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061817619 | abstract | The reactor start-up monitoring apparatus is provided with an SRNM detector, an analog amplifier, an N/D converter, a pulse measurement system, a Campbell measurement system and reactor power monitoring means. The pulse measurement system is provided with pulse counting means for counting the pulse number of output pulses of the detector from the first digital data from the converter, and pulse measurement evaluating means for converting the measurement value to reactor power and evaluating the reactor power. The Campbell measurement system is provided with sum operating means for adding a plurality of sampling values forming the first digital data from the converter and acquiring the second digital data having accuracy of bits more than those of the first digital data, power operating means for obtaining mean square values based on the second digital data and Campbell measurement evaluating means for converting the mean square values to reactor power and evaluating the reactor power. |
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047818840 | claims | 1. In a nuclear reactor having fuel assemblies including an upper end fitting and a lower end fitting and spaced nuclear fuel rod spacer grids therebetween for supporting and spacing elongated nuclear fuel rods which includes a hollow active portion of nuclear fuel filled cladding intermediate the rod'ends and a tapering end cap of solid material on the rod end which first encounters reactor coolant flow, a debris catching strainer grid for capturing and retaining deleterious debris carried by reactor coolant before it enters the active region of a fuel assembly and creates fuel rod cladding damage, comprising in combination: a polygonal perimeter, a plurality of fuel end cap compartments defined by pairs of first and second intersecting and slottedly interlocked grid-forming strips attached to said perimeter and to each other, each said fuel rod end cap extending into a respective one of said end cap compartments, at least some of said end cap compartments defined by two pairs of intersecting and slottedly interlocked strips including vertical rows of integral leaves intermediate their intersections, each of said leaves of a row presenting an edge to the coolant flow, being radially adjacent and radially spaced from said fuel rod end caps and having a distance of projection out of the plane of its respective strip different from the others in its row, and means for attaching said debris catching strainer grid to the lower portion of said fuel assembly. 2. The debris catching strainer grid of claim 1 in which each of the leaves of a row are spaced from its adjacent leaves in the row by an amount equal to the width of a leaf in a row on the opposite side of the strip. 3. The debris catching strainer grid of claim 2 in which the lower leaf projects out of the plane of its strip the most while each successive leaf in the row, as flow proceeds upwardly, projects a lesser amount. 4. The debris catching strainer grid of claim 1 in which the strainer grid is welded to a lower end fitting of the fuel assembly with which it is associated. |
abstract | A fuel assembly mechanical flow restriction apparatus for detecting failure in situ of nuclear fuel rods in a fuel assembly during reactor shutdown. |
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abstract | The present invention relates to a specimen box for an electron microscope, which comprises a first substrate, a second substrate, and a metal adhesion layer. The first substrate has a first surface, a second surface, a first concave, and one or more first through holes, wherein the first through hole penetrates through the first substrate. The second substrate has a third surface, a forth surface, and a second concave. Besides, the metal adhesion layer is disposed between the first substrate and the second substrate to form a space for a specimen placed therein. In addition, the specimen box of the present invention further comprises one or more plugs. When the plug is assembled into the first through hole to seal the specimen box, the in-situ observation can be accomplished by using an electron microscope. |
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048896845 | abstract | In a nuclear boiling water reactor, an improved lower tie-plate and fuel channel interface for a boiling water reactor fuel bundle is disclosed. The fuel bundle has a lower tie-plate for supporting fuel rods and permitting the introduction of fluid interior of the fuel bundle. An upper tie-plate maintains the lower tie-plate supported rods in side-by-side relation and has apertures for discharging a mixture of water and steam. The fuel rods extend between the tie-plates for the generation of steam with some of the fuel rods forming a threaded connection fastening the tie-plates together. A polygon sectioned channel, preferably square, surrounds the tie-plates and fuel rods for the confining of fluid flow between the tie-plates interior of the bundle. The interface of the channel as it surrounds the lower tie-plate is reconfigured. This reconfiguration includes means for inducing a rapid pressure drop from the interior juncture of the lower tie-plate and channel to and towards the exterior juncture of the lower tie-plate and channel. Because of this rapid pressure drop the bottom portion of the square sectioned channel is not subject to the pressure loading, and the bottom portion reinforces the upper portion. In one embodiment, a labyrinth seal configuration is made in the region of overlap between channel and the lower tie-plate, consisting of intermittent interruptions of an otherwise constant flow area between the lower tie-plate channel. The labyrinth seal is disclosed as configured either in the lower tie-plate or channel.. In a second, preferred embodiment, a diffuser is incorporated in the region of overlap between the channel and lower tie-plate. The diffuser causes a pressure distribution in the overlap region which limits the deflection of the channel. |
043839690 | claims | 1. Method for the removal of the small amounts of carbon monoxide, carbon dioxide and gaseous alkanes in which the compounds have radioactive carbons, produced in nuclear power stations and contained in the exhaust gases of the purification plant, which comprises subjecting exhaust gases containing the mixture of carbon monoxide, carbon dioxide and gaseous alkanes in which the compounds have radioactive carbons, to oxidation to effect substantially complete conversion of the mixture of the radioactive compounds to radioactive carbon dioxide, and subsequently removing substantially all said radioactive carbon dioxide from the exhaust gases containing it. 2. Method according to claim 1, wherein said oxidation is obtained by passing said exhaust gas with a slight amount of excess oxygen in contact with palladium contact bodies at a temperature of .gtoreq.450.degree. C. 3. Method according to claim 1, wherein said oxidation is obtained by passing said exhaust gas with a slight amount of excess oxygen in contact with platinum contact bodies at a temperature of about 500.degree. C. 4. Method according to claim 1, wherein said oxidation is obtained by passing said exhaust gas with a slight amount of excess oxygen in contact with CuO contact bodies at a temperature at least about 750.degree. C. 5. Method according to claim 1, wherein said exhaust gas after oxidation is subjected to cooling and said cooled exhaust gas subsequently passed in contact with an absorption medium to effect removal of the .sup.14 CO.sub.2. 6. Method according to claim 5, wherein said absorption medium is a sodium or potassium hydroxide solution with a small amount of BaCl.sub.2. 7. Method according to claim 5, wherein said absorption medium is a Ba(OH).sub.2 solution in which Ba.sup.14 CO.sub.3 precipitates. 8. Method according to claim 5, wherein said absorption medium is a solid alkaline absorbent material such as soda lime and sodium asbestos. 9. Method according to claim 1, wherein a non-radioactive carbon containing carrier gas is admixed with said exhaust gases. 10. Method according to claim 9, wherein the said carrier gas is methane. 11. Method according to claim 10, wherein said carrier gas is about 0.1% by volume of the exhaust gases. |
abstract | A fusion device produces fusion of neutral atoms and ions in an “aneutronic fusion” manner without neutrons as products utilizes strong ion-neutral coupling at high neutral densities. Ions and neutrals rotate together in a cylindrical chamber due to frequent collisions. High magnetic forces make the attainment of high rotation energy possible; the magnetic field in a medium can be set at very high values because of the absence of magnetic charges. The repeated acceleration by strong magnetic forces in the azimuthal direction makes possible very high ion velocity. Fusion takes place mainly between neutral particles. This approach can be applied to fusion with neutrons as well. Conventional fusion schemes and neutron sources can be realized using the principles described above in the generation of neutrals of high energies and densities. |
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claims | 1. An ultraviolet laser sterilization system comprises:an ultraviolet laser module emitting an ultraviolet laser light with a wavelength ranging from 200 nm to 280 nm, the ultraviolet laser light irradiating an area ranging from 1 mm2 to 4 mm2 and having a light intensity of 5 kilowatts (KW) peak power; anda scanning module including a plurality of reflectors for receiving the ultraviolet laser light, and a controller for controlling rotation of the reflectors to adjust an angle of emergence of the ultraviolet laser light for sterilizing a target. 2. The ultraviolet laser sterilization system as claimed in claim 1, wherein the wavelength of the ultraviolet laser light is 266 nm. 3. The ultraviolet laser sterilization system as claimed in claim 1, wherein the system is further provided with an ozone detector module electrically connecting to the controller for transmitting a signal of ozone concentration detected in the environment to the controller, so as to allow the controller to adjust the power and the irradiation time of the ultraviolet laser light on a target. |
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claims | 1. A radioactive waste treatment facility comprising; a transferring means for transferring a solidifying container in a transferring line from an upstream side to a downstream side, a solidifying agent injecting and kneading means for preparing a solidifying agent paste by kneading a solidifying agent and an additive water, and injecting said solidifying agent paste into said solidifying container at a first location at the upstream side of said transferring means, and a waste charging and kneading means, which is capable of charging radioactive waste into said solidifying container at the second location at the downstream side of the first location of the transferring means and which is also capable of kneading the radioactive waste in said solidifying container. 2. A radioactive waste treatment facility as claimed in claim 1 , wherein; claim 1 said solidifying agent injecting and kneading means comprises; a kneading vessel, which the solidifying agent and the additive water supplied; a first kneading blade for agitating an inside of said kneading vessel; an out-drum type kneader of solidifying agent for preparing said solidifying agent paste; and an injecting means for injecting said solidifying agent paste in said kneader of solidifying agent into said solidifying container. 3. A radioactive waste treatment facility as claimed in claim 1 , wherein; claim 1 said waste charging and kneading means comprises; an elevating means for elevating said solidifying container, which has been transferred to the second location by said transferring means, in an upward direction relative to said transferring line of said transferring means; and an in-drum type waste kneader, which charges radioactive waste into said elevated solidifying container and performs kneading in said solidifying container with second kneading blades. 4. A radioactive waste treatment facility as claimed in claim 1 , wherein; claim 1 said solidifying agent injecting and kneading means is installed in an area separated by a partition wall from said waste charging and kneading means. |
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046719270 | abstract | A nuclear fuel rod contains nuclear fuel pellets that have incorporated therein a hybrid burnable absorber that affects a moderation of the burn-out rate of the system containing the rod. The nuclear fuel pellets contain 1 to 20 percent by weight gadolinium oxide and 0.02 to 1.0 percent by weight of boron carbide particles of a size between 20 to 100 microns in diameter, the particles coated with a 0.5 to 10 micron thick coating of a helium gas-impervious coating. |
047044136 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition having an electomagnetic wave shielding effect, and more particularly to a resin composition for shielding the transmission of electromagnetic waves thereby to prevent disorders or trouble caused by electromagnetic waves. 2. Prior Art In conventional systems, electronic instruments, such as business machines, electronic computers and television receivers, generate electromagnetic waves by themselves to cause malfunctions and/or noises in neighboring electronic instruments. On the other hand, the electronic instruments are affected by the electromagnetic waves emitted from the adjacent electronic instruments, leading to malfunction thereof or generation of noises therefrom. Troubles caused by the electromagnetic waves have been obviated to some extent when the housings of such electronic instruments are made of metal plates or aluminum die castings which can shield the transmission of electromagnetic waves. However, plastic materials have been predominantly used for the housings of electronic instruments in recent years, because of the merits that they are easily molded to have various designs and that they are light in weight. However, the plastic materials are generally poor in conductivity and have substantially no electromagnetic wave shielding effect. It is, thus, necessary to process the plastics materials to provide them with electromagnetic wave shielding effect when they are used for the housing of electronic instruments. Particularly, in recent years, radiation of electromagnetic waves has been severely prohibited by domestic and foreign regulations. Under these circumstances, there is an increasing demand for plastic materials provided with electromagnetic wave shielding effects. Various methods for providing the plastic materials with the electromagnetic wave shielding effect have hitherto been investigated, the known methods including application of an aluminum foil or a conductive tape, flame spraying with molten zinc, coating with a conductive paint, metal plating on the plastic materials, vacuum evaporation coating, spattering ion plating and molding a conductive plastic material containing a conductive filler. However, the method of application of an aluminum foil or a conductive tape for the provision of electromagnetic wave shielding effect is not used practically, since it has the disadvantages that extreme skill is required and that it is not suited for housings having complicated shapes. The method of flame spraying with molten zinc and the method of coating with a conductive paint have been predominantly used at the present time. However, these methods have the disadvantages that the thickness of the lining or coating becomes uneven when the housing has a complicated shape and that the adhesiveness of the lining or cooating to the substrate is insufficient, which results in exfoliation of the conductive layer, leading to the loss of the electromagnetic wave shielding effect or even causing a risk of fire. Although the durability and adhesiveness of the metal plated on the plastics materials are satisfactory, only few kinds of plastic materials can be plated with metals and the articles to be plated are limited to those of small dimensions. Satisfactory electromagnetic wave shielding effect can be provided by metal evaporation techniques including vacuum evaporation coating, spattering and ion plating. However, these techniques have not been applied for commercial scale production, since they require expensive apparatuses and skillful operations. Contrary to the aforementioned methods wherein conductive layers are formed on the surfaces of molded plastic materials to provide the electromagnetic wave shielding effect, the molded products made of a composite conductive plastics material containing a conductive filler mixed and dispersed in a matrix plastic material is averted from the impairment of electromagnetic wave shielding effect or from the risk of fire caused by exfoliation of conductive layer. However, the known conductive plastic molded articles have the disadvantages that satisfactory electromagnetic wave shielding effect cannot be obtained unless a large amount of conductive filler is added to the matrix plastic material, and that the physical properties of the resultant plastic material are deteriorated or the appearance of the molded article is impaired with serious increase in cost as the quantity of the filler added to the matrix plastic material is increased. Particularly, as the amount of added conductive filler is increased, the dispersibility of the filler is lowered to result in uneven dispersion thereof. Especially when carbon fibers are used for the conductive filler, the fibers are broken during the kneading step to lower the electromagnetic wave shielding effect. If some part of the expensive carbon fibers is replaced by another inexpensive conductive filler in order to decrease the content of the carbon fibers, the fibrous and pulverized fillers present in the mixed condition become hardly dispersed in the matrix resin, leading to deterioration of moldability of the plastic material and deterioration of the properties of the molded articles. If the resultant plastic material is molded at a higher temperature in order to improve the moldability thereof, the matrix resin is decomposed or otherwise damaged so that the physical properties and the appearance of the molded articles are deteriorated and the coloring property of the resin becomes poor. OBJECTS AND SUMMARY OF THE INVENTION An object of this invention is to provide a resin composition having improved electromagnetic wave shielding effect, comprising a resin ingredient and carbon fibers which are uniformly dispersed in the resin ingredient and are not substantially broken or cut at the step of mixing and dispersing them. Another object of this invention is to provide a resin composition having improved electromagnetic wave shielding effect and having improved fluidity and excellent moldability. A further object of this invention is to provide a resin composition having improved electromagnetic wave shielding effect, which can be molded at a reasonably low melting temperature to avoid deterioration of physical properties, appearance and coloring property of the matrix resin. A still further object of this invention is to provide a resin composition having improved electromagnetic wave shielding effect, which has a flame-retarding property and is improved in thermal and mechanical properties. Yet a further object of this invention is to provide a resin composition, which has an extremely high electromagnetic wave shielding effect and may be colored freely. The above and other objects of this invention will become apparent from the following description. The resin composition having an electromagnetic wave shielding effect, according to the present invention, comprises 35 to 90 wt% of a compolymer of an ethylenic unsaturated nitrile, a diene rubber and an aromatic vinyl compound or a mixture of said copolymer with another copolymer of ethylenic unsaturated nitrile and an aromatic vinyl compound; 1 to 25 wt% of a plasticizer; and 5 to 40 wt% of carbon fibers. |
040299686 | summary | BACKGROUND OF THE INVENTION The present invention relates in general to the storage of nuclear fuel elements and more particularly to the arrangement of racks for the storing of spent nuclear fuel elements in a pool for a nuclear power plant. Heretofore, racks for spent nuclear fuel elements were placed side-by-side in a pool. Thus, a considerable amount of floor space was required. However, the delay in the availability of nuclear fuel reprocessing plants have presented the problem to nuclear power plants of being able to transport the spent fuel elements to a reprocessing plant. When a reactor is refueled, the spent fuel elements are stored in the spent fuel storage pool of a nuclear power plant. Spent fuel storage pools for the nuclear power plant have been designed to store one full reactor core plus one or two reloads of nuclear fuel elements. It is desirable to always maintain enough space in the spent fuel storage pool to unload the full reactor core. Generally, this would leave space for only one or two reloads of nuclear fuel elements. A nuclear power plant should have sufficient space for the spent nuclear fuel elements to enable the nuclear power plant to keep operating and refueling until it is possible to transport spent nuclear fuel elements to a reprocessing plant. SUMMARY OF THE INVENTION Racks for storing nuclear fuel elements are disposed one above the other. By virtue of the present invention, a greater number of spent fuel elements can occupy the same floor space and still maintain the effective multiplication factor (K.sub.eff) below the required limit. Accordingly, nuclear power plants will have sufficient space to store a greater number of spent reactor fuel elements until a reprocessing plant can accommodate the transportation of the spent reactor fuel elements. As a result thereof, the shutdowns of nuclear power plants will be reduced. The decrease in floor space requirements for spent reactor fuel elements achieved by the present invention is applicable to both the boiling water reactor and the pressurized water reactor. By decreasing the floor space requirements, the capacity of a given storage pool for storing spent fuel elements is increased. Hence, the pool can accommodate a greater number of spent nuclear fuel elements. This results in an increase of storage time capability. The additional space capacity for the spent nuclear fuel elements is desirable to enable a nuclear power plant to keep operating and refueling until it is possible to transport spent fuel elements to a reprocessing plant. A feature of the present invention is the employment of guide pins and guide pin receptacles for the alignment of the racks for storing nuclear fuel elements one above the other. Another feature of the present invention is the employment of frame-like support for removably holding racks for storing nuclear fuel elements one above the other. A still further feature of the present invention is the interengaging members between the racks for storing nuclear fuel elements and the frame-like support to retain the racks in position relative to the frame-like support. |
abstract | A boiling water reactor core power level monitoring system includes a desired length of high dielectric, non-linear material insulated coaxial type cable in close proximity to the reactor core and a time domain reflectometry apparatus configured to measure a temporary characteristic impedance change associated with the coaxial type cable in response to at least one of neutron or gamma irradiation generated via the reactor core. |
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claims | 1. A method of adjusting a lithography system, said lithography system including adjustable apparatus for generating a beam and directing the beam to a production mask and onto a target area, said mask having a pattern to be projected onto the target area, said method comprising: positioning a test mask at a location of the production mask in the lithography system, said test mask having a pattern with geometries of about the size of geometries of the pattern of the production mask; projecting the beam to said test mask and thereby projecting the pattern of said test mask onto the target area at an exposure dose below the nominal exposure dose of the pattern of the production mask, thereby forming an underexposed image on the target area; and adjusting the adjustable apparatus of the lithography system based on quality of the underexposed image on the target area. 2. The method of claim 1 wherein the pattern of said test mask has geometries larger than the size of geometries of the pattern of the production mask. claim 1 3. The method of claim 1 wherein said exposure dose is 10%-25% below the nominal exposure dose of the pattern of the production mask. claim 1 4. The method of claim 1 wherein the beam comprises an electron beam or an ultraviolet beam. claim 1 5. The method of claim 1 wherein a substrate is positioned at the target area. claim 1 6. The method of claim 5 wherein said substrate comprises a semiconductor wafer. claim 5 7. The method of claim 5 wherein said exposure dose is such that geometries of the pattern of said test mask are on the verge of clearing to the substrate interface after development of the substrate. claim 5 8. A method of adjusting a lithography system, said lithography system including adjustable apparatus for generating a beam and directing the beam onto a target to develop a production pattern thereon, wherein the improvement comprises: projecting the beam, at an exposure dose below a nominal exposure dose of the production pattern, onto the target to develop an underexposed test pattern thereon, said underexposed test pattern having geometries of about the size of geometries of the production pattern; and adjusting the adjustable apparatus of the lithography system based on quality of said underexposed test pattern. 9. The method of claim 8 wherein said test pattern has geometries larger than the size of geometries of the production pattern. claim 8 10. The method of claim 8 wherein said exposure dose is 10%-25% below the nominal exposure dose of the production pattern. claim 8 11. The method of claim 8 wherein the beam comprises an electron beam. claim 8 12. The method of claim 8 wherein said target comprises a substrate. claim 8 13. The method of claim 12 wherein said substrate comprises a semiconductor wafer or a photolithographic mask. claim 12 14. The method of claim 12 wherein said exposure dose is such that geometries of the test pattern are on the verge of clearing to the substrate interface after development of the substrate. claim 12 |
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claims | 1. A power converter comprising:first and second electrodes;a three-dimensional current collector disposed between the first and second electrodes and electrically coupled to the first electrode;a charge carrier separator disposed on at least a portion of a surface of the three-dimensional current collector;a hole conductor layer disposed on at least a portion of the charge carrier separator and electrically coupled to the second electrode;a counter electrode disposed between the hole conductor layer and the second electrode and electrically coupling the hole conductor layer and the second electrode; andnuclear radiation-emitting material disposed such that at least one nuclear radiation particle emitted by the nuclear radiation-emitting material is incident upon the charge carrier separator;wherein the charge carrier separator is adapted to separate electron-hole pairs generated in the charge carrier separator by impact of the at least one nuclear radiation particle on the charge carrier separator, and further wherein at least a portion of the nuclear radiation-emitting material is disposed such that the counter electrode is between the nuclear radiation-emitting material and the charge carrier separator. 2. The power converter of claim 1, wherein the counter electrode is electrically coupled to the second electrode with a conductive adhesive. 3. The power converter of claim 1, wherein at least a portion of the nuclear radiation-emitting material comprises tritium. 4. The power converter of claim 1, wherein at least a portion of the charge carrier separator comprises quantum dots. 5. The power converter of claim 1, wherein the three-dimensional current collector comprises a porous Ti/TiO2 material. 6. The power converter of claim 1, wherein the hole conductor layer comprises a p-type semiconductor material comprising CuSCN. 7. The power converter of claim 1, wherein at least a portion of the nuclear radiation-emitting material is disposed within the three-dimensional current collector. 8. The power converter of claim 1, wherein at least a portion of the nuclear radiation-emitting material is disposed within the hole conductor layer. 9. The power converter of claim 1, wherein the charge carrier separator comprises a first material and a second material. 10. The power converter of claim 9, wherein the first material is disposed on the at least a portion of the surface of the three-dimensional current collector and the second material is disposed on at least a portion of the first material. 11. The power converter of claim 10, wherein the first material comprises an oxide and the second material comprises quantum dots. 12. An implantable medical device comprising the power converter of claim 1. 13. A power converter comprising:first and second electrodes;a three-dimensional current collector disposed between the first and second electrodes and electrically coupled to the first electrode;a charge carrier separator disposed on at least a portion of a surface of the three-dimensional current collector;a hole conductor layer disposed on at least a portion of the charge carrier separator and electrically coupled to the second electrode;a counter electrode disposed between the hole conductor layer and the second electrode and electrically coupling the hole conductor layer and the second electrode; andnuclear radiation-emitting material disposed such that at least one nuclear radiation particle emitted by the nuclear radiation-emitting material is incident upon the charge carrier separator;wherein the charge carrier separator is adapted to separate electron-hole pairs generated in the charge carrier separator by impact of the at least one nuclear radiation particle on the charge carrier separator, and further wherein at least a portion of the nuclear radiation-emitting material is disposed between the hole conductor layer and the counter electrode. 14. The power converter of claim 13, wherein at least a portion of the charge carrier separator comprises quantum dots. 15. The power converter of claim 13, wherein the three-dimensional current collector comprises a porous Ti/TiO2 material. |
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abstract | There is provided an illumination system. The illumination system includes a first light source and a second light source, each of which are for providing light having a wavelength ≦193 nm, and an optical element. The first light source illuminates a first area of the optical element and the second light source illuminates a second area of the optical element. |
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048184691 | description | In FIG. 1, the housing and, respectively, the mounting of a valve is indicated schematically by the reference character -1-. The housing -1- has an inlet opening -2- and an outlet opening -3- whereby the flow path can be closed off by a valve cone -4-. The valve cone -4- is provided with a passage opening -5- situated in the flow path and effecting an opening or closing of the valve by turning of the valve cone about its own longitudinal axis. Over the valve cone -4- is slid a molded element -6- in the shape of a conical cylinder which is provided on either side with recesses -11- (FIG. 3) opposite the passage opening -5-. The molded element -6- is composed of flexible graphite which, in turn, is coated with a thin, flexible layer of tantalum. The tantalum layer is sufficiently thin so that the flexiblity properties of the graphite are not impaired. The flexible graphite layer may also be built-up of a plurality of thin layers laminated one on top of the other. Cut-outs may be provided in thin, laminated layers of flexible graphite in defined locations in order to create relief surfaces for a more balanced pressure distribution. From FIGS. 2 to 4 it becomes clear that the tantalum coating is of composed an inner tantalum sleeve -7- and an outer tantalum sleeve -8- which, between them, enclose the graphite molded element -6-. At the end faces, and also additionally in the region of the recess -11-, there are provided tantalum covers -9- which, in sections, are placed between the sleeves -7- and as well as over the end face of the molded element -6-. Complete sealing is obtained because the covers -9- are welded (at -10-) together with the inner and outer sleeves -7- and -8-. Advantageously, all welding seams -10- are produced by the precisely focusable electron beam welding process, known in itself. The sealing of the recesses -11- opposite the passage openings -5- is obtained in the same manner as the sealing of the end faces as shown in FIG. 2. Thus, the graphite molded element -6- is hermitically encapsulated within a thin tantalum enclosure. The molded element -6- encapsulated in this manner is fixed on the valve cone -4- by means of a frame-like holding device -12-. Thereby is thus obtained a fixing of the molded element -6- in both the axial direction and the direction of turning. Around the passage openings -5- arranged on either side of the valve cone -4- extends a groove -13- into which is inserted the frame-like holding device -12-. Securing thereof is obtained by a press fit. In the embodiment illustrated, the passage openings -5- and holding device -12- appear rectangular in plan view. Evidently, circular, oval or other openings may be provided. In the exemplifying embodiment shown in FIG. 2, the end face cover -9- is flanged so that it overlaps the graphite molded element -6-. In the embodiment illustrated in FIG. 4, however, the covers are annular disks or rings which without any overlapping are welded to the sleeves -7- and -8- at the welds -10-. In the embodiment represented in FIG. 1 there is also shown in greater detail the arrangement of the valve connected with the seal according to the present invention. At its smaller diameter front end, the valve cone -4- is provided with a cylindrical section -15- which penetrates a cylindrical housing opening -20- (!). Starting from the inlet and outlet openings -2- and -3-, respectively, housing -1- is provided, in the region of the front end of the valve cone -4- with a first conical valve seat -17- in which is guided the molded element -6- of the seal in accordance with the present invention. This is followed, by way of a transverse step or shoulder step -18-, by a second conical valve seat -19- with a smaller diameter, the second diameter corresponding approximately to the diameter there of the valve cone -4-. Thereafter follows a further step or transverse shoulder -20- and, successively, a cylindrical housing recess -21-. On the other side of the valve cone -4- there is also provided a conical valve seat -22- in which is guided the other end of the seal. This is followed by a cylindrical opening -23- of the housing -1- whose diameter is larger (by approximately the wall thickness of the seal -6-) than the diameter of the rear cylindrical portion -16- of the valve cone -4- with the seal mounted on it can slide axially (from the right to the left as shown in FIG. 1). A preferred field of application of the present invention is as a seal for cone valves in the fluidized currents of the Purex process whereby the operational components are comprised of radiation-resistant, flexible and corrosion-resistant materials. By means of the seal according to the present invention there can be achieved a definite increase in service life and also increased maintenance and replacement intervals. Another preferred filed of application of the present invention is the utilization of the seal in chemical plants, e.g., in case of chemicals which do not attack tantalum. In HNO.sub.3 and many other chemicals, tantalum is an absolutely corrosion-resistant material. In contrast to plastics, the flexible graphite enclosed by tantalum retains its characteristics, even at temperatures exceeding 150.degree. C. It does not liquefy and does not change chemically, even on inclusion in tantalum. All technical details contained in the patent claims, the description and the drawing are essential parts of the invention, each by itself and also in any combination whatever. |
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abstract | A method and apparatus for assessing a height of a specimen includes an electron beam unit having an electron beam source, lenses, a table for setting a specimen and controllable in a height direction, and a detector, and a height detection system for detecting height of the specimen set on the table while the specimen is irradiated by an electron beam. The height detection system further includes an illumination system, a collection system, first and second detectors, a device configured to receive output signals from the first and second detectors while the specimen is irradiated by the electron beam and to generate a comparison signal from the output signals, wherein the comparison signal is responsive to the height of the specimen. |
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052251144 | claims | 1. A method for disposing of low-level radioactive waste, comprising the steps of a) introducing the waste into a multipurpose container, the multipurpose container comprising a polymeric inner container disposed within a concrete outer shell, the shape of the inner container conforming substantially to the shape of the outer shell's inner surface, b) transporting the waste in the same multipurpose container to a storage location, and c) storing the container at the storage location. 2. The method of claim 1, in which the polymeric inner container is composed of linear polyethylene. 3. The method of claim 1 in which the concrete shell is reinforced with metal. 4. The method of claim 1, in which a radiation shield is placed within the multipurpose container prior to storage, the radiation shield being positioned between the outer surface of the polymeric inner container and the inner surface of the concrete shell. 5. The method of claim 1, in which the shape of the inner container's outer surface conforms substantially to the shape of the outer shell's inner surface. 6. The method of claim 1, wherein the inner container has a removable lid. 7. The method of claim 6, wherein the lid has a removable secondary lid. 8. The method of claim 1, wherein the outer shell has a removable lid. 9. A method of disposing of low-level radioactive waste, comprising introducing the waste into a preconstructed multipurpose container at a first location, the multipurpose container comprising a polyethylene inner container disposed within an outer concrete shell, transporting the container to a storage location, and storing the container at the storage location. |
description | The present invention is related to a device for directing a beam of charged particles to a target from several different angles during irradiation. A device like this is often referred to as a ‘Gantry’. A known device for directing a charged particle beam from several different angles is a rotating gantry, such as the one described in document U.S. Pat. No. 4,917,344. This type of device comprises a large barrel or squirrel-cage structure, on which magnets are mounted for directing the beam along the axis of rotation, away from it, and back again towards the isocentre, located on the rotation axis. By combining a 2π rotation of the gantry around a horizontal rotation axis with a 2π rotation of the target around a vertical axis, one can irradiate the target from any direction, i.e. from a full sphere (4π solid angle). In order to achieve a good precision in the direction of the beam, the requirements on the mechanical structure in terms of rigidity and precision are very high. The total weight of the rotating structure, including the magnets, may be as high as 100 T. The rotating structure may be as large as 10 m in diameter and 10 m in length, leading to an excessive cost of such a proton or heavy ion therapy system. It has therefore been proposed to achieve the same goal by replacing the rotating structure by a set of different beam lines in a vertical plane. A number of fixed beam lines does not allow to irradiate the target from any direction. Several solutions have been proposed to add some flexibility to a set of fixed beam lines. The most recent prior art in this domain can be found in the article entitled “Planar system replacing gantry for protons and carbon ions beams transportation”, M. M. Kats, Proceedings of the Sixth European Particle Accelerator Conference (EPAC'98), pages 2362-2364. This document describes two versions of a planar magnetic optic system for transportation to the patient of a proton or carbon ion beam from various directions. The beam is bent, focused and directed towards an isocentre in one of a plurality of magnetic channels which are fixed immovably on a vertical wall. The patient is placed at the isocentre. Two additional magnets are used to change the irradiation direction, said magnets being either mobile or immobile. In the mobile magnet version, the magnets are attached to a rotating frame. Even though its weight is inferior to that of a rotating gantry, this is still a complex mechanical structure. Alternatively, the above cited document suggests the use of two large and semi-circular magnets, or of a plurality of sector magnets. These magnets are however unacceptably large and heavy. In all cases, the last two magnets of a particular beam line are used for the deflection of the beam, so that irradiation on the stationary patient is performed from a large range of angles. All of the existing systems are based on the principle of isocentricity, i.e. they aim at irradiating a fixed point in the patient from a plurality of angles. To irradiate a zone around this point, sweeping magnets are added, which scan the beam over a given area at each angular position. Document DE-A-10010523, describes a system with multiple treatment rooms, each room being equipped with one channel for producing a beam. One particular embodiment mentions a system comprising three rooms, two of which having a channel wherein the beam can be deflected over an angle between −15° and +15°. In another room, the beam can be deflected over an angle between −30° and +30°. In each room, the patient is in a horizontal position and can be moved along a vertical line, to obtain different angles of incidence for different deflections. The patient can also be rotated around the vertical axis, in order to irradiate from every angle in the horizontal plane. Within one treatment room, given the limited range of deflection angles, the range of irradiation angles with respect to the patient is equally limited, hence the need for multiple rooms. Equally in document DE-A-10010523, sweeping (also called scanning) magnets may be present in the beam channels, said sweeping magnets being positioned after the deflection magnets. This position requires the sweeping magnets however to move along with the deflection of the beam, necessitating a rather complex technical design. The present invention aims to provide a planar irradiation device for particle beam therapy, which works with light-weight magnets, and allows an irradiation of a zone in the patient from any angle in a continuous range, without the need of an expensive and complex high-precision rotating device. The present invention is related to a device for irradiating a patient by a charged particle beam, said device comprising a plurity beam channels, which are to be connected to a beam source, said channels being placed in a fixed way in a vertical plane, characterised in that one deflecting magnet is present at the end of each channel, said magnet being able to deflect the beam over a deflection angle in said vertical plane, the device comprises a patient positioning system, comprising means to move the patient in said vertical plane. In the preferred embodiment of the invention, said angle of deflection is variable within a predefined range, and said patient positioning system comprises means to move the patient in such a way that the same point within the patient is irradiated by a beam produced by said channel, for different values of said deflection angle. In the preferred embodiment, said patient positioning system comprises means to move the patient in all directions in a vertical plane. The channels are preferably attached to a vertical wall. According to one embodiment, each of said channels further comprises at least one sweeping magnet, for irradiating an area around said point. According to the preferred embodiment, said at least one sweeping magnet is in a fixed position and located—starting from said beam source—before said deflecting magnet. Said patient positioning system preferably comprises means for rotating said patient around a vertical axis. According to some preferred but non-restricitive embodiments, the device of the invention may comprise five channels three channels. As seen in FIG. 1, the device according to the invention comprises a plurality of fixed magnetic channels 2, in a vertical plane, preferably fastened to a vertical wall 1. A channel is defined as a sequence of magnets and lenses, which force a particle beam onto a predefined path, in the plane of the vertical wall. In the case of FIG. 1, five channels are present, but this number may differ within the scope of the present invention. FIG. 2 shows a variant comprising three channels. In the figures shown, the patient 20 is in a reclining position, lying on a couch 13. Each channel comprises a number of deflecting magnets 3 and lenses 4. The beam is produced by a common source, which is a known particle accelerator 5, for example a cyclotron, and a beam transport system. One deflecting magnet 6 is common to all channels, and provides the first deflection in the direction of one of the channels present. In the embodiment with five channels, two adjacent channels may have a number of magnets and lenses, which are common to both channels. In both embodiments, beam monitors 25 are present at the end of all or a part of the channels. Their function is to measure beam position and/or current. In the embodiments of FIGS. 1 and 2, two sweeping magnets 7 (Swx, Swy) are present in each channel for scanning the beam in two directions (x,y) perpendicular to the beam direction, over a given area 21. At the end of each channel, a single deflecting magnet 8 is present, which allows a deflection of the beam over a fixed and predefined angle, with respect to the non-deflected beam direction 9 of said channel (see detail FIG. 3). The deflection is such that the beam remains in the vertical plane of the wall. The maximum range α of deflection angles for a given deflecting magnet 8 is preferably equal or larger than the angular distance β between two neighbouring channels as seen from a point 10, as is illustrated in the detail in FIG. 3. In that case, the angular ranges for each beam line are contiguous or overlap. The angle α may also be less than the angle β, in which case there is a gap between the angular ranges of two successive beam lines. The angular distance β between two successive beam lines need not be constant. Also it is not required that the maximum ranges a of deflection angles for each beam line be equal. In the drawings, the point 10 is shown as the isocentre of the different channels, i.e. the point which is common to the beams produced by all channels 2, in the absence of any deflection by the end magnets 8. However, it should be made clear that the presence of such an isocentre is not necessary according to the invention, as will be made clear in the next paragraph. Contrary to existing devices, the device of the invention is not isocentric. If the patient would remain stationary, the changing of the deflection angle of the top channel beam would cause the irradiation of a line 11 of points, instead of a fixed point. The same is true for the other channels. In order therefore to irradiate a given point in the patient, the couch on which the patient is reclining, is movable in all directions in the vertical plane. A suitable horizontal and/or vertical movement of the couch, combined with the changing of the deflection angle within the range α, allows the beam to remain directed at a fixed point within the patient. The movement in any direction in the vertical plane allows the distance between the deflection magnet and the target to remain constant during irradiation from different angles, which is not the case in prior art systems wherein the patient is moved only along a straight, vertical line. The sweeping magnets 7 allow the irradiation of a predefined area 21 around the point in question. According to the preferred embodiment of the invention, the sweeping magnets 7 are placed in a fixed position in the beam line before the deflection magnets 8 (starting from the source), as can be seen in FIGS. 1 to 3. This position of the sweeping magnets allows them to be installed in a stationary position with respect to the deflection magnets, for all values of the deflection angle. The couch 13 is installed on a patient positioning system or PPS 12. In the preferred case, the patient 20 is in a reclining position on this couch. A system wherein the patient is seated may also be used, especially when using a horizontal beam line. The PPS comprises means to move the couch in the vertical plane. A person 14 attending to the patient must have easy access to the couch or seat. The patient positioning system further has the ability to rotate the patient around a vertical axis, passing trough the target centre, in order to irradiate the patient from the full range of angles 0-360° in the horizontal plane. Before the treatment, the therapist defines a fraction, i.e. the irradiation applied during one session, as being one or more fields. A field is the irradiation of one target volume from one direction. For applying a field, the required beam line is selected, the current fed to the deflecting magnet 8 is adjusted for obtaining the required fixed deflection angle, the PPS is moved so that the target lies in the beam direction, and the irradiation for the first field is applied. This procedure is repeated for all fields in the fraction. For applying the irradiation to a volume around the target centre, the so-called “pencil-beam scanning” may be used. In the “pencil-beam scanning”, the sweeping magnets Swx and Swy are driven with such currents that a narrow beam moves on a path on an area around the target centre. The depth of said area is then varied by changing the energy of the beam particles, with an energy degrader. This procedure is repeated until the whole volume of the field receives the prescribed irradiation dose. In the embodiment of FIG. 1, the full range of 0-360° can be obtained in the horizontal and in the vertical plane. In the embodiment of FIG. 2, a range of [−70°,+70°] is obtained in the vertical plane on both sides of the patient. According to another embodiment of the invention, no sweeping magnet 7 (Swx) for scanning in the plane of wall 1 is present, and the scanning of the area to be treated is done by the changing of the deflection angle (in the range α) itself. A single sweeping magnet 7 (Swy), preferably placed before the deflection magnet, is used for scanning in the direction perpendicular to the plane of the wall. Compared to the prior art, the device of the invention having a plurality of beam channels, provides—within one treatment room—a larger range of irradiation angles with respect to the patient, compared to the system wherein one beam channel is applied. The multi-channel embodiment makes it unnecessary to devise a system having multiple treatment rooms, each equipped with a single beam channel. The two embodiments shown in the FIGS. 1 and 2 will now be described in more detail. In FIG. 1, a five-channel device is shown. It comprises a vertical wall of 9 m in width and 8.5 m in height. The maximum deflection angle range α for each end deflecting magnet 8 is 30° (between +15° or −15° from the non-deflected line). Movement of the patient couch over a distance of maximum about 0.5 m (i.e. inside a sphere centred at the intersection of the multiple undeflected beam lines, and having a radius of 0.5 m) is combined with this deflection in order to irradiate from a continuous range between −90° and +90° in the vertical plane on one side of the patient, so a continuous 0-360° range can be obtained by rotating the couch around the vertical axis. Sweeping magnets allow two-directional scanning (x and y) over a target area with a maximum diameter of 0.3 m. The Source-axis distance (scanning magnets to irradiated point) SAD is 3 m. The device of FIG. 2 is a three channel device, with a wall of 8 m in width and 6 m in height. α=40° (+ or −20° from the non-deflected line). Movement of the patient over a distance of maximum 0.7 m is combined with beam deflection in order to irradiate from a continuous range between −70° and +70° in the vertical plane on one side of the patient. The couch is rotatable over 0-360° in the horizontal plane, around the vertical axis which passes through the target centre. Again, sweeping magnets allow two-directional scanning (x and y) over a target area with a maximum diameter of 0.3 m. The Source-axis distance (scanning magnets to irradiated point) SAD is 3 m. The movements of the couch required for these two embodiments of the invention are easily attainable with PPS and couches or chairs known in the art, e.g. from U.S. Pat. No. 6,094,760. The device according to the invention may be used for irradiating by any type of charged particles, such as protons, but is especially useful for heavy ion beams such as carbon or oxygen ion beams, which would require a very large and heavy structure in a rotating gantry. |
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summary | ||
claims | 1. A first-wall component of a fusion reactor, comprising:at least one heat shield of a graphitic material formed with a closed or open passage;a cooling tube of copper or a copper alloy;a tube segment disposed between said heat shield and said cooling tube, said tube segment consisting of a material selected from the group consisting of molybdenum, molybdenum alloy, tungsten and tungsten alloy, and said tube segment being formed with an opening facing towards a surface of said heat shield exposed to a plasma and having an opening angle α of from 20 to 180°; andcopper-containing layers connecting said tube segment to said heat shield and to said cooling tube. 2. The first-wall component according to claim 1, wherein said opening angle α of said tube segment is 50° to 130°. 3. The first-wall component according to claim 1, wherein an angle bisector of said opening angle α is perpendicular to the surface of said heat shield exposed to a plasma. 4. The first-wall component according to claim 1, wherein said tube segment has a wall thickness of from 0.2 to 1.5 mm. 5. The first-wall component according to claim 1, wherein said heat shield is connected in a region of an opening of said tube segment to said cooling tube via a copper-containing region. 6. The first-wall component according to claim 1, wherein said tube segment consists of Mo—Cu or W—Cu. 7. The first-wall component according to claim 1, wherein said heat shield consists substantially of carbon fiber-reinforced carbon. 8. The first-wall component according to claim 1, wherein said cooling tube consists of Cu—Cr—Zr. 9. The first-wall component according to claim 1, wherein said passage is a bore. 10. The first-wall component according to claim 1, wherein said passage is a laser-structured opening. 11. The first-wall component according to claim 1, wherein said passage has a wall formed of a titanium carbide layer. 12. A first-wall component of a fusion reactor, comprising:a heat shield of a graphitic material formed with a closed or open passage;a cooling tube of copper or a copper alloy;a tube segment disposed between said heat shield and said cooling tube, said tube segment having an opening with an opening angle α of from 20 to 180°; andcopper-containing layers connecting said tube segment to said heat shield and to said cooling tube. 13. The first-wall component according to claim 12, wherein said heat shield is connected in a region of said opening of said tube segment to said cooling tube via a copper-containing region. |
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abstract | Embodiments of the invention provide a downhole tool that includes a photon source, a photon detector having a plurality of detector pixels in a cylindrical row and column arrangement, and a radial collimator having at least two concentric frustoconical collimators circumferentially arranged about the photon detector and at least two azimuthal collimating members radially arranged with respect to the photon detector, wherein one of the azimuthal collimating members is on a first side of a detector pixel and a second azimuthal collimator is on a second side of a detector pixel opposite the first side. |
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048851272 | claims | 1. A nuclear fuel rod support grid, comprising: (a) a plurality of straps being interleaved with one another to form a matrix of hollow cells, each cell for receiving one fuel rod and being defined by intersecting pairs of opposing wall portions of said straps which wall portions are shared with adjacent cells; (b) a plurality of fuel rod clamping springs and dimples being associated with said wall portions of said straps defining each cell and protruding into said cell so as to clamp a fuel rod therebetween; and (c) at least one spacer supporting some of said springs and dimples being separate from and detachably mounted on some of said wall portions of said straps defining each said cell; (d) said spacer being L-shaped in cross-section and made from a metal plate that is bent into a ninety-degree configuration to form a pair of parts disposed generally perpendicular to each other and integrally connected together at their inner edges, each spacer part having a height approximately identical to the height of each of said strap wall portion defining each said cell; (e) said spacer being lodged in a corner of each said cell formed by one intersecting pair of said strap wall portions with said pair of parts of said spacer extending along said wall portions forming said corner. (a) a plurality of straps being interleaved with one another to form a matrix of hollow cells, each cell for receiving one fuel rod and being defined by intersecting pairs of opposing wall portions of said straps which wall portions are shared with adjacent cells; (b) a plurality of fuel rod clamping springs and dimples being associated with said wall portions of said straps defining each cell and protruding into said cell so as to clamp a fuel rod therebetween; and (c) a pair of spacers inserted in each said cell along said strap walls portions defining each said cell, one of said spacers supporting said springs and the other of said spacers supporting said dimples, said spacers being separate from and detachably mounted on said wall portions of said straps defining each said cell; (d) each said spacer being L-shaped in cross section and made from a metal plate that is bent into a ninety-degree configuration to form a pair of parts disposed generally perpendicular to each other and integrally connected together at their inner edges, each part having a height approximately identical to the height of each of said strap wall portions defining each said cell; (e) one of said spacers being lodged in one corner of each said cell formed by one intersecting pair of said strap wall portions with said pair of parts of said one spacer extending along said wall portions forming said one corner; (f) the other of said spacers being lodged in a diagonal opposite corner of each said cell formed by the other intersecting pair of said strap wall portions with said pair of parts of said other spacer extending along said wall portions forming said diagonal opposite corner. (a) a plurality of straps being interleaved with one another to form a matrix of hollow cells, each cell for receiving one fuel rod and being defined by intersecting pairs of opposing wall portions of said straps which wall portions are shared with adjacent cells; (b) a plurality of fuel rod clamping springs and dimples being associated with said wall portions of said straps defining each cell and protruding into said cell so as to clamp a fuel rod therebetween; and (c) at least one spacer supporting some of said springs and dimples being separate from and detachably mounted on some of said wall portions of said straps defining each said cell; (d) said spacer being formed of a pair of parts disposed generally perpendicular to each other and integrally connected together at their inner edges; (e) said spacer being lodged in a corner of each said cell formed by one intersecting pair of said strap wall portions with said pair of parts of said spacer extending along said wall portions forming said corner; (f) said spacer at a central region of each of said parts thereof adjacent to opposite unconnected outer edges of said parts having one of either one said spring or a pair of said dimples formed in said spacer part so as to protrude therefrom into each said cell; (g) said spacer having said dimples formed therein at upper and lower corner regions of each said part thereof adjacent to its outer unconnected edge. (a) a plurality of straps being interleaved with one another to form a matrix of hollow cells, each cell for receiving one fuel rod and being defined by intersecting pairs of opposing wall portions of said straps which wall portions are shared with adjacent cells; (b) a plurality of fuel rod clamping springs and dimples being associated with said wall portions of said straps defining each cell and protruding into said cell so as to clamp a fuel rod therebetween; and (c) a pair of spacers inserted in each said cell along said strap walls portions defining each said cell, one of said spacers supporting said springs and the other of said spacers supporting said dimples, said spacers being separate from and detachably mounted on said wall portions of said straps defining each said cell; (d) each said spacer being formed of a pair of parts disposed generally perpendicular to each other and integrally connected together at their inner edges; (e) one of said spacers being lodged in one corner of each said cell formed by one intersecting pair of said strap wall portions with said pair of parts of said one spacer extending along said wall portions forming said one corner; (f) the other of said spacers being lodged in a diagonal opposite corner of each said cell formed by the other intersecting pair of said strap wall portions with said pair of parts of said other spacer extending along said wall portions forming said diagonal opposite corner; (g) one of said spacers at a central region of each of said parts thereof adjacent to opposite unconnected outer edges of said parts having said spring formed in said spacer part so as to protrude therefrom into each said cell, whereas the other of said spacers at a central region of each of said parts thereof adjacent to opposite outer upper and lower corners at intersections of said upper edge of said parts with upper and lower edges thereof having dimples of a pair thereof formed in said spacer part so as to protrude therefrom into each said cell. 2. The grid as recited in claim 1, wherein each spacer part has a width approximately equal to one-half of the width of each of said strap wall portions defining each said cell. 3. The grid as recited in claim 1, wherein said spacer at a central region of each of said parts thereof adjacent to opposite unconnected outer edges of said parts has one of either one said spring or a pair of said dimples formed in said spacer part so as to protrude therefrom into each said cell. 4. The grid as recited in claim 3, wherein said spacer has said dimples formed therein at upper and lower corner regions of each said part thereof adjacent to its outer unconnected edge. 5. The grid as recited in claim 1, wherein said spacer at a central region of each of said parts thereof adjacent to respective upper and lower opposite edges of said parts has attachment tabs of a pair thereof formed thereon so as to project outwardly therefrom. 6. The grid as recited in claim 5, wherein said upper tabs extend generally perpendicular to said spacer parts, whereas said lower tabs extend generally within a plane of said spacer parts. 7. A nuclear fuel rod support grid, comprising: 8. The grid as recited in claim 7, wherein each part has a width approximately equal to one-half of the width of each of said strap wall portions defining each said cell. 9. The grid as recited in claim 7, wherein one of said spacers at a central region of each of said parts thereof adjacent to opposite unconnected outer edges of said parts has said spring formed in said spacer part so as to protrude therefrom into each said cell, whereas the other of said spacers at a central region of each of said parts thereof adjacent to opposite outer upper and lower corners at intersections of said upper edges of said parts with upper and lower edges thereof has dimples of a pair thereof formed in said spacer part so as to protrude therefrom into each said cell. 10. The grid as recited in claim 7, wherein each said spacer at a central region of each of said parts thereof adjacent to respective upper and lower opposite edges of said parts has attachment tabs of a pair thereof formed thereon so as to project outwardly therefrom. 11. The grid as recited in claim 10, wherein said upper tabs extend generally perpendicular to said spacer parts, whereas said lower tabs extend generally within a plane of said spacer parts. 12. A nuclear fuel rod support grid, comprising: 13. The grid as recited in claim 12, wherein said spacer is L-shaped in cross section being made from a metal plate that is bent into a ninety-degree configuration. 14. The grid as recited in claim 12, wherein each spacer part has a height approximately identical to the height of each of said strap wall portions defining each said cell. 15. The grid as recited in claim 14, wherein each spacer part has a width approximately equal to one-half of the width of each of said strap wall portions defining each said cell. 16. The grid as recited in claim 12, wherein said spacer at said central region of each of said parts thereof adjacent to respective upper and lower opposite edges of said parts has attachment tabs of a pair thereof formed thereon so as to project outwardly therefrom. 17. The grid as recited in claim 16, wherein said upper tabs extend generally perpendicular to said spacer parts, whereas said lower tabs extend generally within a plane of said spacer parts. 18. A nuclear fuel rod support grid, comprising: 19. The grid as recited in claim 18, wherein each said spacer is L-shaped in cross section being made from a metal plate that is bent into a ninety-degree configuration. 20. The grid as recited in claim 18, wherein each part has a height approximately identical to the height of each of said strap wall portions defining each said cell. 21. The grid as recited in claim 20, wherein each part has a width approximately equal to one-half of the width of each of said strap wall portions defining each said cell. 22. The grid as recited in claim 18, wherein each spacer at a central region of each of said parts thereof adjacent to respective upper and lower opposite edges of said parts has attachment tabs of a pair thereof formed thereon so as to project outwardly therefrom. 23. The grid as recited in claim 22, wherein said upper tabs extend generally perpendicular to said spacer parts, whereas said lower tabs extend generally within a plane of said spacer parts. |
abstract | An apparatus for generating electricity that uses at least one jet-type engine fueled with fissile material. The nuclear fueled jet engine is affixed to a connecting member that projects from a central, rotatable shaft, which is in engageable communication with an apparatus for converting the rotation of the central shaft to electricity, such as a stator and rotor combination. The engine is positioned so that the thrust produced by the jet engine causes the engine and connecting member to travel in a radial direction around the longitudinal axis of the central shaft, rotating the central shaft. As the central shaft rotates, the rotational motion of the central shaft is transmitted to conversion apparatus. An operating gas is used to cool the nuclear fueled jet engines and as the propellant for the jet engines. |
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046860681 | description | DETAILED DESCRIPTION OF THE INVENTION Specifically, this invention provides a method of batchwise treating radioactive organic waste, which comprises: introducing radioactive organic waste into a reactor containing an aqueous solution of a fusion-preventing agent composed of one or more powdery solid substances selected from the group consisting of silicon dioxide and carbonates, hydroxides and oxides of calcium, barium, iron and zinc, in an amount within the range from 1.0 to 7.0%, based on the weight of the radioactive organic waste to be treated; tightly closing and heating said reactor to an internal temperature from 180.degree. to 250.degree. C.; supplying an oxygen-containing gas under pressure into the reactor so as to provide an oxygen partial pressure inside the reactor within the range of from 3 to 25 kg/cm.sup.2 ; oxidatively decomposing the radioactive organic waste in the reactor while discharging gaseous effluent composed mainly or carbon dioxide, steam and noncondensable gases, while maintaining the pH value of the aqueous solution between 0.01 and 8; and thereafter supplying another batch of radioactive organic waste end fusion-preventing agent into the inorganic substance, catalyst and aqueous solution that remains in the reactor, and repeating the oxidative decomposition under the same conditions as described above. The wet oxidizing process in this invention is carried out batchwise. The readily suspendable, powdery, fusion-preventing agent is added in each cycle of the oxidizing reaction in order to prevent fusion of the radioactive waste which fusion would otherwise hinder the progress of the oxidative decomposition. As shown in the examples to be described later, it is extremely important to employ the powdery substence in an aqueous solution in the reactor to prevent the waste from fusing. By carrying out the wet oxidization batchwise, most of the radioactive substances contained in the starting waste remain in and are concentrated in the reactor and the volume of the final waste containing the radioactive substances is minimized to the utmost extent. The wet oxidizing process, according to this invention, is carried out in the presence of a catalyst, oxygen and water. The optimum reaction temperature is from 180.degree.-250.degree. C., preferably, 200.degree.-230.degree. C. The total reaction pressure is between 13-120 kg/cm.sup.2, prererably, 15-100 kg/cm.sup.2. If the temperature is lower than 180.degree. C., the reaction rate of the exidizing decomposition is low even when a catalyst is used and the oxygen partial pressure is maintained high. On the other hand, if the temperature is higher than 250.degree. C., an extremely thick-walled reactor will be required in view of the corrosion which will occur. Thus, both excessively low and excessively high temperatures are not practical. The total pressure as described above is the sum of (1) the autogenous steam pressure inside the reactor which is dependent on the temperature employed, (2) the pressure of the oxygen-containing gas supplied for effecting oxidation and (3) the partial pressure of carbon dioxide and other gases formed as the result of the oxidizing reaction. As the substances used for the fusion-preventing agent, substances which can easily be suspended in water and which have a relatively low solubility in water, such as carbonates, hydroxides and oxides of calcium, iron, zinc and barium, and silicon dioxide, are extremely useful. The fusion-preventing agent is added as a powder or in the form of an aqueous slurry into the reactor. The fusion-preventing agent can be added as a single compound or as a mixture of two or more compounds selected from the above-named group of compounds. The amount of the fusion-preventing agent added is from 1.0 to 7.0% by weight, preferably, from 2 to 4% by weight, based on the weight of the radioactive waste introduced in one batch portion to the reactor in the batchwise oxidizing reaction. If the amount of fusion-preventing agent is less than the above-mentioned lower limit, a sufficient fusion-prevention effect cannot be obtained. On the other hand, if it is added in an amount in excess of the above-mentioned upper limit, the amount of the final wastes discharged as the residue of the oxidizing treatment is increased whereby to lessen the volume-reduction ratio obtained by the treatment. In the aqueous solution within the reactor in the method according to this invention, a catalyst metal capable of dissolving in the aqueous solution and/or a catalyst metal deposited on a solid support or carrier can be used as the catalyst. The metals that are effective as a catalyst and are capable of dissolving in the solution are one or more members selected from the group consisting of copper, cobalt, iron, palladium, cerium, nickel, chromium, manganese, lead, platinum and ruthenium. Among them, the use of copper, iron, cobalt, cerium, nickel, chromium and manganese either alone or as a combination of two or more numbers of this group, is effective and inexpensive. These metals are usually introduced into the reactor in the form of a water-soluble compound of the metal, such as a nitrate, sulfate or chloride, in the form of a powder or a solution. The amount of the metal catalyst present in the aqueous solution, expressed as the total amount thereof calculated as the metal, is from 10 to 50,000 ppm by weight, preferably from 50 to 1,000 ppm by weight, based on the weight of the aqueous solution. It is necessary to add from 10 to 1,000 ppm by weight of the metal catalyst to the solution in order to carry out the first batchwise oxidation cycle. Since the aqueous solution in the reactor is not discharged, the metal catalyst remains present for the second and subsequent batchwise cycles of the oxidizing reaction. Moreover, the radioactive wastes often contain small amounts of the metal elements as described above and other inorganic substances which are effective as a catalyst. As the oxidizing decomposition of the radioactive organic waste proceeds, the metal elements effective as a catalyst contained in the waste are leached out into the aqueous solution and, accordingly, the amount of the catalyst metals in the aqueous solution increases as the batchwise oxidizing treatment is repeated. When the amount of the catalyst metals in the aqueous solution reaches a certain level, these metals deposit in the form of various solid compounds, depending on the type and the amount of anions which are present in the aqueous solution. The deposited solid matter also contains other inorganic substances which are contained in the radioactive waste and are deposited similarly. When a large amount of deposited solid matter accumulates within the reactor, the fluidizing property of the aqueous solution is impaired so as to hinder the oxidizing reaction from proceeding at an acceptable reaction rate. When this occurs, it becomes necessary to remove the deposited solid matter. The deposited solid matter is usually removed by drawing the solid matter to the bottom of the reactor and then removing them as a slurry from the reactor, after the previous oxidizing reaction cycle has been completed and before the radioactive waste and the fusion-preventive agent are added for the next cycle. The upper limit for the amount of the catalytic metal element that is present in the aqueous solution within the reactor gives a general criterion for determining the amount of the catalyst that is present at the time when the deposited solid matters are to be drained off. For the reason described above, in the wet oxidizing process, according to this invention, it is not necessary to add a soluble catalyst for each batchwise treatment other than in the case of the first cycle of the batchwise oxidizing reaction and in the case where most of the aqueous solution within the reactor has been drained off in order to remove the accumulated deposited solid matter. Presence of metals, other than the catalyst metals, during the oxidizing treatment gives no undesired effects on the oxidizing decomposition reaction. Instead of a catalyst which is soluble in an aqueous solution, other catalysts can be used comprising one or more metals selected from the group consisting of copper, cobalt, palladium, platinum and ruthenium, or water-insoluble compounds of these metals which metals or water-insoluble compounds thereof are supported on granular carriers, such as alumina, silica-alumina or zeolites. The amount of the catalyst metal or the water-insoluble compound of the catalyst metal is from 1 to 10% by weight based on the sum of the weights of the catalyst metal or water-insoluble compound thereof plus the carrier. The supported catalyst can be present at a weight ratio of from 10 to 200% by weight and, preferably, from 20 to 150% by weight, based on the weight of the radioactive wastes treated in a single batch treatment. The necessary amount of the catalyst metal, when a supported catalyst is used, is from 1,000 ppm to 20% by weight, based on the weight of the radioactive waste treated. If the amount of catalyst is less than 1000 ppm, the reaction rate of the oxidizing decomposition may be extremely slow, depending on the type of the waste being processed, which impairs the practicality of the process as a waste treating method. On the other hand, if the supported catalyst is present in an amount exceeding 20% by weight, the amount of the solid matter in the reactor becomes excessively large and tends to undesirably hinder the oxidizing treatment. By selecting the proper size and configuration for the catalyst carrier, the supported catalyst can easily be separated and recovered from the aqueous solution and the deposited solid matters in the reactor, and can be used repeatedly for many times until its catalytic activity is lost. Accordingly, noble metals can also be used as the catalyst metal for the supported catalyst. Also, when a supported catalyst is used, if various elements, capable of acting as the soluble metal catalyst, are contained in the wastes, these soluble catalyst metals are leached out in the aqueous solution in the same manner as described above and also act as a co-catalyst. The use of the supported catalyst is capable of maintaining the oxidizing decomposition at a high efficiency if the content of the soluble metal catalyst in the wastes is low. Although substantially pure oxygen is best employed as the oxygen source for the oxidizing decomposition, oxygen-enriched air or untreated air can also be used. A suitable oxygen partial pressure in the reactor during the oxidizing treatment is from 3 to 25 kg/cm.sup.2 preferably, from 5 to 20 kg/cm.sup.2. If the oxygen partial pressure is less than the lower limit of the range, the oxidizing treatment is not practical because the reaction rate is low. On the other hand, an oxygen partial pressure in excess of the upper limit is not usually necessary and renders the apparatus expensive to operate. The pH value of the aqueous solution in the reactor during the oxidizing treatment is less than 8 and, preferably, is from 3 to 6. A pH in excess of 8 is not practical because the reaction rate is low. Radioactive waste often contains elements, for example chlorine and sulfur, that produce acidic substances such as hydrogen chloride and sulfuric acid, as a result of the oxidizing treatment. Accordingly, the pH value of the aqueous solution often can be maintained at less than 8 without adding an acidic substance from outside the system to the reactor, because such an acidic substance is formed in the aqueous solution with the progress of the oxidation. If the pH of the aqueous solution in the reactor goes below 7, the fusion-preventing agent starts to dissolve partially. Provided that the fusion-preventing agent does not dissolve rapidly, such partial dissolving does not hinder the fusion-preventing function of the fusion-preventing agent. That is, after the oxidizing reaction has proceeded to some extent, the surface states of the radioactive wastes are changed and the wastes exhibit a reduced tendency to fuse even if they are melted. The pH of the aqueous solution in the reactor during the oxidizing is suitably maintained at more than 0.01, preferably, more than 3, because the materials of which the reactor is made are liable to be corroded at a pH of less than 0.01. Therefore, when the radioactive wastes contain a great amount of chlorine or sulfur, it may be desirable to add a basic substance, for example, an aqueous solution of sodium hydroxide, to the reactor in an amount dependent upon the amount of the elements that are capable of causing the formation of the acidic substances, so that the pH value of the aqueous solution in the reactor is not reduced to less than 0.01 during the oxidation. The materials from which the reactor is made can be selected from various kinds of highly corrosion-resistant materials such as stainless steel, titanium, zirconium, tantalum, glass or ceramics. An autoclave-type reactor equipped with a stirrer and/or sparger for feeding gas under pressure or a bubble tower type reactor equipped with a distributor for feeding in gas under pressure is suitable. During every cycle of the oxidizing decomposition, it is necessary to draw off the carbon dioxide that is evolved as the result of the oxidizing decomposition. when the carbon dioxide is drawn off, other gases and the oxygen-containing gas are partially drawn off simultaneously. The gaseous products contain some, although very little, radioactive substances. Accordingly, the gaseous effluents discharged from the reactor are cooled once to condense the vapors and separate the condensates and, thereafter, are further filtered through a high efficiency particulate air (HEPA) filter to collect the radioactive substances. The thus-cleaned gaseous effluents are then sent out of the system, whereby the external escape of the radioactive substances can completely be prevented. The condensates are preferably returned to the reactor. Further, a defoaming agent can optionally be used for suppressing foaming in the reactor in order to minimize the content of the radioactive substances contained in the gaseous effluents and in order to promote catalytic activity. As the defoamer, any of the well-known defoaming surface active agents can be used, particularly, silicon-type defoamers can provide a satisfactory result. The amount of defoaming agent to use ranges from about 10 to about 2,000 ppm by weight, based on the weight of the aqueous solution. From 1 to 3 hours is sufficient time for completing one batch of the oxidizing decomposition reaction, although this time period will naturally vary depending on the radioactive wastes to be treated. The longest time required for treating a substance, as determined by experimental results. was that activated carbon required three hours. Substances other than activated carbon can completely be treated in two hours or less. The reaction conditions for each cycle of the oxidizing treatment by the method of this invention have been described above. It is not necessary to separate and recover the catalyst, inorganic substances and incompletely oxidized organic substances present in the state of an aqueous suspension or solution thereof, upon the completion of each cycle. The organic wastes and fusion preventing agent for treatment in the next cycle are charged at the beginning of each batchwise cycle of operation and the subsequent oxidizing treatment is performed. In this way, the oxidizing decomposition treatment is repeated for many cycles before it becomes necessary to remove solids and liquids remaining in the autoclave. When the amount of the deposited solid matter in the aqueous solution in the autoclave exceeds 30-35% by weight, it is sufficient to bring about difficulty in charging the radioactive wastes in the reactor or hinder the advance of the oxidizing reaction at a sufficient rate. Then, the deposited solid matters in the aqueous solution are precipitated in the reactor and drained off as a slurry after the residual organic substances in the reactor have completely been oxidized. The slurry is subjected to solid-liquid separation by any conventional procedure to recover the supported catalyst. The liquid component is returned for re-use in the reactor. The cake of deposited solid radioactive waste matter is charged into a container as the final waste product of the oxidizing treatment, with or without drying. The treatment is thus completed. The aqueous solution containing the dissolved catalyst metal remains in the reactor upon draining off the deposited solid matter and can, of course, be used for the subsequent oxidizing decomposition reaction. The aqueous solution containing the soluble catalyst metal can be used for more than 20 cycles. Since the catalyst and the aqueous solution can thus be used repeatedly, the final volume reduction ratio of the radioactive wastes is extremely high. In the overall method according to this invention, it is necessary to charge the radioactive waste, the catalyst and the fusion preventing agent into the reactor at the first cycle of the batchwise oxidizing treatment upon starting the operation of the reactor, but no catalyst is charged during the second or subsequent batchwise cycles of treatment. The method according to this invention is carried out continuously in the sense that the same catalyst is used throughout and the batchwise oxidizing treatment is carried out repeatedly. It is necessary to charge only the radioactive waste and the fusion preventing agent for each batchwise oxidizing treatment and to drain off the deposited solid matters in the reactor every 20-30 cycles of the batchwise oxidizing treatment. The radioactive organic wastes to be oxidatively docomposed by the method according to this invention, include diverse substances, for example, thermoplastic polymeric substances such as polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, natural rubber, synthetic rubber, polychloroprene, polyamide, polyester, polyacrylic ester and polymethyl methacrylate, as well as mixtures of these polymeric substances with various kinds of organic substances such as activated carbon, various hydrocarbons, various alcohols, various organic acids, cellulose, ion exchange resins, thermosetting polyesters, vulcanized but not fused natural rubber, synthetic rubber and polychloroprene rubber, and a certain amount of inorganic substances. Referring to specific embodiments of the radioactive wastes, they include miscellaneous mixtures of rags, wood products, mineral oil products, filtration aids, cloths, safety devices, instruments, table wares, working tools or the like. Radioactive elements are present mainly as inorganic substances in these wastes. These radioactive wastes are charged into the reactor in the state, as they are, pre-treatment is not required and, accordingly, no secondary wastes are generated due to the pre-treatment. It is of course desired that the readioactive wastes be as finely divided as possible for charging into the reactor, provided that the size reduction treatment does not cause generation of secondary wastes. Accordingly, the reactor may have to be equipped with a large size radioactive waste supply port. Those large sized radioactive waste products that cannot pass the waste supply port in the form they are in, are dismantled or broken up in such a way as to prevent the generation of secondary waste and then are charged into the reactor through the waste supply port. The advantages and merits of the invention are summarized as follows. The first advantage is that radioactive waste containing thermoplastic polymeric msterials can be oxidatively decomposed by the wet oxidizing process without necessitating separation and removal of thermoplastic polymeric materials, because of the use of the fusion preventing agent. The second advantage is that the volume-reduction ratio for the organic waste containing the radioactive elements is increased and the inorganic substances containing these elements are concentrated in the reactor to successfully reduce the volume of the final waste to be stored due to the use of the batchwise wet oxidizing process. The method according to this invention will now be described specifically referring to illustrative examples. EXAMPLE 1 In this example, the effectiveness of the fusion preventing agent was tested. An autoclave having an inner volume of 500 ml was used and soft vinyl chloride sheets and polyethylene bottles cut into pieces of an average size of 30 mm square were used as waste. The decomposing treatment was carried out as described below while adding powder of calcium carbonate, calcium hydroxide, iron oxide, zinc oxide, barium carbonate and silicon dioxide as the fusion preventing agent, each in a different addition amount. The autoclave was charged with 10 g of waste, 250 ml of water, 0.2 g of copper sulfate pentahydrate (500 ppm by weight, calculated as copper based on water) as the water-soluble catalyst, from 0.5 to 7.0% by weight of each of the fusion preventing agents based on the weight of the waste and from 2.0 to 4.5 g of solid sodium hydroxide as a neutralizing agent. After tightly closing the autoclave, the autoclave was heated while the contents thereof were stirred by a stirrer rotated at 600 rpm. When the temperature reached 220.degree. C., a gas comprising 99% oxygen by volume was introduced to produce a partial pressure of oxygen inside the autoclave of 17 kg/cm.sup.2 in addition to the autogenous steam pressure. The decomposition reaction was carried out for one hour. During the reaction, gases were occasionally drawn off from the top of the autoclave and oxygen was added to the interior of the autoclave so that the oxygem partial pressure was maintained at 17 kg/cm.sup.2 whereby to keep the total pressure within the autoclave at 40-42 kg/cm.sup.2. The drawn-off gases were indirectly cooled by water, the condensates were returned by means of a pump to the inside of the autoclave and the amounts of the oxygen and carbon dioxide in the uncondensed gases were analyzed. When the reaction was over, the stirring was interrupted and, after cooling the autoclave to room temperature, the internal gases were discharged. Measurement was carried out, after opening the cover of the autoclave for the pH value of the aqueous solution remaining in the autoclave, the total organic content (hereinafter simply referred to as TOC) in the liquid and TOC for the residual solid organic component by using a TOC analyzer. The conversion, for the wastes was calculated by the following equation: ##EQU1## TOCs for the wastes and the residual organic solid component in the above equation were calculated from the result of the elementary analysis. The test results are shown in Table 1. TABLE 1 ______________________________________ Fusion preventing agent Addition NaOH pH value Kind of amount Conversion amount of aqueous wastes Kind % by wt. % gr solution ______________________________________ Sheet CaCo.sub.3 0.5 60.5 2.0 6.8 Sheet CaCo.sub.3 1.0 91.3 5.0 5.7 Sheet CaCo.sub.3 5.0 92.5 4.5 4.1 Sheet CaCo.sub.3 7.0 90.2 4.0 3.9 Sheet Ca(OH).sub.2 5.0 89.8 4.5 3.9 Sheet Fe.sub.2 O.sub.3 5.0 90.8 5.0 4.2 Sheet ZnO 5.0 88.6 4.5 4.3 Sheet BaCO.sub.3 5.0 91.3 4.5 3.9 Sheet SiO.sub.2 5.0 92.0 5.0 4.5 Bottle CaCO.sub.3 5.0 98.2 2.0 5.5 ______________________________________ In Table 1, when 0.5% by weight of calcium carbonate were added, the waste became fused in a large lump and remained incompletely oxidatively decomposed, which reduced the conversion. From the results, it will be apparent that addition of the fusion preventing agent in an amount of from 1 to 7% by weight, based on the weight of the radioactive waste, is effective for preventing the fusion of the waste. EXAMPLE 2 In this example, the same autoclave as in Example 1 was used and the effect of the oxygen pressure was tested. In this example, each sample weighed 2.0 g. The samples were composed of either dried granular ion exchange resins or the same cut pieces of the soft vinyl chloride sheets, as described in Example 1. The test was carried out under the same conditions as those in Example 1 except that 0.1 g of calcium carbonate was used as the fusion preventing agent, 0.9 g of sodium hydroxide was added as the neutralizing agent and the oxygen partial pressure was in the range of from 2 to 25 kg/cm.sup.2. The test results are shown in Table 2. TABLE 2 ______________________________________ Oxygen Total Kind partial reaction of pressure pressure Conversion waste kg/cm.sup.2 kg/cm.sup.2 G % ______________________________________ Sheet 2.0 25.2 47.0 Sheet 3.0 26.5 73.5 Sheet 17.0 41.0 86.5 Sheet 25.0 50.0 93.2 Resin 2.0 25.2 49.0 Resin 3.0 26.5 73.5 Resin 5.0 28.5 81.3 Resin 17.0 41.0 93.5 Resin 25.0 50.0 97.5 ______________________________________ From the above results, it can be seen that an oxygen partial pressure of higher than 3 kg/cm.sup.2 is required. EXAMPLE 3 In this example, the same autoclave as described in Example 1 was used and the effect of the reaction temperature was tested. In this Example, 2 g samples of the same materials as those described in Example 2 were used and the oxygen partial pressure was maintained constant at 17 kg/cm.sup.2. The test was carried out under the same test conditions as those described in Example 1 except that the reaction temperature was varied within the range of from 160.degree. to 250.degree. C. The test results are shown in Table 3. TABLE 3 ______________________________________ Total reaction Reaction Kind of pressure temperature Conversion waste kg/cm.sup.2 G .degree.C. % ______________________________________ Sheet 23.5 160 37.0 Sheet 27.5 180 77.3 Sheet 33.0 200 81.6 Sheet 41.0 220 86.5 Sheet 57.0 250 92.7 Resin 23.5 160 50.3 Resin 27.5 180 80.0 Resin 33.0 200 86.0 Resin 41.0 220 93.5 Resin 57.0 250 98.0 ______________________________________ It can be seen from the results that a reaction temperature higher than 180.degree. C. is necessary. EXAMPLE 4 In this example, the same autoclave as described in Example 1 was used and the effect of the amount of catalyst added to the water was tested. In this example, 0.5 g samples of dried granular ion exchange resins were used as the waste and 0.02 g of powdery calcium carbonate was used as the fusion preventing agent. The test was carried out under the same test conditions as those described in Example 1 except that the amount of copper sulfate catalyst was varied within a range from 0 to 3,000 ppm by weight, calculated as copper, based on the weight of the water and under a total pressure maintained between 40-41 kg/cm.sup.2 G. The results are shown in Table 4. TABLE 4 ______________________________________ Amount of catalyst Conversion pH value for ppm % aqueous solution ______________________________________ 0 51.2 6.5 1 83.3 5.8 10 90.0 5.5 100 90.0 5.5 500 88.8 5.6 1000 88.6 5.7 3000 83.7 5.8 ______________________________________ It can be seen from the results that at least 10 ppm by weight of the water soluble catalyst based on water is necessary as the effective metal catalyst. EXAMPLE 5 In this example, the effect of other water-soluble metal salts was tested. The test was carried out under the same test conditions as those described in Example 1 except that 0.5 g of dry granular ion exchange resin was used as the waste and 0.02 g of calcium carbonate was used as the fusion preventing agent. The results of the test are shown in Table 5. In the Table, the type of catalyst is represented by the chemical formula of the water soluble salt of the metal used as the catalyst. The addition amount is represented by ppm of the weight of the metal used as the catalyst, based on the weight of water. TABLE 5 ______________________________________ addition pH value for Kind of amount Conversion aqueous catalyst ppm % solution ______________________________________ Co(NO.sub.3).sub.2.6H.sub.2 O 471 74.6 6.6 Fe.sub.2 (SO.sub.4).sub.3.5H.sub.2 O 447 73.3 6.8 PdCl.sub.2 851 91.2 5.2 Ce(NO.sub.3).sub.2.6H.sub.2 O 1120 61.3 7.8 NiSO.sub.4.6H.sub.2 O 470 63.9 7.8 Cr.sub.2 (SO.sub.4).sub.2.H.sub.2 O 416 68.3 7.6 MnSO.sub.4.H.sub.2 O 440 82.5 6.2 Pb(NO.sub.3).sub.2 1650 70.5 7.4 H.sub.2 PtCl.sub.6.6H.sub.2 O 1560 84.5 6.1 ______________________________________ The results show that various metals soluble in water are effective as the catalyst. EXAMPLE 6 In this example, the effect of a supported metal catalyst insoluble in water was tested by using the same autoclave as described in Example 1. The waste materials that were used in Example 1, sheets of natural rubber cut into 30.times.30 mm pieces, or activated carbon were used, respectively, as waste materials. Samples of 1 g the waste material, 0.05 g of calcium carbonate as the fusion preventing agent, 250 ml of water and a specified amount of the catalyst as explained below, were charged in the autoclave. The autoclave was raised to a temperature 200.degree. C. while being stirred. When a temperature of 200.degree. C. was reached, oxygen at a partial pressure of 5 kg/cm.sup.2 was introduced and the oxidizing decomposition reaction was permitted to proceed for one hour. The test was carried out in the same manner as described in Example 1 while maintaining the total pressure of the autoclave from 20 to 21 kg/cm.sup.2 G. Measurement for the results of the reaction was done in the same manner as in Example 1. The water-insoluble supported catalysts used in this example were prepared as described below. The dried granular support was immersed in an aqueous solutions containing one of the water-soluble compounds of the group comprising copper sulfate, palladium chloride, chloroplatinic acid, ruthenium chloride and the like. The support was removed from the solution and dried at 110.degree. C. Immersing-drying procedures were repeated a number of times until the amount of metal deposited on the support reached the desired level. The support containing the desired amount of metal was then reduced by contacting it with hydrogen at 300.degree. C. to produce the desired water-insoluble supported catalyst. The support, and the amount and name of the metal contained in the catalyst are listed in the following table. ______________________________________ Catalyst Metal weight No. Kind of metal Kind of support in catalyst(%) ______________________________________ 1 copper alumina 5.0 2 palladium alumina 5.0 3 palladium alumina 1.0 4 palladium alumina 10.0 5 platinum alumina 5.0 6 ruthenium alumina 5.0 7 copper silica alumina 5.0 8 copper zeolite 5.0 9 cobalt .alpha.alumina 5.0 ______________________________________ The test results are shown in Table 6. TABLE 6 ______________________________________ Cata- Catalyst amount Conver- pH value for Kind of lyst based on waste sion aqueous waste No. amount (%) (%) solution ______________________________________ Sheet 1 5.0 53.3 6.8 Sheet 1 10.0 77.9 4.8 Sheet 1 100.0 78.5 4.7 Sheet 1 200.0 80.8 4.5 Bottle 1 200.0 71.8 6.2 Natural 1 200.0 78.6 6.4 rubber Activated 1 200.0 50.0 8.2 carbon Sheet 2 200.0 75.4 5.0 Sheet 3 200.0 73.2 5.2 Sheet 4 200.0 74.8 5.2 Sheet 5 200.0 70.5 5.5 Sheet 6 200.0 62.3 6.0 Sheet 7 200.0 78.2 4.7 Sheet 8 200.0 76.3 4.8 Sheet 9 200.0 78.4 5.0 ______________________________________ It can be seen from the results that the water-insoluable supported catalyst is effective. EXAMPEL 7 In this example, the same autoclave as described in Example 1 was used and the oxidizing decomposition test was carried out for a variety of different materials that may possibly be present in waste. Each 1 g sample of the materials shown in Table 7 was cut into pieces of about 30 mm length and was charged together with 0.2 g of copper sulfate pentahydrate as the water soluble catalyst, 0.05 g of calcium carbonate as the fusion preventing agent, and 0.1 g of solid sodium hydroxide as the neutralizing agent into the autoclave. The autoclave was heated under stirring to 230.degree. C. and oxygen was introduced to establish a partial pressure of 7 kg/cm.sup.2 G. The oxidizing decomposition was carried out for one hour (three hours in the case of activated carbon only). The other test procedures were the same as those described in Example 1and the total pressure of the autoclave was maintained at 35-36 kg/cm.sup.2 G. The test results are shown in Table 7. TABLE 7 ______________________________________ Kinds of waste Conversion (%) ______________________________________ granular cationic exchange resin 97.5 granular anionic exchange resin 85.3 powdered cationic exchange resin 97.1 waste cloth 97.5 wood material 97.7 paper 99.8 polyethylene bottle 97.1 polychloroprene rubber sheet 86.2 hard vinyl chloride tube 79.4 soft vinyl chloride sheet 83.7 polypropylene bottle 96.1 natural rubber sheet 92.4 polymethylmethacrylate plate 96.4 polyvinylidene chloride film 82.1 nylon yarn 67.8 machine oil 94.0 grease 90.4 cellulose type filtration aids 98.7 activated carbon 94.7 ______________________________________ As is shown by the results, a wide variety of the materials that may possibly be incorporated into radioactive wastes can be processed in accordance with the present invention. EXAMPLE 8 In this example, the same autoclave as described in Example 1 was used and the oxidizing decomposition treatment test was carried out using a mixed waste, one-half of which was composed of polyethylene. 4 g of mixed wastes comprising 50 wt. % shredded polyethylene, 20 wt. % shredded waste cloth, 15 wt. % shredded wood materials and 15 wt. % paper pieces, 250 ml of water, 0.2 g of copper sulfate pentahydrate as the water-soluble catalyst, 0.2 g of calcium carbonate as the fusion preventing agent and 0.5 g of solid sodium hydroxide as the neutralizing agent were charged into the autoclave, which was heated under stirring. After reaching 230.degree. C., a partial pressure of 20 kg/cm.sup.2 of oxygen was created in the autoclave and the oxidizing decomposition was carried out at that temperature for three hours. During reaction, gases were occasionally drawn off from the upper end of the autoclave and oxygen was supplemented to maintain the total autoclave pressure from 48-50 kg/cm.sup.2 G. The other test procedures and the treatment for the contents in the autoclave after the reaction were the same as those described im Example 1. Test results indicate a decomposition rate of 99.2% was obtained for such mixed waste, which corresponded to that of the individual wastes. EXAMPLE 9 In this example, the same autoclave as described in Example 1 was used and the test was carried out, repeating the use of the water soluble copper catalyst. Mixed waste comprising 50 wt. % shredded polyethylene, 25 wt. % shredded waste cloth and 25 wt. % shredded chloroprene was used as the waste. For the first cycle of the oxidizing decomposition, 5 g of the mixed wastes, 250 ml of water, 0.2 g of copper sulfate pentahydrate as the catalyst, 0.25 g of calcium carbonate as the fusion preventing agent and 0.5 g of solid sodium hydroxide as the neutralizing agent were charged. Then, the autoclave was heated under stirring and when the temperature reached 230.degree. C., oxygen was introduced at a partial pressure of 15 kg/cm.sup.2. The reaction was permitted to proceed for three hours. Other test procedures during reaction and the analysis of the aqueous solution were the same as those described in Example 1. In the second and the succeeding oxidizing decomposition cycles, the same procedures as those described for the first cycle of the oxidizing decomposition were repeated, except that copper sulfate was not charged into the reactor. The test results are shown in Table 8. The decompusition rate in Table 8 was calculated as the ratio of the TOC of the aqueous solution remaining in the autoclave upon completion of the reaction for each cycle (the residual organic solid component was not present in each cycle) relative to TOC of wastes were charged prior to the start of the oxidizing decomposition of that cycle according to the formula as described in Example 1. TABLE 8 ______________________________________ Number of Conversion pH value for reaction cycle % aqueous solution ______________________________________ 1 96.5 4.3 2 96.3 4.0 3 96.4 5.2 4 96.3 4.8 5 96.3 4.2 10 96.3 5.2 15 95.8 4.8 20 92.0 6.0 ______________________________________ About 14 wt. % of deposited solid components, calculated on a dry weight basis, were present in the aqueous solution within the autoclave after completion of the oxidizing decomposition test at the 20th cycle, and the aqueous solution was still usable. Many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described. |
