patent_number
stringlengths 0
9
| section
stringclasses 4
values | raw_text
stringlengths 0
954k
|
|---|---|---|
abstract | A method of calibrating a nuclear instrument using a gamma thermometer may include: measuring, in the instrument, local neutron flux; generating, from the instrument, a first signal proportional to the neutron flux; measuring, in the gamma thermometer, local gamma flux; generating, from the gamma thermometer, a second signal proportional to the gamma flux; compensating the second signal; and calibrating a gain of the instrument based on the compensated second signal. Compensating the second signal may include: calculating selected yield fractions for specific groups of delayed gamma sources; calculating time constants for the specific groups; calculating a third signal that corresponds to delayed local gamma flux based on the selected yield fractions and time constants; and calculating the compensated second signal by subtracting the third signal from the second signal. The specific groups may have decay time constants greater than 5×10−1 seconds and less than 5×105 seconds. |
|
abstract | A multi-leaf collimator for use in a radiotherapeutic apparatus comprises a plurality of elongate narrow leaves arranged side-by side and supported in a frame, the frame having upper and lower formations for guiding each leaf into which extend ridges on the upper and lower edges of the leaves, thereby to allow the leaves to move in a longitudinal direction, the upper and lower formations being aligned so that the sides of the leaves when fitted are at a non-zero angle to the beam direction, the upper and lower ridges being located on the upper and lower edges of the leaves so that a line joining their centres is at a non-zero angle to the sides of the leaf, tilted relative to the sides in a sense opposite to that of the beam. An outer face of the upper and/or lower ridges can be aligned with a side face of the leaf, for ease of manufacture. A radiotherapeutic apparatus is also disclosed, comprising a source of radiation and a multi-leaf collimator for shaping the radiation emitted by the source, the multi-leaf collimator being as set out above. |
|
049873130 | description | SPECIFIC DESCRIPTION As can be seen from FIGS. 1 and 2, a cast-iron treatment, storage and disposal vessel 1 is centered on an axis A and has a wall thickness of 8 centimeters, 12 centimeters or 18 centimeters and has a unitary closed bottom or floor 2. The upper edge or rim of the vessel 1 is stepped and is interfitted with a lid 3 also formed of cast iron and stepped to be complementary to the rim. The cylindrical outer surface of the vessel is not provided with cooling ribs but is smooth so that it can fit within an electric coil heater 20. The latter can be provided with a thermally conductive shell 21 snugly fitting around the wall 1a of the vessel 1 and in heat exchange relationship therewith, a resistance heating coil 22 received in the shell 21 and an outer lining 23 of thermally insulating material. The interior 24 of the vessel may be lined with lead as shown at 25 and a lead lining may likewise be provided at 26 on the underside of the lid 3. The lid 3 is formed with a pair of throughgoing passages 4 and 5 which can be close together as shown in FIG. 1 but also may be spaced apart as shown, for example, in FIG. 4, the passages 4 and 5 being parallel to and offset from the axis A. The passage 4 serves for the introduction of liquids into the vessel and the passage 5 for the withdrawal of vapors and gases therefrom. Although the lid 3 can be formed with it own screwthread to allow it to be turned or screwed down directly into the rim of the vessel 1, here it is secured in place by machine screws 9 angularly equispaced about and threaded into the vessel 1. In a typical application, the condenser concentrate of a nuclear power plant can be held in this vessel while it is heated with the gases or vapors being withdrawn from the vessel. Low temperature and relatively clean steam is withdrawn at subatmospheric pressure while radioactive particulates are left inside. In order to prevent droplets or particles from being aspirated, a downwardly flaring and generally conical relatively flat horizontal plate 6 interrupts direct vertical and axial flow into the passage 5. Thus any rising gases will have to change direction and move horizontally to pass around the plate 6 and then change direction again to enter the passage 5. Gases arising immediately beneath the plate 6 are forced into two more direction changes. In any case it is apparent that this arrangement effectively strips liquid and solid particles from the gas stream aspirated at the passage. The upwardly tapering surface of the plate 6 allows droplets to run smoothly down and drip from its rim back into the liquid or dryng material within the vessel. The upper surface of the lid 3 is formed at the upper ends of the passages 4 and 5 with a shallow cylindrical recess 8 into which is fitted a cylindrical cover 7 that is in turn fixed in place by screws 13 like the screws 9. However, this cylindrical cover can be provided on its rim with a thread which can be threaded directly into an internal thread of the recess 8. Thus the cover 7 has its upper surface flush with that of the lid 3 and seals off both of the passages 4 and 5 making the container safe and easier to handle. It is also possible as seen in FIG. 3 to provide the lid 3 with a passage 10 which can supply material to the vessel and which may be formed with a tube or lance 11 (see U.S. Pat. No. 4,626,380, whose application Ser. No. 06/505,228 was copending with the above-identified parent application). This allows the container to be filled from the bottom up. A lead lining 12 is formed on this container. The vessel 1 is of sufficiently thin construction that its contents can be readily heated by the jackets. In FIG. 4 we have shown an array of such vessels at 30, 31, 32, 33, 34 and 35, respectively provided with heating jackets 36, 37, 38, 39, 40 and 41 in the process of being filled. While one or more of the vessels may be in various stages of the supply of the liquid waste to the vessel, others may be in heating and evacuating stages. Since the filling of each vessel is done in stages, the various vessels shown may be at various stages in filling. The apparatus, however, will be described only with respect to the filling of one of these vessels. Each of the vessels 30-35 has a valve 42-47 connected to its inlet passage 4 which, in the embodiment shown of the container in FIG. 4, can reach below the baffles 48-53 which have been diagrammatically shown therein. Simultaneously, the outlets 5 located above the baffles 48-53 are provided with valves 54-59 which have ultra filters 60-65 downstream thereof. All of the valves described above and to be described below can be electrically actuated from a manually operated or automatically operated control panel, not shown. The filling plant illustrated in FIG. 4 comprises a metering vessel 66 which is in a radiation shield 67 and which receives a quantity of condensate and sludge from the tank of a nuclear power plant via the line 68 and a valve 69. A pipe 70 provided with a valve 71 and reaching to the bottom of the vessel 66 serves to supply the liquid to be reduced in volume by evaporation to the storage vessels 30-35. Vapor which may form above the liquid in the vessel 66 can be drawn off by a valve 72 and a vacuum pump 73 through a liquid separator or trap 74. Since the vacuum pump 73 operates with oil entrained in the fluid traversing same, an oil separator 75 is provided at the downstream side. The vapor may in part condense as a result of this compression and a line 76 which delivers this condensate to a recovered condensate tank 77. A reflux is provided by the condenser 78 which is cooled by a coolant flow from an intermediate heat exchanger 79, the latter being cooled, in turn, by a refrigeration plant 80. Each of the vessels 30-35 thus can receive the incoming liquid from line 70. Each of the vessels also has an outflow line 81-86 passing through a valve 87-92 to a condenser 93-98 cooled by the circulation from the intermediate heat exchanger 79 which may be provided with a pump 99 for this purpose. Any residual vapors can pass via the valves 100-105 through the liquid separators 106-111 to the intake sides of the respective vacuum pumps 112-117. The outflow sides of these vacuum pumps are, in turn, provided with oil separators 1118-123. The collected oil is delivered via line 124 to the oil tank 125 from which the oil can be reinjected into the vacuum pump. The liquid recovered by the traps 74 and 106-111 can pass via line 126 to a filtrate tank 127. The condensate from the condensers 93-98 passes via valves 128-133 to the condensate tank 134. The liquids in tanks 77, 125, 127 and 134 are radioactive and may be recycled for disposal or disposed of in some other way. The outflow from line 135 passes to an absolute filter system preventing the escape of radioactive vapors. In practice, for each of the vessels 30-35, the respective inlet valve 47 (for example for the vessel 35) is opened after its outflow valve 59 has been closed and the vessel 35 has been evacuated so that, by suction, a quantity of liquid is drawn from the vessel 66 via line 70 into the vessel 35. Valve 47 is then closed, valve 59 is opened and the vessel 35 evacuated via the suction pump 117 while the vessel is heated to reduce the volume in the vessel. The vapors which are thus produced are largely condensed in condenser 98 and flow via valve 133 to the condensate tank 134. Residual vapors are subjected to oil and liquid trapping as described. When suction has once again built up in the vessel 35 to the desired level, valve 59 is closed and valve 47 is opened to repeat the cycle. The process is repeated for each of the vessels 30-35 until each vessel is filled and the contents dried to the desired degree. The cover plate 7 is then applied as each vessel is disconnected from the apparatus and the container may be disposed of in a nuclear safe environment. During the evacuation of each vessel 30-35, the baffle 48-53 largely prevents entrainment of droplets therefrom as has been described in connection with FIGS. 1 and 2. If the condensate in tank 134, usually relatively pure water, is not significantly radioactive, it can be discharged directly via a pump 140 and a valve 141 into an industrial waste water treatment system. |
047059494 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to directed beam irradiation devices and specifically to an improved method and apparatus for mounting and maintaining specimens for observation and characterization in a scanning electron microscope. 2. Discussion of the Prior Art The scanning electron microscope is a powerful instrument which permits observation and characterization on a micrometer or submicrometer scale of heterogeneous organic and inorganic materials. Limited microscopic techniques are available for examining volatile i.e., "wet" samples and biological specimens, where hours of tedious preparation usually is required, resulting in a non-living and disrupted state. Either a relatively low resolution and/or limited depth of focus optical microscope or a specialized high voltage transmission electron microscope equipped with gas reaction cells must be used. The SEM with its great advantage of depth of focus, has only limited capabilities for maintaining a vapor pressure of even a few Torr. In a SEM, an electron beam is scanned across the specimen to be observed and then electrons reflected or generated from the specimen are detected and the signal generated by the detector is processed to form the enlarged image. In order to properly scan a specimen, an extremely low pressure on the order of 10.sup.-4 TORR is necessary in the specimen chamber of the electron microscope. This extremely low pressure is dramatically less than the vapor pressure of water and a number of other liquids comprising structures of interest. Therefore, in attempting to examine solids, such as hydrated cements or biological samples, inevitably, upon exposure to the high vacuum of the electron microscope, fluid in the solid evaporates rupturing and otherwise destroying the structural arrangement of the subject under investigation. A conventional system in which tissue samples are sectioned while frozen in order to form a thin foil still lose most of their water content immediately upon exposure to the high vacuum rendering them impossible to study. Dry preparation techniques for thin foil specimens are tedious and complicated, often resulting in disruption of and artifact formation in the specimen. There have been numerous attempts, by freezing or other methods, to slow down the specimen destruction usually meeting with little success. One such method is disclosed in U.S. Pat. No. 4,071,766 to Kalman et al which utilizes a pressure-balancing buffer system to provide a pressure in the vicinity of the specimen which is greater than the vapor pressure of the liquid in the specimen in order to prevent rapid bursting or deterioration. This system utilizes a separate tank containing a liquid or gas which is connected to the specimen mounting chamber and maintains the desired pressure and moist atmosphere to aid in the preservation of the specimen. The difficulty with such pressure balancing systems is the requirement of an auxiliary pump connected to the electron microscope in order to maintain the high vacuum necessary for the operation of the microscope. Thus, after mounting of the specimen in the microscope, the various pumps are energized and as the microscope nears its operational high vacuum, the balancing system continually evolves a vapor in the chamber in order to attempt to prevent destruction of the specimen. Therefore, the buffer system is generating a vapor and the vacuum pumps are pulling that vapor away in an attempt to reach operational pressure. The buffer system and the vacuum pumps are working at cross purposes and a substantial amount of time is wasted in attempting to reach a stabilized condition in order to begin the electron microscopy. This constant evolution of vapor and then pumping away of the evolved vapor insures that the electron beam must penetrate a substantial thickness of vapor surrounding the specimen in order to accomplish its scanning function. The thickness of vapor penetrated affects the quality of the resultant micrograph and, even though the pressure buffer attempts to maintain the pressure at or about the vapor pressure of the liquid contained in the specimen, deterioration of the specimen is likely. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method and an apparatus facilitating the method for controlling and maintaining specimens in their natural environment, minimizing possible disruption and artifact formation resulting from desiccation during exposure to the high vacuum, while being investigated by a directed beam irradiation apparatus, such as, a scanning electron microscope. It is a further object in accordance with the present invention to provide a method of operating a scanning electron microscope in order to prevent the dehydration and/or disruption of biological tissues before and during operation of a scanning electron microscope. It is a further object in accordance with the present invention to provide an apparatus to contain and protect biological specimens and volatile or wet samples from dehydration and/or disruption prior to and during operation of a directed beam irradiation apparatus, such as, a scanning electron microscope. It is a still further object of the present invention to provide an apparatus to minimize the influence of the high vacuum environments of directed beam irradiation apparatus, such as, the specimen chamber of a scanning electron microscope on a volatile specimen, while at the same time maintaining the specimen in a relatively undisturbed state. Yet another object of the present invention is to provide an apparatus to maximize the ability of a directed beam, i.e. an electron beam to reach the solid surface of the specimen and then allow scattered electrons from that surface to escape from the cell to the appropriate detector. Another object of the present invention is to provide variant designed embodiments for the apparatus that can be easily loaded into and removed from the apparatus to facilitate specific applications of research investigations, both in the physical and biological sciences. The above and other objects are achieved in accordance with an apparatus aspect of the present invention by providing an improved specimen cell for use in the evacuated chamber of a directed beam irradiation device, said cell comprising: a closed specimen means for mounting maintaining and at least partially containing said specimen; means for defining an aperture between said specimen and an electron beam when the beam is directed towards the specimen, where the aperture comprises a means for bidirectionally passing electrons and for restricting passage of vapor from within to without said specimen means; and door means having an opened postion and a closed position, for permitting bidirectional electron flow in said open position and blocking said aperture and preventing passage of vapor from within to without said specimen means in said closed position. The above and other objects are achieved in accordance with a method aspect of applicants' invention in accordance with the steps of: providing a closed specimen means, in the evacuated chamber of a directed beam irradiation device, for mounting maintaining and at least partially containing the specimen where the closed specimen means includes a means for defining an aperture between the specimen and an electron beam when the beam is directed towards the specimen, where the aperture comprises a means for bidirectionally passing electrons and for restricting passage of vapor from within to without said specimen means; providing a door means having an open position and a closed position; locating a specimen in the specimen means and closing and temporarily sealing said door means; reducing the pressure to the normal operating pressure in the evacuated chamber; moving said door means to said open position; scanning said specimen with an electron beam through said aperture; closing said door means after said scanning to prevent further passage of vapor from within to without said specimen means and repeating the sequence of steps from said door opening step should further scanning of the specimen be desired. |
055552803 | abstract | The surface of the component (1, 2) to be protected is scanned, a jet of semitransferred arc plasma (17) into which a metal powder is introduced. The process can be applied to the production of a layer of coating (18) on the outer surface of a region of welding connection (3) between a nozzle (1) and a primary pipe (2) of a pressurized water nuclear reactor or to the coating of the inner surface or the connecting surface of an adapter passing through the reactor vessel head. |
043137938 | summary | BACKGROUND OF THE INVENTION This invention relates to providing apparatus for winding stiff tubing onto and off of a reel in a hostile environment, and in particular, for removing and disposing of in-core instrument assemblies from a nuclear reactor. The local power density in nuclear reactors is often measured by the use of a plurality of in-core detectors, each of which is contained in an elongated guide tube which guides the detector through a nuclear fuel assembly. Together, the detector and guide tube are typically called in in-core instrument or instrument assembly. The in-core instruments (ICI) are exposed to very high radiation levels and therefore become very highly radioactive. This radioactivity makes the ICI tube and detector extremely dangerous to handle when exhausted detectors are to be disposed of, usually during the reactor refueling outage. The removal and transfer of exhausted ICI's is performed entirely under a sufficient depth of water to make use of the radiation shielding effect of the water. This requirement, however, often puts the ICI removal activities on the critical path during reactor refueling, especially in reactor installation where the ICI's enter the core through the top of the reactor vessel. Often, the only place in the reactor installation where sufficient water depth exists is directly over the reactor. Thus, the major refueling operations cannot be performed until the ICI replacement operation is completed. During a typical refueling, twenty to thirty ICI's must be individually removed and disposed of. Prior art ICI removal is performed with the overhead crane, which is intended primarily for moving heavy components and accordingly does not provide fine control of the ICI withdrawal rate. One end of a single ICI is connected to the crane and the ICI is, while dangling from the crane, withdrawn from the reactor and dragged along the refueling pool to a storage or disposal area. This is repeated until all exhausted ICI's have been removed. From the foregoing description, it can be appreciated that significant savings in refueling time can be achieved if the removal and handling of the ICI can be performed somewhere in the refueling pool other than above the reactor. Furthermore, the use of the overhead crane for ICI removal is not only unwieldy but also prevents the use of the crane for other activities that could be performed in parallel with ICI removal. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a remotely operable machine for smoothly and controllably removing the ICI from the nuclear reactor and confining the tube in a compact unit which can be easily moved to a disposal area. Furthermore, it is an object of the invention that the ICI may be unwound from the machine with sufficient force to enter into a cutting apparatus and receptacle without the need for an additional driving apparatus. According to the invention, the machine includes a frame and a circular reel having a substantially continuous helical groove extending around the circumference of the reel. The groove is adapted to receive the ICI tube. Means are provided for driving the reel relative to the frame in both circumferential directions whereby in one direction the ICI tube is wound onto the groove of the reel, and in the other direction the tube is wound off the reel. A plurality of cam rollers are carried by the frame and closely spaced around the circumference of the reel. During the winding operation, the rollers force the tube onto the continuous groove. During the unwinding operation, the rolers provide sufficient friction between the tube and the groove so that the tube may be unwound with enough force to enter the cutting tool or to enter the disposal receptacle. Means are provided to straighten the tube as it unwinds to permit more efficient stacking within a disposal container. In the preferred embodiment, the grooved portion of the reel consists of a removable cartridge. After the ICI tube has been fully wound onto the grooves of the cartridge, the radioactive portion of the tube can be fed into the cutter and the nonradioactive portion remaining on the cartridge can be disposed of by removing the cartridge from the reel and disposing of the cartridge. A new cartridge is then attached to the reel and the machine is ready for use on another ICI tube. The present invention can be operated from a deck above the refueling pool while the overhead crane is used for other purposes. This represents a savings of approximately ten hours in a typical refueling operation. Furthermore, in the preferred embodiment, the disposable cartridge permits using the cutter only on the radioactive portion of the ICI tube. Therefore valuable time and the cost of cutting tool replacement parts are greatly reduced because a large portion of the ICI tube can be conveniently disposed of without cutting. Since the receptacle for the cut portions of the ICI will thus contain only radioactive ICI segments, the number of receptacles, and consequently the protective measures associated with their storage, can be significantly reduced. |
claims | 1. An imaging optical unit for EUV projection lithography for imaging an object field in an object plane into an image field in an image plane, the imaging optical unit comprising:a plurality of mirrors for guiding imaging light from the object field to the image field; andan aperture stop, which is tilted by at least 1° relative to a normal plane which is perpendicular to an optical axis of the imaging optical unit;a tilt drive connected to the aperture stop and arranged to vary a tilt angle of the aperture stop with respect to the normal plane;a sensor arrangement for measuring an image-side numerical aperture of the imaging optical unit; anda regulation unit programmed to calculate a tilt set point based on measurement data from the sensor arrangement and cause the tilt drive to regulate readjustment of the tilt angle to vary the image-side numerical aperture of the imaging optical unit,wherein a center of the aperture stop is at a non-zero distance from the optical axis of the imaging optical unit. 2. The imaging optical unit of claim 1, wherein the aperture stop is arranged so that the following applies to mutually perpendicular planes: a deviation of a numerical aperture NAx measured in one of these planes from a numerical aperture NAy measured in the other one of these two planes is less than 0.003, averaged over the field points of the image field. 3. The imaging optical unit of claim 1, wherein the stop is arranged at a distance from, or tilted relative to, a plane, in which coma rays of the imaging light from spaced apart field points intersect. 4. The imaging optical unit of claim 1, wherein the aperture stop is arranged at a distance from, or tilted relative to, a plane, in which chief rays of the imaging light from spaced apart field points intersect. 5. The imaging optical unit of claim 1, wherein the aperture stop is tilted about a tilt axis which is perpendicular to a tilt normal plane, the tilt normal plane containing an object displacement direction for an object arrangeable in the object plane and with at least one field plane being perpendicular thereto. 6. The imaging optical unit of claim 1, wherein the tilt angle is less than 20°. 7. The imaging optical unit of claim 1, wherein the aperture stop is tilted so that an angle of a stop normal relative to a chief ray of a central field point becomes smaller in comparison with an angle of the optical axis relative to the chief ray of the central field point. 8. The imaging optical unit of claim 1, wherein the aperture stop is tilted so that an angle of a stop normal relative to a chief ray of a central field point becomes larger in comparison with an angle of the optical axis relative to the chief ray of the central field point. 9. The imaging optical unit of claim 1, wherein the aperture stop is configured as a planar stop. 10. The imaging optical unit of claim 1, wherein at least one of the mirrors has a reflection surface embodied as a free-form surface. 11. The imaging optical unit of claim 1, wherein a tilt drive, to which the aperture stop is connected for the purposes of tilting. 12. An optical system, comprising:the imaging optical unit of claim 1; andan illumination optical unit for illuminating the object field with illumination light or imaging light. 13. A method for producing a structured component, comprising:measuring a first numerical aperture NAx and a second numerical aperture NAy of an imaging system composed of a plurality of mirrors and an aperture stop, the aperture stop being tilted by at least 1° relative to a normal plane which is perpendicular to an optical axis of the plurality of mirrors;adjusting a tilt angle of the aperture stop based on the measurements so the following applies to mutually perpendicular planes:a deviation of the first numerical aperture NAx measured in one of these planes from the second numerical aperture NAy measured in the other one of these two planes is less than 0.003, averaged over the field points of an image field of the imaging system;providing a reticle and a wafer;projecting a structure on the reticle onto a light-sensitive layer of the wafer by:illuminating the reticle with EUV light; andimaging the structure on the reticle using the EUV light by guiding the EUV light to the wafer using the imaging system; andgenerating a structure on the wafer. 14. An imaging optical unit for EUV projection lithography for imaging an object field in an object plane into an image field in an image plane, the imaging optical unit comprising:a plurality of mirrors for guiding imaging light from the object field to the image field;an aperture stop, which is tilted by at least 1° relative to a normal plane which is perpendicular to an optical axis of the imaging optical unit;a tilt drive connected to the aperture stop and arranged to vary a tilt angle of the aperture stop with respect to the normal plane;a sensor arrangement for measuring an image-side numerical aperture of the imaging optical unit; anda regulation unit programmed to calculate a tilt set point based on measurement data from the sensor arrangement and cause the tilt drive to regulate readjustment of the tilt angle to vary the image-side numerical aperture of the imaging optical unit. |
|
claims | 1. A drawing apparatus which includes a plurality of charged particle optical elements that are sequentially passed through by a plurality of charged particle beams, and performs drawing on a substrate with the plurality of charged particle beams, the apparatus comprising:a deflector array which includes a plurality of deflectors, including a plurality of electrodes, each of which disposed for corresponding one or more charged particle beams and aligning the corresponding one or more charged particle beams between two of the plurality of charged particle optical elements;a plurality of devices configured to respectively apply a plurality of potentials to the deflector array; anda connector including wirings and configured such that each of the plurality of electrodes and one of the plurality of devices are interconnected via one of the wirings, and electrodes, to which an equal potential is applied, of the plurality of electrodes are connected to a single wiring of the wirings,wherein number of devices included in the plurality of devices is less than number of electrodes included in the plurality of electrodes. 2. An apparatus according to claim 1, further comprising:a detector configured to detect a charged particle beam corresponding to one deflector included in the deflector array; anda controller configured to determine the plurality of potentials based on an output from the detector. 3. An apparatus according to claim 2, wherein the controller is configured to determine the plurality of potentials by changing two potentials applied respectively to two electrodes of a pair of electrodes included in the plurality of electrodes while maintaining a potential difference between the two electrodes such that a potential of at least one of the two electrodes becomes equal to a potential of at least one of two electrodes of another pair of electrodes included in the plurality of electrodes. 4. An apparatus according to claim 3, wherein the controller is configured to change the two potentials such that an amount of change of each of the two potentials is within a predetermined range. 5. An apparatus according to claim 2, whereinthe connector includes a plurality of switching elements for setting a state of connection between the plurality of electrodes and the plurality of devices, andthe controller is configured to store the determined plurality of potentials, and to control the plurality of switching elements in accordance with the stored plurality of potentials. 6. An apparatus according to claim 1, further comprising:a vacuum chamber in which the deflector array is disposed and the drawing is performed, the vacuum chamber including a vacuum feedthrough,wherein the plurality of devices are disposed outside the vacuum chamber, the connector is disposed inside the vacuum chamber, and each of the plurality of electrodes is connected to one of the plurality of devices via the vacuum feedthrough. 7. A method of manufacturing an article, the method comprising:performing drawing on a substrate using a drawing apparatus;developing the substrate on which the drawing has been performed; andprocessing the developed substrate to manufacture the article,wherein the drawing apparatus includes a plurality of charged particle optical elements that are sequentially passed through by a plurality of charged particle beams and performs drawing on the substrate with the plurality of charged particle beams, the apparatus including:a deflector array which includes a plurality of deflectors, including a plurality of electrodes, each of which disposed for corresponding one or more charged particle beams and aligning the corresponding one or more charged particle beams between two of the plurality of charged particle optical elements;a plurality of devices configured to respectively apply a plurality of potentials to the deflector array; anda connector including wirings and configured such that each of the plurality of electrodes and one of the plurality of devices are interconnected via one of the wirings, and electrodes, to which an equal potential is applied, of the plurality of electrodes are connected to a single wiring of the wirings,wherein number of devices included in the plurality of devices is less than number of electrodes included in the plurality of electrodes. 8. A method of manufacturing a deflecting apparatus including a deflector array which includes a plurality of deflectors, including a plurality of electrodes, each of which disposed for corresponding one or more charged particle beams and aligning the corresponding one or more charged particle beams between two of a plurality of charged particle optical elements, a plurality of devices configured to respectively apply a plurality of potentials to the deflector array, and a connector including wirings and configured to perform connection of each of the plurality of electrodes to one of the plurality of devices, the method comprising:performing detection of a position of a charged particle beam corresponding to one deflector included in the deflector array;performing determination of a plurality of potentials applied to the plurality of electrodes based on the detection;providing the plurality of devices of which number of devices is same as number of potentials of the determined plurality of potentials; andcausing the connector to perform the connection such that each of the plurality of electrodes and one of the plurality of devices are interconnected via one of the wirings, and electrodes, to which an equal potential is applied, of the plurality of electrodes are connected to a single wiring of the wirings. 9. A method according to claim 8, wherein the determination determines the plurality of potentials by changing two potentials applied respectively to two electrodes of a pair of electrodes included in the plurality of electrodes while maintaining a potential difference between the two electrodes such that a potential of at least one of the two electrodes becomes equal to a potential of at least one of two electrodes of another pair of electrodes included in the plurality of electrodes. 10. A method according to claim 9, wherein the determination changes the two potentials such that an amount of change of each of the two potentials is within a predetermined range. 11. A method of manufacturing a drawing apparatus for performing drawing on a substrate with a plurality of charged particle beams, the method comprising:assembling a projection system that includes a deflecting apparatus and projects the plurality of charged particle beams onto the substrate,wherein the deflecting apparatus is manufactured using a method defined in claim 8. |
|
claims | 1. A radiation tomography apparatus comprising:an X-ray irradiation device for irradiating an X-ray while scanning helically around an imaging area of an imaging object on a body axis of said imaging object;an X-ray detection array comprising X-ray detection elements arranged in an array for detecting said X-ray and for generating detection data according to said X-ray detected by said X-ray detection elements;an irradiation range adjustment device disposed between said X-ray irradiation device and said X-ray detection array for shielding said X-ray to adjust an irradiation range of said X-ray so that said X-ray is not irradiated to a specified area of said X-ray detection array;a controller for controlling at least said irradiation range adjustment device; anda tomographic image generation device for generating a tomographic image of said imaging area of said imaging object based on said detection data;wherein said detection data of said X-ray detection array comprises first and second detection data, said first detection data results from said X-ray detected by said X-ray detection element corresponding to an area not shielded by said irradiation range adjustment device, and said second data results from said X-ray detected by said X-ray detection element corresponding to an area shielded by said irradiation range adjustment device during at least one of a beginning and an end of said helical scanning;an opening of said irradiation range adjustment device is adjustable during said helical scanning to shield said X-ray during at least one of the beginning and the end of said helical scanning to shield at least a part of an area outside of said imaging area along the body axis, wherein said opening is adjusted by said controller during said helical scanning such that, upon helical scanning of said imaging area from a first end to an opposing second end in a direction along said body axis, said irradiation range adjustment device makes the irradiation range of said X-ray wider than an irradiation range during at least one of the beginning and the end of said helical scanning; andsaid tomographic image generation device correcting said first detection data by using said second detection data from said X-ray detected during at least one of the beginning and the end of said helical scanning, and generating said tomographic image based on a corrected first detection data. 2. The radiation tomography apparatus according to claim 1, wherein a center of said X-ray detection array is oriented with respect to said body axis to align said X-ray detection array at one of the first end and the second end of said imaging area along said body axis such that said irradiation range adjustment device shields said area outside of said imaging area from said X-ray during at least one of the beginning and the end of said helical scanning. 3. The radiation tomography apparatus according to claim 1, wherein in said first and second detection data obtained by said X-ray detection elements arranged correspondingly to positions in said radiation detection array along a channel direction, said tomographic image generation device calculates an average value of said second detection data, calculates a difference between each of said first detection data and said average value of said second detection data to correct each of said first detection data, and generates a tomographic image for said imaging area using said corrected first detection data. 4. A radiation tomography apparatus comprising:an X-ray irradiation device for irradiating an X-ray while scanning around an imaging area of an imaging object on a body axis of said imaging object with more than one rotation;an X-ray detection array comprising X-ray detection elements arranged in an array for detecting said X-ray and for generating detection data according to said X-ray detected by said X-ray detection elements;an irradiation range adjustment device which is disposed between said X-ray irradiation device and said X-ray detection array for shielding said X-ray to adjust an irradiation range of said X-ray so that said X-ray is not irradiated to a specified area of said X-ray detection array;a controller for controlling at least said irradiation range adjustment device; anda tomographic image generation device for generating a tomographic image of said imaging area of said imaging object based on said detection data;wherein said detection data of said X-ray detection array comprises first and second detection data, said first detection data results from said X-ray detected by said X-ray detection element corresponding to an area not shielded by said irradiation range adjustment device, and said second data results from said X-ray detected by said X-ray detection element corresponding to an area shielded by said irradiation range adjustment device during at least one of a first rotation and a last rotation of said scanning;an opening of said irradiation range adjustment device is adjustable during said scanning to shield said X-ray during at least one of the first rotation and the last rotation of said scanning with more than one rotation to shield at least a pan of an area outside of said imaging area along the body axis, wherein said opening is adjusted by said controller during said scanning such that, upon scanning of said imaging area from a first end to an opposing second end in a direction along said body axis, said irradiation range adjustment device makes the irradiation range of said X-ray wider than an irradiation range during at least one of the first rotation and the last rotation of said scanning; andsaid tomographic image generation device correcting said first detection data by using said second detection data from said X-ray detected during at least one of the first rotation and the last rotation of said scanning, and generating said tomographic image based on a corrected first detection data. 5. The radiation tomography apparatus according to claim 4, wherein said first and second detection data obtained by said X-ray detection elements arranged correspondingly to positions in said X-ray detection array along a channel direction, said tomographic image generation device calculates an average value of said second detection data, calculates a difference between each of said first detection data and said average value of said second detection data to correct each of said first detection data, and generates a tomographic image for said imaging area using said corrected first detection data. 6. The radiation tomography apparatus according to claim 4, wherein said irradiation range adjustment device shields said X-ray in a narrower irradiation range during at least one of the first rotation and the last rotation than other rotations. 7. The radiation tomography apparatus according to claim 4, wherein a center of said X-ray detection array in said body axis direction is aligned with one of the first end and the second end of said imaging area along said body axis such that said irradiation range adjustment device shields said area outside of said imaging area from said X-ray during at least one of the first rotation and the last rotation of said scanning. |
|
060382775 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plant apparatus operated by touch operation. 2. Description of the Prior Art Because there is a requirement to maintain safety functions (that is, based on a single failure criteria) of safety system equipment for an atomic power plant or a nuclear power plant as a plant operation apparatus, even if a single failure occurs in any devices or channels forming the plant operation apparatus, it must be required that the safety system equipments for the atomic power plant are the equipments, each is physically separated, electrically isolated, and independently from other equipments, systems, and multiplicity systems. For example, there is the literature 1 as one of conventional examples that satisfy the requirement of the safety protection function described above. Literature 1: "Development of the BWR safety protection system with a new digital control system", IAEA International system on nuclear power plant instrument and control, TOKYO, Japan, pp. 18-22, May, 1992. FIGS. 1A-B are a pictorial view and a diagram showing a configuration of a conventional safety system including touch operated equipment shown in the literature 1 described above. In FIG. 1(b), the reference numbers 152, 153, 154, and 155 designate train control devices as separated into four sections in order to control the operation of trains. That is, the configuration of the conventional safety protection system comprises the four trains. In FIG. 1(a) the reference number 159 designates a central control panel having a plurality of flat displays corresponding to the train control devices DIV-1, DIV-2, DIV-3, and DIV-4, respectively. Each of the trains 152 to 155 is physically separated by the separation means 151. Because the safety protection equipment in the conventional system shown in FIG. 1(a) and 1(b) has the configuration described above, the supervision operation devices, to be separated to each other, in the central control panel 159 such as flat display panels (FDP) and the like must have the configuration in which they are completely and physically separated like the safety protection system downstream from the flat display panels in order to satisfy the separation criteria. It must be required to independently install a flat display panel in each train as the supervision operation panel, as it is described in FIG. 1(b) as "to DIV-1 flat display", for example. Thus, the supervision operation panel is divided independently for each train. Thereby, there is a drawback in the conventional plant operation apparatus that the operation efficiency of operators decreases and the scale or size of the system increases. The conventional example shown in FIG. 1(b) must require at least three flat displays, or it must require at least six flat displays when two flat displays are installed in each train because each train requires at least one flat display for the use of the supervision operation. In addition to the separated flat displays described above, the multiplicity equipment and the switching devices to be required for increasing the reliability and for easy maintenance are commonly and widely used in conventional apparatuses. For example, Japanese patent publication number JP-B-62/75704 discloses a conventional control apparatus. FIG. 2 is a block diagram showing the conventional process control apparatus disclosed in Japanese patent publication number JP-B-62/75704 described above. In this process control apparatus, when an operator operates the operation panel 111, the auxiliary control unit 110 and control units 101, 102, and 103 forming the multiplicity control unit generate operation signals and output them through lines L11, L12, L13, L14, and other wires to a field panel 100, an electrical instrument unit 400, an annunciator 500, and other control units. Thereby, a switch unit 202 switches back and forth between the output signal transferred from the control multiplicity unit and the output signal transferred from the auxiliary control unit 110. The selected output signal is transferred to the process 300 through the wire L2. It is thereby possible to increase the efficiency of the maintenance operation and the reliability. That is, because the conventional control device 100 has the configuration as shown in FIG. 2, the control device 100 can execute normally and can output the normal output operation signal to the process 300 even if one of the control units 101, 102, and 103 breaks down as a result of errors. Furthermore, when the control function of the control units is renewed, the switch unit 202 can switch the output transferred from the control unit to the output transferred from the auxiliary control unit 110 in order to execute the normal operation. However, although the conventional commonly used apparatus comprising the control multiplicity units and the switch unit 202 satisfies the general reliability and maintenance criteria to be required commonly, it is difficult and impossible to apply it to a safety system equipment for atomic power plants or nuclear power plants that require a strict single failure criteria (for separation and independence requirement) in the highest safety requirement. It must be required that the safety system equipment for atomic power plants guarantee the safety protection function when any single failure of component devices occurs. In the conventional example as shown in FIG. 2, there are possibilities of influences from a failure caused when the switch unit 202 breaks down, or to extend to each of the control units 101 to 103 the failure caused when the auxiliary control unit 110 fails, or to lose the safety function caused when all of the functions of the control device 100 fail in a fire. These are drawbacks of the conventional safety protection function. Like the conventional example described above, because the conventional common multiplicity and switching mechanism can not satisfy the separation criteria for atomic power plants. Accordingly, the conventional safety protection system for atomic power plants comprises at least two or four separated trains (in order to form separated equipments). In addition to this configuration, a desired device or devices are multiplicity in each separated train. That is, the conventional safety protection system is designed by using a multiplicity design method. FIG. 3 is a diagram showing the conceptual configuration of a train separation based on the conventional multiplicity design method. In the conventional train separation shown in FIG. 3, the supervision operation flat display panels (FDPS) 171 to 174 are integrated into the central control panel 170. Both the FDP 171 and FDP 172 belong to the A train, both FDP 173 and FDP 174 belong to the B train. Each train is separated from other trains for fire protection by the separator as the separation means such as the metal plate and the like in the central control panel 170. The operation signal transferred from each FDP is transferred to each of the safety protection devices 183 to 186 through the FDP controllers 175 to 178 and the multiplexers (MPX) 179 to 182. The safety protection equipments 183 to 186 operate plant devices in plant processes. All of this equipment placed downstream from the central control panel 170 is divided into trains. The train A and train B are shown in FIG. 3. The control panel includes independent flat display panels 171 to 174 for controlling downstream devices such as the FDP controllers 175 to 178. These devices are not connected to each other in order to protect them from fire and to reduce the effect of any single failure on other devices. Proper separation devices are provided for devices requiring a cross-over wiring) By using the configuration, even if a component device in the train A fails, the train B can maintain its function and can guarantee its operation. Here, if only one of the train A and the train B has the function required for atomic power plants, it is possible to maintain the plant safety functions for any single failure. In addition, there is a case that it is required to multiply the configuration of each train. For example, in the conventional example shown in FIG. 2, the FDP controller and the multiplexer and the like are multiplexed. This multiple in the conventional example shown in FIG. 2 is different in conception from the separation design using the train configuration. Therefore the multiple design in each train can be executed by using the conventional reliability analysis method, for example. The supervision operation equipment in the conventional safety system shown in FIG. 1 is designed and formed. In the conventional example shown in FIG. 1, the devices in the apparatus are separated by using three divided trains DIV-1 to DIV-3. In each train, the required parts such as a safety logic unit (SLU) and a digital trip module (DTM) and the like are redundantly included. Hereinafter, the explanation regarding the general multiple design applied to each of the trains is omitted and conventional drawbacks involved in the conventional method satisfying the train separation to satisfy the single failure criteria, relating to the plant operation apparatus of the present invention, and integrating the supervision operation panel will be explained. Because the conventional plant operation apparatus has the configuration described above, the following matters (1) to (4) must be required to the touch operation devices in the safety protection equipment in atomic power plant based on the safety design examination guidance, the fire guidance like the safety protection system for an atomic reactor. (1) Multiplicity or Diversity It is requested to maintain safety functions (namely, the single failure criteria) even if any device forming a system or channel fails. Therefore it must be required for equipment in the safety protection system to have the multiplicity and diversity function. (2) Independence From the same reason of the case (1) described above, it is requested to design channels forming a system so that the channels are separated from each other and independent from each other as completely for practical applications as possible. Because it is required to electrically isolate devices and to physically separate the devices in the separation satisfying this requirement, the devices to be used for this separation are limited in general. (3) Separation from measurement control system In order to prevent the influence of failure caused by a general measuring control system that is not adapted to the requirements (1) and (2) described above, it must be necessary to design devices and equipment in the safety protection system in a different way from the measuring control system. (4) Preventing occurrence of a fire, detection of a fire, and fighting of a fire, and influence of a fire As the countermeasure to reduce the influence of a fire, it is required to separate devices based on a fire-proofing wall, a bulkhead, an interval (distance), and the like. Because it must be required to separate the supervision operation panel for each train in order to satisfy the separation criteria (the physical separation, the electrical isolation, and the separation to prevent the spreading fire for fire protection), it is thereby necessary to increase the amount of the hardware of the system, the size of the system, the working space for operators, the working time of the operators, the costs of the system, and so on. Accordingly, there is the requirement in the conventional plant operation apparatus, specifically in the atomic power plant field, to increase the operation efficiency of the supervision working, and to obtain the plant operation apparatus that is capable of reducing the cost of the plant operation apparatus by decreasing the hardware size of equipment and devices in the plant operation apparatus under the state in which the separation criteria is satisfied. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is, with due consideration to the drawbacks of the conventional plant operation apparatus, to provide a plant operation apparatus whose configuration includes hardware (H/W) selection devices to select trains based on a hardware mechanism in addition to software (S/W) selection system to select the trains based on a software, so that the plant operation apparatus of the present invention has the configuration in which touch operation panels in the safety system is integrated by using the train separation means having the diversity. An another object of the present invention is to provide a plant operation apparatus that is capable of displaying train selection states to operators in order to process the operations easily and without causing any errors, and of preventing occurrences of any operator errors. In accordance with a preferred embodiment of the present invention, a plant operation apparatus for satisfying a separation criteria, comprises an operation panel including panel switches for common touch operation, for generating operation signal based on the touch operation by operators, and for transferring the operation signal, an operation display screen control device for controlling a display on the operation panel and the touch operation when one of a plurality of trains as equipments placed in a safety protection system being selected, each train being separated independently in order to keep a multiplicity, a diversity, and an independence of supervision operation devices in the safety protection system, the operation display screen control device for selecting one train based on a software selection function according to the operation signal from the operation panel, and for generating a first control signal for the selected train, a selection device comprising momentary type push buttons corresponding to the trains, for resetting other push buttons other than one push button that being pushed by an operator based on a hardware selection function, and for generating and transferring a second control signal corresponding to the selected train, and a train control device for receiving the first control signal and the second control signal transferred from the operation display screen control device and the selection device, for generating a third control signal for the selected train based on both the first control signal and the second control signal, and for transferring the third control signal to the selected train. In the plant operation apparatus, the operation display screen control device, the selection device, and the train control device forms a diversified train selection system satisfying the separation criteria. It is thereby to prevent an occurrence of a mis-operation. In the plant operation apparatus as another preferred embodiment of the present invention, the selection device comprises self diagnosis circuits, each self diagnosis circuit corresponds to each train, and the selection device resets the self diagnosis circuits, based on a software logic function, corresponding to the push buttons for other trains, that are not selected when the operator pushes one of the push buttons in order to select one train. It is thereby possible to prevent an occurrence of a mis-operation caused by an operator. In the plant operation apparatus as another preferred embodiment of the present invention, the selection device further comprises isolators as separation devices corresponding to each train. It is thereby possible to form the train selection system independently from the control device. In the plant operation apparatus as another preferred embodiment of the present invention, the push buttons incorporated in the selection device are mechanical reset type push buttons, and the mechanical reset type push buttons corresponding to other trains that are not selected are reset mechanically when one train is selected. It is thereby possible to prevent an occurrence of a mis-operation caused by an operator. In the plant operation apparatus as another preferred embodiment of the present invention, the push buttons incorporated in the selection device are alternate type push buttons, and one alternate type push button corresponding to one train to be selected is pushed after the alternate type push buttons corresponding to other trains that are not selected are reset manually. It is thereby possible to prevent an occurrence of a mis-operation caused by an operator. In the plant operation apparatus as another preferred embodiment of the present invention, the selection device comprises a module switch having a plurality of channels, and the module switch is formed so that only one channel corresponding to one train is selected. It is thereby possible to prevent an occurrence of a mis-operation caused by an operator. In the plant operation apparatus as another preferred embodiment of the present invention, the selection device comprises a mechanical gear type switch, and the mechanical gear type switch is formed so that only one channel corresponding to one train is selected. It is thereby possible to prevent an occurrence of a mis-operation caused by an operator. In the plant operation apparatus as another preferred embodiment of the present invention, the mechanical gear type switch incorporated in the selection device keeps a neutral position while no train is selected. It is thereby possible to prevent an occurrence of a mis-operation caused by an operator. In the plant operation apparatus as another preferred embodiment of the present invention, the plant operation apparatus further comprises a large type display device for displaying operation information such as train selection states and the like to a plurality of operators simultaneously and a computer for controlling a display of the operation information on the large type display device, wherein the plurality of operators in charge of the train selection operation see the train selection information simultaneously displayed on the large type display device, in order to prevent occurrence of a mis-operation caused by the plurality of operators. It is thereby possible to prevent an occurrence of a mis-operation caused by an operator. In the plant operation apparatus as another preferred embodiment of the present invention, the plant operation apparatus further comprises train pilot lamps for indicating the train selection state based on the train selection information output from the operation display screen control device, and control train pilot lamps for indicating the train selection state based on the train selection information output from the selection device, wherein it is possible to prevent occurrences of a mis-operation by selecting a target train to be selected while the operator sees the train selection state in which the selection train pilot lamp corresponding to the selected train lights. It is thereby possible to prevent occurrences of mis-operations caused by operators. In the plant operation apparatus as another preferred embodiment of the present invention, the operation display screen device controls a display of a flow diagram of a plant system displayed on the operation panel so that a selection state of a target plant device to be operated in the selected train is displayed near the target plant device on the flow diagram in order to prevent an occurrence of a mis-operation caused by an operator. In the plant operation apparatus as another preferred embodiment of the present invention, the selection device comprises a logical circuit for preventing to generate and to output the selection signal even if a mis-operation, caused when the momentary type push buttons corresponding to the trains that are not selected by the operator are pushed, is happened. It is thereby possible to prevent an occurrence of a mis-operation caused by an operator. In the plant operation apparatus as another preferred embodiment of the present invention, the operation display screen control device has a train identification table used for obtaining information of the train to be selected based on information such as a target device to be operated and operation contents included in the operation signal transferred from the operation panel, and the operation display screen control device selects the train based on the information in the train identification table. It is thereby possible to increase reliability of the train selection operation. In the plant operation apparatus as another preferred embodiment of the present invention, the train control device has a train identification table used for obtaining information of the train to be selected based on information such as a target device to be operated and operation contents included in the control signal transferred from the operation display screen control device, and the train control device selects the train based on the information in the train identification table. It is thereby possible to increase reliability of the train selection operation. |
