be collectively or individually referred to herein with the numeral 56. As a general matter, the links 56 are each pivotably connected at one end with the connector 48 and are pivotably connected at the opposite end with the corresponding leg 34. In the depicted exemplary embodiment, the links 56 each have a yoke-type connection with the corresponding leg 34. The inspection system 22 can be said to include a pair of inspection devices that are indicated at the numerals 58A and 58B, and which may be collectively or individually referred to herein with the numeral 58. The inspection system 22 further includes a tractor 62 is movably situated on the base 26 and upon which the inspection devices 58 are disposed. The inspection system 22 additionally includes a drive apparatus 64 that is disposed on the base 26 and which is connected with the tractor 62. The drive apparatus 64 is operable to move the tractor 62 between a first position at one end of the base 26 adjacent the support 28A, as is depicted generally in FIGS. 1-3, and a second position adjacent an opposite end of the base 26 adjacent the support 28B, as is depicted generally in FIG. 4. Such movement of the inspection system 22 between the first and second positions at the opposite ends of the base 26 causes the inspection device 58A to move along an inspection path 68A and to cause the inspection device 58B to move along an inspection path 68B. It is noted that FIG. 3 depicts the inspection device 58B slightly lower than the inspection device 58A, i.e., in slightly different vertical positions, in order to illustrate that the inspection device 58B is situated behind the inspection device 58A in FIG. 3, but in FIG. 4 the inspection devices 58 are depicted as being in the same vertical position. As can be seen in the accompanying drawings, the tractor 62 can be said to include a plate 70 and a number of wheels 74 that are mounted to the plate 70 and that are rollably engaged with inboard surfaces of the base 26. As employed herein, the expression “a number of” and variations thereof shall refer broadly to any non-zero quantity, including a quantity of one. The drive apparatus 64 can be said to include an elongated cylinder 76 that is mounted to the base 26 and which is operably connected with the plate 70. In the depicted exemplary embodiment, the cylinder 76 is a pneumatic cylinder having a magnetic element situated therein and which is caused to translate along the interior of the cylinder 76 due to varying pneumatic pressures in different regions of the cylinder 76. The magnet that is situated within the cylinder 76 is magnetically connected with a ferromagnetic structure that is situated on the plate 70. It is noted, however, that the cylinder 76 can be of any of a wide variety of configurations other than pneumatic, such as hydraulic or motor-operated, by way of example and without limitation. The inspection devices 58 can each be said to include a holder 80 and an inspection element 82. The holder 80 is situated on the plate 70 of the tractor 62. The inspection element 82 is situated on the holder 80 at a location at the end of the holder 80 opposite the plate 70 such that the inspection element 82 is spaced in the first direction 30 away from the base 26. More specifically, the holder 80 can be said to include a platform 86 that is affixed to the plate 70 and to further include an extension mechanism 88 that is situated on the platform 86. The holder 80 can further be said to include a mount that is situated on the extension mechanism 88 and which holds the inspection element 82. The extension mechanism 88 is operable to move the mount 92 and the inspection element 82 that is situated thereon between, for instance, a first position, such as is depicted generally in FIGS. 8-11 and a second position such as is depicted generally in FIG. 12, with the second position being relatively farther away from the base 26 and relatively closer to the upper edge 12 of one of the beams 10 than the first position. As a general matter, it is understood that the inspection elements 82, which may be ultrasonic (UT) inspection elements or other inspection elements, are sensitive devices. By providing the extension mechanism 88, the inspection elements 82 can be in a retracted position relatively closer to the base 26 in order to avoid collisions between the inspection elements 82 and, for instance, the fuel bundles 13 or the beams 10, by way of example, when the apparatus is being received atop a pair of the beams 10. Moreover, the inspection elements 82 need not be situated in the second position of FIG. 12 in order to perform an inspection operation on the beams 10. Rather, an inspection can be performed even if the inspection elements 82 are in the position depicted generally in FIGS. 8-11 as long as the inspection elements 82 are maintained at a predetermined proximity, i.e., at a fixed distance, with respect to the beam 10 that is being inspected by the inspection element 82 as the inspection element is moved through its inspection path. As can be understood from FIGS. 8-12, the alignment assembly 20 is movable between a retracted position, such as is depicted generally in FIGS. 8-9, and an extended position, such as is depicted generally in FIGS. 10-12. In the retracted position, the follower 44 and the connector 48 that is situated thereon are spaced relatively farther away from the stationary portion 44 than in the retracted position of FIGS. 10-12. Movement of the follower 44 and the connector 48 in the first direction 30, i.e., in the downward direction from the perspective of FIG. 8-12, from the extended position to the retracted position causes the links 56 to simultaneously pull the legs 34 in a generally inward direction such that the second portions 52 move generally toward one another and such that one or more of the legs 34 is disengaged from the segments of the beams 10 that are situated adjacent the receptacle 14A. However, when the follower 44 and the connector 48 are caused to move relatively closer to the stationary portion 44, i.e., in the upward direction from the perspective of FIG. 8-12, the legs 34 are simultaneously pivoted in a generally outward direction such that the second portions 52 move generally away from one another to cause the legs 34 to engage the segments of the beams 10 that are situated adjacent the receptacle 14A. For instance, and as can be understood from FIGS. 8 and 9, in the retracted position the leg 34A is spaced away from the beam 10C, the leg 34B is spaced away from the beam 10D, the leg 34C is spaced away from the beam 10B, and the leg 34D is spaced away from the beam 10A. When the actuator 38 is actuated to cause the follower 44 and the connector 48 attached thereto to move in the upward direction from the perspective of FIGS. 8-12 to be relatively closer to the stationary portion 40, however, the legs 34 are simultaneously pushed in a generally outward direction to cause the leg 34A to engage the beam 10C, to cause the leg 34B to engage the beam 10D, to cause the leg 34C to engage the beam 10B, and to cause the leg 34D to engage the beam 10A. Such simultaneous movement of the legs 34 between the retracted position of FIGS. 8 and 9 and the extended position of FIGS. 10-12 causes the housing 16 to self-align with the beams 10 of the receptacle 14, by way of example. For instance, if the apparatus 4 is relatively closer to the beam 10A than it is to the beam 10B, the simultaneous motion of the legs 34 toward the extended position will cause the leg 34D to engage the segment of the beam 10A within the receptacle 14A prior to the time at which the leg 34C engages the segment of the beam 10B within the receptacle 14A. Such engagement of the leg 34D with the beam 10A and such movement of the leg 34D toward the extended position while the leg 34C remains disengaged from the beam 10B will cause the apparatus 4 to be moved generally toward the beam 10B, i.e., generally in the rightward direction with respect to the top guide 8 from the perspective of FIG. 8, until the leg 34C engages the beam 10B. Such a movement of the apparatus 4 is an alignment movement which causes the apparatus 4 to be centered above the beams 10A and 10B. A similar alignment movement occurs simultaneously therewith if the apparatus 4 is relatively closer to one of the beams 10C and 10D than the other, which would be along the left-right direction in FIG. 9. The two simultaneous alignment movements cause the apparatus 4 to be centered with respect to the segments of the beams 10A, 10B, 10C, and 10D above the receptacle 14A, which also causes the supports 28A and 28B to become aligned with the segments of the beams 10C and 10D in the example presented herein. It is understood that FIGS. 8 and 9 depict the housing 16 as already being aligned with the beams 10A, 10B, 10C, and 10D in order to better illustrate the movement of the legs between the retracted and extended positions. It is understood, however, that in actual operation the apparatus 4 typically will be positioned such that the engagement edges 32 of the supports 28 are spaced a certain distance above the upper edges 12 of the beams 10 while the second portions 52 of the legs are received in the receptacle 14. The alignment assembly 20 will then be energized to cause the legs 34 to simultaneously move from the retracted position toward the extended position, which will cause the housing 16 to become aligned with the beams 10A, 10B, 10C, and 10D, at which point the apparatus 4 can be further moved in the downward direction from the perspective of FIGS. 8 and 9 to cause the engagement edges 32 to be received atop the upper edges 12 of the beams 10 that define and that are situated adjacent the receptacle 14B. In this regard, it can be seen in FIG. 6 that the legs 34 are movable within the narrow spaces between the fuel bundles 13 and/or the dummy pair 15, and it can be seen that the free ends of the second portions 52 are narrowed, i.e., compared with the first portions 50, in order to enable such movement between the fuel bundles 13. It can also be seen that the free ends of the supports 28 are narrowed, i.e., compared with the portions of the supports 28 that are directly connected with the base 26, to facilitate the ends of the supports 28 being received between fuel bundles 13 and/or dummy pairs 15 of adjacent receptacles 14. With the alignment assembly 20 in the extended position to enable the engagement edges 32 of the supports 28 to be received on the upper edges 12 of the beams 10C and 10D, the inspection system 22 is ready to inspect the segments of the beams 10A and 10B that are situated adjacent the receptacle 14A. Depending upon the needs of the given application, the inspection elements 82 can be retained in the position spaced a fixed distance above the upper edges 12 of the beams 10A and 10B, as is depicted in FIGS. 10 and 11. The drive apparatus 64 can then be energized to cause the tractor 62 to move the inspection devices 58 between the first location, such as is depicted generally in FIGS. 8-12, and the second location, such as is depicted generally in FIG. 4. Again, such movement between the first and second locations causes the inspection elements 82 to move through a pair of inspection paths 68A and 68B to cause the inspection elements 82 to perform an inspection operation on the segments of the beams 10 that are situated underneath the inspection elements 82. Once the inspection operation of the first pair of segments of the beams 10, which are the segments of the beams 10A and 10B in the example presented herein, the alignment assembly 20 can be moved from the extended position back to the retracted position, and the apparatus 4 can be lifted in the vertically upward direction, if necessary, and can be physically rotated above the top guide 8 through ninety degrees, after which the alignment assembly 20 can be energized to cause the legs 34 to simultaneously return to the extended position to thereby again align the apparatus 4 with the other pair of beams 10 of the receptacle 14. In such a situation, the engagement edges 32 would become aligned with and engaged with the upper edges 12 of the segments of the beams 10A and 10B that had just been inspected by the inspection system 22, and the inspection system 22 would be positioned to perform an inspection on the segments of the beams 10C and 10D, i.e., the beams on which the supports 28 had previously been situated. To perform the inspection, the drive apparatus could be energized to cause the inspection elements 82 to move from the second location that is depicted in FIG. 4 back to the first location that is depicted in FIGS. 1-3. Alternatively, the inspection elements 82 might need to be returned to the first position of FIGS. 1-3 before another inspection operation can be performed. Again, the inspection operation will be performed with the inspection elements 82 situated at the fixed distance from the upper edges 12 of the beams 10, such as is depicted generally in FIGS. 8-11, or the extension mechanism 88 can be operated to cause the inspection elements 82 to move to the second position relatively closer to the beams 10 or, if needed, physically in contact with the upper edges 12 of the beams 10, to perform the inspection as needed depending upon the requirements of the given application. After the inspection of the segments of the beams 10A, 10B, 10C, and 10D adjacent the receptacle 14A is complete, the apparatus 4 can be removed from the receptacle 14A and can be moved to an adjacent receptacle, such as the receptacle 14B. As noted elsewhere herein, the receptacles 14A and 14B are diagonally situated with respect to one another. In this regard, it can be understood that the four segments of the beams 10A, 10B, 10C, and 10D, which were inspected by the inspection system 22 in the exemplary set of operations noted above, are shared by four other receptacles 14 that are adjacent the receptacle 14A. For example, the segment of the beam 10A that was inspected in the aforementioned procedure is shared with the receptacle 14 that is immediately to the left in FIG. 7 of the receptacle 14A. Likewise, the segment of the beam 10C that was inspected in the aforementioned procedure is shared with the receptacle 14 that is situated directly above the receptacle 14A in FIG. 7. It thus can be understood that progressive inspections of receptacles can advantageously occur in a diagonal direction from the perspective of FIG. 7, and it can further be understood that only about one half of the receptacles need to have the apparatus 4 received therein since the segments of the beams 10 are shared by adjacent receptacles 14. It thus can be understood that the apparatus 4 can easily be used to inspect the beams 10 of the top guide 8. The apparatus 4 is relatively small and is provided with a lug 96 that is situated generally centrally on the base 26 and which can be caused to cooperate with poles and the like that can be manually held from locations vertically above the environment of the BWR 6. The apparatus 4 is lightweight and occupies only a relatively small region of the top guide 8, and it therefore does not impede other activities that can be caused to occur on other portions of the BWR at other locations on the top guide 8. It also can be understood that multiple instances of the apparatus 4 can be deployed to inspect different portions of the top guide 8. This is suggested from FIGS. 5 and 7. Furthermore, it can be seen that the inspection system 22 is movable along a sufficient distance that the edges of the beams 10 all the way to the circular frame 98 of the top guide 8 can be inspected, which is desirable. Other benefits will be apparent. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof. |
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claims | 1. A method for forming a coating on a work piece in a vacuum chamber of a charged particle beam system having a particle beam source and a work piece support, comprising:inserting a work piece into the vacuum chamber of the charged particle beam system and onto the work piece support;providing in the vacuum chamber a sputter material source, the sputter material source being positioned between the particle beam source and the work piece;directing a focused or shaped charged particle beam toward the sputter material source so that the charged particle beam impacts the surface of the sputter material source to sputter material from the sputter material source onto an area of the work piece to form a layer of material on the area of work piece, thereby avoiding damage to the work piece; anddirecting the charged particle beam toward the area of the work piece to process or form an image of the work piece. 2. The method of claim 1 in which directing a focused or shaped charged particle beam toward the sputter material source and directing the charged particle beam toward the area of work piece to process form an image of the work piece occur in the same vacuum chamber, without the work piece being removed from the vacuum chamber between the steps of directing the charged particle beam towards the sputter source and directing the charged particle toward the area of work piece, thereby allowing a protective or conductive layer to be applied and a work piece with the protective or conductive layer to be processed or imaged without removing the work piece from the vacuum chamber. 3. The method of claim 1 in which directing a focused or shaped charged particle beam toward an area of the work piece to process an area the work piece includes directing an electron beam toward the work piece to form an image of the area of the work piece using secondary or transmitted electrons. 4. The method of claim 1 in which directing a focused or shaped charged particle beam toward an area of the work piece to process an area of the work piece includes directing a focused ion beam toward the area of work piece to micromachine the work piece or to deposit material onto the work piece. 5. The method of claim 1 in which directing a focused or shaped charged particle beam toward the sputter material source so that the charged particle beam impacts the surface of the sputter material source includes directing a focused or shaped charged particle beam toward a gas injection system nozzle or material coated or material supported on a gas injection nozzle so that the charged particle beam impacts the surface of the gas injection system nozzle or material coated or material supported on a gas injection nozzle. 6. The method of claim 1 in which directing the charged particle beam toward the sputter material source includes directing the charged particle beam toward a source of material to form a protective or conductive layer on the work piece. 7. The method of claim 1 in which directing a focused or shaped charged particle beam toward the sputter material source includes directing the charged particle beam toward the sputter material source to sputter tungsten, chromium, titanium, copper, or aluminum material from the sputter material source onto the work piece. 8. The method of claim 1 in which directing a focused or shaped charged particle beam toward the sputter material source so that the charged particle beam impacts the surface of the sputter material source to sputter material from the sputter material source onto an area of the work piece to form a layer on the area of work piece includes directing a focused or shaped charged particle beam toward the sputter material source so that the charged particle beam impacts the surface of the sputter material source to sputter material from the sputter material source onto a portion of a wafer or other work piece smaller than the entire surface of the wafer or other work piece. 9. A charged particle system including a memory storing computer instructions to perform the steps of claim 1. 10. A method of charged particle beam processing, comprising:placing a work piece in the vacuum chamber of the charged particle beam system;sputtering a coating onto a work piece using a focused or shaped charged particle beam;then, without removing the work piece from the vacuum chamber, processing the work piece using the charged particle beam to etch material from the work piece, deposit material onto the work piece, or to form an image of the work piece, the sputter coating protecting features on the work piece surface during charged particle beam processing. 11. The method of claim 10 in which sputtering a coating onto a work piece includes sputtering a coating onto a portion of a wafer or other work piece smaller than the entire surface of the wafer or other work piece. 12. The method of claim 10 in which sputtering a coating onto a work piece includes directing an ion beam to a sputter material source to sputter material from the source onto the work piece. 13. The method of claim 10 in which processing the work piece using the charged particle beam includes directing the charged particle beam toward the work piece to alter the shape of the work piece. 14. The method of claim 13 which directing the charged particle beam toward the work piece to alter the shape of the work piece includes milling the work piece to expose a cross section. 15. The method of claim 13 in which directing the charged particle beam toward the work piece to alter the shape of the work piece includes milling the work piece to extract a sample from the work piece. 16. The method of claim 14 in further comprising directing an electron beam toward the exposed cross section to form an image of the cross section using scanning electron microscopy and in which the work piece remains in the same vacuum chamber for sputtering, for processing by the focused or shaped charged particle beam, and for directing the electron beam. 17. The method of claim 10 in which sputtering a coating onto a work piece includes using a plasma to sputter material from the source onto the work piece. 18. A charged particle system including a memory storing computer instructions to perform the step of claim 10. 19. A charged particle beam system, comprising:a charged particle source;charged particle beam optical components for forming the charged particles into a focused or shaped beam for processing a work piece positioned within a vacuum chamber;multiple sputter material sources for sputtering different materials, the multiple sputtering material sources positioned within a vacuum chamber;a manipulator for moving the sputter material sources into a first position between the charged particle beam source and the work piece in which the charged particle beam can be directed to the sputter material source to sputter material from the sputter material source onto the work piece to form a coating on the work piece without directing the charged particle beam toward the work piece and to a second position in which the sputter material source is not in the beam path to allow the charged particle beam can be directed to impact the work piece;a memory storing computer instructions to perform the steps of:directing the charged particle beam toward the sputter material source so that the charged particle beam impacts the surface of the sputter material source to sputter material from the sputter material source onto an area of the work piece to form a protective layer on the area of work piece, thereby avoiding damage to the work piece; anddirecting the charged particle beam toward the area of the work piece to process or form an image of the work piece after the protective layer has be formed. |
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abstract | The present invention involves a beam energy identification system, comprising an accelerated ion beam, wherein the accelerated ion beam is scanned in a fast scan axis within a beam scanner, wherein the beam scanner is utilized to deflect the accelerated ion beam into narrow faraday cups downstream of the scanner, wherein a difference in scanner voltage or current to position the beam into the Faraday cups is utilized to calculated the energy of ion beam. |
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abstract | According to the present invention, a novel slat collimator for use in nuclear medicine imaging is provided. The slat collimator comprises a first layer comprising a plurality of spaced apart elongated slats and a second layer comprising a plurality of spaced apart elongated slats. The slats of the second layer are positioned orthogonally with respect to the slats of the first layer. The slats are constructed of a radiation attenuation material and the spaces between the slats may be non-variable or variable. |
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summary | ||
claims | 1. A system, comprising:a particle beam column configured to generate a particle beam directed to a first processing location;a laser system configured to generate a laser beam directed to a second processing location located a distance from the first processing location;a stage comprising a base and an object mount to mount an object, the stage being configured to displace the object mount relative to the base in at least two independent directions;a first stage mount configured to hold the stage in a first position such that, when the stage is in the first position, the object is located in a region of the first processing location;a second stage mount configured to mount the stage in a second position such that, when the stage is in the second position, the object is located in a region of the second processing location; anda transport device configured to transport the stage between the first and second positions. 2. The system of claim 1, wherein at least one of the first and second stage mounts comprises a position sensor to detect a position of the stage mount. 3. The system according to claim 2, wherein the particle beam column is an electron beam column. 4. The system according to claim 2, wherein the particle beam column is an ion beam column. 5. The system according to claim 1, further comprising a vacuum chamber, wherein the first processing location, the second processing location, and a transport path of the stage between the first and second positions are located within the vacuum chamber. 6. The system according to claim 5, wherein the vacuum chamber includes a door separating a first vacuum space in which the first processing location is located from a second vacuum space in which the second processing location is located. 7. The system according to claim 6, wherein the transport device comprises a rod and a connector attached to the rod, the connector is configured to be attached to the stage, the transport device is configured to move the rod between first and second rod positions, the connector is located closer to the first processing location when the rod is in the first rod position than when rod is in the second rod position, and the rod extends through an opening of the door when the rod is in the first rod position. 8. The system of claim 7, wherein at least one of the first and second stage mounts comprises a position sensor to detect a position of the stage mount. 9. The system according to claim 7, wherein the particle beam column is an electron beam column. 10. The system according to claim 7, wherein the particle beam column is an ion beam column. 11. The system of claim 6, wherein at least one of the first and second stage mounts comprises a position sensor to detect a position of the stage mount. 12. The system according to claim 6, wherein the particle beam column is an electron beam column. 13. The system according to claim 6, wherein the particle beam column is an ion beam column. 14. The system of claim 5, wherein at least one of the first and second stage mounts comprises a position sensor to detect a position of the stage mount. 15. The system according to claim 5, wherein the particle beam column is an electron beam column. 16. The system according to claim 5, wherein the particle beam column is an ion beam column. 17. The system according to claim 1, wherein the particle beam column is an electron beam column. 18. The system according to claim 1, wherein the particle beam column is an ion beam column. 19. A method comprising:using the system of claim 1 to modify and/or inspect an object. 20. The method of claim 19, wherein the particle beam column is an ion beam column or an electron beam column. |
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042008646 | claims | 1. A process control installation for mechanical elements in which a determined number of physical characteristics are to be detected or measured, each by several independent probes, comprising: (a) a plurality of comparator circuits including: (b) a plurality of reproduction circuits connected to the output of a corresponding comparator circuit; (c) a plurality of majority decision circuits, each one associated with one of the physical characteristics and each connected to one of the outputs of all said reproduction circuits; (d) at least two pairs of identical functional logic circuit trains connected to the output of said majority decision circuits; (e) a plurality of functional OR logic groups each one connected to outputs from each of the corresponding logic circuit trains and influencing at least one mechanical process control element; and (f) each of said pair of identical logic circuit trains having corresponding outputs connected to functional AND logic circuits, the outputs of the functional AND logic circuits being connected to the inputs of said functional OR logic circuits. 2. An installation according to claim 1, including a third pair of trains of logic circuits whose corresponding outputs are connected to the functional AND logic circuit. 3. An installation according to claim 1, including a plurality of conformity surveillance circuits having two inputs connected to corresponding points in the identical logic circuit trains of a pair, said conformity surveillance circuits including means for activating signalling devices. 4. An installation according to claim 3, wherein all of said conformity surveillance circuits being associated with a pair of identical logic circuit trains and being connected to a general control device, signalling any disagreement between the different conformity surveillance circuits. 5. An installation according to claim 1 wherein said identical logic circuit trains of the same pair are fed by two sources of independent electric current, and the pairs of identical logic circuit trains being fed each one by two different sources chosen among three available sources and in that the AND logic functional circuit terminals of each pair include means for transmitting an alert by the absence of an electric signal. 6. An installation according to claim 1, wherein the two identical logic circuit trains of each pair are fed by the same source of electric current, as the pairs of idependent trains of logic circuits are fed each one by a different source chosen among three available sources and that the AND functional logic circuit terminals of each pair include means for transmitting an alert by the presence of an electric signal. 7. An installation according to claim 1, wherein all said logic circuits are for intrinsic security. |
abstract | A transport/storage cask for a radioactive material has an inner shell, an outer shell and a circular gamma ray shielding layer and a circular neutron shielding layer both of which are placed between the inner shell and the outer shell. The gamma ray shielding layer is formed by aligning a plurality of gamma ray shielding blocks composed of lead in a block shape in the circumferential direction. The entire gamma ray shielding block in the axial direction is covered with a copper tube having a higher elasticity limit than the gamma ray shielding block. In the above transport/storage cask, the gamma ray shielding layer composed of lead or a lead alloy is not easily deformed. |
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description | The present invention pertains to a method for separating at least one first chemical element E1 from at least one second chemical element E2 involving the use of a medium comprising a specific molten salt. In the foregoing and in the remainder hereof it is specified that by <<chemical element>> it is meant any chemical element listed in Mendeleev's periodic table of elements. This method finds particular application in the field relating to the reprocessing of spent nuclear fuel, in particular for the separation of actinide elements from fission products (e.g. lanthanides, transition elements such as molybdenum, zirconium, yttrium, noble metals such as ruthenium, rhodium). At the present time all schemes followed for the commercial reprocessing of irradiated fuel are based on the PUREX hydrometallurgical process (Plutonium Uranium Refining by Extraction). With this process the irradiated fuel is first dissolved in nitric acid. The resulting solution is then placed in contact with an organic solvent acting as extractant non-miscible with nitric acid, two phases being recovered on completion of this process: an organic phase comprising uranium and plutonium; and an aqueous phase comprising minor actinides (e.g. americium and curium) and the fission products, which is also called a <<PUREX raffinate>>. The organic phase comprising the uranium and plutonium undergoes an extraction step to isolate the uranium from the plutonium, these able to be reused to produce uranium and/or plutonium fuel. The PUREX process is currently used in large capacity commercial plants typically having a reprocessing rate in the order of 1000 t/an. It has benefited from numerous improvements making it a reliable, robust process producing little secondary waste. However the PUREX process has some disadvantages: it is often considered as potentially proliferative since, after extraction of the organic phase, it allows a flow of pure plutonium to be obtained; the organic solvent used is sensitive to irradiation and therefore fuels with high burn-up require long cooling times before reprocessing; finally, before being subjected to reprocessing, the fuel must be previously dissolved in nitric acid which raises a problem for refractory fuels non-soluble in nitric acid. Alternatively pyrochemical processes for the reprocessing of spent nuclear fuel using high temperature separating techniques in a molten salt medium were the subject of intensive research in the 70's, either for the reprocessing of spent fuel from conventional reactors or for in-line reprocessing of reactor fuel with molten salt. Molten salts are easily able to dissolve fuels, dedicated targets and refractory matrixes envisaged for the reactors of the future. They use reagents insensitive to irradiation and transparent to neutrons, allowing the reprocessing of fuels with high burn-up after a short cooling time and without constraints of criticality. Finally, they do not allow a flow of pure plutonium to be obtained directly and can therefore be considered less proliferative than the PUREX process. A molten salt medium containing generally alkaline chloride(s) (e.g. LiCl—KCl, NaCl—KCl—CsCl) has mostly been chosen as solvent compared with a molten salt medium containing fluoride(s) since it raises fewer technological problems for implementation, can be implemented at lower operating temperatures, and corrosion problems are easier to manage allowing the use of stainless steel. However a chloride molten salt medium raises problems of long-term confinement of the chloride waste it generates. A fluoride molten salt medium produces waste of fluoride type which unlike chlorides is directly compatible with the glass confinement matrix used for the reprocessing of spent fuel. Once solubilised in the molten salt medium the elements derived from spent fuel must be selectively separated (e.g. the actinides from the fission products), this selective separation possibly having recourse to two different routes (which does not exclude the combination thereof): either electrolysis of the molten salt medium under specific conditions to isolate the selected elements from other elements which will remain in the molten salt medium; or selective extraction from the molten salt medium, using a reducing liquid metal. The principle of pyrochemical reprocessing in a molten salt medium of fluoride(s) involving an extraction step with a liquid reducing metal is in substance based on two successive liquid/liquid extraction steps as illustrated in Mendes et al. (<<Actinides oxidative back-extraction from liquid aluminium in molten chloride media>>, Proceedings of Molten Salts Chemistry and Technology, MS-9, Trondheim, 2011). At the first step, reducing extraction of the actinides is carried out with a phase comprising liquid aluminium in contact with the molten fluoride salt containing the fuel dissolved in fluoride form. The aluminium acts both as reducing agent and as solvent for the actinides. The redox reaction can therefore be described by the following equation 1:AnF3(salt)+Al(metal)An(metal)+AlF3(salt) (1)An representing an actinide element. The choice of fluorides is prompted by the confinement capability of the salt on completion of the process, in particular the possible direct immobilisation of the salt in a glass matrix. At the second step, the actinides are back-extracted from the metal phase comprising the aluminium e.g. via oxidative back-extraction. To do so the metal phase comprising the aluminium is contacted with a chloride salt containing an oxidizing agent e.g. AlCl3, to back-extract the actinides in the saline phase in chloride form, this back-extraction possibly being represented by following equation (2):An(metal)+AlCl3(salt)AnCl3(salt)+Al(metal) (2)An representing an actinide element. The actinide chlorides thus formed can be converted to oxide(s) and again used as fuel. Therefore the processes for reprocessing spent fuel using a fluoride molten salt medium require that the elements forming the fuel must be previously converted to fluorides so that they can be added to the salt. This conversion is conducted (after mechanical and heat treatment of the fuel) at a hydrofluorination step of the fuel by means of chemical digestion with gaseous hydrofluoric acid (dry fluorination). This operation is undeniably one of the most difficult and burdensome steps of the process, since it requires the use of large quantities of toxic gas (HF), placed in contact with a highly active material. In the light of the foregoing, the authors of the present invention set out to develop a process for separating at least one chemical element from another chemical element, both coexisting in oxide form, involving the use of a molten salt medium containing fluoride(s) and not requiring a hydrofluorination step of the said oxides before the contacting of the said oxides with the said molten salt medium, this process being applicable to the reprocessing of spent fuel. The authors have therefore discovered that by selecting a suitable molten salt medium containing fluoride(s) it is possible to separate at least one chemical element from another chemical element initially existing in oxide form without it being necessary to carry out prior conversion of the said oxides to fluorides. The invention pertains to a process for separating at least one first chemical element E1 from at least one second chemical element E2 coexisting in the form of oxides in a mixture, comprising the following steps: a) a step to solubilise a powder of one or more oxides of the said at least one first chemical element E1 and a powder of one or more oxides of the said at least one second chemical element E2 in a medium comprising at least one molten salt of formula MF—AlF3, where M is an alkaline element, after which there is a resulting mixture comprising the said molten salt, a fluoride of said at least one first chemical element E1 and a fluoride of said at least one second chemical element E2; b) a step to contact the mixture resulting from step a) with a medium comprising a metal in liquid state, said metal being a reducing agent capable of predominantly reducing the said at least one first chemical element E1 relative to the said at least one second chemical element E2, after which there is a resulting two-phase medium comprising a first phase called metal phase comprising the said at least one first chemical element E1 in oxidation state 0, and a second phase called saline phase comprising the molten salt of above-mentioned formula MF—AlF3 and a fluoride of the said at least one second chemical element E2. The process of the invention therefore allows the separation of at least one first chemical element E1 from at least one second chemical element E2 initially coexisting in a mixture comprising one or more oxide forms of these elements, by acting: first on the capability of a specific molten salt (MF—AlF3) to solubilise powders of the said oxide(s) to form fluorides of the said elements; and second, on the choice of specific metal in the liquid state capable of predominantly reducing element E1 in fluoride form to reduce element E1 to its 0 state of oxidation relative to element E2 in fluoride form, the said element E1 thereby being in the metal state and concomitantly taken up in full or in part via chemical affinity in the metal phase comprising the reducing metal in the liquid state, E2 subsisting in full or in part in the saline phase in fluoride form. The element(s) E1 can be selected from the group formed by the actinides (e.g. uranium, plutonium and/or minor actinides e.g. curium, americium and neptunium), the transition elements (e.g. zirconium or platinum-group elements e.g. rhodium, ruthenium, palladium), whilst the element(s) E2 can be selected from the group not comprising any actinides, this group possibly comprising: lanthanides (e.g. neodymium, europium, cerium); transition elements other than those of E1 (e.g. molybdenum, ytterbium); alkaline or alkaline-earth elements (e.g. strontium); and/or pnictogenic elements (e.g. antimony). When E1 and E2 meet the above-mentioned specificities, the process of the invention can therefore come within the scope of the reprocessing of spent nuclear fuel, of transmutation targets used for nuclear physics experiments or of refractory matrixes intended to be included in the composition of nuclear reactors, elements E2 then able to be considered as fission products. In this configuration, the process can be qualified as a DOS process (Direct Oxide Solubilisation). Regarding step a), the molten salt is a salt of formula MF—AlF3, where M is an alkaline element. In particular, M is an element selected from among Li, Na, K and the mixtures thereof, and more particularly Li. In relation to the elements to be separated, persons skilled in the art will select a salt of formula MF—AlF3 having a suitable MF/AlF3 molar ratio to obtain efficient separating as a function of the desired objective. AlF3 can play a major role in the solubilisation mechanism of the oxides, the solubilising of the oxides conventionally being promoted by an increase in the AlF3 molar content of the salt. On the other hand, the efficacy of reducing extraction (corresponding to above-mentioned step b)) may also depend on the AlF3 content of the salt, this being promoted through the use of the least fluoroacid salt i.e. the salt having the least AlF3 content. There may therefore be an antagonistic effect between the efficacy of oxide solubilisation and the performance of reducing extraction which is directly related to the AlF3 molar content of the molten salt. For example, the AlF3 molar content of the molten salt may lie within a range of 10% to 40 mole %. More specifically, when one or more actinide elements are to be separated from other elements (such as lanthanides), the molar content of AlF3 may range from 15% to 25 mole %, preferably 25% to 35 mole %. Regarding step b), the metal in the liquid state is a metal selected for its reducing properties of element(s) E1 relative to element(s) E2 that it is desired to separate. An efficient metal, in particular for the separation of one or more actinide elements from other elements, is selected from among aluminium and the alloys thereof. In particular this metal may be in the form of an aluminium alloy or an element selected from among the metal elements meeting the following criteria: metal elements not having any reducing nature with respect to all the elements contained in the saline phase; metal elements producing alloys with aluminium which have a melt temperature compatible with the operating temperature of the process. One metal element advantageously meeting these specificities is copper. In this latter case, the copper included in the formation of the aluminium alloy does not contribute towards to reduction as such, but contributes towards making the metal phase heavier and thereby facilitates separation via settling between the metal phase and the saline phase. Step a), to optimise solubilisation of the oxides, can be implemented in an atmosphere having an oxygen partial pressure that is as low as possible. For this purpose step a) can be conducted in an inert atmosphere i.e. an atmosphere comprising an inert gas such as argon, nitrogen. From a practical viewpoint this may entail setting up a constant gas circulation system for the purpose of removing any oxygen which may be released by oxide solubilisation. To ensure closed circuit operation, this system could be equipped with at least one inert gas purification unit. Step a) can advantageously be conducted at sufficiently high temperature to facilitate solubilisation of the oxides in the molten salt, this temperature being directly dependent on the oxides concerned. For example when the process of the invention is applied to the separation of element(s) E1 of the actinide group from element(s) E2 of another group, the operating temperature may be set at a value ranging from 760 to 860° C., bearing in mind that it is preferable not to exceed 860° C. to prevent major evaporation of AlF3. Finally, step a) can be conducted under agitation, for example: via mechanical means e.g. a rotary paddle; via a counter-current system, in particular when the process is implemented continuously; and/or via a convective system linked to the convection movements of the molten salt when it is heated. In particular when step a) and step b) are implemented simultaneously, agitation will also concern the medium comprising the metal in the liquid state, which will allow: first, the prevented accumulation of fines at the interface of the mixture resulting from step a) and the medium comprising a metal in the liquid state of step b), which could lead to a drop in extraction kinetics; and second, the removal of oxide <<skin>> which may cover the surface of the medium comprising a metal in the liquid state. In addition, the constant renewal of the exchange surface between the mixture of step a) and the medium of step b) should improve the kinetics of extraction. In the process of the invention, provision can be made for a readjustment step of the molar composition of the molten salt. The quantity of AlF3 is subjected to two variations throughout the implementing of the process of the invention. First, the solubilising of the oxides at step a) leads to consumption of AlF3, hence depletion of AlF3 in the molten salt. Second, the implementing of step b) when the metal in the liquid state is aluminium or a mixture thereof leads to formation of AlF3 (hence enrichment of AlF3 in the molten salt). It may therefore be appropriate to determine a material balance between AlF3 consumption and production in order to carry out any necessary readjustment of the molar composition of the salt. Provision may be made in the invention, concomitantly with step a), for a step to determine the amount of alumina in the mixture of step a) (whose formation may be caused by solubilisation of the oxides in the molten salt at step a)) so that the content thereof does not exceed 3% by weight relative to the total weight of the mixture, since over and above this value the solubilisation of the oxides starts to decrease significantly. After this determination step, if the quantity of alumina is too high, a step can be provided to draw off some of the mixture of step a) (the portion drawn off possibly being conveyed towards a purification unit to remove the alumina) and to replace the drawn-off portion by a molten salt free of alumina. When the process is intended to separate elements initially contained in a product containing element(s) E1 and element(s) E2, which is not in the form of a mixture of oxide powders (or a powder that is too coarse) or even which is in non-oxide form (e.g. carbide form), the process before implementing step a) may comprise a step to prepare a mixture of powders intended for step a), this preparation step possibly comprising a step to convert this product to a mixture comprising a powder of one or more oxides of the said at least one first chemical element E1 and a powder of one or more oxides of said at least one second chemical element E2. This notably concerns the case when the process relates to the reprocessing of spent nuclear fuel, of transmutation targets or refractory nuclear matrixes, the latter conventionally being in the form of compact blocks and in some cases also in the form of carbide(s). More specifically, when reprocessing concerns spent nuclear fuel containing uranium oxide UO2, the above-mentioned preparation step may use two different routes: a route involving an operation for mechanical treatment of the spent fuel to form a powder of oxide(s) and a heat treatment operation by voloreduction to remove fission products (called first variant below); and a route involving a voloxidation operation (called second variant below), after which the uranium oxide UO2 is converted to uranium oxide U3O8. According to the first variant, the process comprises an operation to grind the fuel in order to obtain a sufficiently fine oxide powder e.g. having a mean particle diameter ranging from 50 to 100 μm. Throughout this operation all of part of the gaseous or volatile fission products (Kr, Xe, I, Br) are released and optionally conveyed towards a vitrifying unit. The powder obtained is subjected to heat treatment intended to remove volatile fission products, this heat treatment possibly consisting of voloreduction at a temperature ranging from 800° C. to 1500° C. in a controlled atmosphere (e.g. argon with 5% hydrogen). During this treatment the entirety of the caesium, rubidium and tellurium is volatilised as well as all or part of the elements Tc, Cd, As and Se. According to the second variant, the process comprises mechanical treatment and heat treatment in a single step, this operation possibly being voloxidation after which the uranium oxide UO2 is converted to uranium oxide U3O8. More specifically, this operation may consist of oxidation of the fuel conducted at high temperature e.g. a temperature ranging from 480° C. to 600° C., to convert UO2 to U3O8. Oxidation leads to fragmentation (by volume increase) of the fuel which is thus reduced to a fine powder. As previously, the gaseous and volatile fission products should be removed at this step and optionally conveyed towards a vitrifying unit. The conversion of the fuel to a fine powder should largely aid the dissolution kinetics of the oxides in the salt (via increased surface area). More specifically when reprocessing concerns spent nuclear products containing uranium carbide, the conversion step is advantageously implemented following the conditions of the second variant described above. In this case it can be envisaged initially to start treatment at 300° C. to convert the fuel to oxide, and secondly to raise the operating temperature to convert UO2 to U3O8, or directly to start oxidation at voloxidation temperature (the choice is dependent on oxidation performance). Finally, depending on needs, it could be envisaged to carry out heat treatment with successive voloxidation/voloreduction cycles to improve the removal efficacy of volatile fission products and micronization of the oxide powders resulting from the operation. Independently of the foregoing, step a) and step b) described above can be performed successively (called first embodiment below) or simultaneously (called second embodiment below). When the first above-mentioned embodiment is applied to the reprocessing of spent nuclear fuel, of transmutation targets or refractory nuclear matrixes, provision can be made after step a) and before step b) for a digestion step of the element(s) if present in the mixture resulting from step a) and selected from among platinum-group elements (such as Ru, Rh, Pd) and/or molybdenum (the latter being present when the fuel is subjected to a prior voloreduction step as mentioned above) or, if voloxidation/voloreduction cycles are performed, when the last cycle ends with a voloreduction step. For this purpose this digestion step may entail contacting the mixture resulting from step a) with a medium comprising a metal in the liquid state, the said metal being capable of selectively adsorbing the platinum-group elements and/or molybdenum in relation to elements E1 (e.g. actinides) and E2 contained in the molten salt, this metal possibly being zinc alone or a zinc alloy such as zinc alloyed with copper or zinc alloyed with nickel, after which on completion of this step the following are obtained: the mixture of step a), which is henceforth free of the said platinum-group element(s) and/or molybdenum; and a metal phase comprising the above-mentioned metal in the liquid state and the said platinum-group element( )s and/or molybdenum. It is to be understood that the validity of this step is a function of the capability of the oxides such as UO2, to solubilise in the salt in the absence of any reducing agent i.e. the dissolving efficacy of the oxides in a salt free of reducing metal phase. After the digestion step there follows a separation step of the said metal phase and the said mixture of step a) henceforth free of the said platinum-group element(s) and/or molybdenum, so that it is possible to carry out step b). The metal phase derived from the said separation step can be subjected to a processing step to recycle the zinc for example simply by vacuum evaporation, the platinum-group element(s) and/or molybdenum when the zinc is initially alloyed to copper and/or nickel, remaining in a mixture with the copper and/or nickel thereby forming waste which can be sent to a vitrifying unit. If this digestion step is not performed the platinum-group element(s) and/or molybdenum are then extracted with the actinides at step b). When the second embodiment is applied to the reprocessing of spent nuclear fuel, of transmutation targets or refractory nuclear matrices (in other words the oxide powder(s) are contacted both with the molten salt medium of step a) and with the medium comprising a metal in the liquid state of step b)) this makes it possible to combine the solubilising of the oxides in the molten salt medium with the reducing extraction of step b), offering the particular advantage due to immediate initiation of actinide extraction, of producing a shift in equilibrium aiding the solubilisation of the actinide oxides via <<pumping effect>>. This second embodiment does not allow the setting up of the digestion step such as defined in the preceding paragraph, this digesting role being passed onto the metal involved in step b). However this second embodiment in the context of reprocessing is more advantageous than the first embodiment in that it is easier to implement having fewer steps. As mentioned above, after step b) there subsists a first phase called metal phase comprising the said at least one first chemical element E1 in oxidation state 0 and a second phase called saline phase comprising the molten salt of formula MF—AlF3 and a fluoride of the said at least one second chemical element E2. For the reprocessing of spent nuclear fuel, of transmutation targets or refractory nuclear matrixes, the metal phase may comprise: as E1 elements: actinides, some transition element such as zirconium, platinum-group elements; whilst the saline phase may comprise as E2 elements: lanthanide elements; transition elements other than those of E1 (such as molybdenum, ytterbium); alkaline or alkaline-earth elements (such as strontium); and/or pnictogenic elements (such as antimony). The process of the invention, independently of its field of application, and after step b) may comprise a step c) to separate the metal phase from the saline phase. For the reprocessing of spent nuclear fuel mentioned above, the metal phase thus separated can be subjected to the following successive treatments: a back extraction step of the actinide(s) by contacting the metal phase with a molten chloride medium (e.g. LiCl or LiCl—CaCl2) in the presence of an oxidizing agent belonging to the chloride family (for example AlCl3) to convert the actinides in the metal state to actinide chloride(s), a step after which there subsists a metal phase free of actinide(s) and a saline phase (called chloride phase below); optionally a step to draw off a portion of the said metal phase, with injection of the same amount of <<clean>> metal into the aluminium phase; a step to covert the actinide chloride(s) to actinide oxide(s) for example via oxidation with O2− ions generating the precipitation of the said actinide oxide(s). This leaves a product in the form of actinide oxide(s) which can again be used as fuel. When the objective is the above-mentioned reprocessing, the saline phase on completion of the separation step c) can be subjected to the following successive treatment operations: a distilling step, to regenerate the medium comprising at least one molten salt of MX—AlF3 type; a vitrifying step of E2 elements removed from the saline phase after the distillation step. Other characteristics and advantages of the invention will become apparent from the additional description below. Evidently this additional description is given for illustration purposes only and is in no way limiting. The following particular embodiments relate to study campaigns conducted on the behaviour of oxides of strategic interest (more specifically the oxides PuO2, UO2, U3O8, Nd2O3, Eu2O3, CeO2, ZrO2, MoO3, Y2O3, SrO, Sb2O3, PdO, RuO2 and Rh2O3 in specific proportions) in media of LiF—AlF3 molten salt type having different molar compositions (different molar compositions for examples 1 to 3 explained below). The above-mentioned oxides in terms of concentration added to the medium of molten salt type meet the specificities given in the following Table. Concentration of the elementadded to medium of moltenType of oxidesalt type (in mg/g of salt)PuO2101.1UO233.3U3O833.3Nd2O35.2Eu2O34.5CeO25.2ZrO25.0MoO35.7Y2O34.7SrO4.2Sb2O34.1PdO5.0RuO25.8Rh2O33.2 The study campaigns were all conducted following the same protocol which comprised the following steps: a step for intimate mixing of the LiF—AlF3 salt (15 to 20 g depending on experiments) with one or more oxides in the above Table; a step to place the mixture resulting from the preceding step in a reaction crucible containing an ingot of Al—Cu alloy (78-22 mole %) of same weight as the LiF—AlF3 salt; a step to place the crucible in a controlled atmosphere under a constant stream of argon followed by a heating step to about 300° C. to dehydrate the whole; a step to heat the crucible to about 835° C. to obtain melting of the crucible content; a step to leave the molten mixture under agitation at constant speed for 4 hours; a step to take a sample of the two phases (saline phase and metal phase respectively) followed by return to ambient temperature; a step for hot dissolution of the samples in 1M Al(NO3)3, 3M HNO3 for the saline phases (100 mg salt dissolved in 10 mL solution), and in a hot solution of 3M HNO3 and 150 μL of concentrated HF for the metal phases (100 mg of metal dissolved in 10 mL of solution); a filtration step to retain the insolubles; an optional dilution step of the filtrate in 0.5 M HNO3. The concentration of the elements was determined in the two above-mentioned phases: via count and α spectrometry for (239Pu+240Pu); via liquid X fluorescence for uranium; and via ICP-AES elementary analysis for the other elements (namely Nd, Eu, Ce, Zr, Mo, Y, Sr, Sb, Pd, Ru and Rh). On completion of the above analyses a material balance was determined for each element (designated <<m>> below), and compared with the material initially added to the crucible. The percentage of non-solubilised oxide can be estimated rom the following equation:xminsoluble=100−(xmmet+xmsalt)where: xmmet is the percentage of element m contained in the metal phase; and xmsalt is the percentage of element m contained in the saline phase. The quantification of each element m in the saline phase and metal phase allows calculation of the distribution coefficient Dm, using the following equation: D m = Xm met Xm salt where: Xmmet is the molar fraction of the element m contained in the metal phase; and Xmsalt is the molar fraction of the element m contained in the saline phase. The calculation of the distribution coefficient Dm does not include the fraction of non-solubilised oxide. The values xmmet et Xmsalt can be calculated using the following equations:Xmmet=xmmet/(xmmet+xmsalt) and Xmsalt=xmsalt/(xmmet+xmsalt) A global distribution coefficient Em, integrating the fraction of element contained in oxide form after equilibrium (non-dissolved fraction) was evaluated for each element m by determining the ratio:Em=xmmet/(xmsalt+Xminsoluble) This distribution coefficient (although not determined on thermodynamic equilibrium) indicates the amount of element m present in the metal at the end of the experiment in relation to the initial amount added in oxide form to the crucible. It is considered that the implementing of the process of the invention is efficient for selective extraction of actinides, if the following conditions are combined: the actinides are largely in majority in the aluminium phase; and a minimum amount of other elements is contained in the aluminium; which, in other words, means that the value of the global distribution coefficient of the actinides (symbolised EAN) must be high (i.e. Log EAN>0 and ideally Log EAN>1) and that the value of the global distribution coefficient of the fission products (symbolised EFP) must be low (i.e. Log EFP<0 and ideally Log EFP<−1). This example illustrates a campaign of studies conducted on the behaviour of oxides of strategic interest such as defined above conforming to the above-mentioned operating mode in a specific molten salt medium of LiF—AlF3 type (containing 35 mole % of AlF3). This campaign included several tests: a first test with UO2 alone entailing the use of 15.7 g of LiF—AlF3; a second test with U3O8 alone entailing the use of 15.2 g of LiF—AlF3; a third test with a mixture comprising PuO2 and Nd2O3 entailing the use of 17 g of LiF—AlF3; a fourth test with a mixture comprising ZrO2, MoO3, RuO2, Rh2O3, PdO and Nd2O3 entailing the use of 20.1 g of LiF—AlF3; a fifth test with a mixture comprising SrO, Y2O3, Sb2O3, CeO2 and Eu2O3 entailing the use of 15.1 g of LiF—AlF3. For each of these tests the global distribution coefficient Em and the distribution coefficient Dm were determined, the methods of determination being explained below for the element(s) of the oxide(s) involved. The logarithmic values of these coefficients are grouped together in the Table below. ElementxmsaltxmmetxminsolubleLog DmLog EmPu4.5905.51.300.95U (derived4.197.90.01.381.38from UO2)U (derived3.393.63.11.451.16from U3O8)Nd (derived47.18.944.0−0.72−1.01from fourthtest)Eu921.66.5−1.76−1.80Ce80.112.37.6−0.81−0.85Zr28.211.560.3−0.39−0.89Mo50.610.838.6−0.67−0.91Y96.72.11.2−1.66−1.67Sr98.81.20.0−1.90−1.90Sb1.84.993.30.44−1.29Pd18.527.054.50.16−0.43Ru2.19.488.50.65−0.98Rh1.324.873.81.27−0.48 Several important points emerge from this Table. The solubilisation of the actinide oxides in LiF—AlF3 (35 mole % of AlF3) (namely PuO2, UO2 and U3O8) is total or near-total (>94.5%). As a result, the coefficients Dm and Em show similar values. After dissolution of the oxides and extraction equilibrium reached, nearly all the actinides are present in the metal phase which translates as logarithmic values of the distribution coefficients Dm and Em close to 1 or higher than 1. It is probable that the high extraction of the actinides by the aluminium leads to a shift in equilibrium further promoting solubilisation of the oxide (solubility saturation in the salt never being reached). The results obtained with UO2 and U3O8 show very similar behaviour both regarding the solubilisation of the oxides and the uranium extraction yield by the metal. This is an important result since it allows validation of the two choices of heat treatment upstream of the solubilisation/extraction step, namely: either recourse to conventional heat treatment (in H2 or Ar atmosphere, after grinding of the fuel) or heat treatment of the fuel via voloxidation process. The other elements studied all show a very low Log Em value (<0, even <−1 in most cases) which translates their reduced presence, after equilibrium, in the metal phase. Two causes could explain the Log Em values obtained for these elements: either low or very low solubility of the oxides in LiF—AlF3; or low extraction yield in the metal phase. The first of these two causes is fully illustrated for the platinum-group elements (Ru and Rh). They display positive Log Dm values meaning that these elements once solubilised in LiF—AlF3, are mostly extracted by the metal phase. As shown in the Table above, their content is very small in the metal phase due to the very low solubility of these elements in LiF—AlF3 (it is more or less zero if the reducing metal is not present). The second of these causes is fully illustrated for the lanthanide elements and for yttrium and strontium. These elements show very close Log Dm and Log Em values, demonstrating that their respective oxides are well solubilised in LiF—AlF3. These elements are scarcely extracted from the metal phase during reducing extraction. Finally, some elements (Nd, Zr, Mo and Pd) are penalised by the accumulation of these two causes, which translates as low solubility and low extraction yield, resulting in Log Em<0 values (even <−1 for some thereof). Example 1 shows 90% recovery of the plutonium initially placed in the crucible and near-quantitative recovery of uranium, all in a single step. It demonstrates that the initial form of the uranium oxide is compatible with the different envisaged heat treatments for the fuel. Example 1 is a perfect illustration of the feasibility of the separation of actinides/fission products within a DOS process. This example illustrates a campaign of studies conducted on the behaviour of oxides of strategic interest (more specifically PuO2, UO2, Nd2O3, ZrO2, MoO3, PdO, RuO2 and Rh2O3) conforming to the above-mentioned operating mode in a specific molten salt medium of LiF—AlF3 type (comprising 15 mole % AlF3). This campaign comprised several tests: a first test with UO2 alone entailing the use of 15.6 g of LiF—AlF3; a second test with a mixture comprising PuO2 and Nd2O3 entailing the use of 17 g of LiF—AlF3; a third test with a mixture comprising ZrO2, MoO3, RuO2, Rh2O3, PdO and Nd2O3, entailing the use of 21 g of LiF—AlF3. The global distribution coefficient Em and distribution coefficient Dm were determined, the methods of determination being explained below for the element(s) of the oxide(s) concerned. The logarithmic values of these coefficients are grouped together in the Table below. ElementxmsaltxmmetxminsolubleLog DmLog EmPu270281.540.37U (derived3.787.78.61.370.85from UO2)Nd (derived33.928.237.9−0.08−0.40from thirdtest)Zr17.58.873.7−0.30−1.02Mo35.56.657.9−0.73−1.15Pd19.814.066.2−0.15−0.79Ru2.24.793.10.32−1.31Rh5.424.270.40.65−0.49 From this Table the following important points emerge. As previously, extensive solubilisation of the actinide oxides was observed. As in Example 1, the distribution coefficients DAn and EAn obtained after the experiments show values (Log EAn>0) fully compatible with the implementing of the process of the invention to separate actinides/fission products for the reprocessing of spent fuel. The other elements studied all show a very low Log Em value (<0) translating their slight presence, after equilibrium, in the metal phase. As in the preceding example this can be accounted for by the low solubility of their respective oxides in LiF—AlF3, or by a low extraction yield in the metal phase. This example illustrates a campaign of studies conducted on the behaviour of oxides of strategic interest (more specifically PuO2, Nd2O3, ZrO2, MoO3, PdO, RuO2 and Rh2O3) conforming to the above-mentioned operating mode in a specific molten salt medium of LiF—AlF3 type (comprising 25 mole % of AlF3). This campaign comprised several tests: a first test with a mixture comprising PuO2 and Nd2O3 entailing the use of 17 g of LiF—AlF3; a second test with a mixture comprising ZrO2, MoO3, RuO2, Rh2O3, PdO and Nd2O3 entailing the use of 15.7 g of LiF—AlF3. The global distribution coefficient Em and distribution coefficient Dm were determined, the determination methods being explained below, for the element(s) of the oxide(s) involved. The logarithmic values of these coefficients are grouped together in the Table below. ElementxmsaltxmmetxminsolubleLog DmLog EmPu2.2943.81.631.19Nd (derived44.919.535.6−0.36−0.62from secondtest)Zr23.610.066.4−0.37−0.96Mo50.19.240.8−0.74−0.99Pd27.612.160.3−0.36−0.86Ru1.46.991.60.68−1.13Rh1.020.578.51.31−0.59 Several important points emerge from this Table. As previously, extensive solubilisation of plutonium oxide was observed. As in the preceding examples, the distribution coefficients DAn and EAn obtained after the experiments show values (Log EAn>0 or ˜1) that are fully compatible with the implementing of the process of invention to separate actinides/fission products for the reprocessing of spent fuel. The other elements studied all show a very low Log Em value (<0, even <−1 in most cases) translating their slight presence, after equilibrium, in the metal phase. As in the preceding example, this can be accounted for by the low solubility of their respective oxides in LiF—AlF3, or by a low extraction yield in the metal phase. It follows from these examples that the campaigns of experiments allowed results to be obtained in terms of recovery of actinides (by the metal phase) that are fully satisfactory. The separation factors between the actinides and the other elements show that the process of the invention can be fully applied to different molar compositions of the salt LiF—AlF3. As previously indicated, the following conditions must advantageously be met: a high global distribution coefficient EAn, i.e. Log EAn>0 (ideally, Log EAn>1) for the actinides and low global distribution coefficient EFP (FP designating the fission products) i.e. Log EFP<0 (ideally, Log EFP<−1) for all the other elements. The above examples allowed successful fulfilling of these conditions using LiF—AlF3 salts having a composition varying between 15 and 35 mole % of AlF3. The salt of composition LiF—AlF3 (comprising 35 mole % AlF3), preferred to the others for facilitated solubilisation of the oxides, is well suited. The yields Em obtained after experimental validation show that it would be possible to recover more than 99% of the actinides when setting up two stages of extraction. After extraction, the separation factors between actinides and fission products are sufficient to envisage efficient fuel reprocessing. The addition of a washing stage before oxidative back-extraction should further increase the fission product decontamination rates of the actinides. The integration of the process of the invention in a scheme for the reprocessing of nuclear fuel of oxide or carbide type via reducing extraction in molten fluoride medium (LiF—AlF3) leads to a very good actinide recovery rate (typically more than 99% with fewer than three extraction stages) and allows high selectivity between actinides and fission products. In the developed process, the actinides contained in the irradiated fuel (U, Np, Pu, Am and Cm) remain grouped within one same flow which imparts good proliferation resistance to the process and meets the objectives of fourth generation reactors to reduce the noxiousness of waste with long lifetime. This process scheme can be applied to oxide fuels but also to carbide fuels (through application of suitable heat treatment). The field of application of this process can be extended to the reprocessing of all fuels (such as nitrides) or irradiated targets provided it is possible for them to be converted to an oxide at the head-end of the process thereby providing the process with large flexibility. |
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description | This application is a continuation of pending U.S. patent application Ser. No. 15/613,961, filed on Jun. 5, 2017, the content of which is incorporated herein by reference in its entirety. This application also relates to U.S. patent application Ser. No. 15/147,565, filed on May 5, 2016, the content of which is incorporated herein by reference in its entirety. The present disclosure generally relates to design and making method of a neutron generating target which can be used in boron neutron capture therapy. Neutron sources have many potential applications, including medical treatments, isotope production, explosive/fissile materials detection, assaying of precious metal ores, imaging, and others. A particular area of interest is boron neutron capture therapy (BNCT), which is a cancer treatment technique in which boron is preferentially concentrated in a patient's malignant tumor and a neutron beam is aimed through the patient at the boron-containing tumor. When the boron atoms capture a neutron, particles are produced having sufficient energy to cause severe damage to the tissue in which it is present. The effect is highly localized, and, as a result, this technique can be used as a highly selective cancer treatment method, effecting only specifically targeted cells. Many activities employing neutron sources are presently carried out at nuclear research reactors where neutrons are plentiful. However, many practical issues such as safety, nuclear materials handling, and the approach of end-of life and decommissioning of many research reactors make this approach challenging. Accelerator-based neutron sources can be used as a relatively low-cost, compact alternative. For example, a small, relatively inexpensive linear accelerator can be used to accelerate ions, such as protons, which can then be focused on a target capable of generating neutrons. The present disclosure relates to a method for making a neutron generating target. The method can include modifying a surface of a target substrate to form one or more surface features. The method can also include disposing a neutron source layer on the surface of the target substrate. In some embodiments, the method can include a material removal process or a material addition process. The material removal process can include abrasive blasting, etching, or polishing. The material addition process can include vacuum deposition, plating, or printing. In some embodiments, the target substrate can include at least one of copper, aluminum, titanium, molybdenum, and stainless steel. The neutron source layer can include at least one of lithium, beryllium, and carbon. In some embodiments, the neutron source layer can be pressed on the surface of the target substrate. In some embodiments, the neutron source layer can be deposited on the surface of the target substrate by evaporation. In some embodiments, the method can include heating the neutron source layer and the target substrate to an elevated temperature for a duration of time for form a bond between the neutron source layer and the target substrate. In some embodiments, the elevated temperature can be between about 100 degrees Celsius and about 500 degrees Celsius. In some embodiments, the duration of time can be between about 0.1 hours and 10 hours. In some embodiments, the method can also include modifying a top surface of the neutron source layer to form one or more surface features. The present disclosure also relates to a neutron generating target. The target can include a target substrate having an uneven surface. The uneven surface can include one or more surface features. The target can also include a neutron source layer disposed on the surface of the target substrate and bonded to the target substrate. In some embodiments, the one or more surface features can be recessed into the target substrate. The one or more surface features can have a depth of between about 1 micron and about 50 microns. In some embodiments, the one or more surface features can protrude from the target substrate. The one or more surface features can have a height of between about 1 micron and about 50 microns. In some embodiments, the one or more surface features can include a plurality of surface features with an average pitch of between about 1 micron and about 50 microns. In some embodiments, the target substrate can include at least one of copper, aluminum, titanium, molybdenum, and stainless steel. The neutron source layer can include at least one of lithium, beryllium, and carbon. In some embodiments, the neutron source layer can have a thickness of between about 10 microns and about 500 microns. The present disclosure relates to design and manufacture method of a neutron generating target which can be used in boron neutron capture therapy (BNCT). BNCT is a targeted radiation therapy for cancer treatment during which a patient is infused with a boron rich solution such as fructose-BPA. The boron is then selectively absorbed by the cancer cells, e.g., at a tumor site. Neutrons, for example, generated by a lithium neutron source, interact with the boron by the nuclear reaction: 10B+nth→[11B]*→α+7Li+2.31 MeV. By irradiating the patient's tumor site with a flux of epithermal neutrons, which thermalize near the tumor site, the cancer cells are killed by the alpha particles and lithium ions. The alpha particles and lithium ions released have very short ranges, for example about 5-9 microns, and thus are similar in size to a cancer cell. BNCT treatment requires a high flux of epithermal neutrons, typically between 1 eV and 10 keV. Fluxes required for clinical treatments are on the order of 1×109 n/cm2/s. Historically, BNCT treatments have been performed at nuclear research reactor facilities, however accelerator-based neutron sources are preferred for widespread implementation of the treatment in hospital environments. To produce the appropriate level of neutron flux using an accelerator, several nuclear reactions have been proposed. One of the most promising reactions is the 7Li(p,n)→7Be reaction. This reaction has a high neutron yield and produces neutrons of modest energy, both conditions being desirable for many applications. The neutron flux produced by this reaction is desirable for BNCT, for example because the flux can be easily moderated to epithermal neutrons without many high energy neutrons. To accomplish this reaction with an accelerator-based neutron source, a target bearing a source material (e.g., lithium) is presented to a proton beam generated by the proton accelerator. Neutrons are emitted from the source material and may be moderated and collimated by a beam shaping assembly into the desired neutron “beam” for treatment. The proton beam size can be of comparable size or smaller size than the neutron beam at the exit of the beam shaping assembly. For example, the proton beam size can be between about 20 mm and about 150 mm. There are two general approaches to the lithium P,N reaction for BNCT: “near threshold,” where the proton beam energy is about 1.9 MeV, and “above threshold,” where the proton beam energy is about 2.5 MeV. The “near threshold” approach has the advantage that the neutron energy distribution from the target is close to the epithermal energy distribution for treatment, thus only minimal moderation can be used. The “above threshold” approach produces a higher energy distribution of neutrons, and therefore can use more moderation, but takes advantage of a large peak in the reaction cross section at about 2.3 MeV resulting in a much higher initial yield of neutrons. Embodiments of the present disclosure overcome the neutron generation system issues described above using a direct-cooled, modularized rotating target architecture approach. For example, in some embodiments, a rotatable structure such as a disk or a drum includes a plurality of segmented target “petals” (also referred to herein as “segments”) attached to a central hub (also referred to herein as a “rotary fixture”), where each petal is directly cooled via its own dedicated micro-channels. The plurality of target petals, collectively, may be said to constitute a target. Each petal can include a substrate and a solid neutron source layer disposed on a surface of the substrate. An exemplary system includes 16 petals on a planar rotatable structure, each petal occupying 22.5 degrees of a circumference of the rotatable structure, with the rotatable structure having an outer diameter (OD) of about 1 meter, and a semi-continuous strip of lithium deposited on the petals 0.14 meters in the radial direction centered on a 0.84 meter diameter. FIG. 1A is a block diagram of an apparatus suitable for use in BNCT, in accordance with some embodiments of the present disclosure. As shown in FIG. 1A, a rotatable structure 102 includes a plurality of target petals or segments 104A-104D, and each segment of the plurality of segments 104A-104D has a corresponding substrate 106A-106D coupled to a corresponding neutron source layer 108A-108D. The neutron source layer(s) 108A-108D can include solid lithium. One or more of the substrates 106A-106D includes a corresponding coolant channel (110A-110D), such as a micro-channel, for actively cooling the associated substrate and/or neutron source layer (e.g., to maintain the neutron source layer 108A-108D in solid form). The segments 104A-104D are optionally coupled to a rotary fixture 112 having an inlet 112A and an outlet 112B for conducting a coolant fluid. The segments 104A-104D can be coupled to the rotary fixture 112 via one or more of: screws, bolts, quick-disconnect fittings, clamps, and/or the like. The coolant fluid can include one or more of: water (e.g., deionized water, which provides higher heat capacity and thermal conductivity than oils, and lower corrosive activity as compared with city water), glycol, a glycol/water mixture, heat transfer oils (e.g., to avoid possible water/lithium interaction during a failure), “Galinstan” (a commercial liquid gallium/indium/tin mixture), liquid nitrogen, and/or other coolants. The rotary fixture 112 can be configured to couple to an external spindle assembly and/or drive motor via a coupling such as a rotary water seal and/or a rotary vacuum seal. When the segments 104A-104D are connected to the rotary fixture 112, the coolant channels 110A-110D may be in sealed fluid communication with the inlet 112A and outlet 112B of the rotary fixture 112. FIG. 1A also depicts a proton beam generator 113 and a proton beam 113A. Each segment of the segments 104A-104D can have a shape that is one of: a portion of an annulus, a pie-shape or “sector” (defined as the plane figure enclosed by two radii of a circle or ellipse and the arc between them), a truncated sector (i.e., a portion of a sector), a square, and a rectangle. The neutron source layer 108A-108D can include lithium, beryllium, or another suitable neutron source in solid form and at a thickness that is sufficient to produce the desired neutron flux, for example for lithium at least about 10 μm, or at least about 90 μm (e.g., about 400 μm), or between about 10 μm and about 200 μm, or between about 90 μm and about 150 μm. The neutron source layer 108A-108D can be adhered to the substrates 106A-106D of the segments 104A-104D via a thermal bond. For example, in some embodiments, one or more of the substrates 106A-106D include copper, and a lithium neutron source layer 108A-108D is bonded to the one or more copper substrates 106A-106D via a pressure and temperature method. As lithium is a reactive metal, it can form an amalgam with the copper. When properly bonded, a low thermal resistance between the copper and the lithium is formed. At such thicknesses of the neutron source layer(s) 108A-108D, the protons are deposited in the lithium during use, as opposed to the copper that underlies the lithium. In some cases, there is no drop in neutron yield up to doses of 1×1019 ions/cm2, and it can be expected that doses of 1×1020 ions/cm2 and beyond are possible. The neutron source layer 108A-108D can change during irradiation, for example becoming more brittle and/or different in color, however as long as it remains intact and produces the same or nearly the same neutron yield, it is suitable for use. Alternatively or in addition, the neutron source layer 108A-108D can be evaporated onto the substrates 106A-106D in a thin layer, for example of about 100 microns. A very thin, blister-resistant middle layer can be included in such designs as well (as has done in the stationary targets, described above). The base petal or substrate can be made of copper or aluminum. Even materials such as stainless steel, titanium, and molybdenum are possible since the distributed heat power is so much lower than in the stationary case. FIG. 1B is a diagram of a plan view of a disk-shaped rotatable structure, in accordance with some embodiments. As shown, the rotatable structure 102 has a central hub portion “H” with a plurality of segments 104 attached thereto and emanating therefrom. The segments 104 each include a corresponding neutron source layer with a major surface that can be, for example, substantially normal to an axis of rotation of the rotatable structure 102. The axis of rotation may be defined as an axis that passes through the center of the hub “H” and is substantially normal thereto. FIG. 1C is a diagram showing a cross-sectional view of the rotatable structure of FIG. 1B, corresponding to line A-A′ of FIG. 1B. As shown in FIG. 1C, a neutron source layer 108 is disposed on a substrate 106 with an embedded coolant channel 110. FIG. 1D is a diagram of the rotatable structure of FIG. 1B during use as part of boron neutron capture therapy (BNCT), in accordance with some embodiments. As shown, the rotatable structure 102 is rotating about its axis of rotation, and a proton beam generator 113 emits a proton beam 113 toward the rotatable structure 102 such that the proton beam 113A contacts a surface of the rotatable structure 102, e.g., at a neutron source layer of a segment 104. The proton beam 113A can be stationary (e.g., at a predetermined position) or rastering over a predetermined region of the rotatable structure 102, where the predetermined region may be fixed or may change over time. The proton beam 113A can form an angle with the contacting surface of the rotatable structure 102, for example of about 90.degree. Since the rotatable structure 102 is rotating, segments 104 of the rotatable structure 102 can be sequentially contacted by the proton beam 113A. As a result of the interaction of the proton beam 113A with the neutron source layer of segment(s) 104, a neutron beam 113B is generated and directed (e.g., via a collimator or other beam-shaping structure) towards a treatment area of a patient P. One major failure mode of the neutron generating target in the art is hydrogen impregnation within the target. The hydrogen deposited in the target may damage the target materials, cause blistering of the target, limit the lifetime of the target, and necessitate servicing of the target prior to failure. Blistering is material damage (e.g., delamination, exfoliation, bubble, etc.) in the target due to internal hydrogen pressure exceeding the strength of the target material. When the proton beam hits the target, the depth where the protons stop depends on the energy of the proton and the neutron source material. For example, in a target with a thick lithium neutron source layer (about 400 μm) bonded to a copper substrate, a 2.6 MeV proton beam may be stopped in the lithium layer. Instead, if a thinner lithium neutron source layer (between about 100 μm and about 200 μm) is used, the proton beam may be stopped in the copper layer. When the hydrogen concentration reached a point where internal pressure exceeds the strength of the material, a blistering might happen. The blistering can happen in the lithium layer or in the copper layer. The present disclosure provides a target design which significantly reduces target blistering failure. In the target used in the art, the surface of the target substrate is substantially flat and neutron source materials are bonded on the top surface of the target substrate. Protons with similar energies will stop in the target at a same depth. As a result, hydrogen concentration may become high at this depth and lead to target damage. The present disclosure shows a different target design where the surface of the target substrate is modified. In some embodiment, the target substrate can be copper, aluminum, titanium, stainless steel, or other metals. The goal of the surface modification is to increase the roughness of the target substrate. In some embodiments, the target substrate can be modified with a material removal process. For example, the substrate can be modified with abrasive blasting. Different blasting media can be used in accordance with roughness requirements and substrate materials. In some embodiments, the blasting media can be sand, silicon dioxide, metal shot, etc. The substrate can also be modified by etching or polishing. In some embodiments, the target substrate can also be modified with a material addition process. For example, a thin layer of material can be added to the target substrate surface by vacuum deposition, plating, printing, or other techniques. In some embodiments, the material to be added can be copper, aluminum, titanium, stainless steel, or other metals. The roughness or features created on the substrate surface can be periodic or non-periodic. In some embodiments, the average pitch of the features can be between about 1 μm and about 10 μm. The depth/height of the features can be between about 5 μm and about 20 μm. FIGS. 2A-2B shows cross-section views of targets according to some embodiments of the present disclosure. As shown in FIG. 2A, target substrate 202 can be modified to have periodic surface features with a fixed pitch. As shown in FIG. 2B, target substrate 205 can be modified to have non-periodic surface features. The average pitch of the surface features can be between 1 μm and 10 μm. The height of the surface features can be between 5 μm and 20 μm. After the surface is modified, the target substrate can be cleaned thoroughly to remove any debris. Then a neutron source layer can be disposed on the target substrate. The neutron source layer can be lithium, beryllium, graphite (carbon), or other materials, depending on different neutron producing reactions. The neutron source layer can be disposed onto the target substrate surface by pressing, evaporation, or other methods, to make sure the neutron source layer has a close contact with the target substrate surface. For example, lithium can be pressed onto the substrate. In some embodiments, the thickness of the lithium layer can be about 100 μm to about 200 μm for a neutron producing reaction with a proton energy of between about 2 MeV and about 3 MeV. Next the assembly of target substrate and neutron source layer can be heated to an elevated temperature. The heating can be performed with a hot-plate, a thermal chamber, or other equipment which can provide heating power. To maintain the purity of the neutron source layer and prevent any unwanted reactions, the heating can be performed in an inert environment, such as in an argon filled glove-box. The heating temperature and time duration can differ depending on the substrate material and the neutron source material. For example, for a target with lithium on a copper substrate, heating for 4 hours at 200° C. can form a good thermal and mechanical bond between the lithium and the copper. The lithium can form an amalgam with the copper, resulting in a low thermal resistance. In some embodiments, the heating procedure may not be necessary. For example, if the lithium neutron source layer is deposited on the target substrate by evaporation, the heating can be skipped because there can be a good bond between the lithium and the target substrate formed during the deposition. Referring to FIG. 2A, a neutron source layer 203 can be disposed on the surface of target substrate 202. The whole target assembly 201 can be heated to an elevated temperature to form a good bond between the neutron source layer 203 and target substrate 202. As shown in FIG. 2B, Then a neutron source layer 206 can be disposed on the surface of target substrate 205 and the whole target assembly 204 can be heated to an elevated temperature to form a good bond between the neutron source layer 206 and target substrate 205. An advantage of the target design with substrate surface modification described herein over the existing design in the art is that protons will not stop in the target uniformly because of the roughness of the substrate. As a result, the hydrogen will not be concentrated at a same depth. This design can reduce blistering and material exfoliation in the target. FIG. 3 shows a flow chart describing a neutron generating target making method 300 according to some embodiments of the present disclosure. The method 300 starts with step 301 where a surface of a target substrate can be modified, either by a material removal process or a material addition process. In some embodiments, the material removal process can include abrasive blasting, etching, or polishing. In some embodiments, the material addition process can include vacuum deposition, plating, or printing. In step 302, a neutron source layer can be disposed on the surface of the target substrate by pressing, evaporation, or other techniques. Then in step 303, the whole assembly of the neutron source layer and the target substrate can be heated to an elevated temperature for a duration of time to form a good thermal and mechanical bond. FIG. 4 shows a flow chart describing a neutron generating target making method 400 according to some embodiments of the present disclosure. The method 400 starts with step 401 where a neutron source layer can be disposed on a target substrate. In some embodiments, the neutron source layer can be pressed onto the target substrate. In some embodiments, the neutron source layer can be deposited on the target substrate by evaporation. In step 402, the neutron source layer can be bonded to the target substrate. For example, if the neutron source layer is pressed onto the target substrate, the neutron source layer and the target substrate can be heated to an elevated temperature for a duration of time to form a bond. If the neutron source layer is deposited by evaporation, the heating procedure can be skipped. In step 403, a top surface of the neutron source layer can be modified to form one or more surface features. In some embodiment, the modification can be a material removal process which can include abrasive blasting, etching, or polishing. In some embodiment, the modification can be a material addition process which can include vacuum deposition, plating, or printing. The method 400 can create roughness on the neutron source layer surface, which can lead to variations in stopping depth of the protons so that the hydrogen concentration can be reduced. As a result, target blistering can be prevented. The method and system described above for the 7Li(p,n)→7Be can be extended to other neutron producing reactions with other neutron producing materials. In addition to the “near threshold” approach using a 1.9 MeV proton beam and the “above threshold” approach using a 2.5 MeV proton beam on lithium, other reactions that have been proposed for BNCT include: 9Be(p,n) using a 4 MeV proton beam, 9Be(d,n) using a 1.5 MeV deuterium beam, and 13C(d,n) using a 1.5 MeV deuterium beam. To utilize these reactions, a solid sheet of beryllium could be thermally bonded to the petals in place of the lithium and bombarded with either 4 MeV protons or 1.5 MeV deuterons. In addition, the lithium could be replaced with thin sheets of graphite or carbon to produce neutrons using the 13C(d,n) reaction. A general schematic of an embodiment of the present BNCT system and method is shown in FIG. 5. For example, referring to FIG. 5, which is not drawn to scale, BNCT system 500 includes neutron generating system 550 and patient positioning and treatment system 580. Neutron generating system 550 includes proton beam generator 510 and neutron source target 520, which is provided on a rotatable structure (not shown). Any of the rotatable structures of the present disclosure and described above can be used. Proton beam generator 510 can be provided in a variety of different positions relative to neutron source target 520, depending upon, for example, the size and design of the facility in which they are placed. Various known bending or focusing magnets can be used to direct the generated proton beam to the target. Proton beam 590, produced by proton beam generator 510, passes through beam transport system 515, which may include, for example, various types of focusing magnets, and reacts with neutron source target 520, thereby generating neutrons, which are generally produced in multiple directions around the source depending on their energy—higher energy neutrons moving forward from the target and lower energy neutrons scattering perpendicular to or back from the source. To generate neutron beam 570 having the desired energy and direction for BNCT treatment, neutron generating system 550 further includes reflector 526, beam moderator 591, and beam collimator 592. Any neutron beam reflector, moderator, or beam collimator/delimiter known in the art can be used, and each can be positioned around the target as desired in order to capture neutrons having the desired energy range. For example, reflector 526 can be positioned around the sides and behind the target, as shown in FIG. 5, and can comprise any material known in the art that is relatively non-absorbent to neutrons, such as high atomic number material (including lead, bismuth, or alumina), or carbonaceous materials (including graphite). In this way, low energy back-scattered neutrons are reflected back into the system, thereby protecting or shielding surrounding components as well as patient 599. The forward-directed, relatively higher energy neutrons can be captured by moderator 591 (also comprising materials that are relatively non-absorbent to neutrons), in order to reduce their energy to a desired epithermal range. In this way, for example, neutrons having an initial energy of approximately 500 keV can be reduced to a final energy of from about 1 eV to about 10 keV, which is a range desirable for BNCT treatment. Suitable moderator materials are known in the art and include, for example, D2O, MgF, LiF, AlF3, Al, Teflon, and mixtures thereof. Finally, as shown, beam collimator 592 can be positioned after moderator 591 to produce and focus the desired neutron beam onto target 598 in patient 599. As shown in FIG. 5, BNCT system 500 further includes patient positioning and treatment system 580 which includes equipment and controls for delivering the neutron beam to the patient. For example, a boron delivery system and protocol are used in which the chosen boron-containing treating agent is delivered to patient 599 at the prescribed dose in order to produce target 598. Control systems are used to accurately position the target to coincide with expected neutron beam path, and such control systems would be known to one skilled in the art. Additional equipment and components can also be used as needed and would also be well known in the field. As used herein, the terms “about” and “approximately” generally mean plus or minus 10% of the value stated, e.g., a value of about 250 would include 225 to 275, and about 1,000 would include 900 to 1,100. The foregoing description of preferred embodiments of the present disclosure has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Modifications and variations are possible in light of the above teachings, or may be acquired from practice of the invention. The embodiments presented herein were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. |
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description | The present invention relates to an optical path design of scanning-probe type atomic force microscope, especially to a beam tracking system for scanning-probe type atomic force microscope. The present invention is especially useful in reducing the false deflection of the probe of the scanning-probe type atomic force microscope when the probe is moving at high speed in the three-dimensional space, whereby correct measurement results may be obtained. The atomic force microscope (AFM) may be used to produce three-dimensional images of a surface with the resolution of the nanometer level. There are two types of AFM. One is the “scanning-sample type” atomic force microscope and the other is the “scanning-probe type” atomic force microscope. In a scanning-sample type AFM, the sample is moved when it is scanned and the probe is kept stationary. Problems in moving or positioning the sample arise when the sample is large or heavy. In addition, temperature control, such as heating or cooling, of the sample may also affect the performance of the piezoelectric scanner of the AFM, which is provided beneath the sample. For samples in liquid cell, such as biomolecules, it is difficult to obtain correct images by using a scanning-sample type AFM, since samples move during the scan. The scanning-probe type, or stationary sample type, AFM in which the probe scans the sample while the sample is kept stationary, is designed to solve the above problems. In order to achieve such a goal, one approach is to let the whole optical detecting system move along with the probe. However, the optical detecting module, including the laser diode (LD), the photo sensing device (PSD), the alignment mechanism and the frame structure that supports the optical configuration, is often too bulky and too massive to move with the scanner. Moving the whole module to scan the sample is proved not ideal. Many experts have tried to solve this problem by reducing the weight of the optical detecting module. Another approach is the “tracking lens method” presented by Jung et al. See Jung et al., “Novel stationary-sample atomic force microscope with beam-tracking lens”, Electron. Lett., Vol. 29, No. 3, pp. 264-266, 1993. Under such a design, however, the tracking error will limit the resolution of the microscope. For an ideal optical tracking system, when the laser beam emitted by he stationary laser diode perfectly tracks the moving probe, signals picked up by the photo sensing device shall reflect only the deflection of the probe, not the scanning motion. If the PSD signal varies during the scanning while deflection of the probe is null, false deflection or optical tracking error is generated. In order to reduce the false deflection, a one-dimensional beam tacking method that makes the PSD move synchronously with the probe was introduced by Kwon et al. See Kwon e al., “Atomic force microscope with improved scan accuracy, scan speed and optical vision”, Rev Sci. Instrum., Vol. 74, No. 10, pp. 4378-4383, 2003. Another solution was proposed by Hansma et al. to position a convex lens before the PSD to reduce false deflections. See Nansma et al., “A new, optical-level based atomic force microscope”, J. Appl. Pys., Vol 76, No. 2, pp. 796-799, 1994. In these systems, however, the tracking function applies to false deflections in the horizontal directions but not in the vertical direction. A three-dimensional beam tracking system provided with tracking mirrors was later proposed by Nakano to compensate the false deflection. See K. Nakano, “Three-dimensional beam trucking for optical lever detection in atomic force microscope”, Rev. Sci. Instrum., Vol. 71, No, pp. 137-141, 2000. In that system, the working distance from LD to the reflection point, of the probe changes during the scanning. However, the intensity signal of the beam varies if some portions of the beam fall-off the probe due to defocusing of the laser spot on the probe, whereby the shape of the reflected beam will be warped on the PSD and the PSD position signal will he adversely affected. In addition, a special type of twist-probe was proposed, wherein a large mirror portion is provided to reduce the fall-off. Under such a design, its installation will readily limit one dimension of the image size. Another disadvantage of the twist-probe rests in that its distance to the PSD varies during the scanning, whereby constant relation between the probe deformation and the PSD signal can not be guaranteed. The objective of this invention is to provide a novel light path system for scanning-probe type atomic force microscope. Another objective of his invention is to provide a new beam tracking system for the scanning-probe type atomic force microscope. Another objective of this invention is to provide a light path system for scanning-probe type atomic force microscope wherein both horizontal and vertical tracking errors may be reduced. According to this invention, a novel scanning-probe type atomic force microscope is presented. The probe of the scanning-probe type atomic force microscope moves in both the horizontal direction and the vertical direction during the scanning, while the sample is kept stationary. In order to reduce the false deflection brought to the probe due to the scanning motion, two approaches are adopted in this invention. The first is to have the focused laser spot tracking an invariant point on the probe's cantilever, which moves three-dimensionally during the scanning. The second approach is to have the laser beam, which is reflected from the moving cantilever, hitting an invariant point of the PSD, when the sample is distanced from the probe and induces no deflection. Although it is not intended to limit the scope of this invention by any theory, the present invention discloses a novel beam tracking system for a scanning-probe type atomic force microscope that satisfies the above requirements. The beam tracking system for the scanning-probe type atomic force microscope of this invention therefore comprises: a base to carry a sample to be scanned; a cantilevered probe to scan said sample in order to obtain topographic information representing a surface of said sample; a laser source to generate laser beam; an optical module to align and introduce said laser beam to said probe; a feedback module, comprising a photo sensing device, to receive said laser beam reflected from said probe and to introduce said reflected laser beam to said photo sensing device; a probe driving device to drive said probe to scan three-dimensionally; an approach mechanism to drive said probe and to adjust the relative position of said probe and said sample; and an information processing module to pick up signals contained in said reflected laser beam as sensed by said photo sensing device and to convert said information into topographic information representing the surface of said sample; wherein said optical module comprises an objective lens to focus said laser beam; said probe is located approximately at the focal point of said objective lens; and said laser source, said optical module, said feedback module and said probe are driven by said approach mechanism to move in synchronization. According to the present invention, tracking errors in the horizontal and the vertical directions may be limited to from <0.3 nm over a 4 μm scanning distance to <12 μm over a 100 μm scanning distance. These and other objectives and advantages of this invention may be clearly understood from the detailed description by referring to the following drawings. FIG. 1 shows the systematic diagram of the beam tracking system for the scanning-probe type atomic force microscope of this invention. As shown in this figure, the beam tracking system for the scanning-probe type atomic force microscope of this invention comprises a base unit, a laser source unit, an optical unit and a feedback unit. In these units, laser source 1 is used to generate a laser beam. The laser beam generated by laser source 1 is collimated by a collimation lens 2, polarized by a polarizer 3 and enters a beam splitter 4. The laser beam is then partially reflected and reaches the objective lens 6 through the ¼λ wave plate 5. The probe 19 is positioned at approximately the focal point of the objective lens 6, where the objective lens 6 focuses the laser beam at the probe 19. The laser beam reflected from the probe 19 contains deflection information of the probe 19. It reaches mirrors 12, 13 and 14 via objective lens 6, ¼ wave plate 5 and beam splitter 4, and is introduced to a photo sensing device 15 through a correction lens 7. The photo sensing device 15 picks up information contained in the laser beam and outputs to data processing module (not shown). The data processing module processes the information and generates results of scanning. The data processing module comprises a false deflection calculation means to calculate false deflection data of the probe 19 so that results of scanning may be calibrated using such false deflection data. The photo sensing device 15 in general comprises 4 photo diodes to sense magnitude of incident light beam. Magnitude values of incident light beam as sensed by respective photo diodes may be used to determine the relative position of the probe and the hitting spot of the incident laser beam in the three-dimensional space. Results of such determination function as reference information representing deflection of the probe 19. In this figure, 21 represents a base, on which a sample 20 to be scanned is positioned. The sample 20 has a topographic surface. During the scanning deflection of the probe 19 is caused by the force field between the tip of the probe and the surface of the sample. The deflection is sensed and fed into the data processing module to generate a feedback loop forcing the probe moving up and down in order to keep the tip-sample gap constant. With the deflection information, the samples topographic profile may be established. In a scanning-probe AFM, such as the present invention, the vertical scanning of the probe 19 is driven by the vertical tube scanner 8 and the piezoelectric oscillator 17, and the horizontal scanning is driven by the horizontal scanner 9. An approach mechanism 16 is provided on base 21. On the approach mechanism 16 fixed part 10 of the horizontal scanner 9 is supported to control the movement of the horizontal scanner 9 with the help of flexure guiding devices 11, 11. In addition, the probe 19 is supported by lens holder 18, so that the relative position of probe 19 and objective lens 6 is maintained constant. An approach mechanism 16 is provided on base 21. On the approach mechanism 16 fixed part 10 of the horizontal scanner 9 is supported to control the movement of the horizontal scanner 9 with the help of flexure guiding devices 11, 11. In addition, the probe 19 is supported by lens holder 18, so that the relative position of probe 19 and objective lens 6 is maintained constant. Vertical Tracking As shown in FIG. 1, the probe 19 is installed at approximately focus of the objective lens 6. The relative position of probe 19 and objective lens 6 is thus kept constant by lens holder 18. The lens holder 18 may be prepared with a metal material, such as aluminum, and is attached to the bottom of the vertical scanner 8. The collimated laser beam is emitted by the laser diode 1, adjusted by a four-axis laser mount 22, and kept parallel to the up-and-down motion of the vertical scanner 8. The path of the laser beam may be adjusted by adjusting the angles of mirrors 12, 13 and/or 14. The laser beam reflected from the probe 19 is collimated by the objective lens 6 and adjusted by mirrors 12, 13 and 14 to aim at the center of the photo sensing device 15. The relative position of the optical module and the probe remains invariant during the Z-direction movement. In other words, the tracking function in the vertical direction is exactly achieved by the objective lens 6, which moves in synchronization with the optical module. As shown in the figure, the incident laser beam is focused by the objective lens 6 to its focal point and the probe 19 is positioned at the focal point of the objective lens 6. Since the objective lens 6 moves in synchronization with the probe 19, the focused laser beam may track an invariant point on the probe 19 at all times. In addition, it is possible to provide a piezoelectric oscillator 17 to perform tapping mode of the AFM. Theoretically, there should be no vertical tracking errors. However, due to the imperfection of the optical elements and the mechanical misalignment of the optical system, it can not be totally eliminated. Such tracking errors, however, may be calibrated through applicable inspection and calibration procedures. Horizontal Tracking In the data processing module of the beam tracking system for the scanning-probe type atomic force microscope of this invention, a false deflection calculation means is provided to calculate false deflection in the horizontal direction of the probe 19. Variation of the optical configuration of the optical system of this invention during X-direction or Y-direction scanning is shown in FIG. 2. FIG. 2 shows the optical configuration of the invented beam tracking system for scanning—probe type atomic force microscope during X direction scanning. As shown in this figure, when probe 19 shifts by distance xP, the incident beam and the reflected beam do not remain coaxial. The distance between their centers is called beam shift, denoted as xB, which is roughly twice of xP. FIG. 3 shows the optical configuration around the probe of the invented beam tracking system for scanning-probe type atomic force microscope. In this figure, θC represents tilt angle of the probe 19 that helps to guarantee the lowest point of the probe 19 is its tip. Generally speaking, a feasible tilt angle of the probe 19 is approximately 10-15° and is 12° in this embodiment. Moreover, f is the length of the objective lens 6, which is 9 mm in this embodiment. R denotes position of the probe when the incident beam and the reflected beam are coaxial. As shown in this figure, when probe 19 is shifted from position R to position R′, with the distance of XP, the reflected beam moves from position P to position P′, with the distance of XB. The mathematical relation between xB and xP may be described by equation (1), as follows: X B ( X P ) = f 2 + ( X P - f tan θ C ) 2 · sin ( 2 θ R ( X P ) ) sin ( θ P ( X P ) ) θ R ( X P ) = θ C + tan - 1 ( X P f - tan θ C ) , wherein θ P ( X P ) = π 2 - 2 θ C - tan - 1 ( X P f - tan θ C ) . ( 1 ) Therefore , X B ( X P ) = C · X P + X B ( X 0 ) ( 2 ) wherein C is constant and X0 is mechanical misalignment. If displacement of the laser beam and displacement of the probe 19 were equal (i.e. xB=xP), the correction lens 7 would not be needed. The motion of the synchronized photo sensing device could eliminate the false deflection automatically. However, XB is only roughly twice of XP. Fortunately, the relation between them is approximately linear. Taking the example where range of the horizontal scanning is 100 μm, and misalignment of the optical system x0 is 1 mm (i.e. xp travels from 0.95 mm to 1.05 mm), linear approximation as described in equation (2) may be instead of (1) to compensate (the false deflection. The linear compensation may be realized by installing the correction lens 7 at a distance of fC/C above the photo sensing device 15, wherein fC is the focal length of correction lens 7 and C is the same as above. FIG. 4 shows the relation between deflection of the probe V.sub.P and deviation of the laser beam S.sub.B. As shown in this figure, the difference between X.sub.B and X′.sub.B is DELTA.X.sub.B and may be used to calculate false deflection .DELTA..nu..sub.P, according to the following equation (3): .DELTA..times..times..upsilon. P=L3. times. f.times..DELTA..times..times. X B (3) wherein L, is the length of the cantilever and is 0.45 mm in this embodiment. This equation may also describe the optical-level effect. False deflection in the horizontal direction resulted from such structure is shown in FIG. 5. FIG. 5 shows the relation between tracking errors in the horizontal direction and horizontal displacement of the probe in this embodiment. As shown in this figure, when the scanning distance is 100 μm, the tracking error in the horizontal direction is 12 nm. In short, during the horizontal scanning, the non-linear error is represented by Equation (1). The correction lens 7 is helpful to linearly compensate such a non-linear error, which behavior is represented by Equation (2). Such linear compensation may eliminate most false deflection. The residual minor false deflection Δνρ may be easily measured by experiments, as shown in FIG. 5. The false deflection calculation means of this invention calculates the false deflection Δνρ according to Equation (3). The resulted information is then used by the data processing unit to calibrate or correct the topographic information of the sample. Besides the imperfection of the optical elements and the mechanical misassemble, the out-of-plane motion of the horizontal scanner may also contribute to the errors. Such errors, however, may be off-line measured and subtracted from the acquired image. FIG. 6 shows four AFM topographs and height profiles of a standard grating, as scanned by the scanning-probe type atomic force microscope of this invention and of the conventional art. In this figure, (a) is topography scanned by a conventional scanning-sample AFM carrying a 51 g brass block and scanning at 5 μm/s in the horizontal direction, (b) is topography scanned by the same AFM carrying the same brass block at 50 μm/s speed, (c) and (d) are topographs scanned by the invented AFM carrying the same brass block and scanning at 5 μm/s and 50 μm/s speeds, respectively. In the experiments of FIG. 6, the specimen is a standard grating with a step height of 26±1 nm and the horizontal pitch of 3±0.1 μm. The specimen is attached on the brass block to simulate a heavy sample. The experiments demonstrate the performance of the beam tracking system for the scanning-probe type atomic force microscope of this invention. As shown in FIG. 6, in the conventional art the vertical scanner was not able to follow the fast variation of the surface topography of the sample and distortion in the height profile is induced. In contrast, the present invention performs well without image distortion even at higher scanning speed. According to the present invention, tracking errors in the horizontal and the vertical directions may be limited to from <0.3 nm over a 4 μm scanning distance to <12 nm over 100 μm scanning distance. As the present invention has been shown and described with reference to preferred embodiments thereof, those skilled in the art will recognize that the above and other changes may be made therein without departing from the spirit and scope of the invention. |