050776851 | summary | BACKGROUND OF THE INVENTION This invention relates to a method and an apparatus for supporting the operation under radioactive rays, and in particular relates to ones suited for obtaining radioactivity exposure amount through simulation. The operation in regular inspections of an installation dealing with radioactive substances, e.g. a nuclear power plant, are carried out after confirming the schedule, procedure and process of the work operation by meeting before workers or work craftsmen enter the area with controlled radioactive rays. Such a schedule of operation needs to be planned considering the radioactivity exposure amount received by the workers during the operation in the area with controlled radioactive rays. A method for estimating radioactivity exposure amount in planning such a schedule of operation is disclosed in Japanese Patent Application Kokai (Laid-Open) 60-120295. In this method, the total radioactivity exposure amount expected in the operation for this time is estimated by integrating secular change and evaluation factor for the operation with the actual total radioactivity exposure amount in the previous operation (the total radioactivity exposure amount from the beginning until the end of the operation). The evaluation factor for the operation is a degree of effect added to the whole operation for this time by an additional operation when the operation for this time can not be made in the same procedures as of the previous operation for presence of the additional operation. In the next place, the radioactivity amount of first schedule of the operation for each worker is calculated on the basis of the mean value of the newest actual data of contamination result and the determined operation time in the designated work operation area. Further, the radioactivity amount of second schedule of operation for the expected total radioactivity exposure amount is obtained on the basis of the determined operation time and the expected number of workers participating in the operation. The correction of the number of workers participating in the operation and the planning of the schedule of the operation are made, taking the radioactivity amount of the first and second schedules of the operation into account. SUMMARY OF THE INVENTION It is the first object of this invention to provide a method and an apparatus for supporting the operation under radioactive rays, according to which appropriate work procedures for the target operation can be obtained. It is the second object of this invention to provide a method for supporting the operation under radioactive rays, according to which it is easy to determining the part where radioactivity exposure should be restricted when the radioactivity exposure amount does not satisfy a determined value. It is the third object of this invention to provide a method for supporting the operation under radioactive rays, according to which it is easy to know the radioactivity amount in each structure disposed in the area with controlled radioactive rays where the target operation is carried out. It is the fourth object of this invention to provide a method for supporting the operation under radioactive rays, according to which it is possible to recognize the movement of workers carrying out the target work operation. The first characteristic of this invention attaining the first object resides in calculating the radioactivity exposure amount received by workers due to carrying out the target operation, which is carried out in the area with controlled radioactive rays where an apparatus dealing with radioactive substances is disposed and includes a plurality of procedures of work operation, by means of operation processing means, utilizing layout graphic data relating to the area with controlled radioactive rays and radioactive ray data of the structures contained in the layout graphic data, and outputting the procedures of the target operation from the operation processing means when the calculated radioactivity exposure amount satisfies a determined value. The second characteristic of this invention attaining the second object resides in outputting the radioactivity exposure amount for each procedures contained in the target operation from the operation processing means when the obtained radioactivity exposure amount does not satisfy the determined value. Further, the second object can be attained also by providing information relating to the radioactivity exposure amount for each small partitioned area which is divided out of the area where workers move in the area with controlled radioactive rays carrying out the target work operation. The third characteristic of this invention attaining the third object resides in generating a first information for displaying each structure existing in the area with controlled radioactive rays as graphics by use of the layout graphic data, adding a second information for displaying the surface radioactivity rate of each of the structure to the first information, and displaying the first information to which the second information is added on display means. The fourth characteristic of this invention attaining the fourth object resides in generating a first information for displaying the structures existing in the area with controlled radioactive rays within a plant housing where an apparatus dealing with radioactive substances is disposed as graphics on the bases of the layout graphic data showing the layout state of the structures in the area with controlled radioactive rays, generating a plurality of condition approximation graphic data of worker approximators for approximating the movements of the workers carrying out the target work operation in the area with controlled radioactive rays, generating a second information for displaying the worker approximators carrying out the target operation as graphics on the basis of the condition approximation graphic data, displaying the graphics of the structures and the graphics of the worker approximators for carrying out the target work operation on display means on the basis of the first and second information, and calculating the radioactivity exposure amount corresponding to the movements of the worker approximators. According to the first characteristic, because the radioactivity exposure amount received by workers carrying out the target work operation including a plurality of procedures by use of layout graphic data of the area with controlled radioactive rays, a radioactivity exposure amount can be obtained with high precision taking the actual positional relation of a plurality of structures in the area with controlled radioactive rays and a plurality of procedures of work operation into account. Consequently, the determination is approximated further to one for the actual state as to whether the calculated radioactivity exposure amount satisfies a determined value or not, and the procedures of the target work operation obtained when the radioactivity exposure amount satisfies the determined value are appropriate. According to the second characteristic, because the radioactivity exposure amount is obtained for each procedures of work operation, the procedures of operation increasing the radioactivity exposure amount can be recognized easily. The operator can easily devise measures for decreasing the radioactivity exposure amount in this corresponding procedures of work operation. Further, because output of the information concerning with the radioactivity exposure amount is made for each small partitioned area, a small partitioned area increasing the radioactivity exposure amount can be known easily. According to the third characteristic, because the first information for displaying each structure in the area with controlled radioactive rays as graphics and the second information for displaying the surface radioactivity rate of each structure are displayed on the display means, the radioactivity amount of each structure can be recognized easily. According to the fourth characteristic, the graphic of each structure and the graphics of the worker approximators carrying out the target operation are displayed and the radioactivity exposure amount are calculated corresponding to the movements of the graphic of the worker approximators, the movements of workers carrying out the target work operation can be recognized while calculating the radioactivity exposure amount. |
053533143 | summary | BACKGROUND OF THE INVENTION The present invention relates to plasma devices, particularly devices of the tokamak type used in connection with the study and generation of thermonuclear fusion energy. More particularly, the invention relates to a geometry-insensitive high capacity electric field divertor pump that may used to drive plasma through a desired entrance aperture. Fusion is the energy source of the sun and other stars. While science has not yet advanced sufficiently far to allow fusion to be used as a practical energy source, scientists and engineers, working at laboratories around the world, are making great strides relative to fusion research and to the engineering development of fusion for electrical power and other applications. Advantageously, fusion fuel is in abundant supply, and the generation of fusion energy provides a safe and clean energy source. In generating fusion energy, the atoms of two or more fuels, typically deuterium (.sup.2 H) and tritium (.sup.3 H), heavy hydrogen isotopes, are exposed to extremely high temperatures. Such high temperatures separate the positively charged nuclei of the hydrogen isotopes from their normally tightly bound negatively charged electrons, forming a plasma. (A plasma is a hot ionized gas.) When this separation occurs, the neutrons and protons of the nuclei recombine to form a heavier element, such as .sup.4 He, and a neutron or other small nuclear particle. Energy from this reaction is released as kinetic energy of the fast moving reaction products, and it can be converted to heat. The heat thus created provides the high temperature needed to sustain the fusion reaction, and portions thereof can be extracted and used as a useful energy source, e.g., to generate electricity. The conditions for the fusion reaction are very difficult to achieve. For example, in order to kindle a deuterium-tritium fusion fire, the temperature of the fuel must be heated to over 50,000,000.degree. C. Moreover, to sustain the fusion fire, i.e., to keep the fusion reaction going, it is necessary to confine the normally chaotic mass of fast moving, superheated nuclei (the plasma) long enough for the fuel to react and produce energy beyond that necessary to sustain the temperature. To produce enough fusion reactions to make the process worthwhile, the heat losses from the fuel must be low enough so that the fuel can sustain a temperature of around 150,000,000.degree. C. One such a self-sustaining reaction is achieved, it is possible to use the heat thus produced to generate electricity, or for other purposes. Achieving such high temperatures requires supplying energy to the fuel and raising its temperature to a level where the internal fusion reactions can provide further heating. Various techniques are currently used to accomplish such heating, e.g., heating with an internal electric current, heating by various waves, and heating by the injection of energetic neutralized hydrogen atoms ("neutral beam injection"). Unlike the sun and stars, where the massive plasma ball is confined by gravity, fusion reactors require some type of container for holding the 50,000,000.degree. C. plasma fireball in a way that prevents it from touching the container walls. (Plasma, which has a density approximately 100,000 times lower than atmospheric pressure, is a mere puff of gas that would quickly cool if it touched the container walls.) Fortunately, because plasma is an ionized gas, it can be confined with a magnetic field. That is, the otherwise random motion of the charged particles that are found within plasma may be converted to an orderly form of motion that follows the magnetic field lines of an applied magnetic field. Thus, various types of "magnetic bottles" have been developed in the art to create the appropriate magnetic field lines to confine the plasma to a desired volume. One of the most highly developed magnetic bottles is a toroidal bottle known as the "tokamak". Tokamaks were first developed during the 1960s in the USSR, and have subsequently been adopted as the leading magnetic confinement device. A tokamak includes both external toroidal-field coils and poloidal-field coils that generate magnetic fields, as well as means for generating a toroidal electrical current that flows through the plasma itself. The magnetic fields created by such toroidal- and poloidal-field coil currents, as well as by the plasma electric current, all combine to confine the plasma to a general toroidal shape that encircles a major axis of the tokamak. The poloidal-field coils are also used to magnetically shape the general cross section of the plasma. Tokamaks are well documented in the literature. See, e.g., Artsimovich, L. A., Nuclear Fusion, Vol. 12, pp. 215 et seq. (1972); and Furth, H. P., Nuclear Fusion, Vol. 15, pp. 487 et seq. (1975). One of the housekeeping tasks associated with the operation of a tokamak is the efficient removal of spent plasma, or plasma exhaust. The external poloidal-field coils of a tokamak may advantageously be used to create one or more "poloidal divertors". See, e.g., Shimomura et al., Physics of Fluids, vol. 19, pp. 1635 et seq. (1976). Broadly stated, a poloidal divertor sets up a magnetic field that manages the plasma exhaust. More specifically, a poloidal divertor guides a thin boundary layer of escaping plasma, known as the scrape-off layer (SOL), located just outside the separatrix, along magnetic lines to solid "divertor targets." (The "separatrix", explained more fully below, is the magnetic surface defined by the applied magnetic fields that separates plasma confined by the magnetic field from plasma not confined by the magnetic field. Figuratively, the separatrix is the "lip" of a magnetic "jar".) Such targets are designed to absorb high heat and particle flux. Unfortunately, it is difficult to design a divertor target that can withstand the spatially peaked thermal loads that occur during a fusion reaction, particularly a long or sustained fusion reaction. Hence, it is preferable that the fusion reactor employ some means for "sweeping" the divertor strike point across the target so as to reduce the heat flux by time averaging. As the plasma strikes the targets, it cools and neutralizes, becoming a gas, comprised of hydrogen isotopes, helium ash and contaminants eroded from the divertor targets and walls. Such gas needs to be pumped away from the targets in order to prevent its buildup, which buildup (if allowed to continue) would quench the hot plasma. Such buildup has not heretofore been a major problem because the fusion reaction experiments performed to date have been of short duration. However, as the experiments become of longer and longer duration, eventually leading to a continuous nuclear reaction, the need to efficiently remove the neutralized plasma away from the divertor targets will become particularly acute. Unfortunately, due to the very low pressure associated with the neutral gas near the targets (usually <1 milliTorr), adequate pumping of the gas would require many large ducts through the tritium breeding blanket, radiation shield, and magnet coils of the tokamak. Such ducts would not only take up valuable space in the tokamak, but would also significantly complicate the radiation shielding. What is needed, therefore, is a plasma pump that can efficiently pump the plasma exhaust away from the targets without the need for a large number of massive ducts. Disadvantageously, pumping of the plasma exhaust (ash and contaminants) is made even more difficult when the desirable high-plasma-confinement operating mode (H-mode) of the tokamak is employed. This is because in the H-mode the plasma retains all ion species for a relatively longer period of time, and the gas pressure near the divertor targets is thus correspondingly less. Hence, what is needed is a means of efficiently removing or pumping plasma exhaust even when the tokamak is operating in the H-mode. (The H-mode tokamak operating regime is fully described in the literature, see, e.g., ASDEX Team, Nuclear Fusion, vol. 29, pp. 1959-2040 (1989). It is known in the art to build a plenum around the divertor targets designed to collect the plasma exhaust through an aperture opened to the divertor targets. The divertor exhaust gas pressure can be favorably increased by optimizing the entrance aperture geometry for minimum gas backstreaming. However, this makes the pressure very sensitive to small variations of the divertor geometry and plasma conditions. Where the divertor strike point is swept across the target, the entrance aperture geometry is dynamic, and the effectiveness of the plenum at collecting the diverted plasma is severely curtailed. What is needed, therefore, is a means of pumping or forcing the plasma exhaust into the aperture of a collecting plenum that is not significantly geometry sensitive, thereby allowing such plasma pump to be used with a dynamic entrance aperture geometry, such as exists when the divertor strike point is swept across the target. Some experimental work has been done aimed at applying an electric field E to a plasma flow confined by a magnetic field B, and using the resulting E.times.B drift of the plasma particles to divert the plasma in a desired direction. See, e.g., Strait, E. J., "Poloidal Diverter Experiment With Applied E.times.B/B.sup.2 Drift", Nuclear Fusion, Vol. 21, No. 8, pp. 943-51 (1981); and Strait, et al., "Experimental Demonstration of E.times.B Plasma Divertor", Phys. Fluids, Vol. 21, No. 12, pp. 2342-44 (December 1978). Despite some promising data, however, there still remains a need for a practical application of the principles underlying such experiments to the conditions that prevail in high power tokamak divertors. SUMMARY OF THE INVENTION The present invention provides an electric field plasma pump that addresses the above and other needs. The pump includes a toroidal ring bias electrode that is positioned so as to be near the divertor targets and an entrance aperture through which the plasma is to be pumped. In a preferred embodiment, the ring bias electrode functions as the divertor target. An electric field E is established between the ring electrode and an inner vessel wall of the tokamak, or other plasma-confining apparatus. The electric field E interacts with the B fields already existing in the tokamak to create an E.times.B drift velocity that drives the plasma through the entrance aperture. In accordance with one aspect of the invention, a plasma pump is used in a plasma-confining device, such as a tokamak. The tokamak includes means for generating a magnetic field B to confine the plasma to a prescribed volume. The plasma pump may be characterized as including: (a) electrode means for establishing an electric field E that interacts with the magnetic field B to electromagnetically drive the plasma in a desired direction, e.g., towards an aperture point; and (b) duct means for collecting plasma at the aperture point. The electrode means includes a ring electrode that is symmetric with a major axis of the plasma-confining device. The plasma-confining device further includes magnetic divertor means for diverting plasma along the thin scrape-off layer (SOL) just outside the separatrix. The separatrix is the magnetic surface that defines a boundary between plasma that is magnetically confined within the plasma-confining device from plasma that is not confined. The plasma pump of the present invention functions best when the separatrix is positioned to be in contact with the ring electrode, which then also functions as a divertor target. In accordance with another aspect of the invention, the plasma pump is adapted to interface with the plasma diverted to a strike zone of a divertor target by divertor means, e.g., poloidal divertor means, used within plasma-confining apparatus. The plasma pump may be characterized as including: (a) an entrance aperture facing a divertor target, through which the plasma is to be pumped; (b) an electrode positioned proximate the divertor target and the entrance aperture, such electrode being electrically insulated from the walls of the plasma confining apparatus; and (c) means for applying an electric field E between the electrode and the electrically conductive walls. In a preferred embodiment of the plasma pump, the electrode also functions as the divertor target. Advantageously, the electric field combines with the magnetic field so as to impart a E.times.B drift velocity to the plasma, which drift velocity drives the plasma through the entrance aperture. In accordance with a further aspect of the invention, a method is provided for removing plasma exhaust from a tokamak system. The tokamak system, as previously described, includes a vessel and means for generating a magnetic field B that confines plasma to a toroidal volume within the vessel. The tokamak system further includes a poloidal divertor having a separatrix X-point and scrape-off layer (SOL) associated therewith, with plasma being diverted by the poloidal divertor along the SOL to a strike position adjacent the X-point. The tokamak system also includes duct means, such as a plenum, for collecting plasma exhaust. Such duct means are at the same electrical potential as the vessel wall. The method includes the steps of: (a) positioning a ring electrode near the strike position so that the ring electrode makes contact with plasma in the SOL; (b) insulating a plasma-facing side of the ring electrode from the vessel walls and duct means of the tokamak system with a first insulator; (c) insulating a portion of the vessel wall adjacent the strike position but spaced apart from the ring electrode with a second insulator; (d) positioning an entrance aperture of the duct means intermediate to the ring electrode and second insulator; and (e) applying an electric field E between the ring electrode and the vessel wall, whereby a E.times.B drfit force is developed that drives plasma being diverted towards the strike position through the entrance aperture. Advantageously, an electric field plasma pump made or used in accordance with the present invention lends itself to a wide variety of applications, including: (1) reducing the vacuum pumping requirements for steady state plasmas; (2) exhausting plasma from low density plasmas; (3) establishing low collisionality, low density H-mode plasmas for current drive; and (4) making plasma exhaust insensitive to divertor geometry, especially to the variable geometry of swept divertors. It is thus a feature of the present invention to provide an electric field divertor pump for use with a poloidal divertor of a tokamak, or similar plasma-confining device, that efficiently pumps plasma exhaust through an entrance aperture into a duct or collecting plenum whereat the neutralized plasma may be removed as gas. It is a further feature of the invention to provide a plasma divertor pump wherein a bias electrode also functions as a divertor target. It is another feature of the invention to provide such a plasma divertor pump that efficiently performs its pumping function regardless of the operating mode of the tokamak, or similar device. It is a further feature of the invention to provide such a divertor pump that is geometry-insensitive, and that therefore can be efficiently used even when the divertor strike point is swept across the target. It is an additional feature of the invention to provide a divertor pump that uses self consistent internal and applied external electric fields to actively force the plasma to a desired pump entrance aperture. It is yet a further feature of the invention to provide such a divertor pump for use with a poloidal divertor of a tokamak that favorably traps and minimizes backstreaming of the plasma exhaust particles, despite the extremely low pressure associated with the plasma exhaust. |
description | Preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic perspective view of a modular submersible repairing system in a preferred embodiment according to the present invention. The modular submersible repairing system has a working unit including one of various types of tool modules 1 capable of repairing structures, a scanning/pitching module 2 capable of selectively scanning and positioning the tool module 1, a submersible fan module 3 capable of being selectively connected to or disconnected from the scanning/pitching module 2, and a buoyant module 4 (first buoyant module); and a base unit including a manipulator module 5, a adsorbing module 6 capable of being selectively connected to or disconnected from the manipulator module 5 and provided with suction cups 6a, a submersible fan 7, and a buoyant module 8 (second buoyant module). The tool modules 1 are used selectively according to the purpose of work. The scanning/pitching module 2 is provided with a scanning/pitching mechanism 2a for moving and scanning the tool module 1 mounted on the scanning/pitching module 2. The submersible fan modules 3 and 7 are provided with submersible fans 2a and 7a, respectively. The submersible fans 3a and 7a generate thrusts to press the submersible fan modules 3 and 7 against a wall, respectively. The buoyancies of the buoyant modules 4 and 8 are keeping it""s orientation stably. The manipulator module 5 is provided with a pantographic extension mechanism 9. The scanning/pitching module 2 can be detachably joined to the free end of the extension mechanism 9. FIGS. 2(a) and 2(b) are a side view and an elevational view, respectively, of the extension mechanism 9. Internally threaded nuts 10a and 10b attached to the upper and the lower base end, respectively, of the pantographic linkage of the extension mechanism 9 are screwed on a threaded shaft 11. The threaded shaft 11 has an upper threaded section 11a and a lower threaded section 11b provided with threads of the opposite hands, respectively. The upper nut 10a and the lower nut 10b are screwed on the upper threaded section 11a and the lower threaded section 11b, respectively. The threaded shaft 11 is interlocked through a bevel gear mechanism 12 to the drive shaft of a driving motor 13. The joints of the pantographic linkage include bearings 14. The pantographic linkage is extendible. Since the joints of the pantographic linkage includes the bearings 14, the pantographic linkage is able to bend to some extent in a direction perpendicular to a reference plane. The other end of the pantographic linkage is connected to a connecting member 15 connecting the scanning/pitching module 2 and the extension mechanism 9 so as to be vertically slidable on the connecting member 15. The driving motor 13 drives the threaded shaft 11 for rotation. Consequently, the nuts 10a and 10b are moved toward or away from each other to extend or contract the pantographic mechanism horizontally. The modules are detachable from each other. Some modules including the scanning/pitching module 2 and the manipulator module 5 are provided with, for example, a submersible connecting device. The submersible connecting devices are remotely operated in water for connection or disconnection by an engaging/disengaging device. At least the scanning/pitching module 2 and the manipulator module 5 are provided with submersible connecting devices, respectively. The tool module 1 may be provided with a submersible connecting device. FIG. 3 is a schematic view of the submersible connecting device. For example, the scanning/pitching module 2 is provided a male connecting unit 18 including a taper member 16 tapering toward its free end, and a draw-bolt 17 fastened to the extremity of the taper member 16. The male connecting unit 18 projects horizontally from the scanning/pitching module 2. A key groove 19 is formed in the base part of the taper member 16 of the male connecting unit 18. Dints 20 are formed in an upper part of the scanning/pitching module 2. The hooks of a hoisting device, not shown, engage the dints 20. On the other hand, the manipulator module 5, to which the scanning/pitching module 2 is connected, is provided with a female connecting unit 21. A taper hole 22 complementary to the taper member 16 of the male connecting unit 18 is formed in a part of the manipulator module 5 facing the scanning/pitching module 2. A key 23 to be engaged in the key groove 19, and an ultrasonic distance measuring device 24 for measuring the distance between the scanning/pitching module 2 and the manipulator module 5 in a noncontact measuring mode are disposed near the open end of the taper hole 22. The female connecting unit 21 is provided with a gripping mechanism 25 capable of gripping the draw-bolt 17 and of pulling the male connecting unit 18 toward the female connecting unit 21. The gripping mechanism 25 is operated by a hydraulic cylinder actuator 26. A pneumatic locking device 28 is connected to one end of the hydraulic cylinder actuator 26. When the male connecting unit 18 is pulled into the gripping mechanism 25, the pneumatic locking device 28 engages a piston rod 27 included in the hydraulic cylinder actuator 26 to restrain the piston rod 27 from movement. A recess 29 is formed in an upper part of the manipulator module 5. A drawing claw engages the recess 29. When connecting the scanning/pitching module 2 and the manipulator module 5, the taper part 16 of the male connecting unit 18 is inserted in the taper hole 22 of the female connecting unit 21, the stopping members 25a of the gripping mechanism 25 are engaged with the draw-bolt 17, and the hydraulic cylinder actuator 26 is operated to draw the draw-bolt 17 into the taper hole 22. After the scanning/pitching module 2 and the manipulator module 5 have been thus connected, the pneumatic piston having the locking device 28 holds the piston rod 27 of the hydraulic cylinder actuator 26 fixedly to prevent the accidental disengagement of the male connecting unit 18 and the female connecting unit 21 of the submersible connecting device resulting from the faulty operation of the hydraulic cylinder actuator 26 due to faulty operations or loss of pressure applied to the hydraulic cylinder actuator 26 during work. FIGS. 4(a)and 4(b) are a side view and an elevational view, respectively, of a hoisting device 30 for suspending the module or a combination of the modules in water and for connecting the module or a combination of the modules to an existing module. A pair of hooks 32 are supported on a lower end part of the hoisting device 30. The hooks 32 are turned about horizontal axes, respectively, by a pneumatic cylinder actuator 31 to engage the same with or disengage the same from the dints 20 of the module. The hoisting device 30 is provided with an arm 34 capable of being advanced toward and retracted away from the module to be connected to another module, for example, the manipulator module 5, by a pneumatic cylinder actuator 33. A drawing claw 35 and a pushing claw 36 are supported on the arm 34. The claws 35 and 36 are connected pivotally by pin joints 37 to a claw support member 38 held on the arm 34. The claws 35 and 36 hung down from the claw support member 38 by their own weights. The drawing claw 35 is able to turn away when the arm 34 is moved in a pushing direction and is restrained from turning by a stopper 39 when the arm 34 is moved in a drawing direction. The pushing claw 36 is able to turn away when the arm 34 moves in the drawing direction and is restrained from turning by the stopper 39 when the arm 34 is moved in the pushing direction. The claws 35 and 36 and the claw support member 38 are provided with holes 40, 41 and 42, respectively. A pin is inserted in the holes 40 and 42 to hold the drawing claw 35 in a horizontal position when the drawing claw 35 is not used. A pin is inserted in the holes 41 and 42 to hold the pushing claw 36 in a horizontal position when the pushing claw 36 is not used. When connecting the modules together in water contained in the reactor by a remotely controlled operation, the drawing claw 35 is set in a vertical position, the pushing claw 36 is set in a horizontal position, a hoisting hook driving mechanism including a linkage is operated by the pneumatic cylinder actuator 31 to engage the hooks 32 in the dints 20 of the module 2 provided with the male connecting unit 18, and the module 2 is lowered. The module 2 is moved in the reactor so that the male connecting unit 18 of the module 2 approaches the female unit 21 of the module 5, and hoisting wires are controlled so as to insert the taper part 16 in the taper hole 22 of the module 5. The taper part 16 is inserted in the taper hole 22 deep enough to enable the drawing claw 35 to engage in the recess 29 of the module 5 by a manual operation. Then, the pneumatic cylinder actuator 33 is actuated to move the arm 34 in the drawing direction. Consequently, the drawing claw 35 engaged in the recess 29 draws the female connecting unit 21 forcibly toward the male connecting unit 18. Thus, the gripping mechanism 25 is made to grip the draw-bolt 17 by a remotely controlled operation. When disconnecting the modules from each other in water contained in the reactor and taking out the module 2 from the reactor, the drawing claw 35 set in a horizontal position and the pushing claw 36 set in a vertical position are inserted in the reactor, and the hooks 32 are engaged in the dints 20 of the module 2. Then, the gripping mechanism 25 is operated to release the draw-bolt 17 to disconnect the male connecting unit 18 from the female connecting unit 21. Generally, the taper part 16 cannot be removed from the taper hole 22 at this stage. Therefore, the arm 34 is moved in the pushing direction to push the female connecting unit 21 from the male connecting unit 18. The modular submersible repairing system thus constructed carries out work for the maintenance of the shroud of a reactor in the following manner. The modules of the base unit and the working unit are assembled in a vertical arrangement as shown in FIG. 5 such that the base unit and the working unit have the smallest horizontal cross sections, respectively, to build a modular submersible repairing system meeting restrictions placed on the dimensions of the modular submersible repairing system by a space between jet pumps 45 placed in a space between a pressure vessel 43 and a shroud 44. The modular submersible repairing system is suspended and lowered to a predetermined position as shown in FIG. 6, the submersible fan module 7 of the base unit is operated to move the modular submersible repairing system to the outer surface of the shroud 44 by a thrust produced by the submersible fan module 7. Then, the modular submersible repairing system is held fixedly on the shroud 44 by the agency of the suction cups 6a of the adsorbing module 6. The modular submersible repairing system is kept always in a fixed vertical position by the agency of the buoyant module 8 while the modular submersible repairing system is lowered in the pressure vessel 43. The manipulator module 5 for work on the outer surface of the shroud 44 is provided with the pantographic extension mechanism 9. Since the pin joints of the extension mechanism 9 include the spherical bearings 14, the working unit can be moved along the outer surface of the shroud 44 into a space between the jet pumps 45 and the shroud 44 and can be moved near to an objective part. The submersible fan module 3 is operated while the extension mechanism 9 is extending, so that the working unit does not separate from the surface of the shroud 44 and moves along the surface of the shroud 44. The manipulator module 5 is locked after the working unit has been thus moved near to a desired position to complete the positioning of the working unit. Subsequently, the X- and the Y-shaft of the scanning/pitching module 2 are operated to carry out batch work. After the completion of the work, the foregoing procedure is reversed to take out the modular submersible repairing system from the reactor. When repairing the inner surface of the shroud 44, the height of an adjusting module 47 is considered with reference to the height of a defect in the inner surface of the shroud 44 from a core plate 46 (FIG. 8), and an adjusting module 47 of a length and a shape suitable for repairing work is selected. Referring to FIG. 7 showing the adjusting module 47, end members 47b and 47c are connected to an upper part and a lower part, respectively, of a module body 47a of a predetermined length with bolts 48 so that height is adjustable. The end members 47b and 47c are provided with connecting units 49a and 49b, respectively. Referring to FIG. 8, the base unit is built by connecting the manipulator module 5, the adjusting module 47 and a fixing module 50. The base unit is lowered through an opening of an upper grid plate 51 in the reactor by a cable of the hoisting device 30, and is inserted in a control rod guide pipe 53 held on the core plate 46. The orientation of the fixing module 50 is determined by engaging a locating pin, not shown, in a locating hole of the fixing module 50. A locking mechanism, not shown, included in the fixing module 50 is operated to fix the base unit in the control rod guide pipe 53. Then, the cable of the hoisting device 30 is disconnected from the base unit and is taken out of the reactor. Subsequently, the scanning/pitching module 2 combined with the submersible fan module 3 and the buoyant module 4 is suspended and lowered in the reactor by the hoisting device 30. The scanning/pitching module 2 is passed through an opening of the upper grid plate 51 other than that through which the base unit was passed, the scanning/pitching module 2 is moved near to the manipulator module 5 in cooperation with the operation of the arm 34, and the female connecting unit 21 of the manipulator module 5 and the male connecting unit 18 of the scanning/pitching module 2 are engaged, in which the engagement of the taper member in the taper hole is assisted by the drawing claw 35 of the hoisting device 30. Upon the confirmation of the connection of the scanning/pitching module 2 and the manipulator module 5 from a signal provided by the ultrasonic distance measuring device 24, the locking device 28 is actuated to prevent the faulty operation of the hydraulic cylinder actuator 26. Then, the hooks 32 of the hoisting device 30 is disengaged from the scanning/pitching module 2 and the hoisting device 30 is taken out of the reactor. Subsequently, the tool module 1 is suspended and lowered in the reactor by the hoisting device 30, and the female connecting unit of the scanning/pitching module 2 and the male connecting unit of the tool module 1 are engaged. After the modules have been thus connected, the manipulator module 5 is operated to move the working unit near to the objective part, the tool module 1 is pressed against the shroud by the agency of the submersible fan module 3, and the scanning mechanism of the scanning/pitching module 2 carries out batch work. As apparent from the foregoing description, according to the present invention, the shape and configuration of the repairing system can be changed according to the condition of the object of work and is capable of carrying out repairing work for repairing structures of a boiling-water reactor which places severe dimensional restrictions. Various modules provided with standardized connecting units can be used for the efficient operation of the modular repairing system. Since the modules can be connected in water by a remotely controlled operation, the proper modules can be assembled in the reactor, the dimensional restrictions can be relaxed. |
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048266515 | summary | The invention relates to a method for assisting the process of loading a reactor core with new and/or irradiated elongated fuel assemblies, in which a fuel assembly from a storage pit is inserted into the grid position of a reactor core using a refueling machine preferably under a neutron-shielding liquid covering. A method of this kind is known from German Published, Prosecuted Application No. DE-AS 22 46 637. In that publication a container having a plurality of fuel assemblies is supposed to be inserted into the reactor core all at once, in order to speed up the loading process when fuel assemblies are changed. It is also known from German Published, Non-Prosecuted Application No. DE-OS 15 64 301 that when binoculars are used for observation and with a covering of water several meters thick, it is impossible to insert the wavering fuel assemblies into the grid positions of the core without expending a great deal of time. During that time, the fuel assemblies are prevented from wobbling by other means. However, one problem in this respect is that the axis of the carrier or base of the fuel assembly dos not coincide with the desired location of the axis. It is true that the deviations that arise due to bowing, are only on the order of only a few millimeters; nevertheless, they make it considerably more difficult to introduce the fuel assembly carrier into a particular grid position in the reactor core. Furthermore, the mechanical insertion aid proposed in German Published, Non-Prosecuted Application No. DE-OS 15 64 301 cannot be used unless enough space is available between the various grid positions for the insertion of cross-shaped control elements. It is accordingly an object of the invention to provide a method and apparatus for assisting the process of loading a reactor core with elongated fuel assemblies, which overcomes the hereinafore-mentioned disadvantages of the heretoforeknown methods and devices of this general type and with which it becomes possible to insert fuel assemblies in which the axis of the carrier or base deviates from its desired axis. With the foregoing and other objects in view there is provided, in accordance with the invention, a method for assisting the loading of a reactor core with new and/or irradiated elongated fuel assemblies, which comprises inserting a fuel assembly with a fuel assembly carrier from a storage pit into a grid position of a reactor core with a refueling machine having propelling equipment preferably under a neutron-shielding liquid covering, supplying an actual position of the fuel assembly carrier to the propelling equipment of the refueling machine during movement of the refueling machine between the storage pit and the reactor vessel, comparing the actual position of the fuel assembly carrier with a desired position of the fuel assembly carrier to find a deviation, and carrying out a correction of the deviation in the travelling movement of the refueling machine based upon the comparison. Bowing of the fuel assembly, which is entirely to be expected because of its length of over four meters, can accordingly no longer hinder the insertion of the fuel assemblies into the grids of the core supporting structure disposed in the reactor core. If the ascertained actual position of the carrier or base deviates from its desired position, the travel movement of the refueling machine is corrected by the amount of the deviation. In accordance with another mode of the invention, there is provided a method which comprises transmitting a picture from a stationary television camera to a monitor, for recognizing the deviation from the desired position and ascertaining the actual position of the fuel assembly carrier. With the objects of the invention in view there is also provided an apparatus for assisting the loading of new and/or irradiated elongated fuel assemblies having fuel assembly carriers into grid positions of a reactor core in a reactor vessel of a reactor having a storage pit, a flooding pit and a lead through therebetween, comprising a refueling machine having propelling equipment for transferring a fuel assembly from the storage pit to the flooding pit and inserting the fuel assembly into a grid position, means for recognizing the actual position of the fuel assembly carrier at a measuring point in the vicinity of the lead through and for supplying the actual position of the fuel assembly carrier to the propelling equipment of the refueling machine during movement of the refueling machine between the storage pit and the reactor vessel, means for comparing the actual position of the fuel assembly carrier with a desired position of the fuel assembly carrier to find a deviation, and means for carrying out a correction of the deviation in the travelling movement of the refueling machine based upon the comparison. The refueling machine moves to a predetermined position relative to the location of the television camera, so that the actual position of the fuel assembly carrier can be ascertained exactly. In accordance with a concomitant feature of the invention, the lead through includes guide rails for a floodgate and means supported in the guide rails for holding the recognizing means at the measuring point. Fixation of the camera is thus accomplished in a simple manner. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in a method and apparatus for assisting the process of loading a reactor core with elongated fuel assemblies, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. |
description | This application claims priority of French Patent Application No. 09 57929, filed Nov. 10, 2009. 1. Technical Field The present invention relates to the field of transporting and/or storing radioactive materials, such as nuclear fuel assemblies, fresh or irradiated. In particular, the invention relates to a canister comprising a radiological protection device laid out between two concentric shells, forming a barrier against gamma radiation. 2. State of the Prior Art Conventionally, to ensure the transport and/or the storage of nuclear fuel assemblies, storage devices, also known as storage “baskets” or “racks”, are used. These storage devices, normally of cylindrical shape and of substantially circular section, have a plurality of adjacent housings each of which is able to receive a nuclear fuel assembly. The storage device is intended to be housed in the cavity of a canister so as to form jointly with it a container for transporting and/or storing nuclear fuel assemblies, in which the nuclear material is confined. The aforementioned cavity is generally defined by a lateral body extending along a longitudinal direction of the canister, said lateral body comprising for example two concentric metal shells jointly forming an annular space inside which is housed a radiological protection device, in particular to form a barrier against the gamma radiation emitted by the fuel assemblies housed in the cavity. Conventionally, the radiological protection device is formed by means of several prefabricated components made of lead or one of its alloys, spread around the cavity, in the appropriate annular space defined by the two metal shells. To do this, each of these components is inserted between the two shells, along a longitudinal insertion direction. Thus, an assembly clearance must be provided to allow such an insertion, said clearance having as consequence a discontinuity of material in the lateral body of the canister, along the radial direction in which are laid out successively the inner shell, the radiological protection components, and the outer shell. The observed discontinuity of material has the effect of a considerable decrease in the thermal conductivity of the lateral body of the canister, implying a low capacity of the latter to dissipate the heat produced by the fuel assemblies. To minimise the negative impact of the discontinuities of material, the clearances between the radiological protection components and the shells may be reduced by lessening the manufacturing tolerances, but this proves nevertheless to be very costly, and does not in the least enable the discontinuities of material to be eliminated. Other means may be employed to reduce the loss of thermal efficiency, such as that aiming to inject helium into the empty spaces. However, this technique induces a cost and poses serious problems of operating the canister. Another solution consists in separating the radiological protection function from that of heat conduction, this then being fulfilled by means of additional fin type components linking the two shells, laid out alternately with the radiological protection components in the annular space. Nevertheless, this further complicates the design of the canister, and moreover necessitates the use of particular techniques to ensure that the fins are indeed in contact with each of the two shells of the lateral body. The aim of the invention is thus to remedy, at least partially, the aforementioned drawbacks relative to embodiments of the prior art. To do this, the object of the invention is a canister for transporting and/or storing radioactive materials, said canister comprising a lateral body extending around a longitudinal axis of said canister, said lateral body forming a cavity for housing the radioactive materials and comprising an inner metal shell and an outer metal shell, the two shells being concentric and forming jointly an annular space inside which is housed a radiological protection device forming a barrier against gamma radiation, said radiological protection device comprising at least one first and one second metal radiological protection components adjacent along a circumferential direction of the canister. According to the invention, said first component is supported against the outer shell and at a distance from said inner shell, whereas said second component is supported against the inner shell and at a distance from said outer shell. In addition, said first and second components are in contact with each other along an interface taking, in section along any plane orthogonal to the longitudinal axis and crossing this interface, the form of a straight line segment defining with a radial straight line crossing it at its centre an acute angle (A). The invention thus offers a shrewd design enabling the radiological protection components to conduct heat in a satisfactory manner between the two shells. Indeed, the heat is conducted in a continuous manner, firstly between the inner shell and the second radiological protection component, thanks to the contact between these parts, then through the interface between the first and second components, and finally between the first radiological protection component and the outer shell, again on account of the contact provided between these parts. Thus, the particular geometry and arrangement of the radiological protection components make it possible to confer to the lateral body of the canister a satisfactory thermal conductivity. The presence of helium or heat conduction fins is thus no longer necessary, which makes it possible to have a canister of simplified design and manufacture. Moreover, since the first and second radiological protection components are no longer intended, as in the prior art, to come as close as possible to each of the two shells, but each being only in contact with one and at a distance from the other of the two shells, the manufacturing tolerances of said components may be increased. Advantageously an important cost reduction ensues. Finally, thanks to the inclination of the aforementioned interface, the contact force that is observed between the two components, at this interface, radially constrains each of these two components against its associated shell. Thus, with this design, it is possible to increase the intensity of contact between the radiological protection components and their associated shell, simply by further tightening these components along the circumferential direction, in order to obtain a relative displacement of the first in relation to the second component, along the radial direction. This tightening may for example be achieved, during the manufacture of the canister, by means of tightening means housed in the annular space. The increase in the intensity of these contacts is advantageous in the sense that it ensures better heat conduction. In this respect, it is noted that one and/or the other of the radiological protection components may be coated with a heat conducting layer at the contact interface, in order to improve yet further the heat conduction between these components. This layer is preferably of low thickness, and deformable, for example made of lead or one of its alloys. Naturally, this solution of heat conducting layer may also be adopted at the contacts between the radiological protection components and the shells. Preferably, said angle (A) is between 30 and 60°, and, even more preferentially, is close to 45°. The interfaces thereby inclined enable a satisfactory radial pinning of the radiological protection components, when they are constrained circumferentially. Preferably, said interface is flat. Preferably, the canister comprises at least one first metal radiological protection component as well as two second metal radiological protection components arranged on either side of said first component along the circumferential direction, said first component being in contact with each of the two second components along respectively two interfaces each taking, in section along any plane orthogonal to the longitudinal axis and crossing this interface, the form of a straight line segment defining with a radial straight line crossing it at its centre an acute angle (A), the two straight line segments being respectively supported by straight lines coming closer to each other going radially towards the interior and intercepting between the two radial straight lines. In this configuration, the first component is put under strain by the two second components, which thus participate jointly in its pinning against the outer shell. Moreover, this first component participates for its part in the pinning of the two second components against the inner shell. Obviously, a different inclination angle may be adopted for the two interfaces, even if the two angles are preferentially equal. In an analogous manner, the canister preferably comprises at least one second metal radiological protection component as well as two first metal radiological protection components arranged on either side of said second component along the circumferential direction, said second component being in contact with each of the two first components along respectively two interfaces each taking, in section along any plane orthogonal to the longitudinal axis and crossing said interface, the form of a straight line segment defining with a radial straight line crossing it at its centre an acute angle (A), the two straight line segments being respectively supported by straight lines coming closer to each other going radially towards the exterior and intercepting between the two radial straight lines. Preferentially, a plurality of first and second components laid out alternately along the circumferential direction, and cooperating in the aforementioned manner, are provided for, namely that each of them is put under strain by its two adjacent components, which participate jointly in its pinning against its associated shell. Preferably, each first radiological protection component has a section, along any plane orthogonal to the longitudinal axis, of overall trapezium shape, the large base of which is supported against the outer shell and the small base at a distance from the inner shell, each second radiological protection component has a section, along any plane orthogonal to the longitudinal axis, of overall trapezium shape, the large base of which is supported against the inner shell and the small base at a distance from the outer shell, and the faces of the first and second components defining the sides of trapeziums are in two by two contact, so as to form said interfaces. Nevertheless, shapes other than the trapezium could be envisaged, it being in this respect pointed out that the first components could adopt a shape different to that of the second components, in the same way as different shapes could be adopted within the first/second components. By way of indication, other envisaged shapes are for example the triangle, or the trapezium truncated at the two angles between the large base and the sides. Preferably, for each trapezium, the large base is intercepted, locally at its centre, orthogonally by a radial straight line. To facilitate manufacture and to obtain a symmetry in the application of the contact forces, each trapezium is isosceles. It is noted that the large base of each trapezium is preferably straight, and even more preferentially arc of circle shape of diameter identical to that of the shell surface that it contacts, in order to increase the contact surface between these two components. Preferably, for each trapezium, the ratio of lengths between the large base and the small base is between 3 and 8. The higher the ratio, the more efficient the heat transfer. According to a preferred embodiment of the invention, each of said plurality of first and second components is maintained only by contacts in the annular space. This implies, in particular, that no additional means of fixation are added either between a protection component and its associated shell, or between two directly consecutive protection components. The design thus enables these components to maintain each other mutually by contact, by means also of the shells. This possibility is also offered for protection components of different shape to that of the trapezium. The canister may then comprise tightening means housed in said annular space, making it possible to constrain said plurality of first and second components along the circumferential direction, and thus cause the pinning of these components radially, against their associated shell. Preferably, each of said plurality of first and second components takes the form of a prism with trapezoidal base. According to another preferred embodiment of the invention, each of said plurality of first components or each of said plurality of second components is assembled fixedly to its associated shell, for example by gudgeons/nuts or equivalent means, and each of the plurality of other components is maintained only by contacts in the annular space, between its two adjacent components fixed to their shell. To facilitate the assembly of such a canister, each of said plurality of components assembled fixedly to its associated shell has a section reducing in a given direction of the longitudinal direction of the canister, and each of the plurality of other components has a section increasing in said given direction of the longitudinal direction. Here, the intensity of the contacts is thus dependent on the relative longitudinal position between the components. Consequently, during the insertion of one of the protection components by longitudinal sliding between its two associated fixed protection components, the contacts between the components, once established, have an intensity that increases as the insertion is continued. Finally, another object of the invention is a method for producing a canister as described above, in which each first and second metal radiological protection components are inserted into said annular space, then a tightening is carried out making it possible to constrain said components along the circumferential direction. Other advantages and characteristics of the invention will become clear in the detailed non limitative description given hereafter. Firstly with reference to FIG. 1, a container 1 for transporting and/or storing nuclear fuel assemblies may be seen. It is in this respect recalled that the invention is in no way limited to the transport/storage of this type of nuclear material. The container 1 overall comprises a canister 2, object of the present invention, inside of which is a storage device 4, also known as storage basket. The device 4 is provided to be placed in a cavity for housing 6 the canister 2, as shown schematically in FIG. 1, in which it is also possible to perceive the longitudinal axis 8 of this canister, merged with the longitudinal axes of the storage device and the housing cavity. Throughout the description, the term “longitudinal” must be understood as parallel to the longitudinal axis 8 and to the longitudinal direction X of the canister, and the term “circumferential” must be understood as orthogonal to this same longitudinal axis 8, as well as to a transversal direction of the canister. In a conventional manner and by way of reminder, it is noted that the storage device 4 comprises a plurality of adjacent housings arranged parallel to the axis 8, the latter each being able to receive at least one fuel assembly of square or rectangular section, and preferably only one. The container 1 and this device 4 have been shown in a vertical position of loading/unloading the fuel assemblies, different to the horizontal/lying down position normally adopted during the transport of the assemblies. Generally speaking, the canister 2 essentially has a bottom 10 on which the device 4 is intended to lie in a vertical position, a lid 12, and a lateral body 14 extending around and along the longitudinal axis 8, this body 14 defining a canister opening intended to allow the basket to penetrate into the housing cavity 6, and to be then sealed by the lid 12. It is thus this lateral body 14 that defines the housing cavity 6, by means of a lateral inner surface 16 of substantially cylindrical shape and of circular section, and of axis merged with the axis 8. The bottom 10, which defines the bottom of the cavity 6 open at the lid 12, may be formed from a single part with part at least of the lateral body 14, without going beyond the scope of the invention. With reference now to FIG. 2, it is possible to perceive in a detailed manner part of the lateral body 14, which has firstly two concentric metal shells forming jointly an annular space 18 centred on the longitudinal axis of the canister (not visible in this figure), this space 18 housing a radiological protection device 20 specific to the present invention. The shells 22, 24 are for example made of steel. This protection device 20 is in particular designed to form a barrier against the gamma radiation emitted by the irradiated fuel assemblies housed in the cavity 6. Thus, it is housed between the internal shell 22, the inner surface of which corresponds to the inner lateral surface 16 of the cavity 6, and the outer shell 24. As may be seen in FIG. 2, in this first preferred embodiment of the present invention, the protective device 20 comprises a plurality of first and second radiological protection components, respectively referenced 30 and 32, which are laid out alternately along the circumferential direction T, also known as tangential direction. The number of these components 30, 32 may be several tens. The first and second components 30, 32 are metal, preferably blocks made of lead or cast iron or one of their alloys, this type of material making it possible to ensure both radiological protection against gamma radiation, and satisfactory thermal conductivity. Each of the first and second components 30, 32 has a substantially trapezoidal section, which, in this first preferred embodiment, is preferentially constant over its whole length. Indeed, each component here takes the form of a straight prism of axis parallel to the axis 8, with trapezoidal base, housed between the two shells 22, 24, and extending longitudinally over the length of the cavity 6. In addition, the trapezoidal section takes the overall form of an isosceles trapezium. As regards each first component 30, the face that defines the large base is supported, and more preferentially is in direct contact, against the inner surface 24a of the outer shell 24. This contact is preferentially a surface contact, over the whole surface of the prism that is facing the inner surface 24a. To do this, the large base adopts preferentially a convex arc of circle shape of diameter similar or identical to that of the inner surface 24a, and of same centre, even though a large straight base could be envisaged, without going beyond the scope of the invention. Moreover, the small base is at a distance from the outer surface 22a of the inner shell 22, a consequent clearance could be provided for, for example greater than 5 mm, or even much more. Generally speaking, the aforementioned radial clearance represents between 1/30 and 1/10 of the radial thickness of the space 18. Conversely, each second component 32 has its face defining the large base supported, and more preferentially in direct contact, against the outer surface 22a of the inner shell 22. This contact is preferentially a surface contact, over the whole surface of the prism that is facing the outer surface 22a. To do this, the large base here adopts a concave arc of circle shape of diameter similar or identical to that of the outer surface 22a, and of same centre, even though a large straight base could also be envisaged. Moreover, the small base is at a distance from the inner surface 24a of the inner shell 22, a consequent clearance could be provided for, for example greater than 5 mm, or even much more. Here also, the aforementioned radial clearance represents more generally between 1/30 and 1/10 of the radial thickness of the space 18. The faces of the first and second components 30, 32 which define the small bases of the trapeziums may have, in transversal section, various shapes, for example straight or instead arc of circle. The faces of the blocks 30, 32 which define the sides of the trapeziums are in two by two contact, while preferentially forming flat interfaces 40. More precisely, as shown in FIG. 2, each contact interface 40 adopts, in section along any plane orthogonal to the longitudinal axis 8 and crossing this interface, the shape of a straight line segment defining, with a radial straight line 41 crossing it at its centre M, an acute angle A. This acute angle A, which is thus between the values of 0° and 90°, excluded from the interval, is preferably between 30 and 60°, and even more preferentially of the order of 45°. The inclination direction of the aforementioned straight line segment is such that the radial straight line 41 extends firstly through the first component 30 starting from the segment and going radially towards the exterior, and extends firstly through the second component 32 starting from the segment and going radially towards the interior. In other words, the straight line segment 40 extends radially towards the interior from its centre while being offset circumferentially from the radial straight line 41 along a circumferential offset direction corresponding to that of the first component 30 in relation to the second component 32. By way of example, in FIG. 2, the first component 30 the furthest left is offset circumferentially from the second component 32 the furthest left along the clockwise direction. In addition, it is along this same clockwise direction that is offset the radially inner part of the segment 40 in relation to the radial straight line 41. At each first component 30, the two interfaces 40 defined by it thus each take the shape of a straight line segment inclined from the acute angle A in relation to its associated radial straight line 41. In addition, on account of the trapezoidal section, these two straight line segments 40 are respectively supported by two straight lines 40′ coming closer to each other going radially towards the interior, and intercepting at a point I situated between the two radial straight lines 41, 41 crossing these two same segments at their centre. In other words, each segment 40 forms part of the straight line 40′ that supports it. In an analogous manner, at each second component 32, the two interfaces 40 defined by it thus each take the shape of a straight line segment inclined from the acute angle A in relation to its associated radial straight line 41. In addition, also on account of the trapezoidal section, these two straight line segments 40 are respectively supported by two straight lines 40′ coming closer to each other going radially towards the exterior, and intercepting at a point I situated between the two radial straight lines 41, 41 crossing these two same segments at their centre. Moreover, for each component 30, 32, the ratio of lengths between the large base E and the small base e is between 3 and 8. With such a configuration, the heat released by the assemblies is conducted in a continuous manner between the two shells 22, 24, which confers satisfactory thermal conductivity to the lateral body. As shown schematically by the arrows of FIG. 2, the heat is firstly conducted between the inner shell 22 and the faces defining the large bases of the second components 32, then by the contact interfaces 40 between the first and second components 30, 32, and finally between the faces defining the large bases of the first components 30 and the outer shell 24. One of the main advantages of this solution lies in continuous privileged heat conduction paths being obtained between the two shells, with components 30, 32 of simple shape, each in contact with only one of these two shells. This latter point implies that they may be manufactured with high tolerances, reducing their production cost. In the first preferred embodiment, each of the components 30, 32 is thus maintained uniquely by contacts in the annular space 18, each of them being pinned against one of the shells and against its two adjacent protection components. The components 30, 32 may thus be inserted longitudinally one after the other into the space 18, each component next being placed in contact with the last component previously inserted, at one of its lateral faces defining one side of a trapezium, its other lateral face being for its part intended to serve as support contact for the next component to be inserted. The plurality of components 30, 32 may extend in a continuous manner over 360°. Nevertheless, to avoid any difficulties of assembly of the final radiological protection component, said plurality of components 30, 32 may extend over substantially less than 360° in order to leave an angular sector dedicated to the positioning of circumferential tightening means in the space 18. In this respect, a circumferential tightening device 44 is shown schematically in FIG. 3, placed between the two end components of said plurality of components forming an angular sector close to 360°. This device, which may be of any design considered appropriate by those skilled in the art, makes it possible to constrain the components 30, 32 along the circumferential direction, as is schematically shown by the arrows 46. This placing under circumferential constraint of said plurality of components generates, between each pair of any two adjacent components 30, 32, an increase in the contact force that is exerted at the faces defining the sides of trapeziums, this force oriented orthogonally to the interface 40 being represented by arrows 48 in FIG. 3. Thanks to its inclination in relation to the circumferential direction T, the force 48 makes it possible to constrain each of the two components 30, 32 against its associated shell, as has been shown schematically by the arrows 50. In other words, one of the two components 30, 32 exerts on the other a force pinning it against its associated shell, and vice versa. Thus, it is possible to increase the intensity of contact between the components 30, 32 and their associated shell by carrying out a circumferential tightening by means of the device 44, this tightening obviously also bringing about an increase in the intensity of contact between the lateral faces of the components 30, 32 defining the sides of trapeziums. The increase in the intensity of these contacts is advantageous in the sense that it ensures better heat conduction. In another envisaged configuration, only shown schematically in FIG. 4, several circumferential tightening devices 44 are provided for, for example three arranged at 120°. Whatever the number of these devices 44, two of them directly consecutive along the circumferential direction delimit between them a plurality of components 30, 32 that they constrain circumferentially. Thus, in the example shown in FIG. 4, three separate assemblies 52′ are provided, each forming a plurality of components 30, 32 slid into the annular space 18, as well as three tightening devices 44 each participating in bringing under circumferential pressure two adjacent assemblies 52′. In the case where several tightening devices 44 are provided for in the annular space 18, at least one of them may then take the form of a component fixed to one of the shells 22, 24, of identical or similar shape to that of the components 30, 32. Even if this device does not comprise means enabling it to extend circumferentially, it fulfils all the same a tightening function in combination with each tightening device directly consecutive to it, by constituting a pressure stop for the plurality of components with which it is associated. In such a configuration, the fixed component may moreover fulfill a function of angular indexation of the components 30, 32, and also serve as fixed support capable of maintaining in position the first component 30, 32 after it has been slid into the annular space 18, during the manufacture of the canister. With reference to FIGS. 5 to 7, an example may be perceived of an embodiment of a circumferential tightening device 44, capable of extending in this direction in order to constrain said plurality of components 30, 32. It adopts a general shape identical or similar to that of the components 30, 32 by its shape of overall isosceles trapezoidal section, but, unlike the latter preferably made all in one block, it is conceived of three separate parts. Indeed, it comprises firstly two lateral parts 50 each comprising one face intended to form one of the sides of the trapezium, these two faces being intended to contact the two components placed on either side of this device 44. In this respect, if the tightening device 44 takes the form of a first component 30, it then contacts the two second components 32 that are directly adjacent to it in the circumferential direction, and inversely. These parts 50 are symmetrical and define jointly a face intended to form the small base of the trapezium. They each also comprise one face intended to form a portion of the large base of the trapezium, this large base being completed, at its centre, by the base of a tightening component 52 of triangular section, intended to be inserted between the two lateral parts 50. This tightening component 52 is tapering, namely it has a triangular section that reduces along the longitudinal direction X, as may be seen in FIGS. 7a and 7b. If the base of this tightening component 52 is provided to complete the large base of the trapezium, its two flat lateral faces are for their part intended to place under pressure two flat supporting surfaces 54 at a distance and facing, belonging respectively to the two lateral parts 50. In addition, the inclinations of the lateral faces of the tightening component 52 and the supporting surfaces 54 are provided to obtain simultaneously two surface contacts, preferably flat contacts. The device 44 operates in the following manner. Firstly, the two lateral parts 50 are inserted into the inner space defined by the shells, between two components 30, 32. Then, it is the tightening component 52 that is slid longitudinally between the two supporting surfaces 54, until flat contacts are obtained. The continuation of the longitudinal displacement of the tightening component 52 in relation to the parts 50 leads to them being moved away from each other along the circumferential direction T, and thus to constrain in this same direction the plurality of radiological protection components 30, 32, that are then pinned mutually against their associated shell, on account of the relative radial displacement between these components. With reference to FIGS. 8 to 10b, a canister 2 according to a second preferred embodiment of the invention may be perceived. It is distinguished from the first, on the one hand, by the fact that the second components 32 are not uniquely in contact with the inner shell 22, but assembled fixedly to it, for example by gudgeons integral with the shell and nuts (not represented), or by any other means, such as welding. On the other hand, each first component 30 remains maintained only by contacts in the annular space 18, between its two second adjacent components 32 fixed to the shell 22, and the outer shell 24. Moreover, another difference lies in the fact that the second components 32 each have a trapezoidal section reducing in a given direction of the longitudinal direction X, and that, conversely, the first components 30 each have a trapezoidal section increasing in said given direction, this being most clearly visible in FIGS. 10a and 10b. To ensure the manufacture of the canister, each first component 30 is thus slid longitudinally between its two second associated fixed components 32 and between the two shells 22, 24, until flat contacts are obtained between the lateral faces of the components 30, 32 defining the sides of trapeziums, and a flat contact is obtained between the face of the component 30 defining the large base and the outer shell. Just as in the first preferred embodiment, the lateral faces of the components 30, 32, defining the sides of trapeziums, are flat. The continuation of the longitudinal displacement of the first component 30 in relation to the two components 32 leads to increasing the intensity of the contacts, and thus to reinforcing the thermal conductivity. To ensure satisfactory contact forces, on the one hand, and to obtain a jamming effect of the component 30 between the components 32 and the outer shell, on the other hand, the variation in trapezoidal section along the longitudinal direction is such that the lateral faces of the components 30 and 32 are inclined in relation to the longitudinal axis by a value between 1 and 10°. Moreover, it is noted that just the own weight of the component 30 may suffice to obtain the requisite contact forces. Finally, the third embodiment shown in FIG. 11 differs from the preceding embodiments in that the first components 30 have a transversal section of overall truncated trapezium shape at the two angles between the large base and the sides, and in that the second components 32 have a transversal section of overall triangle shape. The other characteristics are identical or similar, in particular as regards the inclination of the contact interfaces 40. Obviously, various modifications may be made by those skilled in the art to the invention that has just been described, uniquely by way of non-limiting examples. |
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abstract | Variations are characterized in feature dimensions of an integrated circuit that is to be fabricated in accordance with a design by a process that produces topographical variation in the integrated circuit, the variations in feature dimension being caused by the topographical variations. The process includes lithography or etch. Predicted characteristics are verified to conform to the design, the characteristics including feature dimensions or electrical characteristics. A process is selected for use in fabricating the integrated circuit based on the relative predicted variations. Chip-level features of a design of an integrated circuit are verified for manufacture within focus limitations of a lithographic tool. Whether a design of a level of an integrated circuit can be lithographically imaged in accordance with the design is predicted, and if it cannot be, the design or processing parameters are adjusted so that it can be. |
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summary | ||
description | 1. Field of the Invention The present invention relates to an in-core nuclear-measuring apparatus of a reactor and, more particularly, to a passage selector acting for selectively switching a passage selecting guide tube through which a detector cable goes with respect to a predetermined number of detector passages in the in-core nuclear-measuring apparatus. 2. Description of the Related Art To measure a neutron flux to be discharged from fuel in a reactor core, the nuclear-measuring facilities for nuclear power plants are generally provided with a passage selector in which a cable equipped with a neutron detector at the leading end is selectively inserted into a plurality of detector passages. Although varied in number depending on its capacity, a reactor is provided with multiple detector passages, and the neutron detector is selectively inserted into these detector passages using the above-mentioned passage selector, thereby enabling to efficiently perform a remote detection of a neutron flux with small numbers of equipments. The construction of nuclear-measuring facilities of a reactor is described in detail, for example, in the Japanese Patent Publication (unexamined) No. 195572/2005. The conventional passage selector is of a system in which by a turning force of a drive motor, a passage selecting guide tube is brought in rotation directly through an index device of various cam mechanisms. As the index mechanism of the above-mentioned cam mechanism, for example, a known roller gear cam mechanism, parallel cam mechanism, and Geneva mechanism can be employed. Furthermore, as the mechanism for positioning the passage selecting guide tube in rotation at an arbitrary detector passage, a mechanism that is referred to as a click stopper system, in which a hard sphere is pressed onto a rotary wheel by a spring force, is generally employed. FIG. 5 is a view illustrating a schematic construction of a passage selector formed in the above-mentioned click-stopper system. In the drawing, reference numeral 1 designates a housing, numeral 2 designates a central rotating shaft, and numerals 3 and 4 designate disks that are provided at both ends of the above-mentioned housing 1 and supported by a fixed rod 15. Numeral 5 designates a passage selecting guide tube that comes in the housing 1 from the center of the above-mentioned disk 3, and going through an internal part of the above-mentioned central rotating shaft 2, comes out of the central rotating shaft 2 on the way, to be connected to the disk 4. In the internal part of this guide tube, a cable (not illustrated), to the leading end of which a neutron detector (not illustrated) is attached, is inserted to go through. Numeral 6 designates a drive motor equipped with a reduction gear, which is directly connected to the shaft of an electromagnetic clutch 7 and fixed to the disk 3. Numeral 8 designates a first gear that is attached to the electromagnetic clutch 7, and meshes with a second gear 9 that is attached to the above-mentioned central rotating shaft 2. That is, these components form an index device directly performing a rotation index of the central rotating shaft 2 by gear ratio setting between the above-mentioned first gear 8 and second gear 9 with the rotation of the drive motor 6. The above-mentioned passage selecting guide tube 5 rotates by the same angle as that of the above-mentioned central rotating shaft 2, so that the above-mentioned passage selecting guide tube 5 is brought in rotation by a predetermined angle having been indexed by means of this index device to select a predetermined passage. The second gear 9 is provided with a cam 10 causing a passage selecting switch 11 to operate. When this cam 10 causes a predetermined passage selecting switch 11 to operate, the power from the drive motor 6 is to be shut off (for example, refer to the Japanese Patent Publication (unexamined) No. 202696, 1989). Furthermore, the central rotating shaft 2 is disconnected due to that the power from the electromagnetic clutch 7 is shut off. In addition, the above-mentioned shaft 2, which otherwise passes by an inertial force of a wheel 12 is made to mechanically stop owing to that a click stopper 14 is pressed onto a dish-shaped groove 13 that is provided in the wheel 12. The click stopper 14, as described above, is constructed so that a hard sphere is pressed by a spring onto the wheel 12 going to rotate, which is the reason of being referred to as a click stopper system. In the above-mentioned conventional selectors, however, the above-mentioned passage selecting guide tube 5 is rotated directly by the above-mentioned index device, and thus a predetermined passage is to be selected. Therefore, every time the number of detector passages is changed, a new index device has to be designed and manufactured, or index devices of different index numbers have to be prepared for respective selectors of different detector passage numbers. Furthermore, in the above-mentioned conventional click stopper system, when the passage selection number is increased, the diameter of the wheel 12 is necessarily enlarged to have a larger number of exit passages. When the diameter of the wheel 12 comes to be larger, since the inertial mass is increased so much, there is a larger possibility that the wheel 12 is not stopped at a predetermined selected position due to its inertial force (never more than about 15 passage selection numbers). Moreover, it is necessary to periodically adjust the pressing force of the click stopper. Additionally, in the above-mentioned conventional device, an electromagnetic clutch for not transmitting a driving force is required, and two power supplies of a power supply (normally AC 100V) for a drive motor and a power supply (normally DC 24V) for an electromagnetic clutch become necessary. In addition, when oil contents and moisture contents stick to a friction plate of the electromagnetic clutch, the friction plate gets slippery and thus the force of transmission is decreased, and the drive side may run idle not to rotate. Furthermore, it is necessary to measure a transmission torque and a braking torque every year, and when these torques come to be outside a reference value, it is necessary to replace the electromagnetic clutch. Moreover, since in the passage selector, pressure application at normal operation time and vacuuming at periodic inspection time are repeated, a further problem exists in that oil contents having been used at, e.g., ball bearings have gradually stuck to the friction plate, and thus the transmission torque is reduced with age. The present invention was made to solve the above-described problems, and has an object of obtaining a passage selector that can be applied by commonly using an index device even if the number of detector passages is changed. The invention has another object of obtaining a passage selector, which needs not to employ any electromagnetic clutch or a click stopper system that is easy to make inspection and maintenance, and small in size and inexpensive. A passage selector of a reactor in-core nuclear-measuring apparatus according to the invention includes: a drive motor; an index device that is driven by the mentioned drive motor and that makes a rotary output of a predetermined index number; a central rotating shaft that is driven to rotate by the mentioned index device and that causes a passage selecting guide tube to be located in opposition to any detector passage; and a speed-increasing and decreasing device that is interposed between an output shaft of the mentioned index device and the central rotating shaft, and that adjusts the index number of the mentioned central rotating shaft. According to this invention, due to that a speed-increasing and decreasing mechanism is interposed between the index device and the central rotating shaft, there is an advantage of obtaining a small and inexpensive passage selector that can be applied to an arbitrary number of detector passages by commonly using the existing index device without designing a new index device even if the detector passage number is changed. The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. A first embodiment of the present invention is hereinafter described. FIG. 1 illustrates a sectional side view of a passage selector of a reactor in-core nuclear-measuring apparatus according to the invention, and FIG. 2 is a bottom view of FIG. 1. FIG. 3 is a sectional view taken along the line III-III of FIG. 1, and FIG. 4 is a table explaining an adjustment method of an index number of a central rotating shaft with varying teeth number. In the drawings, the same reference numerals designate the same or like parts to those of the conventional selector shown in FIG. 5. In the drawing, there are provided upper and lower disks 3 and 4 supported by four fixed rods 15 in a housing 1. With these disks, a central rotating shaft 2 is rotatably supported by a bearing 16. Numeral 5 designates a passage selecting guide tube that comes in the housing 1 from the center of the above-mentioned disk 3 and goes through an internal part of the above-mentioned central rotating shaft 2, comes out of the central rotating shaft 2 on the way, and connected to the disk 4. In the internal part of this guide tube, a cable (not illustrated), to the leading end of which a neutron detector (not illustrated) is attached, is inserted to go through. Furthermore, numerals 17 designate plural numbers (six numbers in this embodiment) of detector passages that are bored in the lower disk 4. Although not illustrated, through these detector passages, a detector that is mounted at the leading end of the cable is inserted in and removed from the reactor core. Incidentally, the above-mentioned wheel 12 is provided for the purpose of holding the passage selecting guide tube 5 and preventing foreign substances coming in the detector passage 17 that is not selected. Numeral 20 designates a known index device, which includes an input shaft 21 that receives a rotary input from a drive motor 6 (a gear motor in this example), and an output shaft 22 that makes an output of a predetermined index rotation angle. Numeral 23 designates a first gear connected to the output shaft 22 of the above-mentioned index device 20. Numeral 24 designates a second gear connected to the central rotating shaft 2 so as to mesh with the above-mentioned first gear 23. With these gears 23 and 24, the output from the index device 20 is increased or decreased in speed to adjust the index number of the central rotating shaft 2. Now, operation of the invention is described. Every time the input shaft 21 of the index device 20 is allowed to make one revolution by the gear motor 6, the output shaft 22 of the index device 20 makes 1/Y revolution in accordance with an index number Y that is specific to the index device 20. In the same manner, the first gear 23 that is fixed to the output shaft 22 of the index device 20 also makes 1/Y revolution, and the second gear 24 that meshes with the first gear 23 is brought in rotation as well. At this time, when letting the teeth number of the first gear 23 Z1 and letting the teeth number of the second gear 24 Z2, every time the input shaft 21 of the index device 20 makes one revolution, the second gear 24, that is, the central rotating shaft 2 is to make 1/Y×Z1/Z2 revolution. As mentioned above, in the first embodiment according to the invention, due to that a speed-increasing and decreasing device that is formed of the first gear 23 and the second gear 24 is interposed between the indexing device 20 and the central rotating shaft 2, by suitably varying the teeth number of the above-mentioned first gear 23 and second gear 24, the index number of the central rotating shaft 2 can be changed comparatively easily. FIG. 4 is a table for explaining the adjustment method of the index number of the central rotating shaft 2 with varying teeth number. The table is a case of applying the selector to a rotary index device, and shows changes in a stop number (index number) of the central rotating shaft 2 in the case where the teeth number Z1 of the above-mentioned first gear 23 and the teeth number Z2 of the second gear 24 are suitably varied. First, letting the stop number Y (index number) of the rotary index device 20, in the case (1) where Z1 is 90 and Z2 is 75, the stop number (index number) of the central rotating shaft 2 is 5. In the case (2) where Z1 is 85 and Z2 is 85, the stop number (index number) of the central rotating shaft 2 is 6. In the case (3) where Z1 is 60 and Z2 is 100, the stop number (index number) of the central rotating shaft 2 is 10. In the case (4) where Z1 is 60 and Z2 is 150, the stop number (index number) of the central rotating shaft 2 is 15. In the case (5) where Z1 is 60 and Z2 is 200, the stop number (index number) of the central rotating shaft 2 is 20. In the case (6) where Z1 is 50 and Z2 is 200, the stop number (index number) of the central rotating shaft 2 is 24. Therefore, as is obvious from the above-mentioned descriptions, the stop number (index number) of the central rotating shaft 2 is Y×Z2/Z1, and thus it is understood that the index number of the central rotating shaft 2 can be changed comparatively easily. A variety of combinations of the teeth number of the above-mentioned first gear 23 and the teeth number of the above-mentioned second gear 24 can be achieved by suitably replacing the above-mentioned first gear 23 and second gear 24 in accordance with the increase or decrease of detector passage numbers with the use of a screw 19. Thus, according to the invention, owing to that the index device can be commonly used regardless of the number of detector passages, a passage selector that is inexpensive and highly versatile can be embodied. Incidentally, although in the above-mentioned first embodiment, an example in which the speed-increasing and decreasing device is formed of a gear train is described, it is not limited to this example. Such a speed-increasing and decreasing device can be formed of the combination of a toothed belt and a pulley or the combination of a chain and a sprocket. Additionally, the teeth number of the pulley in the case of the toothed belt and the pulley, or the teeth number of the sprocket in the case of the chain and the sprocket can be changed in combination as in the case of the gear train, thereby enabling to obtain the speed-increasing and decreasing device. In addition, although the drive source is described taking a gear motor as an example, it is not limited thereto, and the same advantage can be achieved with a servo motor or a stepping motor. Furthermore, although the index device is described taking a rotary index device as an example, it is not limited thereto. A parallel cam system or a Geneva mechanism can be selected without restraint within the scope of the invention as a matter of course. |
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abstract | Elongation measurement apparatuses and systems comprise at least two Linear Variable Differential Transformers (LVDTs) with a push rod coupled to each of the at least two LVDTs at one longitudinal end thereof. At least one push rod extends to a base and is coupled thereto at an opposing longitudinal end, and at least one other push rod extends to a location spaced apart from the base and is configured to receive a sample between an opposing longitudinal end of the at least one other push rod and the base. Nuclear reactors comprising such apparatuses and systems and methods of measuring elongation of a material are also disclosed. |
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abstract | Methods of producing cesium-131. The method comprises dissolving at least one non-irradiated barium source in water or a nitric acid solution to produce a barium target solution. The barium target solution is irradiated with neutron radiation to produce cesium-131, which is removed from the barium target solution. The cesium-131 is complexed with a calixarene compound to separate the cesium-131 from the barium target solution. A liquid:liquid extraction device or extraction column is used to separate the cesium-131 from the barium target solution. |