048470384 | claims | 1. In a method for the complete replacement of a worn-out steam generator (1) of a pressurized water nuclear reactor comprising a reactor building (10) defining a compartment (11) in which the steam generator (1) is retained in a specified position by means of supporting and positioning devices (8, 17) placed in said compartment, and a primary circuit (3, 4, 5) in said reactor building (10) in which primary circuit pressurized water circulates, said primary circuit comprising two pipes (3,5) connected to a lower part of said worn-out steam generator (1) in the region of corresponding nozzles of said worn-out steam generator, said method comprising the steps of separating said worn-out steam generator (1) from said primary circuit by sectioning said pipes (3, 5) in the vicinity of pipework of said worn-out steam generator (1), withdrawing said worn-out steam generator from said compartment (11), placing a replacement steam generator (20) in position in said compartment (11) and welding the nozzles (22a, 22b) of said replacement steam generator to said pipes (3, 5), in the region of welding chamfers, the improvement comprising the steps of (a) carrying out topometric measurements on said replacement steam generator (20) to determine exactly the position of supporting and positioning parts (25) of said replacement steam generator intended to come to bear on said supporting and positioning devices (8, 17) of said compartment (11) and the geometry of said nozzles (22a, 22b) for connection to said primary circuit (3, 5); (b) carrying out topometric measurements in said compartment (11) and on said worn-out steam generator (1) to determine the geometry of said connection to said primary circuit (3, 5) and of said supporting and positioning devices (8, 17) of said compartment; (c) comparing topometric measurements carried out to determine the number and the position of the sectioning operations to be carried out on said pipes (3, 5) of said primary circuit, and modifications to be made to the supporting and positioning devices (8, 17) of said compartment, for positioning said replacement steam generator (20); (d) carrying out sectioning operations and withdrawal of said worn-out steam generator (1) from said compartment (11), and grinding the sectioned surfaces on said pipes (3, 5) of said primary circuit; (e) carrying out topometric measurements in said compartment (11) after withdrawal of said worn-out steam generator (11), to determine the exact position of said supporting and positioning devices (8, 17) of said compartment and of sectioned ends of said pipes (3, 5) of said primary circuit; (f) verifying the feasibility of employing the replacement procedure by comparison of the measurements carried out; (g) determining the exact position of the welding chamfers on the ends of the primary pipes (3, 5); and (h) machining corresponding chamfers, placing said replacement steam generator (20) and its supporting and positioning devices in position and performing the welding connection of said nozzles (22a, 22b) and of said pipes (3, 5). (a) producing a mounting framework reproducing a lower part (20a) of said replacement steam generator (20); (b) producing supporting and positioning devices (64) reproducing said supporting and positioning devices of said replacement steam generator (20); (c) producing members (65), each comprising a means for physically representing a connection plane; (d) positioning said framework (60) onto said lower part (20a) of said replacement steam generator (20); (e) positioning said devices (64) physically representing said devices for supporting and positioning said replacement steam generator, in position on supporting feet (25) of said replacement steam generator (20); (f) aligning said producing members (65) with ends of said nozzles (22a, 22b) of said replacement steam generator (20), so as to represent physically a plane of connection of said nozzles; (g) fastening said produced supporting and positioning devices (64) and said producing members (65) onto said framework (60); and (h) positioning said framework (60) in said compartment (11) of said worn-out steam generator, after withdrawal of said worn-out steam generator, in place of said lower part (1a) of said worn-out steam generator, and thus checking the feasibility of implementing the replacement procedure, the position of planes of connection of said nozzles (22a, 22b) and of said primary pipes (3, 5) of said primary circuit, and the geometry and dimensions of said devices for supporting and positioning said replacement steam generator. 2. The improvement according to claim 1, comprising the steps of 3. The improvement according to claim 2, comprising performing the determination and the scribing of the exact position of said welding chamfers on said ends of said pipes (3, 5) of said primary circuit, by employing said framework (60). |
summary | ||
claims | 1. A lead-free X-ray shielding rubber compound material, comprising:CompositionsContent(phr)Rubber50-100Polymerized rare earth organic complex20-300Inorganic rare earth compound20-500Metal tin &/or tin compound20-500Bismuth element &/or inorganic compound20-550Polymerized bismuth organic complex20-230Metal tungsten &/or tungsten compound20-260Silane coupling agent0.5-10 Softener2-30Crosslinker2-15In-situ reaction initiator0.2-3 where, phr equals grams per 100 g of the rubber,wherein the rare earth organic complex is an unsaturated carboxylic rare earth salt, and the rare earth element in the rare earth organic complex is selected from a group consisting of the elements of the lanthanide series except for promethium; wherein the inorganic rare earth compound is selected from the group consisting of rare earth oxide, rare earth chloride, rare earth carbonate, rare earth hydride and rare earth hydroxide, and the rare earth element in the inorganic rare earth compound is selected from the group consisting of 16 kinds of elements of the lanthanide series except for promethium; wherein the tin compound is selected from the group consisting of tin oxide, tin chloride, tin sulfide and tin fluoride; wherein the bismuth inorganic compound is bismuth oxide or bismuth sulfide; wherein the bismuth organic complex is an unsaturated carboxylic bismuth salt; wherein the tungsten compound is selected from the group consisting of tungsten carbide, tungsten sulfide, tungsten salts and tungsten halide; wherein the lead-free X-ray shielding rubber compound material comprises particles having a size of 40-100 nm; and wherein the particles comprise the polymerized rare earth organic complex and the polymerized bismuth organic complex. 2. The lead-free X-ray shielding rubber compound material of claim 1, wherein the rubber is natural rubber or synthetic rubber, and wherein the synthetic rubber is selected from the group consisting of ethylene propylene dienemonomer rubber, styrene-butadiene rubber, nitrile rubber, acrylic rubber and hydrogenated nitrile-butadiene rubber. 3. The lead-free X-ray shielding rubber compound material of claim 1, wherein the unsaturated carboxylic rare earth salt is acrylic rare earth salt, methacrylic rare earth salt or undecylenic rare earth salt; or wherein the bismuth organic complex is acrylic bismuth salt, methacrylic bismuth salt or undecylenic bismuth salt. 4. The lead-free X-ray shielding rubber compound material of claim 1, further comprising an accelerator, wherein the accelerator is a thiazole accelerator, a sulfenamide accelerator or a thiuram accelerator. 5. The lead-free X-ray shielding rubber compound material of claim 1, wherein the crosslinker is sulfur, peroxide or phenolic resin. 6. The lead-free X-ray shielding rubber compound material of claim 1, wherein the silane coupling agent is bis (triethoxysilyl propyl) tetrasulfide, vinyl tirethoxy silane (A-151) or y-aminopropyl vinyl tirethoxy silane. 7. The lead-free X-ray shielding rubber compound material of claim 1, wherein the in-situ reaction initiator is dicumyl peroxide or benzoyl peroxide. 8. The lead-free X-ray shielding rubber compound material of claim 1, further comprising 1-5 parts per hundred rubber (phr) of zinc oxide and 1-10 parts per hundred rubber (phr) of stearic acid by weight. 9. The lead-free X-ray shielding rubber compound material of claim 1, further comprising 0.5-3 parts per hundred rubber (phr) of accelerator by weight. 10. The lead-free X-ray shielding rubber compound material of claim 1, wherein the softener is alkane oil, aromatic oil or engine oil. 11. The lead-free X-ray shielding rubber compound material of claim 1, further comprising a synthetic plasticizer, wherein the synthetic plasticizer is dibutyl phthalate, dioctyl phthalate or epoxidized soybean oil. |
|
039895890 | description | DESCRIPTION OF THE PREFERRED EMBODIMENTS Throughout the description which follows, like reference characters indicate like elements in the various figures of the drawings. FIG. 1 illustrates a nuclear reactor incorporating the hydraulic control rod drive mechanism provided by this invention. A reactor vessel 10 is shown which forms a hermetically sealed pressurized container when sealed by closure head 11. The reactor vessel 10 has coolant flow inlet nozzles (not shown) and coolant flow outlet nozzles 12 in and through the cylindrical wall thereof. The closure head 11 has a plurality of head penetration adaptors 13 extending through a substantially hemispherical wall and sealingly affixed thereto. A nuclear core comprising a plurality of fuel assemblies 14 is contained within the reactor vessel 10. For purposes of simplicity only two fuel assemblies 14 are shown. Each fuel assembly 14 includes a plurality of fuel rods 15 and a plurality of guide tubes 16 symmetrically interspersed therebetween. The fuel rods 15 and guide tubes 16 are held in a fixed relationship with respect to each other by an egg crate type of grid structure 17. This type of so-called canless fuel assembly 14 is well known in the art. The guide tubes 16 serve as guidance channels or receptacles for full length or part length control rods 18. In FIG. 1, again for purposes of simplicity, four control rods 18 are shown whereas as many as 20 individual control rods are used within a single fuel assembly 14 in a typical large nuclear reactor. This invention however is not thereby restricted to a particular number of control rods in any given fuel assembly. The worth of a single control rod 18 is so calibrated that the insertion of one or two such rods will not greatly change the power distribution of the entire core as would the insertion, for example, of a complete cluster of part length control rods. However, a single control rod 18 would have enough control rod worth to axially trim the power distribution in its immediate vicinity. The distribution of control rods 18 within a fuel assembly 14 is shown in FIG. 5. The part length control rods 18 are joined in pairs at their upper ends to thin gusset plates 19 to which drive shafts 20 are also attached. This can be seen more clearly in FIG. 6. It is to be realized, that although the figures show two control rods 18 attached to one drive shaft 20, either one or, in the alternative, more than two control rods 18 might be used with a single drive shaft 20. Control rod assemblies 21 are not used in all of the fuel assemblies 14; a large nuclear reactor will typically have eight fuel assemblies 14 equipped with part length control rod assemblies 21. In FIG. 1 it is seen that the plurality of drive shafts 20 associated with a fuel assembly 14 pass through a guide tube structure assembly 22. Guide tube structure 22 guides individual drive shafts 20 on passage through a reactor coolant outlet plenum 23 which is positioned above the nuclear core. The drive shaft guide structure 22 consists of a generally square vertical column 24 having guide plates 25 axially disposed therein. The guide tube support structure 22 extends between an upper core plate 26 and an upper support plate 27. The control rod drive shafts 20 pass within and through the reactor vessel head penetration adaptors 13 and terminate within hydraulic control rod drive mechanisms 28 as provided by this invention. The exact manner by which the control rod drive shafts 20 are guided and supported within the head penetration adaptor 13 is shown in FIG. 2. The drive shafts 20 are supported above the upper support plate 26 by a flange 29 to which is attached a vertical central shaft 30. Circular guide plates 31 are attached to the central shaft 30 such as by welding and are provided with holes 32 to support and guide the drive shafts 20. The funnel-shaped member 33 and the slots 34 in guide blocks 31 serve to facilitate assembly. The upper portion of the head penetration adaptor 13 is shown in detail in FIG. 3. A guide block 40 provides final guidance for the control rod drive shaft 20 just prior to exiting from the head penetration adaptor 13. A cylindrical lifting fixture 41 rests on top of guide block 40 and is oriented therewith by means of pin 42. The lifting fixture 41 is provided with vertical holes 43 with ledges 44 into which pistons 45 attached to the drive shafts 20 nest when the control rod assemblies 21 are in their full inserted position in the core. Any anticipated misalignment between the pistons 45 and their guide channels will be compensated for by a slight rotation of the lifting fixture 40. The control rod drive mechanism 28 is attached to the head penetration adaptor 13 as shown in FIGS. 1 and 3. The details of the control rod drive mechanism 28 are shown in FIGS. 3, 4, 7, 8, 9 and 10. Referring now to FIGS. 3 and 4, it is seen that the drive mechanism 28 comprises a pressure bearing member which includes a cylindrical base 50 having an outwardly extending flange 51 at its lower extremity and an upper cylindrical head cap 52 joined by welding to an intermediate heavy walled tube 53. The upper cylindrical head cap 52 is sealed by a threaded and steel welded plug 54 or other suitable means. Flange 51 of the mechanism is sealingly connected to flange 54 of the head penetration adaptor 13 thereby maintaining the pressure containing integrity of the reactor vessel 10. A plurality of cylinders are provided within the control rod drive mechanism; one cylinder being provided for each control rod assembly 21 being actuated by the drive mechanism 28. The cylinders comprise the channel formed by a machined hole 55 in base 50, a long tube 57 within intermediate tube 53 and a machined hole 56 in the head cap 52. The long tube 57 is fixedly supported in tight counter-bores in openings of holes 55 and 56 as shown in FIGS. 3 and 4. Between the counter-bore supporting points, the long tubes 57 are laterally supported by appropriate guide blocks (not shown) axially disposed with intermediate tube 53. As mentioned above, the control rod assemblies 21 are withdrawn from the core by differential hydraulic pressure acting on piston 45. The manner in which this is accomplished is shown in detail in FIG. 3. Referring now to that figure, the central space 60 directly below the flange 51 of the mechanism 28 is opened to the reactor vessel interior and is thereby pressurized to the pressure of the reactor coolant, which in the example shown is approximately 2000 psi. Space 60 is separated from a surrounding annular space 61 having a pressure of approximately 1700 psi. Pressurized areas 60 and 61 are conventionally sealed from each other by means of an O-ring gasket 62 acting in conjunction with tubular member 61'. Space 61 is connected to an exterior adjustable pressure source (not shown) by flow channels 63 machined within flange 54 of the head penetration adaptor 13 and tubing 64 connected thereto. Flow channel 65 within the flange 51 of the control rod drive mechanism 28 is connected at one side to space 61 and at the other side to one port 66 of an electromagnetically operated valve 69. As can be seen, valve 69 is attached to and supported by the lower portion or base 50 of the control rod drive mechanism 28. One valve 69 is provided for each control rod assembly 18. A second port 71 of valve 69 is flow connected to channel 70 which is machined in base 50. Ports 66 and 71 are sealingly separated by a seal connected valve stem 72 of the magnetic valve 69. Flow channel 70 is flow connected to the top of piston 45 by connecting tube 73 and holes 74 and 75, within the upper cylindrical head cap 52 of the mechanism (FIG. 4, FIG. 10). Withdrawal of the control rod assembly from the core is accomplished by energizing the coil of the magnetic valve 69 thereby lifting valve stem 72 from its seat. This has the effect of connecting the 1700 psi hydraulic pressure within space 61 to the top of piston 45. Since approximately 2000 psi hydraulic pressure acts on the lower part of piston 45, a net hydraulic pressure differential of approximately 300 psi acts on the control rod piston 45. This pressure differential causes the control rod assembly 21 to move at a rather high speed toward its fully withdrawn position. So as to lessen the shock of the control rod assembly reaching this final position, a self-damping decelerating mechanism is provided in the upper cylindrical head cap 52 as shown in FIG. 4. The decelerating device comprises a restriction 80 located in the upper part of the hydraulic cylinder 56 dimensioned to give a rather close diametrical clearance between the piston 45 and cylinder 56. A typical diametrical clearance might be of the order of ten to twenty-five thousandths of an inch. When the piston 45 reaches restriction 80, the water trapped above piston 45 is forced through the clearance gap thereby creating a considerable overpressure within the trapped water. This effectively and slowly decelerates the motion of the control rod assembly 21 as it reaches its fully withdrawn position. It is to be observed that restriction 80 has, of course, the effect of increasing the time required to fully insert the control rod assembly by gravity. However, this is a distinct advantage for part length control rods since as previously explained, full insertion of part length control rods has the effect of increasing reactivity of the core. On the other hand, the increased drop time of full length control rods may possibly be a disadvantage especially during reactor scramming operations when rapid insertion of these control rods is required. After a piston 45 has reached its upper limit of travel, it is held that this position by an internal mechanical latching arrangement 81, the magnetic valve 69 is then deenergized so as to conserve the pumping potential of the system. The latching assembly 81, which is located within the upper portion of the cylindrical head cap 52, has a hook shape lower end 82 which engages with a similarly shaped end 83 on the piston 45. The latch assembly 81 fits within an extension 84 of the cylinder 56. Extension 84, however, has a slightly larger diameter than cylinder 56. Extension 84 is closed at its top by a cover plate 85 which is secured to the upper cylindrical head cap 52 by a central bolt 86. The cover plate 85 and the central bolt 86 are located immediately below the threaded and welded seal plug 54. Thus, the pressure containing integrity of the control rod drive mechanism 28 is maintained. A radial projection 87 of the latch 89 fits into a narrow slot 88 (FIG. 7) machined radially in cylinder extension 84. As more clearly shown in FIGS. 7 and 8, the projection 87 serves as a seat and fulcrum for the latch 89 and maintains the correct rotational location of the latch 89 with respect to the bore of cylinder extension 84. A spring 90 which is fitted within a respective hole in the latch 89 tends to rotate the latch 89 around its fulcrum point until the edge of the ledge 91 contacts the wall of the cylinder extension 84. This is the normal position of the latch assembly 81 when the control rod assembly is inserted in the core. When the piston 45 and hence the control rod assembly 21 is lifted by application of the differential hydraulic pressure, the latch 89 will be pushed aside momentarily but will be returned immediately to the latched position (as indicated by the dash and dot lines) by latch spring 90 when the piston 45 reaches its uppermost position which is somewhat higher than that shown in FIG. 4. When the hydraulic differential pressure is removed, by deenergizing the magnet valve 69, the piston 45 will drop slowly until its movement is arrested when the hook shaped ends of the piston and the latch mechanism 82 and 83 respectively, firmly engage thereby holding the control rod assembly 21 in a fully withdrawn position. An electromagnet 100 is provided to permit insertion of the control rod assembly 21 from a withdrawn and latched position. The electromagnet 100 consists of two pole pieces 101 which are attached by welding to a nonmagnetic support tube 102 surrounding the upper cylindrical head cap 52 and resting on top of the seal plug 54. As can be seen most clearly in FIG. 9, the inner faces of the pole pieces 101 are machined to obtain a close fit with the head cap 52. A magnetic coil 103 is conventionally mounted to the pole pieces 101. A magnetic path to the latch 89 which is made of magnetic stainless steel or other suitable material, is completed by plugs 104 made of the same material. The plugs 104 may be threaded into the non-magnetic head cap 52 and may be pressure sealed by welding. When the coil 103 of the electromagnet 100 is energized, a magnetic force of sufficient magnitude is exerted on the latch 89 to disengage the latch mechanism 81 from the piston 45 permitting insertion by gravity of the associated control rod assembly 21. Position indicating electromagnets 110 and 111 are provided for each control rod assembly 21 to ascertain a withdrawn or inserted position, respectively. Electromagnets 110 and 111 are mounted to the non-magnetic support tube 102 in similar fashion as electromagnet 100. To ascertain the position of the piston 45 an AC signal is imposed on the coil of electromagnets 110 and 111. The presence or absence of the piston 45 in the vicinity of the electromagnets will change the AC coil current thereby indicating the position of the control rod assembly. For this purpose, it is necessary that the entire drive shaft 45 be made of a magnetic steel. With this arrangement, it is also possible to ascertain whether any control rod assembly 21 is stuck between its fully inserted end and fully withdrawn position and also which position it is in. Referring again to FIG. 4, it is to be noted that proper design dimensioning of the diametrical clearance between piston 45 and cylinder 56 at restriction 80 is necessary along with proper design dimensioning of a distance given the reference character X, in order to stop the upward piston movement short of impact with the latch 89 but still safely above the latched or engaged position. It will therefore be apparent that there has been disclosed nuclear reactor having drive mechanisms for control rod assemblies which are: capable of positively and mechanically holding a plurality of control rod assemblies in a fully withdrawn position; are capable of hydraulically decelerating a withdrawn control rod thereby preventing possible damage due to impact; and, are capable of positively controlling either a single control rod assembly or a plurality of control rod assemblies which are designed to be either completely inserted or completely withdrawn from a core of a nuclear reactor. Since numerous changes may be made in the above described apparatus, and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. |
053645685 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Thus, in a first embodiment, the present invention relates to a method of selectively isolating a particular metal from a complex reaction mixture by taking advantage of the selective nature of the reaction of an anion of formula (I): EQU [DA.sub.5 M.sub.30-x O.sub.110-x (M'L).sub.x ].sup.m- (I) wherein D is Na.sup.+, Ca.sup.-2 or an ion of similar size; M is w.sup.6+, W.sup.5+, or mixtures thereof; M' is any metallic element from groups 2 to 15 of the periodic table; L is O.sup.2-, OH.sup.-, H.sub.2 O or another suitable ligand, A is P, As, Sb, Si, Ge, or combinations thereof; x is 0-10; and m is the charge based on the valence states of the atoms, typically 10-20; with Z.sup.n+ to afford an anion of the formula (II): EQU [ZA.sub.5 M.sub.30-x O.sub.110-x (M'L).sub.x ].sup.(m+1-n)- (II) wherein Z=Sm, Eu, Gd, Tb, dy, Ho, Er, Tm, Yb, Lu, Y, or Bi, when n=3, and Z=Ce, Np, Pu, or Am, when N=4. In the above-given definition of formula (I), M' may be any metallic element from groups 2 to 15 of the periodic table. For the purposes of the present invention, such groups include the alkaline earth metals, the transition metals, and metals from groups IIIa, IVa, and Va of the main group. Preferred metals for M' include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sn, Nb, Ta, Mo, and combinations thereof. Particularly preferred metals for M' include Mo, V, Nb, Ta and combinations thereof. The choice of L will, in part, depend on the identity of M'. However, the identification and selection of the appropriate choice for L is within the abilities of one having ordinary skill in the art. In addition O.sup.2-, OH.sup.-, and H.sub.2 O, other suitable ligands include CN.sup.-, NH.sub.3, NH.sub.2 R, NHRR', NRR'R" (wherein R, R', and R" are each independently selected from the group consisting of C.sub.1-4 alkyl, phenyl, benzyl, and tolyl), CO, pyridine, C.sub.1-4 alkyl-substituted pyridine, C.sub.1-4 -alkyl, C.sub.6-12 aryl (including phenyl, biphenyl and naphthyl), C.sub.1-4 alkyl-substituted C.sub.6-12 aryl, and C.sub.7-20 aralkyl (including benzyl). Suitably, A is an element selected from the group consisting of P, As, Sb, Si, Ge, and combinations thereof It is preferred that A is P, As, or combinations thereof. It is particularly preferred that A is phosphorus. Preferably, the anion of formula (I) is [NaP.sub.5 W.sub.29 VO.sub.110 ].sup.16- (equal to [NaP.sub.5 W.sub.29 O.sub.109 (VO)].sup.-16) or [NP.sub.5 W.sub.30 O.sub.110 ].sup.14-. It is particularly preferred that the anion of formula (I) is [NaP.sub.5 W.sub.30 O.sub.110 ].sup.14 -. The metallate anion [NaP.sub.5 W.sub.30 O.sub.110 ].sup.14- is known as the Preyssler anion and will hereinafter sometimes be referred to as NaP.sub.5 W.sub.30. This particular anion may be synthesized as described in Jeanin, Y. et al, Inorg. Synth., 1990, 27, 115; or Preyssler, C., Bull. Soc. Chim, Fr., 1970, 30, both of which are incorporated herein by reference. The remaining anions of formula (I) may be prepared by a number of methods. In a first method, Preyssler's anion is treated with base by dropwise addition in an aqueous solution to obtain a solution having a pH of 10 to 12, preferably about 12. The addition of alkali is continued, at a rae such that the pH does not exceed 12 until about 12 equivalents of base have been added. Addition of saturated KCl yields a white precipitate which then is added to an aqueous solution containing 1 to 3 equivalents of M'L. The anion of formula (I) may be precipitated by the addition of saturated KCl. This method is exemplified for K.sub.6 Na.sub.10 [NaP.sub.5 W.sub.29 VO.sub.110 ].multidot.40H.sub.2 O in Alizadeh, M. H. et al, J. Am. Chem. Soc., 1985, 107, 2662, which is incorporated herein by reference. Other anions of formula (I) may be prepared by substituting various sources of M'L for the VOSO.sub.4 used in the above-referenced preparation. Suitable examples of M'L sources include TiCl.sub.4, Cr(NO.sub.3).sub.3, CoSO.sub.4, MnSO.sub.4, Fe(NO.sub.3).sub.3, Ni(NO.sub.3).sub.2, Cu(NO.sub.3).sub.2, Zn(NO.sub.3).sub.2, Ga(NO.sub.3).sub.3, GeCl.sub.4, K.sub.6 Ta.sub.6 O.sub.19, Na.sub.2 MoO.sub.4, KVO.sub.3, K.sub.7 HNb.sub.6 O.sub.19, and C.sub.6 H.sub.5 SnCl.sub.3. Preferred M'L sources include Na.sub.2 MoO.sub.4, KVO.sub.3, K.sub.7 HNb.sub.6 O.sub.19 and C.sub.6 H.sub.5 SnCl.sub.3. Alternatively, the anions of formula (I) may be prepared by carrying out the steps for the synthesis of Preyssler's anion described in the Examples, while replacing a portion of the Na.sub.2 WO.sub.4 .multidot.2H.sub.2 O used in the preparation of Preyssler's anion with a source of M'L. In this case, the suitable and preferred sources of M'L are the same as those described above. The selective encapsulation of Z.sup.n+ with the anion of formula (I) may be carried out as follows. Generally, the anion of formula (I) is contacted, in an aqueous solution, with Z.sup.n+. The order of addition is not critical. Thus, a solid salt containing the anion of formula (I) may be added to an aqueous solution of Z.sup.n+ or a solid containing Z.sup.n+ may be added to an aqueous solution containing the anion of formula (I). It is also possible to mix a solid containing Z.sup.n+ with a solid salt containing the anion of formula (I) and then dissolve them by adding water or an aqueous solution. The contacting of Z.sup.n+ with the anion formula (I) may be carried out over a wide range of conditions. Particularly good results have been obtained by carrying out the contacting step at a temperature of 120.degree. to 200.degree. C., preferably 140.degree. to 180.degree. C., for a time of 5 to 30 hrs, preferably 10 to 15 hrs. The pressure is not critical, and the contacting step may be carried out at atmospheric pressure, slightly reduced pressure, or even elevated pressures as high as 5 atm, preferably 1-2 atm. Although, the aqueous phase in which the anion of formula (I) and Z.sup.n+ are contacted may contain a variety of additional components, it is preferred that the pH of the aqueous phase be maintained within a range of 2 to 10, preferably 4 to 8, during the contacting step. After the contacting step is complete, the anion of formula (II) may be obtained in the form of an isolated salt by a number of methods. For example, addition of KCl to an aqueous solution will precipitate the anion of formula (II) in the form of the potassium salt. Other methods of isolating the anion of formula (II) include: (1) precipitation of other salts, e.g. Cs.sup.+, and NR.sub.4.sup.+ (especially R=Me, Et, n-Pr); (2) Extraction into organic solvent, e.g. toluene, hexane by means of phase transfer agent NR.sub.4.sup.+ ; R=C.sub.7 or greater. [general method described by Katsoulis and Pope, J. Am. Chem. Soc., 1984, 106 2737]; and (3) absorption on to anion exchange material. It should be understood that the present anions of formulae (I) and (II) may exist in the form of salts with a wide variety of one or more cations. The number of cations associated with the anions of formulae (I) or (II) will, of course, depend on the oxidation state of both the cations and anions. It should also be understood that, for any given encapsulation reaction as described above, the identity of the cations associated with the anion of formula (I) may differ from those associated with the anion of formula (II). Thus, it may be desired to start with a salt in which the cations are selected such that the anion of formula (I) is soluble in the aqueous phase under the contacting conditions and then add a salt containing cations that form an insoluble salt with the anion of formula (II) to precipitate the anion of formula (II) after the contacting step is complete. Examples of cations which form soluble salts with the anions of formula (I) include H.sup.+, Li.sup.+, Na.sup.+, K.sup.+, and NH.sub.4.sup.+. Cations which form insoluble salts with the anions of formula (I) include NMe.sub.4.sup.+, NEt.sub.4.sup.+, NPr.sub.4.sup.+, NMePh.sub.3.sup.30 , and Cs.sup.+. Although not intended to be limiting, the selective reaction of Z.sup.n+ with the anion of formula (I) will now be further illustrated by way of a detailed discussion of the reaction of Z.sup.n+ with NaP.sub.5 W.sub.30. A crystallographic investigation (Alizadeh, M. H. et al, J. Am. Chem. Soc., 1985, 107, 2662) of the so-called Preyssler anion revealed it to be [NaP.sub.5 W.sub.30 O.sub.110 ].sup.14- (NaP.sub.5 W.sub.30) and not [HP.sub.3 W.sub.18 O.sub.66 ].sup.8- as first assigned by Preyssler (Preyssler, C., Bull. Soc. Chim. Fr., 1970, 30). The anion has approximate D.sub.5h symmetry (see FIG. 1). It consists of five PW.sub.6 O.sub.22 units derived from the Keggin anion [PW.sub.12 O.sub.40 ].sup.3-, arranged in a crown so that the [NaP.sub.5 W.sub.30 O.sub.110 ].sup.14- anion has an unusual fivefold symmetry axis. The tungsten atoms are distributed in four parallel planes perpendicular to this axis. The two outer planes each contain five tungsten atoms and the two inner planes ten tungsten atoms. The structure leaves a cylindrical vacancy along the five-fold axis and the sodium ion is positioned in this vacancy, not in the center as might be expected, but in one of the inner oxygen planes so that it is coordinated to five oxygens in this plane and to five in an outer oxygen plane at a larger distance, see FIG. 2. The structure explained previously-recorded .sup.31 P NMP (Massart, R. et al, Inorg. Chem., 1977, 16 2916) which showed a single line for the five equivalent phosphorus atoms, and .sup.183 W NMR (Acerete, R. et al, Inorg. Chem., 1984, 23 1478) which gave four lines in a 2:2:1:1 ratio as expected from the dissymmetry introduced by the sodium ion. Sodium-23 NMR showed separate signals for internal and free cationic Na.sup.+ (Alizadeh, M. H. et al, J. Am. Chem. Soc., 1985, 107 2662). The sodium ion was very tightly bound but could apparently be replaced under severe experimental conditions (heating in aqueous solution at 120.degree. C. in a bomb) by Ca.sup.2+, which has a similar radius (1.14 .ANG.) (The "ionic radius" of a cation is known to depend upon its coordination number. In order to compare sizes of the different cations discussed in this application, the inventors have chosen the set of effective ionic radii of Shannon an Prewitt [Acta Crystallogr., 1976, A32, 751] appropriate for six-fold coordination by oxide. The effective coordination number of the central atom in P.sub.5 W.sub.30 is larger than six, of course, but sufficient reliable data are not available for larger coordination numbers) to Na.sup.+ (1.16 .ANG.) (Alizadeh, M. H. et al, J. Am. Chem. Soc., 1985, 107, 2662). The ionic radii of the trivalent lanthanides (Ln) (r=1.17 to 1.00 .ANG.) are similar to those of Na.sup.+ and Ca.sup.2+, and Ln.sup.3+ ions are often used to replace Ca.sup.2+ in complexes in biological studies. Because of their higher charge the lanthanide complexes would be expected to be even more stable than those of Na.sup.+ and Ca.sup.2+. The reaction between Ca.sup.2+ and NaP.sub.5 W.sub.30 has been shown (Alizadeh, M. H. et al, J. Am. Chem. Soc., 1985, 107, 2662) to be accompanied by the appearance of Na.sup.+ in the solution as measured with a sodium electrode, leading to the conclusion that Ca.sup.2+ had replaced Na.sup.+ in the cavity of the heteropolyanion. By reacting a neutral or slightly acid aqueous solution of K.sub.12.5 Na.sub.1.5 [[NaP.sub.5 W.sub.30 O.sub.110 ] at 145.degree.-180.degree. C. with 1-2 equivalents of a variety of lanthanide and other metal ions having radii similar to that of Na.sup.+, products were obtained which contained the reacting cations and which were characterized by cyclic voltammograms and .sup.31 P-NMR spectra that differed from that of NaP.sub.5 W.sub.30, see below. The yields varied with the metal ion and temperature and are summarized in Table 1. TABLE 1 ______________________________________ Conditions and Yields for Preparation of [ZP.sub.5 W.sub.30 O.sub.110 ]: Z.sup.n+ T/.degree.C. % yield ______________________________________ Sm.sup.3+ 160 90 Eu.sup.3+ 145-165 45-90 Gd.sup.3+ 145 90 Tb.sup.3+ 145 90 Dy.sup.3+ 160 90 Ho.sup.3+ 160 90 Er.sup.3+ 160 90 Tm.sup.3+ 160 90 Yb.sup.3+ 160-180 50-70 Lu.sup.3+ 180 40 Ce.sup.4+ 160 50 Y.sup.3+ 160 90 Bi.sup.3+ 160 90 U.sup.4+ 160 30 Ca.sup.2+ 140 90 ______________________________________ [NaP.sub.5 W.sub.30 O.sub.110 ].sup.14- + Z.sup.n+ .fwdarw. [ZP.sub.5 W.sub.30 O.sub.110 ].sup.(15-n)- + C[NaP.sub.5 W.sub.30 ] = 8.0 mM, C.sub.Zn+ = 8-16 mM While Gd.sup.3+ and Tb.sup.3+ reacted practically quantitatively at 145.degree. C., Eu.sup.3+ reacted only partly at this temperature but almost quantitatively at 165.degree. C. The smaller lanthanide ions Yb.sup.3+ and Lu.sup.3+ required still higher temperatures and reacted only partly even at 180.degree. C. All lanthanide ions with ionic radii smaller or equal to that of Sm.sup.3+ (r=1.10 .ANG.) were found to react with NaP.sub.5 W.sub.30, but no reaction was observed for the larger lanthanide ions Nd.sup.3+ (r=1.12 .ANG.), Pr.sup.3+ (r=1.13 .ANG.) and Ce.sup.3+ (r=1.15 .ANG.) even at temperatures up to 180.degree. C. Assuming that the cations have replaced Na.sup.+ in the central cavity, this behavior indicates an extraordinary and unprecedented size selectivity. Although Sm.sup.3+ and Nd.sub.3+ differ in ionic radius by only 0.02 .ANG., Sm.sup.3+ readily entered the heteropolyanion, but no detectable reaction took place with the larger cations. In contrast, other lanthanide-containing heteropolyanions such as [ln(PW.sub.11 O.sub.39).sub.2 ].sup.11- and [Ln(SiW.sub.11 O.sub.39).sub.2 ].sup.13- can be made with all lanthanide ions (Peacock, R. D. et al, J. Chem. Soc. (A), 1971, 1836; and Fedotov, M. A. et al, Polyhedron, 1990, 9, 1249). Although not intended to be limiting, a possible explanation for the dramatic size selectivity of P.sub.5 W.sub.30 O.sub.110 as compared to [Ln(PW.sub.11 O.sub.39).sub.2 ].sup.11- and [Ln(SiW.sub.11 O.sub.39).sub.2].sup.13- may be that the latter complexes are more flexible with the lanthanide ions sandwiched between to lacunary heteropolyanion ligands, while in the P.sub.5 W.sub.30 W.sub.110 heteropolyanion the size of the central cation is restricted by the diameter of the cavity which may not have the flexibility to expand beyond a certain well defined size. The sudden cut-off between Sm.sup.3+ and Nd.sup.3+ is still surprising considering the capability of the lanthanide ions to adopt to a variety of coordination numbers with different effective ionic radii. At the other end of the lanthanide series, Yb.sup.3+ (r=1.01 .ANG.) and Lu.sup.3+ (r=1.00 .ANG.) with the smallest ionic radii replaced Na.sup.+ only partly. A possible, but not limiting explanation for this result is that these ions are too small to compete effectively with Na.sup.+. The smaller yields with Ce.sup.4+ and U.sub.4+ were partly due to the low solubility of the tetravalent cations with the heteropolyanion necessitating using lower concentrations of cations (<1 equivalent compared to two equivalents for the other metal ions). Not only did Ce.sup.3+ not react with NaP.sub.5 W.sub.30 as mentioned above, but no reduction could be observed of Ce.sup.IV P.sub.5 W.sub.30 in aqueous solution (see below) further illustrating the point that Ce.sup.3+ might be too large for the cavity. While ease of substitution of Na.sup.30 by lanthanide ions seems to follow the size of their ionic radii strictly, substitution by other metal ions of similar size did not always proceed as expected. For example, Y.sup.3+ (r=1.04 .ANG.), U.sup.4+ (r=1.03 .ANG.), Bi.sup.3+ (r=1.17 .ANG.), and Ce.sup.4+ (r=1.01 .ANG.) did react, but other metal ions with similar radii such as Ce.sup.2+ (r=1.09 .ANG.), Tl.sup.3+ (r=1.03 .ANG.), Sn.sup.2+, Hg.sup.2+ (r=1.16 .ANG.), and Th.sup.4+ (r=1.08 .ANG.) did not, under the same conditions. The fact that Cd.sup.2+ did not react is especially surprising as the similarly sized Ca.sup.2+ reacted readily. It is certainly possible that sterochemical (Hg.sup.2+, Sn.sup.2+) and "hard-soft" preferences might also contribute to reactivity - the polyanion cavity is lined with "hard" oxide ions. The ZP.sub.5 W.sub.30 ions were stable in aqueous solution for at least 3 weeks in 1 M HCl at 25.degree. C., but a slow decomposition ([XP.sub.5 W.sub.30 O.sub.110 ].sup.(15-n)- .fwdarw.WO.sub.4.sup.2-, HPO.sub.4.sup.2-, Z.sup.n+) took place at pH 9-10 with a halflife of about 2 days in a pH 10, 0.025 M borax buffer and several weeks at pH 9, as measured voltammetrically with GdP.sub.5 W.sub.30 using a supporting electrolyte of 1 M Na.sub.2 SO.sub.4. When a solution containing EuP.sub.5 W.sub.30 in 1 M NaCl was heated at 160.degree. C. for 24 h, no detectable amount of NaP.sub.5 W.sub.30 was observed although LuP.sub.5 W.sub.30 under the same conditions gave mostly NaP.sub.5 W.sub.30. These observations combined with the yields in the preparations of ZP.sub.5 W.sub.30 (Table 1) show increased stability of LnP.sub.5 W.sub.30 over NaP.sub.5 W.sub.30, as expected from the more highly charged Ln.sup.3+ ions, and that LuP.sub.5 W.sub.30 is less stable than EuP.sub.5 W.sub.30. This was further shown by the observation that Eu.sup.3+ replaced ca 85% of Lu.sup.3+ in LuP.sub.5 W.sub.30 when a 2:1 mixture was heated at 160.degree. C. for 20 hr. The observation that different Ln.sup.3+ ions reacted with NaP.sub.5 W.sub.30 with different efficiency suggested that NaP.sub.5 W.sub.30 might be used to separate mixtures of lanthanides. To test this notion some competition experiments were performed in which mixtures of two Ln.sup.3+ ions and NaP.sub.5 W.sub.30 in 1:1:1 ratio were heated at 160.degree. C. for 20 hr and the products examined by .sup.31 P NMR of the reaction mixture. Solutions containing Sm.sup.3+ and the smaller Yb.sup.3+ gave only SmP.sub.5 W.sub.30 as product, while the neighboring Sm.sup.3+ and Eu.sup.3+ reacted to give a mixture of SmP.sub.5 W.sub.30 and EuP.sub.5 W.sub.30 in a 1:4 ratio. When mixtures of Eu.sup.3+ and Tb.sup.3+ were used EuP.sub.5 W.sub.30 was the only product. It thus appears that NaP.sub.5 W.sub.30 efficiently separates smaller Ln.sup.3+ ions from larger ones and preferentially reacts with Eu.sup.3+ rather than Sm.sup.3+. Once incorporated in the heteropolyanion the free Ln.sup.3+ ions can be recovered by basic hydrolysis. IR Spectroscopy The IR spectra of all the products were practically identical and differed only slightly from the parent NaP.sub.5 W.sub.30 heteropolyanion; the only consistent differences being in the position and size of one of the P-O stretching bands (1073 cm.sup.-1 (m) for NaP.sub.5 W.sub.30 and 1060 cm.sup.-` (s) for ZP.sub.5 W.sub.30) and a better resolved peak at 980 cm.sup.-1 for NaP.sub.5 W.sub.30. The splitting of the 1160 cm.sup.-1 P-O stretching band reported (Alizadeh, M. H. et al, J. Am. Chem. Soc., 1985, 107, 2662) for CAP.sub.5 W.sub.30 was not seen and may have been due to an impurity or artifact in the earlier spectrum. NMR Spectroscopy In the .sup.23 Na NMR spectrum of NaP.sub.5 W.sub.30 it was found that the coordinated sodium ion gave rise to a broad line at a slightly different frequency from that of the free sodium ion (Alizadeh, M. H. et al, J. Am. Chem. Soc., 1985, 107, 2662). In order to test whether Na.sup.+ had indeed been replaced by the reacting cations in the ZP.sub.5 W.sub.30 complexes .sup.23 Na NMR spectra of the acid (more soluble) forms of YP.sub.5 W.sub.30 and NaP.sub.5 W.sub.30 were attempted using the same conditions of concentration and instrumentation. The Y.sup.3+ complex was chosen because it is diamagnetic so that no significant shift from NaP.sub.5 W.sub.30 or line broadening would be expected if Na.sup.+ were still coordinated. No Na resonances were observed for YP.sub.5 W.sub.30 supporting the notion that the observed reaction is indeed a displacement of Na.sup.+ by the reacting cations and not attachment at another site of the heteropolyanion. The .sup.31 P NMR chemical shifts of ZP.sub.5 W.sub.30 are shown in Table 2. TABLE 2 ______________________________________ .sup.31 P NMR spectra of ZP.sub.5 W.sub.30 Z.sup.n+ .delta./ppm .DELTA.v.sub.1/2 /Hz LIS.sub.obs.sup.a ______________________________________ Sm -9.5 4.6 +0.6 Eu 0.7 5.0 +10.8 Gd -- -- -- Tb -27.2 175 -17.1 Dy -68.1 241 -58.0 Ho -40.0 222 -29.9 Er 1.8 151 +11.9 Tm 17.6 68 +27.7 Yb 9.1 16 +19.2 Lu -10.1 -- Y -10.2(d).sup.b Bi -8.2 Ce -16.0 4.5 U -15.5 5.5 Na -9.4 Ca -11.1 ______________________________________ .sup.a Lanthanide induced shift, .delta.(Ln) - .delta.(Lu) .sup.b J(P--O--Y) = 1.6 Hz A single .sup.31 P line was observed for all complexes except for YP.sub.5 W.sub.30 which gave a doublet with a coupling constant of 1.6 Hz. These data confirm that all the phosphorus atoms are equivalent (as expected) in ZP.sub.5 W.sub.30, the doublet in YP.sub.5 W.sub.30 presumably being due to splitting caused by .sup.89 Y (100%, I=178 ). .sup.31 P NMR spectra of the ZP.sub.5 W.sub.30 ions (Table 2) gave shifts for diamagnetic Z.sup.3+ ions of -8.2 to -10.2 ppm; for NaP.sub.5 W.sub.30 -9.4 ppm; for CaP.sub.5 W.sub.30 -11.1 ppm; for CeP.sub.5 W.sub.30 -16 ppm; and for UP.sub.5 W.sub.30 -15.5 ppm. For the paramagnetic Ln.sup.3+ ions the shifts varied from +18 to -68 ppm and widths varied from 5-240 Hz except for GdP.sub.5 W.sub.30 which gave no observable spectrum. Some of the lanthanides induced shifts to higher frequency, others to lower frequency, as was also observed for [LN(PW.sub.11 O.sub.39).sub.2 ].sup.11- (Fedotov, M. A. et al, Polyhedron, 1990, 9, 1249). The lanthanide induced shifts, LIS.sub.obs, were taken as the observed shifts for LnP.sub.5 W.sub.30 minus the observed shift for LuP.sub.5 W.sub.30. LIS.sub.OBS are known (Sherry, A. D. et al, Lanthanide Probes in Life, Chemical and Earth Sciences, Bunzli and Choppin, Eds., Elsevier, 1989, and references therein; Bleaney, B., J. Magn. Res., 1972, 8, 91; and Golding, R. M. et al, Aust. J. Chem., 1972, 25, 2577) to be expressed as a sum of the pseudo-contact (dipolar, through-space) shift, LIS.sub.pc, and the contact (scalar, through-bonds) shift, LIS.sub.c. ##EQU1## where C.sub.j =g.sup.2 J(J+1)(2J-1)(2J+3)<J.vertline.a.vertline.J> and r, .theta., .angle. are spherical coordinates of the observed nucleus (P) with respect to the lanthanide, .beta. is the Bohr magneton, A is the electron-nuclear hyperfine coupling constant, .gamma. is the magnetogyric ratio, <r.sup.2 >2A.sub.2.sup.0 and <r.sup.2 >A.sub.2.sup.2 are ligand field terms, and the other symbols have their usual significance. Values of C.sub.j which determine shifts to higher or lower frequency, have been calculated by Bleaney (Bleaney, B., J. Magn. Res., 1972, 8, 91) for each lanthanide ion. The spin expectation values <S.sub.z > are tabulated by Golding and Halton (Golding, R. M. et al, Aust. J. Chem., 1972, 25, 2577). According to equations (Ia) and (Ib) a plot of the measured LIS.sub.obs values versus Bleaney's C.sub.j values should be linear if the origin of the shift is purely pseudo-contact and the complexes are isostructural. Deviation from linearity indicates that the measured LIS.sub.obs values are not purely pseudo-contact. Similarly a linear plot of LIS.sub.obs versus <S.sub.Z > would be expected for purely contact shifts. It has been suggested (Horrocks, W., in NMR of Paramagnetic Molecules, LaMar et al, eds., Academic Press, New York, 1973, p. 479) that isotropic shifts of nuclei four or more bonds removed from the lanthanide may be considered exclusively pseudo-contact in origin. In [Ln(PW.sub.11 O.sub.39).sub.2 ].sup.11- the phosphorus atom is four bonds away from Ln, and the LIS dependence found to be appreciably if not predominantly pseudo-contact by comparison of c.sub.j and LIS.sub.obs values (Fedotov, M. A. et al, Polyhedron, 1990, 9. 1249). The observed deviation from linearity in that case was ascribed to structural changes of the heteropolyanion as the lanthanide varied. In the present series of LnP.sub.5 W.sub.30 O.sub.110, the lanthanide is separated from the phosphorus atoms by only two bonds. A plot of LIS.sub.obs versus c.sub.j showed a fairly good linear dependence (r.sup.2 =0.96) with only TbP.sub.5 W.sub.30 deviating from the line. A plot of LIS.sub.obs versus <S.sub.Z > showed mainly scattering. It thus seems that the pseudo-contact term predominates for LnP.sub.5 W.sub.30 O.sub.110 as well, even if the distance between Ln.sup.3+ and P is only two bonds. Rewriting equations (Ia)+(Ib) as LIS.sub.obs =GC.sub.j +F<S.sub.Z > or LIS.sub.obs /<S.sub.Z >=G(C.sub.j /<S.sub.Z >)+F allows one to determine G and F graphically, and to alculate the pseudo-contact contribution to LIS.sub.obs (Reilley C. N. et al, Anal. Chem., 1976, 48, 1446). A plot of LIS.sub.obs /<S.sub.Z > versus C.sub.j /<S.sub.Z > gave a fairly linear plot (r.sup.2 =0.91) with G=0.67 and F=0.32. The fraction of LIS that may be ascribed to a pseudo-contact contribution may be estimated from .vertline.GC.sub.j .vertline./(.vertline.F<S.sub.Z >.vertline.+.vertline.GC.sub.j .vertline.). Values ranging from 78-96% pseudo-contact were calculated for the coordinated lanthanide ions except for Eu.sup.3+ which gave 44%. The LIS of the samarium derivative was too small to be evaluated accurately and the Gd complex should only have a contact shift, if it could have been observed. It is not inconceivable that some minor structural changes occur along the lanthanide-heteropolyanion series due to the differences in ionic radius of Ln.sup.3+, but no obvious pattern was evident. The .sup.183 W NMR spectrum of EuP.sub.5 P.sub.5 W.sub.30 gave four lines at 62.5 ppm (d, 5W, It is another object of the present invention to .sup.2 J.sub.P-O-W =3.8 Hz), -201.7 ppm (s, 10W), =31 209.5 ppm (s, 10W), and -297.5 ppm (d, 5W, .sup.2 J.sub.P-O-W =1.9 Hz) with an intensity ratio of 1:2:2:1. This spectrum is comparable to that of NaP.sub.5 W.sub.30 which consists of four lines at -209.6 ppm (d, 10W, .sup.2 J.sub.P-O-W =1.25 Hz), -211.6 ppm (d, 10W, .sup.2 J.sub.P-O-W =1.28 Hz), -277.25 ppm (d, 5W, .sup.2 J.sub.P-O-W =1.27 Hz), and -289.6 ppm (d, 5W,.sup.2 J.sub.P-O-W =1.32 Hz. The major difference between the two .sup.183 W NMR spectra is in the downfield shift of one of the 5W lines by ca 350 ppm. In the [LN(PW.sub.11 O.sub.39).sub.2 ] series it was observed that only resonances for the tungsten atoms that were two bonds away from the paramagnetic ion were shifted significantly in comparison to the diamagnetic analogs (Fedotov, M. A. et al, Polyhedron, 1990, 9 1249). The observation that the .sup.183 W spectrum of EuP.sub.5 W.sub.30 displays the same pattern as that of NaP.sub.5 W.sub.30 with only one of the 5W lines displaced significantly to a different frequency confirms that Eu.sup.3+ has replaced Na.sup.30 and occupies a similar site in the complex as did Na.sup.+, being closer to one of the outer 5-tungsten planes than to the other (see FIG. 2). Al illustrated in FIG. 3, the sodium in NaP.sub.5 W.sub.30 is connected to tungsten in the closest outer plan via oxygen atoms which are 2.66 .ANG. from the metal ion, while the Na-O distance in Na-O-W to the other outer ring was 3.64 .ANG.. Tungstens in the inner 10-tungsten rings are four bonds removed from the central ion, and by comparison to Ln(PW.sub.11 O.sub.39).sub.2 would not be expected to be strongly shifted by a paramagnetic species. Electrochemistry As for the parent NaP.sub.5 W.sub.30, several reduction steps to heteropoly blue species were observed for ZP.sub.5 W.sub.30. In 1 M HCl there are five essentially reversible two-electron reduction steps (.DELTA.=30-40 mV) for all ZP.sub.5 W.sub.30 anions down to -600 mV except for EuP.sub.5 W.sub.30 and CaP.sub.5 W.sub.30 which showed only four reduction steps, as shown in Table 3. TABLE 3 ______________________________________ Voltammetric Reduction Potentials.sup.a for [ZP.sub.5 W.sub.30 O.sub.110 ].sup.n- Z.sup.n+ E/V vs Ag/AgCl ______________________________________ Sm.sup.3+ -0.11 -0.20 -0.32 -0.40 -0.40 Et.sup.3+ -0.12 -0.22 -0.32.sup.b -0.49 Gd.sup.3+ -0.11 -0.21 -0.33 -0.41 -0.49 Tb.sup.3+ -0.10 -0.20 -0.32 -0.41 -0.48 DY.sup.3+ -0.12 -0.21 -0.34 -0.41 -0.50 Ho.sup.3+ -0.12 -0.21 -0.32 -0.41 -0.50 Er.sup.3+ -0.11 -0.20 -0.32 -0.40 -0.49 Tm.sup.3+ -0.10 -0.20 -0.31 -0.39 -0.49 Yb.sup.3+ -0.13 -0.22 -0.34 -0.41 -0.50 Lu.sup.3+ -0.10 -0.20 -0.31 -0.38 -0.49 Y.sup.3+ -0.11 -0.20 -0.32 -0.40 -0.49 Bi.sup.3+ -0.11 -0.19 -0.27 -0.34 -0.45 Ce.sup.4+ -0.10 -0.20 -0.31 -0.39 -0.46 U.sup.4+ -0.08 -0.18 -0.32 -0.46 -0.53 Na.sup.+ -0.18.sup.b -0.30.sup.b -0.52 Ca.sup.2+ -0.16 -0.21 -0.33.sup.b -0.49 ______________________________________ .sup.a 1/2(E.sub.pc + E.sub.pa), 1.0M HCl; All are 2electron steps except where noted .sup.b 4electron step This pattern contrasts with that of NaP.sub.5 W.sub.30 under the same conditions, which showed two reduction steps of four electrons each at -0.18 and -0.30 V and one additional multielectron step at -0.52 V (see FIG. 4). It thus appears that the first two reduction steps of the NaP.sub.5 W.sub.30 ion have split into four two electron steps in the ZP.sub.5 W.sub.30 ions, (except for EuP.sub.5 W.sub.30 and CaP.sub.5 W.sub.30, where only the first step was split). At higher pH, further splitting of the reduction steps occurs, as is commonly observed for other heteropolyanions (Pope, M. T., Heteropoly and Isopoly Oxometalates, Springer-Verlag, New York, 1983) and is attributed to the deprotonation of the reduced species. At pH 5-10 eight reductions were observed between 0 and -1400 mV for most ZP.sub.5 W.sub.30, the first two reductions involving one-electron processes, see FIG. 4. While the one-electron steps were nearly reversible (.DELTA.E.about.60 mV), the others were less so (.DELTA.E varied from 80 to 160 mV). No oxidations or reductions of the central cation were observed for any ZP.sub.5 W.sub.30 in aqueous solution, which is surprising. Heteropolyanions are known (Ortega, F. et al, Inorg. Chem., 1984, 23 3292) to stabilize higher oxidation states of coordinated metal ions probably because of the high negative charges of the polyanion. A reversible U.sup.4+/5+ oxidation step has been observed (Termes, S. C. et al, Trans. Met. Chem., 1978, 3 103) at +0.94 V vs SCE (+0.96 V vs Ag/AgCl) for [U.sup.IV (PW.sub.11 O.sub.39).sub.2 ].sup.10- in 1 M H.sub.2 SO.sub.4. No such step was observed for the present UP.sub.5 W.sub.30 at potentials as high as +1.8 V vs Ag/AgCl. The question arises as to whether the isolated CeP.sub.5 W.sub.30 contains Ce(III) or Ce(IV). No Ce(IV/III) CV reduction waves were observed between +1.8 and -0.1 V. Between -0.1 and -1.4 V several W(VI/V) waves appear, but this part of the cyclic voltammogram was identical to those of other LnP.sub.5 W.sub.30. Also an attempted controlled potential electrolysis at +0.1 V in a 1 M HCl solution showed no evidence of reduction. Ce(IV) compounds are generally known to be strong oxidants (E.degree..sub.Ce(IV/III) =+1.44 V (vs NHE) om 1 M H.sub.2 SO.sub.4) and several Ce(IV) heteropolyanions, such as [CeW.sub.10 O.sub.36 ].sup.8-, [Ce(SiW.sub.11 O.sub.39).sub.2 ].sup.12-, [Ce(PW.sub.11 O.sub.39).sub.2 ].sup.10-, [Ce(P.sub.2 W.sub.17 O.sub.61).sub.2].sup.16- have measured Ce(III/IV) redox potentials of +1.1 to +0.8 V.sup.17. Although most Ce(III) compounds are colorless, the Ce(III) heteropolyanions are light brown due to Ce.sup.III .fwdarw.W.sup.VI charge transfer. That the present light yellow CeP.sub.5 W.sub.30 complex is indeed a Ce(IV) compound is thus not evident from its colory only. The .sup.31 p NMR spectrum shows a fairly small downfield shift (5 ppm) from the diamagnetic LuP.sub.5 W.sub.30. This shift is similar in magnitude to the shift observed for paramagnetic [Ce.sup.III (PW.sub.11 O.sub.39).sub.2 ].sup.11- and is also similar to the .sup.31 P chemical shift of UP.sub.5 W.sub.30 which has two unpaired electrons. However, these shifts are relatively small so .sup.31 p NMR does not solve the question of the oxidation state of cerium in CeP.sub.5 W.sub.30. The most compelling evidence for Ce.sup.IV P.sub.5 W.sub.30 comes from its method of preparation. Cerium(III) did not react with NaP.sub.5 W.sub.30 while Ce(IV) did so readily. Indeed by comparison with the other lanthanide ions Ce(III) (r=1.15 .ANG.)should be too big to enter the heteropolyanion while Ce(IV) (r=1.01 .ANG.) has the right size. That no reduction of Ce(IV)P.sub.5 W.sub.30 was observed down to -1.4 V shows an extraordinary stabilization of the Ce(IV) oxidation state by the P.sub.5 W.sub.30 O.sub.110 anion, a stabilization which seems likely to b due to the inability of the ligand to expand its cavity to accommodate the larger Ce(III) ion. ESR Spectroscopy The room temperature X-brand ESR spectrum of GdP.sub.5 W.sub.30, recorded on a polycrystalline sample of GdP.sub.5 W.sub.30, diluted 1:2 in a TbP.sub.5 W.sub.30 matrix, is shown in FIG. 5. The spectrum arises from transitions between the four Kramers doublets of the .sup.8 S.sub.7/2 ground state of Gd(III) (Stephens, E. M., In Lanthanide Probes in Life, Chemical and Earth Sciences, Bunzli and Choppin eds., Elsevier, 1989, and references therein). When the zero-field splitting is small as is the case here, seven allowed transitions are observed at each orientation of the crystal. The powder spectrum represents the sum of individual spectra of all possible orientations. A spectrum recorded at 77.degree. K showed no additional features. Electronic spectroscopy All ZP.sub.5 W.sub.30 complexes absorb strongly in the UV. The low intensity electronic absorption spectrum of UP.sub.5 W.sub.30 is shown in FIG. 6. It is broadly similar, but not identical, to that of [U(IV)Mo.sub.12 O.sub.42 ].sup.8- (Reilley, C. N. et al, anal, Chem., 1976, 48 1446). A concentrated solution of EuP.sub.5 W.sub.30 showed weak absorbances at 464 nm (.sup.7 F.sub.0 .fwdarw..sup.5 D.sub.2) and 525 nm (.sup.7 F.sub.0 .fwdarw..sup.5 D.sub.1). Intense polytungstate absorption below 400 nm obscured further Eu bands. Emission Spectroscopy Excitation of a ca 0.2 M aqueous solution of H.sub.12 [EuP.sub.5 W.sub.30 O.sub.110 ] into the 464.7 nm Eu.sup.3+ absorption line at 30.degree. C. gave the emission spectrum presented in FIG. 7. The spectrum shows broad bands at positions characteristic for EU.sup.3+ luminescence arising from transitions .sup.5 D.sub.0 .fwdarw..sup.7 F.sub.j. The strongest emissions are in the .sup.5 D.sub.0 .fwdarw..sup.7 F.sub.1 and .sup.7 F.sub.3 transition is weak and the .sup.5 D.sub.0 .fwdarw..sup.7 F.sub.0 is either absent or obscured by the .sup.5 D.sub.0 .fwdarw..sup.7 F.sub.1 band. The poor resolution of the bands does not allow any detailed analysis of the symmetry and structural nature of the Eu.sup.3+ coordination site (Gallagher, P. K. J. Chem. Phys., 1964, 41 3061). No emission was observed from solid powdered samples at room temperature or at 0.degree. C. In this respect it resembles K.sub.17 Eu(P.sub.2 W.sub.17 O.sub.61).sub.2 (Blasse, G., et al, J. Inorg. Nucl. Chem., 1981, 43, 2847. Relaxation Studies Labile Gd.sup.3+ complexes with inner sphere coordinated water are known to effectively catalyze the proton relaxation of water. A measure of this effect is the relaxativity, R, which is obtained as the slope of T.sub.1.sup.-1 versus concentration of the Gd complex. The relaxivity is dependent on the hydration number so that for [Gd(H.sub.2 O).sub.8-9 ].sup.3+, R=9.1 mM s.sup.-1 measured at 20 and 90 MHz, for [Gd(H.sub.2 O).sub.2-3 [.sup.3+, R=4.6 mM S.sup.-1 (90 MHz) and for [Gd(H.sub.2 O).sub.ca0 ].sup.3+ R=2.0 mM S.sup.-1 (20 MHz) (Laufler, R. B., Chem. Rev., 1987, 87, 901). One way to determine whether Gd.sup.3+ is indeed situated in the cavity of the P.sub.5 W.sub.30 heteropolyanion where it would have no possibility to be coordinated by water, is to measure its relaxativity. At 21.degree. C. a preliminary value of ca 1.0 mM s.sup.-1 was obtained at 300 MHz using an inversion-recovery sequence. Relaxativities are frequency dependent, but the very low value found seems to confirm that Gd.sup.3+ in GdP.sub.5 W.sub.30 does not have the ability to exchange coordinated water with bulk water and is indeed situated in the cavity. Thus, it has proven possible to replace Na.sup.+ in the stable [NaP.sub.5 W.sub.30 O.sub.110 ].sup.14- with various (but not all) lanthanide and other metal ions having similar ionic radii to that of Na.sup.+. That the observed reactions were actual substitution reactions of Na.sup.+ and not substitution of the metal ions at another site of the heteropolyanion has been shown by a variety of techniques. The lanthanide ions react with different efficiency; the medium sized ions are the most reactive, the smallest react with difficulty, and the largest, Nd.sup.3+, Pr.sup.3+, and Ce.sup.3+, not at all. The difference in reactivity proves useful in separating mixtures of lanthanides. Cerium(IV) reacts readily, but the product could not be reduced to Ce.sup.III P.sub.5 W.sub.30 at potentials more positive than -1.4 V, probably because the cavity in the heteropolyanion is too small to accommodate the larger Ce(III) ion. This is an unprecedented large stabilization of a Ce(IV) compound. Despite the large negative charge on [UP.sub.5 W.sub.30 O.sub.110 ].sup.11- no oxidation of U(IV)P.sub.5 W.sub.30 to U(V)P.sub.5 W.sub.30 is observed. While it is conceivable that the cavity cannot expand to hold the larger Ce(III) ion, it is not clear why a smaller U(V) ion cannot be generated, as it has been observed in other heteropolyanions of similar charge. The complexes exhibited extraordinary stability towards hydrolysis for heteropolyanions, covering a range from 6 M HCl to pH 9-10. The present method of encapsulation is particularly useful for the separation of radioactive lanthanides from the aqueous phase obtained after the leaching step in the reprocessing of nuclear fuel. In this case, the anion of formula (I) is added, either in the form of a solid salt or a salt dissolved in water or an aqueous solution, to an aqueous phase obtained by leaching spent nuclear fuel with HNO.sub.3. Preferably the pH of the aqueous phase is adjusted to 2 to 10, most preferably 4 to 8, before the addition of the anion of formula (I). The present method is also particularly useful for the separation, purification, and encapsulation for long-term storage of U, Np, Pu, and Am from fission products. In this embodiment the actinides, U, Np, Pu, and Am, will not be bound by the anion of formula (I) so long as they are not in the '4 oxidation state. Conveniently, the actinides may be selectively oxidized to MO.sub.x.sup.2+ by oxidizing agents such as Cl.sub.2, K.sub.2 Cr.sub.2 O.sub.7, HClO.sub.4, K.sub.2 S.sub.2 O.sub.8, as described in Fahey, J. A., The Chemistry of the Actinide Elements, Katz, J. J., Seaborg, G. T., and Morss, L. R., eds., 2nd ed., Chapman and Hall, New York, 1986, vol.1, pp. 443-498; and Weigl, F., Katz, J. J., and Seaborg, G. T., ibid, pp. 499-886. After removal of the lanthanide complexes, the actinides may be selectively reduced to the +4 oxidation state with reagents such as Fe.sup.2+, Zn, I.sup.-, NO.sub.2.sup.- as described in Fahey, J. A., The Chemistry of the Actinide Elements, Katz, J. J., Seaborg, G. T., and Morss, L. R., eds., 2nd ed., Chapman and Hall, New York, 1986, vol.1, pp. 4443-498; and Weigl, F., Katz, J. J., and Seaborg, G. T., ibid, pp. 499-886. In fact, as described in Fahey, J. A., The Chemistry of the Actinide Elements, Katz, J. J., Seaborg, G. T., and Morss, L. R., eds., 2nd ed., Chapman and Hall, New York, 1986, vol.1, pp. 443-498; Weigl, F., Katz, J. J.; and Seaborg, G. T., ibid, pp. 499-886; and Ryberg, J. and Sillen, L. G., Acta Chem. Scand., 1955, 9, 1241, it is possible to arrange conditions such that only one of U, Np, Pu, and Am is in the +4 oxidation state. Once the actinide(s) are in the +4 oxidation state they may be separated by the addition of the anion of formula (I), as described above. In many cases, it will be desired to vitrify the salt containing the anion of formula (II) to obtain a glass suitable for long term storage of the radioactive lanthanide or actinide. Such vitrification procedures are well known by those skilled in the art. Typically, a salt containing an anion of formula (II) is heated to a temperature of 1000.degree. to 1200.degree. C., for a time of 2 to 4 hrs. It may be preferred to add certain additional ingredients to the salt containing the anion of formula (II) prior to the vitrification step to adjust the properties of the resulting glass. Such additional ingredients include, for example, silica and borax. The glass prepared as described above may then be placed in stainless steel or ceramic containers prior to storage. Additional layers of materials such as lead, titanium, copper, gold, graphite, ceramics, etc. may be added before storage. The methods of encapsulating glasses containing radioactive wastes prior to long term storage are reviewed in G. R. Choppin and J. Rydberg, Nuclear Chemistry, Pergamon, Oxford, pp. 502-559, 1980, which is incorporated herein by reference. Alternatively, it is also possible to convert the salt containing the anion of formula (II) to a mixed valence tungsten"bronze" material by reduction with, e.g., hydrogen. Such tungsten "bronze" materials are stable enough for long-term storage even without vitrification. These tungsten "bronze" materials may be prepared by the procedures described in Nikitina, E. A.; Kokurina, A. S., Zh. Obshch. Khim, 1950, 20, 1380; 1951, 21, 1181, 1395, 1940; J. Gen. Chem (USSR), 1951, 21, 1527 [Chem. Abs., 45, 1894d; 46, 3441i; 10033b; 49, 8724h], which are incorporated herein by reference. Although some of the anions of formula (I) have been previously reported, a number of these anions are novel. Thus, in another embodiment, the present invention provides novel anions of the formula (Ia) EQU [DA'.sub.5 M.sub.30-x O.sub.110-x (M'L).sub.x ].sup.m- (Ia) in which D is Na.sup.+, Ca.sup.+2 or ann ion of similar size; M is W.sup.6+, W.sup.5+ or mixtures thereof; M' is any metallic element from groups 2 to 15 of the periodic table; L is O.sup.2-, OH.sup.-, H.sub.2 O or another suitable ligand, A' is P, As, Sb, Si, Ge, or combinations thereof; x is 0-10; and m is the charge based on the valence states of the atoms, typically 10-20, with the following provisos: (a) every occurrence of A' is not P when x is 0; and (b) every occurrence of A' is not P, M' is not V, and L is not O, when x is 1. In the definition of the anions of formula (Ia), M' may be any metallic element selected from groups 2 to 15 of the periodic table. Preferred metals for M' include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sn, Nb, Ta, Mo, and combinations thereof. Particularly preferred metals for M' include Mo, V, Nb, Ta, and combinations thereof. Suitably, A' is an element selected from the group consisting of P, As, Sb, Si, Ge, and combinations thereof. It is preferred that A is P, As or combinations thereof. It is particularly preferred at A is phosphorus. The choice of L will, in part, depend on the identity of M'. However, the identification and selection of the appropriate choice for L is within the abilities of one having ordinary skill in the art. The preparation of the novel compounds of formula (Ia) may be carried out as described for the compounds of formula (I). It should be understood that, within the context of the present application, the salts of the anions of formulae I, Ia and II, include any and all hydrates of the corresponding salts. Other features of the invention will become apparent in the course of the following descriptions of exemplary embodiments which are given for illustration of the invention and are not intended to be limiting thereof. EXAMPLES K.sub.12.5 Na.sub.1.5 [NaP.sub.5 W.sub.30 O.sub.110 ].15 H.sub.2 O was prepared either according to Jeannin, Y. et al, Inorg. Synth., 1991, 27, 115 or by the following method: Na.sub.2 WO.sub.4.2H.sub.2 O (33 g) was dissolved in water (30 mL) and 85% H.sub.3 PO.sub.4 (26.5 ml) was added. The mixture was placed in a sample preparation bomb (Parr 4748), which was heated at 120.degree. C. overnight. After cooling to room temperature, water (15 ml) was added to the slightly yellow solution, followed by solid KCl (10 g). The precipitate was separated by filtration and washed with 2 M potassium acetate and methanol. When dry, it was dissolved in hot water (30 ml). On cooling to room temperature white crystals formed. A second recrystallization gave the pure product. Yield 8.8 g (33% based on Na.sub.2 WO.sub.4). The IR spectrum and cyclic voltammogram were as previously reported (Alizadeh, M. H., et al, J. Am. Chem. soc., 1985, 107 2662). [ZP.sub.5 W.sub.30 O.sub.110 ].sup.n- salts. In a typical experiment K.sub.12.5 Na.sub.1.5 [NaP.sub.5 W.sub.30 O.sub.110 ].15H.sub.2) (1 g) was dissolved in 12 ml of water or dilute acid (<1 M HCl) and the solution was heated to 60.degree.-70.degree. C. To this solution was dropwise added two equivalents of Z.sup.n+, the replacing cation, as the chloride or nitrate salt dissolved in water (3 ml). If a persistent precipitate appeared (Z=Ce.sup.4+, U.sup.4+) the addition was stopped after one equivalent of Z.sup.n+ had been added. The mixture was placed in a Parr 4746 or 4748 sample preparation bomb and heated to 140.degree.-180.degree. C. overnight. After the solution had cooled to room temperature, the product was isolated by the addition of 4 g solid KCl. In some cases when the exchange was not complete (monitored by cyclic voltammetry), unreacted NaP.sub.5 W.sub.30 was precipitated first by addition of a small amount of KCl. After filtration, the fitrate was treated with additional KCl to precipitate the product, which was filtered off, washed with ice water, and air-dried. Yields varied from 45 to 90% of isolated material (See Table 1). All products were colorless except CeP.sub.5 W.sub.30 which was light yellow and UP.sub.5 W.sub.30 which was light yellow-green. They were identified by cyclic voltammetry, Ir, .sup.31 P NMR, .sup.183 W NMR, .sup.23 Na NMR, electronic spectra of EuP.sub.5 W.sub.30 and UP.sub.5 W.sub.30, and EPR and elemental analysis of GdP.sub.5 W.sub.30. Anal. Calcd. (found) for K.sub.12 [GdP.sub.5 W.sub.30 O.sub.110 ].54 H.sub.2 O: K, 5.3(5.2); W, 61.1(61.1); Gd, 2.1(1.7); P, 2.2(1.7). Elemental analysis was performed by E+R Microanalytical Laboratory, Inc., Corona, N.Y. The free acid of EuP.sub.5 W.sub.30 was prepared by ion exchange of the potassium salt on a column of Bio-Rad AG 50W-X2 resin, 50-100 mest. The eluate was concentrated for electronic and NMR spectroscopy on a rotary evaporator. Physical Measurements Electrochemical measurements were made using a BAS-100A Electrochemical Analyzer with a PWR-3 Power Module/Potentiostat. CV (cyclic voltammetry) measurements were performed using a glassy carbon working electrode and a Ag/AgCl reference electrode. Unless other wise stated all potentials quoted in this paper are vs Ag/AgCl. For controlled potential electrolysis a platinum gauze electrode was used vs a saturated calomel reference electrode. NMR spectra were recorded on a Bruker AM-300 WB spectrometer operating at a magnetic field of 300.10 MHz for protons. The resonance frequencies were 12.505 MHz for .sup.183 W, 121.496 MHz for .sup.31 P, and 79.391 MHz for .sup.23 Na. The chemical shift standards were saturated Na.sub.2 WO.sub.4 in D.sub.2 O for .sup.183 W, 85% H.sub.3 PO.sub.4 for .sup.31 P, and 1 M NaCO.sub.3 for .sup.23 Na. All NMR spectra were recorded at 21.degree. C. on samples dissolved in water containing ca 15% D.sub.2 O. ESR spectra were recorded on a Varian E-4 spectrometer. A Spex Fluorolog spectrofluorimeter equipped with a xenon lamp was used for the emission measurements. Obviously, numerous 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 practices otherwise than as specifically described herein. |