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summary | ||
summary | ||
claims | 1. A core spray T-box attachment assembly for a core spray nozzle, comprising:a primary cruciform wedge;a secondary cruciform wedge in contact with the primary cruciform wedge to form a cruciform wedge subassembly having an axial bore adapted for insertion within a bore of the core spray nozzle to sealingly engage an interior converging portion of the core spray nozzle;a spider in contact with the cruciform wedge subassembly; anda draw bolt engaging the axial bore of the cruciform wedge subassembly and said spider to a T-box. 2. The core spray T-box attachment assembly of claim 1, wherein the primary cruciform wedge includes a first support member and a second support member that extends between web members. 3. The core spray T-box attachment assembly of claim 2 wherein the secondary cruciform wedge includes a first support member and a second support member that extends between said web members. 4. The core spray T-box attachment assembly of claim 1, wherein the spider includes a cylindrical shell having external threads sized to threadedly engage threads of a thermal sleeve. 5. The core spray T-box attachment assembly of claim 1, wherein the spider connects to the cruciform wedge subassembly via a tongue and groove joint. 6. The core spray T-box attachment assembly of claim 3, wherein the first and second support members of the primary and secondary cruciform wedges make up an outer surface of the cruciform wedge subassembly, the first and second support members of the primary and secondary cruciform wedges are tapered to engage an inside surface of a bore tapered portion of a safe end of the core spray nozzle. 7. The core spray T-box attachment assembly of claim 3, wherein the web members of the primary and secondary cruciform wedges extend to form an “X” shaped configuration. 8. The core spray T-box attachment assembly of claim 1, further comprising:a clamp assembly to sealingly pull the cruciform wedge subassembly against the interior converging portion of a safe end of the core spray nozzle. 9. The core spray T-box attachment assembly of claim 8, wherein the clamp assembly may be adjusted to push against an inner surface of a reactor vessel wall and pull the T-box attachment assembly toward the center of a nuclear reactor pressure vessel. 10. A core spray T-box attachment assembly for a core spray nozzle, comprising:a primary cruciform wedge;a secondary cruciform wedge in contact with the primary cruciform wedge to form a cruciform wedge subassembly having an axial bore adapted for insertion within a bore of the core spray nozzle to sealingly engage an interior converging portion of a safe end of the core spray nozzle;a spider in contact with the cruciform wedge subassembly; anda draw bolt engaging the axial bore of the cruciform wedge subassembly and said spider to a T-box,wherein the cruciform wedge subassembly includes an outer circumferential periphery defined by alternating segments of the primary and secondary cruciform wedges. |
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048184772 | claims | 1. A nuclear reactor core comprising a plurality of generally cylindrical fuel rods, each of said fuel rods comprising a cladding containing a plurality of nuclear fuel pellets stacked end-to-end within said cladding, wherein substantially each fuel pellet of substantially all of the fuel rods is coated with a layer of a refractory material interposed between the fuel pellet and the cladding of sufficient thickness to effectively prevent direct contact between the pellet and the cladding, said layer comprising a burnable poison having a non-naturally occurring tailored isotopic composition adjusted to reduce, in a controlled fashion, initial excess reactivity in said reactor core. 2. The reactor core of claim 1 wherein said burnable poison comprises a boride. 3. The reactor core of claim 2 wherein said boride comprises zirconium diboride. 4. The reactor core of claim 3 wherein said boride contains boron which is depleted in isotope boron-10 with respect to natural boron. 5. The reactor core of claim 2 wherein said layer is on the order of 10-100 microns thick. 6. A nuclear fuel rod comprising a cladding tube having ends and end plugs arranged to close said ends, a plurality of fuel pellets stacked end-to-end within said cladding tube between said end plugs, substantially all of said fuel pellets being coated with a barrier layer comprising a refractory material of sufficient thickness to effectively prevent interaction between said pellets and said cladding tube, said refractory material comprising a burnable poison having a tailored, non-naturally occurring isotopic composition determined on the basis of said thickness. 7. The fuel rod of claim 6 wherein said isotopic composition comprises a boride containing boron-10 and boron-11 in controlled ratios. 8. The fuel rod of claim 7 wherein said boride comprises zirconium diboride. 9. The fuel rod of claim 7 wherein said boride is depleted in boron-10 with respect to natural boron. 10. The fuel rod of claim 6 wherein said layer is on the order of about 10-100 microns thick. 11. A method of controlling excess reactivity and preventing interaction between fuel pellets and fuel rod cladding in a nuclear reactor core having an initial excess reactivity comprising the steps of: providing a predetermined amount of a burnable poison having a naturally occurring isotopic composition; tailoring said isotopic composition from said naturally occurring isotopic composition to effectively counteract said initial excess reactivity; and applying a layer of refractory material to substantially all of said fuel pellets, wherein said layer comprises said predetermined amount of burnable poison and is disposed between the fuel pellets and the cladding, said layer being of sufficient thickness to effectively prevent interaction between said pellets and said cladding. operating said reactor core to burn at least some of said burnable poison; and supplying additional neutron absorbing material to said core to control excess reactivity. determining an amount of burnable poison required to control said initial excess reactivity; determining, based on a predetermined thickness of fuel pellet coating effective for preventing said interaction and said amount of burnable poison required, an isotopic composition of said burnable poison; coating substantially all of the fuel pellets in said core with a layer of a refractory material of said predetermined thickness, said refractory material comprising said amount of burnable poison having said determined isotopic composition. providing a predetermined amount of a burnable poison having an isotopic composition; controlling said isotopic composition to effectively counteract said initial excess reactivity; applying a layer of refractory material to substantially all of said fuel pellets, wherein said layer comprises said predetermined amount of burnable poison and is disposed between the fuel pellets and the cladding, said layer being of sufficient thickness to effectively prevent interaction between said pellets and said cladding; and wherein said reactor core is divided into a plurality of regions distinguished by an enrichment value of nuclear fuel in said fuel pellets, and wherein said step of controlling further comprises adjusting the isotopic composition of said layer in accordance with the enrichment in each of said regions. 12. The method of claim 11 further comprising the steps of: 13. The method of claim 12 wherein said reactor is cooled by a flowing coolant and the step of supplying additional neutron absorbing material comprises supplying a chemical shim to said coolant after said burnable poison in said layer has been at least partially depleted. 14. The method of claim 11 wherein said burnable poison comprises a boride having a boron isotopic composition, and said step of controlling comprises either enriching or depleting an isotope boron-10 in said boride with respect to natural boron in at least some of said rods. 15. A method of controlling excess reactivity of a nuclear reactor core having an overall initial enrichment which creates an initial excess reactivity while preventing interaction between fuel pellets and fuel rod cladding in said core, comprising the steps of: 16. The method of claim 15 wherein said reactor core is uniformly enriched and said layer has a uniform isotopic composition. 17. The method of claim 15 wherein said reactor comprises at least two regions, each of said regions being characterized by a different initial enrichment, wherein said step of determining said isotopic composition further comprises determining said isotopic composition of the coatings for each of said regions based on said different initial enrichments. 18. The method of claim 15 wherein said fuel rods have a characteristic void space and wherein said fuel rods are initially pressurized, said method further comprising the step of adjusting said initial pressurization based on an amount of gas pressure released into said void space by said burnable poison during reactor operation. 19. The method of claim 15 wherein said predetermined thickness is between about 10 microns and 100 microns. 20. A nuclear reactor core comprising a plurality of generally cylindrical fuel rods, each of said fuel rods comprising a cladding containing a plurality of nuclear fuel pellets stacked end-to-end within said cladding, wherein substantially each fuel pellet of substantially all of the fuel rods is coated with a layer of a refractory material interposed between the fuel pellet and the cladding of sufficient thickness to effectively prevent direct contact between the pellet and the cladding, said layer comprising a burnable, boride poison having an isotopic composition adjusted to reduce excess reactivity in said reactor core; wherein a first portion of said plurality of fuel rods contain fuel pellets coated with zirconium diboride having natural boron and a second portion of said plurality of fuel rods contain fuel pellets coated with zirconium diboride depleted in isotope boron-10. 21. A nuclear reactor core comprising a plurality of generally cylindrical fuel rods, each of said fuel rods comprising a cladding containing a plurality of nuclear fuel pellets stacked end-to-end within said cladding, wherein substantially each fuel pellet of substantially all of the fuel rods is coated with a layer of a refractory material interposed between the fuel pellet and the cladding of sufficient thickness to effectively prevent direct contact between the pellet and the cladding, said layer comprising a burnable poison having an isotopic composition adjusted to reduce excess reactivity in said reactor core, and wherein said core is divided into a plurality of regions, each of said regions being characterized by fuel rods having fuel pellets of a different enrichment, wherein said poison isotopic composition is adjusted in accordance with the enrichment of each of said regions. 22. A method of controlling excess reactivity and preventing interaction between fuel pellets and fuel rod cladding in a nuclear reactor core having an initial excess reactivity comprising the steps of: |
claims | 1. A power module assembly comprising:a reactor core;a reactor vessel housing the reactor core, wherein the reactor core is submerged in primary coolant contained within the reactor vessel;a containment vessel which substantially surrounds the reactor vessel, wherein the containment vessel is internally dry and forms a containment region which is maintained at a below atmospheric pressure during normal operation of the power module assembly; anda vent configured to controllably release the primary coolant from the reactor vessel into the containment vessel as primarily steam during an over-pressurization event, wherein the containment vessel is configured to retain all of the released primary coolant within the containment vessel, wherein the containment vessel is at least partially surrounded by a heat sink, and wherein a decay heat of the reactor core is transferred to the heat sink primarily through condensation of the released primary coolant on an inner surface of the containment vessel. 2. The power module assembly of claim 1, wherein the vent comprises a flow limiter connected to the reactor vessel and configured to controllably release the primary coolant at a rate that maintains a steady state containment pressure through the condensation of the primary coolant. 3. The power module assembly of claim 1, further comprising an intake configured to circulate the released primary coolant that condenses in the containment vessel back through the reactor core without the primary coolant leaving the containment vessel. 4. The power module assembly of claim 1, wherein the heat sink is configured to passively remove the decay heat for at least three days without any operator intervention. 5. The power module assembly of claim 1, including cooling fins attached to an outside wall of the containment vessel and in contact with the heat sink to further remove the decay heat of the reactor core. 6. The power module assembly of claim 1, wherein the heat sink comprises water or gas. 7. The power module assembly of claim 1, wherein the heat sink comprises rock, soil, or other solid material. 8. The power module assembly of claim 1, wherein a second containment region formed between the reactor vessel and the containment vessel is maintained at atmospheric pressure, and wherein the steam is released into the second containment region during the over-pressurization event. 9. The power module assembly of claim 8, wherein the reactor vessel is insulated by conventional thermal insulation in the containment region, and wherein the reactor vessel is insulated by reflective insulation in the second containment region. 10. The power module assembly of claim 8, further comprising one or more valves connecting the second containment region to the containment region, and wherein the one or more valves are operatively configured to transfer the condensed primary coolant from the second containment region to the containment region. 11. A power module assembly comprising:a reactor core;a reactor vessel housing the reactor core, wherein the reactor core is submerged in primary coolant contained within the reactor vessel;a containment vessel which substantially surrounds the reactor vessel;means for controllably releasing the primary coolant as steam into the containment vessel in response to a high pressure condition within the reactor vessel, wherein an inner surface of the containment vessel is dry prior to releasing the primary coolant as steam into the containment vessel, and wherein steam that condenses on the inner surface of the containment vessel forms a pool of primary coolant in the containment vessel; andmeans for drawing the pool of primary coolant back into the reactor vessel. 12. The power module assembly of claim 11, wherein the condensation of the steam on the inner surface of the containment vessel reduces pressure in the containment vessel at approximately the same rate that the released steam adds pressure to the containment vessel. 13. The power module assembly of claim 11, wherein the steam is released into the containment vessel to remove a decay heat of the reactor core through the condensation of the steam on the inner surface of the containment vessel, and wherein the decay heat is transferred to a heat sink contacting an outer surface of the containment vessel. 14. The power module assembly of claim 13, wherein heat from the power module is removed primarily through conduction from the outer surface of the containment vessel. 15. The power module assembly of claim 13, wherein the heat sink comprises a pool of water which substantially surrounds the containment vessel and is configured to passively remove the decay heat for at least three days without any operator intervention. 16. The power module assembly of claim 11, wherein the containment vessel is maintained at a below atmospheric pressure prior to controllably releasing the primary coolant as steam, and wherein the containment vessel is maintained at an above atmospheric pressure condition after the primary coolant is released into the containment vessel. 17. The power module assembly of claim 16, wherein an outer surface of the reactor vessel comprises a steel housing, and wherein the steel housing is exposed directly to the below atmospheric pressure during normal operation of the power module. 18. The power module assembly of claim 11, wherein a first containment region formed between the containment vessel and the reactor vessel is maintained at atmospheric pressure, and wherein a second containment region formed between the containment vessel and the reactor vessel is maintained at a below atmospheric pressure prior to the over-pressurization event. 19. The power module assembly of claim 18, wherein the reactor vessel is insulated by conventional thermal insulation in the first containment region, and wherein the reactor vessel is insulated by reflective insulation in the second containment region. 20. The power module assembly of claim 11, wherein the pool of primary coolant extends between an outer wall of the reactor vessel and the inner surface of the containment vessel. |
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claims | 1. A collimation device for an X-ray beam, comprising:an enclosure configured to be placed under vacuum or controlled atmosphere, the enclosure comprising an entrance and an exit for the X-ray beam, and at least one first plate made of a material with a diffracting periodic structure,the first plate comprising first and second principal faces and at least one first aperture broadening out between the first and second principal faces,wherein at least one of the first and second plates is made of a monocrystalline material. 2. The device as claimed in claim 1, in which the first principal face of the at least one first plate is an upstream face, with reference to a direction of propagation of the X-ray beam, and the second principal face is a downstream face, the first aperture widens out from the upstream face to the downstream face of the first plate. 3. The device as claimed in claim 1, in which the at least one first plate made of material with a diffracting periodic structure is arranged at a level of the exit of the enclosure. 4. The device as claimed in claim 3, further comprising, at a level of the entrance of the enclosure, at least one second plate made of a material with a diffracting periodic structure, the second plate comprising third and fourth principal faces and at least one second aperture broadening out between the third and fourth faces. 5. The device as claimed in claim 4, in which the third principal face of the at least one second plate is an upstream face, with reference to the direction of propagation of the beam, and the fourth principal face is a downstream face, and the second aperture widens out from the upstream face to the downstream face of the at least one second plate. 6. The device as claimed in claim 4, in which the first and second plates are identical. 7. The device as claimed in claim 4, in which the first and second plates exhibit different apertures. 8. The device as claimed in claim 1, in which an acute angle θ formed between a direction of broadening out of one of the apertures and one of the principal faces is between 10° and 80°. 9. The device as claimed in claim 8, in which the angle θ is equal to the angle between two crystalline planes of the monocrystalline material of diffracting periodic structure forming the first plate. 10. The device as claimed in the preceding claim, in which:the principal faces of the plates correspond to the {100} plane of the monocrystalline material; andthe faces of the apertures connecting the principal faces of this plate correspond to the {111} plane. 11. The device as claimed in claim 1, in which at least one of the first and second plates is made of a material chosen from among silicon or germanium. 12. An optical device for analyzing a specimen by scattering of an X-ray beam, comprising a device for collimating the beam as claimed in claim 1. 13. The optical device as claimed in claim 12, further comprising an X-ray source. 14. The optical device as claimed in claim 13, in which the X-ray source produces a monochromatic beam. 15. The optical device as claimed in claim 12, further comprising another enclosure configured to be placed under vacuum or controlled atmosphere, the other enclosure, arranged downstream of the specimen, comprising a means for stopping the X-ray beam. 16. The optical device as claimed in claim 15, further comprising a detector, arranged downstream of the other enclosure. 17. A collimator for an X-ray beam, comprising:plural parts, of an X-ray aperture;each part made of a monocrystalline material with a diffracting periodic structure, and comprising at least one aperture broadening out in the thickness thereof;faces of the X-ray aperture, formed by assembling said plural parts, forming a sawtooth structure along a longitudinal axis of the X-ray aperture. 18. The collimator as claimed in claim 17, in which each of the parts is formed of a plate, the plates being adjoining. 19. The collimator as claimed in claim 18, in which the plates are identical. 20. A method for using a collimator for an X-ray beam, comprising:illumination a specimen with X-rays;wherein the collimator comprise at least one plate made of a monocrystalline material with a diffracting periodic structure, the plate comprising two principal faces and at least one aperture broadening out between the faces. 21. The method of claim 20, in which an acute angle θ formed between a direction of broadening out of the aperture and one of the principal faces is between 10° and 80°. 22. The method of claim 20, in which the collimator comprises plural identical plates adjoining one another. |
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claims | 1. A collimator for exposing a specimen to an X-ray field, wherein the X-ray field is in the submicrometer to micrometer range, comprising:a first structure comprising a first planar surface and a second planar surface, wherein said first planar surface comprises one or more grooves; anda second structure having a first planar surface and a second planar surface, wherein said first planar surface on said second structure optionally comprises one or more grooves;wherein said first planar surface of said first structure is in contact with said second planar surface of said second structure such that said second structure covers over the one or more grooves on said first structure through which X-rays penetrate to produce the X-ray field or fields, wherein the groove has a smallest dimension that is in the submicrometer to micrometer range. 2. The collimator of claim 1, wherein the X-ray fields are 0.5-50 micrometers in one dimension and 0.5 micrometers to 3 millimeters in the other direction. 3. The collimator of claim 1, wherein the X-ray fields are 0.5-10 micrometers in one dimension and 0.5 micrometers to 3 millimeters in the other direction. 4. The collimator of claim 1, wherein the X-ray fields are 0.5-2 micrometers in one dimension and 0.5 micrometers to 3 millimeters in the other direction. 5. The collimator of claim 1, wherein said structures are 1-2 centimeters long, 1-2 centimeter wide and 25-400 micrometers thick. 6. The collimator of claim 1 wherein said structure is Silicon. 7. The collimator of claim 1 wherein said structure is gallium arsenide. 8. The collimator of claim 1 wherein said structure is a semiconducting material, a ceramic material, a metallic material, a semi-metal, an alloy, a glass or combinations thereof. 9. The collimator of claim 1 wherein said structures are coated with a SiO2 surface layer, whose etching results in the grooves, through which the X-rays penetrate through the collimator. 10. The collimator of claim 1 wherein at least two plates with grooves are stacked against each other to produce multiple X-ray fields. 11. The collimator of claim 1 further comprising a third structure comprising a first planar surface and a second planar surface, wherein said first planar surface of said third structure optionally comprises one or more grooves; wherein said second structure of said third plate is in contact with said first planar surface of said second structure. 12. The collimator of claim 1, wherein said one or more grooves of each structure is about 0.5-100, 0.5-50, 0.5-10, or 0.5-2 micrometers in depth. 13. The collimator of claim 1, wherein said one or more grooves of each structure is about 0.5 micrometers to 3 millimeters in width. 14. An apparatus comprising a collimator holder and a collimator of claim 1, wherein said holder comprises a first plate and a second plate. 15. The apparatus of claim 14, wherein said collimator holder further comprises a specimen holder. 16. The apparatus of claim 14, wherein the said first and second plate of said collimator holder are contained within a second holder wherein said second holder comprises a third plate and fourth plate, wherein said third and fourth plate comprises a force member allowing the first and second plate to be under pressure. 17. The apparatus of claim 14, further comprising an alignment apparatus. 18. The apparatus of claim 17, wherein said alignment apparatus rotates said holder along an axis that is perpendicular to an X-ray beam axis. 19. The apparatus of claim 17, wherein said alignment apparatus rotates said holder perpendicular to a shortest edge of the produced X-ray field. 20. The apparatus of claim 17, wherein said alignment apparatus comprises a motor. 21. The apparatus of claim 14 further comprising an X-ray source. 22. The collimator of claim 1, wherein said one or more grooves of each structure is 0.5-100 micrometers in depth. 23. The collimator of claim 1, wherein said one or more grooves of each structure is 0.5-50 micrometers in depth. 24. The collimator of claim 1, wherein said one or more grooves of each structure is 0.5-10 micrometers in depth. 25. The collimator of claim 1, wherein said one or more grooves of each structure is 0.5-2 micrometers in depth. |
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description | FIG. 1 is cross-sectional schematic view of a related art reactor pressure vessel 100, such as an ESBWR pressure vessel. Vessel 100 includes a core plate 118 laterally supporting one or more fuel assemblies 110 within core shroud 114. Fluid coolant and/or moderator, such as liquid water, is typically delivered into an annular downcomer region 101 about a perimeter of vessel 100 by a feedwater line, chimney runoff, or other coolant supply source. The fluid flows downward through downcomer 101 a core inlet region below core plate 118. At the core inlet, the fluid turns and flows up into the core, bounded by core shroud 114 and containing assemblies 110. At the bottom of core shroud 114, the fluid is redirected and flows upward through assemblies 110 in a central core of vessel 100. As such, core shroud 114 separates upward flow of coolant through the core and assemblies 110 therein from downcomer flow in an annulus 101. Core plate 118 supports core shroud 114 and may itself be supported by support ring and legs 102. Core plate 118, core shroud 114, and/or support ring 102 may all be cylindrical or annular to extend about a complete inner perimeter or angular length of vessel 100. Top guide 112 may be positioned at the top of the core shroud 114 to provide lateral support and positioning to the top of fuel assemblies 110. As liquid coolant boils among assemblies 110, a heated mixture of steam and water flows upward through top guide 112. Chimney 120, with flow-directing partitions 121, receives the energetic steam/water mixture exiting fuel assemblies 110. Steam separator assembly 140 may be positioned at an upper end of chimney 120, such as at chimney head 122. Any of core shroud 114, core plate 118, top guide 112, and chimney 120 may be movable with respect to one another and removably joined during operation. Chimney head 122 may be laterally supported by chimney restraint 123, which may be paired, slip-fitting brackets on chimney 120 and an inner wall of vessel 100. Atop chimney 120, steam separator assembly 140 may receive the directed energetic fluid flow and separate liquid water from the steam-water mixture rising therethrough. Steam from the steam separator assembly 140 flows upward to steam dryer 141, where additional moisture is removed. The separated and removed liquid is directed back down into downcomer annulus 101, and the dried steam exiting steam dryer 141 is then directed into main steam lines 103 for electrical power production. Example embodiments include one or more seals for use between abutting components in a nuclear reactor environment. Example seals can be installed between components where they are joined or touch, such as in a groove within or other area between the components. Example seals in the groove are compressed by the abutment and thus seal against the components in the direction of the components' joining. The components may divide distinct flow paths inside a nuclear reactor, for example, and example seals can take advantage of different properties of the flow paths to further enhance the seal. For example, seal may include an expandable concavity that opens toward the flow with the higher pressure and is closed against other flows. The higher pressure may expand or drive the concavity and thus seal further in the direction of the components' joining, enhancing the seal. This can better isolate flows with different characteristics across the components and prevent unwanted mixing and deterioration of differences between flows. For example, elastic seals with a C-shaped or E-shaped cross-section in a plane parallel to the fluid flows may take advantage of such pressure differences. Seals may also have O-ring, coiled, and/or helical cross-sections, as additional examples. Example seals can be any shape or size to enhance sealing between distinct components. For example, seals may form a continuous path about a perimeter of the abutting structures in a plane perpendicular to the flow paths. Seals may be ring-shaped, annular, or any other shape in this manner about an axis of the components' joining. Example seals may be held between the abutting components by gravity, a groove in the components, a retaining clip, welding, etc. For example, in the instance the components to be sealed are core supports or plates, shrouds, and/or chimney structures isolating a downcomer flow from a core flow, seals may be held between the components by retainers attached to the same bolts removably joining these structures in the reactor. Because this is a patent document, general broad rules of construction should be applied when reading and understanding it. Everything described and shown in this document is an example of subject matter falling within the scope of the appended claims. Any specific structural and functional details disclosed herein are merely for purposes of describing how to make and use example embodiments or methods. Several different embodiments not specifically disclosed herein fall within the claim scope; as such, the claims may be embodied in many alternate forms and should not be construed as limited to only example embodiments set forth herein. It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be understood that when an element is referred to as being “connected,” “coupled,” “mated,” “attached,” or “fixed” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.). Similarly, a term such as “communicatively connected” includes all variations of information exchange routes between two devices, including intermediary devices, networks, etc., connected wirelessly or not. As used herein, the singular forms “a”, “an” and “the” are intended to include both the singular and plural forms, unless the language explicitly indicates otherwise with words like “only,” “single,” and/or “one.” It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, steps, operations, elements, ideas, and/or components, but do not themselves preclude the presence or addition of one or more other features, steps, operations, elements, components, ideas, and/or groups thereof. It should also be noted that the structures and operations discussed below may occur out of the order described and/or noted in the figures. For example, two operations and/or figures shown in succession may in fact be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Similarly, individual operations within example methods described below may be executed repetitively, individually or sequentially, so as to provide looping or other series of operations aside from the single operations described below. It should be presumed that any embodiment having features and functionality described below, in any workable combination, falls within the scope of example embodiments. The inventors have recognized that structures forming a downcomer region, such as a core plate, core shroud, shroud support, chimney, etc., may be removably joined through mating structures that do not completely seal the downcomer region from internal core flow. Fluid in the downcomer is typically a lower-temperature liquid under forced-flow pressure, while flow up through the core is higher-temperature, potentially two-phase flow. The inventors have newly recognized the potential for leakage between these two flows, such as where a core plate and shroud or shroud support sit on one another as separate pieces through which highly energetic flows may escape. The inventors have further recognized that leakage between downcomer and core flow in newer, natural-circulation reactor designs, such as an ESBWR, may be particularly detrimental in assuring a strong natural circulation drive in the instance of reliance on natural circulation, such as in a loss of offsite power transient. For example, cooler downcomer flow leaking into hotter core flows may cool or condense fluid flowing up through the core, decreasing the natural pressure gradient between these flows and reducing natural circulation cooling. As such, the Inventors have newly recognized a need for resilient sealing between structures separating flows at different pressures as well as sealing between structures separating a lower-energy downcomer flow from a higher-energy core flow, especially in natural circulation reactors where natural circulation is a key element of primary coolant loop flow. Example embodiments described below address these and other problems recognized by the Inventors with unique solutions enabled by example embodiments. The present invention is seals for use in a nuclear reactor environment and systems including the same. In contrast to the present invention, the small number of example embodiments and example methods discussed below illustrate just a subset of the variety of different configurations that can be used as and/or in connection with the present invention. FIG. 2 is a cross-sectional detail about core plate 118 adjacent to downcomer region 101 of vessel 100 from FIG. 1. As shown in FIG. 2, example embodiment seal system 200 is useable inside a nuclear reactor, with several components in the same. Example embodiment seal system 200 includes one or more elastic seals 250 between separate reactor internal components subject to leakage. For example, seals 250a and 250b may be installed between components that divide fluid flows within the reactor, such as components that separate a downcomer region 101 from internal core flows. These components may be a shroud support 102, core plate 118, and/or core shroud 114, as shown in FIG. 2. Of course, seals 250 are also useable in and between other flow-dividing structures, such as between core barrels, top guides, chimney sections, chimney heads, steam separators, reactor heads, etc., as well as any other reactor structures that would benefit from resistive sealing, such as modified reactor internals and/or coolant loop components. In FIG. 2, downward flow ↓ is to the left, or outward radially, in downcomer 101, while upward flow ↑ is inside a core area to the right, or inward radially. Downward flow ↓ may be annular, about an angular perimeter of the reactor, while FIG. 2 is only a cross-sectional schematic showing radial and axial dimensions. Downward flow ↓ in downcomer 101 may be relatively cooler liquid water at a relatively higher pressure from natural circulation, while upward flow ↑ may be hotter steam-and-water mixture flowing under relatively lower pressure. For example, in an ESBWR downward flow ↓ may be condensed liquid at about 270 degrees Celsius and above about 7.2 MPa whereas upward flow ↑ may be at over 280 degrees Celsius, below 7.2 MPa, and contain dual-phase flow. Seals 250 are present in example embodiment system 200 between structures dividing the upward and downward flows in order to prevent fluid leakage, and thus energy transfer, between the flows. Seals 250 may be a continuous annular ring, so as to continuously seal a perimeter of the structures shown in FIG. 2 when taken in three dimensions, or any other shape to provide desired sealing. For example, for a generally flat cylindrical core plate 118 and annular core shroud 114, seal 250a may be a continuous annulus seating between shroud 114 and core plate 118 to reduce flow through a juncture of shroud 114 and core plate 118. Shroud 114 may be removably bolted, or even resting only under gravitational forces, on core plate 118, such that movement and/or uneven contact between shroud 114 and core plate 118 is possible under extreme forces encountered in nuclear hydraulics. Seals 250 reduce or prevent leakage in this instance. Seals 250 may take on a variety of forms to seal contacts between flow-creating structures in a nuclear reactor environment such as in example system 200. FIG. 3 illustrates a first example seal, usable as seal 250b in FIG. 2. As shown in FIG. 3, example seal 250b may be an E-shaped seal with an alternating or labyrinthine shape. A similar seal is described in co-owned application Ser. No. 12/876,567, filed Sep. 7, 2010, now U.S. Pat. No. 8,475,139, which is incorporated by reference herein in its entirety, and whose seals and methods may be similar to example seal 250b if reengineered in accordance with this detailed description. Example seal 250b is sized to fit in a groove 102b machined or otherwise created in a contact surface of the structure to be sealed, such as an upper face of shroud support 102 that would contact a core plate 118 (FIG. 2). Groove 102b is shown in partial cut-away in FIG. 3, and it is understood that groove 102b may be a ledge or completely contained width-wise in a structure such as shroud support 102. Groove 102b and seal 250b may extend an entire circumference of shroud support 102 so as to entirely seal an interior of support 102 from an exterior of the same. Groove 102b may be formed during fabrication or installation of core support 102, such as by molding, machining, stamping, etc., and seal 250b may be placed in groove 102b shortly thereafter. Similarly, groove 102b may be formed during a maintenance period or outage when a reactor core is disassembled and contact surfaces are available for modification to create groove 102b. Seal 250b can also be placed in groove 102b during such maintenance periods, either in newly-formed or existing groove 102b, potentially replacing an existing or worn-out seal. Seal 250b may fit relatively closely in groove 102b and remain in the same via gravity and/or installation of another structure above groove 102b. Similarly, seal 250b may be welded, bolted, or otherwise attached to a surface in groove 102b. Example seal 250b is sized to protrude vertically a distance d from groove 102b and is elastically compressible in the vertical direction along d. For example, groove 102b may be only 1-2 inches deep vertically in core support 102, and seal 250b may extend less than a quarter of an inch above groove 102b in distance d. Seal 250b is configured to compress the distance d and exert spring resistive force due to such compression, forming a seal. Seal 250b may be sized of a thickness and chosen of a nuclear-reactor-environment-compatible material that will not fail or plastically deform when compressed distance d, such as a stainless steel or other metallic alloys like X-750 or Alloy 718 (modified). Alternatively, seal 250b may plastically or permanently deform when compressed distance d, while still forming a seal against a compressing structure. As shown in FIG. 3, example seal 250b may be E-shaped to further take advantage of a pressure differential across sealed structures. For example, P1 may be of a higher pressure than P2 on opposite sides of a shroud support 102, and any leaking fluid may have a tendency to thus flow from P1 across an upper face of shroud support 102 to P2. Expandable gaps 252 in example seal 250b may take advantage of this pressure differential and drive seal 250b to expand vertically in direction d under such pressure differential. Particularly, by shaping and positioning gaps 252 to open toward higher pressure P1, with tines 251 and gaps 252 radially seating in groove 102b, seal 250b may be driven to vertically expand by pressure P1 expanding gaps 252 more than pressure P2. Such vertical force in seal 250b created by a pressure differential may enhance vertical force and thus seal effectiveness between seal 250b and a structure seated on and compressing the same, such as core plate 118 (FIG. 2). Similarly, if P2 is expected to be greater than P1, such as fluid in downcomer 101 (FIG. 2) being expected to have a higher pressure than core fluid flow, example seal 250b may be reversed to better take advantage of the opposite pressure differential. FIGS. 4A and 4B are additional examples of seals useable in example system 200 of FIG. 2. For example, as shown in FIGS. 4A and 4B, example seal 250a may be a C-shaped ring, with in single (FIG. 4A) or double with an inner O-ring (FIG. 4B). A groove 114a may house example seal 250a in an upper face of a flow-directing structure, such as shroud 114. Similar to groove 102b (FIG. 3), groove 114a may be created in any manner to house seal 250a. Similar to FIG. 2, FIGS. 4A and 4B are cross-sectional schematics, and seals 250a extend in non-illustrated depth directions, potentially to form an annular ring or section with a C-shaped cross-section. Example seal 250a may be sized to fit in groove 114a, with a small vertical protrusion to allow for compression and sealing across distance d when shroud 114 is vertically seated against a lower structure, such as core plate 118 in example system 200 (FIG. 2). Because groove 114a may be in a downward-facing vertical orientation and example spring 250a may be installed in groove 114a against the force of gravity, retaining clip 415 may be used to hold example spring in groove 114a when not compressed. For example, retaining clip 415 may adjoin in a gap of a C-shaped example seal 250a (FIG. 4A) or may join to or push-against a curvature of a C-shaped example seal 250a (FIG. 4B), through frictional contact, welding, bolting, or other joining and retaining mechanisms. Bolt 410 may secure retaining clip 415 to the upper structure, such as shroud 114. Bolt 410 may further be used to removably join the overall abutting structures, such as shroud 114 and core plate 118. Similarly, example seals 250a may be used in chimney sections and steam separating and drying equipment described in co-owed application Ser. No. 14/792,512 to “CHIMNEY AND LOADING/UNLOADING METHODS FOR THE SAME IN NUCLEAR REACTORS” filed Jul. 6, 2015 and incorporated herein in its entirety. In such an adaptation, structures 114 or 102 (FIG. 3) may be chimney barrels or extensions, for example. Bolts 410 may be external bolts or seismic pins that removably join the chimney components. Seals 250 may seal an entire perimeter of chimney portions that compress seals 250 when vertically joined, preventing intermixing of opposite flows on either side of the chimney. Example seals 250a in FIGS. 4A and 4B may be shaped to take advantage of a pressure differential between divided flows similarly to other example seals. As shown in FIGS. 4A and 4B, example seals 250a may be C-shaped, such that increased pressure on the side of the opening of the C forces vertical expansion of seals 250a, enhancing vertical force and seal between abutting structures. Seal 250a of FIG. 4A may be a single ring seal, while seal 250a of FIG. 4B includes an additional double internal ring to increase seal spring constant and effectiveness. Example seals 250a are formed of flexible, elastic sealing materials compatible with an operating nuclear reactor environment, such as a metal alloy. Of course, E-shaped and other seals may also be used in groove 250a in example systems to take advantage of pressure differentials. Example embodiments and methods thus being described, it will be appreciated by one skilled in the art that example embodiments may be varied and substituted through routine experimentation while still falling within the scope of the following claims. For example, a variety of different reactor structures that join together to direct flow configurations are compatible with example embodiment systems and seals simply through proper dimensioning of example embodiments—and fall within the scope of the claims. Such variations are not to be regarded as departure from the scope of these claims. |
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description | According to the present invention, leachable lead in treated materials is decreased to levels well below 5.0 mg/l, measured by TCLP test criteria. Waste and process materials having TCLP lead level in excess of 5 mg/l are considered hazardous and must be treated to be brought into compliance with regulatory requirements. Other metal-bearing materials having leachable metals may also be treated according to the present invention to achieve acceptable metal levels. The treatment technology according to another embodiment of the present invention consists of a two step process for treating contaminated soils and/or solid waste materials with chemical treating agents that convert leachable lead to synthetic (man-made) substantially insoluble lead mineral crystals. As used here, xe2x80x9csubstantially insolublexe2x80x9d means the leachable lead content in the treated waste sample is less than 5.0 mg/l in the extract by the TCLP Test. Another preferred embodiment of the present invention consists of applying technical grade phosphoric acid (TGPA) that contains sulfate as an impurity to leachable and soluble radionuclides and other radioactive substances often found in debris, soils and solid materials. The addition of water aids in the dispersion and percolation of TGPA throughout the contaminated host matrix. Water can be added at any point of the process, either before or after the TGPA addition, or by diluting the TGPA and applying the dilute TGPA to the target matrix. Mixing of the TGPA with the host matrix is optional, dependent upon the permeability and porosity of the host material. When employed, mixing enhances the uniformity of reagent dispersion through the host material. The treatment chemicals useful in the present invention may be divided into two groups. The addition of water with the additives may facilitate the ultimate mixing and reaction. A first group, xe2x80x9cgroup onexe2x80x9d, comprises a source of sulfate, hydroxide, chloride, fluoride and/or silicates. These sources are gypsum, lime, sodium silicate, cement, calcium fluoride, alum and/or like similar products. The second group, xe2x80x9cgroup twoxe2x80x9d, comprises a source of phosphate anion. This group consists of products like phosphoric acid (phosphoric), pyrophosphates, triple super phosphate, trisodium phosphates, potassium phosphates, ammonium phosphates and/or similar compounds capable of supplying a phosphate anion. The first step of this novel process comprises the reaction of leachable lead in contaminated soils or solid waste materials with a gypsum powder, calcium sulfate dihydrate (CaSO4.2H2O). Calcium sulfate dihydrate powder reacts with leachable and mobile lead species in wastes to form hard sulfates, which are relatively insoluble in water. In the invention, the powder form of dry calcium sulfate dihydrate, or gypsum, is preferred for blending with lead contaminated materials because it provides a uniform cover or dry coating over the surfaces of the waste particles and aggregates under low moisture conditions. The greatest benefit and fastest reaction is achieved under conditions wherein 95% of the powder is passable through a 100 mesh sieve, and the remaining 5% is passable through a 20 mesh sieve. The amount of gypsum powder employed is typically from 0-30 percent of the weight of solid waste material being treated. The actual amount employed will vary with the degree and type of lead contamination in the waste material or soil, and with the initial composition as well as the condition of the waste material, among other factors, Alternatively, sulfuric acid, or alum in liquid or powder form can also be used as sources of sulfate ion in certain solid wastes that contain sufficient calcium prior to treatment. In a preferred embodiment of the present invention, the radionuclides and other radioactive substances as well as any metal-hazardous waste materials to be treated are contacted with a treatment reagent in the form of a suspension. The suspension is formed from a first component selected from the first group of treatment chemicals and a second component selected from the second group of treatment chemicals. In a preferred embodiment, a third component is included in the suspension, selected from the second group of treatment chemicals. The first component of the suspension can be either a liquid or a solid. The second component of the suspension can also be either a liquid or a solid. In some embodiments, the first and second components are both solids; while in other embodiments, the first and second components are both liquids. It is also within the scope of the present invention for one of the two components to be a solid, while the other component is a liquid. In a preferred embodiment, the second component is an aqueous phosphate reagent. The first component of the suspension supplies a source of sulfate, hydroxide, chloride, fluoride, magnesium, and/or silicates and can be selected from suflfric acid, sodium sulphide, sodium sulphite, sodium peroxide, sodium hydroxide, sodium carbonate, sodium chlorate, sodium nitrate, sodium silicate, magnesium hydroxide, magnesium oxide, magnesium hydrogencarbonate, magnesium sulfate, magnesium carbonate, magnesium chloride, magnesium aluminum silicate, calcium magnesium carbonate, lime, cement, calcium fluoride, calcium chloride, calcium nitrate, calcium sulphate (or gypsum), potassium sulphate, potassium hydroxide, aluminum potassium sulphate (or alum) and/or similar compounds. The second component of the suspension supplies a phosphate source and can be selected from the group consisting of phosphoric acid, super phosphoric acid, phosphinic acid, phosphonic acid, pyrophosphates, superphosphate, triple superphosphate (TSP), trisodium phosphate, potassium phosphates, ammonium phosphates, diammonium phosphates, monocalcium phosphate, calcium triple superphosphate, calcium superphosphate, tricalcium phosphate, tetrasodium pyrophosphate and/or similar compounds which are capable of supplying a phosphate anion. In a preferred embodiment, the suspension includes a third component which supplies at least one phosphate anion. The third component can be a solid or a liquid and can be an aqueous phosphate reagent. The third component of the suspension is selected from the group consisting of phosphoric acid, super phosphoric acid, phosphinic acid, phosphonic acid, pyrophosphates, superphosphate, triple superphosphate (TSP), trisodium phosphate, potassium phosphates, ammonium phosphates, diammonium phosphates, monocalcium phosphate, calcium triple superphosphate, calcium superphosphate, tricalcium phosphate, tetrasodium pyrophosphate and/or similar compounds which are capable of supplying a phosphate anion. In another preferred embodiment, the suspension includes monocalcium phosphate, tetrasodium pyrophosphate and a magnesium aluminum silicate. A similar suspension called xe2x80x9cEmy""s Waste Removal Environmental Formulaxe2x80x9d is commercially available from Emy""s of Walton, Ind. and it has been found to be useful in practicing the present invention. The suspension can include solid particles, liquids or a combination of solid particles and liquids suspended in a solution. The solid particles and liquids can be selected from the first component and the second component, and can include more than one member of the group from which the first and second components are selected. The solution can include a liquid selected from the first component, such as sulfuric acid, or the second component, such as phosphoric acid. The solution can also include combinations of the first and second components. The first and second components in the suspensions of the present invention can be in either the solid or liquid form and can be either the solvent (the liquid) or the solute (the substance dissolved in the liquid). When two liquids are mixed to form the solution, the solvent is the major component and the solute is the minor component. The suspensions of the present invention can also be diluted to facilitate application of the suspensions to the materials being treated. The diluent can be water or a liquid containing the first component or the second component, such as sulfuric acid or phosphoric acid. The diluent can also include a surfactant, such as a detergent, to increase its spreading or wetting properties by reducing the surface tension. At lease one component from group one is added to the mixing vessel or reactor, preferably as a dry powder, although slurries could be pumped under certain circumstances. At least one component from group two is added to the mixing vessel or reactor as either liquid reagent or as granular solid materials. The group one and group two components can also be combined to form a reagent before the reagent is mixed with the hazardous waste materials. In a preferred embodiment, the group one and group two components are combined to form a suspension. The suspension is then contacted with the hazardous waste materials. The ingredients of group one and group two can be added to the hazardous waste materials simultaneously, and they are pre-mixed and added in a single step. Alternatively, the components of group one and two can be added sequentially in a two-step process with either component added first. That is, the two steps may occur in any order. At least one ingredient of group one can be added in step I or step II. Likewise, at least one ingredient of group two can be added in either step I or step II. Enough water may be added to allow good mixing to prevent dust formation, and to permit good chemical reaction. Not too much water is added to solid materials if the treated waste is to pass the paint filter test. In the first step of the instant process, a thorough and uniform mixing of gypsum powder with the solid waste is accomplished by mixing shredded and screened waste particles with small gypsum particles in, for example, a grizzly or other mixing device. The calcium ions from the gypsum powder displace lead from soil complexes and organic micelles present in the contaminated soil and solid waste material The following equations (1) and (2) describe the reaction of leachable lead with gypsum, Pb - Micelle + CaSO 4 · 2 H 2 O -> PbSO 4 Anglesite + Ca - Micelle + 2 H 2 O ( 1 ) Pb ( HCO 3 ) 2 + CaSO 4 · 2 H 2 O -> PbSO 4 Anglesite + CaCO 3 + 3 H 2 O + CO 2 ( 2 ) The reaction of lead with gypsum forms a xe2x80x9chard sulfatexe2x80x9d which crystallizes into mineral species of the barite familyxe2x80x94anglesites and calcium-substituted anglesitesxe2x80x94which are insoluble in water. The solubility product of lead sulfate is 1.8xc3x9710xe2x88x928, indicating that anglesite crystals would continue to develop over the geologic periods. In the second step of the process, the solid waste material as amended with gypsum powder is treated with a phosphate-supplying reagent, such as (for example), phosphoric acid. Upon contact with the soil or solid waste, the phosphate-supplying reagent reacts chemically to immobilize the remaining leachable lead. The phosphate-supplying reagent includes phosphate ion sources having one or more reactive phosphate ions, such as phosphoric acid, trisodium phosphate, a potassium phosphate and monobasic or dibasic calcium phosphates. The quantity of phosphate-supplying reagent employed will vary with the characteristics of the solid waste being treated, including particularly such factors as leachable lead content, total lead, and buffering capacity, among other factors. It has been determined that in most instances a quantity of phosphoric acid up to 30 percent of the weight of the waste material is sufficient. The concentration of phosphoric acid in solution will typically range from about 2 to 75 percent by weight. The solution and treatment process are maintained above 30xc2x0 F. to permit the handling of the phosphoric acid as a liquid reagent. Below 30xc2x0 F., the phosphoric acid tends to gel while water freezes to form ice, thus creating material handling problems. Free lead, along with calcium ions found in the solid waste (including those imparted through the first step of the process), reacts with the phosphate to form insoluble superhard rock phosphates or calcium substituted hydroxy lead Apatites as shown in Equations (3a) and (3b): 4 PbCO 3 + CaCO 3 + 3 H 3 PO 4 -> Pb 4 Ca ( OH ) ( PO 4 ) 3 Hydroxy xe2x80x83 Lead Apatites + 5 CO 2 + 4 H 2 O ( 3 a ) 4 PbCO 3 + CaSO 4 · 2 H 2 O + 3 H 3 PO 4 -> Pb 4 Ca ( OH ) ( PO 4 ) 3 Hydroxy xe2x80x83 Lead Apatites + H 2 SO 4 + 4 CO 2 + 5 H 2 O ( 3 b ) The phosphate ions are added to the contaminated soils in solution form; for example, phosphoric acid may be added to water in amounts ranging from about 2 percent to about 75 percent by weight. Phosphoric acid decomposes carbonates and bicarbonates in wastes leading to the synthesis of Apatites and evolution of carbon dioxide gas. Destruction of carbonates and bicarbonates contributes to desirable volume reductions. Although water molecules are generated during the carbonate and bicarbonate decomposition process, it is preferred to have soil moisture at about 10 percent to about 40 percent by weight of the soil in order to accelerate the fixation of the leachable lead with the phosphate ions. At this moisture range, material handling is also easy and efficient. It is apparent from Equations (2), (3a) and (3b) that gypsum and phosphoric acid decompose carbonates and bicarbonates during synthesis of new stable minerals of the barite, apatite, and pyromorphite families in soils (as shown in Table I). Decomposition of carbonates and bicarbonates is usually associated with the evolution of carbon dioxide, formation of hydroxyl group, (OHxe2x80x94), and the release of water molecules. As the water evaporates and carbon dioxide molecules are lost to the atmosphere, the treated waste mass and volume are decreased significantly. The solid sulfate powder and the phosphate-supplying reagent are added to contaminated soil and solid waste material having a typical moisture content ranging from about 10 percent to about 40 percent by weight. At a moisture level within the foregoing range, the curing time of the treated materials is approximately 4 hours, which provides adequate time for chemical reactions to occur and immobilize the leachable lead species. Crystals of various lead mineral species begin to form immediately, but will continue over long time periods with an excess of treatment chemicals present. This contributes to xe2x80x9cself-healing,xe2x80x9d as noted during treatability studies as well as fall scale treatment operations. Under the foregoing conditions, the immobilization of leachable lead occurs in a relatively dry environment because no wet byproducts, slurries or wastewater are produced by the process of the present invention. Operation of the process under relatively dry conditions beneficially allows cost-efficient handling of the contaminated soils and the waste materials. This allows compliance with Paint Filter Test for solid wastes required by USEPA and RCRA approved solid waste landfill facilities. Effective mechanical mixing, as by a pug mill or other such mixing device, eliminates the need for diffusion in the nonaqueous solid waste matrix. The water resistant and insoluble lead minerals synthesized in soils and solid wastes according to this process are stable, and would behave like naturally occurring rock phosphates and hard sulfates. A list of these synthetic lead mineral species and complexes is presented in Table I below, in order of the relative abundance found during characterization of treated soil by x-ray florescence spectrometry, polarized light microscopy (PLM) and scanning electron microscopy (SEM). Some of the chemical reactions that occur during the curing stage, and lead to the development of mixed minerals containing both sulfates and phosphates, are illustrated in Equations (4) and (5). 18 PbCO 3 + 5 CaSO 4 · 2 H 2 O + 12 H 3 PO 4 → Cure xe2x80x83 Time xe2x80x83 = xe2x80x83 4 xe2x80x83 hrs . xe2x80x83 under xe2x80x83 Ambient Temperature xe2x80x83 ( greater than 30 xc2x0 xe2x80x83 F . ) and xe2x80x83 Pressure xe2x80x83 20 Ca 0.1 Pb 0.9 ( PO 4 ) 0.5 ( SO 4 ) 0.25 Mixed xe2x80x83 Calcium xe2x80x83 Lead Phosphate xe2x80x83 Sulfate + Ca 3 ( PO 4 ) 2 + 18 CO 2 + 28 H 2 O ( 4 ) 6 Pb [ Humus ] + 2 CaSO 4 2 H 2 O + 3 H 3 PO 4 xe2x80x83 → Cure xe2x80x83 Time xe2x80x83 = xe2x80x83 4 xe2x80x83 hrs . xe2x80x83 under xe2x80x83 Ambient Temperature xe2x80x83 ( greater than 30 xc2x0 xe2x80x83 F . ) and xe2x80x83 Pressure xe2x80x83 Ca ( 9 H ) [ Humus ] · Pb 3 ( PO 4 ) SO 4 Organo - Lead xe2x80x83 Phosphate xe2x80x83 Sulfate + 2 H 2 O + Ca 0.3 Pb 0.7 SO 4 Anglesite + Ca 0.7 Pb 2.3 ( PO 4 ) 2 Pyromorphite ( Ca xe2x80x83 substituted ) ( 5 ) The process of the present invention beneficially decreases the volume of the waste materials through: (i) the evolution of carbon dioxide during the chemical decomposition of carbonates and bicarbonates, upon reaction with the acidic components in gypsum and phosphoric acid, and (ii) hardening and chemical compaction as a result of the synthesis of new minerals which result in changes in interstitial spaces and interlattice structures. Applications of the process on a lead contaminated soil was associated with pore space decrease from 38.8% to 34.3% by volume. A decrease in pore space was associated with increased compaction of the treated soils and a decrease in overall waste volume ranging from 21.4% to 23.0%. For different waste types, the volume decrease varies with the amount of treatment chemicals used in the process. In another lead toxic solid waste, application of this process resulted in a volume decrease of the order of 36.4% while decreasing the leachable lead to levels below the regulatory threshold. This reduction in volume of the contaminated soil and the solid waste material makes the process of the present invention particularly beneficial for off-site disposal in a secured landfill by cutting down the costs of transportation and storage space. The process can be accomplished at a cost-efficient engineering scale on-site or off-site for ex-situ treatment of lead-toxic solid wastes. This innovative treatment technology also offers a great potential for in-situ application to immobilize lead most economically without generation of any wastewater or byproducts. FIG. 3 illustrates schematically the process of the present invention. The lead-contaminated uncontrolled hazardous waste site 10 with lead-toxic wastes is subject to excavation and segregation 20 of waste piles based on their total lead and TCLP lead contents into (a) heavily contaminated pile 30A, (b) moderately contaminated waste pile 30B and (c) least contaminated waste pile 30C. The staged soil and solid waste material in piles 30A, 30B and 30C is subjected to grinding, shredding, mixing and screening 50 through an appropriately sized mesh sieve. The screening yields particles that are usually less than 5 inches in diameter for mixing with gypsum powder 40 in a grizzly 65 that allows a uniform coating of gypsum over the soil particles and waste aggregates during the grinding, shredding and/or mixing step. Alternatively, as shown by the dashed line, gypsum powder 40 may be added continuously to the screened solid waste material in prescribed amounts as determined during treatability trials. Most of the leachable lead binds chemically with gypsum at molecular level to form lead sulfate, which crystallizes into a synthetic nucleus of mixed calcium anglesite and pure anglesite minerals identified in the treated material by chemical microscopy techniques. The gypsum-coated waste particles and aggregates are then transported on a belt conveyor 70 or other conveying means to an area where an effective amount of phosphoric acid solution 80 of specified strengths in water 90 is added or sprayed just prior to thorough mixing in a pug mill 100 (or other mixing means). The temperature of the phosphoric solution is preferably maintained above 30xc2x0 F. to prevent it from gelling. The treated soil and wastes are subject to curing 110 and drying 120 on a curing/drying pad, or may less preferably be cured and dried using thermal or mechanical techniques. The end product of the process passes the Paint Filter Test. During the curing time of about four hours, various xe2x80x9csuper-hard phosphatexe2x80x9d mineral species, such as calcium-substituted hydroxy lead-Apatites and mixed calcium-lead phosphate-sulfate mineral species, are formed in treated waste media 130. Crystals of these mineral species (in early stages of development) have been identified in the treated soil materials and solid wastes by geo-chemical and microscopy techniques like PLM and SEM. The proportions of waste materials and reagents used in the process may be varied within relatively wide limits. For example, the amount of gypsum powder should be sufficient to produce lead sulfate in contaminated solid or solid waste material. In addition, the amount of phosphate-supplying reagent is prescribed in an amount sufficient to produce mineral species such as hydroxy-lead apatite in contaminated soil or solid waste material during a relatively short curing time of 4 hours, usually ranging from about 3 to about 5 hours. Further drying of the treated material may take 24 to 96 hours, but has not been required in any application to date. Table II documents the optimum curing time of 4 hours for the process. In all instances, the leachable lead as measured by the EP Toxicity Test Procedure was found below 0.6 mg/l and the differences between analytical values below this level and statistically insignificant. The amount of the gypsum powder and the phosphoric acid employed will be dependent on the amount of contaminant present in the soil, initial characteristics of the solid waste material, whether the material is in-situ or is excavated and brought to an off-site facility for treatment; the same is true for other sulfate compounds and phosphate reagents. The following Example I describes various ratios of the chemical reagents for application to the excavated lead-contaminated solid wastes in order to render the leachable lead substantially insoluble; i.e., to reduce the leachable lead to levels below 5.0 mg/l by EP Toxicity Test lead and TCLP Test criteria now in force under current land-ban regulations, When the present invention is used to treat radionuclides and other radioactive materials, the amounts of treatment chemicals added are a function of the contaminated host matrix geochemistry, the concentration of radionuclides in the host matrix, and the presence of potential interferences that could inhibit the reactions, and the geotechnical properties of the host material. A preferred rate of TGPA addition is in the range of 0.1 to 20% by weight of the matrix to be treated. Preferred water content will also vary with the characteristics of the host material to be treated, but should be in the range of 5% to 50% by weight. Water content may affect the rate of reaction with lower water content requiring longer reaction periods and increased need for supplemental mixing. Higher water content, on the other hand, may adversely impact subsequent material handling, and volume reduction results. Water supplied to an excess will yield a material that will contain free liquids. In these cases, the treated material should be allowed to react for a longer period of time to permit a decrease in moisture content by capillary drying and/or evaporation. In some instances, dewatering or other drying techniques may be used to form a material that contains no free liquids. When TGPA is not utilized as the group two treatment chemical reagent, other compounds that provide soluble phosphates, or phosphates that can be solubilized may be substituted. The phosphates may be applied in a liquid form or as a solid. Prior to employing the process of the present invention at a site, laboratory tests should be conducted to determine the amounts of group one and group two treatment chemicals that will be needed for the contaminated matrix that is to be treated. Identification of carbonates, borates, sulfates, silicates and/or phosphates in the host material will facilitate the selection of the optimum quantities of treatment chemicals. Ambient temperature and pressure may be used for the disclosed treatment process, permitted the operations of the feeding and mixing equipment allow such. Under sub-freezing conditions, phosphoric acid may be heated to 50xc2x0 F. to prevent it from gelling and in order to keep it in a pumpable viscosity range. The treatment may be performed under a batch or continuous system of using, for example, a weight-feed belt or platform scale for the metal-hazardous waste materials and a proportionate weight-belt feed system for the dry ingredient or ingredients and powders of at least one of the groups. A metering device, e.g., pump or auger feed system, may instead, or additionally, be used to feed the ingredients of at least one of the groups. The same equipment used for treating metal-hazardous waste material is used for treating soils and waste materials contaminated with radionuclides and other radioactive substances. Single Step Mixing of Treatment Chemicals A lead contaminated soil from a battery cracking, burning, and recycling abandoned site was obtained and treated with group one and group two chemicals in one single step at bench-scale. The contaminated soil contained total lead in the range of 11.44% to 25.6% and TCLP lead in the ranged of 1781.3 mg/l to 3440 mg/l. The bulk density of contaminated soil was nearly 1.7 g/ml at moisture content of 10.3%. The contaminated soil pH was 5.1 with an oxidation reduction potential value of 89.8 mV. To each 100 g lot of lead hazardous waste soil, sufficient amounts of group one and group two treatment chemicals and reagents were added as illustrated in Table III, in order to render it nonhazardous by RCRA (Resource Conservation and Recovery Act) definition. It is obvious from TCLP lead analyses of fifteen test runs that the single step mixing of at least one component of either or both group one and group two treatment chemicals is very effective in diminishing the TCLP lead values. In test run I, mixing of lime and gypsum from group one additives and phosphoric from group two decreased the TCLP lead to levels below 1 mg/l from 3440 mg/l with a curing time of less than 5 hours. Although the treatment chemicals of group two are more effective in decreasing the TCLP lead than the treatment chemicals of group one, as illustrated by the comparison of test runs XII and XV for this waste soil, but the combined effect of both groups is even more pronounced in decreasing the leachable lead. Results of these bench-scale studies were confirmed during engineering-scale tests. Single step mixing of 5% lime, 11.76% phosphoric acid and 15% water in a 2000 g hazardous soil diminished the TCLP lead values form 3440 mg/A to 0.77 mg/l in less than 5 hours. Likewise, single step mixing of 300 g Triple Super Phosphate (TSP), 200 g Portland Cement (PC) and 300 ml water in 200 g hazardous soil decreased the TCLP lead to levels below 0.3 mg/l within a relatively short curing time. Single step nag of both groups of treatment chemicals can dramatically reduce treatment costs making this invention highly attractive and efficient for commercial use. The first advantage of using lime and phosphoric acid combination over the use of TSP and PC is that in the former a volume decrease of 6% was realized when compared to the original volume of untreated material. In the later case, a volume increase of 37% was measured due to hydration of cement. The second advantage of using phosphoric and lime combination is that the mass increase is less than the mass increase when TSP and PC are added. Quantitatively, the mass increase in this hazardous waste soil treatment was approximately 16.7% due to combination of lime and phosphoric whereas the mass increase was about 40% due addition of TSP and PC. And therefore, those skilled scientists and engineers learning this art from this patent, must make an economic judgment for each lead contaminated process material and waste stream which chemical quantity from each group would be most effective in rendering the treated material non-hazardous. The third advantage in using lime and phosphoric over the use of TSP and PC is that the former does not change in physical and mechanical properties of original material and if a batch fails for shortage of treatment chemicals, it can be retreated rather easily by adding more of the treatment reagent. The material treated with PC hardens and may form a monolith which is difficult to retreat in case of a batch failure. In the lead contaminated soil from the abandoned battery recycling operations, the treatment chemicals of either group can be added first and mixed thoroughly in an amount sufficient to decrease the TCLP lead below the regulatory threshold. Two step mixing method of the group one and group two treatment additives is as effective as single step mixing of same quantity of treatment chemicals selected from group one and group two. Table IV illustrates data that confirm that the application of group one treatment chemicals in step I is about as effective as application in step II. The same is true for group two treatment chemicals. Thus, the two steps are essentially interchangeable. The reversibility of the steps according to the present invention make it very flexible for optimization during commercial use, scaling up and retreatment of any batches that fail to pass the regulatory threshold criteria. A sample of hazardous cracked battery casings of xc2xdxe2x80x3-1xe2x80x3 size containing 14% to 25.2% total lead and about 3298 mg/l of TCLP was obtained for several test runs of the invention to verify the retreatability of batches that fail because of the insufficient dose of treatment chemical added. The results of initial treatment and retreatment are presented in Table V and compared with single step mixing treatment additives from both groups. About 200 g of hazardous material was treated with 10.5% phosphoric acid, 2.5% gypsum and 1.25% lime, all mixed in one single step. The TCLP lead was decreased from 3298 mg/l to 2.5 mg/l as a result of single step mixing in test run V (TABLE V). When the amount of additive from group two was less than the optimum dose needed, the TCLP lead decreased from 3298 mg/l to: (i) 1717 mg/l when 4.2% phosphoric and 1% lime were added during step I and II respectively, and (ii) 2763 mg/l when 4.2% phosphoric and 5% gypsum were added, compared to untreated control. Since the TCLP lead did not pass the regulatory criteria of 5 mg/l, treated material from test runs I and II were retreated during test runs III and IV, respectively, using sufficient amounts to phosphoric acid (an additive from group two) in sufficient amount to lower the TCLP lead to 2.4 mg/l and 2.5 mg/l, respectively. Furthermore, this example confirms that lime is more effective in decreasing TCLP lead than gypsum among different additives of group one. And as a result, the requirement of group two treatment reagent is lessened by use of lime over gypsum. The example also illustrates that one or more compounds of the same group can be used together to meet the regulatory threshold limit. TABLE VI illustrates different types of waste matrix that have been successfully treated employing the one step and two step mixing treatment additives from group one and group two. For these diverse waste types and process materials, total lead ranged form 0.3% to 23.5%. This example discloses the flexibility and dynamics of the treatment process of the invention in rendering non-hazardous, by RCRA definition, a wide range of lead-hazardous and other metal-hazardous materials within a relatively short period of time, usually in less than 5 hours. It is expected that this process will also render bismuth, cadmium, zinc, chromium (III), arsenic (III), aluminum, copper, iron, nickel, selenium, silver and other metals also less leachable in these different types of wastes. The moisture content of the waste matrix is not critical and the invented process works on different process materials and waste types independent of the moisture content. The treatment operations can be carried out at any levelxe2x80x94bench, engineering, pilot and full-scalexe2x80x94on relatively small amounts of hazardous waste material in laboratory to large amounts of contaminated process materials, soils, solid wastes, waste waters, sludges, slurries and sediments outdoor on-site. The process is applicable in-situ as well as ex-situ. Nearly twenty (20) different chemicals and products from various vendors and supply houses were screened for chemical fixation of leachable lead in hazardous solid waste samples. Only six (6) of these treatments chemicals were found effective in decreasing the leachable lead as measured by: (1) the EP Toxicity Test and (2) the TCLP Test. Table VII presents a summary of if leachable lead found in untreated and treated waste samples allowed to cure for a minimum of 4 hours after treatment with at least one of the effective chemicals. Treatment chemicals found relatively ineffective for lead fixation included a variety of proprietary products from American Colloid Company and Oil Dri, different sesquioxides like alumina and silica, calcium silicate, sodium silicate, Portland cement, lime, and alum from different vendors. Results for these ineffective chemicals are not shown in Table VII. Evaluation of a single treatment chemical in one step reveals that phosphoric acid was most effective in fixation of leachable lead followed by granular super-phosphate, a fertilizer grade product available in nurseries and farm supply houses. However, neither treatment effectively treated leachable lead to the USEPA treatment standard of 5.0 mg/l by TCLP methodology. Although both phosphoric acid and granular superphosphate were effective in meeting the now obsolete EP Toxicity Test criteria at 5.0 mg/l, this test has been replaced by TCLP Test criteria for lead of 5.0 mg/l. Single application of the phosphoric acid, granular superphosphate or any other chemical was short of meeting the regulatory threshold of 5.0 mg/l by TCLP Test criteria for lead. In a two-step treatment process, application of gypsum during Step I and treatment with phosphoric acid in Step II resulted in decrease of TCLP-lead consistently and repeatedly below the regulatory threshold of 5.0 mg/l. The results of this two-step treatment process utilizing gypsum in Step I and phosphoric acid in Step II are most reliable and hence, the two-step process may be applied to a wide variety of lead contaminated wastes as exhibited in Example II. A three-step process, as set forth in Table VII, was not perceived to be as economically viable as a two-step treatment process, despite its ability to reduce lead levels in satisfaction of the TCLP Test criteria. A process that employees the beneficial combination of treatment first with a sulfate compound and then with a phosphate reagent in accord with the present invention, in combination with one or more additional treatment steps, may nevertheless be within the scope of the invention. In order to illustrate the relative proportions of two chemicals, e.g., gypsum and phosphoric acid, needed for treatment of lead-toxic wastes, three soil samples from a lead contaminated test site were processed using the present invention, in which gypsum powder was used in the first step, and phosphoric acid solution in water at concentrations of about 7, 15 and 22 percent by weight in the second step. The soil was measured for lead content in accordance with the EP Toxicity Test before and after treatment. A level of leachable lead below 5 mg/l was considered non-hazardous according to this procedure. During these test runs, the EP Toxicity Test criteria were in force for treated waste material. The results of these tests are set forth in Table VIII: The foregoing results demonstrate that the process of the present invention was effective in all three samples, representing 3 different levels of lead contamination. The process is flexible and is usually optimized during bench scale treatability studies for each waste type to immobilize the leachable lead and to decharacterize or transform the lead-toxic waste into non-toxic solid waste acceptable to TSD facilities under current land ban regulations. A net reduction of 36.4% in waste volume through use of the instant process has been observed. Typical volume reductions are set forth in Table IX. The most profound effect of the process of the present invention is at a structural level, where the break-down of granular aggregates is associated with a loss of fluffiness and a decrease in pore space and increased compaction due to physical, mechanical and chemical forces at different levels. At a molecular level, phosphoric acid breaks down the minerals containing carbonates and bicarbonates, including cerussites, in stoichiometric proportions. Soon after the addition of phosphoric acid to a solid waste containing cerussites, extensive effervescence and frothing becomes evident for several minutes and sometimes for a few hours. The phosphoric acid breaks down the acid sensitive carbonates and bicarbonates leading to the formation of carbon dioxide, water and highly stable and insoluble sulfate and phosphate mineral compounds. Thus, structural changes due to interlattice reorganization as well as interstitial rearrangement in waste during processing are associated with an overall decrease in waste volume. Depending on the extent of carbon dioxide loss from the breakdown of carbonates and bicarbonates present in the lead-toxic solid waste, the process may lead to a slight loss of waste mass as well. Water generated during the chemical reactions is lost by evaporation, which further decreases the mass and volume of the treated solid wastes and soils. The cost of the process of the present invention is moderate to low, depending upon (i) waste characteristics, (ii) treatment system sizing, (iii) site access, (iv) internment of final disposition of treated material and (v) site support requirements. The costs of treatment and disposal are presently on the order of $115 per ton of lead-toxic waste, as compared to off-site conventional treatment and disposal costs of over $250 per ton if no treatment in accord with the invention had been performed. Moreover, recent land ban regulations would prohibit the disposal of all lead-toxic wastes in landfills. The foregoing Example makes clear that the process of the present invention provides an efficient technology that is economically attractive and commercially viable in meeting regulatory criteria for landfills. The process of the present invention was applied on bench scale to five different lead-toxic waste materials that were characterized for total lead, TCLP-lead, moisture content and pH before and after treatment. A curing time of 5 hours was allowed for completion of the treatment process. The results compiled in Table X exhibit the profound effects of the process in decreasing the TCLP lead in a wide range of lead-toxic soils and solid wastes containing total lead as high as 39,680 mg/kg and TCLP lead as high as 542 mg/l. In each of the five cases, the instant process immobilizes the leachable lead to levels below the regulatory threshold of 5 mg/l set by the TCLP Test criteria for lead currently in force under the land ban regulations of the United States Environmental Protection Agency. It is obvious from Table X that the instant process operates over a wide range of moisture and pH conditions. It is associated with 8 to 11% rise in moisture content. The end product of the treatment process may contain moisture in a typical range of 18% to 36% on a dry weight basis. The end product passes the Paint Filter Test for solids and there are not other byproducts or side streams generated during the process. The treated solid waste is cured in 4 to 5 hours and may be allowed to dry for 2 to 3 days after treatment for loss of unwanted moisture prior to final internment and disposition. This time is sufficient for the TCLP Tests to be completed as part of the disposal analysis under land ban regulations enforced by the USEPA. It is necessary to establish the quantities of gypsum and phosphate reagent on a case-by-case basis, because the consumption of these materials will depend not only upon the initial lead level in the waste or soil, but also upon other waste characteristics such as cation exchange capacity, total buffering capacity, and the amounts of carbonates and bicarbonates present, among others. Bench scale treatability studies for each solid waste considered will be necessary to determine the optimum levels of the materials that are employed. The treatability studies are designed to optimize the amount and grade of gypsum powder (or other sulfate compound) needed during step I, and the amount and concentration of phosphoric acid (or other phosphate compound) needed in step II for cost-effective operation of the treatment system. Those skilled in the art are knowledgeable of such bench studies, which are usually carried out as precursors to full scale treatment. Several series of studies were performed on host matrices containing leachable and soluble radionuclides and other radioactive substances using the present invention. Sample material from a site in the eastern United States was homogeneously mixed in a container. The material consisted of silts, clays, sand and gravel mixed with glass, nails, rocks and debris. The material was collected from an environmental restoration project where site efforts focused on excavation, packaging, transportation and disposal of Thorium contaminated soil and materials from beneath residential homes. Three 300 g sub-samples of untreated material were prepared from the sample material with the materials in each of the sub-samples sized to less than xe2x85x9c inch and suitable for USEPA SW-846 Method 1311 (TCLP) extraction. Sample 1 (US-1) was extracted using TCLP fluid No. 1, Sample 2 (US-2) was extracted using TCLP fluid No. 2, and Sample 3 (US-3) was extracted using laboratory grade deionized (xe2x80x9cDIxe2x80x9d) water as the only modification to the EPA method. This soil characterization step was conducted for purposes of determining the most harsh extraction conditions for the untreated material. TCLP fluid No. 1 was prepared with glacial acetic acid and 1N NaOH with an end pH of 4.93+/xe2x88x920.05 S.U. TCLP fluid No. 2 was prepared with glacial acetic acid and deionized water with an end pH of 2.88+/xe2x88x920.05 S.U. The laboratory grade DI water had a pH of 6.82+/xe2x88x920.05 S.U. After tumbling 100 g of the 300 g sub-sample in 200 ml of extraction fluid for eighteen (18) hours at 30+/xe2x88x922 rpm in a longitudinal rotary TCLP agitator, the extracts were decanted from the settled solids, filtered as per the method, and then placed in Marinelli containers. Radionuclide leachability was determined by conducting total gamma spectroscopy analysis on each extract in accordance with accepted quantification methods using a Nuclear Data Genie Model ND9900 Gamma Spectrometer integrated with a DEC Micro VAX II computer. Each extract was counted for sixteen (16) hours. All results presented below are in the units of picocuries per liter (pCi/l). As shown by the gamma spectral analysis of each extract, TCLP fluid No. 2 was identified as the most rigorous extraction fluid for the soil material, primarily because of leachable Thorium and Uranium levels. This fluid was then selected to be used for extraction of the treated samples for the remainder of the studies. In the second portion of the study, two (2) 300 g samples were prepared from the eastern U.S. sample material and labeled as TS-1 and TS-2. Each sample was placed in a laboratory beaker and 35 ml of deionized water and 5% (TS-1) and 10% (TS-2) by weight TGPA were added. The contents in each of the beakers were then mixed by folding with a laboratory spatula in order to simulate blending achievable using full-scale methods in the field. The samples were then allowed to react overnight. Each beaker was then sub-sampled, material particles sized to less than xe2x85x9c inch, and prepared for USEPA SW-846 Method 1311 (TCLP) extraction using 100 g of treated sub-sample material and 2000 ml TCLP Fluid No. 2. Table XII presents the data from the gamma spectral analysis with all units reported as pCi/l. The results from Table XI for untreated materials extracted using TCLP Fluid No. 2 were used as a control and are shown in the fourth column. As indicated by the data from Tables XI and XII, TGPA substantially reduces the leachability of radionuclides in soil as determined by USEPA SW-846 Method 1311 (TCLP) extraction with fluid No. 2 and gamma-spectral analysis of resultant extract. It should be noted that the soil sample materials were not sized to less than xe2x85x9c inch until after the TGPA and deionized water were mixed and allowed to cure overnight. The leaching of Thorium, its decay-daughters, and other radionuclides from untreated material was effectively reduced by the addition of TGPA to the material. The treated material was moist after curing overnight, but contained no free liquids. After exposure to the air for forty-eight (48) hours, the treated material was dry and crumbly with nonuniform cohesivity. Volume reduction was observed, but not quantified. In another study, samples of the untreated material used in Example 7 were mixed with TGPA and other compounds. For this study, gypsum, calcium oxide, triple superphosphate (TSP), and TGPA were selected based upon a generally desired pH range of the end product. Four 300 g samples were prepared: TS-3=35 ml DI water+8% gypsum+5% TGPA; TS-4=35 ml DI water+9% calcium oxide+8% TGPA; TS-5=35 ml DI water+3% calcium oxide+5% TGPA; and TS-6=45 ml DI water+10% TSP+1.6% calcium oxide. Treatment samples received variable amounts of water so that after mixing, the consistency of the mixtures was uniform for all of the samples and there were no free liquids. The water assisted in the dispersement of the reagent and calcium oxide hydration; and hence, the disassociation of the phosphate to a soluble form. Additional water was required in TS-6 because of the solid reagent forms and the hydration demand of CaO in the presence of dry TSP. Table XIII presents the data from USEPA SW-846 Method 1311 (TCLP) extracts of TS-3, TS-4, TS-5, and TS-6 analyzed by total gamma-spectroscopy in accordance with procedures outlined in Example 7. All samples were analyzed with TCLP fluid No. 2 (acetic acid+water with a pH of 2.88+/xe2x88x920.05 S.U.). As evidenced by the data, the treatment regimes utilizing gypsum+TGPA, calcium oxide+TGPA, and triple superphosphate (TSP)+calcium oxide resulted in the reduction of nuclide leachability. Each of the treatment regimes provided soluble phosphates, or phosphates that were solubilized by pH manipulation in the presence of a fluid. Each of the treatments resulted in the formation of Apatites within the host material, with mineral crystal nucleation chemically incorporating the radionuclides. The tests in Example 9 were performed to study the volume change of materials treated by the process of the present invention. In Example 9, soil volume was examined prior to and after the addition of TGPA. Because of the difficulty in examining volume changes due to varied conditions, geometric configuration, and chemical properties of material differing between pre- and post-treatment, a special device was constructed to account for changes in density, moisture content, and geotechnical properties. The test apparatus used for measuring the volume consisted of a removable stainless steel cylindrical cup with a flat bottom (xe2x80x9cthe cupxe2x80x9d). The cup had a 10.3 cm inside diameter and a 29.6 inside height and mounted vertically to the base of the test apparatus. Mounted above the cup on the apparatus frame was a pneumatic piston with a 1.4 cm thick plate fixed to the piston shaft. When activated with compressed air, a 10.2 cm diameter close-tolerance plate fixed to the piston shaft extended downward and into the open end of the cup. Compressed air operated the piston and was adjusted with a valve so that from 1 to 100 psi could be exerted on soil placed within the cup. The untreated material from Example 7 was used to prepare ten aliquots (of approximately 100 g) which were individually weighed using a top-loading electronic balance (+/xe2x88x920.01 g). The ten aliquots were then sequentially emptied into the cup. After the addition of each 100 g aliquot, the cylindrical cup was placed in the apparatus and the piston activated to exert a pressure of 10 psi on the soil column. This procedure was repeated until all ten long aliquots had been added and compacted. The height of the soil column was then determined by measuring from the top of the cup to the top of the plate, correcting for the plate thickness, and subtracting the total from the inside height of the cup. The untreated material was then removed from the cup and placed in a laboratory beaker. Care was taken to ensure all visible material was removed and transferred. Water was added to the beaker on a weight basis equal to 12% of the untreated material. TGPA was then added at a dose of 5%, also by weight, of the untreated material. The untreated material and amendments were mixed with a laboratory spatula by folding and allowed to sit overnight. The treated material was then removed from the beaker and placed in the cylindrical cup in ten stages of approximately 100 g each. The pneumatic piston was activated at the same 10 psi pressure each time treated material was added to the cup. After all of the treated material was transferred and compacted with the apparatus, the resultant column height was calculated as previously described. After the material had been allowed to sit for approximately seven (7) days, the volume test was performed again in the same manner. The results of the study are presented in Table XIV. These test results show a total volume reduction of 9.75% after 24 hours and 22.4% after 7 days, relative to the initial untreated material. In the next series of studies, sample material from a site in the Midwestern United States was utilized in treatability studies. The material contained small soil grains (with 100% passing through a 9.5 mm sieve) and was comprised of 30% sand, 47% silt, and 23% clay as determined by ASTM D-422 (Particle-Size Distribution). The average density of the material was 1.43 g/cc and the material had a moisture content of 16 percent by weight and a pH of 6.0 S.U. As in the previous examples, the sample material was characterized for radionuclides and other radioactive substances. Nuclide leachability was examined utilizing the Toxic Characteristic Leaching Procedure (TCLP) extraction procedure (USEPA SW-846, Method 1311). Material was also subjected to other leaching tests including the Synthetic Precipitation Leaching Procedure (SPLP) extraction procedure (USEPA SW 846, Method 1312), and a modified version of the TCLP extraction method, where deionized water was substituted for the extraction fluid (DI/TCLP). Results of the gamma-spectral, Uranium, and Technetium-99 characterization analyses on extraction fluids are presented in Table XV. In this example, four 400 g samples of soil material (TS-7, TS-8, TS-9 and TS-10) were prepared from the untreated Midwestern U.S. sample material and placed in separate laboratory beakers. Sample TS-7 was used as a control and mixed only with 120 ml of deionized water. For each of the three other samples, 120 ml of deionized water and varying amounts of TGPA were added to each beaker and mixed until a uniform consistency was achieved: TS-8=120 ml DI water+3% (wt.) TGPA; TS-9=120 ml DI water+5% (wt.) TGPA; and TS-10=120 ml DI water+10% (wt.) TGPA. When the mixing was completed, no free liquids were present. After sitting overnight, a 100 g sample of treated material was removed from each beaker and extracted by USEPA SW-846, Method 1311 (TCLP), using Fluid No. 2, to simulate exposure to acidic landfill leachate. The radionuclide leachability for each extract was then quantified by gamma spectroscopy. Total Uranium and Technetium-99 tests were also conducted. Uranium-238 was calculated, assuming the total Uranium present was 100% depleted. The levels of leachable radionuclides and other radioactive substances in the sample material after treatment are presented below in Table XVI. The results in Table XVI can be compared to the results for sample US-4 in Table XV for reference. 100 g samples of material treated in Example 10 (TS-7, TS-8, TS-9 and TS-10) were sub-sampled, extracted and analyzed by USEPA SW-846, Method 1312 (SPLP), where the extraction fluid utilized simulated acid rain. Each extract was then quantified for radionuclides by gamma-spectroscopy, and total Uranium and Technetium-99 tests were conducted. Uranium-238 was calculated, assuming the total Uranium present was 100% depleted. The results of the leachable radionuclides and other radioactive substances in the soil after treatment are presented below in Table XVII. The results in Table XVII can be compared to the results for sample US-5 in Table XV for reference. 100 g samples of treated soil material in Example 10 (TS-7, TS-8, TS-9 and TS-10) were subsampled and extracted by USEPA SW-846, Method 1311 with laboratory grade deionized water substituted for the extraction fluid. Although material treated by the invention would never likely be exposed to similar fluid except in the laboratory settings, deionized water is considered by many to be a harsh extraction test as leachable ionic species will tend to diffuse from zones of high concentration to zones of low concentration. Each DI water extract was then quantified for radionuclides by gamma-spectroscopy, and total Uranium and Technetium-99 tests were conducted. Uranium-238 was calculated, assuming the total Uranium present was 100% depleted. The results showing the level of leachable radionuclides and other radioactive substances in the soil after treatment are presented below in Table XVIII for TS-7, TS-8, TS-9 and TS-10. The results in Table XVIII can be compared to the results for sample US-6 in Table XV for reference. Examples 13 and 14 demonstrate additional uses for the present invention. Sample material and RGW for Examples 13 and 14 were obtained from the Midwestern United States site. To establish baseline untreated characterization data, RGW and soil+RGW samples were tested for radionuclides and other radioactive substances using SPLP and RGW/TCLP extraction methods, prior to adding TGPA to the sample material. The following tests were performed: 1) RGW was tested for total radionuclides and other radioactive substances (US-7); 2) RGW was mixed into the sample material at 30% (wt.). Radionuclides and other radioactive substances were examined in the amended sample material""s SPLP extract (US-8); and (3) DI water was mixed into the sample material at 30% (wt.). Radionuclides and other radioactive substances were examined in the amended sample material""s modified TCLP extract where RGW was utilized as the substitute TCLP extraction fluid (US-9). Table XIX presents the baseline data. Previous SPLP extraction test results from the same sample material amended only with DI water (US-5) are presented for comparison. In Example 13, the effects of extracting TGPA treated radioactive sample material containing RGW with USEPA""s simulated acid rain leaching method (SPLP) are presented. In this example, RGW was used as a dispersion agent in place of deionized water. Contaminated sample material (characterized in Table XIX) was mixed with RGW at 30% (wt.). Three (3) equivalent aliquots of the sample material mixed with RGW were placed in separate beakers. In the first beaker, TGPA was added at a dose of 2% (wt.) and mixed (TS-11). In the second beaker, TGPA was added at a dose of 5% (wt.) and mixed (TS-12). In the third beaker, TGPA was added at a dose of 10% (wt.) and mixed (TS-13). The amount of TGPA added was calculated from the base mass of the untreated sample material exclusive of the RGW mass added. Table XX presents the data from the analysis of SPLP extract for each of the treated samples (TS-11, 12, and 13). The untreated characterization data from samples (US-7, and US-8) are presented in Table XIX for comparison. The SPLP extraction (SW-846, Method 1312) is USEPA""s procedure for simulating soil exposure to acid rain. The SPLP method calls for the extraction of 100 g of material with 2000 ml of simulated acid rain fluid. In Example 14, sample materials containing radionuclides and other radioactive substances was treated with varying doses of TGPA and DI water was utilized as a dispersing agent. These treated samples were then extracted using the modified TCLP method (RGW/TCLP) where RGW was substituted for the specified extraction fluid (TCLP Fluid No. 2). The sample material was mixed with DI water and three (3) equivalent aliquots of the material were placed in separate beakers. In the first beaker, TGPA was added at a dose of 2% (wt.) and mixed (TS-14). In the second beaker, TGPA was added at a dose of 5% (wt.) and mixed (TS-15). In the third beaker, TGPA was added at a dose of 10% (wt.) and mixed (TS-16). The percent weight of TGPA added was calculated from the initial base mass of the untreated sample material exclusive of the RGW mass added. Each of the treated samples were then extracted using the RGW/TCLP method with RGW fluid added at the method specified volume and ratio (100 g soil: 2000 ml fluid). Table XXI presents the data from the analysis of the modified RGW/TCLP extract for each of the treated samples (TS-14, 15, and 16). The untreated characterization data from RGW (US-7) and untreated soil extract by RGW/TCLP (US-9) are presented in Table XIX for comparison. Examples 13 and 14 show that the present invention can use radioactive groundwater as a dispersing agent and that materials treated by the present invention can be used to treat RGW. These examples also demonstrate that acid rain will not affect treated material. Example 15 examines the leachability of constituents from a host material based on a calculation of the distribution coefficient (Kd) for a given analyte (e.g., a specific constituent measured by the analyses). The distribution coefficient is expressed in ml/g and calculated as the quotient of the activity of nuclide sorbed per unit mass of host material (expressed in pCi/g), and the activity of the nuclide in extract solution per unit volume of extract (expressed in pCi/ml). Kd is an equilibrium value often calculated to determine the sorption affinity of waste analytes (e.g., nuclides) by host matrix (e.g., contaminated material) in aqueous or other fluid suspensions. In this example, the distribution coefficients are calculated for the untreated (Table XXII) and TGPA treated material (Table XXIII). The same calculations can be made for similar extractions using other extraction fluids such as, deionized water, SPLP or RGW. Tables XXII and XXIII show an increase of the sorption affinity of the radionuclides by the host material as a result of treatment with TGPA. Further, the calculations in Tables XXII and XXIII utilize the MDA values for the equation denominator. The MDA is based on numerous factors, including count times, background, detector efficiency, recovery, decay, and other variables. Therefore, the K values for radionuclides in materials treated with TGPA are actually higher than what can be empirically determined when the nuclide presence in extract is less than MDA. Although the present invention has been described in connection with preferred embodiments, it will be appreciated by those skilled in the art that additions, modifications, substitutions and deletions not specifically described may be made without departing from the spirit and scope of the invention defined in the appended claims. |