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description | This patent application is a continuation application filing of U.S. patent application Ser. No. 15/363,284, filed Nov. 29, 2016, which application is a continuation application filing of U.S. patent application Ser. No. 15/244,708, filed Aug. 23, 2016 and now granted U.S. Pat. No. 9,541,667, which granted patent is further a divisional filing of U.S. patent application Ser. No. 14/475,986, filed Sep. 3, 2014, which application further claims priority to and the benefit of U.S. provisional application Ser. No. 61/873,541, filed Sep. 4, 2013, the contents of all of which as are hereby incorporated herein by reference in their entirety. X-ray scanning devices have historically been used in both the medical and security industries. In security applications, X-ray scanning devices have been used to display the contents of travel bags, shipped items, and/or the like without requiring personnel to undertake the cumbersome task of unpacking and/or disassembling the item in question and subsequently re-packing and/or reassembling the item for further processing. X-ray based security systems have historically been used by airport security entities (e.g., the United States Transportation Security Administration) and common carriers (e.g., United Parcel Service of America, Federal Express, and/or the like) to detect different types of contraband that may be present in items such as baggage, shipping packages, shipping containers, and the like. In operation, X-ray radiation is transmitted through and/or scattered from items within the baggage, packages, containers, and the like. Various systems incorporate a mesh or grid that is placed upon a conveyor belt along which the baggage, packages, containers, and the like travel during the scanning process. For particularly densely packed baggage, packages, containers, and the like, it is important that X-ray radiation emitted by an X-ray scanning device penetrate the entirety of the scanned item so as to provide a desired degree of certainty that no contraband exists there-within. Conventional mesh or grid structures have proven helpful in this regard by placing such adjacent the baggage, package, container, and the like, opposite a directional orientation of the X-ray scanning device contained within the system. In this manner, such mesh or grid structures provide a baseline indicator of penetration, for example such that if the mesh or grid is visible within a scan, the item has been sufficiently penetrated with the scan for clearance or otherwise. Although X-ray scanning devices may facilitate the security screening process for items during processing, the physical properties of X-ray radiation and X-ray detectors may, in various circumstances, obscure objects or components visible in an item scan. In general, X-ray radiation may comprise electromagnetic waves having a wavelength between 0.01 and 10 nanometers. Such electromagnetic waves propagate from an X-ray emitter through the item to be scanned, and are collected by a detector positioned opposite the item to be scanned from the X-ray emitter, the detector comprising one or more detector elements configured to measure the intensity of the transmitted radiation (i.e., the electromagnetic wave) along a radiation ray projected from the X-ray emitter to a detector element. In various embodiments, the one or more detector elements may comprise solid-state detectors generally utilized for digital imaging. The solid-state detectors may comprise a luminescent conversion layer, for example, a scintillator (e.g., a cesium iodide scintillator) in which the radiation received by the solid-state detector causes the scintillator to generate light pulses, which may subsequently be converted into digital signals that may be transmitted to a user device and displayed via a display device. In various circumstances, such conversion layers may maintain or trap radiation, and therefore cause “ghost” images to be created in subsequent intensity signals. Such trapping effects may be caused by, for example, incomplete charge dissipation or low induced energy levels that do not decay prior to receiving additional radiation for a subsequent scan. These residual signals from a previous image remain in the detector and are superimposed on a later generated image. Such effects may become more obvious as the time between successive images is decreased, and the time for previously trapped charge accumulation to decay is likewise decreased. Moreover, stronger electromagnetic signals received by the detector elements may require additional time for the residual electromagnetic signal to decay between images. As an item to be scanned moves to a scanning location within an X-ray scanning device, the X-ray scanning device may cause ghosted streaks to appear in a generated image. These ghosted streaks may appear as solid lines resembling radiopaque objects present within the scanned item. Where a radiopaque bar or other thin radiopaque object is oriented at least substantially parallel to the direction of travel of the item, ghosted streaks may appear to extend the length of the radiopaque object. Such ghosted streaks may cause an operator viewing the generated image to believe that the X-ray beam penetrated completely through a radiopaque object. Therefore, the operator may erroneously determine that the scanned item is clear of any prohibited items even though a complete scan was not performed on the item. When associating a mesh or grid structure with items to be scanned, the ghosting phenomenon described above may inadvertently cause at least a portion of the mesh or grid structure to appear visible in the created image, although the electromagnetic waves did not penetrate completely through the item. For example, ghosted streaks may appear to extend at least a portion of the grid elements in the created image and the resulting image may therefore show these ghosted streaks superimposed over items even where the electromagnetic waves did not penetrate completely through the item. Thus, the mesh or grid structure may be “ghosted” (i.e., appear) in a resulting scan image, even where the item being scanned has not, in reality, been fully (or sufficiently) penetrated to actually detect all portions of the conventional mesh or grid. Consequently, personnel viewing the created image may be led to believe that a complete scan through the entirety of an item was achieved. This “ghosting” phenomena is referred to herein as “ghosting,” “ghosting lines,” “ghost lines,” “ghost images,” “ghosted images,” “ghost radiation,” “ghost signals,” and/or “ghosted lines,” all of which as should be understood to generally and interchangeably describe this phenomena. Historically, efforts to reduce the impact of ghosting have focused on creating improved detector elements, or incorporating complex algorithms utilized to minimize the impact of ghosting. However, such solutions are prone to errors due at least in part to electromagnetic noise and other imperfections in the received signal. For example, even where grids are used, if such are oriented in a manner that results in the grid lines thereof being parallel to the direction of travel, ghosted lines may appear, although such may contain certain distortions therein. While users could conceivably identify such distortions, the risk of a user overlooking a particular distortion remains prevalent. Thus, a need exists for improved mesh or grid structures that substantially minimize the impact of “ghosting” so as to ensure sufficient penetration of all scanned items without resorting to secondary item handling and the like. Various embodiments of the present invention are directed to X-ray detector systems for determining the contents of an item. The X-ray detector systems may comprise: (1) an X-ray emitter configured for emitting X-ray radiation; (2) a detector comprising a receiving surface, the detector configured to receive the X-ray radiation and to generate one or more intensity signals indicative of an intensity of the received X-ray radiation at each of a plurality of locations on the receiving surface; (3) an X-ray penetration grid comprising a first grid structure comprising: a perimeter surrounding the X-ray penetration grid having at least a first side, said first side being oriented in a first primary direction; a first plurality of parallel grid members each having a first end and a second end; and a second plurality of parallel grid members each having a first end and a second end; wherein: the first plurality of parallel grid members are coincident with a first plane; the second plurality of parallel grid members are coincident with a second plane; the first plane and the second plane are parallel; the first end and the second end of each of the first plurality of parallel grid members intersects the perimeter at an angle such that the first plurality of parallel grid members are neither parallel nor perpendicular to the first side of the perimeter; and the first end and the second end of each of the second plurality of parallel grid members intersects the perimeter at an angle such that the second plurality of parallel grid members are neither parallel nor perpendicular to the first side of the perimeter; and (4) a conveying mechanism configured for conveying the item and the X-ray penetration grid in a second primary direction to a location between the X-ray emitter and the detector, said second primary direction being substantially the same as the first primary of direction. Other embodiments of the present invention are direct to computer implemented methods for scanning an item. The computer implemented method comprising steps for: (1) receiving, via a processor, one or more first intensity signals indicative of a first intensity of X-ray radiation received at each of a plurality of locations at a first scan time on a detector, wherein: the detector is configured to receive X-ray radiation from an X-ray emitter and to generate the one or more intensity signals indicative of an intensity of the received X-ray radiation at each of a plurality of locations on the receiving surface; the X-ray radiation is emitted from the X-ray emitter and at least a portion of the X-ray radiation passes through the item and an X-ray penetration grid before being received by the detector, wherein: the X-ray penetration grid comprises a first grid structure comprising: a perimeter surrounding the X-ray penetration grid having at least a first side, said first side being oriented in a first primary direction; a first plurality of parallel grid members each having a first end and a second end; and a second plurality of parallel grid members each having a first end and a second end; wherein: the first plurality of parallel grid members are coincident with a first plane; the second plurality of parallel grid members are coincident with a second plane; the first plane and the second plane are at least substantially parallel; the first end and the second end of each of the first plurality of parallel grid members intersects the perimeter at an angle such that the first plurality of parallel grid members are neither parallel nor perpendicular to the first side of the perimeter; and the first end and the second end of each of the second plurality of parallel grid members intersects the perimeter at an angle such that the second plurality of parallel grid members are neither parallel nor perpendicular to the first side of the perimeter; and the item and the X-ray penetration grid are propelled in a second primary direction, said second primary direction being substantially the same as the first primary direction; (2) causing, via a display device, display of the one or more first intensity signals; (3) receiving, via the processor, one or more second intensity signals indicative of one or more ghosted image extending from an edge of the item; (4) causing, via the display device, display of the one or more second intensity signals, wherein the displayed second intensity signals comprises a radiation ghost based at least in part on the one or more ghosted image; and (5) identifying, via the one or more processors, the presence of a radiation ghost based at least in part on the second intensity signals. Alternative embodiments of the present invention are directed to X-ray penetration grids comprising a first grid structure comprising: (1) a perimeter surrounding the grid structure having at least a first side; (2) a first plurality of parallel grid members each having a first end and a second end; and (3) a second plurality of parallel grid members each having a first end and a second end; wherein: the first plurality of parallel grid members are coincident with a first plane; the second plurality of parallel grid members are coincident with a second plane; the first plane and the second plane are parallel; the first end and the second end of each of the first plurality of parallel grid members intersects the perimeter at an angle such that the first plurality of parallel grid members are neither parallel nor perpendicular to the first side of the perimeter; and the first end and the second end of each of the second plurality of parallel grid members intersects the perimeter at an angle such that the second plurality of parallel grid members are neither parallel nor perpendicular to the first side of the perimeter. In various embodiments, the X-ray penetration grid may additionally comprise a second grid structure comprising: (1) a second perimeter surrounding the second grid structure having at least a first side; (2) a third plurality of parallel grid members each having a first end and a second end; and (3) a fourth plurality of parallel grid members each having a first end and a second end; wherein the third plurality of parallel grid members are coincident with a third plane; the fourth plurality of parallel grid members are coincident with a fourth plane; the third plane and the fourth plane are parallel; the first end and the second end of each of the third plurality of parallel grid members intersects the second perimeter at an angle such that the third plurality of parallel grid members are neither parallel nor perpendicular to the first side of the second perimeter; the first end and the second end of each of the fourth plurality of parallel grid members intersects the perimeter at an angle such that the fourth plurality of parallel grid members are neither parallel nor perpendicular to the first side of the second perimeter; and the third plane and the fourth plane are perpendicular to the first plane and the second plane. The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. Overview Various embodiments are directed to a system for identifying radiopaque objects present in an item scanned using an X-ray scanning device. The system may comprise an X-ray scanning device comprising an X-ray emitter and a detector, a conveying mechanism, and an X-ray penetration grid. The X-ray penetration grid may comprise a radiopaque grid oriented such that the radiopaque grid elements are neither parallel nor perpendicular to the direction of travel of the conveying mechanism. In use, the item to be scanned is oriented relative to the X-ray penetration grid such that, when the item and X-ray penetration grid are located between the X-ray emitter and the detector, X-ray waves produced by the X-ray emitter that pass through the item to be scanned must also pass through the X-ray penetration grid before reaching the detector. Because the radiopaque grid elements are evenly spaced apart and neither parallel nor perpendicular to the direction of travel of the conveying mechanism, no ghosted grid elements are visible in the generated image, such that radiopaque objects contained in a scanned item are easily and/or accurately identified in the generated image. Moreover, various embodiments are directed to methods for identifying radiopaque objects present in an item scanned using an X-ray scanning device. An item is placed on a conveying mechanism with an X-ray penetration grid, and is propelled into an X-ray scanner device. As the item and X-ray penetration grid is scanned, a detector receives radiation emitted from an X-ray emitter that corresponds to the relative intensity of the radiation penetrating the item and X-ray penetration grid and generates intensity signals indicative of the relative intensity of the radiation received at various locations on the detector. The detector then converts the signals indicative of the relative intensity of the received radiation into visible signals, which may be transmitted via a network to one or more computing devices. In certain embodiments the X-Ray scanning device may be configured to scan multiple slices of each scanned item corresponding to different locations along the length of the scanned item (the length of the scanned item being parallel to the direction of travel). The one or more computing devices subsequently display the visible signals to a user monitoring the X-ray scanning device by piecing together the individual slices of the item. At least in part because the radiopaque grid elements are spaced evenly and are neither parallel nor perpendicular to the direction of travel of the conveying mechanism, the ghost lines are substantially, and in certain embodiments entirely, eliminated such that virtually no ghost lines are visible in the displayed visual image. Exemplary Apparatuses, Methods, Systems, Computer Program Products, & Computing Entities Embodiments of the present invention may be implemented in various ways, including as computer program products. A computer program product may include a non-transitory computer-readable storage medium storing applications, programs, program modules, scripts, source code, program code, object code, byte code, compiled code, interpreted code, machine code, executable instructions, and/or the like (also referred to herein as executable instructions, instructions for execution, program code, and/or similar terms used herein interchangeably). Such non-transitory computer-readable storage media include all computer-readable media (including volatile and non-volatile media). In one embodiment, a non-volatile computer-readable storage medium may include a floppy disk, flexible disk, hard disk, solid-state storage (SSS) (e.g., a solid state drive (SSD), solid state card (SSC), solid state module (SSM)), enterprise flash drive, magnetic tape, or any other non-transitory magnetic medium, and/or the like. A non-volatile computer-readable storage medium may also include a punch card, paper tape, optical mark sheet (or any other physical medium with patterns of holes or other optically recognizable indicia), compact disc read only memory (CD-ROM), compact disc compact disc-rewritable (CD-RW), digital versatile disc (DVD), Blu-ray disc (BD), any other non-transitory optical medium, and/or the like. Such a non-volatile computer-readable storage medium may also include read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory (e.g., Serial, NAND, NOR, and/or the like), multimedia memory cards (MMC), secure digital (SD) memory cards, SmartMedia cards, CompactFlash (CF) cards, Memory Sticks, and/or the like. Further, a non-volatile computer-readable storage medium may also include conductive-bridging random access memory (CBRAM), phase-change random access memory (PRAM), ferroelectric random-access memory (FeRAM), non-volatile random-access memory (NVRAM), magnetoresistive random-access memory (MRAM), resistive random-access memory (RRAM), Silicon-Oxide-Nitride-Oxide-Silicon memory (SONOS), floating junction gate random access memory (FJG RAM), Millipede memory, racetrack memory, and/or the like. In one embodiment, a volatile computer-readable storage medium may include random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), fast page mode dynamic random access memory (FPM DRAM), extended data-out dynamic random access memory (EDO DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), double data rate type two synchronous dynamic random access memory (DDR2 SDRAM), double data rate type three synchronous dynamic random access memory (DDR3 SDRAM), Rambus dynamic random access memory (RDRAM), Twin Transistor RAM (TTRAM), Thyristor RAM (T-RAM), Zero-capacitor (Z-RAM), Rambus in-line memory module (RIMM), dual in-line memory module (DIMM), single in-line memory module (SIMM), video random access memory VRAM, cache memory (including various levels), flash memory, register memory, and/or the like. It will be appreciated that where embodiments are described to use a computer-readable storage medium, other types of computer-readable storage media may be substituted for or used in addition to the computer-readable storage media described above. As should be appreciated, various embodiments of the present invention may also be implemented as methods, apparatus, systems, computing devices, computing entities, and/or the like. As such, embodiments of the present invention may take the form of an apparatus, system, computing device, computing entity, and/or the like executing instructions stored on a computer-readable storage medium to perform certain steps or operations. However, embodiments of the present invention may also take the form of an entirely hardware embodiment performing certain steps or operations. Various embodiments are described below with reference to block diagrams and flowchart illustrations of apparatuses, methods, systems, and computer program products. It should be understood that each block of any of the block diagrams and flowchart illustrations, respectively, may be implemented in part by computer program instructions, e.g., as logical steps or operations executing on a processor in a computing system. These computer program instructions may be loaded onto a computer, such as a special purpose computer or other programmable data processing apparatus to produce a specifically-configured machine, such that the instructions which execute on the computer or other programmable data processing apparatus implement the functions specified in the flowchart block or blocks. These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including computer-readable instructions for implementing the functionality specified in the flowchart block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions that execute on the computer or other programmable apparatus provide operations for implementing the functions specified in the flowchart block or blocks. Accordingly, blocks of the block diagrams and flowchart illustrations support various combinations for performing the specified functions, combinations of operations for performing the specified functions and program instructions for performing the specified functions. It should also be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, could be implemented by special purpose hardware-based computer systems that perform the specified functions or operations, or combinations of special purpose hardware and computer instructions. Exemplary Architecture of System 20 FIG. 1 is a block diagram of an X-ray penetration system 20 that can be used in conjunction with various embodiments of the present invention. In at least the illustrated embodiment, the system 20 may include one or more central computing devices 110, one or more distributed computing devices 120, one or more distributed handheld or mobile devices 300, and at least one conveying mechanism 140 and X-ray penetration grid 150, all configured in communication with a central server 200 via one or more networks 130. While FIG. 1 illustrates the various system entities as separate, standalone entities, the various embodiments are not limited to this particular architecture. According to various embodiments of the present invention, the one or more networks 130 may be capable of supporting communication in accordance with any of a number of second-generation (2G), 2.5G, third-generation (3G), and/or fourth-generation (4G) mobile communication protocols, or the like. More particularly, the one or more networks 130 may be capable of supporting communication in accordance with 2G wireless communication protocols IS-136 (TDMA), GSM, and IS-95 (CDMA). Also, for example, the one or more networks 130 may be capable of supporting communication in accordance with 2.5G wireless communication protocols GPRS, Enhanced Data GSM Environment (EDGE), or the like. In addition, for example, the one or more networks 130 may be capable of supporting communication in accordance with 3G wireless communication protocols such as Universal Mobile Telephone System (UMTS) network employing Wideband Code Division Multiple Access (WCDMA) radio access technology. Some narrow-band AMPS (NAMPS), as well as TACS, network(s) may also benefit from embodiments of the present invention, as should dual or higher mode mobile stations (e.g., digital/analog or TDMA/CDMA/analog phones). As yet another example, each of the components of the system 5 may be configured to communicate with one another in accordance with techniques such as, for example, radio frequency (RF), Bluetooth™ infrared (IrDA), or any of a number of different wired or wireless networking techniques, including a wired or wireless Personal Area Network (“PAN”), Local Area Network (“LAN”), Metropolitan Area Network (“MAN”), Wide Area Network (“WAN”), or the like. Although the device(s) 110-300 are illustrated in FIG. 1 as communicating with one another over the same network 130, these devices may likewise communicate over multiple, separate networks. According to one embodiment, in addition to receiving data from the server 200, the distributed devices 110, 120, 140, and/or 300 may be further configured to collect and transmit data on their own. In various embodiments, the devices 110, 120, 140, and/or 300 may be capable of receiving data via one or more input units or devices, such as a keypad, touchpad, barcode scanner, radio frequency identification (RFID) reader, interface card (e.g., modem, etc.) or receiver. The devices 110, 120, 140, and/or 300 may further be capable of storing data to one or more volatile or non-volatile memory modules, and outputting the data via one or more output units or devices, for example, by displaying data to the user operating the device, or by transmitting data, for example over the one or more networks 130. Exemplary Server 200 In various embodiments, the server 200 includes various systems for performing one or more functions in accordance with various embodiments of the present invention, including those more particularly shown and described herein. It should be understood, however, that the server 200 might include a variety of alternative devices for performing one or more like functions, without departing from the spirit and scope of the present invention. For example, at least a portion of the server 200, in certain embodiments, may be located on the distributed device(s) 110, 120, 140 and/or the handheld or mobile device(s) 300, as may be desirable for particular applications. As will be described in further detail below, in at least one embodiment, the handheld or mobile device(s) 300 may contain one or more mobile applications 330 which may be configured so as to provide a user interface for communication with the server 200, all as will be likewise described in further detail below. FIG. 2A is a schematic diagram of the server 200 according to various embodiments. The server 200 includes a processor 230 that communicates with other elements within the server via a system interface or bus 235. Also included in the server 200 is a display/input device 250 for receiving and displaying data. This display/input device 250 may be, for example, a keyboard or pointing device that is used in combination with a monitor. The server 200 further includes memory 220, which preferably includes both read only memory (ROM) 226 and random access memory (RAM) 222. The server's ROM 226 is used to store a basic input/output system 224 (BIOS), containing the basic routines that help to transfer information between elements within the server 200. Various ROM and RAM configurations have been previously described herein. In addition, the server 200 includes at least one storage device or program storage 210, such as a hard disk drive, a floppy disk drive, a CD Rom drive, or optical disk drive, for storing information on various computer-readable media, such as a hard disk, a removable magnetic disk, or a CD-ROM disk. As will be appreciated by one of ordinary skill in the art, each of these storage devices 210 are connected to the system bus 235 by an appropriate interface. The storage devices 210 and their associated computer-readable media provide nonvolatile storage for a personal computer. As will be appreciated by one of ordinary skill in the art, the computer-readable media described above could be replaced by any other type of computer-readable media known in the art. Such media include, for example, magnetic cassettes, flash memory cards, digital video disks, and Bernoulli cartridges. Although not shown, according to an embodiment, the storage device 210 and/or memory of the server 200 may further provide the functions of a data storage device, which may store historical and/or current delivery data and delivery conditions that may be accessed by the server 200. In this regard, the storage device 210 may comprise one or more databases. The term “database” refers to a structured collection of records or data that is stored in a computer system, such as via a relational database, hierarchical database, or network database and as such, should not be construed in a limiting fashion. A number of program modules 400, 425, 450 comprising, for example, one or more computer-readable program code portions executable by the processor 230, may be stored by the various storage devices 210 and within RAM 222. Such program modules may also include an operating system 280. In these and other embodiments, the various modules 400, 425, 450 control certain aspects of the operation of the server 200 with the assistance of the processor 230 and operating system 280. For example, a Visual Module 400 may be configured to covert signals received from the X-ray scanning device 140 into visible signals to be displayed via the display/input device 250; an Analysis Module 425 may be configured to identify a visual ghosting phenomenon; and a Notification Module 450 may be configured to notify relevant personnel of the presence of a ghosting phenomenon in a presented visual display. In still other embodiments, it should be understood that one or more additional and/or alternative modules may also be provided, without departing from the scope and nature of the present invention. In various embodiments, the program modules 400, 425, 450 are executed by the server 200 and are configured to generate one or more graphical user interfaces, reports, instructions, and/or notifications/alerts, all accessible and/or transmittable to various users of the system 20. In certain embodiments, the user interfaces, reports, instructions, and/or notifications/alerts may be accessible via one or more networks 130, which may include the Internet or other feasible communications network, as previously discussed. In various embodiments, it should also be understood that one or more of the modules 400, 425, 450 may be alternatively and/or additionally (e.g., in duplicate) stored locally on one or more of the devices 110, 120, 140, and/or 300 and may be executed by one or more processors of the same. According to various embodiments, the modules 400, 425, 450 may send data to, receive data from, and utilize data contained in one or more databases, which may be comprised of one or more separate, linked and/or networked databases. Also located within the server 200 is a network interface 260 for interfacing and communicating with other elements of the one or more networks 130. It will be appreciated by one of ordinary skill in the art that one or more of the server 200 components may be located geographically remotely from other server components. Furthermore, one or more of the server 200 components may be combined, and/or additional components performing functions described herein may also be included in the server. While the foregoing describes a single processor 230, as one of ordinary skill in the art will recognize, the server 200 may comprise multiple processors operating in conjunction with one another to perform the functionality described herein. In addition to the memory 220, the processor 230 can also be connected to at least one interface or other means for displaying, transmitting and/or receiving data, content or the like. In this regard, the interface(s) can include at least one communication interface or other means for transmitting and/or receiving data, content or the like, as well as at least one user interface that can include a display and/or a user input interface, as will be described in further detail below. The user input interface, in turn, can comprise any of a number of devices allowing the entity to receive data from a user, such as a keypad, a touch display, a joystick or other input device. Still further, while reference is made to the “server” 200, as one of ordinary skill in the art will recognize, embodiments of the present invention are not limited to traditionally defined server architectures. Still further, the system of embodiments of the present invention is not limited to a single server, or similar network entity or mainframe computer system. Other similar architectures including one or more network entities operating in conjunction with one another to provide the functionality described herein may likewise be used without departing from the spirit and scope of embodiments of the present invention. For example, a mesh network of two or more personal computers (PCs), similar electronic devices, or handheld portable devices, collaborating with one another to provide the functionality described herein in association with the server 200 may likewise be used without departing from the spirit and scope of embodiments of the present invention. According to various embodiments, many individual steps of a process may or may not be carried out utilizing the computer systems and/or servers described herein, and the degree of computer implementation may vary, as may be desirable and/or beneficial for one or more particular applications. Distributed Handheld (or Mobile) Device(s) 300 FIG. 2B provides an illustrative schematic representative of a mobile device 300 that can be used in conjunction with various embodiments of the present invention. Mobile devices 300 can be operated by various parties. As shown in FIG. 2B, a mobile device 300 may include an antenna 312, a transmitter 304 (e.g., radio), a receiver 306 (e.g., radio), and a processing element 308 that provides signals to and receives signals from the transmitter 304 and receiver 306, respectively. The signals provided to and received from the transmitter 304 and the receiver 306, respectively, may include signaling data in accordance with an air interface standard of applicable wireless systems to communicate with various entities, such as the server 200, the distributed devices 110, 120, 140 and/or the like. In this regard, the mobile device 300 may be capable of operating with one or more air interface standards, communication protocols, modulation types, and access types. More particularly, the mobile device 300 may operate in accordance with any of a number of wireless communication standards and protocols. In a particular embodiment, the mobile device 300 may operate in accordance with multiple wireless communication standards and protocols, such as GPRS, UMTS, CDMA2000, 1×RTT, WCDMA, TD-SCDMA, LTE, E-UTRAN, EVDO, HSPA, HSDPA, Wi-Fi, WiMAX, UWB, IR protocols, Bluetooth protocols, USB protocols, and/or any other wireless protocol. Via these communication standards and protocols, the mobile device 300 may according to various embodiments communicate with various other entities using concepts such as Unstructured Supplementary Service data (USSD), Short Message Service (SMS), Multimedia Messaging Service (MMS), Dual-Tone Multi-Frequency Signaling (DTMF), and/or Subscriber Identity Module Dialer (SIM dialer). The mobile device 300 can also download changes, add-ons, and updates, for instance, to its firmware, software (e.g., including executable instructions, applications, program modules), and operating system. According to one embodiment, the mobile device 300 may include a location determining device and/or functionality. For example, the mobile device 300 may include a GPS module adapted to acquire, for example, latitude, longitude, altitude, geocode, course, and/or speed data. In one embodiment, the GPS module acquires data, sometimes known as ephemeris data, by identifying the number of satellites in view and the relative positions of those satellites. The mobile device 300 may also comprise a user interface (that can include a display 316 coupled to a processing element 308) and/or a user input interface (coupled to a processing element 308). The user input interface can comprise any of a number of devices allowing the mobile device 300 to receive data, such as a keypad 318 (hard or soft), a touch display, voice or motion interfaces, or other input device. In embodiments including a keypad 318, the keypad can include (or cause display of) the conventional numeric (0-9) and related keys (#, *), and other keys used for operating the mobile device 300 and may include a full set of alphabetic keys or set of keys that may be activated to provide a full set of alphanumeric keys. In addition to providing input, the user input interface can be used, for example, to activate or deactivate certain functions, such as screen savers and/or sleep modes. The mobile device 300 can also include volatile storage or memory 322 and/or non-volatile storage or memory 324, which can be embedded and/or may be removable. For example, the non-volatile memory may be ROM, PROM, EPROM, EEPROM, flash memory, MMCs, SD memory cards, Memory Sticks, CBRAM, PRAM, FeRAM, RRAM, SONOS, racetrack memory, and/or the like. The volatile memory may be RAM, DRAM, SRAM, FPM DRAM, EDO DRAM, SDRAM, DDR SDRAM, DDR2 SDRAM, DDR3 SDRAM, RDRAM, RIMM, DIMM, SIMM, VRAM, cache memory, register memory, and/or the like. The volatile and non-volatile storage or memory can store databases, database instances, database mapping systems, data, applications, programs, program modules, scripts, source code, object code, byte code, compiled code, interpreted code, machine code, executable instructions, and/or the like to implement the functions of the mobile device 300. The mobile device 300 may also include one or more of a camera 326 and a mobile application 330. The camera 326 may be configured according to various embodiments as an additional and/or alternative data collection feature, whereby one or more items may be read, stored, and/or transmitted by the mobile device 300 via the camera. The mobile application 330 may further provide a feature via which various tasks may be performed with the mobile device 300. Various configurations may be provided, as may be desirable for one or more users of the mobile device 300 and the system 20 as a whole. X-ray Penetration Grid (XPG) FIGS. 3A-3C illustrate an exemplary XPG 150 according to various embodiments. As shown therein, an XPG 150 may comprise a frame 151, a first plurality of grid members 152, and a second plurality of grid members 152. In various embodiments, one or more handles 154 may be coupled to the frame 151 to facilitate transportation of the XPG 150. In various embodiments, an XPG 150 may comprise 4 or more handles 154. Such handles 154 may be located at least substantially near the center point of each side of the XPG 150. Alternatively, such handles may be located at least substantially near each corner of the XPG 150. Any of a variety of configurations and handle locations as maybe desirable are possible. FIG. 3A illustrates a top view of an XPG 150 according to various embodiments. As shown therein, the frame 151 may be at least substantially rectangular, and may be at least substantially square in shape, although substantially any shape may be utilized. As a non-limiting example, the sides of the XPG 150 need not be parallel or perpendicular, and may have a parallelogram shape. In various embodiments, the XPG 150 may be sized such that the XPG fits onto a conveying mechanism 141, onto a pallet, onto a trailer, or onto other vehicles that may travel through an X-ray scanning device 140 with an item 10 to be scanned. As non-limiting examples, the sides of the XPG 150 may be at least substantially 800 mm in length, or at least substantially 516 mm in length. In various embodiments, the first plurality of grid members 152 and second plurality of grid members 153 may each comprise a plurality of at least substantially parallel grid members spaced at substantially equivalent intervals (e.g., 1 inch). Alternatively, the first plurality of grid members 152 may comprise a plurality of at least substantially parallel grid members spaced at varying intervals. Likewise, the second plurality of grid members 153 may comprise a plurality of at least substantially parallel grid members spaced at varying intervals. Moreover, the first plurality of grid members 152 may be spaced at intervals different from the spacing intervals of the second plurality of grid members 153, such that the resulting spaces between the grid members have varying side lengths. As a non-limiting example, the spaces between the grid members 152, 153 may be rectangular in shape and have multiple side lengths. The first plurality of grid members 152 may reside within a fist plane that is parallel to, and spaced apart from, a second plane in which the second plurality of grid members 153 resides. Alternatively, the first plane and second plane may be coincident, such that the first plurality of grid members 152 and second plurality of grid members 153 reside in a single plane. In various embodiments, the grid members 152, 153 may be elongated rods having a circular cross-section (as described herein), although any of a variety of cross-sectional shapes may be utilized (e.g., square, rectangular, triangular, circular, and/or the like). The first plurality of grid members 152 and second plurality of grid members 153 may be coupled to the frame 151 of the XPG 150 using one or more fasteners. As a non-limiting example, such fasteners may comprise a weld, an ultrasonic weld, an adhesive, a screw, a bolt, and/or the like. Similarly, one or more of the first plurality of grid members 152 may be coupled to one or more of the second plurality of grid members 153 using one or more fasteners such as those described above. In various embodiments, one or more of the first plurality of grid members 152 may be coupled (e.g., welded) to one or more of the second plurality of grid members 153 at one or more cross points defined as each location within the XPG 150 where one of the first plurality of grid members 152 is in contact with one of the second plurality of grid members 153. As a non-limiting example, the first plurality of grid members 152 is coupled (e.g., welded) to the second plurality of grid members 153 at each cross point. As illustrated in FIG. 3A, the first plurality of grid members 152 crosses the second plurality of grid members 153 at an angle γ. In various embodiments, the angle y is between 75 degrees and 105 degrees, although preferably at least substantially 90 degrees. In various embodiments, the first plurality of grid members 152 and second plurality of grid members 153 may have at least substantially equivalent spacing, such that the resulting gaps within the grid or mesh structure are at least substantially square (e.g., 1 inch squares). Moreover, the first plurality of grid members 152 and second plurality of grid members 153 intersect the frame 151 at angles α and β, respectively. In various embodiments, angles α and β are between 30 degrees and 55 degrees, although preferably at least substantially 45 degrees. In various embodiments where angle γ is 90 degrees, angles α and β may be equivalent. As illustrated in FIG. 3A, the XPG 150 may have a length l and a width w. In various embodiments the length l and width w may be at least substantially equivalent, such that the XPG 150 is square in shape. As non-limiting examples, the length l and width w may be 800 mm or 516 mm. However, the length l and width w need not be equivalent. FIG. 3B illustrates a side view of an XPG 150 according to various embodiments. As illustrated in FIG. 3B, the frame 151 may have a thickness tframe sized such that tframe is at least as large as the combined diameter, width, thickness, height, or other words used herein, of the first plurality of grid members 152 and second plurality of grid members 153. In various embodiments, the first plurality of grid members 152 and second plurality of grid members 153 may be in separate parallel planes, such that the first plurality of grid members 152 may be substantially adjacent the second plurality of grid members 153 such that the first plurality of grid members is above the second plurality of grid members when the XPG 150 is placed horizontally. Alternatively, the first plurality of grid members 152 and second plurality of grid members 153 may be in coincident planes, such that segments of each of the second plurality of grid members resides between each of the first plurality of grid members, or vice versa. As a non-limiting example, the second plurality of grid members 153 may be discontinuous elements, such that segments of each of the second plurality of grid members resides between continuous grid members of the first plurality of grid members 152. Where the first plurality of grid members 152 and second plurality of grid members 153 reside in different planes, each of the plurality of grid members 152, 153 may be continuous elements. FIG. 3C illustrates an exemplary cross sectional view of a grid member such as that in the first plurality of grid members 152 and second plurality of grid members 153. As shown therein, the grid members 152, 153 may have an at least substantially circular cross section, although any of a variety of cross-sectional shapes may be utilized (e.g., square, rectangular, triangular, circular, and/or the like). Moreover, the first plurality of grid members 152 and second plurality of grid members 153 may be radiopaque, such that radiation does not pass through the grid members. As a non-limiting example, the grid members 152, 153 may comprise 6 mm diameter solid steel bars configured to prevent X-ray radiation from passing through the grid members. Alternatively, any of a variety of radiopaque materials (e.g., lead) and configurations (e.g., hollow bars) may be utilized. FIG. 4 illustrates a diagram of an XPG assembly 550 according to various embodiments. As shown in FIG. 4, the XPG assembly 550 may comprise a first grid portion 551, a second grid portion 552, and one or more supports 553. In various embodiments, the first grid portion 551 and second grid portion 552 may be in a perpendicular arrangement, and the support 553 may be configured to maintain the perpendicular arrangement. In various embodiments, a first end portion of the support 553 may be coupled to the first grid portion 551 using one or more fasteners such as those described above and a second end portion of the support may be coupled to the second grid portion 552 using one or more fasteners such as those described above. As a non-limiting example, the one or more fasteners may comprise a weld, an ultrasonic weld, an adhesive, a screw, a bolt, and/or the like. Moreover, as illustrated in FIG. 4, the XPG assembly 550 may be coupled to a support structure 554 or other transport vehicle. As non-limiting examples, such transport vehicles may comprise wooden pallets, plastic pallets, trailers, containers, crates, boxes, cages, luggage, cases, and/or the like. In various embodiments, the support structure 554 may be configured to facilitate movement of the XPG assembly 550 via a fork-truck without a separate pallet. As previously mentioned, various embodiments described herein provide a unique XPG 150 that may be oriented relative to an X-ray scanning device 140 to ensure that the entire contents of a scanned item 10 have been penetrated. In addition to comprising radiopaque grid elements oriented so as to substantially prevent or minimize a ghosting phenomenon, the grid elements may provide a reference indicative of a unit of measure. For example, the grid elements may be spaced to form 1 inch square spaces there-between and may be utilized as a length reference for an item 10 being scanned. The density of the material used within the mesh or grid structure is further sufficiently thick to absorb X-ray radiation penetrating the item(s) 10 being scanned (i.e., radiopaque), such that the mesh or grid structure appears in any resulting scanned image in an accurate and reliable manner only when the item(s) have been fully penetrated by the X-ray radiation 145 imposed thereon. In various embodiments, the material used within the mesh or grid structure is mild steel (plain-carbon steel), although any radiopaque material may be utilized. The mild steel used within the mesh or grid structure may have a density of approximately 7.85 g/cm3, and may contain approximately 0.05% to 0.3% carbon measured by weight. The problem of shadowing or “ghosting” may be understood with reference to a non-limiting example of the screening of dense magazines and newspapers destined for passenger aircraft. Screening companies could not prove to the appropriate authority that they could see through the magazines and paperwork. Indeed, when examined with only partial grid or mesh structures placed adjacent packages, containers, and the like containing such dense items, X-ray imaging results indicated the existence of a full grid or mesh structure. In other words, as previously mentioned, the X-ray imaging results were shadowing or “ghosting” the remainder of the non-existing grid, thus rendering scan and/or penetration results ambiguous and inconclusive. Such ghost images may extend from the edges of one or more grid elements aligned at least substantially parallel to the direction of travel, and may appear superimposed over a dense item in the generated image. From a practical perspective, the shadowing or “ghosting” should be understood to exist at least in part due to the relative orientation of the grid elements formed within such mesh or grid structures 150. For example, where such are aligned substantially parallel to the direction of travel of an item 10, a ghosted image may appear to include an extension of the mesh or grid structure such that a radiopaque object within the scanned item is obscured. A solution is to orient the grid elements within the grid or mesh structures other than at 0 or 90 degree angles relative to the direction of travel of the package. An optimal angle is at least substantially 45 degrees, although angles in ranges of +/−15 degrees relative to a 45 degree angle may be beneficial as well. Still other angular orientations may provide accurate results for particular applications. As previously noted, such angles relative to the direction of travel may be achieved utilizing an XPG having a first plurality of grid members 152 and second plurality of grid members 153 oriented such that angles α and β between the grid members and the frame 151 are at least substantially 45 degrees. Such XPG may be placed such that a first side of the frame is at least substantially parallel to the direction of travel. The impact of ghosted images may be mitigated or substantially prevented when the XPG is oriented such that the first plurality of grid members 152 and second plurality of grid members 153 are neither parallel nor perpendicular to the direction of travel (e.g., at substantially 45 degrees to the direction of travel), such that the edges of the grid members 152, 153 are not substantially parallel to the direction of travel. As a non-limiting example, when the XPG is oriented such that the first plurality of grid members 152 and second plurality of grid members 153 are not parallel to the direction of travel (e.g., at substantially 45 degrees to the direction of travel), ghosted images of the grid or mesh structure are substantially, and in certain embodiments entirely, eliminated such that virtually no ghosted images are visible in the generated image. Moreover, in various circumstances, ghosting may be minimized or substantially prevented by orienting grid members 152, 153 such that they are neither parallel nor perpendicular to the direction of travel. Such orientation ensures no edges of grid elements 152, 153 are at least substantially parallel to the direction of travel, and therefore the resulting image does not comprise ghost images resembling extensions of one or more grid elements. By orienting the grid members 152, 153 such that they are neither parallel nor perpendicular to the direction of travel, any potential ghost images that may result from moving the item and XPG to the scanning location may be minimized or substantially prevented. Orientation of an XPG relative to an X-ray Scanning Device FIGS. 5A and 5B to FIGS. 9A and 9B illustrate schematic diagrams of exemplary methods of using an XPG according to various embodiments of the present invention. As shown in FIG. 5A, an XPG 150 may be utilized with an X-ray scanning device 140 utilizing an X-ray emitter 142 located above a conveying mechanism 141 according to various embodiments of the present invention. As illustrated in FIG. 5A, X-ray radiation (electromagnetic waves) 145 may be emitted from the X-ray emitter 142 and received by a detector 143. Although illustrated as a single component, the detector 143 may comprise a detector array comprising multiple detectors each comprising a conversion layer configured for receiving X-ray radiation and converting the received radiation into visible signals corresponding to the relative intensities of the received radiation. Thus, the X-ray scanning device 140 may be configured to scan one or more items 10 while the item is being propelled by the conveying mechanism 141. Although illustrated as a conveyor belt, the conveying mechanism may comprise any of a plurality of conveying mechanisms, such as, for example, a slide, chute, bottle conveyor, open or enclosed track conveyor, I-beam conveyor, cleated conveyor, and/or the like. FIG. 5B illustrates an exemplary visual display 600 of the item 10 arranged on the XPG 150 being scanned. As illustrated therein, as least a portion of the grid or mesh structure located directly adjacent (e.g., above or below) the item 10 being scanned is still visible in the visual display 600. However, if a particularly dense object is contained within the item 10, the portion of grid or mesh structure located adjacent the dense object would not be visible in the visible display 600. Referring again to FIG. 5A, in order to utilize the XPG 150, the XPG is oriented such that at least one side of the frame is parallel to the direction of travel of the conveying mechanism 141. Consequently, the first plurality of grid members 152 and second plurality of grid members 153 are oriented at an angle with respect to the direction of travel other than 90 degrees or 0 degrees (e.g., at least substantially 45 degrees). An item 10 to be scanned is placed such that the radiation 145 will pass through both the item and the XPG 150 before being received by the detector 143. As a non-limiting example, the item 10 may be placed on top of the XPG 150. FIGS. 6A and 7A illustrate schematic diagrams of an item 10 being scanned by an X-ray scanning device 140 having an alternative configuration. Specifically, the X-ray emitter 142 shown in FIGS. 6A and 7A is located on a first side of the X-ray scanning device 140 and emits X-ray radiation 145 in a direction perpendicular to the direction of travel of the item 10. As shown in FIG. 6A, an XPG assembly 550 may be utilized such that at least one of the first grid portion 551 and second grid portion 552 is visible in the visible display 600. In various embodiments, each of the first grid portion 551 and second grid portion 552 may have a configuration substantially similar to XPG 150. Referring now to FIG. 6A and the corresponding FIG. 6B, which illustrates an exemplary visual display 600 corresponding to a scanned item 10 having an orientation shown in FIG. 6A; at least a portion of the scanned item (located between radiation line 145a and radiation line 145b) is scanned without a corresponding portion of the XPG 550. Only the portion of the item 10 located between radiation line 145b and 145c (illustrated as portion 600b in FIG. 6B) is scanned with a corresponding portion of the XPG assembly 550 usable as a reference. Consequently, the XPG 550 does not provide a reference for determining whether an item was scanned throughout the entire depth of the item 10 over the portion of the item located between radiation line 145a and radiation line 145b (illustrated as portion 600a in FIG. 6B). Thus, a dense object located within this portion of the item 10 may not be identified by personnel operating the X-ray scanning device 140. Referring now to FIG. 7A and the corresponding FIG. 7B, which illustrates an exemplary visual display 600 corresponding to a scanned item 10 having an orientation shown in FIG. 7A; the entirety of the item is scanned with a corresponding portion of the XPG assembly 550 usable as a reference. As illustrated in FIG. 7B, at least a portion of the XPG assembly 550 may be used as a reference for the entirety of the scanned item 10. FIGS. 8A and 9A illustrate exemplary schematic diagrams of an item 10 being scanned by an X-ray scanning device 140 having yet another configuration. Specifically, the X-ray emitter 142 shown in FIGS. 8A and 9A is located above the item to be scanned 10 and on a first side of the item to be scanned. Referring now to FIG. 8A and the corresponding FIG. 8B, which illustrates an exemplary visual display 600 corresponding to a scanned item 10 having an orientation shown in FIG. 8A; at least a portion of the scanned item (located between radiation line 145a and radiation line 145b) is scanned without a corresponding portion of the XPG assembly 550 usable as a reference, and at least a portion of the scanned item (located between radiation line 145c and 145d is scanned with two corresponding portions of the XPG such that the scanned area is obscured by the XPG. Only the portion of the item 10 between radiation line 145b and radiation line 145c (illustrated as portion 600b in FIG. 8A) is scanned with a single portion of the XPG assembly 550 usable as a reference. A dense object located in the portion of the item 10 between radiation line 145a and radiation line 145b (illustrated as portion 600a in FIG. 8B) may not be identified by personnel operating the X-ray scanning device 140. A dense object located in the portion of the item 10 between radiation line 145c and radiation line 145d (illustrated as portion 600c in FIG. 8B) may be obscured by the two portions of the XPG 550 through which the radiation passes between the X-ray emitter 142 and the detector 143. Referring now to FIG. 9A and the corresponding FIG. 9B, which illustrates an exemplary visual display 600 corresponding to a scanned item 10 having an orientation shown in FIG. 9A; the entirety of the item is scanned with a single corresponding portion of the XPG assembly 550 usable as a reference. As illustrated in FIG. 9B, at least a portion of the XPG assembly 550 may be used as a reference for the entirety of the scanned item 10. Method of Use FIG. 10A illustrates an exemplary flowchart of a method of using an XPG 150 (or XPG assembly 550) according to various embodiments. As shown therein, the method begins at block 1001, wherein the item 10 and XPG 150 (or XPG assembly 550) is oriented relative to a conveying mechanism 141 such that the grid members 152, 153 are not parallel to the direction of travel of the conveying mechanism 141. As previously noted, the item 10 may be oriented relative the XPG 150 (or XPG assembly 550) such that radiation from the X-ray emitter 142 passes through both the item and XPG before reaching the detector. Preferably, the item 10 is arranged relative to the XPG 150 (or XPG assembly 550) such that radiation 145 cannot travel through any portion of the item without also passing through the XPG. Thus, the XPG 150 (or XPG assembly 550) may be used as a scan depth reference over the entirety of the scanned item 10. Referring again to FIG. 10A, the item 10 and XPG 150 (or XPG assembly 550) is conveyed into the X-ray scanning device 140 at block 1002. The conveying mechanism 141 may be configured to propel an item 10 and XPG 150 (or XPG assembly 550) at a velocity such that the X-ray scanner device 140 may record multiple scans of each item while the item is within the X-ray scanner device. As a non-limiting example, the X-ray scanner device 140 may be configured to scan a plurality of slices of each item 10. Each successive slice may be at least substantially perpendicular to the direction of travel, and may be scanned as a portion of the item 10 is propelled through a scanning area. In various embodiments, the conveying mechanism 141 may operate continuously at a particular velocity, or it may be configured to temporarily stop moving while the X-ray scanner device 140 scans each item 10. While the item 10 and XPG 150 (or XPG assembly 550) are located within the X-ray scanning device 140, the X-ray emitter 142 emits X-ray radiation 145 through the item 10 and XPG 150 (or XPG assembly 550). In various embodiments, the X-ray emitter 142 may be operating constantly while the X-ray scanner device 140 is operating, such that the X-ray emitter 142 emits pulses of radiation to create X-ray images at least periodically (e.g., every 10 seconds, every 5 seconds, every second, every 500 milliseconds, every 250 milliseconds, every 100 milliseconds, every 10 milliseconds, and/or the like). The radiation 145 emitted by the X-ray emitter 142 is received by the detector 143 at block 1004. At block 1005 the detector 143 determines the relative intensity of the radiation 145 received at each of a plurality of locations on the surface of the detector 143. The relative intensity of the radiation 145 received at each of the plurality of locations may be indicative of the location of various objects having differing densities within the item 10. The grid members 152, 153 of the XPG 150 (or XPG assembly 550) may be radiopaque, such that the detector 143 may detect a negligible or nonexistent intensity of radiation 145 at locations corresponding to the grid members. As a result, the relative intensity of the radiation 145 received by the detector 143 may be indicative of a radiopaque grid or mesh structure in addition to any radiation passed through the spaces in the grid or mesh structure of the XPG 150 (or XPG assembly 550). At block 1006, the intensity data indicative of the relative intensity of the radiation 145 received by the detector 143 is generated. In various embodiments, the intensity data may be transmitted via one or more networks 130 to one or more central computing devices 110, the central server 200, one or more mobile devices 300, and/or one or more distributed computing devices 120. As previously indicated, the detector 143 may trap a portion of the radiation 145 received from a previous emission 42 within the detector such that the radiation does not dissipate prior to receiving a subsequent emission of radiation. As a result, the intensity data generated based at least in part on the relative intensity of the radiation 145 received by the detector 143 may be amplified due to the trapped radiation present in the detector. As a simplified, non-limiting example, as a result of a first radiation emission by the X-ray emitter 142, the detector 143 determines that no items are placed on an XPG 150 (or XPG assembly 550). The intensity data generated by the detector 143 indicates that no radiation was received at locations corresponding to the radiopaque grid members 152, 153, and a maximum amount of radiation was received at all other locations (e.g., locations corresponding to the spaces between grid members). As a result of a second radiation emission by the X-ray emitter 142 occurring immediately following the first radiation emission (e.g., before the detector response generated based on the first emission fully decays), the detector 143 receives radiation with relative intensities indicative of a radiopaque object located on an XPG 150 (or XPG assembly 550). Therefore, at all locations corresponding to the radiopaque object, the detector receives substantially no radiation 145. However, because the previous detector response had not fully decayed, the generated intensity data corresponding to the second emission indicates that “ghost” radiation was received at all locations corresponding to the spaces between grid members 152, 153, including those detector locations also corresponding to the location of the radiopaque object. As a result, the intensity data may appear to indicate that the radiopaque object allowed a small amount of radiation 145 to pass there-through. Although the previously presented example simplifies the process of receiving radiation 145 and generating intensity data including ghost radiation as the conveying mechanism 141 propels an item 10 and XPG 150 (or XPG assembly 550) into the X-ray scanning device 140, each of the plurality of locations of the detector 143 may receive varying intensities of radiation 145. Therefore, where an item 10 is oriented such that a volume of low density (allowing a higher intensity of radiation 145 to pass through the low density volume) is located downstream from a radiopaque volume, the ghosting phenomenon may impact the resulting intensity data corresponding to an emission passing through the radiopaque volume. FIG. 10B illustrates a schematic diagram of the various modules 400-450. In particular, FIG. 10B illustrates the relationship between the visual module 400, the analysis module 425, and the notification module 450. In various embodiments, the various modules 400-450 may facilitate implementation of various steps illustrated in FIG. 10A and described herein. In various embodiments, the visual module 400 of the central server 200 may comprise a visual conversion tool 402 configured to convert the intensity data 401 received for each X-ray image into visible data 403 for each X-ray image comprising visible signals to be displayed via a display device at block 1007 of FIG. 10A. However, as will be understood by one skilled in the art, any of a variety of computing devices may be configured to convert the intensity data into visible signals. The resulting visible signals are displayed via a display device at block 1008. As illustrated in FIG. 10B, the visual module 400 may transmit the visible data 403 to the analysis module 425 for additional processing. The analysis module 425 may be configured to identify the presence of ghost radiation signals in the visible data 403 for each X-ray image. As a non-limiting example, the analysis module 425 may comprise a ghost analysis tool 426 configured to generate ghost presence data 427 indicative of the presence of ghost signals in the X-ray image. Because the grid members 152, 153 are not parallel to the direction of travel, no ghosted images may be present in the intensity data. However, where at least one grid member is oriented such that at least one edge of the radiopaque grid member is substantially parallel to the direction of travel, ghosted images may appear in the visible data 403. Therefore, the orientation of the grid members 152, 153 relative to the direction of travel may facilitate the identification of radiopaque objects within scanned items 10. As a non-limiting example, the analysis module 425 may be configured to identify radiopaque objects within an X-ray image based upon the presence of ghost grid lines appearing over a portion of the X-ray image. In various embodiments, upon a determination that ghost signals are present within the X-ray image, the analysis module 425 may be configured to transmit the ghost presence data to the notification module 450. The notification module 450 may comprise a notification generation tool 451 configured to generate and transmit one or more notifications 452 to relevant personnel indicative of the existence of ghost presence data 427 in an X-ray image. As a non-limiting example, the notification module 450 may be configured to illuminate an indicator light located proximate to a visual display configured to displaying the X-ray image data, or to display a notification message on the visual display. In response to receiving such notification, personnel monitoring the X-ray scanner device 140 may perform additional secondary screening on the item 10 in question. For example, such secondary screening may comprise reorienting the item 10 for an additional scan utilizing the X-ray scanner device 140, unpacking the item for a hand search of the contents of the item, and/or the like. Conclusion Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. |
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062460528 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a high resolution measuring device, and more particularly to a flexure assembly of a micro scanning device. 2. Discussion of the Related Art Flexure carriages and devices are known in the art and are used for high resolution instrumentation and measuring equipment such as scanning probe microscopes and the like. These flexure devices typically carry thereon a probe or a sensor, or a specimen to be analyzed. Either the specimen or the probe is moved in very small increments in a plane relative to the other for determining surface or subsurface characteristics of the specimen. These devices are typically designed so as to move highly precisely and accurately in an X-Y plane and yet move very little in a Z direction perpendicular to the X-Y plane. The sensing probe typically measures surface defects, variation of the specimen's components, surface contour or other surface or subsurface characteristic. These types of devices may also be designed and utilized for other applications as well, such as imaging and measuring properties of computer microchips, computer disc surfaces, and other physical or chemical properties. The range of measurement for such devices is typically on the order of one Angstrom (.ANG.) to several hundred microns (.mu.). In order to provide this type of extremely high resolution measurement, these devices require precise and minute micro-positioning capabilities within an X-Y plane and yet ideally permit no movement in a Z direction perpendicular to the plane. The flexure devices or carriages which hold the sensing probe or specimen of such devices are designed and utilized to provide just such movement. A known flexure carriage construction uses a piezoelectric actuator which utilizes an applied electric potential to micro-position portions of the flexure devices. Conventional or known devices typically can only provide very flat movement in an X-Y plane over a very small relative area. The larger the range of movement, the greater the out-of-plane movement becomes, (i.e., the motion becomes increasingly curved or less flat). This is because of the construction and arrangement of the piezoelectric element in the devices. The piezoelectric elements bend partially out of their longitudinal axis and therefore apply out of axis forces which induce errors. The out of axis forces and resultant errors increase with increased expansion of the piezoelectric elements. One device, disclosed in U.S. Pat. No. 5,360,974 and assigned to International Business Machines Corporation of Armonk, N.Y., provides a fairly flat movement in an X-Y direction or plane utilizing a dual frame arrangement where each frame is supported in opposite directions by flexible legs. Any Z direction motion perpendicular to the plane of one frame of the device is cancelled by movement of the other frame to maintain a very flat movement. However, the disclosed device utilizes long external piezoelectric elements which are oriented parallel to the plane of movement in order to eliminate or reduce rotation or yaw produced by the device. Such a device is much too large in certain applications. Applications that employ such minute micro-positioning and sensing technology increasingly demand higher resolution measurements. For example, computer technology continues to reduce the size and increase the package density for the electronic elements in microchips and circuits. Meanwhile, the volume in which they are being produced and thus the size of the wafers on which they are made is also increasing. It is therefore becoming increasingly necessary to provide flexure devices which are capable of relatively large ranges of movement in an X-Y plane, which prevent movement in a Z axis perpendicular to the plane, and which are relatively small in size so that they may be utilized in equipment that must be smaller, less expensive and more accurate. It should be understood that while measurement on a smaller scale is being discussed, changes to a sample on similar scales, such as nano-lithography and micro-machining, may also need to be performed with this level of accuracy. Thus, the discussion herein is intended to encompass fabrication as well as measurement. SUMMARY OF THE INVENTION The present invention is therefore directed to an improved flexure carriage and assembly useful in high resolution measurement and fabrication devices and instruments. The flexure carriage of the invention provides extremely flat and true movement in an X-Y direction or plane and prevents movement in a Z direction perpendicular to the X-Y plane. Additionally, the flexure carriage of the invention is capable of producing a relatively large range of motion in both the X and the Y direction while producing such a flat plane of motion. The flexure carriage of the invention produces such advantages and yet may be constructed in a relatively small and very sturdy or stiff package to produce the very flat plane of motion in the X and Y directions. To accomplish these and other objects, features and advantages of the invention, a flexure assembly or carriage is disclosed. In one embodiment the flexure carriage of the invention is formed of a substantially rigid material and has four elongate columns arranged spaced apart and parallel to one another. Each of the elongate columns has a first and a second end. The carriage also has four first cross members arranged so that each first cross member extends between and interconnects two first ends of the elongate columns. The carriage also has four second cross members arranged so that each second cross member extends between and interconnects two second ends of the elongate columns. The carriage has a translating section that is disposed within a space between the elongate columns generally equadistant between the first and second ends of the elongate columns. The translating section is interconnected to the elongate columns. The carriage has a plurality of flexures wherein one flexure interconnects each first end of each elongate column to each first cross member. One flexure interconnects each second end of each elongate column to each second cross member. At least one flexure interconnects each elongate column with a translating section. The flexures permit the translating section to move according to an applied force in a plane which is essentially perpendicular to the orientation of the elongate columns. The symmetry of the flexure carriage eliminates virtually any movement in a Z direction perpendicular to the X-Y plane. In one embodiment, a pair of flexures interconnect each elongate column with the translating section. One flexure of each pair is disposed adjacent the translating section on each elongate column nearer the first end. The other flexure of each pair is disposed adjacent the translating section on each elongate column nearer the second end. In one embodiment, each flexure of the flexure carriage includes a first pair of opposed slots formed transversely and extending toward one another into one of the elongate columns. A first web of the substantially rigid material is left remaining between the first pair of slots. A second pair of opposed slots are spaced from the first pair of slots in the same elongate column and formed transversely and extending toward one another into the elongate column. A second web of the substantially rigid material is left between the second pair of slots. The first web and the second web are arranged perpendicular to one another and spaced apart along the same elongate column. In one embodiment, a flexure carriage as described above, is provided with a first piezoelectric assembly connected to the translating section for moving the translating section along only a first linear path generally perpendicular to the elongate columns. A second piezoelectric assembly is connected to the translating section for moving the translating section along only a second linear path generally perpendicular to the elongate columns and perpendicular to the first linear path. In one embodiment, a high resolution measurement device is constructed according to the invention and has a support structure carrying various elements of the device. The measurement device also has a meauring instrument which is carried by the translating section of a flexure carriage provided as described above. Each of the piezoelectric assemblies is affixed at one portion to the support structure of the measurement device and affixed to a portion of the translating section of the flexure carriage for providing applied forces to the translating section for moving the translating section and the measuring instrument therewith. These and other objects, features and advantages of the present invention will be better understood and appreciated when considered in conjunction with the following detailed description and accompanying drawings. It should be understood however that the following description is given by way of illustration and not of limitation though it describes several preferred embodiments. Many changes and modifications may be made to the disclosed embodiments without departing from the spirit and scope of the present invention and the invention is intended to include all such modifications. |
046997571 | description | DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The fuel rod 10, a fraction of which is shown in FIG. 1, has a general construction similar to that of the fuel elements currently used in pressurized water moderated and cooled reactors (PWRs). It comprises a sheath 12, generally of zirconium base alloy, closed by plugs 14 only one of which is shown. The major part of the length of the sheath is occupied by a stack of UO.sub.2 or UO.sub.2 -PuO.sub.2 pellets 16. The fuel rod comprises means for holding the stack 16 applied against the lower plug 14 during handling and transport. In conventional fuel rods, such means comprise a helical spring placed in the chamber or "plenum" receiving the fission products, above the stack of pellets 16. The spring is compressed between the stack and the upper plug of the rod and must be of material having such a resilient force that there is no appreciable modification of the holding force despite the radiation received by the spring and the length increase of the stack when in a reactor. According to the invention, the holding means are of a type immobilized in the sheath 12 when the element is cold and substantially freely movable along the sheath when at the operating temperature which prevails in the reactor. Referring to FIGS. 1 and 2, the holding means comprise a radially expandable element 18 in the form of a thimble or diabolo in which are formed longitudinal slits spaced apart evenly angularly, cut out from the both ends and leaving a continuous central ring 20. The two sets of slits (four in number as shown) define resilient fingers which tend to spread apart until they bear against the internal surface of sheath 12. In other words, the diabolo shaped element 18 has an end diameter at rest such that the finger ends are applied against the sheath when inserted therein and oppose considerable frictional force to longitudinal movement. A washer 24 between element 18 and stack 16 forms a heat shield so that the temperature of element 18 reflects that of the cooling water rather than that of the pellets. A circumferential groove 26 is formed in each set of fingers and receives a split ring 28 of shape memory material which, at atmospheric temperature, follows the movements of the fingers and, above the transition temperature of the material, exerts a radially directed shrink force sufficient for the fingers to be inscribed in a circle of smaller diameter than the inner diameter of sheath 12. When ring 28 thus takes the initial shape which was given to it, it allows elements 18 to slide either under the upward thrust of a stack (should swelling of the pellets occur) or downwards under the action of its own weight and vibrations. However, upon cooling of the reactor after it has been shut down, the temperature of the ring drops below the transition point, the fingers spread out against the force of the ring and frictionally lock element 18, thus retaining the stack of pellets 16. As an example, the following matters may be used for the components of the holding means: Expandable element 18: "INCONEL 718" or 13/8 stainless steel. PA0 Ring 28: titanium-nickel alloy having a titanium content between 51 and 53% (whose transition temperature is about 100.degree. C.). PA0 Washer 24: alumina. Referring to FIGS. 3 and 4, the radially expandable element consists of a bellows 30 having a rotational symetry about the rod axis, whose external folds are arranged for engaging the sheath when the bellows contracts. The temperature responsive means consist of a helical spring 32 made from a shape memory material and located along the axis of the bellows 30, compressed between the end walls of the bellows. As shown in FIG. 3, the bellows is at a temperature lower than the transition point of the spring material, the external folds of the bellows are in frictional contact with the internal surface of sheath 12 and hold the stack of pellets 16 in position. During operation in a reactor, when the temperature of spring 32 is higher than the transition point, the spring expands until it resumes the shape which was initially given to it and the external folds of bellows 13 no longer engage the sheath, which leaves the stack of pellets 16 free to expand. The shape memory element 32 may as well consist of a twisted washer or any element for retracting the folds of the bellows 30 above the transition temperature. In the ebodiment shown in FIGS. 5 and 6 (where the elements identical to those if FIGS. 1 and 2 are again designated by the same reference numeral), the radially expandable element consists of a ring 34 with a C-shaped cross-section. A central groove in the ring receives a continuous ring 36 made of a shape memory material. Referring to FIG. 7, a holding device has a radially expandable element 18 and two rings 28 identical to those shown in FIGS. 1 and 2. However, element 18 is not directly in contact with washer 24. It is separated therefrom by means for accomodating the variations in length of the stack while the temperature is below the transition temperature of the material forming rings 28. The accomodation means comprise two abutment washers 38 and 40 connected together by a spring 42 extending a resilient force tending to spread apart the washers 38 and 40. A second spring 44, opf shape memory alloy, has its ends connected to the washers. The transition temperature of the alloy forming the second spring 44 is lower than that of the alloy of rings 28. For example, rings 28 may be of the abovedefined alloy while spring 44 is of titanium-nickel alloy with 45-45.5% at. of titanium. Thus, when the temperature initially increases after the fuel rod has been placed in the reactor, spring 44 exerts a tractive force which moves washers 38 and 40 towards one another, and retracts spring 42. Then, as the temperature increases further and reaches the transition temperature, rings 28 unlock the radially expandable element 18. Conversely, when the temperature decreases, after shut down of the reactor, rings 28 allow the expandable element 18 to lock onto the sheath. Then spring 44 relaxes and spring 42 applies a force on the stack of pellets and takes up the axial clearance with a resilience which compensates for the variations in length. The embodiment shown in FIGS. 8 to 12 comprises a radially expandable element formed by a split ring 50 which may again be considered as a ring having a C-shaped cross-section. Ring 50 has a diameter at rest larger than the inner diameter of the sheath and is applied resiliently against the internal wall of the sheath of the fuel element when inserted. Then it holds the fuel pellets in position due to the frictional force exerted by the sheath. The temperature responsive means comprise two coiled springs 52 and 54. The two springs are mutually coaxial and have opposite winding directions and different diameters. Each end of each spring has a lug anchored to the ring and the two ends of a spring are anchored close to the edges of the slit. Referring to FIG. 10, the end lugs 56 and 58 of the large diameter spring 52 are illustrated. When the temperature of springs 52 and 54 increases from the ambient temperature, a relative rotation of the end lugs of the springs may occur eve if they are of a material exhibiting normal thermal expansion characteristics. Additionally, the memory effect of the material, if they are of shape memory material, results in a winding action beyond the transition temperature. The material may typically be a titanium-nickel alloy having a titanium atomic content of 51 to 53%. The winding movement of the end lugs anchored in ring 50 tends to "close" this latter and to remove friction between the ring and the sheath. Ring 50 them becomes free to move along the sheath and the stack of pellets may freely expand. During cooling, the lower mechanical resistance of the memory alloy or, if the alloy has a reversible memory, cooling down below the transition temperature, allows ring 50 to resume its initial shape and to engage the sheath, thus retaining the stack of pellets. |
abstract | Methods of producing and isolating 68Ga, 89Zr, 64Cu, 63Zn, 86Y, 61Cu, 99mTc, 45Ti, 13N, 52Mn, or 44Sc and solution targets for use in the methods are disclosed. The methods of producing 68Ga, 89Zr, 64Cu, 63Zn, 86Y, 61Cu, 99mTc, 45Ti, 13N, 52Mn, or 44Sc include irradiating a closed target system with a proton beam. The closed target system can include a solution target. The methods of producing isolated 68Ga, 89Zr, 64Cu, 63Zn, 86Y, 61Cu, 99mTc, 45Ti, 52Mn, or 44Sc further include isolating 68Ga, 89Zr, 64Cu, 63Zn, 86Y, 61Cu, 99mTc, 45Ti, 52Mn, or 44Sc by ion exchange chromatography. An example solution target includes a target body including a target cavity for receiving the target material; a housing defining a passageway for directing a particle beam at the target cavity; a target window for covering an opening of the target cavity; and a coolant gas flow path disposed in the passageway upstream of the target window. |
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040382028 | summary | BACKGROUND OF THE INVENTION The present invention relates to an improved process of washing spherical particles, for example sol-gel spheres of uranium, to remove the organic layer adhering to such spheres with an aqueous solution of a surface active substance. In the preparation of metal and metal oxide spheres such as uranium and the salts thereof, a customary technique to form substantially spherical particles is to disperse an aqueous metal sol into an organic phase, such as kerosene or carbon tetrachloride, such that under dispersing conditions the aqueous phase droplets solidify in the organic phase, the aqueous phase being substantially or completely immiscible with the organic phase. The dispersed droplets of the sol become spherical in shape due to their inherent surface tension in the dispersed state within the immiscible organic liquid. The spheres so produced usually have an organic film adhering to the outside surface of the sphere and it is to the removal of this film that the present invention is directed. It should also be mentioned that during the sphere formation in the organic liquid it has been proposed to add a surfactant to the organic liquid itself in order to prevent the aqueous-phase droplets from coalescing with each other and to maintain the droplets in the dispersed state. This procedure is described in U.S. Pat. No. 3,586,742. In both instances it is usually necessary to wash the spheres with water to remove soluble salts of the gel or hydroxide material that are formed along with the spherical particles. Previous procedures to accomplish the above objectives include the following: After globule or spherical particle formation in a relatively viscous organic phase, the particles were separated and washed with petroleum ether and subsequently eluted with a watery phase. In some cases residues of petroleum ether caused problems. For this reason, washing with petroleum ether was sometimes followed by a re-rinsing operation with methanol. After washing with methanol, the final washing operation, in this case, was performed with a watery rinsing phase. It will be apparent then that this procedure is not only difficult but adds to the cost of manufacture. Another process that has been proposed is regeneration of the organic phase. Forming oils can in some cases be regenerated by contacting the oil with an adsorbing bed, the adsorbing bed collecting decomposition products of the oil. Decomposition products of the forming oil have in the past sometimes continued adhering to the globules, thus interfering with the elution. DETAILED DESCRIPTION OF THE INVENTION The present invention provides an improved washing or elution using an aqueous phase wash solution to rinse inorganic gel or hydroxide grains. According to the present invention a small quantity, say about 0.3 vol.%, of a surface active agent, somewhat hydrophilic in character and having an HLB number between about 10.0 and 14, is added to the aqueous washing solution. Using this washing solution the water-soluble salts contained in the spheres are removed as nitrates and chlorides during the washing operation. Further the film of organic liquid that may adhere to the spheres is also removed by the washing operation. The spherical particles prepared according to the present invention are usually used as fuels or fuel elements in nuclear reactors and are composed of actinide metals and oxides thereof including uranium dioxide, uranium trioxide, thorium dioxide, plutonium dioxide, plutonium trioxide, zirconium dioxide, beryllium oxide and yttrium oxide, and mixtures thereof from which dense metal microspheres can be prepared. Optionally the microspheres contain carbon, usually colloidal carbon, which, following heating and processing conditions known in the art, convert the particles to dense metal carbide microspheres. Prior to the washing process of the present invention the spheres are prepared by dispersing a metal oxide in the form of droplets of a sol of the desired materials, then causing the particles to gel in situ by contact with a gelling agent, usually an ammonia-releasing agent or ammonia itself. The sol may be dispersed directly into an organic liquid of the type described which also contains ammonia, or an ammonia releasing agent -- usually hexamethylene tetramine -- is added to the sol prior to dispersion and gelation. The organic liquid is maintained at a temperature sufficiently high to cause the ammonia to react or be released, as the case may be. The spherical particle formation process is generally well known in the art and is described in the following U.S. Patents, the disclosures of which are incorporated by reference to the extent required to further explain and describe the present invention: U.S. Pat. Nos. 3,290,122; 3,312,632; 3,331,898; 3,586,742; 3,617,585; 3,669,632; and 3,709,963. The specific manner in which the spheres are prepared is not critical to successful subsequent processing and washing of the spheres, so long as the above general procedures are followed. It is preferred that metal salt solutions or anion-deficient metal salt solutions of the type described be mixed with one or more ammonia releasing agents prior to dispersion in the organic phase. According to the present invention suitable ammonia-releasing agents include urea, hexamethylene tetramine, ammonium carbonate, potassium cyanate, ammoniumcyanate, acetamide, formamide, and the like. After mixing the metal salt solution with ammonia-releasing agent, it is preferable to cool the mixed liquids prior to dispersion. It is also possible to maintain a predetermined concentration of ammonia or ammonia-releasing agent in the organic liquid itself such as passing gaseous ammonia through the liquid. The aqueous liquid which is dispersed in the organic liquid contains actinide components if grains of nuclear fissional material are to be prepared. In order to improve the properties of the final products, the aqueous liquid which contains actinide components of the type described may also contain components of the elements Zr.sup.4, Hf.sup.4, Y.sup.3, Sc.sup.3 and trivalent rare earth elements. An aqueous liquid which is particularly suitable for dispersion consists of an aqueous solution consisting essentially of uranyl nitrate or anion-deficient uranyl nitrate and the rinsing liquid is composed of water, surfactant and aqueous annonia. As previously mentioned, surfactants have been included in the organic liquid to prevent the particles from coalescing together; see U.S. Pat. No. 3,586,742. We have found that further improved results are obtained if the surfactant used in the organic liquid and the surfactant used in the aqueous washing liquid bear a relationship to each other, such that the surfactant or surface active substance in the organic liquid is lipophilic in character, that is having an HLB number ranging between 7 and 10.5, and the surfactant or surface active substance used in the aqueous washing liquid is hydrophilic in character, that is having an HLB value of about 10.0 to 14. As used herein and as recognized in the literature, the term "HLB" refers to hydrophile-lipophile balance. A suitable combination of surfactants is as follows: organic liquid -- one or more alkyl substituted benzenes having up to about 12 carbon atoms in the alkyl chain. Dobane Pt-12 is a suitable material containing a mixture of alkyl benzenes having an average of about 12 carbon atoms in the alkyl chain and sold by Shell. Another preferred surfactant is based on a polyoxyethylene sorbitol fatty acid or sorbitan ester - alkyl aryl sulphonate blend, such as Atlox 3386 and Atlox 3335, commercially available from Atlas Chemical Industries. Atlox 3386 has an HLB value of 9.6 and Atlox 3335 has an HLB value of 13.0. The amount of surfactant added to the washing liquid depends upon a large number of factors including the nature of the impurities to be washed out, the type of surfactant, or if a combination of one or more surfactants is used, surfactants, the presence of other materials in the washing solution such as ammonia, the nature of the organic film to be removed if any, and the like. Usually, however, the process is conducted at a surfactant concentration within the limits of about 0.005 to 5 vol percent, calculated on the volume of wash solution employed, and preferably about 0.2 to 1 vol percent, although amounts as low as 0.01 percent by volume may be used. There are a number of surface active agents or surfactants suitable for use in the process of the present invention. Surfactants generally available include the following: (1) Water-soluble salts of sulfuric acid esters of aliphatic alcohols containing from 8 to 18 carbon atoms, and particularly from 12 to 14 carbon atoms. Typical examples of such detergents are the sulfates of higher aliphatic alcohols derived from coconut oil, palm kernel oil, or babassu oil, in the form of their sodium or other water-soluble salts. Such detergents are disclosed, for example, in U.S. Pat. Nos. 1,968,793; 1,968,794; and 1,968,797. (2) Water-soluble salts of sulfuric acid esters of aliphatic polyhydric alcohols incompletely esterified with fatty acids containing from 8 to 22 carbon atoms and particularly from 10 to 14 carbon atoms. Typical examples of such detergents are the mono-sulfates of lauric acid (or coconut oil fatty acid) monoglyceride (sodium salt); mono-sulfate of the lauric acid ester of diethylene glycol (sodium salt); and mono-sulfate of the myristic acid ester of diglycerol (sodium salt). These detergents are disclosed in detail in U.S. Reissue Pat. No. 20,636. (3) Water-soluble salts of alkylated aromatic sulfonic acids wherein the alkyl group contains a chain of from 8 to 22 carbon atoms and particularly where the alkyl chain contains predominantly 12 to 14 carbon atoms. Typical examples of such compounds are the sodium salts of an alkylated benzene sulfonic acid wherein the alkyl group contains approximately 12 carbon atoms and is derived from an olefin polymer such as a propylene tetramer or is derived from a kerosene fraction; the sodium salt of nonyl naphthalene sulfonic acid; and the sodium salt of dodecyl toluene sulfonic acid. Such detergents are disclosed in a large number of U.S. patents typical of which are the following: U.S. Pat. Nos. 1,992,160; 2,161,173; 2,220,099; 2,232,117; 2,232,118; 2,233,408; and 2,283,199. (4) Water-soluble salts of higher molecular weight alkylated aromatic hydroxy-alkyl sulfuric acid esters wherein the higher molecular weight alkyl radical contains from 8 to 22 carbon atoms and more particularly from 10 to 14 carbon atoms. The higher molecular weight alkyl radical is derived from petroleum hydrocarbons, such as special cuts of kerosene, as well as from olefin polymers such as have been described, for example, hereinabove. 5. Sulfated and sulfonated vegetable oils (including mixtures of such sulfated and sulfonated oils). These are conventionally prepared from castor oil, olive oil, or oils containing glycerides of oleic acid by reaction with sulfuric acid or other sulfonating agents and then neutralizing. They are utilized in shampoos of the type which are, generally speaking, non-foaming, but they may be utilized in combination with detergents of the foaming type such as are described herein. 6. Condensation products of hydroxyalkyl amines with fatty acids containing from 8 to 18 carbon atoms and wherein the molar ratio of the hydroxy-alkyl amine to the fatty acid is not substantially less than 2 to 1. Typical examples of such detergents are condensation products of 2 mols of diethanolamine with 1 mol of lauric acid or coconut oil mixed fatty acids; and condensation products of 2 mols of triethanolamine with 1 mol of lauric acid, myristic acid, or coconut oil mixed fatty acids. These detergents are particularly described in U.S. Pat. No. 2,089,212. 7. Polyoxyalkylene glycol ethers of alkylated aromatic compounds in which the nuclear alkyl group contains from 8 to 18 carbon atoms and more particularly from about 10 to 14 carbon atoms. Of course mixtures of one or more surfactants from the same class or from the various different classes 1-7 may be employed. As previously indicated the surfactant used in the aqueous washing liquid has an HLB value of the order of about 10.0 to about 14, making the surfactant hydrophilic in character. According to a preferred embodiment of the invention a lipophilic surfactant, that is a surfactant having an HLB value of about 7 and about 10.5, but preferably less than 10.0, is used in the organic liquid. |
abstract | A pressurizer is for a pressurized water nuclear power plant and it includes an upper cap provided with a tube; an end piece connected to the tube using a weld; and a sleeve protecting the weld, disposed inside the tube. The protective sleeve is mounted in a removable manner, such that the thermal sleeve is removed. |
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039883973 | claims | 1. A process for the production of a block fuel element consisting essentially of providing a block fuel free graphite matrix material having a plurality of noncontiguously disposed channels therein, inserting fissile uranium particles embedded in the same type of graphite matrix material in one group of said noncontiguously disposed channels, inserting breeder thorium particles in the same type of graphite matrix material in a second group of said noncontiguously disposed channel and inserting removable bars into a third group of said noncontiguously disposed channels; then hot pressing said graphite block containing said fissile uranium particles, breeder thorium particles, and removable bars, and then removing said bars to form the block fuel element having noncontiguous (1) uranium containing feed zones; (2) thorium containing breed zones and (3) cooling channels in said fuel free graphite matrix. |
052415732 | abstract | A shield apparatus is arranged for ease of mounting in assembled configuration particularly for use in shielding various radiations, such as relative to nuclear plants. The shielding structure is arranged for use in emergency as well as in a permanent relationship relative to such radiation emitting structure. |
039792552 | claims | 1. A method of operating a system in response to a system parameter excursion of determinable magnitude but of indeterminate length, the method comprising the steps of: a. determining a maximum allowable parameter excursion to determine an excursion margin; b. monitoring said parameter; c. generating a variable excursion setpoint by tracking and holding the minimum value of the sum of said monitored parameter and said excursion margin; d. resetting said excursion setpoint to a value larger than said minimum value of the sum of said excursion margin and said monitored parameter only on permission from an independent decision maker; e. comparing said monitored parameter to said setpoint; and f. instituting responsive action when said monitored parameter exceeds said setpoint. a. determining a maximum allowable parameter excursion to determine an excursion margin; b. monitoring said parameter; c. generating a variable excursion setpoint by tracking and holding the maximum value of the difference of said monitored parameter and said excursion margin; d. resetting said excursion setpoint to a value less than said maximum value of the difference of said monitored parameter and said excursion margin only on permission from an independent decision maker; c. comparing said monitored parameter to said setpoint; and f. instituting appropriate responsive action when said monitored parameter falls below said setpoint. a. scramming said reactor; and b. flooding the core of said reactor with emergency core coolant water. a. determining a maximum allowable parameter excursion to establish an excursion margin; b. monitoring said parameter to generate a parametric signal commensurate with said parameter; c. adding said excursion margin to said parametric signal to generate a signal commensurate with their sum; d. comparing the last existing setpoint to said signal commensurate with said sum; e. decreasing said setpoint only when said setpoint is greater than said signal commensurate with said sum; f. increasing said setpoint when said setpoint is less than said signal commensurate with said sum only when independent permission is supplied from an independent decision maker; g. comparing said signal commensurate with said monitored parameter to said setpoint; and h. instituting responsive action when said comparison to said setpoint of step (g) indicates that said monitored parameter exceeds said setpoint. a. determining a maximum allowable parameter excursion to establish an excursion margin; b. monitoring said parameter to generate a parametric signal commensurate with said parameter; c. subtracting said excursion margin from said parametric signal to generate a signal commensurate with their difference; d. comparing the last existing setpoint to said signal commensurate with said difference; e. increasing said setpoint only when said setpoint is less than said signal commensurate with said difference; f. decreasing said setpoint when said setpoint is greater than said signal commensurate with said difference only when independent permission is supplied from an independent decision rather; g. comparing said signal commensurate with said monitored parameter to said setpoint; and h. instituting responsive action when said comparison to said setpoint of step (g) indicates that said monitored parameter is less than said setpoint. a. determining a maximum allowable parameter excursion to determine an excursion margin; b. monitoring said parameter; c. generating a variable excursion setpoint by adding said excursion margin to the smallest value attained by said monitored parameter; d. resetting said excursion setpoint by adding said excursion margin to a value of said monitored parameter larger than said smallest value attained by said monitored parameter only on permission from an independent decision maker; e. comparing said monitored parameter to said setpoint; and f. instituting responsive action when said monitored parameter exceeds said setpoint. a. determining a maximum allowable parameter excursion to determine an excursion margin; b. monitoring said parameter; c. generating a variable excursion setpoint by subtracting said excursion margin from the largest value attained by sai monitored parameter; d. resetting said excursion setpoint by subtracting said excursion margin from a value of said monitored parameter smaller than said largest value attained by said monitored parameter only on permission from an independent decision maker; e. comparing said monitored parameter to said setpoint; and f. instituting responsive action when said monitored parameter is less than said setpoint. 2. A method of operating a system in response to a system parameter excursion of determinable magnitude but of indeterminate length, the method comprising the steps of: 3. The method as recited in claim 2 wherein said system is a pressurized water nuclear reactor and said system parameter is the pressure of the primary coolant, said step of instituting responsive action including the steps of: 4. The method as recited in claim 1 wherein said system is a nuclear reactor and said system parameter is the operating core power. 5. The method as recited in claim 2 wherein said system is a pressurized water nuclear reactor and said system parameter is the pressure of the secondary coolant. 6. A method of operating a system in response to a system parameter excursion of determinable magnitude but of indeterminate length by means of a continuously generated variable setpoint, the method comprising the steps of: 7. A method of operating a system in response to a system parameter excursion of determinable magnitude but of indeterminate length by means of a continuously generated variable setpoint, the method comprising the steps of: 8. A method of operating a system in response to a system parameter excursion of determinable magnitude but of indeterminate length, the method comprising the steps of: 9. A method of operating a system in response to a system parameter excursion of determinable magnitude but of indeterminate length, the method comprising the steps of; |
054065950 | summary | TECHNICAL FIELD The invention relates to a device intended for closing and sealing a lead-through, wherein the sealing permits the lead-through to be opened, washed clean and closed again. Preferably, the invention relates to sealing of a lead-through in the form of a so-called neutron detector housing which is arranged in a reactor vessel for a nuclear power plant. BACKGROUND ART The vessel of a reactor in a nuclear power plant is provided with a number of lead-through which, where necessary, are prepared for mounting of various sensors or equipment. A number of such lead-throughs are mostly not utilized and then usually closed and sealed by a conventional sealing flange. After a period of one or a few operating seasons, active material, for example in the form of solid corrosion products, accumulates in these lead-throughs sealed by sealing flanges in such a quantity that a noticeable radiation level can be detected from them. This results in drawbacks, especially since the mentioned lead-throughs are usually arranged at the bottom of the reactor vessel close to, inter alia drive devices, on which maintenance is continuously being performed, so personnel are regularly present in the area around the lead-throughs sealed by sealing flanges. Cleaning of a lead-through sealed by a sealing flange is admittedly possible, but must then be carried out by means of complex and difficult methods which, in addition, must be carried out from inside the reactor vessel. The object of the invention is to suggest a device intended to seal the lead-through which enables the lead-through, by means of a simple method, to be opened, washed clean and closed again. SUMMARY OF THE INVENTION With a device applied to close and seal a lead-through in a reactor vessel and designed according to the invention, the lead-through can, when necessary, be opened, cleaned, and closed again. A seal for a tubular lead-through designed according to the invention comprises at least a cone comprising a head, a rod-shaped part and a sealing surface arranged between the head and the rod-shaped part, wherein the cone is arranged with the head inserted into the lead-through, PA1 an annular flange attached to the lead-through and around the rod-shaped cone inserted into the lead-through for retaining the head of the cone in the lead-through, whereby the annular flange comprises a sealing surface, corresponding to the sealing surface of the cone, in the form of a seam with which the sealing surface arranged on the cone is adapted to make contact to close and seal the lead-through, PA1 means for fixing and retaining the sealing surface, provided on the cone, to the seat-shaped sealing surface of the annular flange, in the form of a sealing washer and a so-called detector nut comprising a teflon seal and an intermediate drainage, PA1 the flush pipe is connected to the cone, PA1 the flush pipe is attached and a force is applied which retains the cone in closed position with the sealing surface of the cone sealingly making contact with the seat-shaped sealing surface of the annular flange, PA1 the means comprising a neutron detector nut and a sealing washer, applied for fixing and retaining the cone, are detached and removed, PA1 temporarily during the installation of the flush bottle, when the attachment of the flush pipe has to be released, a nut divided into two parts is preferably mounted for fixing the cone, PA1 the attachment is detached such that the flush bottle can be moved up over the flush pipe, PA1 the flush pipe is again attached before the flush bottle is moved up and is connected to the annular flange, PA1 the drainage connection of the flush bottle is connected, PA1 the attachment is again detached and replaced by a member for operation of the flush pipe and the cone, and PA1 flushing water is connected to the flush pipe. wherein the rod-shaped part of the cone, in the end opposite to the head, comprises a member for connecting the cone to a flush pipe arranged in the form of an extension of the rod-shaped part of the cone. The first end of the above-mentioned flush pipe, which end is fixed to the cone by means of a connection member arranged on the cone, is provided with a number of holes and the second end of the flush pipe is provided with means for connection of flushing water and means for attaching and operating the flush pipe and the cone connected to the flush pipe. In its second end, the flush pipe is preferably arranged with a reduced diameter. The above-mentioned annular flange is provided in its free end with means for connecting a flush bottle arranged around the cone and the flush pipe. In its first end the flush bottle comprises means for connection to the annular flange corresponding to the connection member arranged on the annular flange, and in its second end it is provided with an internal sliding seal for sealing against the flush pipe and with a drainage connection. Before flushing clean a lead-through which is arranged with a seal according to the invention, the following steps are taken: While cleaning the detector housing, the flush pipe and the cone are operated by means of the connected operating member which is capable of moving the flush pipe up and down in the lead-through and to rotate the flush pipe. In connection with the cone being lifted by the operating member and leaving the sealing surface of the seat, the supply of flushing water through the flush pipe is opened after the flush holes of the flush pipe have been maneuvered into the lead-through. The flushing proceeds while operating the flush pipe until it can be determined by activity measurement that the lead-through has been cleaned from contaminated material. The cleaning can be made even more efficient by supplementing the equipment by means for mechanical cleaning by brushing, for example by means of a cleaning brush arranged between the flush pipe and the cone. After completed cleaning, the supply of flushing water is closed while at the same time the sealing surface of the cone is again fixed to the sealing surface of the seat and closes the seal. After that, the flush bottle and the flush pipe are removed while carrying out the above-mentioned operations in reverse order, the cone again being fixed in the seat and retained by means of a sealing washer and a neutron detector nut. |
abstract | A power module assembly includes a reactor core immersed in a coolant and a reactor vessel housing the coolant and the reactor core. An internal dry containment vessel submerged in liquid substantially surrounds the reactor vessel in a gaseous environment. During an over-pressurization event the reactor vessel is configured to release the coolant into the containment vessel and remove a decay heat of the reactor core through condensation of the coolant on an inner surface of the containment vessel. |
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060144181 | abstract | A fuel rod for a light water reactor comprises a cladding tube which comprises a zirconium alloy having a composition including 0.6 to 2.0% by weight of Nb, 0.5 to 1.5% by weight of Sn, 0.05 to 0.3% by weight of Fe, and the balance being Zr and incidental impurities; uranium oxide fuel pellets packed in the cladding tube; and end plugs comprising a zirconium alloy and closing both ends of the cladding tube. The cladding tube is sealed by TIG welding with the end plugs. Grain boundaries in each heat affected zone of the cladding tube, which are adjacent to a bead formed by TIG welding, have structural compositions including 4 to 30% by weight of Nb, and 0.9 to 20% by weight of Fe. |
claims | 1. A method for recovering operating margin in a nuclear reactor, the nuclear reactor including a steam generator, a Reactor Coolant System having a hot leg with a temperature, Thot, and a cold leg with a temperature, Tcold, a Reactor Trip System having an Over Temperature Delta Temperature trip function and an Over Power Delta Temperature trip function, and a control system, the method comprising:measuring a temperature in the hot leg of the Reactor Coolant System and providing a hot leg temperature signal representative thereof;filtering the hot leg temperature signal to smooth signal perturbations resulting from temperature fluctuations;measuring a temperature in the cold leg of the Reactor Coolant System and providing an unfiltered cold leg temperature signal representative thereof;establishing an Over Temperature Delta Temperature setpoint for the Reactor Trip System from the filtered hot leg temperature signal and the unfiltered cold leg temperature signal;establishing an Over Power Delta Temperature setpoint for the Reactor Trip System from the filtered hot leg temperature signal and the unfiltered cold leg temperature signal;measuring the difference between the filtered hot leg temperature signal and the unfiltered cold leg temperature signal;comparing the measured difference between the filtered hot leg temperature signal and the unfiltered cold leg temperature signal to said Over Temperature Delta Temperature setpoint;comparing the measured difference between the filtered hot leg temperature signal and the unfiltered cold leg temperature signal to said Over Power Delta Temperature setpoint; andtripping the nuclear reactor when the measured difference between the filtered hot leg temperature signal and the unfiltered cold leg temperature signal exceeds the Over Temperature Delta Temperature setpoint or the Over Power Delta Temperature setpoint. 2. The method of claim 1 wherein:tripping the nuclear reactor includes sending a trip signal to the reactor control system in order to initiate the reactor trip. 3. The method of claim 1 further comprising:providing a single filter in the hot leg of said Reactor Coolant System; andemploying said single filter to perform said step of smoothing signal perturbations resulting from temperature fluctuations only in the hot leg of said Reactor Coolant System. 4. The method of claim 1 further comprising:isolating the hot leg and cold leg temperatures, Thot, Tcold, for use in the Over Temperature Delta Temperature and Over Power Delta Temperature functions; andproviding separate dynamic compensations for the Over Temperature Delta Temperature and Over Power Delta Temperature functions based upon the values of said isolated Thot and Tcold. 5. The method of claim 1 wherein said nuclear reactor is a pressurized water reactor. |