044473885 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to fastening apparatus particularly useful in nuclear reactor systems, and pressurized power systems. 2. Description of the Prior Art In order to ensure reliability of any structural system including bolt-fastened components, especially components of a nuclear reactor, it is common practice for the bolts to be periodically inspected for evidence of crack initiation or other failure. These bolts are often inaccessible due to radiation and/or position. It is desired to provide accurate, rapid and remote indication of bolt failure particularly for nuclear reactors. SUMMARY OF THE INVENTION A chamber or chambers is to be incorporated into the body of a bolt and the chamber filled with a tag gas. In the event that a crack occurs in the bolt which traverses the space between the chamber and its outside surface, the gas will be released. A gas detection system is provided in a location to which the gas will be transported by natural or forced circulation. This gas detection system will detect and identify the tag gas escaping from the cracked bolt. The detection system can be set up to operate continuously or to be turned on by a trigger gas which also would be enclosed in the bolt chamber. One or more chambers may be provided. The chamber may be coincident with the center line of the bolt where it would have a minimal effect on the strength of the bolt. Additional connected or separate chambers could be provided in the bolt. Each bolt in a circle or group of bolts can have a different tag gas to identify the cracked bolts. Also, each chamber in a multi-chambered bolt can have a different tag gas to localize the failure within the bolt. |
051942143 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an apparatus and method for plugging tubular members and, more particularly, to a tube plug and method for plugging a tube, such as a nuclear steam generator heat exchanger tube. 2. Description of the Prior Art In tube-type heat exchangers, a first fluid flows through the tubes of the heat exchanger while a second fluid surrounds the outside of the tubes such that heat exchange occurs between the two fluids. Occasionally, one of the tubes can become defective such that a leak either is impending or occurs therein which allows the two fluids to mingle. When this occurs, it is sometimes necessary to plug the tube so that the fluid does not flow through the tube thereby preventing leakage from the tube. The tube-type heat exchangers utilized in nuclear reactor power plants are commonly referred to as steam generators. When a defect occurs in the tubes of a nuclear steam generator that allows the primary fluid in the tubes to mingle with the secondary fluid outside of the tubes, a more significant problem arises. Not only does this situation create an ineffective heat exchanger, but it also creates a radioactive contamination problem. Since the fluid flowing in the tubes of a nuclear steam generator is radioactive, it is important that it not be allowed to leak from the tubes and contaminate the fluid surrounding the tubes. Therefore, when a leak occurs in a nuclear steam generator heat exchange tube, the heat exchange tube is plugged so that the primary fluid is not permitted to flow through the tube. This prevents contamination of the fluid surrounding the tubes. There are several kinds of mechanical plugs that can be used to plug heat exchange tubes. One such device used to plug heat exchange tubes in nuclear steam generators is disclosed in U.S. Pat. No. 4,982,763 issued Jan. 8, 1991 to Klahn entitled "Plug Retainer". The plug retainer for retaining a tube plug comprises a locking cup having a bore therethrough and an externally threaded lower portion adapted to be threadably received in the open threaded end of the tube plug and a cap screw having a threaded shank threadably receivable in the threaded mandrel of the tube plug. The locking cup is crimped onto the cap screw by the use of flutes on the cap screw head. However, the locking cup may inadvertently back out of the tube plug due to vibration during the operation of the steam generator. Another type of mechanical plug is disclosed in copending application Ser. No. 07/699416 filed concurrently herewith by Keating entitled "Tube Plug and Method for Plugging a Tube" and assigned to the assignee of the present invention. The tube plug for plugging a tube to prevent fluid flow through the tube comprises a shell, an expander member, bolt means to seal the chamber defined by the shell, and locking means for securing the shell, the bolt means, the expander member, and the locking means together. The locking means comprises a tab portion deformable into at least one recess in the bolt means or the shell. Another type of mechanical plug is disclosed in co-pending application Ser. No. 07/439,118 filed Nov. 20, 1989 by Haberman et al. and assigned to the assignee of the present invention. The tube plug for plugging a tube to prevent flow through the tube comprises a shell, an expander member, and a sealing member to seal the chamber defined by the shell. The sealing member and shell are welded together for locking or fastening the sealing member to the shell to prevent the sealing member and shell from separating. The installation of the sealing member into the shell seals the open end of the shell to prevent coolant from entering the chamber of the shell and exerting pressure on the plug wall, and occupies space within the chamber of the shell to reduce the possibility of residual stresses within the plug wall. Although the tube plug successfully plugs tubes, welding the sealing member and the shell together requires the additional steps of welding and of inspection of the weld during the installation of the tube plug into the tube. Also, if the shell of the tube plug has been recessed a distance into the tube, the sealing member cannot be welded to the shell, and therefore the sealing member and shell cannot be secured together by welding. Therefore, what is needed is a tube plug which includes means for securing the plurality of members comprising the tube plug together so that the members of the tube plug will not vibrate apart. Also, what is needed is a method for installing the tube plug. SUMMARY A plugging device, such as a tube plug, for preventing the flow of fluid through an opening or a tubular member, such as a nuclear steam generator tube, comprises a locking cup for securing together the plurality of members comprising the tube plug. The plugging device comprises a first member, such as a shell of a tube plug, having a bore at least partially therethrough with a portion with inside diameter threads, a second member, such as bolt means of a tube plug, disposed in the bore of the first member, and an annular locking cup disposed in the bore of the first member and having outside diameter threads. The outside diameter threads have a deformed portion for providing significant added resistance to the threading and unthreading of the locking cup into and out of the first member for preventing the inadvertent separation of the first member, the second member, and the locking cup. The deformed portion may have a wave-like pattern formed by at least one offset of the root and of the pitch and formed by at least one protuberance of the outside diameter threads of the locking cup. At least one of the second member and the locking cup has at least one recess for receiving a deformable portion of the other of the second member and the locking cup for securing the first member, the second member, and the locking cup together. The tube plug may also comprise an expander member for threadedly engaging with the bolt means, where the threads of the expander member and bolt means may have a different pitch size than the threads of the locking cup and the shell, thereby providing an additional fastening feature of the tube plug. The metal-to-metal abutment of an outside diameter surface of the locking cup and a plug face of the shell and the metal-to-metal abutment of a taper of the bolt means and a taper of the locking cup seals a chamber within the shell to prevent fluid flow through the tube plug. A method for plugging a tube comprises the steps of installing the shell within a tube, deforming the threads of a locking cup into a wave-like configuration, threading the locking cup into the shell, disposing a bolt means in the locking cup and the shell, and crimping the locking cup into a recess of the bolt means for securing together the shell, the bolt means, and the locking cup to prevent fluid flow through the tube. |
description | Referring now to FIG. 1, there is shown in cross section an embodiment of the invention having three independently controlled variable shape electron beams apparatus immersed in a common solenoid field. These subsystems (subsystems in the overall multi-beam system) are positioned in close proximity (on the order of 20 mm center-to-center) and simultaneously expose an array of stitched subfields that together expose the full field pattern, illustratively an integrated circuit. The imaging system employs high demagnification of the object, thus suppressing flaws in the source (i.e. the surface of a shaping aperture). The overall solenoid magnetic field is provided by coils 12-1, 12-2 and 12-3 in sections 100, 200 and 300, respectively. A capped cylinder of any high permeability magnetic material 6, encloses the coils, except for a gap 65 at the bottom for insertion of a workpiece, such as a resist coated substrate for glass mask production, reticle for projection lithography systems or wafer for direct write integrated circuit exposure. The cap also shields the electron beam from undesirable stray magnetic field influences. In section 100 of each subsystem, electron gun 105, illustratively a conventional cathode of LaB6 crystal that can be controlled and served individually to provide high stability and uniformity, generates the subsystem beam. Electrons emitted from gun 105 are accelerated to anode 107. A first shaping aperture 109 in plate 110 permits the passage of an electron beam having a square cross section, illustratively 175 xcexcm on a side. Electrostatic deflection plates 112 and 114 deflect the square beam over second shaping aperture 210 in plate 205 to position the square beam from the first shaping aperture appropriately with respect to aperture 210. As is described in U.S. Pat. No. 4,945,246 for a single beam system, each column generates a shaped beam having a shape that may be a vertical line, a horizontal line or a rectangle of desired shape by deflecting the square beam from aperture 109 such that only a beam of the desired shape passes through aperture 210. A solenoid field generated in Section 100 by coil 12-1 focuses an image of the beam emerging from aperture 109 at the plane of aperture 210. The number of ampere turns in Section 100 is selected in conjunction with the accelerating voltage of the beam to provide a beam focus in the desired transverse plane. Optionally, a plate 205 of the same magnetically permeable material as enclosure 6 separates the first and second sections of the system. An aperture 206 in plate 205 is oversized to permit the beam to strike shaping aperture 210 without striking plate 205. In Section 200, a demagnifying lens constructed according to the teachings of the referenced copending patent forms a demagnified image of the beam emerging from aperture 210 near the bottom of Section 200. The lenses will be referred to as xe2x80x9cpassivexe2x80x9d since they are not energized by current within the lens, but achieve a focus by affecting the external solenoid field. High permeability plates 205 and 255 separate the magnetic fields in the three sections, reducing the load on the drivers that power the separate solenoid coils and providing the ability to have several different strength solenoids stacked one on top of each other and thus vary the focal length of each section independently. Illustratively, the coil 12-2 for Section 200 is energized with about 2,000 ampere-turns, compound lenses 230 have a magnification of 0.0114, the current density in a beam is about 100A/cm2, and the system generates beam xe2x80x9cflashesxe2x80x9d having a duration of approximately 50 ns, depending on resist sensitivity, beam energy and current density. The alignment, shaping, blanking and deflection of each beam is accomplished in each subsystem with electrostatic fields to prevent coupling between adjacent beams and to assure that the focal planes in the solenoid field are not affected. Proper alignment of the beam can be assured throughout the column by superimposing offset voltages on the aforementioned shaping, blanking and deflection elements, as is standard in the art. Conventional electronic circuits for supplying DC voltage, driving the coils and the electrostatic deflectors are shown schematically by box 175 in the lower right of the Figure. Minor refocussing to compensate for demagnification lens field variations and target height changes can be accomplished by introducing a weak Unipotential (Einzel) lens (most easily by utilizing the magnetic lens pole pieces as ground elements and placing a biassed aperture between them), and/or applying a bias voltage to the substrate 60. At the bottom of the Figure, Section 300 contains deflector plates 312 and 314 that position each beam at a desired location on workpiece 60. In this Figure, workpiece 60 moves in and out of the plane of the drawing on a conventional stage shown schematically as box 66. A preferred embodiment of the invention having demagnifying lens 230, having upper pole tips 232, lower pole tips 234 and high permeability block 236 produced demagnification greater than 80xc3x97, while maintaining spherical and chromatic aberration below 4 mm. Other parameters are: a beam voltage of 10 keV, magnification in the upper lens 232 of 0.133, magnification in the lower lens 234 of 0.086, giving a total demagnification of 87 with CSI=3.25 mm, CC=3.83 mm. The excitation of solenoid 12-2 was 2000 ampere-turns. The diameter of magnetic intermediate piece 236 was nominally the same as the electrostatic deflectors and 20 mm. The diameter of the bore through the pole pieces was 4 mm and the lens gaps were 4 mm for the upper and lower sections, with 7 mrad aperture half angle at the second demagnification lens image plane. The aperture in the plane of plate 210 is the object and the plane of plate 255 is the approximate location of the second image plane in this case. At the intermediate image plane 212, there is a limiting aperture that defines the final semi-angle at the target and also minimizes the isotropic off axis aberrations. Illustratively, the approximate length of the first section was 200 mm, the second 150 mm and the third section 150 mm (to target) for a total system length of approximately 550 mm. Passive pole pieces 230 in the second section are supported by non-magnetic materials. The deflectors in the first and third sections are supported by non-magnetic, non-conducting materials not shown in the drawing for simplicity. Referring now to FIG. 2, there is shown a top view of some alternative embodiments of the invention. Illustratively, the system is to write a pattern directly on a wafer or on a mask, which is later to be used in a stepper to expose integrated circuit patterns. For a typical 4xc3x97 stepper, the area to be exposed extends 3 cm by 4 cm, so that the e-beam system mask must cover an area of 12 cm by 16 cm. Boxes 501-506 in the group of two rows denoted by bracket 500 represent schematically e-beam subsystems constructed according to the invention that have an illustrative deflection range of +/xe2x88x9211 mm in the x and y directions. The e-beam systems in the two rows denoted are separated horizontally by 20 mm (e.g. the center of subsystem 503 is 40 mm from the center of subsystem 501 and the x-position of subsystem 502 is located midway between them), so that there is an overlap region of 2 mm in the x-direction. The first and second rows are displaced for convenience in displaying the Figure. Preferably, the two rows are placed with a distance between centers of 20 mm, denoted by bracket 508, and therefore have the same overlap of 2 mm in the y-direction. Confining our attention for the moment to the group of a single row divided into even and odd sub-rows together labelled 500, a preferred method of operation is to transport the workpiece mechanically (on stage 66 in FIG. 1) vertically downward in FIG. 2. Initially, the systems 502, 504, 506 in the even subrow write a pattern in a first horizontal strip extending 2 cm in the y-direction and subsystems 501, 503 and 505 do not write. Next, the stage is moved by 2 cm in the y-direction, so that the spaces not covered by the even subrow (systems 502-506) in the first step are now covered by systems 501-505 in the odd subrow. The remainder of the first horizontal strip is then written by systems 501-505 while simultaneously systems 502-506 write the next horizontal strip. It will be evident to those skilled in the art that nine iterations will write the desired 16 cm in the y-direction. In the first step, subsystems 501, 503 and 505 do not write and in the ninth step, subsystems 502, 504 and 506 do not write. Alternatively, additional rows denoted with brackets 510-570 could be provided, so that the groups collectively cover the area to be written. In that case, just two steps will write out the area. On the first step, subsystems 501, 503 and 505 do not write and on the second step, subsystems 572, 574 and 576 do not write. FIG. 3 illustrates an alternative embodiment, in which the systems 501xe2x80x2, 502xe2x80x2, 506xe2x80x2 are all in the same single row. In that case, a single step will write a horizontal strip 2 cm along the y-direction. In this embodiment also, additional rows can be provided to reduce the number of steps. When the groups 500xe2x80x2, 510xe2x80x2, . . . 570xe2x80x2 (eight groups) of rows collectively cover the chip, the entire chip can be written in a single step. In this discussion, it has been assumed that the spacing between groups (rows) is related to the coverage of a group along the y-axis so that one step will bring the top of the nth group to the bottom of the (n+1)th group (not counting overlap). This is not required in general, and the spacing could be made greater, so that it takes k steps to bring the top of the nth group to the bottom of the (n+1)th group, whether an individual group is a single row, as in group 500xe2x80x2 of FIG. 3, or staggered rows, as in group 500 of FIG. 2. This approach would reduce the complexity of the hardware and require a longer time to write the entire pattern. Referring to FIG. 4A, a simplified passive lens for use in the invention modifies the magnetic field lines to form a demagnification lens. Illustratively, the material is Ferrite(trademark), a ceramic with high magnetic permeability, available from the Ceramic Magnetics company. As is conventional, coils 10 and 12, forming a solenoid field and pole piece 30 have cylindrical symmetry. The axial solenoid field 20 is modified by pole piece 30 to have a very strong peak in the pole piece gap (also referred to as the lens gap) 33 with negative side lobes (relative to the uniform solenoid field). Pole piece 30 has flat top and bottom surfaces 34 and two pole tips 32, having outer surfaces that make an acute angle with respect to the solenoid axis 101. In general, the closer the outer surfaces of pole tips 32 are to the vertical, the sharper the peak in magnetic field trace 130 in FIG. 4C and the deeper the dips in field strength 132 and 134. Preferably, the pole tip surfaces have an angle of less than 45xc2x0 with respect to the geometric axis. This pole piece configuration has been shown to easily provide demagnification in the 10xc3x97 range (shown in beam trace 120 in FIG. 2B), with spherical and chromatic aberration coefficients below 3 mm. Those skilled in the art will appreciate that the unexpectedly low value for the spherical aberration results from the ability of these lenses to create the dips in magnetic field strength 132 and 134, which have no counterparts in a conventional lenses driven by coils contained within the pole pieces. To achieve even higher demagnification, two or more of these lenses can be used in the same solenoid field, illustrated in FIGS. 5A and 5B. There, pole pieces 32 are the same as those in FIG. 4A. Segments 34 of the poles are not used in this illustration, but could be added to further strengthen the lens field in the pole piece gap, and thereby increase the demagnification. An optional permeable member 36, of the same permeable material, merges with lower pole piece 32 of the upper pair and with the upper pole piece 32 of the lower pair, so that a single piece of material 36 conducts the field lines from the upper gap to the lower gap. A single piece eliminates problems with misalignment between the pieces, but is not required. So long as the three pieces abut and carry the field lines, separate pieces can be used. Filling the region between the two lenses with high permeability magnetic material produces a field free region that can be used for separation and demagnification purposes. While the invention has been described in terms of a few preferred embodiments, those skilled in the art will recognize that the invention can be practiced in various versions within the spirit and scope of the following claims. |
|
summary | ||
047160063 | summary | CROSS-REFERENCES TO RELATED APPLICATIONS This application is related to copending application Ser. Nos. 217,060 entitled "Mechanical Spectral Shift Reactor" by W. J. Dollard et al.; Ser. No. 217,056 entitled "Latching Mechanism" by L. Veronesi; Ser. No. 217,061 entitled "Spectral Shift Reactor" by W. R. Carlson et al.; Ser. No. 217,052 entitled "Displacer Rod For Use In A Mechanical Spectral Shift Reactor" by R. K. Gjertsen et al.; Ser. No. 217,053 entitled "Mechanical Spectral Shift Reactor" by D. G. Sherwood et al.; Ser. No. 217,275 entitled "Mechanical Spectral Shift Reactor" by J. F. Wilson et al.; Ser. No. 217,055 entitled "Hydraulic Drive Mechanism" by L. Veronesi et al.; Ser. No. 217,059 entitled "Fuel Assembly For A Nuclear Reactor" by R. K. Gjertsen; and Ser. No. 217,057 entitled "Fuel Assembly For A Nuclear Reactor" by R. K. Gjertsen et al. all of which are filed Dec. 16, 1980 and to Ser. No. 228,007 entitled "Self-Rupturing Gas Moderator Rod For A Nuclear Reactor" by G. R. Marlatt, filed Jan. 23, 1981 all of which are assigned to the Westinghouse Electric Corporation. BACKGROUND OF THE INVENTION The invention relates to spectral shift reactor control and more particularly to mechanical means for spectral shift reactor control. In typical nuclear reactors, reactivity control is accomplished by varying the amount of neutron absorbing material (poisons) in the reactor core. Generally, neutron absorbing control rods are utilized to perform this function by varying the number and location of the control rods with respect to the reactor core. In addition to control rods, burnable poisons and poisons dissolved in the reactor coolant can be used to control reactivity. In the conventional designs of pressurized water reactors, an excessive amount of reactivity is designed into the reactor core at start-up so that as the reactivity is depleted over the life of the core the excess reactivity may be employed to lengthen the core life. Since an excessive amount of reactivity is designed into the reactor core at the beginning of core life, neutron absorbing material such as soluble boron must be placed in the core at that time in order to properly control the excess reactivity. Over the core life, as reactivity is consumed, the neutron absorbing material is gradually removed from the reactor core so that the original excess reactivity may be used. While this arrangement provides one means of controlling a nuclear reactor over an extended core life, the neutron absorbing material used during core life absorbs neutrons and removes reactivity from the reactor core that could otherwise be used in a more productive manner such as in plutonium fuel production. The consumption of reactivity in this manner without producing a useful product results in a less efficient depletion of uranium and greater fuel costs than could otherwise be achieved. Therefore, it would be advantageous to be able to extend the life of the reactor core without suppressing excess reactivity with neutron absorbing material thereby providing an extended core life with a significantly lower fuel cost. One such method of producing an extended core life while reducing the amount of neutron absorbing material in the reactor core is by the use of "Spectral Shift Control". As is well understood in the art, in one such method the reduction of excess reactivity (and thus neutron absorbing material) is achieved by replacing a large portion of the ordinary reactor coolant water with heavy water. This retards the chain reaction by shifting the neutron spectrum to higher energies and permits the reactor to operate at full power with reduced neutron absorbing material. This shift in the neutron spectrum to a "hardened" spectrum also causes more of the U.sup.238 to be converted to plutonium that is eventually used to produce heat. Thus, the shift from a "soft" to a "hard" spectrum results in more neutrons being consumed by U.sup.238 in a useful manner rather than by poisons. As reactivity is consumed, the heavy water is gradually replaced with ordinary water so that the reactor core reactivity is maintained at a proper level. By the end of core life, essentially all the heavy water has been replaced by ordinary water while the core reactivity has been maintained. Thus, the reactor can be controlled without the use of neutron absorbing material and without the use of excess reactivity at start-up which results in a significant uranium fuel cost savings. The additional plutonium production also reduces the U.sup.235 enrichment requirements. While the use of heavy water as a substitute for ordinary water can be used to effect the "spectral shift", the use of heavy water can be an expensive and complicated technology. Another well known phenomenon related to reactor control is referred to as xenon transient behavior. Xenon-135 is a fission product of uranium fuel some of which is a direct fission product of uranium-235 but most of which originates from the radioactive decay of tellurium-135 and iodine-135 which are produced from the fissioning of uranium-235. The major portion of the xenon thus produced is produced in a delayed manner due to the intermediate isotope production. This results in a time delay of several hours between the fissioning of fissile or fertile material and the production of large quantities of xenon-135. On the other side of the xenon transient phenomenon is the fact that since xenon-135 has a large neutron absorbing cross-section, xenon-135 tends to absorb neutrons and be destroyed thereby. Thus, xenon acts as a neutron poison in a reactor core robbing the core of neutrons that could be used to sustain the chain reaction. The transient usually associated with the xenon phenomenon arises because as power is reduced due to load follow reasons, neutron population in the core decreases which results in less destruction of xenon and in temporary xenon accumulation. This temporary accumulation of xenon further reduces reactor power by xenon absorption of neutrons. However, the reduction in reactor power lowers the core temperature which increases core reactivity due to the negative moderator temperature coefficient of the reactor. Thus, a minor oscillation in reactor power, xenon population, and core temperature can result from transient xenon production. Likewise, a similar result may occur from an attempt to increase reactor power in response to load follow requirements. This may occur since an increase in reactor power requires an increase in neutron population and fuel depletion which increases xenon production in the fuel. But since the xenon production is delayed in time, the poisonous effect of the xenon is temporarily delayed which again produces the transient oscillations between core temperature, xenon population, and reactor power. As is well understood in the art, the effects of these xenon transients can be effectively controlled by the addition or subtraction of boron in the reactor coolant by a feed-and bleed process. The change in boron concentration in the reactor coolant can be timed to correspond to the changes in core reactivity due to the xenon transient thereby negating such transient. This can be accomplished as long as the boron concentration in the reactor coolant is sufficiently high to make a feed-and-bleed process possible in a timely manner. However, when the boron concentration falls below a given level, for example below 100 ppm. as is necessary near the end of core life, boron cannot be removed from the reactor coolant fast enough to compensate for xenon accumulation. Therefore, as the boron concentration in the reactor coolant nears a low level such as at the end of core life, boron compensation of xenon becomes very difficult which effectively prevents load follow maneuvering of reactor power so as to avoid xenon transients. Therefore, what is needed is a method to extend core life and provide for load follow capabilities at low reactor coolant boron concentrations. SUMMARY OF THE INVENTION A method of operating a pressurized water nuclear reactor comprising determining the present core power and reactivity levels and predicting the change in such levels due to displacer rod movements. Groups or single clusters of displacer rods can be inserted or withdrawn based on the predicted core power and reactivity levels to change the core power level and power distribution thereby providing load follow capability, without changing control rod positions or coolant boron concentrations. |
claims | 1. A lithography apparatus for writing a pattern on an exposure mask using a charged particle beam, comprising:an interpreter unit configured, by receiving a data file including character information which uses at least one of letter and numeral and specifies a shape of an identification figure representing identification information of the exposure mask before pattern writing process, to interpret contents of the character information;a generating unit configured, by receiving the character information, to generate pattern writing data of the identification figure on the basis of the character information in a same format as that of a pattern writing data of a pattern written on the exposure mask after the contents of the character information is interpreted;a synthesizing unit configured, by receiving the pattern writing data of the pattern written on the exposure mask, to synthesize the pattern writing data of the pattern and the pattern writing data of the identification figure;a verifying unit configured, by receiving frame information of the pattern written on the exposure mask, to verify whether the identification figure overlaps the pattern on the basis of the character information and the frame information of the pattern in a case that the identification figure and the pattern are written on the exposure mask using a charged particle beam;a correcting unit configured to selectively correct a reference position and a size of the identification figure when the identification figure overlaps the pattern in the case; anda pattern writing unit configured to write the pattern and the identification figure on the exposure mask on the basis of the synthesized pattern writing data in a case that it has been verified that the identification figure does not overlap, using a charged particle beam. 2. The apparatus according to claim 1, whereinas the character information, at least one of information of a time of day at which the pattern writing data of the pattern is input to the lithography apparatus and a time of day at which a pattern writing process is started is included, and at least one of the time of day at which the pattern writing data of the pattern is input to the lithography apparatus and the time of day at which the pattern writing process is started, is automatically input to the data file in the lithography apparatus. 3. The apparatus according to claim 1, whereinas the character information, at least one of information for identifying the exposure mask itself, a name of the pattern writing data of the pattern, identification information of the lithography apparatus, a time of day at which the pattern is written, and an operator name of the lithography apparatus is included. 4. A lithography method comprising:by receiving a data file including character information which uses at least one of letter and numeral and specifies a shape of an identification figure representing identification information of an exposure mask before pattern writing process, interpreting, with an apparatus for writing a pattern on an exposure mask using a charged particle beam, contents of the character information;by receiving the character information, generating, with the apparatus for writing the pattern on the exposure mask using the charged particle beam, pattern writing data of the identification figure on the basis of the character information in a same format as that of a pattern writing data of a pattern written on the exposure mask after the contents of the character information is interpreted;by receiving the pattern writing data of the pattern written on the exposure mask, synthesizing, with the apparatus for writing the pattern on the exposure mask using the charged particle beam, the pattern writing data of the pattern and the pattern writing data of the identification figure;by receiving frame information of the pattern written on the exposure mask, verifying, with the apparatus for writing the pattern on the exposure mask using the charged particle beam, whether the identification figure overlaps the pattern on the basis of the character information and the frame information of the pattern in a case that the identification figure and the pattern are written on the exposure mask using a charged particle beam;correcting, with the apparatus for writing the pattern on the exposure mask using the charged particle beam, selectively a reference position and a size of the identification figure when the identification figure overlaps the pattern in the case; andwriting, with the apparatus for writing the pattern on the exposure mask using the charged particle beam, the pattern and the identification figure on the exposure mask on the basis of the synthesized pattern writing data in a case that it has been verified that the identification figure does not overlap. 5. The method according to claim 4, whereinas the character information, at least one of information of a time of day at which the pattern writing data of the pattern is input to the lithography apparatus and a time of day at which a pattern writing process is started is included. 6. The method according to claim 4, whereinas the character information, at least one of information for identifying the exposure mask itself, a name of the pattern writing data of the pattern, identification information of the lithography apparatus, a time of day at which the pattern is written, and an operator name of the lithography apparatus is included. 7. The apparatus according to claim 1, wherein the generating unit is configured to regenerate pattern writing data of the identification figure so that the identification figure does not overlap a pattern written on the exposure mask when the identification figure overlaps the pattern, andthe synthesizing unit is configured to synthesize the pattern writing data of the pattern and the pattern writing data of the identification figure which does not overlap the pattern written on the exposure mask. 8. The method according to claim 4, further comprising:regenerating pattern writing data of the identification figure so that the identification figure does not overlap a pattern written on the exposure mask when the identification figure overlaps the pattern; andsynthesizing, the pattern writing data of the pattern and the pattern writing data of the identification figure which does not overlap the pattern written on the exposure mask. |
|
summary | ||
abstract | A communication network includes network equipments coupled to a management system. A diagnostic device for the network determines the causes of problems occurring in the network via one or more diagnostic models and adapts the diagnostic models as a function of data provided by the management system that is representative of the composition of the network. |
|
claims | 1. An apparatus for positioning articles at desired positions in a nuclear reactor, the apparatus comprising:a shoulder having a rotatable mount configured to mount at an edge of the reactor;a back arm extending from the shoulder; anda front arm rotatably connected to the back arm, wherein the front arm is shaped to hold an inspection apparatus at an end of the front arm farthest from the back arm, wherein the shoulder includes a motor and a manual drive both configured to rotate the front arm with respect to the back arm. 2. The apparatus of claim 1, further comprising:an installation blade extending vertically upward from the shoulder, wherein the installation blade is shaped to selectively engage with a manual handling pole and move the entire apparatus. 3. The apparatus of claim 1, wherein the back arm connects to the front arm at an elbow permitting rotation of the front arm through a vertical axis with respect to the back arm. 4. The apparatus of claim 3, wherein the back arm and the front arm are at different vertical heights so that the front arm can be rotated at the elbow to fully overlap with the back arm vertically. 5. The apparatus of claim 1, wherein the rotatable mount is a mast extending vertically downward from the shoulder and rotatable on a vertical axis with respect to the shoulder, and wherein the shoulder includes a motor configured to rotate the shoulder with respect to the mast on the vertical axis. 6. The apparatus of claim 5, wherein the shoulder further includes a manual drive configured to rotate the shoulder with respect to the mast on the vertical axis. 7. The apparatus of claim 1, wherein the front arm includes a moveable clamp at the end of the front arm. 8. The apparatus of claim 1, further comprising:a connection providing power and data to the shoulder when submerged in a fluid from operators outside the fluid. 9. An apparatus for positioning articles at desired positions in a nuclear reactor, the apparatus comprising:a shoulder having a rotatable mount configured to mount at an edge of the reactor;a back arm extending from the shoulder; anda front arm rotatably connected to the back arm, wherein,the front arm is shaped to hold an inspection apparatus at an end of the front arm farthest from the back arm,the back arm connects to the front arm at an elbow permitting rotation of the front arm through a vertical axis with respect to the back arm, andthe back arm and the front arm are at different vertical heights so that the front arm can be rotated at the elbow to fully overlap with the back arm vertically. 10. The apparatus of claim 9, further comprising:an installation blade extending vertically upward from the shoulder, wherein the installation blade is shaped to selectively engage with a manual handling pole and move the entire apparatus. 11. The apparatus of claim 9, wherein the front arm includes a moveable clamp at the end of the front arm. 12. The apparatus of claim 9, further comprising:a connection providing power and data to the shoulder when submerged in a fluid from operators outside the fluid. 13. The apparatus of claim 9, further comprising:a float positioned on the back arm away from the shoulder so as to counter torque on the shoulder from the back arm and the front arm when immersed in water. 14. An apparatus for positioning articles at desired positions in a nuclear reactor, the apparatus comprising:a shoulder having a rotatable mount configured to mount at an edge of the reactor, wherein the rotatable mount is a mast extending vertically downward from the shoulder and rotatable on a vertical axis with respect to the shoulder, and wherein the shoulder includes a motor configured to rotate the shoulder with respect to the mast on the vertical axis;a back arm extending from the shoulder; anda front arm rotatably connected to the back arm, wherein the front arm is shaped to hold an inspection apparatus at an end of the front arm farthest from the back arm. 15. The apparatus of claim 14, further comprising:an installation blade extending vertically upward from the shoulder, wherein the installation blade is shaped to selectively engage with a manual handling pole and move the entire apparatus. 16. The apparatus of claim 14, wherein the front arm includes a moveable clamp at the end of the front arm. 17. The apparatus of claim 14, further comprising:a connection providing power and data to the shoulder when submerged in a fluid from operators outside the fluid. 18. The apparatus of claim 14, further comprising:a float positioned on the back arm away from the shoulder so as to counter torque on the shoulder from the back arm and the front arm when immersed in water. |
|
053295617 | summary | FIELD OF THE INVENTION The invention relates to a device for checking the thickness and the cohesion of the interface of a duplex tube, and in particular of a zirconium alloy duplex tube used as a jacket element for a fuel rod of an assembly for a water-cooled nuclear reactor. BACKGROUND OF THE INVENTION The fuel assemblies of water-cooled nuclear reactors, and in particular of pressurized-water nuclear reactors, comprise a framework into which are introduced fuel rods consisting of a Jacket enclosing a nuclear combustible material such as uranium or plutonium oxide in the form of sintered pellets. The Jacket made from a zirconium alloy tube must have a good resistance to corrosion under the effect of the primary fluid circulating in contact with the outer surface of the Jacket. In order to constitute the Jacket of the fuel rods of the assemblies of water-cooled reactors, use is usually made of a zirconium-based alloy containing mainly tin and iron. In order to improve the corrosion stability under irradiation of the Jackets of fuel rods in the operating environment of the nuclear reactor, and thus to increase the lifetime of the fuel assemblies in the core, modifications or adjustments have been proposed to the composition of these zirconium alloys, or alternatively it has been proposed to replace these alloys containing tin, iron and chromium with alloys containing other elements such as vanadium, niobium or copper. It has also been proposed, for example in EP-A-0,212,351, to produce the Jacket in the form of a duplex tube comprising a tubular inner core made from a zirconium alloy of a conventional type such as that described above, and a surface layer consisting of a cladding or a covering improving the corrosion stability of the Jacket. The zirconiumalloy constituting the cladding or covering layer differs from the alloy constituting the core of the tube and contains iron and at least one of the elements vanadium, platinum and copper. This surface layer, the thickness of which represents 5 to 20% of the total thickness of the wall of the jacket, can be produced by extrusion of a billet consisting of an inner tube made from zirconiumalloy of a conventional composition over which is fitted an outer tube having the composition of a surface layer. The jacket is then rolled in a pilgrim step rolling mill to its final diameter. More recently, there has been proposed in FR-A-89-00761 filed Jointly by the companies FRAMATOME, COGEMA, CEZUS and ZIRCOTUBE, a duplex tube, the surface layer of which, having a thickness lying between 10 and 25% of the total thickness of the wall of the Jacket, consists of a zirconium-based alloy containing tin, iron and niobium or vanadium. The tubular core of the duplex tube can be made from a conventional zirconium alloy in the case of the manufacture of the Jackets for fuel rods, or from a zirconiumbased alloy containing mainly niobium as the alloying element. In all cases, it is necessary to ensure the perfect quality of the duplex tubes which are intended to constitute Jackets for fuel rods, in particular in terms of the diameter of the tube, the total thickness of the Jackets, the thickness of the outer cladding layer and the cohesion of the interface zone between the cladding layer and the core of the tube. Checks must be carried out at the factory on very large quantities of tubes, the diameter of which is very small as compared to the length. The checking of the diameter and the total thickness of the jacket can be carried out by using a conventional technique consisting in measuring the distance in the propagation times of pulse-shaped ultrasonic waves which are reflected by the outer surface and by the inner surface of the tube. This ultrasonic checking and measuring technique, known under the name of the "pulse-echo" technique, may be adapted in order to take account of the cladding layer in the calculation of the total thickness of the jacket. It has also been proposed to use a technique using ultrasonic waves in order to check the thickness of the cladding of a duplex tube based on zirconium alloy. This technique, described in FR-A-2,629,586 filed in the name of the company CEZUS, employs an ultrasonic-wave check adapted to the measurement of a layer of small thickness, the acoustic properties of which are very similar to those of the core of the tube of greater thickness. This improved technique does not, however, permit the measurement of cladding thicknesses of less than 0.4 mm, inasmuch as the industrial implementation of the method under satisfactory conditions requires the use of ultrasonic waves whose frequency does not exceed 20 MHz. In the case of-a cladding layer whose thickness lies between 80 and 100 .mu.m, which corresponds to the conditions encountered most commonly in the case of duplex tubes used as Jacket material, it would be necessary to employ ultrasonic waves at very high frequencies (for example of the order of 100 MHz), which makes it extremely difficult to apply the method in an industrial context. Furthermore, in the case of jackets for fuel rods, the cladding layer and the tubular core of the duplex tube consist of very slightly alloyed zirconiumbased alloys which have very similar acoustic properties, with the result that the coefficient of reflection of the acoustic waves at the cladding/core interface is very small (generally less than 2%). The interface echo is then very small and becomes drowned out in the acoustic and electronic noise of the ultrasonic signal. A measurement method and apparatus have been proposed in FR-A-2,534,015 which make it possible to determine the thickness of a zirconium covering on a zirconium-alloy tube, employing the analysis and the measurement of currents induced in the cladding layer of the duplex tube, by magnetic induction, using an exciting current the frequency of which is selected as a function of the nominal thickness of the cladding or covering layer of the tube. The frequency selected and the processing of the signals corresponding to the induced currents likewise make it possible to eliminate, to a certain degree, the measurement errors resulting from a variation in the width of the air gap between the exciting coil and the wall of the tube. This technique, which is relatively complex to implement, does not make it possible, however, to compensate for the variations in the conductivity of the material constituting the core of the tube and the variations in the conductivity of the material constituting the cladding. Furthermore, this technique does not make it possible to check independently the total thickness of the tube and the cohesion of the interface zone between the cladding or covering layer of the tube and the tubular core. SUMMARY OF THE INVENTION The object of the invention is to provide a device for checking the thickness and the cohesion of the interface of a duplex tube comprising a tubular core made from an alloy such as a zirconium alloy and covered with a covering or cladding layer made from an alloy the base metal of which is identical to the base metal of the alloy constituting the tubular core, this device making it possible to check the geometrical dimensions of the duplex tube and, in particular, its total thickness, and the thickness of the covering and cladding layer, and to detect flaws in cohesion at the interface between the covering or cladding layer and the tubular core. To this end, for various measuring and checking zones, around the circumference or along the length of the tube, the following operations are carried out continuously or discontinuously: ultrasonic waves are emitted in such a way that these waves are propagated in the covering and in the core of the tube in substantially radial directions, PA1 the ultrasonic waves reflected by the inner and outer surfaces of the tube, by its interface between the core and the covering and by any flaws in cohesion at the interface, or transmitted by the covering or cladding layer, are collected, PA1 the propagation time of the ultrasonic waves in the thickness of the tube is measured, PA1 the amplitude and shape of the reflected waves is determined, PA1 the tube is subjected, from its outer surface, to a magnetic induction created by a multi-frequency sinusoidal current, PA1 measurements are taken of the phase and/or amplitude of the currents induced in the tube, termed Foucault currents, PA1 the thickness of the covering layer is deduced therefrom, PA1 the total thickness of the tube is calculated from the measurements of the propagation times of the ultrasonic waves and of the thickness of the covering layer, and PA1 the cohesion of the tube at its interface is determined by analyzing the amplitude and the shape of the ultrasonic waves reflected by the interface or transmitted by the covering or cladding layer. |
claims | 1. A diagnostic/prognostic system for a physical system comprising:a plurality of sensors that are configured to repeatedly monitor variables of the physical system during operation;a first associative memory;a novelty detection system that is responsive to the plurality of sensors and that is configured to repeatedly observe into the first associative memory, states of associations among the variables that are repeatedly monitored during a learning phase, that is further configured to thereafter imagine at least one state of associations among the variables that are monitored relative to the states of associations that are observed in the first associative memory, to identify a novel state of associations among the variables, and that is further configured to determine whether the novel state is indicative of normal operation or of a potential abnormal operation;a second associative memory that includes therein associations of attributes of failure modes of the physical system; anda failure mode learning system that is responsive to the novelty detection system and to the second associative memory and that is configured to imagine attributes of the novel state relative to the associations of attributes of failure modes of the physical system to identify and/or predict a potential failure mode of the physical system. 2. A diagnostic/prognostic system according to claim 1 wherein the failure mode learning system comprises:a failure mode identification and diagnostics system; anda trend learning and prognostics system. 3. A diagnostic/prognostic system according to claim 1 further comprising:a third associative memory that includes therein associations of attributes of corrective actions and/or responses to failure modes of the physical system; andan intervention learning system that is responsive to the failure mode learning system and to the third associative memory and that is configured to imagine attributes of the potential failure mode relative to the responses in the third associative memory to identify a potential corrective action and/or response to the potential failure mode. 4. A diagnostic/prognostic system according to claim 1 wherein the novelty detection system is further configured to observe the novel state that is indicative of normal operation into the first associative memory. 5. A diagnostic/prognostic system according to claim 1 wherein the novelty detection system is further configured to assign the variable values that are repeatedly monitored to bins, and wherein the novelty detection system is configured to repeatedly observe by repeatedly observing into the first associative memory, states of associations among the binned values during the learning phase. 6. A diagnostic/prognostic system according to claim 1 wherein the failure mode learning system is further configured to identify a new failure mode for the physical system. 7. A diagnostic/prognostic system according to claim 1 wherein the failure mode learning system is further configured to provide trend learning for prognostics. 8. A diagnostic/prognostic system according to claim 3 wherein the intervention learning system is further configured to apply the potential response to the physical system in real-time. 9. A diagnostic/prognostic system according to claim 3 wherein the novelty detection system, the failure mode learning system, the intervention learning system and the first, second and third associative memories operate on the physical system in real-time. 10. A computer program product, the computer program product comprising computer program code embodied in a computer-readable medium, the computer program code configured to provide the first associative memory, the second associative memory, the novelty detection system and/or the failure mode learning system of claim 1. 11. A diagnostic/prognostic method of a physical system the includes a plurality of sensors that are configured to repeatedly monitor variables of the physical system during operation, the diagnostic/prognostic method comprising:repeatedly observing into a first associative memory, states of associations among the variables that are repeatedly monitored, during learning phase;imagining at least one state of associations among the variables that are monitored relative to the states of associations that are observed in the first associative memory to identify a novel state of associations among the variables;determining whether the novel state is indicative of normal operation or of a potential abnormal operation; andimagining attributes of the novel state relative to associations of attributes of failure modes of the physical system in a second associative memory to identify and/or predict a potential failure mode for the physical system. 12. A diagnostic/prognostic method according to claim 11 further comprising:imagining attributes of the potential failure relative to associations of attributes of responses to failure modes of the physical system in a third associative memory to identify a potential corrective action and/or response to the potential failure mode. 13. A diagnostic/prognostic method according to claim 11 wherein imagining attributes of the novel state relative to associations of attributes of failure modes of the physical system comprises determining failure trends and predictions relative to associations of time-based attributes of failure modes of the physical system. 14. A diagnostic/prognostic method according to claim 11 further comprising:observing the novel state that is indicative of normal operation into the first associative memory. 15. A diagnostic/prognostic method according to claim 12 further comprising:applying the potential response to the physical system in real-time. 16. A diagnostic/prognostic method according to claim 12 wherein identifying a potential response to the future failure potential is performed on the physical system in real-time. 17. A computer program product, the computer program product comprising computer program code embodied in a computer-readable medium, the computer program code configured to perform the method of claim 11. |
|