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claims | 1. A method for calculating a pellet-cladding interaction margin associated with a loading pattern of a nuclear reactor comprising a core in which fuel assemblies are loaded according to the loading pattern, the fuel assemblies comprising fuel rods each including nuclear fuel pellets and a cladding surrounding the pellets,the method being implemented by an electronic system and comprising the following steps:b) calculating a reference principal pellet-cladding interaction margin for a reference loading pattern of the fuel assemblies in the core,c) calculating a reference secondary pellet-cladding interaction margin for the reference loading pattern,d) calculating a modified secondary pellet-cladding interaction margin for a modified loading pattern of the fuel assemblies in the core,e) calculating a modified principal pellet-cladding interaction margin for the modified loading pattern, depending on a comparison of the modified secondary pellet-cladding interaction margin with the reference secondary pellet-cladding interaction margin;the method further comprising controlling the state of the power balance of the nuclear reactor by using the calculated principal pellet-cladding interaction margin for a considered loading pattern of the fuel assemblies in the core to avoid rupture by pellet-cladding interaction of the claddings present in the core,wherein neutronic calculations and thermodynamic calculations are done to calculate each pellet-cladding interaction margin, andwherein the neutronic calculations and the thermomechanical calculations are coupled to calculate a corresponding principal pellet-cladding interaction margin, the thermomechanical calculations being uncoupled from the neutronic calculations to calculate a corresponding secondary pellet-cladding interaction margin. 2. The method according to claim 1, wherein the method further comprises the following step:f) determining a limit value to trigger an emergency stop and/or an alarm from the calculated principal pellet-cladding interaction margin and for the considered loading pattern of the fuel assemblies in the core. 3. The method according to claim 1, wherein when the modified secondary pellet-cladding interaction margin is greater than or equal to the reference secondary pellet-cladding interaction margin, the modified principal pellet-cladding interaction margin is equal to the reference principal pellet-cladding interaction margin, andwhen the modified secondary pellet-cladding interaction margin is less than the reference secondary pellet-cladding interaction margin, the modified principal pellet-cladding interaction margin is less than the reference principal pellet-cladding interaction margin. 4. The method according to claim 3, wherein, when the modified secondary pellet-cladding interaction margin is less than the reference secondary pellet-cladding interaction margin, the modified principal pellet-cladding interaction margin is equal to the reference principal pellet-cladding interaction margin reduced by a corrective factor depending on the deviation between the modified secondary pellet-cladding interaction margin and the reference secondary pellet-cladding interaction margin. 5. The method according to claim 4, wherein the corrective factor depends on a ratio between the modified secondary pellet-cladding interaction margin and the reference secondary pellet-cladding interaction margin and is strictly between 0 and 1. 6. The method according to claim 1, wherein step b) comprises the following sub-steps:b1) simulating at least one operating transient of the nuclear reactor,b2) calculating the value reached by at least one physical quantity during the operating transient in at least part of a cladding of a fuel rod, andb3) determining, as reference principal pellet-cladding interaction margin, the deviation between the maximum value reached by the value calculated in sub-step b2) during the transient and a technological limit of the fuel rod. 7. The method according to claim 6, wherein the transient simulated in sub-step b1) is a transient chosen from among the group consisting of:an excessive load increase,an uncontrolled withdrawal of at least one group of control clusters,a fall of one of the control clusters, andan uncontrolled boric acid dilution. 8. The method according to claim 6, wherein the method comprises, before step b), the following step:a) determining a rupture value of the physical quantity characterizing a rupture of the cladding. 9. The method according to claim 8, wherein step a) includes:subjecting previously irradiated fuel rods to experimental nuclear power ramps,calculating the values reached by the physical quantity in at least one cladding broken during a power ramp, andselecting the rupture value as being the minimum value from among the calculated values reached. 10. The method according to claim 6, wherein the physical quantity is chosen from among the group consisting of:a constraint or a constraint function in the cladding; anda deformation energy density in the cladding. 11. A non-transitory computer-readable medium including a computer program comprising software instructions which, when executed by a computer, carry out a method according to claim 1. 12. An electronic system for calculating a pellet-cladding interaction margin associated with a loading pattern of a nuclear reactor comprising a core in which fuel assemblies are loaded according to the loading pattern, the fuel assemblies comprising fuel rods each including nuclear fuel pellets and a cladding surrounding the pellets, the electronic system comprising:a first calculating module configured to calculate a reference principal pellet-cladding interaction margin for a reference loading pattern of the fuel assemblies in the core;a second calculating module configured to calculate, on the one hand, a reference secondary pellet-cladding interaction margin for the reference loading pattern, and on the other hand, a modified secondary margin for a modified loading pattern of the fuel assemblies in the core; anda comparison module configured to compare the modified secondary pellet-cladding interaction margin with the reference secondary pellet-cladding interaction margin,the comparison module further being configured to calculate a modified principal pellet-cladding interaction margin for the modified loading pattern, depending on the comparison of the modified secondary pellet-cladding interaction margin with the reference secondary pellet-cladding interaction margin,the electronic system configured for controlling the state of the power balance of the nuclear reactor by using the calculated principal pellet-cladding interaction margin for a considered loading pattern of the fuel assemblies in the core to avoid rupture by pellet-cladding interaction of the claddings present in the core,wherein neutronic calculations and thermodynamic calculations are done to calculate each pellet-cladding interaction margin, andwherein the neutronic calculations and the thermomechanical calculations are coupled to calculate a corresponding principal pellet-cladding interaction margin, the thermomechanical calculations being uncoupled from the neutronic calculations to calculate a corresponding secondary pellet-cladding interaction margin. 13. A method for calculating a pellet-cladding interaction margin associated with a loading pattern of a nuclear reactor comprising a core in which fuel assemblies are loaded according to the loading pattern, the fuel assemblies comprising fuel rods each including nuclear fuel pellets and a cladding surrounding the pellets,the method being implemented by an electronic system and comprising the following steps:a) determining a rupture value of the physical quantity characterizing a rupture of the cladding,b) calculating a reference principal pellet-cladding interaction margin for a reference loading pattern of the fuel assemblies in the core,c) calculating a reference secondary pellet-cladding interaction margin for the reference loading pattern,d) calculating a modified secondary pellet-cladding interaction margin for a modified loading pattern of the fuel assemblies in the core,e) calculating a modified principal pellet-cladding interaction margin for the modified loading pattern, depending on a comparison of the modified secondary pellet-cladding interaction margin with the reference secondary pellet-cladding interaction margin;the method further comprising controlling the state of the power balance of the nuclear reactor by using the calculated principal pellet-cladding interaction margin for a considered loading pattern of the fuel assemblies in the core to avoid rupture by pellet-cladding interaction of the claddings present in the core;wherein step b) comprises the following sub-steps:b1) simulating at least one operating transient of the nuclear reactor,b2) calculating the value reached by at least one physical quantity during the operating transient in at least part of a cladding of a fuel rod, andb3) determining, as reference principal pellet-cladding interaction margin, the deviation between the maximum value reached by the value calculated in sub-step b2) during the transient and a technological limit of the fuel rod;wherein step a) includes:subjecting previously irradiated fuel rods to experimental nuclear power ramps,calculating the values reached by the physical quantity in at least one cladding broken during a power ramp, andselecting the rupture value as being the minimum value from among the calculated values reached;wherein each of steps c) and d) includes, for each fuel assembly, the following sub-steps:i) simulating an evolution of the operation of the nuclear reactor by applying, to the fuel rods, a nuclear power ramp from the nil power,ii) calculating the values reached by a physical quantity in the claddings of the fuel rods,iii) comparing the values reached to the rupture value,iv) determining a power at break equal to:I) the power associated with the rupture value, if a minimum value from among the values reached calculated in sub-step ii) is equal to the rupture value, orII) infinity, if no value, from among the values reached calculated in sub-step ii), is equal to the rupture value,v) evaluating a power margin by difference between the power at break determined in sub-step iv) and an estimated maximum power in the fuel assembly,the corresponding secondary pellet-cladding interaction margin, calculated during each of steps c) and d), being equal to the minimum margin from among the power margins evaluated for the fuel assemblies in sub-step v). |
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description | This application is a Continuation of U.S. patent application Ser. No. 16/517,195, titled, “Thorium Molten Salt System for Energy Generation,” filed on Jul. 19, 2019, which is a Continuation of U.S. patent application Ser. No. 16/517,096, titled, “Thorium Molten Salt Assembly for Energy Generation,” also filed on Jul. 19, 2019. Not applicable. Not applicable. The inventions disclosed and taught herein relate generally to a system for generating power using a Thorium-containing liquid molten salt fuel and, more specifically, an accelerator-driven Thorium molten salt system for generating process heat and/or electricity resulting from nuclear fission reactions. Attempts have been made to provide an accelerator-driven system for the generation of energy using fuel material containing Thorium. To date, such systems have primarily been focused on the use of a solid or molten lead (or other heavy metal) spallation target to generate neutrons used to initiate or sustain nuclear fission reaction and fuel initially comprising of mixtures of Plutonium and Thorium. Examples of such systems are discussed below. Ashley, Coats et. al, “The accelerator-driven Thorium reactor power station,” Energy, Vol. 164, Issue EN3 at 127-135 (August 2011 Issue) discusses an accelerator-driven Thorium reactor in which a particle accelerator injects high-energy particles into a molten lead target to release neutrons via the spallation process. The article indicates that a fissile starter, such as Plutonium from spent fuel, is required, and that the core of the system includes a series of fuel pins, each containing mixed-oxide pellets comprised of Plutonium and Thorium. A similar system is disclosed in Ludewig and Aronson, “Study of Multi-Beam Accelerator Driven Thorium Reactor” (March 2011). U.S. Patent Application Publication No. US2013/0051508, “Accelerator Driven Sub-Critical Core” purports to disclose “a fission power generator [that] includes a sub-critical core and a plurality of proton beam generators” where the generated proton beams “via spallation” generate neutrons for use in the system. The use of heavy metal spallation targets poses several challenges as does the use of fuel initially containing Plutonium or Uranium. The present inventions are directed to providing an enhanced system for energy generation providing benefits over, and overcoming shortcomings of, the systems and methods discussed in the materials referenced above, and other existing systems. A brief non-limiting summary of one of the many possible embodiments of the present invention is: A Thorium fuel rod assembly including first and second support elements; and a plurality of Thorium fuel rods positioned between the first and second support elements, where each Thorium fuel rod includes both (a) an outer fuel element containing a solid Thorium containing material that: (i) is in the general form of a fuel element rod having a longitudinal length; (ii) defines an interior cavity extending along at least a majority of the longitudinal length of the fuel element rod; and (iii) defines a plurality of fins that project radially outwardly; and (b) an inner core element formed from a Beryllium-containing material positioned within the interior cavity defined by the outer fuel element that: (i) is generally tubular in form and has longitudinal length; (ii) has a longitudinal length greater than the longitudinal length of the outer fuel element such that at least a portion of the inner core element extends out of the top of the outer fuel element; and (iii) defines an inner cavity extending along at least a majority of the longitudinal length of the inner core element. In this example, the outer fuel element and the inner core element are formed such that beam of high energy particles may be directed into the inner cavity of the inner core element such that particles forming the impinge upon a Beryllium nucleus within the core to produce a (p, n) reaction resulting in the emission of a neutron and the emitted neutron may interact with a Thorium nucleus in the outer fuel element to cause the Thorium nucleus to fission. Additionally, or alternatively, the present disclosure teaches a Thorium fuel rod that includes a fuel element containing solid Thorium, having a length and defining a central bore extending along at least a majority of the length; and an inner core element positioning within the central bore defined by the fuel element, the inner core having a length that extends along at least 75% of the length of the fuel element, the inner core defining an interior cavity, the interior cavity defining a void space, wherein the void space of the interior cavity is subject to a vacuum; and an end cap sealed to the inner core element in such a manner that the vacuum within the void space is maintained, the end cap being formed of a material capable of passing particles through the end cap such that the particles can impinge upon an nucleus forming the inner core, wherein the particles are of a sufficient level that impingement of a particle upon an nucleus forming the inner core can induce a (p, n) reaction resulting in the emission of a neutron having an energy level of 0.7 MeV or greater. Additionally, or alternatively, the present disclosure also teaches a Thorium fuel rod comprising: a first rod-shaped element formed of a solid material containing Thorium, the rod defining a bore extending through at least the majority of its length, and wherein at least a majority of the length of the rod defining a plurality of radially extending fins; and a second rod-shaped element comprising Beryllium, the second rod-shaped element having a first section positioned within the bore defined by the first rod-shaped element and extending longitudinally along at least a majority of the length of the first rod-shaped element and a second section extending longitudinally outwardly from the bore. Other potential aspects, variants and examples of the disclosed technology will be apparent from a review of the disclosure contained herein. None of these brief summaries of the inventions is intended to limit or otherwise affect the scope of the appended claims, and nothing stated in this Brief Summary of the Invention is intended as a definition of a claim term or phrase or as a disavowal or disclaimer of claim scope. FIGS. 1A and 1B illustrate, in block and rough schematic form a first embodiment of an exemplary accelerator-driven sub-critical Thorium molten salt system 1000 for generating useful energy (for example in the form of process heat and/or electricity) in accordance with certain teachings of this disclosure. As reflected in FIG. 1A-1B, the exemplary system 1000 includes a particle beam source 200 for producing a particle beam. In the example of FIG. 1A-1B, the particle beam source 200 is adapted to vary the energy level of the produced particle beam such that the energy of the particles comprising the proton beam can vary between at least a first energy level and a second energy level, where the first energy level is at least approximately 4.5 MeV (and potentially up to or above 6 MeV) and the second energy level is at least 2.4 MeV. As reflected in FIG. 1A the particle beam source 200 includes a power input 201 for receiving the power required to drive the particle source. FIG. 2A provides details of the exemplary particle beam source 200 of FIG. 1. As reflected in FIG. 2, the exemplary particle beam source 200 includes a particle generator 202 for generating charged particles. In the example, of FIG. 2, the charged particles may take the form of a negatively charged hydrogen nucleus (for example, a neutral hydrogen atom with an added electron). The use of a neutral hydrogen atom with an added electron is exemplary for purposes of the present discussion and other charged particles may be used without departing from the teachings of the present disclosure. It should also be noted that the use of negatively charged particles is exemplary as well. One could implement the teachings of the present disclosure using positively-charged particles, although the references to positive and negative voltages in the discussion relating to how the particles are accelerated should be considered reversed when dealing with positively-charged particles (i.e., references to negative voltage should be replaced with positive voltage and vice versa). In the example of FIG. 2A, the negatively charged generated particles from the particle generator 202 are applied to a vacuum accelerator assembly 204 that includes several individual vacuum voltage chambers. The vacuum accelerator assembly 204 receives the negatively charged particles from the particle generator 202 and accelerates the generated particles to provide a high energy particle beam at its output. The high energy output beam from the vacuum accelerator assembly 204 is provided to an electromagnetic forming and steering assembly 208 that converts the received particle beam into an output particle beam having desired shape and directional characteristics. FIG. 2B illustrates an exemplary vacuum accelerator assembly 204 that may be used to form the particle beam source 200 of FIG. 2A. In the example of FIG. 2B, the vacuum accelerator assembly 204 is formed from ten individual vacuum voltage chambers 206a-206j. Each of the vacuum voltage chambers is coupled to a vacuum source and to a source of electrical power such that the voltage chamber can be evacuated to provide a vacuum interior and such that a relatively uniform electrical potential (voltage) level within the chamber can be established. The vacuum voltage chambers may be arranged in four groups, a first group comprising chambers 206a-206b, a second group comprising chambers 206c-206d a third group comprising chambers 206g-206h and a fourth group comprising chambers 206i and 206j. Chambers 206e-206f may collectively be used to form a nitrogen stripping chamber as discussed in more detail below. FIG. 2C generally illustrates the way the exemplary particle beam source 200 may be operated to generate particles having a first energy level. Referring to the figure, in this mode, during operation of the assembly 204, the first and second groups of vacuum voltage chambers (i.e., each of the voltage chambers 206a-206d) is energized such that the voltage potential in these chambers is positive, with the magnitude of the electrical potential increasing from chamber 206a to 206d. Because the particles generated by the particle generator 202 will have a negative charge, the positive voltage potential within chambers 206a-206d, and the differential in the magnitude of the positive voltage between chambers 206a-206d will cause the generate particles to move into and accelerate through chamber 206a towards chamber 206b, with the particles accelerating as they move through the identified chambers as the result of the increasing voltage potential from chamber 206a to 206b. The particles will move into chamber 206b and be accelerated, in the same manner, towards and into chamber 206c. The process will be repeated with the particles continuing to accelerate, and gain energy, as they pass into and through chamber 206d. In the illustrated example of FIG. 2C, during this first mode of operation, vacuum voltage chambers 206e and 206f are configured such that they have no net voltage potential. As a result, the particle moving through these chambers will not be accelerated but will—in essence—“coast” through the chambers 206e and 206f as a result of the momentum created by the movement and acceleration provided by chambers 206a-206d. In the illustrated example, chambers 206e and 206f, while not maintained at a specific voltage level, are filled with charged nitrogen gas to form a nitrogen stripping chamber. This gas will tend to strip off electrons from the particles traveling through chambers 206e and 206f, thus causing the moving particles to transition from negatively charged particles to particles having a positive charge. In the specific example under discussion, the stripping chamber will strip off the two electrons associated with the negatively charged hydrogen generated by particle accelerator to provide a positively charged particle consisting of a single proton. In the illustrated example of FIG. 2C, in the operating mode, the vacuum voltage chambers in the third and fourth groups (i.e., chambers 206g-206j) are activated such that the voltage levels within the chambers are negative, with the magnitude of the voltage levels within the chambers increasing from chamber 206g-206j. As a result of these established voltage levels, the positively charged particles traveling through chamber 206f will be attracted into chamber 206g and accelerated through chamber 206g to chamber 206h where they will be further attracted toward, and accelerated through, chambers 206i and 206j. Because of the increasingly negative voltages created within chambers 206g-206j, the particles passing through the chamber will continue to accelerate as they pass through the identified chambers to and from a high energy particle beam at the exit of vacuum accelerator assembly 204. In the example of FIG. 2B, the voltage levels of the chambers 206a-206j are established such that the energy level of the particles exiting the particle beam source 200 are at least on the order of approximately 4.5 MeV. FIG. 2D illustrates a second mode of operating the particle beam source 200 of FIG. 2A may be operated to produce a proton beam of a second energy level, where the second energy level is less than the first energy level discussed above. The operation reflected by FIG. 2C is like that discussed above with respect to FIG. 2B except that, in the example of FIG. 2C, only the vacuum voltage chambers in the first and third groups are activated such that no voltage potential is established within chambers 206b, 206d, 206h or 206j. As such, the protons traveling through the illustrated assembly will not be accelerated through those chambers and the energy level of the traveling protons will not increase as they pass through the chamber. As a result, the energy level of the protons emitted by the particle beam source 200 will be at a reduced energy level which, in the example of FIG. 2C is an energy level of at least about approximately 2.5 MeV and below the first energy level. While a specific exemplary proton generator was described with respect to FIGS. 2A-2D, it should be accepted that other particle beam sources may be used in the exemplary system 1000 of FIG. 1 without departing from the teachings of this disclosure. Additionally, while the exemplary particle beam source of FIG. 2A was illustrated and described as using a vacuum accelerator assembly having only ten voltage chambers, it should be understood that particle beam sources having fewer or more chambers may be used to carry out the teachings of this disclosure. Still further, while the above example describes operation of a particle beam generator to generate beams comprising particles having either a first or a second energy level it will be appreciated that the teachings of this disclosure can be used to provide a particle beam source where the particles comprising the provided beam can have multiple energy levels in excess of the two discussed herein and/or where the energy levels of the particles comprising the provided beam are well above the first energy level discussed herein, and/or below the second discussed energy level. For example, embodiments are envisioned wherein the first energy level exceeds about 10 MeV. Referring to FIG. 2A, the particle beam generated by the vacuum accelerator assembly 204 is provided to an electromagnetic forming and steering assembly 208 that transforms the received particle beam into an output beam having desired projection pattern (i.e., a desired shape) and directional characteristics. In the example of FIG. 2A, the electromagnetic forming and steering assembly 208 may take the form of a beam focusing/defocusing instrument. Such an instrument may, in some embodiments, take the form of a quadrupole magnetic assembly that may be energized to provide output beams having at least first and second shaped characteristics and multiple directional characteristics. FIGS. 2E1, 2E2, 2E3 and 2E4 illustrate exemplary first, second, third, and fourth beam shapes that may be generated using the exemplary electromagnetic forming and steering assembly 208 of FIGS. 2A-2D As reflected in FIG. 2E1, the beam provided as an output of the forming and steering assembly 208 may take the form of a focused “spot” beam or a beam having a relatively small primary point of focus. Through proper energization of the beam forming and steering assembly 208, the spot beam may be directed to a single point, to various points at different times or, in some embodiments, to scan across a general area. As reflected in FIG. 2E2, the forming and steering assembly 208 can adjust the overall size of the spot beam such that the general diameter of the beam can be greater than the diameter of the narrower spot beam reflected in FIG. 2E1. In addition to providing spot beams of first and second diameters, as reflected in FIG. 2E2, the forming and steering assembly 208 can also be used to provide a spot beam that varies, smoothly or in steps, from a first, relatively narrow spot, to a second, larger-diameter spot. FIGS. 2E3 and 2E4 reflect operation of the forming and steering assembly 208 in an alternate matter to generate a beam that takes the general form of a ring, with FIG. 2E3 illustrating a ring having a first inner and first outer diameter, and FIG. 2E4 illustrating a ring having a second inner and second outer diameter, where the second inner diameter is greater than the first inner diameter and where the second outer diameter is greater than the first. Although not illustrated in FIGS. 2E1-2E4, embodiments are envisioned where rings of various inner and outer diameters can be produced by assembly 208 and/or where rings of variable sizes may be generated such that the beam can be varied from a spot to rings of increasing inner and outer diameters until a maximum outer diameter is reached, down again to a spot through rings of progressively decreasing inner/outer diameters, and then have the process repeated again in a cyclic fashion. This variation can be accomplished by smoothly changing beam shapes or through steps. During such cyclic operation, the amount of time the system is maintained at the various shape and directional points can be varied such that the system, for example, dwells at a spot point for a first period of time, and then cycles through rings of various sizes for a second period of time, where the first period of time is longer than—and potentially multiples of—the second period of time. In addition to providing particle beams of varying shapes and varying general energy levels, the particle beam source 200 of the present example can be controlled to provide particle beams of varying intensity (or current). This can be accomplished by controlling the operation of the particle generator 202 to generate fewer or more particles at any given time. Referring to FIGS. 1A and 1B, in the exemplary system, the particle beam generated by the particle beam source 200 is provided to a Thorium molten salt assembly 300. FIGS. 3A-3H2 and 3J1-3J3 illustrate aspects of exemplary Thorium molten salt assemblies 300 that may be used in connection with the exemplary system 1000 of FIG. 1. Turning first to FIGS. 3A-3D, a first exemplary Thorium molten salt assembly 300 is illustrated. As reflected in the figure, the illustrated Thorium molten salt assembly 300 includes a main body 302 in the form of a large, tub-like structure. The main body 302 forms a vessel which may contain molten salt including Thorium. In general, the main body 302 should be formed from a substance that can withstand the environment that will exist within and outside of the assembly 300. In particular, the main body 302 should be formed from a material that is generally resistant to the chemical characteristics of the molten salt fluid that will be contained within the assembly 300. While a variety of different materials may be suitably utilized, nickel-based steel alloys, such as Hastelloy-N, may be used to form the main body 302 and, indeed, all components in contact with molten salts comprising the various exemplary molten salt assemblies discussed herein. Other potentially suitable materials include stainless steels or Incolloy. Additionally, coatings can optionally be applied to the identified (and other) materials to enhance their resistance to corrosion. As reflected in FIGS. 3A-3D the bottom of the main body 302 is generally rounded. This rounded bottom shape is believed to be beneficial in promoting optional fluid circulation within the assembly 300. The round bottom can also be of benefit in properly locating the assembly 300 within a shielding structure, as discussed in more detail below. In the example of FIGS. 3A-3D the main body 302 is coupled by, for example welding to a lower flange element 304. The lower flange element 304 defines a lower flange surface that, in turn, defines a plurality of bolt openings (unlabeled in FIGS. 3A-3B). An upper lid assembly 306 is coupled to the lower flange element 304. The outer portions of the upper lid assembly 306 define an upper flange section (not separately labeled) that is arranged in general alignment with the lower flange element 304. The upper flange section of the lid assembly 306 defines a plurality of bolt holes where the bolt holes are preferably of the same number and sized to align with the bolt openings of the lower flange element 304. While the number of bolt openings can vary, in preferred embodiments at least eight bolt openings are provided. In the example of FIGS. 3A-3B both the lower flange element 304 and the upper flange section of lid 306 defines sixteen bolt openings. Bolts 308 (only one of which is labeled in FIGS. 3A-3D are used to couple the lid 306 to the lower flange element 304. The use of bolts to couple the lid 306 to the lower flange element 304 is exemplary and other forms of coupling may be used. For example, screws, clamps and other mechanical assemblies may be use. In embodiments where ready separation of the lid assembly from the lower flange element 304 is undesirable, welding may be used. The use of bolts in FIGS. 3A-3D permits ready attachment and separation of the lower flange element 304 and the upper flange section of lid 306, simplifying the assembly and disassembly of the exemplary molten salt assembly 300. As illustrated in FIGS. 3A-3D, the bolt openings in the lid assembly 306 and the lower flange element 304 are such that they open outside the interior of the main body 302 in which the molten salt will be located. As such, the bolt openings do not give rise to any penetrations into the interior of the main body 302. Referring to FIG. 3D, which shows a top-view of the lid assembly 306, it may be seen that in the illustrated exemplary embodiment (in addition to defining bolt openings 310, only four of which are labeled in FIG. 3D) the lid assembly defines four impeller openings 312a-312d that pass from the outside of the lid assembly 306 into the interior of the main body. The lid 306 further defines two heat exchanger openings 314a and 314b that provide openings that extend from the exterior of the main body 302 into the interior of the main body 302. As best reflected in FIG. 3D, the lid 306 is a two-piece assembly that includes a generally ring-shaped main section of a first thickness and an inner disc-element 316 of a second thickness, where the second thickness is less than the first thickness. The window element 316 is intended to provide a “window” into the interior of the main body 302 through which certain types of particles, specifically at least the particles provided by the particle beam source 200 (and, potentially, neutrons) can pass. In the example of FIGS. 3A-3D, the window 316 is formed from a disk of any suitable material and may take the form of titanium, or aluminum titanium, or any other suitable material that will pass the particles provided by the particle beam source 200. The window element 316 should have a thickness sufficient to pass particle beams of the type necessary for operation of the systems described in this disclosure. The window element 316 maybe coupled to the ring-shaped section of lid 306 in any suitable manner. In some embodiments, the window element may be bolted onto, screwed onto, screwed into or otherwise mechanically coupled to the ring-shaped section of lid 306. In other embodiments, the window element 316 may be welded to, brazed to, integrally formed within or otherwise attached to the ring-shaped section. While the window element 316 is illustrated as being circular in shape in FIG. 3D, it should be understood that the window element 316 may take the form of other shapes such as, for example, a square, oval, or pentagon. In still other alternative embodiments, instead of a single large window element 316, multiple window elements are provided where the collection of window elements collectively define multiple passages through which high energy protons can enter the main body 302. As best shown in FIGS. 3A-3C, in the example under discussion, a plurality of motor-driven impeller pumps 318a-318d are provided. The general construction of each of the impeller pumps is shown in FIGS. 3E1-3E2. As reflected in FIGS. 3E1-3E2, in the exemplary embodiment under discussion, each of the impeller pumps 318 includes a variable speed motor 320 that is coupled to a shaft 330. The variable speed motor may take the form of any suitable variable speed motor such as a variable frequency induction motor, a brushless permanent magnetic motor or a switched reluctance motor. In the example of FIGS. 3E1-3E3, the variable speed motor 320 takes the form of a variable frequency driven induction motor. Although not illustrated, it will be understood that such a motor will include a rotor and a stator with windings and the windings will be coupled to a variable frequency drive that can provide power to the motor 320 in such a manner that the rotational speed of the motor can be controlled. As shown in FIG. 3E3, the motor shaft 330 extends downward from the motor and is coupled to an impeller element 332. In the example under discussion, the pump further includes a bearing assembly 322 through which the shaft 330 passes. As described in more detail below, the bearing assembly 322 of each impeller pump 318 in the example under discussion is positioned within one of the impeller openings of the lid 306. Because the impeller shaft has to pass through the top lid, the penetration should include high temperature seals to prevent the leakage of materials and gases from the interior of the main body 302 to the exterior of the body. The illustrated impeller pump 318 also include a pump body 324 that defines an upper fluid opening 326 and a lower fluid opening 328. The impeller pump 318 is designed such that, during operation, activation of the motor 320 will result in rotation of the shaft 330 and, therefore, rotation of the impeller element 332. The rotation of impeller element 330 will create a pressure differential across the inner chamber defined by the pump body 324 such that fluid will tend to be drawn into the upper fluid opening 326, flow through the chamber defined by pump body 324, and out the lower fluid opening 328. The rotational speed of the motor can be controlled to vary the pressure drop through the pump body 324 and, thus, the extent of the fluid flow through the pump. Referring to FIG. 3C it may be seen that the molten salt assembly 300 also includes a tubular member 340 positioned within the main body 302. The tubular member 340 includes openings at both its top and bottom ends such that liquid, such as a Thorium-containing molten salt, can flow into the bottom of the tubular member 340, up through the tubular member, and out, over the top of the tubular member 340. As best reflected in FIG. 3C, the bottom of the tubular member 340 can define a lower ledge structure. In general, the tubular member 340 defines an interior space within the main body 302 within which, and among, various structures can be positioned and through which liquid can flow. Referring to FIGS. 3B, 3C and 3F, it may be seen that the tubular member 340 and the impeller pumps 318 are dimensioned such that the upper fluid opening 326 opening of the pump body 324 includes a portion that extends below the top of the tubular member 340 and the lower fluid opening 328 of the tubular member 340 is positioned above the bottom of the tubular member 340. As reflected in the figures, the length of the tubular member 340 and the impeller pump 318 are such that the bottom end of the tubular member and the lower fluid opening 328 of the impeller pumps 318 are within the lower portion of the main body 302 such that an adequate flow path (to the left in the figure) is provided. In the specific example in the referenced figures, the lower fluid openings of the impeller pumps are within the lower one-third of the main body 302. The result of such positioning is that operation of the impeller pumps 318 will tend to cause fluid to flow up and out of the tubular member 340, over the top of the tubular member 340 and down through the main body 302 (and partially through the pump body 324). Thus, operation of the impeller pumps 318a-318d will tend to cause fluid flow within the main body 302 along the path generally reflected by the arrows in FIG. 3F. As will be appreciated, the fluid flow path depicted in FIG. 3F will exist for each of the four impeller pumps 318a-318d illustrated in FIGS. 3A-3F. As such, operation of the impeller pumps will tend to result in a circulating flow of fluid where fluid flows through a circulation path whereby it initially circulates into the bottom of the tubular member 340, flows up through the tubular member 340, then out and over the top of the tubular member 340, and down the outside of the tubular member 340, where it circulates back up and into the bottom of the tubular member and the cycle is repeated. In the embodiment of the molten salt assembly 300 previously described, and in all embodiments of the assembly 300 discussed herein a Thorium containing molten salt will be held in the main body 302. While the exact composition of the molten salt within the main body 302 will vary, embodiments are envisioned where the molten salt will contain at least a Lithium salt, a Beryllium salt and a Thorium salt, such that Lithium, Beryllium and Thorium exist within the molten salt. One suitable salt is a FLiBe salt containing dissolved Thorium. Other embodiments are envisioned wherein the molten salt does not include Beryllium but does include Lithium. One such salt is FLiNaK. In general, the quantity of molten salt within the main body 302 should be such that the upper level of the molten salt is over the top of the tubular member 340. Still further embodiments are possible where the molten salt is a chloride salt that contains chlorine, as opposed to fluorine. FIG. 3G1 illustrates a cross-section of the main body 302 and includes a dashed line 342 reflecting the general level of molten salt in the exemplary assembly 300. As reflected in FIG. 3G1, the upper level of the molten salt is both above the upper surface of the tubular member 340 and below the lower surface of the lid assembly 306. As such, an open region 346, not including any molten salt, but capable of containing gases, exists between the level of the molten salt and the lower surface of the lid 306 (and the lower surface of window element 317 for the interior region of the illustrated assembly). This open region 346 is further illustrated by the dark gray areas of FIG. 3G2. This open region 346 may be used to store gases generated as a result of fission processes that can occur within the main body 302. In certain embodiments, the open region 346 can initially be filled with an inert gas, such as argon, prior to the operation of the system. In the embodiment of FIGS. 3A-3F, impeller pumps 318a-318d are used to circulate the fluid in the main body 302. Alternate embodiments are envisioned wherein natural circulation is used to provide a fluid flow, generally along the path described above with respect to FIG. 3F. Such an alternate embodiment is depicted in FIGS. 3J1, 3J2 and 3J3. Referring to FIGS. 3J1 and 3J2, it may be noted that the overall structure of the illustrated exemplary molten salt assembly 300′ is like that described above in connection with FIGS. 3A-3F, with the primary differences being that the main body 302′ of the embodiment of FIGS. 3J1 and 3J2 is taller and narrower than the main body 302 of the first-described embodiment, the tubular member 340′ is longer and narrower than the tubular member 340 in the first-described embodiment and the helical heat exchanger assembly 500 (discussed in more detail) below is positioned about the upper two-thirds of the tubular member 340′ and not about the lower one-third of the tubular member 340′. In general, this arrangement creates a situation whereby the removal of heat through use of the helical heat exchanger assembly 500 creates conditions where natural circulation causes the fluid within the main body to flow along the paths identified by the arrows in FIG. 3G2. Advantages of the embodiment reflected in FIGS. 3J1-3J2, include simplification of the design and construction of the assembly 1000 through the elimination of the impeller pumps and the need for equipment to control the pumps; elimination of the need for impeller openings in the lid coupled to the main body 302′, thus reducing the number of penetrations that must be made into the main body, and elimination of the need to provide energy for operation of the motors driving the impeller pumps. The minimal penetrations required for implementation of this embodiment is reflected in FIG. 3J3, where only two penetrations 314a′ and 314b′ into the main body are provided, one for the inflow of a heat exchange fluid for the outflow of heat exchange fluid. In certain embodiments of the molten salt assemblies 300 described previously one or more solid Thorium fuel rods will be positioned and located within the interior of the tubular member 340 (or 340′). References herein to a solid Thorium fuel rod are intended to indicate that the fuel rod contains solid Thorium (as opposed to Thorium dissolved in a molten salt). As such, a solid Thorium fuel rod, as that term is used herein, may define internal openings or chambers. In embodiments as described above, Thorium fuel will be available within the interior of the tubular member 340 (or 340′) both in the form of solid Thorium within the Thorium fuel rod, but also in the form of dissolved Thorium within the molten salt. FIGS. 4A-4E illustrate one example of a novel Thorium fuel rod 400 constructed in accordance with certain teachings of this disclosure. Referring to FIGS. 4A-4E a Thorium fuel rod 400, is illustrated that includes an interior Beryllium core element 402 and an outer, solid Thorium-containing fuel element 404. In the illustrated example, the Thorium containing fuel element 404 is formed from a solid Thorium-containing material, such as metallic Thorium. Alternative embodiments are envisioned where the element 404 is formed from a Thorium-containing solid material (such as Thorium Dioxide) and an outer cladding In the example of FIG. 4A-4E, the outer surface of the Thorium fuel element 404 defines a series of fins that may be twisted to form a generally spiral-like outer structure. Alternative embodiments are envisioned wherein the fins on the Thorium fuel element are straight or generally straight. In the example of FIGS. 4A-4E, the Beryllium core element 402 is formed from a generally tubular element of Beryllium-containing material, such as metallic Beryllium. The generally tubular element is formed from a structure that defines an interior cavity 412 that, at any given cross-sectional point, defines an open cross section roughly in the form of a four-leaf clover surrounding a central circular opening. In the illustrated example, the Beryllium core element 402 has a length that is greater than the length of the solid Thorium fuel element 404 such that the Beryllium core element 402 extends out from the top of the Thorium fuel element. In one embodiment, the length of the Beryllium core element 402 is such that the solid Thorium fuel element 404 can be completely submerged within the molten salt while the top of the Beryllium core element is above the level of the molten salt. In general, the length of the Beryllium core element 402 extends along a majority of the length of the solid Thorium element 404, and preferably along at least 75% of the length of the solid fuel element 404. Embodiments are envisioned wherein the Beryllium core element 404 extends along 100% of the length of the solid fuel element 404. The cross-section of the Beryllium core element 402 at a given exemplary point is roughly reflected in FIG. 4E. As reflected in FIG. 4E, at any given point along the Beryllium core element 402, four solid Beryllium projections (410a, 410b, 410c and 410d) project into the interior of the core and define four lobe-shaped openings 412a, 412b, 412c and 412d and a generally circular central opening 414. The construction of the Beryllium core element 402 is such that, from the top of the element 402 to the bottom, the relative position of the solid Beryllium projections 412a, 412b, 412c and 412d change such that they form a general spiral down the interior of the core element 402. The result of such a construction is that they define a central cavity 412 having a circular cross-section that extends from the top of the core element 402 to approximately the bottom of the element 402 and generally clover-leaf openings 412a-412d that have the characteristics described below. In the illustrated example, the clover-leaf openings are such that, for any particular cross-section, there is at least a portion of at least one of four of the solid projections from a lower cross section that extend into the openings. This means that particles passing through the openings 412a-412d at any given cross-sectional point will always have at least some solid Beryllium beneath the openings upon which the particles may impinge. In general, the specific pitch of the spiral and the size of the projections and lobe-shaped openings will depend on the amount of power to be generated, the energy of the incident protons, and other factors. As reflected in FIGS. 4A-4D, the length of the Beryllium core element 402 is greater than the length of the Thorium fuel element 404 such that the core element 402 extends from the top of the solid Thorium fuel element 404. In at least one embodiment of the present example, the exemplary embodiment of FIG. 4A-4E the interior void space within the Beryllium core will be subjected to a vacuum and the void space of the Beryllium core sealed to maintain a vacuum. The sealing can be done through any suitable end cap provided that the end cap is formed of a material through which the particles provided by the particle beam source 200 can pass. Alternate embodiments are envisioned wherein the top ends of each Beryllium inner core are left open and all the ends are coupled to a manifold assembly that is attached to a vacuum pump to maintain a vacuum within the interior void space of the Beryllium core. In general, each of the Thorium fuel rods 400 is capable of generating power through fission reaction that can be caused to occur by directing a beam of energetic particles, such as protons with an energy level on the order of above 4.2 MeV into the interior of the Beryllium core. Particles in such a beam may pass into the void space of the Beryllium core and travel until they contact a Beryllium nucleus on one of the surfaces extending into the core. The collision of the high-energy particle (in one exemplary embodiment a proton) with the Beryllium nucleus can result in a (p, n) reaction that produces a neutron having an incident energy level on the order of 1 MeV or greater. One or more of such generated “fast” neutrons can strike a Thorium nucleus within the Thorium element 404 and cause a fission reaction in which the Thorium nucleus undergoes nuclear fission and releases a significant amount of energy. Depending on the desired operating characteristics of the assembly 1000 one or more of the Thorium fuel rods 400 may be positioned within the tubular member 340. In certain embodiments, the Thorium fuel rods to be positioned within the tubular member 340 are positioned between two support elements and the support elements are configured to rest within the tubular element 340 in such a manner that the solid Thorium fuel elements 404 in the fuel rods 400 are submerged in the molten salt, and the top portions of the Beryllium cores 402 within the fuel rods extend above the level of the molten salt. In these embodiments, the top positions of the fuel rods 400 are all positioned such they are under the window element 316 such that particles from the particle beam provided by particle beam source 200 can pass through the window 316 and into the various Beryllium core elements. FIGS. 4F1 and 4F2 illustrate an exemplary embodiment in which a single Thorium fuel rod 400 is positioned within the tubular member 340. In the illustrated example, as in the other examples discussed below, the Thorium fuel rod (or rods) 400 are positioned between an upper support element 430 and a lower support element 432. FIG. 4F1 illustrates a top-down view, showing where the Thorium control rod 400 is positioned within the window element 316. FIG. 4F2 provides a generally isometric view indicating the positioning of the assembly containing the Thorium fuel rod 400 relative to the lid 406. In the isometric view of FIG. 4F2—and the isometric views of the other Thorium rod structures discussed in more detail below, the portion of the Beryllium core element 402 that extends out of and above the solid Thorium fuel element 404 is not illustrated but should be understood to be present. FIGS. 4G1 and 4G2, 4H1, 4H2 and 4H3 illustrate alternate fuel arrangements that include either five Thorium fuel rods (FIGS. 4G1 and 4G2), thirteen Thorium fuel rods (FIGS. 4H1 and 4H2) or seventeen Thorium fuel rods (FIG. 4H3). As reflected in FIGS. 4G1, 4G2, 4H1 and 4H2, in certain illustrated embodiments the Thorium fuel rods to be used in the system are combined in a single solid Modular Thorium fuel package that includes the solid Thorium fuel rods (or rod) positioned between two support elements. The use of such a solid Modular Thorium fuel package can permit efficient refurbishing of the system 1000 described herein for subsequent operations. In addition, the use of a Modular Thorium fuel package as disclosed herein also permits the construction of systems of different power levels through the use of one fuel package in place of another. As briefly discussed in the previously illustrated embodiments, the Beryllium core elements are used to provide solid targets upon which high energy protons can impinge to generate high energy (for example over 0.7 MeV) neutrons that can strike Thorium to induce a fission reaction within the Thorium nucleus, generating additional high energy neutrons and energy. FIGS. 4G1 and 4G2 illustrate an alternative solid Modular Thorium fuel package in which a different approach is used to generate high energy neutrons for the fast fission of Thorium. Referring to FIGS. 4J1 and 4J2, a solid Thorium fuel assembly is illustrated that includes four solid Thorium rods (FIGS. 460a-460d) surrounding a single, central solid Beryllium rod 462. In the illustrated embodiment, the central solid Beryllium rod 462 is used as a target in which the high energy particle beam from the particle beam source 200 is projected. When such high energy particles strike the Beryllium rod 462, high energy (fast) neutrons can be generated which can exit the Beryllium rod and impact upon Thorium in the solid Thorium rods (460a-460d) to cause fast Thorium fission reaction. In the embodiments of FIGS. 4J1 and 4J2 the central Beryllium rod 462 is solid. As such, the particles impinging on the rod from the particle beam source 200 may not penetrate the lower portions of the Beryllium rod 462. To promote such penetration and utilization of the entirety of the Beryllium rod to generate fast neutrons, a Beryllium rod in the general form of the one described above in connection with FIGS. 4D and 4E may be substituted for the solid rod 462. In the embodiments discussed above in connection with FIGS. 4A-4H3 and 4J1-4J2 the Beryllium within the Beryllium rods may be in the form of solid Beryllium. Alternative embodiments are envisioned wherein the Beryllium within the Beryllium rods takes alternative forms, such as a Beryllium-containing salt (e.g., FLiBe). In such embodiments, the Beryllium-containing rods would comprise a vessel capable of containing a molten Beryllium-containing salt. Referring to FIGS. 1A and 1B and 3H1 and 3H2 a primary heat exchange assembly 500 is shown as extending around the central tubular member 312. The illustrated exemplary primary heat exchanger includes an input pipe 502 and an output pipe 504. The input pipe 502 is coupled to an input manifold 506 (illustrated in FIGS. 3H1-3H2) and the output pipe 504 is coupled to an output manifold 508. Notably, the lengths of the input and output pipes are sufficiently long so as to pass through the top level of the Thorium-containing molten salt, into the gaseous head maintained above the molten salt and potentially through the top lid of the main body. As reflected in the exemplary figures, a plurality of helically formed coiled pipes 510, ten in the illustrated example, have one end coupled to the input manifold 506 and another end coupled to the output manifold 508. As reflected in the figures, each of the helical pipes 510 winds downwardly around and back up the tubular member 12 from the input manifold to the output manifold 508. The illustrated number of helically formed coiled pipes is exemplary only and a different number of pipes could be used without departing from the teachings of the present disclosure. In the embodiment of FIGS. 1A-1B the primary heat exchange assembly includes a non-Thorium containing molten salt within the pipes 510 and input and output manifolds 506 and 508. As described in more detail below, this non-Thorium containing molten salt is circulated through the primary heat exchanger to remove heat from the Thorium molten salt assembly 300. Pumps (not illustrated) may be used to circulate the non-Thorium containing molten salt. Select details of an exemplary primary heat exchange assembly 500 are shown in FIGS. 3H1 and 3H2. FIG. 3H2 reflects the construction of an exemplary manifold 506. The illustrated manifold construction may be used for both the input manifold and the output manifold. Referring to FIG. 3H1 in the illustrated example, the manifold includes a box-like main manifold base 560 that defines a single input (or output) opening 562 of a first diameter at the top of the base 560 and a plurality of output (or input) openings 564 of a second diameter at the bottom of the base, only two of which are labeled in the figure. In this embodiment, the second diameter is less than the first diameter. In the illustrated example, the input 562 is to axially offset from each of the plurality of openings 564, such that there is no straight flow path through the first opening 562 and any of the second openings 564. In the illustrated example, there are twelve (12) openings 562. Each of the second openings is coupled to a heat exchange coiled pipe 566. Use of the exemplary manifold described above permits the use of a plurality of lesser-diameter heat exchange coils (twelve in the example) within the main body 502, while requiring only two penetrations through the main body 502. In the exemplary embodiment discussed herein, heat generated within the main body 502 will be transferred to the molten salt flowing through the primary heat exchange assembly 500. In the illustrated example, that heat is transferred from the primary heat assembly 500 to a secondary heat assembly 512. Details of the secondary heat exchanger assembly 512 are shown in FIG. 1B. As reflected in FIG. 1B a secondary heat exchange path 516 is provided and arranged to absorb heat from the primary heat exchange coil. In the example of FIG. 1B, a vapor-forming liquid—such as water or carbon dioxide—is contained within the secondary heat exchange path (or coil) 516 and the piping attached to the secondary heat exchanged coil. A condenser 518 is also provided in the illustrated system as is piping (not labeled) that can transport liquid from the condenser 518 to the input of the secondary heat exchange coil and steam from the output of the secondary heat exchange coil to the input of the condenser. Not illustrated in FIG. 1A or 1B are pumps that can be used to circulate non-Thorium containing molten salt through the primary heat exchange loop and vapor-producing liquid (such as water or carbon dioxide) through the secondary heat exchange loop. In the example of FIG. 1, the energy transfer assembly 500 is used to transfer energy from the Thorium molten salt assembly 300 to a power generator assembly 600. High level details of such a system may also be found in FIGS. 1A-1B which reflect the application of the vapor generated by the heat exchange tank 512 to a turbine assembly 602 which, in turn, is coupled to an electric generator 604. In accordance with the general operation of turbine-driven electrical generators, the vapor produced by the energy transfer that occurs within the heat exchange tank 512 is used to drive/turn turbine 602 which turns the rotor of the electrical generator 604, producing electrical power at the output 606 of the electrical generator 604. In the illustrated system the output 606 of the electrical generator 604 is provided to a distribution element which distributes the generated electric power such that the majority of the generated power is provided to a main power output 608 and a portion of the generated power is provided to the power input of the proton generator 201 to drive the particle beam source 200. Because the operating of the system 100 of FIGS. 1A and 1B can generate nuclear particles and radiation emission, appropriate shielding 700 is provided to block the transmission of undesired particles and waves. FIG. 5 illustrates one exemplary way this shielding may be provided. In the illustrated example of FIG. 5, many of the components of the system 1000 are placed in a containment system 700. In the exemplary embodiment, the containment system 700 comprises a first containment structure 702 in which the particle generator 202 and the vacuum accelerator assembly 204 are located. Vacuum tubes (unlabeled) are coupled to the output of the vacuum accelerator assembly 204 and couple the output of the vacuum accelerator 204 to the forming and steering assembly 208, which is positioned in second containment structure 704. The molten salt assembly 300 is partially placed within the ground under the second containment structure 704 such that the lid of the molten salt assembly is accessible above ground. A third containment structure 708 is provided below the molten salt assembly 300. The space 706 between the molten salt assembly 300 and the third containment structure 708 may be filled with any suitable material, such as soil, borated material, concrete, or any other suitable material or blend of materials. Depending on the particular application of the system 1000, and the extent to which safety requirements dictate, the containment units 702, and 704 may take the form of a simple metallic structure (if the earth, rock or ground structure is capable of providing the desired shielding) or a structure intended to block the transmission of radiation (e.g., lead-walls or a lead-brick structure). The structure 708 should be formed of a material sufficient to contain molten salt in the possibility that there is damage to the molten salt assembly. Alternate embodiments are envisioned wherein the containment unit 700 comprises a structure having an internal dry core area into which the components of system 1000 to be shielded are placed and an external structure capable of holding water (or a water/chemical mix (e.g., borated water) which acts as a shielding material. In any or all the various embodiments of the containment unit 700 a surface layer of shielding material 702 (e.g., a lead blanket) may be used. In operation, at a very high level, the system illustrated in FIGS. 1A and 1B operates by powering the particle beam source 200 to generate a proton beam that is applied to the Thorium molten salt assembly 300. One or more of the protons within the proton beam may impact upon one or more of the atoms within the Thorium molten salt assembly 300 to either: (a) produce neutrons or (b) result in a nuclear fission reaction, which will generate heat and further neutrons. These generated neutrons may, in turn, impact and interact with other atoms within the Thorium molten salt assembly 300 to generate additional heat. The generated heat may be removed through operation of the primary and secondary heat exchange systems, and the removed energy may be converted to electric energy through use of the electric generation system 600, described above. The exemplary system 1000 of FIGS. 1A and 1B may be arranged to permit operation of the system in one of several alternative operating modes. In one operating mode, the proton beam provided by the particle beam source 200 is shaped and aimed such that the proton beam provided by the generator is directed through the window element 316 primarily into the Thorium containing molten salt within the tubular member 302 without a substantial number of the protons (or any) impinging upon the Beryllium cores of the Thorium fuel rods 400 positioned within the tubular member 340. In this operating mode, one (or more) of the protons from the proton beam from generator 200 may impact one (or more) of the atoms within the Thorium containing molten salt. For example, one or more of the protons from the proton beam may impact with a Lithium nucleus forming part of the molten salt. This interaction of the proton with the Lithium nucleus can cause a (p, n) reaction under which the Lithium nucleus absorbs the incident proton and emits a neutron. The neutrons emitted by such proton-Lithium reactions may be of varying energy levels, the greatest number of neutrons resulting from several such reactions would be at an energy level of between 0.1 and 0.7 MeV. As another example, one or more of the protons from the proton beam may impact with a Beryllium nucleus forming part of the molten salt to cause a (p, n) reaction in which the Beryllium nucleus may absorb the incident proton and produce a neutron at a particular energy level. The neutrons emitted by such proton-Lithium reactions may be of varying energy levels, the greatest number of neutrons resulting from several such reactions would be at an energy level of between 0.7 MeV and just over 1.0 MeV. Notably, the peak energy level of the neutrons emitted by the described proton-Beryllium (p, n) reaction will be greater than those emitted as a result of the described proton-Lithium (p, n) reaction. In a second operating mode, the proton beam provided by the particle beam source 200 may be shaped and aimed such that all or a substantial portion of the proton beam is directed through the window assembly in such a manner that a substantial number of the protons forming the proton beam are directed to one or more of the Beryllium cores of the Thorium fuel rods within the tubular member 340. This may be accomplished by forming the proton beam into a generally narrow beam shape and directing the narrow beam to the Beryllium core of the central Thorium fuel rod. This may also be accomplished by forming the proton beam into a ring and directing the ring such that it covers either the first group of Thorium fuel rods or the second group of fuel rods. Alternatively, the beam may be formed such that it transitions from a beam directed to the central Thorium fuel rod, to a first ring directed to the first group of fuel rods to a second ring directed to the second group of fuel rods. In general, forming and aiming the proton beam as described in connection with the second operating mode will tend to cause protons within the proton beam to strike Beryllium, thus generating neutrons through the process described above. In the embodiment of FIGS. 1A and 1B the average energy levels of the protons within the proton beam generated by the particle beam source 200 may be varied, depending on the operating mode of the system to prefer proton-Lithium interactions, thus producing neutrons with average energies below 0.7 MeV or to prefer proton-Beryllium interactions, this producing neutrons with average energies above 0.7 MeV. For example, when the system is operated in accordance with the first operating mode, the energy level of the protons provided by the proton generator may be set to be on the order of at least approximately 2.4 MeV and about 3.0 MeV. The size and form of the proton beam, along with the energy level of the proton beam and the fact that it is directed into the Thorium containing molten salt, are such that operation of the system in the first operating mode will tend to result in proton production of neutrons of an energy level on the order of between 0.1 MeV and just over 1.0 MeV with the peak energy level of the produced neutrons being on the order of about 0.7 MeV. In the same example, using the system described above in connection with FIGS. 2A-2D, when the system is operated in accordance with the second operating mode, the particle beam source 200 may be operated to produce a beam of protons where the protons forming the beam have energy levels on the order of 4.5 MeV. The size and form of the proton beam, along with the energy level of the proton beam and the fact that it is directed into the Thorium containing molten salt, are such that operation of the system in the first operating mode will tend result in proton production of neutrons of an energy level on the order of 0.1 MeV-1.2 MeV, with the majority of the produced neutrons having energy levels on the order of between 1.0-1.1 MeV. The likelihood of the particles from the particle beam 200 interacting with one or more of the atoms within the main body 302 will vary depending on a large number of factors including, but not limited to: the energy level of the particle provided by the accelerator, the particular nucleus involved in the potential interaction, and the other atoms within the body 302. The system 1000 takes advantage of some of these variables, and of the different types of reactions that can occur within the main body 302 to provide a system that can be operated in various modes, to provide various output characteristics. To understand the various modes in which the exemplary system of the present disclosure may be operated, it is helpful to understand some of the operations that can occur within the body 302. As briefly discussed above, in the system of FIGS. 1A and 1B, once neutrons are created within the main body 302 (e.g., by a high energy proton provided by the proton beam colliding with a Lithium nucleus or a Beryllium nucleus within the molten salt or as a result of a fission reaction occurring within the main body and producing resultant neutrons) some of the neutrons within the main body 302 may collide with a Thorium nucleus in the molten salt solution and cause a nuclear reaction. In the illustrated system, the nuclear reaction caused by the described collision can be one of at least two different types of reactions. In one type of nuclear reaction, referred to as a “fission” reaction, the nucleus of the involved Thorium atom will split into, typically two, smaller nuclei. Such a fission reaction will release a very large amount of energy and one or more neutrons. The energy released by the fission reaction will tend to increase the amount of energy stored in the molten salt within assembly 300 as heat. One or more of the neutrons released by such fission reaction may interact a Thorium nucleus within the molten salt fuel to cause further Thorium fission reactions. In a second type of nuclear reaction, known as “neutron capture” (or “neutron absorption”) the nucleus of the involved Thorium nucleus will absorb the involved neutron to form an isotope of Thorium, namely Thorium-233 (233TH). Thorium-233 is an unstable isotope that will decay to Protactenium-233. The decay of Thorium-233 to Protactinium occurs relatively quickly as the half-life of Thorium-233 is about 22 minutes. Protactenium-233 is an unstable element that will tend to decay to Uranium-233, with the half-life of Protactinium-233 being to approximately 27 days. Uranium-233 is fissile material. As such, whenever Uranium-233 exists within the molten salt and neutrons are available—either from the particle beam source 200 or from the fission of other atoms within the molten salt—there is the potential that a neutron can strike a Uranium-233 nucleus causing a fission reaction. The fission reaction will produce heat. As with fission of the Thorium nucleus, fission of a Uranium-233 will result in the release of substantial energy and several neutrons, those neutrons may, in turn, interact with a Uranium-233 nucleus within the molten salt to produce a secondary Uranium-233 fission reaction, with a Thorium-232 nucleus to produce a Thorium-233 nucleus, or with other materials within the molten salt assembly 300. Some of the neutrons may pass through and escape the molten salt assembly. Once started and put into operation, the illustrated embodiment of FIGS. 1A and 1B can be self-sustaining in the sense that it can operate to provide usable energy without the addition of any other external power or energy as long as the energy generated by the system is sufficient to provide the power needed to drive and operate the particle beam source 200. Once the embodiment of FIGS. 1A and 1B begins to operate, the constituent components comprising the molten salt solution will change over time. At a high level, in certain embodiments, the composition of the molten salt will initially include no, or negligible, Protactinium and no, or negligible, Uranium. For purposes of this disclosure a negligible amount of an element is intended to refer to a substantially non-detectable amount of an element that exists in the absence of any intentional inclusion or addition of the element to the material. Alternate embodiments are envisioned wherein the molten salt could initially contain at least some Uranium. FIG. 6 provides a very crude, approximated, generalized relative indication of the amount of Thorium-232 and Uranium-233 that can exist for the system of FIG. 1 over time if it assumed that the neutron source provides a relatively constant supply of neutrons. As reflected in FIG. 6, at a time To, before the application of any neutrons to the system, the quantity of Thorium in the molten salt will be at its maximum level. As neutrons begin to be applied to the system, some of the neutrons will interact with the Thorium-233 causing one or more of the nuclear reactions discussed above. These nuclear reactions will cause the quantity of Thorium in the molten salt to decrease over time, as reflected by the line 232Th. As also reflected in FIG. 6, by the time T1, some of the Thorium that were subjected to a nuclear capture reaction will have converted to Protactinium-233 and some of those Protactinium-233 would have decayed to Uranium-233. As such, the number of Uranium-233 in the molten salt will begin to increase over time starting at time T1. It should be appreciated that the representation in FIG. 6 is intended to be a very crude approximation of the relative number of Thorium-232 and Uranium-233 in the molten salt and that the actual shape of the represented curves will not necessarily be in line with the specific curve characteristics illustrated in FIG. 6 (and can potentially be controlled as described below). As those of ordinary skill will appreciate, the likelihood of a nuclear reaction occurring when a specific nucleus is bombarded with a beam of particles having a specific incident energy level, is sometimes described by a concept known as the nuclear cross-section. In general, a nuclear cross-section is a quantity that expresses the extent to which neutrons interact with particles of a given energy level. Nuclear cross-section information may be obtained through consultation of JANIS (the Java based Nuclear data Information System) provided by the Nuclear Energy Agency and accessible at https://www.oecd-nea.org/janis/ FIGS. 7A-7D provide JANIS-generated graph reflecting the cross-sections of various isotopes that may exist within the molten salt assembly 300 of FIGS. 1A-1B. Referring first to FIG. 7A, data reflecting the cross-section of Thorium-232 as a function of the incident energy is illustrated for both the absorption reaction, reflected by line 2, and for the fission reaction, reflected by line 4. Also illustrated in FIG. 7A are the fission 6 and absorption 8 cross-sections for Uranium-233 as a function of incident energy. As the graph indicates, for Thorium-232 and Uranium-233, the cross-sections for the absorption and fission reactions vary as a function of incident energy in such a manner that the cross-section values may be considered to lie, for any incident energy level, within one of four regions. FIG. 7B illustrates the cross-sectional information of FIG. 3A divided into four regions. In the first region, designated by Roman numeral I, the absorption cross-section of Thorium-232 is comparatively large relative to the negligible fission cross section and decreases in a relatively smooth manner with respect to changes in the incident energy level. In that same region, the fission and absorption cross-sections of Uranium-233 exceed the absorption cross-section of Thorium-232. In the example of FIG. 3A, Region I extends from neutron energy levels of roughly 1×10−11 to roughly 1×10−6 mega electron volts (MeV). Within the second region, designated by Roman numeral II, the absorption and fission cross-sections of Thorium-233 and Uranium-233 vary substantially in a resonate-like manner with changes in the incident energy level. Over this region there are specific energy levels where the absorption cross-section of Thorium-232 exceeds both the fission and absorption cross-sections of Uranium-233. It may be further noted that, over this region the absorption cross-section of Thorium-232 reaches its maximum value. In the example of FIG. 3A, Region II extends from neutron levels of roughly 1×10−6 to roughly 0.007 MeV. Within the third region, designated by Roman numeral III, the absorption cross-section of Thorium-232 continues to remain comparatively large relative to the negligible fission cross-section of Thorium-232. Over that same region, the fission cross-section of Uranium-233 exceeds both the absorption cross-section of Thorium-232 and the absorption cross-section of Uranium-233. In the example of FIG. 3A, Region III extends from neutron levels of roughly 0.07 MeV to roughly 0.8 MeV. Finally, within the fourth region, designated by Roman numeral IV, the fission cross-section of Thorium-233 is comparatively large relative to its absorption cross section, and both the fission and absorption cross-sections of Thorium-232 vary in a roughly smooth manner with variations in the incident energy level. Over this same region, the fission cross-section of Uranium-233 exceeds the fission cross-section of Thorium-233 and the absorption cross-section of Uranium-233. The system of FIGS. 1A and 1B takes advantage of the different cross-sections of the various atoms that will exist within the Thorium molten salt assembly 300 to implement a novel operational and control scheme wherein the incident energy level of the particles provided by the particle beam source 200 are varied over time to adjust the operating state of the molten salt system such that the energy provided by the system is predominantly generated by fission of Thorium-232 at certain times, predominantly by fission of Uranium-233 at other times, and—potentially—fission of both Thorium-232 and Uranium-233 at other times. Examples of how such a novel operating method may be implemented are generally reflected in FIGS. 7A-7E. At an initial time, the system of FIGS. 1A and 1B is operated such that the incident energy level of the neutrons provided by particle beam source causes operation of the system in Region IV. This operating region is highlighted in FIG. 7C. This will be accomplished by controlling the energy level of the particles provided by the particle beam source 200 such that they are at a sufficiently high level that interaction between such particles and the Beryllium within the molten salt can result in the generation of neutrons having energy levels within the level of the neutrons within Region IV (i.e., over about 0.7 MeV). During this period of operation, given the small quantity of Uranium-233 in the molten salt assembly 300, the energy generated by the system 1000 will be predominantly generated through fission of Thorium-232. However, as reflected in FIG. 7C, such operation will also result in a non-trivial number of absorption reactions involving Thorium-232, which will ultimately result in the formation and buildup of Uranium-233 in the system 300. As the number of Uranium-233 atoms in the system increases, a point will be reached where the level of Uranium-233 is such that fission of Uranium-233 would be enough to provide the desired output power. At that point, the system of FIGS. 1A and 1B 1 can transition to operate in Region II, by adjusting the incident energy level of the provided proton beam to a level where it will tend to cause interactions between the incident protons and the Lithium within the molten salt assembly such that neutrons having energy levels within Region III are generated by proton-Lithium (p, n) reactions (i.e., neutrons with energy levels between about 1×10−6; to 0.007 MeV). Operation in this region, provides neutrons wherein fission of Uranium-233 is possible, but the fission of Thorium-232 as the result of neutrons generated as a result of bombardment of particles from the particle beam source 200 is negligible. In that same region, the neutrons within the molten salt assembly 300 will—in addition to causing fission reactions of Uranium-233, also cause absorption reactions involving Thorium-232, thus providing a source of Uranium-233 for sustained operation. The system can then operate in Region III for a sustained period of time, providing the desired power output until the number of Uranium-233 atoms in the system is inadequate to support the desired power output, or until other conditions warrant a change in the operation of the system or system shut down. Operation in this Region is reflected by the highlighted portion on FIG. 7D. FIGS. 8A-8H illustrated examples of how the particle beam from the particle source 200 may be directed, shaped and controlled to operate the exemplary systems described herein within the various Regions discussed above in connection with FIGS. 7A-7D. As described above, in the exemplary systems under discussion particle beam source 200 may be used to generate particles (such as protons) having incident energy levels of above 4.5 MeV when the generation of neutrons having energy levels of above 0.7 MeV through a (p, n) reaction of the incident particles and Beryllium, and the direct fission of Thorium, is desired. FIG. 8A, illustrates an example of system 1000, from a top-down perspective, that uses five Thorium fuel rods where of the Thorium fuel rods includes a Beryllium core generally as described above in connection with FIGS. 4A-4D. In the example of FIG. 8A, the proton beam provided by the particle beam source 200 is a solid beam spot concentrated on the Beryllium core of the central Thorium fuel rod. As such the incident high energy protons will potentially collide and interact with Beryllium within the Beryllium core, producing a (p, n) reaction that results in the generation of relatively high-energy (sometimes referred to as “fast” neutrons). These generated “fast” neutrons can then interact with a Thorium nucleus in the solid Thorium fuel element surrounding the Beryllium core to cause a Thorium fission reaction to occur which, in turn, will generate more fast neutrons that can cause further Thorium fissions to occur. FIG. 8B illustrates a similar situation, but this time with the high energy proton beam from the proton beam source 200 being directed to the Beryllium core of the Thorium fuel rod at the top of the image. As will be appreciated, using the approach of FIGS. 8A and 8B, a beam spot of particles of the appropriate type and energy level (e.g., protons with energy levels at or above about 4.5 MeV) provided by the proton beam source 200 and the proton beam may be directed to the Beryllium cores of each of the Thorium fuel rods in the system individually. Thus, by applying the beam for a limited period to each of the Beryllium cores, a supply of fast neutrons can be provided for each of the solid Thorium fuel elements to maintain at least some level of Thorium fission within the system. This energy released by such Thorium fissions can be used to operate the system. FIG. 8C reflects an alternate way the system 1000 can be operated to provide fast neutrons and to produce Thorium fissions. In the example of FIG. 8C, the high energy particle beam from the particle beam source 200 is focused at a spot within the molten salt within the molten salt assembly 300. Because at least some of the particles from the beam will have energy levels in excess of 4.5 MeV, the particles can strike a Beryllium within the molten salt, thus causing a (p, n) reaction and producing a fast neutron that can, in turn strike a Thorium atom within the molten salt or within a solid Thorium fuel element (if present) to cause a Thorium fission reaction. FIGS. 8D and 8E illustrate still other alternate approaches for producing fast neutrons and inducing Thorium fission reactions. In these examples, the beam size of the high energy particle beam from the particle beam source 200 is adjusted such that some of the particles comprising the high energy beam will impinge on both the Beryllium core of one or more Thorium fuel rods (thus producing fast neutrons and inducing Thorium fissions as generally described in connection with FIGS. 8A and 8B) and others may impinge upon Beryllium atoms within the molten salt in the assembly 300 (thus inducing the generation of fast neutrons and Thorium fission as described above in connection with FIG. 8C). Still further alternate embodiments are envisioned wherein the high energy particle beam provided by the particle beam source 200 is “strobed” from a small diameter beam spot (as generally illustrated in FIG. 8A) to a larger diameter beam spot (as generally illustrated in FIG. 8E) to vary the manner in which fast neutrons are generated. FIGS. 8F-8H illustrate yet another alternate mode of generating fast neutrons. In this mode, the particle beam from the particle beam source 200 is configured to a have a ring shape and the dimension and direction of the provided ring is varied to impinge upon the Beryllium cores of the Thorium fuel rods within the system and/or the molten salt within the assembly 300. It should be noted that, while the above discussion focused on the manner in which fast neutrons may be generated and the fast fission of Thorium induced, operation of the system as described above will also result in a number of different nuclear reactions including the generation of neutrons having lower energy levels (sometimes referred to as “thermal” neutrons) and the fission of any fissionable materials (Uranium-233 for example) that may exist within the assembly. This is because the neutrons generated within the assembly (either through reactions involving a particle from the particle beam source 200 or as the result of fission reactions within the assembly) will be of various energy levels, such that—while proton-Beryllium (p, n) reactions, proton-Lithium (p, n) reactions (generating neutrons with lower, potentially thermal, energy levels) will be occurring, as will fission reactions of Thorium and, likely, fission reactions of Uranium-233 (if present). Absorption reactions will also be occurring, as will non-reactions where some of the generated neutrons simply escape the assembly without producing any nuclear reactions within the assembly. Moreover, neutrons generated with “fast” energy levels will tend to have their energy levels reduced as they pass through the materials and elements within the assembly 300 (such as the molten salt) such that they will become thermal neutrons that can be involved in a Uranium-233 fission operation or a Thorium-232 absorption operation. Operation of the system as described above, however, to direct high energy particles (specifically protons) at energy levels sufficient to produce a Beryllium (p, n) reaction will tend to promote the generation of fast neutrons and the direct fission of Thorium within the assembly 300. FIGS. 8A-8H (and primarily FIGS. 8C-8E) also illustrate how the exemplary systems described herein may be operated to promote the generation of thermal neutrons and Uranium-233 fission reactions. By operating the particle beam source 200 to provide particles (such as protons) with energy levels of between about 2.5 MeV and 4.5 MeV, a situation may be created wherein proton-Lithium (p, n) reactions are promoted. These reactions will tend to produce neutrons having an energy level below the fast neutrons generated by a Beryllium (p, n) reactions. These neutrons will typically be at a level below that require for Thorium fission, but at a level where they can be involved in both a fission reaction involving a Uranium-233 reaction, or an absorption reaction in which Thorium-232 is ultimately converted into Uranium-233. Thus, by operating the system 1000 in this manner, Uranium-233 fissions may be promoted. Again, it should be noted however that, because any fission reactions involving of Uranium-233 or Thorium-232 that occurs during a time when the lower energy particles (such as protons) from the particle beam source 200 are provided to the assembly 300 will produce fast neutrons that can result in a fission reaction involving Thorium-232, such that fission reactions involving Thorium-232 can occur within the assembly 300 alongside fission reactions of Uranium-233. Considering the above, it should be clear that the novel system 100 described herein can, by adjustment of the energy level of the particles provided by the particle beam source 200, and by controlling the direction and shape of the provided particle beam, be operated in manner to promote: (i) generation of fast neutrons and the direct fission of Thorium (when high energy particles (such as protons with energy levels above 0.7 MeV) are provided) and (ii) generation of thermal neutrons with energy levels below 0.7 MeV and the fission of Uranium-233. FIG. 9A illustrates one exemplary method of operating a system 1000 constructed in accordance with the teachings of the present disclosure. Over a first initial time period 902, the system will be operated from an external power source (such as a diesel generator) that will provide the input power to the particle source 200. Over this time period, the system 1000 can be operated to promote the generation of fast neutrons and the direct fission of Thorium through the generation of a high energy particle beam and the direction of that particle beam to the Beryllium cores of any Thorium fuel assemblies within the system 1000. Over this time period, the output energy level of the system can be monitored at a step 904. Once it is determined that the energy being produced by the system is adequate to provide power necessary to power the particle beam source 200, the external power source can be removed, and the system can begin to operate without the addition of any external power. After the system begins to operate without the provision of external power, it can continue to operate in accordance with Region IV, described above, where direct fission of Thorium is promoted and used to provide a desired level of energy output. This is reflected by operating step 906. As described above, over this period, Uranium-233 will begin to be produced within the assembly. At step 908, the level of Uranium-233 in the assembly can be monitored and, when it is determined that the quantity of Uranium-233 in the assembly is sufficient to support the desired energy level output through fission of Uranium-233, the operation of the particle beam source 200 can be adjusted to provide particles (such as protons) of a lower energy level to promote Uranium-233 fission reactions in a Region II operation. Notably, over this region, Uranium-233 will continue to be produced as the result of the Thorium-232 absorption reaction occurring within the system. Operation in this mode is reflected by step 910. It is anticipated that the systems 1000 described herein can be operated as described above for Step 910 for most of its operating time, for example over a period of between 5-10 years. Of note, in embodiments where the molten salt does not include Beryllium (for example when the molten salt is FLiNaK, the generation of fast neutrons through use of the particle beam source 200 will be through bombardment of the Beryllium cores within the Thorium fuel rods. In addition to producing desired energy (and generating Uranium-233 for later use) operation of the system 1000 in accordance with a Region IV moderation can beneficially reduce (or “burn up”) undesirable waste elements that could otherwise build up within the assembly 300. In general, nuclear fission reactions typically result in the production of by-products generally known as fission products. Certain fission reactions, such as the fission of Uranium-233 can result in the production of fission products in the form of actinides, including trans-uranium (TRU) actinides, and other long-lived fission products. In general, such by-products are undesirable because they typically emit relatively high amounts of radiation and have relatively long-half-lives. The handling, disposing and processing of such TRUs and long-lived fission products is subject to various regulations and safe-handling precautions that must be followed when dealing with such materials. Many TRU's and long-lived fission products can be broken down into elements and isotopes that are less radioactive and/or have substantially shorter half-lifes such that they are safer to handle than the original fission products. Such TRUs and long-lived fission products can be broken down though interactions with neutrons having certain incident energy levels, typically those on the order of the “fast” neutrons, whose generation can be promoted through operation of the system as described above. Thus, operation of the system in a manner where generation of “fast” neutrons is promoted to reduce the amount of undesirable waste in the system. The exemplary system 1000 described above may be operated in various ways to reduce the amount of undesirable waste in the system. One exemplary operation is reflected in FIG. 9B. In this operational mode, the system can be operated as described above in connection with FIG. 9A for most of its operating life. This operation is reflected at Step 912. Towards the end of its operating cycle, however, the system 1000 can be transitioned to operate in the manner described above, where the generation of fast neutrons is promoted. This is reflected in Step 914. The system 1000 could then be operated at this Step 910 until the desired reduction of waste produces has occurred. Note, that embodiments are envisioned where the “burn-up” Step 914 is accomplished at a location separate from, and using a particle beam source, different from the location at which the main running Step 912 occurs. For example, embodiments are envisioned wherein a system 1000 constructed in accordance with the teachings of this disclosure is operated for a lengthy period of time at a location where energy generation is desired and then the Thorium assembly 300 is removed and taken to a different location where it can be bombarded with high energy particles that result in the generation of fast neutrons for purposes of waste burn up. In accordance with other embodiments, the systems 1000 described to herein may be operated to “burn-up” waste materials during the main period of operation of the assembly. Such embodiments are particularly suited for applications where the energy output demands from the system are not constant. For example, if the system of FIGS. 1A-1B is used to generate electricity, the demand for electricity may vary depending based on time, day, month, or weather conditions. For example, if the system of FIGS. 1A-1B is used to power a remote manufacturing plant, the plant may be operational—and thus have high energy demands—only weekdays during normal business hours or only during certain peak months of the year. In such applications, after an amount of Uranium-233 has been generated that is sufficient to provide the desired power output, the system could be operated in Region II during the periods of high energy demand (such that the production of energy though fission of Uranium-233 is maximized) and then be operated in Region IV during periods of low energy demand, such that the high-energy neutrons generated by the system during such operational periods can be used to burn some of the TRUs and long-lasting fission products within the system, thus reducing the total overall waste produced by the system. This mode of operation is generally discussed in FIG. 9C. Referring to FIG. 9C, the system may initially be operated in accordance where the generation of thermal neutrons and the fission of Uranium-233 is promoted as discussed above at Step 950. During these intervals, the energy demand of the system can be monitored at Step 952. If the output demand of the system is not below a certain threshold (or in alternate embodiments if the output demand is above a certain threshold level), the system will continue to operate in a manner where thermal-neutron production and Uranium-233 fission is promoted. If the energy demand, however, is below a certain threshold (and, potentially predicted to based on data to remain at that lower level for a particular period time) the operation of the system can be adjusted to promote the generation of fast neutrons and the potential burn-up of undesired waste. This is reflected in Step 954. While operating within Step 954, the output demands of the system can be monitored (at Step 956) and, if they increase, the system can transition back to operating in the manner described above in connection with Step 950. In the embodiments described above, the system 1000 is designed (and the particle beam source 200) operated so that the system—not including the neutrons generated as a result of the operation of the particle beam source 200—is operated in a sub-critical manner. As used herein, operation of the system in a sub-critical manner means that, if the power to the particle beam source is removed such that the particle beam source provides no particles to the system, the number of neutrons generated within the Thorium molten salt assembly 300 as the result of fission or other nuclear reactions will be insufficient to sustain permanent and on-going fission reactions within the system. As such, in the embodiments described above, substantial nuclear fission reactions within the system will ultimately cease if the particle beam source ceases to operate. This sub-critical operation of the described systems is believed to provide a safety margin that can eliminate (or at least substantially reduce) the potential for an uncontrolled series of nuclear reactions (sometimes referred to as a “meltdown”) of the assembly 300. In the embodiments discussed previously in this disclosure, the neutrons relied upon to support the nuclear reactions desired for system operation were generated within the Thorium molten salt assembly 300. Alternate embodiments are envisioned wherein the neutrons relied upon for operation on of the system are primarily generated outside the assembly 300. FIG. 10 illustrates one of many alternate embodiments of the system 1000 of FIGS. 1A and 1B in which fast and/or thermal neutrons desired for operation of the system are generated outside of the molten salt assembly. Referring to FIG. 10, the alternate embodiment includes a particle beam source 200, a Thorium molten salt assembly 300, a heat transfer assembly 400, a generator 500, and a shielding assembly 600 substantially as described above. The system 1000′ also includes, however, a neutron source target 230. As described in more detail below, in this alternate embodiment, the neutron source target 230 comprises one or more elements that are bombarded with the particle beam from the particle beam source 220 and that, in response, generates neutrons having various desired energy levels. FIGS. 11A-11F illustrate exemplary neutron source targets 230 that may be used in connection with the embodiment of FIG. 10. For purposes of the following discussion, it is presumed that the particle beam source 200 is as described above in connection with FIGS. 2A-2D in that it can generate protons having energies at two levels, where the first energy level is above 4.5 MeV and the second energy level is between about 2.5 MeV and just below 4.5 MeV. Referring first to FIG. 11A, an exemplary neutron target source 252 is illustrated that comprises a core of neutron reflecting/shielding material (such as graphite) 254 defining an opening passing therethrough and a neutron-generating target 256 positioned within the opening. FIG. 11A illustrates the cross-section of such a structure. In operation, particles from the particle beam source 200 (protons for example) enter the core and pass through the opening on the core and strike the neutron generating target 256. The interaction between the high energy proton beam and the target generates one or more neutrons that pass through the opening within the core and out of the neutron generator 252 where they can be provided to the Thorium molten salt assembly 300 to produce reactions as generally described above. The neutron generating target 256 can take the form of any target that includes a material that, when struck by highly energized particles, emits neutrons. In the example of FIG. 11A the neutron generating target 256 comprises a cone coated with a sufficient amount of Lithium (Li) such that the interaction with the Lithium on the cone with the incident proton beam provided by the particle beam source 200 will cause a Lithium (p, n) reaction producing neutrons at a generally thermal energy level. FIG. 11B illustrates such a Lithium cone 256. When the neutron generating target 256 is Lithium, the incident energy level of the proton beam provided by the accelerator should be greater than about 2.4 MeV to generate the desired neutron density for operation of the system 1000′. As such, the embodiments of the accelerator discussed above that can generate proton beams on the order of 3 MeV can be used with the neutron generating target of FIG. 11B. In the embodiment of FIG. 11B bombardment of illustrated neutron generating target 256 with a proton beam greater than or about 2.4 MeV will result in the generation of neutrons having an energy level of between roughly about 1×10−5 and 0.07 MeV. Neutrons at such an energy level can be applied to the Thorium molten salt system 300 to cause the reactions discussed above during periods where the generation of thermal neutrons is promoted (e.g., fission of Uranium-233). FIG. 11C illustrates an alternative neutron generating target 258. In general, the alternate neutron target 258 is like that of target 256, but it contains Beryllium, instead of Lithium. The target 258 operates generally as described with respect to the target 256, with the exception that the impingement of high energy particles on the Beryllium of target 258 will cause the generation of neutrons having a generally higher energy level than the neutrons generated using the Lithium target 256 of FIG. 11B. In general, the neutrons generated through bombardment of the Beryllium target of FIG. 11C will have an energy level in excess of 0.7 MeV. In the embodiment of FIG. 11C, when the Beryllium target 258 is used the incident energy level of the protons applied to the target should be in excess of 4.5 MeV. The various particle accelerators discussed above in connection with FIGS. 2A-2D would be suitable to provide protons of such an energy level. In some embodiments of the system of FIG. 10, it will be desirable to simultaneously provide neutrons having different energy levels and, specifically at energy levels around those using the Lithium target 256 described above and the Beryllium target 258 described above in connection with FIG. 11C. For such embodiments, it may be possible to utilize the particle beam source 200, discussed above, in combination with two neutron generating targets. Such an arrangement is shown in FIG. 11D, where both Lithium and Beryllium neutron targets are provided and the particle beam can be directed to one or the other target (or alternated between the two) to promote the generation of thermal or fast neutrons, respectively. FIGS. 11E and 11F illustrate still further alternate embodiments for generating fast and thermal neutrons. In the example of FIG. 11E a single neutron generating target is provided that includes upper segments 264 formed of Lithium and a lower core 266 formed of Beryllium. In this example, a particle beam of relatively high energy level particles and a beam shape in the form of a spot can be directed to the lower core to generate fast neutrons and a ring-shaped beam of a lower energy level can be directed to the upper segments to promote the generation of thermal neutrons. In FIG. 11F a neutron generating target is provided in which a Beryllium core 272 is provided and Lithium is sputtered on to produce discrete regions 274 of Lithium containing material. In such an embodiment the surface areas of the target will include areas of both exposed Lithium and exposed Beryllium such that the provision of high energy particles will result in the production of fast and/or slow neutrons. In the example of FIG. 11F, the energy level of the incident particles can be adjusted to promote the generation of fast neutrons over thermal (e.g., by increasing the energy level of the incident particles above 4.5 MeV) or to promote the generation of thermal neutrons over fast neutrons (e.g., by maintaining the energy level of the particles comprising the particle beam between about 2.5 MeV and 3.5 MeV). FIG. 12 generally illustrates the generated neutron flux levels and energy levels when neutron generating targets such as those illustrated in FIG. 11D are used: (a) a Beryllium target is bombarded with protons having energy levels of approximately 4.5 MeV (reflected by the triangles), and (b) a Lithium target is bombarded with approximately 3.0 MeV protons (reflected by the diamonds). The Figures described above, and the written description of specific structures and functions below are not presented to limit the scope of what I have invented or the scope of the appended claims. Rather, the Figures and written description are provided to teach any person skilled in the art to make and use the inventions for which patent protection is sought. Those skilled in the art will appreciate that not all features of a commercial embodiment of the inventions are described or shown for the sake of clarity and understanding. Persons of skill in this art will also appreciate that the development of an actual commercial embodiment incorporating aspects of the present inventions will require numerous implementation-specific decisions to achieve the developer's goal for the commercial embodiment. Such implementation-specific decisions may include, and likely are not limited to, compliance with system-related, business-related, government-related, and other constraints, which may vary by specific implementation, location and from time to time. While a developer's efforts might be complex and time-consuming in an absolute sense, such efforts would be, nevertheless, a routine undertaking for those of skill in this art having benefit of this disclosure. It must be understood that the inventions disclosed and taught herein are susceptible to numerous and various modifications and alternative forms. Lastly, the use of a singular term, such as, but not limited to, “a,” is not intended as limiting of the number of items. Also, the use of relational terms, such as, but not limited to, “top,” “bottom,” “left,” “right,” “upper,” “lower,” “down,” “up,” “side,” and the like are used in the written description for clarity in specific reference to the Figures and are not intended to limit the scope of the invention or the appended claims. Aspects of the inventions disclosed herein may be embodied as an apparatus, system, method, or computer program product. Accordingly, specific embodiments may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects, such as a “circuit,” “module” or “system.” Furthermore, embodiments of the present inventions may take the form of a computer program product embodied in one or more computer readable storage media having computer readable program code. Reference throughout this disclosure to “one embodiment,” “an embodiment,” or similar language means that a feature, structure, or characteristic described in connection with the embodiment is included in at least one of the many possible embodiments of the present inventions. The terms “including,” “comprising,” “having,” and variations thereof mean “including but not limited to” unless expressly specified otherwise. An enumerated listing of items does not imply that any or all the items are mutually exclusive and/or mutually inclusive, unless expressly specified otherwise. The terms “a,” “an,” and “the” also refer to “one or more” unless expressly specified otherwise. Furthermore, the described features, structures, or characteristics of one embodiment may be combined in any suitable manner in one or more other embodiments. Those of skill in the art having the benefit of this disclosure will understand that the inventions may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the disclosure. Aspects of the present disclosure are described with reference to schematic flowchart diagrams and/or schematic block diagrams of methods, apparatuses, systems, and computer program products according to embodiments of the disclosure. It will be understood by those of skill in the art that each block of the schematic flowchart diagrams and/or schematic block diagrams, and combinations of blocks in the schematic flowchart diagrams and/or schematic block diagrams, may be implemented by computer program instructions. Such computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to create a machine or device, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, structurally configured to implement the functions/acts specified in the schematic flowchart diagrams and/or schematic block diagrams block or blocks. These computer program instructions also may be stored in a computer readable storage medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable storage medium produce an article of manufacture including instructions which implement the function/act specified in the schematic flowchart diagrams and/or schematic block diagrams block or blocks. The computer program instructions also may be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions that execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. The schematic flowchart diagrams and/or schematic block diagrams in the Figures illustrate the architecture, functionality, and/or operation of possible apparatuses, systems, methods, and computer program products according to various embodiments of the present inventions. In this regard, each block in the schematic flowchart diagrams and/or schematic block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It also should be noted that, in some possible embodiments, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more blocks, or portions thereof, of the illustrated figures. Although various arrow types and line types may be employed in the flowchart and/or block diagrams, they do not limit the scope of the corresponding embodiments. Indeed, some arrows or other connectors may be used to indicate only the logical flow of the depicted embodiment. For example, but not limitation, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of the depicted embodiment. It will also be noted that each block of the block diagrams and/or flowchart diagrams, and combinations of blocks in the block diagrams and/or flowchart diagrams, may be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions. The description of elements in each Figure may refer to elements of proceeding Figures. Like numbers refer to like elements in all figures, including alternate embodiments of like elements. In some possible embodiments, the functions/actions/structures noted in the figures may occur out of the order noted in the block diagrams and/or operational illustrations. For example, two operations shown as occurring in succession, in fact, may be executed substantially concurrently or the operations may be executed in the reverse order, depending upon the functionality/acts/structure involved. The inventions have been described in the context of preferred and other embodiments and not every embodiment of the invention has been described. Obvious modifications and alterations to the described embodiments are available to those of ordinary skill in the art. The disclosed and undisclosed embodiments are not intended to limit or restrict the scope or applicability of the invention conceived of by the Applicants, but rather, in conformity with the patent laws, Applicants intend to protect fully all such modifications and improvements that come within the scope or range of equivalent of the following claims. |