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046719210 | abstract | Method intended to form a more or less compact bundle of flexible and oblong objects of reduced cross-section dimensions, such as fuel rods of a nuclear reactor, said objects forming, prior to compacting, an assembly wherein they occupy transversally spaced, parallel positions. According to the invention, this method is characterized in that there is arranged, in a generally vertical direction, a plurality of guiding tubes (2) of which the upper ends (2a) are arranged according to the initial disposition of said object assembly, and of which the lower ends (2b) are arranged according to the desired disposition, the dimension of said guiding tubes (2) being such that in each of them one of said objects may slide by means of gravity, and in that said assembly of objects is brought vertically on top of the plurality of guiding tubes, whereafter each object is introduced by its lower end in the upper end of one of said guiding tubes (2), allowing the assembly of said objects to slide downwardly. |
claims | 1. In a method for performing charged-particle-beam (CPB) projection-exposure including the steps of dividing a pattern, to be projection-exposed onto a sensitive substrate, into multiple exposure units each defining a respective portion of the pattern; sequentially illuminating the exposure units with a charged-particle (CP) illumination beam to form a respective CP patterned beam; and projecting the patterned beam onto a sensitive substrate to form images of the exposure units at respective locations on the substrate at which the images of the exposure units are stitched together to form an image of the pattern on the substrate, a method for projection-exposing an exposure unit requiring more than one exposure shot, comprising: (a) with respect to any exposure unit defining a feature requiring two separate exposure shots to fully transfer the feature to the substrate, dividing each of such exposure units into first and second complementary exposure units each defining respective feature portions; (b) defining boundaries around each first complementary exposure unit, and boundaries around each second complementary exposure unit, wherein the boundaries around the first complementary exposure units do not cross over the respective feature portions defined by the first complementary exposure units, and the boundaries around the second complementary exposure units do not cross over the respective feature portions defined by the second complementary exposure units, thereby causing the boundaries around the second complementary exposure units to be shifted relative to the boundaries around the first complementary exposure units; and (c) projection-exposing the first complementary exposure units and the second complementary exposure units onto respective locations on the substrate such that, when projection-exposing a second complementary exposure unit on an image of a respective first complementary exposure unit, the boundaries around the second complementary exposure unit are shifted relative to the boundaries around the respective first complementary exposure unit. 2. The method of claim 1 , wherein, in step (b), the first and second complementary exposure units are defined on at least one stencil reticle. claim 1 3. A segmented reticle for use in charged-particle-beam microlithography, the reticle comprising: (a) multiple exposure units each defining a respective portion of a pattern to be projection-exposed onto a sensitive substrate; (b) at least one exposure unit defining a feature requiring two separate exposures to fully transfer the feature to the substrate, said exposure unit being divided into first and second complementary exposure units each defining respective feature portions; (c) each first complementary exposure unit being surrounded by respective boundaries, and each second complementary exposure unit being surrounded by respective boundaries, wherein the boundaries around the first complementary exposure units do not cross over the respective feature portions defined by the first complementary exposure units, and the boundaries around the second complementary exposure units do not cross over the respective feature portions defined by the second complementary exposure units, thereby causing the boundaries around the second complementary exposure units to be shifted relative to the boundaries around the first complementary exposure units whenever the feature portions defined by the second complementary exposure unit are placed in registration with the feature portions defined by the respective first complementary exposure units. 4. The reticle of claim 3 , configured as a stencil reticle. claim 3 5. A charged-particle-beam microlithographic projection-exposure apparatus, comprising: (a) a substrate stage on which a sensitive substrate is mounted for CPB projection-exposure of the substrate; (b) a reticle according to claim 3 ; claim 3 (c) a reticle stage on which the reticle is mounted; (d) an illumination-optical system situated upstream of the reticle stage, the illumination-optical system being configured to sequentially illuminate the exposure units of the reticle with a CP illumination beam; and (e) a projection-optical system situated between the reticle stage and the substrate stage, the projection-optical system being configured to project, via a patterned beam propagating downstream of the reticle on the reticle stage, an image of the illuminated exposure unit onto a corresponding location on the sensitive substrate so as to stitch together the exposure-unit images and form an image of the pattern on the substrate. 6. The apparatus of claim 5 , wherein the reticle is a stencil reticle. claim 5 7. The apparatus of claim 5 , wherein the reticle comprises a first reticle portion defining the first complementary exposure units and a second reticle portion defining the second complementary exposure units. claim 5 8. The apparatus of claim 7 , wherein the first and second reticle portions are located on separate reticles. claim 7 9. A semiconductor-fabrication process, comprising the steps of: (a) preparing a wafer; (b) processing the wafer; and (c) assembling devices formed on the wafer during steps a and (b), wherein step (b) comprises a method for performing projection microlithography as recited in claim 1 . claim 1 10. A semiconductor-fabrication process, comprising the steps of: (a) preparing a wafer; (b) processing the wafer; and (c) assembling devices formed on the wafer during steps a and (b), wherein step (b) comprises the steps of (i) applying a resist to the wafer; (ii) exposing the resist; developing the resist; and (iv) annealing the resist; and step (ii) comprises providing a charged-particle-beam projection-exposure apparatus as recited in claim 5 ; and using the charged-particle-beam projection-exposure apparatus to expose the resist with the pattern defined on the reticle. claim 5 11. A semiconductor device produced by the method of claim 10 . claim 10 |
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047626470 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT A mixture of depleted resins of either a bead or powdered form and cellulose filter aid containing radioactive residue are drained of excess liquid. The mixture may be simply a drained slurry or can be completely dried. The mixture to be processed may be of a single type, such as an anion or cation resin or it may be a mixture of these different types. Acidic reactive groups remove positively charged ions/cations, from solution making it a cation resins. A commonly used acidic reactive group on ion ecxchange resin is the carboxyl radical, ##STR1## Another frequently used acidic reactive group is the sulfonic radical, ##STR2## As the solution is passed through the cation exchanger, cations replace the H on the resin. A resin having basic reactive groups such as hydroxyl, --OH, remove anions which are negatively charged in solution from the solution by exchange with the OH group. Other basic reactive groups such as primary amine, RNH.sub.2 ; secondary amine R.sub.2 NH; tertiary amine, R.sub.3 N; or quaternary ammonium, R.sub.4 N+, may also be utilized to create an anion resin. Filter aids employed in processing water from a nuclear power plant comprise a wide range of natural and man-made materials, having in common the ability to trap undissolved particles in the water. The filter aids to which the process of the present invention is applicable are reactive with the acidic or basic groups on the ion-exchange resin. The commonly used filter aid with powdered resins is plant cellulose, ##STR3## Other polymeric materials based on the cellulose chain but having other groups substituted for the H and OH groups are acceptable substitutes. In the preferred embodiment the resin contains cellulose filter aids that were used in processing water from the nuclear plant in the amount from about 40 w% to about 70 w% of the mixture. The process of volume reduction is relatively insensitive to the presence of some amount of crud that may result from ion exchange processing of the water. In short, the mixture may be unused or it may be exhausted resin and filter aid that contains extraneous material. Should the resin not contain cellulose filter aid, it would need to be added. Further, bead type resin would benefit from size reduction of the beads. Some benefit in volume reduction is obtained simply by compression resin with or without filter aid at ambient temperatures. The compaction may be in a single or multiple compression stages with a force ranging from 2000 psi to about 6500 psi. While pressure is being applied the resin occupies a compacted reduced volume. After the pressure is removed the resin then occupies a generally larger released volume. For compactions done at ambient temperatures volume reduction factors (that is, original volume divided by reduced volume) of the released resin ranges from approximately 1.2 to approximately 3. It has been found that an increase in the volume reduction factor can be obtained if the resins are dewatered and are heated during the compression. By applying heat, particles can be deformed further fo a given pressure causing them to come closer together, thus reducing the void percentage and thereby the total volume even more than by the simple application of high mechanical pressures. At a temperature of approximately 250.degree. C., for instance, the released volume reduction factor increases from approximately 1.75 to greater than 5. Any method of applying a compressive force to the ion exchange resin may be used. One method, that used in obtaining the experimental results, is the application of the compressive force by a ram press, such as a hydraulically driven piston inside a cylinder. A second method, the method deemed to be preferred in commercial applications, is the employment of an extrusin press. This method would allow the continuous processing of ion exchange resin by feeding the dewatered resin into one end of the extruder, heating, compressing, and removing the sintered material from the other end of the extruder. A third method of heating and compressing the resin is to use heated inert gas to apply isostatic pressure to the resin. The resin is volume reduced by the pressure and heat contained in a gas such as argon. The benefit realized for powdered resins mixed with cellulose filter aid representing 40 to 70 w% of the mixture which is heated to an elevated temperature of approximately 230.degree. C. during the compression and held at temperature and pressure for at least 20 minutes, is that in addition to increasing the volume reduction factor for powdered resins, the combination greatly increases the resins' stability in the presence of water by making it rewet stable. The rewet stable resin forms a monolith that is physically stable in the presence of water and will not fall apart. This gives a waste form that is more desirable for burial since any intrusion of water will not destroy the stability or integrity of the waste form and cause leaching of the radioactive material into the water. A similar benefit is expected for bead resins mixed with filter aid. EXPERIMENTAL RESULTS Several tests were performed on the process in a piston and cylinder apparatus using a calibrated testing machine to measure the force applied and the resultant deflection. The volume reduction factor was then calculated from the original volume of resin and the amount of deflection either under pressure or after release for various applied pressures. A temperature controlled clam shell type oven was also used around the piston cylinder assembly to allow heat to be applied during the compression. Both the piston and cylinder apparatus and the oven are of designs commonly known to those skilled in the art and the particulars are not critical to the process. Table I summarizes the results of the compaction process performed upon wet vacuum dewatered bead resin at ambient temperature. Tests No. 1, 2 and 3 were done with single compression and resulted in released volume reduction factors of up to 1.46. Test No. 4 compaction consisted of multiple compressions of the same sample of bead resin. In this case the released volume reduction factor achieved was 1.77. TABLE 1 ______________________________________ Wet, Vacuum Dewatered Bead Resin Test Compaction Volume Reduction Factor Temp. Rewet No. Force (psi) Compacted Released (.degree.C.) Stable ______________________________________ 1 3180 1.95 1.32 21 No 2 4650 2.05 1.36 21 No 3 5030 2.11 1.46 21 No 4 4580 2.13 1.54 21 4490 2.21 1.63 21 4330 2.25 1.69 21 4460 2.29 1.73 21 4360 2.29 1.75 21 6520 2.41 1.77 21 6270 2.45 1.77 21 No ______________________________________ Table 2 describes the results of compaction at ambient and elevated temperature on dry bead resin. Test 1 was a single compression, whereas Tests 2 and 3 were multiple compressions. In this series of tests, the resin samples were heated in tests 2 and 3. Heating to 125.degree. C. achieved a released volume reduction factor of 1.49, while heating to 250.degree. C. obtained a released volume reduction factor of 1.75. From this series of tests it is expected that worthwhile volume reductions can be obtained from minimum temperatures from about 100.degree. C. and minimum pressures from about 2000 psi. TABLE 2 ______________________________________ Dry Bead Resin Test Compaction Volume Reduction Factor Temp. Rewet No. Force (psi) Compacted Released (.degree.C.) Stable ______________________________________ 1 5030 1.35 1.19 21 No 2 4420 1.29 -- 125 4620 1.32 -- 125 4810 1.34 -- 125 4420 1.47 -- 125 4780 1.51 -- 125 4810 1.53 1.49 125 No 3 4420 -- -- 250 4490 -- -- 250 4420 -- -- 250 4360 -- 1.75 250 No ______________________________________ Table 3 describes the results of compaction at ambient temperature upon wet vacuum dewatered powdered resins with a filter aid. A released volume reduction factor of 2.16 was obtained with multiple compressions. TABLE 3 ______________________________________ Wet, Vacuum Dewatered Powdered Resin, with Filter-Aid Test Compaction Volume Reduction Factor Temp. Rewet No. Force (psi) Compacted Released (.degree.C.) Stable ______________________________________ 1 4650 2.51 1.20 21 No 2 4650 2.63 1.67 21 No 3 5030 2.38 1.50 21 No 4 4490 2.60 1.83 21 4330 2.62 1.86 21 6430 2.89 2.04 21 6490 3.12 2.07 21 6520 3.29 2.16 21 6430 3.50 2.16 21 6300 3.54 2.16 21 No ______________________________________ Finally, compaction of dry powdered resin with a filter aid was tested using both single and multiple compressions and heating the powdered resin to either 200 or 250.degree. C. before applying the compression force. A released volume reduction factor as high as 5.36 was obtained and, in addition, those samples heated to 250.degree. C. were rewet stable upon release. TABLE 4 ______________________________________ Dry Powdered Resin, with Filter-Aid Test Compaction Volume Reduction Factor Temp. Rewet No. Force (psi) Compacted Released (.degree.C.) Stable ______________________________________ 1 4520 3.38 2.98 21 No 2 4650 3.81 3.30 21 4360 3.91 -- 21 5480 4.14 3.45 21 4360 4.14 3.45 21 No 3 4620 -- 4.14 200 No 4 4300 -- 4.82 250 Yes 5 4460 -- 4.89 250 Yes 6 6330 -- 5.36 250 Yes 7 4420 -- 4.76 230 Yes ______________________________________ In summary, an advantage is gained by multiple compression of the resin leading to increased released volume reduction factors. The use of 230.degree. C. temperature during the compression of the powdered resins mixed with filter aid (cellulose) yielded a material that was rewet stable. It is expected that this property would also be obtainable for bead-type resins where the bead type resin is first size reduce and mixed with recommended amount of cellulose. It should be kept in mind that this process can be carried out in any type of equipment that can provide the desired compaction forces and the desired temperature. For example, another system that may be used is an isostatic press that utilizes an inert gas, such as argon, at elevated temperatures and pressures to compress the resin within a chamber, or the resin may be passed through an extrusion press for heating and compaction. |
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description | The present application is a Continuation of U.S. patent application Ser. No. 10/150,650, filed on May 17, 2002 now U.S. Pat. No. 7,006,595. The Ser. No. 10/150,650 application is a Continuation-In-Part of U.S. patent application Ser. No. 09/679,718, filed on Sep. 29, 2000 and issued as U.S. Pat. No. 6,438,199 B1,which is a Continuation-In-Part of U.S. patent application Ser. No. 09/305,017, filed on May 4, 1999 and issued as U.S. Pat. No. 6,198,793 B1, and which claimed priority of (a) International Patent Application PCT/EP00/07258, filed on Jul. 28, 2000, (b) German Patent Application No. 299 02 108.4, filed on Feb. 8, 1999, (c) German Patent Application No. 199 03 807.4, filed on Feb. 2, 1999, and (d) German Patent Application No. 198 19 898.1, filed on May 5, 1998. 1. Field of the Invention The invention concerns an illumination system for wavelengths ≦193 nm as well as a projection exposure apparatus with such an illumination system. In order to be able to further reduce the structural widths of electronic components, particularly in the submicron range, it is necessary to reduce the wavelengths of the light utilized for microlithography. Lithography with very deep UV radiation, so called VUV (Very deep UV) lithography or with soft x-ray radiation, so-called EUV (extreme UV) lithography, is conceivable at wavelengths smaller than 193 nm, for example. 2. Description of the Prior Art An illumination system for a lithographic device, which uses EUV radiation, has been made known from U.S. Pat. No. 5,339,346. For uniform illumination in the reticle plane and filling of the pupil, U.S. Pat. No. 5,339,346 proposes a condenser, which is constructed as a collector lens and comprises at least 4 pairs of mirror facets, which are arranged symmetrically. A plasma light source is used as the light source. In U.S. Pat. No. 5,737,137, an illumination system with a plasma light source comprising a condenser mirror is shown, in which an illumination of a mask or a reticle to be illuminated is achieved by means of spherical mirrors. U.S. Pat. No. 5,361,292 shows an illumination system, in which a plasma light source is provided, and the point plasma light source is imaged in an annular illuminated surface by means of a condenser, which has five aspherical mirrors arranged off-center. From U.S. Pat. No. 5,581,605, an illumination system has been made known, in which a photon beam is split into a multiple number of secondary light sources by means of a plate with concave raster elements. In this way, a homogeneous or uniform illumination is achieved in the reticle plane. The imaging of the reticle on the wafer to be exposed is produced by means of conventional reduction optics. A gridded mirror is precisely provided with equally curved elements in the illumination beam path. The contents of the above-mentioned patents are incorporated by reference. The invention provides an illumination system for microlithography that fulfills the requirements for advanced lithography with wavelength less or equal to 193nm. The system illuminates a structured reticle arranged in the image plane of the illumination system, which will be imaged by a projection objective onto a light sensitive substrate. In stepper-type lithography systems the reticle is illuminated with a rectangular field, wherein a pregiven uniformity of the light intensity inside the field is required, for example better than ±5%. In scanner-type lithography systems the reticle is illuminated with a rectangular or arc-shaped field, wherein a pregiven uniformity of the scanning energy distribution inside the field is required, for example better than ±5%. The scanning energy is defined as the line integral over the light intensity in the scanning direction. The shape of the field is dependent on the type of projection objective. All reflective projection objectives typically have an arc-shaped field, which is given by a segment of an annulus. A further requirement is the illumination of the exit pupil of the illumination system, which is located at the entrance pupil of the projection objective. A nearly field-independent illumination of the exit pupil is required. One embodiment of the present invention is an illumination system for scannertype microlithography along a scanning direction with a light source emitting a wavelength ≦193 nm. The illumination system includes a plurality of raster elements. The plurality of raster elements is imaged into an image plane of the illumination system to produce a plurality of images being partially superimposed on a field in the image plane. The field defines a non-rectangular intensity profile in the scanning direction. Another embodiment of the present invention is an illumination system for scannertype microlithography along a scanning direction with a light source emitting a wavelength ≦193 nm. This embodiment includes a first optical component having a plurality of first raster elements and a second optical component having a plurality of second raster elements. A first member of the plurality of first raster element deflects a first member of a plurality of incoming ray bundles to a first member of the plurality of second raster elements to provide an image of the first member of the plurality of first raster elements on a field in an image plane. A second member of the plurality of first raster element deflects a second member of a plurality of incoming ray bundles to a second member of the plurality of second raster elements to provide an image of the second member of the plurality of first raster elements on the field. The image of the first member of the plurality of first raster element and the image of the second member of the plurality of first raster elements are partially superimposed, and the field defines a non-rectangular intensity profile in the scanning direction. Another embodiment of an illumination system for microlithography with a wavelength ≦193 nm, in accordance with the present invention, includes a primary light source, a first optical component, a second optical component, an image plane, and an exit pupil. The first optical component transforms the primary light source into a plurality of secondary light sources that are imaged by the second optical component in the exit pupil. The first optical component includes a plurality of raster elements that are imaged into the image plane, producing a plurality of images being superimposed partially on a field in the image plane. The field defines a non-rectangular intensity profile in a scanning direction. The plurality of raster elements deflect a plurality of incoming ray bundles to produce a plurality of deflected ray bundles with deflection angles, and at least two of the deflection angles are different from one another. Another embodiment of an illumination system for microlithography with a wavelength ≦193 nm includes a primary light source, a first optical component, a second optical component, an image plane, and an exit pupil. The first optical component transforms the primary light source into a plurality of secondary light sources that are imaged by the second optical component in the exit pupil. The first optical component includes a plurality of first raster elements that are imaged into the image plane, producing a plurality of images being superimposed partially on a field in the image plane. The plurality of first raster elements deflect a plurality of incoming ray bundles to produce a plurality of deflected ray bundles with first deflection angles, and least two of the first deflection angles are different from one another. The first optical component also includes a plurality of second raster elements, where one of the plurality of first raster elements corresponds to one of the plurality of second raster elements. One of the plurality of first raster elements deflects one of the plurality of incoming ray bundles to the corresponding one of the plurality of second raster elements, and the plurality of second raster elements deflects the plurality of deflected ray bundles with second deflection angles to superimpose the plurality of images partially on the field. The field defines a non-rectangular intensity profile in a scanning direction. In another embodiment of the present invention, an illumination system for scannertype microlithography along a scanning direction with a light source emitting a wavelength ≦193 nm includes a first optical component with a first optical element having a plurality of first raster elements. The plurality of first raster elements deflect a plurality of incoming ray bundles to produce a plurality of deflected ray bundles with first deflection angles. The first optical component also has a second optical element having a plurality of second raster elements. One of the plurality of first raster elements corresponds to one of the plurality of second raster elements, and one of the plurality of first raster element deflects one of the plurality of incoming ray bundles to the corresponding one of the plurality of second raster elements. At least two of the first raster elements are arranged symmetric to an axis of symmetry, and the at least two of the first raster elements deflect the plurality of incoming ray bundles with the first deflection angles to the corresponding one of the plurality of second raster elements to fill an exit pupil of the illumination system nearly point symmetric to a center of the exit pupil. Another embodiment of an illumination system for microlithography with a wavelength ≦193 nm, in accordance with the present invention, includes a primary light source, a first optical component, a second optical component, an image plane, and an exit pupil. The first optical component transforms the primary light source into a plurality of secondary light sources that are imaged by the second optical component in the exit pupil. The first optical component includes a first optical element having a plurality of first raster elements that are imaged into the image plane, producing a plurality of images being superimposed at least partially on a field in the image plane, where the plurality of first raster elements deflect a plurality of incoming ray bundles to produce a plurality of deflected ray bundles with first deflection angles. At least two of the first deflection angles are different from one another. The first optical component also includes a second optical element having a plurality of second raster elements, where one of the plurality of first raster elements corresponds to one of the plurality of second raster elements. One of the plurality of first raster element deflects one of the plurality of incoming ray bundles to the corresponding one of the plurality of second raster elements. At least two of the plurality of first raster elements are adjacent to one another and have two corresponding second raster elements, and at least another one of the plurality of second raster elements is arranged between the two corresponding raster elements. An illumination system in accordance with the present invention can also be employed in a projection exposure apparatus for microlithography. Such a projection exposure apparatus includes, in addition to the illumination system, a reticle located at the image plane, a light-sensitive object on a support system, and a projection objective to image the reticle onto the light-sensitive object. Typical light sources for wavelengths between 100 nm and 200 nm are excimer lasers, for example an ArF-Laser for 193 nm, an F2-Laser for 157 nm, an Ar2-Laser for 126 nm and an NeF-Laser for 109 nm. For systems in this wavelength region refractive components of SiO2, CaF2, BaF2 or other crystallites are used. Since the transmission of the optical materials deteriorates with decreasing wavelength, the illumination systems are designed with a combination of refractive and reflective components. For wavelengths in the EUV wavelength region, between 10 nm and 20 nm, the projection exposure apparatus is designed as all-reflective A typical EUV light source is a Laser-Produced-Plasma-source, a Pinch-Plasma-Source, a Wiggler-Source or an Undulator-Source. The light of this primary light source is collected by a collector unit and directed to a first optical element, wherein the collector unit and the first optical element form a first optical component. The first optical element is organized as a plurality of first raster elements and transforms, together with the collector unit, the primary light source into a plurality of secondary light sources. Each first raster element corresponds to one secondary light source and focuses an incoming ray bundle, defined by all rays intersecting the first raster element, to the corresponding secondary light source. The secondary light sources are arranged in a pupil plane of the illumination system or nearby this plane. A field lens forming a second optical component is arranged between the pupil plane and the image plane of the illumination system to image the secondary light sources into an exit pupil of the illumination system, which corresponds to the entrance pupil of a following projection objective. The images of the secondary light sources in the exit pupil of the illumination system are therefore called tertiary light sources. The first raster elements are imaged into the image plane, wherein their images are at least partially superimposed on a field that must be illuminated. Therefore, they are known as field raster elements or field honeycombs. If the light source is a point-like source, the secondary light sources are also point-like. In this case the imaging of each of the field raster elements can be explained visually with the principle of a “camera obscura”, with the small hole of the camera obscura at the position of each corresponding secondary light source, respectively. To superimpose the images of the field raster elements in the image plane of the illumination system the incoming ray bundles are deflected by the field raster elements with first deflection angles, which are not equal for each of the field raster elements but at least different for two of the field raster elements. Therefore individual deflection angles for the field raster elements are designed. For each field raster element a plane of incidence is defined by the incoming and deflected centroid ray selected from the incoming ray bundle. Due to the individual deflection angles, at least two of the incidence planes are not parallel. In advanced microlithography systems the light distribution in the entrance pupil of a projection objective must fulfill special requirements such as having an overall shape or uniformity. Since the secondary light sources are imaged into the exit pupil, their arrangement in the pupil plane of the illumination system determines the light distribution in the exit pupil. With the individual deflection angles of the field raster elements a predetermined arrangement of the secondary light sources can be achieved, independent of the directions of the incoming ray bundles. For reflective field raster elements the deflection angles are generated by the tilt angles of the field raster elements. The tilt axes and the tilt angles are determined by the directions of the incoming ray bundles and the positions of the secondary light sources, to which the reflected ray bundles are directed. For refractive field raster element the deflection angles are generated by lenslets, which have a prismatic optical power. The refractive field raster elements can be lenslets with an optical power having a prismatic contribution or they can be a combination of a single prism and a lenslet. The prismatic optical power is determined by the directions of the incoming ray bundles and the positions of the corresponding secondary light sources. Given the individual deflection angles of the first raster elements, the beam path to the plate with the raster elements can be either convergent or divergent. The slope values of the field raster elements at the centers of the field raster elements has then to be similar to the slope values of a surface with negative power to reduce the convergence of the beam path, or with positive power to increase the divergence of the beam path. Finally the field raster elements deflect the incoming ray bundles to the corresponding secondary light sources having predetermined positions depending on the illumination mode of the exit pupil. The diameter of the beam path is preferably reduced after the collector unit to arrange filters or transmission windows with a small size. This is possible by imaging the light source with the collector unit to an intermediate image. The intermediate image is arranged between the collector unit and the plate with the field raster elements. After the intermediate image of the light source, the beam path diverges. An additional mirror to condense the diverging rays is not necessary due to the field raster elements having deflecting optical power For contamination reasons there is a free working distance between the light source and the collector unit, which results in considerable diameters for the optical components of the collector unit and also for the light beam. Therefore the collector unit has positive optical power to generate a converging ray bundle to reduce the beam diameter and the size of the plate with field raster elements. The convergence of the light rays can be reduced with the field raster elements, if the deflection angles are designed to represent a negative optical power. For the centroid rays impinging on the centers of the field raster elements, the collector unit and the plate with the field raster elements form a telescope system. The collector unit has positive optical power to converge the centroid rays towards the optical axis, wherein the field raster elements reduce the converging angles of the centroid rays. With this telescope system the track length of the illumination system can be reduced. Preferably, the field raster elements are tilted planar mirrors or prisms with planar surfaces, which are much easier to produce and to qualify than curved surfaces. This is possible, if the collector unit is designed to image the primary light source into the pupil plane of the illumination system, which would result in one secondary light source, if the field raster elements were omitted. The plurality of secondary light sources is generated by the plurality of field raster elements, which distribute the secondary light sources in the pupil plane according to their deflection angles. The positive optical power to focus the incoming ray bundles to the secondary light sources is completely provided by the collector unit. Therefore the optical distance between the image-side principal plane of the collector unit and the image plane of the collector unit is nearly given by the sum of the optical distance between the image-side principal plane of the collector unit and the plate with the field raster elements, and the optical distance between the plate with the field raster elements and the pupil plane of the illumination system. Due to the planar surfaces, the field raster elements do not influence the imaging of the primary light source into one secondary light source, except for the dividing of this one secondary light source into a plurality of secondary light sources due to the deflection angles. For point-like or spherical sources the collector unit has ellipsoidal mirrors or conical lenses with a first or second focus, wherein the primary light source is arranged in the first focus, and the secondary light source is arranged in the second focus of the collector unit. Dependent on the focusing optical power of the collector unit, the field raster elements can have a positive or negative optical power. If the focusing power of the collector unit is too low and the primary light source is imaged behind the pupil plane, the field raster elements are preferably concave mirrors or lenslets comprising positive optical power to generate the secondary light sources in or nearby the pupil plane. If the focusing power of the collector unit is too strong and the primary light source is imaged in front of the pupil plane, the field raster elements are preferably convex mirrors or lenslets comprising negative optical power to generate the secondary light sources in or nearby the pupil plane. The field raster elements are preferably arranged in a two-dimensional array on a plate without overlapping. For reflective field raster elements the plate can be a planar plate or a curved plate. To minimize the light losses between adjacent field raster elements they are arranged only with intermediate spaces between them, which are necessary for the mountings of the field raster elements. Preferably, the field raster elements are arranged in a plurality of rows having at least one field raster element and being arranged among one another. In the rows the field raster elements are put together at the smaller side of the field raster elements. At least two of these rows are displaced relative to one another in the direction of the rows. In one embodiment each row is displaced relative to the adjacent row by a fraction of a length of the field raster elements to achieve a regular distribution of the centers of the field raster elements. The fraction is dependent on the side aspect ratio and is preferably equal to the square root of the length of one field raster element. In another embodiment the rows are displaced in such a way that the field raster elements are illuminated almost completely. Preferably, only these field raster elements are imaged into the image plane, which is completely illuminated. This can be realized with a masking unit in front of the plate with the field raster elements, or with an arrangement of the field raster elements wherein 90% of the field raster elements are completely illuminated. It is advantageous to insert a second optical element with second raster elements in the light path after the first optical element with first raster elements, wherein one first raster element corresponds to one of the second raster elements. Therefore, the deflection angles of the first raster elements are designed to deflect the ray bundles impinging on the first raster elements to the corresponding second raster elements. The second raster elements are preferably arranged at the secondary light sources and are designed to image together with the field lens the first raster elements or field raster elements into the image plane of the illumination system, wherein the images of the field raster elements are at least partially superimposed. The second raster elements are called pupil raster elements or pupil honeycombs. To avoid damaging the second raster elements due to the high intensity at the secondary light sources, the second raster elements are preferably arranged defocused of the secondary light sources, but in a range from 0 mm to 10% of the distance between the first and second raster elements. For extended secondary light sources the pupil raster elements preferably have a positive optical power to image the corresponding field raster elements, which are arranged optically conjugated to the image plane. The pupil raster elements are concave mirrors or lenslets with positive optical power. The pupil raster elements deflect incoming ray bundles impinging on the pupil raster elements with second deflection angles in such a way that the images of the field raster elements in the image plane are at least partially superimposed. This is the case if a ray intersecting the field raster element and the corresponding pupil raster element in their centers intersects the image plane in the center of the illuminated field or nearby the center. Each pair of a field raster element and a corresponding pupil raster element forms a light channel. The second deflection angles are not equal for each pupil raster element. They are preferably individually adapted to the directions of the incoming ray bundles and the requirement to superimpose the images of the field raster elements at least partially in the image plane. With the tilt axis and the tilt angle for a reflective pupil raster element or with the prismatic optical power for a refractive pupil raster element the second deflection angle can be individually adapted. For point-like secondary light sources the pupil raster elements only have to deflect the incoming ray bundles without focusing the rays. Therefore the pupil raster elements are preferably designed as tilted planar mirrors or prisms. If both, the field raster elements and the pupil raster elements deflect incoming ray bundles in predetermined directions, the two-dimensional arrangement of the field raster elements can be made different from the two-dimensional arrangement of the pupil raster elements. Wherein the arrangement of the field raster elements is adapted to the illuminated area on the plate with the field raster elements, the arrangement of the pupil raster elements is determined by the kind of illumination mode required in the exit pupil of the illumination system. So the images of the secondary light sources can be arranged in a circle, but also in an annulus to get an annular illumination mode or in four decentered segments to get a Quadrupol illumination mode. The aperture in the image plane of the illumination system is approximately defined by the quotient of the half diameter of the exit pupil of the illumination system and the distance between the exit pupil and the image plane of the illumination system. Typical apertures in the image plane of the illumination system are in the range of 0.02 and 0.1. By deflecting the incoming ray bundles with the field and pupil raster elements a continuous light path can be achieved. It is also possible to assign each field raster element to any of the pupil raster elements. Therefore the light channels can be mixed to minimize the deflection angles or to redistribute the intensity distribution between the plate with the field raster elements and the plate with the pupil raster elements. Imaging errors such as distortion introduced by the field lens can be compensated for with the pupil raster elements being arranged at or nearby the secondary light sources. Therefore the distances between the pupil raster elements are preferably irregular. The distortion due to tilted field mirrors for example is compensated for by increasing the distances between the pupil raster elements in a direction perpendicular to the tilt axis of the field mirrors. Also, the pupil raster elements are arranged on curved lines to compensate for the distortion due to a field mirror, which transforms the rectangular image field to a segment of an annulus by conical reflection. By tilting the field raster elements the secondary light sources can be positioned at or nearby the distorted grid of the corresponding pupil raster elements. For reflective field and pupil raster elements the beam path has to be folded at the plate with the field raster elements and at the plate with the pupil raster elements to avoid vignetting. Typically, the folding axes of both plates are parallel. Another requirement for the design of the illumination system is to minimize the incidence angles on the reflective field and pupil raster elements. Therefore the folding angles have to be as small as possible. This can be achieved if the extent of the plate with the field raster elements is approximately equal to the extent of the plate with the pupil raster elements in a direction perpendicular to the direction of the folding axes, or if it differs less than ±10%. Since the secondary light sources are imaged into the exit pupil of the illumination system, their arrangement determines the illumination mode of the pupil illumination. Typically the overall shape of the illumination in the exit pupil is circular and the diameter of the illuminated region is in the order of 60%-80% of the diameter of the entrance pupil of the projection objective. The diameters of the exit pupil of the illumination system and the entrance pupil of the projection objective are in another embodiment preferably equal. In such a system the illumination mode can be changed in a wide range by inserting masking blades at the plane with the secondary light sources to get a conventional, Dipol or Quadrupol illumination of the exit pupil. All-reflective projection objectives used in the EUV wavelength region have typically an object field being a segment of an annulus. Therefore the field in the image plane of the illumination system in which the images of the field raster elements are at least partially superimposed has preferably the same shape. The shape of the illuminated field can be generated by the optical design of the components or by masking blades that have to be added nearby the image plane or in a plane conjugated to the image plane. The field raster elements are preferably rectangular. Rectangular field raster elements have the advantage that they can be arranged in rows being displaced against each other. Depending on the field to be illuminated they have a side aspect ratio in the range of 5:1 and 20:1. The length of the rectangular field raster elements is typically between 15 mm and 50 mm, the width is between 1 mm and 4 mm. To illuminate an arc-shaped field in the image plane with rectangular field raster elements the field lens preferably comprises a first field mirror for transforming the rectangular images of the rectangular field raster elements to arc-shaped images. The arc length is typically in the range of 80 mm to 105 mm, the radial width in the range of 5 mm to 9 mm. The transformation of the rectangular images of the rectangular field raster elements can be done by conical reflection with the first field mirror being a grazing incidence mirror with negative optical power. In other words, the imaging of the field raster elements is distorted to get the arc-shaped images, wherein the radius of the arc is determined by the shape of the object field of the projection objective. The first field mirror is preferably arranged in front of the image plane of the illumination system, wherein there should be a free working distance. For a configuration with a reflective reticle the free working distance has to be adapted to the fact that the rays traveling from the reticle to the projection objective are not vignetted by the first field mirror. The surface of the first field mirror is preferably an off-axis segment of a rotational symmetric reflective surface, which can be designed aspherical or spherical. The axis of symmetry of the supporting surface goes through the vertex of the surface. Therefore a segment around the vertex is called on-axis, wherein each segment of the surfaces which does not include the vertex is called off-axis. The supporting surface can be manufactured more easily due to the rotational symmetry. After producing the supporting surface the segment can be cut out with well-known techniques. The surface of the first field mirror can also be designed as an on-axis segment of a toroidal reflective surface. Therefore the surface has to be processed locally, but has the advantage that the surrounding shape can be produced before surface treatment. The incidence angles of the incoming rays with respect to the surface normals at the points of incidence of the incoming rays on the first field mirror are preferably greater than 70°, which results in a reflectivity of the first field mirror of more than 80%. The field lens comprises preferably a second field mirror with positive optical power. The first and second field mirror together image the secondary light sources or the pupil plane respectively into the exit pupil of the illumination system, which is defined by the entrance pupil of the projection objective. The second field mirror is arranged between the plane with the secondary light sources and the first field mirror. The second field mirror is preferably an off-axis segment of a rotational symmetric reflective surface, which can be designed aspherical or spherical, or an on-axis segment of a toroidal reflective surface. The incidence angles of the incoming rays with respect to the surface normals at the points of incidence of the incoming rays on the second field mirror are preferably lower than 25°. Since the mirrors have to be coated with multilayers for the EUV wavelength region, the divergence and the incidence angles of the incoming rays are preferably as low as possible to increase the reflectivity, which should be better than 65%. With the second field mirror being arranged as a normal incidence mirror the beam path is folded and the illumination system can be made more compact. To reduce the length of the illumination system the field lens comprises preferably a third field mirror. The third field mirror is preferably arranged between the plane with the secondary light sources and the second field mirror. The third field mirror has preferably negative optical power and forms together with the second and first field mirror an optical telescope system having a object plane at the secondary light sources and an image plane at the exit pupil of the illumination system to image the secondary light sources into the exit pupil. The pupil plane of the telescope system is arranged at the image plane of the illumination system. Therefore the ray bundles coming from the secondary light sources are superimposed in the pupil plane of the telescope system or in the image plane of the illumination system accordingly. The first field mirror has mainly the function of forming the arc-shaped field, wherein the telescope system is mainly determined by the negative third field mirror and the positive second field mirror. In another embodiment the third field mirror has preferably positive optical power to generate images of the secondary light sources in a plane between the third and second field mirror, forming tertiary light sources. The tertiary light sources are imaged with the second field mirror and the first field mirror into the exit pupil of the illumination system. The images of the tertiary light sources in the exit pupil of the illumination system are called in this case quaternary light sources. Since the plane with the tertiary light sources is arranged conjugated to the exit pupil, this plane can be used to arrange masking blades to change the illumination mode or to add transmission filters. This position in the beam path has the advantage to be freely accessible. The third field mirror is similar to the second field mirror preferably an off-axis segment of a rotational symmetric reflective surface, which can be designed aspherical or spherical, or an on-axis segment of a toroidal reflective surface. The incidence angles of the incoming rays with respect to the surface normals at the points of incidence of the incoming rays on the third field mirror are preferably lower than 25°. With the third field mirror being arranged as a normal incidence mirror the beam path can be folded again to reduce the overall size of the illumination system. To avoid vignetting of the beam path the first, second and third field mirrors are preferably arranged in a non-centered system. There is no axis of symmetry for the mirrors. An optical axis can be defined as a connecting line between the centers of the used areas on the field mirrors, wherein the optical axis is bent at the field mirrors depending on the tilt angles of the field mirrors. With the tilt angles of the reflective components of the illumination system the beam paths between the components can be bent. Therefore the orientation of the beam cone emitted by the source and the orientation of the image plane system can be arranged according to the requirements of the overall system. A preferable configuration has a source emitting a beam cone in one direction and an image plane having a surface normal that is oriented almost perpendicular to this direction. In one embodiment the source emits horizontally and the image plane has a vertical surface normal. Some light sources like undulator or wiggler sources emit only in the horizontal plane. On the other hand the reticle should be arranged horizontally for gravity reasons. The beam path therefore has to be bent between the light source and the image plane about almost 90°. Since mirrors with incidence angles between 30° and 60° lead to polarization effects and therefore to light losses, the beam bending has to be done only with grazing incidence or normal incidence mirrors. For efficiency reasons the number of mirrors has to be as small as possible. A very compact configuration of the illumination system can be designed, if the beam path from the plate with the pupil raster elements to the field lens is crossing the beam path from the collector unit to the plate with field raster elements. This is only possible, if the field raster elements and the pupil raster elements are reflective ones and are arranged on plates being tilted to achieve the crossing of the two beam paths. The crossing of the beam paths has the advantage that the beam path after the plate with the pupil raster elements has an angle in the range of 35° to 55° with respect to the beam path in front of the plate with the field raster elements. This was achieved with only two normal incidence reflections. By definition all rays intersecting the field in the image plane have to go through the exit pupil of the illumination system. The position of the field and the position of the exit pupil are defined by the object field and the entrance pupil of the projection objective. For some projection objectives being centered systems the object field is arranged off-axis of an optical axis, wherein the entrance pupil is arranged on-axis in a finite distance to the object plane. For these projection objectives an angle between a straight line from the center of the object field to the center of the entrance pupil and the surface normal of the object plane can be defined. This angle is in the range of 3° to 10° for EUV projection objectives. Therefore the components of the illumination system have to be configured and arranged in such a way that all rays intersecting the object field of the projection objective are going through the entrance pupil of the projection objective being decentered to the object field. For projection exposure apparatus with a reflective reticle all rays intersecting the reticle needs to have incidence angles greater than 0° to avoid vignetting of the reflected rays at components of the illumination system. In the EUV wavelength region all components are reflective components, which are arranged preferably in such a way, that all incidence angles on the components are lower than 25° or greater than 65°. Therefore polarization effects arising for incidence angles around an angle of 45° are minimized. Since grazing incidence mirrors have a reflectivity greater than 80%, they are preferable in the optical design in comparison to normal incidence mirrors with a reflectivity greater than 65%. The illumination system is typically arranged in a mechanical box. By folding the beam path with mirrors the overall size of the box can be reduced. This box preferably does not interfere with the image plane, in which the reticle and the reticle supporting system are arranged. Therefore it is advantageous to arrange and tilt the reflective components in such a way that all components are completely arranged on one side of the reticle. This can be achieved if the field lens comprises only an even number of normal incidence mirrors. The illumination system as described before can be used preferably in a projection exposure apparatus comprising the illumination system, a reticle arranged in the image plane of the illumination system and a projection objective to image the reticle onto a wafer arranged in the image plane of the projection objective. Both, reticle and wafer are arranged on a support unit, which allows the exchange or scan of the reticle or wafer. The projection objective can be a catadioptric lens, as known from U.S. Pat. No. 5,402,267 for wavelengths in the range between 100 nm and 200 nm. These systems have typically a transmission reticle. For the EUV wavelength range the projection objectives are preferably all-reflective systems with four to eight mirrors as known for example from U.S. Ser. No. 09/503,640 showing a six mirror projection lens. These systems have typically a reflective reticle. For systems with a reflective reticle the illumination beam path between the light source and the reticle and the projection beam path between the reticle and the wafer preferably interfere only nearby the reticle, where the incoming and reflected rays for adjacent object points are traveling in the same region. If there is no further crossing of the illumination and projection beam path it is possible to separate the illumination system and the projection objective except for the reticle region. The projection objective has preferably a projection beam path between the reticle and the first imaging element that is convergent toward the optical axis of the projection objective. Especially for a projection exposure apparatus with a reflective reticle the separation of the illumination system and the projection objective is easier to achieve. It shall be shown theoretically on the basis of FIGS. 1-20, how a system can be provided for any desired illumination distribution in a plane, which satisfies the requirements with reference to uniformity and telecentricity. In FIG. 1, a principle diagram of the beam path of a system with two plates with raster elements is illustrated. The light of the primary light source 1 is collected by means of a collector lens 3 and converted into a parallel or convergent light beam. The field raster elements 5 of the first raster element plate 7 decompose the light beam and produce secondary light sources at the site of the pupil raster elements 9. At the position of the secondary light sources the pupil plane of the illumination system is arranged. The field lens 12 images these secondary sources in the exit pupil of the illumination system or the entrance pupil of the subsequent projection objective forming tertiary light sources. The field raster elements 5 are imaged by the pupil raster elements 9 and the field lens 12 into the image plane of the illumination system. In this plane the reticle 14 is arranged. Such an arrangement is characterized by an interlinked beam path of field and pupil planes from the source up to the entrance pupil of the subsequent projection objective. For this, the designation “Köhler illumination” is also often selected. The illumination system according to FIG. 1 is considered segmentally below. If the light intensity and aperture distribution is known in the plane of the field raster elements, the system can be described independent of source type and collector unit. The field and pupil imaging are illustrated for the central pair of field raster element 20 and pupil raster element 22 in FIGS. 2A and 2B. The field raster element 20 is imaged on the reticle 14 or the mask by means of the pupil raster element 22 and the field lens 12. The geometric extension of the field raster element 20 determines the shape of the illuminated field in the reticle plane 14. The image scale is approximately given by the ratio of the distance from pupil raster element 22 to reticle 14 and the distance from field raster element 20 to pupil raster element 22. The field raster element 20 is designed such that an image of primary light source 1, a secondary light source, is formed at the site of pupil raster element 22. If the extension of the primary light source 1 is small, for example, approximately point-like, then all light rays run through the centers of the pupil raster elements 22. In such a case, an illumination device can be produced, in which the pupil raster element is dispensed with. As is shown in FIG. 2B, the task of field lens 12 consists of imaging the secondary light sources in the entrance pupil 26 of projection objective 24 forming tertiary light sources. With the field lens the field imaging can be influenced in such a way that it forms the arc-shaped field by control of the distortion. The imaging scale of the field raster element image is thus almost not changed. A special geometrical form of a field raster element 20 and a pupil raster element 22 is shown in FIG. 3. In the form of embodiment represented in FIG. 3, the shape of field raster element 20 is selected as a rectangle. Thus, the aspect ratio of the field raster element 20 corresponds approximately to the ratio of the arc length to the annular width of the required arc-shaped field in the reticle plane. The arc-shaped field is formed by the field lens 32, as shown in FIG. 4. Without the field lens 32, as shown in FIG. 3, a rectangular field is formed in the reticle plane. As shown in FIG. 4, one grazing-incidence field mirror 32 is used for the shaping of arc-shaped field 30. Under the constraint that the beam reflected by the reticle should not be directed back into the illumination system, one or two field mirrors 32 are required, depending on the position of the entrance pupil of the objective. If the principal rays run divergently into the objective that is not shown, then one field mirror 32 is sufficient, as shown in FIG. 4. In the case of principal rays entering the projection objective convergently, two field mirrors are required. The second field mirror must rotate the orientation of the ring 30. Such a configuration is shown in FIG. 5. In the case of an illumination system in the EUV wavelength region, all components must be reflective ones. Due to the high reflection losses at λ=10 nm−14 nm, it is advantageous that the number of reflections be kept as small as possible. In the construction of the reflective system, the mutual vignetting of the beams must be taken into consideration. This can occur due to construction of the system in a zigzag beam path or by operating with obscurations. The design process will be described below for the preparation of a design for an EUV illumination system with any illumination in a plane, as an example. The definitions necessary for the design process are shown in FIG. 6. First, the beam path is calculated for the central pair of raster elements. In a first step, the size of field raster elements 5 of the field raster element plate 7 will be determined. As indicated previously, the aspect ratio (x/y) results for rectangular raster elements from the shape of the arc-shaped field in the reticle plane. The size of the field raster elements is determined by the illuminated area A of the intensity distribution of the arbitrary light source in the plane of the field raster elements and the number N of the field raster elements on the raster element plate, which in turn is given by the number of secondary light sources. The number of secondary light sources results in turn from the uniformity of the field and pupil illumination. The raster element surface AFRE of a field raster element can be expressed as follows with xFRE, yFRE:AFRE=xFRE·yFRE=(xfield/yfield)·y2FRE whereby xfield, yfield describe the size of the rectangle, which establishes the arc-shaped field. Further, the following is valid for the number N of field raster elements:N=A/AFRE=A/[y2FRE·(xfield/yfield)].From this, there results for the size of the individual field raster element:yFRE=√{square root over (A/[N ·(xfield/yfield)])}andxFRE=(xfield/yfield)·yFRE The raster element size and the size of the rectangular field in the reticle plane establish the imaging scale βFRE of the field raster element imaging and thus the ratio of the distances z1 and z2.βFRE=xfield/yfield=z2/z1 The pregiven structural length L for the illumination system and the imaging scale βFRE of the field raster element imaging determine the absolute size of z1 and z2 and thus the position of the pupil raster element plate. The following is valid:z1=L/(1+βFRE)z2=z1·βFRE Then, z1 and z2 determine in turn the curvature of the pupil raster elements. The following is valid: R FRE = 2 · z 1 · z 2 z 1 + z 2 In order to image the pupil raster elements in the entrance pupil of the projection objective and to remodel the rectangular field into an arc-shaped field, a field lens comprising one or more field mirrors, preferably of toroidal form, are introduced between the pupil raster element plate and the reticle. By introducing the field mirrors, the previously given structural length is increased, since among other things, the mirrors must maintain minimum distances in order to avoid light vignetting. The positioning of the field raster elements depends on the intensity distribution in the plane of the field raster elements. The number N of the field raster elements is pregiven by the number of secondary light sources. The field raster elements will preferably be arranged on the field raster element plate in such a way that they cover the illuminated surfaces without mutually vignetting. In order to position the pupil raster elements, the raster pattern of the tertiary light sources in the entrance pupil of the projection objective will be given in advance. The tertiary light sources are imaged by the field lens counter to the direction of light into the secondary light sources. The aperture stop plane of this imaging is in the reticle plane. The images of the tertiary light sources give the (x, y, z) positions of the pupil raster elements which are arranged at the positions of the secondary light sources. The tilt and rotational angles remain as degrees of freedom for producing the light path between the field and pupil raster elements. If a pupil raster element is assigned to each field raster element in one configuration of the invention, then the light path will be produced by tilting and rotating field and pupil raster elements. Thereby the light beams, generated by the field raster elements, are deviated in such a way that the center rays of the light beams all intersect the optical axis in the reticle plane. The assignment of field and pupil raster elements can be made freely. One possibility for arrangement would be to assign spatially adjacent field and pupil raster elements. Thereby, the deflecting angles become minimal. Another possibility consists of homogenizing the intensity distribution in the pupil plane. This is made, for example, if the intensity distribution has a non-homogenous distribution in the plane of the field raster elements. If the field and pupil raster elements have similar positions, the distribution is transferred to the pupil illumination. By intermixing the light beams the light distribution in the pupil plane can be homogenized. Advantageously, the individual components of field raster element plate, pupil raster element plate and field mirrors of the illumination system are arranged in the beam path such that a beam path free of vignetting is possible. If such an arrangement has effects on the imaging, then the individual light channels and the field mirrors must be re-optimized. With the design process described above, illumination systems for EUV lithography are obtained for any light distribution at the plate with the field raster elements with two normal-incidence reflections for the field and pupil raster elements and one to two normal or grazing-incidence reflections for the field lens. These systems have the following properties: a. An homogeneous illumination of an arc-shaped field b. An homogeneous and field-independent pupil illumination c. The combining of the exit pupil of the illumination system and the entrance pupil of the projection objective d. The adjustment of a pregiven structural length e. The collection of nearly all light generated by the primary light source. Arrangements of field raster elements and pupil raster elements will be described below for one form of embodiment of the invention with field and pupil raster element plates. First, different arrangements of the field raster elements on the field raster element plate will be considered. The intensity distribution can be selected as desired. The introduced examples are limited to simple geometric shapes of the light distributions, such as circle, rectangle, or the coupling of several circles or rectangles, but the present invention is not limited on these shapes. The intensity distribution will be homogeneous within the illuminated region or have a slowly varying distribution. The aperture distribution will be independent of the position inside the light distribution. In the case of circular illumination A of field raster element plate 100, field raster elements 102 may be arranged, for example, in columns and rows, as shown in FIG. 7. As an alternative to this, the center points of the raster elements 102 can be distributed uniformly by shifting the rows over the surface, as shown in FIG. 8. The rows are displaced relatively to an adjacent row. This arrangement is better adapted to a uniform distribution of the secondary light sources in the pupil plane. A rectangular illumination A with a arrangement of the field raster elements 102 in rows and columns is shown in FIG. 9. A displacement of the rows, as shown in FIG. 10, leads to a more uniform distribution of the secondary light sources in the pupil plane. However, without tilting the field raster elements 102 the secondary light sources are arranged within a rectangle corresponding to the arrangement of the field raster elements 102. Since the pupil raster elements are typically arranged inside a circle to get a circular illumination of the exit pupil of the illumination system, it is necessary to tilt the field and pupil raster elements to produce a continuous light path between the corresponding field and pupil raster elements. If illumination A of field raster element plate 100 comprises several circles, A1, A2, A3, A4, for example by coupling several sources, then, intermixing is insufficient with an arrangement of the raster elements 102 with a high (x/y)-aspect ratio in rows and columns according to FIG. 11. A more uniform illumination is obtained by shifting the raster element rows, as shown in FIG. 12. FIGS. 13 and 14 show the distribution of field raster elements 102 in the case of combined illumination from the individual rectangles A1, A2, A3, A4. Now, for example, arrangements of the pupil raster elements on the pupil raster element plate will be described. In the arrangement of pupil raster elements, two points of view are to be considered: 1. For minimizing the tilt angle of field and pupil raster elements for producing the light path, it is advantageous to maintain the arrangement of field raster elements. This is particularly advantageous with an approximately circular illumination of the field raster element plate. 2. For homogeneous filling of the pupil, the tertiary light sources, which are images of the secondary light sources, will be distributed uniformly in the entrance pupil of the projection objective. This can be achieved by providing a uniform raster pattern of tertiary light sources in the entrance pupil of the projection objective. These are imaged counter to the direction of light with the field lens in the plane of the pupil raster elements and determine in this way the ideal site of the pupil raster elements, which are arranged nearby the secondary light sources. If the field lens is free of distortion, then the distribution of the pupil raster elements corresponds to the distribution of the tertiary light sources. However, since the field lens forms the arc-shaped field, distortion is purposely introduced. This does not involve rotational-symmetric distortion, but involves the bending of horizontal lines into arcs. In the ideal case, the y distance of the arcs remains almost constant. Real grazing-incidence field mirrors, however, also show an additional distortion in the y-direction. A raster 110 of tertiary light sources 112 in the entrance pupil of the projection objective, which is also the exit pupil of the illumination system, is shown in FIG. 15, as it had been produced for distortion-free field lens imaging. The arrangement of the tertiary light sources 112 corresponds precisely to the pregiven arrangement of pupil raster elements. If the field lenses are utilized for shaping the arc-shaped field, as in FIG. 16, then the tertiary light sources 112 lie on arcs 114. If the pupil raster elements of individual rows are placed on the arcs that compensate for the distortion, then one can place the tertiary light sources again on a regular raster. If the field lens also introduces distortion in the y-direction, then the distribution of the tertiary light sources is distorted in the y-direction, as shown in FIG. 17. This effect can be compensated by arranging the pupil raster elements on a grid that is distorted in y-direction. The extent of the illuminated area onto the field raster element plate is determined by design of the collector unit. The extent of the illuminated area onto the pupil raster element plate is determined by the structural length of the illumination system and the aperture in the reticle plane. As described above, the two surfaces must be fine-tuned to one another by rotating and tilting the field and pupil raster elements. For illustration, the design of the illumination system will be explained with refractive elements. The examples, however, can be transferred directly to reflective systems. Various configurations can be distinguished for a circular illumination of field raster element plates, as presented below. If a converging effect is introduced by tilting the field raster elements, and a diverging effect is introduced by tilting the pupil raster elements, then the beam cross section can be reduced. The tilt angles of the individual raster elements are determined by tracing the center rays for each pair of raster elements. The system acts like a telescope-system for the central rays, as shown in FIG. 18. How far the field raster elements must be tilted, depends on the convergence of the impinging beam. If the convergence is adapted to the reduction of the beam cross section, the field raster elements can be arranged onto a planar substrate without tilting the field raster elements. A special case results, if the convergence between the field and the pupil raster element plate corresponds to the aperture NAfield at the reticle, as shown in FIG. 19. No diverging effect must be introduced by the pupil raster elements, so they can be utilized without tilting the pupil raster elements. If the light source also has a very small etendue, the pupil raster element can be completely dispensed with. A magnification of the beam cross section is possible, if diverging effect is introduced by tilting of the field raster elements, and collecting effect is introduced by tilting the pupil raster elements. The system operates like a retro-focus system for the central rays, as shown in FIG. 20. If the divergence of the impinging radiation corresponds to the beam divergence between field and pupil raster elements, then the field raster elements can be used without tilting the field raster elements. Instead of the circular shape that has been described, rectangular or other shapes of illumination A of the field raster element plate are possible. The following drawings describe one form of embodiment of the invention, in which a pinch-plasma source is used as the light source of the EUV illumination system. The principal construction without field lens of such a form of embodiment is shown in FIG. 21; FIG. 22 shows the abbreviations necessary for the system derivation, whereby for better representation, the system was plotted linearly and mirrors were indicated as lenses. An illumination system with pinch-plasma source 200 as primary light source, as shown in FIG. 21, comprises a light source 200, a collector mirror 202, which collects the light and reflects it to the field raster element plate 204. By reflection at the field raster elements, the light is directed to the corresponding pupil raster elements of pupil raster element plate 206 and from there to reticle 208. The pinch-plasma source is an expanded light source (approximately 1 mm) with a directional radiation in a relatively small steradian region of approximately Ω=0.3 sr. Based on the etendue of the primary light source, a pupil raster element plate 206 is used. The following specifications are used, for example, for an illumination system for EUV lithography: a. Arc-shaped field: Radius Rfield=100 mm, segment-angle 60°, field width ±3.0 mm, which corresponds to a rectangular field of 105 mm×6 mm b. Aperture at the reticle: NAfield=0.025 c. Aperture at the source: NAsource=0.3053 d. Structural length L=1400.0 mm e. Number of field raster elements, which find place in an x-row: 4 f. z1=330.0 mm With the following equations the optical design of the illumination system can be derived with the pregiven numbers: NA field = D FRE / 2 L ⇒ D FRE = 2 · L · NA field D PRE x FRE = 4.0 ⇒ x FRE = D PRE 4.0 β FRE = x field x FRE = z 4 z 3 ⇒ β FRE = x field x FRE ⇒ z 4 = z 3 · β FRE L = z 3 + z 4 ⇒ z 3 = L 1 + β FRE NA ′ = D FRE / 2 z 3 ⇒ NA ′ = D FRE / 2 z 3 tan ( θ ) = - ( 1 - Ex ) · sin ( θ ′ ) 2 Ex - ( 1 - Ex ) · cos ( θ ′ ) ⇒ Ex = f ( NA source , NA ′ ) Ex col = ( sk - s 1 sk + s 1 ) 2 = ( z 2 - z 1 z 2 + z 1 ) 2 ⇒ z 2 = z 1 · 1 + Ex col 1 - Ex col Ex col = 1 - R col a ⇒ R col = z 1 + z 2 2 · ( 1 - Ex col ) 2 R PRE = 1 z 3 + 1 z 4 ⇒ R PRE = 2 · z 3 · z 4 z 3 + z 4 DFRE: diameter of the plate with the field raster elements xFRE: length of one field raster element yFRE: width of one field raster element βFRE: magnification ratio of the field raster elements DPRE: diameter of the plate with the pupil raster elements Rcol: Radius of the elliptical collector Excol: conical constant of the elliptical collector NA′: aperture after the collector mirror With the pregiven specifications the following system parameters can be calculated: D FRE = 2 · L · NA field = 2 · 1400 mm · 0.025 = 70.0 mm x FRE = D FRE 4.0 = 70.0 mm 4.0 = 17.5 mm y FRE = 1.0 mm β FRE = x field x FRE = 105.0 mm 17.5 mm = 6.0 z 3 = L 1 + β FRE = 1400.0 mm 1 + 6.0 = 200.0 mm z 4 = z 3 · β FRE = 200.0 mm · 6.0 = 1200.0 mm NA ′ = D DRE / 2 z 3 = 70.0 mm / 2 200.0 mm = 0.175 Ex col = f ( NA source , NA ′ ) = 0.078 z 2 = z 1 · 1 + Ex col 1 - Ex col = 100.0 mm · 1 + 0.078 1 - 0.078 = 585.757 mm R col = z 1 + z 2 2 · ( 1 - Ex col ) = 330.0 mm + 585.757 mm 2 · ( 1 - 0.078 ) = 422.164 mm R PRE = 2 · z 3 · z 4 z 3 + z 4 = 2 · 200 · 1200 200 + 1200 = 342.857 mm The total system with the previously indicated dimensions is shown in FIG. 23 up to the reticle plane 208 in the yz section. The central and the two marginal rays are drawn in. Secondary light sources are produced at the plate with the pupil raster elements 206 by the field raster elements 204. The pupil plane of the illumination system is arranged at the plate with the pupil raster elements 206. The total system is shown in FIG. 24 with an x-z fan of rays, which impinge on the central field raster element. FIGS. 25 and 26 show the illumination of the reticle with the rectangular field (−52.5 mm<xfield<+52.5 mm; −3.0 mm<xfield<+3.0 mm). FIG. 25 shows a contour plot, FIG. 26 a 3D presentation. The images of the field raster elements are optimally superimposed in the reticle plane also in the case of the extended secondary light sources, which are produced by the pinch-plasma source, since a pupil raster element plate is used. In comparison to this, the illumination of the reticle without pupil raster element plate is shown in contour lines and 3D representation in FIGS. 27 and 28. The field raster elements are not imaged sharply. This can be due for example to the extended secondary light sources. A similar illumination in the field plane can also be achieved if not all of the first raster elements have the same size, e.g. they have a different extension in y-direction, which is also called the scanning direction. In case the second raster elements have an optical effect another possibility to achieve such an illumination in the filed plane is using second raster elements having different optical power. FIG. 29 shows an intensity profile parallel to the y-axis for x=0.0 for ideally superimposed images of the first raster elements in the image plane. This can be achieved in the case of extended secondary light sources by introducing a pupil raster element plate with second raster elements. In case the images of the first raster elements are ideally superimposed a almost ideal rectangular profile is formed in scanning direction. In case the images are not ideally superimposed e.g. because the secondary light sources are extended and no pupil facets or so called second raster elements are used the profile decomposes and forms a non-rectangular intensity profile in scanning direction. This is shown in FIG. 29 as dotted lines. The gradient of the intensity profile depicted in dashed lines is less than 100% per millimeter. FIG. 30 shows the scanning energy distribution as a function of the field height. The scan energy is defined as the line integral in scanning direction over the intensity distribution in the reticle plane. The homogeneous scanning energy distribution can be clearly recognized. In FIG. 31, the illumination of the exit pupil is shown for a object point in the center of the illuminated field. The x- and y-axis represent not the extent in “mm”, but in the sine of the ray angles in the reticle plane. Corresponding to the arrangement of the pupil raster elements, tertiary light sources 3101 are produced in the exit pupil of the illumination system. The maximum aperture amounts to NAfield=0.025. In FIG. 31, 18 tertiary light sources are shown with sin(ix)=0. The total energy of the 18 tertiary light sources with sin(ix)=0 is plotted in FIG. 32. The tertiary light source 3101 has the number 1 in FIG. 32, the tertiary light source 3105 the number 18. The intensity distribution in the exit pupil has a y-tilt due to the distortion errors introduced by the mirrors tilted about the x-axis. The total energy of the individual tertiary light sources can be adjusted via the reflectivity of the individual raster elements, so that the energy of the tertiary light sources can at least be controlled in a rotational symmetric manner. Another possibility to get a rotational symmetric intensity distribution in the exit pupil of the illumination system is a collector mirror with a spatial dependent reflectivity. The forms of embodiment of the invention, which use different light sources, for example, are described below. In FIGS. 33-39, another form of embodiment of the invention is explained with a laser-plasma source as the primary light source. If the field raster elements are not tilted, then the aperture in the reticle plane (NAtheoretical=0.025) is given in advance by the ellipsoid or collector mirror. Since the distance from the light source to the ellipsoid or collector mirror should amount to at least 100 mm in order to avoid contaminations, a rigid relationship between structural length and collection efficiency results, as presented in the following table: TABLE 1Collection efficiency π (0°-90°):0°: Beam cone is emittedhorizontallyStructuralCollection90°: Rays are is emitted in alength Langle θtorus with a mean angle of 90°.1000 mm14.3° 2%-12%2000 mm28.1° 6%-24%3000 mm41.1°12%-35%4000 mm53.1°20%-45%5000 mm90.0°50%-71%As can be seen from this, the collection efficiency for a structural length of 3000 mm is maximum 35%. In order to achieve high collection efficiencies for justifiable structural lengths, in the particularly advantageous form of embodiment of the invention according to FIGS. 35-39, the illumination system comprises a telescope system. In the represented form of embodiment, a laser-plasma source is used as the primary light source, whereby the field raster element plate is arranged in the convergent beam path of a collector mirror. In order to reduce the structural length of the illumination system, the illumination system is formed as a telescope system (tele-system). One form of embodiment for forming such a telescope system consists of arranging the field raster elements of the field raster element plate on a collecting surface, and of arranging the pupil raster elements of the pupil raster element plate on a diverging surface. In this way, the surface normal lines of the raster element centers are adapted to the surface normal lines of the supporting surface. As an alternative to this, one can superimpose prismatic components for the raster elements on a planar plate. This would correspond to a Fresnel lens as a carrier surface. The above-described tele-raster element condenser thus represents a superimposition of the classical telescope system and the raster element condenser. The compression of the diameter of the field raster element plate to the diameter of the pupil raster element plates is possible until the secondary light sources overlap. In FIGS. 33 to 36, different arrangements are shown schematically, from which the drastic reduction in structural length, which can be achieved with a telescope system, becomes apparent. FIG. 33 shows an arrangement with collector mirror 300 and laser-plasma light source 302. With a arrangement of collector mirror, plate 304 with non-tilted field raster elements and plate 306 with non-tilted pupil raster elements, as shown in FIG. 34, the structural length can be shortened only by the zigzag light path. Since the etendue of a point-like source is approximately zero, the field raster element plate 304, is, in fact, fully illuminated, but the pupil raster element plate 306 is illuminated only with individual intensity peaks. However, now if the raster elements are introduced onto curved supporting surfaces, i.e., the system is configured as a telescope system with a collecting mirror and a diverging mirror, as shown in FIG. 35, then the structural length can be shortened. In the case of the design according to FIG. 36, the individual raster elements are arranged tilted on a planar carrier surface. The pupil raster elements of the pupil raster element plate have the task of imaging the field raster elements into the reticle in the case of expanded secondary light sources and to superimpose these images. However, if a sufficiently good point-like light source is present, then the pupil raster element plate is not necessary. The field raster elements can then be introduced either onto the collecting or onto the diverging tele-mirror. If the field raster elements are arranged on the collecting tele-mirror, they can be designed as either concave or planar mirrors. The field raster elements on the diverging telescope mirror can be designed as convex, concave or planar mirrors. Collecting raster elements lead to a real pupil plane; diverging raster elements lead to a virtual pupil plane. Collector lens 300 and tele-raster element condenser or tele-system 310 produce the pregiven rectangular field illumination of 6 mm×105 mm with correct aperture NAfield=0.025 in the image plane of the illumination system. As in the previous examples, with the help of one or more field lenses 314 arranged between tele-raster element condenser 310 and reticle 316, the arc-shaped field is formed and the exit pupil of the illumination system is arranged at the entrance pupil of the projection objective. An interface plane for the design of the field lens 314 is the plane of the secondary light sources. These secondary light sources must be imaged by the field lens 314 in the entrance pupil of the projection objective forming tertiary light sources. The pupil plane of this imaging is in the reticle plane, in which the arc-shaped field must be produced. In FIG. 37, a form of embodiment of the invention with only one field mirror 314 is shown. In the form of embodiment with one field mirror, the arc-shaped field can be produced and the entrance pupil of the illumination system can be arranged at the exit pupil of the projection objective. Since reticle 316, however, is illuminated with chief ray angles about 2.97°, there is the danger that the light beam will run back into the illumination system. It is provided in a particularly advantageous form of embodiment to use as field mirrors two grazing-incidence mirrors as shown in FIG. 38. This way, the orientation of the arc-shaped field is inverted and the light beam leaves the illumination system “behind” the field lens 314. With such a configuration the illumination system can be well separated from the projection objective. By using two field mirrors, one also has more degrees of freedom in order to adjust telecentricity and uniformity of the light distribution. The design of the illumination systems will now be described on the basis of examples of embodiment, whereby the numerical data not will represent a limitation of the system according to the invention. In the first example of embodiment the illumination system comprises a collector unit, a diverging mirror and a collecting mirror forming a telescope system as well as field lenses, whereby the raster elements are introduced only onto the collecting mirror. All raster elements are identical and lie on a curved supporting surface. The parameters used are represented in FIG. 39 and are selected as follows below: a. Arc-shaped field: Rfield=100 mm, segment=60°, field height±3.0 mm. b. Position of the entrance pupil (Distance between reticle plane and entrance pupil of the projection objective): zEP=1927.4 mm. This corresponds to a principal ray angle of iPB=2.97° for y=100 mm. c. Aperture at the reticle: NAfield=0.025. d. Aperture at the source: NAsource=0.999. e. Distance between the source and the collector mirror: d1=100.0 mm. f. Field raster element size: yFRE=1, xFRE=17.5 mm. g. d3=100 mm. h. Compression factor DFRE/DPRE=4:1. i. Tilt angle α of the grazing-incidence mirrors, α=80°. j. Collector mirror is designed as an ellipsoid with Rcol and Excol. k. Curvatures of the supporting surfaces R2 and R3: spherical. l. Curvature RFRE of the field raster element: spherical. m. The Field mirrors are torical mirrors without concical contributions having the curvatures: R4x, R4y, R5x, R5y. FIG. 40 shows an arrangement of a illumination system with collector mirror 300, whereby the first tele-mirror of the telescope system 310 is not structured with field raster elements. The two tele-mirrors of the telescope system 310 show a compression factor of 4:1. The shortening of the structural length due to the telescope system 310 is obvious. With the telescope system, the structural length amounts to 852.3 mm, but without the telescope system, it would amount to 8000.0 mm. In FIG. 41, a fan of rays is shown in the x-z plane for the system according to FIG. 40. Since there are no field raster elements the light source 302 is imaged into the reticle plane. FIG. 42 in turn represents a fan of rays in the x-z plane, whereby the mirrors of the system according to FIG. 40 are now structured and have field raster elements. Secondary light sources are formed on the second mirror of the telescope system 310 due to the field raster elements on the first mirror of the telescope system 310. In the illuminated field, the light beams from the several field raster elements are correctly overlaid, and a strip with −52.5 mm<xfield<+52.5 mm is homogeneously illuminated. In FIG. 43, the total system up to the entrance pupil 318 of the projection objective is shown. The total system comprises: primary light source 302, collector mirror 300, tele-raster element condenser 310, field mirrors 314, reticle 316 and entrance pupil of the projection objective 318. The drawn-in marginal rays 320, 322 impinge on the reticle and are drawn up to the entrance pupil 318 of the projection objective. FIG. 44 shows an x-z fan of rays of a configuration according to FIG. 43, which passes through the central field raster element 323. This pencil is in fact physically not meaningful, since it would be vignetted by the second tele-mirror, but shows well the path of the light. One sees on field mirrors 314 how the orientation of the arc-shaped field is rotated through the second field mirror. The rays can run undisturbed into the projection objective (not shown) after reflection at reticle 316. FIG. 45 shows a fan of rays, which passes through the central field raster element 323 as in FIG. 44, runs along the optical axis and is focused in the center of the entrance pupil. FIG. 46 describes the illumination of the reticle field with the arc-shaped field produced by the configuration according to FIGS. 40 to 45 (Rfield=100 mm, segment=60°, field height ±3.0 mm). In FIG. 47, the scanning energy is shown for an arrangement according to FIGS. 40 to 46. The scanning energy varies between 95% and 100%. The uniformity thus amounts to ±2.5%. In FIG. 48, the pupil illumination for an object point in the center of the illuminated field is shown. The ray angles are referred to the centroid ray. Corresponding to the distribution of the field raster elements, circular intensity peaks IP result in the pupil illumination. The obscuration in the center M is caused by the second tele-mirror. The illumination system described in FIGS. 31 to 48 has the advantage that the collecting angle can be increased to above 90°, since the ellipsoid can also enclose the source. Further, the structural length can be adjusted by the tele-system. A reduction of structural length is limited due to the angular acceptance of the coating with multilayers and the imaging errors of the surfaces with a high optical power. For point-like light sources, for example, a laser-plasma sources with a diameter ≦50 μm, an arrangement can be produced with only one plate with field raster elements. Pupil raster elements are in this case not necessary. Then the field raster elements can be introduced onto collecting mirror 350 of the tele-system or onto the diverging second tele-mirror 352. This is shown in FIGS. 48A-48C. The introduction onto the second tele-mirror 352 has several advantages: In the case of collecting field raster elements, a real pupil plane is formed in “air”, which is freely accessible, as shown in FIG. 48A. In the case of diverging field raster elements, in fact a virtual pupil plane is formed, which is not accessible, as shown in FIG. 48B. The negative focal length of the field raster elements, however, can be increased. In order to avoid an obscuration, as shown in FIG. 48C, the mirrors of the tele-system 350, 352, can be tilted toward one another, so that the light beam will be not vignetted by the components. A second example of embodiment for a illumination system will be described below, which comprises a plate with planar raster elements. The system is particularly characterized by the fact that the collector unit and the plate with the field raster elements form a telescope system. The converging effect of the telescope system is then completely transferred onto the collector mirror, wherein the diverging effect is caused by the tilt angles of the field raster elements. Such a system has a high system efficiency of 27% with two normal-incidence mirrors (reflectivity≈65%) for the collector mirror and the plate with the field raster elements and two grazing-incidence mirrors (reflectivity≈80%) for the two field mirrors. Further, a large collecting efficiency can be realized, whereby the collecting steradian amounts to 2π, but which can still be increased. Based on the zigzag beam path, there are no obscurations in the pupil illumination. In addition, in the described form of embodiment, the structural length can be easily adjusted. The collector or ellipsoid mirror collects the light radiated from the laser-plasma source and images the primary light source on a secondary light source. A multiple number of individual planar field raster elements are arranged in a tilted manner on a supporting plate. The field raster elements divide the collimated light beam into partial light beams and superimpose these in the reticle plane. The shape of the field raster elements corresponds to the rectangular field of the field to be illuminated. Further, the illumination system has two grazing-incidence toroid mirrors, which form the arc-shaped field, correctly illuminate the entrance pupil of the projection objective, and assure the uniformity of the light distribution in the reticle plane. In contrast to the first example of embodiment of a tele-system with collector unit as well as a telescope system formed with two additional mirrors, in the presently described form of embodiment, the laser-plasma source alone is imaged by the ellipsoid mirror in the secondary light source. This saves one normal-incidence mirror and permits the use of planar field raster elements. Such a savings presupposes that no pupil raster elements are necessary, i.e., the light source is essentially point-like. The design will be described in more detail on the basis of FIGS. 49-51. FIG. 49 shows the imaging of the laser-plasma source 400 through ellipsoid mirror 402. One secondary light source 410 is formed. In the imaging of FIG. 50, a tilted planar mirror 404 deflects the light beam to the reticle plane 406. In the imaging of FIG. 51, tilted field raster elements 408 are dividing the light beam and superimpose the partial light bundles in the reticle plane 406. In this way, a multiple number of secondary light sources 410 are produced, which are distributed uniformly over the pupil plane. The tilt angles of the individual field raster elements 408 correspond, at the center points of the field raster elements, approximately to the curvatures of a hyperboloid, which would image the laser-plasma source 400 in the reticle plane 406, together with the ellipsoid mirror 402. The diverging effect of the telescope system is thus introduced by the tilt angles of the field raster elements. In FIG. 52, the abbreviations are drawn in, as they are used in the following system derivation. For better presentation, the system was drawn linearly with refractive components. The following values are used as a basis for the example of embodiment described below, without the numerical data being seen as a limitation: a. Arc-shaped field radius: Rfield=100 mm, segment angle 60°, field width ±3.0 mm, which corresponds to a rectangular field of 105 mm×6 mm. b. Aperture at the reticle: NAfield=0.025. c. Aperture at the source: NAsource=0.999. d. z1=100.0 mm. e. Structural length L=z3+z4=1400 mm. f. Number of field raster elements within an x-row=4. With the following equations the basic configuration of the illumination system can be derived: NA field = D FRE / 2 L ⇒ D FRE = 2 · L · NA field D PRE x FRE = 4.0 ⇒ x FRE = D PRE 4.0 β FRE = x field x FRE = z 4 z 3 ⇒ β FRE = x field x FRE ⇒ z 4 = z 3 · β FRE L = z 3 + z 4 ⇒ z 3 = L 1 + β FRE NA ′ = D FRE / 2 z 3 ⇒ NA ′ = D FRE / 2 z 3 tan ( θ ) = - ( 1 - Ex ) · sin ( θ ′ ) 2 Ex - ( 1 - Ex ) · cos ( θ ′ ) ⇒ Ex = f ( NA source , NA ′ ) Ex col = ( sk - s 1 sk + s 1 ) 2 = ( z 2 - z 1 z 2 + z 1 ) 2 ⇒ z 2 = z 1 · 1 + Ex col 1 - Ex col Ex col = 1 - R col a ⇒ R col = z 1 + z 2 2 · ( 1 - Ex col ) DFRE: diameter of the plate with the field raster elements xFRE: length of one field raster element yFRE: width of one field raster element βFRE: magnification ratio of the imaging of field raster elements DPRE: diameter of the plate with the pupil raster elements Rcol: curvature of the elliptical collector Excol: conical constant of the elliptical collector NA′: aperture after the collector mirror With the pregiven specifications the following system parameters can be calculated: D FRE = 2 · L · NA field = 2 · 1400 mm · 0.025 = 70.0 mm x FRE = D FRE 4.0 = 70.0 mm 4.0 = 17.5 mm y FRE = 1.0 mm β FRE = x field x FRE = 105.0 mm 17.5 mm = 6.0 z 3 = L 1 + β FRE = 1400.0 mm 1 + 6.0 = 200.0 mm z 4 = z 3 · β FRE = 200.0 mm · 6.0 = 1200.0 mm NA ′ = D DRE / 2 z 3 = 70.0 mm / 2 200.0 mm = 0.175 Ex col = f ( NA source , NA ′ ) = 0.695 z 2 = z 1 · 1 + Ex col 1 - Ex col = 100.0 mm · 1 + 0.695 1 - 0.695 = 1101.678 mm R col = z 1 + z 2 2 · ( 1 - Ex col ) = 100.0 mm + 1101.678 mm 2 · ( 1 - 0.695 ) = 183.357 mm The field mirrors are constructed similar to the case of the first example of embodiment of a illumination system, i.e., two toroid mirrors are again used as field mirrors. In FIGS. 53-58, the propagation of the light rays is shown in a illumination system according to the previously given parameters as an example. In FIG. 53, the ray propagation is shown for an ellipsoid mirror 402, which is designed for a source aperture NA=0.999 and which images the primary light source 400 on a secondary light source 410. In the form of embodiment according to FIG. 54, a planar mirror 404 is arranged at the position of the field raster element plate, which reflects the light beam. The rays are propagated up to the reticle plane 406. Finally, in FIG. 55, the construction according to the invention is shown, in which mirror 404 is replaced by the field raster element plate 412. A fan of rays is depicted, wherein each ray goes through the center of the individual field raster elements. These rays intersect on the optical axis in the reticle plane 406. In this configuration the primary light source 400 is arranged in the object plane of the collector mirror 402, wherein the secondary light source 410 is arranged in the image plane of the collector mirror 402. If the collector unit consists only of one collector mirror 402 the image-side principal plane of the collector unit is located at the vertex of the collector mirror 402. The optical distance between the vertex of the collector mirror 402 and the secondary light source 410 is in this configuration equal to the sum of the optical distance between the vertex of the collector mirror 402 and the plate 412 with the field raster elements and the optical distance between the plate 412 with the field raster elements and the secondary light source 410. If the refraction index is equal to 1.0, the optical distance is equal to the geometrical distance. FIG. 56 finally shows the total illumination system up to entrance pupil 414 of the projection objective with two field mirrors 416. The marginal rays 418, 420 strike on reticle 406 and are further propagated up to the entrance pupil 414 of the projection objective. In FIG. 57, an x-z fan of rays is depicted for the system of FIG. 56, and this fan strikes the central field raster element 422. The rays illuminate the arc-shaped field on reticle 406 with the correct orientation. In FIG. 58, in addition, the entrance pupil 424 of the projection objective is represented. The depicted rays are propagated along the optical axis and are focused in the center of the entrance pupil. The primary light source 400 is imaged into the secondary light source 410 by the collector mirror 402, wherein the field mirrors 416 image the secondary light source 410 into a tertiary light source in the center of the entrance pupil 424 of the projection objective. In FIG. 59, the illumination of the reticle is shown with an arc-shaped field (Rfield=100 mm, segment=60°, field height ±3.0 mm), which is based on an illumination arrangement according to FIGS. 52-58. The integral scanning energy is shown in FIG. 60. The integral scan energy varies between 100% and 105%. The uniformity or homogeneity thus amounts to ±2.5%. FIG. 61 represents the pupil illumination of the above-described system for an object point in the center of the illuminated field. The sines of the ray angles are referred to the direction of the centroid ray. Corresponding to the field raster element distribution, a distribution of tertiary light sources 6101 is produced in the pupil illumination. The tertiary light sources 6101 are uniformly distributed. There are no center obscurations, since in the case of the described second form of embodiment, the mirrors are arranged in zigzag configuration. In FIG. 62, a profile of the intensity distribution at x=0 mm is shown in the scan direction with the use of two different laser-plasma sources. Whereas without the pupil raster elements for the 50-μm source, the desired rectangular profile is obtained, the 200-μm source shows at the edges a clear blurring. This source can no longer be considered point-like. The use of pupil raster elements, such as, for example, in the case of the pinch-plasma source, is necessary for the correct imaging of the field raster elements into the reticle plane. In FIGS. 63A+63B two possibilities are shown for the formation of the field raster element plate. In FIG. 63A, the raster elements 500 are arranged on a curved supporting surface 502. Thus the inclination of the raster elements corresponds to the slope of the supporting surface. Such plates are described, for example, in the case of the first form of embodiment with a collector mirror and a telescope system comprising two mirrors. If the field raster elements 500 are shaped in planar manner, such as, for example, in the case of the second form of embodiment that is described, in which collector unit and field raster element plate are combined into a telescope system, then the individual field raster elements are arranged under a pregiven tilt angle on the raster element plate 504. Depending on the distribution of the tilt angles on the plate, one obtains either collecting or diverging effects. A plate with a diverging effect is illustrated. Of course, raster element plates with planar field raster elements can be used also in systems according to the first example of embodiment with a collector unit and two tele-mirrors. In the case of such a system, the raster elements are then tilted onto one of the mirrors such that a diverging effect is produced and onto the other in such a way that a collecting effect is produced. FIG. 64 shows a form of embodiment of the invention, which is designed as a refractive