041705165 | claims | 1. A method of operating a nuclear reactor during the period when power of the nuclear reactor is raised, comprising the steps of raising the power from zero W/cm after reactor shutdown up to 240 W/cm of a linear heat generating rate of nuclear fuel elements containing UO.sub.2 fuel pellets surrounded by a zirconium alloy and located in a core of the nuclear reactor utilizing a first control means providing coarse power regulation, raising the power of the nuclear reactor in a range over the linear heat generating rate 240 W/cm utilizing a second control means providing fine power regulation, and stopping the power rise to the nuclear reactor and holding the power at a fixed level at least once in a range below a linear heat generating rate corresponding to a length of a shutdown period of time of said nuclear reactor before the linear heat generating rate reaches 240 W/cm, and wherein the power of said reactor is held constant at least once somewhere in the range zero to P which satisfies the relation ##EQU7## where P is a linear heat generating rate at which said nuclear fuel elements initiate the Pellet Clad Mechanical Interaction; T.sub.s is the shutdown period of the reactor; P.sub.0 is a linear heat generating rate which causes said nuclear fuel elements to induce Pellet Clad Mechanical Interaction for the first time, after said reactor is restarted when the reactor shutdown period T.sub.s is zero; and T.sub.so is the reactor shutdown period when P=0. 2. The method of operating a nuclear reactor according to claim 1, wherein the power of said nuclear reactor is raised by pulling out from said core, control rods which are the first control means and are inserted therein. 3. The method of operating the nuclear reactor according to claim 1, wherein letting T denote a period of time during which the power of the nuclear reactor is held constant, .theta. denote a temperature of fuel pellets in said nuclear fuel elements, K.sub.1 denote a constant of proportion, K.sub.2 denote a constant, the power of the nuclear reactor is held constant for the holding period of time which satisfies EQU T.gtoreq.-K.sub.1 .theta.+K.sub.2. 4. the method of operating a nuclear reactor according to claim 3, wherein the power of the nuclear reactor is held constant for the holding period of time which satisfies EQU T .gtoreq.-0.01875 .theta.+17.625. 5. the method of operating a nuclear reactor according to claim 1, wherein said linear heat generating rate is increased by varying a flow rate of a coolant to be supplied to said core. 6. The method of operating the nuclear reactor according to claim 1, wherein when the linear heat generating rate of said nuclear fuel elements has become at least 240 W/cm, the linear heat generating rate is increased in a proportion of at most about 1.8 W/cm/hour, to raise the power of the nuclear reactor. 7. The method of operating a nuclear reactor according to claim 1, wherein the fuel pellets and the surrounding zirconium alloy satisfy the relation EQU G.sub.a /D.sub.i =0.024 8. A method of operating a nuclear reactor during the period when power of the nuclear reactor is raised, comprising the steps of raising the power from zero W/cm after reactor shutdown up to 240 W/cm of a linear heat generating rate of nuclear fuel elements containing UO.sub.2 fuel pellets surrounded by a zirconium alloy and located in a core of the nuclear reactor by manipulating control rods, raising the power of the nuclear reactor in a range over the linear heat generating rate of 240 W/cm by a coolant control means for controlling a flow rate of a coolant supplied to the core, and stopping the power rise of the nuclear reactor and holding the power at a fixed level at least once in a range below a linear heat generating rate corresponding to a length of a shutdown period of time of the nuclear reactor before the linear heat generating rate reaches 240 W/cm, and wherein the power of said reactor is held constant at least once somewhere in the range zero to P.sub.1 which satisfies the relation ##EQU8## where P.sub.1 is a linear heat generating rate at which said nuclear fuel elements initiate the Pellet Clad Mechanical Interaction; T.sub.s is the shutdown period of the reactor; P.sub.o is a linear heat generating rate which causes said nuclear fuel elements to induce Pellet Clad Mechanical Interaction for the first time, after said reactor is restarted when the reactor shutdown period T.sub.s is zero; and T.sub.so is the reactor shutdown period when P=0. 9. The method of operating the nuclear reactor according to claim 8, wherein the power of the nuclear reactor is held constant for the holding period of time which satisfies EQU T.gtoreq.-0.01875.theta.+17.625. 10. The method of operating the nuclear reactor according to claim 8, wherein after the linear heat generating rate of said nuclear fuel elements has become at least 240 W/cm, the linear heat generating rate is increased in a proportion of at most about 1.8 W/cm/hour, to raise the power of the nuclear reactor. 11. The method of operating a nuclear reactor according to claim 8, wherein the fuel pellets and the surrounding zirconium alloy satisfy the relation EQU G.sub.a /D.sub.i =0.024 12. The method of operating the nuclear reactor according to claim 8, wherein the power of said nuclear reactor is held constant for a period of time which satisfies the relation EQU T.gtoreq.-K.sub.1 .theta.+K.sub.2, 13. The method of operating the nuclear reactor according to claim 12, wherein the power of the nuclear reactor is held constant for the holding period of time which satisfies EQU T.gtoreq.-0.01875.theta.+17.625. 14. The method of operating the nuclear reactor according to claim 12, wherein the power of the reactor is held constant at a linear heat generating rate P.sub.1 which satisfies the relation ##EQU9## for a period of time T which satisfies the relation EQU T=-K.sub.1 .theta.+K.sub.2. 15. the method of operating a nuclear reactor according to claim 14, wherein the power of the nuclear reactor is held constant for the holding period of time which satisfies EQU T=-0.01875.theta.+17.625. 16. The method of operating a nuclear reactor according to claim 12, wherein a recovery percentage R.sub.n of self-irradiation damage of said UO.sub.2 pellets, which depends on the temperature .theta..sub.n of said UO.sub.2 pellets, is evaluated, and wherein when ##EQU10## is established, the linear heat generating rate of the nuclear fuel elements packed in the core is raised to 240 W/cm, where n represents the number of times which the power is held at a fixed level. 17. The method of operating a nuclear reactor according to claim 16, wherein after the linear heat generating rate of said nuclear fuel elements has reached at least 240 W/cm, said linear heat generating rate is increased at most about 1.8 W/cm/hour, to raise the power of said nuclear reactor. 18. The method of operating the nuclear reactor according to claim 16, wherein when ##EQU11## a linear heat generating rate P.sub.(n+1), which depends on the temperature .theta..sub.n of said UO.sub.2 pellets and which renders zero the width of the gap between said UO.sub.2 pellets and a fuel cladding of said nuclear fuel elements, is evaluated, and wherein when P.sub.(n+1) .gtoreq.240 W/cm, the linear heat generating rate of said nuclear fuel elements packed in said core is raised by the coolant control means. 19. The method of operating a nuclear reactor according to claim 18, wherein when P.sub.(n+1) .gtoreq.240 W/cm, the linear heat generating rate of the nuclear fuel elements packed in the core is raised to 240 W/cm. 20. The method of operating a nuclear reactor according to claim 18, wherein after the linear heat generating rate of said nuclear fuel elements has reached at least 240 W/cm, said linear heat generating rate is increased at most about 1.8 W/cm/hour, to raise the power of said nuclear reactor. 21. The method of operating a nuclear reactor according to claim 18, wherein when P.sub.(n+1) .gtoreq.240 W/cm, the power of the nuclear reactor is raised up to the linear heat generating rate P.sub.(n+1), whereupon the power of the nuclear reactor is held there for a fixed period of time. 22. A method of operating a nuclear reactor during the period when power of a nuclear reactor is raised so as to prevent Pellet Clad Mechanical Interaction of the fuel elements, comprising the steps of raising the power of the reactor by a first control means providing coarse power regulation from a linear heat generating rate of zero W/cm after reactor shutdown up to a linear heat generating rate of nuclear fuel elements containing oxide fuel pellets surrounded by a zirconium alloy and located in a core of the reactor which is an upper limit of operation of the first control means, raising the power of the reactor above the linear heat generating rate of the upper limit of operation of the first control means by a second control means for providing fine power regulation; and preventing Pellet Clad Mechanical Interaction of the fuel elements during the raising of the power of the reactor by stopping the raising of the power of the reactor and maintaining the power constant at least once in a range below a linear heat generating rate corresponding to a length of a shutdown period of the reactor before the linear heat generating rate reaches the upper limit of operation of the first control means, and wherein the power of said reactor is held constant at least once somewhere in the range zero to P which satisfies the relation ##EQU12## where P is a linear heat generating rate at which said nuclear fuel elements initiate the Pellet Clad Mechanical Interaction; T.sub.s is the shutdown period of the reactor; P.sub.o is a linear heat generating rate which causes said nuclear fuel elements to induce Pellet Clad Mechanical Interaction for the first time, after said reactor is restarted when the reactor shutdown period T.sub.s is zero; and T.sub.so is the reactor shutdown period when P=0. 23. The method of operating a nuclear reactor according to claim 22, wherein the upper limit of operation of the first control means is 240 W/cm, and after the linear heat generating rate of said nuclear fuel elements has reached at least 240 W/cm, the linear heat generating rate is increased by the second control means at most about 1.8 W/cm/hour, to raise the power of said nuclear reactor. 24. The method of operating a nuclear reactor according to claim 23, wherein the first control means for providing a coarse power regulation includes control rods and manipulating the control rods to raise the power of the reactor up to the linear heat generating rate which is an upper limit of operation of the control rods, the second control means providing fine power regulation including coolant control means and controlling the flow rate of a coolant supplied to the core for raising the power above the linear heat generating rate of the upper limit of operation of the first control means. 25. The method of operating a nuclear reactor according to claim 22, wherein the fuel pellets and the surrounding zirconium alloy satisfy the relation EQU G.sub.a /D.sub.i =0.024 26. The method of operating the nuclear reactor according to claim 22, wherein the power of said nuclear reactor is held constant for a period of time which satisfies the relation EQU T.gtoreq.-K.sub.1 .theta.+K.sub.2, 27. The method of operating the nuclear reactor according to claim 26, wherein the power of the nuclear reactor is held constant at a linear heat generating rate P.sub.1 which satisfies the relation ##EQU13## for a period of time T which satisfies the relation EQU T=-K.sub.1 .theta.+K.sub.2. 28. the method of operating a nuclear reactor according to claim 26, wherein the power of the nuclear reactor is held constant for the holding period of time which satisfies EQU T.gtoreq.-0.01875.theta.+17.625. 29. The method of operating the nuclear reactor according to claim 26, wherein a recovery percentage R.sub.n of self-irradiation damage of said fuel pellets, which depend on the temperature .theta. of said fuel pellets, is evaluated, and wherein when ##EQU14## is established, the linear heat generating rate of said nuclear fuel elements packed in said core is raised to the linear heat generating rate which is the upper limit of operation of said first control means, where n represents the number of times which the power is held at a fixed level. 30. The method of operating a nuclear reactor according to claim 29, wherein when ##EQU15## a linear heat generating rate P.sub.(n+1), which depends on the temperature .theta..sub.n of said fuel pellets and which renders zero the width of a gap between said fuel pellets and a fuel cladding of said nuclear fuel elements, is evaluated, and wherein when P.sub.(n+1) .gtoreq. (the linear heat generating rate which is the upper limit of operation of the first control means), the linear heat generating rate of said nuclear fuel elements packed in said core is raised by the second control means. 31. The method of operating a nuclear reactor according to claim 30, wherein when P.sub.(n+1) .gtoreq. (the linear heat generating rate which is the upper limit of operation of the first control means), the linear heat generating rate of said nuclear fuel elements packed in the core is raised to the upper limit of operation of the first control means. 32. The method of operating a nuclear reactor according to claim 30, wherein when P.sub.(n+1) < (the linear heat generating rate which is the upper limit of operation of the first control means), the power of said nuclear reactor is raised up to said linear heat generating rate P.sub.(n+1), whereupon the power of said nuclear reactor is held there for a fixed period of time. 33. The method of operating the nuclear reactor according to claim 32, wherein the first control means for providing a coarse power regulation includes control rods and manipulating the control rods to raise the power of the reactor up to the linear heat generating rate which is an upper limit of operation of the control rods, the second control means providing fine power regulation including coolant control means and controlling the flow rate of a coolant supplied to the core for raising the power above the linear heat generating rate of the upper limit of operation of the first control means. 34. The method of operating a nuclear reactor according to claim 33, wherein the upper limit of operation of the first control means is 240 W/cm, and after the linear heat generating rate of said nuclear fuel elements has reached at least 240 W/cm, the linear heat generating rate is increased by the second control means at most about 1.8 W/cm/hour, to raise the power of said nuclear reactor. |
052710548 | summary | BACKGROUND OF THE INVENTION The invention relates to the use of stress relieving slots in the forming of perimeter strip grid corner-pieces of increased flatness. The grids are elements of nuclear fuel assemblies and particularly are useful as nuclear fuel assembly support grids designed to avoid hang-up of grid corners during insertion into the core of a nuclear reactor vessel. In the past, nuclear fuel grids were constructed with non-formed beveled corners. When loading or unloading nuclear reactors with individual fuel assemblies, assemblies diagonally adjacent to each other could become caught at the outer corner of the grid. This type of hooking has in the past lead to destruction of the perimeter strips of grids, so that the assemblies could not be re-inserted into the core. This is especially true for fuel assemblies which have been bowed during operation. To overcome this problem, it has been proposed to use formed corners. See U.S. Pat. No. 4,705,663 to J. Steven. The corner would be formed by pushing the strip material inward toward the corner fuel rod at the top and bottom strip edges, thus causing the corner to curve inward forming a beveled corner and providing varying radii in the transverse direction with its outer longitudinal portions having a greater radius than its inner portion. Since the corner has a larger bevel the problem of grid hooking less likely. However, these corners have not been used in grids with small cut-out features in the perimeter strips because flexing deformation occurred which destroyed the flatness of the flat side sections on either side of the transverse corner bend line. These deformations were caused by corner forming. This occurrence was denoted "oil canning" and was caused by attempts to design "camming-corner" perimeter strips. SUMMARY OF THE INVENTION To eliminate the problem of flexed deformation or oil canning, additional cut-outs of different sizes, shapes and types were made in the perimeter strip. A slot located next to the support features, i.e., the arches and the springs, if necessary, was determined to provide the best flatness characteristics. It was positioned to eliminate most of the corner forming stresses, thus eliminating the flexed deformation oil canning of the strip. The size of the slot was designed to allow the grid to maintain its overall mechanical strength while only slightly changing the grid's corner cell arch stiffness. Without the addition of these slots the formed beveled corner could not be produced on commercial Inconel grids for nuclear fuel assemblies with small cut-outs for arches and pilot holes. The location and type of slot is not obvious. In fact, two metal forming experts consulted, who together have over 80 years of metal forming experience, did not believe the described slot would solve the problem. However, the addition of the slots eliminated the instability and flexed deformation in the strip and prevented oil canning to provide an improved perimeter strip grid corner-piece of increased flatness on either side of the transverse bend line. |
039322157 | claims | 1. In a nuclear reactor of the type having an elongated tube for guiding an absorber, a control rod mechanism having raised and lowered positions for rapidly and safely shutting off the nuclear reactor comprising, a flexible absorber guided in said tube for movement between a raised shut-off and a lowered position, a connecting means suspending said absorber within said elongated tube, spring means operatively connected to said connecting means, a drive mechanism connected for compressing said spring means and lowering the absorber release means for releasably holding said spring means in said compressed condition wherein release of said spring means causes the latter to effect accelerating vertical displacement of said connecting means and absorber to the raised position of the absorber and means for disposing said spring means, drive mechanism and release above said elongated tube. 2. A control rod mechanism according to claim 1 comprising means for separating a portion of said connecting means from said absorber including pin means and slot means for simultaneously locking said absorber in its raised position, the pin means mounted in slots in the lower portion of the separating means, the pins having latches, a tube connected to the absorbing means, said latches engaging openings in said tube. 3. A control rod mechanism according to claim 1 wherein said elongated tube is traversible by coolant and is formed with an open lower end section, said absorber comprising a plurality of members hinged to one another to allow their longtudinal axes to intersect at an angle, said absorber being guided in said elongated tube, the lowermost of said absorber members being receivable in said lower end section of said elongated tube said lowermost absorber member closely fitting into said lower end section in its lowered position, so as to substantially seal the bottom of said guide tube, thereby preventing the flow of coolant through said guide tube. 4. A control rod mechanism according to claim 1 wherein said connecting means has a tie rod with hollow interior containing a wire rope secured at both ends thereof. |
058964320 | claims | 1. A method of brazeless bonding of dissimilar materials to fabricate a sensor for measuring electrochemical corrosion potential in a nuclear reactor comprising: joining an electrical tip conductor to a sensor tip; joining an electrical cable to said tip conductor; and fusing under heat a ceramic powder around said tip conductor to form an integral annular electrically insulating band therearound. firstly applying a bond coating to said tip conductor; and secondly plasma spraying said ceramic powder over said bond coating to form a ceramic coating thereon. positioning a pre-formed ceramic sleeve around said band; and sealing said sleeve at opposite ends thereof to said tip and said cable. welding said sleeve to a metal transition piece; and welding said transition piece to said cable, with said cable having a central conductor spot welded to said tip conductor. a sensor tip electrically joined to a conductor; electrical cable electrically joined to said tip conductor; and an annular electrical insulating ceramic band bonded to said tip and tip conductor without ceramic-to-metal brazes. 2. A method according to claim 1 wherein said band is also bonded to said tip conductor to form a hermetic seal. 3. A method according to claim 2 wherein said band includes an outer exposed surface formed of yttria-stabilized-zirconia or magnesia-stabilized-zirconia. 4. A method according to claim 3 wherein said fusing step comprises plasma spraying said powder over said tip conductor. 5. A method according to claim 4 wherein said fusing step further comprises: 6. A method according to claim 5 further comprising applying successively a plurality of said bond and ceramic coatings atop said tip conductor to effect redundant layers of electrical insulation and sealing. 7. A method according to claim 6 further comprising: 8. A method according to claim 7 further comprising packing a ceramic powder between said sleeve and said band to remove voids therebetween, prior to sealing said sleeve to said cable. 9. A method according to claim 8 wherein both said sleeve and packing powder are yttria-stabilized-zirconia. 10. A method according to claim 9 wherein said sealing step comprises plasma spraying additional amounts of said ceramic powder over said sleeve ends at said tip and said cable. 11. A method according to claim 3 wherein said fusing step comprises molding and sintering said ceramic powder over said tip conductor to form a one-piece insulating band bonded to said sensor tip. 12. A method according to claim 11 further comprising fusing a metal sleeve around one end of said band spaced apart from said sensor tip. 13. A method according to claim 12 wherein said sleeve fusing step comprises hot isostatic pressing of said sleeve to said band. 14. A method according to claim 12 wherein said sleeve fusing step comprises hot pressure bonding of said sleeve to said band. 15. A method according to claim 12 further comprising: 16. A sensor for measuring electrochemical corrosion potential in a nuclear reactor comprising: 17. A sensor according to claim 16 wherein said band comprises a plurality of layers of fused ceramic powder. 18. A sensor according to claim 16 wherein said band comprises a plurality of alternating layers of fused ceramic powder atop corresponding bond coatings. 19. A sensor according to claim 16 further comprising a ceramic sleeve surrounding said band, and sealingly joined to said sensor tip and cable, and said band and sleeve comprise yttriastabilized-zirconia or magnesia-stabilized-zirconia. 20. A sensor according to claim 16 wherein said band comprises fused ceramic powder bonded in one-piece to said tip and conductor. |
054240425 | abstract | A system for vitrifying all kinds of waste, including toxic, industrial, household and radioactive wastes such as those generated by nuclear power plants, including dry active wastes, ion exchange resins and aqueous wastes wherein the wastes are conditioned, blended, mixed with glass formers and then fed into a heating chamber where organic constituents of the waste are burned and inorganic constituents are melted with the glass formers to form a waste glass. The aqueous waste may be conditioned by concentrating its solids content up to as much as 90% solids. The dry active waste is conditioned, and mixed to some extent by shredders. The conditioned waste may be blended to achieve a uniform heat energy content of the waste being fed into the heating chamber. The heating chamber has a larger combustion zone to handle the greater amount of organic waste than would be expected in conventional melters, and a melting zone having a replaceable crucible and liner. The combustion takes place in an oxygen-enriched atmosphere formed by a mixture of oxygen enriched gas and including a portion of the off-gas if desired, which is still enriched following combustion. Particulate removed from the off-gas is returned to the melting chamber or is solidified by the liquid/solids blender/dryer. The molten waste glass is cooled and put into a form suitable for storage, such as a glass frit, globules, or glass monoliths. |
description | First Preferred Embodiment First, the whole structure of an electron microscope with which the sample holders etc. of the present invention are used is briefly described. FIG. 1 is a schematic diagram showing an example of the structure of an electron microscope which uses the sample holders etc. of the invention. Some drawings including FIG. 1 are shown with an XYZ orthogonal coordinate system as needed, to clearly show how they are directed relative to each other. The electron microscope shown in FIG. 1 is a transmission electron microscope (TEM). The TEM 1 has a body tube 2 which principally contains an electron gun 3, a condenser lens system 4, and an objective lens system 5. The sample holder 10 can be inserted in and removed from the body tube 2 sideways. The sample holder 10 on which a sample to be observed is set is inserted into the body tube 2 to hold the observed sample in the sample chamber between the condenser lens system 4 and the objective lens system 5. The inside of the body tube 2 is highly evacuated and the electron gun 3 emits electrons accelerated at high acceleration voltage. As shown by the arrow AR1, the electrons emitted from the electron gun 3 are condensed by the condenser lens system 4 and the electron beam hits the observed sample along the Z direction. The incident electrons are transmitted through the observed sample (part of them are scattered) and the objective lens system 5 causes the transmitted electrons to form an image on the fluorescent plane 7. The user observes the image formed on the fluorescent plane 7 from the observing window 6. The TEM 1 of FIG. 1 is equipped with EDS (Energy Dispersive X-ray Spectroscopy); its detector 8 is attached to the body tube 2. In the EDS, the detector 8 measures the energy of characteristic X-rays generated as the electron beam enters the observed sample to analyze the composition of the observed sample. The TEM 1 may be equipped with other functions, such as a mechanism for photographing the image formed by the objective lens system 5, EELS (Electron Energy Loss Spectroscopy), etc. FIG. 2 is a diagram showing the structure of the sample holder 10. This diagram shows the sample holder 10 seen from above, i.e. from the direction of incidence of the electron beam. The sample holder 10 has the main part 11, holding part 30 and connecting part 20 connecting the two. The main part 11 contains a motor 12 and the holding part 30 contains a bevel gear 15 and a bevel gear 14. The motor 12 and the bevel gear 14 are coupled through a rotating shaft 13 provided through the connecting part 20. As shown in FIG. 3, the observed sample SA, a semiconductor device processed for observation with TEM, is fixed on a sample mount 17 with an adhesive such as a thermosetting resin. The sample mount 17 is fastened to the rotating mount 16 with screws 19 and the rotating mount 16 is fastened to the bevel gear 15 with a screw 18. The rotating mount 16 can rotate relative to the holding part 30 as the bevel gear 15 rotates. The bevel gear 15 is meshed with the bevel gear 14, which in turn is coupled to the motor 12 through the rotating shaft 13. With this structure, normal or reverse rotation of the motor 12 on its axis extending in the X direction is transferred through the rotating shaft 13 to the bevel gear 14, which is then converted by the bevel gear 14 and the bevel gear 15 into rotation on the axis extending in the Y direction. The bevel gear 15 rotates to rotate the rotating mount 16, the sample mount 17 and the observed sample SA affixed on the sample mount 17 on the axis in the Y direction. The rotatable range of the sample mount 17 is not specifically limited; it can rotate in the range of 0 to 360xc2x0 as needed. The sample holder 10 itself can be turned on the axis extending in the X direction. The sample holder 10 is turned in a predetermined angle range by a goniometer attached to the body tube 2 of the TEM 1. The sample holder 10 turns to turn the observed sample SA around the axis in the X direction. Thus the sample mount 17 on which the observed sample SA is affixed can be turned around the axis in the X direction by the goniometer attached to the TEM 1 and can be also rotated by the motor 12 in the range of 0 to 360xc2x0 around the axis in the Y direction. The observing direction, or the direction of incidence of the electron beam, is in the Z direction, which means that the sample mount 17 on which the observed sample SA is affixed rotates in the range of 0 to 360xc2x0 about the axis directed in a different direction from the incidence direction of the electron beam. Thus the electron beam can enter the observed sample SA from many directions; particularly it can enter the periphery around the Y axis in any directions, thus allowing the sample SA to be observed from many directions. The sample holder 10 of this preferred embodiment also allows the sample SA to be FIB-processed without being removed from the sample holder 10. FIG. 4 is a diagram showing the FIB processing to the sample SA set on the sample holder 10. With the sample SA affixed on the sample mount 17 of the sample holder 10, the sample holder 10 is set in an FIB processing apparatus and a beam of Ga ions is applied to the sample SA from the Y direction as shown by the arrows AR4 in FIG. 4. For the FIB processing, the holding part 30 has an opened space on the (+Y) side seen from the sample SA. The ion beam can be applied to the sample SA from many directions since the sample mount 17 and the sample SA affixed on it can be rotated by the motor 12 in the range of 0 to 360xc2x0 on the axis in the Y direction, which allows the sample SA to be processed in many directions. In this way, the use of the sample holder 10 permits the sample mount 17 and the sample SA affixed on it to rotate in the range of 0 to 360xc2x0 about the axis in the Y direction which is different from the electron beam incidence direction, thus allowing the sample SA to be observed from many directions. Moreover, it is possible to apply FIB processing to the sample SA in many directions without removing the sample SA from the sample holder 10, which simplifies the handling in the FIB processing. Second Preferred Embodiment Next, a second preferred embodiment of the present invention is described. The second preferred embodiment differs from the first preferred embodiment in that the connecting part 20 including the rotating shaft 13 is not integrally formed as one unit but can be disconnected; the structure is the same as that of the first preferred embodiment in other respects. FIG. 5 is a diagram showing the main part of the structure of the connecting part 20 of the second preferred embodiment. The connecting part 20 can be separated into a cartridge section 21 and a fixed section 22. The cartridge section 21 is coupled to the holding part 30 including the sample mount 17. The fixed section 22 is fixed to the main part 11. The holding part 30 including the sample mount 17 and the main part 11 are the same in structure as those in the first preferred embodiment. The first rotating shaft 24 is connected to the motor 12 and hence rotates as the motor 12 rotates. The second rotating shaft 23 is connected to the bevel gear 14 and the bevel gear 14 hence rotates as the second rotating shaft 23 rotates. When the cartridge section 21 is moved in the direction shown by the arrow AR5 in FIG. 5, the end of the cartridge section 21 fits into the fixed section 22. Further moving the cartridge section 21 causes the spline shaft 23a of the second rotating shaft 23 to fit into the spline hole 24a of the first rotating shaft 24. The spline shaft 23a has grooves formed along the length direction of the second rotating shaft 23 and the spline hole 24a has grooves into which they fit. The cartridge section 21 is then fastened to the fixed section 22 with fixing screws 25, with the spline shaft 23a fitting in the spline hole 24a. The spline shaft 23a and the spline hole 24a are fitted together through the so-called spline fit, where their grooves engage with each other to transfer the rotating power. That is to say, when the cartridge section 21 is fixed to the fixed section 22 with the fixing screws 25, the spline shaft 23a fits in the spline hole 24a so that the rotation of the motor 12 is transferred to the bevel gear 14 through the first rotating shaft 24 and the second rotating shaft 23. Hence, as in the first preferred embodiment, the sample mount 17 on which the observed sample SA is affixed can be rotated in the range of 0 to 360xc2x0 on the axis extending in the Y direction which is different from the direction of incidence of the electron beam, which allows the electron beam to enter the observed sample SA from many directions so that the observed sample SA can be observed from many directions. Furthermore, in the FIB processing, the ion beam can be applied to the observed sample SA from many directions, thus allowing FIB processing of the sample SA from many directions. When the cartridge section 21 is connected to the fixed section 22, the cartridge section 21 can be separated and removed from the fixed section 22 just by loosening the fixing screws 25. Conventionally, the process of replacing the sample has been very difficult and unavoidably inefficient because the TEM-observed sample SA is so small. According to the second preferred embodiment, however, the sample can be replaced easily to improve the working efficiency by preparing a plurality of samples SA affixed on a plurality of sample mounts 17 coupled to the cartridge sections 21 and changing the cartridge sections 21 as needed. As described above, in the second preferred embodiment, the cartridge section 21 coupled to the sample mount 17 can be attached to and removed from the fixed section 22 coupled to the main part 11 of the sample holder 10. It thus provides the same effects as those of the first preferred embodiment when the cartridge section 21 is connected to the main part 11. Further, the samples can be easily changed just by replacing the cartridge section 21, thus improving the working efficiency. The means for connecting the first rotating shaft 24 and the second rotating shaft 23 is not limited to the spline fit; any means can be used as long as it can connect them so that the rotating power can be transferred from the first rotating shaft 24 to the second rotating shaft 23. Third Preferred Embodiment Next, a third preferred embodiment of the invention is described. The third preferred embodiment shows a sample mount jig for grasping and holding the sample mount 17 attached to the above-described sample holder 10. FIGS. 6A and 6B are diagrams showing a sample mount jig 35 for grasping and holding the sample mount 17. FIG. 6A is a side view of the sample mount jig 35 and FIG. 6B is a bottom view of the sample mount jig 35. The sample mount jig 35 has a protector section 36 which, when grasping the sample mount 17, covers the sample SA affixed on the sample mount 17, and a grip 37 fixed to the protector section 36. The protector section 36 has a fitting portion 36a in which the sample mount 17 fits and openings 36b. The fitting portion 36a is a groove shaped to fit the longer side of the sample mount 17. FIG. 7 is a diagram used to explain how the sample mount 17 is attached and removed using the sample mount jig 35. With the sample mount 17 fixed to the rotating mount 16 with the screws 19, the sample mount jig 35 is moved closer to the sample mount 17 from the (+Y) direction and the sample mount 17 then fits in the fitting portion 36a. The protector section 36 of the sample mount jig 35 thus covers and protects the sample SA affixed on the sample mount 17. The screws 19 stay uncovered in the openings 36b. The screws 19 are then loosened through the openings 36b and the sample mount jig 35 is separated from the sample holder 10; the sample mount 17 grasped by the sample mount jig 35 is also separated from the rotating mount 16. The sample SA is then stored on the sample mount 17 fitted in the sample mount jig 35, so that the protector section 36 protects the observed sample SA from breakage etc. The sample mount 17 can be attached to the sample holder 10 by the reverse procedure. That is to say, the sample mount jig 35 grasping and holding the sample mount 17 on which the sample SA is affixed is moved closer to the rotating mount 16 and the screws 19 are tightened through the openings 36b with the sample mount 17 abutting on the rotating mount 16. The sample mount jig 35 is then moved apart from the rotating mount 16 so that the sample mount 17 comes out from the fitting portion 36a of the sample mount jig 35, leaving the sample mount 17 attached to the sample holder 10. As above, the use of the sample mount jig 35 of the third preferred embodiment eliminates the need for handling with tweezers to replace the sample SA, which facilitates the process and enhances the process efficiency. Furthermore, the use of the sample mount jig 35 allows the sample SA to be stored together with the sample mount 17 on which it is affixed, with the protector section 36 protecting the sample SA from damage etc. Instead of the structure where the sample mount 17 is fixed to the rotating mount 16 with the screws 19, the sample mount 17 may have a threaded part which screws in the rotating mount 16. Also in this case, the above effect can be obtained by rotating the sample mount jig 35 with the sample mount 17 fitted in the fitting portion 36a. Fourth Preferred Embodiment Next, a fourth preferred embodiment of the invention is described. In the fourth preferred embodiment, a sample mount which is attached to the sample holder is described. FIG. 8 is a perspective view showing a sample mount 40 of the fourth preferred embodiment. FIGS. 9A, 9B and 9C are a front view, side view and plane view of the sample mount 40, respectively. The sample mount 40 is formed of a mount plate 41 on which the observed sample SA is affixed and mounted and a support plate 42 supporting the mount plate 41; the mount plate 41 and the support plate 42 are combined together in L shape in section. The mount plate 41 has a gap 43 narrower than the length of the observed sample SA. The observed sample SA is laid over the opposite sides of the gap 43. The gap 43 continues in part of the support plate 42. The length direction, height direction and width direction of the observed sample SA affixed on the sample mount 40 are defined as shown in FIG. 8. According to the sample mount 40 of the fourth preferred embodiment, the gap 43 allows the sample SA to be observed also in its height direction. FIG. 10 shows a sample holder 10 for use with the sample mount 40 of the fourth preferred embodiment. This sample holder 10 differs from those shown in the first to third preferred embodiments in that the holding part 30 has a fixing groove 45. The support plate 42 of the sample mount 40 is inserted in the fixing groove 45 and the fixing screw 46 is tightened to fix the sample mount 40 to the holding part 30. The support plate 42 of the sample mount 40 may be fixed to the rotating mount 16 with the screws 19 as explained in the first to third preferred embodiments. In other respects the sample holder 10 of the fourth preferred embodiment is equivalent to the sample holder 10 shown in the first to third preferred embodiments (see FIG. 2). In the fourth preferred embodiment, the sample SA can be observed from its length direction, height direction and width direction through the use of the sectionally L-shaped sample mount 40. FIGS. 11 and 12 are diagrams showing the sample SA being observed by using the sample mount 40 of the fourth preferred embodiment. In FIG. 11, the support plate 42 of the sample mount 40 is fitted in the fixing groove 45 with the normal direction of the mount plate 41 directed along the Z direction, i.e. the direction of the incidence of the electron beam. The mount plate 41 has the gap 43 and the observed sample SA is positioned over the gap 43 across its opposite sides, so that the electron beam incident from the Z direction and transmitted through the observed sample SA in its height direction can pass through the gap 43. The sample SA can thus be observed from its height direction. In FIG. 12, the support plate 42 of the sample mount 40 is fixed to the rotating mount 16. The direction of incidence of the electron beam (Z direction) and the mount plate 41 are parallel with each other in FIG. 12. In this case, as in the first preferred embodiment, the sample mount 40 on which the observed sample SA is affixed can be rotated by the motor 12 in the range of 0 to 360xc2x0 about the axis in the Y direction. Therefore the sample SA can be observed from arbitrary directions in the plane formed by the length direction and the width direction of the sample SA, depending on the rotation angle of the sample mount 40. As above, in the fourth preferred embodiment, the use of the sample mount 40 having the gap 43 enables the sample SA to be observed not only from its length direction and width direction but also from its height direction; the sample SA can thus be observed from a greater number of directions. Furthermore, the sample SA can be handled easily since it can be attached to and removed from the sample holder 10 by attaching and removing the relatively large sample mount 40 to and from the sample holder 10. Fifth Preferred Embodiment Next, a fifth preferred embodiment of the present invention is described. FIG. 13 is a perspective view showing a sample mount 50 of the fifth preferred embodiment. As already stated, the TEM 1 has EDS, where the detector 8 measures the energy of the characteristic X-rays generated as the electron beam enters the observed sample SA to analyze the composition of the observed sample SA. When the sample mount 40 as shown in the fourth preferred embodiment is used in this process, the scattered electron beam from the support plate 42 affects the sensitivity of the detector 8 to reduce the measuring accuracy. Accordingly, the fifth preferred embodiment uses the plate-like sample mount 50 having a gap 53. The gap 53 has a width narrower than the length of the observed sample SA and the observed sample SA is laid over the opposing sides of the gap 53. The sample mount 50 on which the observed sample SA is affixed is fixed in the fixing groove 45 of the sample holder 10 of the fourth preferred embodiment, for example. The sample mount 50 is fixed with its normal direction directed along the Z direction or the direction of incidence of the electron beam. Thus, as in the fourth preferred embodiment, the electron beam passed through the sample SA in its height direction can pass through the gap 53 and the sample SA can be observed from the height direction. Since the sample mount 50 is formed in the form of a flat plate, the measurement with EDS provides good accuracy without suffering from scattered electron beam which may be caused by the support plate 42 of the sample mount 40. Sixth Preferred Embodiment Next, a sixth preferred embodiment of the invention is described. FIGS. 14A and 14B are diagrams showing a sample holder 60 of the sixth preferred embodiment. FIG. 14A is a plane view of the sample holder 60 and FIG. 14B is a front view showing its structure. This sample holder 60 is constructed by adding a clamp plate 62 and a screw 63 to the conventional common two-axis inclined sample holder (see FIG. 19). The sample mount 40 of the fourth preferred embodiment can be attached to the sample holder 60 by pressing the support plate 42 of the sample mount 40 with the clamp plate 62 and tightening the screw 63. That is to say, the clamp plate 62 and the screw 63 function as a holding portion for holding the support plate 42 of the sample mount 40. In other respects it is the same as the conventional two-axis inclined sample holder. The sample holder 60 can be said to be a modification of the conventional two-axis inclined sample holder which has been modified to allow attachment of the sample mount 40 of the fourth preferred embodiment. As shown in the fourth preferred embodiment, the sample SA is laid over the opposing sides of the gap 43 of the mount plate 41. Then the sample mount 40 is attached to the sample holder 60 in such a manner that the Z direction or the direction of the electron beam incidence extends parallel to the mount plate 41. Accordingly the electron beam incident from the Z direction passes through the observed sample SA in its width direction to allow observation of the sample SA from its width direction. Needless to say, the sample holder 40 on which the observed sample SA is affixed is capable of the X-axis inclination and the Y-axis inclination like the conventional sample mount. As stated in the first preferred embodiment, an ion beam is applied from the Y direction when applying the FIB process to the sample SA. As shown in FIG. 14B, the clamp plate 62 and the screw 63 hold the sample mount 40 in such a manner that the part of the mount plate 41 where the observed sample SA is affixed protrudes from the sample holder 60. Accordingly, when the sample mount 40 is attached to the sample holder 60, the (+Y) side seen from the observed sample SA is opened. It is therefore possible to FIB-process the sample SA without removing the sample SA from the sample holder 60, which facilitates the handling in the FIB processing. Seventh Preferred Embodiment Next, a seventh preferred embodiment of the invention is described. FIG. 15 is a diagram showing a sample holder 70 of the seventh preferred embodiment. A holding part 71 for holding the sample mount 40 is provided at the end of the sample holder 70. The holding part 71 has a holding screw 72, a holding screw 73, and a holding groove 75. The sample mount 40 shown in the fourth preferred embodiment is used in the seventh preferred embodiment. The sample holder 70 of the seventh preferred embodiment does not have a rotating mechanism. This sample holder 70 can hold in three ways the sample mount 40 on which the sample SA is affixed. FIGS. 16A to 16C are diagrams showing the ways in which the sample mount 40 is attached to the sample holder 70. First, as shown in FIG. 16A, the support plate 42 of the sample mount 40 is inserted between the holding groove 75 and the clamp plate 74 and the holding screw 72 is tightened to fix the sample mount 40. The mount plate 41 of the sample mount 40 extends parallel with the direction of the electron beam incidence and the normal direction of the mount plate 41 or the height direction of the observed sample SA extends along the Y direction. In this case, the electron beam incident from the Z direction passes through the observed sample SA in its width direction, thus allowing observation of the sample SA from the width direction. Next, the support plate 42 is fixed to the holding part 71 with the holding screw 73 as shown in FIG. 16B to attach the sample mount 40. The support plate 42 has a hole through which the holding screw 73 passes. The normal direction of the mount plate 41 (the height direction of the observed sample SA) extends along the X direction. In this case, the electron beam incident from the Z direction passes through the observed sample SA in its length direction to allow observation of the sample SA from its length direction. Finally, the support plate 42 is fixed to the holding part 71 with the holding screw 73 as shown in FIG. 16C to attach the sample mount 40. Unlike that shown in FIG. 16B, the normal direction of the mount plate 41 (the height direction of the observed sample SA) is directed along the Z direction. Since the mount plate 41 has the gap 43 as already stated and the observed sample SA is laid over the opposite sides of the gap 43, the electron beam incident from the Z direction and transmitted through the observed sample SA in its height direction can pass through the gap 43. The sample SA can thus be observed from its height direction. As explained above, in the seventh preferred embodiment, the holding part 71 and the holding screw 73 realize a first holding portion which holds the support plate 42 with the normal direction of the mount plate 41 extending along the electron beam incidence direction (Z direction) in the TEM 1, and a second holding portion which holds the support plate 42 with the normal direction of the mount plate 41 extending along the X direction which is vertical to the electron beam incidence direction. Also, the holding part 71 and the holding screw 72 realize a third holding portion which holds the support plate 42 with the normal direction of the mount plate 41 extending along the Y direction which is vertical to both of the electron beam incidence direction and the X direction. Accordingly the sample SA can be observed from three directions, i.e. from a greater number of directions than in the conventional one. Further, when the sample mount 40 is fixed as shown in FIG. 16B, the (+Y) side seen from the sample SA is opened. Then it is possible to FIB-process the sample SA without removing the sample SA from the sample holder 70, which facilitates the handling in the FIB process. Eighth Preferred Embodiment Next an eighth preferred embodiment of the invention is described. FIG. 17 is a diagram showing a sample holder 80 of the eighth preferred embodiment. The sample holder 80 has at its one end a holding part 81 for holding the sample mount 40. The holding part 81 includes a holding screw 83, a holding screw 84 and a holding groove 82. The sample mount 40 of the fourth preferred embodiment is used in the eighth preferred embodiment. The sample holder 80 of the eighth preferred embodiment does not have a rotating mechanism. However, the entirety of the sample holder 80 including the holding part 81 can be rotated in the range of 0 to 360xc2x0 around the X-direction axis by a goniometer attached to the body tube 2 of the TEM 1. FIGS. 18A to 18C are diagrams showing the ways in which the sample mount 40 is attached to the sample holder 80. In FIG. 18A, the support plate 42 of the sample mount 40 is inserted in the holding groove 82 and pinched between the holding screw 83 and the holding screw 84, whereby the sample mount 40 is fixed. The mount plate 41 is parallel to the direction of the electron beam incidence (Z direction) and its normal direction is directed along the X direction. Accordingly, in the condition shown in FIG. 18A, the electron beam incident from the Z direction passes through the observed sample SA in its length direction, whereby the sample SA can be observed from its length direction. The entirety of the sample holder 80 can be rotated in the range of 0 to 360xc2x0 on the axis in the X direction. FIG. 18B shows the sample holder 80 rotated by 90xc2x0 from the condition shown in FIG. 18A. Since the normal direction of the mount plate 41 lies along the X direction, the mount plate 41 stays parallel to the direction of the electron beam incidence (Z direction) even when rotated on the axis in the X direction. Accordingly, in the condition shown in FIG. 18B, the electron beam incident from the Z direction passes through the observed sample SA in its width direction, whereby the sample SA can be observed from the width direction. Thus, when the sample holder 80 is rotated, the sample SA can be observed from arbitrary directions on the plane formed by the length direction and the width direction of the sample SA depending on the rotated angle. Also in FIG. 18C, the support plate 42 of the sample mount 40 is inserted in the holding groove 82 and is pinched between the holding screw 83 and the holding screw 84, whereby the sample mount 40 is fixed. In this case, unlike that shown in FIG. 18A, the normal direction of the mount plate 41 extends along the Z direction. Since the mount plate 41 has the gap 43 and the sample SA is laid over the opposite sides of the gap 43, the electron beam incident from the Z direction and transmitted through the observed sample SA in the height direction can pass through the gap 43. The observed sample SA can thus be observed from its height direction. As described above, in the eighth preferred embodiment, when the holding part 81 holds the support plate 42 of the sample mount 40 in such a manner that the normal direction of the mount plate 41 is directed along the direction of the electron beam incidence in the TEM 1 (Z direction) or along the X direction which is vertical to the direction of the electron beam incidence. Further, since the entirety of the sample holder 80 including the holding part 81 can be rotated in the range of 0 to 360xc2x0 about the X-direction axis, the sample SA can be observed from arbitrary directions in the plane formed by the length direction and the width direction of the sample SA and also from the height direction of the sample SA. The sample SA can thus be observed from a greater number of directions than in the seventh preferred embodiment. In the eighth preferred embodiment, the (+Y) side seen from the observed sample SA is opened. Therefore it is possible to FIB-process the sample SA without removing the sample SA from the sample holder 80, which facilitates the handling in the FIB processing. While the preferred embodiments above have shown applications of the sample holders etc. to a transmission electron microscope (TEM), they can be applied also to other types of electron microscopes, such as scanning electron microscopes (SEM), as needed. While the invention has been described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is understood that numerous other modifications and variations can be devised without departing from the scope of the invention. |
|
abstract | Disclosed is an X-ray reflecting device and an X-ray reflecting element constituting the X-ray reflecting device capable of facilitating a reduction in weight and being prepared in a relatively simple manner. The X-ray reflecting element of the present invention comprises a body made of a solid silicon, and a plurality of slits formed in the body in such a manner as to penetrate from a front surface to a back surface of the body. Each of the slits has a wall surface serving as an X-ray reflecting surface. To allow the slits in the respective X-ray reflecting elements to be located in a given positional relationship with each other, the X-ray reflecting device of the present invention comprises a plural number of the X-ray reflecting elements, which are formed into a multilayered structure in such a manner or arranged side-by-side in a horizontal direction in such a manner as to allow the slits in the respective X-ray reflecting elements to be located in a given positional relationship with each other, or stacked on each other in a vertical direction to form a stacked structure in such a manner as to allow the slits in the respective X-ray reflecting elements to be located in a given positional relationship with each other. Further, the X-ray reflecting device may comprise a plural number of the stacked structures arranged side-by-side in a horizontal direction. |
|
048328995 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT In the operation of a commercial pressurized water reactor it is desirable to be able to prolong the life of the reactor core to better utilize the uranium fuel thereby reducing the fuel costs. The invention described herein provides a means to extend reactor core life by controlling reactor core moderation. Referring to FIG. 1, the nuclear reactor is referred to generally as 20 and cmprises a reactor vessel 22 with a removable closure head 24 attached to the top end thereof. An inlet nozzle 26 and an outlet nozzle 28 are connected to reactor vessel 22 to allow a coolant such as water to circulate through reactor vessel 22. A core plate 30 is disposed in the lower portion of reactor vessel 22 and serves to support fuel assemblies 32. Fuel assemblies 32 are arranged in reactor vessel 22 and comprise reactor core 34. As is well understood in the art, fuel assemblies 32 generate heat by nuclear fissioning of the uranium therein. The reactor coolant flowing through reactor vessel 22 in heat transfer relationship with fuel assemblies 32 transfers the heat from fuel assemblies 32 to electrical generating equipment located remote from nuclear reactor 20. A plurality of control rod drive mechanisms 36 which may be chosen from those well known in the art are disposed on closure head 24 for inserting or withdrawing control rods (not shown) from fuel assemblies 32. In addition, a plurality of displacer rod drive mechanisms 38 are also disposed on closure head 24 for inserting or withdrawing displacer rods 40 from fuel assemblies 32. Displacer rod drive mechanism 38 may be similar to the one described in copending U.S. patent application Ser. No. 217,055, filed herewith in the name of L. Veronesi et al. entitled "Hydraulic Drive Mechanism" and assigned to the Westinghouse Electric Corporation now U.S. Pat. No. 4,550,941 dated Nov. 5, 1985. For purposes of clarity, only a selected number of displacer rods 40 are shown in FIG. 1. However, it should be understood, that the number of displacer rods 40 are chosen to correspond to the number of displacer rod guide tubes in fuel assemblies 32. A plurality of displacer rod guide structures 42 are located in the upper section of reactor vessel 22 with each being in alignment with a displacer rod drive mechanism 38 for guiding the movement of displacer rods 40 through the upper section of reactor vessel 22. A calandria 44 may be arranged between fuel assemblies 32 and displacer rod guide structures 42 and comprises a multiplicity of hollow stainless steel tubes arranged in colinear alignment with each displacer rod and control rod for providing guidance of the displacer rods and control rods through the calandria area and for minimizing flow induced vibrations in the displacer rods and control rods. Referring now to FIGS. 2-4, fuel assemblies 32 comprise fuel elements 48, grids 50, bottom nozzle 52, top nozzle 54, and guide tubes 56. Fuel elements 48 may be elongated cylindrical metallic tubes containing nuclear fuel pellets and having both ends sealed by end plugs. Fuel elements 48 may be arranged in a substantially 20.times.20 rectangular array and are held in place by grids 50. Guide tubes 56 which may number 25 are arranged in a generally 5.times.5 array within each fuel assembly 32. Each guide tube 56 occupies the space of about four fuel elements 48 and extend from bottom nozzle 52 to top nozzle 54 and provide a means to support grids 50, top nozzle 54 and bottom nozzle 52. Guide tubes 56 may be hollow cylindrical metallic tubes manufactured from Zircaloy and capable of accommodating rods such as displacer rods 40 or control rods. Displacer rods 40 and control rods are manufactured to be approximately the same size so that each guide tube 56 can equally accommodate either a displacer rod or a control rod. When not occupied by a rod, guide tubes 56 are filled with reactor coolant; however, when displacer rods 40 are inserted in guide tubes 56 displacer rods 40 displace the coolant therein. Grids 50 are positioned at various locations along the length of fuel assembly 32 and serve to space fuel elements 48 and guide tubes 56 at appropriate distances from each other and to allow the reactor coolant to circulate in heat transfer relationship with fuel elements 48. A more detailed description of a similar grid may be found in U.S. Pat. Nos. 3,379,617 and 3,379,619, both issued in the name of H. N. Andrews et al. As can be seen in FIG. 4, displacer rods 40 are elongated cylindrical substantially hollow rods which can be manufactured out of Zircaloy and may be of the type described in copending U.S. patent application Ser. No. 217,052 entitled "Displacer Rod For Use In A Mechanical Spectral Shift Reactor" filed Dec. 16, 1980 in the name of R. K. Gjertsen et al. and assigned to the Westinghouse Electric Corporation, now U.S. Pat. No. 4,432,934 dated Feb. 21, 1984. Displacer rods 40 may also contain ZrO.sub.2 or Al.sub.2 O.sub.3 pellets for weighting the rod and enhancing its lowerability. As described in U.S. Pat. No. 4,432,934, the Zircaloy members 40 are thin-walled and can contain a filling of solid or annular zirconium oxide pellets or aluminum oxide pellets to provide structural support as well as mass. The construction of displacer rod 40 is such that is provides a low neutron absorbing rod that is capable of displacing reactor coolant-moderator when inserted into a fuel assembly. Displacer rods 40 are arranged so as to be in colinear alignment with guide tube 56 so that displacer rods 40 may be inserted in guide tubes 56 when it is desired. Displacer rods 40 are supported from a common attachment known as a spider 58. Spider 58 comprises a body 60 with struts 62 radially extending from body 60. Displacer rods 40 are individually attached to each strut 62 to form an array corresponding to the array of guide tubes 56 into which displacer rods may be inserted. Spider 58 is attached to drive shaft 64 which is connected to displacer rod drive mechanism 38. Activation of displacer rod drive mechanism 38 causes drive shaft 64 to be either lowered or raised thereby inserting or withdrawing displacer rods 40 from fuel assemblies 32 of core 34. It is important to note that each spider 58 is arranged to be able to insert displacer rods 40 into more than one fuel assembly 32. For example, as shown in FIG. 4, spider 58 is capable of inserting 25 displacer rods in center fuel assembly 32 and 4 displacer rods in each of the adjacent 4 fuel assemblies. In this manner displacer rods 40 can be moved in and out of fuel assemblies 32 without increasing the number of spiders and drive mechanisms. Referring now to FIGS. 5 and 6, displacer rod guide structures 42 comprise a plurality of split tube guides 70 which are designed to allow rods such as displacer rods or control rods to pass therethrough. Displacer rod guide structures 42 are located between calandria 44 and closure head 24 as shown in FIG. 1 and are arranged to correspond to each displacer rod drive mechanism 38. A number of spacers 72 are located at various locations along split tube guides 70 and together with split tube guides 70 serve to guide displacer rods 40 through the upper section of reactor vessel 22. As can be seen in FIG. 6, 8 split tube guides 70 may be provided for guiding displacer rods 40. The "split" in split tube guides 70 along with slots 74 in spacers 72 allow spider 58 to pass therethrough while maintaining alignment of the rods with guide tubes 56 in fuel assemblies 32. A center slot 76 is also provided for accommodating drive shaft 64 so that spider 58 may be moved therethrough. Referring again to FIG. 1, calandria 44 which comprises a multiplicity of tubes provides guidance for the rods such as displacer rods 40 through the calandria area. In general, the tubes in calandria 44 are not split tubes, as are split tube guides 70, so that spider 58 stops its descent when spider 58 nears the top of the tubes in calandria 44. When stopped at the top of calandria 44 all rods extend through the calandria tubes and are fully inserted in fuel assembly 32. While inserted in the calandria tubes, the rods are protected from the flow of reactor coolant thereby minimizing vibrations that would otherwise be induced by the velocity of the reactor coolant in that area. In the invention as described herein, at least three different types of rods are capable of being inserted into guide tubes 56. For example, displacer rods, control rods, and gray rods may be arranged to be inserted in guide tubes 56. All of the rods are approximately the same size and configuration, but because of the materials with which they are made serve different purposes. Displacer rods 40 which may be either a hollow thick walled tube or may contain a low neutron absorbing material such as ZrO.sub.2 or Al.sub.2 O.sub.3 pellets are used to displace reactor coolant and thereby control reactor moderation. Control rods contain neutron absorbing material as is well understood in the art and serve to control core reactivity in a commonly understood fashion. Gray rods are similar to displacer rods 40 but are made of an intermediate neutron absorbing material such as stainless steel so that their reactivity worth per rod is greater than that of displacer rods 40. Referring now to FIGS. 7-11, the quarter core arrangement of fuel elements 48, displacer rods 40, control rods 80, gray rods 82, and unrodded locations 84 are shown. It is to be understood that the full reactor core configuration can be established by extrapolating the quarter core shown in FIG. 7. Actually, the quarter core shown in FIG. 7 is a mirror image of the eighth core taken along line A--A of FIG. 7. However, the quarter core of FIG. 7 is being shown for clarity. As can be seen in FIG. 10, each fuel assembly 32 comprises an array of fuel elements 48 and an array of guide tubes 56. Generally, control rods 38 and gray rods 82 are used only in the diagonally arranged guide tubes 56 while displacer rods 40 are generally used in all guide tubes 56 of a given fuel assembly. In addition, an instrument tube 88 is provided near the center of each fuel assembly 32 for accommodating data instrumentation such as movable fission chambers. While each fuel assembly 32 is essentially identical to the one shown in FIG. 10, each fuel assembly 32 can produce a different function depending on whether guide tubes 56 are occupied by reactor coolant, displacer rods 40, control rods 80, or gray rods 82. Displacer rods 40 and gray rods 82 are generally chosen to be approximately the same size so as to displace approximately the same volume of water. However, gray rods 82 can be thick walled stainless steel cylindrical rods which can have higher worths per rod than do displace rods 40 so that they may be used to offset the effects of Xenon transients during load follow operations in addition to moderator displacement as described in copending U.S. Pat. application Ser. No. 217,061 filed herewith in the name of W. R. Carlson et al. entitled "Spectral Shift Reactor" and assigned to the Westinghouse Electric Corporation. Referring now to FIG. 11, a fuel assembly 32 in which no control rods 80 or gray rods 82 are used and in which only displacer rods 40 are used in guide tubes 56 is referred to generally as displacer assembly 90. A fuel assembly 32 in which both displacer rods 40 and control rods 80 are employed (but no gray rods) is referred to as control assembly 92. Similarly, a fuel assembly 32 in which both displacer rods 40 and gray rods 82 are used is called a gray assembly 94. It should be noted that in FIG. 11 fuel elements 48 have been omitted for clarity and that those fuel assemblies are similar to those shown in FIG. 10. Still referring to FIG. 11, each of the control rods 80 and gray rods 82 are attached to a spider (not shown) similar to spider 58 except that the spider for control rods 80 or gray rods 82 generally only effects one fuel assembly. In this manner, all control rods 80 or gray rods 82 in a given fuel assembly can be raised or lowered by a single drive mechanism. Furthermore, since each displacer rod spider 58 can extend into the adjacent fuel assemblies (as illustrated in the center portion of FIG. 11 and in FIG. 4), the displacer rod spider's 58 movement effects the control on five fuel assemblies and reduces the number of displacer rod drive mechanisms needed. Of course, on the periphery of the quarter core (as shown in FIG. 7) the particular spiders may move less than the usual number of rods because there are no adjacent fuel assemblies or there are unrodded locations 84. Referring again to FIGS. 8 and 9 which comprise FIG. 7, a quarter core arrangement. Each row or partial row is numbered 100-114 and each column or partial column is numbered 116-130 and comprises: ______________________________________ Fuel Assembly ______________________________________ (100,116) quarter displacer assembly (100,118) half control assembly (100,120) half displacer assembly (100,122) half control assembly (100,124) half displacer assembly (100,126) half control assembly (100,128) half displacer assembly (100,130) half gray assembly (102,116) half control assembly (102,118) full displacer assembly (102,120) full gray assembly (102,122) full displacer assembly (102,124) full gray assembly (102,126) full displacer assembly (102,128) full control assembly (102,130) full displacer assembly (104,116) half displacer assembly (104,118) full gray assembly (104,120) full displacer assembly (104,122) full control assembly (104,124) full displacer assembly (104,126) full control assembly (104,128) full displacer assembly (104,130) partial control-unrodded assembly (106,116) half control assembly (106,118) full displacer assembly (106,120) full control assembly (106,122) full displacer assembly (106,124) full control assembly (106,126) full displacer assembly (106,128) full control assembly (106,130) full displacer assembly (108,116) half displacer assembly (108,118) full gray assembly (108,120) full displacer assembly (108,122) full control assembly (108,124) full displacer assembly (108,126) full control assembly (108,128) full displacer assembly (110,116) half control assembly (110,118) full displacer assembly (110,120) full control assembly (110,122) full displacer assembly (110,124) full control assembly (110,126) full displacer assembly (110,128) partial displacer unrodded assembly (112,116) half displacer assembly (112,118) full control assembly (112,120) full displacer assembly (112,122) full control assembly (112,124) full displacer assembly (112,126) partial displacer unrodded assembly (114,116) half gray assembly (114,118) full displacer assembly (114,120) partial control unrodded assembly (114,122) full displacer assembly ______________________________________ As can be seen from the above description of the quarter core, the core configuration based on this concept can be illustrated generally as shown in FIG. 11. Basically, the fuel assembly in the center of the full core as represented by fuel assembly (100,116) in FIG. 7 can be chosen to be either a control assembly 92 or preferably a displacer assembly 90. Once this is chosen, the four fuel assemblies immediately adjacent to the flat sides of the center fuel assembly are chosen to be the other type and the fuel assembly on the diagonal are chosen to be the same type as the center assembly. This pattern is then continued in an alternating fashion. For example, the center fuel assembly (100,116) in FIG. 7 was chosen to be a displacer assembly 90 so that the fuel assemblies on its adjacent flat sides are chosen to be either control assemblies 92 or gray assemblies 94 while those on the diagonal are chosen to be displacer assemblies 90. This pattern is repeated in alternating fashion until the periphery of the core is reached where the end fuel assemblies may be chosen to be hybrid assemblies based on the nuclear physics of the particular core. Whether a particular assembly is chosen to be a control assembly 92 or a gray assembly 94 is determined by first selecting the number and location of control assemblies needed based on conventional core design. The remainder of the assemblies not chosen to be control assemblies 92 are then used as gray assemblies 94. Thus, substantially the entire core can be arranged on an alternating pattern of displacer assemblies and control or gray assemblies with practically all the fuel assemblies being served by at least one displacer rod spider 58 and with each displacer rod spider 58 serving generally 5 fuel assemblies. Moreover, each fuel assembly is served by at least one drive mechanism for either displacer rods, control rods or gray rods. The illustrated core arrangement provides a means by which the neutron spectrum can be controlled in a "spectral shift" fashion by controlling the moderator volume in the core. This can be accomplished by displacing and replacing the water coolant in the core at appropriate times thereby changing the moderation of the core. In the present invention, displacer rods 40 and gray rods 82 can be used to effect this moderation change. In operation, all displacer rods 40 and gray rods 82 are inserted in core 34 at the beginning of the core life. However, none of the control rods 80 need be inserted at that time. The insertion of displacer rods 40 and gray rod 82 is done by activating the appropriate drive mechanism such as displacer rod drive mechanism 38. When the drive mechanism is activated, displacer rods 40 and gray rods 82 fall into the appropriate guide tubes 56 in fuel assemblies 32. The displacer rods and gray rods will displace their volume of coolant (water) thus reducing the volume of moderator in core 34. The reduction of moderator hardens the neutron spectrum of the core and increases plutonium production. This hardening of the neutron spectrum is generally referred to as "spectral shift". The harder neutron spectrum reduces boron chemical shim requirements, results in a more negative moderator temperature coefficient, and reduces or eliminates burnable poison requirements. As the uranium fuel in the core is depleted over the life of the core, a certain number of displacer rods 40 and/or gray rods 82 may be withdrawn from the core by activating their respective drive mechanisms. The withdrawal of the rods allows more water-moderator into the core region and increases moderation of the core. This, in effect, introduces reactivity worth at a time when fuel depletion is causing a reactivity worth depletion. Thus, the reactivity of the core can be maintained at appropriate levels for a longer time. The withdrawal of the rods can continue at a selective rate (depending on core conditions) until, near the end of core life, all displacer rods 40 and all gray rods 82 have been withdrawn from the core. The selection and manipulation of the displacer rods can be chosen in the manner disclosed in copending U.S. patent application Ser. No. 217,054 filed herewith in the name of A. J. Impink entitled "Spectral Shift Reactor Control Method" and assigned to the Westinghouse Electric Corporation. The displacer rods can be used at start-up to displace approximately 20% of the core water volume and can remain inserted until the boron shim concentration nears zero ppm which is approximately 60% into the fuel cycle. The use of displacer rods in this manner can result in approximately 10% reduction in uranium fuel requirements for a given core life which results in an 10% fuel cost savings. In addition, the use of burnable poison rods can be effectively eliminated, a further cost reduction. Therefore, it can be seen that the invention provides a means to effectively control the reactivity of a nuclear reactor through moderator control by the use of displacer rods. |