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047088427 | summary | CROSS-REFERENCES TO RELATED APPLICATIONS This application is related to copending application Ser. No. 626,847, entitled FUEL ASSEMBLY filed Feb. 7, 1984, (W.E. 49,102) by R. K. Gjertsen, et al. which is assigned to Westinghouse Electric Corporation. BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates in general to the field of spectral shift pressurized water nuclear reactors and in particular to apparatus for seal connecting between fuel assemblies and the means used to provide the spectral shift control. 2. Description of the Prior Art In conventional, state of the art, pressurized light water nuclear reactors, the reactor core is designed to contain excess reactivity. As the reactor operates, the excess reactivity is very gradually consumed until such point as the reactor core will no longer sustain the nuclear reaction and then the reactor must be refueled. Usually this occurs over a period of years. It is very advantageous to maximize the time between reactor refuelings (extend the life of the core) since refueling requires complete shutdown of the reactor and is quite time consuming. Extending the life of the core is usually accomplished by providing the core with a significant amount of excess reactivity. Typically, control over the fission process, or reactivity control, including control necessitated by the excess reactivity is accomplished by varying the amount of neutron-absorbing materials within the core of the reactor. Control rods which contain neutron-absorbing materials and are movable into and out of the core provided one method of controlling the reactivity. Burnable and nonburnable poisons dissolved inthe reactor coolant provide another method of reactivity control. As the reactivity decreases, due to reactor operation, the poisons are gradually removed by being burned by reactor operation or are physically removed by a separate system designed for such purpose. Most often, a combination of dissolved poisons and control rods are used to control the reactor and the excess reactivity. Unfortunately, control with control rods and poisons, absorb neutrons which could otherwise be used in a productive manner. For example, the neutrons produced by the excess reactivity could be used to convert fertile materials within the fuel assemblies to plutonium or fissile uranium which can then be fissioned and contribute to an even further extension of core life. Thus, while the use of control rods and dissolved poisons provide very effective reactor control, their use comprises a relatively inefficient depletion of high cost uranium. It would be, therefore, advantageous to control the excess reactivity, but not suppress the neutrons associated with the excess reactivity, in order to further extend core life or time between refuelings, and to lower fuel costs. It is known that fuel element enrichment can be reduced and the conversion ratio of producing fissile materials can be increased by employing a "hardened" (nuclear energy) spectrum during the first part of the fuel cycle to reduce excessive reactivity and to increase the conversion of fertile material to fissile material; then employing a "softer" (lower energy) neutron spectrum during the latter part of the fuel cycle to increase reactivity and extend the core life by fissioning the previously generated fissile material. One such method utilizing the above is known as spectral shift control which provides a reactor with an extended core life while reducing the amount of neutron absorbing material inthe reactor core. One example of such method of control comprises a mechanical spectral shift reactor whereby hollow displacer rods are provided within fuel assemblies within the core (which, of course, displace) an equal volume of water within the fuel assemblies) and which are mechanically withdrawn or punctured to accomplish water flooding of the available volume. In the early stages of core life, the neutron spectrum is hardened by the dissplacement of a portion of the water within the core by the displacer rods. The spectrum is later softened by the addition of water within the core by the aforesaid rod withdrawal or puncturing U.S. Pat. No. 4,432,930, entitled "Spectral Shift Reactor Control Method" by A. J. Impink, Jr., et al., issued Feb. 21, 1984, assigned to Westinghouse Electric Corporation, discloses one such mechanical spectral shift reactor. Another method of achieving a spectral shift is to utilize heavy water or deuterium oxide to replace an equivalent volume of core water during the early stages of core life then to gradually reduce the volume of heavy water and replace it with regular reactor coolant (light water) during the later stages of core life. The less effective moderator, heavy water, allows for less fuel enrichment and a higher ratio of converting fertile material to fissile material which in combination provides for a reduction of fuel costs and an extension of core life. An example of this art is found in patent application Ser. No. 626,847, entiteld "Fuel Assembly" by R. K. Gjertsen, et al., filed on Feb. 7, 1984, and assigned to Westinghouse Electric Corporation. In the "Fuel Assembly" patent application, there is explained the need for a seal connector between the fuel element assembly and the lower core support plate which allows for the introduction of the heavy water replacing the light water moderator and the subsequent reintroduction of the moderator while effectuating a sealed connection between the fuel assemblies and the core support plate. The use of such seal connectors is new to pressurized water reactors. Such seal connectors must provide for sealing to guard against sudden increases in reactivity and for a nonfixed or nonpermanent sealed connection because of the inaccessibility of the bottom of the fuel assembly during core fueling. Accordingly, it is a primary object of the present invention to provide a seal connector which minimizes the possibility of leakage into the connector so as to prevent an inadvertent increase in reactivity. Another object of the present invention is to provide a seal connector which is integral with the fuel assembly and allows for automatic connection upon positioning of the fuel assembly within the reactor core. Still another object of the present invention is to provide a seal connector which allows for repair or replacement so as to avoid premature scrapping of an entire fuel assembly due to a damaged seal connector. SUMMARY OF THE INVENTION The present invention comprises apparatus for sealingly connecting moderator fluid flow channels in the core support plate with moderator fluid flow channels in fuel assemblies for flowing a desired amount of a combination of deuterium oxide and light water through a portion of the nuclear core to achieve spectral shift. The connector comprises a first portion mechanically fixed and sealed to the fuel assembly and a second portion which is slip fitted to the core support plate. A bellows mechanically fixed to each of the first and second portions allows for relative motion and seals between the two portions. The second motion includes a primary seal comprising a ball and cone seal and a backup seal comprising a plurality of piston ring seals. The primary seal is loaded by the fuel assembly weight and spring load. A second embodiment is provided whereby one or more piston ring seals are utilized between the first and second portions to provide a backup seal in the event of a failure of the bellows. Various other objects, advantages and features of the invention will become apparent to those skilled in the art from the following discussion taken in conjunction with the following drawings, in which: |
050154362 | abstract | A water-cooled direct cycle nuclear plant including a nuclear reactor, a turbine, a condenser, a purifying means and a feed water heater successively arranged as main constitution, further comprises means for measuring iron concentration in cooling water, and means for injection iron into cooling water for controlling iron amount in cooling water at an optimum level. The iron amount to be injected into cooling water is calculated based on the measured iron concentration so as to make the iron accumulation rate on fuel rod to be not less than 0.5 mg/m.sup.2 /hr. |
description | This application is the U.S. National Phase under 35 U.S.C. §371 of International Application No. PCT/JP2009/004205, filed on Aug. 28, 2009, which in turn claims the benefit of Japanese Application No. 2008-234270, filed on Sep. 12, 2008, the disclosures of which Applications are incorporated by reference herein. The present invention relates to a charged particle beam device for inspecting a substrate on which a circuit pattern is formed, by using a charged particle beam. The substrate as an inspection sample is such as a semiconductor substrate for a semiconductor device or a deflection array substrate for a liquid crystal display. In a manufacturing process for a substrate with a circuit pattern for a semiconductor device or a liquid crystal display, a defect such as a break, a short circuit, a flaw, or a foreign material affects the performances of the semiconductor device or the liquid crystal display manufactured from the substrate. For this reason, it is important to early detect such a defect. Along with finer circuit patterns, the inspection device, which uses an electron beam and to which the technique of an electron microscope is applied, has been put into practical use, as well as an optical inspection device using reflected light. Defect detection with the inspection device using such a charged particle beam is performed by capturing images of a region with a repetitive pattern and an adjacent region thereof and comparing the images with each other. Namely, the defect detection is performed based on knowledge that the above circuit pattern has a feature repeating the same pattern. Alternatively, there is used a defect detecting method of storing an image with a defect-free pattern in a device as a reference image and comparing an image to be detected with the reference image. In such a defect detection, pixel(s) different in signal intensity such as brightness are extracted from the captured image by the pixel. A pixel in which signal intensity exceeds a predetermined threshold is taken as a defect candidate and the representative coordinates thereof is obtained. The reason the image is taken as a defect candidate is that noises are superimposed on the image itself due to various reasons and can be detected as a defect. An operator visually views an image having a detect candidate to determine whether the image is a true defect. As described above, in the defect detection, images to be compared with each other since are subjected to a computing process, an inspection speed of the inspection device is basically rate-determined by a speed at which an image is captured. However, an area where the inspection device using the charged particle beam can image at one time is very small compared with an area of a substrate to be inspected, so that various methods for reducing an inspection time or improving an inspection speed without decreasing inspection accuracy are attempted. As an example, there has been known a sampling method which reduces the number of scanning stripes for capturing an image in an image pickup process (hereinafter referred to as a swath sampling). For example, Documents 1 or 2, or Non-Patent Document 2 listed below discloses an inspection device with a function for automatically setting the number of scanning stripes to be set in a chip according to the setting value of a sampling ratio by setting a sampling ratio in setting an inspection region. According to the swath sampling, an imaging area on the substrate to be inspected although is reduced in comparison with a general inspection method, provided the imaging area is sampled by a statistically meaningful method, a problem in manufacture of the substrate can be analyzed by analyzing the distribution of the detected defect candidate or the defect candidate in detail. Patent Document 3 and Non-Patent Document 1 listed below disclose a reference image averaging (RIA) technique in which, since the swath sampling has a relationship of trade-off between a signal-to-noise ration (S/N) and an image capturing speed, a defect determination method is devised to realize a high-speed inspection. However, a more improved device is demanded to detect an image at a high-speed. Patent Document 1: Japanese Patent Application Laid-Open No. 2000-161932 Patent Document 2: Japanese Patent Application Laid-Open No. 2002-026093 Patent Document 3: Japanese Patent Application Laid-Open No. 2005-274172 Non-Patent Document 1: T. Hiroi et al, “Robust Defect Detection System Using Double Reference Image Averaging for High Throughput SEM Inspection Tool,” 2006 IEEE/SEMI Advanced Semiconductor Manufacturing Conference, pp. 347-352. Non-Patent Document 2: M. Ikota et al, “In-line e-beam inspection with optimized sampling and newly developed ADC,” Proceedings of SPIE Vol. 5041 (2003), pp. 50-60. In the swath sampling, it is known that up to 10% sampling is a statistically meaningful sampling ratio, from evaluation experiment results disclosed in Non-Patent Document 2. This corresponds to a speed increase of 10 times. Furthermore, provided the defect determination method described in Non-Patent Document 2 is combined with the up to 10% sampling described above, it is possible to realize a speed increase of approximately 20 times. A typical user needs an inspection in which 70% (effective area) of a 300 mm diameter wafer can be inspected by a 35-nm-pixel 200 Mpps clock in one hour. Under this condition, if any speed increasing method is not used, the inspection requires approximately 80 hours. For this reason, a speed increase of approximately 20 times that can be achieved by a conventional swath sampling is not enough, so that a further speed-increase of approximately 4 times to 10 times is required. An object of the present invention is to provide a charged particle beam device and a substrate inspection device using the charged particle beam capable of more quickly extracting a defect candidate than ever before. The above object can be achieved by an inspection device with a function of setting a predetermined inspection stripe in a sample to be inspected, the sample having plural regions where predetermined patterns are formed respectively, capturing plural partial region-images in the inspection stripe, and executing an inspection using the captured partial region-images. Put another way more simply, an inspection skipped region where an image is not captured, is set in the area of the inspection stripe. The inspection device according to the present invention has a function of sampling plural partial inspection regions from the sample to capture the partial inspection images while moving a sample-stage on which the above sample to be inspected is placed. The irradiation in the inspection stripe with a primary charged particle beam is performed by moving the stage and scanning sequentially the partial inspection regions with the charged particle beam in a direction intersecting with a sample stage-movement direction. Accordingly, the above sampling function is realized by executing a beam scanning deflection control in accordance with the velocity of sample stage-movement so that only the partial inspection region are sequentially irradiated with the primary charged particle beam. This allows an inspection to be executed at a higher speed than ever before by performing an inspection by sampling only the partial inspection regions interesting an operator, i.e., region of interest (ROI) (hereinafter referred to as “ROI inspection”) or by a simple sampling. A typical ROI region includes, for example, a corner portion and an edge portion of a memory mat formed in a semiconductor device or all the pattern portions excluding non-pattern portion in a case where a pattern density is low. In the embodiment of the present invention, in order to increase the inspection speed, it is desirable to move the stage at a speed higher than an image capturing velocity with a charged particle column for executing the beam scanning deflection control. In this case, an image capturing timing since is asynchronous with the velocity of the sample stage movement, a beam deflecting-back deflection control is also used to avoid displacement in beam irradiation positions resulting therefrom. The inspection device of the present invention may have a management console for displaying a screen for setting the dimension of the above ROI region and a repetitive pitch. Furthermore, the inspection device may compute the above mentioned stage movement velocity and the amount of deflection control of the primary charged particle beam based on control parameters such as values for setting the dimension of the ROI region and the repetitive pitch. The inspection device captures images using the computed values, executes a trial inspection by comparing the images with each other, and sets an inspection recipe by determining whether an inspection condition is accepted. According to the present invention, the charged particle beam device capable of extracting a defect candidate at a higher speed than ever before can be realized. The embodiment of the present invention is described below with reference to drawings. FIG. 1 is a vertical section showing a configuration of an inspection device according to the present embodiment. The inspection device of the present embodiment is the one to which a scanning electron microscope is applied. The principal units are contained in a vacuum container. This is because a substrate such as a semiconductor wafer is irradiated with a primary charged particle beam. The inspection device of the present embodiment includes a charged particle column comprising an electron source 1 for irradiating a wafer 6 placed on a sample table 9 with a primary charged particle beam 2, a detector 13 for detecting a secondary charged particle 10 such as secondary electrons generated on the wafer or a reflection electrons from the wafer to output a signal as a secondary charged particle signal. The inspection device further includes the followings: an X-Y stage 7 for moving the sample table 9 in an X-Y plane; a defect determination section 17 for imaging the secondary charged particle signal output from the column, comparing the image obtained from the secondary charged particle signal with a reference image and extracting a pixel or pixels having a difference in the amount of signals as a result of a comparison therebetween, namely extracting the pixel or pixels as a defect candidate; and a general control section 18 for generally controlling the charged particle column, the X-Y stage 7, and the defect determination section 17. The X-Y stage 7 and the sample table 9 are held in a vacuum sample chamber. Since the primary charged particle beam 2 is greatly narrowed by an object lens 4 to converge the energy of the primary charged particle beam 2 onto the wafer 6, the diameter of the primary charged particle beam 2 is significantly small on the wafer 6. The primary charged particle beam 2 is deflected by a deflector 3 in the predetermined region on the wafer 6 to scan the wafer 6. The position of movement by scanning is synchronized with the detection timing of a secondary signal 10 to form a two dimensional image. A circuit pattern is formed on the surface of the wafer 6. However the wafer 6 since is made of various materials, the wafer 6 may produce a charging phenomenon in which an electric charge is accumulated on the wafer by the irradiation of the primary charged particle beam 2 on the wafer 6. The charging phenomenon since changes the brightness of an image or deflects the orbit of incident primary charged particle beam 2, a charging control electrode 5 is provided in front of the wafer 6 to control field strength. Before the wafer 6 is inspected, a reference sample 21 is irradiated with the primary charged particle beam 2 to form an image, then calibrations for the coordinates of the primary charged particle beam-irradiating position and a focal point are executed respectively. As described above, the diameter of the primary charged particle beam 2 is significantly small, the scanning width of the deflector 3 is much smaller than the size of the wafer 6 and the image formed by the primary charged particle beam 2 is vary small. For this reason, the wafer 6 is placed on the X-Y stage 7 before the inspection, an coordinate calibration use alignment mark on the wafer 6 is detected from an image with a comparatively low magnification rate using an optical microscope 20, the X-Y stage 7 is moved to position the alignment mark under the primary charged particle beam 2, thereby calibration of the coordinates is executed. A calibration for focus is performed by the followings: measuring the height of the reference sample 21 with a Z-sensor 8 for measuring the height of the wafer 6, next measuring the height of the alignment mark on the wafer, and adjusting excitation strength of the object lens 4 so that a focus range of the primary charged particle beam 2 narrowed by the object lens 4 includes the alignment mark. A large number of the secondary signals 10 are caused to strike on a reflection board 11 with a secondary signal reflector 12 to detect as many of the secondary signals 10 generated on the wafer 6 as possible. Second secondary electrons generated with the reflection board 11 are detected with the detector 13. The general control section 18 controls the above-mentioned operations for configuration as to the coordinates and focus. The general control section 18 sends a control signal (a) to the deflector 3 and sends a control signal (b) of the excitation strength to the object lens 4. The general control section 18 receives a measurement (c) of height of the wafer 6 sent from the Z-sensor 8 and sends the X-Y stage 7 a control signal (d) to control the X-Y stage 7. The signal detected by the detector 13 is converted into a digital signal 14 by an AD converter 15. The defect determination section 17 generates an image from the digital signal 14, compares the image with a reference image, extracts a plurality of pixels having a difference with respect to the reference image in brightness as defect candidates, and sends the general control section 18 a defect information signal (e) including the coordinates on the wafer 6 corresponding to the image signal. The inspection device according to the present embodiment includes a console 19. The console 19 is connected to the general control section 18 to display a defect image on the screen of the console 19. The general control section 18 computes the control signal (a) for the deflector 3, the control signal (b) of the excitation strength for the object lens 4, and the control signal (d) for controlling the X-Y stage 7. The console 19 is equipped with a key board for inputting the above inspection conditions and a pointing device such as a mouse. A device user operates the key board and the pointing device to input the inspection conditions. FIGS. 2A to 2D are plan views of the wafer 6 to be inspected. As shown in FIG. 2A, the semiconductor wafer 6 is a disk-shaped silicon substrate with a diameter of 200 mm to 300 mm and a thickness of approximately 1 mm. A plurality of dices 30 to be a semiconductor chip is formed from the wafer. The size of the wafer 6 has been already standardized, so that the number of the dice 30 formed on the single wafer 6 is determined depending on the size of the die 30. As shown in FIG. 2B, the single die 30 includes a plurality of memory mat groups 31 and memory-mat peripheral circuit group excluding the memory mat groups 31. For a general memory device, a pattern layout of the die 30 is configured by four memory mat groups 31. As shown in FIG. 2C, each single memory mat group 31 is formed of a plurality of memory mats 32. For a general memory device, the memory mat group 31 is formed of approximately 100×100 memory mats 32. As shown in FIG. 2D, the memory mat 32 is comprised of a plurality of memory cells 33 with repeatability in the two-dimensional direction. Several million memory cells 33 form the single memory mat 32. Each of the memory cells 33 can be a hole (a contact hole or a via hole) formed in the insulation film or the hole can be plugged with a wiring material (referred to as a plug). A determination as to what state the wafer is inspected depends on a condition that the wafer is inspected under what production process of a semiconductor device. Prior to inspection, a recipe for determining inspection conditions and an inspection procedure is formed. FIGS. 3A and 3B are flow charts showing the procedure for creating a recipe and the inspection procedure conducted along the set recipe respectively. In FIG. 3A, the general control section 18 reads a previously created and stored standard recipe. In step 301, the wafer 6 to be inspected is loaded into the inspection device. The general control section 18 starts a process for reading the standard recipe and loading the wafer 6 with instructions input by the operator using the console 19, namely the instructions act as a trigger for starting the process. The loaded wafer 6 is placed on the sample table 9. In step 302, the general control section 18 sets the followings: optical conditions such as the voltage applied to the electron source 1, the excitation strength of the object lens 4, the voltage applied to the charging control electrode 5, and the current applied to the deflector 3 based on the read standard receipt; the general control section 18 sets alignment conditions for obtaining correction between the coordinates with reference to the alignment mark of the wafer 6 and the X-Y stage 7 of the inspection device based on the image of the reference sample 21; the general control section 18 sets inspection region information indicating a region to be inspected on the wafer 6, and sets calibration conditions for registering both of coordinates used for capturing the image for adjusting the amount of light of the image and the initial gain of the detector 13. The corner portion of the memory mat 32 shown in FIG. 2D is liable to cause a defect on the production process because the corner portion is a boundary between a region where a large number of the memory cells 33 with repeatability exists and a region where the memory cell 33 with repeatability does not exist. Since a material is different between the regions where the memory cell 33 with repeatability exists and does not exist, if a defect inspection is performed by comparing the image at the corner portion of the memory mat 32 captured without changing the electro-optical condition with the image at the region excluding the corner portion, the memory cell that is not actually defective may be extracted as a defect by mistake because pixels are different in brightness between the corner portion and the region excluding the corner portion. Therefore, in step 303, in order to inspect the corner portion of the memory mat 32 as shown in FIG. 2D, the corner portion is selected by displaying the pattern layout of the wafer 6 on the screen of the console 19 and surrounding the region of corner portion of the memory mat 32 by a square on a GUI screen. In step 304, the optical conditions for imaging the corner are set. Actually, prior to the selection of corner portion of the memory mat, setting for an arrangement of the inspection stripe in any region of the die is executed. In setting of the arrangement of the inspection stripe, the inspection stripe is set so that the desired corner portion of the memory mat is included, thereafter, the corner portion is selected in step 303. In step 305, the inspection conditions are set to perform a trial inspection for confirming whether the set optical conditions are correct. In step 306, the trial inspection described later is executed. In step 307, the operator determines the result of the trial inspection and confirms whether the inspection condition is correct. In step 308, if the operator determines that any of the inspection conditions needs correcting, it is corrected in step 305. If the operator determines that the inspection conditions do not need correcting, the recipe is stored, the wafer 6 is unloaded and the formation of the recipe is finished in step 309. FIG. 3B shows procedures for the inspection. In step 310, the recipe stored in FIG. 3A is read. In step 311, the wafer 6 to be inspected is loaded into the inspection device. By using the console 19, and according to the specification of the wafer 6, the operator sets the optical conditions to the general control section 18 by selecting or specifying any suitable stripe to be actually used from among inspection stripes capable of including the corner portion of the memory mat, as well as a pixel dimension, and the number of times of line addition (step 312); the operator performs coordinate-alignment between the semiconductor wafer 6 and the X-Y stage 7 (step 313), and performs calibration for adjusting the amount of light of the image (step 314). In step 315, the defect inspection is started. The following series of processes for the defect inspection is repeated until the inspection of a predetermined die is finished: capturing an image in the selected inspection region, comparing the captured image with the reference image to extract a difference therebetween and determining the difference as a defect candidate (step 315); and storing the captured image with the difference, the reference image and representative coordinates of the defect candidate in a storage device (step 316). In step 317, when the inspection of a final die placed on the wafer 6 is finished, the wafer 6 is unloaded. FIG. 4 shows an example of an inspection region setting screen 40 displayed on the screen of the console 19 when executing steps 303 and 304 of the flow chart shown in FIG. 3A. A general schematic diagram of the die 30 shown in FIG. 2B is displayed in a map display region 41 on the left of the screen 40 in FIG. 4. The image of the memory mat 32 shown in FIG. 2D is displayed in an image display region 42 on the right of the screen 40 in FIG. 4. The image on the coordinates specified in the map display region 41 is displayed in the image display region 42. The screen 40 also displays an ROI condition setting section 43 for confirming and changing the ROI conditions. When selecting any one of objects to be inspected in the ROI region (namely, the objects are a mat corner, simple sampling, a combination of the mat corner with the simple sampling, and any pattern portion to be selected from all pattern portions in the case that densities of all pattern portions are low), for example, selecting the mat corner, detailed specification is needed about mat corner portion to be inspected (for example, how many corner potions to be inspected among four corner portions or what percentage of memory mats among the corners of a plurality of memory mats to be inspected). Furthermore, when selecting the mat corner, the specification is needed about what dimension to be inspected including the mat corner. The operator inputs various conditions into the ROI condition setting section 43 to set an inspection region. The corner portion of the memory mat 32 shown in FIG. 2D since has a high frequency as to defect, the inspection device of the present embodiment has a function by which only a corner portion can be set as the inspection region. A rectangular region 44 is specified on the image display region 42 in FIG. 4 to set the corner portion of the memory mat 32 as the region to be inspected. In a typical image comparison inspection, adjacent similar patterns are compared with one another to extract a difference. However, in the inspection of a memory-mat portion, adjacent similar patterns since do not exist, a comparison inspection is performed by previously producing a reference defect-free image for the memory-mat portion (the defect-free image is called as a golden image) and comparing the golden image with the captured image of the real mat portion to extract a difference therebetween. The inspection region setting screen 40 shown in FIG. 4 shows an example in which a “mat corner” is set as ROI, “four corners” as detail, “10 μm” as dimension, and “golden” as defect detection in the ROI condition setting section 43. This means that four corner portions of the memory mat 32 shown in FIG. 2D are selected as the ROI region, all the four corners of the memory mat 32 are inspected, an image capture-dimension is 10 μm, and the golden image is produced. When the operator clicks an “IMAGE-CAPTURE” button, it is possible to capture images on a full-inspection stripe or a partial region including at least the ROI region. A computing device included in the console 19 produces the golden image by clipping partial images of the ROI region from the captured images, performing registration of the partial images and then performing averaging of them. The operator confirms the golden image in the image display region 42 and pushes a “COMPLETION” button to store the golden image in the recipe. The golden image may be produced by the defect determination section 17. Contents of the trial inspection shown in step 306 in FIG. 3A are described below with reference to FIGS. 5 to 7. (a) of FIG. 5 is an enlarged view of the plurality of dice 30 shown in FIG. 2A. (b) of FIG. 5 is a diagram further enlarging a part of the inspection stripe set in a certain die. In (a) of FIG. 5, reference numerals 51A, 51B, and 51C denote the plurality of dice 30 arranged adjacent to each other and a reference numeral 52 represents the ROI scan region set in an inspection stripe 53. In the present embodiment, the ROI scan region 52 is set in the inspection stripe 53 with a width of L and a pitch of P between the adjacent ROI scan regions. An arrow passing through the center of the inspection stripe 53 shows the center in the y-direction of scan of the primary charged particle beam and means the direction in which the sample stage 7 is moved. In the trial inspection in step 306, the inspection device scans the ROI scan region 52 with the primary charged particle beam in a direction orthogonal to a direction of the X-Y stage 7 movement while moving the X-Y stage 7 in the direction indicated by the arrow along the plurality of dice 51A, 51B, and 51C to capture images in the partial region including the corner portion in the ROI scan region 52. A detail configuration in the ROI scan region 52 is described below with reference to (b) of FIG. 5. As shown in (b) of FIG. 5, in the present embodiment, the inspection stripe 53 is set so that six edges of the memory mat are included in the ROI scan region 52. For this reason, two sets of four corners formed at the memory mat-edges opposing each other are included in the single ROI scan region 52. In (b) of FIG. 5, an ROI capturing region 54 corresponding to the rectangular region 44 in FIG. 4 is set in the eight memory mat corners in the ROI scan region 52. The ROI scan region 52 and the ROI capturing region 54 are set by providing information of inspection stripe arrangement on the die to be inspected and information of the ROI set on the inspection region setting screen 40 in FIG. 4 to all the dice to be inspected on the wafer 6. The computing process for such setting is executed by the general control section 18. The width and length of the memory mat 32 are substantially constant in all the memory mats formed in the wafer and the layout thereof is previously specified. For this reason, the general control section 18 can obtain information about coordinates of each ROI scan region 52 arranged on the inspection stripe 53 from information about the width L and the P of the ROI scan region 52, thereby can controlling beginning timing and end timing at which each ROI scan region 52 is irradiated with the primary charged particle beam. The captured image data in each ROI scan region 52 are transferred to the defect determination section 17. The defect determination section 17 extracts an image of the ROI capturing region 54 using information about the layout of the memory mat and information about each ROI scan region 52 obtained by the general control section 18, compares the captured image with the golden image described later to execute the defect inspection. The golden image being the reference image for a comparison inspection is produced by performing averaging of plural ROI capturing regions 54. The defect determination section 17 compares the golden image with the captured image in the plurality of the ROI capturing regions 54. If there is a difference in brightness therebetween for each pixel, the pixel is extracted to produce an image as defect candidate. The image as a defect candidate and the coordinates of the defect candidate are stored in the defect determination section 17 as defect information and can be displayed on the screen of the console 19. Next, control of moving the stage in the ROI inspection according to the present embodiment is described below. In a conventional comparison inspection, in order to capture the image on the inspection stripe 53 shown in (a) of FIG. 5, the primary charged particle beam 2 is one-dimensionally scanned within a width of the inspection stripe 53 in the direction substantially perpendicular to the direction indicated by the arrow in (a) of FIG. 5 while continuously moving the X-Y stage 7 in the direction indicated by the arrow. On the other hand, the inspection device according to the present embodiment has only to scan only a part of the inspection stripe 53, i.e., only the ROI scan region 52 including the ROI capturing region 54, so that the movement velocity of the X-Y stage 7 can be made quicker correspondingly, than that in the conventional comparison inspection. The reason the movement velocity of the X-Y stage 7 can be made quicker in the present embodiment is described below with reference to FIG. 6. (a) and (d) in FIG. 6 are schematic diagrams showing time distances on the length L of the ROI scan region 52 and on the arrangement pitch P in a predetermined stage movement velocity. (b) and (e) in FIG. 6 are schematic diagrams showing how the ROI scan regions 52 are arranged on the inspection stripe 53 in the actual wafer. (c) and (f) of FIG. 6 are schematic diagrams showing a positional relationship among scanning lines in a visual field region with a size M. (a), (b) and (c) of FIG. 6 correspond to a case where a stage movement velocity V0 is equal to a conventional one. (d), (e) and (f) of FIG. 6 correspond to a case where a stage movement velocity is set to Vs faster than the stage movement velocity V0. As shown in (b) of FIG. 6, assume that the plurality of the ROI scan regions 52 are arranged on the inspection stripe 53 with a pitch P and the ROI scan region 52 is formed of n scanning lines of the primary charged particle beams arranged in a stage movement direction. For the sake of simplicity of description, the length of each ROI scan region 52 is taken as L, the width of the inspection stripe 53 (the width is a measurement in the short-side direction perpendicular to the long-side direction of the inspection stripe) is taken as I, and the center of the inspection stripe (the dotted line in (b) of FIG. 6 is taken as the center of scanning deflection of the primary charged particle beam. In the above case, when capturing all the images on the inspection stripe 53 with the primary charged particle beam scanning, the stage has to move only by the distance of one scanning line in the stage movement direction (the distance is corresponding to one pixel) during the time required for scanning of per one scanning line. The time required for scanning of the primary charged particle beam per one scanning line is equal to 1/f with the deflection frequency of the scanning deflector as f. Usually, the detector 13 of the inspection device outputs image data for one scanning line per the above time of 1/f, so that 1/f is referred to as one-line image capturing time. A normal stage movement velocity V0 refers to the velocity at which the sample stage can move by one pixel size during the time corresponding to the one-line image capturing time. In the present embodiment, the V0 may be represented by the stage movement velocity synchronized with the beam scanning. As shown in (b) of FIG. 6, assuming that that plural ROI scan regions 52 are arranged on the inspection stripe 53 with a pitch P and the stage is continuously moved at the velocity V0, as shown in (c) of FIG. 6, the first scanning line 61a and an n-th scanning line 61b arranged in the ROI scan regions 52 move only by the length corresponding to n pixels, i.e., an actual distance L on the wafer within the range of the visual field region M. This is because, as described above, the stage movement velocity is synchronized with the beam scanning speed. On the other hand, assuming that the stage is moved at a velocity Vs faster than the stage movement velocity V0, the irradiation position of the primary charged particle beam is moved to the adjacent scanning line before the scanning of one line is finished, thereby failing to scan an imaged position on the actual wafer. More specifically, if the stage movement velocity Vs is faster than the image capturing speed, it is impossible to capture the images on the full-inspection stripe 53. However, as shown in (e) of FIG. 6, even at the stage movement velocity Vs, when only an image in the intermittently arranged ROI scan region 52 has to be captured on the inspection stripe 53, as shown in (f) of FIG. 6, if an image-capture is started just when a first scanning line 61c enters the visual field region with a size M (namely, at the point when the first scanning line 61c lies on the left side-edge of the visual field region M in (f) of FIG. 6) and the final pixel of an n-th scanning line 61d is completed to be captured while the n-th scanning line 61d exists in the visual field region M, images can be captured in the ROI scan region 52 without failure, by the following conditions. The size M of the visual field region is normally maximized within the range of maximum value of visual field determined by the performance of an electro-optical system. The electro-optical system has a visual field with a certain size and images substantially equivalent in the influence of aberration and distortion can be captured in the visual field. The maximum value of the visual field is determined by the performance of an electro-optical system such as the deflection distance of a scanning deflector or the degree of aberration of curvature of field. The greater the visual field region to be set, the greater the region of a sample which can be imaged at one time, thereby enabling a high-speed inspection also in the ROI inspection. To be more exact, if the primary charged particle beam irradiation is started at a head pixel in the first scanning line 61c at the instant when an actual wafer's position to be the head pixel of the first scanning line 61c comes into the visual field region M, and if the primary charged particle beam irradiation is finished at the instant when an actual wafer's position to be the final pixel of the n-th scanning line 61d comes out of the visual field region M, the entire ROI scan region 52 can be imaged without failing to capture the images. Reference numeral 61e denotes a first scanning line in the next ROI scan region 52. Hereinafter, the beam is sequentially scanned to the set plurality of ROI scan regions. In addition, in this case, the stage movement velocity Vs since is asynchronous with the scanning deflection frequency of the beam, the beam irradiation position in the ROI scan region 52 is gradually displaced from the position on the scanning line to be originally irradiated with the beam with respect to the stage movement direction if nothing is done. The inspection device of the present embodiment cancels the displacement due to asynchronism between the beam scanning deflection frequency and the stage movement velocity by deflecting back the irradiation position of the primary charged particle beam to the same direction as the stage movement direction by a deflecting-back deflection. This control is realized by the general control section 18 causing the scanning deflector 3 to perform the deflecting-back deflection to cancel the above displacement due to asynchronism. The aforementioned displacement due to asynchronism increases along with advancement in the repetition of scanning from the first scanning line to the n-th scanning line, so that the deflection distance of deflecting-back deflection of the primary charged particle beam 2 (the beam deflection angle of the scanning deflector 3) increases. The greater the beam deflection angle of the scanning deflector, the more advantageously the stage movement velocity is increased. However, the stage movement velocity Vs cannot be limitlessly increased but is restricted by the ratio of the size M of the visual field region to the length L of the ROI scan region 52 (substantially, the area of the ROI scan region). A mathematical formula 1 given below indicates the above constraint condition and shows that, if an imaging region with a length L is set in the visual field region with a size M, the stage movement velocity should be smaller than the right side value of the mathematical formula 1 to image throughout the imaging region.Vs≦{(L+M)/L}V0 [mathematical formula 1] On the other hand, the upper limit of the stage movement velocity is restricted also by the length L of the ROI scan region 52 and the arrangement pitch P in the stage movement direction in the ROI scan region 52. The following mathematical formula 2 shows the constraint condition.Vs≦(P/L)V0 [mathematical formula 2] If a scan skip region is considered to be provided between the ROI scan regions from which images are captured, the mathematical formulas 1 and 2 are understandable. The greater the length of the skip region, the faster the stage movement velocity can be made. On the other hand, the greater the width of the ROI scan region, the slower the stage movement velocity needs to be made. For this reason, the stage movement velocity is set according to the ratio of the width of the scan region to the width of the skip region. As shown in (b) and (e) of FIG. 6, if the length of the ROI scan region 52 is L and the arrangement pitch in the stage movement direction is P, the size of the scan skip region is equal to difference between P and L, namely (P−L). If a scanning skip distance is taken as S, S is represented by S=P−L, and S=P−L can be rewritten as P=S+L. Substituting P=S+L for the mathematical formula 2 gives the following formula:Vs≦{L+S)/L}V0 [mathematical formula 3] Apparently, the mathematical formula 3 is equal to the mathematical formula 1. More specifically, the mathematical formulas 1 and 2 show that the maximum value of the scan skip region is M−L, i.e., the condition under which one ROI scan region can be set in the visual field with a size M (the condition under which the beginning edge and ending edge scanning lines in the ROI scan region can exist in the same visual field M) is the upper limit of the scan skip region; and the increase of the number of the ROI scan regions and the area thereof in the visual field M requires that the stage movement velocity should be reduced by just that much. The mathematical formula 3 can be changed into the following formula:Vs−V0=ΔV=(S/L)V0 [mathematical formula 4]This formula shows that the increment of the stage movement velocity from V0 in the ROI inspection is determined according to the ratio of the length of the skip region to that of the ROI scan region 52 or the ratio of visual field size M to the length of the ROI scan region 52. As described above, it is possible to capture the images to be captured at a high speed by moving the scanning position of the beam 2 under the restraints of the mathematical formulas 1 and 2 according to the region where images are desired to be captured. For example, when the width L=10 μm, the visual filed M=100 μm, and the pitch P=60 μm, V≦11×V0 or V≦6×V0 can be obtained from the mathematical formula 1. This means that, even if the stage is moved at most six times faster than the case where full images in the inspection stripe 53 are captured, the images can be captured in the ROI capturing region 54. The above description is made on the premise that the general control section 18 executes the stage control. It is needless to say that a stage movement control means configured to dedicatedly execute the stage movement control may be separately provided. FIG. 7 shows a trial inspection execution screen which is displayed in the trial inspection in step 306. The trial inspection execution screen includes a map portion 70 on which the inspection stripe 53 is dividedly displayed, an image display portion 71 on which a defect image is displayed, and a defect information display portion 72 on which various attribute information (RDC information) such as conditions for detecting defects and characteristics of defects is displayed. In FIG. 7, four ROI scan regions 52 indicated by reference numeral 75 are displayed on the map portion 70. A rectangle 76 indicating the ROI capturing region 54 and a pointer 73 for highlighting a defect candidate are displayed in each scan region 75. Although a detailed description is omitted, the rectangle 76 indicating the ROI capturing region 54 can be edited by switching a condition setting tab into an ROI region setting tab 77. Clicking the pointer 73 displays the image and information of a defect candidate corresponding to the pointer 73 on the image display portion 71. Moving the slider of a display threshold setting tool bar 74 allows selecting the pointer 73 of a defect candidate displayed on the map portion 70. In other words, information in which a defect candidate can be selected on condition that the display threshold is lower than a certain value, is predetermined; and by moving the slider in the tool bar, only the defect candidate satisfying the conditions is displayed as itself in accordance with the threshold determined by slider. The map portion 70 includes a mode for selecting an image display mode of the image display portion 71. There can be switchably displayed the image of the defect candidate, a part of the captured images stored in the memory, the images re-captured by moving the stage according to the mode. According to the image of the defect candidate, it is possible to confirm detailed determination of a defect therethrough. According to the part of the captured images, it is possible to determine whether another defect to be detected exists around a certain defect. According to the re-captured images, it is possible to observe whether the detected defect is a true defect in a case where the detected defect is observed under an optical condition of a high magnification or a high S/N. Switching the selection mode enables displaying the captured image itself including the defect candidate on the image display portion 71. The general control of the GUI screen is made by a computing device in the console 19. Although not illustrated, by clicking a golden image capturing button, it is possible to re-capture the golden image based on the currently captured image, thereby allowing the image to be updated. By updating such an image or by being selectable as to the image used for averaging in producing the golden image, it is possible to produce a reference image with a fewer noise components such as a defect. After the inspection condition is set, information is stored in the recipe, the wafer is unloaded, and the production of the recipe is completed. FIG. 8 is a diagram describing a method of determining a defect. There are several kind of modes in defects of interest (DOI) among the defects detected by the inspection device, for example: a black-pattern white-defect mode in which a hole portion of the contact hole normally appearing black appears white because of non-conduction; a small-hole defect mode in which a black pattern appears small because the hole diameter of the contact hole is reduced; and a white-pattern white-defect mode in which a plug portion normally appearing white make a short-circuit with an adjacent plug and thereby it appears whiter than the normally appearing white. The appearance of the defect pattern is determined according to the above modes. As to a nuisance which is a noise desired not to be detected, it typically is exampled as a white bright-spot defect-mode in which a white bright spot appears in an insulation-film region due to electrical charges therein. The defect determination section 17 compares an ROI capturing region image 81 with a golden image 80 to produce a first difference image 82 with a size of an ROI capturing region including a pixel different in brightness (whose position coordinates corresponds to the position of a defect candidate) and produces a second difference image 83 in the order of a region in size including only the vicinity of the position of a defect candidate using the difference image 82. The defect determination section 17 uses images 84A, 84B, 84C, and 84D of various defect modes such as previously obtained black-pattern white-defect mode, small-hole defect mode, and white bright-spot defect-mode in an insulation film thereby to produce a “reference image 85 for determining a matching rate”, the reference image 85 to be compared with the second difference image 83 in terms of the above various defect modes. A plurality of reference images 85 for determining a matching degree are collated with the second difference image 83 to calculate a matching rate with respect to the various defect modes. A table 86 shows calculation results of a matching rate corresponding to the defect modes A to D and also shows that the defect mode A is the highest in a matching rate. By selecting the mode being the highest in the matching rate, it is possible to know the certain defect mode as to the detected defect. Images previously captured for reference image are exampled as follows: namely, images with a non-conductive defect mode in which the holes' resistances are the same kind (non-conduction, for example) but the values of the resistances are different from each other, or images with different defect modes (a non-conductive defect mode in which the holes' resistances of the hole are different from each other and a small hole defect mode in which the diameters of the holes are different from each other, for example) or any one of the both different modes. Therefore, the inspection device of the present embodiment is provided with a memory for storing image data of the above-mentioned defect modes in the defect determination section 17. According to the present embodiment, it since is possible to compare images captured to be inspected with a reference sample (reference mode) previously captured as defect mode, it can obtain information only as to the interesting defect mode as well as information such as occurrence frequency of defect in which any defect mode is not specified or information of defect-distribution, by filtering the compared image with any defect mode. FIG. 9 is a sequence diagram for capturing an image used for the comparison inspection. FIG. 10 is a graph showing a change in the amount of obtained signals with time. In FIG. 9, a line number (in which the finally obtained line is numbered in the order of coordinates in a case where a single image is captured by a plural number of times of electron beam scanning) is provided in the vertical direction and a line scanning order is represented by a number in a square showing an image. For example, in a line [1], a data-obtaining is performed four times in the fourth, seventh, tenth, and thirteenth line-scanning orders. These data are subjected to a weighted averaging. The contents of the weight are described below. In FIG. 10, the amount of signals obtained from the wafer 6 is decreased with the lapse of time. At the beginning, the wafer-surface state can be discriminated and thereafter the amount of signals is differently decreased between a normal portion and a defect portion due to a difference in a charging state caused by a difference in the structure of the region irradiated with the primary charged particle beam 2. This enables discriminating between the normal portion and the defect portion. Then, the weight of time for which inner information of the wafer can be available is increased. Contrarily, the weight of time for which only surface information of the wafer can be obtained is made negative, thereby the process using data added with a weight can provide more accurate information than the process using data added without a weight. By executing the inspection using information as to such a signal amount-transient characteristic, the inspection accuracy can be improved because of excluding an influence from image data including a large amount of surface information and increasing the inner information. The present embodiment is characterized in that the use of such a transient characteristic increases the inspection accuracy. The above description although is made on the premise that the whole ROI scan region 52 is irradiated with the primary charged particle beam and the region corresponding to the ROI capturing region 54 is extracted from the captured image and inspected, the inspection device may use a configuration in which only the ROI capturing region 54 is irradiated with the beam at the time of scanning the ROI scan region 52. FIG. 11 is a graph showing a relationship between the image-obtained region and the deflection voltage applied to the deflector 3 by the inspection device with a function of irradiating only the ROI capturing region 54 with the beam. As an example, described below is a method of controlling a primary charged particle beam scanning for imaging only regions 110a and 110b shown in (a) of FIG. 11. (b) of FIG. 11 shows the time waveform of a deflection voltage applied to the deflector 3 in a case where the whole ROI scan region 52 is imaged. The ordinate shows time and the abscissa shows the deflection voltage. Since the deflection voltage is zero (V) at the center of the scanning deflection, the deflection voltage is negative at the time of scanning the upper half of the ROI scan region 52 shown in (a) of FIG. 11, and the deflection voltage is positive at the time of scanning the lower half of the ROI scan region 52. In the case of imaging only the regions 110a and 110b, as shown in (c) of FIG. 11, the deflection voltage applied to the scanning deflector 3 at a time of 0 is set to the voltage corresponding to a scanning beginning position (the upper end portion in the region 110a) in the region 110a. In other words, scanning is started in a state where a time region (i) shown in (b) of FIG. 11 is skipped. The deflection voltage increases with time. When the deflection voltage reaches the voltage corresponding to a scanning ending position in the region 110a (the lower end portion in the region 110a), the deflection voltage is stepwise changed to the voltage corresponding to a scanning beginning position in the region 110b (the upper end portion in the region 110b). Such a stepwise change corresponds to the skip of a time region (ii) shown in (b) of FIG. 11. Thereafter, the deflection voltage increases with time. When the deflection voltage reaches the voltage corresponding to a scanning ending position in the region 110b (the lower end portion in the region 110b), scanning of one line is finished. Thereafter, the deflecting-back deflection control to the stage movement direction resets the deflection voltage to the voltage in a position corresponding to the scan beginning position on the following scanning line. The above beam scanning control realizes the ROI control imaging only the regions 110a and 110b. The above beam scanning control reduces a scanning time per one scanning line (a beam irradiation time) by time (i)+(ii)+(iii) shown in (c) of FIG. 11. In other words, the stage movement velocity Vs (substantially, V0) can be made faster by the above reduced time. The above beam scanning control is realized such that the general control section 18 computes the time waveform of the deflection voltage based on the dimension and arrangement pitch of the memory mat 32 and arrangement information about the ROI capturing region 54 on the memory mat and controls the scanning deflector 3 based on the computed deflection voltage with the time waveform. Although the above description takes, as an example, a beam scanning control method in which only the regions 110a and 110b including two ROI capturing regions 54 are irradiated with the beam, it is to be understood that the beam scanning control can also be executed so as not to irradiate the region expect the ROI capturing region 54 in the regions 110a and 110b. As described above, the inspection device of the present embodiment realizes the inspection device whose inspection speed is much higher than ever before. The embodiment 1 describes the example in which the ROI capturing region 54 is set in the memory mat, a defect in which the device user is interested may be unevenly distributed in units of structure of a wafer larger in dimension than the visual field of the detection optical system, for example, in units of structure such as a die or a wafer with a dimension of mm order. In the present embodiment, an inspection method is described in a case where the ROI is set in units of structure larger than the one in the embodiment 1. The general configuration of the inspection device is substantially similar to that shown in FIG. 1, so that the description is not repeated. FIGS. 12A, 12B, and 12C show examples of arrangement of the ROI of the present embodiment on the die or the wafer. FIG. 12A is a chart showing a layout of part of the die to be inspected and shows an example where the inspection stripe 53 is arranged on the memory mat group 31. In FIG. 12A, the ROI being the interesting inspection region is only the memory mat group 31 in the memory mat regions 121a and 121b. In other words, the peripheral circuit portion excluding the memory mat group is thin in pattern and low in probability that a defect occurs, so that the peripheral circuit portion is excluded from our interest. FIG. 12B shows an example where the ROI is set in memory mat both-side regions 122a to 122d. In general, in the region where the rate of change in pattern density is high, defects tend to frequently occur. Therefore, defects tend to frequently occur in the both side region of the memory mat group. FIG. 12C shows an example where the ROIs are set in the dice around the periphery of the wafer. A wafer peripheral die 123 hatched in FIG. 12C causes defects more frequently than a wafer inner die because of different conditions for a manufacturing process, so that wafer peripheral region dice 124a and 124b are truly interesting regions. In a case where an image is captured only in the aforementioned region, the region for an inspection image is set on the inspection region setting screen shown in FIG. 4 and the general control section 18 is caused to execute a stage movement control according to the information about the position in the set region. More specifically, the stage movement velocity V is made variable, only the above memory mat regions 121a and 121b, the memory mat both-side regions 122a to 122d, the wafer peripheral regions 124a and 124b are moved at a low velocity, and the regions other than those are moved at a high velocity. In other words, the sample stage is moved at a velocity higher than the velocity at which an image is detected in the region excepting a predetermined region on the same inspection stripe. This enables the inspection time to be made shorter than ever before. In the present embodiment, another modification for setting an ROI capturing region is described below. The general configuration of the inspection device used in the present embodiment is similar to that shown in FIG. 1 as is the case with the embodiment 2. FIG. 13A is a schematic diagram showing the layout of the ROI capturing regions in the memory mat 32 in a case where each of the ROI capturing region 131 is set larger than the previously mentioned memory mat corner portion. In FIG. 13A, each of the ROI capturing regions 131 is set as a partial region 131 which is equal to the memory mat in vertical length (namely length in the direction where the beam is scanned) and includes approximately several memory cells in the length direction of the memory mat (namely, in the stage movement direction). The plurality of partial regions 131 (three partial regions in the present embodiment) are arranged in the length direction of the memory mat. In FIG. 13A, the area of the partial regions 131 set on the memory mat 32 accounts for approximately 40% of area of the memory mat. In a case where inspection images are sampled from the set region shown in FIG. 13A, there can be realized the stage movement and inspection speed which are faster by 2.5 times than those of typical whole surface inspection. When the above inspection is performed, the visual filed region M is set to such a size as to include at least one memory mat 32 and the general control section 18 executes the stage control according to the length of the partial region 131 in the stage movement direction and the length of the skip region between the plurality of partial regions 131. The partial regions 131 are set on the inspection region setting screen shown in FIG. 4. A defect detection is executed by a method of using the golden image described in the embodiment 1 where the same pattern is repeated in the beam scanning direction and/or the stage movement direction. Furthermore, a method using an RIA method (described in Patent Document 3 and Non-Patent Document 1) in which the repetitive patterns are mutually subjected to averaging and the averaging-subjected images are arranged and taken as a reference image, and a die comparison using the same pattern for each die. As is the case with the embodiment 1, the golden image used for defect-detecting comparison computing is produced with the console 17 by computing the averaging value of the plurality of partial regions 131. As shown in FIG. 13A, the partial regions 131 are not always set at equally spaced intervals. In that case, the displacement between the scanning line position and the beam irradiation position arranged in each partial region 131 is cancelled by any of the adjustment of the stage movement velocity or the control of amount of the deflecting-back deflection. In the case of adopting the adjustment of the stage movement velocity, there since may be problem in mechanical accuracy, it is more advantageous to adopt the control method of the deflecting-back deflection with high controllability. FIG. 13B is a schematic diagram showing a layout of the ROI capturing regions set at certain memory mats positioned in a plurality of memory mats forming a memory mat group in a case where each of the certain memory mats is set as a unit to be detected. In the example shown in FIG. 13B, the ROI capturing regions are set to several certain memory mats respectively at four corners of the memory mat group 31, at the mid-points of each side portions of the memory mat group 31, and at the center of the memory mat group 31. Furthermore, in a plurality of memory cells constituting each of memory mats selected as the ROI capturing regions as described above, memory cells at only each corner-region in all the memory cells are to be inspected. Thereby, it is possible to increase the speed of inspection in comparison with that of the embodiment 1 in accordance with the rate of selection of the memory mats. According to the present embodiment, the inspection time is substantially made shorter than that in a case where the whole surface of the wafer is inspected because both of speed-up by image capturing for sampling in units of memory mat and speed-up by image capturing for sampling with specifying corner portions in the memory mat. In the case of inspecting under the condition setting the ROI capturing regions shown in FIG. 13(b), required is the following two kinds of control parameters: one is a control parameter for performing the beam scanning control and the stage movement control in the memory mat 32; another is a control parameter for performing the beam scanning control and the stage movement control in a case where the visual filed region M is on the order of the memory mat group 31. More specifically, there are required parameters: information about the layout of corner portions (information about size and position of the rectangular region 44 shown in FIG. 4) and information about the dimension of the memory mat required for capturing images, only at the corner portions in the memory mat; information about the layout of memory mats specified in units in the memory mat group 31 to perform a sampling inspection (namely the information is about size and position of the specified memory mat in the memory mat group 31) and information about the dimension of the memory mat group. The above control parameters may be set through the GUI by appropriately switching the visual field size of the image to be displayed on the image display region 42 of the inspection region setting screen shown in FIG. 4. The set control information is transferred to the general control section 18 and used for the beam scanning control and the stage movement control. Even if the above sampling is performed and if the occurrence of a defect is distributed, it is possible to capture the distribution. The present modification has an advantage in that a required defect distribution can be obtained and the inspection time can be made further shorter than ever before. In the present embodiment, still another modification for setting the ROI capturing region is described below. FIG. 14 shows the relationship of layout in a case where three ROI capturing regions are set in one memory mat. That is, in this embodiment, in order to inspect partially specified regions in the memory mat 32, the inspection is done by specifying the plural ROI capturing regions 54 to be irradiated for scanning with the charged particle beam in order by arrangement in the stage movement direction, and by scanning the specified ROI capturing regions in their arrangement order with the charged particle beam irradiation and the stage movement. A plurality of memory mats 32 are arranged on the wafer, so that the ROI capturing regions 54 are regularly arranged in sequential inspection region 141. In addition, in a non-inspection region 142 including near an inspection start side-edge portion of the die and wide gaps existing in the arrangement of the memory mats 32, dummy inspection regions 143 are arranged as densely as the sequential inspection region 141. This “as densely as the sequential inspection region” means that the dummy inspection regions 143 are arranged based on a logic similar to the arrangement of the ROI capturing regions 54 by virtually assuming the repetition of the memory mat or the repetition of the die, or means that the dummy inspection regions 143 are arranged at regular intervals determined in accordance with the stage-velocity. The arrangement of the dummy inspection regions enables electro static charge on the wafer 6 to be uniformly held by beam irradiation. The dummy inspection regions 143 may be captured as images or may be only irradiated with the charged particle beam. The same effect can be expected by increasing the scanning interval of each charged particle beam instead of arranging the dummy inspection region 143 at regular intervals. It is needless to say that the same effect can be expected by performing scanning incompletely with the scanning interval of the charged particle beam increased, instead of completely scanning even between the ROI capturing regions 54. In the above embodiments 1 to 4, description although is made using a method in which a defect is detected by comparing a previously obtained golden image 45 with a captured image of interest as to defect detection, any defect detection method may also be used such as actual pattern comparison methods such as cell comparison, RIA method, die comparison, and mat comparison, and a comparison method with a design pattern generated from design. According to the present embodiment, it is possible to provide the inspection system capable of making high-speed image capturing time almost six times as speed as time required for normally capturing an image on a whole surface of the wafer and capable of inspecting a defect occurrence frequency distribution in the ROI region at a high throughput. Furthermore, the present embodiment can provide the inspection device and method for efficiently monitoring a defect occurrence frequency and a characteristic likelihood. 2: Primary charged particle beam, 3: Deflector, 4: Object lens, 5: Charging control electrode, 6: Wafer, 7: X-Y stage, 8: Z-sensor, 9: Sample table, 10: Secondary signal, 17: Defect determination section, 18: General control section, 19: Console, 20: Optical microscope, 21: Reference sample, 30: Die, 31: Memory mat group, 32: Memory mat, 33: Memory cell, 41: Map display region, 42: Image display region, 43: ROI condition setting section, 44: Rectangular region, 52: ROI scan region, 53: Inspection stripe, 54: ROI capturing region, 70: Map, 71: Image display portion, 72: Defect information display portion, 73: Mark, 74: Display threshold setting toolbar, 80: ROI capturing region image, 81: Golden image, 82: Difference image |
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047675918 | description | DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT FIG. 1 illustrates a probe in accordance with the present invention, designated generally be reference numeral 2. Probe 2 comprises a substrate 4 which may be, for example, glass or silica. A pair of inner metal contacts 6 are supported by substrate 4. Contacts 6 preferably comprise metal films deposited onto the substrate. A pair of outer metal contacts 8 are also provided. Contacts 8 may likewise comprise metal films deposited on substrate 4. A carbon film 10 is deposited on substrate 4 over and in intimate electrical contact with metal contacts 6 and 8. Carbon film 10 includes an implant area 12 which is exposed to a plasma when the probe is used in plasma analysis, as described in greater detail hereinafter. Thus, particles of the plasma will bombard carbon film 10 within area 12. An inner contact 6 and an outer contact 8 are positioned on each side of implant area 12. Probe 2 may optionally comprise an insulating layer 14 of silicon or the like, for a purpose to be described in greater detail hereinafter. In preparing the probe 2, it is important to anneal the films at about 700.degree. C. for approximately one hour in a vacuum to reduce the initial resistance of the films. Upon exposure of carbon film 10 to a plasma, the resistance thereof will vary in accordance with the number of particles implanted in the film. In use, probe 2 is exposed to the edge of a plasma in such manner that implant area 12 is bombarded by particles of the plasma. An electrical current is applied to carbon film 10 across outer contacts 8. Voltage across implant area 12 is measured by means of inner contacts 6. From the known current and measured voltage, the electrical resistance of the implant area may be calculated. Use of four contacts 6, 8 avoids undesired effects of contact resistance. Measurements were made of the changes in electrical resistance of carbon films caused by implantation of hydrogen, deuterium and carbon at various energies. The probes were prepared by evaporation of metal contacts and carbon films onto fused silica substrates, as described above. Two sets of probes were prepared. The first set had a carbon film thickness of 49.+-.5 nm with gold contacts. The second set had a carbon film thickness of 92.+-.9 nm with contacts comprising 50 nm Ni on 10 nm of Cr. The thinner (49 nm) carbon film was deposited at 0.1 nm/s in a 5.times.10.sup.-7 torr vacuum and the thicker (92 nm) film at 0.17 nm/s in a 2.times.10.sup.-7 torr vacuum. A density of 1.8 g/cm.sup.3 for the carbon was assumed. The resistance of the probes as deposited was 5 k.OMEGA. for the thin carbon film and 1 k.OMEGA. for the thicker film. Annealing in a vacuum at 700.degree. C. for one hour lowered the resistance to 420.+-.40 .OMEGA. for the thin film and 180.+-.20 .OMEGA. for the thick film giving a resistivity after annealing of 1.75.+-.0.2 m.OMEGA.cm for each film. The film resistance seemed to be unaffected by exposure to air. A series of experiments was conducted in which the resistance of the annealed carbon films was measured as a function of incident particle fluence as determined by current integration. The resolution of the resistance measurement (1 in 10.sup.5 ) determined the lowest fluence at which measurements could be made. However, use of a bridge-type of measurement circuit to provide an offset should allow measurements to be made at much lower fluences. The temperature coefficient of resistance was measured on a carbon film probe after the initial annealing treatment but before exposure to a plasma. The temperature coefficient was found to be -3.75.times.10.sup.-4 /.degree.C. Temperature changes during the experimental exposures of the respective probes, as monitored by a thermocouple, were noted to be much less than 1.degree. C., resulting in resistance changes much less than those caused by particle implantation. FIG. 2 is a graph showing the fractional change in resistance of a 92 nm thick carbon film resulting from implantation with deuterium at 3 keV. At this energy, the entire thickness of the film is implanted. The resistance increases proportionally with deuterium fluence up to a fluence of approximately 10.sup.16 D/cm.sup.2. At approximately 10.sup.17 D/cm.sup.2 the resistance begins to increase much more rapidly with D fluence. This is the fluence where the deuterium retention in the carbon saturates. It was also observed that the implantation decreased the optical density of the carbon film. FIG. 3 graphically illustrates the relative changes in the resistance of carbon films when the range (depth) of the implanted particles is less than the thickness of the film. Data sets A, B and C (points corresponding generally to curves A, B and C, respectively) show the results for probes having a carbon film thickness of 45 nm implanted with deuterium at 500, 250 and 125 eV, respectively. The solid line curves were calculated using a model to be described in greater detail hereinafter. At fluences below approximately 10.sup.15 D/cm.sup.2 the change in resistance is proportional to D fluence as discussed above. A fluences of about 10.sup.17 D/cm.sup.2 the resistance is no longer increasing with D fluence. The reason for this saturation effect is that the conductivity of the implanted carbon has become negligible compared to the conductivity of the underlying unimplanted carbon. Further implantation has little effect on the net resistance of the carbon film which becomes dependent primarily upon the conductivity of the unimplanted portion of the film. In this high fluence limit the fractional change in resistance can be expressed as: ##EQU1## wherein .delta. is the thickness of the implanted layer and .tau. is the carbon film thickness. Table 1 gives the values of .delta. obtained from the saturation values of .DELTA.R/R.sub.o (from FIG. 3 at a fluence of 10.sup.17 atoms/cm.sub.2) using Equation 1. For data sets A, B and C, .delta. varies nearly linearly with the incident particle energy. Data set D was measured for the same implant conditions as data set C but with a thicker (92 nm) carbon film. Data set E in FIG. 3 was measured under the same conditions as set D except that hydrogen was implanted instead of deuterium. The resistance changes at saturation (and therefore .delta.) for the hydrogen and deuterium implants are nearly equal as would be expected from the fact that the ranges of these particles are almost the same. However, at low fluence, the resistance change for the hydrogen implant is less than that for the deuterium implant at the same energy and fluence by a factor of 2. Data set F in FIG. 3 was measured for a probe having a carbon film thickness of 49 nm implanted with carbon ions at 3 keV. The fact that the high fluence saturation level in the resistance change for the carbon implant is slightly below the level for the 500 eV deuterium implant is consistent with the range of these particles (see Table 1). TABLE 1 __________________________________________________________________________ Carbon Implanted Energy Thickness .delta. R .sigma. .epsilon. .epsilon. .epsilon. Sample* Atoms (eV) (nm) (nm) (nm) (nm) (0 eV) (5 eV) (25 eV) __________________________________________________________________________ A D 500 49 35 5.6 7.5 0.53 0.40 0.23 B D 250 49 18 2.5 3.8 0.62 0.44 0.18 C D 125 49 10 0.9 2.2 0.64 0.39 0.098 D D 125 92 8.0 0.9 2.2 0.64 0.39 0.098 E H 125 92 8.7 0.7 2.3 0.43 0.19 0.0095 F C 3000 49 31 3.9 6.4 0.83 0.81 0.74 __________________________________________________________________________ *Sample Designations refer to the data of FIG. 3. The increase in resistance caused by the carbon implant indicates that the cause of the resistance increase is lattice damage. It will be seen below that the dependence of the resistance change on the energy and mass of the incident particles is consistent with this. The TRIM Monte Carlo particle transport code, as described in Biersack et al, Nucl. Inst. and Methods, Volume 174, P. 257 (1980), was used to calculate the particle and damage deposition profiles for hydrogen, deuterium and carbon projectiles onto a carbon target. The depth profiles of the energy into atomic displacements obtained from these calculations could be closely represented by a Gaussian distribution: ##EQU2## where E is the incident particle energy and .epsilon. is the fractional portion of E into atomic collisions which exceeds the damage threshold energy. The values of .epsilon., the centroid R and standard deviation .sigma. of the distribution are given in Table 1 for a damage threshold of 5 eV. For comparison, the values of .epsilon. for damage thresholds of 0 eV and 25 eV are also provided. Measurements of changes in electrical resistance of carbon films during electron irradiation indicate a displacement threshold energy of 25 eV. Since the resistance change is caused by lattice damage, it is reasonable to expect that the resistivity change should be proportional to the energy transformed into damage. If we define an effective local resistivity .rho.(x) at depth x and assume that this increases linearly with the amount of energy resulting in local damage, then: EQU .rho.(x)=.rho..sub.o +.alpha..phi..GAMMA.(x) (3) where .rho..sub.o is the resistivity of the unimplanted material, .phi. is the particle fluence and .alpha. is a coefficient which gives the resistivity change per unit damage. If we then assume that the resistance of the film can be expressed as an integral of the contributions from each depth increment, the relative resistance change is: ##EQU3## The solid line curves shown in FIG. 3 were calculated using Equation 4 with a single value of the coefficient .alpha.=1.3.times.10.sup.-26 .OMEGA.cm(eV/cm.sup.3).sup.-1 which resulted in a reasonably good fit for all of the data. The damage profiles used for these calculations were obtained from the TRIM code. However, it was found that a correct fit to the saturation levels requires that the actual damage profiles are broader by a factor of 1.4 than the calculated ones. Therefore, use of values for .sigma. in the calculations 1.4 times larger than the values in Table 1 obtained from the TRIM code is indicated. A further point to note is that, in the low fluence limit where .alpha..phi..GAMMA.(x)/.rho..sub.o <<1, Equation 4 can be approximated by: ##EQU4## which shows how the resistance depends on the various parameters in the low fluence region. The solid line curves in FIG. 3 were calculated using values of .epsilon. from the TRIM calculations using a damage threshold energy of 5 eV. The values of .epsilon. for threshold energies of 0 or 25 eV (Table 1) would give worse fits to the data. This is evidenced by a comparison of the resistance change for the hydrogen and deuterium implants at 125 eV (curves D and E in FIG. 3). The resistance change caused by particle bombardment, as described herein, can be advantageously used for plasma edge studies, as discussed above. A significant advantage offered by the presently disclosed device and method is that the effect of exposure of the carbon film to the plasma can be continuously monitored during the exposure. It may even be possible to obtain time resolved measurements during a single discharge. In earlier studies, the fact that more energetic particles penetrated deeper into a film has been used to determine the energy of the incident particles. A resistance probe in accordance with the invention could be used in a similar fashion by measuring the resistance change as a function of exposure time or number of discharges. From the saturation level of .DELTA.R/R.sub.o at high fluence, the particle energy can be determined. Once the particle energy is known, the flux can also be deduced from the slope of .DELTA.R/R.sub.o versus .phi. at low fluence using Equation 5. An alternative way to determine the particle energy for ions would be to measure how the resistance change caused by the incident ions varies with positive bias potential applied to the probe. When the bias potential exceeds the incident particle energy, the ions should no longer reach the probe. Biasing the probe would also facilitate independent measurement of the fluxes of ions and neutral atoms. Another technique may involve exposure of two carbon films, one of which is covered by a thin layer of insulating material to shield the film from low energy particles. By comparing the response of the two carbon films, one with and one without the insulating layer, information about particle energies could be obtained. Silicon has been found to be sufficiently insulating for this purpose. A silicon layer having a thickness of 200 Angstrom (20 nanometer) has been found to completely exclude hydrogen particles having an energy below about 500 eV, permitting penetration of substantially all such particles having an energy above about 1 keV. Likewise, a silicon layer having a thickness of 800 Angstrom (80 nanometer) has been found to effectively exclude particles having an energy below about 2 keV and permit penetration of substantially all particles having an energy above about 4 keV. This technique provides a way to detect low energy hydrogen doses as low as 10.sup.12 H/cm.sup.2 in the presence of much larger amounts (10.sup.15 to 10.sup.16 H/cm.sup.2) of background hydrogen. This has been very difficult using previously available methods. In probe studies of the plasma edge, it is believed that, in some cases, the incident particles have a distribution of energies and angles of incidence to the probe. To calculate the response of resistance probes in this case, TRIM was used to calculate the damage profiles for deuterium incident to a carbon film assuming a Maxwellian velocity distribution for the incident deuterium. These calculations show that the damage profiles can be closely approximated by an exponential: ##EQU5## with .lambda.=0.0556 (kT(eV)).sup.0.926 nm, 50 eV<kT<1000 eV, where kT is the Maxwellian temperature. Fro Maxwellian particles, the fraction of incident energy resulting in damage is .epsilon.=0.35.+-.0.03 (assuming a displacement threshold of 5 eV) in the energy range 50<kT<200 eV, similar to the value for monoenergetic particles in the same energy range. FIG. 4 graphically illustrates calculated relative resistance changes for a carbon film having a thickness of 100 nm implanted with deuterium for various Maxwellian temperatures. The curves were calculated using Equations 4 and 6 with the same values for .alpha. and .rho..sub.o as for the monoenergetic case. In this case, the integral in Equation 4 can be solved analytically. For probe studies in which the incident particles can be assumed to have a Maxwellian velocity distribution, this model can be used to fit measurements of the fluence dependence of the resistance change, with energy and flux to be determined from the fit. Alternatively, probe biasing or insulated surface layers might be used to give energy discrimination, as described above. The small size and relative ease of connecting current-inducing and voltage-measuring equipment to probes in accordance with the invention permits them to be used in positions which are difficult to access or where tritium contamination would complicate other methods of sample analysis. Probe resistance data can be continuously monitored during exposure of the probe to a plasma, a significant advantage over prior art devices and techniques. While the invention has been described with reference to the accompanying drawings and particular embodiments, it is not limited to the details illustrated or described as various modifications may be made within the scope of the invention, the invention being limited only by the claims appended hereto. |
059230401 | description | DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing wherein like reference characters are used for like parts throughout the several views, a wafer sample retainer 10, shown in FIG. 1, includes a base 12 and a sample holder 14. The base 12 is slidably positionable along a conventional dove-shaped rail 16 which is driven by a threaded rod 18. In this way, the position of the base 12 along the rail 16 can be adjusted to appropriately locate the samples for viewing in the electron microscope. The base 12 includes a central opening 20 which receives a pin 22 connected to the sample holder 14. Thus, the sample holder 14 is removably securable on the base 12 in appropriate alignment therewith. The illustrated sample holder 14 is arranged to hold two sets of samples "A" and "B". Each of the samples may be made up of one or more semiconductor wafer pieces which may be sandwiched together for conjoined viewing. In some instances, only one of the sample holders may be utilized. Each set of samples is secured against an upstanding post 24 by a spring biased pivotal member 26. The member 26 is secured for pivoting about the axial pin 28 secured in a plate 30 which is part of the sample holder 14. Referring to FIG. 2, the member 26 may be L-shaped having a first portion 34 which includes a spring keeper 32 and a second portion 38 which includes a rounded bump 40. The bump 40 contacts the semiconductor wafers "B" and, because of its rounded configuration, avoids damaging those samples. The foot 42 of the holder 14 also includes a spring keeper 44 which maintains one end of a spring 36 while the other end is maintained in the keeper 32 in the portion 34. The illustrated sample holder 14 is symmetrical and similar parts are contained on each side. For example, the sample retaining opening 50 could be on the order of 0.0170 of an inch which would receive 6 normal thickness semiconductor wafer samples. The retainer 10 is operated by depressing the tops of the first portions 34, forming the sample retaining openings 50, as shown in FIG. 2. Once released, the member 26 biases the samples against the opposite side of the upstanding post 24. While the present invention has been described with respect to a single preferred embodiment, those skilled in the art will appreciate numerous modifications and variations therefrom. For example, while the illustrated embodiment includes two spring biased members, in some instances one such member may be sufficient. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of the present invention. |
abstract | Provided is a high-output X-ray generation tube in which thermal damage to a target is reduced. The X-ray generation tube includes a target, an electron source, and a grid electrode having multiple electron passage apertures disposed between the target and the electron source. A source-side electron beam on the electron source side with respect to the grid electrode has a current density distribution, and the grid electrode has an aperture ratio distribution so that a region of the source-side electron beam in which a current density is largest is aligned with a region of the grid electrode in which an aperture ratio is smallest. |
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046726527 | description | DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In FIG. 1 is shown a wheelable radiodiagnostic apparatus 1 with wheels 2 and 3, such as is frequently used in surgery. It comprises a vertical support 4 adjustable in height with a sleeve 5 in which a horizontal support 6 is slidably mounted. At the end of the horizontal support 6 a C-arch 7 is slidably arranged. At one end of C-arch 7 which is located the housing 8 for an x-ray image intensifier and a television camera, and at the other end the x-ray tube housing 9. At the x-ray tube housing 9 a primary ray shield 10 is arranged, to which a tube (barrel) 11 is fastened. In FIG. 2, the schematic construction of a semitransparent diaphragm 12 arranged in the primary ray shield 10 is represented. Diaphragm 12 consists of a plurality of strip-shaped blades 13 arranged parallel and side by side in two opposed groups. The blades 13 which have in their distal areas 14 an absorption value which corresponds to an iron plate of a thickness of 0.4 mm to 3.5 mm. In their rear areas the blades 13 are formed as a toothed rack 15, into which there engage toothed rollers 16 driven by motors 17 (only one shown). Each rack 15 of the blades 13 has associated with it a coupling magnet 18, which upon actuation of the racks 15 presses against the motor-driven toothed rollers 16 and establishes a disconnectable connection with them. The mechanism is connected with a diaphragm ring 19, which has on its outer edge tooth segments 20. A worm gear 22 driven by a motor 21 engages the tooth segments 20, so that the entire diaphragm 12 can be rotated about its center. An evaluating circuit 23, to which the video signal BAS is supplied, controls the motors 17 and 21 and the coupling magnets 18. At the evaluating circuit 23 are additionally connected two key switches 24 and 25, which respectively bring about the automatic closing and opening of the diaphragm 12. The circular field 26 indicates the area irradiated by x-rays and corresponds to the x-ray picture reproduced on the monitor (not shown) of the x-ray/television system. As one exemplary object 27 being examined, there has been shown a knee joint. In its initial position the diaphragm 12 is opened all the way; all blades 13 are outside the field 26. At start of radioscopy, after actuation of switch 24, the coupling magnets 18 are actuated by the evaluating circuit 23, so that the racks 15 engage in the toothed roller 16. At the same time the motors 17 are actuated in such a way that the blades 13 move toward each other and the diaphragm 12 closes slowly. Dependent on the video signal BAS, the individual coupling magents 18 are actuated, as will be explained later, by the evaluating circuit 23 in such a way that they drop one after the other and thus the racks 15 of the individual blades 13 are no longer in engagement with the still rotating toothed roller 16 when the video signal BAS belonging to the respective blade 13 drops below a certain preselected brightness level. The control of motor 21 by the evaluating circuit 23 causes a rotation of the diaphragm ring 19, so that the slit of diaphragm 12 is aligned relative to the object 27 being examined. After completed radioscopy, the motors 17 and the coupling magnets 18 are actuated by operation of switch 25 via the evaluating circuit 23 in such a way that the diaphragm is again opened completely. In FIG. 3 is shown the evaluating circuit 23, which comprises a circuit 28 for position determination of the blades 13 within the video picture. It coordinates the effective video signal BAS with the individual blades 13. It contains a circuit 29 for determining the areas correlated with the individual blades 13, i.e. the area which each blade 13 can completely cover. The circuit 29 may be, for example, a memory in which these areas are contained. To this circuit 29 a control signal T is supplied which identifies the blade 13 just then selected. A detector 30 is also contained in circuit 28, to which the horizontal and vertical pulses H and V and the clock pulse B of the television chain are supplied, serves to determine the instantaneous position of the scanned video signal BAS. The output signals of circuit 29 and of detector 30 are supplied to a first comparator 31, which generates an output signal if the video signal BAS lies within the area of the blade 13 currently being actuated. The video signals BAS coming from the television camera is supplied to an analog/digital converter A/D 32, which acts as an adaptation stage and to which the clock pulse is supplied for digitization. The digital output signal of the A/D converter 32 is supplied to an AND element 33 acting as gate circuit. The digital output values of the A/D converter 32 are transmitted by the AND element 33 only if the circuit 28 has determined that the arriving video signal BAS belongs to the blade 13 currently being actuated. The output of the AND element 33 is connected to a memory 34 whose output is placed on a second comparator 35, to the second input of which the effective video signal of the A/D converter 32 is supplied. The second comparator 35 generates an output signal if the new image element of the video signal BAS is greater than the old image element supplied by the memory 34, so that at the end of the scanning always the maximum amplitude value contained in the video signal area associated with the actuated blade 13 is present in memory 34. Thereby the memory 34, the second comparator 35, and the AND element 33 operates as a peak value detector. By the vertical pulses V the memory 34 is erased after each television picture, so that the maximum value can be determined anew. The output of memory 34 is supplied to a third comparator 36, at the second input of which an adjustable threshold value S is present. The output signal of the third comparator 36 controls the selected copuling magnet 18 if the value stored in memory 34 exceeds the threshold value S. In the following, the operation of the evaluating circuit 23 will be explained more specifically. To simplify matters, only one of the blades 13 will be considered. At start of radioscopy, a logically high, or H signal is supplied by circuit 28 as long as the image point supplied by the A/D converter 32 lies within the area in the television picture belonging to the actuated blade 13. Since at the start no value is as yet contained in memory 34, the second comparator 35 also supplies an H signal, so that the first image point is read into memory 34. This takes place within the area belonging to the actuated blade 13 until the maximum value of the image points is contained in memory 34 and the following image points are equal to or smaller than the stored image point, so that the second comparator 35 supplies a logically low, or L signal to the AND element 33, thus blocking it. If the stored image point is brighter than the adjusted threshold value S, the third comparator 36 supplies an output signal, so that the coupling magnet 18 belonging to the actuated blade 13 is actuated and blade 13 is moved by motor 17, so that the diaphragm 12 closes in this area. By the vertical pulse V the memory 34 is erased, so that for the next television frame again the maximum value can be read into the memory. This takes place until blade 13 has approached the object 27 being examined, after which the maximum value of the image points decreases within the area of blade 13. If the maximum value falls below the threshold value S supplied to the comparator 36, the coupling magnet 18 of the actuated blade 13 is no longer excited, so that it drops and blade 13 remains in this half-closed position. Subsequently the other blades 13 are actuated in the same manner, so that they assume for example the position shown in FIG. 2. Instead of the successive actuation of the coupling magnets 18 and of the blades 13, they may be actuated alternately in multiplex operation if at least one memory 34 and a third comparator stage 36 are provided for each of the blades 13. By a multiplex circuit then required, the output signal of the AND element 33 is supplied to the corresponding memory 34, and the output signal of this memory 34 to the second comparator and the respective third comparator. As a result there occurs an almost simultaneous displacement of the blades 13, so that the diaphragm 12 closes as far as is needed over its entire width within a very short time. The threshold value S supplied to the third comparator 36 can, for example, be adjusted continuously by the person being examined. Alternatively, organs, for example, can be represented correspondingly if the threshold value is selectable via pushbuttons to correspond to the transmission characteristics of the organ under investigation. Instead of the rack 15 and toothed roller 16, a rubber roller and a friction surface may being about the adjustment of the blades 13. The coupling magnets 18 may be replaced, for each side of the diaphragm 12, by a coupling magnet which is displaced mechanically and couples each blade 13 individually and successively with the rack 16. The rotation of the diaphragm ring 19 and hence the orientation of the slit of diaphragm 12 may jointly be coupled with the television camera, so that the longitudinal direction of the blades always lies along the scanning direction of the television camera. Or it may be effected by a similar evaluation of the television image from the video signal BAS. Those skilled in the art will understand that changes can be made in the preferred embodiments here described, and that these embodiments can be used for other purposes. Such changes and uses are within the scope of the invention, which is limited only by the claims which follow. |
abstract | Systems and methods for a method for determining a critical effective k at an off-rated core state of a nuclear power plant includes determining, for the off-rated core state a control rod density, a percent core power, a gadolinium reactivity worth, a doppler reactivity worth, and a xenon reactivity worth responsive to a control rod pattern, a reactor power plan including the off-rated core state, and a reference effective k, calculating a change in an effective k from the reference effective k at the off-rated core state responsive to two or more parameters selected from the group consisting of the control rod density, the percent core power, the gadolinium reactivity worth, the doppler reactivity worth, and the xenon reactivity worth, and generating the critical effective k for the off-rated core state responsive to the change in the effective k from the reference effective k. |
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044514280 | summary | BACKGROUND OF THE INVENTION This invention relates to control rods and method of producing same, and more particularly it is concerned with a control rod having a prolonged service life and a method for producing such control rod. A control rod has the function of controlling the number of neutrons concerned in a chain reaction of nuclear fission involving 235U in the fuel rods disposed in the core of a nuclear reactor, by virtue of the presence of materials of large neutron absorption cross section in the control rod. Thus control rods are used for controlling the power of a nuclear reactor. Control rods used in a boiling-water nuclear reactor will be described. A control rod includes blades in the form of a cross in transverse cross section having arranged therein a plurality of sealed poison tubes each containing powder of boron carbide (hereinafter B.sub.4 C) serving as a neutron absorber. The blade has a sheath enclosing the plurality of poison tubes. SUMMARY OF THE INVENTION This invention has as its object the provision of a control rod of prolonged service life which is capable of flattening a neutron flux distribution in the vicinity of the forward end portion of the control rod being inserted in the reactor core. The outstanding characteristic of the invention is that in a control rod comprising first neutron absorber causing an (n, .alpha.) reaction to take place and a second neutron absorber causing an (n, .UPSILON.) reaction to take place, the second neutron absorber is disposed in an end portion of the control rod at which the control rod is inserted in the core and formed of an alloy containing a material of large neutron absorption cross section and a material of small neutron absorption cross section. |
summary | ||
abstract | The invention provides apparatus by which a cooling gas is supplied from a stationary source to the back side of batch ion implanter workpieces being implanted in a rotating or spinning batch implanter process disk. The cooling gas provides improved heat transfer from the workpieces to the process disk, which may be advantageously combined with circulation of cooling fluid through passages in the process disk to remove heat therefrom. The invention further includes a rotary feedthrough employed to transfer the cooling gas from a stationary housing to a gas chamber in a rotating shaft which spins the batch implanter process disk. In addition, a seal apparatus is provided which seals the cooling gas applied to the back sides of the workpieces from the vacuum in which the front sides of the workpieces are implanted. |