system with lenses for wavelengths, for example, of 193 nm or 157 nm. The system comprises a light source 600, a collector lens 602, as well as a field raster element plate 604 and a pupil raster element plate 606. Prisms 608 arranged in front of the field raster elements serve for adjusting the light path between the field raster element plate 604 and the pupil raster element plate 606. FIG. 65 shows another embodiment for a purely refractive system in a schematically view. The beam cone of the light source 6501 is collected by the aspherical collector lens 6503 and is directed to the plate with the field raster elements 6509. The collector lens 6503 is designed to generate an image 6505 of the light source 6501 at the plate with the pupil raster elements 6515 as shown with the dashed lines if the plate with the field raster elements 6509 is not in the beam path. Therefore without the plate with the field raster elements 6509 one secondary light source 6505 would be produced at the plate with the pupil raster elements. This imaginary secondary light source 6505 is divided into a plurality of secondary light sources 6507 by the field raster elements 6509 formed as field prisms 6511. The arrangement of the secondary light sources 6507 at the plate with the pupil raster elements 6515 is produced by the deflection angles of the field prisms 6511. These field prisms 6511 have rectangular surfaces and generate rectangular light bundles. However, they can have any other shape. The pupil raster elements 6515 are arranged nearby each of the secondary light sources 6507 to image the corresponding field raster elements 6509 into the reticle plane 6529 and to superimpose the rectangular images of the field raster elements 6509 in the field 6531 to be illuminated. The pupil raster elements 6515 are designed as combinations of a pupil prism 6517 and a pupil lenslet 6519 with positive optical power. The pupil prisms 6517 deflect the incoming ray bundles to superimpose the images of the field raster elements 6509 in the reticle plane 6529. The pupil lenslets 6519 are designed together with the field lens 6521 to image the field raster elements 6509 into the reticle plane 6529. Therefore with the prismatic deflection of the ray bundles at the field raster elements 6509 and pupil raster elements 6515 an arbitrary assignment between field raster elements 6509 and pupil raster elements 6515 is possible. The pupil prisms 6517 and the pupil lenslets 6519 can also be made integrally to form a pupil raster element 6515 with positive and prismatic optical power. The field lens 6521 images the secondary light sources 6507 into the exit pupil 6533 of the illumination system forming tertiary light sources 6535 there. FIG. 66 shows another embodiment for a purely refractive system in a schematically view. Corresponding elements have the same reference numbers as those in FIG. 65 increased by 100. Therefore, the description to these elements is found in the description to FIG. 65. The aspherical collector lens 6603 is designed to focus the light rays of the light source 6601 in a plane 6605 which is arranged behind the plate with the pupil raster elements 6615 as indicated by the dashed lines. Therefore the field raster elements 6609 have a positive optical power to produce the secondary light sources 6607 at the plate with the pupil raster elements 6615. The field raster elements 6609 are designed as combinations of a field prism 6611 and a field lenslet 6613. The field prisms 6611 deflect the incoming ray bundles to the corresponding secondary light sources 6607. The field lenslets 6613 are designed to generate the secondary light sources 6607 at the corresponding pupil raster elements 6615. The field prisms 6611 and the field lenslets 6613 can also be made integrally to form field raster elements 6609 with positive and prismatic optical power. FIG. 67 shows another embodiment for a purely refractive system in a schematically view. Corresponding elements have the same reference numbers as those in FIG. 66 increased by 100. Therefore, the description to these elements is found in the description to FIG. 66. The aspheric collector lens 6703 is designed to focus the light rays of the light source 6701 in a plane 6705 which is arranged between the plate with the field raster elements 6709 and the plate with the pupil raster elements 6715 as indicated by the dashed lines. Therefore the field raster elements 6709 have negative optical power to produce the secondary light sources 6707 at the plate with the pupil raster elements 6715. The field raster elements 6709 are designed as combinations of a field prism 6711 and a field lenslet 6713. The field prisms 6711 deflect the incoming ray bundles to the corresponding secondary light sources 6707. The field lenslets 6713 are designed to generate the secondary light sources 6707 at the corresponding pupil raster elements 6715. The field prisms 6711 and the field lenslets 6713 can also be made integrally to form field raster elements 6709 with negative and prismatic optical power. FIG. 68 shows another embodiment for a purely refractive system in a schematically view. Corresponding elements have the same reference numbers as those in FIG. 67 increased by 100. Therefore, the description to these elements is found in the description to FIG. 67. The aspheric collector lens 6803 is designed to generate a parallel light bundle. Wherein in FIGS. 65 to 67 the plate with the field raster elements is arranged in a convergent beam path, the plate with the field raster elements 6809 in FIG. 68 is arranged in a parallel beam path. The field raster elements 6809 are designed as combinations of a field prism 6811 and a field lenslet 6813. The field prisms 6811 deflect the incoming ray bundles to the corresponding secondary light sources 6807. The field lenslets 6813 are designed to generate the secondary light sources 6807 at the corresponding pupil raster elements 6815. They have positive optical power and a focal length that corresponds to the distance between the field raster elements 6809 and the pupil raster elements 6815. Since the light source 6801 is a point-like source, also the secondary light sources 6807 are point-like. Therefore, the pupil raster elements 6815 are designed as prisms 6817. FIG. 69 shows another embodiment for a purely refractive system in a schematically view. Corresponding elements have the same reference numbers as those in FIG. 66 increased by 300. Therefore, the description to these elements is found in the description to FIG. 66. The aspheric collector lens 6903 is designed to focus the light rays of the light source 6601 in a plane 6905 which is arranged in front of the plate with the field raster elements 6909 as indicated by with the dashed lines. Nearby this image of the light source a transmissions filter 6937 is arranged. This filter can also be used to select the used wavelength range. In the plane 6905 also a shutter can be arranged. The field raster elements 6909 have a positive optical power to produce the secondary light sources 6907 at the plate with the pupil raster elements 6915. FIG. 70 shows an embodiment for a purely reflective system in a schematically view. Corresponding elements have the same reference numbers as those in FIG. 69 increased by 100. Therefore, the description to these elements is found in the description to FIG. 69. The beam cone of the light source 7001 is collected by the ellipsoidal collector mirror 7003 and is directed to the plate with the field raster elements 7009. The collector mirror 7003 is designed to generate an image 7005 of the light source 7001 between the plate with the field raster elements 7009 and the plate with the pupil raster elements 7015 if the plate with the field raster elements 7009 would be a planar mirror as indicated by the dashed lines. The convex field raster elements 7009 are designed to generate point-like secondary light sources 7007 at the pupil raster elements 7015, since the light source 7001 is also point-like. Therefore the pupil raster elements 7015 are designs as planar mirrors. Since the intensity at the point-like secondary light sources 7007 is very high, the planar pupil raster elements 7015 can alternatively be arranged defocused from the secondary light sources 7007. The distance between the secondary light sources 7007 and the pupil raster elements 7015 should not exceed 20% of the distance between the field raster elements and the pupil raster elements. The pupil raster elements 7015 are tilted to superimpose the images of the field raster elements 7009 together with the field lens 7021 formed as the field mirrors 7023 and 7027 in the field 7031 to be illuminated. Both, the field raster elements 7009 and the pupil raster elements 7015 are tilted. Therefore the assignment between the field raster elements 7009 and pupil raster elements 7015 is defined by the user. In the embodiment of FIG. 70 the field raster elements 7009 at the center of the plate with the field raster elements 7009 correspond to the pupil raster elements 7015 at the border of the plate with the pupil raster elements 7015 and vice versa. The tilt angles and the tilt axes of the field raster elements are determined by the directions of the incoming ray bundles and by the positions of the corresponding pupil raster elements 7015. Since for each field raster element 7009 the tilt angle and the tilt axis is different, also the planes of incidence defined by the incoming and reflected centroid rays are not parallel. The tilt angles and the tilt axes of the pupil raster elements 7015 are determined by the positions of the corresponding field raster elements 7009 and the requirement that the images of the field raster elements 7009 has to be superimposed in the field 7031 to be illuminated. The concave field mirror 7023 images the secondary light sources 7007 into the exit pupil 7033 of the illumination system forming tertiary light sources 7035, wherein the convex field mirror 7027 being arranged at grazing incidence transforms the rectangular images of the rectangular field raster elements 7009 into arc-shaped images. FIG. 71 shows another embodiment for a purely reflective system in a schematically view. Corresponding elements have the same reference numbers as those in FIG. 70 increased by 100. Therefore, the description to these elements is found in the description to FIG. 70. In this embodiment the light source 7101 and therefore also the secondary light sources 7107 are extended. The pupil raster elements 7115 are designed as concave mirrors to image the field raster elements 7109 into the image plane 7129. It is also possible to arrange the pupil raster elements 7115 not at the secondary light sources 7107, but defocused. The influence of the defocus on the imaging of the field raster elements 7109 has to be consider in the optical power of the pupil raster elements. FIG. 72 shows in a schematic view the imaging of one field raster element 7209 into the reticle plane 7229 forming an image 7231 and the imaging of the corresponding secondary light source 7207 into the exit pupil 7233 of the illumination system forming a tertiary light source 7235. Corresponding elements have the same reference numbers as those in FIG. 70 increased by 200. Therefore, the description to these elements is found in the description to FIG. 70. The field raster elements 7209 are rectangular and have a length XFRE and a width YFRE. All field raster elements 7209 are arranged on a nearly circular plate with a diameter DFRE. They are imaged into the image plane 7229 and superimposed on a field 7231 with a length Xfield and a width Yfield, wherein the maximum aperture in the image plane 7229 is denoted by NAfield. The field size corresponds to the size of the object field of the projection objective, for which the illumination system is adapted. The plate with the pupil raster elements 7215 is arranged in a distance of Z3 from the plate with the field raster elements 7209. The shape of the pupil raster elements 7215 depends on the shape of the secondary light sources 7207. For circular secondary light sources 7207 the pupil raster elements 7215 are circular or hexagonal for a dense packaging of the pupil raster elements 7215. The diameter of the plate with the pupil raster elements 7215 is denoted by DPRE. The pupil raster elements 7215 are imaged by the field lens 7221 into the exit pupil 7233 having a diameter of DEP. The distance between the image plane 7229 of the illumination system and the exit pupil 7233 is denoted with ZEP. Since the exit pupil 7233 of the illumination system corresponds to the entrance pupil of the projection objective, the distance ZEP and the diameter DEP are predetermined values. The entrance pupil of the projection objective is typically illuminated up to a user-defined filling ratio σ. The data for a preliminary design of the illumination system can be calculated with the equations and data given below. The values for the parameters are typical for a EUV projection exposure apparatus. But there is no limitation to these values. Wherein the schematic design is shown for a refractive linear system it can be easily adapted for reflective systems by exchanging the lenses with mirrors. The field 7231 to be illuminated is defined by a segment of an annulus. The Radius of the annulus isRfield=138 mm.The length and the width of the segment areXfield=88 mm, Yfield=8 mmWithout the field-forming field mirror, which transforms the rectangular images of the field raster elements into arc-shaped images, the field to be illuminated is rectangular with the length and width defined by the segment of the annulus. The distance from the image plane to the exit pupil isZEP=1320 mm.The object field of the projection objective is an off-axis field. The distance between the center of the field and the optical axis of the projection objective is given by the radius Rfield. Therefore the incidence angle of the centroid ray in the center of the field is 6°. The aperture at the image plane of the projection objective is NAwafer=0.25. For a reduction projection objective with a magnification ratio of βproj=−0.25 and a filling ratio of σ=0.8 the aperture at the image plane of the illumination system is NA field = σ · NA wafer 4 = 0.05 D EP = 2 tan [ arcsin ( NA field ) ] · Z EP ≈ 2 NA EP · Z EP ≈ 132 mm The distance Z3 between the field raster elements and the pupil raster elements is related to the distance ZEP between the image plane and the exit pupil by the depth magnification α:ZEP=α·Z3 The size of the field raster elements is related to the field size by the lateral magnification βfield:Xfield=βfield·XFRE Yfield=βfield·YFRE The diameter DPRE of the plate with the pupil raster elements and the diameter DEP of the exit pupil are related by the lateral magnification βpupil:DEP=βpupil·DPRE The depth magnification α is defined by the product of the lateral magnifications βfield and βpupil:α=βfield·βpupil The number of raster elements being superimposed at the field is set to 200. With this high number of superimposed images the required field illumination uniformity can be achieved. Another requirement is to minimize the incidence angles on the components. For a reflective system the beam path is bent at the plate with the field raster elements and at the plate with the pupil raster elements. The bending angles and therefore the incidence angles are minimum for equal diameters of the two plates: D PRE = D FRE 200 · X PRE · Y PRE = 200 · X field · Y field β field 2 = D EP 2 β pupil 2 = β field 2 α 2 D EP 2 The distance Z3 is set to Z3=900 mm. This distance is a compromise between low incidence angles and a reduced overall length of the illumination system. α = Z EP Z 3 = 1.47 Therefore β field ≈ 200 · X field · Y field D EP 2 α 2 4 ≈ 2.05 β pupil ≈ α β field ≈ 0.7 D FRE = D PRE = β field α D EP ≈ 200 mm X FRE = X field β field ≈ 43 mm Y FRE = Y field β field ≈ 4 mm With these values the principal layout of the illumination system is known. In a next step the field raster elements 7309 have to be distributed on the plate as shown in FIG. 73. The two-dimensional arrangement of the field raster elements 7309 is optimized for efficiency. Therefore the distance between the field raster elements 7309 is as small as possible. Field raster elements 7309, which are only partially illuminated, will lead to uniformity errors of the intensity distribution in the image plane, especially in the case of a restricted number of field raster elements 7309. Therefore only these field raster elements 7309 are imaged into the image plane which are illuminated almost completely. FIG. 73 shows a possible arrangement of 216 field raster elements 7309. The solid line 7339 represents the border of the circular illumination of the plate with the field raster elements 7309. Therefore the filling efficiency is approximately 90%. The rectangular field raster elements 7309 have a length XFRE=46.0. 0 mm and a width YFRE=2.8 mm. All field raster elements 7309 are inside the circle 7339 with a diameter of 200 mm. The field raster elements 7309 are arranged in 69 rows 7341 being arranged one among another. The field raster elements 7309 in the rows 7341 are attached at the smaller y-side of the field raster elements 7309. The rows 7341 consist of one, two, three or four field raster elements 7309. Some rows 7341 are displaced relative to the adjacent rows 7341 to distribute the field raster elements 7309 inside the circle 7339. The distribution is symmetrical to the y-axis. FIG. 74 shows the arrangement of the pupil raster elements 7415. They are arranged on a distorted grid to compensate for distortion errors of the field lens. If this distorted grid of pupil raster elements 7415 is imaged into the exit pupil of the illumination system by the field lens a undistorted regular grid of tertiary light sources will be generated. The pupil raster elements 7415 are arranged on curved lines 7443 to compensate the distortion introduced by the field-forming field mirror. The distance between adjacent pupil raster elements 7415 is increased in y-direction to compensate the distortion introduced by field mirrors being tilted about the x-axis. Therefore the pupil raster elements 7415 are not arranged inside a circle. The size of the pupil raster elements 7415 depends on the source size or source étendue. If the source étendue is much smaller than the required étendue in the image plane, the secondary light sources will not fill the plate with the pupil raster elements 7415 completely. In this case the pupil raster elements 7415 need only to cover the area of the secondary light sources plus some overlay to compensate for source movements and imaging aberrations of the collector-field raster element unit. In FIG. 74 circular pupil raster elements 7415 are shown. Each field raster element 7309 corresponds to one of the pupil raster elements 7415 according to an assignment table and is tilted to deflect an incoming ray bundle to the corresponding pupil raster element 7415. A ray coming from the center of the light source and intersecting the field raster element 7309 at its center is deflected to intersect the center of the corresponding pupil raster element 7415. The tilt angle and tilt axis of the pupil raster element 7415 is designed to deflect this ray in such a way, that the ray intersects the field in its center. The field lens images the plate with the pupil raster elements into the exit pupil and generates the arc-shaped field with the desired radius Rfield. For Rfield=138 mm, the field forming gracing incidence field mirror has only low negative optical power. The optical power of the field-forming field mirror has to be negative to get the correct orientation of the arc-shaped field. Since the magnification ratio of the field lens has to be positive, another field mirror with positive optical power is required. Wherein for apertures NAfield lower than 0.025 the field mirror with positive optical power can be a grazing incidence mirror, for higher apertures the field mirror with positive optical power should be a normal incidence mirror. FIG. 75 shows a schematic view of a embodiment comprising a light source 7501, a collector mirror 7503, a plate with the field raster elements 7509, a plate with the pupil raster elements 7515, a field lens 7521, an image plane 7529 and an exit pupil 7533. The field lens 7521 has one normal-incidence mirror 7523 with positive optical power for pupil imaging and one grazing-incidence mirror 7527 with negative optical power for field shaping. Exemplary for the imaging of all secondary light sources, the imaging of one secondary light source 7507 into the exit pupil 7533 forming a tertiary light source 7535 is shown. The optical axis 7545 of the illumination system is not a straight line but is defined by the connection lines between the single components being intersected by the optical axis 7545 at the centers of the components. Therefore, the illumination system is a non-centered system having an optical axis 7545 being bent at each component to get a beam path free of vignetting. There is no common axis of symmetry for the optical components. Projection objectives for EUV exposure apparatus are typically centered systems with a straight optical axis and with an off-axis object field. The optical axis 7547 of the projection objective is shown as a dashed line. The distance between the center of the field 7531 and the optical axis 7547 of the projection objective is equal to the field radius Rfield. The pupil imaging field mirror 7523 and the field-forming field mirror 7527 are designed as on-axis toroidal mirrors, which means that the optical axis 7545 paths through the vertices of the on-axis toroidal mirrors 7523 and 7527. In another embodiment as shown in FIG. 76, a telescope objective in the field lens 7621 comprising the field mirror 7623 with positive optical power, the field mirror 7625 with negative optical power and the field mirror 7627 is applied to reduce the track length. Corresponding elements have the same reference numbers as those in FIG. 75 increased by 100. Therefore, the description to these elements is found in the description to FIG. 75. The field mirror 7625 and the field mirror 7623 of the telescope objective in FIG. 74 are formed as an off-axis Cassegrainian configuration. The telescope objective has an object plane at the secondary light sources 7607 and an image plane at the exit pupil 7633 of the illumination system. The pupil plane of the telescope objective is arranged at the image plane 7629 of the illumination system. In this configuration, having five normal-incidence reflections at the mirrors 7603, 7609, 7615, 7625 and 7623 and one grazing-incidence reflection at the mirror 7627, all mirrors are arranged below the image plane 7629 of the illumination system. Therefore, there is enough space to install the reticle and the reticle support system. In FIG. 77 a detailed view of the embodiment of FIG. 76 is shown. Corresponding elements have the same reference numbers as those in FIG. 76 increased by 100. Therefore, the description to these elements is found in the description to FIG. 76. The components are shown in a y-z-sectional view, wherein for each component the local co-ordinate system with the y- and z-axis is shown. For the collector mirror 7703 and the field mirrors 7723, 7725 and 7727 the local co-ordinate systems are defined at the vertices of the mirrors. For the two plates with the raster elements the local co-ordinate systems are defined at the centers of the plates. In table 2 the arrangement of the local co-ordinate systems with respect to the local co-ordinate system of the light source 7701 is given. The tilt angles α, β and γ about the x-, y- and z-axis are defined in a right-handed system. TABLE 2Co-ordinate systems of vertices of mirrorsX [mm]Y [mm]Z [mm]α [°]β [°]γ [°]Light source 77010.00.00.00.00.00.0Collector mirror0.00.0125.00.00.00.07703Plate with field0.00.0−975.010.5180.00.0raster elements7709Plate with pupil0.0−322.5−134.813.50.0180.0raster elements7715Field mirror 77250.0508.4−1836.1−67.80.0180.0Field mirror 77230.0204.8−989.7−19.70.0180.0Field mirror 77270.0−163.2−2106.249.4180.00.0Image plane 77310.0−132.1−1820.245.00.00.0Exit pupil 77330.0−1158.1−989.445.00.00.0 The surface data are given in table 3. The radius R and the conical constant K define the surface shape of the mirrors according to the formula z = 1 R h 2 1 + 1 - ( 1 + K ) ( 1 R ) 2 h 2 ,wherein h is the radial distance of a surface point from the z-axis. TABLE 3Optical data of the componentsFieldPupilCollectorrasterrasterFieldFieldFieldmirrorelementelementmirrormirrormirror770377097715772577237727R [mm]−235.3∞−1239.7−534.7−937.7−65.5K−0.778550.00.0−0.0435−0.0378−1.1186Focal length f [mm]—∞617.6−279.4477.0−757.1 The light source 7701 in this embodiment is a Laser-Produced-Plasma source having a diameter of approximately 0.3 mm generating a beam cone with an opening angle of 83°. To decrease the contamination of the collector mirror 7703 by debris of the source 7701 the distance to the collector mirror 7703 is set to 125 mm. The collector mirror 7703 is an elliptical mirror, wherein the light source 7701 is arranged in the first focal point of the ellipsoid and wherein the plate with the pupil raster elements 7715 is arranged in the second focal point of the ellipsoid. Therefore the field raster elements 7709 can be designed as planar mirrors. The distance between the vertex of the collector mirror 7703 and the center of the plate with the field raster elements 7709 is 1100 mm. The field raster elements 7709 are rectangular with a length XFRE=46.0 mm and a width YFRE=2.8 mm. The arrangement of the field raster elements is shown in FIG. 73. The tilt angles and tilt axis are different for each field raster element 7709, wherein the field raster elements are tilted to direct the incoming ray bundles to the corresponding pupil raster elements 7715. The tilt angles are in the range of −4° to 4°. The mean incidence angle of the rays on the field raster elements is 10.5°. Therefore the field raster elements 7709 are used at normal incidence. The plate with the pupil raster elements 7715 is arranged in a distance of 900 mm from the plate with the field raster elements 7709. The pupil raster elements 7715 are concave mirrors. The arrangement of the pupil raster elements 7715 is shown in FIG. 72. The tilt angles and tilt axis are different for each pupil raster element 7715, wherein the pupil raster elements 7715 are tilted to superimpose the images of the field raster elements 7709 in the image plane 7731. The tilt angles are in the range of −4° to 4°. The mean incidence angle of the rays on the pupil raster elements 7715 is 7.5°. Therefore the pupil raster elements 7715 are used at normal incidence. The field mirror 7725 is a convex mirror. The used area of this mirror defined by the incoming rays is an off-axis segment of a rotational symmetric conic surface. The mirror surface is drawn in FIG. 77 from the vertex up to the used area as dashed line. The distance between the center of the plate with the pupil raster elements 7715 and the center of the used area on the field mirror 7725 is 1400 mm. The mean incidence angle of the rays on the field mirror 7725 is 12°. Therefore the field mirror 7725 is used at normal incidence. The field mirror 7723 is a concave mirror. The used area of this mirror defined by the incoming rays is an off-axis segment of a rotational symmetric conical surface. The mirror surface is drawn in FIG. 77 from the vertex up to the used area as dashed line. The distance between the center of the used area on the field mirror 7725 and the center of the used area on the field mirror 7723 is 600 mm. The mean incidence angle of the rays on the field mirror 7723 is 7.5°. Therefore the field mirror 7723 is used at normal incidence. The field mirror 7727 is a convex mirror. The used area of this mirror defined by the incoming rays is an off-axis segment of a rotational symmetric conic surface. The mirror surface is drawn in FIG. 77 from the vertex up to the used area as dashed line. The distance between the center of the used area on the field mirror 7723 and the center of the used area on the field mirror 7727 is 600 mm. The mean incidence angle of the rays on the field mirror 7727 is 78°. Therefore the field mirror 7727 is used at grazing incidence. The distance between the field mirror 7727 and the image plane 7731 is 300 mm. In another embodiment the field mirror and the field mirror are replaced with on-axis toroidal mirrors. The vertices of these mirrors are arranged in the centers of the used areas. The convex field mirror has a radius Ry=571.3 mm in the y-z-section and a radius Rx=546.6 mm in the x-z-section. This mirror is tilted about the local x-axis about 12° to the local optical axis 7745 defined as the connection lines between the centers of the used areas of the mirrors. The concave field mirror has a radius Ry=−962.14 mm in the y-z-section and a radius Rx=−945.75 mm in the x-z-section. This mirror is tilted about the local x-axis about 7.5° to the local optical axis 7745. FIG. 78 shows the illuminated arc-shaped area in the image plane 7731 of the illumination system presented in FIG. 77. The orientation of the y-axis is defined in FIG. 77. The solid line 7849 represents the 50%-value of the intensity distribution, the dashed line 7851 the 10%-value. The width of the illuminated area in y-direction is constant over the field. The intensity distribution is the result of a simulation done with the optical system given in table 2 and table 3. FIG. 79 shows the illumination of the exit pupil 7733 for an object point in the center (x=0 mm; y=0 mm) of the illuminated field in the image plane 7731. The arrangement of the tertiary light sources 7935 corresponds to the arrangement of the pupil raster elements 7715, which is presented in FIG. 74. Wherein the pupil raster elements in FIG. 74 are arranged on a distorted grid, the tertiary light sources 7935 are arranged on a undistorted regular grid. It is obvious in FIG. 79, that the distortion errors of the imaging of the secondary light sources due to the tilted field mirrors and the field-shaping field mirror are compensated. The shape of the tertiary light sources 7935 is not circular, since the light distribution in the exit pupil 7733 is the result of a simulation with a Laser-Plasma-Source which was not spherical but ellipsoidal. The source ellipsoid was oriented in the direction of the local optical axis. Therefore also the tertiary light sources are not circular, but elliptical. Due to the mixing of the light channels and the user-defined assignment between the field raster elements and the pupil raster elements, the orientation of the tertiary light sources 7935 is different for nearby each tertiary light source 7935. Therefore, the planes of incidence of at least two field raster elements have to intersect each other. The plane of incidence of a field raster element is defined by the centroid ray of the incoming bundle and its corresponding deflected ray. FIG. 80 shows another embodiment in a schematic view. Corresponding elements have the same reference numbers as those in FIG. 76 increased by 400. Therefore, the description to these elements is found in the description to FIG. 76. In this embodiment the beam path between the plate with the pupil raster elements 8015 and the field mirror 8025 is crossing the beam path from the collector mirror 8003 to the plate with the field raster elements 8009. With this arrangement it is possible to have light sources 8001 emitting a beam cone horizontally and to arrange the reticle horizontally in the image plane 8029 simultaneously. FIG. 81 shows a similar embodiment to the one of FIG. 80 in a detailed view. Corresponding elements have the same reference numbers as those in FIG. 80 increased by 100. Therefore, the description to these elements is found in the description to FIG. 80. The definition of the local co-ordinate systems is the same as in FIG. 77. The positions of the local co-ordinate systems are given in table 4. TABLE 4Co-ordinate systems of vertices of mirrorsX [mm]Y [mm]Z [mm]α [°]β [°]γ [°]Light source 81010.00.00.00.00.00.0Collector mirror0.00.0100.00.00.00.08103Plate with field0.00.0−10.010.5180.00.0raster elements8109Plate with pupil0.0−322.5−159.831.00.0180.0raster elements8115Field mirror 81250.01395.9−1110.3−20.30.0180.0Field mirror 81230.0746.5−645.413.60.0180.0Field mirror81270.01053.2−1784.286.3180.00.0Image plane 81310.0906.0−1537.182.00.00.0Exit pupil 81350.0−413.5−1491.082.00.00.0 The surface data are given in table 5. TABLE 5Optical data of the componentsCol-FieldPupillectorrasterrasterFieldFieldFieldmirrorelementelementmirrormirrormirror810381098115812581238127R [mm]−200.00−1800.0−1279.7−588.9−957.1−65.5K−1.00.00.0−0.0541−0.0330−1.1186Focal—900.0639.8−317.5486.8−757.1length f[mm] The light source 8101 in this embodiment is also a Laser-Produced-Plasma source. The distance to the collector mirror 8103 is set to 100 mm. The collector mirror 8103 is a parabolic mirror generating a parallel ray bundle, wherein the light source 8101 is arranged in the focal point of the parabola. Therefore the field raster elements 8109 are concave mirrors to generate the secondary light sources at the corresponding pupil raster elements 8115. The focal length of the field raster elements 8109 is equal to the distance between the field raster elements 8109 and the corresponding pupil raster elements 8115. The distance between the vertex of the collector mirror 8103 and the center of the plate with the field raster elements 8109 is 1100 mm. The field raster elements 8109 are rectangular with a length XFRE=46.0 mm and a width YFRE=2.8 mm. The arrangement of the field raster elements 8109 is shown in FIG. 73. The mean incident angle of the rays intersecting the field raster elements 8109 is 10.5°, the range of the incidence angles is from 8° up to 13°. Therefore the field raster elements 8109 are used at normal incidence. The plate with the pupil raster elements 8115 is arranged in the focal plane of the field raster elements 8109. The pupil raster elements 8115 are concave mirrors. The arrangement of the pupil raster elements 8115 is similar to the arrangement shown in FIG. 74. The mean incidence angle of the rays intersecting the pupil raster elements 8115 is 10.0°, the range of the incidence angles is from 7° up to 13°. Therefore the pupil raster elements 8115 are used at normal incidence. Between the plate with the pupil raster elements 8115 and the field mirror 8125 the beam path is crossing the beam path between the collector mirror 8103 and the plate with the field raster elements 8109. The field mirror 8125 is a convex mirror. The distance between the center of the plate with the pupil raster elements 8115 and the center of the used area on the field mirror 8125 is 1550 mm. The mean incidence angle of the rays intersecting the field mirror 8125 is 13°, the range of the incidence angles is from 11° up to 15°. Therefore the field mirror 8125 is used at normal incidence. The field mirror 8123 is a concave mirror. The distance between the center of the used area on the field mirror 8125 and the center of the used area on the field mirror 8123 is 600 mm. The mean incidence angle of the rays intersecting the field mirror 8123 is 7.5°, the range of the incidence angles is from 6° up to 9°. Therefore the field mirror 8123 is used at normal incidence. The field mirror 8127 is a convex mirror. The distance between the center of the used area on the field mirror 8123 and the center of the used area on the field mirror 8127 is 600 mm. The mean incidence angle of the rays intersecting the field mirror 8127 is 78°, the range of the incidence angles is from 73° up to 82°. Therefore the field mirror 8127 is used at grazing incidence. FIG. 82 shows another embodiment in a schematic view. Corresponding elements have the same reference numbers as those in FIG. 76 increased by 600. Therefore, the description to these elements is found in the description to FIG. 76. In this embodiment the field mirror 8225 and the field mirror 8223 are both concave mirrors forming an off-axis Gregorian telescope configuration. The field mirror 8225 images the secondary light sources 8207 in the plane between the field mirror 8225 and the field mirror 8223 forming tertiary light sources 8259. In FIG. 82 only the imaging of the central secondary light source 8207 is shown. At the plane with the tertiary light sources 8259 a masking unit 8261 is arranged to change the illumination mode of the exit pupil 8233. With stop blades it is possible to mask the tertiary light sources 8259 and therefore to change the illumination of the exit pupil 8233 of the illumination system. Possible stop blades has circular shapes or for example two or four circular openings. The field mirror 8223 and the field mirror 8227 image the tertiary light sources 8259 into the exit pupil 8233 of the illumination system forming quaternary light sources 8235. FIG. 83 shows another embodiment in a schematic view. Corresponding elements have the same reference numbers as those in FIG. 82 increased by 100. Therefore, the description to these elements is found in the description to FIG. 82. In this embodiment the collector mirror 8303 is designed to generate an intermediate image 8363 of the light source 8301 in front of the plate with the field raster elements 8309. Nearby this intermediate image 8363 a transmission plate 8365 is arranged. The distance between the intermediate image 8363 and the transmission plate 8365 is so large that the plate 8365 will not be destroyed by the high intensity near the intermediate focus. The distance is limited by the maximum diameter of the transmission plate 8365, which is in the order of 200 mm. The maximum diameter is determined by the possibility to manufacture a plate being transparent at EUV. The transmission plate 8365 can also be used as a spectral purity filter to select the used wavelength range. Instead of the absorptive transmission plate 8365 also a reflective grating filter can be used. The plate with the field raster elements 8309 is illuminated with a diverging ray bundle. Since the tilt angles of the field raster elements 8309 are adjusted according to a collecting surface the diverging beam path can be transformed to a nearly parallel one. Additionally, the field raster elements 8309 are tilted to deflect the incoming ray bundles to the corresponding pupil raster elements 8315. FIG. 84 shows an EUV projection exposure apparatus in a detailed view. The illumination system is the same as shown in detail in FIG. 77. Corresponding elements have the same reference numbers as those in FIG. 77 increased by 700. Therefore, the description to these elements is found in the description to FIG. 77. In the image plane 8429 of the illumination system the reticle 8467 is arranged. The reticle 8467 is positioned by a support system 8469. The projection objective 8471 having six mirrors images the reticle 8467 onto the wafer 8473, which is also positioned by a support system 8475. The mirrors of the projection objective 8471 are centered on a common straight optical axis 8447. The arc-shaped object field is arranged off-axis. The direction of the beam path between the reticle 8467 and the first mirror 8477 of the projection objective 8471 is convergent to the optical axis 8447 of the projection objective 8471. The angles of the chief rays 8445 with respect to the normal of the reticle 8467 are between 5° and 7°. As shown in FIG. 84, the illumination system 8479 is well separated from the projection objective 8471. The illumination and the projection beam path interfere only nearby the reticle 8467. The beam path of the illumination system is folded with reflection angles lower than 25° or higher than 75° in such a way that the components of the illumination system are arranged between the plane 8481 with the reticle 8467 and the plane 8483 with the wafer 8473. In a scannertype lithography projection exposure apparatus equipped with a pulsed light source the dose at a specific point within the object to be illuminated depends on the number of light pulses hitting the reticle plane. Assuming a stable pulse frequency of the light source and a rectangular intensity profile this number fluctuates by one count. To obtain a high dose uniformity it is advantageous that the fluctuation of the dose due to the discrete pulse sequence is minimized. This can be achieved if the first pulse and the last pulse of a pulse sequence do not contribute to the dose of an object point as much as the pulses in the middle of a pulse sequence do. A trapezoid intensity profile as shown in FIG. 87B can provide for such a behavior. Also other intensity profiles except an perfect rectangular profile are possible, e.g. a Lorentz-profile or a Gaussian profile. FIGS. 85 to 87 show the influence of superposition of the images of different first raster elements in the image plane on the intensity profile of the illumination in scanning direction, here in y-direction. To describe the effect the illumination system it is assumed to have no field mirrors for forming the arc-shaped field. Therefore images of the rectangular first raster elements are also rectangular in the image plane having the same aspect-ratio as the field raster elements. Such a rectangular field in the image plane is shown in FIG. 85 and denoted with reference number 8500. If the images 8600, 8602, 8604 of the first raster elements are superimposed almost congruently, as shown in FIG. 86A, an almost rectangular intensity profile 8606 as shown in FIG. 86B results in scanning direction. In FIG. 87A a case is shown where the images of the first raster element are not superimposed congruently in the image plane. In this application non-ideal superposition means that the images of the first raster elements are not fully congruent in the field plane. This can be achieved in that the first raster elements of the first raster element plate have a different size, e.g. a different extension in y-direction, which coincides with the scanning direction in a scannertype lithography projection exposure apparatus. To superimpose three different images 8700, 8702, 8704 not congruently in the image plane in a first embodiment the raster element plate comprises three different raster elements with a different extension in y-direction and therefore different aspect ratios. The intensity profile in y-direction resulting from the field in the image plane as shown in FIG. 87A is depicted in FIG. 87B. As it is apparent from FIG. 87B a nearly trapezoid intensity profile results from the field as shown in FIG. 87A. A non-congruent superposition of the images of the first raster elements in the image plane can also be achieved if all first raster elements have identical size, i.e. a identical aspect ratio but the corresponding second raster elements have different optical power. In such a case the images of the first raster elements have a different size in the image plane and thus are not superimposed congruently. To achieve a non-congruent superposition of the images of the first raster elements in the image plane it is possible to combine the two aforementioned methods, i.e. first raster elements of different size and different optical power of the second raster elements. A raster element plate with first raster elements as shown in FIG. 73 having raster elements of different size, i.e. extension in y-direction and therefore different aspect ratio is shown in FIG. 88. FIG. 88 shows a raster element plate with four first raster elements with a first extension in y-direction 8800.1, 8800.2, 8800.3 8800.4, four first raster elements with a second extension in y-direction 8802.1, 8802.2, 8802.3, 8802.4 and four first raster elements with a third extension in y-direction 8804.1, 8804.2, 8804.3, 8804.4. The raster elements are arranged symmetric on the raster element plate in respect to the x- and the y-axis. For obtaining also a sufficient telecentricity during the scan process it is necessary to fill the exit pupil for each field point for the different first raster elements of different size with tertiary light sources in a uniform manner. This can be achieved if the deflection angles of the deflected ray bundle of the plurality of the first raster elements is chosen in such a manner that the corresponding plurality of second raster elements are nearly point symmetric to the center of the pupil raster element plate shown, for example, in FIG. 74. In this application nearly point symmetric means that the telecentricity error in the exit pupil for each field point is less than 1 mrad, preferably less than 0.1 mrad. Since the tertiary light sources in the exit pupil for each field point of the object field corresponds to the arrangement of the second raster elements on the pupil raster element plate, the exit pupil of each field point is also filled point symmetric with tertiary light sources as shown in FIG. 89. FIG. 89 shows schematically the principle of arrangement of first and second raster elements. Two first raster elements 8900.1 and 8900.2 of identical size, which are arranged symmetrically with respect to an axis of symmetry 8910 in the first raster element plate 8950. In this case the axis of symmetry is the x-axis, which is perpendicular to the scanning direction. The deflection angles of the first raster elements 8900.1 and 8900.2 are chosen such that the corresponding pupil facets 8980.1 and 8980.2 are arranged point symmetrically with respect to the center of the second raster element plate 8990. As discussed in the examples before e.g. in FIGS. 73-79 the light source, which illuminates the first raster element plate is denoted as primary light source. The plurality of first raster elements forms a plurality of secondary light sources. The second raster element plate is arranged in or near the site of the secondary light sources. The exit pupil for seven field points is shown in FIG. 90. Point 9000 lies outside the field in the image plane. Therefore no illumination occurs in the exit pupil 9050 for this point. Point 9002 lies within the filed. The images of the first raster elements 8804.1, 8804.2, 8804.3, 8804.4 of the filed raster element plate shown in FIG. 88 are superimposed in this field point. Therefore four tertiary light sources 9010.1, 9010.2, 9010.3, 9010.4 illuminate the exit pupil 9052. The four tertiary light sources 9010.1, 9010.2, 9010.3, 9010.4 are symmetric to the center C of the exit pupil. In field point 9003 the images of eight first raster elements 8804.1, 8804.2, 8804.3, 8804.4, 8802.1, 8802.2, 8802.3, 8802.4 of the raster element plate shown in FIG. 88 are superimposed. In the exit pupil 9054 eight uniformly distributed tertiary light sources 9010.1, 9010.2, 9010.3, 9010.4, 9012.1, 9012.2, 9012.3, 9012.4 are depicted which are point symmetric to the center of the exit pupil. In field point 9004 the images of all twelve first raster elements 8804.1, 8804.2, 8804.3, 8804.4, 8802.1, 8802.2, 8802.3, 8802.4, 8800.1, 8800.2, 8800.3, 8800.4 of the raster element plate in FIG. 88 are superimposed. In the exit pupil 9056 twelve uniformly distributed tertiary light sources 9010.1, 9010.2, 9010.3, 9010.4, 9012.1, 9012.2, 9012.3, 9012.4, 9014.1, 9014.2, 9014.3, 9014.4 are depicted which are point symmetric to the center of the exit pupil. For field point 9005 the images of eight first raster elements are superimposed. The situation corresponds to the situation in filed point 9003. The exit pupil 9058 is illuminated by eight tertiary light sources. For field point 9006 the images of four first raster elements are superimposed. The situation corresponds to the situation in filed point 9002. The exit pupil 9060 is illuminated by four tertiary light sources. Point 9007 lies outside the field, therefore the exit pupil 9062 is not illuminated. If one scans an object in y-direction at the beginning 4 tertiary light sources are turned on then 8 and at last 12 light sources are turned on. Then four light sources to a total of eight light sources are turned off, in the next step further four light sources to a total of four light sources are turned off and outside the field in the image plane the exit pupil is not illuminated. As a result of the special assignment of first raster elements and second raster elements the center of gravity of the illumination of the exit pupil is located in the center of the exit pupil for each field point. Thus the telecentricity of the illumination system does not depend on the field position, a prerequisite for telecentric wafer exposure. The described feature of the exit pupil holds for any axially symmetric illumination of the first raster elements and is purely based on the assignment of first and second raster elements. According to the invention an illumination system is provided which is insensitive to fluctuations of the pulse sequence of the primary light source. Moreover the illumination system according to the invention is characterized by a optimal telecentricity during all phases of the scan process. In contrast to that illumination systems of the state of the art consider only scanning integrated telecentricity. |
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claims | 1. A spent fuel dry reprocessing method for directly obtaining a zirconium alloy nuclear fuel, comprising the steps:a. determining components and a ratio for a molten salt composition used for melting a spent fuel according to a zirconium alloy fuel design requirement and contents of actinium series metals in the spent fuel, wherein the molten salt composition comprises zirconium fluoride, potassium fluoride and lithium fluoride, and wherein a mole ratio of zirconium fluoride to potassium fluoride to lithium fluoride is 1:(10-20):(25-80);b. melting the spent fuel in the molten salt composition; andc. forming a zirconium alloy comprising uranium, zirconium and plutonium with a composition according to said zirconium alloy fuel design requirement, wherein said zirconium is derived from said molten salt composition, and said zirconium alloy is formed by an under-potential deposition process on an electrode, thereby obtaining a zirconium alloy nuclear fuel through uranium-plutonium-zirconium co-electrodeposition on the electrode. 2. The spent fuel dry reprocessing method according to claim 1, wherein a mixture of the spent fuel and the molten salt composition is molten at 600-1050° C. 3. The spent fuel dry reprocessing method according to claim 1, wherein the molten spent fuel has excess metal ions, and a pre-electrodeposition process is carried out through a second electrode pair so the excess metal ions in the spent fuel are separated. 4. The spent fuel dry reprocessing method according to claim 3, wherein the spent fuel is a metal oxide spent fuel, a positive electrode of the second electrode pair used in the pre-electrodeposition process to separate out the excess metal ions and a positive electrode of the first electrode pair selected for the electrodeposition process to form the zirconium alloy nuclear fuel are made of inert material. 5. The spent fuel dry reprocessing method according to claim 3, wherein the spent fuel is a metal spent fuel, and a positive electrode of the second electrode pair used in the pre-electrodeposition process to separate out the excess metal ions is the metal spent fuel. |
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summary | ||
summary | ||
047730870 | abstract | The quality of x-ray shadowgraphic images is improved by beam equalization controlled to ensure that just the right amount of radiation is used to accomplish the desired result, be it a desired image density and contrast or a desired signal-to-noise ratio or some other desired characteristic. The new techniques include: (1) maintaining a substantially constant signal-to-noise ratio throughout the image by measuring both scattered and primary radiation and using the results in a feedback loop to control the x-ray tube output, (2) raster scanning an x-ray beam along straight lines at constant velocity within a line by using a curved slit rotating aperture, (3) simultaneously controlling each of the intensity and hardness of a scanned x-ray beam as determined by post-patient x-ray measurements, and (4) using a segmented fan to scan the patient in a direction transverse to the plane of the fan and individually modulating each beam segment to achieve desired image characteristics. |
059321784 | description | DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS From the above-mentioned point of view, extensive studies were carried out to develop an FDG synthesizer, in which a synthesizing process is simplified, with a higher yield of a synthesized product, and the time of synthesis is reduced. As a result, the following findings were obtained: there is available an FDG synthesizer, in which a synthesizing process is simplified, with an improved yield of a synthesized product and the time of synthesis is reduced, by using a column filled with a polymer-supported phase-transfer catalyst resin obtained by fixing a phosphonium salt or a pyridinium salt to a polystyrene resin in place of a conventional labeling reaction vessel for performing a labeling reaction, and using a column filled with a cation-exchange resin in place of a conventional hydrolysis reaction vessel. The present invention was developed on the basis of the foregoing findings. An FDG synthesizer of a first embodiment of the present invention comprises: a labeling reaction resin column comprising a column filled with a polymer-supporter phase-transfer catalyst resin for trapping an .sup.18 F! fluoride ion contained in a target water, and performing a labeling reaction between the thus trapped .sup.18 F! fluoride ion and triflate, on the one hand, and a hydrolysis reaction vessel for receiving a reaction intermediate product obtained from said labeling reaction, and performing a hydrolysis reaction by adding a strong acidic aqueous solution or a strong alkaline aqueous solution, on the other hand. The above-mentioned polymer-supporter phase-transfer catalyst resin can be obtained by fixing a phosphonium salt or a pyridinium salt to a polystyrene resin. An FDG synthesizer of a second embodiment of the present invention is characterized in that said hydrolysis reaction vessel comprises a cation-exchange resin column, and said reaction intermediate product obtained from said labeling reaction is brought into contact with a cation-exchange resin adjusted to an H.sup.+ -type in said cation-exchange resin column, to perform the hydrolysis reaction. An FDG synthesizer of a third embodiment of the present invention is characterized in that said hydrolysis reaction vessel comprises a cation-exchange resin column having a heating means and a flow rate control means of said reaction intermediate product containing an organic solvent, and in said cation-exchange resin column, said reaction intermediate product containing said organic solvent obtained from said labeling reaction is heated, to evaporation-eliminate said organic solvent, and at the same time, the reaction intermediate product after the elimination of said organic solvent is brought into contact with a cation-exchange resin adjusted to an H.sup.+ type to perform said hydrolysis reaction, thereby simultaneously performing said elimination of organic solvent and said hydrolysis reaction in said cation-exchange resin column. An FDG synthesizer of a fourth embodiment of the present invention comprises: (a) a cartridge-type labeling reaction resin column, (b) a cartridge-type cation-exchange resin column, and (c) a disposable cartridge base into which paths and switchover valves for communicating said labeling reaction resin column and said cation-exchange resin column are incorporated; said cartridge-type labeling reaction resin column comprising a disposable column filled with a polymer-supported phase-transfer catalyst resin, said cartridge-type labeling reaction resin column being one-touch-releasably attachable to said cartridge base, trapping an .sup.18 F! fluoride ion contained in target water, and performing a labeling reaction between the thus trapped .sup.18 F! fluoride ion and triflate; and said cartridge-type cation-exchange resin column comprising a disposable column filled with a cation-exchange resin adjusted to an H.sup.+ type, said cartridge-type cation-exchange resin column being one-touch-releasably attachable to said cartridge base, and bringing a reaction intermediate product obtained from said labeling reaction into contact with said cation-exchange resin adjusted to an H.sup.+ type in said cation-exchange resin column to perform a hydrolysis reaction. Now, the present invention is described below with reference to the drawings. FIG. 2 is a schematic descriptive view illustrating the FDG synthesizer of the first embodiment of the present invention. The FDG synthesizer of the first embodiment of the present invention comprises a labeling reaction resin column 25 for trapping an .sup.18 F! fluoride ion contained in target water, and then performing a labeling reaction between the thus trapped .sup.18 F! fluoride ion and triflate, on the one hand, and a hydrolysis reaction vessel 35 for receiving a reaction intermediate product obtained from the labeling reaction and performing a hydrolysis reaction, on the other hand. In FIG. 2, 21 is a target box for producing an O-18 (.sup.18 O) water, i.e., target water, 42 is an ion retardation resin column, and 43 is a refining column. The labeling reaction resin column 25 comprises a column filled with a polymer-supported phase-transfer catalyst resin comprising a fixed phosphonium salt or a fixed pyridinium salt, which is obtained by fixing a phosphonium salt or a pyridinium salt to a polystyrene resin. The target water is passed through the labeling reaction resin column 25 to trap therein an .sup.18 F! fluoride ion contained in the target water, and then, an acetonitrile aqueous solution is passed through the labeling reaction resin column 25, in which the .sup.18 F! fluoride ion has been trapped, to dry the labeling reaction resin column 25. Then, a triflate solution is passed through the thus dried labeling reaction resin column 25 to perform a labeling reaction between the trapped .sup.18 F! fluoride ion and triflate. The O-18 (.sup.18 O) water, which has been passed through the labeling reaction resin column 25 and has been separated from the .sup.18 F! fluoride ion trapped therein, is recovered into an O-18(.sup.18 O) water recovery container 26 by the operation of a three-way valve 30. Then, the acetonitrile solution and the like used for drying the labeling reaction resin column 25 are recovered into a waste liquid recovery container 31 by the operation of three-way valves 30, 34. In the labeling reaction resin column 25, as described above, the .sup.18 F! fluoride ion is trapped, and then, the labeling reaction is performed there. A special process for recovering the O-18(.sup.18 O) water is not therefore required. Since moisture hinders the labeling reaction, on the other hand, moisture must be eliminated. However, by replacing the labeling reaction vessel with a column, it is possible to eliminate moisture in the column 25 only by passing the organic solvent through the column 25. Further, since the catalyst is fixed to the resin, a special process for separating and eliminating the catalyst is not required, and the labeling reaction efficiency is improved. In the hydrolysis reaction vessel 35, there is performed a hydrolysis reaction for separating a protecting group (usually an acetyl group) from a reaction intermediate product labeled through the labeling reaction in the labeling reaction resin column 25. More specifically, an acetonitrile solution of triflate is passed through the labeling reaction resin column 25 having trapped the fluoride ion, to perform a labeling reaction of triflate in the labeling reaction resin column 25. Then, the solution containing the reaction intermediate product labeled through the labeling reaction, is received in the hydrolysis reaction vessel 35 in which the above-mentioned solution is then heated to evaporate acetonitrile. Then, a strong acidic aqueous solution or a strong alkaline aqueous solution such as a hydrochloric acid aqueous solution or a sodium hydroxide aqueous solution is added to the hydrolysis reaction vessel 35, and the hydrolysis reaction vessel 35 is heated to perform a hydrolysis reaction. After the completion of the hydrolysis reaction, germfree water is added to a reaction product in the hydrolysis reaction vessel 35, and the reaction product is passed together with germfree water sequentially through the ion retardation resin column 42 and the refining column 43 to synthesize FDG. In the ion retardation resin column 42, unnecessary hydrochloric acid aqueous solution or sodium hydroxide aqueous solution is eliminated. In the refining column 23, FDG is further refined. A target water container 22, an acetonitrile container 28 and a triflate container 32 communicate with the labeling reaction resin column 25 through syringes 23, 27 and three-way valves 24, 29, 33. Further, the O-18(.sup.18 O) water recovery container 26 and the waste liquid recovery container 31 communicate with the labeling reaction resin column 25 through the three-way valves 30, 34. The labeling reaction resin column 25 communicates with the hydrolysis reaction vessel 35 through the three-way valves 30, 34. A germfree water container 39 and a hydrochloric acid aqueous solution container 36 communicate with the hydrolysis reaction vessel 35 through a syringe 37 and three-way valves 41, 38. Further, the ion retardation resin column 42 and the refining column 43 communicate with the hydrolysis reaction vessel 35 through a three-way valve 40. FIG. 3 is a schematic descriptive view illustrating the FDG synthesizer of the second embodiment of the present invention. The FDG synthesizer of the second embodiment of the invention comprises a labeling reaction resin column 48 for trapping an .sup.18 F! fluoride ion contained in a target water, and then performing a labeling reaction between the thus trapped .sup.18 F! fluoride ion and triflate, on the one hand, and a cation-exchange resin column 58 for bringing a reaction intermediate product obtained from the labeling reaction into contact with a cation-exchange resin adjusted to an H.sup.+ type and heating same for a hydrolysis reaction, on the other hand. In FIG. 3, 44 is a target box for producing an O-18(.sup.18 O) water, i.e., a target water, and 63 is a refining column. The labeling reaction resin column 48 comprises a column filled with a polymer-supported phase-transfer catalyst resin comprising a fixed phosphonium salt or a fixed pyridinium salt, which is obtained by fixing a phosphonium salt or a pyridinium salt to a polystyrene resin. As in the first embodiment of the present invention, the target water is passed through the labeling reaction resin column 48 to trap therein an .sup.18 F! fluoride ion contained in the target water, and then, an acetonitrile aqueous solution is passed through the labeling reaction resin column 48, in which the .sup.18 F! fluoride ion has been trapped, to dry the labeling reaction resin column 48. Then, a triflate solution is passed through the thus dried labeling reaction resin column 48 to perform a labeling reaction between the trapped .sup.18 F! fluoride ion and triflate. The O-18(.sup.18 O) water, which has been passed through the labeling reaction resin column 48 and has been separated from the .sup.18 F! fluoride ion trapped therein, is recovered into an O-18(.sup.18 O) water recovery container 49 by the operation of a three-way valve 53. Then,.the acetonitrile solution and the like used for drying the labeling reaction resin column 48 are recovered into a waste liquid recovery container 54 by the operation of three-way valves 53, 57. In the labeling reaction resin column 48, as described above, the .sup.18 F! fluoride ion is trapped, and then, the labeling reaction is performed there. A special process for recovering the O-18(180) water is not therefore required. Since moisture hinders the labeling reaction, on the other hand, it is necessary to eliminate moisture. However, by replacing the labeling reaction vessel with a column, it is possible to eliminate moisture in the column 48 only by passing the organic solvent through the column 48. Further, since the catalyst is fixed onto the resin, a special process for separating and eliminating the catalyst is not required, and the labeling reaction efficiency is improved. In the cation-exchange resin column 58, a hydrolysis reaction is performed for separating a protecting group (usually, an acetyl group) from a reaction intermediate product labeled through the labeling reaction in the labeling reaction resin column 48. More specifically, an acetonitrile solution of triflate is passed through the labeling reaction resin column 48 having trapped the .sup.18 F! fluoride ion, to perform a labeling reaction of triflate in the labeling reaction resin column 48. Then, the solution containing the reaction intermediate product labeled through the labeling reaction, is passed through the cation-exchange resin column 58, in which the above-mentioned solution is brought into contact with the cation-exchange resin adjusted to an H.sup.+ type, and, at the same time, acetonitrile is evaporation-eliminated. Then, the cation-exchange resin column 58 is heated at a temperature of about 130.degree. C. for 10 to 15 minutes to perform a hydrolysis reaction. In the second embodiment, unlike the first embodiment, the use of a hydrochloric acid aqueous solution or a sodium hydroxide aqueous solution is not required upon the hydrolysis reaction, thus making it unnecessary to use an ion retardation resin for eliminating such an aqueous solution or a reagent for neutralizing the same, and a reaction vessel becomes unnecessary. After the completion of the hydrolysis reaction, germfree water is added to the reaction product in the cation-exchange resin column 58, and the reaction product is passed together with the germfree water through the refining column 63 to synthesize FDG. It is thus possible to obtain FDG in the germfree water through a simple operation of only passing the reaction product together with the germfree water through the cation-exchange resin column 58 after the hydrolysis. A target water container 45, an acetonitrile container 51 and a triflate container 55 communicate with the labeling reaction resin column 48 through syringes 46, 50 and three-way valves 47, 52, 56. Further, the O-18(.sup.18 O) water recovery container 49 and the waste liquid recovery container 54 are communicated with the labeling reaction resin column 48 through the three-way valves 53, 57. The labeling reaction resin column 48 communicates with the cation-exchange resin column 58 through the three-way valves 53, 57. A germfree water container 59 communicates with the cation-exchange resin column 58 through a syringe 60 and a three-way valve 61. Further, the refining column 63 communicates with the cation-exchange resin column 58 through a three-way valve 62. FIG. 4 is a schematic perspective view illustrating the FDG synthesizer of the third embodiment of the present invention. The FDG synthesizer of the third embodiment of the present invention comprises a labeling reaction resin column 48 for trapping an .sup.18 F! fluoride ion contained in a target water, and then performing a labeling reaction between the thus trapped .sup.18 F! fluoride ion and triflate, on the one hand, and a cation-exchange resin column 58' for heating a reaction intermediate product containing an organic solvent obtained from the labeling reaction, to evaporation-eliminate the organic solvent, and at the same time, bringing the reaction intermediate product after the elimination of the organic solvent into contact with a cation-exchange resin adjusted to an H.sup.+ type, to perform a hydrolysis reaction, on the other hand. In the cation-exchange resin column 58' of the third embodiment of the present invention, the reaction intermediate product of FDG from which the organic solvent has been evaporation-eliminated in the column 58', is brought into contact with the cation-exchange resin in the column 58', by increasing the amount of evaporation per unit time of an organic solvent passing through the column 58' larger than the flow rate per unit time of an organic solvent flowing anew into the column 58', through the adjustment of the flow rate of the reaction intermediate product containing the organic solvent, passing through the column 58', and the temperature in the column 58'. The cation-exchange resin column 58' has a heating means (not shown) for adjusting the temperature in the column 58' and a flow rate control means (not shown) for controlling the flow rate of a reaction intermediate product containing an organic solvent. It is possible to increase the amount of evaporation per unit time of an organic solvent passing through the column 58' larger than the flow rate per unit time of an organic solvent flowing anew into the column 58', by adjusting the temperature in the column 58' within a range of from 90 to 150.degree. C. with the use of the heating means, and by controlling the flow rate of the reaction intermediate product containing the organic solvent within a range of from 0.5 to 1.5 cc/minute with the use of the flow rate control means. A cation-exchange resin containing moisture or a dried cation-exchange resin may be used for the cation-exchange resin column 58' of the third embodiment of the present invention. When using a cation-exchange resin containing moisture, it is desirable to use the cation-exchange resin in a sufficient amount. When using a dried cation-exchange resin, it is possible to achieve an effective hydrolysis reaction with the use of the dried cation-exchange resin in a slight amount, because of the easy separation of the reaction intermediate product from the organic solvent. When using a dried cation-exchange resin, it is necessary to add water upon the hydrolysis reaction. In FIG. 4, 44 is a target box for producing an O-18(.sup.18 O) water, i.e., a target water, and 63 is a refining column. The labeling reaction resin column 48 comprises a column filled with a polymer-supported phase-transfer catalyst resin comprising a fixed phosphonium salt or a fixed pyridinium salt, which is obtained by fixing a phosphonium salt or pyridinium salt to a polystyrene resin. As in the first embodiment of the present invention, the target water is passed through the labeling reaction resin column 48 to trap therein an .sup.18 F! fluoride ion contained in the target water, and then, an acetonitrile aqueous solution is passed through the labeling reaction resin column 48, in which the .sup.18 F! fluoride ion has been trapped, to dry the column 48. Then, a triflate solution is passed through the thus dried labeling reaction resin column 48 to perform a labeling reaction between the trapped .sup.18 F! fluoride ion and triflate. The O-18(.sup.18 O) water, which has been passed through the labeling reaction resin column 48 and has been separated from the .sup.18 F! fluoride ion trapped therein, is received into an O-18(.sup.18 O) water recovery container 49 by the operation of a three-way valve 53. Then, the acetonitrile solution and the like used for drying the labeling reaction resin column 48 are recovered into a waste liquid recovery container 54 by the operation of three-way valves 53, 57. In the labeling reaction resin column 48, as described above, the .sup.18 F! fluoride ion is trapped, and then, the labeling reaction is performed there. A special process for recovering the O-18(.sup.18 O) water is not therefore required. Since moisture hinders the labeling reaction, on the other hand, it is necessary to eliminate moisture. By replacing the labeling reaction vessel with a column, however, it is possible to eliminate moisture in the column 48 only by passing the organic solvent through the column 48. Further, since the catalyst is fixed to the resin, a special process for separating and eliminating the catalyst is not required, and the labeling reaction efficiency is improved. In the cation-exchange resin column 58', a hydrolysis reaction is performed for separating a protecting group (usually, an acetyl group) from a reaction intermediate product labeled through the labeling reaction in the labeling reaction resin column 48. More specifically, an organic solvent (acetonitrile) is evaporation-eliminated by passing the reaction intermediate product containing the organic solvent at a flow rate within a range of from 0.5 to 1.5 cc/minute through the cation-exchange resin column 58' with the use of the flow rate control means (not shown), and at the same time, the reaction intermediate product after the elimination of the organic solvent is heated at a temperature of about 130.degree. C. for 10 to 15 minutes, while bringing the same into contact with the cation-exchange resin adjusted to an H.sup.+ type, to perform a hydrolysis reaction. It is therefore possible to prevent the reaction intermediate product produced in the labeling reaction from flowing out together with the organic solution from the cation-exchange resin column 58' without being trapped by the column 58'. Furthermore, since the use of a hydrochloric acid aqueous solution or a sodium hydroxide aqueous solution is not required upon the hydrolysis reaction, it is not necessary to use an ion retardation resin for eliminating such an aqueous solution or a reagent for neutralizing the same, and a reaction vessel becomes unnecessary. According to the FDG synthesizer of the third embodiment of the present invention, it is possible to perform the elimination of the organic solvent upon the passing of the reaction intermediate product through the cation-exchange resin column 58', and then, to perform a hydrolysis reaction in the column 58'. After the completion of the hydrolysis reaction, germfree water is added to the reaction product in the cation-exchange resin column 58', and the reaction product is passed together with the germfree water through the refining column 63 to synthesize FDG. It is thus possible to obtain FDG in the germfree water through a simple operation of only passing the reaction product together with the germfree water through the cation-exchange resin column 58' after the hydrolysis. As in the second embodiment, a target water container 45, an acetonitrile container 51 and a triflate container 55 are communicated with the labeling reaction resin column 48 through syringes 46, 50 and three-way valves 47, 52, 56. Further, the O-18(.sup.18 O) water recovery container 49 and the waste liquid recovery container 54 communicate with the labeling reaction resin column 48 through three-way valves 53, 57. The labeling reaction resin column 48 communicates with the cation-exchange resin column 58' through the three-way valves 53, 57. A germfree water container 59 communicates with the cation-exchange resin column 58' through a syringe 60 and a three-way valve 61. Further, the refining column 63 communicates with the cation-exchange resin column 58' through a three-way valve 62. FIG. 5 is a schematic descriptive view illustrating the FDG synthesizer of the fourth embodiment of the present invention. The FDG synthesizer of the fourth embodiment of the present invention comprises (a) a cartridge-type labeling reaction resin column 67, (b) a cartridge-type cation-exchange resin column 80, and (c) a disposable cartridge base 89 into which paths and switchover valves for communicating the labeling reaction resin column 67 and the cation-exchange resin column 80 are incorporated. The above-mentioned FDG synthesizer of the fourth embodiment of the present invention is one-touch-attachable to a synthesizer body (not shown) comprising a driving means for driving the switchover valves, a syringe driving means for driving syringes, a heating means for heating the columns 67, 80, and a gas supply means for transferring liquid and for drying the columns 67, 80. In FIG. 5, P1 to P16 are pinch valves. The cartridge-type cation-exchange resin column 80 is disposable, and one-touch-releasably attachable to the cartridge base 89. In the cartridge-type cation-exchange resin column 80, a reaction intermediate product of FDG from which an organic solvent has been evaporation-eliminated in the column 80, is brought into contact with the cation-exchange resin in the column 80, by increasing the amount of evaporation per unit time of an organic solvent passing through the column 80 larger than the flow rate per unit time of an organic solvent flowing anew into the column 80, through the adjustment of the flow rate of the reaction intermediate product containing the organic solvent, passing through the column 80, and the temperature in the column 80. The cation-exchange resin column 80 has a heating means (not shown) for adjusting the temperature in the column 80, and a flow rate control means (not shown) for controlling the flow rate of a reaction intermediate product containing an organic solvent. It is possible to increase the amount of evaporation per unit time of an organic solvent passing through the column 80 larger than the flow rate per unit time of an organic solvent flowing anew into the column 80, by adjusting the temperature in the column 80 within a range of from 90 to 150.degree. C. with the use of the heating means, and by controlling the flow rate of the reaction intermediate product containing the organic solvent within a range of from 0.5 to 1.5 cc/minute with the use of the flow rate control means. As in the third embodiment, a cation-exchange resin containing moisture or a dried cation-exchange resin may be used for the cation-exchange resin column 80 in the fourth embodiment of the present invention. When using a cation-exchange resin containing moisture, it is desirable to use the moisture-containing cation-exchange resin in a sufficient amount. When using a dried cation-exchange resin, it is possible to achieve an effective hydrolysis reaction with the use of the dried cation-exchange resin in a slight amount, because of the easy separation of the reaction intermediate product from the organic solvent. When using a dried cation-exchange resin, it is necessary to add water upon hydrolysis reaction. The cartridge-type labeling reaction resin column 67 is disposable and one-touch-releasably attachable to the cartridge base 89. The cartridge-type labeling reaction resin column 67 comprises a column filled with a polymer-supported phase-transfer catalyst resin comprising a fixed phosphonium salt or a fixed pyridinium salt, which is obtained by fixing a phosphonium salt or a pyridinium salt to a polystyrene resin. As in the first embodiment of the present invention, the target water is passed through the labeling reaction resin column 67 to trap therein an .sup.18 F! fluoride ion contained in the target water, and then, an acetonitrile aqueous solution is passed through the labeling reaction resin column 67, in which the .sup.18 F! fluoride ion has been trapped, to dry the column 67. Then, a triflate solution is passed through the thus dried labeling reaction resin column 67 to perform a labeling reaction between the trapped .sup.18 F! fluoride ion and triflate. The O-18(.sup.18 O) water, which has been passed through the labeling reaction resin column 67 and has been separated from the .sup.18 F! fluoride ion trapped therein, is recovered into an O-18(.sup.18 O) water recovery container (not shown) connected to a connector 68 by the operation of the pinch valves P3, P7, P10. Then, the acetonitrile solution and the like used for drying the labeling reaction resin column 67 are recovered into a waste liquid recovery container (not shown) connected to a connector 75 by the operation of the pinch valves P3, P7, P10. In the labeling reaction resin column 67, as described above, the .sup.18 F! fluoride ion is trapped, and then the labeling reaction is performed there. A special process for recovering the O-18(.sup.18 O) water is not therefore required. Since moisture hinders the labeling reaction, on the other hand, it is necessary to eliminate moisture. By replacing the reaction vessel with a column, however, it is possible to eliminate moisture in the column 67 only by passing the organic solvent through the column 67. Further, since the catalyst is fixed to the resin, a special process for separating and eliminating the catalyst is not required, and the labeling reaction efficiency is improved. Furthermore, since the labeling reaction resin column 67 is of the cartridge type, it is possible to easily make a replacement and a setup thereof, and to prevent fluctuations of the synthesizing yield and quality of FDG. In the cartridge-type cation-exchange resin column. 80, a hydrolysis reaction is performed for separating a protecting group (usually, an acetyl group) from a reaction intermediate product labeled through the labeling reaction in the labeling reaction resin column 67. More specifically, a triflate solution is passed through the labeling reaction resin column 67 in which the .sup.18 F! fluoride ion has been trapped, and then, the solution produced by the labeling reaction is brought into contact a cation-exchange resin adjusted to an H.sup.+ type, and, at the same time, acetonitrile is evaporated, and then, a hydrolysis reaction is performed at a temperature of about 130.degree. C. for 10 to 15 minutes. In the cartridge-type cation-exchange resin column 80, as described above, a reaction intermediate product of FDG from which an organic solvent has been evaporation-eliminated in the column 80, is brought into contact with the cation-exchange resin in the column 80, by increasing the amount of evaporation per unit time of an organic solvent passing through the column 80 larger than the flow rate per unit time of an organic solvent flowing anew into the column 80, through the adjustment of the flow rate of the reaction intermediate product containing the organic solvent, passing through the column 80, and temperature in the column 80. Therefore, since the use of a hydrochloric acid aqueous solution or a sodium hydroxide aqueous solution is not required upon the hydrolysis reaction, it is not necessary to use an ion retardation resin for eliminating such an aqueous solution or a reagent for neutralizing the same, and a reaction vessel becomes unnecessary. Further, because the cation-exchange resin column 80 is of the cartridge type, it is possible to easily make a replacement and a setup thereof, and to prevent fluctuations of the synthesizing yield and quality of FDG. After the completion of the hydrolysis reaction, germfree water is added to the reaction product in the cation-exchange resin column 80, and the reaction product is passed together with the germfree water through a refining column 88 to synthesize FDG. It is thus possible to obtain FDG in the germfree water through a simple operation of only passing the reaction product together with the germfree water through the cation-exchange resin column 80 after the hydrolysis. A target water container 64, an acetonitrile container 70, a triflate container 77, a germfree water container 83 and syringes 65, 69, 84 are attached to the cartridge base 89. Connectors of the individual cartridge-type columns can be easily attached to and detached from the cartridge base 89. For example, a Luer-type connector is preferable. Paths communicating between two pinch valves or between a pinch valve and a connector comprise a teflon tube or a polypropylene tube. These paths may be formed by directly piercing throughholes in the cartridge base 89 itself. FIG. 6 is a schematic descriptive view illustrating the FDG synthesizer of the fifth embodiment of the present invention. The FDG synthesizer of the fifth embodiment of the present invention comprises (a) a cartridge-type labeling reaction resin column 67, (b) a cartridge-type cation-exchange resin column 80, and (c) a disposable cartridge base 89 into which paths and switchover valves for communicating the labeling reaction resin column 67 and the cation-exchange resin column 80 are incorporated. The above-mentioned FDG synthesizer of the fifth embodiment of the present invention is one-touch-attachable to a synthesizer body (not shown) comprising a driving means for driving the switchover valves, a syringe driving means for driving syringes, a heating means for heating the columns 67, 80, and a gas supply means for transferring liquid and for drying the columns 67, 80. In FIG. 6, 66, 71 to 74, 76, 78, 79, 81, 82 and 85 are three-way valves each incorporating a three-way switchover cock therein. The FDG synthesizer of the fifth embodiment differs from the FDG synthesizer of the fourth embodiment described above in that three-way valves are used in the fifth embodiment, whereas pinch valves are used in the fourth embodiment. As in the fourth embodiment, the cartridge-type cation-exchange resin column 80 of the fifth embodiment of the present invention is disposable, and one-touch-attachable to the cartridge base 89. In the cartridge-type cation-exchange resin column 80, a reaction intermediate product of FDG from which an organic solvent has been evaporation-eliminated in the column 80, is brought into contact with the cation-exchange resin in the column 80, by increasing the amount of evaporation per unit time of an organic solvent passing through the column 80 larger than the flow rate per unit time of an organic solvent flowing anew into the column 80, through the adjustment of the flow rate of the reaction intermediate product containing the organic solvent, passing through the column 80, and the temperature in the column 80. As in the fourth embodiment, the cation-exchange resin column 80 has a heating means (not shown) for adjusting the temperature in the column 80, and a flow rate control means (not shown) for controlling the flow rate of a reaction intermediate product containing an organic solvent. It is possible to increase the amount of evaporation per unit time of an organic solvent passing through the column 80 larger than the flow rate per unit time of an organic solvent flowing anew into the column 80, by adjusting the temperature in the column 80 within a range of from 90 to 150.degree. C. with the use of the heating means, and by controlling the flow rate of the reaction intermediate product containing the organic solvent within a range of from 0.5 to 1.5 cc/minute with the use of the flow rate control means. As in the third embodiment, a cation-exchange resin containing moisture or a dried cation-exchange resin may be used for the cation-exchange resin column 80 in the fifth embodiment of the present invention. When using a cation-exchange resin containing moisture, it is desirable to use the moisture-containing cation-exchange resin in a sufficient amount. When using a dried cation-exchange resin, it is possible to achieve an effective hydrolysis reaction with the use of the dried cation-exchange resin in a slight amount, because of the easy separation of the reaction intermediate product from the organic solvent. When using a dried cation-exchange resin, it is necessary to add water upon hydrolysis reaction. The cartridge-type labeling reaction resin column 67 is disposable and one-touch-releasably attachable to the cartridge base 89. The cartridge-type labeling reaction resin column 67 comprises a column filled with a polymer-supported phase-transfer catalyst resin comprising a fixed phosphonium salt or a fixed pyridinium salt, which is obtained by fixing a phosphonium salt or a pyridinium salt to a polystyrene resin. As in the first embodiment of the present invention, the target water is passed through the labeling reaction resin column 67 to trap an .sup.18 F! fluoride ion contained in the target water, and then, an acetonitrile aqueous solution is passed through the labeling reaction resin column 67, in which the .sup.18 F! fluoride ion has been trapped, to dry the column 68. Then, a triflate solution is passed through the thus dried labeling reaction resin column 67 to perform a labeling reaction between the trapped .sup.18 F! fluoride ion and triflate. The O-18(.sup.18 O) water, which has been passed through the labeling reaction resin column 67 and has been separated from the .sup.18 F! fluoride ion trapped therein, is recovered into an O-18(.sup.18 O) water recovery container (not shown) connected to a connector 68 by the operation of the three-way valve 74. Then, the acetonitrile solution and the like used for drying the labeling reaction resin column 67 are recovered into a waste liquid recovery container (not shown) connected to a container 75 by the operation of the three-way valves 74, 78. In the labeling reaction resin column 67, as described above, the .sup.18 F! fluoride ion is trapped, and then, the labeling reaction is performed there. A special process for recovering the O-18(.sup.18 O) water is not therefore required. Since moisture hinders the labeling reaction, on the other hand, it is necessary to eliminate moisture. By replacing the reaction vessel with a column, however, it is possible to eliminate moisture in the column 67 only by passing the organic solvent through the column 67. Further, since the catalyst is fixed to the resin, a special process for separating and eliminating the catalyst is not required, and the labeling reaction efficiency is improved. Furthermore, since the labeling reaction resin column 67 is of the cartridge type, it is possible to easily make a replacement and a setup thereof, and to prevent fluctuations of the synthesizing yield and quality of FDG. In the cartridge-type cation-exchange resin column 80, a hydrolysis reaction is performed for separating a protecting group (usually, an acetyl group) from a reaction intermediate product labeled through the labeling reaction in the labeling reaction resin column 67 is performed. More specifically, a triflate solution is passed through the labeling reaction resin column 67 in which the .sup.18 F! fluoride ion has been trapped, and then, the solution produced by the labeling reaction is brought into contact with a cation-exchange resin adjusted to an H.sup.+ type, and at the same time, acetonitrile is evaporated, and then, a hydrolysis reaction is performed at a temperature of about 130.degree. C. for 10 to 15 minutes. In the cartridge-type cation-exchange resin column 80, as described above, a reaction intermediate product of FDG from which an organic solvent has been evaporation-eliminated in the column 80, is brought into contact with the cation-exchange resin in the column 80, by increasing the amount of evaporation per unit time of an organic solvent passing through the column 80 larger than the flow rate per unit time of an organic solvent flowing anew into the column 80, through the adjustment of the flow rate of the reaction intermediate product containing the organic solvent, passing through the column 80, and temperature in the column 80. Therefore, since the use of a hydrochloric acid aqueous solution or a sodium hydroxide aqueous solution is not required upon the hydrolysis reaction, it is not necessary to use an ion retardation resin for eliminating such an aqueous solution or a reagent for neutralization of the same, and a reaction vessel becomes unnecessary. Further, because the cation-exchange resin column 80 is of the cartridge type, it is possible to easily make a replacement and a setup thereof, and to prevent fluctuations of the synthesis product yield and quality of FDG. After the completion of the hydrolysis reaction, as in the fourth embodiment, germfree water is added to the reaction product in the cation-exchange resin column 80, and the reaction product is passed together with the germfree water through a refining column 88 to synthesize FDG. It is thus possible to obtain FDG in the germfree water through a simple operation of only passing the reaction product together with the germfree water through the cation-exchange resin column 80 after the hydrolysis. A target water container 64, an acetonitrile container 70, a triflate container 77, a germfree water container 83 and syringes 65, 69, 84 are attached to the cartridge base 89. Connectors of the individual cartridge-type columns can be easily attached to and detached from the cartridge base 89. For example, a Luer-type connector is preferable. Paths communicating between two three-way valves or between a three-way valve and a connector comprise a teflon tube or a polypropylene tube. These paths may be formed by directly piercing throughholes in the cartridge base 89 itself. The FDG synthesizer of the present invention is described further in detail by means of examples. EXAMPLE 1 A labeling reaction resin column 25 (refer to FIG. 2) of the first embodiment of the present invention was formed by filling a stainless steel cylinder having an inside diameter of 2 mm and a length of 5 cm with a slurry-like mixture which was prepared by mixing 100 to 200 mesh resin powder with a mixed solvent of ethanol and water. As shown in FIG. 2, a target water, i.e., an irradiated O-18(.sup.18 O) water containing an .sup.18 F! fluoride ion was sent from a target box 21 to a target water container 22. Then, the target water was sucked up from the target water container 22 by means of a syringe 23, by switching over a three-way valve 24, and then, the thus sucked up target water was sent to the labeling reaction resin column 25 heated to a temperature within a range of from 80 to 100.degree. C. by switching over three-way valves 24 and 29. The .sup.18 F! fluoride ion was trapped into the resin in the labeling reaction resin column 25, and at the same time, the O-18(.sup.18 O) water was separated. Then, the separated O-18(.sup.18 O) water was sent to an O-18(.sup.18 O) water recovery container 26, by switching over a three-way valve 30. Then, acetonitrile was sucked up from an acetonitrile container 28 by means of a syringe 27, by switching over three-way valves 29, 33, and then, the thus sucked up acetonitrile was passed through the labeling reaction resin column 25 by switching over the three-way valves 24, 29, to dry the labeling reaction resin column 25. Then, the used acetonitrile was discharged into a waste liquid recovery container 31, by switching over the three-way valves 30, 34. Then, a triflate solution was sucked up from a triflate container 32 by means of a syringe 27 by switching over the three-way valve 33, and then, the thus sucked up triflate solution was passed through the labeling reaction resin column 25, by switching over the three-way valves 24, 29, 33, to perform a labeling reaction of triflate in the labeling reaction resin column 25. Then, the solution containing the reaction intermediate product was sent to a hydrolysis reaction vessel 35, by switching over three-way valves 30, 34, 41. Then, the hydrolysis reaction vessel 35 was heated to evaporate acetonitrile, and then, a hydrochloric acid aqueous solution was sucked up from a hydrochloric acid aqueous solution container 36 by means of a syringe 37, by switching over a three-way valve 38, and then, the thus sucked up hydrochloric aqueous acid solution was sent to the hydrolysis reaction vessel 35, by switching over the three-way valves 38, 41, 34. Then, the hydrolysis reaction vessel 35 was heated to a temperature of about 130.degree. C. for 10 to 15 minutes to perform a hydrolysis reaction. After the hydrolysis reaction, germfree water was sucked up from a germfree water container 39 by means of the syringe 37, by switching over the three-way valves 38, 41, and then, the thus sucked up germfree water was sent to the hydrolysis reaction vessel 35, by switching over the three-way valves 38, 41, 34. Then, the reaction product was passed, together with the germfree water, sequentially through an ion retardation resin column 42 and a refining column 43, by switching over a three-way valve 40, to obtain FDG. Results of sythesis of FDG according to the FDG synthesizer of the first embodiment of the present invention are shown in Tables 1 and 2. TABLE 1 ______________________________________ FDG synthesizer FDG synthesizer of the prior art of the invention Time Time No. Operation (min:sec) No. Operation (min:sec) ______________________________________ 1 Recovery of 1:38 1 Recovery of 1:38 0-18 (.sup.18 O) 0-18 (.sup.18 O) water water 2 Addition of 0:47 K.sub.2 CO.sub.3 3 Addition of 0:32 kryptofix 0:32 222 4 Evaporation 3:30 2 Evaporation 3:00 -1 (Addition of CH.sub.3 CN) 5 Addition of 0:35 acetonitrile 6 Evaporation 1:45 -2 7 Addition of 0:56 triflate 8 Labeling 5:00 3 Labeling 1:00 reaction reaction 9 Addition of 0:49 water 10 Collection 1:09 of SepPak 11 Addition of 0:49 water 12 Washing of 1:10 SepPak 13 Extraction 1:22 of SepPak 14 Concentra- 2:36 4 Concentra- 2:36 tion tion 15 Addition of 0:35 5 Addition of 0:35 hydrochloric hydrochloric acid acid 16 Hydrolysis 10:00 6 Hydrolysis 10:00 reaction reaction 17 Elimination 2:00 7 Elimination 2:00 of hydro- of hydro- chloric acid chloric acid 18 Refining 1:15 8 Refining 1:15 Total time 36:28 Total time 22:04 required required ______________________________________ TABLE 2 ______________________________________ FDG synthesizer FDG synthesizer of the prior art of the invention ______________________________________ Yield rate of labeling about 30-70% about 80% reaction product Total time required about 45 minutes about 25 minutes for FDG synthesis Yield rate of FDG about 23-54% about 69% synthesis product ______________________________________ According to the FDG synthesizer of the first embodiment of the present invention, as is clear from Table 1, the FDG synthesizing process can be simplified to about half that of the prior art, and the total time required for FDG synthesis is largely reduced. Further, according to the FDG synthesizer of the first embodiment of the present invention, as is clear from Table 2, the FDG synthesis can be performed in a shorter period of time and a higher yield rate of the FDG synthesis product is achieved, as compared with the prior art. EXAMPLE 2 A labeling reaction resin column 48 (refer to FIG. 3) of the second embodiment of the present invention was formed, in the same manner as in the Example 1, by filling a stainless steel cylinder having an inside diameter of 2 mm and a length of 5 cm with a slurry-like mixture which was prepared by mixing 100 to 200 mesh resin powder with a mixed solvent of ethanol and water. A cation-exchange resin column 58 (refer to FIG. 3) of the second embodiment of the present invention was formed, by filling a stainless steel cylinder having an inside diameter of 12 mm and a length of 4 cm with a cation-exchange resin adjusted to an H.sup.+ type. As shown in FIG. 3, a target water, i.e., an irradiated O-18(.sup.18 O) water containing an fluoride ion was sent from a target box 44 to a target water container 45. Then, the target water was sucked up from the target water container 45 by means of a syringe 46, by switching over a three-way valve 47, and then, the thus sucked up target water was sent to the labeling reaction resin column 48 heated to a temperature within a range of from 80 to 100.degree. C. by switching over the three-way valves 47, 52. The .sup.18 F! fluoride ion was trapped into the resin in the labeling reaction resin column 48, and at the same time, the O-18(.sup.18 O) water was separated. Then, the separated O-18(.sup.18 O) water was sent to an O-18(.sup.18 O) water recovery container 49, by switching over a three-way valve 53. Then, acetonitrile was sucked up from an acetonitrile container 51 by means of a syringe 50, by switching over the three-way valves 52, 56, and then, the thus sucked up acetonitrile was passed through the labeling reaction resin column 48, by switching over the three-way valves 52, 47, to dry the labeling reaction resin column 48. Then, the used acetonitrile was discharged into a waste liquid recovery container 54, by switching over the three-way valves 53, 57. Then, a triflate solution was sucked up from a triflate container 55 by means of the syringe 50, by switching over a three-way valve 56, and then, the thus sucked up triflate solution was passed through the labeling reaction resin column 48, by switching over the three-way valves 56, 52, 47, to perform a labeling reaction of triflate in the labeling reaction resin column 48. Then, a reaction intermediate product containing acetonitrile was sent to the cation-exchange resin column 58, by switching over the three-way valves 53, 57. Then, acetonitrile was evaporated in the cation-exchange resin column 58, and then, the cation-exchange resin column 58 was heated to a temperature of about 130.degree. C. for 10 to 15 minutes to perform a hydrolysis reaction. After the hydrolysis reaction, germfree water was sucked up from a germfree water container 59 by means of a syringe 60, by switching over a three-way valve 61, and then, the thus sucked up germfree water was sent to the cation-exchange resin column 58, by switching over the three-way valves 61, 57. Then, the reaction product was passed, together with the germfree water, through a refining column 63, by switching over a three-way valve 62, to obtain FDG. Results of synthesis of FDG according to the FDG synthesizer of the second embodiment of the present invention are shown in Table 3. TABLE 3 ______________________________________ FDG synthesizer FDG synthesizer of the prior art of the invention Time Time No. Operation (min:sec) No. Operation (min:sec) ______________________________________ 1 Recovery of 1:38 1 Recovery of 1:38 0-18 (.sup.18 O) 0-18 (.sup.18O) water water 2 Addition of 0:47 K.sub.2 CO.sub.3 3 Addition of 0:32 kryptofix 222 4 Evaporation 3:30 2 Evaporation 3:00 -1 (Addition of CH.sub.3 CN) 5 Addition of 0:35 acetonitrile 6 Evaporation 1:45 -2 7 Addition of 0:56 triflate 8 Labeling 5:00 3 Labeling 1:00 reaction reaction 9 Addition of 0:49 water 10 Collection 1:09 of SepPak 11 Addition of 0:49 water 12 Washing of 1:10 SepPak 13 Extraction 1:22 of SepPak 14 Concentra- 2:36 4 Concentra- 2:36 tion tion 15 Addition of 0:35 hydrochloric acid 16 Hydrolysis 10:00 5 Hydrolysis 10:00 reaction reaction 17 Elimination 2:00 of hydro- chloric acid 18 Refining 1:15 6 Refining 1:15 Total time 36:28 Total time 19:29 required required ______________________________________ According to the FDG synthesizer of the second embodiment of the present invention, as is clear from Table 3, the FDG synthesizing process can be simplified to about a half that of the prior art, and the total time required for the FDG synthesis is largely reduced. Furthermore, as is clear from Tables 1 and 2, the time required for FDG synthesis in the synthesizer of the second embodiment is shorter by two minutes and 35 seconds than the time required for FDG synthesis in the synthesizer of the first embodiment. EXAMPLE 3 A labeling reaction resin column 48 (refer to FIG. 4) of the third embodiment of the present invention was formed, in the same manner as in the Example 1, by filling a stainless steel cylinder having an inside diameter of 2 mm and a length of 5 cm with a slurry-like mixture which was prepared by mixing 100 to 200 mesh resin powder with a mixed solvent of ethanol and water. A cation-exchange resin column 58' (refer to FIG. 4) of the third embodiment of the present invention was formed, by filling a stainless steel cylinder having an inside diameter of 12 mm and a length of 4 cm with a cation-exchange resin adjusted to an H.sup.+ type. A heating means (not shown) for adjusting the temperature in the cation-exchange resin column 58' and a flow rate control means (not shown) for controlling the flow rate of a reaction intermediate product containing an organic solvent passing through the column 58' were provided in the column 58'. As shown in FIG. 4, a target water, i.e., an irradiated O-18(.sup.18 O) water containing an .sup.18 F! fluoride ion, was sent from a target box 44 to a target water container 45. Then, the target water was sucked up from the target water container 45 by means of a syringe 46, by switching over a three-way valve 47, and then, the thus sucked up target water was sent to the labeling reaction resin column 48 heated to a temperature within a range of from 80 to 100.degree. C. by switching over the three-way valves 47, 52. The .sup.18 F! fluoride ion was trapped into the resin in the labeling reaction resin column 48, and at the same time, the O-18(.sup.18 O) water was separated. Then, the separated O-18(.sup.18 O) water was sent to an O-18(.sup.18 O) water recovery container 49, by switching over a three-way valve 53. Then, acetonitrile was sucked up from an acetonitrile container 51 by means of a syringe 50, by switching over the three-way valves 52, 56, and then, the thus sucked up acetonitrile was passed through the labeling reaction resin column 48, by switching over the three-way valves 52, 47, to dry the labeling reaction resin column 48. Then, the used acetonitrile was discharged into a waste liquid recovery container 54, by switching over the three-way valves 53, 57. Then, a triflate solution was sucked up from a triflate container 55 by means of the syringe 50, by switching over the three-way valve 56, and then, the thus sucked up triflate solution was passed through the labeling reaction resin column 48, by switching over the three-way valves 56, 52, 47, to perform a labeling reaction of triflate in the labeling reaction resin column 48. Then, a reaction intermediate product containing acetonitrile was sent to the cation-exchange resin column 58', by switching over the three-way valves 53, 57. Then, by operating the flow rate control means (not shown) and the heating means (not shown) described above, the flow rate of the reaction intermediate product containing acetonitrile in the column 58' was adjusted to 0.7 cc/minute, and the temperature in the column 58' was adjusted to about 120.degree. C. As a result, the amount of evaporation per unit time of acetonitrile passing through the column 58' was increased larger than the flow rate per unit time of acetonitrile flowing anew into the column 58'. Therefore, acetonitrile was substantially completely evaporation-eliminated in the cation-exchange resin column 58', and at the same time, the reaction intermediate product could be effectively trapped in the column 58'. Then, the cation-exchange resin column 58' was heated to a temperature of about 130.degree. C. for 10 to 15 minutes to perform a hydrolysis reaction. After the hydrolysis reaction, germfree water was sucked up from a germfree water container 59 by means of a syringe 60, by switching over a three-way valve 61, and then, the thus sucked up germfree water was sent to the cation-exchange resin column 58', by switching over the three-way valves 61, 57. Then, the reaction product was passed, together with the germfree water, through a refining column 63, by switching over a three-way valve 62, to obtain FDG. Results of synthesis FDG according to the FDG synthesizer of the third embodiment of the present invention were the same as the results of synthesis in the Example 2 shown in Table 3. According to the FDG synthesizer of the third embodiment of the present invention, as is clear from Table 3, the FDG synthesizing process can be simplified to about a half that of the prior art, and the total time required for the FDG synthesis is largely reduced, as in the Example 2. EXAMPLE 4 A cartridge-type labeling reaction resin column 67 (refer to FIG. 5) of the fourth embodiment of the present invention was formed, by filling a stainless steel cylinder having an inside diameter of 2 mm and a length of 5 cm with a slurry-like mixture which was prepared by mixing a 100 to 200 mesh resin powder with a mixed solvent of ethanol and water. A cartridge-type cation-exchange resin column 80 (refer to FIG. 5) of the fourth embodiment of the present invention was formed, by filling a stainless steel cylinder having an inside diameter of 12 mm and a length of 4 cm with a cation-exchange resin adjusted to an H.sup.+ type. As shown in FIG. 5, a target water, i.e., an irradiated O-18(.sup.18 O) water containing an .sup.18 F! fluoride ion was sent from a target box (not shown) to a target water container 64. Then, the target water was sucked up from the target water container 64 by means of a syringe 65, by operating pinch valves P1, P2, and then, the thus sucked up target water was sent to the labeling reaction resin column 67 heated to a temperature within a range of from 80 to 100.degree. C. by operating the pinch valves P1, P2, P6. The .sup.18 F! fluoride ion was trapped into the resin in the labeling reaction resin column 67, and at the same time, the O-18(.sup.18 O) water was separated. Then, the separated O-18(.sup.18 O) water was sent to an O-18(.sup.18 O) water recovery container (not shown) connected to a connector 68, by operating pinch valves P3, P7, P10. Then, acetonitrile was sucked up from a acetonitrile container 70 by means of a syringe 69, by operating the pinch valves P6, P8, P5, P4, P9, and then, the thus sucked up acetonitrile was passed through the labeling reaction resin column 67, by operating pinch valves P5, P6, P2, to wash the interior of the labeling reaction resin column 67. Then, a helium gas was passed through the labeling reaction resin column 67, by operating pinch valves P8, P6, P2, to sufficiently dry the column 67. On the other hand, the used acetonitrile was discharged into a waste liquid recovery container (not shown) connected to a connector 75, by operating the pinch valves P3, P7, P10, P11. Then, a triflate solution was sucked up from a triflate container 77 by means of the syringe 69, by operating pinch valves P4, P9, and then, the thus sucked up triflate solution was passed through the labeling reaction resin column 67, by operating the pinch valves P4, P9, P8, P2, to perform a labeling reaction of triflate in the labeling reaction resin column 67. Then, a reaction intermediate product containing acetonitrile was sent to the cation-exchange resin column 80, by operating the pinch valves P3, P7, P10, P11, P13. At this point, the reaction intermediate product containing acetonitrile had a flow rate of 0.7 cc/minute in the column 80, and the temperature in the column 80 was 120.degree. C. Then, a helium gas was passed through the cation-exchange column 80, by operating the pinch valves P10, P11, P13, to evaporation-eliminate acetonitrile remaining in the column 80, and the reaction intermediate product was trapped in the column 80. Then, the cation-exchange resin column 80 was heated to a temperature of about 130.degree. C. for 10 to 15 minutes to perform a hydrolysis reaction. At this point, the pinch valves P7, P10, P11 had been switched over toward the waste liquid recovery container 75. After the completion of the hydrolysis reaction, germfree water was sucked up from a germfree water container 83 by means of a syringe 84, by operating pinch valves P14, P15, and then, the thus sucked up germfree water was sent to the cation-exchange resin column 80, by operating the pinch valves P15, P14, P13, P11, P10. Then, the reaction product was passed, together with the germfree water, through a refining column 88, by operating pinch valves P12, P16, to obtain FDG. Results of FDG synthesis according to the FDG synthesizer of the fourth embodiment of the present invention were the same as the results of synthesis in the Example 2 shown in Table 3. According to the FDG synthesizer of the fourth embodiment of the present invention, as is clear from Table 3, the FDG synthesizing process can be simplified to about a half that of the prior art and the total time required for the FDG synthesis can largely be reduced, as in the Example 2. EXAMPLE 5 A cartridge-type labeling reaction resin column 67 (refer to FIG. 6) of the fifth embodiment of the present invention was formed, in the same manner as in the Example 4, by filling a stainless steel cylinder having an inside diameter of 2 mm and a length of 5 cm with a slurry-like mixture which was prepared by mixing a 100 to 200 mesh resin powder with a mixed solvent of ethanol and water. A cartridge-type cation-exchange resin column 80 (refer to FIG. 6) of the fifth embodiment of the present invention was formed, in the same manner as in the Example 4, by filling a stainless steel cylinder having an inside diameter of 12 mm and a length of 4 cm with a cation-exchange resin adjusted to an H.sup.+ type. As shown in FIG. 6, a target water, i.e., an irradiated O-18(.sup.18 O) water containing an fluoride ion was sent from a target box (not shown) to a target water container 64. Then, the target water was sucked up from the target water container 64 by means of a syringe 65, by switching over a three-way valve 66, and then, the thus sucked up target water was sent to the labeling reaction resin column 67 heated to a temperature within a range of from 80 to 100.degree. C. by switching over the three-way valves 66, 72. The .sup.18 F! fluoride ion was trapped into the resin in the labeling reaction resin column 67, and at the same time, the O-18(.sup.18 O) water was separated. Then, the separated O-18(.sup.18 O) water was sent to an O-18(.sup.18 O) water recovery container (not shown) connected to a connector 68, by switching over a three-way valve 74. Then, acetonitrile was sucked up from a acetonitrile container 70 by means of a syringe 69, by switching over the three-way valves 71, 76, and then, the thus sucked up acetonitrile was passed through the labeling reaction resin column 67, by switching over the three-way valves 71, 73, 72, to wash the interior of the labeling reaction resin column 67. Then, helium gas was passed through the labeling reaction resin column 67, by switching over the three-way valves 72, 73, to sufficiently dry the column 67. On the other hand, the used acetonitrile was discharged into a waste liquid recovery container (not shown) connected to a connector 75, by switching over the three-way valves 74, 78. Then, a triflate solution was sucked up from a triflate container 77 by means of the syringe 69, by switching over a three-way valve 76, and then, the thus sucked up triflate solution was passed through the labeling reaction resin column 67, by switching over the three-way valves 76, 71, 73, 72, to perform a labeling reaction of triflate in the labeling reaction resin column 67. Then, a reaction intermediate product containing acetonitrile was sent to the cation-exchange resin column 80, by switching over the three-way valves 74, 78, 79. At this point, the reaction intermediate product containing acetonitrile had a flow rate of 0.7 cc/minute in the column 80, and the temperature in the column 80 was 120.degree. C. Then, helium gas was passed through the cation-exchange resin column 80, by switching over the three-way valves 79, 81, to evaporation-eliminate acetonitrile remaining in the column 80, and the reaction intermediate product was trapped in the column 80. Then, the cation-exchange resin column 80 was heated to a temperature of about 130.degree. C. for 10 to 15 minutes to perform a hydrolysis reaction. After the completion of the hydrolysis reaction, germfree water was sucked up from a germfree water container 83 by means of a syringe 84, by switching over a three-way valve 85, and then, the thus sucked up germfree water was sent to the cation-exchange resin column 80, by switching over the three-way valves 85, 81, 79. Then, the reaction product was passed, together with the germfree water, through a refining column 88, by switching over a three-way valve 82, to obtain FDG. Results of FDG synthesis according to the FDG synthesizer of the fifth embodiment of the present invention were the same as the results of synthesis in the Example 2 shown in Table 3. According to the FDG synthesizer of the fifth embodiment of the present invention, as is clear from Table 3, the FDG synthesizing process can be simplified to about a half that of the prior art, and the total time required for the FDG synthesis can largely be reduced as in the Example 2. According to the FDG synthesizer of the present invention, as described above in detail, there is provided an FDG synthesizer, in which a synthesis process of FDG is simplified, with an improved yield of a synthesis product, and the time of synthesis is largely reduced, thus providing many industrially useful effects. |