abstract | Illustrative embodiments provide a reactivity control assembly for a nuclear fission reactor, a reactivity control system for a nuclear fission reactor having a fast neutron spectrum, a nuclear fission traveling wave reactor having a fast neutron spectrum, a method of controlling reactivity in a nuclear fission reactor having a fast neutron spectrum, methods of operating a nuclear fission traveling wave reactor having a fast neutron spectrum, a system for controlling reactivity in a nuclear fission reactor having a fast neutron spectrum, a method of determining an application of a controllably movable rod, a system for determining an application of a controllably movable rod, and a computer program product for determining an application of a controllably movable rod. |
|
claims | 1. A laser irradiation apparatus comprising:a first laser light source configured to emit a first polarized pulse laser beam;a second laser light source configured to emit a second polarized pulse laser beam which is different from the first polarized pulse laser beam;an optical path combining member configured to guide the first polarized pulse laser beam and the second polarized pulse laser beam to pass through a same optical path;a polarization control member arranged in a direction perpendicular to a traveling direction of laser beams, wherein the polarization control member includes a first polarization control portion and a second polarization control portion, each of which controls a polarization state of beam components of the pulsed laser beam from the optical path combining member, wherein the polarization state controlled by the first polarization control portion is different from that controlled by the second polarization control portion; anda laser beam superimposing member configured to superimpose the pulsed laser beam which has passed through the first polarization control portion and the pulsed laser beam which has passed through the second polarization control portion with each other on a surface to be irradiated of an object,wherein the first laser light source and the second laser light source emit linearly-polarized pulse laser beams of which polarization directions are at 90° to each other,wherein the first polarization control portion and the second polarization control portion are quarter wave plates which each have an optical axis at an angle of 45° with respect to each of the polarization directions of the pulsed laser beams emitted from the first laser light source and the second laser light source, andwherein the optical axes of the first polarization control portion and the second polarization control portion are at 90° to each other. 2. The laser irradiation apparatus according to claim 1, further comprising a pulse control device which controls the first laser light source and the second laser light source so as not to synchronize timing of emission of the pulsed laser beams from the first laser light source and the second laser light source. 3. The laser irradiation apparatus according to claim 1, further comprising a beam expander which adjusts a shape of the pulsed laser beam from the optical path combining member so that the pulsed laser beam from the optical path combining member has an elongated shape and which sends the pulsed laser beam having an elongated shape to the polarization control member. 4. The laser irradiation apparatus according to claim 1,wherein the length of the first polarization control portion in an arrangement direction and the length of the second polarization control portion in an arrangement direction are set so that a total amount of energy of beam components of the pulsed laser beam which have passed through the first polarization control portion is substantially equal to a total amount of beam components of the pulsed laser beam which have passed through the second polarization control portion. 5. The laser irradiation apparatus according to claim 1,wherein at least one of the first polarization control portion and the second polarization control portion is divided into plural parts so as to sandwich all or a part of the other of the first polarization control portion and the second polarization control portion in an arrangement direction. 6. The laser irradiation apparatus according to claim 1,wherein an optical path length of the pulsed laser beam inside the second polarization control portion is substantially equal to an optical path length of the pulsed laser beam inside the first polarization control portion. |
|
claims | 1. A flow rate verification failure diagnosis apparatus comprising:a gas supply pipe system including:flow rate control devices; anda flow rate verification unit having a pressure measurement device, the flow rate verification unit detecting flow rate abnormality by measuring a flow rate of fluid in each of the flow rate control devices on the basis of pressure of the fluid measured by the pressure measurement device; anda failure diagnosis device having a mode to diagnose a failure in the pressure measurement device in a case of the flow rate verification unit detecting the flow rate abnormality;a gas box for storing the flow rate control devices and the flow rate verification unit;a gas box temperature measurement device for measuring temperature in the gas box; anda temperature change failure diagnosis device for determining flow rate abnormality occurring due to temperature change in the gas box in a case where the flow rate verification unit detects the flow rate abnormality in any of the flow rate control devices and where temperature measured by the gas box temperature measurement device changes. 2. The flow rate verification failure diagnosis apparatus according to claim 1, whereinthe failure diagnosis device comprising a zero-point shift detection device for determining a failure that a zero point of the pressure measurement device shifts when a difference between an average value of pressure measured by the pressure measurement device and a reference value exceeds an allowable range. 3. The flow rate verification failure diagnosis apparatus according to claim 2, whereinthe failure diagnosis device comprising an output fluctuation abnormality detection device for determining a failure that output fluctuation abnormality occurs in the pressure measurement device when a difference between an output fluctuation band of pressure measured by the pressure measurement device and an output fluctuation band initial value of the pressure measurement device exceeds another allowable range. 4. The flow rate verification failure diagnosis apparatus according to claim 1, whereinthe failure diagnosis device comprises an output fluctuation abnormality detection device for determining a failure that output fluctuation abnormality occurs in the pressure measurement device when a difference between an output fluctuation band of pressure measured by the pressure measurement device and an output fluctuation band initial value of the pressure measurement device exceeds an allowable range. 5. A flow rate verification failure diagnosis system comprising:a gas supply pipe system including:flow rate control devices; anda flow rate verification unit having a pressure measurement device, the flow rate verification unit detecting flow rate abnormality by measuring a flow rate of fluid in the flow rate control devices on the basis of pressure of the fluid measured by the pressure measurement device;a flow rate control device failure diagnosis device for determining a failure causing the flow rate abnormality in other devices besides the flow rate control devices when the flow rate verification unit determines a flow rate abnormality in all of the flow rate control devices and a failure causing the flow rate abnormality in a specific one of the flow rate control devices when the flow rate verification unit determines the flow rate abnormality only in the specific flow rate control device;a gas box for storing the flow rate control devices and the flow rate verification unit;a gas box temperature measurement device for measuring temperature in the gas box; anda gas box temperature fluctuation failure diagnosis device for determining the flow rate abnormality caused by temperature changes in the gas box in a case where temperature measured by the gas box temperature measurement device is changed. 6. The flow rate verification failure diagnosis system according to claim 5, further comprising a pressure measurement device failure diagnosis device for diagnosing a failure in the pressure measurement device. |
|
abstract | Apparatuses and methods for the moderation of positrons are provided herein. The apparatus includes a structure consisting of linear arrays of electrode and semiconductor structures of generally planar or cylindrical form with vacuum gaps between each element electrode. This structure may be contained within a vacuum chamber. The positron source is positioned adjacent to the moderator structure or the electrodes may act as the positron source by pair production through bombardment of high energy photons, electrons, or neutrons. Positrons from this source are implanted into the moderator material and drift to the moderator surfaces through the influence of the electric fields produced by the electrodes. Positrons are emitted from the surfaces of the moderator material and are confined by orthogonal electric and magnetic fields while they drift out from the vacuum gap between cathodes and anodes for extraction. |
|
053032748 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention is concerned with provision of a satellite or stand-by passive containment cooling system for a nuclear reactor system. It can be embodied as part of an original nuclear reactor system construction, but it is primarily intended for retrofitting an existing nuclear reactor system with passive cooling capacity. More specifically, the invention is applicable to retrofitting nuclear reactor systems of the type wherein a suppression pool is confined in a separate space directly underlying the drywell space in which the nuclear reactor pressure vessel is located, this containment configuration being one in which a reactor core meltdown could result in rending of the floor separating the drywell and suppression pool space thereby creating but a single space in the containment from whence no venting of pressurized, heated non-condensables would be possible. Referring to the drawing, the nuclear reactor system 10 includes a heavy reinforced concrete containment structure 12 which has a base as at 13, a widened, generally cylindrical lower part 14 and a, e.g., tapered, conical or cylindrical upper part 16, there being a heavy cover unit 17 at the top of the structure. Containment structure 12 includes a horizontal floor 18 located proximal the juncture of parts 14 and 16, and this floor separates the containment interior into an upper or drywell space 20 and a lower or suppression pool space 22. The containment structure 12 can be located within a larger building enclosure shown generally at 24 and which serves to house other equipment and devices used in the system, this other equipment, devices, flooring etc not being depicted but being readily understood by one of ordinary skill in the art as being present in the building and employed in conjunction with operation, maintenance, fuel replenishment and like tasks. One of ordinary skill in the art will readily recognize the types of such stystems in which the invention can be employed, and also note the herein depicted system is representative of the Assignee's BWR Mark II system. A nuclear reactor pressure vessel 26 is located in the drywell space 20 of structure 12, being supported on a hollow cylindrical pedestal 28 extending up some distance from and generally formed as an integral part of the floor 18. The pressure vessel sits on a saddle part 30 at the top of the pedestal 28 and a concrete bio-shield 32 encircles the vessel. Nuclear reactor core 34 is located within the pressure vessel as shown in dashed lines. Other components of the system such as steam and condensate feed lines, and reactor core control rod assemblies are not depicted as same is not necessary for proper understanding of the invention. A plurality of vertically disposed vent pipes 36 are arrayed around the floor 18 and have entry ends at the floor which are in communication with the drywell space 20. The pipes 36 extend down through the floor and into a pool of water 38 in the space 22, lower outlet ends of these pipes locating submerged a distance below the level 40 of pool 38, there being an airspace 42 above the pool of water, gas flow communication between airspace 42 and drywell 28 being only possible via passage through the pool of water 38. In the event of a LOCA which may involve one or more of a break in a steam pipe or the pressure vessel, or a loss of coolant in the pressure vessel from other cause, there will be an immediate initial heat buildup in the drywell 28 represented by presence of highly heated steam and non-condensable gasses, chiefly nitrogen in the drywell. Due to the high steam/gas pressure, it will vent through pipes 36 into pool 38, the steam condensing, and the non-condensable gasses being cooled in the pool and venting therefrom to airspace 42. As noted earlier, recirculation of the pool water to a cooling operation outside the containment will be carried out since the buildup of heat in the pool will be rapid and of high magnitude. Recirculation of the feed water in the pressure vessel to a cooling operation as a containment heat removal agency also may be employed depending on whether or not the LOCA cause involves rupture in that vessel. Should the accident be an event that involves core meltdown with an ensuing breach in the structure of floor structure 18, the airspace 42 is opened to and becomes merged with the drywell atmosphere so there no longer exists a separate space to which non-condensable fraction of heated fluid in the drywell can be passed to effect cooling and venting of same. To offset this loss of wetwell cooling and venting in the containment structure as such, there is provided satellite heat removal means which can supplement drywell heat removal during an accident wherein the containment wetwell remains intact, but which also can assume all cooling function if core meltdown has rendered the containment wetwell cooling inoperable. This satellite heat removal means is described in detail next. Referring to the drawing Figure, a satellite building 50 is erected adjacent to large building enclosure 24, the satellite structure being either constructed as part of the original system erection, but more usually and in line with the type of system with which it is most efficaciously used, being a retrofit installation added on subsequent to system installation. Building 50 defines a structure having space enclosing an upper chamber 52 therein which is separated by a floor or slab 54 from a lower space constituting a lower chamber 56. A vent stack 58 communicates upper chamber 52 with outside or ambient environment. A pool of cooling water 60 is present in upper chamber 52, and at least one isolation condenser 62 will be submerged in pool 60. Lower chamber 56 also contains a water pool 63 which in volume should be at least about as large as the water volume capacity of suppression pool 38. Gas space 64 above pool 63 should be at least as large but more preferably about two to three times the volume of the containment wetwell space 42. An inlet to the isolation condenser 62 is connected to the containment drywell 20 by means of an inlet conduit 66, and an outlet from the isolation condenser is communicated to the containment drywell by an outlet conduit 68. One or more normally open valves 69 can be disposed in inlet conduit 66, and a condensate/non-condensable gas collector 70 can be fitted to the outlet end of the isolation condenser. The inlet and outlet conduits 66, 68 it will be noted have communication with the drywell elevated some location above floor 18 and other parts of the containment so that same are above any anticipated flood level of water as might be expected to invest the containment during a LOCA or core melt down where the suppression pool and water from the pressure vessel become one pool. It also is seen that these conduits are inclined so that the ends communicating with the containment are located at an elevation below the conduit ends connected to the isolation condenser. A vent pipe 72 connects the gas collector 70 with a submerged location in water pool 63, and a vacuum breaker 74 is fitted on the vent pipe at a location in the lower chamber gas space so it can operate to dmit gas from the gas space to the vent pipe whenever a reduced pressure condition in drywell 20 is such that it would induce a siphon effect draw of water from pool 63 to the drywell via isolation condenser 62. During an accident not involving core meltdown, the satellite heat removal means will provide supplemental cooling for the drywell. Highly heated fluid present in the drywell comprising steam and non-condensable gasses can access the isolation condenser 62 by way of inlet conduit 66, be cooled so that steam converted to water condensate will return by way of the outlet conduit 68 to the drywell. Non-condensables will be separated and collected in gas collector 70 for outlet via vent pipe 72 to the pool 63, from which the cooled gas vents to gas space 64. Cooling is by way of transfer of heat to the water in pool 60, water evaporating from the pool and this in turn venting to atmosphere by way of stack 58. Make up or replenishment for pool 60 can be provided in known manner. Where core meltdown occurs and the floor structure 18 is breached, all drywell heat removal will be accomplished with the satellite heat removal means. Having described preferred embodiments of the invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims. |
048204790 | claims | 1. A guide pin assembly for aligning the upper hold down plate of the top nozzle of a fuel assembly with the upper core plate of a pressurized water nuclear reactor comprising: a guide pin having a generally circular cross-section including: a guide pin having a generally circular cross-section including: a top nozzle, a bottom nozzle, and a plurality of guide tubes extending between said top nozzle and said bottom nozzle, said top nozzle having an upper hold down plate with at least one second bore therethrough aligned with a first bore in the upper core plate of a said pressurized water nuclear reactor, said first and second bores being adapted to receive a guide pin to align said fuel assembly with said upper core plate so that said fuel assembly is disposed below, and spaced from, said upper core plate; at least one guide pin having a generally circular cross-section, a nose, a threaded portion adjacent said nose, a shaft adjacent said threaded portion, and an end adjacent said shaft, said nose having engagement means thereon, said threaded portion having a threaded outer surface, said shaft having an upper section, a lower section, and a radial alignment section between said upper and lower sections, said radial alignment section of said shaft having a diameter that is approximately the diameter of said first bore in said upper core plate of a nuclear reactor, said lower section of said shaft having a diameter less than that of said radial alignment section, said end including a top having a diameter greater than that of the diameter of said first bore in said upper core plate, said guide pin being inserted within a said second bore in said top nozzle and a said first bore in said upper core plate so that said nose and at least a portion of said threaded portion of said guide pin protrude above said upper core plate; a nut, including a top and a bottom, threaded on to said threaded portion of said threaded surface of said guide pin so that said bottom of said nut abuts the upper surface of said upper core plate; and an annular locking cup secured about said nut and engaging said engagement means on said nose of said guide pin. 2. The guide pin assembly of claim 1 in which said engagement means on said nose is a plurality of elongated, annularly spaced slots. 3. The guide pin assembly of claim 2 in which said locking cup is adapted to be crimped about said nose of said guide pin. 4. The guide pin assembly of claim 1 in which said nut includes a first groove in the inner surface thereof and said locking cup includes an annular flange about the lower end thereof which is receivable within said first groove of said nut. 5. The guide pin assembly of claim 1 in which said locking cup is permanently securable to said nut. 6. A guide pin assembly for aligning the upper hold down plate of the top nozzle of a fuel assembly with the upper core plate of a pressurized water nuclear reactor comprising: 7. A fuel assembly for a pressurized water nuclear reactor comprising: 8. The nuclear reactor fuel assembly of claim 7 in which said fuel assembly includes two guide pins. 9. The nuclear reactor fuel assembly of claim 7 in which said engagement means on said nose is a plurality of elongated, annularly spaced slots. 10. The nuclear reactor fuel assembly of claim 9 in which said locking cup is crimped about said nose of said guide pin. 11. The nuclear reactor fuel assembly of claim 7 in which said nut includes a first groove in the inner surface thereof and said locking cup includes an annular flange about the lower end thereof which is received within said first groove of said nut. 12. The nuclear reactor fuel assembly of claim 7 in which said locking cup is permanently secured to said nut. |
048715085 | description | DETAILED DESCRIPTION FIG. 1 shows a small part of a horizontal section of a reactor core for a boiling reactor with vertical fuel assemblies. The section comprises nine full fuel assemblies 10. The total number of fuel assemblies in a complete cross-section amounts to several hundred. Each fuel assembly, for example 10a, is built up of a bundle of 64 fuel rods 11 in a square lattice and of a fuel channel 12 of zircaloy-4 of square cross-section surrounding the fuel rod bundle. The rods are held in their positions by so-called spacers (not shown) which are evenly distributed between the top tie plate and the bottom tie plate (also not shown) on the fuel assembly. Each fuel rod consists of a number of circular-cylindrical pellets of uranium dioxide as fuel, which are stacked on top of each other and canned in a cladding tube 13 of zircaloy-2. The spaces 14 between the fuel rods within the fuel channel are traversed by a coolant, in the exemplified case light water. The gaps 15a and 15b between the fuel assemblies are also traversed by a coolant of the same kind. The gaps 15b into which control rods 16 can be inserted are, in the illustrated case, wider than the gaps 15a in which there are no control rods. The cross-section also comprises neutron sources 17 as well as neutron detectors 18. One or more of the fuel rods may be exchanged for a non-energy producing rod. Thus, for example, rod 19 could be exchanged for a solid or water-filled rod of zircaloy-2. The fuel rods 20, 21, 22 and 23 are tie rods and are anchored to top tie plate and bottom tie plate in the fuel assembly. The control rods 16 have absorber blades 24, 25, 26 and 27 arranged in a cruciform. The centre of the control rod cross is designated 28. As will be clear from Figure 1, the fuel assemblies 10 are arranged in a symmetrical lattice with each fuel assembly included in two rows of fuel assemblies which are perpendicular to each other. The control rods 16 are arranged with each one of their blades between two fuel assemblies located in the same row. In this way, each control rod, for example 16b, together with four fuel assemblies 10b, 10c, 10d, 10e, arranged around its blades can be said to form a unit 30, previously called control rod unit, which in FIG. 1 is surrounded by a dashed line. A control rod unit has an at least substantially square cross-section, and, as will also be clear from FIG. 1, the control rod units are arranged in a symmetrical lattice with each control rod unit included in two rows of control rod units which are perpendicular to each other. FIG. 2 shows the control rod units in the reactor core and a number of separate fuel assemblies 10 arranged in outer regions of the core. The control rod units 30 are illustrated as light squares in those positions where, at the time of the fuel rod exchange, control rods used during the earlier operating period are arranged, and as dark squares where control rods used during the earlier operating period are replaced by new control rods with a higher reactivity worth, in the exemplified case with a 15% higher reactivity worth in a cold shutdown reactor, than the original reactivity worth of the control rods used during the earlier operating period. In the exemplified case, the exchange of control rods for new control rods has only been carried out in control rod units in a central zone 31 in the reactor core, which is located inside an edge zone 32 extending around the reactor core and comprising those control rod units 30a which are located furthest out in the reactor core in each row of control rod units. As will be clear from FIG. 2, after the control rod exchange a number of control rod units (light squares), which have been used during the earlier operating period, are distributed over the central zone. It is also clear that the control rods in those control rod units, for example 30c, 30d, 30e and 30f, which are located adjacent to each such control rod unit, for example in unit 30b, and which are located in the same rows perpendicular to each other as this control rod unit, consist of control rod units having a higher reactivity worth. From the case exemplified in FIG. 2 it is also clear that the reactor core comprises regions within the central zone comprising 3.times.3 control rod units, for example units 30g, 30h, 30i, 30j, 30k, 30l, 30m, 30n and 30o, where control rods used during the earlier operating period are exchanged for new control rods having a higher reactivity worth in that control rod unit which is located in the centre, i.e. in unit 30g, and in those four control rod units, i.e. in units 30h, 30i, 30j and 30k, which are located in the same rows perpendicular to each other as the control rod unit located in the centre, whereas control rods used during the earlier operating period are used in the remaining four control rod units, i.e. in units 30l, 30m, 30n and 30o. New control rods having a higher reactivity worth are arranged in three control rod units at the most, located adjacent to each other, for example in units 30g, 30h and 30i, in the same row of control rod units in the central zone 31. In the case illustrated in FIG. 2, 47% of the total number of control rods included in the reactor core and 63% of the total number of the control rods included in the central zone of the reactor are replaced by new control rods having a higher reactivity worth. |
description | 1. Field of the Invention The present invention relates to a vibration-type cantilever holder to fasten a cantilever having a probe in its leading end vibratably with a predetermined frequency and amplitude, and a scanning probe microscope having the vibration-type cantilever. 2. Description of the Related Art As is generally known, an SPM (Scanning Probe Microscope) has been known as a device to measure a sample of a metal, semiconductor, ceramic, resin, macromolecule, biomaterial, insulator, etc. within a micro-scale area, and perform observation, etc. concerning physical property information including the viscoelasticity of a sample and the surface profile of a sample. As for such SPM, there are various measuring modes depending on targets for measurement. As one of them has been known a vibration mode SPM, by which measurement is performed by vibrating a cantilever set on a cantilever holder (see e.g. JP-A-2003-42931). Such vibration mode SPMs include, for example: DFM (Dynamic Force Mode Microscope), by which scan is performed while the distance between a probe and a sample is controlled so that vibration amplitudes of the cantilever vibrated sympathetically are stable; VE-AFM (Viscoelastic AFM), by which the distribution of viscoelasticity is measured by detecting the amplitude, sine component and cosine component of bending of the cantilever when a sample is driven into small vibration in Z direction perpendicular to a sample surface or the cantilever is driven into small vibration in Z direction perpendicular to the sample surface thereby to apply a periodic force to the cantilever during the time of operation of AFM; and LM-FFM (Lateral Force Modulation Friction Force Microscope), by which the distribution of friction force is measured by detecting the amplitude of torsional vibration of the cantilever when a sample or the cantilever is driven into lateral vibration in a horizontal direction in parallel to a sample surface during the time of operation of AFM. However, measurements by the above-described conventional vibration mode SPMs have problems as described below. Usually in vibrating a cantilever, a predetermined voltage is applied to a vibration source mounted to a cantilever holder to vibrate the source, and then the vibration is transmitted to the cantilever, whereby the cantilever is made to vibrate with a predetermined vibration frequency and amplitude. However, the vibration of the vibration source also travels to surrounding structures other than the cantilever to vibrate the surrounding structures. These vibrations affect vibrational characteristics of the cantilever, and thus the vibrational characteristics are other than those of ideal vibrating state. As a result, when measurement of Q curve (a curve showing sympathetic vibrational characteristics of a cantilever) is performed, other collateral sympathetic vibrations B, which are additional sympathetic vibrations, in addition to the sympathetic vibration A of the cantilever arise as shown in FIG. 7. As a consequence, the resultant characteristics includes vibrational characteristics coming from surrounding structures other than the cantilever, which makes it difficult to correctly discriminate the sympathetic vibrational characteristics of the cantilever. Therefore, in some instances it is difficult to make precise settings for vibrational characteristics of the vibration frequency, amplitude, and phase. Further, in some instances, sympathetic vibrational characteristics of the cantilever are influenced when a probe is made to approach a sample, and thus the probe cannot be brought close to a measurement area, or the probe is brought excessively close to the measurement area, resulting in the collision with the sample because of the change in optimum measurement condition. Still further, in some instances, sympathetic vibrational characteristics of the cantilever are influenced during the time of scan, and thus it becomes difficult to continue a stable and precise measurement because of the change in optimum measurement condition. The invention was made in consideration of those circumstances. It is an object of the invention to provide a vibration-type cantilever holder, which cuts off (or balance out) an additional vibration and vibrates a cantilever so that vibrational characteristics of only the cantilever are demonstrated, and a scanning probe microscope having the vibration-type cantilever holder. To achieve the object, the invention provides a means as follows. A vibration-type cantilever holder according to the invention may be a vibration-type cantilever holder for fastening a cantilever which is opposed to a sample, has a probe on its leading end, and is supported on a main body part at only a base end thereof, characterized by including: a cantilever-attaching stand on which the main body part is placed and fastened with the cantilever tilted at a predetermined angle with respect to the sample; a first vibration source fastened to the cantilever-attaching stand and vibrating with a phase and an amplitude depending on a predetermined waveform signal; a holder main body to which the first vibration source is fastened; and a second vibration source fastened to at least one location on the holder main body, and generating vibrations to balance out vibrations traveling from the first vibration source to the cantilever-attaching stand and holder main body. With the vibration-type cantilever holder in connection with the invention, the cantilever can be fastened so as to be opposite to a sample by placing and fastening a cantilever main body part on a cantilever-attaching stand fastened to the holder main body with the first vibration source interposed therebetween. At this point, the cantilever-attaching stand tilts the cantilever by a predetermined angle with respect to the sample, and in this condition the cantilevered is fastened. After the cantilever is fastened, the first vibration source is made to vibrate according to a predetermined waveform signal. This vibration is transmitted to the cantilever through the cantilever-attaching stand. Thus, the cantilever vibrates with an amplitude and delay of phase depending on a waveform signal input to the first vibration source. On the other hand, the vibration generated by the first vibration source not only vibrates the cantilever, but also travels to the cantilever-attaching stand and holder main body and thus vibrates the cantilever-attaching stand and holder main body at the same time. However, as the second vibration source is fastened in at least one place on the holder main body, unwanted vibration traveling from the first vibration source can be balanced out by operating the second vibration source concurrently with the first vibration source, and therefore the holder main body and cantilever-attaching stand can be prevented from vibrating as far as possible. That is, operating the first and second vibration sources in parallel allows vibrations generated by first and second vibration sources to counteract each other, and thus unwanted vibrations traveling to surrounding structures other than the cantilever can be cut off. Therefore, unlike a conventional cantilever holder, only the cantilever can be vibrated, whereby vibrational characteristics of only the cantilever can be obtained. Hence, in measuring a Q curve, sympathetic vibrational characteristics of the cantilever can be discriminated correctly, and therefore precise settings can be made for vibrational characteristics of the vibration frequency, amplitude, phase, etc. of the cantilever. Thus, measurements by vibration mode SPM can be performed precisely at all times. This enables improvement of the accuracy of measurement, and makes the measurement by vibration mode SPM easier to use, which leads to enhancement of its convenience. In addition, as vibrational characteristics of only the cantilever can be obtained reliably, unlike a conventional SPM, the probe can be brought close to a desired measurement area precisely when the probe is brought close to a sample. Also, from this point of view, the accuracy of measurement can be increased. In addition, since sympathetic vibrational characteristics of the cantilever are unchanged during the time of scan, stable measurements can be performed continuously. Incidentally, more than one second vibration source may be fastened to the holder main body. A vibration-type cantilever holder according to the invention may be the above-described vibration-type cantilever holder characterized in the second vibration source vibrates on receipt of a waveform signal adjusted at least in its phase based on a relative positional relation with the first vibration source and the predetermined waveform signal input to the first vibration source. In the vibration-type cantilever holder in connection with the invention, t-h-e second vibration source vibrates on receipt of a waveform signal adjusted at least in phase (e.g. a signal inverted in phase) based on the relative positional relation with the first vibration source and the waveform signal input to the first vibration source. Accordingly, regardless of the place on the holder main body where the second vibration source is fastened, unwanted vibrations traveling to surrounding structures other than the cantilever from the first vibration source can be counteracted, and therefore vibrations other than the sympathetic vibration of the cantilever can be made minimum. The second vibration source may be vibrated by timely adjusting the amplitude together with the phase. As a result of the adjustment, it is possible that the second vibration source accepts the same signal as that input to the first vibration source. Since the place where the second vibration source is fastened can be selected freely as described above, the design flexibility can be enhanced. A vibration-type cantilever holder according to the invention may be the above-described vibration-type cantilever holder characterized by further including a weight part for urging the second vibration source toward the holder main body. With the vibration-type cantilever holder in connection with the invention, since the weight part urges the second vibration source toward the holder main body utilizing gravity, the force is easy to transmit. Thus, the vibration generated by the second vibration source can be transmitted to the holder main body efficiently. In other words, as transmission of vibration is furthered, unwanted vibrations traveling to surrounding structures other than the cantilever can be balanced out more reliably. Hence, it is possible to obtain vibrational characteristics of the cantilever more correctly. A vibration-type cantilever holder according to the invention may be the above-described vibration-type cantilever holder characterized in the following three matters. The first is that the holder main body is formed in a tabular shape having a first face and second face opposite to each other. The second is that the first and second vibration sources are fastened on the first and second faces respectively so as to be opposed to each other with the holder main body interposed therebetween. The third is that the second vibration source vibrates on receipt of a predetermined waveform signal, identical to the predetermined waveform signal input to the first vibration source. With the vibration-type cantilever holder in connection with the invention, the first and second vibration sources are fastened on the first and second faces respectively and opposed to each other with the holder main body interposed therebetween. On receipt of the same waveform signal as that input to the first vibration source, the second vibration source vibrates with the same amplitude and phase as those for the first vibration source. Thus, signals generated by both the vibration sources counteract each other, and unwanted vibrations traveling from the first vibration source to surrounding structures other than the cantilever can be balanced out more reliably. Particularly, since the waveform signal input to the second vibration source is not a specially adjusted signal, but the same signal as that input to the first vibration source, complicated operation control is not required and the configuration thereof can be simplified. A vibration-type cantilever holder according to the invention may be the above-described vibration-type cantilever holder characterized by further including a weight part for urging the second vibration source toward the holder main body. With the vibration-type cantilever holder in connection with the invention, since the weight part urges the second vibration source toward the holder main body utilizing gravity, the force is easy to transmit. Thus, the vibration generated by the second vibration source can be transmitted to the holder main body efficiently. In other words, as transmission of vibration is furthered, unwanted vibrations traveling to surrounding structures other than the cantilever can be balanced out more reliably. Hence, it is possible to obtain vibrational characteristics of the cantilever more correctly. A vibration-type cantilever holder according to the invention may be the above-described vibration-type cantilever holder characterized in the weight part is identical in shape and weight to the cantilever-attaching stand. With the vibration-type cantilever holder in connection with the invention, since the weight part is identical with the cantilever-attaching stand in shape and weight, it can be considered that an arrangement such that two identical cantilever-attaching stands are provided on both opposing sides of the holder main body is adopted. Therefore, unwanted vibrations traveling to surrounding structures other than the cantilever can be counteracted more reliably. Hence, vibrational characteristics of the cantilever can be obtained more reliably. A scanning probe microscope according to the invention is characterized by including: one of the above-described vibration-type cantilever holders; a cantilever having a probe on its leading end and supported on a main body part at only a base end thereof, the main body part fastened to the vibration-type cantilever holder; a stage on which a sample opposed to the probe is placed; a driving unit for relatively moving the probe and sample along a direction in parallel to a sample surface for scan and relatively moving the probe and sample along a direction perpendicular to the sample surface; a measurement unit for measuring displacement of a vibrating state of the cantilever; and a control unit for controlling the driving unit based on a result of the measurement by the measurement unit thereby to control a distance between the probe and sample surface so that the vibrating state of the cantilever is made stable during the scan, and for collecting observational data. With the scanning probe microscope in connection with the invention, the cantilever depending on a sample is selected first, and its main body part is put on and fastened to the cantilever-attaching part. Thus, the cantilever is fastened to the vibration-type cantilever holder in the condition where it is tilted at a predetermined angle with respect to the sample. Subsequently, the first and second vibration sources are activated at the same time, thereby to vibrate the cantilever. Then, the probe is brought into contact with or close to a sample surface. In this condition, the probe and sample are relatively moved by the driving unit to execute scan. In this step, the control unit makes the driving unit adjust the distance between the cantilever and sample (or the height of the cantilever with respect to the sample) based on the result of measurements by the measurement unit so that vibration motion of the cantilever, e.g. the vibration amplitude (or frequency at the time of self-excited vibration), is made constant. Thus, it becomes possible to detect observational data, e.g. data concerning the height, and a change in phase thereby to perform the measurement of data about various kinds of physical properties (magnetic force, electric potential, etc.) and the like. Particularly, since the scanning probe microscope includes a vibration-type cantilever holder which can correctly discriminate sympathetic vibrational characteristics of the cantilever by vibrating only the cantilever separately, measurement by the vibration mode SPM can be performed precisely and the reliability of the result of measurement can be increased. In the case of using a technique such that a Q value is increased by controlling the Q value of the cantilever thereby to increase the sensitivity, the sensitivity can be improved more than usually expected because vibrations other than the vibration of the cantilever make factors to increase the measurement error. A scanning probe microscope according to the invention may be the above-described scanning probe microscope characterized by further including: a detection part for detecting an additional waveform signal vibrating with an amplitude and a phase other than an amplitude and a phase coming from vibration of the cantilever, from the result of the measurement by the measurement unit; and a vibration source-dedicated power supply for inputting an adjustment signal adjusted at least in amplitude and phase to the second vibration source so as to balance out the additional waveform signal detected by the detection part. With the scanning probe microscope in connection with the invention, the detection part detects an additional waveform vibrating with an amplitude and a phase other than those coming from vibration of the cantilever, from the result of measurement by the measurement unit. That is, the detection part detects a waveform of unwanted vibration which has traveled from the first vibration source to the surrounding structures such as the holder main body. Then, the vibration source-dedicated power supply feeds back and inputs an adjustment signal adjusted at least in amplitude and phase to the second vibration source so as to balance out and eliminate the waveform of unwanted vibration. Now, it is noted that a waveform synthesized by a combination of other different frequencies may be used as the adjustment signal. This makes it possible to counteract unwanted vibration traveling from the first vibration source to surrounding structures other than the cantilever more reliably. Therefore, sympathetic vibrational characteristics of the cantilever can be discriminated more correctly and the accuracy of measurement can be improved further. With the vibration-type cantilever holder in connection with the invention, parallel operations of the first and second vibration sources allow the vibrations generated by the sources to be counteracted mutually, and thus vibrations traveling to surrounding structures other than the cantilever, can be cut off. Hence, sympathetic vibrational characteristics of the cantilever can be discriminated correctly, and precise measurements by a vibration mode SPM can be performed at all times thereby to improve the accuracy of measurement. In addition, the measurement by a vibration mode SPM becomes easier to use, which leads to enhancement of its convenience. With the scanning probe microscope in connection with the invention, since it includes a vibration-type cantilever holder which can correctly discriminate sympathetic vibrational characteristics of the cantilever, measurement by the vibration mode SPM can be performed precisely and the reliability of the result of measurement can be increased. A vibration-type cantilever holder according to the first embodiment of the invention and a scanning probe microscope with the cantilever holder will be described with reference to FIGS. 1 to 3. It is noted here that as for this embodiment, a sample-scan method such that a sample is moved along a direction in three dimensions will be described as an example. As shown in FIG. 1, the scanning probe microscope 1 according to the embodiment includes: a vibration-type cantilever holder 2; a cantilever 3 having a probe 3a on its leading or free end and supported on a main body part 3b at only a base end thereof, and fastened to the vibration-type cantilever holder 2 by the main body part 3b; a stage 4 to place a sample S on so that the sample is opposed to the probe 3a; a driving unit 5 for relatively moving the probe 3a and the sample S in X and Y directions in parallel with a sample surface S1 to scan the sample surface, and relatively moving the probe 3a and the sample S in the Z direction perpendicular to the sample surface S1; a measurement unit 6 for measuring displacement of the vibrating state of the cantilever 3; and a control unit 8 for controlling the driving unit 5 based on the result of the measurement by the measurement unit 6 so that the vibrating condition of the probe 3a of the cantilever 3 is made constant with respect to the sample surface S1 during the time of scan and for collecting observational data. Here, it is noted that in this embodiment, the case where the control unit 8 controls the driving unit 5 so that the amplitude of vibration of the cantilever 3 is made constant will be described as an example. As shown in FIG. 2, the vibration-type cantilever holder 2 includes an attachment member in the form of a sloped block (cantilever-attaching stand) 10 having a cantilever-attaching face 10a on which the main body part 3b is placed and fastened with the cantilever 3 tilted at a predetermined angle with respect to the sample S; a vibration source (first vibration source) 11 fastened to the sloped block 10 and vibrating with a phase and an amplitude depending on a predetermined waveform signal; a holder main body 12 to which the vibration source 11 is fastened; and an opposing vibration source (second vibration source) 13 fastened to at least one location on the holder main body 12 and balancing out the vibrations transmitted from the vibration source 11 to the sloped block 10 and the holder main body 12. The holder main body 12 is formed in a tabular shape, having a first face 12a and a second face 12b opposite to each other, and the first face 12a is arranged so as to face toward the sample S. Also, the holder main body 12 has an opening 12c formed therein, through which a laser light L to be described later reaches a reflecting face (not shown) of the fastened cantilever 3 and the laser light L reflected off the reflecting face is allowed to go out. The vibration source 11 is fastened on the first face 12a, and is arranged so as to vibrate with a predetermined phase and amplitude according to a waveform signal input from a vibration source-dedicated power supply 7 shown in FIG. 1. The sloped block 10 is fastened to a lower face of the vibration source 11 so that the cantilever-attaching face 10a is made to face the sample S. The main body part 3b of the cantilever 3 is placed on the cantilever-attaching face 10a, and fastened to the sloped block by use of e.g. a wire (not shown). The opposing vibration source 13 is fastened in a position opposite (facing) to the vibration source 11 with the holder main body 12 interposed therebetween. The opposing vibration source 13 is arranged so that it receives a waveform signal from the vibration source-dedicated power supply 7, which is the same as that applied to the vibration source 11, and vibrates in the same phase and amplitude as the vibration source 11. Further, the vibration-type cantilever holder 2 according to the embodiment includes a weight part 14 to urge the opposing vibration source 13 toward the holder main body 12. The weight part 14 is formed so as to have the same form and weight as those of the sloped block 10, and mounted on the opposing vibration source 13. The vibration-type cantilever holder 2 thus configured is fastened by a pedestal (not shown) above the sample S, as shown in FIG. 1. The stage 4 is placed on an XY scanner 20. The XY scanner 20 is placed on a Z scanner 21. Further, the Z scanner 21 is placed on a vibration-proof table (not shown). The XY scanner 20 and Z scanner 21 are e.g. piezo-devices, and arranged so that they are moved by a small distance in an appropriate direction when an XY driving part 22 and a Z driving part 23 apply a voltage to them respectively. In other words, the XY scanner 20 and Z scanner 21, XY driving part 22 and Z driving part 23 constitute the driving unit 5. Also, above the vibration-type cantilever holder 2 are provided a light-illumination part 26 and a light-detection part 28. The light-illumination part 26 utilizes a mirror 25 to irradiate the reflecting face (not shown) formed in a rear face of the cantilever 3 with a laser light L. The light-detection part 28 utilizes a mirror 27 to receive the laser light L reflected off the reflecting face. The laser light L emitted by the light-illumination part 26 goes through the opening 12c of the holder main body 12 to reach the reflecting face, and is reflected by the reflecting face. After that, the laser light L goes through the opening 12c again, and then enters the light-detection part 28. The light-detection part 28 may be e.g. a photodetector, which detects vibrating state (i.e. an amplitude) of the cantilever 3 relative to an incident position of the laser light L. Then, the light-detection part 28 outputs the displacement of the detected vibrating state of the cantilever 3, to a preamplifier 29 as a DIF signal. In other words, the light-illumination part 26, mirrors 25 and 27, and light-detection part 28 constitute the measurement unit 6. The DIF signal output from the light-detection part 28 is amplified by the preamplifier 29, sent to an AC-DC conversion circuit 30, converted into a DC signal there, and then sent to a Z voltage feedback circuit 31. The Z voltage feedback circuit 31 controls the feedback of the Z driving part 23 so that the DIF signal after the DC conversion is made constant at all times. Thus, the distance between the probe 3a and sample surface S1 can be controlled so that the vibrating state of the cantilever 3 becomes stable, i.e. the amplitude thereof is made constant when the scan is performed by the driving unit 5. Also, the Z voltage feedback circuit 31 is connected with the control part 32. Therefore, the control part 32 can measure a surface profile of the sample S based on the DIF signal after the DC conversion, and detect the change in phase thereby to measure various kinds of information about physical properties (e.g. a magnetic force, an electric potential, etc.). In other words, the Z voltage feedback circuit 31 and the control part 32 constitute the control unit 8. Incidentally, the control unit 8 has the function of comprehensively controlling the above constituent parts. Now, the case where a sample S is measured in a DFM, which is one of vibration mode SPMs, by use of a vibration type cantilever holder 2 and a scanning probe microscope 1 arranged like this will be described below. First, initial settings for measurement are to be made. Specifically, an optimum cantilever 3 is selected depending on a sample targeted for the measurement. The cantilever 3 is fastened to the vibration-type cantilever holder 2. Subsequently, the sample S is placed on the stage 4, and then the positions of the light-illumination part 26 and light-detection part 28, the mounting condition of the cantilever 3, etc. are adjusted so that a laser light L impinges on the reflecting face of the cantilever 3 reliably and the laser light L after the reflection surely enters the light-detection part 28. After that, the vibration source-dedicated power supply 7 outputs identical waveform signals to the vibration source 11 and the opposing vibration source 13 concurrently, whereby the vibration source 11 and the opposing vibration source 13 are made to vibrate with the same amplitude and phase. The vibration generated by the vibration source 11 is transmitted to the cantilever 3 through the sloped block 10, and therefore the cantilever 3 can be vibrated with the amplitude and the delay of phase depending on the waveform signal. Further, the vibration not only forces the cantilever 3 to vibrate, but also travels to the sloped block 10 and holder main body 12, and therefore it causes these surrounding structures to vibrate simultaneously. However, as the vibration coming from the opposing vibration source 13 opposed to the vibration source 11 with the holder main body 12 interposed between them is transmitted to the holder main body 12 and sloped block 10, the vibration transmitted from the vibration source 11 is counteracted. As a result, unwanted vibrations coming from the vibration source 11 can be balanced out to prevent the holder main body 12 and sloped block 10 from vibrating. That is, parallel operations of the vibration source 11 and opposing vibration source 13 allow the vibrations generated by the sources to be counteracted mutually, and thus unwanted vibrations traveling to surrounding structures other than the cantilever 3, can be cut off. Therefore, unlike a conventional cantilever holder, as only the cantilever 3 can be made to vibrate, vibrational characteristics of the cantilever 3 can be gained separately. Subsequently, the cantilever 3 is made to vibrate, followed by making Q-curve measurement and setting of an operation point, which is an optimum value of frequency of applied vibrations. In this step, because the opposing vibration source 13 prevents from causing the constituent parts (i.e. surrounding structures) other than the cantilever 3 to vibrate as described above, it is hard to create collateral sympathetic vibrations other than the sympathetic vibration A of the cantilever 3 as shown in FIG. 3. (It is clear that the generated collateral sympathetic vibrations B are less than that in FIG. 7.) Thus, characteristics of the sympathetic vibration of the cantilever 3 can be discriminated correctly, and therefore it becomes possible to make correct settings with respect to vibrational characteristics of the vibration frequency, amplitude, phase, etc. of the cantilever 3. After the above initial settings have been made, measurement of a sample S is performed. Specifically, the distance between the probe 3a and a surface of the sample S targeted for measurement is controlled so that the amplitude is made constant. In this condition, the XY scanner 20 is moved by the XY driving part 22 and then scan of the sample S is performed. During the time of scan, the amplitude of the cantilever 3 tends to widen and narrow according to the asperity of the sample surface S1, and thus the amplitude of a laser light L entering the light-detection part 28 (i.e. laser light reflected off the reflecting face) varies. The light-detection part 28 outputs a DIF signal depending on the amplitude to the preamplifier 29. The output DIF signal is amplified by the preamplifier 29 and converted into a DC signal by the AC-DC conversion circuit 30, and then sent to the Z voltage feedback circuit 31. The Z voltage feedback circuit 31 performs the feedback control while making the Z driving part 23 move the Z scanner 21 in Z direction by a small distance so that the DIF signal after DC conversion is made constant at all times, i.e. the amplitude of the cantilever is made stable. This enables the scan to be performed under the condition where the distance between the probe 3a and a surface of the sample S targeted for measurement is controlled so as to be constant. Also, the control part 32 measures the surface profile of the sample S based on the signal which is made to rise and fall by the Z voltage feedback circuit 31. Particularly, as correct settings with respect to the vibrational characteristics of the cantilever 3 have been made by the vibration-type cantilever holder 2, measurement by DFM can be made correctly at all times in measurement of a Q curve, and therefore the accuracy of measurement can be improved. In addition, the measurement by DFM becomes easier to use, which leads to enhancement of its convenience. Further, as vibrational characteristics of the cantilever 3 alone can be obtained reliably, the probe 3a can be made to come close to a desired measurement area reliably when the probe 3a is brought near to the sample S. Also, on this account, the accuracy of measurement can be improved. In addition, as sympathetic vibrational characteristics of the cantilever 3 are unchanged during the time of scan, stable measurements can be performed continuously. As described above, the scanning probe microscope 1 according to the embodiment includes a vibration-type cantilever holder 2 which allows the cantilever 3 to be vibrated separately, thereby making possible to correctly discriminate sympathetic vibrational characteristics of the cantilever 3. Thus, the measurement by DFM can be performed correctly, and therefore the reliability of the result of the measurement can be increased. Also, since the waveform signal input to the opposing vibration source 13 is not a particularly adjusted signal, but the same signal as that input to the vibration source 11, the vibration source-dedicated power supply 7 does not have to output different waveform