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055576508 | description | DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION FIG. I is a sectional side view of a radiographic imaging arrangement. A tube 1 generates and emits x-radiation 2 which travels toward a body 3. Some of the x-radiation 4 is absorbed by the body while some of the radiation penetrates and travels along paths 5 and 6 as primary radiation, and other radiation is deflected and travels along path 7 as scattered radiation. Radiation from paths 5, 6, and 7 travels toward a photosensitive film 8 where it will become absorbed by intensifying screens 9 which are coated with a photosensitive material that fluoresces at a wavelength of visible light and thus exposes photosensitive film 8 (the radiograph) with the latent image. When an anti-scatter grid 10 is interposed between body 3 and photosensitive film 8, radiation paths 5, 6, and 7 travel toward the anti-scatter grid 10 before film 8. Radiation path 6 travels through translucent material 11 of the grid, whereas both radiation paths 5 and 7 impinge upon absorbing material 12 and become absorbed. The absorption of radiation path 7 constitutes the elimination of the scattered radiation. The absorption of radiation path 5 constitutes the elimination of part of the primary radiation. Radiation path 6, the remainder of the primary radiation, travels toward the photosensitive film 8 and becomes absorbed by the intensifying photosensitive screens 9 that fluoresce at a wavelength of visible light and thus exposes photosensitive film 8 with the latent image. FIG. 2 is a sectional side view a portion of an anti-scatter x-ray grid 10. As discussed above, an important parameter in the design is the grid ratio r, which is defined as the ratio between the height h of the x-ray absorbing strips 12 and the distance d between them. For medical diagnostic radiography the ratios generally range from 2:1 to 16:1. Another interdependent variable in the design parameters is the line rate of strips per centimeter. An absorbing strip must be thin enough to permit the total combined thicknesses of the strips and the distances between them to fit within a given centimeter and provide the predetermined line rate. Typically, line rates vary from 30 to 80 lines per centimeter and the absorbing strips have a width w along the sectional side view on the order of 15 to 50 .mu.m. Using the present invention, higher line rates (up to about 300) can be achieved, and therefore image contrast can be improved. FIGS. 3 and 4 are front and sectional side views respectively of a cutting blade 21. FIG. 5 is a partial perspective view of a channel through a substantially non-absorbent substrate. According to an embodiment of the present invention, an anti-scatter x-ray grid is fabricated by cutting the surface of a solid sheet of non-absorbent substrate material 11 to form the desired plurality of linear absorber channels of the desired dimensions. The substrate may comprise any substantially non-absorbent material having appropriate structural and thermal properties to withstand further processing and use. The words "substantially non-absorbent" mean that the substrate thickness and material are sufficient to prevent substantial attenuation of x-radiation such that at least 85% (and preferably at least 95%) of the x-radiation will pass through the substrate. In one embodiment the substrate comprises a plastic such as Ultem.RTM. polyetherimide (Ultem is a trademark of General Electric Co.). Other examples of appropriate substrate material include substantially non-absorbent polyimides, polycarbonates, other polymers, ceramics, woods, graphite, glass, metals, or composites thereof. The substrate may further include filler material such as particles or fibers including carbon, glass, or ceramic, for example, which can be useful to provide proper mechanical characteristics. The substrate provides structural support for the grid, and plastic materials are particularly useful because they absorb less radiation than aluminum strips. The saw may comprise a blade adapted to cut appropriately thin and deep channels in substrate 11. Examples of such saws 21 include saws of the type used in the semiconductor industry for dicing silicon wafers such as manufactured by Tokyo Seimitsu of Japan and Semitec of Santa Clara, Calif., for example. A thin blade portion 20 extends from a thicker inner portion 22 which is rotated about an axis 24. Preferably, the blade thickness ranges from about 15 to 70 .mu.m so that these saws can provide desired line rates. In one embodiment the blade comprises a diamond-coated resin. Other materials appropriate for the saw blades include, for example, materials such as metals or resins having hard carbide coatings such as silicon or tungsten carbide. Either a plurality of blades can be arranged side by side to cut the channels simultaneously or a single blade can cut each of the channels sequentially. If the blade is not of sufficient depth, then one fabrication technique is to turn the substrate over and cut on the opposite surface of the substrate to form a channel having two portions 26a and 26b such as shown in FIG. 5a. Preferably, for ease of later fabrication, channels do not extend completely through the substrate. The channel configuration may be one of several types. In one embodiment, the channels are each perpendicular to the surface of the substrate. In another embodiment, some of the channels are at a predetermined angle to the surface to form a focused grid. Commercially available cutting saws typically cut perpendicular to flat substrates. If an angle is desired, the angle can be obtained, for example, as shown in the embodiment of FIG. 6, which is a sectional side view of a substrate support surface which is rotatable for providing the desired angle of substrate channel. Even if angled channels are not desired, a movable support table for use under the substrate such as available from Anorad Corporation of Hauppaugue, N.Y., is useful because blades for cutting semiconductor wafers are not always large enough (or do not always have enough range of motion) to create the desired length of channels. The channels are not limited to the rectangular shapes obtainable with the above described cutting saw. The channels can alternatively be round or comprise other types of cavities and can be formed by any of a number of methods such as etching, molding, heat deforming and/or reforming, milling, drilling, or any combination thereof. After the channels are formed, absorbing material 12, which is substantially absorbent, is applied to the channels. The words "substantially absorbent" mean that the thickness and material density are sufficient to cause substantial attenuation of x-radiation such that at least 90% (and preferably at least 95%) of the x-radiation will be absorbed. In one embodiment of the present invention, the channels are filled under vacuum conditions with an absorbing material that can be readily melt-flowed into the channels. In a preferred embodiment the absorbing material comprises a lead-bismuth alloy. Other substantially absorbent materials can include metals such as lead, bismuth, gold, barium, tungsten, platinum, mercury, thallium, indium, palladium, silicon, antimony, tin, zinc, and alloys thereof. The substrate material and absorbing material must be chosen so that the substrate material is able to withstand the temperatures required for melting and flowing the absorbing material during the amount of time required for the fabrication process. FIG. 7 is a sectional side view of the channel 26 coated with an optional adhesion promoting material 34. To aid in the adhesion of the absorbing material, the adhesion promoting material can be formed on the channel surfaces. In one embodiment, copper is coated to a sufficient thickness to provide a substantially continuous coating on the channel surfaces. Other appropriate adhesion promoting materials include nickel and iron, for example. Any residual adhesion promoting material on an outer surface of the substrate can be removed either at this time or at a later time simultaneously with residual absorbing material. FIG. 8 is a view similar to that of FIG. 7 after the channel has been filled with the absorbing material. An alloy commercially available from Belmont Metals of Brooklyn, N.Y., has a eutectic at 44% lead-56% bismuth with a melting point of 125.degree. C. Ranges of 40% lead-60% bismuth through 50% lead-50% bismuth would also be advantageously close to the eutectic. This is the preferred filling material since it forms a low melting point eutectic and it has a mass absorption coefficient of 3.23 at 125 KeV, which is superior to that of pure lead (3.15 at 125 KeV). The use of a plastic non-absorbent substrate material with a lead-bismuth absorbing material is advantageous because the substrate remains stable at the low melting point of the absorbing material. Any residual adhesion promoting material and/or non-absorbing material remaining on the outer surfaces of the substrate can be removed by a technique such as polishing, milling, or planing, for example. Any of a variety of finishing techniques such as polishing, painting, laminating, chemical grafting, spraying, gluing, or the like, may be employed if desired to clean or encase the grid to provide overall protection or aesthetic appeal to the grid. FIG. 9 is a view similar to that of FIG. 8 after the surfaces of the substrate and absorbing material are coated with a protective layer 38. The protective layer may comprise similar materials as those described with respect to the substrate. In one embodiment, protective layer 38 comprises a plastic such as polyetherimide. The protective layer comprises substantially non-absorbent material and helps to protect the substrate and absorbing material surfaces from scratches. Furthermore, the protective layer is useful for safety concerns when the absorbing material includes a metal such as lead. EXAMPLE A grid prototype of a substrate comprising Ultem polyetherimide 1000 was made using a precision dicing saw where a 10.times.10.times.0.5 cm sample was cut on one face to produce channels in the surface that had a width w of 50 .mu.m, a height h of 600 .mu.m and a length l of 10 cm (w, h, and l shown in FIG. 5), and such that the line rate was 67 lines/cm, the lines being equally spaced to give a grid ratio of 6:1. The substrate was then vacuum filled with the 44% lead-56% bismuth alloy at 140.degree. C. by immersing the substrate into the molten metal and subjecting it to a pressure of less than 10 Torr. The substrate was removed and allowed to cool to ambient temperature and was then polished smooth to remove any excess or stray metal. The device was examined microscopically, and the channels were found to be completely and uniformly filled. The device of the present invention is reworkable in that the absorbing material which is not completely or properly flowed in the channels can be removed by heating the assembly and reflowing the absorbing material. Furthermore, this feature can be used to reclaim (remove) the absorbing material before later disposal of any grids. This removal capability is advantageous, especially in situations where lead may cause a safety-related concern and in situations where recycling of the substrate material is desired. While only certain preferred features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. |
description | The present invention relates generally to an x-ray beam system. There are various applications which utilize conditioned beams, which include, but are not limited to, directed, monochromatized, collimated or focused x-rays. For example, medical radiotherapy systems utilize x-rays to destroy malignant tissue, x-ray diffraction or scattering analysis systems channel x-ray radiation at a sample, crystal or non-crystal, to generate a diffraction or scattering pattern corresponding to its structure, and x-ray fluorescence and spectroscopy systems employ an x-ray beam to generate secondary radiation and analyze the secondary radiation to obtain compositional information. In the field of x-ray diffraction, an x-ray instrument, such as a diffractometer, employs an x-ray beam conditioned by an optical system to meet certain requirements, including spatial definition (such as parallelism), spectrum purity, and intensity, as well as other requirements. These parameters, however, are typically interdependent and, therefore, cannot be optimized independently. That is, usually, improving or optimizing one parameter often times results in an unavoidable cost to the other parameters. Different optical systems have been developed for different purposes in the aforementioned x-ray systems, such as, for example, parabolic multilayer reflectors for producing monochromatic parallel beams, parabolic multilayer reflectors coupled with channel-cut monochromator for producing Kα1 parallel beams, and elliptical multilayer reflectors for producing monochromatic focusing beams. Different optical systems are needed for different applications, or the capability of a diffractometer is limited. Significant effort may be required to change and align an optical component whenever it is installed or changed. Further, having these various optical systems can be costly. In satisfying the above need, the present invention provides an improved x-ray optical system which provides more than one type of beam. The system includes an x-ray source which emits x-rays, a first optical element which conditions the x-rays to form two beams, a second optical element and an optional third element which further conditions one of the two beams from the first optical element and delivers it to the desired location. The desired location can be the location where a sample is positioned or the location where a detector is positioned. The first optical element delivers two beams that are collimated in at least one plane. The two beams, however, do not have to be in parallel to each other. Some of the embodiments of the invention may provide the following advantages. The optical system produces different formalities of beams with a minimum number of components and with minimal effort to align the components. Further advantages and features of the invention will become apparent from the following detailed description and from the claims. The x-ray beam system disclosed in invention mainly concerns x-ray scattering and x-ray diffraction. Referring now to FIG. 1a, an x-ray system embodying the principles of the present invention is illustrated therein and designated at 10. As its primary components, the x-ray system 10 includes a source 12, such as, for example a laboratory x-ray source in point geometry or line geometry if the optical system is a one-dimensional system, a first optical element 14, and a second optical element 16. The first optical element 14 delivers two parallel beams and the second optical 16 element further conditions one of the two beams delivered by the first optical element. The first optical element 14 can be a Kirkpatrick-Baez optical system including two optics in which at least one of the two reflection surfaces of each optic is a multilayer reflector. Particularly, the optic in can be a “2-corner” side-by-side optical element, in which two reflectors are facing each other and the third reflector is perpendicular to the first two reflectors. The third reflector can be a multilayer reflector. Generally, multilayer reflectors may be employed as the reflecting surfaces for high flux and better spectrum definition. Shown in FIG. 1b is a cross-sectional view of the x-ray system 10 in a particular arrangement as a two-dimensional system. Further note that in other arrangements FIG. 1b also illustrates the cross-sectional view of the system as a one dimensional system in which all the reflections occur in the cross-sectional plane. The x-ray system 10 may include a slit 18 that is moveable as indicated by the arrow 19 and a detector 21. The first optical element 14 includes two working zones or optics 20 and 22, and the second optical element 16 is typically a focusing element with a reflecting surface 24. The source 12 emits x-rays 26 at the first optical element 14, which in turn conditions the x-rays to form two collimated beams 28a and 30. The beams 28a and 30 are generally parallel beams in the reflection plane, or diffraction plane when the optical elements are multilayer reflectors. Both the reflection plane or diffraction plane are represented by the cross-sectional plane as shown in the figures, that is, the plane of the paper. As shown in this implementation, the reflection plane, diffraction plane and cross-section plane are the same. The beams 28a and 30 may or may not be parallel to each other in the cross-sectional plane. One beam 30 is directed at a sample S while the second optical element 16 focuses the beam 28a into a focused beam 28b at the sample S position or location as shown in FIG. 1b. The second optical element 16 may focus the beam 28b at the detector 21 or at any other suitable position depending on the application of the system 10. At any moment, in particular applications, only one beam 28b or 30 passes through an opening 32 of the slit 18. That is, the slit 18 can be employed to select the beam 30 and block the focusing beam 28b, or in other situations, the slit 18 blocks the focusing beam 28b and allows the parallel beam 30 to pass through the opening 32. In certain applications, the slit is able to allow both the focusing beam 28b and the parallel beam 30 to pass through the opening 32. As viewed in an axial plane which is perpendicular to the reflection plane or diffraction plane, and therefore perpendicular to the cross-sectional plane, the beams 28a and 30 delivered from the first optical element 14 may be divergent beams, parallel beams, or focused beams. If the working zones 20 and 22 in the first optical element 14 are one-dimensional optics such as, for example, parabolic cylinder mirrors, the beams 28a and 30 are divergent in the axial plane. In this case, the reflection surface which is perpendicular to the working zones 20 and 22 is not employed. If the beams 28a and 30 are parallel beams in the axial plane, the optics 20 and 22 are two-dimensional collimating optics. Either optic 20 or 22 (or both optics 20 and 22) can be made of two reflectors in the Kirkpatrick-Baez arrangement in either a sequential order or in the “side-by-side” arrangement as described in U.S. Pat. No. 6,041,099 and U.S. Pat. No. 6,014,423, both of which are incorporated herein by reference in their entirety. In some implementations, the first optical element 14 can be made of a full revolution of a parabloidal optic coupled with a slit, which delivers two parallel beams as well. If the beams 28a and 30 are focusing beams in the axial plane, which are focused at the sample S, the detector 21, or any other desired position, each optic 20 and 22 in the first optical element 14 can also be may be made of two reflectors in the Kirkpatrick-Baez arrangement in sequential order or in the side-by-side arrangement. In such an arrangement, both reflectors 20 and 22 are collimating reflectors, such as, for example, parabolic reflectors, and the other reflector generally perpendicular to 20 and 22 is a focusing reflector, such as, for example, an elliptical reflector. Referring now to FIG. 2a, an x-ray system 100 includes a channel-cut monochromator 102 as the second optical element to improve spectrum purity, angular resolution, or both. Shown in FIG. 2b is a cross-sectional view of the x-ray system 100 in a particular arrangement as a two-dimensional system. Further note that in other arrangements FIG. 2b also illustrates the cross-sectional view of the system as a one dimensional system in which all the reflections occur in the cross-sectional plane. As shown in FIG. 2b, the x-ray system 100 may also include the moveable slit 18 and the detector 21 described above in relation to the x-ray system 100. The channel-cut monochromator 102 includes two reflection surfaces 104 and 106. The channel-cut monochromator 102 and the first optical element 14 are arranged in such a manner that the reflection surface 106 of the channel-cut monochromator 102 reflects the beam 28a as a beam 28c towards the beam 30. The reflection surface 104 of the channel-cut monochromator 102 further reflects the beam 28c as a beam 28d that is coincident with the beam 30 so that the beam 28a is further conditioned by the channel-cut monochromator 102. The beam 30 has the characteristic of high flux. The beam 28d has the characteristics with both high energy resolution and high spatial resolution. In this arrangement, switching between beam 30 and beam 28d involves the positioning and alignment of the channel-cut monochromator 102. The x-ray system 100 optical system with the channel-cut monochromator 102 delivers a highly parallel beam with a well defined spectrum. The beam with high flux can be selected by moving the channel-cut monochromator 102 out of the path of beam 30. The beam with better definition can be selected by positioning the channel-cut monochromator 102 in its appropriate working position. When two reflecting surfaces 104 and 106 of the channel-cut monochromator 102 are parallel to each other, the atomic planes reflecting x-rays are the same. In this case, the two collimated beams delivered by the first optical element 14 are in parallel to each other. Such a channel-cut monochromator is commonly referred to as a (+n, −n) monochromator. Sometimes, to provide sufficient spectrum purity, a channel-cut monochromator having two reflecting surfaces 104 and 106 with different atomic planes may be used. Such a channel-cut monochromator is often referred to as a (+m, −n) channel-cut monochromator. A (+m, −n) channel-cut monochromator has two reflecting surfaces at an angle (that is, not parallel to each other). To utilize a (+m, −n) channel-cut monochromator, the first optical element 14 delivers two collimated beams at an angle matching the (+m, −n) channel-cut so that the delivered beam 28d by the channel-cut is coincident with the beam 30. The x-ray beam system disclosed in invention mainly concerns x-ray scattering and x-ray diffraction. The channel-cut monochromator 102 can be a crystal made from, for example, a single crystal silicon or germanium. When the system 100 is in use, a multilayer optic arrangement of the first optical element 14 can be employed to select a particular characteristic line Kα. The channel-cut monochromator can then be used to select the finer structure Kα2 or preferably Kα1 which is much more intense than Kα2. Shown in FIG. 3a, an x-ray optical system 200 combines the two-beam element 14, the channel-cut monochromator 102, and the parabolic reflector 16 in one system. Shown in FIGS. 3b and 3c are cross-sectional views of the x-ray system 200 in a particular arrangement as a two-dimensional system. Further note that in other arrangements FIGS. 3b and 3c also illustrate the cross-sectional views of the system as a one dimensional system in which all the reflections occur in the cross-sectional plane. FIGS. 3b and 3c further show the x-ray optical system 200 with the slit 18 and the detector 21 which were described above. Depending on the application of the x-ray system 200, the system 200 delivers a parallel beam with highly defined spectrum and angular resolution or a focused beam with a highly defined spectrum. When providing parallel beam 28d that passes through the sample S, the channel-cut monochromator 102 is arranged as shown in FIG. 3b. In such an arrangement, the beam 30 is blocked by the channel-cut monochromator and the parallel beam 28d is produced as described above with reference to FIG. 2b. When focusing a beam at the sample S or at the detector 21 or at any other suitable position, the channel-cut monochromator 102, initially in the position shown in FIG. 3b, is flipped 180° about an axis 108 as shown in FIG. 3c. As such, the channel-cut monochromator 102 blocks the beam 28a from the first optical element 14 while the reflection surface 106 reflects the beam 30 as a beam 30a towards the reflection surface 104 which in turn reflects the beam 30a as a beam 30b towards the parabolic reflector 16. The parabolic reflector 16 then reflects the beam 30b as a focused beam 30 towards the sample S or the detector 21 or any other desired position. Of course, changing back to the arrangement shown in FIG. 3b merely requires flipping the channel-cut monochromator in the position shown in FIG. 3c 180° about the axis 108 to the position shown in FIG. 3b. The x-ray reflectors in optical elements 14 and 16 can be either total reflection optics or multilayer optics. The first 2-beam optical element 14 can be a 1-dimensional x-ray optic, that is, it reflects the x-rays in one plane only, commonly referred to as reflection plane or diffraction plane if it is a multilayer reflector. Such a plane is shown as the cross section plane in FIG. 1b, FIG. 2b and FIG. 3b. The first 2-beam optical element 14 can also be a 2-dimensional optic, that is, it reflects the x-rays in two planes, that is, both in the reflection/diffraction plane and the axial plane to form a 2-dimensional beam (a “pencil-like” beam). If the first 2-beam optical element 14 is a 1-dimensional optic, then the parabolic reflector 24 of the optical element 16 provides a beam focused in one plane. And if the first 2-beam optical element 14 is a two-dimensional optic and with focusing characteristics in the axial plane, then the parabolic reflector 24 is a one-dimensional optic that focuses the beam 30c either at the sample S or the detector 21 or any other desired position. For other arrangements, if the first optical 2-beam element 14 is a 2-dimensional optic and with collimating characteristics in the axial plane, then the optical element 14 with the parabolic reflector 24 can be either a one-dimensional optic that focuses the beam 30c in only one plane or a two-dimensional optic that focuses the beam 30c to a point at the sample S or the detector 21 or any other suitable position. When any of the x-ray optical systems 10, 100, or 200 are employed as x-ray diffraction systems, a specific characteristic emission line is often chosen. Typical characteristic lines include Co Kα, Cr Kα, Cu Kα, Mo Kα, Ag Kα, as well as others. Multilayer optics are often employed to select one of these characteristic lines from a continuous spectrum, and these optics are further employed to collimate/focus x-rays to form a beam. These aforementioned characteristic lines, however, have fine structures that include multiple lines. For example, the characteristic line Cu Kα is a doublet that includes Kα1 and Kα2, and Kα1 is about twice intense as Kα2. In particular applications, for instance, in high resolution diffractometry, the combination of multilayer optics for the optical element 14 and the channel-cut monochromator 102 is employed to provide a highly defined spectrum by selecting only one of these multiple fine structured lines. In summary, the aforementioned systems can provide a variety of beams of different spatial and spectral characteristics as shown in the following table: TABLE 1ReferenceCannel-cutFIGS.monocromator (102)Movable slit (18)High intensity Kα1bRotated 90 degrees In the “down” collimated at least from its nominalposition as it is in one planeposition in FIG. 2ashown in FIG. 1bHigh brightness Kα 1a, 1bRotated 90 degrees In the “up” positionbeam focused in from its nominal“ as it is shown one or two planesposition in FIG. 2ain FIG. 3cLow divergence 2bIn nominal positionIn the “down” Kα1 beamposition as it is shown in FIG. 1bFocused Kα1 beam 3cRotated 90 degreesIn the “up” position in one or two planesfrom its nominalas it is shownposition in FIG. 2ain FIG. 1b Among other features, the beams produced by the above-described systems pass the same desired location (sample). To achieve this, these systems are arranged such that all the optical elements match with each other, including the optic positions, the curvatures and d-spacing designs, the channel-cut selection and the design for the beam displacement. Further, in some applications, any of four beams produced by the above-described systems can be delivered to the sample location by changing the positions of only two elements, such as the channel-cut monochromator and the slit. Changing the slit position does not affect the system alignment at all because its major function is blocking unwanted beams and its opening can be larger than the working cross-section of the beam. The channel-cut monochromator is a sensitive element and may need to be realigned after changing its position. However, because two working positions of the channel-cut monochromator can be realized by a rotation about an axis in its diffraction plane, such rotation and positioning can be realized with good precision by the using precision mechanical components so that only fine alignment is needed. Finally, the above systems enable one to choose an optimal solution for a specific application by simply repositioning and fine-aligning a small number of components manually or using computer controlled motorized means. It avoids having to have many optical systems that are sophisticated and require tedious change and system alignment and therefore saves cost and effort. As a person skilled in the art will readily appreciate, the above description is meant as an illustration of implementation of the principles of this invention. This description is not intended to limit the scope or application of this invention in that the invention is susceptible to modification, variation and change, without departing from spirit of this invention, as defined in the following claims. |
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044951400 | abstract | A gas cooled nuclear reactor is permanently deactivated on occurrence of an emergency by pyrolytic deposition of boron or refractory or stable compounds of boron in the fluid channels of the fuel elements of the reactor. The boron is enriched in boron 10. The deposition takes place in so short a time interval as to preclude a major catastrophe by reason of penetration of water into the reactor. Carbon and/or nitrogen-containing boron compounds are injected directly into the reactor or compounds generated by reaction in the working fluid of the reactor between diborane and other boron hydrides with unsaturated compounds, such as acetylene and ammonia flow through the reactor. The compounds are carried by the working fluid through the core and are pyrolized in the heat of the core to produce more stable boron, or boron-carbon and boron-nitrogen compounds or metal borides which adhere to the walls of the channels in the fuel elements, deactivating the core. |
claims | 1. A method for testing whether fuel rods of fuel assemblies resting on a working base and under water, of a nuclear reactor are leaking, which comprises the steps of: fitting a common hood over all fuel assemblies of a first division of fuel assemblies, the first division containing at least a first group and a second group having in each case a plurality of the fuel assemblies, each of the first and second group including a first fuel assembly and a second fuel assembly; heating all fuel assemblies of the first division of fuel assemblies by passing a filling gas under the hood, for driving radioactive fission products out of a defective fuel rod contained in the fuel assemblies of the first division; subjecting the fuel assemblies belonging to the first group to a first common preliminary test and independently subjecting the second group to a second common preliminary test by continuously extracting samples of water and continuously degassing the water removed from an area around the fuel assemblies of the first division even during the heating resulting in gas; continuously recording a radioactivity of gaseous fission products contained in the gas being continuously released; carrying out the first common preliminary test by using a first device for extraction, a first device for degassing and a first device for recording the radioactivity in order to jointly test all the fuel assemblies belonging to the first group to determine if they are leaking; carrying out the second common preliminary test by using a second device for extraction, a second device for degassing and a second device for recording the radioactivity in order to jointly test all the fuel assemblies belonging to the second group to determine if they are leaking; performing an individual test of each of the fuel assemblies belonging to one of the first group and second group only if the first or second preliminary common test detects excessive radioactivity, carrying out the individual test using in each case a dedicated device for extraction, a dedicated device for degassing and a dedicated device for recording the radioactivity for each of the fuel assemblies, the dedicated device for extraction, the dedicated device for degassing and the dedicated device for recording the radioactivity provided for the individual test of the individual fuel assemblies already being in use for subjecting in each case the fuel assemblies belonging to one of the first and second group to the first and second common preliminary test; and heating the fuel assemblies belonging to a second division of fuel assemblies only if the first division of fuel assemblies has been tested. 2. The method according to claim 1 , which comprises disposing of the gas which is continuously released after the radioactivity has been recorded, and recording the radioactivity in a detector configuration through which the gas is passed only a single time before being disposed of. claim 1 3. The method according to claim 2 , wherein the degassing step comprises passing a carrier gas through the water that has been extracted, and passing the carrier gas through the detector configuration together with the gaseous fission products that have been released. claim 2 4. The method according to claim 1 , which comprises heating the first fuel assembly belonging to the first division of fuel assemblies by at most a predetermined temperature difference beneath the hood which is fitted over the fuel assemblies belonging to the first division and providing the hood with a gas fill surrounding a top fitting of the first fuel assembly. claim 1 5. The method according to claim 4 , which comprises passing a filling gas under the hood until a filling-level test line, leading out of the hood, indicates a predetermined height of a water level beneath the hood. claim 4 6. The method according to claim 1 , wherein the common hood has transverse walls dividing the common hood into individual cells, and a filling-level test line, a height of which can be adjusted individually, leads outward from each of the individual cells, which comprises the step of: claim 1 passing a filling gas into all of the individual cells until the filling-level test lines contain the filling gas. 7. The method according to claim 1 , which comprises controlling automatically the heating, testing and recording steps using a test program. claim 1 8. The method according to claim 1 , which comprises performing the first and second common preliminary test on the first and second group simultaneously. claim 1 9. The method according to claim 1 , which comprises performing the individual test of each of the fuel assemblies belonging to one of the first or second group simultaneously. claim 1 10. The method according to claim 1 , which comprises heating the fuel assemblies belonging to the first group under a common hood by injecting a filling gas into individual cells formed above the fuel assemblies by side walls of the common hood, the common hood being common to all the fuel assemblies belonging to the first division, and the common hood only being lifted off the fuel assemblies when the fuel assemblies have completed testing. claim 1 11. The method according to claim 10 , which comprises passing the filling gas into the individual cells until filling-level test lines which lead out of the cells indicate a predetermined height of a water level in the individual cells. claim 10 12. The method according to claim 11 , which comprises height-adjusting the filling level test lines individually in the individual cells in accordance with a predetermined height of the water level in each of the individual cells, and the filling gas is introduced until the individual cells have each been vented by an associated one of the filling-level test lines. claim 11 13. An apparatus for testing fuel assemblies resting on a working base and under water, of a nuclear reactor, the apparatus comprising: a hood to be positioned above all fuel assemblies of a first division of fuel assemblies and having a downwardly facing opening formed therein, said downwardly facing opening able to be fitted over a top fitting of the fuel assemblies, the first division containing at least a first group and a second group having in each case a plurality of the fuel assemblies, each of the first and second group including a first fuel assembly and a second fuel assembly; a first device connected to and introducing a gas into said hood; and a plurality of second devices for continuously extracting water positioned under the gas introduced into said hood, said second devices being connected to extraction lines provided for each of the fuel assemblies of the first division, said second devices for extracting water is equal in number to a number of the fuel assemblies belonging to one of the groups of the fuel assemblies, at least some of said second devices to be switched from said extraction lines of the fuel assemblies belonging to one group to said extraction lines of the fuel assemblies belonging to another group and to a combination of said extraction lines belonging to one group; a plurality of third devices, each of said third devices connected to a respective one of said second devices and receiving the water previously extracted, said third devices continuously degassing the water resulting in a released gas; a plurality of fourth devices, each of said fourth devices connected to a respective one of said third devices and receiving the released gas for continuously recording a radioactivity of the released gas; and a control device connected to said second, third and fourth devices, said control device running a program for controlling said second, third and fourth devices. 14. The apparatus according to claim 13 , including a disposal line connected to said third device for degassing, said fourth device for recording the radioactivity of the released gas is disposed in said disposal line connected to said third device for degassing and during the continuous extraction of the water said fourth device can only be connected to said third device through said disposal line. claim 13 15. The apparatus according to claim 13 , wherein said third devices are connected to a line for introducing a carrier gas into the water. claim 13 16. The apparatus according to claim 13 , wherein said hood has transverse walls dividing said hood into individual cells, and including dedicated, height-adjustable filling-level test lines, one of said dedicated, height adjustable filling-level test lines associated with each of said individual cells and said individual cells can be vented through said dedicated, height adjustable filling-level test lines. claim 13 17. The apparatus according to claim 16 , including video cameras for observing said dedicated, height-adjustable filling-level test lines. claim 16 18. The apparatus according to claim 13 , wherein said hood has transverse walls dividing said hood into individual cells each to be positioned above a top fitting of a group of the fuel assemblies, and each of said individual cells to be separately connected to said second devices for extraction and said third devices for degassing. claim 13 19. The apparatus according to claim 13 , including: claim 13 a vent line for each of the fuel assemblies disposed on a top fitting of the fuel assemblies; and an extraction line for each of the fuel assemblies disposed beneath said hood, said extraction line having a first end positioned in a predetermined position beneath said vent line, said extraction line leading out of said hood, on the top fitting of and over fuel rods of the fuel assemblies. |
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description | FIG. 1 depicts schematically an electron beam lithography system 100 in accordance with one embodiment of the present invention. System 100 includes a light illumination system 102 and a photoconverter system 104. Light illumination system 102 outputs a light image 103 by, for example, exposing an optical mask with light. In accordance with one embodiment of the present invention, photoconverter system 104 converts the light image 103 into an electron emission pattern 105, whose demagnified image 108 is projected onto substrate 106 by electron optical system 107. A suitable illumination system 102 is any device that generates a light image. For example, a suitable conventional illumination system includes an illumination source that exposes an image defining mask and a lens that focuses the defined image onto the photoconverter system 104. Another suitable illumination system 102 is a laser system, i.e., a photolithographic device which creates one or more focused and modulated laser beams. One such laser system is described in U.S. Pat. Application Ser. No. 08/769,169, entitled xe2x80x9cShort Wavelength Pulsed Laser Scannerxe2x80x9d, inventors Paul C. Allen et al., filed Dec. 18, 1996, attorney docket no. M-4485 US; and U.S. Pat. Nos. 5,255,051, issued Oct. 19, 1993, to Paul C. Allen, 5,327,338, issued Jul. 5, 1994, to Paul Allen, et al., and 5,386,221, issued Jan. 31, 1995, to Paul C. Allen, et al., all incorporated herein by reference in their entirety. In accordance with one embodiment of the present invention, FIG. 2 depicts in side view, one embodiment of photoconverter system 104, as well as electron optics system 107, and a substrate 106. Photoconverter system 104 includes a photocathode 304 that converts light image 103 into electron emission pattern 105; a motor 306 that revolves photocathode 304; extraction electrode 320; and a regeneration source 308 that regenerates a portion of photocathode 304. Electron optics system 107 projects a demagnified image 108 of emission pattern 105 onto substrate 106. In this embodiment, a vacuum casing 318 encloses photoconverter system 104, electron optics system 107, and substrate 106. A conventional vacuum pump device (not depicted) controls the pressure within the vacuum casing 318. The vacuum casing 318 includes a transparent window 324 that is aligned coaxial with light image 103 and allows light image 103 to expose photocathode 304. FIG. 3 depicts a ring shaped photocathode 304 in accordance with this embodiment. A suitable radius R of photocathode 304 is approximately 3 to 5.5 cm. FIG. 4 depicts a cross sectional view of a photocathode 304 along line Axe2x80x94A of FIG. 3. Photocathode 304 includes a conventional substrate layer 330, being a transparent material such as, e.g., sapphire or quartz, on a photoemission layer 332 being, e.g., gold, tin oxide, or cesium iodide (CsI). A suitable thickness T of photocathode 304 is approximately 1 mm to 5 mm. Referring to FIG. 2, photocathode 304 absorbs the photons of incident image 103 from light illumination system 102 and thereby causes electrons present in the photoemission layer 332 to be excited above the vacuum level. Electrons which gain sufficient energy to escape from the surface of photoemission layer 332 are emitted in the -Z direction from the photoemission layer 332. With respect to photoconverter system 104, the term xe2x80x9cdownstreamxe2x80x9d means along the (-)Z direction from photocathode 304. Extraction electrode 320 is positioned in the -Z direction from photocathode 304, and coaxial with the path of beam 103. In other embodiments, a conventional field lens could be used in conjunction with extraction electrode 310. Hereafter the term xe2x80x9cextraction devicexe2x80x9d refers to extraction electrode 320 with or without a field lens unless otherwise specified. A suitable implementation of the extraction device is described in U.S. patent application Ser. No. 09/272,086, entitled xe2x80x9cCompact Photoemission Source, Field And Objective Lens Arrangement For High Throughput Electron Beam Lithographyxe2x80x9d, filed Mar. 18, 1999, inventors Veneklasen and Mankos, now U.S. Pat. No. 6,315,128, which is incorporated by reference in its entirety. When a voltage (typically tens of kilovolts) is applied to the extraction device, the extraction device extracts the electrons which have escaped from the photoemission layer of photocathode 304 and accelerates them to generate electron image 108 of the emission pattern 105 on the photocathode. In this embodiment, photocathode 304 is mounted to a rotating spindle 326 driven by motor 306, located within the vacuum casing 318 of photoconverter system 104. Motor 306 rotates ring-shaped photocathode 304 about axis 322, so that incident light image 103 exposes a ring-shaped area of the rotating photocathode 304. In one embodiment, motor 306 is located outside of the vacuum casing 318 of photoconverter 104. Spindle 326 of motor 306 is divided into two portions. A portion of spindle 326 is external to the vacuum casing 318 (xe2x80x9cexternal portionxe2x80x9d) and directly coupled to motor 306 and a portion of spindle 326 is inside the vacuum casing (not shown) (xe2x80x9cinternal portionxe2x80x9d) The external and internal portions are separated by a non-magnetic thin membrane being, e.g., stainless steel foil. The external and internal portions are coupled by a permanent magnet so that they rotate at the same rate. Thereby, motor 306, located outside of the vacuum casing, rotates the photocathode 304. The purpose of rotating photocathode 304 is to average variations in the level of electron emissions from photocathode 304. Such variations are due, e.g., to local defects on the photoemission layer 332 such as particulate or chemical contamination and overexposure of a local area. Such defects cause variations in the electron conversion factor of the photocathode 304, which in turn cause dose errors in an electron image 108 written on the substrate 106. When the rotating photocathode is illuminated by light image 103 to generate a single pixel imaged on the substrate 106 (hereafter image pixel), the effective electron conversion factor to generate the image pixel is the average of the electron conversion factors of the pixel areas of the photocathode illuminated by light image 103 during exposure of the pixel. The photocathode 304 should move fast enough so that each image pixel on the substrate receives its exposure from many corresponding pixel areas on the photocathode 304, where a pixel area on the photocathode 304 is the larger than an image pixel by, e.g., the square of the demagnification factor of the electron optics system 107. A typical range of a demagnification factor of the electron optics system 107 is 3 to 10 times. For example, if photocathode 304 moves at linear speed of 5 cm/s and a pixel on the photocathode 304 is exposed for a duration of 5 ms, then the photocathode has moved 0.025 cm. If the size of an image pixel on the photocathode is 1 xcexcm and is demagnified 10 times to expose a 0.1 xcexcm size pixel on the substrate 106, 250 corresponding pixel areas on photocathode 304 are used to expose each image pixel. Conventional regeneration source 308 (FIG. 2) is located in the -Z direction from photocathode 304, but is offset from the path of image 103, but interior to the outer edge of photocathode 304. The region coaxial and immediately downstream of emission pattern 105 becomes available to include additional componentry such as extraction electrode 320 and does not have to accommodate a regeneration source. The length of the photoconverter system 104 can be reduced, thereby reducing electron-electron interactions which can cause blurring of the electron image 108. Regeneration source 308 continuously or periodically regenerates a portion of photoemission layer 332 of photocathode 304. Regenerating the photocathode stabilizes the photocathode""s xe2x80x9celectron conversion factorxe2x80x9d at an optimum value. In this embodiment, regeneration source 308 regenerates a part of the photoemission layer 332 by, e.g., sputtering; depositing of additional photoemission layer material; molecular beam epitaxial deposition; ion beam deposition; condensation from gas; exposure to gas; exposure to a molecular beam; or plasma exposure. A suitable implementation of regeneration source 308 is a source 309 that outputs molecules 311 of, for example, Cesium. In one embodiment, regeneration source 308 includes a nozzle 310 that controls the shape of the area exposed by the regeneration source 308. In one embodiment, an electron optical lens system 107, shown schematically in FIG. 2, is used to demagnify the emission pattern 105 and focus the demagnified emission pattern 105 to an image 108 on the substrate 106. In this embodiment, the electron optical lens system 107 is positioned in the -Z direction from the photocathode 304 and coaxial with emission pattern 105. In this embodiment, electron optical lens system 107 and the substrate 106 are located within vacuum casing 318. In another embodiment, electron optical lens system 107 is positioned within the vacuum casing while the substrate 106 is positioned within a separately pumped vacuum casing. A suitable implementation of electron optical lens system 107 is described in U.S. patent application Ser. No. 09/272,086, filed Mar. 18, 1999, entitled xe2x80x9cCompact Photoemission Source, Field And Objective Lens Arrangement For High Throughput Electron Beam Lithographyxe2x80x9d. FIG. 5 depicts schematically a differentially pumped regeneration source 370, used in place of regeneration source 308. In this embodiment, there is a small gap between the regeneration source nozzle 360 and photocathode 304. Another conventional vacuum pumping device 362 is coupled to pump the regeneration region 364. This differential pumping arrangement allows the pressure in the regeneration region 364 to be higher than that in region 358; within vacuum casing 318 (FIG. 2), in which the electron emission pattern 105 is formed. This is desirable when byproducts of the regeneration source 370, e.g., water and gas, are undesirable on the rest of the photocathode surface 304. For example, regeneration source 370 is used where plasma deposition or condensation are applied. In this embodiment a suitable pressure in regeneration region 364 and region 358 are respective 1xc3x9710xe2x88x928 Torr and 1xc3x9710xe2x88x9210 Torr. In one embodiment, the opening of nozzle 360 is trapezoid shaped to compensate for unequal exposure dose of the photocathode due to differing linear velocities along increasing radii from the axis of rotation. FIG. 6 depicts a top side view of photocathode 304 (from the -Z direction in FIG. 2), the trapezoid shaped opening 366 of nozzle 360, and emission pattern 105. When photocathode 304 moves, it is possible to regenerate photocathode 304 while simultaneously using another segment of photocathode 304 to convert incident light into an electron beam. Thereby, by both moving photocathode 304 and regenerating the photocathode;, the photocathode""s xe2x80x9celectron conversion factorxe2x80x9d is continuously stabilized at an optimum value and the photocathode""s electron conversion factor is averaged. In one embodiment, photocathode 304 is simultaneously rotated and rotating spindle 326 moved within the plane of photocathode 304 so that photocathode 304 moves radially to and from the beam axis and incident image 103 exposes regions at varying radii from the center of photocathode 304. This allows emission to be averaged over a larger area, providing a longer cathode life. In one embodiment, photocathode 304 is moved in an X-Y direction, within the plane of the photocathode 304, by for example a conventional X-Y stage. Thus by use of a displacement device such as motor 306 or a conventional stage, photocathode 304 is moved while illuminated. The above-described embodiments are illustrative and not limiting. It will thus be obvious to those skilled in the art that various changes and modifications may be made without departing from this invention in its broader aspects. Therefore, the appended claims encompass all such changes and modifications as fall within the scope of this invention. |
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claims | 1. A control rod for a nuclear reactor, comprising: a cladding tube closed hermetically at both ends thereof by means of a top and a bottom end plugs, respectively; a neutron absorber loaded into said cladding tube and including a reduced-diameter portion having a smaller diameter than the other portion, said reduced-diameter portion being disposed at the bottom end plug side of said control rod, said other portion of said neutron absorber having a lower peripheral edge, said edge having an inwardly facing chamfer; a hold-down spring for pressing said neutron absorber downwardly against said bottom end plug; a sleeve being disposed within an annular space defined between an outer peripheral surface of said reduced-diameter portion of said neutron absorber and an inner peripheral surface of said cladding tube, said sleeve having an upper peripheral edge, said edge being chamfered on its inner side; and said chamfered edges of said sleeve and said other portion of said neutron absorber being complementary to each other, said chamfered edge of said sleeve being positioned on said chamfered edge of said other portion of said neutron absorber. 2. A control rod according to claim 1 , wherein said chamfered portion of said sleeve has an axial length not greater than ca. 20 mm. claim 1 3. A control rod according to claim 2 , wherein said reduced-diameter portion has a diameter which is substantially equal to a value obtained by subtracting from the diameter of said other portion of said neutron absorber the sum of 0.13 mm and not more than about 0.7 mm. claim 2 4. A control rod according to claim 3 , wherein said sleeve has an outer diameter which is substantially equal to the outer diameter of said other portion of said neutron absorber. claim 3 |
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abstract | A mobile system for intervention in an atmosphere of radioactive gas, notably tritium, which includes: a dynamic confinement device, including a removable confinement barrier to surround an intervention zone and a device for controlled extraction of air to keep the zone at a lower pressure than the exterior; a device for monitoring the radioactive gas concentration in the air of the zone; a device to detect and signal the exceedance of a predefined threshold by this concentration to the persons present in the zone. |
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abstract | An end effector for supporting an ultrasonic testing probe on a robot arm having a robot mounting bracket for use in a nuclear reactor pressure vessel. The end effector has a wrist assembly with a rotatable wrist axle. The wrist assembly is coupled to the robot mounting bracket and a probe assembly is coupled to the wrist shaft. The ultrasonic testing probe is floatably disposed within the probe assembly. |
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048250899 | abstract | Metallized film is used as a radiant barrier to prevent the transfer of heat by reflecting long wave radiation. Radiant energy apparatus includes several embodiments, including flat strips, wrinkled strips, crinkled chips, bubbles, bubbled sheets, and mesh netting with metallized layers, for different applications. Bubbled sheets and mesh netting embodiments may be used for wall installation and the like, and the other embodiments may be used for blown or loose fill insulation. |
claims | 1. A CT detector comprising:a scintillator module including at least one scintillator configured to be impinged with radiographic energy from a radiographic energy source;at least one indexing pin connected to the scintillator module; anda collimator assembly having a plurality of collimator elements and a plurality of teeth configured to define a relative position of the plurality of collimator elements and a portion of the plurality of teeth configured to engage the at least one indexing pin, and wherein at least two of the plurality of teeth are constructed to flank an indexing pin. 2. The CT detector of claim 1 wherein the at least one scintillator includes a plurality of scintillators uniformly arranged in a scintillator array. 3. The CT detector of claim 1 further comprising at least one photodiode configured to detect illumination of the at least one scintillator. 4. The CT detector of claim 1 incorporated into a rotatable gantry of a CT imaging system. 5. A scintillator-collimator combination comprising:a plurality of collimator elements configured to collimate x-rays projected thereat;a scintillator module having a scintillator pack formed of a material configured to illuminate upon reception of x-rays;a comb having a plurality of teeth constructed to align the plurality of collimator elements and constructed to engage the collimator module and align the scintillator module relative to the plurality of collimator elements; andwherein the scintillator module further comprises a locating pin constructed to snuggly engage a recess of the comb, wherein the recess is defined between two of the plurality of teeth. 6. The scintillator-combination of claim 5 wherein the locating pin is configured to align the scintillator pack with respect to the plurality of collimator elements such that the scintillator module does not overlap two collimator elements spaced apart from one another a distance equal to a width of the scintillator module. 7. The scintillator-collimator combination of claim 5 configured to be optically coupled to a photodiode array and configured to detect illumination from the scintillator pack and output electrical signals responsive thereto. 8. The scintillator-collimator combination of claim 5 incorporated into a CT imaging system designed to acquire diagnostic data of a medical patient. 9. A CT system comprising:a rotatable gantry having a bore centrally disposed therein;a table movable fore and aft through the bore and configured to position a subject for CT data acquisition;a high frequency electromagnetic energy projection source positioned within the rotatably gantry and configured to project high frequency electromagnetic energy toward the subject; anda detector array disposed within the rotatably gantry and configured to detect high frequency electromagnetic energy projected by the projection source and impinged by the subject, the detector array including:a plurality of scintillator modules, each having a scintillator array and an indexing pin;a collimator assembly having a plurality of collimator plates; anda detector support having at least one comb of alignment teeth, the alignment teeth constructed to align the plurality of collimator plates and engage an indexing pin to align a scintillator array with the plurality of collimator plates. 10. The CT system of claim 9 wherein the alignment teeth define a uniform spacing between collimator plates of the plurality of collimator plates. 11. The CT system of claim 9 wherein the indexing pin laterally extends beyond an end of a respective scintillator array. 12. A method of manufacturing a CT detector comprising the steps of:providing a scintillator away having at least one locator extending beyond the scintillator array;providing a comb having a plurality of teeth constructed to define a spacing between collimating elements of a collimator; andpositioning the at least one locator between at least two of the plurality of teeth. |
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063013207 | claims | 1. A fuel assembly comprising a multiplicity of fuel rods including a first fuel rod type provided with mixed oxide fuel and a second fuel rod type provided with mixed oxide fuel in conjunction with a neutron poison, the mixed oxide and neutron poison being intimately mixed in the second fuel rod type, the fuel rods having peripheral fuel rods wherein between 50 and 100% of the,peripheral fuel rods of the assembly being of the second fuel rod type. 2. A fuel assembly according to claim 1 in which between 0 and 50% of the fuel rods adjacent the peripheral fuel rods are of the second type. 3. A fuel assembly according to claim 1 in which between 0 and 15% of the non peripheral fuel rods are of the second type. 4. A fuel assembly according to claim 1 in which the neutron poison is Gadolinia. 5. A fuel assembly according to claim 1 in which the neutron poison is provided at between 0.5 and 2 weight percent. 6. A fuel assembly according to claim 1 in which only first and second type fuel rods are present. 7. A fuel assembly according to claim 1 in which the first type rod contains mixed oxide fuel with a plutonium content of between 3 and 12% by weight of the total fuel content of the first type rod. 8. A fuel assembly according to claim 7 in which the plutonium content of the second type fuel rod is between 20% and 75% that of the first type. 9. A fuel rod assembly according to claim 1 which is a pressurized water reactor fuel assembly. 10. A system comprising: a pressurized water nuclear reactor; and the fuel assembly as recited in claim 1 disposed within the pressurized water nuclear reactor. 11. A pressurized water nuclear rector core comprising a fuel assembly having a multiplicity of fuel rods including a first fuel rod type provided with mixed oxide fuel and a second fuel rod type provided with mixed oxide fuel in conjunction with a neutron poison, the mixed oxide and neutron poison being intimately mixed in the second fuel rod type, the fuel rods having peripheral fuel rods wherein between 50 and 100% of the peripheral fuel rods of the assembly being of the second fuel rod type. 12. A pressurized water nuclear reactor core according to claim 11, the reactor core having a peak rod power to an average assembly power ratio between 1:65:1 and 1:4:1. |
abstract | Spent nuclear fuel assemblies are stacked in a spent nuclear fuel assembly pool by structurally supporting a second tier nuclear fuel assembly storage rack in the spent nuclear fuel assembly pool over and independently of previously installed first nuclear fuel assembly racks. The spent fuel assemblies then are introduced into the second tier fuel assembly storage racks while vertically oriented. |
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048204730 | summary | BACKGROUND OF THE INVENTION The present invention relates to a novel method of reducing radioactivity, particularly to a method of suppressing adherence of radioactive substances to structural materials used in contact with a liquid containing the radioactive substances dissolved therein, for example, primary cooling water piping in a nuclear power plant, and to a method of suppressing release of metallic ions or metallic oxides released from the structural materials and activated in a reactor core. Piping, pumps, valves etc. used in a primary cooling water system of a nuclear power station are made of stainless steel, Stellite which is a Co based alloy, etc. (hereinafter briefly referred to as "structural members"). These metals are subject to corrosion or damages in the course of long-term services thereof. As a result, constituent metallic elements are dissolved in reactor cooling water (hereinafter briefly referred to as "cooling water") to be entrained into the reactor. Most of the dissolved metallic elements are converted into oxides thereof, which then adhere to fuel rods. In this state, the metallic elements are irradiated with neutrons. As a result, radioactive nuclides such as .sup.60 Co, .sup.58 Co, .sup.51 Cr, and .sup.54 Mn are formed. These radioactive nuclides are dissolved into primary cooling water again to suspend in the form of ions or insoluble solid components (hereinafter referred to as "crud"). Part of them is removed in a demineralizer, etc. for purification of reactor water, but the rest adheres to the surfaces of structural members in the course of circulation through the primary cooling water system. Therefore, the dose rate on the surfaces of the structural members increases, thus presenting a problem of radiation exposure of workers during the course of maintenance and inspection. Accordingly, there have been proposed methods of suppressing causative dissolution of the above-mentioned metallic elements for decreasing the amount of the adhering radioactive substances. These methods include, for example, a method of suppressing corrosion of the structural members by using a corrosion-resistant material, and a method of suppressing corrosion of the structural members by introducing oxygen into a water supply system. However, in either method, corrosion of the structural members in the primary cooling water system including the water supply system cannot be sufficiently suppressed, and hence the amount of the radioactive substances in primary cooling water cannot be sufficiently decreased. Therefore, the does rate on the surfaces of the structural members due to the adherence of the radioactive substances thereto is increased. On the other hand, methods of removing radioactive substances adhering to the structural members have been investigated and practiced. These methods include (1) mechanical washing, (2) electrolytic washing, and (3) chemical washing. The methods (1) and (2) encounter a difficulty in removing radioactive substances strongly adhering to the surfaces of the structural members, and are unable to decontaminate systematically over a wide area. The method (3) comprises dissolving an oxide film on the steel surface by a chemical reaction using a chemical such as an acid solution to remove radioactive substances present in the film. In this method, even if the dose rate is temporarily decreased, rapid recontamination occurs when the structural members are exposed to a liquid containing the radioactive substances dissolved therein at a high concentration again. A method of suppressing adherence of radioactive substances by preliminarily providing an oxide film on the surfaces of structural members is disclosed in, for example, Japanese Patent Laid-Open Nos. 121197/1980 and 37498/1984. In this method, however, the adherence behavior of the radioactive substances markedly varies depending on the properties of the oxide film preliminarily provided. For example, the behavior of radioactive ions varies depending on the charged state of the oxide film. Also the rate of growth of oxide films newly formed on the surfaces of structural members after immersion in a liquid containing radioactive substances dissolved therein varies depending on the properties of the existent film. Thus a satisfactory film is not always formed. SUMMARY OF THE INVENTION An object of the present invention is to provide a method of reducing radioactivity in a nuclear plant having a contact with pure, high-temperature and high-pressure water containing radioactive substances. In accordance with the present invention, there is provided a method of reducing radioactivity by preliminarily forming oxide films on the surfaces of metallic structural members to be in contact with high-temperature and high-pressure reactor water containing radioactive substances before the metallic structural members are exposed to said reactor water, characterized in that, after a first-step oxidation treatment of heating said metallic structural members in a high-temperature environment, the metallic structural members thus treated are further subjected to a second-step oxidation treatment of heating them in an environment having a higher oxidizing capacity than that of the environment in said first-step oxidation treatment to form denser oxide films that those obtained in the first step oxidation treatment. That is, the method of suppressing adherence of radioactive substances to structural members to be in contact with reactor cooling water containing radioactive substances according to the present invention comprises formation of oxide films having a relatively high porosity but a sufficient film thickness in the first-step treatment and subsequent formation of thin but dense films in the second-step treatment. The formation of a thick and porous film in the firststep treatment may be attained by an oxidation treatment with heated water or steam having a low oxidizing capacity, while the formation of a thin but dense film in the secondstep treatment may be attained by an oxidation treatment with heated water or steam having a higher oxidizing capacity than that in the first-step treatment. The present invention is based on an idea that adherence of radioactive substances may be suppressed by reducing the rate of corrosion of structural members in view of the fact that the radioactive substances contained in high-temperature and high-pressure water are confined into the structural members in the course of formation of oxide films caused by corrosion of the structural members with high-temperature and high-pressure water. The film grows thick by the first-step treatment alone in heated water having a low oxidizing capacity but is insufficient in the corrosion-suppressing effect in an environment of reactor cooling water. Therefore, the film is not sufficient in the effect of suppressing adherence of radioactive substances. On the other hand, the second-step treaatment alone in heated water having a high oxidizing capacity provides a very thin but dense film, which is, however, subject to scratches and denaturation. Thus, in an environment of reactor cooling water, film breakage easily occurs because of the thinness of the film. Therefore the corrosion-suppressing effect and hence the effect of suppressing adherence of radioactive substances cannot be sufficiently exhibited. It has been found that, when a thick film treated in heated water having a low oxidizing capacity is treated in heated water having a high oxidizing capacity, the resultant corrosion-suppressing effect is very remarkable. The reason why a thick film is formed with a low oxidizing capacity may be that an iron oxide forming the oxide film is a little easily dissolved in an environment of reactor cooling water so that the film may become porous enough to promote the growth of the oxide film due to the progress of oxidation through the micropores. On the other hand, the reason why only a thin film is formed in heated water having a high oxidizing capacity may be that an iron oxide forming the film is scarcely dissolved with the high oxidizing capacity so that the film may become dense enough to suppress the subsequent growth of the film. The dense film has a high corrosion-suppressing effect but is so liable to be broken that no sufficient effect can be obtained in an environment of reactor cooling water. Accordingly, formation of a thick and dense film provides the effects of greatly suppressing the corrosion in an environment of reactor cooling water and, hence, greatly suppressing the adherence of radioactive substances. In view of the above, when a thick but porous film is first formed in an environment having a low oxidizing capacity and then treated in an environment having a high oxidizing capacity, micropores in an initial oxide film are filled with a dense oxide to form a dense and thick film as a whole, thus enhancing the effect of suppressing corrosion after contact with an environment of a reactor. As a result, the effect of suppressing the adherence of radioactive substances is enhanced. With an appropriate treatment, there is a possibility that as dense a film as the secondary oxide film may be formed on the primary oxide film. The oxidizing capacity of heated water used in the first-step treatment of the two-step process must be, in principle, lower than that of reactor cooling water, while that in the second-step treatment must be higher than that of reactor cooling water. These oxidation treatments can be effected by heated water, steam, and a heated non-oxidizing gas having a high purity. Ar, N.sub.2, He, etc. can be used as such gas. For example, cooling water for a boiling water reactor usually contains 200 ppb of dissolved oxygen. The oxidizing capacity of cooling water depends on the dissolved oxygen concentration of the cooling water. Accordingly, in short, the cooling water is preferably pure water of 200.degree. C. or higher having a dissolved oxygen concentration of less than 200 ppb, particularly preferably 40 to 100 ppb, in the first-step treatment, and a dissolved oxygen concentration of more than 200 ppb, more preferably 300 ppb to 8 ppm, particularly preferably 300 to 1,000 ppb, in the second-step treatment. The treatment time in each step is preferably 100 to 500 hours, more preferably 100 to 200 hours. Control of the dissolved oxygen concentration can be achieved by deaeration, introduction of oxygen, or the like. The thickness of a film in the first-step treatment is about 0.5 to 3 .mu.m, while that of a film in the second-step treatment is about 0.05 to 0.5 .mu.m. In the case of treatment of austenite stainless steel, the amount of an oxide film in the first-step treatment is preferably 100 to 200 .mu.g/cm.sup.2 with a porosity of 60 to 70%, while that of an oxide film in the second-step treatment is preferably 10 to 100 .mu.g/cm.sup.2 with a porosity of 20 to 40%. In order to reduce the oxidizing capacity in the firststep treatment, addition of a reducing substance such as hydrazine, hydrogen, or an organic chemical may be useful besides lowering of the dissolved oxygen concentration. The amount of the reducing substance that may be added is preferably 1,000 ppm or less. In order to increase the oxidizing capacity in the second-step treatment, besides increase of the dissolved oxygen concentration, addition of an oxidizing substance such as hydrogen peroxide, a permanganate, or a chromate may be useful. The amount of the oxidizing substance that may be added is preferably 1,000 ppm or less. A denser film can be formed with a weak alkalinity, too. A pH of 8 to 10 is preferred. These treatments may not necessarily be effected with complete separation of the first-step treatment and the second step treatment. For example, oxidation may be effected under conditions continuously variable from a low oxidizing capacity to a high oxidizing capacity. Instead of two steps, several steps of different oxidation conditions may be employed. A theoretical background which has led to the present invention will now be described in more detail. Radioactive substances dissolved in reactor water are confined into an oxide film formed on the surface of stainless steel due to corrosion of the stainless steel during the course of formation of the oxide film. The oxide film grows toward the inner side (side of the body metal) in the interface between the oxide film and the body metal in water of a high temperature. The radioactive substances diffuse and move through the film toward the inner side to be confined into the oxide film in the same interface. The flux (J.sub.0) of the radioactive substances can be expressed by formula (1): ##EQU1## wherein d: thickness of oxide film k.sub.0 : proportional constant PA1 D: diffusion constant PA1 C.sub.1 : concentration of radioactive substance in reactor water, and PA1 C.sub.2 : concentration of radioactive nuclide in the interfare between film and metal. PA1 k.sub.1 : proportional constant, and PA1 m: amount of oxide film. The thickness (d) of the oxide film can be expressed by the following formula: EQU d=k.sub.1 m (2) wherein Thus, J.sub.0 can be alternately expressed by formula (3): ##EQU2## On the other hand, the rate (J.sub.1) of confinement of radioactive substances into the film can be expressed by formula (4) using a rate (dm/dt) of growth of the oxide film: EQU J.sub.1 =k.sub.2 C.sub.2 (dm/dt) (4) wherein K.sub.2 : proportional constant. The rate (J) of accumulation of radioactive substances is expressed by the formula: J=J.sub.0 =J.sub.1. Thus, when C.sub.2 is eliminated from the formulae (3) and (4), the following formula is obtained. ##EQU3## On the other hand, when the rate of accumulation of radioactive substances is determined by the step of diffusion, the rate (J) can be expressed by formula (6): ##EQU4## The formula (6) demonstrates that the rate (J) of accumulation of radioactive subtances is proportional to the diffusion constant (D) and the radioactive substance concentration (C.sub.1) of reactor water, and inversely proportional to the amount of the film, namely the thickness of the film. Accordingly, formation of a dense and thick oxide film having a low diffusion constant is one measure useful for suppressing the rate of accumulation of radioactive substances. Another measure is reduction in the concentration of the radioactive substance in reactor water, namely suppression of release of ions and oxides of metals, such as, cobalt or nickel to be activated in a reactor core, and iron capable of promoting activation of these metals, into reactor water due to corrosion of structural members. The corrosion of these structural members can be suppressed by forming a dense and thick oxide film. As described above, in order to suppress the accumulation of radioactive substances, a dense and thick oxide film has only to be preliminarily formed on structural members to be in contact with reactor water before nuclear heating begins in a nuclear plant. For example, in the case of stainless steel used in the structural members, the rate of adherence of radioactive substances shows an interrelation with the rate of growth of the film according to the study of the present inventors. Thus, suppression of film growth is presumed to lead to reduction in adherence of them. The reason why the rate of adherence of radioactive substances shows an interrelation with the rate of film growth may be that the radioactive substances are confined in growth points of the film. Accordingly, as the film growth is suppressed, the frequency of confinement of the radioactive substances is decreased. An increase in the amount (m) of the film on the stainless steel in an environment of cooling water is expressed by formula (7) including the logarithm of time (t): EQU m=a log (bt+1) (7) wherein a and b are constants. Accordingly, the rate of film growth is initially high, but gets lower as the film grows further. Therefore, preliminary formation of an adequate non-radioactive oxide film particularly exerts effects of suppressing confinement of radioactive substances and dissolution of metal ions. In other words, renewed film formation after immersion in a liquid containing radioactive substances dissolved therein can be suppressed and, hence, adherence of radioactive substances frequently observed during film formation can be suppressed. As a result of investigations on conditions of film formation with attention paid to the fact that adherence of radioactive substances can be suppressed by preliminary formation of an adequate non-radioactive oxide film on metallic structural members to be used in contact with reactor cooling water containing radioactive substances dissolved therein, and particularly to the fact that the rate of adherence of radioactive substances depends on the thickness and density of the preliminarily formed oxide film, the inventors of the present invention have found that the abovementioned rate of adherence can be remarkably reduced when an additional oxidation treatment of the film under strongly oxidizing conditions is conducted after an oxidation treatment of the film under weakly oxidizing conditions. There are several types of nuclear plants and the method of the present invention can be applied to any of them. In a boiling water nuclear plant, a pressure vessel of a reactor, piping in a recycling system, piping in a primary coolant purification system, etc. are in contact with reactor water containing radioactive substances. In a pressurized water nuclear plant, a pressure vessel of a reactor, structural materials in the reactor, a steam generator, etc. are in contact with reactor water as described above. Therefore, when all or part of structural members made of stainless steel, Inconel, carbon steel and stellite and to be in contact with a liquid containing radioactive substances is subjected to the oxidation treatment of this invention, adherence of radioactive substances can be suppressed, leading to minimization of radiation exposure of workers. On the other hand, in the boiling water nuclear plant, since the concentration of radioactive substances in primary cooling water in contact with structural members of water supply and steam condensation systems is comparatively low, the adherence of the radioactive substances is low and, hence, a problem of an increase in dose rate does not substantially arise. However, metallic ions or metallic oxides released due to corrosion of structural members in these systems are entrained with supply water into a pressure vessel of a reactor, thus increasing the concentration of radioactive substances in reactor cooling water. Therefore, suppression of corrosion of structural members in these systems is an important problem, too. The method of this invention is basically aiming at suppression of corrosion of structural members. Prior to start of the operation of a nuclear plant, the above-mentioned systems, namely the water supply and steam condensation systems, are subjected to the first-step treatment under weakly oxidizing conditions and the second-step treatment under strongly oxidizing conditions to form oxide films highly protective against corrosion on the surfaces of the structural members. Thus, release of metallic ions or metallic oxides into primary cooling water can be reduced. As a result, the amount of radioactive substances adhering to the recycling system and the reactor water purification system can be decreased. |
047755091 | description | DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 shows schematically the only components concerned by the invention of a nuclear fuel assembly which may include, in a usual way, an upper end piece 10 and a lower end piece 12 connected together by guide tubes 14. On the guide tubes 14 are mounted several grids 16 spaced apart along the assembly. Some at least of the grids are fixed to the guide tubes 14 and hold the fuel rods 18 in position in a regular array. The assembly described by way of example has a hexagonal cross-section and the grids 16 hold the rods in position at the nodal points of an array or "Lattice" whose elementary cell is an equilateral triangle whose sides are parallel to the plates which form the girdle 20 of grid 16. Guide tubes 14 are substituted for the rods 18 at some nodes of the array. Some at least of the grids 16 are as shown in FIGS. 2 to 5. They each include a plurality of beds of mutually parallel plates for holding and spacing the rods, fixed to the girdle 20 and spaced in the longitudinal direction. In the embodiment shown in FIGS. 2 to 5, the grid 16 has three beds of plates, each bed being perpendicular to the longitudinal axis of the assembly. Each bed is formed of a series of mutually parallel plates. The plates of the set forming the top bed 24 are at 60.degree. from the plates 22 and 23 and all the plates are fixed to the girdle in a conventional way, generally by welding. In the construction shown in FIGS. 2 to 5, the girdle is formed of a flat bent metal strip and the plates of the three beds are undulated or corrugated at the spacing pitch of the rods. In order to provide resilient holding of the latter, support means are provided on the girdle and on the plates. The support means include two rows of support bosses 26 and 28 provided on the girdle 20, halfway between the beds of plates (FIG. 2). The bosses are formed by portions cut out in the metal strip which forms the girdle 20 and bent so as to projet inwardly of the girdle. The support means further include, on each of plates 22, 23 and 24, resilient tongues for engagement with the rods. Some of these tongues, designated 30, have an S-shape so as to cooperate with adjacent rods of the lattice. Others, designated at 32, only project from a single side. They will more particularly be provided at a position where the plates define a pocket for receiving not a fuel rod 18 but a tube 14. With such an arrangement, each rod is supported at four points at the level of each bed. The four support points are offset angularly by 120.degree. when passing from one bed to the next. The girdle and the plates may be formed, in a conventional way, from an alloy called "INCONEL", from stainless steel or from a zirconium based alloy. Each guide tube 14, such as the one shown in dot dash lines in FIGS. 3, 4 and 5, is fixed to each of the three beds of the grid 16. Fixing is advantageously provided by means of a split sleeve or sheath 34, as shown in FIGS. 6 and 7. Each sleeve 34 is fixed to a guide tube 14, at a suitable position, by imprisoning the guide tube in the sleeve, as is clear from FIG. 6. The presence of the longitudinal slit 38 in the sleeve provides the flexibility required for inserting the guide tubes and clamping them. Pairs of flats 40, 42 and 44 formed on the sleeve are provided for positioning and retaining the associated plates 24, 23 and 22. These plates may be welded to the sleeve 38 or simply positioned. On this latter assumption, in a variant of construction shown in FIGS. 8 and 9 (where the members already shown in FIGS. 6 and 7 bear the same reference numbers), the plates have punctured portions 36 for imprisoning the lugs 48 formed for this purpose in sleeve 34, these punctured portions then serving as rod supporting elements. The grid shown in FIG. 2 further includes fins 50 formed on the edge of the girdle and facilitating the introduction of the assemblies in the core, simultaneously with mixing of the coolant. In the grids shown in FIGS. 2 to 9, the beds of plates 22, 23 and 24 are disjointed and separated by a gap which is of the same order as the height of the plates. But it would also be possible to use jointing beds, the plates of one bed being engaged with those of the adjacent bed, or on the contrary the gap between the beds may be increased. The plates may further be provided with mixing fins, so as to provide both a supporting function and a function of mixing the fluid streams. These fins may have one of the constructions which will now be described, in their application to grids having a mixing function. These mixing grids may be alternated with support grids in the same fuel assembly. The mixing grids must provide the best compromise possible between requirements which are to some extent contradictory. Their neutron absorption must be as low as possible, which leads to reducing as much as possible the mass of material which forms them and in choosing, as far as possible, a material with a small capture section such as a zirconium based alloy. The mixing fins must homogenize the flow and reduce the temperature differences by causing transverse redistribution of the coolant streams. But the presence of the fins must not cause an increase of the pressure loss such that there is an unacceptable reduction of the flow rate. The distribution of the plates in several beds offset in the axial direction decreases the pressure loss. When the plates are provided with fins, these latter may be distributed axially between the beds so as to obtain a three-dimensional effect. Several exemplary types will now be described with advantageous distributions, leading to different flow modes, some of which are particularly well adapted to a triangular mesh and others to a square mesh. By way of a first example of a mixing grid, FIG. 10 shows a lattice of 5.times.5 rod reception pockets 18. Grid 16a, a fraction of which is shown, includes two spaced beds 50 and 52. The beds are connected together by corner rods or bars. Each bed includes plates oriented in two different directions, but each bed is incomplete in that a pocket is only completely defined by plates belonging to the two beds. It can be seen, for instance, that bed 52 includes plates 56 oriented in a first direction and plates 58 oriented in the perpendicular direction. The set of plates having the first direction is completed by plates 60, disposed in staggered fashion with respect to the first ones, but belonging to bed 50. Plates 56, 58, 60 include means for mixing the fluid streams. These means are formed of half-fins each placed on a single elementary pocket and disposed in opposite pairs at the corners of the pockets. In the variant of construction shown in FIG. 11, plates 56 have complete fins 62 cut out in a non-emergent window of the plates. FIG. 11 also shows centering fingers 64 which may have a construction similar to that shown in FIG. 2. In a further variant of construction, shown in FIG. 12, two opposite half-fins 64 are formed by stamping and deformation in each window of a plate 56. FIG. 13 shows an advantageous distribution of the half fins 66 in the case of a grid 16b having two beds 50 and 52, each bed being formed of a set of plates all having the same direction, the plates of one set being orthogonal to the plates of the other set. The half-fins 66 carried by the same plate are spaced apart at regular intervals, equal to the dimension of a pocket and directed alternately in one direction and in the other. The projection on the same plane of two sets of fins leads to a complete lattice of orthogonal fins. But, contrary to what would happen if all the plates were in the same plane, each lattice of fins causes its own cross flow mode. This flow mode is shown schematically by the arrows F1 in so far as bed 50 is concerned and F2 in so far as bed 52 is concerned. On its passage through the first bed, the air gaps of the same direction are swept in a given direction by the coolant. On passing through the second bed, it is the air gaps of perpendicular direction which are swept in their turn. In the variant of construction shown in FIG. 14, each of the two beds 50 and 52 of grid 16c include half of the fins belonging to one set of fins parallel to a first direction and another half of fins of the set directed in the orthogonal direction. In other words, in a given set, each plate belongs alternately to the upper bed and to the lower bed. In a given bed, the plates belonging to a set (plates 56 for example) include two half-fins at each intersection with the plates 58 of the other set, the two half-fins being in opposite directions. And plates 58 of the same bed include two half-fins in the middle of the space which extends between two crossing points. In axial projection, the superimposition of the two fin lattices again leads to a complete lattice of opposite fins. But, if all the fins were in the same plane, they would generate a circumferential coolant current about each rod. On the contrary, in the grid shown in FIG. 14, the two half fins which, about a given rod, cause the flow of the coolant about the rod, are situated at different axial sides and promote the appearance of a helical current more favorable from the mixing point of view. The plates may include, instead of the straight plates of FIGS. 13 and 14, plates bent in the form of a staircase or in crenellated form. FIGS. 15 and 16 show schematically two possible arrangements of the plate in a two bed grid, each plate having a staircase shape (FIG. 15) or a crenellated shape (FIG. 16). Other combinations are further possible, having two or three superimposed beds. In yet another variant of construction, the beds are jointing and some of the plates of each bed have lugs criss-crossing with other beds. This solution has the advantage of providing good mechanical strength and facilitating the distribution of the fins, particularly in the case of a rectangular mesh lattice. FIGS. 17 to 20 show possible construction of a three-bed grid, the plates of each bed 22, 23 and 24 being bent in the form of a staircase. It can be seen that the arrangement of the plates is such that, in projection, they completely define the pockets: FIG. 18 is such a top view of the three beds of a grid, showing the superimposition of the plates of the three beds, represented for the sake of clarity respectively in continuous lines, broken lines, dotted lines. Some pocket walls include grid sections placed one above the other. The beds may then be secured together in a simple way by providing the plates, in the sections in coincidence, with securing lugs 60 (FIG. 19). These lugs may be interfitted with each other as shown schematically in FIG. 20. Another solution consists in forming, in some of the lugs, buttons such as 62 which engage in recesses in the associated plates. The number of lugs may then be reduced. Another solution consists in providing fixing by rivets or spot welding. The rivets may also form means for centering the rods. A grid thus formed has the advantage of good mechanical strength and simple manufacture, especially when it uses centering rivets. The arrangement of the plates in two perpendicular directions introduces heterogeneities promoting mixing. Finally, the fins may be disposed both in the upper layer and in the lower layer. When the grid has three beds of plates, it is possible to distribute the mixing fins in the three beds. In particular, a bed with three grids may be provided for reconstituting by superimposition a half-fin arrangement of the kind shown in FIG. 21 or the half-fin distribution shown in FIG. 22 which may be termed "braided lattice" and which creates diagonal and opposite flows in the air gaps between rods. For that, the following may be provided: an upper bed of plates 24 having a braided lattice of half-fins organizing in a first direction; a middle bed of fins 23 having fins in a similar braided arrangement, but on opposite direction; a lower layer not having any fins, but only lugs for fixing it to the upper and middle beds so as to create a mechanicaly rigid grid. Each cell containing a rod is then provided with two half-fins, one belonging to the upper bed and the other to the middle bed, which tends to cause the coolant to rotate in spiral fashion about the rod in one direction which changes when going from one cell to the next cell. With this combination of two braided lattices, we find again the effects of the network shown in FIG. 21, but using fins placed in two planes offset in the general flow direction and whose relative distribution is shown in FIG. 22a. The design which has just been described in the case of a square lattice is directly transposable to the case of a triangular lattice. The plates are then bent at 60.degree. and not at 90.degree. and the lower bed is complete so as to define a triangle of plates about each rod and not a diamond shape. With this arrangement, the support element carried by the plate may be perpendicular to each rod. The plates of the lower bed may be provided with lugs for fixing to the upper and middle beds. FIGS. 23 and 24 show respectively a possible construction of the three beds and the fin arrangement obtained by the superimposition of these three beds. It will be generally seen that the invention provides great flexibility of construction and permits the most advantageous solution in each case. The plates may be straight or bent in the form of a staircase or in crenellated form; the beds may be non-jointing; the fins may be provided on one or more beds so as to provide a mixing function. The fins may be stamped in the plates themselves and be placed at the level of the air gaps between rods because of the absence of crossing of plates at the same level. The plates may have a perforated or crenellated shape. Finally, it is possible to brace the beds so as to ensure good mechanical strength, possibly using means which also participate in centering the rods. |
summary | ||
051679094 | summary | FIELD OF THE INVENTION The invention relates to a lower connector of a fuel assembly of a nuclear reactor cooled by light water, especially of a pressurized-water nuclear reactor. BACKGROUND OF THE INVENTION Pressurized-water nuclear reactors comprise a core consisting of prism-shaped assemblies arranged side by side in vertical position. The assemblies comprise a framework consisting of longitudinal guide tubes and spacer grids and closed by connectors in which the fuel rods are arranged. One of the connectors of the assemblies, called the lower connector, comes to rest on the lower core plate which is pierced with holes in the region of each of the assemblies, to allow the cooling water of the reactor to pass through the core vertically and from the bottom upwards. This connector comprises supporting feet which come to rest on the lower core plate, and an element transverse relative to the direction of the fuel rods of the bundle fixed to the supporting feet. This transverse element consists of an adapter plate, in which the lower ends of the guide tubes of the assembly are fastened and through which extend orifices allowing the passage and ensuring the distribution of reactor cooling water which circulates in the vertical direction and in contact with the outer surface of the rods of the assembly, after passing through the lower connector. The adapter plate of the lower connector of a fuel assembly of a water-cooled reactor thus contributes to the rigidity of the framework of the assembly, ensures the absorption of forces exerted on the lower connector and particularly the absorption of the weight of the framework and of the bundle transmitted by the guide tubes and must, furthermore, allow the passage and distribution of the cooling water of the assembly. The adapter plate is mainly subjected to bending and undergoes high stresses, especially in the vicinity of its upper face and lower face. This plate, produced in one piece, must have a large thickness ensuring that the lower connector has high rigidity. The adapter plate must also ensure that the fuel rods of the assembly are retained, in the event that some of these rods are no longer held sufficiently effectively by the holding elements of the spacer grids and tend to slide in the axial direction of the bundle under the effect of their own weight. Insofar as the water passage holes extending through the adapter plate are generally of a diameter larger than the diameter of the fuel rods, it is necessary to provide a network of holes in positions offset relative to the transverse positions of the fuel rods, so that each of the fuel rods is vertically in line with a solid part of the adapter plate. Even when all or some of the holes passing through the adapter plate have a diameter smaller, even markedly smaller, than that of the fuel rods, it is desirable to avoid placing these holes of small diameter vertically in line with the fuel rods which, in the event of an accidental fall, risk blocking one or more water passages and therefore reducing or locally eliminating the cooling of the fuel rods by water circulation. Moreover, in view of the thickness of the adapter plate, it is necessary to provide water passage holes which are such that the head loss of the cooling water through the lower connector is as small as possible. It is extremely difficult to design an adapter plate which can satisfy the various mechanical and hydraulic requirements mentioned above. The machining of this adapter plate is an extremely difficult operation requiring high accuracy of execution. Furthermore, debris particles may be present in the primary circuit of the reactor and are liable to be carried along by the circulating pressurized water. If they are of a small size (for example, smaller than 10 mm), they can pass through the adapter plate of the lower connector, the water passage holes of which have a diameter generally larger than 10 mm. Such debris may become jammed between the fuel rods and the elements holding the rods in the region of the first grid, i.e., the spacer grid holding the rods according to a regular network and being the lowest in the assembly. This debris subjected to the axial and transverse hydraulic stresses which are high in this zone, can wear the sheathing of the fuel rod. This risks a loss of sealing of this sheathing and an increase in the rate of activity of the primary circuit of the reactor. To prevent this debris from being carried along inside the assembly, it has been proposed to carry out filtration of the cooling fluid in the region of the adapter plate of the lower connector by providing holes which pass through this adapter plate, and the diameter of which is sufficiently small to stop the debris liable to be jammed in the first grid of the assembly. However, to ensure that the flow of cooling fluid passes through the adapter plate with only moderate head loss, it is necessary to provide a very dense network of passage holes, thus further complicating the machining of the adapter plate. The lower connectors of the fuel assemblies can be produced in one piece by the machining of a molded part or, on the contrary, from a plurality of molded and machined parts which are joined together by welding. In this case, it can be especially advantageous to carry out the welding by electron beam. The connectors of the assembly consist, for example, of a reticular structure limited externally by a frame, the cross-section of which corresponds substantially to the cross-section of the assembly, and having walls connected to one another and to the frame, delimiting large-size cells introducing only a negligible head loss into the circulation of the cooling water of the reactor. A plate of small thickness which can be die-stamped is attached and secured removably to one of the faces of the reticular structure. To regulate the flow of the cooling water through the connector, the plate is pierced with orifices, the shape, dimensions and arrangement of which make it possible to set the head loss and distribution of the water passing through the connector. Such connectors are mainly used as upper connectors of the assemblies and are unsuitable for use as lower connectors in which they must ensure both the retention of the rods and the distribution and adjustment of the flow of cooling water entering the assembly. Moreover, these connectors do not ensure that debris transported by the reactor cooling water is stopped and retained. These processes for producing lower connectors of fuel assemblies from attached parts therefore make it impossible to provide a completely satisfactory solution to the problems regarding the mechanical stability and hydraulic behavior of the adapter plates and the possibility of stopping and retaining the debris transported by the cooling water. SUMMARY OF THE INVENTION The object of the invention, therefore, is to provide a lower connector of a fuel assembly of a nuclear reactor cooled by light water, consisting of a framework comprising longitudinal guide tubes, spacer grids and end connectors, and a bundle of parallel fuel rods held in the framework by holding elements in the region of the spacer grids, one of the connectors, or lower connector, intended to come to rest on a support plate of the core of the reactor comprising a transverse element for the absorption of force and for retaining the fuel rods, comprising a reticular structure resistant to bending and limited externally by a frame, the cross-section of which corresponds substantially to the cross-section of the assembly, and having walls delimiting large-size cells; this lower connector possessing, furthermore, properties of optimized mechanical resistance and hydraulic behavior and capable of being produced in a simple way by means of conventional machining operations, while at the same time allowing debris circulating in the cooling water of the reactor to be stopped. To this end, the transverse element is in the form of a box comprising a retaining plate of small thickness in relation to the reticular structure and pierced with a regular network of orifices, the dimension of which is smaller than the maximum dimension of the spaces reserved between the rods and the elements holding these rods in the spacer grids, and superposed on and fastened to the reticular structure in an arrangement parallel to the faces of this structure and with a particular spacing of the same order of magnitude as the thickness of the reticular structure, so as to provide within the box, between the reticular structure and the anti-debris retaining plate, a free space for steadying the flow of the cooling water of the reactor and for recovering the debris. |
claims | 1. An electrically conductive textile yarn for the production of protective garments for conducting maintenance on live high-voltage wires, wherein the said yarn comprises:a first element comprising one or more electrically conductive threads, each of the electrically conductive threads comprising a core composed of polyamide covered with a layer of silver; anda second element, which is different from the said first element, and comprises one or more threads provided with good resistance to fire, the second element not comprising metallic or mineral fibres;the yarn being produced by twisting together one or more threads of the second element with one or more electrically conductive threads of the first element;wherein the fraction by weight of the electrically conductive threads of the first element compared with the weight of said yarn is approximately 30%-35%. 2. The electrically conductive textile yarn according to claim 1, wherein the said second element consists substantially of fibres selected from the group comprising: aramide fibres, meta-aramide fibres, and flame-retardant cotton. 3. The electrically conductive textile yarn according to claim 2, wherein the second element also has anti-static properties and/or anti-bacterial properties, and/or properties of resistance to acids or bases and/or of resistance to temperatures higher than 200° C. 4. The electrically conductive textile yarn according to claim 1, wherein the second element also has anti-static properties and/or anti-bacterial properties, and/or properties of resistance to acids or bases and/or of resistance to temperatures higher than 200° C. 5. A garment comprising a layer created by a yarn according to claim 1 wherein a surface area of the said layer is substantially equal to the surface area of the garment. |
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052895092 | claims | 1. A comb-line antenna comprising: a plurality of parallel current straps supported in a plane above a conductive surface, each current strap having a specified length l and width W, each strap having a first end that is substantially aligned with the first ends of the other straps, each strap being separated a distance S from an adjacent strap, whereby an array of current straps is formed having approximate dimensions of l by N(W+S), where N is the number of current straps in the array; input means for applying rf input power to a first current strap of said plurality of parallel current straps, said first current strap being located on one edge of said current strap array, a portion of said rf input power applied to said first current strap being inductively coupled to a second current strap adjacent the first current strap, and a portion of the rf input power coupled to the second current strap being inductively coupled to a third current strap adjacent the second current strap, and so on, with the rf input power being inductively coupled from one current strap to an adjacent current strap; a multiplicity of U-shaped wickets connected to said conductive surface that enclose, but do not touch, each of said current straps, said multiplicity of U-shaped wickets functioning as a Faraday shield; the current straps in said current strap array being configured to launch a portion of the input rf power away from said conductive surface and said current straps into a medium having a frontal surface that is more or less parallel to said current strap array, whereby said current strap array functions as an antenna that launches rf power into the medium. (a) supporting a multiplicity of parallel current straps an equal distance apart, and positioning said equally-spaced, parallel current straps so as to front said plasma; (b) applying rf input power to a first of said plurality of parallel current straps, said rf input power being inductively coupled from one current strap to an adjacent current strap, whereby a portion of the rf input power applied to said first current strap is inductively coupled to a second current strap adjacent said first current strap, and a portion of the rf power coupled to the second current strap is inductively coupled to a third current strap adjacent said second current strap, and so on, with the rf input power being inductively coupled from one current strap to an adjacent current strap so that each of said current straps receives some rf power, and with some of the rf power present at each current strap being launched from the respective current strap as a magnetosonic wave into said plasma; and (c) shielding said plasma from electrostatic fields present at said current straps. 2. The comb-line antenna as set forth in claim 1 wherein said medium comprises a plasma mass, and wherein said launched rf power assumes the form of a magnetosonic wave within said plasma mass. 3. The comb-line antenna as set forth in claim 2 wherein said current strap array is mounted within a conductive, open box having cross-sectional dimensions that are slightly larger than l by N(W+S), said box having an open top that faces the plasma mass, said conductive surface comprising a bottom surface of said box. 4. The comb-line antenna as set forth in claim 3 wherein said box is attached to a wall of a plasma-confining structure, said current strap array being exposed to the interior of said plasma-confining structure through the open top of said box, whereby rf power is launched into the interior of said plasma-confining structure from said comb-line antenna. 5. The comb-line antenna as set forth in claim 4 wherein said plasma-confining structure comprises a tokamak. 6. The comb-line antenna as set forth in claim 1 further including extraction means for extracting rf output power from a last current strap of said plurality of parallel current straps, said last current strap being positioned on an edge of said current strap array that is opposite said first current strap where rf input power is applied to said current strap array, whereby any of the rf input power that is applied to said first current strap and that is coupled through said current straps to said last current strap without being launched into said medium may be extracted from said current strap array. 7. The comb-line antenna as set forth in claim 6 further including means for recirculating the rf power extracted from said extraction means back to the input means. 8. The comb-line antenna as set forth in claim 6 wherein said rf input power has a frequency in the range of 100 to 200 MHz. 9. The comb-line antenna as set forth in claim 8 wherein the number N of current straps within said array is at least 10. 10. The comb-line antenna as set forth in claim 9 wherein the length l of said current straps comprises approximately 15 to 30 cm, the separation distance S between adjacent current straps comprises approximately 2.5 to 5.0 cm, and the width W of said current straps comprises approximately 2.5 to 5.0 cm. 11. The comb-line antenna as set forth in claim 9 wherein the current straps are positioned a standoff distance d.sub.1 from said conductive surface, where d.sub.1 comprises approximately 2.5 to 5.0 cm. 12. A comb-line antenna comprising a plurality of parallel current straps, each current strap being enclosed within a multiplicity of wickets, each of said wickets being grounded to a conductive ground plane, said conductive ground plane being a prescribed stand-off distance from said plurality of parallel current straps, and input power means for applying rf input power to a first one of said plurality of parallel current straps, each of said current straps being spaced apart from an adjacent current strap a specified distance so that some of the rf input power applied to said power input means is inductively coupled from one current strap to an adjacent current strap, with each of said current straps receiving some rf power, where the rf power at each current strap produces an electromagnetic field. 13. The comb-line antenna as set forth in claim 12 further including output power means for extracting output power from a last one of said plurality of parallel current straps, whereby any rf power remaining at the last current strap may be extracted and recirculated back to the input power means. 14. The comb-line antenna as set forth in claim 13 further including support means for supporting said plurality of parallel current straps adjacent a plasma mass, with the electromagnetic wave launched from said plurality of current straps comprising a magnetosonic wave that propagates within said plasma, and with said multiplicity of wickets functioning as a Faraday shield that shields said plasma mass from electrostatic fields that are present in the vicinity of said current straps. 15. The comb-line antenna as set forth in claim 14 wherein said plasma mass is confined within a tokamak, and wherein said support means is mounted on the inside of an exterior wall of a vacuum vessel within said tokamak so that said plurality of parallel current straps fronts said plasma mass. 16. A method of launching magnetosonic waves into a plasma comprising: 17. The method as set forth in claim 16 wherein step (c) comprises enclosing each of said multiplicity of parallel current straps within a multiplicity of conductive wickets, each of said wickets having an appropriate shape that encloses, but does not touch, the respective current strap about which it is placed, each of said wickets further being grounded to a ground plane that is a prescribed stand-off distance from said parallel current straps. 18. The method as set forth in claim 17 further including extracting rf power from a last of said multiplicity of current strips and recirculating said extracted rf power back to said first current strip. |