06278756& | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Illustrated schematically in FIG. 1 is a sensor 100 configured for measuring the electrochemical corrosion potential of reactor surfaces in circulating water 102 inside a pressure vessel 104 of a conventional boiling water nuclear reactor, shown in relevant part. The sensor 100 includes a sensor tip 110 electrically connected to a central conductor 112. The sensor tip 110 may have any suitable configuration such as a cylindrical plug or tubular cup formed of stainless steel, for example, or of a noble metal such as platinum. An electrical insulator 120, e.g. of ceramic, is joined at one end to the tip 110 around the conductor 112. A connecting member 122 is joined to the insulating member 120 at an end opposite the tip 110, also around the conductor 112, and is electrically insulated from the tip 110 by the insulating member 120. In the exemplary embodiment illustrated in FIG. 1, the connecting member 122 includes a first portion 122a joined by a weld 124 to a second portion 122b to which the insulator 120 is directly attached. The first portion 122a may be formed of stainless steel, for example, and the second portion 122b may be formed of a conventional material such as Kovar, an iron-nickel-cobalt material, or from Invar also known as alloy 42, which is an iron-nickel material without cobalt for eliminating irradiation thereof during use in the boiling water reactor. The insulator 120 is typically formed of sapphire. The sensor 100 is connected to a conducting cable 128 which electrically joins the sensor tip 110 to a conventional monitoring device such as a digital voltmeter (DVM) 132 for measuring the electrochemical corrosion potential in volts. The cable 128 includes a central conductor 130 which may be stainless steel spot welded to the tip conductor 112, and an outer electrically insulating sheath which may comprise a mineral oxide ceramic, for example. In practice, a plurality of sensors are typically used in a boiling water reactor to measure electrochemical corrosion potential. The sensors are mounted in the boiling water reactor and may extend through a pressure vessel wall 104 for monitoring electrochemical corrosion potential of in-core surfaces in the water 102 circulating through the reactor core. The sensor 100 can therefore be subject to a high nuclear radiation environment, with elevated water temperatures, typically greater than 275.degree. C., and with substantial water flow rates, e.g. in excess of 10 m/s. The various components of the sensor 100 are typically sealed to prevent leakage of the water into the sensor 100. For example, the insulating member 120 is typically joined to the tip 110 and to the connecting member 122b at ceramic-to-metal braze joints 113. The brazing material may comprise, for example, a conventional silvercopper-titanium alloy, pure silver, or a silver-copper alloy. The braze joints 113 are formed by conventional brazing methods which typically occur at elevated temperatures such as about 940.degree. C. In order to reduce the likelihood of undesirable cracking between the insulating member 120 and the tip 110 and connecting member 122b, the materials of these components preferably have coefficients of thermal expansion generally similar to that of the insulating member 120 for reducing differential thermal expansion and contraction during the brazing process. For the connecting member 122b, the Kovar or alloy 42 material provides this advantage; and for the sensor tip 110, platinum is typically used. The insulating member 120 extends in part from both of its opposite ends into the tip 110 and the connecting member 122b, with a central exposed cylindrical surface 115 axially separating the tip 110 and connecting member 122b. Due to the hostile environment of high radiation, high temperature water, and relatively high flow rates of water, one known failure mode of a sensor involves dissolution of the sapphire insulator which ablates away over time. According to an exemplary embodiment of the invention, the sensor 100 is provided with a sleeve which protects the sapphire insulating member 120 and prevents deterioration thereof. An example of the sleeve is shown in FIG. 1. The sleeve 135 covers the exposed surface 115 of the insulating member 120 and overlaps adjoining portions of the tip 110 and connecting member 122b to prevent dissolution of the insulating member 120 by the circulating water 102. The sleeve 135 typically has a thickness of about 0.38-0.64 mm (15-25 mil), for example, a length of about 0.63-1.27 cm (0.25-0.5 inches) and an inner diameter of about 0.38-0.43 cm (0.15-0.17 inches). These values are of course merely exemplary. The sleeve 135 preferably extends over the braze joints 113 for protection of the braze joints 113 and for providing a redundant seal. The sleeve 135 provides an effective barrier layer atop the otherwise exposed sapphire insulator 120. The sleeve typically comprises magnesia stabilized zirconia (MSZ), yttria stabilized zirconia (YSZ), or a zirconium alloy ("zircaloy") such as zircaloy-2 or zircaloy-4. These materials have a demonstrated ability to withstand the high temperature, high flow rate, radiation environment of nuclear reactors, based on in-reactor exposure experience. The sleeve 135 may be formed by conventional methods. For example, the MSZ and YSZ sleeves may be formed by sintering a ceramic powder compact of the appropriate shape, e.g. in the shape of a cylindrical tube. The zircaloy sleeve may be formed by molding melted zircaloy into the appropriate shape, e.g. in the shape of a cylindrical tube. The sleeve 135 can also be made by forming a solid cylindrical block of MSZ, YSZ or zircaloy and boring a hole through the cylindrical block. The sleeve 135 provides enhanced protection and lifetime to the sensor 100 due to its robust nature and sealing engagement with the sensor tip 110 and connecting member 122. For example, the process of preforming the sleeve by sintering or molding provides good mechanical strength and high density. The density of the sleeve 135 is typically greater than 97.5% of the theoretical density of the selected material, more typically greater than 98 or 99% of theoretical density, most typically greater than 99.95% of theoretical density. After forming the sleeve 135 and sliding the sleeve on the sensor 100, the sleeve 135 can be further sealed in place over the insulating member 120 and portions of the sensor tip 110 and connecting member 122. According to a first embodiment shown in FIG. 1, after the sleeve 135 has been positioned on the insulating member 120, a suitable thickness of ceramic coating 137 is plasma sprayed over both ends of the sleeve 135 and a portion of the electrode tip 110 and connecting member 122b. The ceramic coating may comprise yttria stabilized zirconia (YSZ) or magnesia stabilized zirconia (MSZ), and may have a thickness of 0.5-1.0 mm, for example. Typically, a bond coat 136 is applied, e.g. by plasma spraying, to each end of the sleeve 135 and to portions of the electrode tip 110 and connecting member 122b prior to applying the ceramic coating 137. The bond coat may comprise a material such as M-Chromium-Alumina-Yttrium alloy (MCrAIY alloy), where M=NiCoFe or Ni+Co. The bond coat 136 may have a thickness of about 0.125-0.25 mm, for example. The bond coat 136 and ceramic coating 137 together seal the sleeve 135 onto the remainder of the sensor 100. Sealing of the sleeve 135 prevents water from circulating around the sapphire insulating member 120 and causing it to deteriorate. The additional coating layers 136, 137 on both ends of the sleeve 135 and portions of the sensor tip 110 and connecting member 122b provide a barrier layer for preventing corrosion along the crevice formed between both ends of the sleeve 135 and the connecting member 122b and sensor tip 110. According to a second embodiment of the invention, the sleeve is sealed onto the remainder of the sensor by threading it into adjacent components. As shown in FIG. 2, wherein like reference numbers refer to like components, threads 236, 237 are provided on the ends of the sleeve 235, on the sensor tip 210, and on the connecting member 222b. The sleeve 235 has inner threads which engage with corresponding outer threads on the sensor tip 210 and connecting member 222b. The connecting member 222b and the sensor tip 210 are typically threaded prior to applying the braze joints 113. The sleeve 235 can be screwed into the connecting member 222b to form a watertight seal. The sensor tip 210 can be screwed into the sleeve 235 to form a watertight seal. As shown in FIG. 3, the threads 236 and 237 at opposite ends of the sleeve 235 may have different diameters. For example, the threads 237 may have a larger diameter than the threads 236. In this way, the insulating member 120 can be brazed to both the connecting member 222b and the sensor tip 210 first, and then the sleeve 235 can be slid over the sensor tip 210 and insulating member 120 and screwed into the connecting member 222b. The threaded connection at 236 and 237 produces a good liquid seal to prevent water from reaching the insulator 120. Even if some water penetrates into a crevice between the sleeve and the sapphire, the sapphire will not typically experience high dissolution, because the water is stagnant. By contrast, high dissolution of sapphire has typically taken place in high flow rate water in laboratories and reactors. The sleeve can extend the lifetime of the sensor to beyond a fuel cycle and provide reliable readings of electrochemical corrosion potential in high temperature water. Accordingly, the electrochemical corrosion potential sensors having sleeves as illustrated in FIGS. 1 and 2 provide protection of the insulator 120 against dissolution in the high temperature and flow condition of the reactor water in a high radiation environment. This results in a corresponding increase in the useful life of the sensor. While there have been described herein what are considered to be preferred and exemplary embodiments of the present invention, other modifications of the invention shall be apparent to those skilled in the art from the teachings herein, and it is, therefore, desired to be secured in the appended claims all such modifications as fall within the true spirit and scope of the invention. |
description | This application is a division of U.S. application Ser. No. 11/462,999, entitled “Gamma Source for Active Interrogation,” filed Aug. 7, 2006, which claims priority to U.S. Patent Provisional Application 60/705,763, filed Aug. 5, 2005, the disclosure of which are both expressly incorporated by reference in their entirety. The invention described and claimed herein was made in part utilizing funds supplied by the U.S. Department of Energy under Contract No. DE-ACO3-76SF00098. The government has certain rights in this invention. 1. Field of the Invention This invention relates generally to detection of special nuclear materials, and, more specifically, to a compact, low-cost gamma ray generator to aid in such detection. 2. Background Many non-intrusive active interrogation techniques utilize neutrons or gamma rays to detect special nuclear material (SNM) concealed in cargo. For active interrogation systems with neutron sources, neutron induced gamma rays are detected and, sometimes, transmitted neutrons are measured. Neutron induced gamma spectra of different materials are used as the fingerprints for them. Fast neutrons are often in use to obtain a deep penetration into large inspected objects and, thus, generate a very high background from surrounding materials. While this high background restricts the maximum screening speed of many neutron-based systems, neutrons also tend to activate the surrounding materials after an extensive long period of operation. On the other hand, gamma-based systems detect neutrons produced from photonuclear reactions or transmitted gamma rays. Because the neutron production cross sections of many special nuclear materials due to photofission are much higher than that of most common materials, the neutron background in gamma-based interrogation techniques is fairly low. Furthermore, the induced radioactivity of surrounding materials due to gamma rays of less than 16 MeV is rather small due to the high threshold energy of photonuclear reactions. However, most existing gamma-based interrogation systems use electron linacs and microtrons to generate the gamma beams; thus, the deployment of these systems is limited by their size, complexity and high cost of ownership. Thus there is a need for low-cost, portable gamma sources to use in active interrogation systems to detect SNM. In general, cylindrical gamma generators can be designed using a coaxial RF-driven plasma ion source, as has been done earlier in U.S. Pat. No. 6,907,097 for neutron generators and is included by reference herein. A plasma is produced by RF excitation in a plasma ion generator using an RF antenna. A cylindrical gamma-generating target is coaxial with, or concentrically arranged around, the ion generator and is separated therefrom by plasma and extraction electrodes which can contain many slots. The plasma generator emanates ions radially over 360°, and the cylindrical target is thus irradiated by ions over its entire inner surface area. The plasma generator and target can be made as long as desired. A co-axial gamma-tube design has several advantages that would carry over from the neutron tube system. The advantages include (i) high beam current, (ii) good cooling, (iii) simple design, (iv) compactness, and (v) spatially uniform photon flux. FIGS. 3 and 4 show different schematic views of a coaxial type gamma source that is very similar to the neutron tube design. For the (p,γ) target material, Table 1 lists four possible low-energy nuclear reactions that produce gamma-rays with energies greater than 6-MeV (the photofission threshold energy is approximately 5.5 MeV). Of these, the 163-keV 11B and 203-keV 27Al reactions may be the simplest to work with to create a gamma tube system through modification of co-axial neutron generator technology. Suitable target materials for these reactions include LaB6 or B4C (for p-B) and Al (for p-Al), which are easy to fabricate and also have good thermal, electrical, and mechanical properties. TABLE 1Four promising (p,γ) reactions for highenergy gamma (6 to 18 MeV) productionProtonGamma EnergyCross SectionenergyTargetEγ (MeV)σ (mb)Ep (keV)Fabrication11B(p,γ)12C16.1, 11.7, 4.40.16160Easy27Al(p,γ)28Si11.5, 9.8, 1.8<0.03202.8Easy120~180632.219F(p,αγ)16O6.1, 6.92, 7.12160340Difficult7Li(p,γ)8Be12.24, 14.74,6441Moderate17.64 The p-B based system is particularly suitable for special nuclear material (SNM) detection. More than 90% of the excited 12C* produced from a 160 keV proton beam hitting on a B target decays directly to its ground state. Therefore, a p-B gamma generator can produce an intense 16.1 MeV gamma beam. Many SNMs have a much higher photoneutron production cross-section at 16.1 MeV gamma energy compared to other common materials. For example, the photoneutron production cross-sections of 235U at 16 MeV is ˜0.7 b as shown in FIG. 1, while the photoneutron production cross-section of 56Fe at the same energy is ˜0.01 b as shown in FIG. 2. The p-B based system can use a high current, low energy coaxial accelerator system because of its relatively small (p,γ) cross section. Lanthanum hexaboride (LaB6) is a rigid ceramic with good thermal shock resistance and good chemical and oxidation resistance. LaB6 also has high electron emissivity and good electrical conductivity. Similarly, boron carbide (B4C) is one of the hardest materials known, ranking third behind diamond and cubic boron nitride. B4C has very good chemical resistance, good nuclear properties (commonly used as a neutron absorber in reactors), and has low density (2.52 g/cm3). B4C can be formed as a coating on a suitable substrate by vapor phase reaction techniques, e.g., using boron halides or di-borane with methane or another chemical carbon source. The p-Al system reaction is also capable of detecting SNM and other contrabands because its branching ratios to different excited states are comparable to each other. Varying the proton beam energy can also change the energy level of 28Si* and, thus, the branching ratios. There are six resonances for the p-Al reaction between 500 to 680 keV. Gamma ray transmission spectroscopy can be used to detect elements besides SNM while neutron detectors can be used to monitor the presence of SNM. On the other hand, the system based on p-Al uses a modest-energy axial accelerator. Other possible materials to use as targets include LaB6, B4C, Al, LiF, Teflon™, and Mg The main drawback with both the p-B and p-Al reactions is their low cross sections which necessitate operating the gamma tube at a high proton current to increase the source output. For example, in a boron-based interrogation system, a co-axial source producing an ampere of proton current at the 163-keV reaction resonance will only generate about 6×10% gammas/sec. The next boron resonance occurs at a higher energy (675 keV) and its cross section is even smaller (0.05 mb). Similarly, the resonant nuclear reaction for aluminum at a proton energy of 203-keV has a cross section of less than 0.03 mb. The other (p, γ) reactions in Table 1 have significantly larger reaction cross sections, but require scaling the gamma tube source voltage to higher energies. For the production of multiple discrete high-energy gammas, a beam of protons with energy greater than 340 keV are required. However, it is difficult to scale the coaxial tube design to these higher proton voltages. To achieve these higher energies, a simple axial accelerator concept can be used, as will be discussed later. FIG. 3 shows cross-section view of a gamma source geometry according to an embodiment of the invention. Gamma generator 10 has a cylindrical plasma ion source 12 at its center. There is a cylindrical gamma generating target 22 disposed around and spaced apart from the cylindrical plasma ion source 12. The principles of plasma ion sources are well known in the art. Conventional multicusp ion sources are illustrated by U.S. Pat. Nos. 4,793,961; 4,447,732; 5,198,677; 6,094,012, which are herein incorporated by reference. The ion source 12 includes an RF antenna (induction coil) 14 for producing an ion plasma 20 from hydrogen gas which is introduced into the ion source 12. Antenna 14 is typically made of copper tubing, which may be water cooled. For gamma generation, the plasma 20 is preferably a hydrogen ion plasma. The ion source 12 can also include a pair of Spaced electrodes, plasma electrode 16 and extraction electrode 18, along its outer circumference. The electrodes 16, 18 control the passage of ions electrostatically from the plasma 20. The electrodes 16, 18 can contain many longitudinal slots along their circumferences so that ions radiate out in a full 360° radial pattern. In an alternative embodiment (not shown), the electrodes 16, 18 can be grids. Coaxially or concentrically surrounding ion source 12 and spaced therefrom is the cylindrical target 22. The target 22 is the gamma generating element. Ions from the plasma source 12 pass through the slots 19 in the electrodes 16, 18 and impinge on the target 22, typically with energy of 120 keV to 150 keV. The target 22 may be made of any of the materials listed in Table 1, or others. In one embodiment, the target 22 is made of LaB6 or B4C. In another embodiment, the target 22 is made of aluminum. Gamma rays are produced in the target 22 as the result of ion induced (p,γ) reactions. Outer cylinder 24 defines the vacuum chamber in which the entire assembly 10 is enclosed. The extraction apertures in electrodes 16, 18 can be in the form of slots 19 whose length can be extended to any desired value. The hydrogen ion beam hits the target 22 in 360° and therefore the target area is very large. By making the gamma generator as long as practical in the axial or longitudinal direction, a high gamma flux can be obtained. For p-B gamma-based interrogation system, a long co-axial source that can produce ampere(s) of current is useful. FIG. 4 is a schematic cutaway drawing of a coaxial type gamma source 11, which is very similar to a coaxial neutron generator design. A cylindrical ion source is located at the center of the gamma generator. Hydrogen plasma is formed by RF induction discharge. An antenna 14 can be water-cooled copper tubing enclosed inside a quartz tube. It has been demonstrated that RF discharge plasma is capable of generating atomic hydrogen ion species from a hydrogen gas source higher than 90%. An extraction grid 17 controls the passage of ions electrostatically from the plasma. The ions are accelerated across a gap and impinge on a target 22 with full 160 keV energy. Permanent magnets 30 are in a regular arrangement around the plasma source and running longitudinally to form a magnetic cusp plasma ion source. The principles of magnetic cusp plasma ion sources are well known in the art, as cited above. To ensure reliable high voltage operation the gamma-ray generator 11 can also be vacuum pumped. With reasonable pumping, the pressure can drop to the 10−4 Torr range, which allows trouble free high voltage operation. The ion source can protected from the secondary electrons with a filter rod structure (not shown); this prevents high-energy electrons from accelerating back to the source and potentially over-heating it. The protection from the secondary electrons is especially important when generating gammas. Due to the fairly small cross-section of some of the nuclear reactions, the generator run at fairly high current, which can cause the ion beam power at the target to be on the order of 200 kW. Although the large surface area of the target helps to dissipate the thermal load, higher power operation of the gamma source may be more successful with appropriate target cooling systems, as have been used for neutron generators. FIGS. 6A-6D show gamma ray spectra collected from LiF, conductive Teflon™, B4C, and Mg, respectively, bombarded with a continuous beam of protons. Each spectrum was collected with a 5-inch NaI detector and normalized to I-μC of charge. The (p,γ) target to detector distance was set at 7 cm. Both boron carbide and magnesium have rather low gamma-ray yield which is consistent with the reported 11B cross section value given in Table 1. Magnesium was tested because it had been reported that a 6.19-MeV gamma-ray (in addition to 4.86-MeV and 0.82-MeV gammas) is produced corresponding to the 317-keV resonance of the 25Mg(p,γ)26Al reaction. The spectra clearly show the 6.19-MeV gamma-ray and also gammas that arise from higher energy (4-MeV) branching channels that can occur for the 25Mg(p,γ)26Al reaction. The LiF and Teflon™spectra are dominated by the characteristic 6.13-MeV fluorine gamma-ray which was even observed for 250-keV protons from the accelerator (fluorine has a small resonant cross section of −0.2 mb at 224-keV proton energy). As indicated in Table 1, the resonant reaction for lithium occurs at 441-keV which accounts for the significant jump in the measured yield between the 350-keV and 450-keV spectra. The Li reaction is of interest because it produces 17.64-MeV (63% emission/reaction) and 14.74-MeV (37% emission/reaction) gamma-rays which coincide well with the peak of the photofission cross section. There also appears to be an unidentified, weak low-energy nuclear reaction in Teflon that produces 12-MeV gammas and may be due to a trace impurity in the material. As mentioned above, it is difficult to scale the coaxial tube design to proton voltages with energies greater than 340 keV, as are used for the larger cross section reaction shown in Table 1. To achieve these higher energies, a simple axial accelerator 40, as shown in FIG. 5A, can be used. In this system, the protons are first produced in an rf-driven plasma source. The rf antenna is shown as 44. The protons are then extracted and accelerated to their full energy using a simple electrostatic accelerator column 45. The accelerated protons then impinge on a water-cooled, V-shaped target 42 (rather than a cylindrical target as in the coaxial design). The chamber 46 is vacuum pumped through a pumping port 48 to minimize the electrons produced by ionizing the gas in the beam path. A significant advantage of the source designs is its potential to scale to almost any length by stacking together individual base units. For example, the coaxial gamma tube can be taken to an order of magnitude higher power level by stacking ten of the 1-Amp systems together. In the base units, the lower vacuum plate is at ground potential and the upper one is at the target potential (e.g., ˜165 kV for the p-B reaction). These sources can be stacked on top of each other in a sequence, (as shown in FIG. 5B) where two high voltage flanges 46 are shared in one end of the two generators 40 with a shared high voltage source 47 and, on the other end, the pumping chamber 49 is shared with another generator 40 through a common pumping port 48. In this exemplary embodiment, the stack of ten generators 40 can be operated with only five high voltage feeds, five vacuum pumps and five rf-systems. Another embodiment of the invention integrates gamma-ray and neutron generators to produce a new active interrogation source. Owing to its linear scalability, the dual source may be useful for many diverse applications ranging from very large fixed site interrogation systems to intermediate-size mobile or remote inspection systems to compact systems for assaying the internal contents of hazardous waste drum containers. While a simple, compact, and low-cost gamma source design is important for the wide deployment of these gamma-based interrogation systems, a sophisticated detection system and a contraband database are also desirable in order to make the best use of these systems. FIG. 7 shows a conceptual drawing of an exemplary embodiment for an integrated system design. A shielded 51 gamma source 50 is located in the ground as an easy way to shield inspection workers from the radiation. An array of detectors (one neutron detector is shown as 54, and location for a stack of gamma ray detectors is shown as 52) is positioned around a cargo container 58 to monitor neutrons and gammas coming out of the container 58 for signals that indicate the presence of SNM. Some of the detectors are sensitive to both gammas and neutrons, as fission also produces a significant amount of prompt gammas. It would be useful to have a database of induced gamma/neutron ratios for various combinations of materials and packaging. As discussed above for the p-Al based system, gammas of different discrete energies are produced by the gamma generator. Thus gamma detectors can be set on the top of the cargo container 58 for gamma transmission spectroscopy to identify other hazardous materials. This invention has been described herein in considerable detail to provide those skilled in the art with information relevant to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the invention can be carried out by different equipment, materials and devices, and that various modifications, both as to the equipment and operating procedures, can be accomplished without departing from the scope of the invention itself. |
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043269214 | claims | 1. A fuel assembly for a nuclear reactor comprising an array of fuel rods held in spaced relationship with each other by a series of grids spaced along the fuel rod length, multiple control rod guide thimbles interspersed among the fuel rods extend the length of said assembly and are attached to said grids to provide a basic skeleton structure for the assembly, and an extension attached to the upper end of each of said guide thimbles; insets in the form of local deformations in the guide thimble walls which project inwardly toward the guide thimble axis, said insets serving to reduce the force, and therefore the wear, caused by lateral vibrating motion between the guide thimble and control rod adapted to reciprocate therein. 2. The fuel assembly according to claim 1 wherein said insets are spaced at uniform intervals around the periphery of said guide thimble and along the guide thimble length. 3. The fuel assembly according to claim 2 wherein the length of each of said insets is approximately four times the inset width in order to promote line contact between said control rod and insets to thereby minimize wear of said guide thimble. 4. The fuel assembly according to claim 1 wherein said insets are formed on a liner secured to the inside of said guide thimble. 5. The fuel assembly according to claim 4 wherein said liner extends downwardly into said guide thimble for less than about 15 percent of the length of said guide thimble. |
claims | 1. A functionalized brine sludge material comprising:10 g to 50 g of brine sludge;50 g to 100 g of fly ash;6 g to 13 g of sodium hydroxide;250 ml to 500 ml of ethylene glycol;1 g to 10 g of cetyl trimethyl ammonium bromide; and12 ml to 26 ml of water. 2. The material as claimed in claim 1, wherein the material is useful for the preparation of radiation shielding materials, geopolymeric materials, and chemically designed composite materials. 3. The material as claimed in claim 1, wherein the material comprises 45 g of brine sludge, 45 g of fly ash, 6 g of sodium hydroxide, 300 ml of ethylene glycol, 10 g of cetyl trimethyl ammonium bromide, and 12 ml of water. 4. A process for the preparation of the functionalized brine sludge material as claimed in claim 1, the process comprising:(a) refluxing a homogenized mixture of brine sludge, fly ash, sodium hydroxide, ethylene glycol, cetyl trimethyl ammonium bromide, and water in a round bottom flask; and(b) filtering the mixture as obtained in step (a) followed by drying in an air oven at a temperature of 100 to 110 degrees C. for a period of 1 to 2 hours, resulting in an in-situ synthesized functionalized brine sludge material. 5. The process as claimed in claim 4, wherein refluxing in step (a) is done at a temperature of 190 to 250 degrees C. for a duration of 2 to 6 hours using conventional heating. 6. The process as claimed in claim 4, wherein refluxing in step (a) is done at a temperature of 40 to 45 degrees C. for a duration of 15 to 20 minutes using microwave heating. 7. The process as claimed in claim 4, wherein drying in step (b) is done at a temperature of 110 degrees C. for a duration of 1 to 2 hours. |
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045267120 | claims | 1. A process for treating radioactive sludge waste comprising the steps of: pulverizing radioactive sludge waste which is wet, insoluble and combustible, while heating the radioactive sludge waste to make a dry powder suitable for combustion, said step of pulverizing the radioactive sludge waste including the steps of making thin films of the radioactive sludge waste during grinding of the waste into powder, and heating the thin films and the powder to vaporize the water contained in the powder; burning the dry powder by dispersing the powder over flames to form ashes and to reduce the volume of the radioactive waste while exhausting combustion gas from the zone of combustion; collecting the ashes; and pelletizing the ashes to form pellets having a volume substantially less than the volume of the ashes. storing various kinds of radioactive sludge waste in a storage tank; feeding the radioactive sludge waste from the storage tank to a thin film drier; making thin films of the radioactive sludge waste and grinding the waste into powder within said thin film drier; heating the thin films and the powder by contacting the waste with a heat conduction wall heated to a temperature above 100.degree. C. within the drier to remove water therefrom; air transporting the powder to a combustion furnace by a pneumatic conveyor; burning the powder to form ashes by dispersing the powder over flames generated in the combustion furnace along with air used for transporting the powder; separating the resulting ashes from a combustion gas generated in the burning of the powder; collecting the ashes separated and the ashes discharged from the combustion furnace; purifying and exhausting the combustion gas to the atmosphere; and pelletizing the ashes collected to form pellets having a volume substantially less than the volume of said ashes. 2. The process as defined in claim 1, wherein the step of pulverizing the radioactive sludge waste is effected using a thin film drier provided with a heat conduction face and a rotor with a plurality of moving blades for pressing the radioactive sludge waste on the heat conduction face to make thin films and grind the waste into powder while heating by the heat conduction face. 3. The process as defined in claim 5, wherein the radioactive sludge waste is radioactive sludge waste obtained from in a nuclear power plant, and the water content of the dry powder formed of the radioactive sludge waste is less than 3%. 4. A process for treating radioactive sludge waste obtained from nuclear power plants, comprising the steps of: 5. The process as defined in claim 4, wherein the powder has an average particle diameter of 10.mu., and the water content less than 3% by weight. 6. The process as defined in claim 1 or in claim 4, wherein the volume of the ashes is reduced to one-half during the formation of the pellets by pelletizing. |
description | FIG. 1 shows a time-of-flight mass spectrometer according to one embodiment of the invention. The ion source 10 emits a primary ion beam 12, which is focused and/or collimated. An orthogonal accelerator 14 applies carefully timed voltage pulses to deflect a fraction of the ions 20 into a secondary collector 22 for mass analysis. The remainder of the ions continue undeflected to the primary collector 16. The current due to these ions striking the collector 16 is measured at ammeter 18 to determine the beam current (the ammeter 18 may be an electrometer which amplifies small currents into measurable voltages). A separate conventional pressure gauge 24 also measures the pressure in the chamber; the ammeter 18 and the pressure gauge 24 are connected to a processor 26. When the fraction of ions being deflected to the secondary collector 22 is known, the current at the primary collector 16 can be corrected to determine the ion source pressure (the number of ions leaving the ion source 10). The ion source pressure is a function of the chamber pressure (among other parameters). Thus, the beam current can be used to determine the pressure in the chamber. Beam current can be read at rates as fast as 50 kHz, effectively continuously. (In this disclosure, measurement rates greater than about 1 kHz are treated as continuous). As discussed above, beam current alone is not generally used to monitor pressure, because it can vary with changes in instrument tuning, as the ion source becomes xe2x80x9cdirty,xe2x80x9d as a source filament ages, or in response to other perturbations of the spectrometry system. All of these changes typically take place over a timescale of minutes or even hours, however. According to the invention, the effects of these perturbations can be greatly reduced or even eliminated by calibrating the relationship between beam current and pressure by reference to the conventional pressure gauge on a frequent basis. In preferred embodiments, the ammeter 18 and the pressure gauge 24 are connected to analog-to-digital converters (not shown) to produce digital signals. These signals are combined in a data processor 26, which generates a combined signal that may be used for process control as described below. The data processor may comprise a computer running standard data capture software, such as National Instruments"" LabView(trademark), or it may be a custom processor. Alternatively, the analog-to-digital converters may be omitted, and the processor 26 may be an electrical circuit used to combine the ammeter and pressure gauge signals to produce an analog output. In preferred embodiments of the invention, the relationship between beam current and pressure is recalibrated at the reading frequency of the pressure gauge. This relationship is shown schematically in the graph of FIG. 2. Solid line 30 represents the actual chamber pressure as a function of time. This pressure is measured by the pressure gauge at points 32. The pressure at times between the pressure gauge measurements is determined by reference to the beam current, as shown by dotted segments 34. These measurements may deviate from the true pressure as shown, as xe2x80x9cdriftxe2x80x9d in pressure measurement occurs (deviations have been exaggerated in FIG. 2 for clarity). At each gauge measurement, the calibration of the beam current/pressure relationship is reset, and changes in pressure from the newly determined gauge pressure are calculated using the beam current. In other embodiments of the invention, less frequent pressure gauge measurements may be used. For example, the xe2x80x9ctruexe2x80x9d pressure may be measured once a minute or even less frequently, as long as the interval is short compared to the timescale of drift of the beam current/pressure relationship. Comparison of the pressure gauge and beam current measurements to produce the curve of FIG. 2 may be performed by standard circuits familiar to those skilled in the art, or by computer-based measurement and acquisition systems. These measurements may then be directly displayed on a monitor or other output means, or may be used to provide feedback for process control, for example for concentration monitoring in deposition systems. Even if a dynamic feedback system is not used, the pressure measurement system of the invention can be used to very quickly cut off a plasma torch during deposition in response to a pressure fluctuation outside normal tolerances. Such a cut-off system reduces the risk of destroying a wafer which may be worth many thousands of dollars. Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification or practice of the invention disclosed herein. It is intended that the specification be considered as exemplary only, with the true scope of the invention being indicated by the following claims. |
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054694809 | summary | FIELD OF THE INVENTION The present invention relates to a mid-loop operating method for nuclear power plants, and a facility therefor. BACKGROUND OF THE INVENTION In the currently used nuclear power plants, the nuclear fuel has to be replaced periodically. During this replacement of fuel, other major sections are checked for maintenance. During the checking and maintenance, a particularly important thing is that the steam generator tube is checked, so that it can be confirmed as to whether there is a leaking tube or a foreseeable leaking tube. Thus the leaking of tubes is prevented before entering into the next normal operation of the atomic reactor. In carrying out the checking of the steam generator tube, there is a pre-step to be undergone. That is, as shown in FIG. 1, the level of the cooling water for the atomic reactor is lowered, and then, there is installed a nozzle dam in the entrances of a hot leg and a cold leg. However, even under this condition, the residual heat is continuously released from the atomic reactor, and therefore, this heat has to be eliminated. Such a low water head operation is called a mid-loop operation. For example, in the Korean atomic reactors such as No 3 and 4 of Youngkwang, and No. 3 and 4 of Ulchin, the discharge hole of the steam generator is not high enough relative to the hot leg. Therefore, the maximum extra height of the hot leg in which the residual heat removal outlet lies reaches only a height which is only one half of the diameter of the hot leg. Therefore, the water head becomes insufficient in the opening of the residual heat removing system, and air is introduced to induce cavitations, with the result that the pump for the residual heat removing system is lost. The residual heat removing pump which is used in nuclear power plants has a capacity of 4000 GPM. Below 3000 GPM, the pump shows a rumbling phenomenon, and therefore, the flow rate is maintained above the level which is just necessary for removing the residual heat. Consequently, even under an insufficient water head in the hot leg during the mid-loop operation, a flow rate of over 3000 GPM is required, thereby increasing the possibility of air suction. For this reason, the Palo Verde atomic reactor which is the original model of the atomic reactors of Youngkwang and Ulchin of Korea could not carry out the mid-loop operation so far, in spite of the fact that a permission for the mid-loop operation had been obtained from the NRC. In the economic aspect, it is reported that there is a significant difference between the case of carrying out the mid-loop operation and the case of not carrying out it. Even by referring to the domestically applied nuclear refueling program, it is found that the maintenance checking period is increased by about 15 days or more, if the mid-loop operation cannot be carried out. Further, as shown in FIG. 2, according to the analysis of B & W company, in the case of the Palo Verde atomic reactor, if the steam generating nozzle dam can be installed when the used nuclear fuel is taken out and when the nuclear fuel is filled after opening the head of the reactor, then the repair period can be shorted by about 12-15 days. ABB-CE installs a single nozzle dam instead of the generally used double nozzle dam in order to install the nozzle dam just after lifting the head of the atomic reactor, so that the water head within the suction hole of the residual heat removing system in the hot leg should be heightened. If the method of ABB-CE is used, a low water level alarm can heighten the water head by 2" from 101' 5" to 101' 7", while a low low water level alarm can heighten the water head by 1" from 101' 4" to 101' 5". Therefore, the nozzle dam can be installed so much faster, while the damage due to the air introduction can be excluded during the mid-loop operation. However, even in such a method, the flow rate of the pump has to be maintained at the normal level, and therefore, even if the water head is raised by 2", if waves are formed on the water, the air introduction cannot be prevented. Further, according to the domestically performed experiment, it is certain that the air introduction cannot be prevented with the increase of the water head by 2" at the mid-loop. SUMMARY OF THE INVENTION Therefore it is the object of the present invention to provide a partial water filled operating method and a facility therefor, in which the above described disadvantages of the conventional techniques are overcome. |
description | This application is a divisional application of co-pending U.S. application Ser. No. 12/748,367, filed Mar. 26, 2010, the disclosure of which is incorporated herein by reference. This application claims priority benefits under 35 U.S.C. §1.119 to Korean Patent Application No. 10-2010-0006469 filed Jan. 25, 2010. 1. Field of the Invention The present invention relates to a top nozzle for a nuclear fuel assembly having a spring insert hole. 2. Description of the Related Art As is well known to those skilled in the art, a nuclear reactor is a device in which a fission chain reaction of fissionable materials is controlled for the purpose of generating heat, producing radioactive isotopes and plutonium, or forming a radiation field. Generally, in light-water reactor nuclear power plants, enriched uranium, which is increased in the ratio of uranium-235 to 2% through 5%, is used. To process enriched uranium into nuclear fuel to be used in nuclear reactors, a forming process, by which uranium is formed into a cylindrical pellet having a weight of about 5 g, is conducted. Several hundreds of pellets are retained into a bundle and inserted into a zirconium tube under vacuum conditions. A spring and helium gas are supplied into the tube and a cover is welded and sealed onto the tube, thus completing a fuel rod. A plurality of fuel rods constitutes a nuclear fuel assembly and is burned in a nuclear reactor by nuclear reaction. FIG. 1 is a front view showing a typical nuclear fuel assembly. FIG. 2 is a perspective view of a top nozzle 30 provided with spring clamps 31 having spring insert holes 31a formed by milling, according to a conventional technique (U.S. Pat. No. 5,213,757). As shown in FIG. 1, the nuclear fuel assembly includes a plurality of support grids 10 through which fuel rods (not shown) are inserted, and a plurality of guide thimbles 20 which are coupled to the support grids 10. The nuclear fuel assembly further includes a top nozzle 30 which is coupled to the upper ends of the guide thimbles 20, a bottom nozzle 16 which is coupled to the lower ends of the guide thimbles 20, and the fuel rods (not shown) which are supported by springs and dimples which are formed in the support grids 10. As shown in FIG. 2, the top nozzle 30 includes fastening parts 15, spring clamps 31 and hold-down spring units 32. The fastening parts 15 function to couple the top nozzle 30 to alignment pins in an upper core plate. Each spring clamp 31 has the spring insert holes 31a formed therein. The end of each hold-down spring unit 32 is inserted into a corresponding spring insert hole 31a. Fastening pin holes 33′ are formed through the upper surface of each spring clamp 31 above the corresponding spring insert holes 31a. T-slots 14 are formed in each spring clamp 31 and respectively communicate with the fastening pin holes 33′. The hold-down spring units 32 are inserted into the corresponding spring insert holes 31a and fastened to corresponding spring clamps 31. Each spring insert hole 31a is formed by milling in such a way to insert a milling tip (not shown) into the T-slot 14 formed in the upper surface of the spring clamp 31. Each hold-down spring unit 32 includes a first spring 32a having a first neck part 32a′, and a second spring 32b and a third spring 32c which are coupled to the first neck part 32a′. The hold-down spring unit 32 is configured such that the first, second and third springs 32a, 32b and 32c are stacked on top of one another. To couple the hold-down spring unit 32 to the top nozzle 30, a spring junction end of the hold-down spring unit 32, which is opposite to the first neck part 32a′, is inserted into the corresponding spring insert hole 31a in a horizontal direction. Thereafter, a fastening pin 33 is inserted both into the corresponding fastening pin hole 33′ of the spring clamp 31 and a fastening pin hole 32a″ of the hold-down spring unit 32 in the vertical direction. Thereby, the hold-down spring unit 32 is coupled to the top nozzle 30. Here, to prevent the fastening pin 33 from being removed, the upper end of the fastening pin 33 is fastened to the spring clamp 31 by spot welding. In FIG. 2, reference numeral 40 denotes an upper plate, and reference numeral 41 denotes an upper plate slot. As shown in FIG. 1, the top nozzle 30 having the above-mentioned construction is assembled with the elements of the nuclear fuel assembly. Subsequently, as is well known, the nuclear fuel assembly is installed in a core and disposed between an upper core plate (not shown) and a lower core plate such that the hold-down spring units 32 are supported by the lower surface of the upper core plate. As such, the nuclear fuel assembly is installed in the core of the nuclear reactor in which nuclear fission is caused and is used as fuel for nuclear power generation. When the nuclear fuel assembly, which is installed in the nuclear reactor, is used as nuclear fuel, the hold-down spring units 32 of the top nozzle 30 conduct a shock absorption function against vibrations generated by a hydraulic uplift force induced by the flow of coolant during the operation of the nuclear reactor, thermal expansion attributable to an increase in temperature, irradiation growth of the nuclear fuel tube due to neutron irradiation for a long period of time, or axial length variation owing to creep. Thereby, a mechanical-structural stability of the nuclear fuel assembly is ensured. However, in the top nozzle 30 according to the conventional technique, when the uplift force is applied to the T-slot 14 provided for forming each spring insert hole 31a by the end of the hold-down spring unit 32 inserted into the spring insert hole 31a, the T-slot 14 widens, causing the hold-down spring unit 32 fastened to the spring clamp 31 to become loosened. Thereby, a force supporting the nuclear fuel assembly is markedly deteriorated. Furthermore, in a case where the spring insert holes 31a are formed in the top nozzle 30 by milling in the direction in which the hold-down spring units 32 are inserted into the spring insert holes 31a without forming the T-slots 14, the milling operation is impeded by the fastening parts 15 which protrude from the upper surface of the top nozzle 30 at positions opposite to the spring clamps 31. Thus, it is very difficult to precisely machine each spring clamp 31 such that the interior of the spring insert hole 31a has a shape corresponding to the end of the hold-down spring unit 32. Thereby, the end of the hold-down spring unit 32 cannot be brought into close contact with the inner surface of the spring insert hole 31a. As a result, the hold-down spring units 32 cannot reliably absorb vibrations of the nuclear fuel assembly when the unclear reactor is operated. Moreover, in an extreme case, the above-mentioned problems in the conventional technique may cause a deformation or breakage of the nuclear fuel assembly. Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a top nozzle for a nuclear fuel assembly in which a spring insert hole can be formed in a spring clamp without forming a T-slot, thus enhancing the structural stability of the spring clamp holding a hold-down spring unit. Another object of the present invention is to provide a top nozzle for a nuclear fuel assembly in which the spring insert hole can be easily and precisely formed such that the end of the hold-down spring unit is brought into close contact with the inner surface of the spring insert hole, thus enhancing a manufacturing efficiency. A further object of the present invention is to provide a method of manufacturing a top nozzle for a nuclear fuel assembly which makes precise machining possible, thus enhancing the structural stability of the spring clamp having the spring insert hole, thereby increasing the stability of the hold-down spring unit fastened to the spring clamp. In order to accomplish the above mentioned objects, the present invention provides a top nozzle for a nuclear fuel assembly, including: a coupling plate coupled to a guide thimble of the nuclear fuel assembly; a perimeter wall protruding upwards from a perimeter of the coupling plate, with a spring clamp provided on an upper surface of the perimeter to wall; and a hold-down spring unit mounted to the upper surface of the perimeter wall in such a way as to couple a corresponding end of the hold-down spring unit to the spring clamp. A fastening pin hole is vertically formed through an upper surface of the spring clamp, and a spring insert hole is formed by electro-discharge machining in a insert direction of the hold-down spring so that the hold-down spring unit is coupled into the spring insert hole of the spring clamp. Preferably, before the electro-discharge machining process is conducted, the coupling plate and the perimeter wall can be integrally formed by casting into a single body. The fastening pin hole, which defines a part of the spring insert hole, can have an elliptical pin head seat formed in the upper surface of the clamp. The spring insert hole can be formed by electro-discharge machining without having a T-slot. The spring insert hole can be formed in such a way as to form a premachined hole having a cross-section less than a cross-section of the spring insert hole and conduct an electro-discharge machining process. The top nozzle can further include a fastening pin provided with a head having a shape corresponding to the elliptical pin head seat, the fastening pin being inserted into the fastening pin hole to hold the hold-down spring unit. In order to accomplish the above object, the present invention provides a method of manufacturing a top nozzle for a nuclear fuel assembly, including: forming a fastening pin hole in a vertical direction through an upper surface of a spring clamp provided on the top nozzle; forming a spring insert hole in a insert direction of the hold-down spring into which a hold-down spring unit is inserted using an electro-discharge machining process; and coupling the hold-down spring unit to the spring clamp in such a way as to insert an end of the hold-down spring unit into the spring insert hole. The electro-discharge machining process can be conducted without forming a T-slot. The forming of the fastening pin hole can include forming an elliptical pin head seat in such a way as to form an upper end of the fastening pin hole into an elliptical shape. The forming of the spring insert hole through the electro-discharge machining process can include forming a premachined hole through the elliptical pin head seat before the electro-discharge machining process is conducted. The method can further include casting a main body of the top nozzle before the forming of the fastening pin hole, the main body including a coupling plate coupled to a guide thimble of the nuclear fuel assembly, and a perimeter wall protruding upwards from a perimeter of the coupling plate, with the spring clamp provided on an upper surface of the perimeter wall. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. FIG. 3 is a perspective view of a top nozzle 30′, according to an embodiment of the present invention. As shown in FIG. 3, the top nozzle 30′ can include a coupling plate 25, a perimeter wall 20 and a plurality of hold-down spring units 100. The coupling plate 25 is coupled to guide thimbles (not shown) of a nuclear fuel assembly. The perimeter wall 20 protrudes upwards from the perimeter of the coupling plate 25. Spring clamps 31 and fastening parts 15 are provided on the upper surface of the perimeter wall 20. Spring insert holes 31a are formed in each spring clamp 31. The hold-down spring units 100 are provided on the upper surface of the perimeter wall 20 and inserted into corresponding spring insert holes 31a of the spring clamps 31. In accordance with an embodiment of the present invention, the top nozzle 30′ has no separate T-slots (refer to FIG. 2), unlike the conventional technique. Here, because the top nozzle 30′ of the present invention is manufactured by the method of FIG. 4, the spring insert holes 31a can be formed without forming the T-slots 14. FIG. 4 is a flowchart of the method of manufacturing the top nozzle 30′ of FIG. 3. FIGS. 5A and 5B are views showing circular fastening pin holes 33a formed in the spring clamp 31 of the top nozzle 30′. FIG. 5A is a plan view of the spring clamp 31, and FIG. 5B is a sectional view taken along line 5B-5B of FIG. 5A. Below, the method of manufacturing the top nozzle 30′ of FIG. 3 will be explained in detail with reference to FIGS. 3 through 5. As shown in FIG. 3, to manufacture the top nozzle 30′, a main body 30a′ is produced in such a way to integrally couple the coupling plate 25 to the perimeter wall 20 having the spring clamps 31 and the fastening parts 15. Preferably, the main body 30a′ is formed by casting using a mold which is configured such that the coupling plate 25 is integrated with the perimeter wall 20 having the spring clamps 31 and the fastening parts 15. When the main body 30a′ is formed by casting (S10: a casting step, refer to FIG. 4), the spring insert holes 31a can be approximately formed. The casting step S10 of FIG. 4 is only one example selected from various methods of manufacturing the top nozzle 30′. Hence, the main body 30a′ of the top nozzle 30′ can be manufactured by other well known methods other than the casting step. At step S20 (forming the fastening pin holes), after the main body 30a′ is formed through the casting step S10, the fastening pin holes 33a (refer to FIGS. 5A and 5B) are vertically formed at predetermined positions through the upper surfaces of the spring clamps 31 by drilling or the like. At step S30 (forming the spring insert holes through an electro-discharge machining process), after the fastening pin holes 33a are formed, an electro-discharge machining process for forming the spring insert holes 31a is conducted. When the electro-discharge machining process is conducted to form each spring insert hole 31a, an electrode having the same shape as that of the end of the hold-down spring unit 100 is used. In this case, the precision of the electro-discharge machining process can be similar to or superior than that of the case of the milling process. Furthermore, in the case of the electro-discharge machining process, the operation of forming spring insert hole 31a is not impeded by the to fastening part 15. Therefore, the spring insert hole 31a can be more precisely formed. Thereby, the stability of the hold-down spring unit 100 fastened to the spring clamp 31 can be markedly enhanced. Various electro-discharge machining methods, for example, a method which was proposed in Korean Patent Laid-open Publication No. 1999-46308 and in which an object is immersed in machining dielectric liquid and then machined, can be used in the electro-discharge machining process of the present invention. At step S40 of fastening the hold-down spring units 100 to the spring clamps 31, after the spring insert holes 31a are formed at step S30 of forming the spring insert hole by the electro-discharge machining process, as shown in FIGS. 5A and 5B, the end of each hold-down spring unit 100 is inserted into the corresponding spring insert hole 31a. Here, as shown in FIG. 3, the hold-down spring unit 100 includes a first spring 110 having a first neck part 112, a plate spring 120, and a second spring 130. Thereafter, a fastening pin 33 is fitted into each fastening pin hole 33a to fasten the hold-down spring unit 100 to the corresponding spring clamp 31, thus completing the manufacture of the top nozzle 30′. Here, the head of the fastening pin 33, which is fitted into the fastening pin hole 33a, can be processed by spot welding in the same manner as that of the cited reference U.S. Pat. No. 5,213,757. To reduce the stress of the upper surface of the spring clamp 31 attributable to uplift force applied to the hold-down spring unit 100 upwards, the spring clamp 31 can have elliptical pin head seats 33a″ each into which an elliptical head 33″ of a fastening pin 34 is seated (refer to FIGS. 7A and 7B). FIG. 6 is a flowchart of a method of manufacturing a top nozzle 30″ having elliptical pin head seats 33a″ into which elliptical heads 33″ of elliptical fastening pins 34 (refer to FIG. 7) are seated, according to another embodiment of the present invention. FIGS. 7A and 7B are views showing elliptical pin head seats 33a″ formed in a spring clamp 31′ of the top nozzle 30″ manufactured by the method of FIG. 6. FIG. 7A is a plan view of the spring clamp 31′. FIG. 7B is a sectional view taken along line 7B-7B of FIG. 7A. The method of FIG. 6 for manufacturing the top nozzle 30″ having the elliptical pin head seats 33a″ further includes step S21 of forming elliptical pin head seats and step S22 of forming premachined holes as well as including the steps of FIG. 4, that is, the casting step S10, the fastening pin hole forming step S20, the spring insert hole electro-discharge machining step S30 and the hold-down spring unit fastening step S40. Here, the casting step S10, the fastening pin hole forming step S20, the spring insert hole electro-discharge machining step S30 and the hold-down spring unit fastening step S40 are the same as those of the description of FIGS. 3 through 5, therefore further explanation is deemed unnecessary. In the method of manufacturing the top nozzle 30″ of FIG. 6, a main body 30a′ (refer to FIGS. 3, 7A and 7B) is formed by casting (S10) or another well-known method. After the fastening pin holes 33a′ (refer to FIGS. 7A and 7B) are formed at the fastening pin hole forming step S20, the elliptical pin head seats 33a″ are respectively formed in the upper ends of the fastening pin holes 33a′, as shown in FIGS. 7A and 7B. The elliptical pin head seats 33a″ are formed in the upper surface 31a′ (refer to FIG. 7B) of the spring clamp 31′ above the spring insert hole 31a, at the elliptical pin head seat forming step S21. Thereafter, at the premachined hole forming step S22, to rapidly form each spring insert hole 31a, before the electro-discharge machining process is conducted, a drill tip or milling tip is inserted into the elliptical pin head seat 33a″ and then the interior of the spring clamp 31′ is machined into the spring insert hole 31a, thus forming a premachined hole (not shown). The “premachined hole” (not shown) means a space which is formed in advance by removing a portion of the body of the spring clamp 31′ to form the spring insert hole 31a so as to reduce the time taken to conduct the electro-discharge machining process. The premachined hole can be formed by piercing the body of the spring clamp such that the end of the hold-down spring unit 100 can be inserted thereinto. Alternatively, the premachined hole can be formed in a hollow shape but not pierced. Subsequently, in the same manner as the description of FIGS. 3 through 5, the spring insert hole electro-discharge machining step S30 and the hold-down spring unit fastening step S40 are consecutively conducted, thus completing the manufacture of the top nozzle 30″ having the elliptical pin head seats 33a″. Here, in this embodiment, because the premachined hole forming process S22 is conducted, the volume of a portion to be electro-discharge machined is reduced. Thereby, the spring insert hole electro-discharge machining process S30 can be rapidly conducted. After the elliptical pin head seats 33a″ are formed, the elliptical fastening pins 34 having the elliptical heads 33″ are fitted into the corresponding fastening pin holes 33a′ and the fastening pin holes 32a″ of the relative hold-down spring units 100, thus fastening the hold-down spring units 100 to the spring clamps 31′ such that the elliptical heads 33″ can directly support the ends of the hold-down spring units 100. Thereby, stress applied to the upper surface 31a′ of the spring clamps 31′ by the hold-down spring units 100 can be markedly reduced. Therefore, the spring clamps 31′ are prevented from being deformed or broken, so that the hold-down spring units 100 can be more stably retained despite being used for a long period of time. As described above, in the present invention, because spring insert holes are formed by electro-discharge machining in spring clamps provided on a top nozzle, a T-slot for conducting a milling process is not required. Thereby, the structural stability of the spring clamps can be enhanced, thus preventing the spring clamps from being deformed or damaged by ends of hold-down spring units which are inserted into the spring insert holes. Furthermore, in the present invention, the spring insert holes are precisely formed by the electro-discharge machining such that the ends of the hold-down spring units can be closely fitted into the spring insert holes. The force of supporting the hold-down spring units can be similar to or superior than that of the conventional technique which conducts mechanical machining using the T-slot. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. |
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summary | ||
claims | 1. A system for compressing a fuel source, the system comprising:a first component configured to segregate a first plurality of ions based upon their corresponding isotopes into a first plurality of microbunches, each microbunch comprising a grouping of said ions, each group associated with a same species;a second component configured to:separate the first plurality of microbunches in space by applying a first electromagnetic wave in a resonant radiofrequency (RF) structure at a first RF frequency; andadjust the first electromagnetic wave to reduce the distance between the microbunches of the first plurality of microbunches;a third component configured to reduce the distance between a center of mass of the first plurality of ions and a center of mass of a second plurality of ions; anda fuel chamber comprising at least one layer surrounding at least a portion of a fuel source, the at least one layer configured to receive the first plurality of ions and the second plurality of ions such that compression of the one or more layers is maximized relative to one or more Bragg peaks associated with the first plurality of ions and the second plurality of ions. 2. The system of claim 1, wherein the second plurality of ions are more widely dispersed than the first plurality of ions and wherein the system is configured to provide the second plurality of ions to a fourth component before the first plurality of ions are delivered to the second component, wherein the fourth component is configured to:separate the second plurality of microbunches in space by applying a second electromagnetic wave; andincrease the frequency of the second electromagnetic wave to reduce the distance between the microbunches of the second plurality of microbunches. 3. The system of claim 1, wherein the third component is a telescope configured to merge a plurality of ion beams. 4. The system of claim 1, wherein the first component comprises a species alignment device. 5. The system of claim 1, wherein the first, second, and third components comprise RF cavities. 6. The system of claim 1, wherein first plurality of ions is configured to drive the waists of the fuel source. 7. The system of claim 1, wherein second plurality of ions is configured to compress end caps located in the fuel chamber. 8. A system for preparing an ion composition, the system comprising:a first component configured to segregate a first plurality of ions based upon their corresponding isotopes into a first plurality of microbunches, each microbunch comprising a grouping of said ions, each group associated with a same species;a second component configured to:separate the first plurality of microbunches in space by applying a first electromagnetic wave in a resonant radiofrequency (RF) structure at a first RF frequency; andadjust the first electromagnetic wave to reduce the distance between the microbunches of the first plurality of microbunches; anda third component configured to reduce the distance between a center of mass of the first plurality of ions and a center of mass of a second plurality of ions. 9. The system of claim 8, wherein the third component is a telescope configured to merge a plurality of ion beams. 10. The system of claim 8, wherein the first component comprises a species alignment device. 11. The system of claim 8, wherein the first, second, and third components comprise RF cavities. 12. The system of claim 8, wherein first plurality of ions is configured to drive the waists of the fuel source. 13. A system for compressing and igniting fuel in a fuel capsule, the system comprising:a first component configured to produce a timed sequence of continuous blocks of ions in a plurality of parallel streams in independent channels, each of said blocks based upon a different one of a set of isotopes, said plurality of parallel channels being replicated in a plurality of parallel units of said first component, each parallel unit comprising an array of a plurality of originating ion sources, each one of the said plurality of originating ion sources in each of the said arrays being based upon a different one of the respective isotopes;a second component configured to subdivide each one of the sequences of continuous blocks of the pluralities of parallel streams of the first pluralities of ions based upon their respective isotopes in the first pluralities of parallel channels and transform the continuous blocks into regular time-sequences of first blocks of pluralities of microbunches, each of said blocks of microbunches comprising ions of only one of the respective isotopes, by applying a first electromagnetic wave in a resonant radiofrequency (RF) structure at a first RF frequency;a third component comprising a system of magnets, one or more of of which comprise pulsed magnetic fields and one or more of which comprise continuous magnetic fields, configured to route in individual channels, each one of the pluralities of parallel beams of the sequences of blocks of microbunches comprising ions of the respective isotopes originated in the ion sources of the first component, in each of the plurality of parallel units of the first component, said routing culminating in directing all of the parallel beams of each one of the plurality of parallel units, in the unchanged time-sequence of blocks of microbunches of the respective isotopes, into a single beamline, the number of said beamlines having a same plurality as that of the plurality of parallel units of the first component;a fourth component configured to step-wise compact in space and time, pairs of the beams, reducing the number of parallel beamlines from the plurality of parallel units of the first component by a defined factor, said factor being a defined power of two, by interlacing the microbunches within the pluralities of blocks of microbunches of the respective isotopes as created at a first RF frequency in the second component, into a next plurality of beams comprising the unchanged sequence of blocks of mirobunches of the respective isotopes, with each of the regularly time-spaced microbunches appropriately positioned on RF waves of a second RF accelerator structure, said second RF accelerator structure at a RF frequency that is twice that of the first RF frequency, said interlacing halving a distance between a center of mass of successive microbunches, resulting in the blocks of the second plurality of beams comprising the unchanged sequence of blocks of microbunches of the respective isotopes having twice the number of microbunches of their respective isotopes as compared to the number of microbunches comprising the blocks of the same isotopes in each of the first plurality of beamlines in the first RF accelerator structure;said fourth component comprising multiple steps of doubling a beam current by said interlacing of the microbunches of pairs of beams from an upstream accelerator structure at one RF frequency into a second, downstream RF accelerator structure operating at twice the RF frequency of the upstream RF accelerator structure, said multiple steps of interlacing microbunches at doublings of the RF frequency of the RF accelerator structures increasing the number of microbunches in the blocks of respective isotopes by a factor that is a power of two, wherein said power of two comprises a multiplicity of interleaving steps, said increase in number of microbunches per block increasing the beam currents by a same factor. |
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041359747 | claims | 1. In a nuclear reactor which comprises a nuclear core including a plurality of vertically oriented elongated fuel assemblies supported in a side-by-side relationship, and wherein the assemblies are supported between an upper core plate and a lower core plate and each assembly includes nozzles which are supported within openings in said core plates for laterally positioning same; a radial restraint system surrounding said fuel assemblies for applying a constraining force to said nuclear core when said core is under operating conditions; vertically oriented resilient members positioned adjacent the core and supported at at least one end; load transmitting means interposed between said resilient members and the periphery of said nuclear core for transmitting resistance to displacement to said fuel assemblies as same tend to be displaced by thermal bowing and nuclear induced swelling and creep; a first relatively stiff band surrounding said resilient members and displaced therefrom a first predetermined distance so as to increase the resistance to displacement of said resilient member and said fuel assemblies after a small displacement of same, said band being arranged and constructed to expand only a predetermined fraction of the expansion of the core upon an increase in temperature, a second relatively stiff band surrounding said resilient members and displaced a second predetermined distance from said resilient members, said second predetermined distance being greater than said first predetermined distance so as to further increase resistance to displacement as greater displacements occur. 2. In the nuclear reactor of claim 1, some of said assemblies including a plurality of fuel elements having a central active fuel region with a breeder fuel region axially adjacent each end thereof, and wherein said first relatively stiff band, said load transmitting means and said second relatively stiff band are located within the axial region defined by the breeder content of said some of said fuel elements. 3. In the nuclear reactor of claim 2, a thin walled member surrounding at least a substantial number of said fuel assemblies, spacer pads affixed to said thin walled member about the surface of same, said pad being located within the region defined by the breeder fuel content of said some of the fuel elements. 4. In the nuclear reactor of claim 3 wherein the spacer pads of each fuel assembly are arranged opposite the spacer pads of each adjacent fuel assembly, predetermined gaps being provided between each set of pads, said gaps being larger above the active fuel region. 5. In the nuclear reactor of claim 4 wherein the openings within which the nozzles are supported are larger than the nozzles under non-operating conditions, said nozzles being constructed from a material having a larger coefficient of thermal expansion than the material from which the core plates are constructed so that the space about the nozzles in the openings are closed under operating conditions. 6. In the nuclear reactor of claim 5, a plurality of flexible support members connected to each of said core plates and mounted to bend to allow for movement of said core plate attached thereto, said flexible members supporting said core plates within the reactor. |
abstract | The invention relates to a method for producing a radioisotope, which method comprises irradiating a volume of radioisotope-precursor fluid contained in a sealed cell of a target using a beam of particles of a given current, which beam is produced by a particle accelerator. The target is cooled and the internal pressure in the sealed cell is measured. During the irradiation, the internal pressure (P) in the sealed cell is allowed to vary freely. The irradiation is interrupted or its intensity is reduced when the internal pressure (P) in the sealed cell departs from a first tolerated range defined depending on various parameters that influence the variation in the internal pressure in the sealed cell during the irradiation. These parameters for example comprise, for a given target, particle beam and radioisotope-precursor fluid: the degree of filling of the hermetic cell, the cooling power used to cool the given target, and the beam current (I). The invention also relates to an installation for implementing the method. |
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H00006270 | claims | 1. A toroidal plasma confining device, comprising: a toroidal field generating means including a plurality of toroidal field coils disposed about said torodial plasma for generating a toroidal magnetic confinement field about said toroidal plasma; a poloidal field generating means including at least one electrical current conducting coil encircling said toroidal plasma adjacent the outer radius of said toroidal plasma for generating only a vertical magnetic field component within said toroidal plasma which together with said toroidal magnetic confinement field defines a toroidal plasma confinement region for confining said toroidal plasma concentrically about a main vertical axis thereof having an aspect ratio less than 2 and a natural elongation of about 2 such that said toroidal plasma exists in the form of a compact, generally-spherical, toroidal shape; and a vacuum containment means for encapsulating said toroidal plasma in a vacuum environment. a toroidal field generating means including a plurality of toroidal field coils disposed about said toroidal plasma for generating a toroidal magnetic confinement field about said toroidal plasma; a poloidal field generating means including at least one electrical current conducting coil encircling said fusion region torus adjacent the outer radius of said torus for generating only a vertical magnetic field component within said torodial plasma which together with said toroidal magnetic confinement field defines a toroidal plasma confinement region for confining said toroidal plasma in said fusion region torus having an aspect ration less than 2 and a natural elongation of at least 2 such that said toroidal plasma exists in the form of a compact, generally-spherical, toroidal shape; a vacuum containment means for encapsulating said toroidal plasma in a vacuum enviroment; and a radiation shielding means disposed over said fusion region for intercepting neutrons irradiating from the outer surface of said fusion region torus. 2. A device as set forth in claim 1 wherein each of said plurality of toroidal field coils includes a straight inner segment positioned adjacent the inner side of said toroidal plasma and extending parallel to said main vertical axis to points above and below the elongated extent of said toroidal plasma and an outer segment. 3. A device as set forth in claim 2 wherein each of said plurality of toroidal field coils are formed of a solid electrically conductive material. 4. A device as set forth in claim 3 wherein said straight inner segments of said plurality of toroidal field coils are formed of electrically insulated segments of pie-shaped cross section which wedge together about said main axis to provide a substantially free-standing toroidal field coil arrangement in which the radially inward magnetic forces acting on said inner segments of said toroidal field coils are reacted by the wedged orientation thereof about said main axis. 5. A device as set forth in claim 4 wherein said straight inner segments of said toroidal field coils form a substantially circular cross section center conductor post disposed coaxially with said main axis. 6. A device as set forth in claim 5 wherein said toroidal field coils are rectangular in configuration about said toroidal plasma. 7. A device as set forth in claim 6 wherein said vacuum containment means includes a toroidal vacuum casing surrounding said toroidal plasma immediately adjacent thereto forming a first wall relative to said plasma. 8. A compact toroidal fusion reactor having a toroidal plasma containing fusion region torus concentrically disposed about a main vertical axis, comprising: 9. A compact toroidal fusion reactor as set forth in claim 8 wherein each of said plurality of toroidal field coils is a generally rectangular field coil formed of a solid conductor and each having a straight inner segment positioned immediately adjacent the inner side of said toroidal plasma and extending parallel to said main vertical axis to points above and below the elongated extent of said plasma and each of said inner segments of said toroidal field coils formed of electrically insulated segments of pie-shaped cross section which wedge together to form a composite circular center conductor post concentric with said with said main vertical axis. 10. A compact toroidal fusion reactor as set forth in claim 9 wherein said vacuum containment means includes a toroidal vacuum casing surrounding said fusion region and disposed within said plurality of toroidal field coils forming a plasma first wall and including a support means for supporting said plurality of toroidal field coils. 11. A compact toroidal fusion reactor as set forth in claim 10 wherein said radiation shielding means is disposed outboard of said plurality of toroidal field coils and wherein said at least one poloidal field coil includes first and second poloidal field coils disposed in a spaced apart relationship above and below the equatorial midplane of said fusion region torus, respectively, and form an integral part of said radiation shielding means. 12. A compact toroidal fusion reactor as set forth in claim 11 wherein said toroidal plasma has a major radius of 1.5 meters and a toroidal magnet field B.sub.o of 2 tesla and an aspect ratio of 1.5, thereby providing a plasma beta of 24%. |
description | 1. Field Example embodiments generally relate to mechanical connections and methods. Example embodiments also relate to nuclear plants and to mechanical connections and methods for repairing piping within reactor pressure vessels of the nuclear plants. 2. Description of Related Art A reactor pressure vessel (“RPV”) of a boiling water reactor (“BWR”) may have a generally cylindrical shape and/or may be closed at both ends (e.g., by a bottom head and a removable top head). A core shroud, or shroud, may surround the reactor core and may be supported by a shroud support structure. BWRs have numerous piping systems, and such piping systems may be utilized, for example, to transport water throughout the RPV. For example, core spray piping may be used to deliver water from outside the RPV to core spray spargers inside the RPV. The core spray piping and/or spargers may deliver water flow to the reactor core. In the event of a reactor plant casualty, such as a loss of coolant accident (“LOCA”), cooling water may be delivered to the reactor core through a core spray distribution header that may include a horizontal section and/or a vertical section. The vertical section may be referred to as a downcomer pipe. Water from the downcomer pipe may flow to sparger distribution header pipes inside the RPV via, for example, a sparger T-box. If required, repair of piping between the downcomer pipe and the distribution headers may include the use of a coupling apparatus. The coupling apparatus also may be used in the event of full piping replacement. Related art coupling apparatuses are discussed, for example, in U.S. Pat. No. 5,947,529 to Jensen (“the '529 patent”) and U.S. Pat. No. 6,131,962 to Jensen et al. (“the '962 patent”). The disclosures of the '529 patent and the '962 patent are incorporated in this application by reference in their entirety. Intergranular stress corrosion cracking (“IGSCC”) is a known phenomenon occurring in reactor components, such as structural members, piping, fasteners, and welds, exposed to high temperature water. The reactor components may be subject to a variety of stresses associated with, for example, differences in thermal expansion, the operating pressure needed for the containment of the reactor cooling water, and/or other sources such as residual stresses from welding, cold working, and other inhomogeneous metal treatments. In addition, water chemistry, welding, heat treatment, and/or radiation may increase the susceptibility of metal in a component to IGSCC. Conditions may exist in the reactor that contribute to IGSCC of the core spray piping. One area of susceptibility in the core spray piping may be the welded joints between the sparger T-box and its associated distribution headers. The sparger T-box may be the junction where the core spray downcomer pipe penetrates the shroud and/or branches to sparger distribution header pipes. Specifically, the sparger T-box may be a straight section of pipe capped by a flat plate welded to the end of the pipe. Two sparger pipes may be welded to the sparger T-box, forming a piping tee. These three welded joints may be susceptible to cracking and, in the event that through-wall circumferential cracking should occur at these welded joints, unpredictable leakage may occur. Another area of concern may be to ensure that the core spray system may prevent excessive fuel clad temperature in the event of a LOCA by delivering cooling water to the core region of the reactor. In the event that through-wall circumferential cracking should occur at these welded joints, the system may be compromised. In order to prevent unacceptable leakage and to ensure that the core spray system delivers the necessary volumetric flow rate to the reactor core, it may be desirable to provide a clamping system to ensure structural integrity of the sparger T-box and/or to hold the welded joints together in the event that one or more of these welds fail. Related art clamping systems are discussed, for example, in U.S. Pat. No. 6,456,682 B1 to Jensen (“the '682 patent”) and U.S. Pat. No. 7,724,863 B2 to Jensen (“the '863 patent”), as well as U.S. Patent Publication No. 2010/0246744 A1 to Wroblewski et al. (“the '744 publication”). The disclosures of the '682 patent, the '863 patent, and the '744 publication are also incorporated in this application by reference in their entirety. Example embodiments may provide mechanical connection devices and methods for repairing piping within reactor pressure vessels of such nuclear plants. Example embodiments also may provide mechanical connection devices and methods for mechanically clamping the core spray downcomer piping to the shroud, and structurally replacing welds that attach the cover plate and sparger pipe to the sparger T-box. In example embodiments, a core spray sparger T-box attachment assembly for a nuclear reactor pressure vessel is disclosed. The pressure vessel may include a shroud, a sparger T-box penetrating the shroud, a plurality of sparger distribution header pipes coupled to the sparger T-box, and/or a downcomer pipe. The sparger distribution header pipes may include at least one sparger nozzle. The attachment assembly may include a downcomer pipe coupling and/or a sparger T-box clamp. The sparger T-box clamp may include an anchor plate having a draw bolt opening to receive a draw bolt, a first clamp block substantially aligned at a first end of the anchor plate, and/or a second clamp block substantially aligned at a second end of the anchor plate. The anchor plate may be connected to the first clamp block by a first multiple-degree-of-freedom connection. The anchor plate may be connected to the second clamp block by a second multiple-degree-of-freedom connection. In example embodiments, the first multiple-degree-of-freedom connection may have at least two degrees of freedom. In example embodiments, the first multiple-degree-of-freedom connection may have at least two degrees of freedom that include one or more of roll, pitch, and yaw. In example embodiments, the first multiple-degree-of-freedom connection may have at least two degrees of freedom that include two or more of roll, pitch, and yaw. In example embodiments, the first multiple-degree-of-freedom connection may have at least three degrees of freedom. In example embodiments, the first multiple-degree-of-freedom connection may have at least three degrees of freedom that include one or more of roll, pitch, and yaw. In example embodiments, the first multiple-degree-of-freedom connection may have at least three degrees of freedom that include two or more of roll, pitch, and yaw. In example embodiments, the first multiple-degree-of-freedom connection may have at least three degrees of freedom that include roll, pitch, and yaw. In example embodiments, the first multiple-degree-of-freedom connection may have at least four degrees of freedom. In example embodiments, the first multiple-degree-of-freedom connection may have at least four degrees of freedom that include one or more of roll, pitch, and yaw. In example embodiments, the first multiple-degree-of-freedom connection may have at least four degrees of freedom that include two or more of roll, pitch, and yaw. In example embodiments, the first multiple-degree-of-freedom connection may have at least four degrees of freedom that include roll, pitch, and yaw. In example embodiments, the first multiple-degree-of-freedom connection may have at least two degrees of freedom and/or the second multiple-degree-of-freedom connection may have at least two degrees of freedom. In example embodiments, the first multiple-degree-of-freedom connection may have at least three degrees of freedom, and/or the second multiple-degree-of-freedom connection may have at least three degrees of freedom. In example embodiments, the first multiple-degree-of-freedom connection may have at least four degrees of freedom, and/or the second multiple-degree-of-freedom connection may have at least four degrees of freedom. In example embodiments, a mechanical connection between adjacent components of a system may include a first component of the system, a second component of the system, and/or a multiple-degree-of-freedom connection between the first component and the second component. The multiple-degree-of-freedom connection may have at least four degrees of freedom. In example embodiments, the multiple-degree-of-freedom connection may include a post connected to the first component. The post may fit into a guide in the second component to form the multiple-degree-of-freedom connection. In example embodiments, the post may include a proximal end, a middle portion, and/or a distal end. The proximal end may be wider than the middle portion. The distal end may be wider than the middle portion. In example embodiments, the proximal end may include first, second, and/or third surfaces. The distal end may include fourth, fifth, and/or sixth surfaces. The first and the fifth surfaces may be disposed at opposite ends of the post. The second and fourth surfaces may be disposed at opposite ends of the middle portion. In example embodiments, the third surface may be disposed at a widest part of the proximal end. The sixth surface may be disposed at a widest part of the distal end. The third surface may include lands and grooves to support the mechanical connection. In example embodiments, the fourth surface may be spherical. In example embodiments, the fifth surface may be conical. In example embodiments, a method for establishing a mechanical connection between adjacent components of a system may include disposing a first component of the system adjacent to a second component of the system, and/or connecting the first component to the second component using a multiple-degree-of-freedom connection. The multiple-degree-of-freedom connection may have at least four degrees of freedom. These and other features and advantages of this invention are described in, or are apparent from, the following detailed description of various example embodiments of the apparatuses and methods according to the invention. Example embodiments will now be described more fully with reference to the accompanying drawings. Embodiments, however, may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope to those skilled in the art. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. It will be understood that when an element is referred to as being “on,” “connected to,” “electrically connected to,” or “coupled to” to another component, it may be directly on, connected to, electrically connected to, or coupled to the other component or intervening components may be present. In contrast, when a component is referred to as being “directly on,” “directly connected to,” “directly electrically connected to,” or “directly coupled to” another component, there are no intervening components present. 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 although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, and/or section from another element, component, region, layer, and/or section. For example, a first element, component, region, layer, and/or section could be termed a second element, component, region, layer, and/or section without departing from the teachings of example embodiments. Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like may be used herein for ease of description to describe the relationship of one component and/or feature to another component and/or feature, or other component(s) and/or feature(s), as illustrated in the drawings. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Reference will now be made to example embodiments, which are illustrated in the accompanying drawings, wherein like reference numerals may refer to like components throughout. FIG. 1 is an isometric, partial cross-sectional view, with parts cut away, of a related art RPV of a BWR. FIG. 1 illustrates a shroud showing the spatial arrangement of downcomer piping and a lower sectional replacement that encompasses a coupling and replacement piping elbow. As discussed above, the coupling apparatus also may be used in the event of full piping replacement. RPV 100 may include vessel wall 102 and/or shroud 104 that surrounds the reactor core (not shown) of RPV 100. Annulus 106 may be formed between vessel wall 102 and shroud 104. The space inside annulus 106 may be limited, as most reactor support piping may be located within annulus 106. In the event of a reactor plant casualty, such as a LOCA, cooling water may be delivered to the reactor core through a core spray distribution header. The core spray distribution header may include a horizontal section (not shown) and/or a vertical section commonly referred to as downcomer pipe 108. A portion of downcomer pipe 108, which is in close proximity to shroud 104, may be removed, leaving a remnant 110 of the vertical downcomer piping. Connected between remnant 110 and a lower sectional replacement (“LSR”) pipe may be coupling apparatus 112. Coupling apparatus 112 may allow replacement of a lower portion of downcomer pipe 108, if needed, and/or may avoid the use of field welding. Downcomer pipe 108 may include lower elbow 114 which, in turn, may be connected to shroud 104 via elbow flange 116. As discussed below, downcomer pipe 108 may direct coolant to a sparger T-box that may be attached to a lower sparger pipe and/or an upper sparger pipe. If a sparger T-box is attached to a lower sparger pipe, for example, a similar sparger T-box at another shroud location may be attached to an upper sparger pipe. FIG. 2 is a detailed isometric view of a related art downcomer pipe coupling. As shown in FIG. 2, replacement downcomer pipe 108 may include first end 200 and/or second end 202. First end 200 may include elbow flange 116 having first end 204 and/or second end 206. First end 204 of elbow flange 116 may be configured to couple to replacement downcomer pipe 108 by any suitable means (e.g., by welding). Second end 206 may include flange member 208 extending from elbow flange 116. Flange member 208 may be received into a circular groove (not shown) machined into shroud 104. The groove may be located so as to be concentric with a sparger T-box that penetrates through shroud 104. Center portion 210 of elbow flange 116, having axial bore 212 threaded through it, may be connected to elbow flange 116 by a plurality of vanes 214 extending from an inner surface of elbow flange 116 to center portion 210. Vanes 214 may be designed to allow adequate passage of cooling water. A draw bolt may threadedly engage axial bore 212 of center portion 210. The draw bolt may connect replacement downcomer pipe 108 to an anchor plate, legs of which may bear on an internal curved surface of shroud 104. It should be appreciated that a draw bolt may be preloaded so as to create a leak-tight joint at the connection on shroud 104. The connection may be of a tongue and groove type. Second end 202 of replacement downcomer pipe 108 may include mating flange 216 to be connected to coupling apparatus 112, which in turn may be connected to remnant 110. Mating flange 216 may include a plurality of coupling slots 218 to receive a plurality of coupling bolts (not shown). FIG. 2 shows four coupling slots 218, but there may be more than four or fewer than four, as well. Coupling slots 218 may accommodate angular rotational misalignment between remnant 110 and replacement downcomer pipe 108. The coupling bolts may be designed to share load and/or prevent eccentric loading. It should be appreciated that mating flange 216 may include a spherical concave seat (see FIG. 2) to receive a seal ring (not shown) for accommodating misalignment of replacement downcomer pipe 108 and mating flange 216. The concave seat and seal ring in mating flange 216 may allow angular articulation, along the vertical axis, between remnant 110 and replacement downcomer pipe 108. FIG. 3 is an isometric view of a portion of a related art T-box assembly viewed from the inside of RPV 100. The core spray system may supply water to the reactor core region through sparger T-box 300, which may penetrate through shroud 104. Sparger T-box 300 may be a junction where the core spray downcomer supply flowstream is directed to lower sparger pipe 302 and/or upper sparger pipe 304. For example, downcomer pipe 108 may direct coolant to sparger T-box 300, which may be attached to lower sparger pipe 302 and/or upper sparger pipe 304. FIG. 3 shows sparger T-box 300 attached to lower sparger pipe 302. At another shroud location, a similar sparger T-box 300 may be attached to upper sparger pipe 304. As shown in FIG. 3, sparger T-box 300 may be part of a section of lower sparger pipe 302 that may be capped by flat plate 306, welded at location 308 to an end of lower sparger pipe 302. Further, lower sparger pipe 302 may be welded at location 310 on sparger T-box 300 to form a piping tee. However, vibration fatigue and/or weld cracking due to IGSCC, for example, may cause weld failure at location 308 and/or weld failure at location 310, joining lower sparger pipe 302 to sparger T-box 300. In the event that through-wall circumferential cracking should occur in the weld at location 308 and/or in the weld at location 310, the core spray system may provide unpredictable leakage of fluid and/or fail to deliver the necessary volumetric flow rate to the reactor core. Further, as shown in FIG. 3, lower sparger pipe 302 may include vertical slots 312 to receive associated T-bolts. In general, the operation of the T-bolts in vertical slots 312 may ensure a T-box clamp with a structural connection capable of creating a tight seal against lower sparger pipe 302. In other words, the operation of the associated T-bolts in vertical slots 312 may help maintain the position of lower sparger pipe 302 and/or upper sparger pipe 304 in relation to sparger T-box 300 should one or more welds fail. Lower sparger pipe 302 and/or upper sparger pipe 304 also may receive support from one or more brackets 314. Vertical slots 312 may be machined into lower sparger pipe 302 by any suitable method, for example, electrical discharge machining (“EDM”). Accordingly, vertical slots 312 machined in lower sparger pipe 302 may be provided to receive the distal ends of associated T-bolts. As discussed below, the associated T-bolts may be oriented vertically and thus allowed to pass through vertical slots 312 of lower sparger pipe 302. As the associated T-bolts are rotated 90 degrees by the action of rotating an associated T-bolt nut, the “T” at the distal end of the associated T-bolts may assume a horizontal orientation and come to bear against the inner surface of lower sparger pipe 302. FIG. 4 is a detailed isometric view of a related art seal plate assembly. FIG. 5 is an exploded view of the related art seal plate assembly of FIG. 4. Referring to FIGS. 4 and 5, seal plate assembly 402 may include seal plate 404, seal plate cover 406, draw bolt 400, seal plate bolts 408 and 410, and/or swivel sleeve 500. Seal plate 404 may include seal plate bolt openings 412 and 414, and/or bolt opening 502. Draw bolt 400 may include proximal end 416 and distal end 418. Ratchet teeth 420 may be machined into the periphery of proximal end 416 of draw bolt 400. Ratchet teeth 420 may be equally spaced. Seal plate bolt 408 may include proximal end 422 and distal end 504. Ratchet teeth 426 may be machined into the periphery of proximal end 422 of seal plate bolt 408. Ratchet teeth 426 may be equally spaced. Seal plate bolt 410 may include proximal end 424 and distal end 506. Ratchet teeth 428 may be machined into the periphery of proximal end 424 of seal plate bolt 410. Ratchet teeth 428 may be equally spaced. Seal plate cover 406 may include central opening 508 to receive draw bolt 400. Seal plate cover 406 also may include one or more openings 430 and/or one or more openings 432 around central opening 508. One or more openings 430 may accept a tool (e.g., spanner wrench) for installation and/or tightening of seal plate cover 406. One or more openings 432 may receive dowel pin 510 to secure seal plate cover 406 to seal plate 404 and prevent seal plate cover 406 from rotating. Distal end 504 of seal plate bolt 408 may include circumferential groove 512. Distal end 506 of seal plate bolt 410 may include circumferential groove 514. Circumferential grooves 512 and 514 may be sized to receive dowel pins 516 that may be pressed into openings 518 in seal plate 404 to secure seal plate bolts 408 and 410 to seal plate 404. FIG. 6 is an isometric view of a related art T-bolt 600. Referring to FIG. 6, T-bolt 600 may include proximal end 602 and distal end 604. Each T-bolt 600 may include machined threaded section 606 at or near proximal end 602. T-bolt 600 also may include key 608. FIG. 7 is an isometric view of a related art pipe seal 700. Referring to FIG. 7, pipe seal 700 may include bore opening 702, slot 704, and/or external key 706. FIG. 8 is a partially exploded, perspective view of a related art sparger T-box clamp 900 in the upper-pipe configuration. FIG. 9 is an isometric view of the related art sparger T-box clamp 900 in the lower-pipe configuration. In FIGS. 8 and 9, anchor plate 800 may include plurality of legs 802 extending from a face of anchor plate 800 to provide further support. Legs 802 on anchor plate 800 may bear on an internal surface of shroud 104 and, thus, may carry preload of draw bolt 400 extending through seal plate 404 and/or transmit load from anchor plate 800 to shroud 104. Legs 802 may be configured to engage an inside surface of shroud 104. Legs 802 may be machined and/or trimmed so that anchor plate 800 is parallel to an exterior surface of sparger T-box 300. Clamp blocks 804 and 806 may be attached at ends of anchor plate 800 using dove-tail joints 808 and 810, respectively. In FIGS. 8 and 9, clamp blocks 804 and 806 each may include T-bolts 600, T-bolt nuts 812, and/or pipe seals 700 to be assembled. It may be appreciated that T-bolts 600, T-bolt nuts 812, and/or pipe seals 700 may be pre-assembled with the respective clamp blocks 804 and 806 prior to introduction into RPV 100. Distal end 604 of T-bolts 600 may be inserted into vertical slots 312, which may be machined (e.g., EDM) into lower sparger pipe 302 and/or upper sparger pipe 304. At proximal end 602 of T-bolts 600, machined threaded section 606 may engage internal threaded section 814 of T-bolt nuts 812. Ratchet teeth 816 may be machined into the outer circumference of the head of T-bolt nuts 812. Ratchet teeth 816 may be equally spaced. T-bolts 600 may be rotated 90 degrees and/or drawn up tight when providing a torque on T-bolt nuts 812 to bring pipe seals 700 into contact with lower sparger pipe 302 and/or upper sparger pipe 304 and, thus, seal vertical slots 312. In order to achieve minimal leakage, pipe seals 700 may be machined to match the contour of lower sparger pipe 302 and/or upper sparger pipe 304. Further, the 90 degree rotation of T-bolts 600 may be facilitated by the interfacing action of key 608 in T-bolt 600 with slot 704 in the pipe seal bore 702, and/or external key 706 on pipe seal 700 interfacing with slot 818 of T-bolt openings 820 in clamp blocks 804 and 806, as shown in FIGS. 3 and 6-8. Moreover, pipe seals 700 and T-bolt nuts 812 may include spherical seats to allow minor articulation of pipe seals 700 against lower sparger pipe 302 and/or upper sparger pipe 304. Attaching clamp blocks 804 and 806 at ends of anchor plate 800 using dove-tail joints 808 and 810 presents several problems. First, dove-tail joint 808 provides only a single degree of freedom between clamp block 804 and anchor plate 800. Second, dove-tail joint 810 provides only a single degree of freedom between clamp block 806 and anchor plate 800. Third, because of these degree-of-freedom limitations, anchor plate 800, clamp block 804, and clamp block 806 may need to be installed as a unit to ensure proper mutual alignment. Such a need to install anchor plate 800, clamp block 804, and clamp block 806 as a unit may complicate and lengthen the installation process, leading to additional radiation exposure for operators conducting the installation and other problems. Fourth, because of these degree-of-freedom limitations, dimensions associated with the installation may need to be more precisely measured and/or anchor plate 800, clamp block 804, and/or clamp block 806 may need to be repeatedly machined so that they may be installed with proper mutual alignment. In FIGS. 8 and 9, taking anchor plate 800 as stationary—and assuming a three-dimensional Cartesian coordinate system with its origin at dove-tail joint 808, the +x direction being approximately to the right in FIG. 9 along the body of clamp block 804, the +y direction being approximately into the page in FIG. 9, and the +z direction being approximately up the page in FIG. 9—the single degree-of-freedom connection between anchor plate 800 and clamp block 804 provided by dove-tail joint 808 is in the ±y direction. This single degree-of-freedom connection does not allow relative movement between anchor plate 800 and clamp block 804 in the ±x direction, in the ±z direction, in roll, in pitch, or in yaw. Similarly, taking anchor plate 800 as stationary—and assuming a three-dimensional Cartesian coordinate system with its origin at dove-tail joint 810, the +x direction being approximately to the right in FIG. 9 along the body of anchor plate 800, the +y direction being approximately into the page in FIG. 9, and the +z direction being approximately up the page in FIG. 9—the single degree-of-freedom connection between anchor plate 800 and clamp block 806 provided by dove-tail joint 810 is in the ±y direction. This single degree-of-freedom connection does not allow relative movement between anchor plate 800 and clamp block 806 in the ±x direction, in the ±z direction, in roll, in pitch, or in yaw. FIG. 10 is an isometric view of a sparger T-box clamp in the upper-pipe configuration according to example embodiments. FIG. 11 is a partially exploded view of a sparger T-box clamp according to example embodiments. Sparger T-box clamp 1000 may provide: 1) a restraining structure for draw bolt 1002, which may pass through clearance hole in sparger T-box cover plate 306; and 2) a restraining structure for lower sparger pipe 302 and/or upper sparger pipe 304 to limit movement of these pipes relative to the position of the sparger T-box 300 in the event that welds crack circumferentially. In FIG. 10, sparger T-box clamp 1000 may include anchor plate 1004, first clamp block 1006, and/or second clamp block 1008. Anchor plate 1004 may be positioned central to sparger T-box clamp 1000 with first clamp block 1006 and second clamp block 1008 connected to opposite sides 1010 and 1012, respectively, of anchor plate 1004. First clamp block 1006 and second clamp block 1008 may be positioned to be substantially aligned with one another. Specifically, first clamp block 1006 and second clamp block 1008 may be connected to opposite sides 1010 and 1012 of anchor plate 1004 with multiple degree-of-freedom connections 1014 and 1016, respectively, discussed in more detail below. Multiple degree-of-freedom connections 1014 and 1016 may permit first clamp block 1006 and/or second clamp block 1008 to move relative to anchor plate 1004. Such movement may reduce or eliminate the imposition of stress on upper sparger pipe 304 and/or associated welds (similarly, for sparger T-box clamp 1000 in the lower-pipe configuration, such movement may reduce or eliminate the imposition of stress on lower sparger pipe 302, the weld at location 308, and/or the weld at location 310). In FIG. 10, anchor plate 1004 may include a substantially large recessed cavity 1018 to accommodate adjustable plate 1020. Adjustable plate 1020 may provide a bearing surface for draw bolt 1002 and/or permit adjustments for draw bolt 1002 to receive central portion of sparger T-box 300. Adjustable plate 1020 may move in the vertical direction because recessed cavity 1018 may be relatively larger than adjustable plate 1020. Adjustable plate 1020 may include draw bolt opening 1022 to receive draw bolt 1002 and/or crimp collar 1024 around draw bolt 1002. Draw bolt 1002 may have a cylindrical head and/or a hexagonal socket 1026 for tightening. If a ratchet lock arrangement is to be used, ratchet teeth (not shown) on draw bolt 1002 may be oriented such that rotation is permitted in only one direction. Crimp collar 1024 may be located under and/or surrounding the head of draw bolt 1002. Crimp collar 1024 may have a first spherical surface that may interface with a second spherical surface on adjustable plate 1020. This interfacing may allow draw bolt 1002 to remain in-line with elbow flange 116 and/or axial bore 212 while anchor plate 1004 adjusts to the inner surface of shroud 104, as needed, in terms of roll, pitch, and/or yaw. Crimping of crimp collar 1024 after the application of preload on draw bolt 1002 may prevent rotation of draw bolt 1002 so that draw bolt 1002 may be removed only after crimp collar 1024 is removed or defeated. In FIGS. 10 and 11, anchor plate 1004 may include openings 1028 and 1030 to receive seal plate bolts 1032 and 1034. Openings 1028 and 1030 may be threaded to receive seal plate bolts 1032 and 1034. Anchor plate 1004 may further include machined slots 1036 and 1038 to accommodate latch springs 1040 and 1042, respectively. Latch springs 1040 and 1042 may reside in slots 1036 and 1038. Latch springs 1040 and 1042 may interface with seal plate bolts 1032 and 1034, respectively. Seal plate bolts 1032 and 1034 may include equally spaced ratchet teeth (not shown) that may be machined into the periphery of the heads of seal plate bolts 1032 and 1034. The ratchet teeth of seal plate bolt 1032 may engage teeth of latch spring 1040 to lock seal plate bolt 1032 in position and/or to prevent seal plate bolt 1032 from rotating. Similarly, the ratchet teeth of seal plate bolt 1034 may engage teeth of latch spring 1042 to lock seal plate bolt 1034 in position and/or to prevent seal plate bolt 1034 from rotating. The rotation of seal plate bolts 1032 and 1034 may be performed with a hexagonal wrench that accommodates an internal hexagon slot in the head of seal plate bolts 1032 and 1034. The load produced by the rotation may advance seal plate 1120 against the respective sparger T-box cover plate (e.g., in the lower-pipe configuration, sparger T-box cover plate 306). First clamp block 1006 and second clamp block 1008 may be attached to anchor plate 1004 at opposite sides 1010 and 1012. First clamp block 1006 may include T-bolt openings 1044 and 1046 extending through first clamp block 1006. Second clamp block 1008 may include T-bolt openings 1048 and 1050 extending through second clamp block 1008. In FIG. 11, T-bolts 1100 may extend through each of T-bolt openings 1044, 1046, 1048, and 1050. Each T-bolt 1100 may include a machined threaded section 1102 on proximal end 1104 of T-bolt 1100 so as to engage with internal threaded section 1108 of T-bolt nut 1106. T-bolt nuts 1106 may preferably be threaded with an internal tap of 5/8 18 Unified Thread Standard, fine series (“UNF”), for example. However, a person of ordinary skill in the art (“PHOSITA”) would understand that various tap dimensions may be used. First clamp block 1006 may include machined slots 1052 and 1054 to accommodate latch springs 1056 and 1058, respectively. Second clamp block 1008 may include machined slots 1060 and 1062 to accommodate latch springs 1064 and 1066, respectively. Each latch spring 1056, 1058, 1064, and 1066 may include ratchet teeth (not shown) to engage with respective T-bolt nuts 1106. In FIG. 11, ratchet teeth 1110 may be machined into the outer circumference of the head of T-bolt nuts 1106. Ratchet teeth 1110 may be equally spaced. Ratchet teeth 1110 may engage with latch springs 1056 and 1058 in first clamp block 1006 and/or latch springs 1064 and 1066 in second clamp block 1008. Latch springs 1056, 1058, 1064, and 1066 may lock respective T-bolt nuts 1106 and/or allow rotation in only one direction, which may increase preload in T-bolts 1100. An anti-rotation feature of T-bolts 1100 may be accomplished by the feature of a key on T-bolts 1100 (similar to key 608 on T-bolts 600) that may interface with a slot of pipe seal 1112 (similar to slot 704 of pipe seal 700) integral with a bore opening of pipe seal 1112 (similar to bore opening 702 of pipe seal 700). The slot of pipe seal 1112 may be designed to permit only 90 degrees rotation of T-bolt 1100. As T-bolt nut 1106 is rotated, the key of T-bolt 1100 may advance through the distal end (surface adjacent to lower sparger pipe 302 or upper sparger pipe 304) of pipe seal 1112. As a result, the key may reach the middle or intermediate section of the bore opening, at which point friction in the interfacing threaded section 1102 of T-bolt 1100 and with internal threaded section 1108 of T-bolt nut 1106 may cause T-bolt 1100 to rotate 90 degrees. This action may orient distal “T” end 1114 of T-bolt 1100 horizontally. As rotation of T-bolt nut 1106 is continued, the key may be drawn into the proximal section of the bore opening. The proximal section of the bore opening, in addition with external key 1116 of pipe seal 1112 interfacing with slot 1122 of T-bolt openings 1124 of clamp block 1008, for example, may lock T-bolt 1100 in the desired orientation. Accordingly, rotation of T-bolt nut 1106 may advance distal “T” end 1114 of T-bolt 1100 to come to bear against the internal surface of lower sparger pipe 302 or upper sparger pipe 304 and, thus, pull the surface (that may be contoured) of pipe seal 1112 into full contact with the external surface of lower sparger pipe 302 or upper sparger pipe 304 and, thus, seal the remainder of vertical slots 312 in lower sparger pipe 302 or upper sparger pipe 304. In FIG. 11, slots 1122 may assume any orientation. Each slot 1122 may assume the same orientation or one or more slots 1122 may assume different orientations from each other. For example, slots 1122 may face away from draw bolt 1002, may face toward draw bolt 1002, or may both face away and face toward draw bolt 1002. In another example, slots 1122 may be oriented vertically, horizontally, diagonally, or a mixture thereof. FIG. 12 is an isometric view of sparger T-box clamp 1000 in the lower-pipe configuration according to example embodiments. In FIGS. 10-12, anchor plate 1004 may include plurality of legs 1118 extending from a face of anchor plate 1004 to provide further support. Legs 1118 on anchor plate 1004 may bear on an internal surface of shroud 104 and, thus, may carry preload of draw bolt 1002 extending through seal plate 1120 and/or transmit load from anchor plate 1004 to shroud 104. Legs 1118 may be configured to engage an inside surface of shroud 104. For related art sparger T-box clamp 900, where anchor plate 800 is connected to clamp block 804 using dove-tail joint 808 and also connected to clamp block 806 using dove-tail joint 810, the single degree-of-freedom connections result in the faces of anchor plate 800, clamp block 804, and clamp block 806 being parallel. In contrast, for sparger T-box clamp 1000, where anchor plate 1004 is connected to first clamp block 1006 using multiple degree-of-freedom connection 1014 and also connected to second clamp block 1008 using multiple degree-of-freedom connection 1016, the multiple degree-of-freedom connections do not require that the face of anchor plate 1004 be parallel to the face of either first clamp block 1006 or second clamp block 1008, nor do the multiple degree-of-freedom connections require that the face of first clamp block 1006 be parallel to the face of second clamp block 1008. Thus, multiple degree-of-freedom connections 1014 and 1016 may permit first clamp block 1006 and/or second clamp block 1008 to move relative to anchor plate 1004. In FIGS. 10-12, taking anchor plate 1004 as stationary—and assuming a three-dimensional Cartesian coordinate system with its origin at multiple degree-of-freedom connection 1016, the +x direction being approximately to the right in FIG. 12 along the body of second clamp block 1008, the +y direction being approximately into the page in FIG. 12, and the +z direction being approximately up the page in FIG. 12—the multiple degree-of-freedom connection between anchor plate 1004 and second clamp block 1008 provided by multiple degree-of-freedom connection 1016 may be in the ±y direction, in roll, in pitch, or in yaw. This multiple degree-of-freedom connection does not allow relative movement between anchor plate 1004 and second clamp block 1008 in the ±x direction or in the ±z direction. Similarly, taking anchor plate 1004 as stationary—and assuming a three-dimensional Cartesian coordinate system with its origin at multiple degree-of-freedom connection 1014, the +x direction being approximately to the right in FIG. 12 along the body of anchor plate 1004, the +y direction being approximately into the page in FIG. 12, and the +z direction being approximately up the page in FIG. 12—the multiple degree-of-freedom connection between first clamp block 1006 and anchor plate 1004 provided by multiple degree-of-freedom connection 1014 may be in the ±y direction, in roll, in pitch, or in yaw. This multiple degree-of-freedom connection does not allow relative movement between first clamp block 1006 and anchor plate 1004 in the ±x direction or in the ±z direction. Multiple degree-of-freedom connection 1014 and/or multiple degree-of-freedom connection 1016 may have at least two degrees of freedom. The at least two degrees of freedom may include one or more of roll, pitch, and yaw. The at least two degrees of freedom may include two or more of roll, pitch, and yaw. Multiple degree-of-freedom connection 1014 and/or multiple degree-of-freedom connection 1016 may have at least three degrees of freedom. The at least three degrees of freedom may include one or more of roll, pitch, and yaw. The at least three degrees of freedom may include two or more of roll, pitch, and yaw. The at least three degrees of freedom may include roll, pitch, and yaw. Multiple degree-of-freedom connection 1014 and/or multiple degree-of-freedom connection 1016 may have at least four degrees of freedom. The at least four degrees of freedom may include one or more of roll, pitch, and yaw. The at least four degrees of freedom may include two or more of roll, pitch, and yaw. The at least four degrees of freedom may include roll, pitch, and yaw. As shown in FIGS. 10-12, multiple degree-of-freedom connection 1014 may include a post connected to anchor plate 1004 and a corresponding guide in first clamp block 1006. In the alternative, multiple degree-of-freedom connection 1014 may include a post connected to first clamp block 1006 and a corresponding guide in anchor plate 1004. As also shown in FIGS. 10-12, multiple degree-of-freedom connection 1016 may include a post connected to anchor plate 1004 and a corresponding guide in second clamp block 1008. In the alternative, multiple degree-of-freedom connection 1016 may include a post connected to second clamp block 1008 and a corresponding guide in anchor plate 1004. FIG. 13 is a side view of post 1300 according to example embodiments. Post 1300 may include proximal end 1302, middle portion 1304, and/or distal end 1306. Proximal end 1302 may be wider than middle portion 1304. Distal end 1306 may be wider than middle portion 1304. Proximal end 1302 may include first surface 1308, second surface 1310, and/or third surface 1312. Distal end 1306 may include fourth surface 1314, fifth surface 1316, and/or sixth surface 1318. First surface 1308 and fifth surface 1316 may be disposed at opposite ends of post 1300. Second surface 1310 and fourth surface 1314 may be disposed at opposite ends of middle portion 1304. Third surface 1312 may be disposed at a widest part of proximal end 1302. Sixth surface 1318 may be disposed at a widest part of distal end 1306. Third surface 1312 may include lands and/or grooves to support mechanical connection to anchor plate 1004, first clamp block 1006, and/or second clamp block 1008. Fourth surface 1314 may be spherical. Fourth surface 1314 may interface with a corresponding cylindrical surface in a corresponding guide. This interfacing may accommodate movement in one or more of the multiple degrees of freedom. Fifth surface 1316 may be conical. For ease of machining and/or other purposes, post 1300 may be made separately from anchor plate 1004 and then connected to anchor plate 1004 by, for example, a pinned or threaded connection. However, post 1300 also may be made as a one-piece unit together with anchor plate 1004. Similarly, post 1300 may be made separately from first clamp block 1006 and/or second clamp block 1008 and then connected to first clamp block 1006 and/or second clamp block 1008 by, for example, a pinned or threaded connection. However, post 1300 also may be made as a one-piece unit together with first clamp block 1006 and/or second clamp block 1008. The guide corresponding to post 1300 may have a similar shape as and/or dimensions similar to post 1300. A PHOSITA would understand the relationship between post 1300 and a corresponding guide. This relationship may accommodate movement in one or more of the multiple degrees of freedom. FIG. 14 is a flowchart of a method for establishing a mechanical connection between adjacent components of a system according to example embodiments. A method for establishing a mechanical connection between adjacent components of a system may include disposing a first component of the system adjacent to a second component of the system (S1400) and/or connecting the first component to the second component using a multiple-degree-of-freedom connection (S1402). The multiple-degree-of-freedom connection may have at least four degrees of freedom. Disposing a first component of the system adjacent to a second component of the system means disposing the first component close enough to the second component so that the first and second components may be connected using the multiple-degree-of-freedom connection. While example embodiments have been particularly shown and described, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. |
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abstract | According to one aspect of the invention, a method for separating and recovering uranium from a nuclear fuel element. The method includes immersing a nuclear fuel element containing nuclear fuel and cladding in a molten metal. The nuclear fuel includes uranium. The cladding is selectively dissolved from the nuclear fuel element when immersed in the molten metal. The nuclear fuel is separated from the cladding. The method then includes loading the nuclear fuel into a permeable basket that is electrically configured as an anode of an electrolytic cell. There are also a molten salt electrolyte and a cathode in the electrolytic cell. Then, the method includes applying an electric charge across the electrolytic cell. The molten salt electrolyte selectively transfers uranium from the anode to the cathode. |
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050531883 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a reactor system according to an embodiment of the invention includes a reactor pressure vessel 20, a primary containment vessel 22 accommodating the reactor pressure vessel and disposed in a reactor building 21, a main turbine 24 disposed in a turbine building 23, a main steam piping 25, an inside main steam isolation valve 26 of a quick closure type, an outside main steam isolation valve 27 of a conventional type, a main steam stop valve 28, a main steam control valve 29 and a piping 31. The main steam piping 25 extends through the reactor building 21 and turbine building 24 to supply main steam generated in the reactor pressure vessel to the main turbine 24. The inside main steam isolation valve 26 can be closed within 0.1 second which corresponds to one thirtieth of a period of time required for the closure of a conventional inside main steam isolation valve, and is provided on the main steam piping 25 inside the primary containment vessel 22 to serve as a quick closure valve operable in case of a break accident of the main steam piping 25. The outside main steam isolation valve 27 is provided on the main steam piping 25 outside and near the primary containment vessel 22. The main steam stop valve 28 and the main steam control valve 29 are provided on the main steam piping 25 near the main turbine 24. The main steam stop valve 28 is a conventional quick closure valve, and the inside main steam isolation valve acts in a similar manner to the main steam stop valve 28. The piping 31 provided with a safety relief valve 30 is connected to the main steam piping 25 at a position between the reactor pressure vessel 20 and inside main steam isolation valve 26. As shown in FIG. 1, a portion of the main steam piping 25 extending from the outside main steam isolation valve 27 towards the reactor pressure vessel is designed in the aseismic highest class category I while the other portion of the main steam piping 25 extending from the outside main steam isolation valve 27 towards the main turbine, the main steam stop valve 28 and the turbine building 23 supporting them are designed in the seismic non-category I class. The reactor pressure vessel 20 in the embodiment of the invention is for a natural circulation reactor, and is of a simple construction to be dispensed with such piping 15 of reactor pressure vessel recirculation system and many steam separators 16 for forced circulation, unlike a reactor pressure vessel 14 of a prior forced circulation reactor shown in FIG. 3. Accordingly, the reactor pressure vessel 20 in the embodiment of the invention has in its upper construction only a solid portion one third of that in a prior forced circulation reactor. As shown in FIG. 2, the reactor pressure vessel 20 includes a reactor core 33, a cylindrical chimney 34 disposed above the reactor core and having a height of 9 meter, a dryer 35 disposed above the cylindrical chimney, an upper dryer tube 36 and a steam dome section 32. The cylindrical-shaped, upper dryer tube 36 is arranged in the steam dome section 32 above the reactor core 33, so that the steam dome section 32 has a larger volume than that in a prior boiling water type reactor which has the same level of output as that of the present reactor system. Therefore, an additional volume to be enlarged corresponding to a possible quick closure of the inside main steam isolation valve 26 caused in case of a break accident of the main steam piping can be made small, so that the transient phenomenon in the reactor pressure vessel 20 can be readily mitigated. In the embodiment of the invention, when breakage accidentally occurs on a portion of the main steam piping 25 on the side of the main steam turbine 24 from the outside main steam isolation valve 27, the inside main steam isolation valve 26 quickly closes to enable substantially reducing an amount of coolant flowing out of a broken portion of the main steam piping 25 as compared with that in a prior reactor system. In this case, how severe the transient pressure phenomenon in the reactor pressure vessel 20 upon the quick closure of the inside main steam isolation valve 26 is problematic. Since the volume of the steam volume section 32 in the reactor pressure vessel 20 and the volume between the inside main steam isolation valve 26 and reactor pressure vessel 20 are adequately ensured, however, it is possible to mitigate the transient pressure phenomenon in the reactor pressure vessel 20. An analysis will be given hereinbelow to a transient phenomenon in application of the present invention on a natural circulation reactor. Referring to FIG. 4, a calculation model of the reactor system employed for the analysis comprises the safety relief valve 30, main steam stop valve 28, inside main steam isolation valve 26 of a quick closure type, outside main steam isolation valve 27, steam dome section 32, feed water piping 40, downcomer 41, chimney 34, flow channel 43 of fuel assembly, fuel element 44 and lower plenum 45. The flow channel 43 of fuel assembly and fuel element 44 constitute the reactor core 33 as shown in FIG. 1. In FIG. 4, the same elements as shown in FIG. 1 are designated by the same reference numerals. A length of flow passage extending from the steam dome section 32 to the inside main steam isolation valve 26 is simulated be decreasing the volume of the flow passage, and quick closure of the inside main steam isolation valve 26 is simulated by rapidly decreasing an area of flow passage or the valve module to zero. Reactivities taken into consideration include void reactivity, doppler reactivity and reactivity of control rods. FIG. 5 shows a result of a transient analysis in the case of quick closure of the inside main steam isolation valve 26. Pressure in the reactor pressure vessel 20 is raised upon the quick closure of the inside main steam isolation valve 26, and then the safety relief valve 30 operates to suppress the highest pressure. The pressure rise in the reactor pressure vessel 20 is accompanied by decrease of voids in the reactor core and causes void reactivity increase, which results in an increase of neutron flux. However, the volume in the reactor pressure vessel for accommodating vapor is large to make a speed of pressure rise low and scram (insertion of control rods) corresponding to a signal of quick closure of the inside main steam isolation valve 26, so that increase in neutron flux is suppressed to the extent of 1.1 times as large as that during the normal operation of the reactor system. Heat flux of fuel assembly is also suppressed while synchronizing in a time lag with a change in neutron flux. On the other hand, the flow rate of circulating reactor coolant is once increased since pressure rise causes voids in the reactor core to decrease thus reducing the flow resistance of two phase flow (liquid phase and vapor phase). Thereafter, the voids are reduced due to reduction of heat flux of fuel assembly and the average density of reactor coolant in the reactor core is increased to reduce the flow rate of the coolant. As a result, the change of the minimum critical power ratio (.DELTA.MCPR) is suppressed to 0.05 since the flow rate of reactor coolant is large at the time of large power immediately after the transient phenomenon and the power is small at the time of small flow rate. The above value is adequately small in comparison with the thermal margin in the normal operation, and no boiling transition phenomena occurs even upon the quick closure of the inside main steam isolation valve. In this manner, it is confirmed that the provision of the inside main steam isolation valve 26 of a quick closure type in the interior of the primary containment vessel 22 offers no problem in terms of a transient characteristics to enable quickly closing the valve 26 upon a break accident of the main steam piping 25. Such quick closure of the inside main steam isolation valve 26 decreases an amount of reactor coolant flowing out. Thus even when the main steam piping 25 is accidentally broken at a position between the inside main steam isolation valve 26 and the main turbine 24 by an earthquake corresponding to the seismic class: Seismic Category I, the inside main steam isolation valve 26 of a quick closure type quickly closes to decrease an amount of reactor coolant flowing out of a broken portion of the main steam piping 25, thereby suppressing the exposure dose to a slight extent as compared with the prior art. Accordingly, a portion of the main steam piping 25 extending from the outside main steam isolation valve 27 towards the main turbine, the main steam stop valve 28 and the turbine building 23 supporting these members can be designed in the non-category I class to thereby facilitate reduction of an amount of structural materials for equipments and pipings and construction of the turbine building. The enlarged steam volume section of the reactor pressure vessel mitigates a transient phenomenon associated with pressure rise caused due to vapor generated in the reactor pressure vessel after a break accident of the main steam piping to ensure safety and stability of a reactor system. While the inside main steam isolation valve 26 is of a quick closure type in the above embodiment, the outside main steam isolation valve may be alternatively of a quick closure type, in which the length of a flow passage extending from the steam dome section to the outside main steam isolation valve is larger than in the above embodiment to further mitigate the transient phenomenon for an improved effect. Referring to FIG. 6, there is shown a reactor system of a conventional, typical boiling water type atomic power plant. Main steam generated in a reactor pressure vessel 1 flows from a reactor building 6 to a turbine building 7 through a main steam piping 2 disposed in a main steam tunnel 11, and is supplied via a main steam stop valve 8 and a main steam control valve 9 to a main turbine 10 for driving the same. The main steam piping 2 is provided with an inside main steam isolation valve 4 and an outside main steam isolation valve 5, both of which are disposed near a primary containment vessel 3. The main steam stop valve 8 acts to shut off a supply of main steam to the main turbine 10, and it takes 0.1 second to close the valve 8, so that it can close several tens of times as fast as the main steam isolation valves do. The inside and outside main steam isolation valves 4 and 5 are opened during a normal operation of the plant, and function to close in case of a break accident of the main steam piping 2 for the prevention of outflow of reactor coolant within a predetermined period of time. The inside and outside main steam isolation valves 4 and 5 are limited to 3 to 4.5 seconds in a period of time for closure. Therefore, some reactor coolant in the form of vapor will flow out of the reactor pressure vessel until the inside and outside main steam isolation valves have been fully closed. A portion of the main steam piping 2 on the side of the reactor pressure vessel 1 from the outside main steam isolation valve 5 is designed in the highest seismic class seismic category I class, and a portion of the main steam piping 2 on the side of the main turbine 10 from the outside main steam isolation valve 5 and the main steam stop valve 8 are designed in the seismic category I class on the basis of an evaluated exposure dose upon a break accident of the main steam piping, which takes into consideration a period of time (3 to 4.5 seconds) required for the closure of the main steam isolation valves. The turbine building which is required to have a shielding function is designed as a whole in the non category I class. Since the main steam piping 2 and the main steam stop valve 8 within the turbine building 7 are designed in the seismic category I class as described above, however, those elements which support these main steam piping and main steam stop valve are also designed corresponding to the seismic category I class to be of a firm construction. Referring to FIG. 7, there is shown a reactor system of a conventional underground type atomic power plant. Reactor building 3a and turbine building 7a are spaced away from each other due to the terrain, so that a main steam piping 2a disposed in a main steam tunnel 11a is large in length. The main steam piping 2a is provided with a quick closure valve 13a which is disposed between an outside main steam isolation valve 5a and a main steam stop valve 8a. In the drawing, the reference numeral 4a designates an inside main steam isolation valve, and 9a a main steam control valve. With this arrangement, steam and water flowing out upon a break accident of the main steam piping 2a are prevented from flowing into the reactor building 3a and the turbine building 7a. Construction downstream of the quick closure valve 13a is designed in the non category I class. While the invention has been described by way of an embodiment, it is to be understood that the invention is not limited to the embodiment but to the scope of the appended claims. |
claims | 1. An imaging system comprising:(a) an optical unit comprising a radiation collection unit and a detection unit for detecting radiation collected by the radiation collection unit, the radiation collection unit comprising at least two mask arrangements defining at least two radiation collection regions respectively, each of the mask arrangements being configured and operable to sequentially apply a plurality of a predetermined number of spatial filtering patterns applied on radiation collected thereby from a region of interest, each filtering pattern being formed by a predetermined arrangement of apertures in the corresponding collection region, the detected radiation thereby comprising at least two elemental image data pieces corresponding to the collected radiation from said at least two collection regions;(b) a control unit comprising: a mask controller module; and an image processing module; wherein the mask controller module is configured for operating each of said at least two mask arrangements to selectively apply said different filtering patterns during selected exposure time periods, each of said at least two elemental image data pieces thereby corresponding to the radiation collected during the selected exposure time period; and the image processing module is configured for receiving and processing said at least two elemental image data pieces, said processing comprising utilizing predetermined data indicative of a total effective transmission function of each of said at least two mask arrangements, and determining a plurality of at least two restored elemental images respectively, being together indicative of a three dimensional arrangement of the region of interest from which the input radiation is being collected. 2. The system of claim 1, wherein said selected plurality of the predetermined number of spatial filtering patterns of each of said at least two mask arrangements being preselected to provide said effective transmission function which provides non-null transmission for spatial frequencies lower than a desired predetermined maximal spatial frequency for each of said at least two collection regions. 3. The system of claim 1, wherein said detection unit comprises at least two detection regions corresponding with said at least two collection regions such that detection of the collected input radiation from said at least two collection regions is non overlapping. 4. The system of claim 3, wherein said at least two detection regions are regions of a common radiation sensitive surface or at least two separate radiation sensitive surfaces respectively. 5. The system of claim 1, wherein at least one of said at least two mask arrangements comprises an array of replaceable mask units carrying said predetermined number of the spatial filtering patterns and being mechanically replaceable in the corresponding radiation collection region. 6. The system of claim 5, wherein said array of replaceable mask units is configured as a mechanical wheel comprising said predetermined number of the arrangements of apertures each defining the corresponding filtering pattern. 7. The system of claim 1, wherein at least one of said at least two mask arrangements is configured as an electronic mask arrangement configured and operable for varying the aperture arrangement defining the spatial filtering pattern, said control unit being configured to operate said mask arrangement to selectively vary the aperture arrangement to thereby provide one of the spatial filtering patterns in the respective of said at least two collection regions. 8. The system of claim 1, wherein at least one of said at least two mask arrangements comprises a multiplexed arrangement of apertures corresponding to said predetermined number of spatial filtering patterns, said multiplexed arrangement of apertures comprising groups of apertures corresponding to different filtering patterns, each group of apertures comprises a wavelength selective filter configured for transmission of a predetermined wavelength range being a part of a total wavelength range for imaging. 9. The system of claim 1, wherein said optical unit comprises an array of more than two of the collection regions, said array having at least one of the following arrangements of the collection regions: 2×2, 2×3, 2×4, 2×5, 3×3, 3×4, 3×5, 4×4, 4×5 and 5×5. 10. The system of claim 1, wherein said control unit further comprises a 3D image processing module configured and operable for receiving and processing said plurality of the restored elemental images to thereby determine data about the three dimensional arrangement of the region of interest. 11. The system of claim 1, wherein the control unit further comprises a set selection module configured to be responsive to input data comprising data about desired resolution and brightness and to determine a corresponding set of the filtering patterns having non-null effective transmission function. 12. The system of claim 1, configured for imaging with input radiation of at least one of the following wavelength ranges: IR radiation, visible light radiation, UV radiation, X-ray radiation, Gamma radiation. 13. A method for imaging a region of interest comprising:(a) collecting input radiation from the region of interest through at least two collection regions, said collecting comprising applying at each of said at least two collection regions a selected sequence of at least two different filtering patterns during predetermined collection time periods, wherein said selected sequence of the at least two different filtering patterns and the corresponding collection time periods defining a total effective transmission function of the radiation collection which provides non-null transmission for spatial frequencies lower than a desired predetermined maximal spatial frequency for each of said at least two collection regions,(b) generating at least two elemental image data pieces, each corresponding to the collected input radiation with said sequence of the at least two filtering patterns,(c) processing the at least two elemental image data pieces utilizing said total effective transmission function of each of the radiation collection regions, and determining at least two restored elemental images of the region of interest respectively being together indicative of a three-dimensional arrangement of the region of interest. 14. The method of claim 13, wherein each of said at least two different filtering patterns is in the form of an aperture array comprising a predetermined number and arrangement of pinholes. 15. The method of claim 13, wherein said predetermined collection time periods of the selected at least two different filtering patterns are selected for optimizing transmission intensities for selected spatial frequencies. 16. The method of claim 13, wherein said maximal spatial frequency is defined by a minimal aperture size. 17. The method of claim 13, further comprising detecting image data pieces corresponding to each of said at least two collection regions using a single readout mode for all of said collection time periods of the aperture arrays, thereby integrating said image data pieces to form the corresponding elemental image data pieces in one scan time while selectively using the different filtering patterns. 18. The method of claim 13, wherein said processing of the at least two elemental image data pieces for generating the restored elemental images of the region of interest comprises: determining a sum of intensity maps of said image data pieces and utilizing inverting the distortion effect caused by the total effective transmission function, to thereby generate said restored image data. 19. The method of claim 13, wherein said selected sequence of at least two different filtering patterns comprising a plurality of a predetermined number of aperture arrays and is selected in accordance of a desired Radiation Intensity Improvement (RII) factor to provide imaging of the region of interest with improved image quality. 20. The method of claim 13, wherein said collection of input radiation through said at least two collection regions comprising arranging said at least two collection regions for collecting input radiation from said region of interest along at least two different optical axes, said at least two different optical axes being parallel to each other. |
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047553499 | summary | The present invention concerns an anti-seismic damping mechanism for the encased primary pumps of nuclear reactors, and, more particularly, such a mechanism intended to limit the pendulum effect of the pump in the case of a seismic disturbance. It is known that in nuclear reactors equipped with so-called "encased" pumps of great height, it is necessary, in the event of earthquakes, to immobilize the lower part of the pumps relative to the reactor vessel. If this precaution is not taken, the pumps could suffer significant damage from harmful effects due to flexing of the pump body, damage occurring at the area of attachment of the pump to the foundation slab, or other damage. The immobilization mechanisms provided must react instantaneously and without external intervention to interdict any significant displacement of the base of the pump. These mechanisms, moreover, must permit relative displacements of the pump and the reactor bed to accommodate differential horizontal and vertical thermal expansion between the vessel and the slab during increases in the reactor temperature. In current breeder reactors, the primary pumps are seated on the slab through the intermediary of an elastic ring or sliding mechanism, which systems allow slow movements during differential thermal expansion between the slab and the vessel. Elastic ring type arrangements allow inclination of the axis of the pump, whereas the sliding mechanism allows variable displacement of the vertical axis of the pump. The connection between this axis and the bed is fixed when the pump is seated on an elastic ring, and an articulated sleeve connecting the pump to the tank is used in the configuration comprising a sliding mechanism. Differential expansion between the vessel and the slab in the radial or vertical direction is permitted by sliding of the base of the pump within the connection between the pump and the bed, or by modification of the length of the articulated sleeve. The object of the invention is to provide an anti-seismic damping mechanism for such encased primary pumps within nuclear reactors, which enables a rigid attachment of the primary pumps directly on the slab and which furnishes a clearly more economical solution than that of familiar systems. Of course, the damper mechanism according to the invention must also permit hydraulic hermeticity, the continuity of the hydraulic seam between the base of the pump and the elastic ring regardless of the axial and/or radial differential expansion due to temperature differences between the slab and the bed, and must also hold the pump steady or fixed to avoid the pendulum effect of the pump in the event of an earthquake. Summarizing the invention, this goal is achieved by virtue of an improved mechanism for anti-seismic connection between the base of the pump and the so-called "dome" of a nuclear power station (the dome, despite its name, may include cylindrical components). The mechanism is characterized by the fact that the pump base is provided externally with a flange seated with a slight axial play and significant radial play within a socket which is closed by an immovable cover. The flange can slide axially with a small play within a cylindrical portion of the dome. A radial damping mechanism is mounted between the flange and the socket, so as to permit, without constraint, slow displacements of the flange with respect to the socket, and to block such displacements when they are rapid. At the same time, the lower end of the socket has an external collar, which, through the intermediary of a metallic journal, can slide axially upon a cylindrical bearing which is solidly bound with the internal lateral wall of the dome. Calibrated passages arranged in the periphery of the vessel enable controlled circulation of the heat-carrying fluid of the reactor between the base of the pump and the upper part of the space between the pump and the dome. It will be understood that this mechanism permits slow displacements of the base of the pump with respect to the dome in the horizontal direction by sliding of the flange in its socket and in the vertical direction, by sliding of the socket and the collar of the lower part of the pump base within the dome. In fact, the passages arranged in the journal of the collar and at the periphery of the socket have the effect that the fluid bathing the assembly offers practically zero resistance to very slow axial or vertical displacements, such as those resulting from differential thermal expansions. The same applies in the horizontal direction, since, as stated above, the damper mechanism mounted between the flange and its socket permits, without constraint, relative displacements between these two entities, so long as the displacements are very slow. In an advantageous embodiment of the present invention, the radial damping mechanism specified above is constituted by a damper ring surrounding the flange of the pump base, preserving the significant play which must exist, in the radial direction, between this flange and the socket, and, preferably, this ring displays projections spaced at regular angles, for example, four projections separated by 90.degree., which bear upon corresponding sufaces of the periphery of the flange or on the internal lateral wall of the socket, and which delimit a number of chambers between the ring and the flange and between the ring and the wall of the socket. In the case in which the ring displays four projections 90.degree. from one another, and in which the projections are arranged alternately on the interior and the exterior of the ring, there are obtained two pairs of diametrically opposite chambers, one interior and one exterior. Preferably, the projections in question terminate in a flat end which bears against a corresponding plane surface of the wall of the socket or the flange. In another embodiment of the invention, the radial damper mechanism specified above is constituted by a number of fluid-escape dampers, for example four in number, angularly spaced in a regular manner, with one end of each bearing upon the internal lateral wall of the socket, and the other end upon the periphery of the flange. It will be understood that the possibility of slow horizontal displacements, for example due to differential thermal expansions, is ensured in the first case by escape of fluid among the various chambers of the damper ring, and, in the second case, by escape passages provided in conventional fashion in the fluid-escape dampers known colloquially as "dashpots." Conversely, rapid displacements, resulting for example from earthquakes, are blocked, through the fact that the fluid cannot move very rapidly through the very narrow calibrated passages specified above. Of course, the same applies for vertical displacements, the fluid being unable to pass very rapidly through the passages provided at the periphery of the socket and within the journal fixed to the collar surrounding the pump base. |
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052895092 | description | DETAILED DESCRIPTION OF THE INVENTION The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims. In order to better understand the primary application of the present invention, i.e., a launcher of magnetosonic waves into a plasma-forming device, it will first be helpful to provide an brief description of a tokamak --the preferred plasma-forming device with which the invention is used. Hence, reference is made to FIG. 1 where there is shown a diagrammatic view of the main elements of a tokamak 20, with a portion thereof cutaway. The design and operation of such a tokamak is well described in the art, see, e.g., Artsimovich and/or Furth, supra, so only a very cursory overview of the tokamak's construction is presented herein. Basically, the tokamak 20 includes a toroidal vacuum vessel 22 that is centered about a major axis 24. A minor axis 25, centrally located within the toroidal vessel 22, encircles the major axis 24. The relationship of the major and minor axes 24 and 25 is shown in FIG. 1A. The vessel 22 is made from a conductive material, such as non-magnetic stainless steel or inconel, and is constructed with sufficiently thick walls to withstand the vacuum pressures that are developed therein. A large number of toroidal field magnetic coils 26 are equally spaced around the vessel 22, each encircling the minor axis 25 and a respective segment of the vessel 22. Eighteen such coils 26 are illustrated in FIG. 1, but this number is only exemplary. When energized with an electrical current, the toroidal coils 26 combine to produce a toroidal magnetic field B.sub.T, represented by the arrow 28, that encircles the major axis 24 within the vacuum vessel 22. A plurality of poloidal field magnetic coils 30 are positioned inside of the toroidal field coils 26, yet still outside of the vacuum vessel 22, so as to encircle the major axis 24. As depicted in FIG. 1, the windings of the poloidal field coils 30 are substantially perpendicular to the windings of the toroidal field coils 26. When energized with an appropriate electrical current, the poloidal field magnetic coils 30 combine to produce a poloidal magnetic field B.sub.P, represented by the arrow 32, that encircles the minor axis 25 of the vacuum vessel 22. Because plasma is an ionized gas, it is also an electrical conductor, with the movement of electrons (negatively charged particles) in one direction and the movement of positively charged ions in the other direction representing the flow of electrical current. An important part of the operation of a tokamak is the creation of axial current flow through the plasma contained within the vessel 22. Such current flow serves to heat the plasma, and is frequently referred to as the "current drive" of the tokamak. The current drive follows the minor axis 25 of the tokamak and is depicted in FIG. 1 by the arrow 36. The current drive may be initiated and maintained by launching a suitable plasma wave into the vacuum vessel 22 that propagates in the direction of the minor axis. The comb-line antenna structure described hereinafter provides one means for launching such a wave. In addition, ohmic heating primary windings 34 may be positioned inside of the toroidal field coils 26, in close contact with the vacuum vessel 22, so as to encircle the primary axis 24, much like the poloidal field coils 30. When energized with an electrical current, the field coils 30 (acting as a transformer primary winding) induce an electrical current, I.sub.P, in the plasma (acting as a transformer secondary winding), which electrical current I.sub.P also contributes to the current drive of the tokamak. Not shown in FIG. 1, but understood to be part of any tokamak or similar plasma-confining structure are conventional means for establishing a desired vacuum pressure within the vessel 22, and means for injecting the appropriate gases into the vessel from which plasma may be formed. In operation, appropriate gases are introduced into the vacuum vessel 22 at the appropriate pressure. These gases, e.g., .sup.2 H and .sup.3 H, are heated to extremely high temperatures in order to form a hot plasma. The toroidal magnetic field B.sub.T confines the plasma to a toroidal volume inside of the vessel 22 that does not touch the walls of the vessel. This occurs because the toroidal magnetic field B.sub.T has lines of magnetic force coincident or parallel with the minor axis 25, and plasma, as a whole, is substantially confined to and follows magnetic lines of force, forming as it were a plasma ring. The poloidal magnetic field B.sub.P is needed to complete the plasma confinement against drifts caused by gradients in B.sub.P. The combined fields form, as it were, a plasma and magnetic vortex. The externally applied component of B.sub.P is also used to shape the cross sectional area of the plasma ring within the toroidal plasma volume to a desired shape. For example, at some points within the vessel, or at some times when the plasma is within the vessel, the cross sectional area of the plasma cloud may be "squeezed", thereby compressing the plasma into a smaller volume, and further increasing its temperature. At other points within the vessel, or at other times, the cross sectional shape of the plasma cloud may be expanded, with some of the plasma particles being diverted away from the main plasma body. Such control of the cross-sectional shape of the plasma cloud is, as indicated, controlled by the poloidal field coils 30. For this reason, such coils are sometimes referred to as the "shaping field coils" or "shaping field windings". Referring next to FIG. 2, the manner in which a comb-line antenna structure 40 made in accordance with the present invention may be used to launch unidirectional plasma waves into the plasma of a tokamak is diagrammatically illustrated. The toroidal vacuum vessel 22 of a tokamak is depicted in FIG. 2 from a view along the major axis 24. Once formed, the plasma is confined within the vessel 22 so as not to touch the walls of the vessel 22, i.e., to reside within the area bounded by the dotted lines 38, thereby forming a plasma ring 39. One or more comb-line antenna structures 40, described more fully below, are mounted to the inside of an outer wall of the vessel 22 so as to front or face the toroidal plasma ring 39. Two such structures 40 are shown in FIG. 2, but such is only exemplary. Typically, the comb-line structures 40 will be recessed within the outer wall of the vessel 22. However, as will be evident from the description that follows, the comb-line structures are sufficiently shallow to enable their mounting on the inside of the outer wall of the vessel 22 without being recessed and still not encroach on the area to which the plasma ring 39 is confined. Still referring to FIG. 2, an rf generator 44 generates rf input power, represented by the arrow 45, that is applied to an input port 48 of the comb-line structure 40 through a conventional waveguide 46. As described more fully below, the rf input power 45 is directly coupled to a first current strap within the comb-line structure 40, and inductively coupled to other current straps within the comb-line structure by means of a traveling wave propagating along the structure. In the vacuum region immediately surrounding the comb-line structure, the electromagnetic field of this traveling wave is evanescent in the radially inward direction. Such wave traveling along the comb-line is diagrammatically illustrated in FIG. 2 by the arrows 42. If the distance to the plasma 39 is small, such an evanescent field couples to a magnetosonic wave suitable for providing current drive and heating in the plasma mass, while the power flow along the comb-line structure is damped by the power transfer to the plasma. The comb-line structure 40 also includes an rf output port 50. Any of the rf input power 45 that is coupled to a last current strap within the comb-line structure 40 without being converted to the traveling wave 42, or without otherwise being dissipated within the comb-line structure 40, is received at the output port 50. This rf output power may either be applied through a conventional waveguide 54 (or other suitable transmission line) to a load 58, or to a recirculation system 52. If applied to a recirculation system, the recovered rf power is combined with the input power generated from the rf generator 44 in order to reapply it to the input port 48, thereby improving the efficiency of the comb-line structure 40. A representative recirculation system 52 is described below in conjunction with the description of FIG. 5. Referring next to FIGS. 3A and 3B, one embodiment of a comb-line antenna structure 60 is shown. FIG. 3A shows a "top" view, similar to the view orientation of FIG. 2, and FIG. 3B shows a "side" view, showing the comb-line structure as viewed from the plasma. As with the generic comb-line structure 40 of FIG. 2, the comb-line structure 60 includes a single input port 62 and a single output port 64. The structure 60 resembles, electrically as well as mechanically, a comb-line bandpass filter. The structure 60 includes a plurality of parallel current straps 66 that are supported in a plane above a conductive surface 68. Each strap 66 has an approximate length l, width W, and thickness t. As best seen in FIG. 3B, discrete capacitors 72 are placed at one end of each of the straps 66. What is shown as item 72 in FIG. 3B is one plate of the capacitor, with the conductive wall 70 functioning as the other plate. Each current strap 66 is separated a distance S from an adjacent strap. The plane formed by the straps 66 thus has the approximate dimensions of l by N(W+S), where N is the number of current straps that are used. The plane of the straps 66 is separated from the conductive surface 68 by a standoff distance d.sub.1. Such plane is spaced adjacent to the plasma mass 39 a distance d.sub.2. In operation, the edge of the plasma mass 39, as well as the density of the plasma at its edge, will vary. Thus, it is understood that the distance d.sub.2 will also vary. While the plane of the straps 66 is depicted in FIG. 3A as being straight, it is also to be understood that there will typically be some curvature associated with such plane as it fits against or within the outer wall of the toroidal vacuum vessel 22 (FIG. 2). Still referring to FIGS. 3A and 3B, side walls 70 are attached to the conductive surface 68, thereby forming a housing or "box", within which the straps 66 are supported. The straps 66 may be mechanically supported from one section of such wall 70. A first conductive strap 66', on one edge of the plane formed by the straps 66, is electrically connected to the rf input port 62. A last conductive strap 66", on an opposing edge of the current strap plane, is electrically connected to the rf output port 64. In operation, the comb-line structure 60 is inherently a traveling wave device, in the sense that power applied to its input port 62 launches a wave traveling toward the output port 64, with power being inductively coupled between adjacent straps. The structure 60 shown in FIGS. 3A and 3B, as well as the preferred structure shown below in FIGS. 4A and 4B, offers the significant advantage that far fewer feedthroughs and tuning elements are required to launch the same total power than are used in prior art devices that individually drive each current strap. Such feedthroughs (input and output ports) and tuning elements are costly and occupy valuable space near the tokamak. Of course, approximately the same current per strap is required to launch a given power per strap regardless of whether the straps are fed directly or inductively. However, the power per feedthrough can be much higher for the comb-line structure shown in FIGS. 3A and 3B (as well as in FIGS. 4A and 4B) because the input port 62 sees a matched load. That is, with individually fed straps, the standing wave ratio at each feedthrough is necessarily high because the resistive component of the strap impedance is typically only a few ohms. In contrast, the input impedance of the comb-line structure 60 reflects the accumulated loading of all the straps. The resonant elements are internal to the comb-line structure 60, so the standing wave ratio is low at the feedthrough (input port 62). The concept of using a comb-line structure to launch fast waves into a plasma is described in Chiu, et al., Nuclear Fusion, Vol. 24, p. 717 (1984), cited previously. An analysis of a more practical form of the comb-line structure 60 is provided in Moeller et al., "A Comb Line Structure For Launching Unidirectional Fast Waves", Europhysics Conference Abstracts on Radiofrequency Heating and Current Drive of Fusion Devices, Vol. 16E, pp 53-56, Brussels (Jul. 7-10, 1992). These two references--the Chiu et al. and Moeller et al. references--are incorporated herein by reference. A preferred comb-line structure 80, made in accordance with the present invention, is depicted in FIGS. 4A and 4B. Such structure 80 resembles the structure 60 described in connection with FIGS. 3A and 3B above except for two major differences: (1) there are no discrete capacitors used with the structure 80; and (2) the structure 80 includes a multiplicity of wickets (or hoops) 92 that enclose each current strap. FIG. 4A shows a "top" view, similar to the view orientation of FIG. 2, and FIG. 4B shows a "side" view, showing the comb-line structure 80 as viewed from the plasma 39. As with the generic comb-line structure 40 of FIG. 2, the comb-line structure 80 includes a single input port 82 and a single output port 84. The structure 80 includes a plurality of parallel current straps 86 that are supported in a plane above a conductive surface 88. Each strap 86 has an approximate length l, width W, and thickness t. Each current strap 86 is separated a distance S from an adjacent strap. The plane formed by the straps 86 thus has the approximate dimensions of l by N(W+ S), where N is the number of current straps that are used. The plane of the straps 86 is separated from the conductive surface 88 by a standoff distance d.sub.1. Such plane is further spaced adjacent to the plasma mass 39 a distance d.sub.2. In operation, the edge of the plasma mass 39, as well as the density of the plasma at its edge, will vary. Thus, it is understood that the distance d.sub.2 will also vary. Like the description above in connection with FIGS. 3A and 3B, it is noted that while the plane of the straps 86 is depicted in FIG. 4A as being straight, it is to be understood that there will typically be some curvature associated with such plane as it fits against or within the outer wall of the toroidal vacuum vessel 22 (FIG. 2). Still referring to FIGS. 4A and 4B, side walls 90 are attached to the conductive surface 88, thereby forming a housing or "box", within which the straps 86 are supported. The straps 86 may be mechanically supported from one section of such wall 90. A first conductive strap 86', near one edge of the plane formed by the straps 86, is electrically connected to the rf input port 82. A last conductive strap 86", on an opposing edge of the current strap plane, is electrically connected to the rf output port 84. A multiplicity of current wickets 92 (or conductive hoops) enclose each of the current straps 86. These wickets are oriented so as to lie substantially orthogonal to the current straps. Such wickets are grounded to the conductive surface 88. In some instances, it may be desirable to mechanically support the wickets 92 to standoff bars 94 (only a couple of which are shown in FIG. 4A) that are attached to, or form an integral part of, the conductive surface 88. Such standoff bars 94 not only facilitate the mechanical connection of the wickets to the surface 88 (which surface 88 may be referred to as a conductive "backplane"), but also help to stiffen the backplane in the region where the attachment of the wickets is made. The wickets 92 are made from a suitable conductive wire, such as inconel, molybdenum, titanium, or other high temperature conductor. Such wire is formed in the general shape of a hoop, and mounted to the backplane 88 so as to loop around or enclose the current strap, as best seen in FIG. 4A. It is important that the wicket 92 be kept close to the current strap 86, but not touch the current strap 86. Keeping the wicket close to the current strap increases the capacitance between the strap and shield, which is advantageous because it reduces the required length of the strap. In general, the separation distance between a given wicket 92 and the respective current strap that it encloses may be on the order of 0.5 to 1.0 cm with the U-shaped conductive wire being more or less equally spaced from the three sides of the current strap about which it loops. At an input frequency in the range of 100 to 200 MHz, the number N of current straps within the comb-line structure should be at least 10, with the length l of each strap being approximately 15 to 30 cm, the separation distance S between adjacent current straps being approximately 2.5 to 5.0 cm, and the width W of the current straps also being about 2.5 to 5.0 cm. In lieu of wickets 92, some applications of the invention may utilize a row of posts that separate the current straps, which posts may be substantially the same as the legs of the wickets. Such posts would extend up from the backplane 88 just past the current straps, and would provide electrostatic shielding between the straps. In most instances, only a single row of posts would be required between current straps, although a double row could be used to increase the capacitance, if needed. Further, it is noted that while each current strap 86 will generally have the same number of wickets enclosing it as do the other current straps, the wickets may be arranged in alternate rows so as to overlap, as shown in FIG. 4C, which shows a partial view of the antenna from the same vantage point as FIG. 4B. An advantage achieved by the comb-line structure 80 shown in FIGS. 4A and 4B over the structure 60 shown in FIGS. 3A and 3B is the avoidance of discrete capacitors. At a typical operating frequency of 120 MHz, such discrete capacitors, when used, need only have a capacitance value of from 16 to 20 pf. However the peak voltage seen by such capacitors is on the order of tens of kilovolts. Given the type of hostile environment associated with plasma, this means that a spacing of at least 1 cm is needed between the plates of the capacitor in order to avoid breakdown if solid dielectrics are not used. Solid dielectrics do not survive well in or near a plasma environment. A spacing of 1 cm, in turn, translates to approximately a 200 cm.sup.2 area that is required to order to achieve the necessary capacitance. Such area is not readily available. Hence, being able to avoid the use of discrete capacitors, as is accomplished with the comb-line antenna structure 80 shown in FIGS. 4A and 4B, offers an important advantage. Another advantage achieved by the comb-line structure 80 (FIGS. 4A and 4B) over the structure 60 (FIGS. 3A and 3B) is the electrostatic shielding provided by the wickets 92. There is no such shielding provided by the structure 60. That is, the wickets 92 (FIGS. 4A and 4B) function as a Faraday shield, shielding the plasma 39 from the electrostatic fields that are present at the current straps. The desired plasma wave is excited inductively by the currents flowing in the current straps 86, and is referred to as a "magnetosonic" wave. Unfortunately, an electrostatic field is also produced by such straps that can excite undesired plasma waves. Such undesired waves not only represent wasted power, but also lead to acceleration of ions near the walls of the vessel 22 (FIG. 2). Advantageously, the Faraday shield provided by the wickets allows the divergence free, inductive field to readily pass therethrough, thereby allowing the desired inductive coupling between adjacent current bars to take place, but also blocks the curl free, electrostatic field. That is, because the wickets are electrically grounded, the electric field lines associated with such electrostatic fields terminate at the wickets, thereby confining the electrostatic fields to the immediate region surrounding the wickets. However, the wickets 92, by virtue of being more or less orthogonal to the direction of current flow in the current straps, allow the magnetic fields associated with the current flow in the current straps to readily pass therethrough. The passage of the magnetic fields through the wickets provides for the desired inductive coupling between adjacent current straps, as well as permits the appropriate plasma wave to be launched in the desired direction within the plasma 39. The magnetosonic wave is launched from the current straps into the plasma through an evanescent layer, which concept is well understood by those of skill in the art. An advantage of the comb-line structures 60 or 80 is that the axial wave number of the traveling wave in the structure, usually referred to as n.sub..parallel., can be made to vary by adjusting the input frequency within the passband of the structure. Referring next to FIG. 5, there is shown a schematic diagram of a recirculation system 52 that may be used to maintain a traveling wave in a comb-line structure, such as the comb-line structure 80 of FIGS. 4A and 4B. Such recirculation system 52 is used whenever it is not convenient, especially in existing tokamaks, to use a comb-line structure of sufficient length (i.e., having a sufficient number of current straps, N) to give complete damping under the conditions of poorest coupling. In such instances, a unidirectional wave is maintained by making the comb-line structure 80 part of a ring resonator, as shown schematically in FIG. 5. As seen in FIG. 5, a group of three 3 dB couplers, 102, 104 and 106, in combination with a conventional stub tuner pair 108, form a variable directional coupler 110. An additional 3 dB hybrid coupler 112 and stub tuner 114 form an adjustable phase shifter 116. The phase shifter 116 is the only critical tuning element, in the sense that the resonance condition only requires an integral number of wavelengths around the ring. If the variable coupler 110 is not optimally adjusted, some fraction of the input power, generated by the rf amplifier 44, will go to a dummy load 118, but the ring will remain unidirectional and the generator 44 will not see a reflection, as long as the ring remains resonant. The phase shifter 116 need not have rapid adjustment capability. Rather, any rapid fluctuations in the electrical length of the antenna structure 80 due to plasma movement may be compensated for by small adjustments in the frequency. Also, for reasonable loading of the antenna structure, the circulating power and hence the Q of the ring are low. Specifically, if T is the fraction of power incident at the antenna structure 80 that arrives at the output port 84, and C is the power coupling factor of the adjustable coupler 110, the ratio G of circulating power to generator power is G=C/[1-(1-C).sup.1/2 T.sup.1/2 ].sup.2, which is maximized when C=1-T and G=1/(1-T) and all the power is damped in the antenna. For example, if T=1/e, then G=1.58, which represents a very low Q. This means that resonance is not critical under such conditions. To demonstrate the advantage of using the Faraday shield formed using the wickets 92, the electrical behavior of the comb-line structure 80 with and without an ideal Faraday shield will be compared. An ideal Faraday shield is considered as a shield that is transparent to magnetic fields, but appears as a perfect conductor to curl fee electric fields. For purposes of the comparison, it is assumed that the number of current straps is infinite, so that there are no end effects. Also, to simplify the comparison, the plasma is assumed to be a conducting wall. Using this simplified approach, it is also possible to calculate the plasma loading that determines the actual plasma impedance presented to the antenna structure as a perturbation. Such calculation is carried out in Appendix A for the discrete capacitor embodiment (FIGS. 3A and 3B). It is noted that such calculation is not related to the shielded verses non-shielded comparison presented below. The coordinate system used for the comparison that follows is shown in FIG. 6. Note, in FIG. 6 the Y coordinate is out of the paper. Considering first the unshielded case, and designating I.sub.r (y) and V.sub.r (y) as the current and voltage, respectively, along the r.sup.th strap, the array of straps can be regarded as a multi-conductor TEM mode transmission line. Such transmission line is governed by the equations: ##EQU1## where C.sub.rs is the mutual capacitance per unit length between the r and s strap, with the other straps (other than the r.sup.th strap) grounded, and L.sub.rs is the mutual inductance per unit length. (Note that Eqs. (1)-(3) are in Appendix A). If it is assumed that all of the straps are identical, and that there are no end effects, then it is only necessary to consider a typical element, r=0, and determine L.sub.oS and C.sub.0S. The currents and voltages in the straps may be expressed as: ##EQU2## The dependence of the current and voltage on y is a consequence of the TEM nature of the mode, and the assumption that the straps are all shorted to ground at y=0. The dependence on e.sup.-ir.theta. comes from Floquest's theorem. In this case, .beta.=.omega./c, where .omega. is the angular frequency, and c is the speed of light. The propagation constant along the structure, k.sub.z, is just k.sub.z =.theta./P, where P is the period. Using Eqs. (5a) and (5b) in (4b), it is seen that, looking at the typical r=0 strap, ##EQU3## Although L(.theta.) is defined as a fourier series having mutual inductances as coefficients, it is noted that L(.theta.) simply represents the self inductance per unit length of a strap when the phase shift from strap to strap is .theta.. Combining Eqs. (2a) and (2b), it is also seen that ##EQU4## where l is the length of the straps. If there is an admittance Y.sub.0 at the end of each strap, then ##EQU5## Combining Eqs. (3a) and (4), a dispersion relation is obtained as ##EQU6## where it is assumed that Y.sub.0 =i.omega.C.sub.e, where C.sub.e is the discrete capacitance at the end of each strap, if any. Since .omega./c=.beta., and k.sub.z =.theta./P, a relationship between .omega. and k.sub.z is thus obtained. The phase velocity along the structure is just .omega./k.sub.z, while the group velocity, related to the energy flow, becomes d.omega./dk.sub.z. As the end capacitance, C.sub.e, approaches zero, however, .beta.tan(.beta.l) approaches .infin., which means than .beta.l approaches .pi./2. Thus, .beta., and therefore .omega., are then fixed, independent of .theta., and hence independent of k.sub.z. The group velocity then approaches 0, so that there is no energy flow, and the antenna structure is cut off. In contrast, when a Faraday shield is used, the equations for the shielded multi-conductor transmission line are: ##EQU7## For an ideal Faraday shield, L.sub.rS and L(.theta.) are unchanged from the above unshielded case. C.sub.0 is the capacitance per unit length between a given strap and its shield. From Eqs. (9a), (5a) and (5b), it is seen that Eq. (8a) is again obtained. However, using Eqs. (9b), (5a) and (5b) it is seen that ##EQU8## Eq. (10) thus shows that .beta. is no longer equal to .omega./c. Equivalently, Eq. (7) demonstrates that the velocity of light along the strap, for the shielded case, becomes ##EQU9## and is dependent upon .theta.. The consequence of this is that even if C.sub.e =0, by making .beta.l=.pi./2, the antenna structure is no longer cut off. In fact, when the quantity .beta.=.pi./2l is substituted into Eq. (10), it is seen that ##EQU10## Since C.sub.0 in the shielded case is always greater than C(.theta.) in the unshielded case, .beta. will always be greater than .omega./c, and the larger C.sub.0 becomes, the greater will be .beta.. The advantage of having a large C.sub.0 and large .beta. is that the strap length, l=.pi./2.beta., can be shorter, which is normally desirable. In general, if C.sub.e .noteq.0, Eqs. (8) and (10) show that the dispersion relation ##EQU11## takes the form ##EQU12## where U=l.omega.[L(.theta.)C.sub.0 ].sup.1/2. This means that ##EQU13## where F is some complicated function of l and C.sub.0 /C.sub.e, which reduces to .pi./2 when C.sub.e .fwdarw.0. The form of the dispersion relation remains unchanged from the case where C.sub.e =0, except for a scaling factor. That is, the ratio of the upper to lower cut off frequency, the "pass band ratio", ##EQU14## is independent of l, C.sub.0 and C.sub.e, as is the functional dependance of .omega. on .theta., except for a scaling factor in the latter case. Adding C.sub.e allows l to be smaller, but does not effect the pass band ratio. As described above, it is thus seen that the present invention provides a comb-line antenna structure that launches magnetosonic waves into an adjacent plasma mass. This it does, in the preferred embodiment (shown in FIGS. 4A and 4B) without the need for a discrete capacitor at the end of each current strap. In other embodiments (FIGS. 3A and 3B or variations thereof), it may be desirable to add a small end capacitance. Moreover, as also seen from the above, the described comb-line structure effectively shields the plasma and adjacent current straps from electrostatic fields, yet still retains the requisite inductive coupling needed for the operation of a comb-line device. As further seen from the above, the comb-line launching structure described further provides significant mechanical advantages over prior art launching devices in that the wickets used to enclose each current strap are flexible, yet strong, and are thus able to react to thermal stress, without significant distortion or breakage. While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims. ##SPC1## |
description | The present application claims benefit of U.S. Provisional Application No. 60/542,393, entitled “Method for Monitoring Combustion Dynamics Stability Margin,” filed on Feb. 6, 2004, and incorporated herein by reference as if set forth in full. This invention relates to combustors in gas turbine engines, afterburners, industrial processing devices, and other combustor devices, and more particularly, to systems and methods of monitoring the dynamic stability margin in such combustors. In order for turbine operators and/or control systems to optimize overall system performance across competing demands of emissions levels, power output, and engine life, maximum information about each component's health and performance is needed. One key issue that has emerged in combustion systems is that of combustion instabilities—that is, self-excited, combustion driven oscillations that generally occur at discrete frequencies associated with the combustor's natural acoustic modes. Minimizing the amplitude of these oscillations is essential for maximizing hot section part life—however, tradeoffs between dynamics amplitude, emissions, and power output are routinely encountered. Currently, when turbines are being commissioned or simply going through day to day operation, the operator has no idea how the stability of the system is affected by changes to fuel splits/operating conditions unless, of course, the system actually becomes unstable. Johnson et al. pursued an analysis technique for determine stability margin quantifications in a publication entitled “Experimental Determination of the Stability Margin of a Combustor Using Exhaust Flow and Fuel Injection Rate Modulations” presented at the Proceedings of the Combustion Institute, Vol. 28, 2000. Their technique required, however, a pulsing fuel injector and acoustic driver. Such external actuation is not a practical practice for operating combustors in day to day operations. As such, this technique may be useful in a lab setting but is not practical for a fielded system. Hobson et al also attempted to infer combustor damping by monitoring the bandwidth of pressure or compressor casing vibration in a publication entitled “Combustion Instabilites in Industrial Gas Turbines—Measurements on Operating Plant and Thermoacoustic Modeling” as presented to the International Gas Turbine & Aeroengine Congress & Exhibition in June of 1999. However, the use of frequency domain techniques to determine damping are much more susceptible to noise and less robust than those described here. Thus, there exists a need in the industry for a system and method to provide the combustor operator a quantitative description of how near a combustor is to its stability boundary, so that the user can determine whether small changes in fuel splits, operating or ambient conditions are likely to effect combustor dynamics. The present invention comprises systems and methods for determining stability margin of a combustor. One embodiment of the present invention includes the steps of providing a measuring device in communication with the combustor, wherein the measuring device generates signals indicative of physical quantities in the combustor; performing an autocorrelation calculation on the signals to determine the correlation of the signals in the combustor; and determining the damping coefficient from the autocorrelation calculation, wherein the damping coefficient signifies a proximity of the combustor to instability. The damping coefficient may be estimated from the oscillatory envelope of the autocorrelation calculation data. In one aspect of the present invention, the oscillatory envelope is calculated from a Hilbert Transform of the autocorrelation calculation data. In another aspect, the fit is a least squares fit. The stability margin may be estimated from the time rate of change of the estimated damping coefficient. An increase of the damping coefficient over time may signify the combustor's approach to stable conditions and a decrease of the damping coefficient over time may signify the combustor's approach to unstable conditions. In yet another aspect of the invention, the measuring device may measure a combustor quantity such as pressure, chemiluminescence, species concentration, temperature, ion current, rotor vibration, combustor can vibration, and casing vibration. In another aspect of the invention, a combustor controller may control combustor parameters to prevent instability in response to the increase of the damping coefficient over time. The combustion parameters may include engine fuel splits, power output, or other parameters that influence combustor stability. Another embodiment of the present invention includes a system for detecting stability margin in a combustor. The system includes a measuring device in communication with the combustor, wherein the measuring device generates signals indicative of a combustor quantity, and a stability margin detection unit that receives the signals and performs an autocorrelation technique on the pressure signal to determine the proximity of the combustor to instability. The measuring device measures a combustor quantity such as pressure, chemiluminescence, species concentration, temperature, ion current, rotor vibration, combustor can vibration, and casing vibration. In yet another aspect, the autocorrelation technique includes a calculation of the autocorrelation data of the signal, a determination of an oscillatory envelope of the autocorrelation data, a determination of the damping coefficient from the oscillatory envelope of the autocorrelation data, and a determination of the stability margin based on the value of the damping coefficient. In another aspect of the invention, the autocorrelation technique is implemented in real-time. The stability margin may be determined by the increase and decrease of the damping coefficient, respectively. In one aspect of the invention, the combustor controller controls combustor parameters in response to the results of the autocorrelation technique. The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The present invention is described below with reference to block diagrams and flowchart illustrations of systems, methods, apparatuses and computer program products according to an embodiment of the invention. It will be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, respectively, can be implemented by computer program instructions. These computer program instructions may be loaded onto a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions which execute on the computer or other programmable data processing apparatus create means for implementing the functions specified in the flowchart block or blocks. These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means that implement the function specified in the flowchart block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Accordingly, blocks of the block diagrams and flowchart illustrations support combinations of means for performing the specified functions, combinations of steps for performing the specified functions and program instruction means for performing the specified functions. It will also be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, can be implemented by special purpose hardware-based computer systems that perform the specified functions or steps, or combinations of special purpose hardware and computer instructions. The present invention comprises systems and methods for accurately and robustly predicting the stability margin for combustors. The present invention is applicable to all types of combustors and is designed to operate over a diverse range of environmental condition, including varying temperatures, humidity, air compositions, and fuel compositions. Exemplary embodiments of the present invention will hereinafter be described with reference to the figures, in which like numerals indicate like elements throughout the several drawings. FIG. 1 illustrates a combustor system 100 in accordance with the present invention. Advantageously, the present invention can be utilized with different types of combustors. Combustors applicable to this invention include but are not limited to combustors such as those found in industrial systems, land based or aeronautical gas turbine engines, afterburners, or ramjets. The design of the combustor and its disposition in an engine casing is well known to those skilled in the art and is in no way limited to the examples enumerated herein. For purposes of illustrating the present invention, the combustion system 100 comprises a combustor 110 that is generally designed to receive compressed air from a compression section and fuel from fuel nozzles. The air and the fuel mix and burn to operate the engine. For purposes of the present invention, the combustor can be of any shape or configuration. The combustion system may further include a stability margin detection unit 120, a measuring device 130, and a combustor controller 140. The stability margin detection unit 120 identifies the stability margin of the combustor at any given time. By identifying the stability margin one can prevent system failure or inefficient operation due to instability by making appropriate adjustments through the combustor controller 140. The measuring device 130 is coupled to the combustor 110 and configured to detect one or several of many physical quantities, such as pressure, chemiluminescence, temperature, species concentration, ion current, rotor vibration, combustor can vibration, casing vibration, or any other physical quantity impacted by the heat release in the combustor or by combustor vibrations. In an exemplary embodiment, the measuring device 130 detects pressure. The measuring device 130 may be a pressure transducer or any other suitable device that accurately measures pressure and may be either analog or digital. In an exemplary embodiment, the measuring device 130 is a pressure transducer capable of measuring pressure oscillations up to roughly 5 KHz. The measuring device 130 may be mounted in the combustor, tangential to the combustor, or any other acceptable location that sufficiently measures a combustor quantity that is affected by heat release or combustor vibrations. The measuring device 130 also may be attached to a stand-off tube that may be mounted into the combustor 110 and extend out of the combustor 110. The stability margin detection unit 120 is in communication with the measuring device 130. FIG. 2 shows a block diagram illustrating components comprising a stability margin detection unit 120 of the combustion system 100, according to one aspect of the present invention. The stability margin detection unit 120 is preferably configured with an operator interface for enabling the stability margin unit 120 to accept system setup information, input threshold settings and additional information applicable to detection of the stability margin. Alternatively, such information may be inputted by other suitable means, such as the combustion controller 140. The stability margin detection unit 120 is designed to receive data from the measuring device 130 and based thereon determine the stability margin of the combustor through an autocorrelation method as described herein. According to an exemplary embodiment of the present invention, the stability margin detection unit 120 comprises software running on a microprocessor or other suitable computing device. The stability margin detection unit 120 may be embodied as a method, a data processing system, or a computer program product. Accordingly, the stability margin detection unit 120 may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the stability margin detection unit 120 may take the form of a computer program product on a computer-readable storage medium having computer-readable program code means embodied in the storage medium. Any suitable computer-readable storage medium may be utilized including hard disks, CD-ROMs, optical storage devices, or magnetic storage devices. As shown in FIG. 2, the stability margin detection unit 120 may comprise a processor 215, a memory 222, an operating system 220, an input/output interface 160 and a database 240, all in communication via a local interface bus 230. Briefly, the processor 215 executes the operating system 220, which controls the execution of other program code such as that comprising the signal processing logic 235 for implementing the functionality described herein. The local interface bus 230 may be, for example but not limited to, one or more buses or other wired or wireless connections. The local interface bus 230 may have additional elements, which are omitted for simplicity, such as controllers, buffers (caches), drivers, repeaters, and receivers, to enable communications. Furthermore, the local interface bus 230 may include address, control, and/or data connections to enable appropriate communications among the aforementioned components. The processor 215 is a hardware device for executing software, particularly that stored on memory 222. The processor 215 may be any custom-made or commercially-available processor, a central processing unit (CPU), an auxiliary processor among several processors associated with the system 100, a semiconductor-based microprocessor (e.g., in the form of a microchip or chip set), a macroprocessor, or generally any device for executing software instructions. The memory 222 may comprise an operating system 220 and the signal processing logic 235. The architecture, operation, and/or functionality of signal processing logic 235 will be described in detail below. The memory 222 may include any one or combination of volatile memory elements (e.g., random access memory (RAM), such as DRAM, SRAM, SDRAM, etc.) and non-volatile memory elements (e.g., ROM, hard drive, tape, CD-ROM, etc.). The memory 222 may incorporate electronic, magnetic, optical and/or other types of storage media. Furthermore, memory 222 may have a distributed architecture, in which various components are situated remote from one another, but can be accessed by processor 215. The software in memory 222 may include one or more separate programs, each of which comprising executable instructions for implementing logical functions. In the example of FIG. 2, a software in memory 222 includes the signal processing logic 235 according to the present invention. The memory 222 may further comprise a suitable operating system 220 that controls the execution of other computer programs, such as the signal processing logic 235, and provides scheduling, in-output control file and data management, memory management, and communication control and related services. The input/output interfaces 160 may be any device or devices configured to facilitate communication with the pressure measuring device 130. The communications can be with a communication network, such as a public or private packet-switched or other data network including the Internet, a circuit switched network, such as the public switch telephone network, a wireless network, an optical network, or any other desired communication infrastructure. Alternatively, the input/output interfaces may also include any one of the following or other devices for facilitating communication with local interface bus 230: a user interface device such as a keyboard or mouse, a display device such as a computer monitor, a serial port, a parallel port, a printer, speakers, a microphone, etc. During operation of the stability margin detection unit 120, a user may interact with the signal processing logic 235 via such user interface and display devices. The signal processing logic 235 may be a source program, executable program (e.g., object code), script, or any other entity comprising a set of instructions to be performed. When implemented as a source program, then the program needs to be translated via a compiler, assembler, interpreter, or like, which may or not be included within the memory 222, so as to operate properly in connection with the operating system 220. Furthermore, the signal processing logic 235 may be written as an object oriented program language, which has classes of data and methods, or a procedure program language, which has routines, sub-routines, and/or functions, for example but not limited to, C++, Pascal, Basic, Fortran, Cobol, Perl, Java, and Ada. It will be appreciated by one of ordinary skill in the art that one or more of the stability margin detection unit 120 components may be located geographically remotely from other stability margin detection unit 120 components. Furthermore, one or more of the components may be combined, and additional components performing functions described herein may be included in the stability margin detection unit 120. In addition, one or more, if not all, of the components of the stability margin detection unit 120 may be incorporated into the combustor controller 140. The stability margin detection unit 120 is configured to receive through the input/output interface 160 data captured by the measuring device 130. As discussed in regards to the FIG. 3, the signal processing logic 235 utilizes an autocorrelation method to analyze pressure data for the detection of a stability margin. One of ordinary skill in the art will appreciate that the signal processing logic 235 is not limited to pressure data but may be any combustor quantity. The signal processing logic 235 may include hard-coded threshold values for stability margin detection or may use input threshold values inputted into the memory 222 through the input/output interface 160. The detection of a stability margin may result in a signal being communicated to the combustion controller 140 that indicates that the combustor is near unstable conditions. The combustion controller 140 may control the operation of the combustor 110 and is in communication with the stability margin detection unit 120. Such controllers controlling the operation of a combustor are well known, and therefore are not described in detail as a part of this disclosure. Upon receiving a signal indicating the value of the stability margin of the combustor by the signal processing logic 235, the combustion controller 140 will make appropriate adjustments to the operating parameters of the combustor 110 to ensure stable operation of the combustor. Combustor parameters adjusted may include but are not limited to the amount of fuel from the fuel inlet nozzles, the amount of compressed air allowed in the combustion chamber, and the desired engine power output. FIG. 3 is a flow chart illustrating the architecture, functionality and/or operation of the signal processing logic 235 in a accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, pressure data may be used in the method of FIG. 3. One of ordinary skill in the art will appreciate that the method of FIG. 3 is not limited to pressure data but may be any combustor quantity including chemiluminescence, species concentration, temperature, ion current, rotor vibration, combustor can vibration, casing vibration, or any other physical quantity impacted by the heat release in the combustor or by combustor vibrations. For illustrative purposes only, the remainder of the detailed description will use pressure data as an example combustor quantity; however, any combustor quantity may be used in the present invention. As illustrated in FIG. 3, the method 300 begins by receiving pressure data from the pressure measuring device, as indicated in step 320. The data may be received from either a digital or analog pressure measuring device 130. If the pressure measuring device 130 is analog, one of ordinary skill in the art would appreciate the step of sampling the data and performing known signal processing techniques to ensure an accurate and quality digital representation of the analog signal, such as implementing anti-aliasing filters. The received pressure data may be analyzed using an autocorrelation technique, as indicated in step 340. The autocorrelation technique calculates autocorrelation data that represent the correlation of the pressure data within the combustor. After calculating the autcorrelation data in step 340, the stability margin is determined at step 360. As described in more detail to follow, the stability margin may indicate the combustor's proximity to unstable operating conditions. The method for determining stability margin may end after the stability margin detection step 360, or alternatively, the method may continuously operate on the pressure data as it is received from the combustor. The autocorrelation technique provides a more robust method of determining the stability margin than viewing the pressure data alone. As illustrated in FIG. 4, the pressure data may be used to determine instability of the combustor. It is understood by one of ordinary skill in the art that increased dynamic pressure amplitudes in the combustor typically indicate unstable operating conditions. It also is understood by one of ordinary skill in the art that decreases in dynamic pressure amplitude in the combustor typically indicate stable operating conditions. FIG. 4 represents a plot of the normalized pressure within the combustor versus the mean inlet velocity. The data represented in FIG. 4 was generated from a combustor at Georgia Institute of Technology, though the teaching of the results of FIG. 4 are not limited to the exemplary combustor but are applicable to all combustors. As shown in FIG. 4, a low normalized pressure level signifies a stable operating conditions of the combustor. As the normalized pressure increases, the combustor enters unstable operating conditions. For example, at approximately 25 m/s in the exemplary combustor of FIG. 4, the normalized pressure begins to increase from zero, and the combustor becomes unstable. It is evident from FIG. 4 that monitoring the pressure amplitude in stable conditions does not indicate the proximity of the combustor to instability, but only that the system is either stable or unstable. For instance, at mean inlet velocity of 18 m/s the normalized pressure is zero, and at 22 m/s, the normalize pressure remains zero. It cannot be determined from the pressure data alone whether the combustor approaches instability as the mean inlet velocity increases from 18 m/s to 22 m/s. Thus, the proximity of the combustor to instability cannot be measured by viewing the pressure data alone. Conversely, the proximity of the combustor to instability may be identified based on the rate at which acoustic oscillations are damped in a stable combustor. In normal operation, inherent combustor noise is continuously exciting pressure oscillations in the combustor system. Under stable conditions, these pressure oscillations and background noises in the combustor are naturally damped. In contrast, under unstable conditions, the pressure oscillations are self-excited resulting in undamped conditions. The autocorrelation technique applied at step 340 may be used to determine stability margin based on a time series of pressure data from within the combustor. The autocorrelation technique can determine the correlation of the pressure in combustors operating in normal operating conditions. The length of time over which the pressure data is correlated is related to the level of system damping. Pressure signals correlated over a long period of time signify a system that is less damped than a system with pressure correlated over a short time interval. As appreciated by one of ordinary skill in the art, as the damping of a system decreases, the system tends towards instability. The autocorrelation technique of step 340 operates on the pressure naturally occurring in the combustor. That is, no external pressure excitations are required to determine the damping characteristics of the system. Therefore, the autocorrelation technique can be used on a combustor in normal operating conditions to determine the stability margin. The autocorrelation technique operates solely in the time domain as opposed to the frequency domain. Operation in the time domain provides a more robust solution than operation in the frequency domain. This is due to the fact that the autocorrelation is more noise insensitive than the Fourier transform. (e.g., see A. Papoulis, “The Fourier Integral and its Applications”, 1962). In addition, subtle variations in the rate of decay of the autocorrelation are much more evident in the autocorrelation than the Fourier transform. Inferring the damping coefficient from autocorrelation data requires a mathematical model. A representative model is shown below. However, this invention is not limited to the regimes of validity of this model. The following mathematical operations may be used to determine the autocorrelation of the pressure data in the combustor and ultimately estimate the damping coefficient. Pressure oscillations in combustion chambers can be described as a superposition of nonlinearly interacting oscillators of the form in equation (1) below: p ′ ( t ) = ξ ( t ) + ∑ i = 1 N η i ( t ) ( 1 ) Where the sum of η(t) is the acoustic mode, N is the number of acoustic modes, ξ(t) is random noise, and p′(t) is the measured pressure. The dynamics of the acoustic modes can be described as follows in equation (2): ⅆ 2 η i ( t ) ⅆ t 2 + 2 Ϛ ~ i ω i ⅆ η i ( t ) ⅆ t + ω ~ i 2 η i ( t ) = f i ( η j ( t ) , ⅆ η j ( t ) ⅆ t , … ) + E i ( t ) ( 2 ) where, ω is the frequency of the acoustical oscillations at the particular acoustic mode, the function f(η(t),d η/dt) describes the linear and nonlinear forcing terms, ζ is the damping coefficient, and E(t) describes external forcing of the oscillator by noise. One of ordinary skill in the art will appreciate that this model is provided for exemplary purposes and that this invention is not limited to the regimes of validity of this model. Under stable conditions, the oscillations are generally of sufficiently low magnitude such that nonlinear terms are negligible reducing the dynamics of the acoustic modes to equation (3) below: ⅆ 2 η i ( t ) ⅆ t 2 + 2 ϛ i ω i ⅆ η i ( t ) ⅆ t + ω i 2 η i ( t ) = E i ( t ) ( 3 ) The acoustic mode equation above is not directly solved without knowing the temporal evolution of E(t). Thus, an autocorrelation technique may be used to solve the above equation. In an exemplary embodiment, the autocorrelation equation for the acoustic modes may be defined as follows in equation (4): C i ( τ ) = ∫ 0 T η i ( t ) η i ( t + τ ) ⅆ t ∫ 0 T η i 2 ( t ) ⅆ t ( 4 ) Assuming the background noise is white noise, the autocorrelation equation in the exemplary embodiment can be reduced to equation (5) below:Ci(τ)=e−ωiζiτ(cos(ωiτ√{square root over (1−ζi2)})+ζ/√{square root over (1−ζi2)} sin(ωiτ√{square root over (1−ζi2)})) (5) The damping coefficient ζ is relatively small in typical combustors. Therefore, the second term of the above autocorrelation equation is neglible compared to the first term. As such, the autocorrelation oscillates at a frequency roughly equal to co and has an envelope that decays as exp(−ωiζit). Therefore, the damping coefficient can be directly related to the decay in the envelope of autocorrelation for various acoustical modes. Applying the autocorrelation equation to pressure data in stable conditions, the oscillations correlation time is very short. As the combustor system approaches instability however, the correlation time increases. Monitoring the correlation time of the oscillations, therefore, provides a means for identifying the proximity of the combustor system to instability. FIGS. 5 and 6 provide non-limiting examples of the autocorrelation technique in stable and unstable operating systems in accordance with the present invention. As shown in FIG. 5, the autocorrelation value has an amplitude of 1 at cycle zero. Over the time series, the autocorrelation value decreases, thereby, indicating that oscillations over these time intervals are increasingly uncorrelated. Uncorrelated data represents a stable combustor system. Conversely, as shown in FIG. 6, the autocorrelation value has an amplitude of approximately 1 at cycle zero. As can be viewed from the time series data, the autocorrelation value does not decrease over time indicating correlated data and, therefore, unstable combustor conditions. The value of the autocorrelation data is not limited in magnitude herein. One of ordinary skill in the art would appreciate that any autocorrelation value is applicable to the methods of this invention. From the autocorrelation data, the stability margin can be determined from an envelope of the oscillatory autocorrelation data. In one exemplary embodiment, this can be done by obtaining these points directly from the autocorrelation. In another exemplary embodiment, the envelope of the oscillatory autocorrelation data may be calculated using the Hilbert Transform and may be defined as follows in equation (6): H i ( τ ) = 1 π ∫ - ∞ ∞ C i ( t ) τ - t ⅆ t ( 6 ) An example of the oscillatory envelope for a damped, stable combustor calculated by the Hilbert transform is shown in FIG. 7. The oscillatory envelope describes the rate of decay of the oscillations in the combustor. In an exemplary embodiment, the damping coefficient can be determined from a fit of the oscillatory envelope describing the decay rate of the oscillations from the fit of the equation exp(−ωiζit). In one aspect of this embodiment, the damping coefficient was estimated by taking the natural logarithm of Hi(t) and performing a least squares fit of exp(−ωiζit). Equation (7) below is an example of how the damping coefficient may be calculated from the oscillatory envelope. Ϛ ( t ) = - 1 2 π ∑ j = 1 Nlags τ j ln H ( τ j ) ∑ k = 1 Nlags ( τ k ) 2 ( 7 ) Where, τ is the time lag between zero and the autocorrelation time lag interval over which the damping coefficient is determined. Nlag represents the number of time lag data points. However, this invention is not limited to fits of the form exp(−ωiζit) or equation (7). For example, more complex fits of the autocorrelation envelope are also contemplated herein such as those which include effects of heat release dynamics, non-whiteness of background noise, or parametric noise sources. One of ordinary skill in the art will further appreciate that any other method for calculating the oscillatory envelope is contemplated herein such as manually locating the peaks of the autocorrelation or other methods. The Hilbert transform approach described here is only provided as an exemplary embodiment. One of ordinary skill in the art will appreciate that any method of predicting the rate of decay and the damping coefficient of the oscillatory envelope also is contemplated herein including other forms of curve fitting besides the least squares regression described above. The stability margin may be calculated from the value of the damping coefficient as it changes over time. For example, changes in environmental conditions that impact the combustor stability margin could be monitored by the technique shown here. The stability margin may be used either in a closed loop feedback control system, or by a manual operator to suitably adjust the engine fuel splits, power output, or any other parameter impacting combustor stability. FIG. 8 illustrates an exemplary method of estimating the damping coefficient in the combustor using pressure data. Step 810 begins by reading the pressure data in the combustor using the measuring device 130. The pressure data may be filtered at step 820. In the exemplary embodiment, a bandpass filter (with pass and stop band frequencies fi[1−W] and fi[1−W]) is used on the pressure data about each center frequency, fi. W represents the width of the bandpass filter and represents the center frequency of each mode to be monitored. One of ordinary skill in the art will appreciate that any appropriate filter may be used. At step 830, a moving average of the autocorrelation data from the filtered data may then be calculated at each update time, t. The time interval used in this step may include t−Tcorr/2<t<t+Tcorr/2, where Tcorr is the moving window width over which autocorrelation of data is estimated. The autocorrelation may then be determined over time lags 0<t<Tlag, wherein the time lag, Tlag, represents a autocorrelation time lag interval over which estimated damping coefficient is determined. The Hilbert transform may then be calculated from the oscillatory envelope at step 840. From the oscillatory envelope, the damping coefficient may be determined at step 850. In an exemplary embodiment, equation (7) above may be used to calculate the damping coefficient. As illustrated in step 860, steps 810 through 850 may be repeated for all modes or center frequencies of the combustor. One of ordinary skill in the art will appreciate that the method of FIG. 8 is for illustrative purposes and does not limit the invention to that embodiment. The present invention can be further understood with the following non-limiting example relating to the estimation of the damping coefficient. The invention was tested with a gas turbine combustor simulator. A set of 18 test runs were chosen where a premixer velocity was varied between 17–39 m/s at a fixed flow rate and equivalence ratio (φ=0.89). These particular test runs were chosen because of the large variations in amplitude that occurred in two of the combustor modes and some variations in several others as well; as such, they serve as a useful demonstrator of the capabilities of the proposed method to simultaneously track the stability characteristics of several modes. A typical Fourier transform illustrating these modes is shown in FIG. 9. The two dominant instabilities occur at 430 and 630 Hz. The dependence of pressure amplitudes upon premixer velocity is shown in FIG. 10, wherein the (□) plot represents pressure amplitudes at 430 Hz and (*) plot represents pressure amplitudes at 630 Hz. The FIGS. 11 and 12 plot the simultaneous dependence of the pressure amplitude and damping coefficient of each of the instability modes. The damping coefficients were determined using the methods of this invention, and fitting a least squares fit over four cycles of data. FIG. 11 plots the pressure amplitude and damping coefficient for the 430 Hz mode, wherein the (□) plot is the pressure amplitude and the (ο) plot is the calculated damping coefficient. Starting at the premixer velocity of 40 m/s for example, the estimated damping coefficient monotonically decreases with a decrease in premixer velocity, even while the actual pressure amplitude stays essentially zero. The decreasing damping coefficient suggests that the combustor stability margin is decreasing, a fact that is evident from an overall view that the pressure data begins increasing. A similar result is shown in FIG. 12 for the 630 Hz mode. The damping coefficient monotonically decreases as the premixer velocity increases from 15–25 m/s indicating a decreasing stability margin as the premixer velocity increases. In this case however, the corresponding pressure amplitude actually decreases slightly across this velocity range. If the pressure amplitude alone was analyzed to determine stability, one would wrongly conclude that the stability margin were increasing—that is, becoming more stable. As is clear from analyzing the 430 Hz and the 630 Hz modes, the damping coefficient can be used to predict the stability margin of the combustor to determine the proximity of the combustor to instability. Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in generic and descriptive sense only and not for purposes of limitation. |