signals. Therefore, complicated control is not required, and the configuration thereof can be simplified. Further, as the weight part 14 urges the opposing vibration source 13 toward the holder main body 12 utilizing gravity, the force is easy to transmit. Thus, the vibration generated by the opposing vibration source 13 can be transmitted to the holder main body 12 efficiently. In other words, as transmission of vibration is furthered, unwanted vibrations traveling from the vibration source 11 to constituent parts other than the cantilever 3 can be balanced out more reliably. Hence, it is easier to obtain vibrational characteristics of the cantilever 3 correctly. Moreover, in this embodiment, since the weight part 14 is identical with the sloped block 10 in shape and weight; it can be considered that an arrangement such that two identical sloped blocks 10 are provided on both opposing sides of the holder main body 12 is adopted. Therefore, unwanted vibrations traveling from the vibration source 11 to constituent parts other than the cantilever 3 can be counteracted more reliably, and vibrational characteristics of the cantilever 3 can be obtained with higher accuracy. Now, a vibration-type cantilever holder according to the second embodiment of the invention and a scanning probe microscope with the cantilever holder will be described with reference to FIGS. 4 and 5. Here, like parts in the second embodiment are discriminated by the same reference numerals as those in the first embodiment, and the descriptions are omitted. The second embodiment is different from the first embodiment as follows. That is, while in the first embodiment the opposing vibration source 13 is fastened on the second face 12b of the holder main body 12 so as to be opposed to the vibration source 11, the scanning probe microscope 40 according to the second embodiment includes a vibration-type cantilever holder 41, in which an opposing vibration source 13 is not opposed to the vibration source 11, as shown in FIG. 4. Specifically, in this embodiment the vibration-type cantilever holder 41 is fastened on an end portion of a second face 12b as shown in FIG. 5. On the opposing vibration source 13 is mounted a weight part 42 for urging the opposing vibration source 13 toward the holder main body 12 as in the first embodiment. However, unlike the weight part 14 in the first embodiment, the weight part 42 is formed so as to have a different size and weight, which are different from those of the sloped block 10. In this embodiment, the opposing vibration source 13 is arranged so as to vibrate on receipt of a waveform signal previously adjusted at least in its phase based on its relative positional relation with the vibration source 11 and a waveform signal input to the vibration source 11. Specifically, a signal having an inverted phase with respect to the phase of a waveform signal input to the vibration source 11 by the vibration source-dedicated power supply 7 is input to the opposing vibration source 13, thereby to vibrate the opposing vibration source 13. Thus, regardless of the place on the holder main body 12 where the opposing vibration source 13 is fastened, unwanted vibrations traveling to constituent parts other than the cantilever 3 from the vibration source 11 can be counteracted, and therefore vibrations other than the sympathetic vibration of the cantilever 3 can be reduced. Further, since the vibration-type cantilever holder 41 includes a weight part 42 as in the first embodiment, vibrations caused by the opposing vibration source 13 can be transmitted to the holder main body 12 efficiently. Incidentally, in this embodiment, the opposing vibration source 13 may be vibrated by timely adjusting the amplitude together with the phase (, or synthesizing another waveform resulting from a combination of different frequencies depending on the circumstances). Also, it is conceivable that the signal as that input to the vibration source 11 makes an optimum signal as a result of the adjustment. Particularly, with the vibration-type cantilever holder 41 according to this embodiment, as the position where the opposing vibration source 13 is fastened can be selected freely, the design flexibility can be enhanced. Next, a vibration-type cantilever holder according to the third embodiment of the invention and a scanning probe microscope with the cantilever holder will be described with reference to FIG. 6. Here, like parts in the third embodiment are discriminated by the same reference numerals as those in the second embodiment, and the descriptions are omitted. The third embodiment is different from the second embodiment as follows. That is, while in the second embodiment a signal previously adjusted at least in its phase is input to the opposing vibration source 13, the scanning probe microscope 50 according to the third embodiment measures other vibrations except the vibration of the cantilever 3 and causes the opposing vibration source 13 to vibrate based on the result of the measurement. Specifically, the scanning probe microscope 50 according to the third embodiment includes: a cut filter (detection part) 51 for detecting a waveform signal vibrating with an amplitude and a phase other than the vibration of the cantilever 3 from the result of the measurement by the measurement unit 6; and an adjustment circuit 52 for outputting an adjustment signal to the vibration source-dedicated power supply 7, which has been adjusted at least in its amplitude and phase (or which has a waveform synthesized by a combination of other different frequencies depending on the circumstances) so as to balance out the other waveform signals detected by the cut filter 51. Also, the vibration source-dedicated power supply 7 vibrates the opposing vibration source 13 based on the adjustment signal sent from the adjustment circuit 52. Here, the cut filter 51 cuts off only the sympathetic vibration frequency of the cantilever 3 among DIF signals amplified by the preamplifier 29, and detects other signals other than that (other waveform signals). The adjustment circuit 52 inverts in phase an input signal and adjusts the signal in gain so that detected other waveform signals are made minimum, and then outputs a signal inverted in phase to the vibration source-dedicated power supply 7 as an adjustment signal subjected to amplitude adjustment. Then, the vibration source-dedicated power supply 7 vibrates the opposing vibration source 13 with a phase and an amplitude depending on the adjustment signal. Thus, it becomes possible to counteract unwanted vibration traveling from the vibration source 11 to constituent parts other than the cantilever 3 with more reliability. Therefore, sympathetic vibrational characteristics of the cantilever 3 can be discriminated more correctly, and thus the accuracy of measurement can be improved. The technical scope of the invention is not limited to the above embodiment, and various changes and modifications may be made without departing from the subject matter of the invention. While in the first embodiment, for example, the weight part has the same shape and weight as those of the sloped block, it is not so limited. The size and weight of the weight part may be set freely. Further, the weight part is not essential, and it does not have to be provided. However, it is preferable to provide such weight part because it allows the vibration of the opposing vibration source to be transmitted to the holder main body efficiently. Further, it is more preferable to provide a weight part having the same shape and weight as those of the sloped block as in the embodiment. Further, while in the second and third embodiments the opposing vibration source is fastened on the second face of the holder main body, the position of the opposing vibration source is not limited to such position. The opposing vibration source may be fastened e.g. on the first face as in the case of the vibration source, or it may be fastened on a side face of the holder main body. In addition, more than one opposing vibration sources may be fastened, and the number of the opposing vibration sources is not limited to one. Further, the above embodiments are arranged so that a laser light goes through an opening formed in the holder main body and then impinges on the cantilever, and the reflected laser light goes out through the opening. However, the invention is not so limited. For example, the holder main body 12 may be formed from an optically transparent material (e.g. glass) to eliminate the opening 12c, as shown in FIG. 8. In this case, a laser light L emitted by the light-illumination part 26 enters the holder main body 12 at right angles to the second face 12b of the holder main body and impinges on the reflecting face of the cantilever 3. Then, the laser light L reflected off the reflecting face is incident on the first face 12a of the holder main body 12 on the skew, repeats refractions, and then goes out toward the light-detection part 28. Thus, the opening 12c can be eliminated by forming the holder main body 12 from an optically transparent material, and therefore the time and labor to form the opening 12c can be saved. Further, in the embodiments, the distance between the probe and a sample is controlled so that the vibration amplitude of the cantilever is made constant during the time of scan. However, this is not limited to the vibration amplitude, the distance between the probe and a sample may be controlled so that the vibrating state of the cantilever is made stable. For example, the distance may be controlled so that the frequency or angle of the cantilever is made constant. Still further, while the embodiments have been described taking, as an example, a sample-scan method by which a sample is moved along a direction in three dimensions, the invention is not so limited. A cantilever-scan method by which the cantilever is moved along a direction in three dimensions may be adopted. For example, as shown in FIG. 9, in a scanning probe microscope 60, the vibration-type cantilever holder 2 is fastened on the side of a rear face of the XY scanner 20 through a pedestal (not shown). The XY scanner 20 is fastened on a rear face of the Z scanner 21. The sample S is placed on a fixed stage 4. Thus, when the XY scanner 20 and Z scanner 21 are operated by the XY driving part 22 and Z driving part 23, the probe 3a and sample S can be relatively moved along a direction in three dimensions. Furthermore, on the side of the rear face of the XY scanner 20, the light-illumination part 26 and light-detection part 28 are fastened together with the vibration-type cantilever holder 2. Thus, a laser light L can impinge on the reflecting face of the cantilever 3 at all times. Also, the scanning probe microscope 60 configured like this can bring about the same effects and advantages as those achieved by the scanning probe microscope 1 according to the first embodiment. These microscopes are merely different in scanning method. It is noted that an arrangement such that the sample S and cantilever 3 can be moved along a direction in three dimensions together may be adopted. While in the embodiments the case where measurement by DFM is performed as an example of the vibration mode SPM has been taken, the invention is not so limited. For example, an MFM (Magnetic Force Microscope), by which measurements on a distribution of magnetism, a magnetic domain structure, etc. Of a magnetic material's sample are performed by vibrating a cantilever having a probe capable of sensing magnetism in the same way, and detecting the bending amplitude and phase of the cantilever during this time, also can bring about the same effects and advantages. In addition, not only the MFM, but also other SPMs e.g. SMM (Scanning Maxwell-stress Microscope) and KFM (Kelvin Probe Force Microscope), by which measurements concerning e.g. a potential distribution on a surface of a sample, etc. are performed by sensing the bending amplitude of a conducting probe (cantilever), while an AC bias voltage is applied between the cantilever and sample to vibrate the cantilever by means of capacitive coupling of the probe and sample, can bring about the same effects and advantages. Also, the following microscopes can bring about the same effects and advantages, for example: LM-FFM (Lateral Force Modulation Friction Force Microscope), by which the distribution of friction force is measured by detecting the amplitude of torsional vibration of a cantilever when a sample or the cantilever is driven into lateral vibration in a horizontal direction in parallel to a sample surface during the time of operation of AFM and; VE-AFM (Viscoelastic AFM), by which the distribution of viscoelasticity is measured by detecting the amplitude, sine component and cosine component of bending of a cantilever when a sample S is driven into small vibration in Z direction perpendicular to a sample surface S1 thereof or the cantilever is driven into small motion in Z direction perpendicular to the sample surface thereby to apply a periodic force to the cantilever during the time of operation of AFM. Moreover, while in the above embodiments the displacement of the cantilever is detected by use of an optical lever technique as the measurement unit, the invention is not limited to the optical lever technique. For example, a self-sensing technique, by which the cantilever is provided with e.g. a piezoresistor element so that the cantilever itself has the function of detecting the displacement, may be adopted. |
|
abstract | In a charged particle beam applying apparatus such as an electron beams lithography system, there is a technology that facilitates positional adjustment of a crossover and improves throughput of the apparatus. A front focal plane of a condenser lens is provided with a sharp end face (crossover regulation edge) for regulating the height of the crossover on a beam axis. By using the crossover regulation edge to measure the shape of an electron beam, the shape of the beam on the front focal plane of the condenser lens can be always checked even if the height of the crossover formed by an electron gun or the resistance of a source forming lens is changed. |
|
claims | 1. A particle-optical device for irradiating an object with a beam of particles, comprising a housing in which are located positioning means for positioning the object within the housing, comprising a reference body supported against a supporting portion of the housing and a kinematic system holding the object and controllably move-able with respect to the reference body, for manipulating the object in at least one degree of freedom with respect to the reference body, and further comprising a control mechanism and at least one combination of a piezo-electric position actuator and a piezo-electric force sensor positioned in series, whereby the control means receives at least one input signal from at least one sensor and—generates a control signal for at least that actuator associated with the sensor, characterized in that the at least one combination is positioned between the housing and the reference body, the support of the reference body against the supporting portion of the housing occurring via said at least one combination wherein each actuator is clamped between, respectively, a first printed circuit body, in conducting contact with a first actuator pole of the actuator, and a second printed circuit body, in conducting contact with a second actuator pole of the actuator, which first printed circuit body and which second printed circuit body are in conducting contact with the control mechanism. 2. A device according to claim 1, wherein the control mechanism comprises a first combining mechanism for the purpose of combining at least a first input signal and a second input signal—from, respectively, at least a first sensor and a second sensor—into a first combined input signal, in dependence upon which the control mechanism generates a first mutual control signal for the respective actuators associated with at least both the first sensor and the second sensor. 3. A device according to claim 2, wherein the control mechanism comprises second combining mechanism for the purpose of combining at least the second input signal and a third input signal, from at least the second sensor and a third sensor, respectively, into a second combined input signal, in dependence upon which the control mechanism generates a second mutual control signal for the respective actuators associated with at least the second sensor and the third sensor, whereby the control mechanism comprises a third combining mechanism for the purpose of combining the first mutual control signal and the second mutual control signal into a combined mutual control signal for the second actuator. 4. A device according to claim 1, wherein plate-like intermediate body is provided between the at least one combination, and the reference body, wherein the reference body can be displaced in a direction parallel to the plate-like intermediate body with the aid of an adjusting mechanism. 5. A device according to claim 4, wherein the adjusting mechansim is embodied so as to allow the reference body to be displaced in three degrees of freedom. 6. A device according to claim 4, wherein the reference body is supported against the intermediate body with a force that lies in the range between twice and twenty times the total weight of the positioning mechanisms that are to be supported. 7. A device according to claim 6, wherein a spring mechanism is provided for the purpose of forcing the reference body and the intermediate body toward one another. 8. A device according to claim 1, wherein each sensor is clamped between, respectively, a first printed circuit body, in conducting contact with a first sensor pole of the sensor, and a second printed circuit body, in conducting contact with a second sensor pole of the sensor, which first printed circuit body and which second printed circuit body are in conducting contact with the control mechansim. 9. A device according to claim 8, wherein printed circuit bodies that are located between the actuator and the sensor of a combination are provided, at the sides facing one another, with contact points that are conductively connected to each other. 10. A device according to claim 9, wherein at least a portion of the printed circuit bodies is provided—on at least one external surface—with at least one isolated conducting track for direct electrical contact either with a pole of an actuator or of a sensor or with a contact point or conducting track of a printed circuit body. 11. A device according to claim 1, wherein the actuator and associated printed circuit bodies are provided with mutually connecting holes that collectively form a through-hole through which a traction organ extends for the purpose of clamping the actuator between the associated printed circuit bodies. 12. A device according to claim 1, wherein one of the two printed circuit bodies associated with the actuator of a combination is provided with two contact points that are in conducting contact with both poles of the associated actuator. 13. A device according to claim 12, wherein one of four printed circuit bodies associated with the actuator and the sensor of a combination is provided with four contact points that are in conducting contact with both poles of both the actuator and the sensor. 14. A particle-optical device for irradiating an object with a beam, comprising:a housing with a supporting portion to support a reference body;a reference body supported by the supporting portion of the housing;a kinematic system supported by the reference body, the kinematic system adapted to hold and move the object in at least one degree of freedom with respect to the reference body;a plurality of sensor-actuator combinations, spaced apart and positioned between the housing supporting portion and the reference body, so that each sensor can sense vibration at a different point, and so that each actuator can react to reduce vibration of the reference body and kinematic system in response to control signals derived from signals from the sensors; anda controller to form control signals from combinations of signals received from a plurality of sensors, and to distribute control signals to each of a plurality of actuators of the combinations to make the actuators absorb vibrations of the reference body with respect to the housing wherein an actuator of a sensor-actuator combination comprises a stack of discs, comprising a piezoelectric actuator disc between and in contact with two printed circuit board discs to couple poles of the actuator to the controller, and further wherein a sensor of the sensor-actuator combination comprises a stack of discs, comprising a piezoelectric sensor disc between and in contact with two printed circuit board discs to couple poles of the sensor to the controller. 15. The device of claim 14, wherein a printed circuit board disc associated with a sensor is in conducting contact with a printed circuit board disc associated with an actuator. 16. The device of claim 14, wherein a first printed circuit board disc is in conducting contact with the second printed circuit board disc. 17. The device of claim 14, wherein a sensor of a sensor-actuator combination comprises a stack of discs, comprising a piezoelectric sensor disc between and in contact with two printed circuit board discs to couple poles of the sensor to the controller. 18. The device of claim 17, wherein a first printed circuit board disc is in conducting contact with the second printed circuit board disc. 19. The device of claim 14, wherein a control signal for an actuator of a first sensor-actuator combination is derived from a signal from the sensor of the first combination and from signal of a sensor of a second sensor-actuator combination. 20. The device of claim 19, wherein the control signal for the actuator of the first combination is further derived from a signal from a sensor of a third sensor-actuator combination. 21. The device of claim 20, wherein the control signal for the actuator of the first combination is further derived from a signal from a sensor of a fourth sensor-actuator combination. 22. The device of claim 14, wherein a control signal for an actuator is derived from a sum of the signals from each of two sensors. 23. The device of claim 14, wherein a control signal for an actuator is derived from the signals from each of three sensors to stabilize the reference body without substantial torsion. 24. The device of claim 14, wherein at least three sensor-actuator combinations are positioned at rectangular coordinates to generate X and Y control signals derived from the sensor signals to compensate for pivot of the reference body with respect to the housing about an X axis and/or a Y axis. 25. The device of claim 14, further comprising a plate-like intermediate body between the sensor-actuator combinations and the reference body, with adjusting means to laterally position the reference body with respect to the intermediate body. 26. The device of claim 25, wherein the reference body is supported against the intermediate body with a force that lies in the range between twice and twenty times the total weight of the reference body and kinematic system that are to be supported. |
|
description | This is a divisional application of application Ser. No. 09/968,584, filed Oct. 1, 2001 now U.S. Pat. No. 6,898,260; which was a continuing application, under 35 U.S.C. §120, of International application PCT/EP00/02681, filed Mar. 27, 2000; the application also claims the priority, under 35 U.S.C. §119, of German patent application No. 199 14 013.8, filed Mar. 29, 1999; the prior applications are herewith incorporated by reference in their entirety. The invention relates to a fuel element for a pressurized water reactor, with a laterally open skeleton containing control-rod guide tubes, to which are fastened a plurality of spacers and also a fuel element head and a fuel element foot. Gastight multilayer cladding tubes are inserted into the skeleton and in each case surround a column of fuel pellets. FIG. 1 illustrates a fuel element of this type, with a head 1, a foot 2 and spacers 3 and 4 that are fastened to guide tubes 5, thus producing a laterally open skeleton, into which fuel rods 6 are inserted. During operation, cooling water flows from the bottom upward through the fuel element and can also enter adjacent fuel elements laterally from the interspaces between the fuel rods. It can also be seen from FIG. 1 that additional mixing grids 7, which serve as carriers for flow guide blades, may be provided between the spacers 4 in an upper part of the fuel element. Such flow guide blades are advantageously likewise provided in the upper part of the fuel element, at least on a top side of the spacers 4, in order to achieve a turbulent mixing of the cooling water and a better flow onto the fuel rods 6. Corresponding blades are described, for example, in Published, Non-Prosecuted German Patent Application DE 15 64 697 A and are reproduced in FIG. 2. It is also possible, however, to have other spacers (for example, formed of sleeves welded to one another) and other geometries of flow guide blades 8, while a different number of mixing vanes may also be provided in the interspaces between adjacent fuel rods 6. In the pressurized water reactor, only a small fraction (normally at most 5%) of the liquid cooling water is evaporated on the outer surfaces of the fuel rods, on the contrary the heat generated in the fuel by nuclear fission is discharged essentially in that water having a corresponding temperature and maintained under high pressure is transported away by convection. In contrast, a boiling water reactor operates with lower pressure and lower temperatures, the heat from the fuel rods being transported away, at least in the upper part of the fuel element, essentially by isothermal evaporation in a two-phase mixture. In this case, it is necessary to channel the steam that occurs. The fuel elements are therefore surrounded laterally by fuel element boxes. The techniques of the boiling water reactor and of the pressurized water reactor have developed in different directions. For the purpose of plant protection and for similar reasons, the pressurized water has admixed with it, for example, lithium hydroxide and similar additives which cannot be used in boiling water and lead to a different water chemistry (for example, a different oxygen concentration). The size and number of fuel rods in the fuel elements and the configuration of control elements in the reactor core are also different. The differences in the temperature and pressure of the cooling water also lead to different loads on the cladding tubes and to a different behavior of the fuel, in particular to different time constants of the reactor core when the latter is considered as a self-contained control system with feedback. The result of this different control behavior is that the power output of pressurized water reactors is changed only very slowly, that is to say the pressurized water reactor is operated almost virtually in the steady state and is suitable particularly for covering basic loads. For covering peak loads of the consumer connected to the reactor, boiling water reactors, the power output of which is run up, for example, substantially more quickly and in a ramp-like manner, are more suitable. The result of this is that the cladding tubes, which are already exposed on their outer surface, according to the different water chemistry and operating temperatures, to different chemical loads (for example, nodular corrosion in the boiling water reactor or uniform corrosion in the pressurized water reactor) and have to withstand different operating pressures, are also subjected to different loads on the inside. The outcome of this has been that the cladding tubes of boiling water reactors are formed, as a rule, of a different alloy (to be precise, zircaloy-2) from the cladding tubes of pressurized water reactors for which zircaloy-4 was developed. A zirconium alloy with 2.5% niobium, which is also used in Russian light-water cooled reactors, is also known for the pressure tubes of high-temperature reactors. Table 1 indicates the standardized composition of industrially pure zirconium for the nuclear industry (so-called “zirconium sponge”), zircaloy-2 (“zry-2”), zircaloy-4 (“zry-4”) and zirconium niobium (“Zr/Nb”), oxygen being considered as an impurity acceptable in small quantities, even when, because of its hardening effect on zirconium, it is often desirable and is therefore added. If use is made of a higher enrichment of the fuel pellets with fissionable isotopes of uranium and/or plutonium and therefore of a greater useful energy content (so-called “burn-up”) of the fuel, then the fuel elements can remain in the core for longer, should their cladding tubes be capable of meeting the corresponding requirements due to the longer service life. Therefore, in pressurized water fuel elements, the outer surfaces of the cladding tubes must be particularly resistant to the uniform corrosion occurring in the pressurized water and should not be pressed onto the fuel by the increased pressure, even in the event of relatively long service lives, in such a way that they thereby experience damage. In the development of cladding tubes that meet the increased requirements of a longer service life in the pressurized water reactor, it is therefore necessary to pay particular attention to the mechanical stability of the entire tube and to the resistance of the outer surface to uniform corrosion. These conditions are fulfilled satisfactorily by single-layer cladding tubes, such as are described in European Patent EP 0 498 259 B and, in general, consist of zirconium with 0.8 . . . 1.7% Sn, 0.07 . . . 0.5% Fe, 0.05 . . . 0.35% Cr, 0.07 . . . 0.2% O, up to about 0.015% Si and up to a maximum of 0.1% Ni. In this context, it has proved particularly important that the metals, Fe, Cr and Ni, which are virtually insoluble in zirconium and are precipitated (so-called “secondary precipitations”) as intermetallic compounds (“secondary phases”), have an average particle size of about 0.1 to 0.3μ. The particle size is set by the thermal treatment to which the alloy is subjected after it has first been brought to a temperature at which the precipitations are dissolved (so-called “solution annealing”) and has then been rapidly cooled (so-called “quenching”). The resulting size and distribution of the secondary precipitations can be calculated by a “particle growth parameter” and in manufacturing practice are set by a cumulative “standardized annealing duration” A A = ∑ t i · exp ( - Q / T ) ,in which T is the temperature in Kelvin during a manufacturing step i, ti is the duration of the manufacturing step and Q corresponds to an activating energy, and the value Q=40,000 Kelvin may be adopted. FIG. 3 shows the daily growth of the uniform oxidation layer on the surface of a cladding tube formed of zircaloy-4 in a pressurized water reactor at operating temperatures of about 300° C. as a function of the standardized annealing duration A which was used in the production of the cladding tube. In general, for pressurized water reactors, standardized annealing durations of between 2·10−18 and 50·10−18 hours are considered favorable for zircaloy-like alloys of this type, such as are described in European Patent EP 0 498 259 B (Garzarolli et al. in “Zirconium in the Nuclear Industry: Eighth International Symposium”, Philadelphia 1989 (ASTM Special Technical Publication 1023), pages 202 to 212). However, such a high annealing duration conflicts with the efforts of a person skilled in the art, by a pilgrim-step method with cold formings, to break down the alloy grain, which likewise ripens into large grains at high temperatures, into small grains by cold formings, in order to increase the mechanical stability of the cladding tube, since a fine grain leads to high stability along with high ductility. Consequently, according to the patent specification mentioned, the high standardized annealing duration is achieved by the quenched material first being forged, still at a high temperature, before it is extruded to form a tube blank and is then cold-formed in subsequent pilgrim steps with moderate intermediate annealings. Another way is to have a composite tube that, as a so-called “duplex”, formed of a relatively thick matrix layer with a thin outer protective layer formed of another zirconium alloy. The matrix ensures the necessary mechanical stability, while the outer protective layer is resistant to the uniform corrosion posing a threat in the pressurized water reactor. Such a duplex is described for the first time in European Patent EP 0 212 351 B, where 0.1 to 1% V and up to 1% Fe is used as alloying additives for the outer protective layer. European Patent EP 0 301 395 B describes a duplex, in which the outer alloy contains 0.2 to 3% Nb and/or a total content of Fe, Cr, Ni and Sn of between 0.4 and 1% (remainder: in each case zirconium of industrial purity). It is known from European Patent EP 0 630 514 B that an outer layer of this type for a zircaloy matrix may also contain a larger total content of Fe, Cr, Ni, Sn, insofar as specific restrictions are maintained for the individual alloying additives, in particular the tin content is below the tin content of the zircaloy. The cladding tubes mentioned have proved appropriate, even under the operating conditions of the pressurized water reactor, and make it possible to achieve the desired long service lives. The graph of FIG. 3 would be entirely different in the case of a boiling water reactor. There, because of the lower operating temperatures, virtually no uniform corrosion occurs, but oxide pustules are formed. Here, high secondary precipitations cannot act as any of the pustules that, however, are avoided when the material of the secondary phases is finely distributed and has undergone only a particularly low standardized annealing duration. Often, however, cladding tubes of boiling water fuel rods exhibited corrosion damage that emanated from inside the tubes and was attributed to stress crack corrosion. Such damage was minimized by a composite tube, in which a matrix of zircaloy had on the inside a protective layer of industrially pure zirconium, that is to say a soft material, but one susceptible to corrosion. In this case, however, the susceptibility of pure zirconium to corrosion is a disadvantage, since the situation is unavoidable where, in rare instances, due to slight damage in the tube, water from the boiling water reactor enters the cladding tube interior and then triggers corrosion leading to extensive cracks by which the water of the reactor may be contaminated to a substantially greater extent than by a multiplicity of fuel rods with locally limited damage. Instead of a protective layer of pure zirconium, therefore, a protective layer is often used, in which the zirconium contains up to 1% of another alloying additive. Thus, European Patent EP 0 726 966 B describes a cladding tube with a thick matrix layer of zircaloy, in which the secondary precipitations have a particle size of between about 0.03 and 0.1μ, and a lining of zirconium with 0.2 to 0.8% iron is bonded metallurgically to the inside. The composite tube is particularly advantageous in the boiling water reactor, because, due to the small size of the secondary precipitations on the outer surface, a particularly low A-value becomes necessary, which, in the case of the appropriate alloying of the protective layer on the inside of the cladding tube, likewise brings about only a slight growth of secondary precipitations and grain, so that the inside is both protected more effectively against corrosion and remains soft because it is not subject to any excessive dispersion hardening as a result of Fe secondary precipitations. However, a cladding tube of this type, configured for boiling water conditions, is entirely unsuitable for pressurized water applications, since the small size of the secondary precipitations on the outer surface would accelerate the uniform corrosion and necessitate an exchange of the cladding tube even after short service lives. On the other hand, the inner lining is not necessary, even under the operating conditions of the pressurized water reactor which have existed hitherto, since, up to now, no damage emanating from the inner surface (stress crack corrosion) has been observed. Moreover, the power output of the pressurized water reactors is not changed rapidly in the ramp-like manner, as is customary in boiling water reactors. Instead, the control conditions of the pressurized water reactor make it necessary, in any case, for the power output to be changed only slowly, there being predetermined for the control a rate of change which also takes account of the fact that the cladding tubes are not to be subjected to inadmissible stress. In the case of a higher enrichment of the fuel and longer service lives, even the behavior of the fuel itself must be taken into consideration. Since a multiplicity of gaseous fission products occur during decomposition, the fuel swells and thereby experiences an enlargement of volume which leads to a widening of the cladding tube, especially since the latter, in the course of time, particularly under the higher pressures of the pressurized water reactor, is compressed and creeps onto the fuel. When the fuel, which is in contact with the inside of the cladding tube even at a low reactor power output, is quickly heated as a result of a rapid increase in power output customary in the boiling water reactor, however, the thermal expansion of the fuel constitutes an additional load on the cladding tube. In configuration terms, the loads can be taken into account in as much as a gas collecting space is provided at least in the upper end of the fuel rods, a gap is left free between the cladding tubes and the fuel pellets and the fuel element is efficiently and quickly cooled, for example by the initially mentioned flow guide blades on the spacers and, if appropriate, additionally introduced intermediate grids. The load has hitherto been unimportant in the control of the power output of pressurized water reactors, since, in any case, in control terms a restricted rate of change of the power output seems permissible. It is accordingly an object of the invention to provide a fuel element for a pressurized water reactor and a method for producing cladding tubes that overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, which, on the one hand, can remain in the reactor for a sufficiently long time and, on the other hand, allows a more flexible operation of the pressurized water reactor, in particular use of the pressurized water reactor for covering peaks in demand of the consumer or power supply network connected to the reactor. In particular, the object, at the same time, is to produce a cladding tube suitable for the novel fuel element. With the foregoing and other objects in view there is provided, in accordance with the invention, a fuel element for a pressurized water reactor. The fuel element contains a laterally open skeleton having control-rod guide tubes each with a first end and a second end, spacers fastened to the control-rod guide tubes, a fuel element head disposed at the first end of the control-rod guide tubes, and a fuel element foot disposed at the second end of the control-rod guide tubes. Gastight cladding tubes are inserted into the skeleton and each is filled with a column of fuel pellets. At least some of the gastight cladding tubes have a multilayer wall. The multilayer wall is formed of a mechanically stable matrix containing a first zirconium alloy disposed in a middle of the multiplayer wall; and a thinner protective layer of a second zirconium alloy alloyed to a lesser extent than the first zirconium alloy. The thinner protective layer is bound metallurgically to the matrix and is disposed on an inside of the matrix facing the fuel pellets. The invention proceeds, in this case, from the knowledge that the control restrictions in the control of the power output make it possible per se to have greater rates of change in the power output of a pressurized water reactor than has been conventional hitherto. Flexible operation would therefore be possible if the fuel element were also to withstand the loads occurring during rapid load changes. To achieve the object, the invention provides the fuel element with a laterally open skeleton containing the control-rod guide tubes, to which are fastened the spacers, the fuel element head and the fuel element foot. Inserted into the skeleton are the cladding tubes which in each case surround a column of fuel pellets in a gastight manner, at least some cladding tubes each having a multilayer wall. In the middle of the wall is located, according to the invention, a mechanically stable matrix of a first zirconium alloy, alloyed to a greater extent, to which a thinner protective layer of a second zirconium alloy alloyed to a lesser extent is bound metallurgically. The protective layer is in this case located on the matrix inside facing the fuel pellets. Preferably, the two zirconium alloys have precipitations of secondary phases that, by thermal treatments with different standardized annealing durations, are ripened to a different average size. The invention is in this case based on the fact that the configuration of the fuel element satisfies all hydraulic and cooling requirements of relatively long operation under full load or part load, particularly when at least the spacers in an upper part of the fuel element carry, on their side facing away from the flow of pressurized water, flow guide blades for intermixing the pressurized water. The configuration of the fuel rods can also satisfy these requirements, particularly when the cladding tubes are filled with a gas of increased pressure and have a gas collecting space (“plenum”) at least at the upper end and the pellets are introduced with an annular gap in relation to the inner surface of the cladding tube. Moreover, the invention also takes account of the fact that a matrix, in particular when it has the features described in European Patent EP 0 498 259 B, is already sufficiently corrosion-resistant for relatively long operation under full load. If appropriate, a further protective layer, such as is described, for example, in European Patents EP 0 212 351 B, EP 0 301 295 B or EP 0 630 514 B mentioned, may also be bonded metallurgically around the matrix on the outside of the cladding tube. A matrix of this type, formed of a zircaloy-like zirconium alloy (1 to 1.8% by weight Sn; 0.2 to 0.6% by weight Fe; up to 0.3% by weight Cr; remainder: industrially pure zirconium, if appropriate with an oxygen content of up to 2.0%), best displays the desired properties when it is treated with a standardized annealing duration A of between 2 and 80·10−18 hours. Another preferred possibility for a matrix having the desired properties is a zirconium alloy with 0.8 to 2.8% Nb (if appropriate, up to 2.7% of further additives, remainder: zirconium of industrial purity, including, if appropriate, an oxygen content of up to 2.0%). Preferably, in this case, the quantity of further additives is below the quantity of the niobium. However, such a niobium-containing zirconium alloy displays the most favorable properties when it is subjected to a substantially lower standardized annealing duration, in particular A lower than 0.5·10−18 h. Admittedly, the mechanical stability of the alloys is not so high that they ensure the annular gap for a relatively long time and could prevent the cladding tube from creeping down onto the fuel. The alloys overcome the fact that the cladding tube is widened again due to the growth in volume of the fuel after relatively long service lives. The alloys also withstand load changes during which the power output falls considerably below the maximum value for only a short time and is soon raised again to the maximum value. To control the power output, however, the rate of change must be adapted to the most unfavorable case. This occurs when, during the operation of the reactor, a plurality of load changes have already taken place and then only part-load operation takes place for a relatively long time, in which the fuel contracts thermally and a renewed creeping of the cladding tube consequently occurs. There is then the threat of sudden loads when the reactor is quickly run up again and the fuel expands thermally again. This, in actual fact, requires a particularly high ductility of the cladding tube, which, however, would itself be conducive to undesirably rapid creeping. Moreover, when, by the control elements being moved out, the reactor is run up from a state in which it was operated only under part load, with control elements inserted partially into the reactor core, the fuel pellets adjacent to the control elements which are moving past experiencing a sudden thermal load, since they were previously protected by the control elements from the high neutron flux to which they are then suddenly exposed. The pellets, which were initially intact according to FIG. 4, therefore shatter and experience a structural change evident from FIG. 5. In this case, individual fragments of a shattered pellet may be displaced and press locally against the inside of the cladding tube. It must therefore be assumed that, after a lengthy period under part load, close contact occurs at least locally between the fuel rod and the fuel (“deconditioning”) and then, in the case of a sudden thermal change in volume of the fuel, generates considerable stresses in the cladding tube. If the cladding tube is formed completely of the alloys mentioned hitherto, only slow increases in power output would therefore nevertheless be possible. According to the invention, however, the stresses are absorbed by the protective layer bound metallurgically to the inside of the matrix and formed of the zirconium alloyed to a lesser extent, the protective layer formed preferably of zirconium of industrial purity which is alloyed with 0.2 to 0.8% by weight of iron. As a rule, the second zirconium alloy contains more than 0.3% by weight, preferably at least 0.35% of iron. The preferred maximum value is around 0.5 or, in any event, is below 0.6%. However, the alloy displays the most favorable properties when the precipitations of the secondary phases have an average size which corresponds to a standardized annealing duration of about 0.1 . . . 3·10−18 h. Such small secondary precipitations of a ZrSe alloy on the inside of the cladding tube are known from the initially mentioned European Patent EP 0 726 966 B and can be manufactured from a composite tube blank produced by the coextrusion of tubes inserted one into the other, but the result of the further processing of the blank is that, after quenching, the two layers acquire either a high A-value, this being detrimental to the action of the protective layer, or a low A-value, that is to say the outside also has correspondingly fine secondary precipitations, which conforms to the requirements of a boiling water reactor, but is harmful to a pressurized water reactor. However, different precipitation sizes on the inner surface and the outer surface of a cladding tube can be produced by a method that is known as “partial quenching”. In this, in the case of a cladding tube which already possesses relatively large secondary precipitations due to relatively long annealing durations, the inside is maintained at a low temperature by a coolant stream, while the outside is increased briefly (for example, inductively) to solution temperature. During cooling, a fine dispersion of precipitations occurs on the outside, that is to say, ultimately, a “metallurgic gradient” with respect to the precipitations in the cladding tube is generated. However, the result of the “metallurgic gradient” is precisely that there are substantially finer secondary precipitations on the outside than on the inside, that is to say precisely the distribution likewise suitable only for boiling water, if both layers are formed of a niobium-free ZrFe alloy. The “partial quenching” is complicated, but is possible, at least theoretically, in the case where the matrix is formed from a ZrNb alloy. However, such a cladding tube with a matrix of ZrNb, which is bonded metallurgically to the inside of the cladding tube by a protective layer of ZrFe, can also be produced by the two zirconium alloys first being thermally treated independently of one another, in each case solution annealing, with subsequent different standardized annealing durations A, being carried out. From the first zirconium alloy and at least the second zirconium alloy, a multilayer composite tube is then produced, the wall of which contains in the middle a thick layer of the first zirconium alloy as the matrix, a protective layer of the second alloy being bonded metallurgically to the inside of said wall. The composite tube is then processed further into the finished cladding tube, in such a way that the two layers are in this case subjected to virtually the same thermal conditions, without solution annealing. In this case, the second zirconium alloy is treated, up to the completion of the cladding tube, with a standardized annealing duration which differs by at least 80% from the standardized annealing duration to which the first zirconium alloy is subjected up to the completion of the cladding tube. Preferably, even before the production of the composite tube, the second zirconium alloy is subjected to a standardized annealing duration of between 0.1·10−18 h and 3·10−18 h, advantageously at most to a standardized annealing duration of below 2·10−18 h. Preferably, at all events, before the production of the composite tube, a zirconium alloy with 0.8 to 2.8% niobium is treated with a lower standardized annealing duration than the zirconium alloy of the protective layer. However, a similar method with the same composition and similar treatment of the protective layer (at most a standardized annealing duration of below 3·10−18 h, advantageously below 2·10−18 h) can also be adopted when a zirconium alloy of 1 to 1.8% Sn; 0.2 to 0.6% Fe; up to 0.3% Cr (remainder: industrially pure zirconium) is used as matrix, although the matrix should be treated with a standardized annealing duration of 2 to 80·10−18 h before the production of the composite tube. For the further processing of the composite tube to form the finished cladding tube, forming steps are necessary (in particular pilgrim steps), between which intermediate annealing is carried out in each case. At the same time, a maximum standardized annealing duration (for example, 3·10−18 h) is preferably also maintained for this further processing. Even annealing durations of below 2·10−18 h can easily be controlled in manufacturing terms. Insofar as increased protection of the outer surface against uniform corrosion is desired, during the production of the composite tube a third zirconium alloy may also be bound metallurgically to the first zirconium alloy. In accordance with an added feature of the invention, the second zirconium alloy contains at least 0.2% by weight of iron, a remainder being zirconium of industrial purity. In accordance with an additional feature of the invention, an iron content of the second zirconium alloy is 0.40±0.04% by weight. In accordance with another feature of the invention, the second zirconium alloy has precipitations of secondary phases, a size of which corresponds to a standardized annealing duration of about 0.1 to 3·10−18 h. In accordance with a further feature of the invention, the first zirconium alloy contains 1.3±0.1% Sn; 0.28±0.04% Fe; 0.16±0.03% Cr; 0.01±0.002% Si and 0.14±0.02% O. In accordance with a further added feature of the invention, the first zirconium alloy has precipitations of secondary phases, a size of which corresponds to a higher standardized annealing duration than an annealing duration to which a size of the precipitations in the second zirconium alloy corresponds. In accordance with a further additional feature of the invention, the size of the precipitations in the first zirconium alloy corresponds to a standardized annealing duration of 2 to 80·10−18 h. In accordance with another further feature of the invention, the first zirconium alloy is formed of 0.8 to 2.8% niobium and zirconium of industrial purity and also at most 2.7% of further additives. In accordance with another added feature of the invention, in the first zirconium alloy, a quantity of the further additives is smaller than a quantity of the niobium. In accordance with another additional feature of the invention, the first zirconium alloy contains 1.0±0.2% niobium, 0.14±0.02% oxygen, a remainder being the zirconium of industrial purity. In accordance with an added feature of the invention, the first zirconium alloy contains precipitations of secondary phases, a size of which corresponds to a lower standardized annealing duration, as compared with the second zirconium alloy. In accordance with an additional feature of the invention, flow guide blades are provided, and at least the spacers in an upper part of the fuel element carry, on a side facing away from a flow of pressurized water, the flow guide blades for intermixing the pressurized water. In accordance with another feature of the invention, the gastight cladding tubes each have an upper end with a plenum formed therein at the upper end, and including a gas of an increased pressure filling the gastight cladding tubes. In accordance with a further feature of the invention, the column of fuel pellets have ends and bodies containing virtually no fissionable material disposed at the ends. In accordance with another added feature of the invention, a further protective layer of a third zirconium alloy which is thinner than the matrix and is bonded metallurgically to an outside of the multilayer wall. In accordance with another additional feature of the invention, the second zirconium alloy contains at least 0.30% by weight of iron, a remainder being zirconium of industrial purity. Optionally, the second zirconium alloy contains up to 0.8% by weight of iron, the remainder being zirconium of industrial purity. Alternatively, the second zirconium alloy contains at most 0.6% by weight, of iron, the remainder being zirconium of industrial purity. In accordance with another further feature of the invention, the first zirconium alloy contains at least 1.2% Sn, at least 0.24% Fe and at least 0.10% Cr, a remainder being zirconium of industrial purity. Optionally, the first zirconium alloy contains at most 1.5% Sn, at most 0.5% Fe and at most 0.25% Cr, a remainder being zirconium of industrial purity. In accordance with a concomitant feature of the invention, the size of the precipitations in the first zirconium alloy corresponds to a standardized annealing duration of 30±10·10−18 h. 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 fuel element for a pressurized water reactor and a method for producing cladding tubes, 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. The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. Referring now to the figures of the drawing in detail and first, particularly, to FIG. 6 thereof, there is shown a cladding tube 10 of the fuel rods 6 is in each case closed in a gastight manner at upper and lower ends by an end plug 11. At the upper end a spring 12 subjected to compressive stress ensures that a corresponding plenum 13 is maintained at least at the upper end. A column of fuel pellets 14 contains in each case, at its upper and lower end, a body 15 that contains virtually no fissionable material and may consist, for example, of aluminum oxide or else natural uranium or depleted uranium. In this case, in order to increase conductivity between the pellets 14 and the cladding tube 10, the cladding tube 10 is filled with a high-pressure gas (for example, helium). In the present case, a supporting body 16 at the lower end of the fuel rod also keeps free a corresponding plenum. The outside diameter of the cladding tube is about 9.55 mm, and its wall thickness is about 0.61 mm. According to FIG. 7, a cladding tube 20 is formed of a matrix 21, the thickness of which is about 75 to 95% of a cladding tube wall. A protective layer 22 is bound metallurgically to the matrix 21 on the inside of the cladding tube 20, and it is also indicated that a further protective layer 22′ may also be attached to the outside. Table 2 indicates the lower and upper limit values for the composition I of the matrix 21. Here, the values given in brackets in each case describe preferred relatively narrow limits for the contents of the individual alloy constituents or the particularly preferred limit values for the accompanying elements of the alloy constituents which are already contained as impurities in the zirconium of industrial purity (“sponge”, see Table 1) and can be maintained for the lower limits which are also advantageous, as in the case of oxygen or silicon. In the preferred exemplary embodiment, the matrix 21 contains 1.3±0.1% Sn; 0.28±0.04% Fe; 0.16±0.03% Cr; 0.01±0.002% Si and 0.14±0.02% O. The size of the precipitated secondary phases is in this case 30·10−18 h. The protective layer 22 consists of 0.4±0.04% Fe and zirconium sponge, the precipitation size being determined by A=1·10−18 h. In the second phase, the precipitations consist virtually of intermetallic ZrFe compounds, in the case of the matrix 21 of mixed compounds of zirconium with iron and chromium, and, in FIG. 8, it can be seen under I that, up to temperatures of about 820° C., there is an α-phase of ZrSn in addition to the corresponding secondary phase γ of these precipitations. In the range between about 820 and 960° C., there is also a β-phase of ZrSn in addition to the α-phase, and at about 840° C. (“solution temperature”) the γ-phase of the intermetallic compounds becomes a solution. Above 960° C., only the β-phase with the dissolved precipitations is still stable. If, therefore, the matrix is heated into the β-range (temperatures of above 960° C.) and is then rapidly cooled, a fine-grained α-phase is first formed, in which part of the iron is distributed in a finely dispersed manner as precipitations of the γ-phase, while the rest of the iron remains bound as metastable supersaturation in the α-phase. In this case, the finely dispersed precipitations correspondingly form nuclei, on which the excess iron fraction is accreted the more rapidly and the more highly, the higher the temperature and duration in which the matrix material is exposed to further thermal treatments in the α-range (temperatures of below 820° C.). To produce the cladding tube 20, first, the first alloy of ZrSnFeCr, provided for the matrix 21, is remelted a plurality of times under a vacuum in a step 30a (FIG. 9) to homogenize the alloy constituents, in a step 31a the alloy is forged to a shape suitable for the processing of a tube blank and, in a further step 32a, the alloy is rapidly cooled (“β-quench”) from a temperature in the β-range (above 960° C.). This may be followed by further forging (step 33), the first tube blank Ra being produced at the latest during a step 34. The step 34 is also followed by further annealings, in order to set the parameter A=30·10−18 h in the first tube blank. In a similar way, the second zirconium alloy (ZrFe) provided for the protective layer 22 is likewise remelted in a step 30b, in a step 31b is heated into the β-range (temperatures of above 960° C.) and in the step 32b is rapidly cooled. During these steps, a second tube blank Rb is also produced. In this case, the β-quenching (step 32b) is followed by virtually no further heating, instead the two blanks, the shapes of which have been adapted to one another, are placed one into the other, welded to one another and jointly extruded in a step 35. This coextrusion does not, in practice, contribute to the ripening of the precipitations, so that, in the composite tube obtained, the matrix material possesses the value A=30·10−18 h and the second zirconium alloy possesses virtually the value A=0. Subsequently, a plurality of pilgrim steps 36 are carried out, between which brief annealings at temperatures well below 820° C. are carried out in each case, in order to recover the cold-formed material and prepare it for the next pilgrim step. What is then achieved by terminal annealing 37 is that the parameter A=1·10−18 h is set for the entire processing of the composite tube to form the finished cladding tube, that is to say the first zirconium alloy of the matrix has the value A=31·10−18 h, but the second zirconium alloy of the protective layer has the value A=1·10−18 h. For steps 33 and 34, a range A=2 to 80·10−18 h is maintained, values of above 5·10−18 h being advantageous. Values of above 60·10−18 h signify long annealing durations at high temperatures which do not seem necessary. For steps 35 to 37, in general, values A of below 2·10−18 may be maintained. For the finished zirconium alloy of the matrix, therefore, values A=5 to 60·10−18 h seem advantageous, while A=1 to 3·10−18 h should be maintained for the second zirconium alloy of the protective layer. In the second exemplary embodiment according to FIG. 10, a cladding tube 40 is formed of the matrix 41 with the composition 1.0±0.2% Nb, 0.14±0.02% O, remainder: zirconium of industrial purity, see Table 2 indicating under II the preferred limits for the constituents in similar compositions. It can be seen in FIG. 8, under II, that, in the phase diagram of the alloy, at temperatures of up to 580° C. there is a stable α-phase in which about half the niobium is dissolved, while the remainder is precipitated as a stable β-phase of the niobium. At 580° C., there is a mixed phase α+β, in which virtually all the niobium is dissolved, while, at temperatures of above 960° C., only a β-phase of the zirconium, with the completely dissolved niobium, still exists. The second zirconium alloy in a protective layer 42 of the cladding tube 40 is formed of the same ZrFe alloy as in the first preferred exemplary embodiment already described. To produce the cladding tube 40, a diagram according to FIG. 11, similar to that of FIG. 9, is obtained. In this case, however, after multiple remelting under a vacuum (step 50a) and forging in the β-range (temperatures of above 960° C.) (step 51a), the first zirconium alloy ZrNb of the matrix is quenched (step 52), a first tube blank Rc being produced from the matrix material, without the β-quenching (step 52a) being followed by thermal treatment with an appreciable parameter value A. A step of this kind is provided only for the second zirconium alloy of the protective layer, in which multiple remelting in a vacuum (step 50b) and forging in the β-range (step 51b) and annealing at temperatures of below about 600° C., in particular below 580° C. (α-range), take place. In this case, the second tube blank Rd is produced, which is inserted exactly into the interior of the first tube blank Rc. For the first tube blank Rc produced in steps 51a and 52a, virtually the parameter value A=0 is obtained, while, in steps 51b, 52b and 53, the second tube blank Rd can be produced with a parameter value below 2·10−18 h. In the exemplary embodiment, A=1·10−18 h was set in step 53. The two tube blanks inserted one into the other are welded to one another and extruded together, subsequently brought to the final dimensions of the cladding tube (step 55) in a plurality of pilgrim steps, with recovery annealings interposed between them, and subjected to terminal annealing 56. In steps 54 to 56, A lower than 0.5·10−18 h is maintained, even values A lower than 0.1·10−18 h being possible (here: A=0.9·10−18 h). According to the value A being lower than 0.5·10−18 (preferably, A lower than 0.2·10−18, at all events at least lower than 0.3·10−18) for steps 50a to 52a, in the finished cladding tube preferably a value A lower than 0.1·10−18 h is obtained for the first zirconium alloy of the matrix 41, whereas a value A=0.1 to 3·10−18 h, preferably between 0.2 and 1.5·10−18 h, is obtained for the second zirconium alloy. The cladding tubes produced in this way are filled with the columns of relatively highly enriched fuel pellets and with the high-pressure gas, are closed in a gastight manner by the end plugs and are inserted into the skeleton mentioned. They have a high burn-up which makes it possible to have a long period of utilization in the pressurized water reactor. When the pressurized water reactor is in operation, in the control of the power output the permissible rates of change need to be coordinated essentially only with the time constants defined by the physics of the fuel and of the reactor, only minor account needing to be taken of possible material damage which, even after lengthy operating times under part load, could occur on the cladding tubes when the reactor power output is being run up. TABLE 1Zry2Zyr4SpongeGradesGradesZr/NbGradeR60802R60804GradeElementR60001R60812R60814R60901Composition, Weight %Tin. . .1.20–1701.20–170. . .Iron. . .0.07–0.200.18–0.24. . .Chromium. . .0.05–0.150.07–0.13. . .Nickel. . .0.03–0.08. . .. . .Niobium. . .. . .. . .2.40–2.80Oxygen{circumflex over ( )}{circumflex over ( )}{circumflex over ( )}0.09–0.13Iron + chromium +. . .0.18–0.38. . .. . .nickelIron + chromium. . .. . .0.28–0.37. . .Maximum Impurities, Weight %Aluminum0.00750.00750.00750.0075Boron0.000050.000050.000050.00005Cadmium0.000050.000050.000050.00005Carbon0.0270.0270.0270.027Chromium0.020. . .. . .0.020Cobalt0.00200.00200.00200.0020Copper0.00500.00500.00500.0050Hafnium0.0100.0100.0100.010Hydrogen0.00250.00250.00250.0025Iron0.150. . .. . .0.150Magnesium0.00200.00200.00200.0020Manganese0.00500.00500.00500.0050Molybdenum0.00500.00500.00500.0050Nickel0.0070. . .0.00700.0070Nitrogen0.00800.00800.00800.0080Silicon0.01200.01200.01200.0120Tin0.0050. . .. . .0.0050Tungsten0.0100.0100.0100.010Uranium (total)0.000350.000350.000350.00035{circumflex over ( )}When so specified in the purchase order, oxygen shall be determined and reported. Maximum or minimum permissible values, or both, shall be as specified in the purchase order. TABLE 2IIIMin.Max.Min.Max.Sn1.0 (1.2)%1.8 (1.5)%. . .1.2 (0.005)Fe0.2 (0.24)%0.6 (0.5/0.4). . .1.2 (0.15)Cr(0.8/0.10/0.12)0.3 (0.25/0.20). . .0.3 (0.02)Nb. . .. . .0.82.8 (1.3)Remainder: “Zr sponge” with:O(0.10/0.12)(0.20/0.18/0.16)(0.10/0.12)(0.20/0.18/0.16)C. . .(0.01). . .(0.02)N. . .(0.005). . .(0.005)Si(0.005/0.007)(0.012). . .(0.012)P. . .(0.03). . .(0.03) |