abstract | A temperature sensor array includes several temperature sensors at different positions for installation within an instrumentation tube of a nuclear reactor. The temperature sensors measure temperature at multiple axial positions of the nuclear reactor, and plant operators are able to access and interpret this measurement data. Temperatures associated with vessel coolant boiling or loss and/or fuel damage can be detected by the temperature sensors to permit more direct determinations of core fluid levels. Multiple temperature sensor arrays permit vessel fluid levels and conditions to be measured at multiple core locations. |
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description | This divisional application claims the benefit of U.S. provisional patent application: Ser. No. 60/775,677, filed Feb. 21, 2006; PCT application serial no. PCT/US2007/04403, filed Feb. 20, 2007; and U.S. utility patent application Ser. No. 12/224,015, filed Oct. 13, 2010. This invention relates to a method of performing radiation therapy. More specifically the invention relates to a new technique in IMRT conformal gamma radiation dose delivery using a linear accelerator with no flattening filter. The new technique improves patient radiation therapy by reducing radiation scattered to surrounding normal tissue without a filter. Intensity modulated radiation therapy (IMRT) is a treatment method for cancer patients requiring radiation treatment. IMRT is an extremely precise method of treatment delivery where the radiation dose conforms to the target and avoids the surrounding critical structures. Rather than having a single large radiation beam pass through the body, with IMRT the treatment is delivered from various angles and the intensity of the radiation beam is varied across the treatment area. The radiation is effectively broken up into thousands of tiny pencil-thin radiation beams. With millimeter accuracy, these beams enter the body from many angles and intersect on the cancer. This results in a high radiation dosage to the tumor and a lower radiation dose to the surrounding healthy tissues. One method for modulating the intensity of the radiation beam is based upon moving a multi-leaf collimator (MLC) in and out of radiation beam from the radiation treatment machine. An MLC comprises a plurality of thin width mechanical blades or leaves, which are individually controlled by miniature motors and mechanical drive linkages. A computer controls the miniature motors for driving the individual blades in and out to shape the radiation beam. An advantage of an MLC based IMRT treatment machine is that the same MLC can be automatically controlled to support the individual needs of each patient receiving radiation treatment. In other words, the MLC is reconfigured for each new patient. Linear accelerators have for decades come with a photon flattening filter to make the photon profile of planar fluence and thus, the dose distribution more uniform. These filters have then resulted in fluence attenuation and contamination of the beam. Now in the age of techniques such as intensity modulated radiation therapy (IMRT) the function of the flattening filter becomes redundant and the flattening filter now merely reduce the efficiency of the beam by reducing the fluence and increase scattered radiation. Other objects and advantages of the present invention will become apparent to those skilled in the art upon a review of the following detailed description of the preferred embodiments and the accompany drawings. Our technique involves removal of the flattening filter for complex treatments and using inverse planning along with multi-leaf collimators to shape the dose distribution. With the flattening filter removed the dose rate is increased and he lateral scatter is reduced. This improves patient treatment by reducing dose to the normal tissue surrounding the target and also reduces treatment times. The flattening of the beam profile is redundant in techniques such as IMRT since the planar fluence is controlled by the multi-leaf collimator (MLC). For many modern linear accelerators, removal of the flattening filter requires no physical modification of the unit since the flattening filter can simply be mechanically moved out of the beam path. This new technique is in IMRT and 3D conformal gamma radiation dose deliver using a linear accelerator with no flattening filter. The technique improves patient radiation therapy by reducing radiation scattered to surrounding normal tissue and reducing electron contamination. It increases does rate to shorten treatment time. Linear accelerators have for decades come with a photon flattening filter to make the photon profile of planar fluence to make the dose distribution more uniform. These filters, however, have resulted in fluence attenuation and contamination of the beam. Now in the age of techniques such as intensity modulated radiation therapy (IMRT) the function of the flattening filter becomes redundant. The flattening filter now merely reduces the efficiency of the beam by reducing the fluence and increasing scattered radiation. IMRT (Intensity Modulated Radiation Therapy) is rapidly becoming a common treatment modality with a recent study claiming that it is used by a third of the radiation oncologists in the United States. The modern treatment machines are designed with dynamic MLC and IMRT-ready systems integrated into them but many of the current linear accelerators still used today, have the MLC as an add-on. In either case the linear accelerator is designed such that IMRT treatments and standard treatments can be carried out on the same unit. The conventional 3D conformal therapy treatment requires a flat beam because generally dose compensation to achieve uniformity within target volume for each individual beam is not performed. However, in generating IMRT treatment plans, the planner ends up with a non-uniform density matrix to deliver the desired dose with the target volume, and spare the surrounding normal or critical structures. To achieve this goal, a flat beam is not required. Modulation of beam during IMRT planning and delivery is performed through segmented fields and many beamlets within the delivery port and in fact thinking out side of convention, one would see the advantages in having a cleaner beam that does not need to suffer all the scattering through a thick chunk of metal, namely the flattening filter. It is therefore, expected that removal of the flattening filter would lead to better IMRT treatments due to the reduction in lateral photon scatter and the increase in central axis photon fluences. More specifically, by moving the flattening filter out of the path of the beam solely for IMRT treatments, higher dose rates and sharper, more geometrically defined fields can be expected thus leading to better IMRT plans and treatments. The deleterious properties of the flattening filter care caused by the increased lateral scatter and the decreased central axis fluence that the filter produces. In the special case of IMRT, where fluence is varied by a combination of MLC movements and beam modulation at the patient level, the filter is no longer required. This has been shown for the specific case of tomotherapy; a dedicated IMRT system. Here we show Monte Carlo simulations of radiation characteristics for the more general case of a linear accelerator. Preferably, the higher dose rates are X-rays ranging from 4 MV to 25 MV. Methods and Materials Monte Carlo Simulations of an Elektra SL-25 Monte Carlo simulations were carried out using the BEAMnrc code. Using an Elektra precise model SL-25 photon beams of 6 MV and 10 MV energies were initially modeled and commissioned by comparing the simulations to data measured using a Welhofer (Scanditronix Wellhofer) scanning water phantom. In the models the head of the accelerator was broken down into component modules, namely the target, primary collimator, flattening filter, monitor chamber, mirror, MLC and X and Y jaws. An additional component was used to simulate the air gap between the exit of the accelerator and the water phantom surface, where the phase space plane was located. The energy cutoffs for transport were set as ECUT=0.7 MeV, PCUT-0.01 MeV and global electron cut-off-2.0 MeV. Electron range rejection and selective Bremsstahlung splitting were used, with SBS parameters Nmin=10 nd Nmax=100. Russian roulette and photon forcing were not employed. The phase space file created at the plane 100 cm from the source was then used as the input for the phantom, simulated using the DOSXYZarc code. 400×106 histories were used for the simulation of the accelerator. For the DOSXYZ phantom, 200×106 histories were used for all field sizes, resulting in adequate statistics for the larger field sizes. Both depth dose and transverse profiles depend greatly on the properties of the electron beam as it strikes the photon target. The parameters of importance are the mean electron energy, the energy spread and the spatial distribution of the beam. For the 6 MV and 10 MV beams respectively, the electron energy used was 6.50 MeV and 9.50 MeV, the energy spread was 1.0 MeV and 0.8 MeV FWHM and the radial distribution was 0.11 cm and 0.10 cm FWHM. Depth dose curves obtained from these simulations deviated less than 1% in the region of dose-maximum and less than 5% at all other depths, when compared to water phantom measurements. Once the Monte Carlo simulation was found to match the measured data to adequate levels, the flattening filters were removed from both of the 6 MV and 10 MV beam models. All other parameters remained unchanged. Measurements Made in Water. All measurements were made at 100 cm SSD in a Welhofer scanning water phantom, with a 0.1 cc ionization chamber. Both 6 MV and 10 MV beams were studied for comparison with the Monte Carlo simulations. After the Monte Carlo model commissioning data was obtained the 6 MV and 10 MV flattening filters were removed from the primary rotating carousel in the head of the accelerator. This left a hole in the carousel which the photon beam could pass through. Depth-ionization profiles, transverse inline (gun-target direction) and cross-plane profiles were measured at dmax and 10 cm. Depth dose profiles were measured to a depth of 30 cm and normalized to the maximum chamber reading on the central axis. Transverse profiles were measured in the inline and cross-plane directions for field sizes ranging from 5×5 to 30×30 cm2. These profiles were also normalized to the maximum chamber reading on the central axis. Results Monte Carlo Model Commissioning As mentioned, Monte Carlo simulations of the standard, flattened 6 MV and 10 MV beams where carried and they matched well with the measured data obtained with the scanning water phantom. The purpose of these measurements was to show that the Monte Carlo models accurately match the measurements of dose performed in the water phantom. FIGS. 1(a) and 1(b) show Monte Carlo and water phantom measurements of the CAX percent depth-dose for 6 MV and 10 MV. Central axis percent depth-dose profiles for a 10×10 cm2 field at 100 cm SSD are shown for 6 MV and 10 MV, with the experimental measurements shown as solid points and the Monte Carlo model shown as hollow points. Transverse profiles of a 30×30 cm2 field were also obtained for comparison of the flatness and symmetry of the Monte Carlo models with respect to the measured data. FIGS. 2(a) and 2(b) show 6 MV and 10 MV Monte Carlo calculated transverse profiles for the inline direction at depths of dmax and 10 cm, compared to the measured data. A good agreement between measured and Monte Carlo modeled data was found in all cases. FIG. 3 shows a comparison between Monte Carlo and measured data for a 6 MV 10×10 cm2 beam. The top two curves are for a depth of 1.6 cm (dmax) and the bottom two curves are for a depth of 10 cm. Monte Carlo Modelling of a Non-Flat Beam Simulations were then carried out without the filter and compared to data measured after the flattening filters had been removed from the primary filter carousel of the Elekta accelerator. The purpose of these measurements was to verify the accuracy of the Monte Carlo models to accurately simulate a beam without the flattening filter. A comparison for the cross-plane profiles is shown in FIG. 3. Not shown are the comparisons between the inline (gun-target) direction measured and Monte Carlo profiles. These measured transverse profiles had poor symmetry and this was believed to be due to difficulties of steering the beam after removal of the flattening filter. It can be concluded from FIG. 3 that the Monte Carlo models of filter free 6 MV and 10 MV beams were shown to accurately match the measured data. Simulations were then carried out for various field sizes ranging from 2×2 cm2 to 30×30 cm2. The graph below shows the transverse profiles obtained at 1.6 cm depth for a 6 MV beam without a flattening filter. The curves in FIG. 4 are all normalized to the CAX dose of the 10×10 cm2 field. FIG. 4 shows Monte Carlo computed transverse cross-plane profiles at a depth of 1.6 cm for a 6 MV filter free photon beam of field size ranging from 2×2 to 30×30 cm2. The next step was to compare the Monte Carlo models of the flattened and unflattened beams. FIG. 5 shows Monte Carlo calculated transverse profiles and the effect on the central axis (CAX) dose of removing the flattening filter. It was found that for the 6 MV photon beam of 10×10 cm2 field size the CAX dose was increased by a factor of 2.35 with the filter removed, compared to the standard flattened beam. This figure also shows the CAX dose was increased by a factor of 2.35 with the filter removed, compared to the standard flattened beam. This figure also shows the CAX dose for a 10×10 cm2 10 MV beam with and without the flattening filter. In this case, since the 10 MV flattening filter for the Elekta is more substantial in terms of mass of material used the CAX dose without the filter is 4.18 times higher than the standard flattened beam. FIGS. 5(a) and 5(b) show a comparison between Monte Carlo simulations for a standard, flattened and an unflattened 6 MV and 10 MV 10×10 cm2 beam at dmax. All profiles are normalized to the central axis dose of the standard beam to show the effect on the CAX dose of removing the flattening filter. C. Quantification of Beam Flatness The flatness of each transverse profile was calculated using the variation over the mean at 80% of the field size, with the equation, flatness = 100 × D max - D min D max + D min For the 6 MV simulation of a 10×10 cm2 beam, the flatness at dmax was 2.37% and 6.21% for the flattened ad unflattened beam, respectively. Similarly, at 10 cm depth the equivalent percentages were 1.88% and 5.77%. For the 10 MV simulations, flatness percentages of 3.96% and 7.71% were obtained at depths of 2.3 cm (dmax) and 10 cm for the standard and unflattened beam, respectively. At 10 cm depth flatness was calculated to be 2.92% for the flattened beam and 8.39% for the unflattened beam. D. Dose on the Central Axis FIGS. 6(a) and 6(b) show Monte Carlo percent depth-dose curves comparing the standard flattened 6 MV and 10 MV beams to the equivalent filter-free beams. The faster decrease in dose with depth for the filter-free beam is consistent with a softer central axis beam. Depth dose curves on the central axis were also obtained from simulations of the flattened and unflattened 10×10 cm2 6 MV and 10 MV beams. The dose deposited at depths greater than dmax was found to decrease more rapidly with the filter removed. This is due to the fact that, with the filter removed the beam in the region of the central axis is no longer hardened by the filter. The faster decrease in dose with depth is consistent with a softer central axis beam. To investigate the effect of the flattening filter on the photon energy spectrum an analysis of various phase space files with the program BEAMDP was performed. Photon fluence as a function of photon energy was graphed for the filter free beams versus the standard Beams. As expected, the photon fluence per unit energy is significantly greater for the filter free beam, especially in the region of the peak photon energy. FIGS. 7(a) and 7(b) show photon fluences spectra for a 6 MV beam and a 10 MV beam showing the effect of removing the photon flattening filter. FIG. 7 shows the photon fluence spectra across a 10×10 cm2 field for both the 6 MV and the 10 MV beam. In both cases the peak photon energy is increased by removing the flattening filter, showing that the flattening filter has the effect of hardening the beam. For the 6 MV beam the peak energy with and without the flattening filter are 0.48 MV and 0.33 MeV respectively. Similarly, for the case of the 10 MV beam, where the design of the flattening filter leads to a greater beam hardening effect, the peak photo energies are 1.13 MeV and 0.33 MeV for the standard beam and the filter free beam. E. Out of Field Dose With the flattening filter removed, one would expect the amount of lateral photon scatter to decrease, the effect being that the dose at a point outside the field would be reduced. To investigate this effect a comparison between the relative dose at and beyond the edge of the radiation field was made between simulations made of a 6 MV beam with and without the flattening filter. Simulations were run for a 6 MV beam for various field sizes ranging from 2×2 cm2 to 30×30 cm2. In all cases the dose at the edge of the field was greater for the filter-free beam. In FIG. 8 below, 2×2 cm2, 10×10 cm2 and 30×30 cm2 fields are shown for a flattened and filter-free 6 MV beam. It can be seen that, in the wings of the profile the relative dose for the filter-free beam is greater than that of the standard field in all cases. The profiles below are at a depth of 1.6 cm. The same profiles at a depth of 10 cm showed the same effect; the out of field dose being higher for the filter free beam. FIG. 8 is a comparison of absolute dose obtained from simulations of 2×2, 10×10 and 30×30 cm2 fields. The simulations shown here were for a 6 MV beam at a depth of 1.6 cm. For each field size a profile of the flattened beam and the unflattened beam are shown so that the dose at the edges of the radiation field can be compared. It can be seen that for all field sizes the dose at the edge of the field is greater for the filter-free beam. To quantify the out of field dose were considered a point 2 cm outside of the field (e.g. at an off axis distance of 3 cm for a 2×2 cm2 field) and took the average of the relative doses for the voxels to the right and left of the central axis. The table below shows the relative dose (the normalization is with respect to the CAX dose for the standard, flattened beam for that field size) at a point 2 cm outside the radiation field, for both the flattened and unflattened 6 MV beams. All profiles considered here are at a depth of maximum dose. TABLE 1Relative Dose (0%)with filterNo filter2 × 2 cm20.631.1010 × 10 cm22.864.5530 × 30 cm26.037.64Table 1. Shows a comparison of out of field relative dose for various field sizes. For each field size the relative doses is given at a point outside or on the edge of the radiation field. With flattening filter removed, the photon beams will not suffer the remarkable scattering that they will go through otherwise, resulting in a much cleaner beam at the patient's level. The conventional treatments requiring a flat photon beam are not necessary for IMRT treatments as the beams are modulated to achieve dose uniformity within the target volume. In fact the fluence maps as generated from a beam end up being very nonuniform for IMRT cases. The substantial increase in dose rate from a flattening filter free accelerator is significant in delivering a less contaminated beam at much shorter times. The computed depth dose plots for both 6 and 10 MV photon beams indicate that by removing the flattening filter out of the beam, better dose fall off beyond depth of maximum dose is achieved. On the other hand, because of a less hardened beam, the point of maximum dose ate depth will get closer to the surface (1-2 mm for 6×, and 2-3 mm for 10×). The out of field dose is a phenomenon that requires further study and will be discussed in detail in future works, but the measured and computed dose profiles in treatment fields indicate less scatter, significantly higher photon fluence, and overall a cleaner beam to be used for the IMRT treatment. The better fall-off of the dose beyond depth of maximum dose in a flattening free accelerator is also another indication to cleaner beams when filter is removed. The quantities of scatter and lower energy photons contributing to dose depth is directly proportional to the energy of the beam and is considerable for clinical photon beams. Specific compositions, methods, or embodiments discussed are intended to be only illustrative of the invention disclosed by this specification. Variation on these compositions, methods or embodiments are readily apparent to a person of skill in the art based upon the teachings of this specification and are therefore intended to be included as part of the inventions disclosed herein. The above detailed description of the present invention is given for explanatory purposes. It will be apparent to those skilled in the art that numerous changes and modifications can be made without departing from the scope of the invention. Accordingly, the whole of the foregoing description is to be construed in an illustrative and not a limitative sense, the scope of the invention being defined solely by the appended claims. |
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summary | ||
054328292 | abstract | A fuel assembly comprises fuel rods arrayed in a square lattice pattern of 10 rows and 10 columns, and three large-diameter water rods arranged along a diagonal line of the fuel assembly in such a region as able to accommodate 10 fuel rods. Partial length fuel rods are arranged in an outermost layer of the fuel rod array at fuel rod setting positions other than corners of the outermost layer. Ordinary fuel rods are arranged in a layer inside the outermost layer and adjacent to the outermost layer at positions adjacent to the partial length fuel rods in the outermost layer.. The struction of the fuel assembly enables a reduction in the void coefficient and an improvement in the reactivity control capability. Also, the void coefficient can be reduced without lowering reactivity, and fuel economy is improved. |
claims | 1. A method for the large scale production of a high-purity carrier-free or non-carrier added radioisotopes in a quantity suitable for medical applications comprising the following steps:(a) activation of a target by a particle beam,(b) separation of the isotope from the irradiated target under vacuum or in an inert atmosphere,(c) ionisation of the separated isotope in an ion source,(d) extraction of the ionized isotope from the ion source in an ion beam and acceleration of the ion beam,(e) mass-separation of the isotope, and(f) collection of the isotope including implanting,the isotope in the mass-separated ion beam into an implantation substrate and separating the isotope from the implantation substrate containing the isotope, wherein separating the isotope from the implanation substrates includes dissolving the implantation substrate in a small volume of water or an eluting agent. 2. The method according to claim 1, wherein the mass separation process is controlled by mass marking. 3. The method according to claim 1, wherein before step (c) the isotope of interest is introduced into an oven from where a sample is fed into the ion source. 4. The method according to claim 1, wherein the ionisation in step (c) is surface ionisation, laser ionisation or plasma ionisation. 5. The method according to claim 1, wherein the mass separation of step (e) is an on-line or an off-line mass separation. 6. The method according to claim 1, wherein in step (f) the isotope of interest is collected by implantation into a prepared chemical substrate. 7. The method according to claim 1, wherein radioisotopes in carrier-free or non-carrier added form are produced. 8. The method according to claim 1, wherein an implantation energy is selected in order to adjust the implantation depth. 9. The method according to claim 1, wherein the implantation is performed through a thin cover layer into the implantation substrate. 10. The method according to claim 1, wherein the implantation substrate is a salt layer, a water-soluble substance, a thin ice layer of frozen water or another liquid, or a solid matrix. 11. A method for direct radioisotope-labelling of a bioconjugate, comprising(i) performing a method according to claim 1,(ii) obtaining the product fraction containing the radioisotope of interest in a small volume, and(iii) direct radioisotope-labelling of the bioconjugate and/or direct injection into a chromatographic system for further purification,wherein the bioconjugate is an immuno-conjugate, antibody, protein, peptide, nucleic acid, oligonucleotide, or fragment thereof. 12. The method according to claim 11, wherein the bioconjugate further comprises a nanoparticle, microsphere or macroaggregate that is conjugated with, or covalently or noncovalently attached to, said immuno-conjugate, antibody, protein, peptide, nucleic acid, oligonucleotide or a fragment thereof. 13. The method according to claim 1, wherein the implantation substrate is a nanoparticle, macromolecule, microsphere, macroaggregate, ion exchange resin, or other matrix used in a chromatographic system. |
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046648690 | abstract | A method for simultaneously preparing Radon-211, Astatine-211, Xenon-125, Xenon-123, Iodine-125 and Iodine-123 in a process that includes irradiating a fertile metal material then using a one-step chemical procedure to collect a first mixture of about equal amounts of Radon-211 and Xenon-125, and a separate second mixture of about equal amounts of Iodine-123 and Astatine-211. |
description | This application is a continuation in part of U.S. patent application Ser. No. 10/226,096 filed on Aug. 22, 2002, which claims the benefit of U.S. Provisional Application No. 60/314,943, filed Aug. 24, 2001. The present invention relates generally to computed tomography (CT) systems and, more particularly, to volumetric CT (VCT) systems. Conventional x-ray imaging is based on the absorption of x rays as they pass through different parts of a patient's body. Depending on the absorption in a particular tissue such as muscle or lung, a different intensity of x rays will pass through and exit the body. During conventional x-ray imaging, the exiting or transmitted x rays are recorded with a detection device, such as an x-ray film or other image receptor, and provide a two dimensional projection image of the tissue within the patient's body. While these images can be very useful, when there is one structure in front or behind another, their images are superimposed in a single projection image and it is impossible to know which is in front, and each may obstruct the visibility of the other. While also based on the variable absorption of x rays, Computed Tomography (CT) imaging provides a different form of imaging known as cross-sectional imaging. CT imaging, also known as Computerized Axial Tomography (CAT) scanning, has been developed and used for many years to generate images of cross-sectional planes or slices of anatomy. Each image is generated by a computer synthesis of x-ray transmission data obtained in many different directions in a given plane. Because CT scans reveal organs, bone, blood vessels, and soft tissues, including lung, muscles, and tumors, with great clarity and detail, CT systems are particularly useful as a diagnostic or therapeutic guidance tool for medical purposes. CT systems have also been known to be useful in industrial, security, and other systems where imaging data are to be obtained. A CT system typically has a circular opening and includes an x-ray source and a detector array. A motorized table is commonly used to move a subject to be examined, such as an object, a patient, or a region of interest thereof, up or down and in or out of the circular opening. The x-ray source and the detector array are mounted on opposite sides of a rotating gantry. As the patient passes through the system, the x-ray source rotates around the inside of the circular opening. The x-ray source produces x-rays that pass through the patient and impinge on the detector array, which may be arc-shaped and also revolving. This process is also known as scanning. In known third generation CT systems, the x-ray source, comprising an x-ray tube, provides x-rays emanating from a point commonly referred to as a “focal spot”. The x-ray beam emanating from the focal spot to the array of detectors resembles the shape of a fan and therefore is sometimes referred to as a “fan beam”. The narrow, fan-shaped beam of x rays is used to irradiate a section or slice of the patient's body. The thickness of the “fan beam” may be as small as 0.5 millimeter or as large as 10–20 millimeters. A typical scanning process usually involves many rotations, each generating a different slice. Thus, the scanning process could involve dozens or hundreds of rotations of the x-ray source around the patient in coordination with the motorized table through the circular opening. The x-ray source is coupled to the detector array in a manner that the focal spot of the x-ray tube and the detector array are on one plane. The x-ray source and the detector array rotate together about an axis of rotation, such as an axis through the patient, perpendicular to the plane. For each position of the rotating gantry, the detector array records x rays exiting the section of the patient's body being irradiated as a projection, also known as a view or an x-ray profile. Many different views are collected during one complete rotation, typically a 360 degrees rotation. A single rotation takes about 1 second. During each rotation, the detectors may record about 1,000 views (x-ray profiles). The x-ray projection data collected/measured/sampled are then sent to a computer for reconstructing all of the individual views into a cross-sectional image (slice) of the internal organs and tissues for each complete rotation. Multiple computers are typically used to control the entire CT system. Despite the discrete nature of the sampled data, a number of known reconstruction algorithms are able to convert the collected data into high quality images of the slice. In this scanning mode, a three dimensional image can be made by producing images of slices, one at a time. The thickness of the slice and the spacing between slices are adjustable. Most modern CT imaging systems are capable of performing “spiral”, also called “helical”, scanning as well as scanning in the more conventional “axial” mode as described above. Spiral CT systems are well known in the art. An exemplary teaching can be found in U.S. Pat. No. 5,966,422, “MULTIPLE SOURCE CT SCANNER,” issued on Oct. 12, 1999 to Dafni et al. and assigned to Picker Medical Systems, Ltd. of Haifa, Israel. Briefly, the term “spiral” comes from the shape of the path, relative to the object, taken by the x-ray beam during scanning. The motorized (examination) table advances at a constant rate through the scanning gantry while the x-ray source rotates continuously around the patient, tracing a spiral path relative to the patient. This spiral path gathers continuous x-ray profile data without gaps. The pitch of a spiral scan, or helix, is defined as how far the patient is translated during one rotation divided by the thickness of the fan beam. In a typical procedure, the pitch ranges from about 1 to 2. A single rotation takes approximately 0.5 to 1 second. Some CT imaging systems, also called multi-detector CT or multi-row CT systems, are capable of imaging multiple slices simultaneously, allowing relatively larger volumes of anatomy to be imaged in relatively less time. In such a system, a number of planes or slices are sampled simultaneously via multiple rows of detectors. Since data for several slices can be obtained in one scan, total scanning time is greatly reduced. Exemplary teachings can be found in U.S. Pat. No. 6,047,040, “DETECTOR SIGNAL INTEGRATION IN VOLUMETRIC CT SCANNER DETECTOR ARRAYS,” issued to Hu et al. on Apr. 4, 2000; and U.S. Pat. No. 6,137,857, “SCALABLE DETECTOR FOR COMPUTED TOMOGRAPH SYSTEM,” issued to Hoffman et al. on Oct. 24, 2000 and assigned to General Electric Company of Milwaukee, Wis., USA. However, these multi-detector or multi-row CT systems still require more than one revolution during image scanning to produce data for a thick volume. A logical extension to the multi-slice or multi-detector scanning mode is called a cone beam CT. The goal is to enable the reconstruction of an entire three-dimensional (3D) object using a single rotation. Unfortunately, this imaging geometry suffers from several known drawbacks such as image artifacts, sometimes referred to as cone beam artifacts, and image reconstruction errors. Briefly, the divergence of the x-ray beam in the direction of the axis of rotation causes the reconstruction problem to be ill-posed. Indeed, even in multi-row CT systems, as the angle spanned by the multiple rows increases, so do the image reconstruction problems caused by the image artifacts. As such, the system will increasingly suffer from cone beam artifacts. Additionally, if one tries to reduce these artifacts by using more accurate reconstruction algorithms, image reconstruction can be computationally intensive and slow in cone beam CT systems. Accordingly, it is a primary object of the present invention to provide a fast and reliable volumetric CT system capable of providing image data for reconstructing an entire 3D object using a single rotation without suffering from image artifacts such as cone beam artifacts, overcoming image reconstruction errors and beam divergence problems common in known cone-beam CT systems. The goal is achieved in a CT system capable of providing data for reconstructing an entire 3D object using a single rotation, the system comprising, in a preferred embodiment, an array of x-ray sources distributed along a line parallel to an axis of rotation, a plurality of flat collimator plates positioned perpendicular to the axis of rotation and near the x-ray sources so to limit the x-rays illuminating the object to contain only x-rays that travel substantially along lines perpendicular to the axis of rotation, and a flat panel x-ray detecting means comprising an array of small and fast x-ray detectors for detecting and measuring transmitted x-rays emitted by the entire source array. In a preferred embodiment, a reversed imaging geometry is used. The x-ray source includes a 2D array of source positions and the detector is an array that spans the extent of the object being imaged in the direction parallel to the axis of rotation. Preferably a collimating means restricts the x-rays primarily to those directed at the detectors. The collimating means may be an array of collimators, one in front of each source position, or a piece of dense metal having a plurality of holes one in front of each source position. Still further objects and advantages of the present invention will become apparent to one of ordinary skill in the art upon reading and understanding the following drawings and detailed description of the preferred embodiments. As it will be appreciated by one of ordinary skill in the art, the present invention may take various forms and may comprise various components and steps and arrangements thereof. As such, the drawings are for purposes of illustrating a preferred embodiment(s) of the present invention and thus are not to be construed as limiting the present invention. FIG. 1 illustrates a prior art cone beam CT system 100. System 100 includes an x-ray source 101, which employs an x-ray tube, for providing x-rays 120 emanating from a point 103, hereinafter referred to as the focal spot 103. The detector array 102 can be a wide arc or a flat 2-dimensional array containing dozens or hundreds of rows of x-ray detectors. Detector 102 measures x-rays emanating in all directions from the focal spot 103. The cone beam CT system 100 is characterized by the shape of x rays 120 emanated from the focal spot 103 onto the detector array 102. Both the x-ray source 101 and the detector array 102 may be mounted on a gantry (not shown), and may revolve around an axis of rotation of a circular opening 130. The gantry could be a C-arm. An object 104, typically a patient, is positioned in the circular opening 130 via an examination platform, e.g., a motorized table (not shown) that can move up or down and slide in or out of the circular opening 130, so as to place the region to be imaged within the x-ray beam. As discussed herein, employing the many rows of detectors in array 102, system 100 can produce multiple slices at a time, thereby providing a relatively faster scanning of subject 104 than a conventional CT system with a fan-shaped beam in spiral (helical) scanning mode. However, as is well known in the art, this cone beam imaging geometry suffers from several drawbacks, such as image artifacts and image reconstruction errors, caused by the divergence of the x-ray beam in the direction of the axis of rotation. The divergence problem and hence the cone beam artifacts worsens as the number of rows in the detector array 102 increases. That is, in a multi-row or cone-beam CT system, as the angle spanned by the multiple rows increases, so do the image reconstruction problems caused by the cone beam artifacts. The cone beam artifacts would be mitigated if, for each point in the object being imaged, x-ray transmission was measured along rays lying on the plane through the point and perpendicular to the axis of rotation, and in many directions through the point. FIG. 2 shows a prior art volumetric CT scanner 200. In system 200, a part of a human body 204 to be scanned is placed between an x-ray source 201 and an arc-shaped detector assembly 202. The x-ray source 201 is disposed in an evacuated envelope 211 including an electron gun assembly 212, a magnetic deflector assembly 213, a target 214, and a window (not shown) for passing x-rays to a vane collimator 215. The electron gun assembly 212 generates an electron beam 220, which is deflected by the magnetic deflector assembly 213. The target 214 receives the deflected electron beam 220 and generates cones of x rays responsive to the incident electron beam. The beam is linearly scanned across target 214 along a line 203 thereby generating a plurality of successive cone beams. The vane collimator 215 which includes a plurality of spaced parallel vanes forming a plurality of slots is placed opposite the target 214 and serves to pass only a thin fan beam of x-rays emanating from the point where the electron beam strikes the target. As the beam scans across the target successive adjacent fan beams are formed. The plurality of spaced adjacent fan beams traverse the volume of the object under examination as shown between the fan beams 221a and 221b. The detector 202 comprising a linear array of elongated detector elements 232 receives the x rays after they traverse the object 204. In order to provide a CT image of the volume being scanned, the x-ray source 201 is rotated relative to the object 204 such that the plurality of scanned fan beams are transmitted over an angle of 180° plus the fan beam angle with respect to the object 204, although typically a 360° rotation is used. The output from each of the detector elements 232 can be amplified with a conventional preamplifier (not shown). The output is multiplexed and digitized by a conventional multiplexer and a conventional A/D converter (not shown). Sufficient data for reconstruction are obtained in this way. The digitized signals are stored in a cache (not shown) during acquisition. The stored digitized signals are conventionally processed in a reconstruction system (not shown) and applied to a display (not shown) for displaying a 3D image of the interior of the object 204. For further detailed teachings of system 200, readers are referred to U.S. Pat. No. 5,712,889, titled “SCANNED VOLUME CT SCANNER” and issued to Lanzara et al. on Jan. 27, 1998. In system 200, in order to acquire data for multiple slices, e.g., 40 slices, the detector signal must be sampled an equal amount, i.e., 40 times, for each angular position of the gantry. With an effective sampling speed of approximately 20 microseconds per detector, rendering a data rate of 50 thousand samples per second per detector, 50 million samples per second are collected for a system of 1,000 detectors. Because the x-ray source position in the system of FIG. 2 is moved in the direction of the axis of rotation over a distance equal to the thickness of the volume being imaged, this system can be immune from cone beam artifacts. One limitation of the prior art system of FIG. 2 is that the resolution of the system in the direction of the axis of rotation is determined by the thickness of the fan beams emanating from the vane collimator 215. To obtain high resolution, the fan beams must be very thin, which can be difficult to achieve. In addition, restricting the x-rays to such thin fan beams discards the vast majority of the x-rays generated in source 201, which could lead to a high image noise level, or a long scan time to allow a sufficient number of x-rays to be detected. Referring to FIG. 3, an improved VCT system 300 according to a first embodiment of the present invention is illustrated. System 300 is capable of producing data to reconstruct a large number of slices in a single rotation in a fast and reliable manner without suffering from cone beam artifacts. Like the system of FIG. 2, system 300 comprises an x-ray source with an array of source positions 303, including source position 303a, distributed along a line parallel to the axis of rotation, and with an axial extent comparable to the extent of an subject 304 to be imaged in this direction, as shown in FIG. 3. The source could function, like the sources in system 200 of FIG. 2, by scanning an electron beam 320 along a line on the target 314. The linear anode 314 may be a copper block with a target made of another metal plated on or embedded in the copper surface. The metal is most often tungsten, but other metals can be used, such as molybdenum, or rhodium. During operation, electrons are produced at the cathode 312 and accelerated to the target 314. Interactions between high energy electrons of the electron beam 320 and atoms of the target 314 cause deceleration of the electrons and production of x-ray photons 321. The accelerating potential (e.g., 150 kV) determines the spectrum of wavelengths (or photon energies) of the emitted x-rays 321. The cathode 312 and the target 314 (and hence the source positions 303) are positioned in an evacuated housing (not shown). The electron beam 320 can be steered by electromagnetic steering means, such as electromagnetic coils (not shown), positioned inside or outside of the housing. X-rays 321 emanate in all directions from each focal spot (source) positions 303 and exit the housing through an x-ray transparent window of the housing (not shown). This x-ray source is substantially similar to the electron gun assembly 212, steering means, target 214, and window of system 200 of FIG. 2. According to an aspect of the invention, in contrast to the prior art system of FIG. 2, an array 302 of x-ray detectors elements 332 is used to measure the transmitted x-rays 321 that were emitted from each point in the source array 303. The detector array 302 is a two dimensional array, i.e., multiple columns and rows, of small and fast x-ray detectors elements 332 arranged in a flat- or arc-shaped panel. Detector elements 322 are small and provide high resolution in both directions along the array, and in particular, provide resolution in the axial direction, i.e., the direction of the axis of rotation of the system. Thus, it is no longer necessary for the x-rays illuminating object 304 to be thin fan beams. An array of collimator vanes 315 can be used to somewhat limit the divergence of the x-rays in the direction of the axis of rotation, but this limitation need not be perfect. Thus, more of the x-rays produced by the source are allowed to illuminate the object, are detected, and are used to produce the volumetric CT image. Each source position illuminates more than one detector row. It may but need not illuminate the entire detector array. Such X-ray illumination of more than one but not all detector array rows by a source position is shown by lines 504 on FIG. 5. Such X-ray illumination of all detector array rows by a source position is shown by lines 502 on FIG. 5. The x-ray source and the detector array 302 rotate about the axis of rotation. X-ray measurements through the object 304 are made as this structure rotates one revolution. These measurements provide line integrals of the distribution of attenuation coefficients for all lines through the subject 304 that are paths through which x-ray transmission measurements were made, i.e. lines connecting the source positions to the position of detector illuminated by that source position. Since the target point from which x-rays emanated at any point in time is controlled by the operation of the x-ray source and is therefore known, the line through which unscattered photons traveled is known precisely and is not ambiguous. Subject 304 is not limited to a patient or a region of interest thereof and can be any object from which imaging data are to be obtained, e.g., anatomy of a physical structure, such as internal structure of an animal, plant, or other organism, or of any of its parts. Note that in this system there is some divergence of the x-ray beam in the axial direction, all x-rays do not travel along a set of planes that are parallel to each other and perpendicular to the axis of rotation (i.e., transaxial planes). However, the measured data are a superset of all projections needed for an accurate 3D image reconstruction. That is, given a sufficient number of sources, detectors, and views, the measured data will contain projection measurements for lines that lie on transaxial planes (in-plane rays) and also additional line integrals along lines that cross through planes (cross-plane rays). The in-plane rays are sufficient by themselves to provide an artifact-free image of all planes. The cross-plane rays can also be efficiently used to improve the signal-to-noise ratio (SNR) of the image without introducing cone beam artifacts. When the divergence is small, algorithms similar to those used in conventional multi-detector CT systems or variations of the so-called “Feldkamp” method could be used. When the divergence is larger or when accurate reconstructions are necessary, algorithms that properly use all the data should be used. Reconstruction algorithms that are able to do this are well known in the art, e.g., in Pelc, N. J., “A Generalized Filtered Backprojection Algorithm for Three Dimensional Reconstruction”, Doctoral dissertation, Harvard University, 1979. Such algorithms are also used in 3D PET, and thus are not further described herein. The x-ray detector elements employed are preferably very fast since they must measure separate x-ray readings for each source position and each view. The faster the detector elements, the faster data can be collected for the entire volume in one revolution. To be able to image a large object with high spatial resolution, detector array 302 must be large and contain a large number of detector elements. This need for a large number of very fast detectors is avoided in the system of FIG. 4. A preferred embodiment of the present invention will now be described with reference to FIG. 4, where a reversed imaging geometry compared to FIG. 3 is illustrated. In FIG. 4, a VCT system 400 comprises a 2D array, e.g., 100×100, of source positions 403, including source position 403a, and a detector array 402. Both the source array and the detector array are as long in the axial direction as the region being imaged. While the detector array 402 in this system is as long in the axial direction as detector 302 of the system shown in FIG. 3, it need not be as wide, and therefore can contain fewer detector elements. An electron beam (not shown) is produced and accelerated, and is steered to land on the source positions 403 by steering means (not shown) An array 415 of collimators, one in front of each source position, restricts x-rays to those x-rays 421 directed at the detector array 402. The collimator array 415 comprises a plurality of holes, one corresponding to each of source positions 403. For example, as shown in FIG. 4, hole 415a corresponds to source position 403a. While in FIG. 4 x-rays appear to all be traveling on paths that are parallel to the axis of rotation, this need not be so. During a single revolution, an electron beam scans the x-ray source array 403, one source position at a time, many, many times (e.g., hundreds or thousands). Each element of the detector array 402 acquires x-ray measurements for each source position, and since the point from which x-rays were generated at any point in time is known, the projection line corresponding to each measurement is also known. The x-ray measurements are used for image reconstruction of the subject 404 in the same manner and with the same algorithm as in the system of FIG. 3, e.g., processing the measured data in a computer (not shown) equipped with appropriate image reconstruction algorithms and software. The detector array 402 can be but need not be a single line (column) of detector elements. Components needed for this system such as a 2D scanned anode x-ray source and arrays of small and fast detector elements have been developed by NexRay Inc., Los Gatos, Calif., U.S.A. FIG. 6 shows unequal source and detector spacings for the embodiment of FIG. 4. In this embodiment, source array 403 has unequal spacing along the axis or rotation, and detector array elements 602 are also unequally spaced along the axis of rotation. Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions, and alternations can be made without departing from the principles and the scope of the present invention. For example, the source and/or detector arrays can have equally spaced elements. Alternatively, the source and/or detector arrays can have unequally spaced elements. Such equal or unequal element spacing can be in either (or both) of the directions of a two-dimensional source or detector array. Some embodiments of the invention include a collimator as described above, and other embodiments do not include such a collimator. The source array can use a single scanned electron beam, as described above, or as an alternative multiple cathodes can be used (in the limit, one cathode for each source position) as long as the source position from which the x-rays illuminating each detector element is known or can be determined. Accordingly, the scope of the present invention should be determined by the following claims and their legal equivalents. |
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047073241 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT The pressurized water reactor, PWR, electric power generating system disclosed in FIG. 1 includes a reactor core 1 contained in a reactor vessel 3. A reactor coolant in the form of ordinary water circulates through the reactor core 1 where it absorbs heat generated by controlled fission reactions. The heated reactor coolant is pumped through a hot leg 5 to a steam generator 7 and then back to the reactor core through cold leg 9 by a recirculating pump 11. The steam generator 7 utilizes the thermal energy in the reactor coolant to generate steam which is supplied through a steam header 13 and throttle valve 15 to a turbine 17 which in turn, drives an electric generator 19. Vitiated steam from the turbine is condensed in condenser 21 and the condensate is returned to the steam generator 7 through conduit 23 by pump 25 for regeneration. A typical PWR plant may have two to four steam generators 7 supplying steam to the turbine through separate loops. The throttle valve 15 on the turbine 17 is positioned by a turbine controller 27 in response to a dispatch signal received from a central load dispatcher which allocates load to individual plants in a power grid, and/or from local commands such as operator generated load commands or limits. The temperature of the reactor coolant is controlled by control rods 29 which are inserted into and withdrawn from the reactor core 1 by a rod control system 31. The control rods 29 contain neutron absorbing material which affects the density of thermal neutrons in the core available for sustained fission reactions. The rod control system positions the control rods to maintain a setpoint reactor temperature. The actual reactor coolant temperature is fed back to the rod control system through lead 33. A pressurizer 35 regulates the pressure of the reactor coolant. The typical pressurizer 35 in a PWR includes a heater system which increases coolant pressure by raising the pressure in a head of steam maintained in the pressurizer and a spray system which reduces coolant pressure through condensation of an appropriate proportion of the steam head. Pressurizer pressure is controlled at a setpoint value by a pressurizer control system 37. A protection system 39 monitors the operation of the nuclear steam supply system, which includes the reactor core 1, the steam generator 7, and their associated and interconnecting components such as the pressurizer 35, by gathering data such as various temperatures, pressures, flow rates, the neutron flux density and certain status indications, through numerous inputs represented by leads 41, 43 and 45. The protection system analyzes the data and generates a trip signal on lead 47 which shuts down the reactor by fully inserting the control rods into the reactor core when selected operating limits are exceeded. A load signal derived from the steam pressure in the impulse chamber of the turbine 17, and representative of the load imposed on the reactor by the turbine-generator set, is applied to a rapid power change control 49 through lead 51. This control 49, which forms the core of the present invention, generates a temperature reference setpoint signal which is applied to the rod control system 31 through lead 53. Signals representative of certain operating limits used in the present invention, as more fully discussed below, are sent by the protection system 39 to the rapid power change control 49 as represented by lead 55. The pressurizer control system 37 also sends a setpoint signal to and receives an adjusted setpoint signal from the rapid power change control as represented by lead 57. In addition to rod position control, the temperature of the reactor is also regulated by dissolving controlled amounts of a neutron absorbing material, typically boron, in the reactor coolant. Due to the large amount of reactor coolant, the long loop through which it is circulated and the physical limitations involved in removing boron from the coolant, boron control is used for long term, relatively slow changes in reactor power. The control rods on the other hand, affect reactor power and hence, temperature immediately and hence, are ideal for responding to rapid fluctuations in load. However, continued movement of the control rods results in excessive wear on the rod drive mechanisms and even on the rods themselves as they move relative to guide tubes inside the reactor core. The solution to the problem of controlling a PWR to follow rapid load changes without excessive wear on the control rod positioning and other system components lies in the fact that a decrease in reactor temperature, while maintaining constant control rod position and boron concentration, results in an increase in reactivity. This is the result of two phenomenon. First, the PWR has a negative doppler coefficient which means that a decrease in fuel temperature produces an increase in the rate of fission reactions within the fuel. Secondly, the reactor coolant, in addition to serving as a heat transfer medium, also serves as moderator for slowing down the neutrons released by the fission reactions to the thermal velocities required for sustained reactions. With a negative temperature moderator coefficient, a reduction in the temperature of the coolant increases its density and therefore its moderator effect so that more neutrons in a given neutron generation produce another fission reaction. Thus, when additional load is placed on the nuclear steam supply system, more thermal energy is extracted from the reactor coolant which lowers its temperature and the fuel temperature. This in turn, results in an increase in reactivity to a level which satisfies the new demand. On the other hand, a reduction in the load causes an increase in reactor temperature which results in a decrease in reactivity. Such an increase in temperature, however, could approach various temperature related operating limits which would cause the protection system to trip the reactor. The present invention overcomes these limitations by adjusting the temperature reference setpoint signal for the rod control system 31 as a function of the rapid fluctuations in load so that the setpoint signal matches the variations in the actual temperature resulting from the rapid power changes. Thus, the control rods do not move in response to the rapid power changes and the change in reactivity required is accommodated by a change in temperature. This change in temperature affects other systems such as the pressurizer pressure. In order to preclude excessive wear on the pressurizer spray and heater components, the setpoint signal for pressurizer pressure control can also be adjusted as a function of the rapid power changes to match the setpoint to the expected change in pressure resulting from the rapid power changes. Similarly, the setpoint signals for the controllers for other system parameters such as pressurizer water level, boron concentration and gray rod insertion (in some of the newer PWRs) can be adjusted alone or in combination with others to minimize control action in response to rapid power changes. The present invention also provides for the use of a widened deadband in the response of the rod control system to rapid load fluctuations over the full power range of the reactor. This is accomplished by varying the width of the deadband as a function of the magnitude of the flucuations in load occurring above a predetermined frequency and by reducing the set point for the rod control loop so that the upper temperature edge of the deadband remains within all temperature limits. A wider deadband can also be used in controlling other system parameters either by itself or with adjustment of the associated controller setpoint. The load signal on lead 51 is passed through a low pass filter 59 to eliminate the rapid power changes and is converted to a load derived temperature reference signal in function generator 61 in a conventional manner. In the typical prior art rod control system, this reference signal is used as the setpoint in a conventional rod control loop 63. In the present invention, the rapidly changing component of the turbine load signal on lead 51 is extracted by a conventional high pass filter 65 which may employ a simple rate/lag transfer function or a more complex function as desired. The particular bandpass frequency of the high pass filter 65 depends upon the specific installation and the characteristics of the load pattern to which the plant is subjected, however, typically fluctuations having a frequency of more than one or two cycles per hour would be extracted from the load signal. Typically, but not necessarily, if the transfer function of the high pass filter 65 is H.sub.2 (S), the transfer function H.sub.1 (S) for the low pass filter 59 is 1-H.sub.2 (S). The high frequency component of the load signal is applied to a filter 67 having a transfer function: ##EQU1## where T(S) is the laplace transform of the reactor coolant temperature, and Q.sub.turb (S) is the laplace transform of the load signal from the turbine. The output of the filter 67 is the expected fluctuation in temperature resulting from the rapid variations in turbine load. This signal is passed through a limiter 69 and is added in summer 71 to the temperature reference signal generated by function generator 61 to produce an adjusted temperature reference signal. The adjusted temperature reference signal is applied to an Auctioneer Low module 73, which as will be seen below, passes the signal along to the rod control loop 63 as T.sub.ref as long as it does not exceed permissible temperature limits. While in theory, the adjusted temperature reference signal should match the variations in reactor coolant temperature induced by the rapid load changes, in practice it is desirable to have a deadband in the response of the rod loop control 63 to assure that the small rapid fluctuations in load do not induce control action. This invention provides a deadband which varies as a function of the magnitude of the rapid power changes. In order to achieve this, the high frequency component of the load signal from filter 65 is also fed to a square law module 75 and then through a unity gain low pass filter 77 which may be a simple first order lag device or a more complex design if desired. The resulting output signal .sigma..sup.2 is a measure of the average squared value (i.e. the variance) of the magnitude of the rapidly changing component of the load. The signal .sigma..sup.2, representing the average squared value of the magnitude of the rapid fluctuations in the load signal, is applied to a gain module 79 which generates a temperature related deadband signal as a function of the magnitude of the variance. The deadband output for a given variance is selected to limit the rod stepping frequency to acceptable limits while also providing good control response. A lower limit on the deadband is required for stability, and an upper limit is required to limit temperature variations for reasons such as component fatique. The intermediate portion may be linear or nonlinear as desired. Since the plant may experience other large transients, such as load rejection, in addition to those normally occuring as a results of economic load regulation, an active high bistable 81 determines when load changes exceed those expected from load regulation and thus, indicates that other large transients are underway which may require more precise control than the control rods 29 can provide with the wider deadband. Such an output by the active high bistable 81 is memorized by a latch 83 whose active (logic 1) output operates a switch 85 to apply a fixed deadband signal to a lead 87. A logic 0 output from latch 83 operates switch 85 to apply the output of gain module 79 to lead 87. The latch 83 can be reset by an operator manual control. The output of switch 85 which appears on lead 87 is the variable deadband signal which is applied to the rod control loop 63. While the signal .sigma..sup.2 can be applied to the bistable 81 as an indication of the magnitude of the fluctuations in load, the output of the square law module 75 may be used instead as illustrated by the dashed line in FIG. 2 and probably is superior for detecting large transients. In order to prevent the reactor temperature from exceeding the license limit and to maintain adequate margins to trip limits, the varible deadband is substracted in summer 89 from the maximum allowable temperature obtained on lead 91 from an auctioneer low module 93. The auctioneer low module 93 selects the lowest of several temperature limiting signals received from the protection system 39 over leads 55. These signals, which are already available in the protection system, can include: (A) the DNBR (departure from nucleant boiling ratio) limit with an appropriate margin to prevent an unnecessary reactor trip; (B) an exit quality limit which is a measure of the absence of vapor in the reactor coolant leaving the reactor, again with an appropriate margin; (C) the license limit which is the maximum temperature at which the reactor is permitted to operate, and in fact, any other temperature dependent parameter (D) desired, with or without a margin. The maximum allowable temperature adjusted for the deadband in summer 89 is applied to the auctioneer low module 73 along with the adjusted temperature reference signal derived from the load signal in module 61. The lowest of these two signals is selected by the auctioneer low module 73 as the temperature reference signal, T.sub.REF, which becomes the setpoint signal for the rod control loop 63. For moderate thermal loads on the reactor, the temperature reference signal derived from the load signal will be lower in magnitude and will be used as the temperature reference. Near full power, is where it can be expected that conditions would arise where the temperature limiting signals adjusted for the deadband would be likely to be selected as the temperature reference signal, T.sub.REF. With the present invention, however, control of the reactor can be achieved without excessive movement of the control rods right up to full power. The invention can be applied to other control loops in the PWR in addition to, or in place of, the rod control loop 63. For instance, it may be applied to the pressurizer pressure control loop 59 to minimize operation of the pressurizer spray and heater systems. As shown in FIG. 2, the high frequency component of the load signal, which is extracted in high pass filter 65, is applied to a filter 95 having the following transfer characteristic: ##EQU2## where P.sub.PZR (S) is the laplace transform of pressurizer pressure and Q.sub.TURB (S) is as explained in connection with equation 1. The output of filter 95 is the variation in the pressurizer pressure setpoint which matches the expected variation in pressurizer pressure resulting from the rapid changes in load. It is limited in magnitude by module 97, passed through gate 99 and added to the standard (fixed) nominal reference pressure setpoint supplied by the pressurizer control system 37 (see FIG. 1) in summer 101. The adjusted pressurizer pressure setpoint is then returned to the pressurizer control system for use in controlling pressurizer pressure. Since it is very desirable to avoid large pressure deviations which may lead to opening pressurizer power operated relief valves, an interlock which includes gate 99 and an active low bistable with hysteresis 103 is included to allow fluctuations in reference pressure only when pressurizer pressure is below a fixed setpoint. FIG. 3 illustrates schematically the rod control loop 63 to which the temperature reference signal, T.sub.REF from the auctioneer low module 73 in FIG. 2 is applied. The measured reactor temperature on lead 33 is subtracted from T.sub.ref in summer 105 to generate an error signal. Dynamic compensation is applied to the error signal in a compensation circuit 107. The compensated error signal can be summed with other control signals 109 such as, for instance, a power mismatch signal, in summer 111 and the resultant signal is applied to a known control circuit 113 which generates a drive signal for the control rod drives 115 as a function of the applied signal. The control circuit 113 incorporates mean for generating a deadband, D, in the output response. In other words, no drive signal is generated at the output until the applied signal exceeds the magnitude of the deadband. The width of the deadband is controlled by the magnitude of the deadband control signal applied to the control circuit 113 through lead 87. The lockup, L, may be adjusted as a function of the deadband, D, if desired. Activation of the rod drives 115 causes repositioning of the control rods which are indicated collectively components in the plant 117. Similar control of the deadband can be applied to other control systems in the PWR. From the above description, it can be appreciated that the present invention is directed to apparatus which automatically adjusts reference setpoints in the control systems of a PWR in response to rapid fluctuations in turbine load. The system works for all ranges of automatic reactor control up to 100% power. The modules 67 and 95 may use time varying transfer functions to account for normal changes in plant response with core life. Suitable transfer functions can be obtained through well-known system identification techniques, such as those given in Franklin and Powell, "Digital Control of Dynamic Systems", Chapter 8, Addison-Wesley Publishing Co., copyright 1980, second printing June, 1981. The system can be implemented by conventional continuous circuitry or by digital technology. It can also be appreciated that the invention provides for a variable deadband in the response of the rod control system to rapid fluctuations in load on a PWR and that the width of the deadband is a function of the variance of the magnitude of the fluctuations above a predetermined frequency. It can be further appreciated, that the invention permits variable deadband rod control to be used up to full power by limiting the temperature reference signal in the rod control loop such that the high temperature edge of the deadband response is within all reactor temperature limits. The result is reduced wear on rod control components while maintaining full capability to load follow. In an alternate embodiment of the invention, the output of filter 67 or limiter 69 can be used as the input to square law module 75 rather than the output of the high pass filter 65, thus basing the variable deadband width on the anticipated changes in temperature. The setpoints for modules 77, 79, 81 and 83 would have to be changed accordingly. 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. For instance, while the invention has been described as being implemented by hard wired circuitry, many of the functions can be performed by appropriate software in a programmed digital computer. Accordingly, the particular arrangements 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. |
description | 1. Field of the Invention The present invention relates to a particle beam irradiation system, and more particularly to a particle beam irradiation system for irradiating a charged particle beam, such as a proton or carbon ion beam, to an affected part of the body for treatment. 2. Description of the Related Art There is known a therapy method of irradiating a charged particle beam (ion beam), such as a proton or carbon ion beam, to an affected part, e.g., a cancer, in the body of a patient. A particle beam irradiation system for use with such a therapy method comprises a charged particle beam generator, a beam line, and a treatment room. The charged particle beam accelerated by an accelerator in the charged particle beam generator reaches an irradiation device in the treatment room through the beam line, and it is irradiated to the affected part of the patient body from the irradiation device after being scanned by a scanning magnet disposed in the irradiation device. In that type irradiation system, it has also hitherto been known to stop output of the charged particle beam from the irradiation device, to change (scan) an exposure position (spot) of the charged particle beam by controlling the scanning magnet in the state where the output of the charged particle beam is stopped, and after the change of the exposure position, to start the output of the charged particle beam again from the irradiation device (see, e.g., Patent Document 1; Japanese Patent No. 2833602 (FIG. 1, etc.)) In the known particle beam irradiation system described above, a dose monitor for measuring a beam dose distribution and a beam position monitor are disposed within the irradiation device at a position downstream of the magnet and immediately upstream of the patient as an irradiation object (target) so that exposure to normal tissue is minimized and irradiation therapy is performed in a normal manner without causing excess or deficient dose. In irradiation to each spot, a target dose is set per spot. When an integrated value of dose detected by the dose monitor reaches the target dose, a beam extraction stop signal is outputted to the accelerator, whereupon the accelerator stops extraction of the charged particle beam. However, the inventors have found a possibility that, in the accelerator, a slight response delay occurs after the input of the beam extraction stop signal to the accelerator. In the case employing a synchrotron that is one type of accelerators, ions introduced from a pre-stage accelerator and having low energy are circulated within the synchrotron, and the circulating charged particle beam is accelerated up to a setting energy desired to the irradiation, and the accelerated charged particle beam is brought to a resonated state of betatron oscillation. Then, an RF electromagnetic field is applied to the circulating charged particle beam to increase the betatron oscillation of the charged particle beam in excess of the separatix, thereby extracting the charged particle beam. As a result, even with the beam extraction stop signal inputted as mentioned above, the extraction of the charged particle beam is not stopped at once in the strict sense and a slight response delay occurs. Stated another way, even after reaching the target dose, the charged particle beam is continuously irradiated to the relevant spot for the response delay time. Accordingly, an object of the present invention is to provide a particle beam irradiation system capable of ensuring a more uniform dose distribution at an irradiation object. To achieve the above object, the present invention is featured in that, when the sum of a first dose irradiated after output of a beam extraction stop signal with respect to a first exposure position preceding a second exposure position and a second dose irradiated to the second exposure position reaches a setting dose, the beam extraction stop signal is outputted to stop the extraction of the charged particle beam irradiated to the second exposure position. With the present invention, when the sum of the first dose and the second dose reaches the setting dose, the beam extraction stop signal is outputted to stop the extraction of the charged particle beam irradiated to the second exposure position. Therefore, the dose irradiated to the first exposure position during a period in which the extraction of the charged particle beam from the accelerator is actually stopped after the output of the beam extraction stop signal can be added to the dose measured as being irradiated to the second exposure position. As a result, the dose irradiated to each exposure position can be held substantially equal to the setting dose, and a dose distribution at the irradiation object can be made more uniform even when a certain time is required from the output of the beam extraction stop signal to the time when the extraction of the charged particle beam from the accelerator is actually stopped. Preferably, the control unit determines the presence of an abnormality based on the dose irradiated to the first exposure position during the period from the output of the beam extraction stop signal to the stop of extraction of the charged particle beam from the accelerator. With the determination on the presence of an abnormality, it is possible to reliably confirm that the extraction of the charged particle beam from the accelerator is stopped without failures after the output of the beam extraction stop signal. Thus, according to the present invention, a dose distribution at the irradiation object can be made more uniform even when a certain time is required from the output of the beam extraction stop signal to the time when the extraction of the charged particle beam from the accelerator is actually stopped. A particle beam irradiation system according to a first embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a proton beam irradiation system, i.e., one example of the particle beam irradiation system according to the first embodiment of the present invention, comprises a charged particle beam generator 1 and a beam line 4 connected downstream of the charged particle beam generator 1. The charged particle beam generator 1 comprises an ion source (not shown), a pre-stage charged particle beam generator (linac) 11, and a synchrotron (accelerator) 12. The synchrotron 12 comprises an RF knockout device 9 and an accelerating unit 10. The RF knockout device 9 includes an RF knockout electrode 93 disposed in a circulating orbit in the synchrotron 12 and an RF power supply 91, which are connected to an on/off switch 92. The accelerating unit 10 includes an RF cavity (not shown) disposed in the circulating orbit, and an RF power supply (not shown) for applying RF power to the RF cavity. Ions (e.g., protons or carbon ions) generated from the ion source are accelerated by the pre-stage charged particle beam generator (e.g., a linear charged particle beam generator) 11. An ion beam (proton beam) emitted from the pre-stage charged particle beam generator 11 enters the synchrotron 12. The ion beam in the form of a charged particle beam is accelerated in the synchrotron 12 in which energy is given to the ion beam with RF power applied from the RF power supply through the RF cavity. After energy of the ion beam circulating in the synchrotron 12 has been increased up to a setting level (e.g., 100-200 MeV), an RF wave for beam extraction is supplied from the RF power supply 91 to the RF knockout electrode 93 through the closed on/off switch 92 and is applied to the circulating ion beam from the RF knockout electrode 93. With the application of the RF wave, the ion beam circulating within a separatrix is forced to transit to the outside of the separatrix and to exit from the synchrotron 12 through a beam extraction deflector 8. At the time of extracting the ion beam, currents supplied to a quadrupole magnet 13 and bending magnets 14, which are disposed in the synchrotron 12, are held at current setting values, and therefore the separatrix is also held substantially constant. The extraction of the ion beam from the synchrotron 12 is stopped by opening the on/off switch 92 and ceasing the application of the RF power to the RF knockout electrode 93. The ion beam extracted from the synchrotron 12 is transported to the downstream side through the beam line 4. The beam line 4 includes quadrupole magnets 18 and a bending magnet 17, and also includes a quadrupole magnet 21, a quadrupole magnet 22, a bending magnet 23 and a bending magnet 24 which are successively arranged on a beam path 62 in this order from the upstream side in the direction of beam advance. The beam path 62 is communicated with an irradiation device 15 disposed in the treatment room. The ion beam introduced to the beam line 4 is transported to the irradiation device 15 through the beam path 62. The treatment room includes the irradiation device 15 mounted to a rotating gantry (not shown) that is installed inside the treatment room. The irradiation device 15 and a beam transport, which has an inverted U-shape and includes a part of the beam path 62 in the beam line 4, are mounted to a substantially cylindrical rotating drum (not shown) of the rotating gantry (not shown). The rotating drum is rotatable by a motor (not shown). A treatment cage (not shown) is formed inside the rotating drum. The irradiation device 15 has a casing (not shown) mounted to the rotating drum and connected to the inverted U-shaped beam transport. Scanning magnets 5A, 5B for scanning the beam, a dose monitor (dose detector) 6A, a position monitor 6B, etc. are disposed inside the casing. The Scanning magnets 5A, 5B bend the beam, by way of example, in directions (X- and Y-directions) orthogonal to each other on a plane that is vertical to an axis of the beam, thereby moving the exposure position in the X- and Y-directions. Before irradiating the ion beam from the irradiation device 15, a treatment bed 29 is moved by a bed driver (not shown) to be inserted in the treatment cage, and is then properly positioned to be ready for the irradiation of the ion beam from the irradiation device 15. The rotating drum is rotated by controlling the rotation of the motor with a gantry controller (not shown) so that the beam axis of the irradiation device 15 is directed to an affected part in the body of a patient 30. The ion beam introduced from the inverted U-shaped beam transport to the irradiation device 15 through the beam path 62 is sequentially scanned in its position for irradiation by the scanning magnets (charged particle beam scanner) 5A, 5B and is irradiated to the affected part (area where a cancer or tumor is generated) in the body of the patient 30. The ion beam releases the energy in the affected part of the patient body to form a high dose region. The scanning magnets 5A, 5B in the irradiation device 15 are controlled by a scanning controller 41 that is disposed in, e.g., a gantry room inside a treatment system. A control system 90 installed in the proton beam irradiation system of this embodiment will be described with reference to FIG. 1. The control system 90 comprises a central controller 100, a storage (database) 110 for storing treatment plan information, the scanning controller 41, and an accelerator/beam line controller (referred to as an “accelerator controller”) 40. Further, the proton beam irradiation system of this embodiment includes a treatment planning system 140. The treatment plan information (patient information) stored in the storage 110 per patient contains, though not specifically shown, data such as the patient ID number, dose (per irradiation), irradiation energy, irradiating direction, and exposure position. The central controller 100 comprises a CPU 101 and a memory 103. The CPU 101 reads the treatment plan information regarding the patient, who is now going to take the treatment, out of the storage 110 by using the patient ID information inputted to the CPU. Of the treatment plan information per patient, the value of irradiation energy decides a control pattern for excitation power supplied to the above-mentioned various magnets. The memory 103 stores a power supply control table in advance. More specifically, corresponding to various values (70, 80, 90, etc. [Mev]) of the irradiation energy, for example, values or patterns of excitation power are set in advance which are supplied to the quadrupole magnet 13 and the bending magnet 14 in the charged particle beam generator 1 including the synchrotron 12, and to the quadrupole magnets 18, the bending magnet 17, the quadrupole magnets 21, 22 and the bending magnets 23, 24 in the beam line 4. Also, the CPU 101 serves as a control information preparing unit and, by using the treatment plan information and the power supply control table, it prepares control command data (control command information) for controlling the magnets, which are disposed in the charged particle beam generator 1 and in the beam paths, regarding the patient who is now going to take the treatment. Then, the CPU 101 outputs the thus-prepared control command data to the scanning controller 41 and the accelerator controller 40. In the proton beam irradiation system of this embodiment, the central controller 100, the scanning controller 41, and the accelerator controller 40 execute control in a cooperated manner based on the treatment plan information prepared by the treatment planning system 140. With that control, the extraction of the ion beam from the synchrotron 12 is stopped, and the scanning magnets 5A, 5B are scanned to change the exposure position (spot) of the ion beam in the state where the extraction of the ion beam is stopped. After the change of the exposure position, the extraction of the ion beam from the synchrotron 12 is started. The stop of the extraction of the ion beam from the synchrotron 12 stops the irradiation of the ion beam from the irradiation device 15, and the extraction of the ion beam from the synchrotron 12 starts the irradiation of the ion beam from the irradiation device 15. Details of the cooperated control executed by the controllers will be described in detail below with reference to FIGS. 2-10. First, the relationship between the depth of a target and the energy of the ion beam is described. The target is a region of an irradiation object including the affected part of the body where the ion beam is to be irradiated, and it is slightly larger than the affected part of the body. FIG. 2 shows, by way of example, the relationship between the depth into the body and the dose irradiated by the ion beam. A peak shown in FIG. 2 is called the Bragg peak. The irradiation of the ion beam to the target is performed at a position of the Bragg peak. The position of the Bragg peak is changed depending on the energy of the ion beam. Accordingly, the ion beam can be uniformly irradiated to the whole of the target (target region) having a thickness in the direction of depth into the body by dividing the target into a plurality of slices (layers) in the direction of depth into the body (i.e., the direction in which the ion beam advances in the body), and by changing the energy of the ion beam depending on the depth (each slice). From that point of view, the treatment planning system 140 decides the number of slices into which the target region is to be divided in the direction of depth into the body. FIG. 3 shows one example of the slices decided as described above. In the example of FIG. 3, the affected part of the body is divided into four slices, i.e., slices 1, 2, 3 and 4, from the lowermost slice toward the body surface of the patient 30. Each slice has dimensions of 20 cm in the X-direction and 10 cm in the Y-direction. The dose distribution of FIG. 2 represents the dose distribution in the direction of depth into the body taken along the section A-A′ in FIG. 3. Further, the treatment planning system 140 decides the spot position in a direction perpendicular to the direction of depth into the body within each slice (target cross-section) and the dose irradiated to each spot so that a dose distribution suitable for the treatment is formed. Then, the treatment plan information planned and stored in the storage 110 as described above is read out by the central controller 100 and stored in the memory 103. Based on the treatment plan information stored in the memory 103, the CPU 101 prepares the information regarding irradiation of the ion beam (such as the number of slices, the number of exposure positions (number of spots), the exposure positions in each slice, the target dose (setting dose) at each exposure position, the values of currents supplied to the scanning magnets 5A, 5B for all the spots in each slice), and then transmits the prepared information to the scanning controller 41. Here, the target dose (setting dose) at each exposure position is defined as integrated exposure dose (integrated dose) measured from the start of the first irradiation to the affected part of the body. Accordingly, when the treatment plan information sets the dose for each of the exposure positions, the central controller 100 successively integrates the individual doses set for the exposure positions, thereby preparing the target dose information to be transmitted to the scanning controller 41. The scanning controller 41 stores the treatment plan information in a memory 41M1 (see FIG. 6). Also, the CPU 101 transmits all the data of accelerator parameters for the synchrotron 12 regarding all the slices, which are contained in the treatment plan information, to the accelerator controller 40. The data of accelerator parameters contain the current values for excitation of the various magnets in the synchrotron 12 and the beam line, as well as the RF power value applied to the RF cavity, which are decided depending on the energy of the ion beam irradiated to each slice. Those data of accelerator parameters are grouped into, for example, a plurality of acceleration patterns in advance. A part of the treatment plan information stored in the memory 41M1 of the scanning controller 41 will be described with reference to FIG. 4. The part of the information contains irradiation parameters, i.e., information regarding the X-directional position (X-position) and the Y-directional position (Y-position) for each exposure position in the slice, and the target dose (setting dose) at each exposure position. The part of the information also contains information regarding a slice change flag. For all the spots in each slice, the spot numbers (spot number j described later) are assigned in the order of irradiations to those spots. In this embodiment, the dose for each exposure position is set to 70 in the first slice, 25 in the second slice and 18 in the third slice, respectively. The target dose is given as a value obtained by integrating those individual doses in the order of irradiations. With reference to FIG. 5, a more concrete description is made of control processes executed by the scanning controller 41 and the accelerator controller 40 when spot scanning is performed in this embodiment. When an irradiation start instructing unit (not shown) disposed in the treatment room is operated, the accelerator controller 40 initializes an operator i representing the slice number to 1 and an operator j representing the spot number to 1 in step 201. After the end of the initialization in step 201, the accelerator controller 40 reads and sets, from among the plural patterns of accelerator parameters stored in the memory, one pattern of accelerator parameters corresponding to the i-th (i=1 at this time) slice in step 202, and then outputs those set accelerator parameters to the synchrotron 12 in step 203. More specifically, in step 203, the accelerator controller 40 outputs, to respective power supplies for the various magnets in the synchrotron 12 and the beam line 4, the information regarding the excitation currents for those magnets, which is contained in the i-th pattern of accelerator parameters, and then controls the respective power supplies so that the relevant magnets are excited by the predetermined currents in accordance with the excitation current information. Also, in step 203, the accelerator controller 40 controls the RF power supply for applying RF power to the RF cavity, thereby increasing the RF power and the frequency to predetermined values. As a result, the energy of the ion beam circulating within the synchrotron 12 is increased to the value decided in the treatment plan. Then, the accelerator controller 40 advances to step 204 in which it outputs an extraction preparation signal to the scanning controller 41. After receiving the information initialized in step 201 and the extraction preparation signal outputted in step 204 from the accelerator controller 40, the scanning controller 41 reads and sets, in step 205, the current value data and the target dose data for the j-th (j=1 at this time) spot from among the current value data (i.e., data put in columns “X-position” and “Y-position” of FIG. 4) and the target dose data (i.e., data put in column “target dose” of FIG. 4), which are already stored in the memory 41M1 as described above (see also FIG. 6 described later). Similarly, for the later-described target count number stored in the memory 41M1, data corresponding to the j-th (j=1 at this time) spot is also read and set. Then, the scanning controller 41 controls the relevant power supplies so that the scanning magnets 5A, 5B are excited at the current values for the j-th spot. After the irradiation preparation for the relevant spot has been completed in such a way, the scanning controller 41 outputs a beam extraction start signal in step 300 and controls the RF knockout device 9, thus allowing the ion beam to be extracted from the synchrotron 12. More specifically, the on/off switch 92 is closed by the beam extraction start signal having passed through the accelerator controller 40, and an RF wave is applied to the ion beam from the RF knockout electrode 93, whereupon the ion beam is extracted from the synchrotron 12. Because the scanning magnets 5A, 5B are excited such that the ion beam reaches the position of the first spot, the extracted ion beam is irradiated to the first spot in the relevant slice by the irradiation device 15. When the dose irradiated to the first spot reaches the relevant target dose, the scanning controller 41 outputs a beam extraction stop signal in step 300. The beam extraction stop signal passes through the accelerator controller 40 and closes the on/off switch 92, whereupon the extraction of the ion beam is stopped. At this time, the irradiation to the first spot in the slice 1 is just completed. Thus, because a determination result in step 208 is “No”, the scanning controller 41 shifts to step 209 in which the spot number j is incremented by 1 (namely, the exposure position is moved to an adjacent spot). Then, the above-described processing in steps 205, 208 and 300 is repeated. Stated another way, until the irradiation to all the spots in the slice 1 is completed, the ion beam is irradiated while successively moving the ion beam to the adjacent spot one after another by the scanning magnets 5A, 5B (while the irradiation of the ion beam is stopped during the beam movement) (such process is called spot scanning irradiation). When the irradiation to the all the spots in the slice 1 is completed, the determination result in step 208 becomes “Yes”. At this time, the scanning controller 41 outputs a slice change signal to a CPU in the accelerator controller 40. The CPU in the accelerator controller 40 having received the slice change signal increments the slice number i by 1 (namely, changes the irradiation target to the slice 2) in step 213 and outputs a remaining beam deceleration signal to the synchrotron 12 in step 214. In response to the output of the remaining beam deceleration signal, the accelerator controller 40 controls the power supplies for the various magnets in the synchrotron 12 such that the excitation currents for the magnets are gradually reduced and are finally set to certain preset values, e.g., current values suitable for injection of the ion beam. The ion beam circulating within the synchrotron 12 is thereby decelerated. In this way, a beam extraction enable period differs depending on the number of spots in the slice and the dose irradiated therein. At this time, the irradiation to the slice 1 is just completed and a determination result in step 215 is “No”. Therefore, the pattern of accelerator parameters corresponding to the second slice (slice 2) is read and set from the memory in the accelerator controller 40 in step 202. Subsequently, the above-described processing in steps 203-215 is executed for the slice 2. Likewise, the above-described processing in steps 202-215 is executed until the irradiation to all the spots in the slice 4 is completed. When the determination result in step 215 becomes “Yes” (i.e., when the predetermined irradiation to all the spots in all the slices for the target in the body of the patient 30 is completed), the CPU in the accelerator controller 40 outputs an irradiation terminate signal to the CPU 101. As described above, the ion beam accelerated in the synchrotron 12 and extracted from the synchrotron 12 is transported through the beam line 4. Then, the ion beam is irradiated to the target in the body of the patient 30 in accordance with the treatment plan through the irradiation device 15 in the treatment room where the patient lies as the irradiation object. On that occasion, the detected signal from the dose monitor 6A disposed in the irradiation device 15 is inputted to the scanning controller 41. The feature of this embodiment resides in the beam dose control based on the integrated dose using that detected signal. Details of the beam dose control will be described below with reference to FIGS. 6-9. FIG. 6 is a functional block diagram showing details of a functional configuration of the scanning controller 41. As shown in FIG. 6, the scanning controller 41 includes a counter 41c as a component related to the dose detection. The dose monitor (beam monitor) 6A is of the known type outputting a pulse depending on the quantity of electrical charges ionized upon the passage of the ion beam. More concretely, the dose monitor 6A outputs one pulse for each small predetermined quantity of the electrical charges. The counter 41c counts the number of pulses outputted from the dose monitor 6A to measure the dose. In addition to the counter 41c, the scanning controller 41 includes memories 41M1 and 41M2, a first delay timer 41Ba, a second delay timer 41Bb, a first register 41Bc, a second register 41Bd, a difference calculating section 41Be, a determining section 41Bf, a NOT circuit 41Bg, an AND circuit 41D, and a beam on/off signal generator 41E. Also, the counter 41c has a pulse input section 41ca, a setting value input section 41cb, an initialization (clear) signal input section 41cc, a count value read section 41ce, and a setting-value comparison result output section 41cf. Detailed procedures executed by the scanning controller 41 in steps 205 and 300 of FIG. 5 will be described below with reference to FIG. 7. As described above, the operator i and the operator j are each initialized to 1 in advance. In step 301, the scanning controller 41 outputs a counter setting command corresponding to the target count number for the counter 41c, which is already stored in the memory 41M1, to the setting value input section 41cb of the counter 41c. In accordance with the counter setting command, the counter 41c sets, in step 302, the target count number for the first spot in the slice 1. The target count number is a value corresponding to the target dose up to the relevant spot in the relevant slice, which is put in column “target dose” of FIG. 4. The target count number is calculated in the scanning controller 41 based on the target dose up to each relevant spot before the start of irradiation of the ion beam for that spot. The calculation of the target count number using the target dose may be executed immediately before the counter 41c receives the counter setting command, or before the central controller 100 transmits data to the scanning controller 41 if the central controller 100 executes that calculation. After the end of the processing in step 301, the scanning controller 41 advances to step 303 in which the current setting commands for the scanning magnets 5A, 5B (i.e., the current value data put in columns “X-position” and “Y-position” of FIG. 4) corresponding to the relevant spot are outputted to the power supplies for the scanning magnets 5A, 5B. The scanning magnets 5A, 5B generate bending electromagnetic forces in accordance with the relevant current values. To the scanning controller 41, the power supplies for the scanning magnets 5A and 5B output respective current setting end signals each indicating that the current setting has been completed. On condition that the current setting command is outputted (step 303) and the current setting end signals are inputted from the power supplies for the scanning magnets 5A, 5B (step 304), the scanning controller 41 outputs the beam extraction start signal in step 305. The beam extraction start signal passes through the accelerator controller 40 and reaches the on/off switch 92 to close it. Responsively, the RF power is applied to the RF knockout electrode 93, whereby the ion beam is extracted from the synchrotron 12 and is irradiated to the relevant spot (e.g., the first stop in the slice 1). When the beam irradiation is started with the output of the beam extraction start signal in step 305, the detected signal from the dose monitor 6A is converted to a train of dose pulses by a current/frequency converter (I/F converter, not shown) and inputted to the counter pulse input section 41ca of the scanning controller 41 for counting the number of the pulses, as described above. The count number represents the dose integrated from the start of the counting. When the value counted based on the input pulses from the pulse input section 41ca reaches or exceeds a setting value of the target count number set in step 302 (step 309), the counter 41c outputs a trigger signal from the setting-value comparison result output section 41cf in step 310. In response to the trigger signal, the scanning controller 41 produces the beam extraction stop signal and outputs it to the accelerator controller 40 (step 312). The beam extraction stop signal passes through the accelerator controller 40 and reaches the on/off switch 92. Thus, the scanning controller 41 enables the on/off switch 92 to be controlled essentially by the beam extraction stop signal so that the on/off switch 92 is opened. As a result, the extraction of the ion beam from the synchrotron 12 is stopped and the irradiation of the ion beam to the patient is stopped as described above. The output of the beam extraction start signal and the beam extraction stop signal from the scanning controller 41 will be described below with reference to FIG. 6. The current setting end signals outputted from the power supplies for the scanning magnets 5A, 5B are inputted to the AND circuit 41D in the scanning controller 41. When the trigger signal is not outputted from the counter 41c in that state, the NOT circuit 41Bg outputs “1” to the AND circuit 41D. When the AND circuit 41D receives the beam extraction stop signal and “1” from the NOT circuit 41Bg, it outputs “1” to the beam on/off signal generator 41E. When the trigger signal is outputted from the counter 41c, the NOT circuit 41Bg outputs “0” to the AND circuit 41D. When the AND circuit 41D receives “0” from the NOT circuit 41Bg while receiving the beam extraction stop signal, it outputs “0” to the beam on/off signal generator 41E. The beam on/off signal generator 41E outputs the beam extraction start signal when it receives “1”, and outputs the beam extraction stop signal when it receives “0”. The scanning controller 41 includes the first delay timer 41Ba and the second delay timer 41Bb. The trigger signal is inputted as a command signal to start the first delay timer 41Ba (step 314). Then, when the time lapsed from the timer start reaches a predetermined setting time (=first delay time, corresponding to “delay 1” in FIG. 8 described later) which is set in advance, a first delay time arrival signal is outputted to the first register 41Bc (step 315). On condition of the input of both the first delay time arrival signal and the first delay-timer start command signal, the first register 41Bc outputs a counter read signal to the counter 41c in step 316, whereupon the count value at that time is inputted to the first register 41Bc from the count value read section 41ce of the counter 41c. Simultaneously, though not shown in FIG. 7 for the sake of avoiding complicacy, the first delay time arrival signal is also inputted to the second delay timer 41Bb as a command signal to start the second delay timer 41Bb. Then, as with the first delay timer 41Ba, when the time lapsed from the start of the second delay timer 41Bb reaches a predetermined setting time (=second delay time, corresponding to “delay 2” in FIG. 8 described later) which is set in advance, a second delay time arrival signal is outputted to the second register 41Bd. On condition of the input of both the second delay time arrival signal and the second delay-timer start command signal, the second register 41Bd outputs a counter read signal to the counter 41c, whereupon the count value at that time is inputted to the second register 41Bd from the count value read section 41ce of the counter 41c. The count value inputted to the first register 41Bc and the count value inputted to the second register 41Bd are inputted to the difference calculating section 41Be. The difference calculating section 41Be calculates the difference between both the count values and applies the calculated difference to the determining section 41Bf. The determining section 41Bf determines whether the count number is a normal value (i.e., whether the calculated difference is within a predetermined proper range) (step 317). If it is determined in step 317 that the count number is an abnormal value, an abnormality signal is outputted to the central controller 100 (step 318). The central controller 100 receives the abnormality signal and executes predetermined processing in the event of the abnormality. If it is determined in step 317 that the count number is the normal value, the count value is stored, as actual dose information, in the memory 41M2 by the determining section 41Bf and then outputted to the central controller 100. The actual dose information may be outputted to the central controller 100 per spot irradiation or in a lot after the end of the irradiations per slice or per unit task. Also, the conversion from the count number to the dose may be executed in the scanning controller 41 or in the central controller 100. FIG. 8 shows, in the form of a timing chart, a series of the above-described operations of the counter 41c. The thus-constructed particle beam irradiation system of this embodiment has advantages as follows. In the particle beam irradiation system of the type described above, a dose monitor for measuring dose of the ion beam irradiated to the affected part of the body is usually disposed to minimize exposure of normal tissue to the ion beam and to perform the irradiation treatment in a normal manner without causing excess or deficient dose. In the irradiation to each of the spots, the target dose is set per spot. When an integrated value of the dose measured by the dose monitor reaches the target dose, a beam extraction stop signal (beam stop command) is outputted to the accelerator, whereupon the accelerator stops the extraction of the charged particle beam. On that occasion, there is a possibility that, in the accelerator, a slight response delay occurs after the input of the beam stop command. In the case using a synchrotron that is the accelerator used in this embodiment, ions introduced from a pre-stage accelerator and having low energy are circulated within the synchrotron and accelerated to reach a level of required energy. Then, the circulating charged particle beam having high energy is brought into a resonated state of betatron oscillation, and an RF electromagnetic field is applied to the circulating charged particle beam to increase the betatron oscillation of the charged particle beam in excess of the separatix in resonance, thereby extracting the charged particle beam. Accordingly, even with the beam stop command inputted as mentioned above, the extraction of the charged particle beam is not stopped at once in the strict sense and a slight response delay may occur. In this embodiment, when the dose counted by the counter 41c based on the output of the dose monitor 61A reaches the target dose (see step 309), the scanning controller 41 outputs, to the RF knockout device 9, a trigger signal serving as a trigger for the output of the beam extraction stop signal (see step 312). At this time, the counter 41c continues the counting even after the output of the beam extraction stop signal without clearing the count number. FIG. 8 is a timing chart showing behaviors of the counter 41c in that process. As shown in FIG. 8, after the output of the beam extraction stop signal, a response delay may occur until the extraction of the ion beam from the synchrotron 12 is actually stopped (as indicated by “delay” in FIG. 8). During a period (of response delay) from the output of the beam extraction stop signal to the actual stop of the extraction of the ion beam, the dose irradiated as the ion beam extracted from the synchrotron 12 is continuously measured by the dose monitor 6A and is integrated by the counter 41c. After the extraction of the ion beam has been actually stopped, the exposure position is changed to the next one (spot) through the processing of steps 209 and 205 (see FIG. 5), and the target count number (target dose) for the next exposure position is set in step 302 (in FIG. 8, for example, change from a condition A (target dose up to until irradiation to the relevant spot at a certain position is completed) to a condition B (target dose up to until irradiation to the next spot is completed). The target count number means the count number corresponding to the target dose. Further, the scanning magnets 5A, 5B are controlled in accordance with the current setting command outputted in step 303 so that the exposure position of the ion beam is aligned with the next spot. Then, the extraction of the ion beam from the synchrotron 12 is restarted in accordance with the beam extraction start signal in step 305. Here, the count number counted for the next spot contains not only the count number based on the value measured by the dose monitor 6A after the restart of the extraction of the ion beam, but also the count number during a period of response delay from the output of the beam extraction stop signal for the preceding spot to the actual stop of the extraction of the ion beam. In other words, the count number for the next spot is given as a value obtained by setting, as an initial value, the count number counted during the period of response delay with respect to the preceding spot, and by adding up the count number after the restart of the extraction of the ion beam to the initial value. When such a count number for the next spot reaches the target count number (i.e., the dose indicated by “target dose” in FIG. 8), the scanning controller 41 outputs the beam extraction stop signal. Then, the ion beam is further irradiated to the next spot during a subsequent period of response delay. The dose irradiated during the period of response delay with respect to the irradiation for the next spot is substantially equal to the dose irradiated during the period of response delay with respect to the irradiation for the preceding spot (i.e., the above-mentioned initial value). Therefore, the dose actually irradiated to the next spot (i.e., the dose indicated by “actual dose” in FIG. 8) is substantially equal to the target dose. The dose irradiated during the period of response delay with respect to the next spot is set as an initial value for the succeeding spot irradiation after the spot is moved to a further next position, followed by adding up the count number to the thus-set initial value. Thereafter, a similar counting process is repeated in a similar manner. Thus, because the scanning controller 41 executes the above-described control in accordance with the count number, the irradiation to each spot is performed such that the ion beam is always irradiated to the spot until the dose irradiated to the relevant spot, which includes as the initial value the dose irradiated during the period of response delay with respect to the irradiation for the preceding spot, reaches the target dose for the relevant spot. In the case controlling the dose not taking into account the above-described response delay, as shown in FIG. 9 (in which target total dose is represented by 1.0), there is a possibility that excess irradiation corresponding to the above-mentioned initial value is performed and the target total dose for all the spots becomes 1.2. In contrast, by executing the above-described control in this embodiment, excess irradiation corresponding to the above-mentioned initial value is essentially compensated, as shown in FIG. 10, for all the spots except the spot to which the irradiation is made for the first time (i.e., the spot at the left end in FIG. 10), and the ion beam can be irradiated to each of all the spots except the left-end spot at dose (about 1.0), which is substantially equal to the preset target dose, with high accuracy. As a result, the ion beam can be uniformly irradiated to the affected part of the body (i.e., the irradiation object) and a dose distribution in the affected part of the body can be made uniform. Also, by executing control to read the dose after the preset delay time (first delay time) has lapsed from the output of the beam extraction stop signal, as described above, the dose irradiated to each spot can be measured with high accuracy even with a response delay occurred when the extraction of the ion beam from the accelerator is stopped. Further, by executing control to read both the dose after the lapse of the first delay time and the dose at a subsequent point in time after the lapse of the second delay time, and to determine whether the difference between both the doses is not larger than (or smaller than) the predetermined value, it is possible to reliably confirm that the extraction of the ion beam from the accelerator is stopped without failures, and to increase the irradiation accuracy of the ion beam. Moreover, the scanning controller 41 in this embodiment employs the counter that measures (counts) the integrated value of the dose and continues the counting except when the count number is cleared to 0 at the start of the irradiation. Therefore, neither 0-clearing of the count number nor start/stop control are so frequency performed in the counter, and the counter is less susceptible to malfunction. Additionally, the controller may be provided with the determining function of calculating the difference between the actual dose and the target dose, and outputting an abnormality signal when the calculated result exceeds a preset allowable range. The provision of the determining function enables the dose of the irradiated ion beam to be monitored and avoided from causing large variations due to the response delay in the accelerator, and also enables an abnormal state of the system to be detected for improvement of safety. A risk of excess irradiation caused by malfunction of the dose monitor and the counter can be reduced by disposing a plurality of dose monitors and a plurality of counters for integrating doses based on respective outputs of the dose monitors, and by setting the target dose for one of the counters to be larger than the dose planned in the treatment plan. In this case, it is possible to reduce the risk of simultaneous malfunction due to a single failure and to improve safety by operating two or more dose monitors and/or counters with power supplied from separate power supplies, and by increasing independency of individual detection systems through change of respective signal paths. A proton beam irradiation system according to a second embodiment of the present invention will be described below. The proton beam irradiation system of this second embodiment differs from that of the first embodiment just in the scanning controller. The scanning controller in the proton beam irradiation system of the second embodiment is constituted as a scanning controller 41A shown in FIG. 13. As in the first embodiment, the proton beam irradiation system of this second embodiment comprises the central controller 100, the scanning controller 41A, and the accelerator controller 40, which execute control in a cooperated manner based on the treatment plan information prepared by the treatment planning system 140. As a result of that control, the output of the ion beam from the irradiation device 15 is stopped, and the scanning magnets 5A, 5B are controlled to change the exposure position (spot) of the ion beam in the state where the output of the ion beam is stopped. After the change of the exposure position, the synchrotron 12 and the irradiation device 15 are controlled so as to start the output of the ion beam from the irradiation device 15 again (for the so-called scanning). Also, as in the first embodiment, the CPU 101 of the central controller 100, shown in FIG. 1, reads the treatment plan information stored in the memory 103 out of the storage 110 and loads the read treatment plan information in the memory (not shown) of the scanning controller 41A. On that occasion, unlike the first embodiment, the target dose for each spot to be transmitted to the scanning controller 41A is the dose separated per spot. Further, as in the first embodiment, the CPU 101 transmits, from among the treatment plan information, the data of operation parameters regarding all the slices (i.e., the degrader numbers and the excitation current values for the various magnets in the beam line which are decided depending on the energy of the ion beam irradiated to each slice) to the accelerator controller 40. When the spot scanning is performed in this embodiment, the scanning controller 41A and the accelerator controller 40 execute similar control procedures to those shown in FIG. 5. However, because the target dose at each exposure position is not the integrated value as mentioned above, the scanning controller 41A differs from the scanning controller 41 in functional configuration and internal operation. FIG. 12 is a functional block diagram showing details of the functional configuration of the scanning controller 41A. As shown in FIG. 12, the scanning controller 41A includes a preset counter 41a and a record counter 41b, which are related to the dose detection. The preset counter 41a and the record counter 41b measure the dose by counting the number of pulses outputted from the dose monitor 6A. The scanning controller 41A differs from the scanning controller 41 in point of using the preset counter 41a and the record counter 41b instead of the counter 41c. The preset counter 41a has a pulse input section 41aa, a setting value input section 41ab, an initialization (clear) signal input section 41ac, and a setting-value comparison result output section 41af. The record counter 41b has a pulse input section 41ba, an initialization (0-clear) signal input section 41bc, and a count value read section 41be. Detailed procedures executed by the scanning controller 41A in steps 205 and 300 of FIG. 5 will be described below with reference to FIG. 13. Processing in steps 303-305, 312, 314, 315, 317 and 318 is the same as that executed by the scanning controller 41 in those steps. Processing in steps 302 and 309-311 is executed by the preset counter 41a, and processing in steps 316 and 319 is executed by the record counter 41b. The operator i and the operator j are each initialized to 1 in advance. The following description is made of the processing executed by the scanning controller 41A primarily in points differing from the processing executed by the scanning controller 41. In step 301, the scanning controller 41A outputs a preset counter setting command corresponding to the target count number for the preset counter 41a, which is already stored in the memory 41M1, to the setting value input section 41ab of the preset counter 41a. In accordance with the preset counter setting command, the preset counter 41a sets, in step 302, the target count number for the first spot in the slice 1. The target count number is a value corresponding to the target dose for the relevant spot in the relevant slice, which is put in column “target dose” of FIG. 11. After the end of the processing in step 301, the scanning controller 41A executes the processing of step 303-305. When the beam irradiation to the patient 30 is started with the output of the beam extraction start signal in step 305, the detected signal from the dose monitor 6A is converted to a train of dose pulses and inputted to each of the pulse input section 41aa of the preset counter 41a and the pulse input section 41ba of the record counter 41b. These counters 41a, 41b count the number of the pulses concurrently. Each count number represents the dose integrated from the start of the counting. When the number counted based on the detected signal from the dose monitor 6A exceeds the preset target count number (step 309), the preset counter 41a outputs a trigger signal from the setting-value comparison result output section 41af (step 310). The trigger signal is inputted as a first reset signal to the initialization (0-clear) signal input section 41ac, whereby the count number of the preset counter 41a is reset to 0 (step 311). After the reset, the preset counter 41a starts again the counting based on the detected signal from the dose monitor 6A. In response to the trigger signal, the scanning controller 41A outputs the beam extraction stop signal in step 312. Consequently, as described above, the extraction of the ion beam from the synchrotron 12 is stopped and the irradiation to the patient is stopped. In such a way, the irradiation of the ion beam is stopped. As in the scanning controller 41, the scanning controller 41A produces the beam extraction start signal and the beam extraction stop signal in the beam on/off signal generator 41E. In step 314, the scanning controller 41A starts the operation of the first delay timer 41Ba upon the input of the trigger signal. After the lapse of the first delay time, a first delay time arrival signal is outputted to the first register 41Bc (step 315). The first register 41Bc outputs a counter record-counter read signal to the record counter 41b in step 316, whereupon the count number at that time is outputted from the count value read section 41be to the first register 41Bc. Also, when a counter record-counter read signal is outputted from the second register 41Bd to the record counter 41b, the count number at that time is inputted to the second register 41Bd from the count value read section 41be. The difference calculating section 41Be calculates the difference between both the count numbers inputted from the first and second registers 41Bc, 41Bd, and the calculated difference is inputted to the determining section 41Bf. The determining section 41Bf determines whether the count number is a normal value (i.e., whether the calculated difference is within a predetermined proper range) (step 317). If the determination result in step 317 is “No”, i.e., if it is determined that “the count number is an abnormal value”, an abnormality signal is outputted to the central controller 100 in step 318. If it is determined in step 317 that the count number is the normal value, the determining section 41Bf applies a second reset signal for resetting the record counter 41b to the initialization (0-clear) signal input section 41bc of the record counter 41b via an OR circuit, whereupon the record counter 41b is reset to start the counting again (step 319). At the same time, the count number is recorded, as actual dose record, in the memory 41M2 by the determining section 41Bf and is then outputted to the central controller 100. The output of the actual dose record to the central controller 100 may be performed per spot irradiation or in a lot after the end of the irradiations per slice or per unit task. Also, the conversion from the count number to the dose may be executed in the scanning controller or in the central controller. FIG. 14 shows, in the form of a timing chart, a series of the above-described operations of the counters 41a, 41b. The thus-constructed particle beam irradiation system of the second embodiment has similar advantages to those obtainable with the first embodiment. In addition, according to this embodiment, since the count number counted by each of the preset counter and the record counter is decided depending on the dose for each spot, a maximum count number can be made smaller than the case integrating the count for all the spots as in the first embodiment. Therefore, the amount of data transmitted and received between the central controller 100 and the scanning controller can be reduced, and the time required for transmitting and receiving the data can be cut. The control system can be thereby constituted with a smaller-scaled circuit. As a result, it is possible to increase the processing speed in comparison of the count number with the setting value. In the second embodiment, the dose irradiated during the period of response delay in the synchrotron 12 with respect to the irradiation to a certain spot is assumed to be included in the dose irradiated to the next spot, and based on such an assumption, the ion beam is irradiated to the next spot until reaching the target dose for the next spot. However, the following other methods (1) and (2) can also provide the similar advantages. (1) In step 309 executed by the preset counter 41a, from the target dose for a certain spot, the dose irradiated during the period of response delay with respect to the irradiation to the preceding spot is subtracted, and the count number during the irradiation to the certain spot is further subtracted from the remaining dose. Then, when the remaining dose after the two subtractions becomes 0, the trigger signal is outputted in step 310. (2) The target count number set by the preset counter in step 302 is given as the dose obtained by subtracting, from the target dose for a certain spot, the dose irradiated during the period of response delay with respect to the irradiation to the preceding spot. It is to be noted that the irradiation of the ion beam based on the above-described spot scanning is also applicable to a proton beam irradiation system using a cyclotron as the accelerator. |