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claims | 1. An inspection apparatus for inspecting a pattern formed in a sample by using an electron beam, characterized in comprising:a holding mechanism for holding the sample;a stage with the holding mechanism mounted thereon and adapted to be movable in at least one direction;an electron beam source for generating electrons for irradiation of the electron beam directed to the sample;a first electro-optical system for guiding the electron beam generated from the electron beam source onto the sample for irradiation of the electron beam to the sample;a detector for detecting electrons emanating from the sample;a second electro-optical system for guiding the electrons to the detector; anda control unit to provide a control so that the stage is moved at a speed in synchronism with an operating speed of the detector during inspection of the pattern, and the stage is accelerated when being moved to another pattern on the sample,wherein the charging period and the discharging period of a substrate is input previously into the control unit, and is combined with the position data of the pattern to be inspected for calculating the condition where the distance or time period of movement between the patterns is minimized and the period of movement between the patterns is equal among all patterns. 2. An inspection apparatus in accordance with claim 1, characterized in that the apparatus comprises a laser source, and the surface potential of the sample is modified by the irradiation of laser light. 3. An inspection apparatus in accordance with claim 1, characterized in that the pattern to be inspected includes two or more patterns consisting of different sectional structures or different materials, and a plurality of patterns are inspected concurrently. 4. An inspection method for inspecting a pattern formed in a sample by using an electron beam, the method characterized in that a stage holding a sample thereon is moved at a frequency in synchronism with an operating frequency of a sensor during inspection of a pattern to be inspected, a moving speed of the stage is controlled so that a time required for movement is minimized during the stage being moved to another pattern to be inspected, and the charging period and the discharging period of a substrate is input previously into a control unit, and is combined with the position data of the pattern to be inspected for calculating the condition where the distance or time period of movement between the patterns is minimized and the period of movement between the patterns is equal among all patterns. 5. An inspection method in accordance with claim 4 characterized in that the pattern to be inspected includes two or more patterns consisting of different sectional structures or different materials, and a plurality of patterns are inspected concurrently. 6. An inspection apparatus for inspecting a pattern formed in a sample by using an electron beam, characterized in comprising:a holding mechanism for holding the sample;a stage with the holding mechanism mounted thereon and adapted to be movable in at least one direction;an electron beam source for generating electrons for irradiation of the electron beam directed to the sample;a first electro-optical system for guiding the electron beam generated from the electron beam source onto the sample for irradiation of the electron beam to the sample;a detector for detecting electrons emanating from the sample;a second electro-optical system for guiding the electrons to the detector; anda control unit to provide a control so that the stage is moved at a speed in synchronism with an operating speed of the detector during inspection of the pattern, and the stage is accelerated when being moved to another pattern on the sample,wherein the charging period and the discharging period of a substrate is input previously into a control unit, and is combined with the position data of the pattern to be inspected for calculating a number of the patterns to be required for inspection and calculating the condition where the inspection time is minimized and the period of movement between the patterns is equal among all patterns. 7. An inspection apparatus in accordance with claim 6, characterized in that the apparatus comprises a laser source, and the surface potential of the sample is modified by the irradiation of laser light. 8. An inspection apparatus in accordance with claim 6, characterized in that the pattern to be inspected includes two or more patterns consisting of different sectional structures or different materials, and a plurality of patterns are inspected concurrently. 9. An inspection method for inspecting a pattern formed in a sample by using an electron beam, the method characterized in that a stage holding a sample thereon is moved at a frequency in synchronism with an operating frequency of a sensor during inspection of a pattern to be inspected, a moving speed of the stage is controlled so that a time required for movement is minimized during the stage being moved to another pattern to be inspected, andthe charging period and the discharging period of a substrate is input previously into a control unit, and is combined with the position data of the pattern to be inspected for calculating a number of the patterns to be required for inspection and calculating the condition where the inspection time is minimized and the period of movement between the patterns is equal among all patterns. 10. An inspection method in accordance with claim 9 characterized in that the pattern to be inspected includes two or more patterns consisting of different sectional structures or different materials, and a plurality of patterns are inspected concurrently. |
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summary | ||
abstract | In a shielded chamber for neutron therapy including a therapy room which has a central beam axis along which a high-energy therapy beam is introduced into the Chamber through one end wall thereof and which includes at the opposite end a labyrinth entrance with at least two shielding wall sections displaced longitudinally along the central beam axis and extending into the room from opposite side walls, the wall sections include structures for causing spallation to thereby generate from the high energy neutrons in the high energy neutron beam a plurality of low energy neutrons which are then moderated by the wall sections. |
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039909417 | abstract | A nuclear reactor pressure vessel is installed in the pit of a biological shield forming a concrete wall surrounding the vessel and which defines an annular space around the vessel. A heat insulating layer of concrete surrounds the vessel within the annular space and partially fills the latter, and between the insulation and the concrete wall, steam I or H beams are vertically positioned with their flanges engaging the heat insulating layer and the concrete wall so as to support the heat insulating layer against radial motion when the pressure vessel thermally expands radially, thereby providing the latter with rupture protection. The steel beams are circumferentially interspaced very closely together and possibly with their flange edges abutting, thus forming a large number of vertically extending coolant flow passages which are open at the tops of the vertical beams around the periphery at the top of the vessel, and which are interconnected by an annular manifold at their bottom ends so that a coolant under pressure can be introduced for upward flow, thus protecting the concrete wall from excessive thermal stressing. |
description | The present invention relates generally to radiation shielding for humans, more specifically but not by way of limitation, radiation shielding clothing such as but not by way of limitation, undergarments, manufactured from a fabric constructed according to the present invention. Everyday millions of people are exposed to electromagnetic radiation. There are different sources of radiation that can produce harmful effects for humans. The higher the frequency of the radiation the more damage it is likely to cause to a human. Microwaves are an exemplary source of radiation that is known to cause damage to human cells. A very common type of radiation that most humans are exposed to is electromagnetic radiation. Sources of electromagnetic radiation are commonly utilized devices such as but not limited to cell phones and wireless routers. This type of radiation emitted by electronics is non-ionizing radiation, which does not have the ability to break chemical bonds as some of the other stronger types of radiation can do. Electromagnetic radiation does however interact with our body, which can potentially lead to indirect damage following longer term exposure. The proliferation of electronic devices in the world has placed great concern on the ability to shield electromagnetic interference. Given the unknown long term exposure effects, humans could potentially be vulnerable to the consistent exposure to radiation. Electromagnetic shielding has become a more prominent concern but few options are available for the everyday consumer to protect themselves from radiation exposure. As is known in the art, attenuation is a principal indicator for measuring the effectiveness of electromagnetic interference shielding. It refers to the difference between an electromagnetic signal's intensity before shielding and its intensity after shielding. Attenuation is measured in decibels (dB) that correspond to the ratio between field strength with and without the presence of a protective medium. The decrease in a signal's intensity, or amplitude, is usually exponential with distance, while the decibel range falls along a logarithmic scale. By way of example but not limitation, an attenuation rating of 50 dB indicates a shielding strength ten times that of 40 dB. Existing clothing has been shown to be incapable of blocking radiation at a level of 50 dB. Further, attempts to manufacture garments from radiation blocking cloth have not yielded a fabric composition that provides both effective radiation blocking and comfort to the wearer. Accordingly, there is a need for a cloth having a composition that is operable to block radiation up to a level of 50 dB wherein the cloth is utilized to manufacture clothing such as but not limited to undergarments. It is the object of the present invention to provide a radiation blocking clothing that comprises a composition of materials that is operable to block radiation having an effectiveness of at least 50 dB. Another object of the present invention is to provide radiation blocking garments manufactured from a fabric composition wherein the fabric composition includes a first fiber wherein the first fiber is a silver fiber. A further object of the present invention is to provide a radiation blocking garment manufactured from a fabric composition wherein the fabric composition includes a second fiber wherein the second fiber is formed from a combination nylon and silver. An additional object of the present invention is to provide a radiation blocking garment manufactured from a fabric composition wherein the fabric composition includes a third fiber wherein the third fiber is formed from cotton. An alternative object of the present invention is to provide a radiation blocking garment manufactured from a cloth having a first fiber, a second fiber and a third fiber, wherein the first fiber, second fiber and third fiber are structured in a particular pattern. Yet a further object of the present invention is to provide a radiation blocking garment manufactured from a cloth having a first fiber, a second fiber and a third fiber, wherein the pattern of the first fiber, second fiber and third fiber functions as a Faraday shield. An additional object of the present invention is to provide a radiation blocking garment manufactured from a cloth wherein the cloth provides alternate materials on opposite sides of the cloth. Still another object of the present invention is to provide a radiation blocking garment manufactured from a cloth wherein the structure of the cloth provides a surface resistance of a range between 0.01 to 0.5 ohms. Yet a further object of the present invention is to provide a radiation blocking garment manufactured from a cloth wherein at least one embodiment of the present invention is an undergarment to be worn by a user. To the accomplishment of the above and related objects the present invention may be embodied in the form illustrated in the accompanying drawings. Attention is called to the fact that the drawings are illustrative only. Variations are contemplated as being a part of the present invention, limited only by the scope of the claims. Referring now to the drawings submitted herewith, wherein various elements depicted therein are not necessarily drawn to scale and wherein through the views and figures like elements are referenced with identical reference numerals, there is diagrammed a radiation shielding clothing material 100 constructed according to the principles of the present invention. An embodiment of the present invention is discussed herein with reference to the figures submitted herewith. Those skilled in the art will understand that the detailed description herein with respect to these figures is for explanatory purposes and that it is contemplated within the scope of the present invention that alternative embodiments are plausible. By way of example but not by way of limitation, those having skill in the art in light of the present teachings of the present invention will recognize a plurality of alternate and suitable approaches dependent upon the needs of the particular application to implement the functionality of any given detail described herein, beyond that of the particular implementation choices in the embodiment described herein. Various modifications and embodiments are within the scope of the present invention. It is to be further understood that the present invention is not limited to the particular methodology, materials, uses and applications described herein, as these may vary. Furthermore, it is also to be understood that the terminology used herein is used for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention. It must be noted that as used herein and in the claims, the singular forms “a”, “an” and “the” include the plural reference unless the context clearly dictates otherwise. Thus, for example, a reference to “an element” is a reference to one or more elements and includes equivalents thereof known to those skilled in the art. All conjunctions used are to be understood in the most inclusive sense possible. Thus, the word “or” should be understood as having the definition of a logical “or” rather than that of a logical “exclusive or” unless the context clearly necessitates otherwise. Structures described herein are to be understood also to refer to functional equivalents of such structures. Language that may be construed to express approximation should be so understood unless the context clearly dictates otherwise. Referring now to the drawings submitted herewith, the radiation shielding clothing material 100 includes a first side 5 and a second side 10 and is configured to be flexible. The radiation shielding clothing material 100 is contemplated within the scope of the present invention to be utilized to manufacture various clothing articles. A preferred clothing article to be manufactured within the scope of the present invention are various forms of undergarments such as but not limited to underwear. It is further contemplated within the scope of the present invention that the radiation shielding clothing material 100 could be utilized to manufacture numerous styles and types of clothing. Referring in particular to FIG. 1 herein, the specific thread structure of the present invention is illustrated therein. The radiation shielding clothing material 100 comprises a first thread fiber 15, a second thread fiber 20 and a third thread fiber 25 structured in a specific pattern so as to achieve the desired results of blocking radiation with an effectiveness of 50 dB. The exemplary preferred pattern of the present invention illustrated in FIG. 1 herein is known as double sided knit structure. The aforementioned structure provides a completed radiation shielding clothing material 100 that has a first material on the first side 5 and a second material on the second side 10. In the present invention as will be further discussed herein, having a first material on the first side 5 and second material on the second side 10 provides a technique to accomplished the desired radiation blocking effectiveness. The first thread fiber 15 of the present invention is 84D FDY silver fiber. As is known in the art, D is an abbreviation for denier, which is a unit of measure for the linear mass density of the fiber. Thread fibers are manufactured utilizing various techniques and the first thread fiber 15 is manufactured utilizing a fully drawn yarn(FDY) technique. While good results have been achieved utilizing 84D FDY silver fiber to manufacture the first thread fiber 15, it is contemplated within the scope of the present invention that the first thread fiber 15 could be manufactured having a denier range of 70D to 94D and still achieve the desired outcome wherein the radiation shielding clothing material 100 is capable of blocking radiation with an effectiveness of 50 dB. The second thread fiber 20 of the present invention is 90D DTY silver fiber of which a detailed illustration is provided in FIG. 2 herein. As is known in the art, a DTY thread fiber is manufactured from a process referred to as draw textured yarn(DTY). The second thread fiber 20 includes a core material 22 of nylon or similar synthetic fiber and an outer layer 24 of silver. The second thread fiber 20 functions in conjunction with the first thread fiber 15 so as to provide the desired radiation blocking effectiveness described herein. While a 90D DTY silver fiber is the preferred embodiment for the second thread fiber 20, it is contemplated within the scope of the present invention that the second thread fiber 20 could be manufactured within a denier range wherein the radiation shielding clothing material 100 could still achieve the desired radiation blocking effectiveness. More specifically but not by way of limitation, the second thread fiber 20 could be manufactured within a denier range of 80D to 95D. The third thread fiber 25 of the present invention is a 40S cotton fiber. As is known in the art, 40S refers to the count of cotton within a thread fiber. It is contemplated within the scope of the present invention that the third thread fiber 25 could be manufactured from alternate materials or a combination of cotton and alternate materials. By way of example but not limitation, it is contemplated within the scope of the present invention that the third thread fiber 25 could comprise of a cotton and spandex blend. The aforementioned structure of the radiation shielding clothing material 100 of the present invention is such that the first thread fiber 15 and second thread fiber 20 will be present on the first side 5 creating the outer layer of the radiation shielding clothing material 100. While the third thread fiber 25 will be present on the second side 10 of the radiation shielding clothing material 100 which enables the ability to provide an improved comfort to the wearer of the garment manufactured utilizing the radiation shielding clothing material 100. The structure of the radiation shielding clothing material 100 is such that the first thread fiber 15 and second thread fiber 20 are adjacent due to the weave structure discussed herein and present on the first side 5. The proximity of the first thread fiber 15 and second thread fiber 20 are such that the surface resistance of the first side 5 approximately ranges between 0.01 to 0.5 ohms. The aforementioned structure in combination with the materials utilized to construct the first thread fiber 15 and second thread fiber 20 enable the radiation shielding clothing material 100 to possess Faraday properties. Faraday properties are achieved through utilization of the conductive materials of the first thread fiber 15 and second thread fiber 20 and the proximity of the first thread fiber 15 and second thread fiber 20 to each other. The low surface resistance of the first side 5 resulting from the aforementioned structure facilitates the blocking of electromagnetic radiation with an effectiveness of 50 dB. It is the combination of materials utilized to construct the first thread fiber 15 and second thread fiber 20 in conjunction with the radiation shielding clothing material 100 structure described herein that achieve the desired effectiveness of radiation blocking. The silver content of the first thread fiber 15 and second thread fiber 20 present on the first side 5 and the low surface resistance acts as a conducting surface thus absorbing the electromagnetic radiation. The radiation shielding clothing material 100 composition, specifically the percentage of silver provides the desired radiation blocking effectiveness of 50 dB. The percentage silver as a part of the total composition of the radiation shielding clothing material 100 utilized is 48 to 62 percent. Remaining percentages consistent of cotton or a blend of cotton and other suitable fabric such as but not limited to spandex. Good results have been achieved incorporating approximately four percent of spandex material as part of the overall composition of the radiation shielding clothing material 100. It is further contemplated within the scope of the present invention that the percentage of cotton as part of the overall composition of the radiation shielding clothing material 100 be within the range of 38 to 52 percent. While in the preferred embodiment, silver has been utilized as the source for conductive material in order to achieve the desired radiation blocking effectiveness. It is further contemplated within the scope of the present invention that other conductive metals could be utilized in place of and/or in conjunction with silver. More specifically but not by way of limitation, it is contemplated within the scope of the present invention that copper could be utilized in place of silver wherein the amount of copper would be equal to the amount of silver described herein both in thread fiber construction and total composition percentage of the radiation shielding clothing material 100. In the preceding detailed description, reference has been made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments, and certain variants thereof, have been described in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that other suitable embodiments may be utilized and that logical changes may be made without departing from the spirit or scope of the invention. The description may omit certain information known to those skilled in the art. The preceding detailed description is, therefore, not intended to be limited to the specific forms set forth herein, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents, as can be reasonably included within the spirit and scope of the appended claims. |
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description | 1. Field of the Invention The present invention relates generally to spacer grids for nuclear fuel assemblies and, more particularly, to a spacer grid for a nuclear fuel assembly which is formed from grid strips of an improved structure, thus reducing flow-induced high-frequency vibration. 2. Description of the Related Art A nuclear reactor refers to a device that is designed to exert artificial control over the chain reaction of the nuclear fission of fissile materials and use thermal energy generated from the nuclear fission as power. Generally, nuclear fuel that is used in a nuclear reactor is formed in such a way that enriched uranium is molded into a cylindrical pellet of a predetermined size and many pellets are inserted into fuel rods. The fuel rods constitute a nuclear fuel assembly. The nuclear fuel assembly is loaded in a core of the nuclear reactor before it is burned up in a nuclear reaction. Referring to FIG. 1, a typical nuclear fuel assembly includes a plurality of fuel rods 10 which are located in an axial direction, a plurality of spacer grids 20 which are provided in a transverse direction of the fuel rods 10 and support the fuel rods 10, a plurality of guide thimbles 30 which are fixed to the spacer grid 20 and form a framework of the assembly, and a top nozzle 40 and a bottom nozzle 50 which respectively support upper and lower ends of the guide thimbles 30. About 200 or more fuel rods 10 are used to form the nuclear fuel assembly. Enriched uranium is molded into a pellet of a predetermined size and installed in each fuel rod 10. The top nozzle 40 and the bottom nozzle 50 support the upper and lower ends of the guide thimbles 30. The top nozzle 40 is provided with elastic bodies to push down an upper end of the nuclear fuel assembly, thus preventing the pressure of a coolant flowing from a lower end of the nuclear fuel assembly towards the upper end thereof from lifting up the nuclear fuel assembly. The bottom nozzle 50 supports the lower ends of the guide thimbles 30. A plurality of flow holes through which the coolant is supplied into the nuclear fuel assembly are formed in the bottom nozzle 50. The several spacer grids 20 are arranged at predetermined intervals with respect to the axial direction of the fuel rods 10. According to the arrangement location and function, the spacer grids 20 are classified into medial spacer grids, mixing spacer grids which enhance the performance of mixing the coolant, and a protective spacer grid which filters out foreign substances. Referring to FIG. 2, the spacer grids are commonly formed by a plurality of grid strips assembled in a lattice shape. In each spacer grid, a single fuel rod or guide thimble is disposed in each of the lattice cells. In detail, the spacer grid 20 includes a plurality of an outer grid strip 21 which forms an outer frame of a structure, and horizontal grid strips 22 and vertical grid strips 23 which are arranged and fixed inside the outer grid strip 21 and form a lattice shape. The fuel rods are disposed in the corresponding lattice cells 20a formed in the spacer grid 20 having the above-mentioned construction. Further, guide thimble lattice cells 20b into which the guide thimbles are inserted are formed in the spacer grid 20. The fuel rods are assembled with the spacer grid in such a way that dimples and grid springs are provided on the grid strips that form the lattice cells so that the grid strips elastically support the fuel rods. Each guide thimble may be welded to the spacer grid or may be mechanically fixed thereto by a sleeve. FIG. 3 is a perspective view illustrating a protective spacer grid according to a conventional technique. Only one of lattice cells formed from a plurality of grid strips is shown in this drawing. Referring to FIG. 3, the typical spacer grid 20 includes horizontal grid strips 22 and vertical grid strips 23 which are crisscrossed and adhered to each other to form a lattice shape, thus forming lattice cells. One fuel rod is disposed in one lattice cell. Each fuel rod is supported in the corresponding lattice cell by dimples 24 which are made by bending or curving portions of the grid strips 23 and protrude from the surfaces of the grid strips 23. A grid spring may be provided to elastically support the fuel rod along with the dimples, although it is not shown in the drawing. As such, each grid strip generally has a planar surface. The dimples or grid springs are provided to be bent or curved from the planar surface of the grid strips inwards or outwards with respect to the lattice cell. The surfaces of the grid strips that are disposed above and below the dimples and the grid springs are formed to be planar without having any specific structure. Recently, the structure of a spacer grid which can improve the flow of a coolant that passes around fuel rods is required, for example, in such a way that mixing blades are attached to the spacer grid or the structure of a flow channel of the coolant is improved, thus making it more efficient to transfer heat from the fuel rods to the coolant. However, such methods for promoting heat transfer may cause flow-induced vibration which creates greater turbulence in the coolant that flows around the fuel rods, thus vibrating the fuel rods. The flow-induced vibration of the fuel rods causes the fuel rods to slip out of the grid spring or dimples, causing a fretting phenomenon in which partial abrasion occurs on the contact surface between the fuel rods and the grid spring or dimples, thus gradually damaging the fuel rods. For example, a spacer grid for preventing the fretting of fuel rods was proposed in Korean Patent Registration No. 10-0932436 (date: Dec. 9, 2009), which improves a contact structure between the fuel rods and the grid springs to prevent flow-induced vibration from causing axial or lateral vibration of the fuel rods. As such, different kinds of means for reducing flow-induced vibration of the coolant in the spacer grid of the nuclear fuel assembly have been devised. The present invention is to provide a structure of a spacer grid that can reduce flow-induced vibration. Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a spacer grid for a nuclear fuel assembly that is configured to reduce the vibration which may be caused by a coolant and, in particular, to provide a spacer grid for a nuclear fuel assembly which can reduce high frequency vibration by using a simply improved structure of the surface of the grid regardless of a grid spring or dimple structure. In order to accomplish the above object, the present invention provides a spacer grid for a nuclear fuel assembly having a dimple or grid spring for supporting a fuel rod, the spacer grid including a plurality of grid strips assembled in a lattice shape to form lattice cells, each of the grid strip having at least one slot formed in a planar portion of the grid strip separately from the dimple or grid spring. The slot may have a curved or bent pattern extending in a lateral direction of the grid strip. The slot may comprise two or more slots arranged at upper and lower positions, the slots having a same curved or bent pattern extending in a lateral direction of the grid strip. The slot may comprise two or more slots arranged at upper and lower positions, the slots having different curved or bent patterns extending in a lateral direction of the grid strip. The slot may comprise two or more slots arranged to be vertically symmetrical. The slot may be formed in each of upper and lower portions of the grid strip based on the dimple or grid spring. The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments are shown. Specific structures or a functional description described in the embodiments are given only to explain the embodiments according to the concept of the present invention. This invention may be embodied in many different forms, and should not be construed as being limited to the embodiments set forth herein. All possible modifications, additions and substitutions must be considered as falling within the scope and spirit of the invention. 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 element. For instance, a first element discussed below could be termed a second element without departing from the teachings of the present invention. Similarly, the second element could also be termed the first element. It will be understood that when an element is referred to as being “coupled” or “connected” to another element, it can be directly coupled or connected to the other element or intervening elements may be present therebetween. On the other hand, it should be understood that when an element is referred to as being “directly coupled” or “directly connected” to another element, there are no intervening elements present. Other expressions for describing a relationship between elements, e.g. “between” and “directly between” or “adjacent to” and “directly adjacent to”, must also be construed in the same way. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprise”, “include”, “have”, etc. when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components, and/or combinations of them but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or combinations thereof. Hereinafter, a preferred embodiment of the present invention will be explained in detail with reference to the attached drawings. FIGS. 4A and 4B are views illustrating a spacer grid of a nuclear fuel assembly according to the present invention. FIG. 4A is a perspective view showing only one of grid strips that forms a single lattice cell in the spacer grid. FIG. 4B is a front view of the grid strip of FIG. 4A. Referring to FIGS. 4A and 4B, the spacer grid for a nuclear fuel assembly according to the present invention includes a plurality of grid strips which are assembled in a lattice shape and form lattice cells in which fuel rods are disposed, in the same manner as the conventional technique. As shown in FIGS. 4A and 4B, dimples D for supporting a fuel rod are provided in a grid strip 110. It will be obviously understood by the structure of the typical spacer grid for a nuclear fuel assembly that a grid spring may be integrally provided on the grid strip 110. Preferably, the spacer grid of the present invention is technically characterized in that at least one elongated slot 111 is formed in a planar portion of the grid strip 110 separately from the dimples D or grid spring. Each dimple D is configured such that it bends and protrudes in an arc-shape from the grid strip 110 inwards or outwards based on the corresponding lattice cell. Here, although cutting slits O are formed adjacent to the dimples D (or the grid springs) in the grid strip 110, the elongated slot 111 is independent of the cutting slits O that pertain to the dimples or the grid springs. In other words, it must be understood that the elongated slot 111 is formed in the planar surface of the grid strip 110 regardless of the dimples D or the grid springs. As shown in FIGS. 4A and 4B, the elongated slot 111 may be formed in a planar portion of the grid strip 110 above the dimples D in a curved shape of a predetermined length H1 and a vertical amplitude H2. In the present invention, a variety of modifications of the elongated slot are possible. As shown in different examples of FIGS. 5A through 5G, the shape of the elongated slot formed in the grid strip may be that of a saw tooth wave (5A) that is bent several times, or a curved line (5B) of a small vertical amplitude. Alternatively, the elongated slot may comprise two or more elongated slots (5C) of the same pattern, a combination of two or more elongated slots (5D) of different patterns, two or more elongated slots (5E) of the same pattern which are formed in each of planar surfaces above and below the dimples D, or a combination of two or more elongated slots (5F) of different patterns which are formed in each of planar surfaces above and below the dimples D. As a further alternative, the elongated slot may comprise two or more slots (5G) which are arranged to be vertically symmetrical. As such, because the elongated slots are formed in the grid strips 101 that form the spacer grid, characteristics of vibration of the spacer grid can be set in a variety of ways, thus reducing flow-induced high-frequency vibration. Furthermore, in the present invention, the position, size or shape of the slot formed in the grid strip can be variously modified without reducing the structural strength of the grid strip. As described above, a spacer grid for a nuclear fuel assembly according to the present invention includes dimples or grid springs which support fuel rods. At least one elongated slot is formed in a planar surface of each of grid strips of the spacer grid regardless of the dimples or springs. Thus, characteristics of the vibration of the spacer grid can be set in a variety of different manners by modifying the position, size, shape, etc. of the slot(s) so that flow-induced high-frequency vibration can be reduced. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. |
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claims | 1. A method for thinning a sample, the method comprising:providing a sample attached to a probe,providing a sample carrier, said sample carrier having a rigid structure, said rigid structure having a boundary to which the sample can be attached,attaching the sample to the boundary of the rigid structure, andexposing the sample to a milling process or an etching process so as to at least partially thin the sample,removing a portion of the film beneath the portion of the sample that extends beyond the rigid structure using a charged particle beam,characterized in thatthe sample carrier is provided with a supporting film adhered to said rigid structure, said supporting film at least partially extending beyond the boundary of the rigid structure to which the sample can be attached, andbefore attaching the sample to the rigid structure the sample is placed completely on the supporting film. 2. The method of claim 1 in which the sample is placed on the surface of the film opposite to the rigid structure. 3. The method of claim 2 in which, after placing the sample on the supporting film, a part of the supporting film is situated between a part of the sample and the rigid structure. 4. The method of claim 1 in which the boundary is an outer boundary, so that the supporting film is not completely surrounded by the rigid structure. 5. The method of claim 1 in which exposing the sample to a milling process or an etching process comprises exposing the sample to a particle beam. 6. The method of claim 1 in which attaching the sample is performed with EBID or IBID or LBID. 7. The method of claim 1 in which during the milling process or etching process the supporting film is at least partly removed. 8. The method of claim 7 in which the milling process or etching process completely removes the supporting film from at least the thinned part of the sample. 9. The method of claim 1 in which the supporting film is a carbon film or a polymer film. 10. The method of claim 1 in which the rigid structure comprises a metal. 11. A method for thinning a TEM sample, the method comprising:providing a TEM sample attached to a probe,providing a sample carrier for holding the TEM sample, the carrier comprising: a rigid structure having an upper surface and an outer boundary, and a supporting film for supporting the TEM sample, a portion of said supportingfilm adhered to the upper surface of the rigid structure, and a portion of said supporting film extending beyond the outer boundary of the rigid structure,placing the TEM sample completely on the supporting film so that at least a portion of the TEM sample is located on the portion of the supporting film with no underlying rigid structure,removing a portion of the film beneath the portion of the sample that extends beyond the rigid structure using a charged particle beam,attaching the sample to the carrier, andexposing the sample to a milling process or an etching process so as to at least partially thin the portion of the sample extending beyond the outer boundary of the rigid structure. 12. The method of claim 11 in which placing the TEM sample on the supporting film so that at least a portion of the TEM sample is located on the portion of the supporting film with no underlying rigid structure comprises placing the sample on the supporting film opposite the rigid structure so that a portion of the sample overlaps the underlying rigid structure; andin which attaching the sample to the carrier comprises attaching the sample to the carrier by EBID or IBID, such that the supporting film is removed while performing the EBID or IBID and the sample is attached directly to the rigid structure. 13. The method of claim 1 in which before attaching the sample to the rigid structure the sample is placed on the supporting film so that the sample is not touching the rigid structure and a weld that attaches the sample to the rigid structure bridges a gap to connect the sample and the rigid structure. 14. The method of claim 1 in which placing the TEM sample on the supporting film so that at least a portion of the TEM sample is located on the portion of the supporting film with no underlying rigid structure include placing the TEM sample on the supporting film so that the sample is not touching the rigid structure and a weld that attaches the sample to the rigid structure bridges a gap to connect the sample and the rigid structure. 15. The method of claim 1 in which the sample is placed on the surface of the film that is not adhered to the rigid structure. 16. The method of claim 1 in which the sample and the supporting film form a first area of contact, and the supporting film and the rigid structure form a second area of contact, and wherein a portion of the supporting film is situated between the first area of contact and the second area of contact. |
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054901847 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a nuclear electric power generating plant 1 in which a nuclear steam supply system (NSSS) 3 supplies steam for driving a turbine-generator 5 to produce electric power. The NSSS 3 has a pressurized water reactor (PWR) 7 which includes a reactor core 9 housed within a reactor vessel 11. Fission reactions within the core 9 generate heat which is absorbed by a reactor coolant, light water, which is passed through the core. The heated coolant is circulated through a hot leg 13 to a steam generator 15. Reactor coolant is returned to the reactor 3 from the steam generator by a reactor coolant pump (RCP) 17 through a cold leg 19. Typically, a PWR has at least 2 and often 3 or 4 steam generators 15 each supplied with heated coolant through a hot leg 13 forming with a cold leg and an RCP 17 a primary loop, and each supplying steam to the turbine-generator 5. For clarity, only one loop has been shown. Coolant returned to the reactor flows downward through an annular downcormer 18 and then upward through the core 9 in the direction indicated by the arrows in FIG. 1. The reactivity of the core 9, and therefore the power output of the reactor, is controlled on a short term basis by control rods 20 which may be selectively inserted into the core 9. Long term reactivity is regulated through control of the concentration of a neutron moderator such as boron dissolved in the coolant. Regulation of the boron concentration affects reactivity uniformly throughout the core as the coolant circulates through the entire core. On the other hand, the control rods 20 affect local reactivity and therefore, result in an asymmetry of axial and radial power distribution within the core 9. Conditions within the core 9 are monitored by several different sensor systems. These include the excore detector system 21 which measures neutron flux escaping from the reactor vessel. The excore system 21 includes source range detectors (not shown) used when the reactor is shut-down, intermediate range detectors (also not shown) used during start-up and shut-down, and power range detectors used when the reactor is above about 5% power. The power range excore detectors comprise top and bottom equal length un-compensated ion chambers 21.sub.t and 21.sub.b stacked on top of each other to form a power range excore detector channel. There are four power range detector channels (only 2 shown in FIG. 1) symmetrically located, radially and axially, just outside the reactor vessel 11. Older PWR's are equipped with a moveable incore detector system 23. This system includes moveable detectors 25 which are inserted into the reactor core through tubes 27. These moveable detectors 25 are used by the system 23 to map the axial and radial power distribution in the core 9. Newer PWR's are provided with strings of fixed incore detectors 29 in place of, or in some instances in addition, to the moveable incore detector system 23. The moveable incore detector system 23 is used only periodically, such as once a month. On the other hand, the fixed incore detectors permit continual mapping of the axial and radial power distribution within the core such as, for instance, every few minutes. Instrumentation relevant to the present invention also includes resistance temperature detectors (RTDs) 31 which measure the core inlet temperature. RTDs 31 are provided for each of the loops of a multi-loop system. An array of core exit thermocouples (TCs) 33 are distributed across the top of the reactor core to measure core exit temperatures. These core exit temperatures can be utilized by a system such as that described in U.S. Pat. No. 4,774,050 which is hereby incorporated by reference as another means for determining core axial and radial power distribution. The currents measured by the detectors 21.sub.t and 21.sub.b of each of the channels of the power range excore detectors system 21, the inlet temperature measured by the RTDs 31 and the output of the moveable detector system 23 and the core exit temperatures measured by the thermocouples 33 are all provided to the power monitoring system 35 which provides an absolute measurement of core power in a manner to be discussed below. The core power signal generated by the system 35 can be used in a known manner in the reactor control and protection systems. Reactor coolant heated as it passes through the reactor core 9 is delivered through the hot leg 13 to the steam generator 15 where it converts feed water delivered through the feedwater system 37 into steam which is delivered through the steam line 39 to the turbine generator 5. The flow of feedwater to the steam generator 15 is measured by a venturi 41. As mentioned above, the power which can be generated by the PWR 7 for licensing purposes is determined by a calorimetric measurement calculated from parameters including feedwater flow measured by the venturi 41. It is fouling of this venturi 41 over time which creates the error in the thermal power calculations referred to above. In accordance with the present invention, only a thermal power measurement taken at a base time when the venturi 41 is not fouled, or at some other time when the thermal power is known to be accurate, is used to calibrate the power range excore detector power measurement. As indicated above, the reactor power determined from the Power Range excore detectors 21.sub.t and 21.sub.b is subject to power indication deviations caused by relative changes in the core axial and radial power distribution, in addition to the changes caused by variations in the absolute core power output. The indicated power from the Power Range channels is also subject to errors caused by changes in the density of the water in the vessel downcomer region 18 and fuel that occur when the vessel inlet temperature changes. In order to utilize the Power Range channels for power indication in an absolute sense, the factors which cause non-power level changes in the excore detector currents must be understood and compensated for in the relationship between excore detector signal level and core power level. The Power Range excore detector current for the top detector 21.sub.t in a Power Range channel (I.sub.t) for a core of height H may be expressed: ##EQU1## where: A.sub.t =a parameter proportional to the top detector sensitivity and detector/core geometry; .SIGMA..sub.R =the effective macroscopic removal fast neutron cross section of the material between the core and the detector; PA1 d.sub.t =the effective distance between the top excore detector and the assemblies contributing to the signal measured by the detector; PA1 w.sub.t (z)=an axial weighting factor for the top detector which describes the relative contribution of neutrons produced at core axial location z, in the vicinity of the excore detector, to the total signal measured by the detector; PA1 P.sub.r =the core relative power level, in terms of fraction of full power, and; PA1 P.sub.wa (z)=the radially weighted core relative power distribution at core elevation z. Equal to the sum of products of relative assembly powers and the corresponding radially varying weighting factors. PA1 T.sub.i.sup.R =the value of T.sub.i present when the reference conditions are measured. A w.sub.t (z) function needs to be developed for each PWR application of this methodology. The axial power weighting factor may even be unique to each detector in every excore detector channel. This function is developed utilizing shielding type neutron transport codes as known in the art, and once established should not change unless the physical characteristics of the detector, or the detector/core geometry, are changed. An example of this type of function is shown in FIG. 2, where the curves 45 and 47 represent the top and bottom detector weighting factors respectively. The radial relative assembly power weighting factors used to develop the value of P.sub.wa (z) are not a function of axial core position. They are developed for each type of plant (e.g., 2 loop, 3 loop, 4 loop), using methods similar to the axial weighting factor determination methods. An example of the radial weighting factors used for a 4 loop plant is provided to FIG. 3. Equation 1 describes what excore detector current would be observed at a combination of reactor axial and radial power distribution conditions, and core power level, with explicit consideration given to changes in the environment between the fast neutron sources in the core and the detector. The ability to determine the influences of these factors on the excore detector currents allows the excore detectors to be used in an absolute fashion to determine reactor power level. The complexity of determining the value of A.sub.t and .SIGMA..sub.R makes Equation 1 of little practical benefit. However, the form and fashion of Equation 1 does allow for the fairly straightforward determination of changes in the excore detector currents from a reference set of conditions. The reference conditions may be expressed in an equation of the form: ##EQU2## where the superscript R denotes the reference condition value of the parameters defined for Equation 1. The determination of changes in the excore detector currents due to core power distribution and detector/core environmental condition changes from a reference condition allows the actor power level to be determined accurately from the excore detector currents. For ease of notation, define the integral portions of Equations 1 and 2 to be the following: ##EQU3## where the superscript R denotes the reference value. The ratio of the measured top detector current to the detector current measured at the reference condition may be expressed: ##EQU4## The value A.sub.t should be the same as the reference value of A.sub.t, unless the detector/core geometry changes or the detector sensitivity changes in the time interval between the reference and current measurements. Therefore, the A coefficients will cancel in Equation 5, and the actual core power level may be expressed: ##EQU5## Equation 6 may be solved directly utilizing measured conditions for all the parameters except the .SIGMA..sub.R 's and d.sub.t. The values of the reference and current .SIGMA..sub.R values will have a temperature dependence not expressed in Equation 6. In order to account for the temperature dependence of the .SIGMA..sub.R values, a simple temperature dependent expression for .SIGMA..sub.R.sup.R, relative to the reference .SIGMA..sub.R, may be developed. The value of .SIGMA..sub.R which exists following a deviation in the core downcomer and fuel region water temperature from the reference condition, assuming a linear variation in .SIGMA..sub.R with temperature over the range of applicability, may be expressed: ##EQU6## where: T.sub.i =the vessel inlet temperature measured by the RTD 33 in the vessel inlet located nearest the encore detector channel, and; Substituting this expression for .SIGMA..sub.R into Equation 6 yields: ##EQU7## Equation 8 contains the temperature correction necessary to compensate the excore detector indicated power for downcomer and fuel region temperature variations, but can not be solved until the partial differential term and effective distance term in the exponential portion of the equation are known. It is not necessary to determine the partial differential and effective distance terms in Equation 8 separately or analytically in order to properly utilize the equation to determine an accurate compensated excore detector power. Determining the product of these terms will suffice. Solving Equation 8 for the product in the exponent yields: ##EQU8## The value of K.sub.t can be determined from measurements at two different temperatures and power levels during actor start-up testing, and should remain essentially constant from one cycle to the next. A typical value in a four loop plant for K.sub.t is 0.012/.degree.F. Utilizing the definition of K.sub.t in Equation 9, Equation 8 becomes: ##EQU9## An expression of the form of Equation 10 may be developed for both the top and bottom detector in each encore detector channel. The subscript "t" is replaced with the subscript "b" in Equation 10 for the bottom detector in the channel. Separate axial power weighting factors are needed for the bottom section detectors. The average of all the excore detector compensated relative power values is the most accurate indication of core power, relative to the reference condition accuracy, available from the excore detectors. FIG. 4 is a flow chart for a program 49 for determining the constant K used to make adjustments for changes in temperature. A value for K is calculated for each detector. As shown at 51, the first step is to determine the radial relative assembly power weighting factors for each detector channel i for each x, y radial core location j as shown for instance in FIG. 3. The axial weighting factors for each measured core axial interval, z, for radially weighted relative assembly power for each detector j and each channel i is then determined at 53 using for instance the weighting factors illustrated in FIG. 2. Next the measured reactor three-dimensional power distribution, thermal power level, excore detector signals, and vessel inlet temperatures at the two different power settings P.sub.1 and P.sub.2 are determined at 55 and 57. Then, at 59, Q.sub.wa is calculated for each channel i at the power levels P.sub.1 and P.sub.2. Finally, the constant K is calculated for each detector j at 61. FIG. 5 is a flow chart for a program 63 which can be used by a computer in the core monitoring system 35 for determining the current power output P from the excore detector currents. The reference values of the core power using the calorimetric measurement, each of the detector currents, and the inlet temperature for each channel are determined at 65 and used to determine Q.sub.wa for each channel. The program then enters a loop 65 in which the current power is determined from the excore detectors periodically. This includes calculation of the relative power for each detector current calculated at 67. The average power is then determined at 69 and output as the excore detector power determination at 71 for each new determination of power. 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 arrangements disclosed are meant to be illustrative only and not limiting as to the scope of invention which is to be given the full breadth of the claims appended and any and all equivalents thereof. |
description | The present invention relates to a fuel assembly used in a light-water reactor, especially a pressurized water nuclear reactor (PWR nuclear reactor) and in particular to a fuel assembly for a PWR nuclear reactor which is equipped with a structure for restraining the fretting wear between the outer surfaces of the control rod and the inner surface of control rod guide tubes in the fuel assembly. In general, as is disclosed in Patent Document 1 (Japanese Patent Laid-Open No. S62-46292) and Patent Document 2 (Japanese Patent Laid-Open No. H2-6784), a fuel assembly used in a pressurized water nuclear reactor has such a structure that several fuel rods are bundled, that is, in general, several fuel assemblies each composed of bundled several fuel rods are loaded in a reactor vessel suspended in a reactor vessel incorporating an inlet nozzle and an outlet nozzle for a coolant. The fuel assembly has an upper nozzle and a lower nozzle which are opposed to and spaced from each other, and which are connected to each other through the intermediary of control rod guide tubes attached thereto with a plurality of support grids. The control rod guide tubes are inserted in a part of cells in each support grid, and the several fuel rods are inserted in the remaining part of cells. FIGS. 10 to 13 show a specific configuration of the fuel assembly. Referring to FIG. 10, a control rod assembly used in a pressurized water nuclear reactor is composed of a plurality of control rods 51 suspended from a spider 52 adapted to be driven by a control rod drive unit which is not shown. In the control rod assembly as stated above, as shown in FIG. 11, the control rods 51 are driven by the control rod drive unit so that the control rods are inserted and pulled in the control guide tubes 53 within the fuel assembly loaded in the nuclear reactor, deeply and shallowly in order to control the reactivity of the nuclear reactor core. However, the control rods 51 are used, being inserted in the control guide tubes 53 within the fuel assembly while they are driven by the control rod drive mechanism during operation of the nuclear reactor, and accordingly, the control rods 51 vibrate due to flows of a coolant during operation of the nuclear reactor so as to make contact with the control guide tubes, possibly resulting in such a risk that the outer surfaces of the control rods are worn. Further, the inner surfaces of the control rod guide tubes 53 would be possibly worn due to the vibration of the control rods 51. The above-mentioned abrasions are caused by affection of vibration of the control rods 51 due to turbulence of a coolant flow, that is, the coolant in the flow (a core flow directing upward from the lower side) flows transversely through a gap between the control guide tubes 54 (which will be hereinbelow referred to as “G/T”) which have a role of guiding the control rods when the control rod assembly is driven by the control rod drive mechanism, and an upper core plate 55 (which will be referred to as “UCP”) and a gap between the UCP 55 and the upper nozzle 56 of the fuel assembly located therebelow (refer to FIG. 12). Thus, it is construed that the control rods vibrate due to the transverse flow, and accordingly, the abrasion would be gradually progressed. It is noted here that in comparison with the control rods 51 which are located on the side which is near to the attachment positions of support pins 57 (two pins arranged, left-right symmetrically) for preventing transverse displacement of the G/T 54, the control rods 51 on the side where no support pins 57 are present seem to be greatly affected by the coolant flow. Thus, it is considered that those of the control rods located on the side where no support pins 57 are present are locally worn by a large degree. Further, there would be such a risk that the associated control rod guide tubes 53 in which those of the control rods 51 are inserted are worn at their inner surfaces on the fuel assembly side. As shown in FIG. 13, it would be also considered that the longitudinal directions of passage holes formed in an adapter plate 58 which constitutes the lower part of the upper nozzle 56 of the fuel assembly greatly affect upon the degree of abrasion. That is, the passage holes 58A are all formed in one and the same direction (the longitudinal direction of the passage hole 58A is indicated by the arrow B as shown in FIG. 13), and accordingly, the flow of the coolant flowing upward from the bottom of the fuel assembly (in the direction piercing the sheet of FIG. 3 from the rear surface to the front surface) passes through the passage holes 58A in the upper nozzle 56, and is then jetted into the upper nozzle 56, being guided by the shapes of the passage holes. The area of the passage holes is greater in the vicinity of the walls on the sides A, that is, on the support pin 57 sides, than in the vicinity of the walls on the sides B where no support pins 57 are present, which are adjacent to the sides A, and accordingly, the quantity of the jetted coolant becomes remarkably greater on the sides A. Since the flows of the coolant impinge upon an overhang formed at the upper end of the upper nozzle 56, and are then directed toward the center of the adapter plate 58, the degree of jetting is different between the sides A and the sides B, resulting in occurrence of such a risk that the flows toward the center of the adapter become unbalance. Further, due to instability caused by the unbalance flows of coolant toward the center of the adapter 56, there would be caused such a risk that the associated control guide tubes in which the control rods 51 are inserted are greatly worn at their inner surfaces on the fuel assembly side. Thus, there would be presented such a problem that the cause of accelerating the abrasion as stated above is duplicated in such a case that the direction in which no support pines are located coincides with the direction of the passage holes 58A in the upper nozzle 56. Thus, Patent Document 3 (Japanese Patent Laid-Open No. 2003-98285) discloses a configuration in which the passage holes formed in the adapter plate constituting the lower structure of the upper nozzle are arranged such that the direction of the passage holes is orthogonal to the direction of the sides where there are presented no support pins attached to the control guide tubes and inserted in the upper core plate for preventing the control guide tubes from being transversely shifted. Further, Patent Document 3 also discloses a configuration of the adapter plate constituting the lower structure of the upper nozzle, in which the number of passage holes having a longitudinal direction along the sides where no support pins are present, is decreased with respect to the total number of them, and a configuration in which the passage holes are arranged in the passage surface of the adapter plate so that the passage areas in four zones partitioned by two orthogonal lines passing through the center and diagonal corners of the passage surface of the adapter plate become uniform. With this configuration, the vibration caused by the coolant flow can be uniformed so as to restrain local abrasion. As stated above, since the control rods in the conventional fuel assembly vibrate due to the transverse coolant flow, there would be possibly caused such a problem that the outer surface of the control rods and the inner surfaces of the control rod guide tubes are worn. Although the configuration disclosed in Patent Document 3 may more or less improve such abrasion, the present invention proposes such a technology that the vibration of the control rods is further settled in order to minimize the abrasion. The present invention is devised in view of the above-mentioned problems inherent to the conventional technology as stated above, and accordingly, one object of the present invention is to provide a fuel assembly for a PWR nuclear reactor, which can stably create flows of coolant directed toward the center of the control rods in order to press and fix control rods for restraining vibration of the control rods so that the outer surfaces of the control rods and the inner surfaces of the control rod guide tubes can hardly worn locally. To the end, according to the present invention, there is provided a fuel assembly for a PWR nuclear reactor, including an upper nozzle arranged in the upper part of the fuel assembly and comprising an adapter plate constituting a lower structure of the upper nozzle, an upright side wall extended along the periphery of the adapter plate, and an overhang projected into a space above the adapter plate from the upper part of the side wall, apertures for attaching control guide tubes and passage holes formed in a passage surface of the adapter plate, characterized in that at least those of the passage holes which are located at positions where coolant impinges upon the overhang, are generally arranged, line-symmetric with respect to two orthogonal lines passing through the center and diagonal corners of the passage surface, and ligaments around those of the passage holes which are located inside and outside of the those of the attaching apertures which are located on the outer peripheral side, are greater than ligaments around those of the passage holes which are located on opposites transverse sides of the attaching apertures. According to the preset invention, the coolant from the passage holes are directed toward the center of the adapter plate, after being turned into a direction toward the center of the adapter after impinging upon the overhang, can flow smoothly without being hindered by jet streams from elongated holes in the adapter plate, on the wide ligaments, and further, a pressure increase upon impingement against the overhang propagates on the ligaments so as to increase a pressing force toward the center of the upper nozzle, against the control rods arranged in the attaching apertures, and accordingly, it is possible to restrain vibration of the distal end parts of the control rods. Thus, since the vibration of the control rods can be restrained, it is possible to restrain the inner surfaces of the control rod guide tubes and the outer surfaces of the control rods from being worn. Further, since the arrangement of the passage holes is line-symmetric about the symmetric axes, and since arrangement patterns of passage holes in four zones which are partitioned from one another by the symmetric axes are set to be identical with each other, the vibrations of the distal end parts of the control rods located on the outer peripheral side can be restrained, commonly in the four zones. Further, the present invention is characterized in that passage holes for rectifying the coolant flow are arranged in the vicinity of the attaching apertures located along the symmetric lines. Thus, with the provision of the passage holes for rectifying the coolant flow, transverse flows directed toward the control rods are created so as to secure the control rods which are therefore restrained from vibrating, thereby it is possible to restrain the inner surfaces of the control guide tubes and the outer surfaces of the control rod from being worn. Further, the present invention is characterized in that elongated passage holes for rectifying flows of coolant are arranged in the vicinity of the center part of the passage surface. In view of the above-mentioned configuration, it is possible to prevent the coolant flow around the center part of the passage surface from being diffused, and to create the coolant flow for pressing the control rods. Moreover, the present invention is characterized in that those of the passage holes which are located at positions where the coolant impinges upon the overhang, are elongated having a length longer than that of the passage holes located in the inner side of the passage surface. With this configuration, the pressing force against the control rods by the flows of the coolant can be increased, and accordingly, it is possible to further restrain vibration of the control rods. Further, the present invention is characterized in that a plurality of fuel assemblies according to the present invention as stated above are uniformly arranged in the core of the nuclear reactor. Thus, with a plurality of the fuel assemblies arranged uniformly in the core of the nuclear reactor, it is possible to effectively restrain vibration of the control rods in the core. As stated above, according to the present invention, since the ligaments around the passage holes have sizes which are different from one another, the pressing force acts upon the control rods, being directed toward the centers thereof, and accordingly, vibration of the distal ends of the control rods can be restrained while vibration of the control rods can be also restrained, thereby it is possible to restrain the inner surfaces of the control rod guide tubes and the outer surfaces of the control rods from being worn. Further, the passage holes are arranged, line-symmetric about the symmetric axes, and the arrangement patterns of the zones which are partitioned by the symmetric axes are identical with each other, thereby it is possible to restrain vibration of the distal end parts of the control rods which are present in the outer peripheral part, commonly in the four zones. Next, explanation will be made of preferable exemplary embodiments of the present invention with reference to the accompanying drawings. It is noted here that the dimensions, materials, shapes and relative arrangements of components stated in these embodiments are mere examples for explaining the present invention, and accordingly, should not be intended to limit the technical scope of the present invention thereto unless otherwise specified. FIG. 1 is a perspective view illustrating a fuel assembly for a PWR nuclear reactor, in the embodiments of the present invention, and FIGS. 2 to 9 are views for explaining an upper nozzle of the fuel assembly in embodiments 1 to 8. At first, referring to FIG. 1, a fuel assembly for a PWR nuclear reactor, according to the present invention, will be outlined. In this figure, the fuel assembly 1 used in the PWR nuclear reactor incorporates an upper nozzle 5 and a lower nozzle (which is not shown), which are opposed to each other, being vertically spaced from each other, the upper nozzle 5 and the lower nozzle having a plurality of coolant passages, and being connected to each other through the intermediary of a plurality of control rod guide tubes 3. A plurality of support grids (which are not shown) are secured to the control rod guide tubes 3, at intervals in the longitudinal direction of the fuel assembly 1, and support several fuel rods 2 so that the fuel rods 2 are extended in parallel with one another. The control rod guide tubes 3 serve as guides for driving control rods by means of a control rod drive unit. The upper nozzle 5 is composed of a planar adapter plate 6 for constituting the lower structure of the nozzle, an upright side wall 7 extended along the periphery of the adapter plate 6, and an overhang 8 projected into a space above the adapter plate from the upper part of the side wall 7. Further, the adapter plate has a passage surface which is formed therein with a plurality of apertures for attaching control rod guide tubes 3, and as well, a plurality of coolant passage holes. The configurations of attaching apertures and the coolant passage holes will be detailed in embodiments 1 to 10 which will be explained hereinbelow. The control rods 4 are driven by a control rod drive unit so as to be inserted into and pulled from the control rod guide tubes 3 in order to control the reactivity of the nuclear reactor core. Further, coolant flows from the lower part to the upper part of the fuel assembly, and then flow upward from the passage holes in the adapter plate 6 after cooling the fuel rods 2. (Embodiment 1) Referring to FIG. 2, explanation will be made of the aperture for attaching the control rod guide tubes and the passage holes 15, which are formed in the adapter plate 6 of the fuel assembly in an embodiment 1. In this embodiment, two orthogonal lines passing through the center and the diagonal corners of the passage surface of the adapter plate 6 are used as symmetric axes (diagonal lines) Q, and the attaching apertures and the passage holes as stated above are generally arranged, line symmetric with respect to the symmetric axes Q. Thus, FIG. 2 shows one of rectangular four zones into which the adapter plate 6 is equally divided, having an equal passage area. The broken line R shown in the figure indicates a position corresponding to the overhang 8 The adapter plate 6 is formed therein with passage holes 15 (A to H, J, N to P) which are arranged, line-symmetric with respect to the symmetric axis Q. It is noted that at least passage holes 15A, 15B, 15C, 15D which are formed at positions where the coolant impinges upon the overhang 8, should be arranged line-symmetrically, but the other passage holes should not be arranged line-symmetrically. Further, the passage holes 15A, 15B, 15C, 15D which are arranged at the positions where the coolant impinges upon the overhand 8, are preferably elongated holes extended in parallel with the overhang 8. Further, the adapter plate 6 is formed therein with apertures 10a, 10b, 11a, 11b, 12, 13a, 13b for attaching the control guide tubes. In this embodiment, those 11A, 11b of the attaching apertures, which are located on the outer peripheral side of the adapted plate and which are arranged on lines that pass through the center of the adapter plate and extend in parallel with sides of the adapter plate are formed such a way that ligaments 21 around the passage holes located on the outer peripheral side of the attaching apertures 11a, 11b are larger than ligaments 22 around the passage holes which are arranged on opposite transverse sides of the attaching apertures 11a, 11b. That is, the ligaments 21 on the outer peripheral side are wider, but the ligaments 22 on the opposite transverse sides are narrower as possible as it can. With this configuration, the transverse flows of the coolant from the above-mentioned passage holes 15A, 15B, 15C, 15D, merge into the wide ligaments 21, and can hardly flows on the narrower ligaments 22. Thus, the pressing force against the control rods set in the attaching apertures 11a, 11b, directed toward the center of the upper nozzle becomes larger, thereby it is possible to restrain vibration of the distal ends of the control rods. Thus, due to the restraint to the vibration of the control rods, it is possible to prevent abrasion of the inner surfaces of the control rod guide tubes and the outer surfaces of the control rods. The above-mentioned technical effects and advantages can be also applied to the control rods on both sides I and II of the adapter plate 6 since the passage holes are arranged, symmetric with respect to the axes Q. Further, even the ligaments 21 around the passage holes which are located on the outer peripheral sides of the attaching apertures 10a, 10b are set to be larger than the ligaments 22 around the passage holes on opposite transverse sides of the attaching apertures 10a, l0b. With this configuration, the control rods can also hardly be vibrated. Further, since the passages holes 15A, 15B, 15C located at positions where the coolant impinges upon the overhand 8 are elongated in parallel with the overhang 8, the flows of the coolant from the passage holes 15A, 15B, 15C have larger pressing forces, thereby it is possible to further restrain vibration of the control rods. Further, in this embodiment, it is preferable to evenly arrange a plurality of fuel assemblies according to the present invention in the core of a nuclear reactor, thereby it is possible to effectively restrain the vibration of the control rods in the core. (Embodiment 2) Next, explanation will be made of the apertures for attaching the control rod guide tubes, and the passage holes 15, which are formed in the adapter plate 6 of the fuel assembly, in an embodiment 2. It is noted that explanation to the configurations similar to those explained in the embodiment 1 will be omitted in the following embodiments 2 to 8 shown in FIGS. 3 to 9. FIG. 3 shows only one of four divided zones of the adapter plate 6, similar to the embodiment 1. In the embodiment 2, of the attaching apertures, those 10a which are located on the outer peripheral side of the adapter plate and which are located in the vicinity of the center of the subdivided zones into which the zone shown is further bi-divided by the symmetric line Q are configured so that the ligaments 21 around the passage holes located on the outer peripheral sides of the attaching apertures 10a, 10B are larger than the ligaments 22 around the passage holes on opposite transverse sides of the attaching apertures 10a, 10b. That is, the ligaments 21 on the outer peripheral sides and the ligaments 23 on the inner peripheral sides are set to be larger, but the ligaments 22 on the transverse opposite sides are set to be small as possible as it can. Thereby it is possible to obtain technical effects and advantages which are similar to those obtained in the embodiment 1. (Embodiment 3) FIG. 4 shows an arrangement pattern of apertures for attaching the control guide tubes and passage holes 15 formed in an adapter plate 6 of a fuel assembly in an embodiment 3 in which only one of the four divided zones of the adapter plate 6 is shown, similar to the embodiment 1. In this embodiment 3, explanation will be specifically made of those 12 of the attaching apertures, which are located on the outer peripheral side of the adapter and which are located on the symmetric axe Q. Since these apertures located as mentioned above are positioned in the vicinity of the corners of the adapter plate, the flows of the coolant are complicated. Thus, passage holes 15K for rectifying the flows of the coolant are formed in the vicinity of the attaching apertures 12, thereby it is possible to restrain vibration of the control rods in order to stabilize the control rods. Further, since the arrangement pattern of the passage holes 15N in this embodiment is different from that of the embodiment 1 so that the passage holes 15N are elongated in parallel with the overhand 8, the flows of the coolant toward the attaching holes 12 are further stabilized, thereby it is possible to further restrain vibration of the control rods. Further, the shapes of the passage holes 15C in the sides I and II are preferably set to be asymmetric. In this embodiment, the passage holes 15C on the side I have a major diameter which is greater than that of the passage holes 15C on the side II. Thereby it is possible to obtain such technical effects and advantages that the flows of the coolant can be prevented from being complicated. (Embodiment 4) FIG. 5 shows the arrangement pattern of apertures for attaching control rod guide tubes and passage holes 15, which are formed in an adapter plate 6 of a fuel assembly in an embodiment 4 in which only one of four divided zones of the adapter plate 6 is shown, similar to the embodiment 1. In this embodiment 4, elongated passage holes for rectifying flows of coolant are located in the vicinity of the center part of the passage surface of the adapter plate. Specifically, elongated passage holes 15P, 15P are formed, surrounding the center, and small diameter holes 15L are formed, which occupy between the passage holes 15P, 15P. With this configuration, the flows of the coolant in the center part of the passage surface are diffused, thereby it is possible to create flows capable of pressing the control rods. Further, the shapes of passage holes 15C on the sides I and II are set to be asymmetric, thereby it is possible to obtain such technical effects and advantages that the flows of the coolant can be prevented from being complicated. (Embodiments 5 to 8) FIGS. 6 to 9 show arrangement patterns corresponding to those of the embodiments 1 to 4, as applied examples, that is, an arrangement pattern in an embodiment 5 shown in FIG. 6 corresponds to that of the embodiment 1, an arrangement pattern in an embodiment 6 shown in FIG. 7 to that of the embodiment 2, an arrangement pattern in an embodiment 7 shown in FIG. 8 to that of the embodiment 3, and an arrangement pattern 8 in an embodiment 8 shown in FIG. 9 to that of the embodiment 4. In each of these embodiments, the passage holes 15A, 15B, 15C which are located at positions where the coolant impinges upon the overhang 8 are connected together so as to form elongated passage holes 15A′ having a length which is longer than the passage holes located in the inner side of the passage surface. In these embodiments, although the three passage holes are connected together so as to form a long elongated passage hole 15A′, the present invention should not be limited to such configurations. Accordingly, the present invention may include such a configuration that elongated passage holes formed at positions where the coolant impinges upon the overhang 8 have lengths which are longer than that of the passage holes located inside thereof. In view of the above-mentioned embodiments, the pressing force caused by the flows of the coolant from the passage holes 15A′ becomes larger, thereby it is possible to further restrain vibration of the control rods. Industrial Applicability According to the present invention, the vibration of the control rods can be restrained so that the outer surfaces of the control rods and the inner surfaces of the control guide tubes can hardly be locally worn, thereby the present invention can preferably applied in a pressurized water nuclear reactor. |
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description | Referring now to the single FIGURE of the drawing, it is seen that an antiradiation shell 2 disposed around two beam passages 1 is part of a radiation source that is not shown in more detail, for example, a reactor core in a nuclear power plant. The two beam passages 1 are, for example, part of a measurement configuration in the monitoring region of a reactor plant or nuclear power plant. To shield the non-illustrated reactor core (radiation source), the latter is disposed in a tank 4. The configuration of the tank 4 is dependent on the configuration of the plant. The tank 4 is adjoined by the reactor well 6. Depending on the type of plant, the tank 4 and the reactor well 6 may also form a single unit. The reactor well 6 is delimited by a reactor well wall 8. For the controlled removal and guidance of the radiation emanating from the reactor core, the two beam passages 1 are disposed in the antiradiation shell 2. The antiradiation shell 2 is disposed in a fuel sheath 12, including a liner tube 12A, a cladding tube 12B, and a compensator tube 12C, between the tank 4 and the outer wall of the reactor well wall 8. The cavity to be filled up by the antiradiation shell 2 is delimited by the inner walls of the liner tube 12A, the cladding tube 12B, the compensator tube 12C, and the inner side of a beam tube projection 10 that is led into the tank 4. These components or structural elements are attached, e.g., bolted, to the corresponding support 16 by attachment elements 14. To avoid continuous gaps, the fuel sheath 12 is stepped a number of times in the axial direction. For such a purpose, the tubes that form the fuel sheath 12xe2x80x94namely the liner tube 12A, the cladding tube 12B, and the compensator tube 12Cxe2x80x94have, for example, a correspondingly decreasing diameter. The fuel sheath 12, which is also referred to as the cladding tube, may be one element, e.g., a cast element, or a plurality of tubes or partial elements. After the antiradiation shell 2 has been installed in the fuel sheath 12, the fuel sheath 12 is closed on the side of the liner tube 12A by a closure plate 18. To shield the (laterally scattering) neutron radiation and gamma radiation emerging from the two beam passages 1, the two beam passages 1 are completely enclosed in cross section by a metal shell 19. The metal shell 19 is preferably formed from a stainless ferritic material and causes the minimum possible self-activation of the antiradiation shell 2 that follows it in cross section. Furthermore, the static and dynamic loads on the antiradiation shell 2 determines the thickness of the metal shell 19. To achieve different shielding properties of the antiradiation shell 2, the antiradiation shell 2 is divided into a number of wall regions 2a to 2z which each completely enclose the two beam passages 1 and are each formed from an antiradiation concrete or concrete 22a to 22z that contains different quantitative proportions of aggregates and, therefore, has different bulk densities. The thickness of the wall region 2a to 2z is determined by the respective diameter of the individual elements of the fuel sheath 12. Both the number and thickness and also the chemical composition and the bulk density of the wall regions 2a to 2z are determined by the prior dimensioning according to requirements. Therefore, the concretes 22a to 22z forming the wall regions 2a to 2z may vary. The concrete 22a to 22z associated with a respective wall region 2a to 2z has, depending on the desired requirements, corresponding proportions of a first boron-containing aggregate with a grain size of up to 1 mm and of a second metallic aggregate with a grain size of up to 7 mm. A boron-containing mineral, for example, colemanite, is provided as the first fine-grained aggregate. Granulated iron or granulated steel is preferably provided as the second aggregate, which is referred to as coarse-grained on account of its grain size. The proportions of the first and second aggregates in the concrete 22a to 22z are decisively determined by the shielding properties to be achieved, in particular, gamma absorption and absorption and moderation of neutrons, by the antiradiation shell 2 in the associated wall region 2a to 2z. To achieve particularly high absorption and moderation of neutrons, the concrete 22a that forms the wall region 2a disposed closest to the radiation source, namely the reactor core, on account of its high level of the first mineral-containing aggregatexe2x80x94colemanitexe2x80x94is primarily suitable for the absorption of neutron radiation. For such a purpose, the first concrete 22a has a minimum cement content of between 8 and 9% by weight, a minimum water content (mixing water) of between 4.5 and 6.5% by weight, a minimum first aggregate (colemanite) content of 7.8% by weight up to the same proportion by weight as cement, a minimum second aggregate (granulated iron or steel) content of between 30 and 35% by weight and a minimum fourth mineral-containing aggregate (serpentine) content of between 40 and 50% by weight. Due to the low proportion of the second aggregatexe2x80x94granulated iron or steelxe2x80x94the concrete 22a is only secondarily suitable for the absorption of the gamma radiation. In the set state, the first concrete 22a has a minimum bulk density of up to 3000 kg/m3. To improve the binding within the first concrete 22a and to significantly increase the water of crystallization content, serpentine is used as a fourth mineral-containing aggregate. For advantageous mixing of the first concrete 22a, it has proven expedient for the minimum serpentine content with a first grain size of up to 3 mm to lie between 12 and 16% by weight. For the second grain size of between 3 and 7 mm, the minimum content is between 28 and 34% by weight. The first concrete 22a, which has serpentine as its principal constituent, is referred to as serpentine concrete and has particularly high compressive and splitting tensile strength. For particularly good shielding of a considerable part of the gamma radiation formed, the wall region 2b that is disposed as the second layer, as seen from the radiation source, is formed from a second concrete 22b having a different chemical composition from the first concrete 22a. The second concrete 22b that forms the second wall region 2b preferably has a minimum cement content of between 4 and 4.5% by weight, a minimum water content (mixing water) of between 1.5 and 2.5% by weight, a minimum first aggregate (colemanite) content of between 1 and 1.5% by weight, a minimum second aggregate (granulated iron or steel) content of between 85 and 89% by weight, a minimum third, in particular, metallic, aggregate (barite sand) content of between 4.5 and 5% by weight and a minimum content of at least one auxiliary of from 0.1 to 0.15% by weight. Due to the composition of the second concrete 22b, the second concrete 22b is preferably suitable for particularly high shielding of the gamma radiation and for lower absorption and moderation of the neutron radiation emanating from the radiation source, due to the colemanite proportion, as compared to the first concrete 22a. Due to the grain structure of the first and second aggregate, to achieve particularly good binding of the second concrete 22b, barite sand with a grain size of up to 1 mm is expediently provided as third aggregate. To improve and accelerate the setting process and, therefore, the ease of production of the second concrete 22b, a flux or a retarding substance is provided as auxiliary. A second concrete 22b of this type, which is formed from the abovementioned proportions of cement, water, aggregates and auxiliaries, in the set state has a bulk density of up to 6000 kg/m3. This bulk density is decisively responsible for the particularly high shielding of the gamma radiation. Furthermore, in order to achieve particularly high binding of the water content as water of crystallization in the second concrete 22b, the cement used is, in particular, alumina cement based on calcium aluminate. The water of crystallization effects particularly good slowing-down of the neutron radiation. The addition of colemanite with a boric oxide content of up to 41% by mass likewise results in particularly high absorption of thermal neutrons. The two-layer configuration has proven particularly advantageous because, in this way, the neutrons that emerge at high speed from the radiation source and do not enter the two beam passages 1 are particularly well moderated and absorbed in the first wall region 2a of the antiradiation shell 2 due to the high proportion of colemanite in the first concrete 22a. Furthermore, shielding of a considerable proportion of gamma radiation is already achieved in accordance with the bulk density that characterizes the first concrete 22a. In the second wall region 2b, predominantly gamma radiation is shielded on account of the greater proportion of granulated steel or iron compared to the first concrete 22a, while the neutrons emerging laterally from the beam passages 1 due to scatter radiation are moderated and absorbed in a similar way to the first concrete 22a because of the proportion of the first aggregate (colemanite). Further wall regions 2c to 2z may be filled with further suitably selected concrete 22c to 22z depending on the nature and intensity of the radiation source. The concrete associated with the respective wall region 2a to 2z has particular shielding properties or actions depending on the respectively selected proportions of the raw materials of the concrete. For example, by changing the proportion of granulated iron or steel it is possible to adjust the bulk density of the concrete 22a to 22z. Furthermore, the proportion of boron in the respective concrete 22a to 22z can be adjusted by changing the proportion of colemanite. Furthermore, the use of concrete 22a to 22z for certain layers or wall regions 2a to 2z of the antiradiation shell 2 allows the radiation source to be completely enclosed and, therefore, allows a particularly high shielding action for the radiation source, even with difficult and complex geometry or configurations. In particular, the concrete 22a to 22z allows even cavities to be closed off as a result of being introduced into formwork, for example, into the fuel sheath 12. Alternatively, the wall region 2a of the antiradiation shell 2 may be constructed as a shell, a wall, or a floor of a room or a building in which, for example, there is an X-ray device or another radiation source. The table provided below details the particularly advantageous minimum and maximum limits for the constituents that are important for the two extreme situations a) and b) described above, and for the shielding properties of the first concrete 22a (serpentine concrete) and second concrete 22b (granulated steel concrete) that can be achieved in these cases. The minimum and maximum limits for the grain size of the granulated constituents that have been found to be particularly advantageous for particularly simple production and processing of the two concretes 22a and 22b are also given in the table. Other mixing ratios between the two concrete mixtures are also possible. Because of the highly effective radiation shielding provided by the respective composition of the concretes 22a and 22b to 22z, the antiradiation shell 2 has a particularly good performance both in terms of self-activation and thermal influences and in terms of absorption and moderation of neutrons and shielding of gamma radiation. Therefore, the antiradiation shell 2 is particularly suitable for direct use at radiation sources, e.g., in beam tubes of research devices, on the primary circuit of a reactor plant, etc. Furthermore, the antiradiation shell 2 may, on one hand, have a large-area and single-layer configuration, for example, in the form of walls, floors, and ceilings. on the other hand, the antiradiation shell 2 may be made of a plurality of layers or wall regions 2a to 2z each having different shielding properties. Furthermore, the particularly radiation-shielding construction of the antiradiation shell 2 eliminates significant exposure of the operating staff to radiation. |
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