|
abstract | A process which allows separation of americium present in an acid aqueous phase or in an organic phase from the other metal elements also found in this phase, by complexation of the americium with a water-soluble ethylenediamine derivative; and a process for selective recovery of americium from an acid aqueous phase containing, in addition to americium, other metal elements, which comprises the application of this separation process. |
|
abstract | A spent fuel storage rack 1 according to the present invention is installed in a fuel storage pool of a nuclear facility, and has a rectangular parallelepiped shape forming a plurality of lattice-like cells 2a that are configured to separately accommodate a plurality of fuel assemblies in a matrix of rows and columns. As shown in FIG. 1, the spent fuel storage rack 1 includes: a base 17 configured to support lower parts of fuel assemblies, the base 17 forming a bottom surface of the spent fuel storage rack 1; an outer frame 3 located above the base 17, the outer frame 3 forming an outermost periphery of the spent fuel storage rack 1; and a lattice body 2 disposed inside the outer frame 3, the lattice body 2 forming the lattice-like cells 2a. The lattice body 2 includes: a main lattice 4 having a height equivalent to an active length of the fuel assembly; an upper lattice 5 disposed above the main lattice 4 so as to be fitted to an upper end of the main lattice 4; and a lower lattice 6 disposed between the base 17 and the main lattice 4 so as to be fitted to a lower end of the main lattice 4. Thus, the main lattice 4 can be formed without welding, whereby the main lattice 4 can be made of a boron-added stainless steel to which a sufficient amount of boron is added to absorb neutrons. |
|
claims | 1. A system for electronic commerce transactions that provides for tracking the usage of rented digital assets over a computer network, the system comprising:a server including an asset database, the asset database to store a digital asset, a title of the digital asset, and a server usage count for the digital asset;a computing device coupled to the server over the computer network, the computing device to store a rented digital asset downloaded from the server and an asset usage count list that includes a title of the rented digital asset and a usage count indicating the amount of usage of the rented digital asset by the computing device;a security device coupled to the computing device, the security device storing a unique identifier associated with the security device and a user key associated with the unique identifier, the server including a user information database storing a plurality of registered unique identifiers and a plurality of user keys, the server requesting the unique identifier and proof of knowledge of the user key when a computing device attempts to log on to the server in order to identify the security device, and if the security device is identified by the server, allowing the computing device to be associated with a user's data in the user information database;wherein the server:uploads the asset usage count list from the computing device;matches the title of the rented digital asset from the asset usage count list of the computing device with the title of the digital asset in the asset database; andadds the usage count from the asset usage count list of the computing device to the server usage count for the digital asset in the asset database of the server. 2. The system of claim 1, wherein the usage count of the asset usage count list of the computing device is numerically updated by one for each day the rented digital asset is used. 3. The system of claim 1, wherein the asset usage count list of the computing device further includes a dates asset used field which includes each date the rented digital asset was used by the computing device. 4. The system of claim 1, wherein after the asset usage count list is uploaded from the computing device to the server, the asset usage count list at the computing device is cleared. 5. The system of claim 1, wherein the digital asset is an audio digital asset. 6. The system of claim 1, wherein when the computing device attempts to log onto the server over the computer network, the server:requests a unique identifier from the security device;verifies whether the unique identifier received from the security device is stored as one of the plurality of registered unique identifiers in the user information database;if the unique identifier is stored within the user information database, the server obtains the associated user key and computes a challenge and computes an expected response based on the associated user key, the server sends the challenge to the security device over the computer network; andif the server receives a response back from the security device in response to the challenge that matches the expected response, the server allows the computing device to log onto the server. 7. The system of claim 6, wherein the expected response computed at the server and the response computed at the security device, are both based on a one-way hashing function of the user key. 8. The system of claim 1, wherein the unique identifier and the user key are sealed in a secure memory of the security device. 9. The system of claim 1, wherein the unique identifier is a serial number. 10. The system of claim 1, wherein after the computing device has been allowed to log onto the server, the computing device to transmit a purchase request to rent a digital asset from the server. 11. The system of claim 10, wherein the purchase request to rent the digital asset is automatically verified by a trusted authority, and if the trusted authority verifies the charge request, an associated charge for the rental of digital asset is automatically charged to an associated credit card. 12. The system of claim 11, wherein the rented digital asset is transmitted from the server to the computing device over the computer network. 13. The system of claim 12, wherein the server encrypts the rented digital asset with an asset key and sends the encrypted rented digital asset to the computing device, the computing device storing the encrypted rented digital asset. 14. The system of claim 13, wherein the server encrypts the asset key with the user key and sends the encrypted asset key to the computing device, the computing device storing the encrypted asset key. 15. The system of claim 14, wherein the security device decrypts the asset key that is encrypted with the user key using the user key stored by the security device. 16. The system of claim 15, wherein the security device transmits the decrypted asset key to the computing device such that the computing device uses the decrypted asset key to decrypt the rented digital asset for use. 17. A method for electronic commerce transactions that provides for tracking the usage of a rented digital assets over a computer network, the method comprising:uploading an asset usage count list from a computing device to a server, the computing device coupled to the server over the computer network, the asset usage count list including a title of a rented digital asset and a usage count indicating the amount of usage of the rented digital asset downloaded from the server by the computing device, wherein a security device is coupled to the computing device, the security device storing a unique identifier associated with the security device and a user key associated with the unique identifier, the server including a user information database storing a plurality of registered unique identifiers and a plurality of user keys, the server requesting the unique identifier and proof of knowledge of the user key when a computing device attempts to log on to the server in order to identify the security device, and if the security device is identified by the server, allowing the computing device to be associated with a user's data in the user information database;matching the title of the rented digital asset from the asset usage count list of the computing device with a title of a digital asset stored in an asset database of the server, the asset database to store the digital asset, the title of the digital asset, and a server usage count for the digital asset; andadding the usage count from the asset usage count list of the computing device to the server usage count for the digital asset in the asset database of the server. 18. The method of claim 17, further comprising numerically updating by one the usage count of the asset usage count list of the computing device for each day the rented digital asset is used. 19. The method of claim 17, wherein the asset usage count list of the computing device further includes a dates asset used field which includes each date the rented digital asset was used by the computing device. 20. The method of claim 17, further comprising clearing the asset usage count list at the computing device after the asset usage count list is uploaded from the computing device to the server. 21. The method claim 17, wherein the digital asset is an audio digital asset. 22. The method claim 17, wherein the unique identifier and the user key are sealed in a secure memory of the security device. 23. The method claim 17, wherein the unique identifier is a serial number. 24. The method claim 17, wherein after the computing device has been allowed to log onto the server, transmitting a purchase request to the server to rent a digital asset from the server. 25. The method claim 24, wherein the purchase request to rent the digital asset is automatically verified by a trusted authority, and if the trusted authority verifies the charge request, an associated charge for the rental of digital asset is automatically charged to an associated credit card. 26. The method of claim 25, further comprising transmitting the rented digital asset from the server to the computing device over the computer network. 27. The method of claim 26, further comprising;encrypting the rented digital asset with an asset key;sending the encrypted rented digital asset to the computing device; andstoring the encrypted rented digital asset at the computing device. 28. The method of claim 27, further comprising:encrypting the asset key with the user key;sending the encrypted asset key to the computing device; andstoring the encrypted asset key at the computing device. 29. The method of claim 28, wherein the security device decrypts the asset key that is encrypted with the user key using the user key stored by the security device. 30. The method of claim 29, wherein the security device transmits the decrypted asset key to the computing device such that the computing device uses the decrypted asset key to decrypt the rented digital asset for use. |
|
claims | 1. An X-ray collimator comprising:three or more high attenuation layers, each comprising a high-Z material, wherein each high attenuation layer includes two or more through holes;wherein the high attenuation layers are arranged in a layer by layer stack to form a collimator having an input face and an output face;wherein the through holes of the high attenuation layers combine to form four or more channels extending through the collimator from the input face and to the output face;wherein at least two of the channels intersect within the collimator at a location other than at the input face or at the output face. 2. The X-ray collimator of claim 1, wherein said high-Z material is selected from the group consisting of brass, tungsten, lead, molybdenum, and mixtures or alloys thereof. 3. The X-ray collimator of claim 1, wherein at least one pair of adjacent said high attenuation layers are separated by an air gap. 4. The X-ray collimator of claim 1, wherein at least one pair of adjacent said high attenuation layers are separated by a transparent layer. 5. The X-ray collimator of claim 4, wherein said transparent layer comprises a material selected from the group consisting of low-Z materials, low density plastics, fiber material, carbon fiber, Al, and microspheres in an epoxy matrix. 6. The X-ray collimator of claim 1, wherein at least one of said channels intersects with two or more of said channels within the collimator at locations other than at said input face or at said output face. 7. The X-ray collimator of claim 1, wherein each of said channels is centered on a straight line. 8. The X-ray collimator of claim 1, wherein each of said channels is larger at said output face than at said input face. 9. The X-ray collimator of claim 1, further comprising a filter layer adjacent to said input face and covering one or more of said channels, wherein said filter layer provides independently predetermined levels of X-ray attenuation for each of the covered channels. 10. The X-ray collimator of claim 1, further comprising a filter layer adjacent to said output face and covering one or more of said channels, wherein said filter layer provides independently predetermined levels of X-ray attenuation for each of the covered channels. 11. The X-ray collimator of claim 1, further comprising a filter layer between said input face and said output face and interrupting one or more of said channels, wherein said filter layer provides independently predetermined levels of X-ray attenuation for each of the interrupted channels. 12. An X-ray imaging system comprising:one or more X-ray sources providing two or more X-ray source locations;two or more X-ray detectors;an X-ray collimator according to claim 1; andwherein each said channel of said X-ray collimator is aligned to permit X-rays to travel from one of the X-ray source locations to one of the X-ray detectors. 13. The imaging system of claim 12, wherein X-rays emitted from said source locations and directed away from any of said X-ray detectors are substantially absorbed in said X-ray collimator. 14. The imaging system of claim 12, wherein said channels permit X-rays to travel from each of said X-ray source locations to all of said X-ray detectors. 15. The imaging system of claim 12, wherein said channels permit X-rays to travel from each of said X-ray source locations to one or more of said X-ray detectors. 16. The imaging system of claim 12, wherein said imaging system is selected from the group consisting of computerized tomography systems, x-ray fluoroscopy systems, or tomosynthesis systems. |
|
summary | ||
description | The present disclosure relates generally to a jet pump of a boiling water nuclear reactor and more specifically to a sealing device for linking an inlet mixer and jet diffuser and reducing jet pump slip joint vibration. Jet pumps are used to circulate a coolant fluid, such as water, through the fuel core of a boiling water nuclear reactor. The jet pumps are located in a downcomer annulus between a shroud surrounding the core and the interior of the pressure vessel where the coolant is forced into the inlet end or bottom of the core. A slip joint is used along the length of the jet pump typically to accommodate differential thermal expansion that may occur along the jet pump. The slip joint typically has a narrow gap between two nearly concentric cylinders through which coolant fluid may pass under differential pressure. Boiling water reactor jet pumps experience flow induced vibrations. Flow induced vibration occurs in leakage flow situations under certain circumstances such as flow through a narrow passage with a differential pressure imposed, among which include the BWR slip joint. U.S. Pat. Nos. 6,394,765, 6,438,192, 8,197,225, 8,475,139, 8,964,929, U.S. Pub No. 2014/0079468 and U.S. Pub. No. 2015/0159790 disclose assemblies for jet pump slip joints An object of the present invention is to address slip joint leakage and prevent damage from the flow induced vibration at slip joints, while achieving a strong mechanical linkage of the mixer and the diffuser. A sealing device for a jet pump of a boiling water reactor is provided. The jet pump includes an inlet mixer and a diffuser receiving the inlet mixer at a slip joint such that an outer circumferential surface of the inlet mixer is received in an inner circumferential surface of the diffuser at the slip joint. The diffuser includes a plurality of guiding fins, each guiding fin including a radially inner surface, a radially outer surface and lateral surfaces extending radially between the inner and outer surfaces. The sealing device includes a seal configured for sealingly contacting the outer circumferential surface of the inlet mixer and a collar configured for holding the seal against the outer circumferential surface of the inlet mixer. The collar includes portions configured for being received radially between the radially inner surfaces of the guiding fins and the outer circumferential surface of the inlet mixer. The sealing device further includes a clamp configured for contacting the radially outer surfaces of the guiding fins to axially clamp the guiding fins. In one or more embodiments, the sealing device may include one or more of the following features: the collar includes a support ring having a circumferentially extending groove formed in an inner circumferential surface thereof holding the seal; the clamp includes a plurality of grooves each being contoured to contact the radially outer surface of a respective one of the guiding fins; the clamp is formed by a plurality of clamp sections, each of the clamp sections including a fin engagement section being configured for contacting the radially outer surface of a respective one of the guiding fins; each of the clamp sections includes a first fastener connected to the collar configured for axially moving the respective fin engagement section toward the respective fin; the collar includes a plurality of first connectors, each of the first connectors receiving one of the first fasteners; each of the fin engagement sections is pivotable about the respective first fastener when the fin engagement section is in a movable orientation to allow each fin engagement section to be pivotable toward and away from the respective guiding fin; each of the clamp sections includes a second fastener extending upwardly from a top surface of the respective fin engagement section, the collar including a plurality of second connectors, each of the second fasteners being received in a respective one of the second connectors in a clamping orientation of the respective clamp section; the radially outer surface of each of the guiding fins includes a tapered section extending from an outer circumferential surface of the diffuser and an axially extending section extending axially from a radially outer end of the tapered section, the clamp contacting the tapered section; a further seal connected to the collar below the seal, the further seal configured for sealingly contacting the outer circumferential surface of the inlet mixer below; a bottom edge of the collar is configured for contacting the inner circumferential surface of the diffuser. A method of mounting a sealing device onto a slip joint of a jet pump of a boiling water reactor is also provided. The slip joint is defined by an outer circumferential surface of an inlet mixer being received in an inner circumferential surface of a diffuser. The diffuser includes a plurality of guiding fins, each guiding fin including a radially inner surface, a radially outer surface and lateral surfaces extending radially between the inner and outer surfaces. The method includes fixing a collar of the sealing device onto the outer circumferential surface of the inlet mixer such that a seal held by the collar is compressed radially against the outer circumferential surface of the inlet mixer by the collar and portions of the collar are received radially between the radially inner surfaces of the guiding fins and the outer circumferential surface of the inlet mixer; and forcing a clamp of the sealing device axially against the radially outer surfaces of the guiding fins to axially clamp the guiding fins. In one or more embodiments, the method may include one or more of the following features: providing the collar onto the outer circumferential surface of the inlet mixer such that each of the guiding fins is partially received in one of a plurality of axially extending grooves in an outer circumferential surface of the collar; the providing the collar onto the outer circumferential surface of the inlet mixer includes holding a further seal held by the collar onto the outer circumferential surface of the inlet mixer below the seal; the providing the collar onto the outer circumferential surface of the inlet mixer includes holding a bottom edge of the collar axially against the inner circumferential surface of the diffuser; the seal includes at least one cylindrical metal tube, the fixing the collar of the sealing device onto the outer circumferential surface of the inlet mixer including radially compressing the at least one cylindrical metal tube on the outer circumferential surface of the inlet mixer such that the at least one cylindrical metal tube permanently deforms around the inlet mixer; the clamp includes a plurality of clamp sections each including a first fastener and a fin engagement section, the forcing the clamp of the sealing device axially against the radially outer surfaces of the guiding fins to axially clamp the guiding fins includes forcing, via each of the first fasteners, an angled surface of the respective fin engagement section axially against a tapered section of the radially outer surface of the respective guiding fin; each of the clamp sections includes a second fastener, the forcing the clamp of the sealing device axially against the radially outer surfaces of the guiding fins to axially clamp the guiding fins includes forcing the second fasteners into bores in the collar. Known slip joint assemblies do not address leakage and prevent damage from the flow induced vibration, while achieving a strong mechanical linkage of the mixer and the diffuser. Some assemblies restrict the flow from the slip joint but do not restrain the components in any way. Embodiments of the present invention include a metal o-ring to seal against the jet pump mixer and swing clamp sections on the body of the repair to engage the diffuser to secure the assembly together. A seal feature is also included in the lower edge of the collar to seal against the counter-bore of the diffuser. The combination of seals and the restraint features provide advantages with respect to addressing leakage and preventing damage from the flow induced vibration, while achieving a strong mechanical linkage of the mixer and the diffuser, thus providing a restraint system that locks the inlet mixer and diffuser together while still allowing thermal growth in the axial direction. FIG. 1 schematically shows the lower portion of a boiling water nuclear reactor 50. Reactor 50 includes a pressure vessel 14 closed at a lower end by a dish shaped bottom head 10. A shroud 26 is located radially inside of pressure vessel 14. Between a wall of pressure vessel 14 and shroud 26 is a downcomer annulus 4. A reactor core fuel assembly 28 is housed inside of shroud 26, which comprises fuel assemblies 2. Fuel assemblies 2 may be arranged in groups of four, with each group being attached to guide tubes 12 at lower ends of fuel assemblies 2. Upper ends of guide tubes 12 are sealed by a horizontal bottom grid plate 6 mounted across the bottom of shroud 26. Multiple jet pumps 18, one of which is shown schematically in FIG. 1, are mounted in downcomer annulus 4 circumferentially spaced about shroud 26. FIG. 2 shows an isometric view of a jet pump assembly 40. Jet pump assembly 40 includes two jet pumps 18 that are coupled to a riser pipe 42 by a ram's head 22. Water enters riser pipe 42, passes through ram's head 22 and is then driven downward into an inlet mixer 30 by drive nozzles 20. Inlet mixer 30 merges with a diffuser 32 at a slip joint 16, with inlet mixer 30 being independently supported with respect to diffuser 32 so that inlet mixer 30 is longitudinally slidable with respect to diffuser 32. FIG. 3a shows a cross-sectional side view of a sealing device 44 in accordance with an embodiment of the present invention fixed to the bottom of inlet mixer 30 and the top of diffuser 32. A top end of diffuser 32 receives a bottom end of inlet mixer 30 at a slip joint 46 such that an outer circumferential surface 48 of inlet mixer 30 is received in an inner circumferential surface 50 of diffuser 32 at slip joint 46. Diffuser 32 and inlet mixer 30 are coaxially arranged on a center axis 52. As used herein, the terms radially, axially and circumferentially are used with respect to center axis 52. Diffuser 32, at the top end thereof, includes a plurality of upwardly and radially outwardly protruding guiding fins 53. Each guiding fin 53 includes a radially inner surface 54, a radially outer surface 56 and two lateral surfaces 58 extending radially between the inner and outer surfaces 54, 56 on opposite sides of each fin 53. Radially inner surfaces 54 each include a first section 54a, extending axially and parallel to center axis, and a second section 54b, tapering radially outward from a top edge of first section 54a, with sections 54a, 54b being joined together at an elbow 54c. Radially outer surfaces 56 each include a first section 56a tapering radially outward from an outer circumferential surface 58 of the diffuser and an second section 56b extending axially from a radially outermost and top edge of first section 56a, with sections 56a, 56b being joined together at an elbow 56c. Tapering radially outward from a bottom edge 60 of inlet mixer 30, and just below slip joint 46, inlet mixer 30 includes a lead-in portion 62 to allow for ease of inserting inlet mixer 30 into diffuser 32. Above lead-in portion 62, outer circumferential surface 48 includes an inner slip joint surface 64 extending parallel to center axis 52. Tapering radially outward from the top of inner slip joint surface 64, outer circumferential surface 48 of inlet mixer 30 includes a frustoconical surface 66, a top edge of which transitions into an axially extending portion 67 at an elbow 69. Facing inner slip joint surface 64, inner circumferential surface 50 of diffuser 32 includes an outer slip joint surface 68 also extending parallel to center axis 52, with surfaces 64, 68 defining slip joint 46. As water is forced downward through inlet mixer 30 into diffuser 32, leakage can occur upward through slip joint 46, causing inlet mixer 30 to oscillate laterally, which causes inlet mixer 30 and diffuser 32 to disadvantageously vibrate and potentially impact each other. In order to address leakage at slip joint 46 and prevent damage from flow induced vibrations, while achieving a strong mechanical linkage of mixer 30 and diffuser 32, sealing device 44 is provided on mixer 30 and diffuser 32. Sealing device 44 includes a first seal 70 configured for sealingly contacting outer circumferential surface 48 of inlet mixer 30, a collar 72 configured for clamping first seal 70 radially against outer circumferential surface 48 of inlet mixer 30 and a clamp 74 configured for contacting radially outer surfaces 56 of guiding fins 53 to axially clamp guiding fins 53. Clamp 74 is formed of a plurality of individual clamp sections 75, one of which is shown in FIG. 3a. Collar 72 includes an inner circumferential surface 76 including a circumferentially extending dovetail groove 78 formed therein holding first seal 70. Inner circumferential surface 76 surrounds outer circumferential surface 48 of inlet mixer 30 above slip joint 46. Collar 72 includes a cylindrically shaped ring 71 and a plurality of connecting features, which are described in further details with respect to FIGS. 4a to 5, protruding radially outward from outer circumferential surface 81 of ring 71. Ring 71 includes a plurality of grooves 80 in outer circumferential surface 81 thereof, with each groove 80 receiving one of guiding fins 53. Grooves 80 are contoured to portions of sections 54a, 54b of radially inner surfaces 54 and receive elbow 54c. More specifically, grooves 80 includes a radially inner surface 82 including first section 82a, extending axially and parallel to center axis 52, and a second section 82b, tapering radially outward from a top edge of first section 82a, with sections 82a, 82b being joined together at an elbow 82c. Grooves 80 also each include two lateral surfaces 84 extending radially outward from surface 82 on opposite sides of each groove 80, with each lateral surface 84 facing one of the lateral surfaces 58 of the respective fin 53. Grooves 80 are each defined by a bottom section 86 of ring 71 and a top section 88 of ring 71. Bottom section 86, at each fin 53, has an axially extending elongated shape and is positioned radially between outer circumferential surface 48 of inlet mixer 30, above slip joint 46, and first section 54a of radially inner surface 54 of fin 53. At the bottom end of thereof, bottom section 86 includes a circumferentially extending groove 90 holding a second seal 92 against of elbow 69 and surfaces 66, 67 adjacent to elbow 69. The bottom end of bottom section 86, at a bottom edge of radially inner surface 82, further includes a frustoconical surface 94 for contacting a frustoconical surface 96 of inner circumferential surface 50 of diffuser 32. Top section 88, at each fin 53, has a wedge shape, which includes the dovetail groove 78 holding first seal 70. For jet pumps that do not have a counter-bore in the diffuser, seal 92 may be omitted and the collar may be clamped to the top surface of the diffuser to provide a seal that is restricts leakage but may still have leak paths around the diffuser guiding fins. FIG. 3a shows a connecting feature, specifically one of first connectors 98, protruding radially outward from outer circumferential surface 81 of ring 71. Connector 98 includes an axially extending bore 99 (FIGS. 4a to 5) passing entirely therethrough formed receiving a first fastener 100, which in this embodiment is a shoulder screw, of clamp 74. Shoulder screw 100 includes a head 102 (FIGS. 4a to 5) resting on top of a shoulder inside of bore 99 in connector 98. Protruding downward from connector 98, shoulder screw 100 includes threaded portion 104 of a shaft 106. A fin engagement section 108 of clamp 74 is connected to threaded portion 104, by a corresponding threaded bore receiving threaded portion 104. A retainer 107 is provided at the bottom end of shoulder screw 100, below threaded portion 104, for preventing fin engagement section 106 from coming off of shoulder screw 100. Above threaded portion 104, and below head 102, shoulder screw 100 includes a smooth portion allowing shoulder screw 100 to freely rotate in the bore of connector 98. Rotation of shoulder screw 100, via engagement of head 102 with an appropriate tool, causes fin engagement section 108, via engagement of the threads of its threaded bore with threaded portion 104, to upward or downward depending on the direction of rotation. Fin engagement section 108 is formed as a bar extending in the horizontal direction including a wedge section 110 having an angled surface 112 angled at the same angle as first section 56a of radially outer surface 56. Angled surface 112 is recessed with respect to a radially inner surface 114 of fin engagement section 108, which faces outer circumferential surface 58 of diffuser 32, and a top surface 116 of fin engagement section 108, which faces a bottom surface 118 of connector 98. Two inner lateral walls 120, which face each other and each extend from angled surface 112 to surfaces 114, 116, and angled surface 112 define a wedge-shaped groove 121 in fin engagement section 108 for receiving fin 53, more specifically first section 56a of radially outer surface 56. In the view shown in FIG. 3a, clamp 74 is in a non-clamping orientation, with angled surface 112 being spaced apart from first section 56a of radially outer surface 56. FIG. 3b shows clamp 74 in a clamping orientation axially clamping fin 53. Angled surface 112 of wedge section 110 is forced longitudinally (i.e., upwardly) against first section 56a of radially outer surface 56 by shoulder screw 100 such that the upward force on fin engagement section 108 from shoulder screw 100 and the engagement between wedge section 110 and first section 56a of radially outer surface 56 holds clamping device 44 axially in place on fins 53. From the view in FIG. 3a to the view in FIG. 3b, head 102 (FIGS. 4a to 5) of shoulder screw 100 has been rotated such that threads of threaded portion 104 of shoulder screw 100 slide along the threads of the threaded bore of fin engagement section 108 to move fin engagement section 108 upwardly, with top surface 116 of fin engagement section 108 being moved closer to bottom surface 118 of connector 98. In the clamping orientation, lateral walls 120 of fin engagement section 108 each face a corresponding one of the lateral surfaces 58 of fin 53. The longitudinal engagement of fin 53 with clamp 74 forces ring 71 axially downward to fix collar 73 axially in place on inlet mixer 30. FIGS. 4a and 4b show oblique views of sealing device 44. FIG. 4a shows collar 72 in a closed configuration and FIG. 4b shows collar 72 in an open configuration. As shown in FIGS. 4a, 4b, collar 72 includes two half sections 72a, 72b hinged together by a hinge 122. As noted above, collar 72 includes a ring 71 having outer circumferential surface 81 and a plurality of connecting features—i.e., first connectors 98, hinge 122, second connectors 124 and end connectors 126—protruding radially from outer circumferential surface 81, as well as inner circumferential surface 76 including circumferentially extending dovetail groove 78 formed therein holding first seal 70. Because collar 72 is split into half sections 72a, 72b, groove 78 is split into two half section 78a, 78b, each receiving a cylindrical tube 70a, 70b. Cylindrical tubes 70a, 70b are semicircles formed of metal in this embodiment, and when collar 72 is fixed onto mixer 30 (FIGS. 2 to 3b), compressed on mixer 30 to the point that tubes 70a, 70b permanently deform around the mixer to provide seal 70 similar to that of a metal o-ring in a radial seal configuration. To clamp half sections 72a, 72b of collar 72 together on inlet mixer 30 and radially force seal tubes 70a, 70b into outer circumferential surface 48 of inlet mixer 30, an end fastener 128 passes tangentially through bores in end connectors 126 provided at the ends of half sections 72a, 72b to hold circumferentially facing faces 130a, 130b of half sections 72a, 72b, respectively, in contact with each other. As shown in FIGS. 4a, 4b, a first lateral end 132 of fin engagement section 108 includes the threaded bore and is connected to shoulder screw 100 and a second lateral end 134 of fin engagement section 108 is provided with a second fastener 136, in the form a tapered dowel, protruding upwardly from top surface 116. Each of the fin engagement sections 108 is pivotable about the respective shoulder screw 100 when the fin engagement section 108 is in a movable orientation, i.e., when the respective dowel 136 is not received in the respective second connector 124, to allow each fin engagement section 108 to be pivotable toward and away from the respective guiding fin 53. Clamp 134 is thus swingable about shoulder screw 100 at end 132 to move end 134 toward and away from ring 71. Wedge-shaped groove 121 is formed in fin engagement section 108 between first and second lateral ends 134. Second connectors 124 are provided on outer surface 81 of ring 71 near a bottom edge of ring 81 and each includes a bore 138 passing axially therethrough. When clamp 74 is in a clamping orientation axially clamping fin 53, as shown in FIG. 3b, dowel 136 is received, tapered end first, in bore 138 and top surface 116 of fin engagement section 108 contacts a bottom surface of second connector 124. When dowel 136 is engaged in bore 138 of connector 124, and the swing clamp 74 is tightened into the clamp orientation, fin engagement section 108 of clamp 74 contacts the first section 56a of radially outer surface 56 (FIG. 3a, 3b). The combination of the dowel 136 engagement and the threaded fastener 100 results in a clamping action that engages collar 72 to diffuser 32 (FIGS. 2 to 3b). In the embodiment shown in FIGS. 4a, 4b, sealing device 44 is provided with four grooves 80, two grooves 80 in each collar section 72a, 72b, each for receiving one of fins 53 (FIG. 3a, 3b). Clamp 74 is formed by four separate clamp sections 75—one for each groove 80—and each groove 80 is formed circumferentially between one first connector 98 and one second connector 124. FIG. 5 shows an oblique view of sealing device 44 fixed to the bottom of inlet mixer 30 and the top of diffuser 32. Sealing device 44 is positioned on inlet mixer 30 and diffuser 32 such that each fin 53 is received in one of grooves 80. For illustrative purposes, the clamp section 75 at the left side of FIG. 5 is in the unclamped orientation, while the other two clamp sections 75 shown are in the clamping orientation. With respect to the clamp sections 75 in the clamping orientation, each fin 53 is partially receiving in one wedge shaped groove 121 such that fin engagement section 108, via contact between angled surface 112 (FIGS. 3a, 3b) of engagement section 108 and first section 56a of radially outer surface 56 of fin 53 caused by the longitudinal, i.e., axial, clamping by shoulder screw 100, axially clamps the respective fin 53. A method according to the embodiment of the invention shown in FIGS. 3a to 5, involves providing sealing device 44, in the open configuration, onto inlet mixer 30, and bringing ends 126 together while positioning sealing device 44 such that portions of collar 72, specifically sections 86, 88 at grooves 80, are positioned radially inside of fins 53, with each fin 53 being received in one of grooves 80 when collar 72 is in the closed configuration. More specifically, ring 71, at grooves 80, is positioned such that bottom section 86 of ring 71 is positioned radially between outer circumferential surface 48 of inlet mixer 30 and radially inner surfaces 54 of fins 53, second seal 92 is held against outer circumferential surface 48 of inlet mixer 30 at elbow 69 and surfaces 66, 67 adjacent to elbow 69, and the bottom edge of radially inner surface 82, at frustoconical surface 94, is axially held against inner circumferential surface 50 of diffuser 32 frustoconical surface 96. Next, end fastener 128 is provided through the tangentially extending holes in ends 126 and tightened to clamp collar half sections 72a, 72b together, which forces seal 70 radially against outer circumferential surface 48 of inlet mixer 30. Tubes 70a, 70b of seal are joined to form a complete circle that is radially compressed against outer circumferential surface 48 of inlet mixer 30. Tubes 70a, 70b are compressed on outer circumferential surface 48 of inlet mixer 30 to the point that tubes 70a, 70b permanently deform around mixer 30 to provide a seal similar to that of a metal o-ring in a radial seal configuration. After end fastener 128 is sufficiently tight, clamp 74 is forced into the clamping orientation to axially clamp fins 53. More specifically, for each clamp section 75, shoulder screw 100 forces wedge section 110 of fin engagement section 108 axially against first section 56a of radially outer surface 56. The upward force on fin engagement section 108 from shoulder screw 100 and the engagement between wedge section 110 and first section 56a of radially outer surface 56 holds clamping device 44 axially in place on fins 53. The axially forcing is done by rotating shoulder screw 100 such that threads of threaded portion 104 of shoulder screw 100 slide along the threads of the threaded bore of fin engagement section 108 to move fin engagement section 108 upwardly, with top surface 116 of fin engagement section 108 being moved closer to bottom surface 118 of connector 98. In the preceding specification, the invention has been described with reference to specific exemplary embodiments and examples thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense. |
|
description | The present application claims priority from Japanese Patent application serial no. 2009-241370, filed on Oct. 20, 2009, the content of which is hereby incorporated by reference into this application. 1. Technical Field The present invention relates to an underwater remote inspection device and a method for underwater remote inspection, and more particularly, to an underwater remote inspection device and a method for underwater remote inspection suitable for inspecting a surface condition of a reactor internal of a boiling water reactor and a pressurized water reactor. 2. Background Art As a device for inspecting the presence of a crack on a surface of a reactor internal installed in a nuclear reactor of a nuclear plant, an underwater remote inspection device has been known. Some examples of the underwater remote inspection device are described in Japanese Patent No. 3890239 and Japanese Patent Laid-open No. 2003-255074. The underwater remote inspection devices described in these publications have an etching device and a replica sampling device. The etching device includes electrode members and an electrolytic etchant supply device. An electrolytic etchant (oxalic acid) comes in contact with a surface to be inspected of a reactor internal, and the surface is etched by applying electricity to the electrode members. By etching the inspection surface of the reactor internal, the surface is corroded, making the grain boundaries of the metal structure of the surface easier to see. After the etching is completed, the replica sampling device is used to sample a replica of the etched surface. Japanese Patent Laid-open No. 9(1997)-89786 discloses an underwater remote inspection device in which, an etchant (oxalic acid) soaked into a sponge is applied to a surface to be inspected of a reactor internal and the surface is etched. Using a magnifying camera provided to the underwater remote inspection device, an image is taken of the metal structure of the etched surface to be inspected of the reactor internal. The magnifying camera has a magnifying lens capable of enlarging the image to a few hundreds of times the standard, allowing the enlarged image of the metal structure to be taken. The image of the metal structure taken by the magnifying camera is displayed on a monitor so that any over sensitization in the inspection surface can be checked. Patent literature 1: Japanese Patent No. 3890239 Patent literature 2: Japanese Patent Laid-open No. 2003-255074 Patent literature 3: Japanese Patent Laid-open No. 9(1997)-89786 When studying a cause of cracking occurred on a surface of a reactor internal of a nuclear reactor, it is important to check if the crack is extending along a grain boundary or not to determine whether the crack is an intergranular stress corrosion crack or not. For this reason, it has been preferred that the grain boundaries in the proximity of the crack be easily checked. As a method for checking the grain boundaries of a metal structure, electrolytic etching using an oxalic acid solution has been generally known. In a welding portion and a heat-affected zone in the vicinity of the welding portion, their corrosion resistance will be varied due to a high-temperature process of welding and dilution of the base metal and a welding metal, thus, the condition of electrolytic etching (current, voltage, a running time of the current, etc.) cannot be explicitly determined. For this reason, electrolytic etching of the metal surface and checking of the degree of etching of the metal surface are alternatively performed in actual work. In this case, since installation operation of an inspection device is repeatedly required, the etching work would take long time. In the underwater remote inspection device disclosed in Japanese Patent Laid-open No. 9(1997)-89786, the degree of etching of the inspection surface of a reactor internal can be easily checked by looking at an image taken by the magnifying camera. However, since this underwater remote inspection device has a mechanism for applying the etchant to the inspection surface with a sponge, a size of the underwater remote inspection device is increased. The underwater remote inspection devices disclosed in Japanese Patent No. 3890239 and Japanese Patent Laid-open No. 2003-255074 for electrolytic etching are smaller than the underwater remote inspection device stated in Japanese Patent Laid-open No. 9(1997)-89786. The inventors, thus, have come up with an idea to apply a magnifying camera to the underwater remote inspection device having an electrolytic etching mechanism (for example, see Japanese Patent No. 3890239 and Japanese Patent Laid-open No. 2003-255074). In this case, however, it has become clear that a new problem has emerged as shown below. In the underwater remote inspection device described in Japanese Patent Laid-open No. 9(1997)-89786, a sponge provided to the distal end portion of an arm, soaked with an etchant is pressed onto the inspection surface of a reactor internal by extending the arm and the etchant soaked into the sponge is applied to the inspection surface. After the etching of the inspection surface of the reactor internal is completed, the arm is retracted to store the sponge inside a tightly-closed container. Since the pressing of the sponge onto the inspection surface of the reactor internal is done in front of a magnifying camera provided to the underwater remote inspection device, the degree of etching of the inspection surface can be observed by the magnifying camera when the sponge has been stored in the tightly-closed container. In the underwater remote inspection device for electrolytic etching such as those described in Japanese Patent No. 3890239 and Japanese Patent Laid-open No. 2003-255074, electrodes are provided to a chamber, which is pressed onto the inspection surface of the reactor internal and supplied with an etchant inside. In order to improve the efficiency of etching of the inspection surface, the electrode should be disposed facing the etching execution surface of the inspection surface. This makes it difficult to install the magnifying camera to the chamber so as to make the camera facing the etching execution surface. The magnifying camera, thus, is required to be installed outside the chamber, facing the surface of the reactor internal, as the underwater camera shown in FIG. 9 of Japanese Patent Laid-open No. 2003-255074. In such a configuration, the chamber must be shifted upward (or downward) after etching is completed to position the magnifying camera facing the etching-completed etching execution surface and then, an image of the etching execution surface must be taken by the magnifying camera to check the degree of etching of the etching execution surface. A sealing member is installed to a portion of the chamber of the etching device, the portion facing the surface of the reactor internal, to prevent the etchant in the chamber from leaking outside. When an image of the etching execution surface is to be taken by the magnifying camera, the etching device should be moved as soon as possible to reduce the execution time of etching. In consideration of such moving of the etching device, the airtightness between the chamber and the reactor internal is needed to prevent the etchant from leaking out of the chamber during etching, and the etching device should be swiftly moved to take an image of the etching execution surface. It is an object of the present invention to provide an underwater remote inspection device and a method for underwater remote inspection that can prevent leakage of an etchant and reduce execution time of etching. A feature of the present invention for attaining the above object is an underwater remote inspection device having a supporting member, and an etching device and a magnifying camera device mounted to the supporting member, wherein the etching device has a chamber mounted to the supporting member, electrode members provided to the chamber, an agent supply pipe for supplying an agent for etching, connected to the chamber to communicate to an etchant filling region formed in the chamber, and a sealing device provided to a distal end portion of the chamber, facing a surface of an inspection object, and wherein the sealing device has an annular first sealing member attached to the distal end portion of the chamber, an annular second sealing member surrounding the first sealing member, attached to the distal end portion of the chamber, and a pipe line communicated to a sealing region formed between the first and the second sealing members, connected to a suction apparatus for reducing the pressure in the region. Since the sealing device has the annular first sealing member, the annular second sealing member surrounding the first sealing member, and the pipe line communicated to the region formed between the first and the second sealing members, connected to the suction apparatus for reducing the pressure in the region, the pressure in the region formed between the first and the second sealing members can be reduced after the distal end portions of the first and the second sealing members have come into contact with the surface of the inspection object. Consequently, the distal end portions of the first and the second sealing members are firmly pressed on the surface of the inspection object, and more tightly adhered to the surface of the inspection object. In this way, the chamber is reliably sealed inside and outside, and the agent supplied into the etchant filling region can be surely prevented from leaking out of the chamber. In addition, the sealing device can be swiftly detached from the surface of the inspection object by raising the pressure in the region. Consequently, the magnifying camera device can be moved to the position of the etching-completed inspection area in a short period of time, reducing the execution time of etching. According to the present invention, leakage of the etchant can be prevented and the execution time of etching of the surface of the inspection object can be reduced. Embodiments of the present invention will be described below. [Embodiment 1] An underwater remote inspection method in embodiment 1, which is a preferred embodiment of the present invention, will be described with reference to the drawings. An underwater remote inspection device 1 used in the present embodiment is, as shown in FIG. 1, provided with an etching device 2 and a magnifying observation device (a magnifying camera device) 15. The etching device 2 has a chamber 3, a negative electrode 5 and a positive electrode 6 as electrode members, an etchant supply pipe 7, an etchant exhaust pipe 8, and a sealing device 9. The magnifying observation device 15 has a magnifying camera 16, a waterproof container 17, and a plurality of LED lights (an illuminating device) 19. The etching device 2 and the magnifying observation device 15, or to be more specific, the chamber 3 and the waterproof container 17 are installed to a supporting member 20 provided to the underwater remote inspection device 1. The chamber 3 is made up of a cylinder member 4A fixed to a plate member 4B. The plate member 4B is installed to a plurality of supporting members 22 fixed to the supporting member 20. In this way, the chamber 3 is held to the supporting member 20. An etchant filling region 12 surrounded by the cylinder member 4A and the plate member 4B is formed in the chamber 3. The negative electrode 5 is disposed in the etchant filling region 12 and attached to the plate member 4B. A plurality of positive electrodes 6 are disposed outside the chamber 3 and installed to the chamber 3. The etchant supply pipe 7 is fixed to the chamber 3 to communicate with the etchant filling region 12. The etchant exhaust pipe 8 is fixed to the chamber 3 to communicate with the etchant filling region 12. The sealing device 9 has sealing members 10A and 10B and a suction passage 11. The sealing members 10A and 10B are each provided to an end portion of the cylinder member 4A, facing a surface to be inspected (an inspection surface) of an inspection object. The sealing members 10A and 10B each have a continuous annular shape, and are concentrically disposed to each other. The sealing member 10B is disposed outside the sealing member 10A, surrounding the sealing member 10A. A distal end portion of the sealing member 10A is curved inward from the chamber 3, and a distal end portion of the sealing member 10B is curved outward from the chamber 3. An annular sealing region 13 is formed between the sealing members 10A and 10B. The sealing region 13 surrounds the sealing member 10A and communicates to the suction passage 11 formed in the cylinder member 4A. The suction passage 11 communicates to a suction pipe 21 connected to the chamber 3. The waterproof container 17 of the magnifying observation device 15 is installed to the supporting member 20. The magnifying observation camera 16 having a remote focus function is installed in the waterproof container 17, and a window 18 is formed in front of the magnifying camera 16 by fitting a sheet of glass to the waterproof container 17. The plurality of LED lights 19 is disposed outside the waterproof container 17 and installed to the waterproof container 17. The underwater remote inspection method in the present embodiment for inspecting a surface of an underwater inspection object, using the underwater remote inspection device 1 will be described below. In the underwater remote inspection method, the inspection object is a core shroud, which is a reactor internal provided in a reactor pressure vessel of a boiling water reactor. A general structure of the boiling water reactor will be described using FIG. 2. A boiling water reactor has a reactor pressure vessel 33, inside which a core (not shown) is disposed, and a cylindrical core shroud 34, an upper grid plate 35, a core plate 36, and so on are installed in the reactor pressure vessel 33. The core loaded with a plurality of fuel assemblies (not shown) is surrounded by the core shroud 34. In the core shroud 34, the upper grid plate 35 is disposed to an upper end portion of the core shroud 34 and installed to the core shroud 34. The core plate 36 is disposed below the upper grid plate 35 in the core shroud 34 and installed to the core shroud 34. A lower end portion of each fuel assembly loaded in the core is supported by the core plate 36 and an upper end portion of each fuel assembly is supported by the upper grid plate 35. A plurality of control rod drive mechanism housings (hereinafter, referred to as CRD housings) 71 is provided to the bottom portion of the reactor pressure vessel 33, penetrating the bottom portion. Each CRD housing 71 penetrates a stub tube 72 fixed to the bottom surface of the reactor pressure vessel 33 and attached to the stub tube 72. The underwater remote inspection method is performed as one agenda of a periodic inspection performed after shutdown of operation of the boiling water reactor. After the shutdown of the operation of the boiling water reactor, a top head (not shown) of the reactor pressure vessel 33 is removed and the reactor pressure vessel 33 is opened up. Cooling water is filled in the reactor pressure vessel 33 and in a reactor well (not shown) located above the reactor pressure vessel 33. After the top head of the reactor pressure vessel 33 has been removed, a steam dryer (now shown) and a steam separator (not shown) installed above the upper grid plate 35 in the reactor pressure vessel 33 are sequentially removed and carried out of the reactor pressure vessel 33. Among the fuel assemblies loaded in the core, at least each of those found near the inner surface of the core shroud 34 is grasped by a fuel exchange apparatus (not shown), and then, this fuel assembly is taken out from the reactor pressure vessel 33 by the fuel exchange apparatus and transferred to a fuel storage pool (not shown). After those fuel assemblies have been carried out of the core into the fuel storage pool, the underwater remote inspection method in the present invention is executed. To execute the underwater remote inspection of the inner surface of the core shroud 34, the underwater remote inspection device 1 should be transported into the core shroud 34. This transporting of the underwater remote inspection device 1 is achieved by moving an underwater scanning device 23 (see FIG. 2), in which the underwater remote inspection device 1 is stored, into the core shroud 34. A worker riding the fuel exchange apparatus, which runs on an operation floor (now shown) surrounding the reactor well, formed in a reactor building (not shown), transports the underwater scanning device 23 by using a tong to a region in the core shroud 34 below the upper grid plate 35 through a grid formed in the upper grid plate 35 while checking, on a TV monitor, an image around the underwater remote inspection device 1, taken by an underwater camera. A lower end portion of the underwater scanning device 23 is held to the core plate 36 (see FIG. 2). The underwater scanning device 23 held to the core plate 36 is in cooling water inside the reactor pressure vessel 33. Now, a structure of the underwater scanning device 23 will be described using FIG. 3. The underwater scanning device 23 has a casing 24, transporting rods 25A and 25B, moving bodies 26A and 26B, and motors (driving devices) 31. The motors are stepping motor. The casing 24 has a U-shaped cross section, practically having three side walls (see FIG. 4). One side surface of the casing 24 opens along an axial direction. Two motors 31 are installed to an upper end of the casing 24. Two transporting rods 25A and 25B are disposed side by side in the casing 24 (see FIG. 4), and the lower end portion of each of the transporting rods 25A and 25B is separately supported in the lower end portion of the casing 24 by one of two bearings (not shown) provided in the casing 24. A screw thread is formed on the surface of each of the transporting rods 25A and 25B. A rotating shaft of one motor 31 is coupled to an upper end of the transporting rod 25A. A rotating shaft of the other motor 31 is coupled to an upper end of the transporting rod 25B. The moving bodies 26A and 26B are disposed in the casing 24. The moving body 26A is engaged with the thread formed on the transporting rod 25A, and the moving body 26B with the thread formed on the transporting rod 25B. The transporting rod 25A penetrates through a through-hole formed in the moving body 26B and is not engaged with the moving body 26B. The transporting rod 25B penetrates through a through-hole formed on the moving body 26A and is not engaged with the moving body 26A. One end portion of a link 27 is rotatably attached to the moving body 26A with a pin. One end portion of a link 28 is rotatably coupled to the other end portion of the link 27 with a pin. A linear motor 29 is linked to the links 27 and 28 (see FIG. 7). One end of a link 30 is rotatably attached to the moving body 26B with a pin. The underwater remote inspection device 1 is disposed in the casing 24. The other end portion of the link 28 is rotatably attached to the supporting member 20 of the underwater remote inspection device 1 with a pin. The other end portion of the link 30 is rotatably attached to the supporting member 20 with a pin. While the lower end portion of the underwater scanning device 23 is held to the core plate 36, the motors 31 are located above the top surface of the upper grid plate 35. The underwater remote inspection method in the present embodiment after the lower end portion of the underwater scanning device 23 has been held to the core plate 36 will be specifically explained using FIG. 5. The underwater remote inspection device is moved to the vicinity of an inspection area of an inspection object (step S1). The links 27 and 28, the supporting member 20, and the link 30 are practically parallel to the transporting rods 25A and 25B and a distance between the moving bodies 25A and 25B is the longest (see FIG. 3). The underwater remote inspection device 1 is completely stored in the casing 24 of the underwater scanning device 23. Also when the underwater scanning device 23 was passed through a grid of the upper grid plate 35, the underwater remote inspection device 1 has been stored in the casing 24 in the same manner. The two motors 31 of the underwater scanning device 23 are turned in the same direction at the same rotating speed. Since this turns the transporting rods 25A and 25B in the same direction at the same rotating speed, the moving bodies 25A and 25B can be moved downward while keeping their distance from each other between the moving bodies 25A and 25B. The etching device 2 and the magnifying observation device 15 are also moved downward simultaneously with the moving bodies 25A and 25B. When the chamber 3 of the etching device 2 reaches the position facing an inspection area (an inspection surface) 14 of the core shroud 34, which is a reactor internal that is an inspection object, the rotation of the two motors 31 is stopped to stop the moving bodies 25A and 25B from moving downward. In the step S1, the etching device 2 is moved downward to the level where the inspection area 14 is located in the core shroud 34. For moving the moving bodies 25A and 25B in the axial direction of the core shroud 34, a nut rotatably installed to each of the moving bodies 25A and 25B may be turned instead of each motor 31. In this case, each motor 31 for turning each of the transporting rods 25A and 25B becomes no longer necessary, and the transporting rods 25A and 25B are not turned. The nut provided to each of the moving bodies 25A and 25B is engaged with the respective transporting rod, and each nut is turned by a motor provided to each of the moving bodies 25A and 25B, through a gear. The underwater remote inspection device is moved in the horizontal direction (step S2). The two motors 31 are turned at the same rotating speed in an opposite directions from each other. The transporting rod 25A is turned to move the moving body 26A downward and the transporting rod 25B is turned to move the moving body 26B upward in the opposite direction from the transporting rod 25A. The distance from each other between the moving bodies 25A and 25B is reduced, and the etching device 2 supported by each moving body with the link moves outward from the casing 24, moving in the horizontal direction toward the inspection area 14 of the core shroud 34. This moving of the etching device 2 is performed while an image from an underwater camera 37 (see FIG. 7) is being checked on a TV monitor. When the distal end portions of the sealing members 10A and 10B of the sealing device 9 provided to the chamber 3 are pressed on the inner surface of the core shroud 34 (see FIGS. 6 and 7), the two motors 31 are stopped to stop the etching device 2 from moving in the horizontal direction. At this time, the sealing members 10A and 10B are surrounding the inspection area 14, and cooling water is present in the etchant filling region 12 and the sealing region 13. The plurality of positive electrodes 6 come into contact with the surface of the core shroud 34. When the etching device 2 is tilted in relation to the central axis of the core shroud 34, the linear motor 29 is driven before the distal end portions of the sealing members 10A and 10B are pressed on the inner surface of the core shroud 34, to adjust the angle that the links 27 and 28 make, positioning the chamber 3 parallel to the central axis of the core shroud 34. In this way, the orientation of the underwater remote inspection device 1 can be adjusted. The position of the etching device 2 while the chamber 3 is covering the inspection area 14 by having the distal end portions of the sealing members 10A and 10B pressed onto the inner surface of the core shroud 34 is set to a point zero. The coordinate position of the point zero is shown by a coordinate in a circumferential direction of the core shroud 34 (x-coordinate) and a coordinate in the axial direction of the core shroud 34 (y-coordinate). The x-coordinate is determined by the position, in the circumferential direction of the core shroud 34, of the grid of the upper grid plate 35 through which grid the underwater scanning device 23 is inserted. The y-coordinate is obtained by a computer (not shown) based on an output signal of an encoder (not shown) provided to each of the two motors 31. The x- and