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description | The inventive improvements disclosed herein generally relate to electron-impact x-ray sources. More particularly, the disclosure is directed to the reduction of debris and improvement of x-ray brightness in electron-impact x-ray sources having a liquid-jet anode. X-rays have been used for imaging ever since the discovery thereof by Roentgen at the turn of the 19th century. Since available x-ray optics are severely limited, x-ray imaging is still mostly based on absorption shadow-graphs. This is basically true even for modern Computer Tomography (CT) imaging and, as a consequence, the brightness of the x-ray source is a figure of merit limiting both the exposure time and the attainable resolution in many applications. Today x-ray imaging is a widespread and standard method in science, medicine and industry. Although well established, there are numerous applications that would greatly benefit from an increased brightness. Among these are applications in medicine requiring high spatial resolution, such as mammography and angiography, and emerging techniques requiring monochromatic radiation which currently can not be achieved with reasonable exposure times. Also, certain protein crystallography, today only possible at synchrotron radiation facilities, may be feasible with a compact source. Furthermore, a significant increase in the brightness of compact x-ray sources could enable phase imaging with reasonable exposure times. This is important since the phase contrast is often much higher than the absorption contrast. In addition, phase contrast imaging could reduce the absorbed dose during imaging. The basic physics relied upon for x-ray production in compact electron-impact sources has been the same since the days of Roentgen. As the electrons impact the target they lose energy in one of two ways: either they can be decelerated in the electric field close to an atomic nucleus and emit continuous bremsstrahlung radiation, or they can knock out an inner-shell electron, resulting in the emission of a characteristic x-ray photon when the vacancy is filled. The efficiency of x-ray production by electron impact is very poor, typically below 1%, and the bulk of the energy carried by the electron beam is converted to heat. The brightness of current state-of-the-art compact electron-impact x-ray sources is limited by thermal effects in the anode. The x-ray spectral brightness [i.e. photons/(mm2·sr·s·BW), where BW stands for bandwidth] is proportional to the effective electron-beam power density at the anode, which must be limited not to melt or otherwise damage the anode. Since the first cathode-ray tubes only two fundamental techniques, the line focus and the rotating anode, have been introduced to improve the power load capacity of the anode. The line focus principle, introduced in the 1920s, utilizes the fact that the x-ray emission is non-Lambertian to increase the effective power load capacity by extending the targeted area but keeping the apparent source area almost constant by viewing the anode at an angle. Ignoring the Heel-effect and field of view, this trick increases the attainable power load capability by up to ˜10×. The rotating anode was introduced in the 1930s to further extend the effective electron-beam-heated area by rotating a cone-shaped anode to continuously provide a cool target surface. After these improvements, progress with respect to brightness has been rather slow for compact electron-impact sources and has only been due to engineering perfection in terms of target material, heat conduction, heat storage, speed of rotation etc. Current state-of-the-art sources now allow for 100-150 kW/mm2 effective electron-beam power density. Typical high-end implementations are, e.g., 10 kW, 0.3×0.3 mm2 effective x-ray spot size angiography systems and 1.5 kW, 0.1×0.1 mm2 effective x-ray spot size fine-focus mammography systems. Low-power micro-focus sources (4 W, 5 μm effective x-ray spot diameter) have similar effective power densities (200 kW/mm2) and are also limited by thermal effects. The power load limit of a modern rotating anode can be calculated by P A effective = π l ( T max - Δ T margin - T base ) λρ c p fR δ 4 δ 2 ( 1 + k tf δ π R ) , ( 1 ) where Aeffective is the apparent x-ray source area, R is the anode radius, l is the spot height, 2δ is the spot width, Tmax is the maximum permissible temperature before breakdown, ΔTmargin is a safety margin, Tbase is the anode starting temperature, λ is the thermal conductivity, ρ is the density, cp is the specific heat capacity, f is the rotation frequency, t is the load period, and k is a correction factor taking into account radial heat conduction, heat loss by radiation and anode thickness. As can be seen from Eq. 1, the only way to increase the power load limit is to increase the spot speed, i.e., f and R. Unfortunately even a quite unrealistic set of parameters (1 m diameter anode and 1 kHz rotation) would only increase the output flux ˜6×. It therefore seems unlikely that conventional x-ray source technology can be developed much further, even with significant engineering efforts. A way to increase the brightness in compact electron-impact based hard-x-ray sources would be a fundamentally different anode configuration allowing a higher electron-beam power density. To this end, there has previously been reported a new liquid-metal-jet anode concept. This anode configuration could allow a significantly higher (>100×) thermal load per area than current state of the art due to fundamentally different thermal limitations, as explained below. Liquid-jet systems have been extensively used as targets in negligible-debris laser-produced plasma soft x-ray and EUV sources. A liquid-gallium jet has also been used as target in hard x-ray production in femto-second laser-plasma experiments. Furthermore, an electron beam has been combined with a water jet for low power soft x-ray generation via fluorescence. X-ray tubes with liquid anodes, either stationary or flowing over surfaces, have previously been reported but their advantages for high-brightness operation are limited due to the intrinsically low flow speed and cooling capacity of such systems. Recent work also includes a liquid anode flowing behind a thin window. The much higher power-density capacity of liquid-metal-jet systems compared to conventional anodes (2-3 orders of magnitude or more) is, in brief, due to three main reasons: (i) different thermal properties of the liquid-jet anode compared to a solid anode, (ii) the potential for higher jet speeds than what is possible for a rotating anode, and (iii) the regenerative nature of the liquid jet, which makes the requirement of keeping the anode intact more relaxed. However, when attempting to increase the power for such systems, emission of debris is a potential practical difficulty. Hence, improvements are called for to reduce the debris issue for liquid-jet anode x-ray sources. In short, it is proposed herein a method for generating x-ray radiation, which is characterized in that the full width at half maximum of the electron beam in the transverse direction of the target jet is about 50% of the target jet transverse dimension or less. It has now been discovered that this results in a considerable shielding effect of the very hot electron-beam impact area on the target jet, thus advantageously reducing the amount of debris produced. In addition, the further technical effect is obtained that the effective power density is increased when the x-ray spot is viewed from the side. This latter is in analogy with the line focus principle described in the introduction. Hence, the inventive principles disclosed herein have the attractive advantage that reduction of debris can be obtained without significantly increasing the target-jet propagation speed, but rather by employing an electron beam having, at impact on the target, a full width at half maximum (FWHM) which is about half the transverse dimension of the target jet or less. By employing an electron beam which is considerably smaller than the transverse dimension of the target jet, the target jet will give rise to a shielding effect which limits the amount of produced debris in an advantageous manner. The inventive principles also extend to a system for generating x-ray radiation, said system comprising means for carrying out the method. It should be understood that the size (FWHM) of the electron beam at impact upon the target jet could be slightly larger than 50% of the target jet transverse dimension and still produce the inventive shielding effect. Suitably, the generated x-ray radiation could be used in applications such as imaging, medical applications, crystallography, x-ray microscopy, proximity or projection lithography, photoelectron spectroscopy or x-ray fluorescence, to name a few. FIG. 1 shows the experimental arrangement of the liquid-metal-jet x-ray source, i.e. a system 10 for generating x-ray radiation according to the present invention. A liquid-metal jet 15 consisting of 99.8% tin is injected through a 30-μm or 50-μm diameter glass capillary nozzle into an evacuated chamber 18. Jet speeds of up to 60 m/s can be achieved by applying 200 bars of nitrogen pressure over the molten tin. The speed of the target jet is, thus, comparable to the fastest rotating anodes. The electron-beam system 20 is based on a 600 W (50 kV, 12 mA) e-beam gun in continuous operation. The e-beam is focused by a magnetic lens into a ˜15 or ˜25 μm full-width-at half-maximum (FWHM) diameter spot depending on the size of the LaB6 cathode (50 μm or 200 μm diameter). The e-gun is pumped with a separate 250 l/s turbo-drag pump, and the apertures at the ends of the magnetic lens are small enough to maintain a sufficient differential pressure between the main vacuum chamber (˜10−4 mbar) and the electron gun (˜10−7 mbar). However, as will be understood, the pump may be omitted in some embodiments. The cathode is shielded from tin vapor by a 1 mm diameter hole in a 120 μm thick aluminum foil, which is placed between the jet and the magnetic lens. The vacuum around the cathode is kept in the low 10−7 mbar range even during high-power operation of the gun resulting in a reasonable lifetime (>1000 h) for the LaB6 cathode. Debris witness plates 12 are placed at four different positions in the main tank about 150 mm from the x-ray source. For x-ray imaging we use a 4008×2672 pixel phosphor-coated CCD detector 14 with 9 μm pixels and a measured point-spread function (PSF) of ˜34 μm FWHM. A gold mammography resolution object 16 (20 μm thick gold with 25 μm wide lines and spaces) is placed 50 mm from the source and 190 mm in front of the CCD. A 12× zoom microscope 17 is used for optical inspection of the jet. Experiments were carried out in order to evaluate the inventive principle of producing x-rays. Debris deposition rates for several different system parameters were studied: an e-beam power between 38 W and 86 W, a jet speed of 22 or 40 m/s, a 30 or 50 μm jet diameter, and an e-beam focus of 15 or 26 μm. The witness plates 12 were exposed to tin vapor for 6-24 minutes and analyzed with a surface profilometer (KLA Tencor P-15). FIG. 2 shows the results. Curve 1 (22 m/s, 30 μm diameter jet, 24±2 μm diameter spot) shows that the debris deposition rate is exponentially dependent on the power applied on the jet, which is in agreement with the increasing vapor pressure of tin as a function of temperature. Curve 2 depicts the debris emission from a 22 m/s, 50 μm diameter jet with a 24±2 μm spot. By comparing Curves 1 and 2 it should be noted that an increased jet diameter leads to a decreased debris emission rate. This is believed to be due to two reasons: (i) the increased mass flow of the larger jet leads to a reduced average temperature of the jet and, thus, a reduced evaporation rate, and (ii) increasing the jet diameter, but keeping the size of the e-beam constant, results in a more effective shielding of the very hot electron-beam impact area on the jet as seen from the debris witness plates. It should be noted that the same effect could be obtained generally by increasing the jet size to e-beam size ratio. It has been found particularly advantageous to have an e-beam size that is 50% or less compared to the jet size. Curve 3 provides further evidence for the shielding concept. Curve 3 has the same jet parameters as Curve 2 but the x-ray spot is smaller (15.5±1.5 μm FWHM), clearly resulting in improved shielding. At the applied power of 72 W the smaller focus yielded a reduction of the debris emission rate by a factor of ˜16× compared to the 24±2 μm operation. Finally, Curve 4 shows the impact on the debris rate of an increased target speed (40 m/s, 30 μm diameter jet, 24±2 μm spot). An ˜80% increase of the jet velocity in combination with a ˜50% increase of the applied power resulted in the same rate of debris emission. The debris rates will naturally increase when higher-brightness operation is attempted by increasing the e-beam power and power density. We note that for sub-kW e-beam guns, the technological e-beam power density limit due to the cathode emissivity is a few tens of MW/mm2, i.e. two orders of magnitude above the highest power density of the metal-jet anode reported here. A significant improvement of the power density capacity of the jet anode may be achieved by having a much faster jet, and it has, in fact, been shown that it should be possible to produce stable tin jets at speeds up to at least ˜500 m/s. On the other hand, this may not necessarily be the only way to modify the jet for reduced debris production. As is indicated by the results in FIG. 2, and in accordance with the inventive principles disclosed herein, a medium-speed jet with a larger diameter (compared to the e-beam) may prove to have better debris reduction properties than considerably faster, but thinner, jets (cf. curves 3 and 4). It should be noted that the spot of the electron beam on the target jet may be circular, elliptical or a line focus as desired. For example, and as shown in FIG. 3, it may be preferred to use an elliptic electron beam spot (a line focus)—having its major axis transverse to the longitudinal extension of the target jet and having, as suggested and claimed herein, a FWHM along the major axis which is about 50% or less of the target jet diameter. According to the well known line focus principle, this will give increased effective power load capacity for the target without sacrificing the brightness of the x-ray source when the targeted area is viewed from the side. However, when an elongated electron beam spot is used according to the above, it is not required that the extension thereof is transverse to the target jet. Any general orientation of the elliptic or line focused electron beam spot is conceivable, and an effective increase of the x-ray brightness may be obtained by viewing (collecting) the generated x-ray from an appropriate angle. For example, if an electron beam spot is used having a line focus extending generally along the target jet, increased x-ray brightness may be obtained by viewing the spot from a slanting angle along the target jet. Moreover, it should be pointed out that the line focus principle may be used also when a circular electron beam spot is utilized. The reason is the following. When the electron beam impacts on the target jet, x-ray radiation will typically be generated within the first few microns of target material as the electrons penetrate the target jet. As a non-limiting example, the electrons may typically penetrate about 4 microns into the target material. This is schematically shown in the enlarged side view of FIG. 1. Hence, when viewed from the side, as shown in FIG. 1, the x-ray radiation will be generated in a region having an elongated profile of only a few microns width. As a practical example, consider a circular electron beam spot having a size (FWHM) of 50 microns which impacts upon a target jet of about 100 microns diameter. This will produce an x-ray region (or “volume”) in the target jet roughly resembling a cylinder having a diameter of 50 microns and a “height” of slightly more than 4 microns (due to the curvature of the target jet surface). If this x-ray region is viewed along the electron beam, the apparent x-ray spot will be a circle of 50 microns diameter. However, when the same x-ray region is viewed from the side, it will have the general shape of an elongated area having a length of about 50 microns and a width of slightly more than 4 microns, i.e. a radical decrease of the apparent area resulting in improved brightness for the x-ray source from this viewing direction. Hence, it may be preferred to collect the generated x-ray emission from a direction that is at an angle with respect to the electron beam. For example, if the target jet propagation direction and the electron beam propagation direction are at right angles with respect to each other, then the brightness of the x-ray source may be maximized by collecting the generated radiation from a direction that is at a right angle to the electron beam. The principle of using a reduced-size electron beam in order to reduce debris may advantageously be combined with prior-art techniques for reducing debris, such as increased jet-propagation speed, debris mitigation systems, etc. The target jet may be electrically conductive or non-conductive. For example, the target jet may comprise a metal (e.g. tin or gallium), a metal alloy or a low melting-point alloy, a cryogenic gas or any other liquid substance suitable as a target for electron-impact x-ray sources. It should also be understood that the target jet may have any cross-sectional shape, for example circular, rectangular or elliptical. Typical diameters for the target jet are from about 10 μm to about 100 μm, such as 30 μm or 50 μm. However, in some applications even larger target jet cross-sections are conceivable. The propagation speed of the target jet in the area of interaction can be up to about 500 m/s, and typical values are from about 20 m/s to about 60 m/s. As will be understood, an increase in propagation speed for the target jet will lead to an improved power density capacity of the jet anode. It will be understood that the examples given above are only for illustrative and enabling purposes, not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims. |
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claims | 1. A plasma processing apparatus, comprising:a vacuum chamber;a plasma reactor arranged in the vacuum chamber for plasma processing;a radio-frequency (RF) power source for providing RF signals for the plasma reactor;an RF power transmission unit for transmitting the RF signals from the RF power source to the plasma reactor inside the vacuum chamber, wherein the RF power transmission unit comprises a transmission line for transmitting the RF signals and an outer conductor for shielding the electromagnetic field around the transmission line;wherein a diameter of the transmission line is larger than or equal to 10 mm; andthere is a gap of less than or equal to 10 mm between the outer conductor and the transmission line. 2. The plasma processing apparatus as claimed in claim 1, wherein the outer conductor is a conduit, a conductive foil or a metal cover. 3. The plasma processing apparatus as claimed in claim 2, wherein the vacuum chamber is provided with an inner wall, the plasma reactor is provided with an outer wall, and one end of the outer conductor is connected to the inner wall of the vacuum chamber, while the other end of the outer conductor is connected to the outer wall of the plasma reactor. 4. The plasma processing apparatus as claimed in claim 3, wherein both the outer wall of the plasma reactor and the inner wall of the vacuum chamber are conductive, and the outer wall of the plasma reactor, the inner wall of the vacuum chamber and the outer conductor provide a closed electromagnetic shielding body. 5. The plasma processing apparatus as claimed in claim 3, wherein the transmission line is in a tubular, columnar, netlike or wirelike shape. 6. The plasma processing apparatus as claimed in claim 3, wherein the transmission line is cylindrical, and the outer conductor has a cylindrical inner surface. 7. The plasma processing apparatus as claimed in claim 1, wherein a pressure in the vacuum chamber is 0.03-3 mbar, and the voltage of the RF power source is 100-500V. 8. The plasma processing apparatus as claimed in claim 1, wherein the gap is of larger than or equal to 1 mm. 9. The plasma processing apparatus as claimed in claim 8, wherein an inner diameter of the outer conductor is larger than 12 mm but smaller than or equal to 60 mm. 10. The plasma processing apparatus as claimed in claim 9, wherein the material of outer conductor comprise one or more selected from the group consisting of Cu, Au, Ag, Fe, Zn, Cr, Pb, Ti and their alloys. 11. The plasma processing apparatus as claimed in claim 10, wherein the material of transmission line comprise one or more selected from the group consisting of Cu, Al, Au, Ag, Fe, Zn, Cr, Pb, Ti and their alloys. 12. The plasma processing apparatus as claimed in of claim 1, wherein a space between the transmission line and outer conductor is filled with an insulating medium. 13. The plasma processing apparatus as claimed in claim 1, wherein the transmission line is coaxial with the outer conductor. 14. The plasma processing apparatus as claimed in claim 1, wherein the vacuum chamber is provided with a vacuum chamber pressure adjustment unit which comprises a first gas outlet. 15. The plasma processing apparatus as claimed in claim 14, wherein the plasma reactor is provided with a plasma reactor pressure adjustment unit which comprises a second gas outlet. 16. The plasma processing apparatus as claimed in claim 15, wherein the first gas outlet and the second gas outlet are connected to a same exhaust pump. 17. The plasma processing apparatus as claimed in claim 15, wherein the first gas outlet and the second gas outlet are connected to different exhaust pumps, respectively. 18. The plasma processing apparatus as claimed in claim 1, wherein the plasma reactor has an RF electrode and a first gas inlet communicated with the RF electrode. 19. The plasma processing apparatus as claimed in claim 18, wherein one end of the transmission line is connected to the RF power source, and the other end of the transmission line is connected to the RF electrode. 20. The plasma processing apparatus as claimed in claim 19, wherein the RF power source is arranged outside the vacuum chamber. 21. The plasma processing apparatus as claimed in claim 19, wherein the RF power source comprises an RF generator unit and a match box connected to the RF generator unit, and the match box serves as a conditioner for regulating a coupling power of RF signals. |
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summary | ||
abstract | A nuclear fission reactor fuel assembly and system configured for controlled removal of a volatile fission product and heat released by a burn wave in a traveling wave nuclear fission reactor and method for same. The fuel assembly comprises an enclosure adapted to enclose a porous nuclear fuel body having the volatile fission product therein. A fluid control subassembly is coupled to the enclosure and adapted to control removal of at least a portion of the volatile fission product from the porous nuclear fuel body. In addition, the fluid control subassembly is capable of circulating a heat removal fluid through the porous nuclear fuel body in order to remove heat generated by the nuclear fuel body. |
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claims | 1. Gripping and locking/unlocking system comprising:an outer tube comprising at its periphery at least one groove;an inner tube designed to be fitted inside the outer tube, the inner tube comprising at least one catching device connected at its upper end and at least one notch formed in the thickness of the inner tube from its upper end;a gripper member with a gripper head designed to be housed in the inner tube, the gripper head comprising at its periphery at least one groove,wherein the at least one catching device comprises:a first hook, referred to as a locking hook, mounted to pivot about a pivot pin orthogonal to the longitudinal axis of the inner tube between a locked position in which it is housed in the groove of the outer tube to lock the inner and outer tubes together, and an unlocked position in which it is distant from the said groove of the outer tube;a second hook referred to as a gripping hook, mounted to pivot on the first hook about a pivot pin orthogonal to the longitudinal axis of the inner tube, between a gripping position in which it is housed in the groove of the gripper head so as to grip the inner tube by the gripper head and at least one release position in which it is distant from the said groove of the gripper head;an actuating lever mounted on the pivot pin about which the locking hook pivots between a first neutral position in which it is distant from the at least one notch and does not project into the inner tube and a second neutral position in which it is housed in the at least one notch, passing via an actuating position in which it does project into the inner tube, the actuating lever being connected to rotate with the locking hook between its actuating position and its second neutral position, and free to rotate independently of the locking hook between its first and second neutral positions;a first elastic return means for returning the gripping hook from a released position to its gripping position;wherein the system is configured so that:when the inner tube is fitted inside the outer tube and locked thereto by the locking hook, a downwards translational movement of the gripper head in the inner tube over a given travel (A) causes the actuating lever to pivot from its actuating position into its second neutral position and thus simultaneously causes the locking hook to pivot from its locked position to its unlocked position, then causes the gripping hook to pivot both under the effect of its self-weight and under the elastic effect of the first elastic return means into the groove of the gripper head, thus unlocking the inner and outer tubes from one another and then causing the inner tube to be gripped by the head, at the end of the travel (A);when the gripper head and the inner tube are locked together by the gripping hook, a downwards translational movement of the gripper head and of the inner tube inside the outer tube over a given travel (B) greater than the travel (A) causes the gripping hook to be released from the groove of the head then causes the actuating lever to disengage from its second neutral position and thus simultaneously causes the locking hook to pivot from its unlocked position into its locked position under the effect at least of its self-weight, thus unlocking the inner tube from the gripper head and locking together the inner and outer tubes, at the end of the travel B. 2. The gripping and locking/unlocking system according to claim 1, comprising a plurality of catching devices connected to the upper end of the inner tube, the catching devices being distributed about the periphery of the inner tube in order to provide a statically determinate distribution of locking and gripping loads. 3. The gripping and locking/unlocking system according to claim 2, comprising three catching devices arranged 120° apart about the longitudinal axis (X) of the inner tube. 4. The gripping and locking/unlocking system according to claim 1, the first elastic return means consisting of a torsion coil spring mounted around the pivot pin about which the gripping hook pivots, with its two end turns fixed and a pressing central turn configured to press against the gripping hook. 5. The gripping and locking/unlocking system according to claim 1, comprising a second elastic return means for returning the locking hook from its unlocked position to its locked position. 6. The gripping and locking/unlocking system according to claim 5, the second elastic return means consisting of a coil torsion spring mounted around the pivot pin about which the locking hook pivots, with its two end turns fixed and a central pressing turn configured to press against the locking hook. 7. The gripping and locking/unlocking system according to claim 1, the locking hook consisting of a finger of a shape complementing the groove of the outer tube, and of a substantially V-shaped yoke connected to the finger and inside which the gripping hook is mounted. 8. The gripping and locking/unlocking system according to claim 1, in which the groove of the outer tube extends around the entire periphery thereof. 9. The gripping and locking/unlocking system according to claim 1, comprising at least one groove of the outer tube extending over only a part thereof. 10. The gripping and locking/unlocking system according to claim 1, in which the groove of the gripper head extends over the entire periphery thereof. 11. The gripping and locking/unlocking system according to claim 1, the actuating lever consisting of a lug. 12. The gripping and locking/unlocking system according to claim 1, the inner tube and/or the outer tube comprising one or more seals in order to create a sealed assembly with one another. 13. The gripping and locking/unlocking system according to claim 12, the gripper member and/or the catching device(s) being dimensioned to overcome the friction forces of the seal(s) as the inner tube is introduced into or extracted from the outer tube. 14. The gripping and locking/unlocking system according to claim 1, the inner tube constituting a material specimen holder tube, the outer tube constituting a measurement instrumentation holder tube. 15. The gripping and locking/unlocking system according to claim 14, constituting a system for inserting and extracting a specimen holder tube intended to house a specimen of nuclear materials, into and from a measurement instrumentation holder tube intended to house measurement sensors and a cooling system. |
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062263439 | summary | TECHNICAL FIELD The invention relates to an water rod in a fuel assembly of a boiling water nuclear reactor and, more particularly, to a water rod that is directly attachable to the upper and lower tie plates of the fuel assembly without an end plug. BACKGROUND A fuel assembly in a nuclear reactor includes a matrix of parallel rods containing fissionable fuel and/or water coolant flow. These parallel rods are held at a fixed spacing by spacer meshes located intermittently along the length of the fuel assembly. The matrix of fuel rods is supported at their lower ends by a lower tie plate, which also guides the fuel rod end plugs laterally. The lower tie plate also includes flow holes to provide an inlet for coolant flow into the fuel assembly. Similarly, the top end of the rod matrix is covered by an upper tie plate that restrains the fuel rod upper end plugs laterally and provides flow holes for the exit of coolant from the fuel assembly. One or more of the water and/or fuel rods is used as a structural member that is attached to both the lower and upper tie plates and serves the purpose of carrying a structural load of the assembly and maintaining a fixed distance between the lower and upper tie plates. Prior designs using the water rod as the structural member typically have complex assemblies including members to transition from a large to a smaller diameter and/or end fittings to attach to the lower and upper tie plates as illustrated in FIG. 1. Even when the water rod is not used as the structural member, the assembly is complex as shown in FIG. 2 with many of the same components. In particular, referring to FIG. 1, a conventional water rod has a central cylindrical tube 10 secured between an upper tie plate 12 and a lower tie plate 14. The central tube 10 has a plurality of inlet flow holes 16 that allow water to be driven through the rod, thus introducing moderating material within the fuel rod matrix. An upper reducer 18 and a lower reducer 20 are welded to upper and lower end of the central tube 10 respectively. The reducers 18, 20 effectively reduce the diameter of the central tube 10 to accommodate end fittings. An upper end fitting 22 and a lower end fitting 24 are welded to the upper and lower reducer 18, 20, respectively and are configured to be secured to the upper and lower tie plate, respectively. Referring to FIG. 2, when the water rod is not intended to be the structural member for the fuel assembly, even more intricate end fittings are coupled to the central tube for connection to the upper and lower tie plates. DISCLOSURE OF THE INVENTION Accordingly, it is an object of the invention to provide a water rod for a fuel assembly of a boiling water nuclear reactor that is simple in construction, inexpensive to manufacture, and that has reduced inspection requirements. It is another object of the invention to provide a water rod that is directly attachable to a tie plate of the fuel assembly without an end plug. These and other objects and advantages of the invention are achieved by providing a water rod for a fuel assembly of a boiling water nuclear reactor that includes a first end and a second end, wherein at least one of the first and second ends is directly attachable to a tie plate of the fuel assembly without an end plug. The at least one of the first and second ends may include threads adapted to be received by a threaded aperture in the tie plate. Moreover, the at least one end may be swaged such that it comprises a narrower diameter than a remainder of the water rod. The end may be flared such that it has a diameter that is greater than a diameter of a tie plate aperture and/or keyed to prevent rotation of the water rod, or the end may be provided with one of a male and female portion of a bayonet fitting adapted to be received by the other of the male and female portion of the bayonet fitting in the tie plate. An end insert may be disposed within the water rod at the at least one end, wherein the end insert may be provided with a plurality of flow apertures therethrough. An end cap that is attachable over the end may also be provided, and similar to the end insert, the end cap may be provided with a plurality of flow apertures therethrough. In accordance with another aspect of the invention, there is provided a fuel assembly for a boiling water nuclear reactor that includes an upper tie plate; a lower tie plate; and a water rod having first and second ends and being supported between the upper and lower tie plates, wherein at least one of the first and second ends is directly attachable to a respective one of the upper and lower tie plates without an end plug. |
062263404 | abstract | A hermaphroditic absorber exploits the inherent spatial change in the neutron spectrum within a lumped poison mass in a thermal reactor neutron flux field. The hermaphroditic absorber (poison mass) incorporates two types of absorbers, the first being a strong thermal absorber near the surface of the mass, and the second being a strong resonant absorber in the interior of the poison mass. The outer regions of the poison mass are comprised of a strong "1/v" thermal absorber, and the inner region of the poison mass is comprised of a resonance absorber. This resonance absorber more appropriately exploits the hardened characteristics of the neutron spectrum within the absorber mass by selectively absorbing the epi-thermal neutrons. The creation of the hermaphroditic poison mass permits an increase in the control material worth while maintaining the external dimension of the structure containing the control material, such as a BWR control rod. |
055880363 | claims | 1. An X-ray CT apparatus for performing a scanning operation on an examined region of a patient lying on a bed, in which an X-ray from an X-ray tube irradiating the patient passes through the patient and is detected by a detecting means, the X-ray CT apparatus comprising: a scan condition file means into which past scan condition including a predetermined scan pitch and a predetermined slicing width for patients to be scanned are stored, the past scan condition being acquired by means of previously performing at least one scanning operation on the examined region of the patient; means for individually designating a specific one of the patients; means for reading out the past scan condition of the designated specific one of the patient from the scan condition file means; and a main controller for setting a scan condition in accordance with the past scan condition of the examined region of the designated patient and for performing the scanning operation on the examined region of the designated patient in accordance with the set scan condition. preliminary storing past scan condition including a predetermined scan pitch and a predetermined slicing width for patients to be scanned into a scan condition file, the past scan condition being acquired by means of previously performing at least one scanning operation on the examined region of the patient; individually designating a specific one of the patients; reading out the past scan condition of the designated specific one of the patients from the scan condition file means; setting a scan condition in accordance with the past scan condition of the examined region of the designated patient; and performing the scanning operation on the examined region of the designated patient in accordance with the set scan condition. preparing an information of the patient; entering the information into the main controller; carrying out a scanographing operation and displaying the scanographic image on the monitor; indexing the past scan condition of the patient from the scan condition file; confirming whether the past scan condition is indexed; converting a slice information in the indexed past scan condition into a slice information image data in a case where the past scan condition is indexed; displaying the indexed past scan condition as numerical data and displaying the slice information as slice information image data; confirming whether a scanning condition is set in accordance with the displayed past scan condition; inversely converting the slice information image data into the slice information; setting and storing the scanning condition in a case where the scanning condition is set in accordance with the displayed past scan condition; and performing the scanning operation with the set scanning condition. preparing an information of the patient; entering the information into the main controller; indexing the past scan condition of the patient from the scan condition file; confirming whether the past scan condition is indexed; displaying the indexed past scan condition as numerical data in a case where the past scan condition is indexed; confirming whether a scanning condition is set in accordance with the displayed past scan condition; setting and storing the scanning condition in a case where the scanning condition is set in accordance with the display past scan condition; and performing the scanning operation with the set scanning condition. 2. An X-ray CT apparatus according to claim 1, further comprising a bed drive means controller, a gantry drive means controller and a high-voltage controller, through which said bed drive means, said gantry drive means and said X-ray tube are controlled, respectively, by the main controller. 3. An X-ray CT apparatus according to claim 2, wherein said main controller comprises a central processing unit, a scan control means for controlling said high-voltage controller, said bed drive means controller and said gantry drive means controller, an input/output control means for said scan condition file means and means for converting a slice information data within the exposure information into a slice information image data and controlling the data for display, said scan control means, said input/output control means and said converting means are operatively connected to said central processing unit. 4. An X-ray CT apparatus according to claim 3, further comprising a monitor means operatively connected to the means for converting data and controlling data for display of the main controller, said monitor means including a main monitor for displaying an image information and a sub-monitor for displaying the exposure information as numerical data. 5. An X-ray CT apparatus according to claim 1, wherein each of said past scan condition includes a number of scans, scanned area, a tube voltage of the X-ray tube, and a tube current of the X-ray tube. 6. A method of performing a scanning operation on an examined region of a patient lying on a bed using an X-ray CT apparatus, wherein said method comprises the steps of: 7. A method of performing a scanning operation according to claim 6, wherein said at least one scanning operation on the examined region of the patient is previously performed by the steps of: 8. A method of performing a scanning operation according to claim 7, wherein said scanning operation further comprises the step of modifying a numerical data of the scanning condition in the displayed past scan condition. 9. A method of performing a scanning operation according to claim 7, wherein in a case where the past scan condition is not indexed, the scanning condition is set manually and stored and the scanning operation is then performed with the set scanning condition. 10. A method of performing a scanning operation according to claim 7, wherein in a case where the scanning condition is not set, it is confirmed whether further index is to be continued, and in a case where the index is continued, another past scan condition for the patient is further indexed, and in a case where the index is not continued, the scanning condition is set manually and stored. 11. A method of performing a scanning operation according to claim 7, wherein the slice information includes slicing pitch and a tilt angle of a gantry of the X-ray CT apparatus. 12. A method of performing a scanning operation according to claim 7, wherein a predetermined number of a plurality of past scan condition for the patient are stored in accordance with the time order and when a new scanning condition is stored as past scan condition, an oldest past scan condition automatically vanishes. 13. A method of performing a scanning operation according to claim 6, wherein said scanning operation is performed by the steps of: 14. A method of performing a scanning operation according to claim 13, wherein said scanning operation further comprises the step of modifying a numerical data of the scanning condition in the displayed past scan condition. 15. A method of performing a scanning operation according to claim 13, wherein in a case where the past scan condition is not indexed, the scanning condition is set manually and stored and the scanning operation is then performed with the set scanning condition. 16. A method of performing a scanning operation according to claim 13, wherein in a case where the scanning condition is not set, it is confirmed whether further index is to be continued, and in a case where the index is continued, another past scan condition for the patient is further indexed, and in a case where the index is not continued, the scanning condition is set manually and stored. 17. A method of performing a scanning operation according to claim 13, wherein a predetermined number of a plurality of past scan condition for the patient are stored in accordance with the time order and when a new scanning condition is stored as past scan condition, an oldest past scan condition automatically vanishes. 18. A method of performing a scanning operation according to claim 6, wherein each of said past scan condition includes a number of scans, a scanned area, a tube voltage of the X-ray tube, and a tube current of the X-ray tube. |
claims | 1. A method for controlling deflection of an ion beam, comprisingproviding an electrode configuration comprising a plurality of upper and lower electrode pairs, the upper and lower electrodes of each pair positioned on opposite sides of an ion beam;grading a deceleration of the ion beam,obtaining a deflection factor function along a length of the lens to obtain a beam angle correction; andobtaining electrode voltages for the plurality of upper and lower electrode pairs to adjust the grading, the deflection factor, and a focus of the ion beam such that a central ray trajectory (CRT) of the ion beam is positioned at a center of the lens center;wherein adjusting the grading and deflection factor is achieved using at least one virtual knob that adjusts at least one parameter of the ion beam. 2. The method of claim 1, wherein the at least one virtual knob controls the beam focus and residual energy contamination. 3. The method of claim 1, wherein the at least one virtual knob controls an upstream electron suppression of the ion beam, preventing electrons from being stripped from the ion beam. 4. The method of claim 1, wherein the at least one virtual knob controls a deflection of the beam, and centers the beam at the exit of the lens. 5. The method of claim 4, further comprising measuring currents on inner and outer final ground electrodes of the plurality of electrode pairs, and centering the beam by varying beam deflection until the currents on the inner and outer final ground electrodes are equal. 6. The method of claim 4, further comprising providing a collimated light sensor vertically centered within an exit aperture of the lens to determine beam centering. 7. The method of claim 1, wherein the at least one virtual knob controls a final deflection angle of the ion beam and constrains the position of the ion beam at the exit of the lens. 8. The method of claim 1, wherein the step of grading a deceleration of the ion beam further comprises calculating the energy of the beam's central ray trajectory (CRT) along a length of the lens. 9. The method of claim 1, wherein electrode voltages are assigned to the upper and lower electrode pairs such that voltages of outer electrodes of the plurality of upper and lower electrode pairs remain negative. 10. The method of claim 1, wherein an outer suppression electrode of the plurality of electrodes remains below an upstream beamline potential. 11. A system for controlling deflection of a charged particle beam, comprisinga graded lens comprising a plurality of sets of electrodes, each set of electrodes spaced apart by a gap to allow a charged particle beam to pass therebetween;a controller for controlling different combination of voltage potentials to be applied to the plurality of sets of electrodes; anda machine readable storage medium encoded with a computer program code such that, when the computer program code is executed by a processor, the processor performs a method comprising:grading a deceleration of the ion beam,obtaining a deflection factor function along a length of the lens to obtain a beam angle correction; andobtaining electrode voltages for the plurality of upper and lower electrode pairs to adjust the grading, the deflection factor, and a focus of the ion beam such that a central ray trajectory (CRT) of the ion beam is positioned at a center of the lens center;wherein adjusting the grading and deflection factor is achieved using at least one virtual knob that adjusts at least one parameter of the ion beam. 12. The system of claim 11, wherein the at least one virtual knob controls the beam focus and residual energy contamination. 13. The system of claim 11, wherein the at least one virtual knob controls an upstream electron suppression of the ion beam, preventing electrons from being stripped from the ion beam. 14. The system of claim 11, wherein the at least one virtual knob controls a deflection of the beam, and centers the beam at the exit of the lens. 15. The system of claim 14, further comprising instructions for measuring currents on inner and outer final ground electrodes of the plurality of electrode pairs, and centering the beam by varying beam deflection until the currents on the inner and outer final ground electrodes are equal. 16. The system of claim 14, further comprising instructions for providing a collimated light sensor vertically centered within an exit aperture of the lens to determine beam centering. 17. The system of claim 11, wherein the at least one virtual knob controls a final deflection angle of the ion beam and constrains the position of the ion beam at the exit of the lens. 18. The system of claim 11, wherein the step of grading a deceleration of the ion beam further comprises calculating the energy of the beam's central ray trajectory (CRT) along a length of the lens. 19. The system of claim 11, wherein electrode voltages are assigned to the upper and lower electrode pairs such that voltages of outer electrodes of the plurality of upper and lower electrode pairs remain negative. |
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claims | 1. A collimating device for controlling a radiation field of an X-ray radiated from an X-ray radiator, the device comprising:a first plurality of collimating leaves;a second plurality of collimating leaves opposing the first plurality of collimating leaves;a laser beam generator configured to generate a laser beam which emanates between the first and second plurality of collimating leaves, the laser beam having an axis perpendicular to an axis of the radiated X-ray between the first and second plurality of collimating leaves;a detector configured to detect the laser beam;a memory configured to store position information of each leaf of the first and second plurality of collimating leaves when said each leaf is determined to intersect the laser beam based on the detection; anda controller configured to position said each leaf based on the position information to control the radiation field. 2. The device according to claim 1, further comprising:a reflector configured to reflect the laser beam generated by the laser beam generator so that the reflected laser beam emanates between the first and second plurality of collimating leaves. 3. The device according to claim 1, further comprising:a reflector configured to reflect the laser beam emanated between the first and second plurality of collimating leaves so that the reflected laser beam is detected by the detector. 4. The device according to claim 1, whereinthe memory stores the position information when the detector detects a predetermined percentage of the laser beam. 5. The device according to claim 1, further comprising:a compensation unit configured to compensate the position information, wherein the controller positions said each leaf based on the compensated position information. 6. The device according to claim 5, whereinthe compensation unit compensates the position information in accordance with an incident angle of the laser beam between the first and second plurality of collimating leaves. 7. The device according to claim 5, whereinthe memory is further configured to store the compensated position information. 8. The device according to claim 1, further comprising:a second memory configured to store compensation distance information for compensating the position information, wherein the compensation distance information is based on a distance caused by a gear engagement in a gear rotation when said each leaf is driven by a gear. 9. The device according to claim 8, whereinthe second memory stores first distance information and second distance information as the compensation distance information;the first distance information is used when said each leaf is driven to move by a first predetermined distance in a first direction; andthe second distance information is used when said each leaf is driven to move by a second predetermined distance in a second direction. 10. A collimating device for controlling a radiation field of an X-ray radiated from an X-ray radiator, the device comprising:a first plurality of collimating leaves;a second plurality of collimating leaves opposing the first plurality of collimating leaves;a laser beam generator configured to generate at least first and second laser beams, wherein the first laser beam extends alone a first axis to intersect the first plurality of collimating leaves and the second laser beam extends along a second axis to intersect the second plurality of collimating leaves, wherein the first and second axis are perpendicular to an axis of the radiated X-ray;a detector configured to detect the first and second laser beams;a memory configured to store first position information of each leaf of said first plurality of collimating leaves when each leaf of said first plurality of collimating leaves is determined to intersect the first laser beam based on the detection;said memory further configured to store second position information of each leaf of said second plurality of collimating leaves when each leaf of said second plurality of collimating leaves is determined to intersect the second laser beam based on the detection; anda controller configured to position said each leaf of said first plurality of collimating leaves based on the first position information and the each leaf of said second plurality of collimating leaves based on the second position information so as to control the radiation field. 11. The device according to claim 10, whereinthe laser beam generator generates a third laser beam which emanates between the first and second plurality of collimating leaves, the third laser beam having an axis perpendicular to an axis of the radiated X-ray between the first and second plurality of collimating leaves;the detector is further configured to detect the third laser beam;the memory is further configured to store third position information of each leaf of the first and second plurality of collimating leaves when said each leaf is determined to intersect the third laser beam based on the detection; andthe controller is configured to position said each leaf based on the third position information in addition to the first and second position information. 12. The device according to claim 10, whereinthe laser beam generator generates third and fourth laser beams which emanate between the first plurality of collimating leaves and the second plurality of collimating leaves, the third laser beam extends along a third axis to intersect the first plurality of collimating leaves and the fourth laser beam extends along a first axis to intersect the second plurality of collimating leaves, wherein the third and fourth axis are perpendicular to an axis of the radiated X-ray;the detector is further configured to detect the third and fourth laser beams;the memory is further configured to store the first position information when said each leaf of the first plurality of collimating leaves is positioned furthest from the second plurality of collimating leaves and determined to intersect the first laser beam with one side far from the second plurality of collimating leaves based on the detection;said memory further configured to store the second position information when said each leaf of the second plurality of collimating leaves is positioned furthest from the first plurality of collimating leaves and determined to intersect the second laser beam with one side furthest from the first plurality of collimating leaves based on the detection;said memory further configured to store third position information when said each leaf of said first plurality of collimating leaves is positioned closest to the second plurality of collimating leaves and determined to intersect the third laser beam with another side closest to the second plurality of collimating leaves based on the detection;said memory further configured to store fourth position information when said each leaf of said second plurality of collimating leaves is positioned closest to the first plurality of collimating leaves and determined to intersect the fourth laser beam with another side closest to the first collimating leaves based on the detection; andthe controller is configured to position said each leaf of said first plurality of collimating leaves based on the first and third position information and the said each leaf of said second plurality of collimating leaves based on the second and fourth position information. 13. The device according to claim 10, whereinthe laser beam generator generates a first group of laser beams including the first laser beam and a second group of laser beams including the second laser beam as the plurality of laser beams, the first group of laser beams extends along a third axis to intersect the first plurality of collimating leaves and the second group of laser beams extends along a fourth axis to intersect the second plurality of collimating leaves, wherein the third and fourth axis are perpendicular to an axis of the radiated X-ray;the detector is further configured to detect the first and second groups of laser beams;the memory configured to store first information of positions of each leaf of said first plurality of collimating leaves where said each leaf of said first plurality of collimating leaves is determined to intersect the first group of laser beams with one side close to the second plurality of collimating leaves based on the detection;said memory further configured to store second information of positions of each leaf of said second plurality of collimating leaves where said each leaf of said second plurality of collimating leaves is determined to intersect the second group of laser beams with one side close to the first plurality of collimating leaves based on the detection; anda controller configured to position said each leaf of said first plurality of collimating leaves based on the first information and said each leaf of said second plurality of collimating leaves based on the second information. 14. A radiotherapy apparatus for radiating an X-ray and concentrating the X-ray towards a predetermined part of an object, the apparatus comprising:an X-ray radiator configured to radiate the X-ray; anda collimator configured to control a radiation field of the X-ray radiated by the X-ray radiator, including:a first plurality of collimating leaves;a second plurality of collimating leaves opposing the first plurality of collimating leaves;a laser beam generator configured to generate a laser beam which emanates between the first and second plurality of collimating leaves, the laser beam having an axis perpendicular to an axis of the radiated X-ray between the first and second plurality of collimating leaves;a detector configured to detect the laser beam;a memory configured to store position information of each leaf of the first and second plurality of collimating leaves when said each leaf is determined to intersect the laser beam based on the detection; anda controller configured to position said each leaf based on the position information. 15. The apparatus according to claim 14, further comprising:a display configured to display information of the collimator. 16. The apparatus according to claim 14, whereinthe laser beam generator is rendered operative when said apparatus is powered. 17. The apparatus according to claim 14, whereinthe laser beam generator is rendered operative at predetermined intervals. 18. The apparatus according to claim 14, further comprising an input unit configured to input an instruction, wherein the laser beam generator is rendered operative in response to the instruction. 19. A method of positioning collimating leaves for use in a collimator which controls a radiation field of an X-ray radiated from an X-ray radiator, whereinthe collimating leaves include a first and second plurality of collimating leaves, said plurality of second collimating leaves opposing the first plurality of collimating leaves, the method comprising:generating a laser beam which emanates between the first and second plurality of collimating leaves, the laser beam having an axis perpendicular to an axis of the radiated X-ray between the first and second plurality of collimating leaves;detecting the laser beam;storing position information of each leaf of the first and second plurality of collimating leaves when said each leaf is determined to intersect the laser beam based on the detection; andpositioning said each leaf based on the position information to control the radiation field. 20. A method of positioning collimating leaves for use in a collimator which controls a radiation field of an X-ray radiated from an X-ray radiator, whereinthe collimating leaves include a first and second plurality of collimating leaves, the plurality of second collimating leaves opposing the first plurality of collimating leaves, the method comprising:generating at least first and second laser beams, wherein the first laser beam extends along a first axis to intersect the first plurality of collimating leaves and the second laser beam extends along a second axis to intersect the second plurality of collimating leaves, wherein the first and second axis are perpendicular to an axis of the radiated X-ray;detecting the first and second laser beams;storing first position information of each leaf of said first plurality of collimating leaves when said each leaf of said first plurality of collimating leaves is determined to intersect the first laser beam based on the detection and storing second position information when each leaf of said second plurality of collimating leaves is determined to intersect the second laser beam based on the detection; andpositioning said each leaf of said first plurality of collimating leaves based on the first position information and said each leaf of said second plurality of collimating leaves based on the second position information to control the radiation field. |
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summary | ||
051587424 | abstract | A reactor steam isolation cooling system includes a containment building surrounding a reactor pressure vessel having a reactor core for generating reactor steam. An isolation pool is disposed outside the containment building and is vented to the atmosphere. An isolation condenser includes a plurality of heat pipes collectively defining at one end thereof a condenser assembly disposed outside the containment building and inside the isolation pool, and at an opposite end thereof an evaporator assembly extending inside the containment building. Reactor steam is selectively channeled to the evaporator assembly for heating a working liquid therein and condensing the reactor steam to form reactor condensate for return to the pressure vessel. The working liquid is vaporized in the evaporator assembly and flows to the condenser assembly wherein it releases heat into the isolation pool with the working condensate therefrom returning to the evaporator assembly. |
claims | 1. A storage apparatus with gamma radiation shielding for spent nuclear fuel comprising:a fuel basket comprising a plurality of elongated fuel storage tubes extending along a longitudinal axis, each of the tubes defining a cell configured to hold a nuclear fuel assembly;a plurality of gamma radiation attenuation inserts each one of which is nested inside a respective cell of at least some of the storage tubes of the fuel basket;each radiation attenuation insert comprising a longitudinally elongated tubular body including an open top end, a bottom end, and plurality of sidewalls extending between the ends;wherein the radiation attenuation insert is composed of a dense material operable to block gamma radiation;each radiation attenuation insert including a downwardly open flow cutout formed in each sidewall of the insert at its bottom end;each storage tube containing a radiation attenuation insert including a downwardly open flow cutout formed in each sidewall of the tube at its bottom end, the flow cutouts in the tube each being laterally aligned with and overlapping a corresponding one of the flow cutouts of the radiation attenuation insert;an elastically deformable spring angle clip affixed to each sidewall of each radiation attenuation insert, each angle clip protruding laterally outwards and downwards from the sidewall into the flow cutout of the radiation attenuation insert and engaging a corresponding locking edge formed by the flow cutout on its respective storage tube when the insert is fully inserted into the storage tube;wherein the flow cutouts of the storage tubes and radiation attenuation insert remain open after being engaged by one of the angle clips such that air or gas can pass through the flow cutouts. 2. The apparatus according to claim 1, wherein the radiation attenuation insert is formed of a non-ferrous material having a density greater than 8.0 grams/cubic centimeter. 3. The apparatus according to claim 2, wherein the non-ferrous material is selected from the group consisting of copper, aluminum bronze, Admiralty brass, and copper-nickel alloy. 4. The apparatus according to claim 2, wherein the non-ferrous material is copper. 5. The apparatus according to claim 1, further comprising a nuclear fuel assembly disposed in a longitudinally-extending internal chamber of a first insert of the plurality of radiation attenuation inserts, the first insert arranged in a gap between cell walls of a first tube of the plurality of tubes and the fuel assembly. 6. The apparatus according to claim 1, wherein the radiation attenuation inserts have a height substantially coextensive with heights of the storage tubes. 7. The apparatus according to claim 6, wherein the radiation attenuation inserts and the storage tubes are affixed to and supported by a common baseplate. 8. The apparatus according to claim 1, further comprising an elastically deformable locking member affixed to each sidewall of each radiation attenuation insert proximate to the bottom end of the insert, the locking member including an outwardly projecting locking protrusion configured to detachably engage a corresponding locking edge formed proximate to a bottom end of the storage tube in which the insert is inserted. 9. The apparatus according to claim 8, wherein each locking member has an undulating body formed of spring steel including an upper fixed end portion rigidly attached to an exterior surface of the radiation attenuation insert sidewall, and a resiliently deformable and cantilevered lower free-end locking portion which defines the locking protrusion. 10. The apparatus according to claim 9, wherein the locking protrusion has a triangular shape. 11. The apparatus according to claim 8, further comprising an outwardly flared and angled securement flange extending upwards from the top end of the sidewalls of each radiation attenuation insert sidewalls, the securement flanges arranged and configured to engage a top end of a respective storage tube in which each insert is inserted. 12. The apparatus according to claim 6, wherein the plurality of storage tubes includes peripheral outboard tubes forming a perimeter of the fuel basket and inboard storage tubes disposed in a central region of the fuel basket inside the outboard tubes, and wherein the radiation attenuation inserts are disposed in some of the outboard tubes. 13. The apparatus according to claim 1, wherein all of the peripheral outboard tubes contain a radiation attenuation insert forming a continuous barrier against radiation emanating in a lateral direction from the fuel basket. 14. A storage apparatus with gamma radiation shielding for spent nuclear fuel comprising:a canister comprising a baseplate and an elongated cylindrical shell defining an internal cavity;a fuel basket disposed in the internal cavity, the fuel basket comprising a plurality of metal fuel storage tubes extending upwards from the baseplate along a longitudinal axis and each defining a fuel storage cell;a gamma radiation attenuation insert nested inside a first cell of a first tube of the fuel basket;the radiation attenuation insert comprising a longitudinally elongated cuboid body including open top and bottom ends, and a plurality of sidewalls extending between the ends;an upper securement feature of the radiation attenuation insert engaging a top end of the first tube; andan elastically deformable lower securement feature on the radiation attenuation insert engaging a bottom end portion of the first tube and configured to detachably affix the radiation attenuation insert to the first tube;wherein the radiation attenuation insert is composed of a dense material operable to block gamma radiation;wherein the radiation attenuation insert further includes a downwardly open flow cutout formed in each sidewall of the insert at its bottom end;wherein the first tube also includes a downwardly open flow cutout laterally aligned with the flow cutout of the radiation attenuation insert;wherein the lower securement feature comprises an elastically deformable spring angle clip affixed to one sidewall of the radiation attenuation insert, the angle clip protruding downwards from the one sidewall into the flow cutout of the radiation attenuation insert and having a locking protrusion engaging a corresponding locking edge formed on a corresponding downwardly open flow cutout of the first tube when the insert is fully inserted into the first tube;wherein the flow cutouts of the first tube and radiation attenuation insert remain open after being engaged by the spring angle clip such that air or gas can pass through the flow cutouts. 15. The apparatus according to claim 14, wherein the upper securement feature comprises an angled securement flange flared outwards from the one sidewall of the radiation attenuation insert and engaging a top edge of the first tube. 16. The apparatus according to claim 14, wherein the radiation attenuation insert has a height substantially coextensive with the height of the first tube and is supported at its bottom end by the baseplate of the canister. 17. The apparatus according to claim 14, wherein the radiation attenuation insert is formed of a non-ferrous material having a density of at least 7.0 grams/cubic centimeter. |
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summary | ||
summary | ||
039379710 | claims | 1. A method of making a focused shield for use in connection with a radiation therapy machine or the like, said method comprising the steps of: forming a shield blank having a planar top side and an opposite, rounded bottom side; forming a shield blank holding fixture having a rounded shield blank supporting surface provided with a radius of curvature complementary to the curvature of the bottom side of said shield blank; selectively placing on the top side of said shield blank an outline having a configuration corresponding to a predetermined area of a patient to be exposed to a field of radiation; placing said fixture on a cutting table of a band saw or the like; positioning said shield blank on said fixture with the rounded bottom side of said shield blank resting on said rounded surface of said fixture; and cutting said shield blank along said outline with said saw or the like while maintaining the shield blank in contact with said rounded surface to provide a focused shield having a bevel-walled aperture corresponding to said predetermined area. a focused shield blank having a planar top side and a rounded bottom side opposite said top side; a shield blank holding fixture having a rounded shield blank supporting surface provided with a radius of curvature complementary to the curvature of the bottom side of said shield blank; and means for placing at a predetermined location on the top side of said shield blank an outline representing a required boundary of a field of radiation and having a configuration corresponding to a predetermined area of a patient to be exposed to a field of radiation whereby a focused shield having a bevel-walled aperture with a transverse configuration corresponding to that of said predetermined area is provided when said shield blank is cut along said outline by a band saw or the like while maintaining the bottom side of said shield blank in contact with the rounded surface of said fixture. a generally rectangular body having a planar top side and a rounded bottom side opposite said top side; and an aperture extending through said body from said top side to said bottom side and having a transverse irregular configuration corresponding to that of a predetermined area of a patient to be exposed to a field of radiation, said aperture being selectively located in said body and having beveled sidewalls for permitting those radiation rays in alignment with said aperture to enter the same and to pass therethrough unimpeded when said focused shield is operably inserted in a radiation therapy machine. 2. A method as claimed in claim 1, wherein said shield blank forming step includes shaping said bottom side to present a convexly rounded contour; and wherein the step of forming said shield blank holding fixture includes shaping said rounded surface to present a bowl-shaped concavity. 3. A method as claimed in claim 2, wherein said shield blank forming step includes premolding said shield blank in a rectangular shape having said planar top side and said convex bottom side. 4. A method as claimed in claim 1, wherein said step of placing said outline on said blank includes the step of drawing the desired radiation field boundary on paper or the like for placement on said shield blank. 5. A method as claimed in claim 4, wherein said step of placing said outline on said shield blank includes the step of indicating on said paper or the like the required location of the center of a radiation beam relative to said radiation field when the focused shield is properly inserted in a radiation therapy machine. 6. A method as claimed in claim 5, wherein said placement step further includes the step of positioning said paper or the like on said shield blank such that the indicated radiation beam center is superimposed over the center of the shield blank and is transversely centered relative to a radiation beam when said focused shield is inserted in a radiation therapy machine. 7. A method as claimed in claim 6; and the step of trimming the outer edges of said focused shield while the same is in said holding fixture to present a focused shield having beveled outer edges in angular alignment with the periphery of said radiation beam, said trimming step including reducing said focused shield to a size in which the perimeter of said top side encloses an area at least equal to that encompassed by the periphery of a radiation beam at the point the latter strikes said focused shield. 8. Apparatus for making a focused shield for use in connection with a radiation therapy machine or the like, said apparatus including: 9. Apparatus as claimed in claim 8, wherein said rounded bottom side has a convex contour, and wherein said rounded surface of said fixture presents a bowl-shaped concavity. 10. Apparatus as claimed in claim 8, wherein said outline placement means includes a piece of sheet material on which said outline is drawn, said outline displacement means further including means for retaining said sheet material on said top wall during the cutting of said aperture in said shield blank. 11. Apparatus as claimed in claim 10, wherein said sheet material has indicated thereon a marking representing the location of the center of a radiation beam when said focused shield is operably inserted in a radiation therapy machine, said outline being positioned on said sheet material at a predetermined location relative to said marking. 12. Apparatus as claimed in claim 11, wherein said sheet material is positioned on said top wall with said center marking on said sheet material superimposed over the center of said shield blank. 13. Apparatus as claimed in claim 12, wherein said sheet material is of a rectangular size having an area at least equal to that encompassed by the periphery of said radiation beam at the point the latter strikes said focused shield when the same is inserted in said therapy machine. 14. A focused shield for use in connection with a radiation therapy machine or the like, said focused shield comprising: 15. A focused shield as claimed in claim 14, wherein each aperture sidewall is in substantial parallelism with the path of travel of those radiation rays adjacent thereto. 16. A focused shield as claimed in claim 15, wherein said aperture sidewalls diverge as said bottom side is approached. 17. A focused shield as claimed in claim 14, wherein said body is of sufficient length and breadth to at least span the transverse width of a radiation beam at the point the latter strikes said focused shield when the same is operably inserted in said therapy machine. |
description | This application is a divisional of U.S. application Ser. No. 14/663,229 filed on Mar. 19, 15, which claims the benefit of priority under 35 U.S.C. § 365(c) and § 120 as a continuation of PCT/EP2013/074420 filed on Nov. 21, 2013, which claims the benefit of priority to European Patent Application No.: EP 121 961 95.7 filed Dec. 7, 2012. The full contents of the International Application are incorporated herein by reference. A portion of the disclosure of this patent document contains material which is subject to copyright protection. This patent document may show and/or describe matter which is or may become trade dress of the owner. The copyright and trade dress owner has no objection to the facsimile reproduction by anyone of the patent disclosure as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright and trade dress rights whatsoever. The disclosure relates to a test disc and to a test system having a test disc for testing the seal of gloves which are installed in ports of an isolator. The glove forms with the isolator a region which is separated spatially from the surroundings, and a test system which comprises a multiplicity of test discs and a method for comprehensive evaluation of the acquired data and their use serve to increase the safety, reliability and productivity of systems with such regions. Isolators are used in various industrial fields, for example in the chemical, pharmaceutical and nuclear industries but also in medicine in order to produce a volume which is separated from the surroundings and in which selected substances can be stored and manipulated, for example subjected to chemical reaction, wherein the transportation of material is prevented in (at least) one direction (from the isolator to the surroundings or else from the surroundings to the isolator). For instance, isolators used in the nuclear industry may be referred to as glove boxes, wherein a technician may reach into the box using a sealed glove to manipulate the contents therein without the atmosphere/material within the box leaking. The prevention of the transportation of material from the isolator into the surroundings is necessary, for example, if radio-active substances or powderous chemicals are stored and handled in the isolator. Isolators in the nuclear field (i.e., glove boxes) are operated here under a high underpressure in order to prevent radio-active substances from escaping into the surroundings under all circumstances. On the other hand, in the case of chemicals a low underpressure compared to the atmospheric pressure is sufficient. In contrast, a transportation of material from the surroundings into the isolator must be prevented, in particular in the case of isolators for aseptic pharmaceutical processes, in order to avoid contamination of the isolator volume or interior with germs from the surroundings. A relatively low excess pressure compared to the atmospheric pressure is already sufficient for this. Handling of the substances in the isolator is preferably carried out in both cases using remote-controlled mechanical manipulators. However, there are a multiplicity of processes in which such automation is not possible, or is possible only at unacceptably high cost, with the result that it is not possible to dispense with human beings as the operator. The access of the operator to the interior of the isolator is carried out here by means of breakthroughs in the wall of the isolator, referred to as ports, which are equipped with flexible gloves which are clamped in a hermetically sealed fashion and are composed of a sufficiently resistant material. The gloves can, on the one hand, ensure the seal (integrity) of the isolator volume, but on the other hand they can also give the operator the necessary freedom of movement in order to carry out the necessary manipulations in the interior. Any disruption of the integrity of the isolator entails economic or even health risks. If, for example, germs penetrate the isolator from the surroundings, an entire batch of aseptically manufactured pharmaceutical products may become unusable. If, in the inverse case, toxic substances escape from the isolator, they can endanger the operator and the surroundings. For this reason, such disruptions must be prevented in all cases and if they nevertheless occur despite all counter-measures, they must be detected and eliminated immediately. Internationally recognized prescriptions such as, for example, the Guideline “Guidance for Industry—Sterile Drug Products Produced by Aseptic Processing—Current Good Manufacturing Practice” of the U.S. Food and Drug Administration (FDA), which is addressed specifically to the pharmaceutical industry and was updated in 2004, therefore recommends implementation of a comprehensive preventive maintenance programme. Gloves, seals, sealing means and also transfer systems should be subjected to daily testing. In addition, the actual period of use of all the critical components should be carefully logged in writing in order to ensure prompt replacement before the expiry of the permissible period of use. The FDA Guideline pays particular attention to gloves. Damaged gloves or sleeves form contamination channels and constitute a critical breach of the integrity of the isolator. A preventive maintenance programme is recommended, said maintenance programme already starting with the selection of a particularly durable glove material and a data-based definition of the times of replacement of the glove. Whenever the gloves are used, they should be inspected visually for macroscopic defects. Physical integrity tests should be carried out routinely. The monitoring and maintenance programme should identify any glove with compromised integrity and initiate its replacement. The FDA Guideline refers to the risk of a microbial migration through microscopic holes in gloves and to the lack of highly sensitive integrity tests for gloves and therefore recommends careful hygienic handling of the interior of the glove and the additional wearing of thin disposable gloves by the operator. Within the territory of the EU, comparable regulations apply which were updated in 2008 and which are laid down in a German translation in the “Anhang 1 zum EG-Leitfaden der Guten Herstellungspraxis—Herstellung sterile Arzneimittel” [Annex 1 to the EC Guideline for Good Manufacturing Practice—Manufacturer of Sterile Medicines]. However, the recommendations contained therein regarding isolators do not go beyond the prescriptions of the FDA Guideline, and the latter can therefore be considered to be a generally valid standard. In order to meet the prescriptions of the FDA Guideline, a multiplicity of measures (handling instructions, measurement method and testing methods as well as prescriptions regarding comprehensive documentation) which are to be implemented in combination have already been developed and described in the literature. However, the known measures have considerable disadvantages: The working sequences are very complex and require frequent and time-consuming training of personnel who have to be enabled to carry out a multiplicity of manual steps in the predefined sequence with constant quality at all times. The precondition for this are highly motivated employees who act on their own initiative and follow the operating instructions precisely at all times, even when there is no supervision and when deadlines are pressing. Nevertheless, infringements of the regulations due to negligence or unintention are unavoidable. Many data items with a safety-relevant character, in particular the running period of use and the conditions of use for each individual glove (glove history) are not detected since until now this would have been possible only by means of documentation of a manual kind, which is therefore very time-consuming and susceptible to errors. The safety is instead ensured by shortening the glove-changing intervals. The previously developed methods for testing the integrity of isolators, in particular of the gloves installed in the glove ports, are very time-consuming and laborious, irrespective of whether the testing is routine testing or unscheduled owing to an incident. In many methods, the gloves must be removed for testing, tested in a test device and then installed again. The high degree of expenditure in terms of time and work during the application of these methods results in a series of further disadvantages: the methods cannot be integrated into ongoing production sequences. When the gloves are removed and installed again, they can be damaged. Damage which only occurs during the reinstallation after the testing, and resulting leaks, cannot be detected. Since the sequence of the gloves is generally not monitored during the removal and reinstallation, it is not readily possible to produce a glove history with these methods. Although methods which permit testing of gloves in the installed state have already been described, the equipment which has been available for these purposes until now is cumbersome and heavy and accordingly difficult to handle. For example, DE102004030766A1 describes a computer-supported test system and test method for measuring the seal of gloves which are installed in isolators of pharmaceutical systems, in which system and method a voluminous measurement chamber which covers the isolator port to be tested with the installed glove over a large area is coupled in a gas-tight fashion to the outer wall of the isolator in order to test the integrity. The measurement chamber is equipped with pressure and temperature measuring devices and can optionally be operated with an underpressure or with an excess pressure. The measured values of the pressure and temperature are fed to a central processor unit which evaluates the pressure profile as a function of the time. If the change in pressure during a predefined measuring time is below a defined limiting value, the glove is classified as being sealed. During the testing, the glove cannot be used for manipulations, and the testing is therefore to be carried out outside ongoing operation. The central processor unit can be connected to a plurality of measurement chambers allowing the simultaneous testing of a plurality of gloves, only of one per chamber. A particular advantage is considered by the applicant to be the pressure measurement directly in the measurement chamber (in contrast to previously known devices where measuring devices which are located at a distance are connected via pressure hoses which are susceptible to faults). The computer-assisted evaluation permits the quantitative determination of leakage rates, and each measurement chamber and each glove are uniquely identifiable. A first disadvantage of this solution is the use of relatively heavy, large measurement chambers whose own integrity, that is to say the gas-tight coupling to the outer wall of the isolator, has to be firstly ensured at high cost. In addition, as a result of their intrinsic weight they load the isolator wall very unevenly (tensile stress in the upper part, compressive stress in the lower part) and therefore can themselves give rise to integrity problems, particularly leakages in the region of the seals of the isolator port. The time-consuming coupling and uncoupling of the measurement chamber leads also to productivity losses since not only during the measurement but also during these equipping times the port cannot be used for its intended purpose. A second disadvantage is that although individual identification elements are provided for each measurement chamber and each glove, there is no assignment to the ports. It is therefore not possible to detect and document the position of the individual gloves automatically. In order to be able to trace back the production processes for which a glove is used and to track with which chemicals it has been in contact and for how long, manual documentation would have to be carried out to determine at which isolator ports the glove was installed during its previous period of use, which is impractical. It is therefore virtually impossible to define individually the residual period of use of the glove on the basis of its actual loading with chemicals. Only fixed intervals for the changing of the glove are practical. Even if different, process-dependent periods of use are known for the gloves from reliable experiments, for safety reasons the shortest change interval is always selected, which gives rise to further productivity losses owing to the expenditure of time for the premature changing of a glove and to higher costs for the purchase of gloves. Solutions are already known which eliminate the first disadvantage of the above solution by replacing the cumbersome measurement chambers which have to be coupled from the outside to the isolator by easy-to-handle, compact test discs which are inserted directly into an isolator port and close it off in a gas-tight fashion by expansion of a sealing element. Such a test disc is described in U.S. Pat. No. 6,810,715 B2. It comprises a base plate, a cover plate and a sealing device, for example a plate made of neoprene, located between them. A bore in the centre of the three plates accommodates a screw mechanism with which the base plate and cover plate are drawn one toward the other and in the process they press the neoprene plate together, which consequently expands in the radial direction and closes off the port with the installed glove in a gas-tight fashion. Two further bores serve to accommodate a pressure sensor and an inlet valve which is connected to a pressure bottle and/or a pump. The somewhat complicated manufacture of the seal-forming connection of the isolator port and the test disc by manual actuation of the screw mechanism and the production of the excess pressure which is necessary for testing by means of the connection to an external pressure bottle and/or pump are somewhat disadvantageous. Attempts have been made to address some of these shortcomings, such as DE 10 145 597 A1 and DE 20 115 261 U1, which disclose methods for testing the seal on a working glove and a sealing disc which permit pressure profiles to be measured and stored in a microprocessor, and the values to be read out via an interface. There remains a need for a more comprehensive method for testing glove seals on isolators which reduces the amount of time and effort involved and increases accuracy to prevent leaks and extend glove life. The present application discloses a test disc, a test system and a method for testing the seal of a glove which is installed in a port of an isolator. The application also describes a glove and an isolator for use with the test system. An object of the invention is to eliminate the disadvantages of the prior art and to make available a test disc, a test system or a method for operating the test system with which a history of process data relating to the glove can be produced and a prediction about an anticipated residual service life of the glove can be made, wherein system safety and process safety are to be improved and a period of use of the glove is to be extended. In one aspect of the present application, a test disc for testing the seal of a glove which is installed in a particular port of an isolator is provided. The test disc has a seal for connecting to the port in a hermetically sealed fashion, a pressure-measuring device, a microprocessor, a memory and a data interface for transmission of information. The test disc further includes a reading device configured to determine the identity of the particular isolator port. A glove has an open end sized to be sealed between the test disc and port by the seal so as to define an internal glove volume which can be placed under excess pressure. The pressure-measuring device of the test disc is arranged to measure the glove volume pressure, and the microprocessor and memory are configured to record and store a glove volume pressure profile. The glove further has a first identification element which can be read by the reading device of the test disc to determine a glove identity, and the microprocessor being programmed to store both the identity of the glove and the identity of the particular isolator port in the memory. The test disc seal is preferably a radially-expanding sealing device and the test disc further includes a first micro-air pump connected to the test disc to expand the sealing device. In addition, the test disc may further include a second micro-air pump with a pre-filter connected to the test disc to fill the glove volume. An electrical energy source in the form of an accumulator may be mounted to the test disc. The reading device preferably has a reader selected from the group consisting of: an RFID module, a CCD sensor and a laser sensor. The test disc microprocessor may have a control device for automatically setting a pressure in the glove volume. The test disc data interface desirably has a wireless transmitter such that the glove pressure profile and information regarding the glove and port identities may be transmitted wirelessly to an evaluation unit of an external test system. For example, the wireless transmitter of the data interface is selected from the group consisting of: a WiFi module, an W-LAN module, a Bluetooth module or a radio-based transceiver module. In accordance with another aspect of the application, a test system has at least one of the test discs as well as an evaluation unit comprising a memory unit and an output unit connected to a user database. The glove pressure profile can be assigned with the identification data precisely to one glove and one port, and the evaluation of a state and/or an estimate of a residual period of use of the glove are/is carried out. The evaluation unit may have a WiFi module, a W-LAN module, a Bluetooth module or some other radio-based transceiver module. The test system enables process-related data about the use of the glove to be stored in the evaluation unit and taken into account during the evaluation. The test system preferably has a multiplicity of test discs for simultaneously testing a plurality of gloves, wherein the test discs communicate with the evaluation unit. In accordance with a further aspect of the application, a glove for a test system as described above is adapted to be inserted in a hermetically sealed fashion into the port of an isolator, wherein the glove has an identification element for reading out by the reading device of the test system. A still further aspect is an isolator for the use of the test disc, test system and glove as described above has at least one port into which the glove can be inserted in a hermetically sealed fashion. The test disc may be connected in a sealed fashion to the port, and the isolator has an identification element for each port. A method for evaluating the seal of a glove having a test disc is also disclosed, and preferably uses the test system as described above. In the method, the pressure profile is detected over a predefined time period and information data about the glove and the port is assigned to the pressure profile. Subsequently, a pressure drop, which is compared with a limiting value, is determined from the pressure profile. Preferably, historical data, in particular process data, is taken into account during the evaluation of the state, wherein in particular a residual period of use of the glove is estimated. Moreover, the pressure profiles for a multiplicity of gloves are desirably received simultaneously from a plurality of test discs and processed, wherein the respective pressure profiles are assigned unambiguously to a corresponding glove and port. Removal of the test disc from the port is prevented if a defect in the glove is detected. In the method, a pressure profile which is recorded for a specific glove at a relatively early point in time is compared with a pressure profile which is recorded for this glove at a relatively late point in time, and this comparison is taken into account for the estimation of a residual period of use. By providing identification elements on the glove and on the port, the reading device can perform uniquely defined identification not only of the glove but also of the port and can compare corresponding identification data directly with a recorded pressure profile. The identification data of the port then results in a reference to the processes which have expired in the surroundings of the glove, wherein a uniquely defined and traceable assignment is made by means of the identification of the glove. It is therefore possible, for example, to store a history for each glove and to permanently block a glove once it has been detected as faulty. Insertion of the glove at another port is also reliably detected by means of the test disc or by means of the test system. By means of the test system according to the invention, the data which is acquired, in particular, simultaneously for a plurality of gloves using a multiplicity of the test discs according to the invention can be buffered. This data can be subjected to initial evaluation, where necessary immediate measures can be initiated in the event of a leak being detected, and the data including the results of the initial evaluation can be stored in a database. Manual documentation in order to ensure the traceability as far as the specific port and glove is replaced by automatic solutions, and therefore the efficiency of the human/machine interface is increased and its susceptibility to errors is reduced. As a result, an expanded evaluation method in which the information which is acquired using the totality of test discs and test system is connected to process information of the user in such a way that an increase in the system safety and reliability as well as optimum utilization of the service life of process means, in particular of the gloves, is achieved. The present application provides a test system and a corresponding method for testing the seal of a glove which is installed in a port of an isolator, including a test disc which can be connected in a hermetically sealed fashion to the port. Various terms are described below. The term “region separated spatially from the surroundings” includes any desired designs of what are referred to as isolators and barrier systems (Restricted Area Barrier Systems—RABS) in which the interior is separated completely from the surroundings (in the case of an isolator) or partially (in the case of RABS as half-open systems), and a permanent difference in pressure is maintained between the exterior (surroundings) and the separated interior. This permanent difference in pressure prevents a direct (unfiltered) transportation of material in the direction of the region with the relatively high pressure. Depending on the setting in the difference in pressure, this relates to the transportation of material from the separated region to the surroundings or else from the surroundings to the separated region. In the case of a RABS, the difference in pressure is selected in such a way that a permanent laminar flow (expulsion flow) comes about in the opposing direction. In the case of an isolator, the transportation of material in the opposing direction is also prevented, with the result that the atmosphere in its interior can also experience turbulent movement. As in the “Annex 1 to the EC Guideline for Good Manufacturing Practice—Manufacturer of Sterile Medicines” updated in 2008, the present application does not differentiate between the isolators and RABS. Instead, the term “isolator” is used as a generic term. Corresponding systems in nuclear technology, usually referred to as glove boxes are also to be subsumed under this. The walls of the isolator generally have ports in the form of breakthroughs which permit manipulations to be carried out in its interior by an operator located in the exterior. However, the ports must not adversely affect the separation between the interior and the exterior and are therefore usually equipped with impermeable protective gloves which are inserted in a gas-tight fashion and have long sleeves. For manipulations which require a particularly large degree of freedom of movement, the ports can be widened and equipped, for example, with half-suits which are used in a gas-tight fashion. The term “glove” is used as a generic term for such protective gloves and half-suits. A leak is understood to be a defect in the separation between the interior of the isolator and the exterior, which defect permits a transportation path in the prohibited direction and therefore the entry of material-bound contamination from the surroundings into the interior or from the interior into the surroundings. A leak is also referred to as an infringement of the integrity or seal of the isolator. In the illustrated embodiment, FIG. 1 shows a test disc 1. An on/off switch 3, a start/stop pushbutton key 4, an inflation valve 5 for filling a glove volume, a pre-filter 6 and an LCD display 7 are arranged on a front side of the test disc 1. The test disc is surrounded in a radially circumferential fashion by a sealing device 2 which is embodied as a hose. Inflating the hose causes the latter to expand outward in a direction which is symbolized by arrows. FIG. 1 therefore illustrates a test disc 1 which can be inserted into a breakthrough which forms the port, and forms a seal from the inside to the outside. FIG. 2 shows a schematic internal view of the test disc 1 with the components arranged therein. These include a pressure sensor 8 for detecting a pressure in the glove volume, a pressure measuring device with a microprocessor 9 and a pressure sensor for detecting the pressure in the sealing device 2. In addition, a valve for inflating the sealing device 2 via a first micro-air pump 12 is provided. A second micro-air pump 13 serves to inflate the glove volume. An RFID module 15 is used as a reading device for reading out identification elements of the glove and of the port, wherein an interface with a WiFi module 14 is provided for transmitting data to an evaluation unit. An energy source 16 serves to supply energy to the individual components (FIG. 3b). FIGS. 3a and 3b illustrate an embodiment of the test disc 1′ which, in contrast to the embodiment according to FIGS. 1 and 2, is embodied as a test disc which forms a seal from the outside to the inside. Identical components are provided here with the same reference numerals, and corresponding components have a dashed reference numeral. In contrast to the test disc 1 which forms a seal from the inside to the outside, as illustrated in FIGS. 1 and 2, the test disc 1′ which forms a seal from the outside to the inside has an extension in the form of a support ring 17, wherein the sealing device 2′ which is formed by a hose is arranged on a radial inner side of the support ring 17. In order to secure the sealing device 2′ more firmly, a groove is formed here on the inside. A direction of expansion is symbolized in turn by arrows. During installation at a port of an isolator, the test disc 1′ engages over an attachment connector 18 of the port with the support ring 17. As a result of pressure being applied to the sealing device 2′, the latter expands radially inwards and therefore comes to bear from the outside on the attachment connector 18 of the port. This ensures a secure seal. Otherwise, the design of the test disc 1′ which forms a seal from the outside to the inside corresponds to the design of the test disc 1 which forms a seal from the inside to the outside. FIG. 4 illustrates an embodiment of the test system with a multiplicity of test discs 1. The test discs are connected via a wireless connection to an evaluation unit 21 which is embodied as an evaluation computer. The evaluation unit 21 has access here to a database 22 of the user in which, for example, historical data for every glove, material properties and/or process-related data are stored. FIG. 5 shows a spatial illustration of a rear side of the test disc 1′. Here, the energy source 16 which is embodied as an accumulator is arranged centrally on the rear side. As long as the test disc is not installed at a port, simple access or replacement of the energy source is therefore possible. Exemplary Embodiment 1 A test of the seal of the gloves installed in the ports of the isolator of a pharmaceutical system is to be carried out. The isolator volume is at atmospheric pressure during the test. In good time before the test it is ensured that all the ports have a uniquely defined identification element. RFID elements are selected as the identification element, said elements being let irreversibly into a bore at the edge of the port without compromising the integrity of the isolator volume. As a result of this one-time marking, the ports can be identified unambiguously during all the tests which occur during their period of use. In this exemplary embodiment, the gloves can already be equipped by the manufacturer with RFID elements on a standard basis and can therefore also be identified unambiguously. Other identification elements (barcodes, engraving, impressed numbers) can also be used, but they give rise to increased expenditure during evaluation. A sufficient number of test discs which are matched to the shape and size of the ports are also made available in good time before the testing. The shape of the ports permits the use of a test disc 1 which forms the seal from the inside to the outside, with the result that this embodiment of the test disc is selected. The test disc 1 is inserted into the isolator port. In order to activate the test disc, the on/off switch 3 is actuated. Furthermore, the LCD display 7 is switched on with the actuation of the start/stop switch 4, said LCD display 7 transmitting user instructions, fault messages and warning signals to the operator and displaying the state of charge of the energy source 16 and the pressure, measured by the pressure sensor 8, in the volume to be tested. In addition, the micro-air pump 12 is switched on, said micro-air pump 12 inflating the inflatable hose 2 which functions as a seal device and causing it to expand. The expansion device is characterized in FIG. 1 by arrows. The pressure sensor 10 measures the rising pressure in the hose 2 and switches off the micro-air pump 12 when a preset target pressure is reached. The inflated hose closes the port so that the glove and the test disc 1 form a glove volume which is closed off in a gas-tight fashion. The described sealing process lasts approximately 30 seconds. During the entire test, the pressure sensor 10 continuously monitors the pressure in the hose 12 and in the event of a preset minimum pressure being undershot it pumps said hose 12 back again to the target pressure. The pressure in the glove volume, closed off in a gas-tight fashion, between the test disc and the glove is monitored by the pressure sensor 8 during the entire subsequent test process and is recorded by the microprocessor 9 of the pressure-measuring device. Before the test process can be started, the compressed air supply present at the isolator is connected to the inflation valve 5, embodied as a handle, for the glove. Alternatively, the handle and inflation valve can also be embodied as stand-alone elements. In this context, the inflation valve can be let in, for example flush with a front side of the test disc. Via the inflation valve 5, the glove volume which is closed off in a gas-tight fashion is firstly subjected to an excess pressure which is below the actual test pressure (initial inflation). If the preset target pressure of the initial inflation is reached, the pressure sensor 8 causes the inflation valve 5 to close and therefore separates it from the outer compressed air supply. For the purpose of fine setting of the preset test pressure, it now brings about the activation of the micro-air pump 13, which supplies the glove volume which is closed off in a gas-tight fashion with contamination-free air which is cleaned by the pre-filter 6. When the precise test pressure is reached, the pressure sensor 8 switches the micro-air pump 13 off. This two-stage inflation process lasts approximately 30-60 seconds. The inflation pressure can also take place in a single stage, i.e. by means of the exclusive use of the micro-air pump 13, but it would then have to be made more powerful, and the energy source 16 likewise, which is generally not expedient. After the test pressure is reached, the test process is initiated. The system then firstly waits for a predefined relaxation time in which the glove reacts to the pressure load with a delayed expansion, which leads to a pressure drop which is not due to a leak. The relaxation time is dependent on the glove material. After the expiry of this stabilization phase, the actual measurement, during which the pressure profile is detected over a time period of, for example, 5 minutes, starts. The measured pressure profile is passed on from the pressure sensor 8 directly to the microprocessor 9. The microprocessor 9 detects that the pressure drop which has occurred during the measurement time, given by the difference between the pressure at the point in time of the starting of the measurement and the pressure at the point in time at the end of the measurement, does not exceed a preset value, with the result that the presence of an acute leak can be ruled out. An alarm signal is therefore not triggered. The RFID module 15 reads out the RFID elements of the port and the glove and signals the information about the identity of the tested port and of the glove installed there to the microprocessor 9, which links this identification data to the measured pressure profile and transmits the complete data record, using the WiFi module 14, to the evaluation unit which is embodied as an evaluation computer 21. The evaluation computer 21 receives the data record, stores it and checks whether a data record is already present from an earlier test of the same glove. In this exemplary embodiment, said evaluation computer 21 finds such a data record and detects that even though the pressure drop is still within permissible limits, it has significantly speeded up during the new measurement compared to the preceding measurement, which indicates a small local, but continuously growing defect or an accelerated degradation of the glove material. By using the available data records, it predicts the still remaining residual period of use of the glove and transmits it to the microprocessor 9 of the test disc 1. The microprocessor 9 can subsequently cause the test disc to be disabled, in that the relief valve 11 of the sealing device 2 is blocked, a warning signal is triggered and the predicted residual period of use is displayed on the LCD display 7. The operator then has to decide whether to leave the test disc 1, now functioning as the sealing disc, in the port and bring about an immediate change of glove or else to cancel the blocking by switching off the test disc 1 by means of the on/off switch 3, removing the test disc 1 and initially continuing the production process in order to change the glove at the next scheduled interruption in the production process. The described test process can simultaneously be carried out with any desired number of the test discs according to the invention on a corresponding number of ports which are equipped with gloves. Exemplary Embodiment 2 A further seal test of the gloves installed in the ports of the isolator of a pharmaceutical system is to be carried out in a way analogous to the task described in the exemplary embodiment 1. The equipping of the ports and of the gloves with identification elements as described in exemplary embodiment 1 is ensured. In good time before the test it is determined that the ports have a conically tapering shape, with the result that a test disc 1 which forms a seal from the inside to the outside cannot be reliably secured in the port. However, the outwardly protruding attachment connector 18 of the port is suitable for attaching a test disc. The embodiment 1′ of the test disc which forms a seal from the outside to the inside (illustrated in FIGS. 3a and 3b) is therefore selected. The test disc 1′ is equipped with an expansion in the form of a support ring 17, the internal dimensions of which are somewhat larger than the external dimensions of the attachment connector 18, with the result that it can be fitted thereon. An inflatable hose 2′ which is secured by a groove and which functions as a sealing device is arranged in an inner face of the support ring 17. The hose 2′ has a sufficiently rigid sealing material, with the result that even in the non-expanded state it bears firmly against the inner edge of the support ring 17. A sufficient number of test discs which are matched to the shape and size of the port are made available. The test disc 1′ is fitted onto the attachment connector 18 of the isolator port. The following sequence is completely analogous to the sequence in exemplary embodiment 1, with the result that a renewed detailed illustration can be dispensed with. It is merely to be noted that the inflatable hose 2′ which functions as a sealing element runs here around the attachment connector 18 of the port and expands from the outside to the inside during inflation, with the result that the glove, port and test disc form a glove volume which is closed off in a gas-tight fashion. The direction of expansion is characterized by arrows in FIGS. 3a, 3b and 5. The pressure profile which is measured in the course of the test and transmitted to the evaluation computer corresponds to the results illustrated in exemplary embodiment 1. However, in contrast to the situation illustrated in exemplary embodiment 1, the evaluation computer 21 has access here to selected, process-related data in the database 22 of the user, with the result that an expanded evaluation method can be used. The evaluation computer 21 receives and stores the data record which contains the measured pressure profile and the identification data of the port and of the glove. It tests whether a data record from an earlier test of the same glove is already present. It finds such a data record and determines that the pressure drop during the new measurement is within the permissible limits and has not speeded up compared to the preceding measurement. The test therefore does not provide any indication at all of the defect or of already present degradation of the glove material, with the result that the glove appears to be capable of being used without restriction on the basis of the data used here. Within the scope of the extended evaluation method, the evaluation computer now extracts the entire previous loading of the glove (type, duration and concentration of the acting chemicals) from the process data of the user and calculates the current state of degradation of the glove using the data relating to the resistance of the glove material compared to the chemicals used, said data being also present with the user. The evaluation computer detects that speeded up degradation of the glove has already started owing to the previous chemical loading, even though said degradation cannot yet be proved by the test. As in exemplary embodiment 1, the evaluation computer predicts the still remaining residual period of use of the glove and transmits this to the microprocessor 9 of the test disc 1′. The microprocessor then brings about the measures described in exemplary embodiment 1, to which measures the operator has to react as described there. It is therefore ensured that the glove is changed in good time, but not unnecessarily early. The extended evaluation method can also be carried out simultaneously with any desired number of test discs at a corresponding number of ports equipped with gloves. The data flow between the individual test discs, the evaluation computer 21 and the database 22 of the user is illustrated in FIG. 4. In FIG. 4, the test system has a multiplicity of test discs according to the embodiment 1 illustrated in FIGS. 1 and 2. However, the test discs can also be formed by test discs according to the embodiment 1′ or by a combination of the two embodiments. The following sections describe preferred characteristics of various components of the test system described herein. Test Disc The test disc according to the invention is distinguished in comparison with the test discs which are known from the prior art by the fact that, in addition to already known components, it has a reading device for reading out identification elements and an interface for wireless and encrypted communication with an evaluation device. In this context, the reading out of a plurality of identification elements, that is to say that of the glove and that of the port is possible in succession or in parallel. The individual components are preferably integrated into the interior of the test disc. The device for reading out identification elements may be, for example, an RFID module, a CCD sensor or a laser sensor, while the interface for wireless and encrypted communication can be formed by a WiFi module, W-LAN module, Bluetooth module or some other radio-based solution. The components which are known from the prior art and are sufficient for the functioning of the test disc comprise an expandable sealing device, two micro-air pumps, a pressure sensor and a temperature sensor, which are preferably arranged in the interior of the test disc. In addition, a compressed air port and an energy source, arranged on the outside of the test disc, are usually provided, the compressed air supply being located on the front side, while the energy source, which supplies all the components of the test disc with electrical energy, is preferably located on the rear side of the test disc facing the glove volume. In one preferred embodiment, a display with an outwardly visible display area, for example an LCD display which supplies the operator directly with information on the current state of the test disc and on the ongoing test process, is contained in the interior of the test disc. The test disc can be additionally equipped with an LED display, by means of which the state of the glove which is defined during the test can be directly displayed. This energy source, preferably an accumulator, and the arrangement of the pressure sensor and of the module for the purpose of wireless communication in the interior of the test disc permit their completely autonomous operation without coupling to remote measuring devices or a remote energy supply. Without changing the method of functioning of the test disc, its shape and size can be varied over a wide range. This variability is necessary to allow for the large variety of isolator ports used in practice. The test disc is preferably embodied as a test disc which seals from the inside to the outside and which can be somewhat smaller than the port to be tested, and can therefore be inserted therein. The seal-forming connection is produced in this case by causing a sealing device which runs around the outer edge of the test disc to expand radially, with the result that it closes the gap between the port and the test disc. This can be done, for example, by applying pressure using the micro-air pump which is arranged on the test disc. In certain cases, for example in the case of conically tapering ports, stable securement of a test disc in the port is, however, not possible. In this case, the test disc is embodied as a test disc which seals from the outside to the inside, with a widened portion in the form of a support ring which encloses the attachment connector of the port on the outside. The support ring can be embodied here in one piece with the test disc and surrounds a receptacle space for the port. A circumferential sealing device, which is located radially on the inside of the support ring and can be expanded towards the inside, ensures that the gap between the test disc and the attachment connector is closed. The shape of the support ring is matched here to the geometry of the port, that is to say it is not necessarily circular but rather, for example, also oval. Other shapes with a closed circumference are also possible. In both embodiments of the test disc, the expandable sealing device is preferably embodied as an inflatable hose which is, in particular, of annular design. Both embodiments of the test disc are explained in more detail in the exemplary embodiments. Compared to conventional test devices, described for example in DE102004030766A1, the test disc according to the invention for testing gloves installed in isolator ports is small, lightweight, easy to handle and simple to install. During the use of the test disc, only a uniform pressure is applied to the edge of the respective port but the isolator wall is only slightly loaded, with the result that the test discs cannot themselves cause breaches of integrity (leaks). During their handling, no heavy physical work at all has to be carried out. The test discs can easily be transported from one location to another, under certain circumstances even without a service vehicle which is provided for this purpose, and they can therefore be used in an extremely flexible way. Both scheduled and unscheduled testing, due to an incident, can be carried out quickly at any time. The testing of the seal of a glove occurs, for example, as follows: The test disc is installed at the isolator port and the sealing element is made to expand, with the result that the port is closed and the glove and the test disc form a glove volume which is closed off in a gas-tight fashion. This volume is then subjected to a defined excess pressure (compared to the pressure prevailing in the interior of the isolator). For this purpose, coarse setting of the excess pressure (initial filling) is firstly carried out using an external supply, present on a standard basis on pharmaceutical systems, of contamination-free compressed air, and fine setting of the excess pressure is subsequently ensured by means of the micro-air pump which is provided for this purpose on the test disc and which feeds in contamination-free air which has been cleaned by a pre-filter. The production of a connection (compressed air hose line) to remote compressed air sources, for example pressure bottles, is not necessary then. The pressure sensor monitors the build-up of pressure and switches the micro-air pump off when the target pressure has been reached. Since the glove materials react to the pressure loading with delayed expansion, the system first awaits for a predefined relaxation time, during which an expansion-induced drop in pressure, which cannot be traced back to a leak, is observed. Since different glove materials exhibit a different relaxation behaviour, the expedient duration of this relaxation time should be determined experimentally in advance. After the expiry of this relaxation time (stabilization phase), the actual measurement begins, during which measurement the pressure profile is detected over a predefined time period. The measured pressure profile is passed on by the pressure sensor directly to the microprocessor of the pressure measuring device. The microprocessor also receives the information about the identity of the tested port and of the glove installed there from the reading device for reading out identification elements, preferably an RFID module. Said microprocessor links this identification data to the measured pressure profile and transmits the entire data record to an evaluation unit, for example an evaluation computer, by means of the interface for wireless and encrypted communication, preferably a WiFi module. The precondition for this is the equipment both of the port and of the glove with a uniquely defined identification element. The combined use of identification elements for the glove and port is a significant component of the invention. It is particularly advantageous if the reading device and the identification elements permit radio-based reading out. Identification elements which can be irreversibly connected to the ports or the gloves and which are suitable for this are commercially available. Test System The described test process can be carried out simultaneously with any desired number of the test discs according to the invention on a corresponding number of ports which are equipped with gloves. In this context, a flexible and autonomous test system which is available at any time and with which simultaneous testing of a seal of a plurality of gloves is possible can be obtained by means of a (preferably wireless) connection of the test discs (any desired number thereof, but at least one) to a single central evaluation computer. Owing to the autonomy of the individual test discs (no coupling of external energy sources, measuring devices or communication means), the equipping times which are necessary for preparing and subsequent processing of the test are very short. Compared to known test systems, in which an evaluation computer is connected to a plurality of measurement chambers, which, however, do not have, or only partially have, the autonomy features specified in the preceding paragraph, the test system which is based on the test discs according to the invention permits a significant shortening of the overall duration of the test. Correspondingly, the time which is available for the actual production processes is lengthened, which gives rise to a considerable increase in productivity. The evaluation computer or the evaluation unit has the known components which are essential for the functional capability: a receiver unit, a control unit, an evaluation unit, a memory unit and an output unit. It is particularly advantageous if it has a connection to the database of the user and therefore can also access selected process-related data (for example type of the chemicals used in an isolator and duration of their use). In one preferred embodiment of the test system, the measurement results (pressure profiles), the test results which are obtained in the subsequently described evaluation method and the associated identification data of the glove and of the port are presented visually on a display of the evaluation unit. As a result, relatively simple and fast identification and determination of the location of the test discs is ensured, with the result that the measurement and test results of the individual ports and gloves can also be assigned easily, quickly and unambiguously. If the test discs of the test system have a display as a preferred feature, the measurement and test results of each glove which is installed on a port can also be displayed on the display of the test disc which is inserted at the respective port and, if said test disc is equipped with an additional LED, are additionally displayed by the lighting up of a specific LED or a combination of LEDs. A successful test of a seal can therefore be indicated by the lighting up of a green LED, and an unsuccessful test of a seal can, in contrast, be indicated by the lighting up of a red LED on the respective test disc. Further states which are determined as a result of the expanded evaluation method described below can also be displayed. For example, a seal test which has been successful, but during which accelerated degradation of the glove material was detected, can be indicated by the lighting up of a yellow LED. This visual indication by means of an LED display provides the operator with a rapid and direct overview of the state of all the ports and gloves of the monitored production systems without the operator having to evaluate the quantitative measurement and test results which are displayed on the display. In a further preferred embodiment, the test system is equipped with a device for user authentication, in order to prevent unauthorized operation. Both the evaluation computer and the test discs are not released for use until the operator has been authenticated. Only then can the seal test described above be initiated. For the purpose of authentication, electronic key systems, fingerprint sensors, iris recognition means, safety codes which have to be input and other means can be used. Evaluation Method The evaluation unit or the evaluation computer receives the data (pressure profiles) which have been acquired by any desired number of test discs (in a serial or parallel fashion), stores them and prepares them immediately (while the measurement is still ongoing). If the evaluation computer detects here an irregularity (in particular an excessively rapid pressure drop) which indicates a breach of integrity by a faulty glove (acute leak), it immediately transmits a signal, with the result that the operator is immediately informed of the breach of integrity and of the need for immediate counter-measures. In addition, there is the possibility of automatically disabling the expanded sealing element of the affected test disc with the result that the test disc cannot be removed after the conclusion of the measurement. The test disc therefore functions as a sealing disc and ensures the integrity of the isolator until the detected breach of integrity is eliminated. In one particular embodiment which is suitable for applications with very high safety requirements, the microprocessor of the test disc already analyses the pressure profile and, in the event of an excessively rapid pressure drop being detected, which indicates an acute leak, triggers the reactions specified in the preceding paragraph. In this case, the breach of integrity therefore is detected even if the connection between the test discs and the evaluation computer fails. Owing to the high level of reliability of the connection between the test discs and the evaluation computer, which is implemented in a wireless fashion by means of W-LAN technology, WiFi technology, Bluetooth technology or some other radio-based technology, this embodiment is not used so frequently. All the test results (pressure profiles, identification numbers and test parameters), the results of both the scheduled tests and of the unscheduled tests owing to an incident are stored in the memory unit of the evaluation computer and can be called again at any time. Since they also include uniquely defined identification data of the port and of the glove, it is possible to track at any point in time the port at which they have been obtained, and for which glove. By comparing the results of two successive routine tests of the same glove, the evaluation computer determines whether the state thereof has changed within the limits of the expected use or whether an accelerated degradation has occurred which makes additional measures such as, for example, shortening of the test interval or premature replacement of the glove necessary. The profile of the degradation of each individual glove is therefore detected completely. If the evaluation computer detects such an accelerated degradation which requires real-time replacement of the glove, the evaluation computer immediately transmits a message to the associated test disc. A warning signal then appears at this test disc so that the operator is immediately informed about the irregularity. In addition, there is the possibility of automatically disabling the expanded sealing element of the affected test disc with the result that the test disc cannot be removed after the conclusion of the measurement and the integrity of the isolator is ensured until further notice. However, since it is not a case of an acute leak here but rather of gradual worsening, the operator can decide whether he initiates counter-measures immediately or postpones them until the next scheduled interruption in production. In contrast to the acute leak, he can, if appropriate, release the test disc again here and remove it in order to continue the production over a limited time period. In order to assist the operator in his decision, the evaluation computer predicts, on the basis of the results of the last successive routine tests, the expected development of the leakage rate of the glove and determines its permissible residual period of use, which is communicated to the operator. The evaluation method therefore evaluates the seal of the glove not only qualitatively (decision between sealed and leaking) but also quantitatively. An accelerated degradation can have various causes: it can be brought about by a very small local defect which is caused without being noticed by the operator and which develops gradually into a relatively large defect, but it can also be due to a degradation in the glove material as a whole. It is desirable to cause the glove to be exchanged before such degradation can be measured, but without unnecessarily shortening the period of use of the glove. Local defects which are caused without being noticed cannot be predicted, but the degradation of the glove material as a whole can be predicted if all the damaging influences which act during the period of use of the glove are known quantitatively, for example a duration of effect and concentration of a particularly aggressive chemical. In addition, the reaction of the glove material on this chemical must be known. Known test systems do not provide any possibilities for this, or only provide restricted possibilities, since the gloves are removed for the tests, wherein the ports at which they were installed in the course of their period of use is not detected. It would therefore certainly not be possible to track what influences they were subjected to. However, equipping all the gloves and ports with unique identification elements makes it possible to extend the evaluation method by utilizing the access to selected process-related data of the user, in such a way that said method detects the entire life cycle of each individual glove, i.e. the profile of its degradation including the causes thereof. The extended evaluation method includes linking the data supplied by the test discs according to the invention to further process-related data detected by the user (for example a type and duration of the production process which is carried out, chemicals used, number of the production system). Furthermore, data on the resistance of the glove materials used compared to the chemicals used in the production processes could also be included. This data can be included in the safety data sheets of the chemicals or can be determined experimentally by the user. This data combination permits new quality in process safety which meets all the prescriptions of the FDA Guidelines and goes beyond them. The individualization of the gloves and ports and the automatic collection of data eliminate errors completely during the manual documentation and during the equipment of the ports with gloves. It is therefore ensured that a glove made of the material provided for it with the prescribed thickness is used for each production step. The combination of the test results, material data and process data makes it possible to know the state of any individual glove at any point in time, i.e. to produce a complete glove history which detects its conditions of use, in particular the chemical loading, and the profile of its degradation over its entire period of use. As a result, each individual glove can be used until its individual period of use expires, without endangering the integrity of the isolator and therefore the safety of the system through inadmissibly degraded gloves. The access to the process data of the user which is necessary for the extended evaluation method can be implemented in different ways: The evaluation unit or the evaluation computer of the test system can receive, for example, access rights to selected data of the user which is necessary for the evaluation described above. The evaluation takes place in this case by means of the evaluation unit of the test system. The results are then transmitted to the database of the user and stored there, so that they can be available to the user at any time. The transmission of data can be limited to specific conditioned data, for example the quantitative evaluation of the seal of a glove, but substantially less comprehensive data, for example, complete pressure profiles, can also be transmitted. Alternatively, the test system can be configured as a system-integrated solution and can be incorporated completely into the process sequences of the user. In this case, the test results (pressure profiles) are not stored by the evaluation computer of the test system but instead transmitted directly into the database of the user, which database is correspondingly adapted for this purpose. The evaluation then takes place on the system of the user. For a person skilled in the art it is obvious that the possibilities of use of the test discs or of the test system according to the invention with one or more test discs and of the evaluation method are not restricted to pharmaceutical systems. Of course, applications in isolators in the medical field, which isolators are operated with excess pressure or underpressure depending on the application, as well as in glove boxes in the nuclear field, which are operated with a high underpressure, and in all other systems (both excess pressure systems and underpressure systems), which have to ensure a high degree of tightness owing to their function, are possible. By using a plurality of test discs it is possible here to test a plurality of gloves simultaneously. 1 Test disc (forming a seal from the inside to the outside) 1′ Test disc (forming a seal from the outside to the inside) 2 Sealing device for 1, embodied as an inflatable hose 2′ Sealing device for 1′, embodied as an inflatable hose 3 On/Off switch 4 Start/Stop pushbutton key 5 Inflation valve for glove 6 Pre-filter 7 LCD display 8 Pressure sensor 9 Microprocessor 10 Pressure sensor for seal 11 Valve 12 Micro-air pump 13 Micro-air pump 14 WiFi module 15 RFID module 16 Energy source 17 Support ring 18 Attachment connector of the port 21 Evaluation computer 22 Database of the user Of course, with the exception of the sealing device, the positions of the elements of the test disc which are illustrated in the drawings are not compulsorily prescribed. Likewise, the shape and size of the test disc are not prescribed either. In addition to the oval shapes, round shapes and any other shapes are also possible, wherein only correspondence with the shape and size of the port to be tested has to be ensured. |
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summary | ||
abstract | A high temperature gas cooled reactor steam generation system (1) includes a nuclear reactor (2) that has helium gas as a primary coolant and heats the primary coolant by heat generated by a nuclear reaction that decelerates neutrons by a graphite block, a steam generator (3) that has water as a secondary coolant and heats the secondary coolant by the primary coolant via the nuclear reactor (2) to generate steam, a steam turbine (4) that is operated by the steam from the steam generator (3), and a generator (5) that generates electricity according to an operation of the steam turbine (4). Moreover, the system (1) includes pressure adjustment means for setting a pressure of the secondary coolant in the steam generator (3) to be lower than a pressure of the primary coolant in the nuclear reactor (2). |
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047913037 | abstract | The present invention concerns methods and apparatus for laminating polymeric sheet materials wherein the use of a separate adhesive and/or the use of heat as a bonding means are avoided. In particular, methods and apparatus are disclosed wherein at least one polymeric sheet is exposed to a flowing of gaseous cold plasma to form free radicals on the surface thereof. Said free radicals serve to effect bonding upon application of such treated polymeric sheet to a second polymeric sheet. In preferred embodiments, approximately 180,000 to 500,000 volts of electromagnetic energy are applied to a stream of gaseous material, such as argon gas, and utilizing a radio wave frequency discharge of approximately 12.56 megaHertz. In some preferred embodiments, the cold plasma may be applied at an effective pressure of approximately 1.1 Torr in the reaction area. |
047626763 | description | DETAILED DESCRIPTION OF THE INVENTION In the following description, like reference characters designate like or corresponding parts throughout the several views. Also in the following description, it is to be understood that such terms as "forward", "rearward", "left", "right", "upwardly", "downwardly", and the like, are words of convenience and are not to be construed as limiting terms. In General Referring now to the drawings, and particularly to FIG. 1, there is shown an elevational view of a reconstitutable nuclear fuel assembly, represented in vertically foreshortened form and being generally designated by the numeral 10. Basically, the fuel assembly 10 includes a lower end structure or bottom nozzle 12 for supporting the assembly on the lower core plate (not shown) in the core region of a reactor (not shown), and a number of longitudinally extending guide tubes or thimbles 14 which project upwardly from the bottom nozzle 12. The assembly 10 further includes a plurality of transverse grids 16 axially spaced along the guide thimbles 14 and an organized array of elongated fuel rods 18 transversely spaced and supported by the grids 16. Also, the assembly 10 has an instrumentation tube 20 located in the center thereof and an upper end structure or top nozzle 22 removably attached to the upper end portions 24 of the guide thimbles 14 to form an integral assembly capable of being conventionally handled without damaging the assembly parts. As mentioned above, the fuel rods 18 in the array thereof in the assembly 10 are held in spaced relationship with one another by the grids 16 spaced along the fuel assembly length. Each fuel rod 18 includes nuclear fuel pellets (not shown) and is closed at its opposite ends by upper and lower end plugs 26,28 to hermetically seal the rod. The fuel pellets composed of fissile material are responsible for creating the reactive power of the nuclear reactor. A liquid moderator-coolant such as water, or water containing boron, is pumped upwardly through the guide thimbles 14 and along the fuel rods 18 of the fuel assembly 10 in order to extract heat generated therein for the production of useful work. To control the fission process, a number of control rods (not shown) are reciprocally movable in the guide thimbles 14 located at predetermined positions in the fuel assembly 10. Since the control rods are inserted into the guide thimbles 14 from the top of the fuel assembly 10, the placement of the components forming the top nozzle 22 and their attachment to the upper end portions 24 of the guide thimbles 14 must accommodate the movement of the control rods into the guide thimbles from above the top nozzle 22. Top Nozzle Removably Mounted on Guide Thimbles Turning now to FIGS. 2 and 3, as well as FIG. 1, there is shown in greater detail the separate components making up the top nozzle 22 which is removably mounted on the upper end portions 24 of the guide thimbles 14 of the fuel assembly 10. The top nozzle 22 basically includes an upper hold-down plate 30, an enclosure 32 composed of a lower adapter plate 34, having a construction in accordance with the present invention to be described below, and an upstanding discontinuous sidewall 36 formed by a plurality of spaced upstanding wall portions 38 surrounding and attached to the periphery of the adapter plate, a plurality of tubular alignment sleeves 40 disposed between the upper and lower plates 30,34, and a plurality of hold-down coil springs 42 extending between the upper and lower plates 30,34 and about the respective sleeves 40. The upper hold-down plate 30 has a plurality of passageways 44 defined therethrough, while the lower adapter plate 34 has a plurality of openings 46, the passageways 44 and openings 46 being arranged in respective patterns which are matched to that of the guide thimbles 14 of the fuel assembly 10. More particularly, the upper end portions 24 of the guide thimbles 14 extend upwardly through the openings 46 in the lower adapter plate 34 and above the upper surface 48 thereof. A plurality of lower retainers 50 are attached, such as by brazing, to the guide thimbles 14 below the adapter plate 34 for limiting downward slidable movement of the adapter plate 34 relative to the guide thimbles 14 and thereby supporting the adapter plate on the guide thimbles with the upper end portions 24 thereof extending above the adapter plate. Each lower retainer 50 on one guide thimble 14 has a series of scallops 52 formed on its periphery which are aligned with those of the fuel rods 18 grouped about the respective one guide thimble so that the fuel rods may be removed and replaced during reconstitution of the fuel assembly 10. Furthermore, the top nozzle 22 includes a plurality of upstanding bosses 54 having respective central bores 56 defined therethrough. The bosses 54 are disposed above the upper hold-down plate 30, and each boss is attached to the hold-down plate 30 such that its central bore 56 is aligned with a respective one of the passageways 44 of the hold-down plate. Additionally, each boss 54 is of a cross-sectional size adapted to interfit within one of a plurality of holes 58 (only one of which is seen in FIG. 5) formed in the upper core plate 60 which opens at a lower side 62 of the core plate. The upper circumferential edge 64 of each boss 54 is chamfered for mating with a complementarily chamfered edge 66 on the lower side 62 of the upper core plate 60 at the entrance to each of the holes 58 defined therein. Edges having such shapes act as guiding surfaces which facilitate alignment and insertion of the respective bosses 54 into the corresponding holes 58 in the upper core plate 60 during installation of the fuel assembly 10 within the reactor core. As mentioned above, the hold-down coil springs 42 are disposed about the respective elongated alignment sleeves 40 within the enclosure 32. Further, the springs 42 extend between the lower adapter plate 34 and the upper hold-down plate 30 and support the upper plate in a spaced relation above the lower plate at a stationary position in which the upper plate abuts the lower side 62 of the upper core plate 60 with the upstanding bosses 54 interfitted within the holes 58 of the upper core plate 60. Also, as seen in FIG. 5, the upper hold-down plate 30 is composed of an array of hubs 68 and ligaments 70 which extend between and interconnect the hubs. Each of the hubs 68 has one of the passageways 44 defined therethrough. Furthermore, one boss 54 is disposed above and connected to each of the hubs 68 with the bore 56 of the boss aligned with the respective passageway 44 of the hub. Referring also to FIGS. 4 to 6, the top nozzle 22 also includes means interconnecting the spaced upper and lower plates 30,34 so as to accommodate movement of the lower plate 34 toward and away from the upper plate 30 upon axial movement of the guide thimbles 14 of the fuel assembly 10, such as due to thermal growth, toward and away from the upper core plate 60. Also, the interconnecting means is effective to limit movement of the lower adapter plate 34 away from the upper hold-down plate 30 so as to maintain the springs 42 in a state of compression therebetween. In particular, the interconnecting means includes a plurality of lugs 72 connected to and extending downwardly from peripheral ones of the ligaments 70. The lugs 72 are respectively coupled to the upstanding wall portions 38 of the discontinuous sidewall 36 of the enclosure 32. Specifically, a generally vertical slot 74 is formed in each wall portion 38 and opens at the upper end thereof. A removable locking pin 76 is inserted horizontally into the upper end of the wall portion 38 to close the upper end of the slot 74 and a pin 78 mounted in the lower end of each lug 72 extends into the slot 74 below the locking pin 76 for slidable movement therealong as the upper and lower plates 30,34 move relative to one another. In such arrangement, the locking pin 76 and the lower end of the slot 74 respectively define the limits of movement of the lower adapter plate 34 toward and away from the upper hold-down plate 30. Referring now to FIG. 4, there is shown one of the elongated tubular alignment sleeves 40 extending through one of the hold-down coil springs 42 between the upper and lower plates 30,34 and the threaded features on the sleeve 40 and on the upper end portion 24 of the one guide thimble 14 for attaching the sleeve and guide thimble together. Also illustrated in the figure is the reusable locking arrangement, generally designated as 80, integrally associated with both the sleeve 40 and the guide thimble upper end portion 24 for locking the attached sleeve and guide thimble together. Since a description of the details of the reusable locking arrangement 80 is not necessary for understanding the adapter plate of the present invention, it will not be presented herein. Such arrangement comprises the invention disclosed and illustrated in the above cross-referenced patent application. With respect to the threaded features on the guide thimble 14 and sleeve 40, the upper end portion 24 of the guide thimble 14 has an annular externally threaded section 82, whereas the tubular alignment sleeve 40 has a lower annular internally threaded section 84. The sleeve 40 is mounted through the passageway 44 and bore 56 of the hold-down plate hub 68 and boss 54 for rotatable and vertical axial movement relative to the guide thimble upper end portion 24 for threading and unthreading its internally threaded section 84 onto and from the externally threaded section 82 of the guide thimble upper end portion 24 in order to attach and detach the top nozzle 22 onto and from the guide thimble 14. The sleeve 40 is hollow so that, in addition to accommodating insertion of a control rod through it, a suitable tool (not shown) can be inserted into the sleeve for gripping it internally to rotate it in either direction for threading on and unthreading from the upper end portion 24 of the guide thimble 14. When threaded on the guide thimble upper end portion 24, the sleeve 40 cooperates with the lower retainer 50 to clamp the adapter plate 34 therebetween. Adapter Plate with Fuel Rod Capture Grid having Pressure Drop Adjusting Feature Referring now to FIGS. 1 to 4 and 6 to 9, there is also shown the top nozzle adapter plate 34 of the present invention. The adapter plate 34 includes an upper structural component, generally designated 86, and a lower functional component, generally designated 88, being supported below and from the upper component 86. As seen in FIG. 6, the upper structural component 86 of the adapter plate 34 includes spaced and interconnected hubs 90 and ligaments 92 arranged to define substantial open areas 94 for coolant flow therethrough. With such an open configuration, the component 86 has a very low pressure loss. At the same time, the upper structural component 86 provides a rigid framework capable of transmitting lifting loads imposed by the fuel assembly 10 from the wall portions 38 on the ligaments 92, through the ligaments and hubs 90, to the guide thimbles 14 which are connected to the hubs 90 and comprise the elongated structural members of the fuel assembly. The upper component 86 also includes a plurality of open corner flanges 96 connected to and extending outwardly of the hubs 90. Referring specifically to FIGS. 2, 4 and 7 to 9, it is seen that the lower functional component 88 of the adapter plate 34 includes a grid, generally designated 98, composed of a plurality of spaced and interleaved straps 100 which extend in vertical planes generally parallel to the direction of coolant flow through the grid 98 and cross one another to form intersections 102 aligned with individual fuel rods 18 (a few of which are shown in dotted outline form in FIG. 2). Such alignment of the grid 98 with the fuel rods 18 restrains movement of the fuel rods upward from the fuel assembly 10 and thereby provides the fuel rod capture function of the adapter plate 34. The interleaved straps 100 of the grid 98 also define open channels 104 therethrough for allowing passage of coolant flow with very slight pressure drop. Preferably, the grid 98 is positioned under the upper structural component 86 and has upstanding corner extensions or strips 106 for attachment to the corner flanges 96 of the adapter plate upper component. Specifically, the corner strips 106 fit into recesses 108 in the upper component corner flanges 96 where the strips are welded to the upper component 86. Further, as seen in FIG. 7, the grid 98 contains void areas 110 through which extend the hubs 90 of the upper component 86. As seen in FIGS. 1, 2, 4 and 7 to 9, the lower functional component 88 of the adapter plate 34 also includes coolant flow directing means, in the form of a plurality of tabs 112, being operable to establish a predetermined desired pressure drop across the top nozzle 22 of the fuel assembly 10. The tabs 112 are connected to the upper edges of the grid straps 100 and extend upwardly therefrom. For the sake of clarity, the tabs are only shown on a portion of the grid straps in FIG. 7. It is to be understood that any arrangement of the tabs 112 is within the purview of the present invention, for instance, there can be a tab associated with each open channel 104 or only some of them. The tabs 112 are bendable or adjustable into various desired positional relationships with respect to the open grid channels 104 for controlling coolant flow therethrough. By bending the tabs to extend at various predetermined angles across their respective channels, different pressure drops across different areas of the grid 98 and thus across the fuel assembly 10 can be established. Coolant flow can be biased to certain positions of the top nozzle. For example, if more flow is desired through the center of the nozzle and less around the areas where the hold-down springs 42 are located, the tabs of the grid can be bent to provide a higher pressure drop in the spring region than that is in the center. Since only the grid 98 is involved in these changes, the structural design of the upper component 86 of the adapter plate 34 remains unchanged. This ability to alter the pressure drop can be used advantageously in matching pressure drops of different fuel assemblies existing in a mixed vendor core. In a modified form of the coolant flow directing means as seen in FIG. 10, a thin flat plate 114 having holes 116 of predetermined desired sizes and shapes formed therein, such as by punching, can be used instead of the tabs 112. The plate 114 is attached to the upper side of the grid 98 and extends along the interleaved straps 100 thereof with its holes 116 generally aligned with the open channels 104 of the grid 98. This design of the flow directing means provides structural strength and variability of flow area. While this design probably has less flexibility with the tabs 112, it may be more economical to manufacture. While both the tabs 112 and plate 114 are illustrated as being positioned on the upper side of the grid 98, they could just as readily be positioned on the lower side thereof. Also, it should be understood that the upper side of the grid straps 100 can abut against the lower side of the ligaments 92 of the upper component 86 with the tabs 112 projecting upwardly into the open areas 94 of the component 86. It is thought that the present invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement thereof without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred or exemplary embodiment thereof. |
description | This application is a continuation of U.S. Ser. No. 12/671,924, filed Feb. 3, 2010, now granted and issuing on Nov. 15, 2016 under U.S. Pat. No. 9,492,690, which claims benefit of national stage filing under 35 U.S.C. 371 of PCT/US2008/067473, filed Jun. 19, 2008, which claims benefit of provisional application No. 60/999,746, filed Aug. 31, 2007, the disclosure of which is incorporated by reference in their entirety herein. Generally, this disclosure relates to methods and systems for determining the conditions of components, particularly the disclosure relates to methods and systems for determining conditions of components removably coupled to articles of personal protection equipment (PPE), by tracking their usage in a monitored working environment against a predetermined criterion, such as a change-out protocol. Maintaining the safety and health of workers is a major concern across many industries. Various rules and regulations have been developed to aid in addressing this concern, which provide sets of requirements to ensure proper administration of personnel health and safety procedures. To help in maintaining worker safety and health, some individuals may be required to don, wear, carry, or otherwise use a PPE article, if the individuals enter or remain in work environments that have hazardous or potentially hazardous conditions. Known types of PPE articles include, without limitation, respiratory protection equipment (RPE), e.g., for normal condition use or emergency response, protective eyewear, such as visors, goggles, filters or shields, protective headwear, such as hard hats, hoods or helmets, hearing protection, protective shoes, protective gloves, other protective clothing, such as coveralls and aprons, protective articles, such as sensors, safety tools, detectors, global positioning devices, mining cap lamps and any other suitable gear. For example, personnel in the nuclear industry may be required to wear radiation protective clothing and personal dosimeter devices. Law enforcement personnel are sometimes required to wear protective vests and helmets. There are numerous situations in the medical field in which healthcare workers must wear protective gowns, masks, face shields, gloves, etc. Workers in the food service industry are often required to wear hair netting, gloves, masks, etc. For example, there are also many industrial manufacturing scenarios in which personnel are required to wear protective or other specially designed articles in order to ensure a “clean” environment. For example, personnel in the micro-electronics manufacturing industry, biotech industry, laboratory/testing industry, are required to wear PPE articles not only to ensure their own safety, but to protect the equipment and devices which they assemble or perform various procedures with. There are also many industrial manufacturing scenarios in which personnel working in mines, oil refineries, metal grinding facilities, smelting facilities, industrial painting operations or pharmaceutical factories may be required to wear respiratory protection equipment (RPE). There are many different kinds of respirators (e.g., RPE) utilized to prevent or reduce inhalation of hazardous or toxic materials. These RPE articles include, without limitation, components, for example, air-purifying filters, cartridge components, or canisters that remove specific air contaminants by passing ambient air through their air-purifying element. Typical chemical respirators use replaceable filter cartridge components that are coupled. Their proper use is contingent upon the respirators including the cartridges/canisters being replaced before they fail or that the correct types of respirators are to be used. However, many traditional respirators that include replaceable cartridges/canisters, typically, do not include any mechanism of indicating when their ability to remove contaminants from the air has been reduced. Therefore, to ensure their replacement before they fail or are otherwise in need of further processing, several U.S. guidelines require use of end of service life indicators. Presently, the availability of end of service life indicators is rather limited. Alternatively, a commonly utilized change-out schedule for respirators is based upon the identity and concentration levels of compounds expected to be encountered within the workplace over a period of time. Typically, a change-out schedule is based on an initial determination of average exposure and the corresponding duration of the component to that exposure. This initial determination establishes a required time period of service life. The user or an authorized person documents the first day of usage and keeps track of the required time period for purpose of determining when the component is not usable and needs to be disposed or otherwise processed. Clearly, the making and keeping of extensive records that contain all of the above-referenced information present a substantial administrative task. Moreover, facilities in which workers wear PPE articles are often required to keep detailed records regarding the PPE articles as well as the individuals wearing the PPE articles. Some such records include information regarding use of PPE articles, maintenance, and condition of PPE articles, as well as training of the workers to use the PPE articles. In addition, records of certain mandatory regulations and compulsory audit histories must be kept. For example, in some cases, RPE articles require maintenance to be carried out by properly trained personnel at least every three months and after each use. Despite the extensive records that are required to be collected regarding PPE articles and their associated components, adherence to various predetermined criteria, including a change-out criterion, is typically the responsibility of the user. Thus, compliance with a particular criterion may become an issue in work environments involving relatively large numbers of workers and/or respirators because of the relative difficulty in tracking worker habits and diligence. Clearly, workers are at a higher risk of exposure upon breakthrough of the contaminants when schedules are not adhered to. Thus, there is a need for electronic methods and systems that could make the implementation of determining condition of components easier and more efficient, particularly in regard to tracking of components that are removably coupled to PPE articles. In one exemplary embodiment, the present disclosure is directed to a method of determining a condition of a component coupled to an article of personal protection equipment wherein the method comprises: providing at least one component removably coupled to an article of personal protection equipment; providing at least one smart tag coupled to the component or the personal protection equipment article; tracking usage of the component, wherein the tracking comprises retrieving data from the smart tag; and, determining a condition of the component based on comparing tracked usage data of the component against at least one predetermined criterion. In another exemplary embodiment, the present disclosure is directed to a system of determining a condition of a component coupled to an article of personal protection equipment. The system comprises: at least one article of personal protection equipment; at least one component removably coupled to the article of personal protection equipment; at least one smart tag coupled to the component or the personal protection equipment article; a system for retrieving data from the smart tag; a data processing system coupled to the data retrieving system; wherein the data processing system includes a mechanism for determining a condition of the component based on comparing tracked usage data of the component against at least one predetermined criterion. The present disclosure substantially reduces the drawbacks and shortcomings of the known approaches for determining the conditions of components that are removably coupled to PPE articles. The foregoing is achieved through a method and system that determines conditions of such components by using at least a smart tag coupled with the component or the PPE article removably coupled to the component so as track usage of the component. Tracking is accomplished by retrieving data from the smart tag and determining a condition of the component based on comparing the tracked usage data of the component to at least one predetermined criterion. FIG. 1 illustrates a block diagram of a component condition determining system 100, according to one exemplary embodiment of the present disclosure. The component condition determining system 100 includes an information retrieval system 102 networked to a computer system 150. The component condition determining system 100 is utilized for implementing a process for determining a condition of one or more accessories or components 110a-n (collectively, 110). The components 110 are of the type that are removably coupled to one or more articles, such as articles of personal protection equipment (PPE) 120 a-n (collectively, 120). The removably coupled components 110 and the PPE articles are to be used in one or more working environments 125 (only one is illustrated). Exemplary working environments include, without limitation, paint shops, petrochemical refineries, mines, smelting facilities, pharmaceutical factories, or the like. The term “coupled” as used in the present application means that a component is physically or operatively coupled to a PPE article so that they can function together. In an illustrated exemplary embodiment, the PPE article 120 is an article of respiratory protective equipment (RPE) 120, and the removable coupled accessory or component 110 is a respirator filter cartridge 110. For example, the RPE article 120 may be a 7502 half face piece respirator that is commercially available from 3M Company of St. Paul, Minn. The respirator filter cartridge component 110 may be a 6001 Series organic vapor cartridge that is commercially available from 3M Company of St. Paul, Minn. The present disclosure is not limited by the foregoing combination of removably coupled components and PPE articles, but envisions all suitable combinations. Other known types of components 110 that may be tracked according to the present disclosure include, without limitation, a nose piece, a valve cover, a strap assembly, a face piece, a hood, a helmet, a motor, a hose, a filter of a welding helmet, a visor, power supply, a lighting mechanism, such as a mini-cap lamp, etc. The components may be removably coupled to the PPE article through any appropriate mechanical mechanism including, without limitation, snap-fit connections, such as one that prevents improper connection; hook and loop mechanisms; repositionable adhesives; clips; slots; threaded screw-in connections; bayonets; as well as other known and suitable approaches. Other known types of PPE articles 120 that may be coupled to the components 110 include, without limitation, respiratory protection equipment (RPE), e.g., for normal use or emergency response, protective eyewear, such as visors, goggles, filters or shields, protective headwear, such as hard hats, hoods or helmets, hearing protection, protective shoes, protective gloves, other protective clothing, such as coveralls and aprons, protective articles, such as sensors, safety tools, detectors, air or liquid sampling devices, global positioning devices, mining cap lamps and any other suitable gear. Accordingly, any wide number of suitable combinations may be tracked according to the present disclosure. The component condition determining system 100 essentially tracks usage of smart tags attached to either the removably coupled component used with PPE articles or the PPE article that is known to be coupled to the component of interest, or both. In one exemplary embodiment, the information retrieval system 102 includes one or more smart tags 130a-n (collectively, 130); one or more data acquiring devices 140a-n (collectively, 140) that acquire data from the smart tags; and, one or more sensors 145a-n (collectively, 145) that, as will be described, sense for variables that are related to usage of the component being tracked. Given the number of different kinds of smart tags, data acquiring devices, and sensors that can be used, there exists a large number of combinations for the system 102 that can be constructed depending on the type of components and PPE articles to be tracked. Accordingly, the exemplary information retrieval system 102 is but one of many different and suitable types. The present disclosure contemplates use of any suitable smart tag known in the art. In one exemplary embodiment, the smart tag 130 may be attached to a component. In another exemplary embodiment, the smart tag 130 may be attached to an article of PPE for use in determining the condition of the removably coupled component. Essentially, a smart tag is a data carrier that carries data accessible by suitable methods, including, but not limited to, electronic, optical, or other wireless technology. Data on a smart tag may, typically, at least, include tag identification information, such as an identification number (e.g., serial number). In addition, the smart tag 130 may contain other information relating to the article of PPE 120 or its component(s) 110, such as the type of article and/or component(s) used; historical information relating to the article and/or the component(s), information about the user (who used it, where it was used, under what condition it was used, etc.), maintenance or other type of processing, information about who wrote information onto the smart tag; any requirements relating to the article, component(s) and/or their use, whether any such requirements have been satisfied, such as any certifications obtained, and any other useful information, such as component change-out history, or the working environment. Also, information regarding the user of the article of PPE may be on the smart tag 130; such as, medical information, information relating to fit-testing, training, job responsibilities, seniority or experience, access privileges or any other information. Smart tags include passive and active types. Generally, passive tags do not include an internal power source and the data carried thereby may be encoded at manufacture. Data information may be acquired from a passive smart tag, for example, by radio frequency, microwave, infrared, or other wireless modes; or by optical readers or other appropriate electronic or optical technology. One type of passive smart tag is radio frequency identification (RFID) tag, wherein a transponder carries read-only data. Another type of passive smart tags may be rewritable. RFID technology is known and understood by those skilled in the art and, hence, only a brief description is included herein for facilitating understanding of the present disclosure. Passive RFID type smart tags are typically provided in the form of small labels or the like that include a coiled, etched or stamped antenna, a capacitor, and a substrate on which the components are mounted or embedded. For some metallic smart tags, the metallic portion itself may serve as the antenna. The RFID type smart tag may be embedded in or attached to the components 110 and/or PPE articles 120 by any suitable approach. For example, the smart tags may be joinable as by being adhered, fastened, sewn, friction fitted, mechanically clipped, welded (e.g., ultrasonically) or molded, etc. onto or into the components, included as an integral component of the article or securely attached by any suitable means. Besides passive RFID smart tags, other passive smart tags may include, without limitation, optical kinds including barcode and optical character recognition systems; electromagnetic systems; and acoustomagnetic systems. On the other hand, active smart tags tend to carry their own internal power source as well as data, and an appropriate antenna for allowing exchanging of their data. The internal power supply may include a micro-battery, a thin film battery, or the like. Active smart tags may be reprogrammable and may include, besides an antenna, a microchip to receive and store additional information beyond the information contained in its fixed code. Active smart tags may exchange their data information with data acquiring and/or transmitting devices, such as including, without limitation, readers and/or writers, scanners, and/or data receivers, such as wireless receivers. The exchange may be initiated by the active smart tag itself once it finds a suitable or designated, reader, scanner, or receiver. The active smart tags may transmit their data in response to triggering or interrogating signals, they may actively transmit their data independent of such signals. For instance, the active smart tags may continuously or periodically transmit data to appropriate readers and/or writers, scanners, or receivers. As noted, some active smart tags include the capability to receive and store additional information beyond that contained by its encoded data. Other kinds of active smart tags may be configured to be rewritable. For instance, an active RFID smart tag may be rewritable, as by an RFID reader/writer. Other kinds of active smart tags include a real time location system (RTLS) smart tag. An RTLS active smart tag is an active tag having a transmitter and a receiver and it communicates with a network according to a particular protocol. RTLS systems can work to determine the position of the smart tag in a 2-dimensional or 3-dimensional space. For example, a RTLS smart tag generally uses one or both of the following wireless location-based methods for determining the position of a smart tag or the object the tag is attached to. The first is a Time Difference of Arrival (TDOA) method. In one implementation of this method, the smart tag will broadcast a signal to multiple wireless receivers 140 at known locations. The time at which the signal is received by each receiver is measured, and a set of equations can be used to determine the position of the smart tag. Examples of systems using this method are a global positioning system (GPS) or a system using low frequency radio transmitters that use the time interval between radio signals (LORAN). Another example is an active smart tag used in a WiFi system that determines how long a signal takes to reach a receiver. Other companies that use this principle for RTLS systems are AeroScout Inc., Redwood City, Calif.; NanoTron Technologies, GmbH, Berlin, Germany; WhereNet, Santa Clara, Calif.; and, MultiSpectral Solutions, Inc., Germantown, Md. A RTLS may also use a Received Signal Strength Indicator (RSSI) method. This latter method requires tags or fixed transceivers to measure the received power (signal strength) of the incoming signals. Then, using either known variations of signal strength vs. distance from transmitters, or by measuring the signal strengths at various locations and matching these measured strengths to the measured strengths, position can be determined. Other companies that provide commercially available products using the RTLS system include Wavetrend, Fairfax Va., and PanGo Networks, Framingham, Mass. One example of an active smart tag suitable for use in an RTLS system is an Ekahau™ smart tag, which communicates with wireless receivers in a wireless local area network (WLAN) through IEEE 802.11b and 802.11g standards. The Ekahau™ smart tag is commercially available from Ekahau, Inc., Reston Va. and may be used in the present exemplary embodiment. Other examples of suitable smart tags may be provided, and include those, such as described, in U.S. Pat. No. 6,853,303, which is incorporated herein. As noted, the data from the smart tag may be acquired by data acquiring devices 140, such as readers 140, readers/writers 140, scanners 140, or receivers, such as wireless receivers 140, as well as other suitable devices. A reader or scanner may include an antenna for transmitting a trigger signal to a smart tag and receiving a return signal from the tag containing information. The data acquiring devices 140 may be placed in any one or more of the critical spots of the process including but not limited to the area where the components 110 and/or PPE articles 120 are handed out to the individual. In some exemplary embodiments, one or more data acquiring devices 140, such as readers or scanners 140 are hand-held. For example, a receiver 140 may be a wireless node of a wireless local area network (WLAN) that may provide internet access point. The readers 140 may be linked to a remote programmable electronic system 150 through the network 160. The programmable electronic system 150 includes functionalities that enable tracking usage of the components against at least a predetermined criterion, such as a in the exemplary embodiment a change-out criterion. These predetermined criteria may include, but are not limited, to circumstances regarding the components in terms of their servicing, repairing, cleaning, maintaining, decontaminating, or other processing. For example, change-out may occur if: the time weighted exposure level of the component in the working environment exceeds a threshold value(s); the concentration level(s) of particular contaminants exceed threshold value(s); the presence of unexpected contaminants in the working environment; persons with particular profiles should not be exposed to various contaminants; particular kinds of PPE articles should not be used when certain contaminants are present, or concentration and exposure thresholds exceeded. As illustrated in FIG. 1, the reader 140a may be stationed at the entrance of the work environment 125 and acquires relevant data of the wearer; component 110, and the PPE article 120, such as at the start of the workday or shift and at the end of the work day or shift. The readers may be in several other locations, such as where the components are removably coupled to the PPE article. This information is sent to a database of the computer system 150 for the purpose which will be described. Alternatively or additionally, one or more readers 140 may be located within the actual work environment 125 so as to provide opportunities for wearers obtaining readings in the work environment 125. Alternatively or additionally, a portable reader 140 may be utilized (see FIG. 5), such as when the PPE 120 and the component 110 are issued prior to entering the work environment. A typical portable reader 140 may have a display 132 and keypad 134 for data input and are wirelessly connected to the network 160. The portable reader 140 may be used when the tagged components or PPE article are in the work environment 125 or uncoupled to the PPE article 120 at the end of a work shift. The present disclosure does not place limitations on the locations or timing of reading of the tagged components or PPE article. Exemplary suitable sensors 145 of some exemplary embodiment may include, without limitation, measurement of the following analytes/parameters: electromagnetic radiation (such as thermal and visible), ionizing radiation, nuclear radiation, chemicals (such as liquids, solids, vapors, gases and mists/aerosols), biological analytes, particulates, noise, heat stress, motion, as well as others. The transducers may be of the electrical or optoelectronic type. The sensors 145 may be mobile or stationary in the work environment and connected, as for example, by wireless to the network. In a mobile mode, the sensors 145 may be disposed on the PPE or on the component. The sensed information data is generally related to the usage of the component being tracked as will be explained. The data, as noted, concentration levels, types of contaminants, presence or absence of contaminants, insufficient or no current to run a circuit of the component, inadequate pressure for a SCBA, insufficient or no battery power, breakthrough of a chemical through a filter, or inoperable safety mechanisms. The present disclosure is not limited by these examples since what is sensed encompasses all known factors that may relate to the condition of a component that is to be coupled to PPE articles. The network 160 may include, without limitation, a local-area network (LAN), wide area network (WAN), the internet, or a wireless network, such as a wireless local area network (WLAN). The programmable electronic system 150 may represent any type of computer system, programmable logic devices, or the like. The computer system 150 may include server computers, client computers, PC-based servers, minicomputers, midrange computers, mainframe computers; or other suitable devices. In some exemplary embodiments, the computer system 150 may include portable computer systems including laptops, handheld computer systems. In addition, the system 100 may include one or more local computer systems 170 located in the work environment 125. As such, workers may be able to obtain pertinent data, for example, a real-time assessment of the condition of the component while in the work environment 125. The local computer system 170 typically includes portable computer systems including laptops, handheld computer systems. The local computer system 170 may also include other computer systems, such as, client computers, PC-based servers, minicomputers, midrange computers, mainframe computers; or other suitable devices. With continued reference to FIG. 2, there is depicted a server computer system 150. It is depicted as comprising at least one system interconnect bus 180 to which various components are coupled and communicate with each other. Coupled to the system interconnect bus 180 is at least a single processor unit 182, storage device 184, memory such as random access memory (RAM) 186, read only memory (ROM) 188, a relational database management system (DBMS) 189, and input/output (I/O) ports 191. The relational database is a computer database management system 189 controlling the storing, updating, and retrieving of data to database files for use in tracking usage of components against one or more predetermined criteria. The database files contain all relevant information pertaining to the operational parameters of the readers. Furthermore, one or more output devices 192 such as a display, as well as one or more user interface input devices 194, such as a keyboard and/or pointing device is respectively coupled to the I/O ports 191. In known fashion, the output and input devices 192 and 194; respectively permit wearer interaction with the computer system 150. The I/O port 191 typically includes various controllers (not shown) for each input device 194, such as a keyboard, mouse, joystick, and the like, as well as the output device 192, such as an Ethernet network adapter, infrared device and display (not shown). The processor 182 controls the input device 194 which provides a user interface for allowing a wearer to access information, such as usage history of components being tracked. The processor unit 182 may be any suitable processor and sends and receives instructions and data to and from each of the computer system's components that are coupled to the system interconnect bus 180 to perform system operations based upon the requirements of the computer system's operating system (OS) 196, and other specialized application programs 198a-198n (collectively 198). The ROM 188 typically controls basic hardware operations. The storage device 184 may be a permanent storage medium, such as a hard disk, CD-ROM, tape, or the like, which stores the operating system 196 and the specialized applications programs 198. The RAM 186 is volatile memory. The contents of the RAM 186 may be retrieved from the storage device 184 as required. Illustratively, the RAM 186 is shown with the operating system 196 and application programs 198 concurrently stored therein. The program code of the operating system 196 and/or application programs 198 is sent to the RAM 186 for temporary storage and subsequent execution by the processor 182. Additionally, the RAM 186 is capable of storing files from the operating system 196, as well as files from one or more application programs. An information retrieval system application program(s) 198a is one typically utilized for controlling operations of the information retrieval system 102 including the functionalities described herein with respect to the smart tags 130, data acquiring devices 140, and sensors 145. Provision is made for a suitable database management system application 198b to run the database 189 in a manner consistent with the present disclosure. Also, provision is made for an establish predetermined criteria application 198c. This may, in some cases, be a software application provided by a manufacturer of the components or PPE article that are to be tracked. In some exemplary embodiments, this software application may be used to establish conditions for proper usage of the component or PPE article as determined by the rules and regulations established by the government, insurance company or other entity interested in the results. The establish condition determining application 198c is updatable to establish a new or current criteria related to actual conditions of the component in the working environment, as for example, by using the data acquired. A report generating application 198d is provided that may generate reports containing a variety of data in different reporting formats tailored for purposes including those described below. These reports may be generated to allow workers, supervisors, health professionals to access the history and status of components and/or articles; their medical information, information relating to fit-testing, training, job responsibilities, seniority or experience, access privileges or any other information, history of component servicing, maintenance, change-out, as well as other information. The determining component condition application 198n of the present disclosure enables determining the conditions of the tagged components following retrieval of tag information against predetermined criteria established by the establish predetermined criteria application 198c. Reference is made to FIG. 6 for illustrating one exemplary embodiment of a tracking process 600 that may be implemented by the component condition determining system 100. The tracking process 600 enables the condition of a component 110 that is tagged with a smart tag 130 to be determined based on comparing its tracked usage against at least a predetermined criterion which in the exemplary embodiment is a change-out condition of a filter cartridge 110 relative to a respirator (RPE) 120. Alternatively, the present disclosure also envisions that the PPE article 120, that is to be coupled to the component 110, may be tagged with the smart tag towards the end of determining the condition of the component. Such circumstances may arise if the component is not easily tagged or cannot be tagged. The term “condition” as utilized in the present application means the particular state of one or more factors that affect the operational life or usefulness of one or more component(s) utilized as accessories for PPE articles. In a Sense Initial Condition block 610 of the tracking process 600, sensing is performed by one or more of the sensors 145. In this embodiment, the type of component being tracked determines which variables in the working environment should be sensed and, therefore, which sensors to be used. Since filter cartridges are being tracked in this exemplary embodiment, the sensor 145 is of the type that collects data bearing upon the component's condition. In particular, concentration levels of particular hazardous materials over a period of time may be sensed. As will be explained, the concentration levels assist in establishing a predetermined criterion regarding the condition of the tagged component. The initial data collected may reflect low, average, and peak concentration levels of the particular hazardous material(s). While hazardous materials are being monitored in the exemplary embodiment, the present disclosure envisions that there are no limits on the variables that may be sensed and the relationship these variables have in determining the condition of the component. For example, variable factors relating to other aspects of usage of a component may include: charge of a battery, amps in a circuit, circulating air pressure of a filter and/or respirator. The tracking process allows this data to be forwarded to the database. The tracking process 600 then proceeds to Retrieve Criteria block 620, whereat the establish a predetermined criteria application 198c retrieves the appropriate criteria for the component being tracked. If the exemplary component being monitored is a filter cartridge, the pertinent criterion (or criteria) that is relevant to the condition of the filter cartridge is selected. The set of criteria is stored in memory. The set of criteria may be obtained from many different sources that provide guidance on the proper usage of the component. The set of criteria may be downloaded, for example, from the internet. Typically, the manufacturer of the component may provide the set of criteria relevant to the condition of the component. The set of criteria may be developed by government, industry, the company operating the system 100, an insurance company, a standards body, and persons of interest, such as a safety officer, industrial hygienist, or the like. In one exemplary embodiment, the set of criteria may relate to minimum or maximum exposure times that a filter cartridge or respirator may safely operate. Another example of a set of criteria relates to proper battery charge of a component relative to acceptable limits of performance of the component. Still another example of a set of criteria governs use of when a filter cartridge component should be serviced, repaired, or otherwise treated is based on inadequate pressure exists in a self-contained breathing apparatus (SCBA). Following the Retrieve Criteria, block 620, the tracking 600 proceeds to an Establish Predetermined Criteria block 630. In the block 630, the initial data that may be sensed in the block 610 is processed in the database by the establish predetermined criterion application 198c. As a result, a predetermined criterion for the component 110 may be established in the actual working environment. In such exemplary embodiments, the predetermined criteria application(s) 198c analyzes the collected monitored data in terms of the set of criteria the rules retrieved in the block 620 to determine the predetermined criterion that will determine the condition of the component during actual operation in the working environment is satisfied. For example, based on the initial concentration levels in work environment, then a maximum exposure time for the filter cartridge may be determined. The predetermined criterion takes into account what the exposure time should be for the filter cartridge in the work environment. The tracking 600 may further include a Reporting block 640 that follows the Establish Predetermined Criteria block 630 under the control of the reporting application 198b. The Reporting block 640 is capable for generating a report relevant to a wide variety of subjects including, but not limited to, the condition of the component, the worker, the PPE article, the initial sensed data, the work environment, and other pertinent information. Typically, the Reporting block 640 generates a report in a format acceptable by an entity requesting the report, for example, the business entity using the system 100, or a governmental agency, such as OSHA. While the Report block 640 follows Establish Predetermined Criteria block 630, reports may be generated at any one or more other points in the process. The reports may be generated by the workers or other persons of interest or even in response to requests by the government. The reports generated may be transmitted across the internet as well. There is no time limit to generating the reports. The tracking process 600 proceeds to a Retrieve Tag Information block 650. In this embodiment, the system 102 retrieves or acquires the data, as noted above, from the smart tags 130 by the data acquiring devices 140, such as a receiver 140, as well as the sensors 145. The smart tag 130 of this embodiment may be an Ekahau™ type to provide location information as well as the data of the smart tag. Other smart tags can be provided. The receiver 140 may be located in any number of places, such as the entrance to a work environment 125. In particular, retrieving information from the smart tag 130 may provide data as to when and where the wearer enters the working environment, exits the working environment, or passes another location. Optionally, in order to identify the wearer, the latter may present his/her badge to an appropriate data acquiring device 140. The smart tag 130 or the badge may also include other data regarding the wearer, such as medical, fit test, job description, seniority, training, and other qualifications. The retrieved data is forwarded to the database 189 of the computer system 150, and, if operational, the local computer system 170. The data may include the identification of an article, date, and or timestamp, as well as the location of the data acquiring device. The present disclosure envisions that the retrieving of tag information may occur more than once and at any suitable number of different points in the tracking process. The tracking process 600 then may proceed to the Sense In Work Environment block 660. In the Sense In Work Environment block 660, the sensor 145 is operable for providing current sensed data, for example, regarding current concentration levels of benzene vapor, in the work environment 125. This data is forwarded to the database. The tracking process 600 then may proceed to the Update Criterion block 670. In the Update Criterion block 670, the data from the database from the sensor 145 is acted upon by the establish predetermined criteria application 198c, where a new analysis is conducted to determine whether an update predetermined criterion is to be used. Such updating enhances the overall advantages provided by the present disclosure. While the Sense In Work Environment block 660 and the Update Criterion block 670 are illustrated, they need not be present used in the tracking process 600. In such a case, the process 600 may proceed to the Determine Condition of Component block 680. The tracking process 600 then may proceed to the Determine Condition of Component block 680. In the Determine Condition of Component block 680, the condition determining application 198n determines if the condition of the component satisfies the initial or updated criterion. In particular, in an exemplary embodiment, a determination is made as to whether a filter cartridge has an exposure time that exceeds the recommended exposure time of the component in the working environment as determined in the Establish Predetermined Criterion block 630. In the exemplary embodiment, in the Determine Condition of Component block 680, the filter cartridge has satisfied the change-out condition (i.e., Yes) if its actual exposure time does exceed the recommended exposure time, when compared to the recommended exposure time, indicated in the Establish Predetermined Criteria block 630 or the Updated Criterion block 670. Conversely, the change-out condition is not satisfied (i.e., No) if the actual exposure time does not exceed recommended exposure time as determined in the Establish Predetermined Criteria block 630 or the Updated Criterion block 670. The determining may further include determining the extent-of-service life remaining for the component in the one or more working environments. The tracking process 600 may also include a Communicate block 685, whereat compliance or non-compliance is communicated, using any known communication methodology, to appropriate persons, or reporting entities. Such a communication may be transmitted to the user, the database, the user's supervisor, industrial hygienist or other appropriate personnel. The process of this block may be occurring at other times. In one exemplary embodiment, such determinations may be made as a message to display screen of the computer or to a personal digital assistant (PDA). It will be appreciated that other suitable software applications may be used to provide such communication. In one exemplary embodiment, such communications may be made as a message to display screen of the computer or to a personal digital assistant (PDA). It will be appreciated other suitable software applications may be used to provide such communication. In some exemplary embodiments, such communications may include an alarm or audible signal to appropriate persons including the user and/or supervisor. The tracking process 600 also includes a Process Article block 690 that may follow the Communicate block 685. A wide variety of processes may be performed to handle the article or component, such as cleaning, refurbishing, disposal, maintenance or the like of the article or component. A wide variety of disposal methods are contemplated, for example, being displaced in a bin, this will ensure that the component will not be used until some other steps are undertaken. The tracking process 600 may then proceed to Verify Processing block 695. In the Verify Processing block 695, a data acquiring device 140 may be stationed adjacent to the processing area, such as a disposal bin, for acquiring relevant identification data from its smart tag 130 that the processing of article or component has been verified. The verification data is transferred to the server's database for storage in the internal memory and subsequent use. As a consequence, processing is duly recorded in the database. The following examples are prophetic examples using the principles of the present disclosure. In this example, the system includes a respirator cartridge component tagged with a passive smart tag, such as an RFID tag, a tag reader at a (portal) stationed at the entry of a work area (e.g. paint booth). The database stores information when the smart tags are read at the tag reader. Safety personnel/workers may access or use the information by a computer system in the work environment that is configured to allow safety personnel/workers to obtain a change-out determination or obtain other data while in the work environment. Within an automotive paint shop, methyl ethyl ketone is identified as a principal organic vapor hazard. For respiratory protection, workers use 6000 series half face piece respirators equipped with 60921 P100/OV cartridge components. Based on air sampling data, a time weighted average (TWA) concentration of 300 ppm MEK is sensed. Based on change-out software calculations, an 8 hr. shift change-out schedule is put in place. A worker dons a respirator RPE with new filter cartridge components at the beginning of the working day. The filter cartridge components may be labeled with passive Smart tags (as shown in FIG. 3). At the time of issue of the filter cartridge components, the smart tags may be encoded with the identity of the wearer. On the way into the paint booth, the worker passes through a tag reader as illustrated in FIG. 4. The smart tags are read and a time point is entered in an associated database to mark the beginning of use. Throughout the working day, additional time points may be entered for the specific tags when the individual passes through the portal. At the end of the working day, the respirator is stored outside the paint booth. The following day, the worker dons the same respirator and proceeds through the portal into the booth. The smart tags may be read, and the time data within the database are to be used to determine that exposure time for the component has been exceeded and a change-out condition is present. Any suitable user warning device, such as an audible beep, notifies the wearer that the filter cartridge components have been used beyond baseline conditions. Such information is recorded and stored in the database, enabling review by the safety coordinator. In this example, the system comprises the following: respirator cartridge components tagged with passive RFID smart tags; a portable tag reader utilized within a central respirator storage location; a database which stores information when tags may be read; and a software interface which allows safety personnel/workers to access the use or tracking information and history. Within a petrochemical refinery, benzene vapor is identified before use of the smart tags as a contaminant. For respiratory protection, workers use 6000 series half face piece respirators equipped with 60921 P100/OV cartridge components. The presence of benzene makes change-out after an 8-hr. work shift a requirement. Respirators may be kept within a common area of the facility, and the supply person uses a portable tag reader (FIG. 5), with which he reads the smart tags before a worker takes the respirator to begin work. At the time of issue of the cartridge components, the smart tags may be read and linked to the identity of the wearer, and an initial time point is entered in an associated database to mark the beginning of use. At the end of the workday, the respirator is checked back in to the common storage/maintenance area. If the cartridge components have not been disposed of, an audible sound will cue the supply person and worker the following day when they are added to the respirator and read again prior to reissue. A system, as in Example 1, is utilized to track filter cartridge component change-out. In this instance, however, re-writable RFID smart tags on the component may be employed so that the time data may be logged on the smart tag rather than in a database, each time the individual passes through the portal. A time interval greater than 8 hours after the initial tag reading triggers an alert to the wearer that cartridge components must be changed by the change-out conditions determining mechanism. A system, such as in Example 2, is utilized to track cartridge component change-out. The cartridge components may be again read by a supply person prior to issue to the worker. In this instance, however, an additional reader is placed on a common waste barrel where cartridge components are disposed of. Each cartridge is read as it is placed into waste so that disposal within a single work shift is ensured. Cartridge components that remain in use beyond a single shift trigger an electronic alert notice to the supply person, worker, safety personnel, and/or the industrial hygienist. In this example, the system comprises the following: respirator face pieces tagged with re-writable RFID smart tags; a portable tag reader utilized within a central respirator storage location; disposable 60921 P100/OV cartridge components for protection against organic vapors. In this embodiment, the cartridge is tagged although it need not be. Within a petrochemical refinery, benzene vapor is identified as a contaminant. For respiratory protection, workers use 6000 series half face piece respirators equipped with 60921 P100/OV cartridge components. The presence of benzene makes change-out after an 8-hr. work shift a requirement. Respirators may be kept within a common area of the facility, and the supply person uses a portable tag reader (FIG. 5), with which he/she programs the re-writable RFID tag on the respirator face piece before the worker takes the respirator to begin work. The smart tag is programmed with the identity of the wearer, and an initial time point/date to mark the beginning of use of fresh respirator cartridge components. At the end of the workday, the respirator is checked back in to the common storage/maintenance area. When the utilized cartridge components are disposed of and replaced with fresh ones, the smart tag is re-programmed to log the change-out and the new start time point. If the cartridge components are not disposed of (and the smart tag reprogrammed), a beep/visual from the reader will cue the supply person and worker the following day when the smart tagged face piece is read again prior to reissue. In this example, the information retrieval system 100 comprises the following: respirator cartridge components tagged with passive RFID smart tags; a portable tag reader utilized within a central respirator storage location; a database which stores information when tags are read; a fixed wireless chemical sensors (PID sensors) that stream data to the database; a software interface which allows safety personnel/workers to access the use information and history. Within an automotive paint shop, methyl ethyl ketone (MEK) is identified as a principal organic vapor hazard. For respiratory protection, workers use 6000 series half face piece respirators equipped with 60921 P100/OV cartridge components. A worker dons a respirator with new cartridge components at the beginning of the working day. Both cartridge components may be labeled with passive RFID smart tags (as shown in FIG. 3). At the time of issue of the cartridge components, the smart tags may be read, and the time of issue and identity of the wearer may be stored within the database. During the workday, wireless chemical sensors placed throughout the shop record and stream concentration data on the MEK vapor to the same central database that maintains the smart tag information. The chemical concentration data may be utilized to update the change-out conditions by calculating remaining service life and timing for change-out of the respirator cartridge components utilized by employees within the facility. At the end of the workday, the respirator is checked back in to the common storage/maintenance area. The smart tags on the cartridge components are read, and if the duration of issue exceeds the calculated service life, a visual cue in the software interface will indicate the need to change the cartridge components. The system of Example 6 is utilized to track cartridge components and to monitor the environment so as to calculate cartridge service life. In this instance, however, the wireless chemical sensors are worn on the individual workers, so that the chemical concentration data for a particular individual may be utilized to allow the establish change-out conditions application to calculate that person's unique remaining cartridge service life. The passive RFID smart tags are employed as described in Example 6 for tracking appropriate disposal and issue of fresh cartridge components relative to the calculated individual change-out schedule. It will be appreciated that based on the above description, aspects of the disclosure include methods, systems, and computer program products for determining change-out conditions for component joinable to articles, such as articles of personal protection equipment (PPE), by tracking their usage in monitored working environments against predetermined change-out criteria. Further aspects of the disclosure include methods, systems, and computer program products utilized for ensuring worker safety, and providing for appropriate change-out of components. Still further aspects of the disclosure include methods, systems, and computer program products utilized for achieving the foregoing economically and expeditiously. It will be appreciated that numerous and varied other arrangements may be readily devised in accordance with these principles by those skilled in the art without departing from the spirit and scope of the invention as claimed. Although the methods and system of the present disclosure have been described with referent to specific exemplary embodiments, those of ordinary skill in the art will readily appreciate that changes and modifications may be made thereto without departing from the spirit and scope of the present invention. |
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claims | 1. An apparatus for treating a tumor of a patient, comprising:a cancer therapy treatment system, comprising:a synchrotron configured to: (1) accelerate cations at a first time and (2) accelerate electrons at a second time, said synchrotron comprising a turning magnet, said turning magnet comprising:a set of magnet coils wrapped around a magnet core, said set of magnet coils configured to turn the cations;a set of correction coils, said set of correction coils configured to turn the electrons, andsaid set of correction coils wound about said magnet core,said cancer therapy treatment system configured to: (1) treat a first depth of the tumor with the cations and (2) treat the tumor using the electrons. 2. The apparatus of claim 1, further comprising:a set of power supplies connected to said set of magnet coils; andan additional set of power supplies connected to said set of correction coils, said additional set of power supplies configured to correct a magnetic field generated by said set of magnet coils at the first time. 3. The apparatus of claim 1, further comprising:a current controller configured to switch polarity of said turning magnet between the first time and the second time. 4. The apparatus of claim 2, further comprising said cations comprising at least one of:H+; andC6+. |
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