y-coordinates of the point zero are stored in a memory of the computer. Seal between the etching device and the inspection object is performed (step S3). A pump (a suction apparatus, not shown) connected to the suction pipe 21 is driven. Cooling water in the sealing region 13 formed between the inner surface of the core shroud 34 and the sealing members 10A and 10B pressed onto the inner surface of the core shroud 34 is sucked by the drive of the pump connected to the suction pipe 21. This reduces the pressure in the sealing region 13 lower than the pressure outside the sealing members 10A and 10B, tightly adhering each distal end portion of the sealing members 10A and 10B onto the inner surface of the core shroud (the inspection object) 34. The inspection area is electrolytically etched (step S4). An etchant (for example, a 10% oxalic acid aqueous solution) filled in a bath tank (not shown) is supplied, by opening a valve, into the etchant filling region 12 formed by the surrounding chamber 3 and the core shroud 34, through a bath hose (not shown) and the etchant supply pipe 7 connected to the bath hose. The etchant is injected into the etchant filling region 12 while an exhaust pump (not shown) connected to an exhaust hose (not shown) connected to the etchant exhaust pipe 8 is driven to discharge the cooling water in the etchant filling region 12. The bath tank is placed on the operation floor. The etchant is filled in the etchant filling region 12, coming into contact with the inspection area 14 of the core shroud 34. Then, a direct current is applied between the negative electrode 5 and the positive electrodes 6 for a predetermined period of time. The direct current passes through the positive electrodes 6, the inspection area 14, the etchant in the etchant filling region 12, and the negative electrode 5. Due to the action of the direct current and the etchant, the surface of the inspection area (the surface come into contact with the etchant) is electrolytically etched to corrode the grain boundaries of the metal structure of the surface of the inspection area 14. The sealing between the etching device and the inspection object is removed (step S5). By switching a valve, the etchant supply pipe 7 is connected to a pure water tank instead of the bath tank. The exhaust pump connected to the exhaust hose is driven to suck the etchant in the etchant filling region 12, and the etchant is discharged to a waste solution tank (not shown) through the exhaust hose. The operation of the exhaust pump supplies pure water in the pure water tank into the etchant filling region 12 through the etchant supply pipe 7. The pure water supplied into the etchant filling region 12 also is discharged to the waste solution tank through the exhaust hose. This waste solution tank is placed on the operation floor. The pure water is supplied into the etchant filling region 12 for a predetermined period of time to completely discharge the etchant in the etchant filling region 12 from the etchant filling region 12. After the predetermined period of time has passed, cooling water is supplied into the sealing region 13 through the suction pipe 21. The cooling water is supplied by stopping the operation of the pump connected to the suction pipe 21 and opening a valve provided to a branching pipe of the suction pipe 21 to communicate the sealing region 13 with a region outside the chamber 3 in the core shroud 34. This allows the cooling water in the core shroud 34 to flow through the suction pipe 21 into the sealing region 13 having a low pressure. The pressure in the sealing region 13 is recovered, the pressing force of the sealing members 10A and 10B onto the inner surface of the core shroud 34 is released, and the etching device 2 becomes easier to be detached from the core shroud 34. The branching pipe provided with the above valve is a pressure recovery apparatus for the sealing region 13. The magnifying observation device 15 is moved to the inspection area (step S6). In the state shown in FIG. 7, the two motors 31 are turned in the opposite directions from each other at the same rotating speed to slightly shift the chamber 3 in the horizontal direction, detaching the distal end portions of the sealing members 10A and 10B from the inner surface of the core shroud 34. Then, the two motors 31 are turned in the same direction at the same rotating speed to move the moving bodies 26A and 26B downward while keeping the distance from each other between the moving bodies 26A to 26B. When the magnifying observation camera 16 reaches the position facing the inspection area 14 (see FIG. 8), the moving bodies 26A and 26B are stopped from being moved downward. An image of the inspection area 14 after etching is taken by the magnifying observation camera 16. When the image of the inspection area 14 is to be taken, the focus of the magnifying observation camera 16 is adjusted. This focus adjustment is achieved by, first, roughly setting the location of the magnifying observation camera 16 by turning the transporting rods 25A and 25B in the opposite directions and moving the underwater remote inspection apparatus 1 in the horizontal direction, then, by finely adjusting the focus with a remote focus. When the magnifying observation camera 16 is tilted in relation to the central axis of the core shroud 34, i.e., to the surface of the inspection area 14, as described before, the linear motor 29 is driven to adjust the orientation (an angle) of the magnifying observation device 15 to focus the magnifying observation camera 16. The inspection area is observed under magnification (step S7). Light emitted from the plurality of LED lights 19 is irradiated on the etched inspection area 14. The inspection area 14 is diagonally irradiated from the LED lights 19. The magnifying observation camera 16 takes an image of the inspection area 14 and outputs the obtained image data to, for example, a TV monitor (a display device) placed on the operation floor. Whether it is possible to distinguish a crack from the grain boundaries of the metal structure of the inspection area is determined (step S8). An operator looks at the image of the etched inspection area 14, displayed on the TV monitor, and determines whether the grain boundaries of the metal structure of the inspection area 14 and a crack that occurred in the grain boundaries are distinguishable. If the degree of electrolytic etching of the inspection area 14 is appropriate, the grain boundaries of the metal structure can be confirmed by eye, and when there is a crack in the inspection area 14, the crack can be easily distinguished from the grain boundaries. When the grain boundaries and a crack are distinguishable, it is determined as “Yes” in the step S8. When the operator determines that the grain boundaries and a crack are not distinguishable in the step S8, the determination in the step S8 will be “No”. When the determination in the step S8 is “No”, the operator determines if it is over-etched or not based on the image of the etched inspection area 14, displayed on the TV monitor (Step S9). When the determination in the step S9 is “No”, it means that the degree of etching is not enough, thus, the operations of the steps S1 to S4 are repeated to electrolytically etch the inspection area 14 again, followed by the operations of the steps S5 to S8. When the determination in the step S9 is “Yes”, the etched inspection area 14 is too over-etched to distinguish between the grain boundaries and a crack. In this case, the etched inspection area 14 is mirror polished (step S10). To the mirror-polished inspection area 14, the operations of the steps S1 to S8 are repeated. The enlarged image of the inspection area is recorded (step S11). When the determination in the step S8 becomes “Yes”, the enlarged image of the inspection area 14 taken by the magnifying observation camera 16 is recorded in a memory of the above-mentioned computer. The magnifying observation device is moved away from the surface of the inspection object (step S12). The two motors 31 are turned in the opposite directions from the rotating directions of the transporting rods 25A and 25B in the step S2 to turn the transporting rods 25A and 25B in the opposite directions from each other at the same rotating speed. The moving bodies 26A and 26B are moved along the transporting rods 25A and 25B in the direction away from each other. This moves the underwater remote inspection device 1 away from the core shroud (the inspection object) 34 in the horizontal direction. The magnifying observation device 15 also is moved away from the core shroud 34. The distance between the moving bodies 26A and 26B is further expanded, and the underwater remote inspection device 1 is stored in the casing 24 of the underwater scanning device 23 as shown in FIG. 3. The underwater remote inspection device is moved away from the position facing the inspection area (step S13). The two motors 31 are driven to turn the transporting rods 25A and 25B in the opposite direction from the step S1 at the same rotating speed. The moving bodies 26A and 26B move upward, moving the underwater remote inspection device 1 upward as well. When there is another inspection area 14 above the previously-described inspection area 14, the moving bodies 26A and 26B are moved to move the underwater remote inspection device 1 upward in the same manner as in the step S13. The etching device 2 of the underwater remote inspection device 1 is brought to face the other inspection area 14. To this inspection area 14, each operation described above shown in FIG. 5 is performed. The underwater remote inspection device is retrieved from the reactor pressure vessel (step S14). After the etching is completed for the inspection areas 14 on the inner surface of the core shroud 34 in the axial direction of the core shroud 34 while the underwater scanning device 23 is inserted through the grid of the upper grid plate 35 described above, the underwater remote inspection device 1 is taken out from the reactor pressure vessel 33. This removal of the underwater remote inspection device 1 is done by a worker using a tong. When there is an inspection area 14 in the other location on the inner surface of the core shroud 34 in the circumferential direction of the core shroud 34, the underwater scanning device 23 storing the underwater remote inspection device 1 is inserted into the grid of the upper grid plate 35, which is the grid closest to the location of the inspection area in the circumferential direction of the core shroud 34. The underwater scanning device 23 is held by the core plate 36. Then each operation shown in FIG. 5 is performed. In the present embodiment, the sealing device 9 of the chamber 3, provided to the portion facing the inspection object (the core shroud), has a double structure including the annular sealing members 10A and 10B, and the sealing region 13 formed between the sealing members 10A and 10B communicates with the suction passage 11 formed in the side wall of the chamber 3. For this reason, when the distal end portions of the sealing members 10A and 10B are pressed onto the inner surface of the core shroud 34, the cooling water in the sealing region 13 can be pumped out through the suction passage 11, reducing the pressure in the sealing region 13 lower than the pressure of the cooling water outside the chamber 3 and the pressure in the etchant filling region 12. The distal end portions of the sealing members 10A and 10B are firmly pressed onto the inner surface of the core shroud 34, more tightly adhered onto the inner surface of the core shroud 34. The inside and outside sealing of the chamber 3 can be reliably achieved by the sealing members 10A and 10B, and leakage of the etchant supplied into the etchant filling region 12 to the outside of the chamber 3 can be surely prevented. In addition, if by any chance, the etchant in the etchant filling region 12 leaks out to the sealing region 13 through the joint between the sealing member 10A and the core shroud 34, the leaked etchant will be sucked into the suction pipe 21, allowing nothing to leak out of the chamber 3 through the joint between the sealing member 10B and the core shroud 34. The present embodiment is provided with the magnifying observation camera 16, allowing the magnifying observation camera 16 to take an image of the grain boundaries of the metal structure in the inspection area 14 after being etched by the etching device 2, so that the degree of etching of the inspection area 14 can be checked swiftly. This can shorten the executing time of etching. When the image is to be enlarged to the level that allows observation of the structure of the grain boundaries, only a small range is available for a point (a distance and an angle) to which the magnifying observation camera 16 can focus with a remote focus. However, the orientation of the magnifying observation camera 16 can be adjusted by the operation of the linear motor 29 to correct tilting of the camera in relation to the central axis of the core shroud 34, so that the magnifying observation camera 16 can be easily focused by the operation of the linear motor 29 and the image of the grain boundaries in the inspection area 14 can be clearly taken. In the present embodiment, since the circular negative electrode 5 provided to the chamber 3 of the etching device 2 is facing the inspection area 14, the inspection area 14 can be etched effectively. The magnifying observation camera 16 is provided to the outside of the chamber 3 because it cannot be disposed in the chamber 3 due to the installation of the negative electrode 5. For this reason, the underwater remote inspection device 1 is moved to take an image of the etched inspection area 14 by the magnifying observation camera 16. In the present embodiment, as described above, while the distal end portions of the sealing members 10A and 10B are tightly adhered onto the inner surface of the core shroud 34 to seal between the chamber 3 and the core shroud 34 using the double structure of the sealing members 10A and 10B and the suction passage 11, the sealing between them can be quickly released by raising the pressure in the sealing region 13. Consequently, the magnifying observation camera 16 can be moved to the etched inspection area 14 in a short period of time from the time when etching is completed. The etching is performed using the electrodes and the etchant so that the underwater remote inspection device 1 can be downsized. This allows the underwater remote inspection device 1 to inspect a surface of a structural member, facing a narrow portion in the reactor pressure vessel 33. [Embodiment 2] An underwater remote inspection method in embodiment 2, which is another embodiment of the present invention, will be described using FIGS. 9 and 10. In the present embodiment, the underwater remote inspection device 1 used in embodiment 1 is used. An underwater scanning device 23A is used to move the underwater remote inspection device 1 in the present embodiment. The underwater scanning device 23A has the transporting rods 25A and 25B, the moving bodies 26A and 26B, motors (driving devices) 31A and 31B, and a casing 38. The motors 31A and 31D are stepping motor. A screw thread is formed on the surface of each of the transporting rods 25A and 25B, which are disposed in the casing 38 and rotatably attached to the casing 38. The transporting rod 25A is coupled to the rotating axis of the motor 31A, and the transporting rod 25B to the rotating axis of the motor 31B. The moving body 26A is engaged with the thread of the transporting rod 25A, and the moving body 26B with the thread of the transporting rod 25B. The link 30 rotatably attached to the supporting member 20 of the underwater remote inspection device 1 is coupled to the moving body 26B. A link 28A is rotatably attached to each of the supporting member 20 and the moving body 26A. The underwater remote inspection device 1 is stored in the casing 38. A worker holds a tong 45 attached to the casing 38 and lowers the underwater scanning device 23A holding the underwater remote inspection device 1 in the reactor pressure vessel 33 without the top head, filled with cooling water. The underwater scanning device 23A is passed through a grid of the upper grid plate 35 and reaches the position facing the inspection area 14 on the inner surface of the core shroud 34. The underwater scanning device 23A is pressed onto the inner surface of the core shroud 34 by a fixing device 39. At this time, the sealing member 10A of the sealing device 9 is surrounding the inspection area 14. The fixing device 39 has a cylinder 40, a rod 41, and a pressing plate 42. The rod 41 is coupled to a piston (not shown) in the cylinder 40. The pressing plate 42 is fixed to the distal end of the rod 41. The cylinder 40 is attached to a supporting member 43 attached to a pressing plate 44. A tong 46 is attached to the supporting member 43. Before the underwater scanning device 23A is carried into the reactor pressure vessel 33, a plurality of fuel assemblies located in front of the inspection area 14 has been carried out of the reactor pressure vessel 33. A metallic supporting post 47 is carried by a fuel exchange apparatus to the region in the core shroud 34 where the fuel assemblies have been removed. The lower end portion of the supporting post 47 is held by the core plate 36 and the upper end portion of the supporting post 47 by the upper grid plate 35. A worker holds the tong 46 and transports the fixing device 39 in the core shroud 34. The fixing device 39 is disposed between the supporting post 47 and the underwater scanning device 23A that has reached the position facing the inspection area 14. The pressing plate 44 comes into contact with one side surface of the supporting post 47, and high-pressure water is supplied into the cylinder 40 through a high-pressure hose connected to the cylinder 40. The piston in the cylinder 40 moves to move the rod 41 toward the underwater scanning device 23A. The pressing plate 42 comes into contact with the casing 38 of the underwater scanning device 23A to press the casing 38 onto the inner surface of the core shroud 34. In this way, the underwater scanning device 23A is pressed onto and fixed to the inner surface of the core shroud 34 by the fixing device 39. In the underwater remote inspection method in the present embodiment also, each process shown in FIG. 5 performed in embodiment 1 is performed. However, the underwater remote inspection device 1 in the present embodiment is moved in the axial and the horizontal directions of the core shroud 34 in the following ways. The underwater remote inspection device 1 is moved in the axial direction of the core shroud 34 along the transporting rods 25A and 25B by turning the motors 31A and 31B in the same direction at the same rotating speed. By turning the motors 31A and 31B in the opposite directions at the same rotating speed, the underwater remote inspection device 1 is moved in the horizontal direction. Each effect attained in embodiment 1 can also be obtained in the present embodiment. [Embodiment 3] An underwater remote inspection method in embodiment 3, which is another embodiment of the present invention, will be described with reference to the drawings. An underwater remote inspection device 1A (see FIG. 11) used in the present embodiment has a structure in which an ultrasonic cleaning device 50 is added to the underwater remote inspection device 1. The other structures of the underwater remote inspection device 1A are the same as the underwater remote inspection device 1. The ultrasonic cleaning device 50 has an ultrasonic oscillator 51, a waterproof container 52, and an ultrasonic diaphragm 53. The ultrasonic cleaning device 50 is disposed above the magnifying observation device 15. The ultrasonic oscillator 51 is installed in the waterproof container 52 provided to a supporting member 54 attached to the supporting member 20. The ultrasonic diaphragm 53 is disposed in front of the ultrasonic oscillator 51 and attached to the waterproof container 52. The ultrasonic diaphragm 53 is facing the surface of the inspection object (for example, the core shroud 34). A nozzle 56 is disposed in the proximity of the ultrasonic cleaning device 50 and attached to the supporting member 20. A high pressure hose 57 is connected to the nozzle 56. A water supply hose 58 provided with an opening/closing valve 59 and a water suction hose 60 provided with an opening/closing valve 61 are connected to the high pressure hose 57. In the underwater remote inspection method in the present embodiment, each process shown in FIG. 12 is performed. The processes of the underwater remote inspection method shown in FIG. 12 are the processes of the underwater remote inspection method shown in FIG. 5 performed in embodiment 1 with the addition of each process of the steps S15 and S16. The steps S15 and S16 are performed between the steps S5 and S6. In the underwater remote inspection method in the present embodiment, the ultrasonic cleaning device is moved to the front of the inspection area (step S15) after each processes of the steps S1 to S5 has been performed. The two motors 31 are driven to turn each motor 31 in the same direction at the same rotating speed so that the transporting rods 25A and 25B are turned in the same direction at the same rotating speed. The underwater remote inspection apparatus 1A moves downward, and the ultrasonic cleaning device 50 is moved to the position facing the etched inspection area 14 of the core shroud 34, which is the inspection object. The inspection area is ultrasonically cleaned (step S16). The ultrasonic oscillator 51 is vibrated to propagate oscillating waves to the ultrasonic diaphragm 53. The ultrasonic diaphragm 53 vibrates to generate an ultrasonic wave 55. This ultrasonic wave 55 propagates through cooling water and hits the etched inspection area 14. Extraneous matter adhered on the surface of the inspection area 14 is removed by the ultrasonic wave 55. In this way, the surface of the inspection area 14 is ultrasonically cleaned. The extraneous matter detached from the surface is sucked, with the cooling water in the core shroud 34, into the nozzle 56 by opening the opening/closing valve 61 and driving a pump (not shown) connected to the water suction hose 60, to be discharged through the water suction hose 60. The opening/closing valve 59 may be opened instead of the opening/closing valve 61 and a pump (not shown) connected to the water supply hose 58 may be driven to eject pressurized water from the nozzle 56. It is the operator's choice whether to open the opening/closing valve 61 or 59. After the process of the step S16 is completed, each process of the steps S6 to S8 is performed. When the determination in the step S8 is “No”, the determination of the step S9 is performed, and when the determination in the step S9 is “No”, each process of the steps S1 to S5, S15, S16, and S6 to S8 is performed. When the determination in the step S9 is “Yes”, each process of the steps S10, S1 to S5, S15, S16, and S6 to S8 is performed. When the determination in the step S8 is “Yes”, each process of the steps S11 to S14 is performed. Each effect attained in embodiment 1 can also be obtained in the present embodiment. Since the inspection area 14 is ultrasonically cleaned in the present embodiment, the image of the inspection area 14 taken by the magnifying observation camera 16 will be clearer. Consequently, the degree of etching of the inspection area 14 can be distinguished with better accuracy. [Embodiment 4] An underwater remote inspection method in embodiment 4, which is another embodiment of the present invention, will be described with reference to the drawings. An underwater remote inspection device 1B (see FIG. 13) used in the present embodiment has a structure in which a replica sampling device 62 is added to the underwater remote inspection device 1. The other structures of the underwater remote inspection device 1B are the same as the underwater remote inspection device 1. The replica sampling device 62 is provided with a replica sampling head 63, a replica agent cartridge 67, a replica agent supply pipe 68, and a hydraulic cylinder 69, and disposed above the magnifying observation device 15. The replica sampling head 63 is attached to the supporting member 20 with a plurality of supporting members 70. The replica sampling head 63 forms a replica agent filling region 66 inside itself. A sponge 64 coming into contact with the inner surface of the core shroud 34, which is the inspection object, is provided to the distal end of the replica sampling head 63. The replica agent supply pipe 68 communicated to the replica agent filling region 66 is fixed to the replica sampling head 63. The replica agent cartridge 67 is removably attached to the supporting member 20, and removably connected to the replica agent supply pipe 68. The hydraulic cylinder 69 disposed above the replica agent cartridge 67 is attached to the supporting member 20. In the underwater remote inspection method in the present embodiment, each process shown in FIG. 14 is performed. The processes of the underwater remote inspection method shown in FIG. 14 are the processes of the underwater remote inspection method shown in FIG. 5 performed in embodiment 1 with the addition of each process of steps S17, S18, S19, and S20. The steps S17 to S19 are performed between the steps S12 and S13, and the step S20 is performed after the step S14. In the underwater remote inspection method in the present embodiment, each process of the steps S1 to S8 is sequentially performed. When the determination in the step S8 is “No”, the determination of the step S9 is performed, and when the determination in the step S9 is “No”, each process of the steps S1 to S8 is performed. When the determination in the step S9 is “Yes”, each process of the steps S10 and S1 to S8 is performed. When the determination in the step S8 is “Yes”, each process of the steps S11 and S12 is performed. After the process of the step S12 is completed, the replica sampling device is moved to the inspection area (step S17). The two motors 31 are driven to turn each motor 31 in the same direction at the same rotating speed to turn the transporting rods 25A and 25B in the same direction at the same rotating speed. The underwater remote inspection device 1B moves downward, moving the replica sampling device 62 down to the position facing the etched inspection area 14 of the core shroud 34, which is the inspection object. Then, the two motors 31 are turned in the opposite directions at the same rotating speed to turn the transporting rods 25A and 25B in the opposite directions from each other at the same rotating speed. This moves the underwater remote inspection device 1B in the horizontal direction, and the annular sponge 64 of the replica sampling device 62 comes into contact with the inner surface of the core shroud 34. The underwater remote inspection device 1B is stopped from being moved in the horizontal direction. The sponge 64 is surrounding the etched inspection area 14. A replica of the inspection area is sampled (step S18). The hydraulic cylinder 69 is driven to eject the replica agent filled in the replica agent cartridge 67 into the replica agent supply pipe 68. The ejected replica agent passes through the replica agent supply pipe 68 and is supplied to the replica agent filling region 66 surrounded by the replica sampling head 63. This replica agent is accumulated in the replica agent filling region 66 as coming into contact with the inspection area 14, and eventually fills the replica agent filling region 66. Whether the replica agent filling region 66 is completely filled with the replica agent or not can be confirmed based on an image taken by the underwater TV 37, showing if the replica agent is in an air-vent hole 65 formed on the upper end portion of the replica sampling head 63 for communicating with the replica agent filling region 66, opened to the outside of the replica sampling head 63. The sponge 64 coming into contact with the inner surface of the core shroud 34 prevents the replica agent supplied into the replica agent filling region 66 from leaking out of the replica sampling head 63 through the joint between the replica sampling head 63 and the core shroud 34. The replica agent filled in the replica agent filling region 66 cures after a predetermined period of time has passed, and the surface form of the inspection area 14 is transferred to the cured replica agent. The replica sampling device is moved away from the surface of the inspection object (step S19). In the same manner as the step S12 in embodiment 1, the two motors 31 are driven to turn the transporting rods 25A and 25B in the opposite directions from each other at the same rotating speed. This moves the underwater remote inspection device 1B in the horizontal direction away from the core shroud 34, and the replica sampling device 62 is also moved away from the core shroud 34. Eventually, the underwater remote inspection device 1B is stored in the casing 24 of the underwater scanning device 23. After the completion of the step S19, each process of the steps S13 and S14 is performed to retrieve the underwater remote inspection device 1B and the underwater scanning device 23 on the operation floor. Then, the transfer surface of the replica is observed and the observation result is recorded (step S20). The replica is removed from the replica sampling device 62 of the retrieved underwater remote inspection device 1B, and the transfer surface (the surface that had come into contact with the inspection area 14) of the replica is enlarged by an optical microscope, etc. for observation. This observation result is loaded into a personal computer and stored in a memory. Each effect attained in embodiment 1 can also be obtained in the present embodiment. The present embodiment is provided with the replica sampling device 62 so that a replica, to which the surface form of the inspection area 14 is transferred, can be obtained. In addition, the present embodiment is provided with the sealing device 9 and the magnifying observation camera 16 so that the time can be shortened, which is required from the time when the underwater scanning device 23 is supported by the core plate 36 to the time when the retrieval of the underwater remote inspection devices 1B is completed after sampling the replica. [Embodiment 5] An underwater remote inspection method in embodiment 5, which is another embodiment of the present invention, will be described with reference to the drawings. An underwater remote inspection device 1C (see FIG. 15) used in the present embodiment has a structure in which, an ultrasonic cleaning device 50 is added to the underwater remote inspection device 1B used in embodiment 4. This ultrasonic cleaning 50 is provided to the replica sampling head 63, and the distal end portion, which is a part of the ultrasonic cleaning device 50, is disposed in the replica agent filling region 66. The other structures of the underwater remote inspection device 1C are the same as the underwater remote inspection device 1B. The ultrasonic cleaner 50 used in the present embodiment has the same structure as the ultrasonic cleaner 50 used in Embodiment 3. In the underwater remote inspection method in the present embodiment, each process of the steps S15 and S16 is performed between the steps S5 and S6 in the processes shown in FIG. 14 in the same manner as the processes in embodiment 3 shown in FIG. 12. Each effect attained in embodiment 4 and the effect attained by the ultrasonic cleaning in embodiment 3 can be obtained in the present embodiment. In the present embodiment, since the ultrasonic cleaning device 50 is installed to the replica sampling head 63, the supporting member 54 provided in embodiment 3 is no longer necessary. [Embodiment 6] An underwater remote inspection method in embodiment 6, which is another embodiment of the present invention, will be described with reference to the drawings. An underwater remote inspection device 1D (see FIGS. 16, 17, and 18) used in the present embodiment is provided with the etching device 2 and the magnifying observation device 15 in the same manner as in the underwater remote inspection device 1. This etching device 2 and the magnifying observation device 15 are the etching device 2 and the magnifying observation device 15 used in embodiment 1. In addition, the underwater remote inspection device 1D is provided with a driving device 74 and arms 76 and 78. The driving device 74 has a casing 75, a rotating device 80 and a lifting/lowering device (now shown). The casing 75 is installed on the rotating device 80. A plurality of links 77 is attached to the lifting/lowering device, and further attached to the arm 76. A plurality of links 79 is attached to the lifting/lowering device and further attached to the arm 78. The lifting/lowering device is installed in the casing 75 to move the links 77 and 78 up and down separately. The etching device 2 is rotatably attached to the lower end portion of the arm 76. The magnifying observation device 15 is rotatably attached to the lower end portion of the arm 78. A side-viewing mirror 81 is provided to the distal end portion of the magnifying observation device 15 (see FIG. 18). The underwater remote inspection method in the present embodiment using the underwater remote inspection device 1D will be specifically described. The inspection area in the present embodiment is a surface of a welding portion 73 between the reactor pressure vessel 33 and the stub tube 72, to which the CRD housing 71 is fixed (see FIGS. 16 and 17). The underwater remote inspection device 1D is lowered using, for example, a crane provided to a fuel exchange apparatus, and set on an upper end portion of the CRD housing 71 fixed to the stub tube 72 joined by the welding portion 73 which will be the inspection object. To be more specific, the rotating device 80 of the underwater remote inspection device 1D is set on the upper end portion of the CRD housing 71. The arms 76 and 78 are disposed around the mentioned CRD housing 71, and stay between the CRD housing 71 and the other CRD housing 71 adjacent to the CRD housing 71. The lifting/lowering device is driven to lower the arm 76, and the etching device 2 is moved to the position facing the welding portion 73 of the stub tube 72. The etching device 2 is turned in relation to the arm 76 to set the chamber 3 of the etching device 2 to the predetermined position facing the welding portion 73 (see FIG. 17). The sealing members 10A and 10B of the sealing device 9 come into contact with the bottom portion of the reactor pressure vessel 33, the stub tube 72, and the welding portion 73. The steps S3, S4, and S5 performed in embodiment 1 are also performed in the present embodiment. After the process of the step S5 is completed and etching of the surface of the predetermined portion of the welding portion 73 is completed, the rotating device 80 is rotated to dispose the side-viewing mirror 81 provided to the magnifying observation device 15 in the position facing the etched area in the surface of the welding portion 73 (see FIG. 18). In the present embodiment, each processes of the steps S6 and S7 performed in embodiment 1 is performed. In the step S7, an image of the etched surface of the welding portion 73 is taken by the magnifying observation camera 16. When the determination in the step S8 after the completion of the step S7 is “No”, the determination of the step S9 is performed, and when the determination in the step S9 is “No”, each process of the steps S1 to S8 is performed. When the determination in the step S9 is “Yes”, each process of the steps S10 and S1 to S8 is performed. When the determination in the step S8 is “Yes”, the process of the step S11 is performed. Then, the underwater remote inspection device 1D is removed from the CRD housing 71. Each effect attained in embodiment 1 can also be obtained in the present embodiment. The etching device 2 of the underwater remote inspection device 1D can be inserted between CRD housings 71, which are narrow portions, allowing inspection in the narrow portion to be performed. The above-described embodiment 6 is applicable also for inspecting a surface of a structure in a pressurized water reactor. In the pressurized water reactor, a plurality of in-core instrumentation tubes is fixed to the bottom portion of the reactor pressure vessel, penetrating the reactor pressure vessel. After the operation of the pressurized water reactor is shutdown, fuel assemblies and reactor internals in the reactor pressure vessel of the pressurized water reactor are taken out outside. Then, the underwater remote inspection device 1D is carried into the reactor pressure vessel to be installed to the upper end portion of the in-core instrumentation tube in the same manner as in embodiment 6. The etching device 2 and the magnifying observation device 15 are rotated around the in-core instrumentation tube to etch the surface of the welding portion between the in-core instrumentation tube and the inner surface of the reactor pressure vessel in the same manner as in embodiment 6. [Industrial Applicability] The present invention can be used for inspection of a surface of a structure in a reactor pressure vessel of a boiling water reactor plant and a pressurized water reactor plant. [Reference Signs List] 1, 1A, 1B, 1C, 1D: underwater remote inspection device, 2: etching device, 3: chamber, 5: negative electrode, 6: positive electrode, 8: etchant exhaust pipe, 9: sealing device, 10A, 10B: sealing member, 11: suction passage, 12: etchant filling region, 13: sealing region, 14: inspection area, 15: magnifying observation device, 16: magnifying observation camera, 17, 52: waterproof container, 19: LED light, 23, 23A: underwater scanning device, 24, 38, 75: casing, 25A, 25B: transporting rod, 26A, 26B: moving body, 27, 28, 28A, 30: link, 31, 31A,31B: motor, 33: reactor pressure vessel, 34: core shroud, 39: fixing device, 50: ultrasonic cleaning device, 51: ultrasonic oscillator, 53: ultrasonic diaphragm, 62: replica sampling device, 63: replica sampling head, 66: replica agent filling region, 67: replica agent cartridge, 68: replica agent supply pipe, 71: control rod drive mechanism housing, 74: driving device, 76, 78: arm, 80: rotating device. |
|
claims | 1. An asymmetric inertial confinement fusion method comprising:fixing in position a target capsule comprising an inertial confinement fusion fuel, wherein the target capsule is spherical; andasymmetrically applying a first oscillatory compression to the target capsule at a first time with more energy along a first axis of the target capsule than a second axis orthogonal to the first axis of the target capsule, wherein no oscillatory compression is applied to the target capsule prior to the first time;asymmetrically applying a second oscillatory compression to the target capsule at a second time with more energy along the second axis than the first axis; andcausing an ovoid shaped implosion of the target capsule by applying a third oscillatory compression to the target capsule at a third time, wherein the first time occurs before the second time and the second time occurs before the third time, and wherein no oscillatory compression after the third time is applied to the target capsule prior to the ovoid shaped implosion. 2. The asymmetric inertial confinement fusion method of claim 1, wherein the target capsule includes one or more of deuterium, tritium, or helium-3. 3. The asymmetric inertial confinement fusion method of claim 1, wherein the target capsule is held inside a hohlraum. 4. The asymmetric inertial confinement fusion method of claim 3, wherein the target capsule is cooled in the hohlraum and held in the hohlraum by support structures. 5. The asymmetric inertial confinement fusion method of claim 1, wherein the first, second, and third oscillatory compressions are performed by one or more of a laser beam or an ion beam. 6. The asymmetric inertial confinement fusion method of claim 1, wherein the third oscillatory compression applies equal energy along the first axis and the second axis. 7. The asymmetric inertial confinement fusion method of claim 1, wherein the third oscillatory compression applies more energy along the first axis than the second axis. 8. The asymmetric inertial confinement fusion method of claim 1, wherein the third oscillatory compression applies less energy along the first axis than the second axis. 9. The asymmetric inertial confinement fusion method of claim 1, wherein the first axis is an equatorial axis. 10. The asymmetric inertial confinement fusion method of claim 1, wherein the second axis is a polar axis. 11. The asymmetric inertial confinement fusion method of claim 1, wherein the first, second, and third oscillatory compressions are delivered via direct drive to the target capsule. 12. The asymmetric inertial confinement fusion method of claim 3, wherein the first, second, and third oscillatory compressions are delivered to the target capsule by directing beams that impinge on an inside surface of the hohlraum before reaching the target capsule. 13. The asymmetric inertial confinement fusion method of claim 1, wherein asymmetrically applying one or more of the first or the second oscillatory compression causes the target capsule to become ovoid in shape. |
|
summary | ||
061635901 | summary | FIELD OF THE INVENTION This invention relates generally to the high resolution imaging of features of very small objects utilising penetrating radiation such as x-rays. The invention is especially suitable for carrying out x-ray phase contrast microscopic imaging, and may be usefully applied to the ultra high spatial resolution imaging of microscopic objects and features, including small biological systems such as viruses and cells and possibly including large biological molecules. BACKGROUND ART A known approach to microscopy utilising x-rays is projection x-ray microscopy, in which a focussed electron beam excites and thereby generates a spot x-ray source in a foil or other target. The object is placed in the divergent beam between the target and a photographic or other detection plate. There have more recently been a number of proposals for using the electron beam of an electron microscope to excite a point source for x-ray microscopy. Integration of an x-ray tomography device directly into an electron microscope was proposed by Sasov, at J. Microscopy 147, 169, 179 (1987). Prototype x-ray tomography attachments for scanning electron microscopes using charge coupled device (CCD) detectors have been proposed in Cazaux et al, J. Microsc. Electron. 14, 263 (1989), Cazaux et al, J. Phys. (Paris) IV C7, 2099 (1993) and Cheng et al X-ray Microscop) III, ed. A. Michette et al (Springer Berlin, 1992), page 184. Ferreira de Paiva et al (Rev. Sci. Instrum. 67(6), 2251 (June 1996)) have developed and studied the performance of a microtomography system based on the Cazaux and Cheng proposals. Their arrangement was an adaptation of a commercially available electron microprobe and was able to produce images at around 10 .mu.m resolution without requiring major alterations to the electron optical column. The authors concluded that a 1 .mu.m resolution in tomography was feasible for their device. All system components and methods of interpretation of image intensity data in these works were based on the mechanism of absorption contrast. A review article by W. Nixon concerning x-ray microscopy may be found in "X-rays: The First Hundred Years", ed. A Michette & S. Pfauntsch, (Wiley, 1996, ISBN 0.471-96502-2), at ps 43-60. The present applicant's international patent publication WO 95/05725 disclosed various configurations and conditions suitable for differential phase-contrast imaging using hard x-rays. Other disclosures are to be found in Soviet patent 1402871 and in U.S. Pat. No. 5,319,694. Practical methods for carrying out hard x-ray phase contrast imaging arc disclosed in the present applicant's co-pending international patent publication WO 96/31098 (PCT/AU96/00178). These methods preferably involve the use of microfocus x-ray sources, which could be polychromatic, and the use of appropriate distances between object and source and object and image plane. Various mathematical and numerical methods for extracting the phase change of the x-ray wavefield at the exit plane from the object are disclosed in that application and also in Wilkins et al "Phase Contrast Imaging Using Polychromatic Hard X-rays" Nature (London) 384, 335 (1996) and our co-pending international patent application PCT/AU97/00882. The examples given in these references primarily related to macroscopic objects and features, and to self contained conventional laboratory type x-ray sources well separated in space from the sample. It is an object of the present invention, at least in a preferred application, to facilitate x-ray phase contrast imaging of microscopic objects and features. DISCLOSURE OF THE INVENTION The invention entails a realisation that the objective just mentioned can be met by a novel approach in the adaptation of electron microscopes to x-ray imaging or by the use of intense laser sources or x-ray synchrotron sources to produce a microfocus x-ray source. In a first aspect of the invention, there is provided a sample cell for use in x-ray imaging, including structure defining a chamber for a sample, and, mounted to the structure, a body of a substance excitable by an appropriate incident beam to generate x-ray radiation, the cell being arranged so that, in use, at least a portion of the x-ray radiation traverses the chamber to irradiate the sample therein and thereafter exits the structure for detection. In one embodiment, the cell is an integral self-contained unit adapted and dimensioned to be inserted in complementary holder means, e.g. the sample stage, of a scanning electron microscope or microprobe at a position where the electron beam of the microscope or microprobe is focussed on the body of excitable substance, and thereby provides the incident beam for exciting the substance to generate x-ray radiation. In another embodiment, the substance is excitable by an incident focussed beam of electromagnetic radiation, e.g. a laser beam or synchrotron radiation beam, to generate x-ray radiation. The cell is preferably an array of layers, of dimensions parallel to the plane of the layers in the range a micron or so to a few e.g. 10 millimeters. The cell is advantageously adapted for use in phase contrast imaging in that said layers through which the excited x-ray radiation passes are highly homogeneous and have very smooth surfaces for preserving high spatial coherence of the incident beam in the radiation that irradiates the sample, and thereby optimising useful contrast in the image. This is especially desirable for the exit surface from the layer of said excitable substance, and for subsequent layers in the sample cell. The excitable substance is preferably a layer of the substance applied to the structure defining the cell but may also be free standing. This structure preferably includes a substrate and/or spacer layer, transparent generally to x-rays or to a selected x-ray energy band(s), separating the layer of excitable substance from the sample. Although largely transparent to the radiation energy band(s) of interest, the substrate and/or spatial layer may also be chosen such as to be strongly absorbing for energies outside this band(s) in order to enhance the chromatic coherence of the x-ray beam contributing to the image. The said cell may be open, or may be arranged to be hermetically sealed, eg. to permit evacuation of the electron-microscope chamber after placement of the sample in the chamber. The chamber or cell may be adapted to be enclosed and if so the structure includes an x-ray transparent window by which the said x-ray radiation exits the structure for detection. The layer of excitable substance is preferably of a thickness in the range 10 to 1000 nm, and the separation of this layer from the sample may be in the range 1 to 1000 .mu.m. In this first aspect, the invention extends to an x-ray microscope or microprobe, eg. a scanning x-ray microscope or microprobe, having means to generate a focussed electron beam, and a sample cell, as described above in any one or more of the variations described, retained in holder means at a position where said electron beam is focussed on said body of excitable substance and thereby provides said incident beam for exciting said substance to generate x-ray radiation. Preferably, for very high resolution imaging, the means to generate a focussed electron beam includes a field emission tip electron source. In a second aspect, the invention provides a method of deriving a magnified x-ray image of one or more internal boundaries or other features of a sample, comprising: disposing the sample in a sample cell according to the first aspect of the invention and fitting the cell into holder means of an electron microscope or microprobe at a position where the electron beam of the microscope or microprobe is focussed on said body of excitable substance and thereby provides said incident beam for exciting said substance to generate x-ray radiation; PA1 irradiating the excitable substance with an electron beam to cause the substance to generate x-ray radiation, at least a portion of which traverses the chamber to irradiate the sample, including the one or more internal boundaries or other features, and thereafter exits the cell structure; and PA1 detecting and recording at least a portion of said radiation after it has irradiated the sample, to provide an image of the one or more internal boundaries or other features of the sample. The x-ray imaging may be absorption-contrast or phase-contrast imaging or both. The invention is especially suited to performance of phase contrast imaging. The image(s)) may be energy filtered by the detector system or other means, or may be simultaneously collected as a set of images corresponding to a series of x-ray energy bands. The x-ray radiation generated by the excitable substance is preferably in the medium to hard x-ray range, ie. in the range 1 keV to 1 MeV, and may be substantially monochromatic, or polychromatic. In the former case, the method may further include enhancing the degree of monochromaticity. In the practice of the method or use of the apparatus, the sample to image plane distance is preferably of the order of 10 to 200 mm. In a still further aspect, the invention provides an x-ray microscopic imaging configuration comprising means to support a sample, a body of a substance excitable by an appropriate incident beam to generate x-ray radiation, said body being retained on a substrate disposed in use between said body and said sample and thereby serving as a spacer; and means to adjust the relative position of said sample and said body. |
summary | ||
abstract | A transport container for nuclear fuel is provided with an outer container having internal insulation, the insulation defining an internal cavity. The cavity receives a plurality of fuel containers wherein the internal volume of the fuel containers is at least 5% of the external volume of the outer container. The container allows substantially higher volume proportions of enriched fuel to be safely transported than is possible with prior containers. |
|
claims | 1. A rotatable fixture, comprising:a base;a rotating disc pivotally connected to the base through a central axle and capable of rotating with respect to the base;a fastening frame uprightly fastened to the rotating disc for allowing a device under test to be securely fastened thereto; andat least one fastening member movably passing through the rotating disc and the base for fastening the rotating disc and limiting a rotation of the rotating disc with respect to the base;wherein the fastening frame includes a pair of fixing plates, the pair of fixing plates being secured to opposite surfaces of the fastening frame for allowing the device under test to be mounted thereon. 2. The rotatable fixture according to claim 1, wherein the central axle includes a central cone, a spring, and a headless screw bolt, all of which are sequentially mounted in a perforation which is located in the center of the base, the central cone being exposed through the perforation of the base for allowing the rotating disc to be mounted thereon. 3. The rotatable fixture according to claim 1, wherein the base is configured to provide support for the rotation of the rotating disc by at least four rolling steel ball assembly. 4. The rotatable fixture according to claim 3, wherein the rolling steel ball assembly includes a rolling steel ball, a rolling ball cushion, a spring, a spring cushion, and a headless screw bolt, all of which are sequentially superimposed in perforations of the base, such that the rolling steel balls are slightly exposed from their located perforations through the spring recoiling force when the rotating disc is rotating, thereby propping up the rotating disc. 5. The rotatable fixture according to claim 1, wherein each fixing plate includes a plurality of lock holes for fastening the device under test. 6. The rotatable fixture according to claim 1, wherein each fixing plate is secured to one side of the fastening frame by screws. 7. The rotatable fixture according to claim 1, wherein the fastening frame is formed of a H-shaped steel plate. 8. The rotatable fixture according to claim 7, wherein the H-shaped steel plate is configured as a hollow rectangle. 9. The rotatable fixture according to claim 1, wherein the fastening frame is set to be secured to the rotating disc, such that the basic natural frequency of the fixture is larger than 33 Hz. |
|
abstract | A device for producing electricity. The device comprises an indium gallium phosphide semiconductor material comprising a plurality of indium gallium phosphide material layers each layer having different dopant concentrations and doped with either n-type dopants or p-type dopants, a first terminal on a first surface of the semiconductor material, a beta particle source proximate the first surface for emitting beta particles that penetrate into the semiconductor material, and a second terminal on a second surface of the semiconductor material; the semiconductor material for producing current between the first and second terminals responsive to the beta particles penetrating into the semiconductor material. |
|
claims | 1. A contamination barrier configured to permit radiation from a radiation source to pass through and to capture debris from the radiation source, the contamination barrier comprising:a support structure comprising an inner ring;a plurality of plate members arranged on the support structure and extending in a radial direction from an axis of the support structure; anda shield configured to shield the inner ring of the support structure from being hit by radiation or debris from the radiation source. 2. A contamination baffler according to claim 1, wherein the shield is a first shield and further comprising a second shield configured to block thermal radiation from the first shield. 3. A contamination baffler according to claim 1, wherein the shield is a first shield and further comprising a second shield configured to reduce heating of the first shield caused by direct radiation from the radiation source, wherein the second shield is disposed upstream of the first shield with respect to the direction of propagation of the radiation emitted by the radiation source. 4. A contamination baffler according to claim 3, wherein the second shield is substantially thermally isolated with respect to the first shield. 5. A contamination baffler according to claim 4, wherein the second shield is connected to the first shield. 6. A contamination baffler according to claim 1, further comprising a cooling spoke to support the shield, the cooling spoke being thermally connected to a structure displaced from the support structure. 7. A contamination barrier according to claim 6, wherein the shield comprises a plurality of shield members, each shield member being connected to the structure displaced from the support structure via a separate cooling spoke. 8. A contamination barrier according to claim 1, further comprising a first cooling device arranged to cool the shield. 9. A contamination barrier according to claim 8, further comprising a second cooling device arranged to cool the support structure. 10. A contamination barrier according to claim 1, wherein each of the plate members is disposed along a respective plane that includes an axis along which the radiation propagates in use. 11. A contamination barrier according to claim 1, wherein at least one end of each of the plurality of plate members is movable relative to the support structure. 12. A contamination barrier according to claim 1, wherein the support structure further comprises an outer ring, and at least one outer end of each of the plurality of plate members is connected to the outer ring. 13. A lithographic projection apparatus comprising:a radiation system configured to form a beam of radiation, the radiation system comprising:a contamination barrier configured to permit radiation from a radiation source to pass through and to capture debris from the radiation source, the contamination barrier comprising a support structure comprising an inner ring, a plurality of plate members arranged on the support structure and extending in a radial direction from an axis of the support structure, and a shield configured to shield the inner ring of the support structure from being hit by radiation or debris from the radiation source;a support structure to support a patterning structure to be irradiated by a beam of radiation to pattern the beam of radiation;a substrate support to support a substrate; anda projection system to image an irradiated portion of the patterning structure onto a target portion of the substrate. 14. A lithographic apparatus according to claim 13, wherein the radiation system further comprises a collector configured to collect radiation passing the contamination barrier. 15. A lithographic apparatus according to claim 13, further comprising a cooling spoke to support the shield, the cooling spoke being thermally connected to a structure displaced from the support structure. 16. A lithographic apparatus according to claim 15, further comprising a first cooling device arranged to cool the shield. 17. A method of manufacturing an integrated structure by a lithographic process, the method comprising:generating radiation with a radiation source;capturing debris from the radiation source using a contamination barrier comprising a support structure comprising an inner ring, a plurality of plate members arranged on the support structure and extending in a radial direction from an axis of the support structure, and a shield configured to shield the inner ring of the support structure from being hit by radiation or debris from the radiation source;patterning the radiation with a patterning structure; andimaging the patterned radiation onto a target portion of a substrate. 18. A method according to claim 17, wherein the contamination barrier comprises a further shield configured to reduce heating of the shield caused by direct radiation from the radiation source, wherein the further shield is disposed upstream of the shield with respect to the direction of propagation of the radiation emitted by the radiation source. 19. A method according to claim 18, wherein the further shield is substantially thermally isolated with respect to the shield. 20. A method according to claim 17, wherein the contamination barrier comprising a cooling spoke to support the shield, the cooling spoke being thermally connected to a structure displaced from the support structure. 21. A method according to claim 17, further comprising cooling the shield. |
|
041994051 | description | The side reflector is formed of a plurality of layers of superimposed rings, which consist of blocks disposed alongside one another, of which three are shown in FIG. 1. The inner and outer end faces of all the blocks form the preferably cylindrical inner and outer face respectively of the side reflector, which are concentric to each other. According to FIG. 1, which shows the formation of the inner end face of the blocks in two preferred forms, the vertical side faces of each block, which adjoin the next adjacent blocks, extend in a wedge-shaped pattern towards the centre of the cylinder formed by the side reflector, so that each block as the sector shape of a "piece of cake" with the point cut off. The upper and lower face of each block are plane and parallel. As can be seen especially from FIGS. 2a and 2b, the inner end face of the central block 5 illustrated in FIG. 1 is furnished with two mutually perpendicular sets of slits 6 and 7, which can be made for example by sawing, the width of each slit 6 and 7 being equal to the thickness of the saw blade. In order, in nuclear reactors charged with spherical fuel elements, to prevent the densest possible packing of the spheres 8, a discontinuity 9 is formed as shown in FIGS. 2a and 2b in the end face of each block 5, centrally placed and superimposed upon the sets of slits 6 and 7, this discontinuity in the example shown having the form of a truncated conical depression. Preferably, the depression extends at a maximum to the base of the slit, which is situated radially outwards between 20 and 200 m from the machined inner end face of the block 5. The block 11 shown at the left in FIG. 1 differs in the form of its end inner face from block 5, in that the vertical slits 12 extending perpendicularly to the slits 7 are of larger width than the slits 6 and 7, thus producing, amongst other things, the already explained by-pass advantages. In this connection, it is only necessary to emphasise once again that in a form as represented by block 11, the thermal reservoir existing in the side reflector blocks in total is utilised to an optimum extent especially in the case of a shutdown or failure of cooling, since the radiation influences the heat transfer by the difference of the fourth powers of the temperatures, which in the case of this example of embodiment therefore leads to an enormous emission, because, if the cooling is absent, the by-pass rendered possible by the wider vertical slits 12 lead to a comparatively high temperature difference. As also shown in FIG. 1, vertical grooves 14 are provided in the mutually facing, vertical lateral surfaces 13 of each block, these grooves 14 forming in pairs vertical passages, into which keys for fixing the blocks and interrupting the outwardly radiating, continuous gaps between adjacent blocks, are introduced. |
055552790 | abstract | A computer-based power oscillation detection system and method for detecting, monitoring and indicating thermal-hydraulic stability margin in a nuclear reactor is provided. A group of neutron flux detectors is distributed throughout the reactor core, in contiguous relation to the reactor fuel assemblies, with each flux detector providing an output signal indicative of the power density of the portion of the core adjacent to the detector. A computer-based system processes the detector output signals utilizing a period based algorithm that employs an oscillation detection counting function wherein a count corresponding to the level of periodicity of the signal is determined. Since a representative oscillation count for each reactor stability state usually only occurs on the order of several minutes for a single detector signal, a unique simulated decay ratio algorithm reduces the time required to obtain a representative count by processing the group of detector signals spread throughout the core. The highest count for any detector in the group is utilized by the simulated decay ratio algorithm to provide a simulated decay ratio signal that corresponds to the reactor thermal-hydraulic stability. To overcome statistical variations in successive oscillation period counts, a spike rejection function and a smoothing function may be employed to provide improved simulated decay ratio signal performance. A corrective signal issues when the simulated decay ratio signal reaches a predetermined level which may be used to take corrective action, activate an alarm, provide a visual indication of decay ratio, or to initiate an automatic reactor suppression function. |
claims | 1. A method for use in a lithography process, comprising:providing an integrated circuit (IC) layout design in a graphic database system (GDS) grid;converting the IC layout design GDS grid to a first exposure grid;applying a non-directional dither technique to the first exposure grid;applying a grid shift to the first exposure grid to generate a grid-shifted exposure grid;applying non-directional dithers to the grid-shifted exposure grid; andafter applying the non-directional dither technique to the first exposure grid and after applying non-directional dithers to the grid-shifted exposure grid, adding, by a computer, the first exposure grid to the grid-shifted exposure grid to generate a second exposure grid. 2. The method of claim 1, wherein the first exposure grid is formed by a two-dimensional array of pixels, and wherein the pixel size is selected to be larger than the pixel size of the IC layout design grid. 3. The method of claim 1, wherein the non-directional dithers include dithering along a first direction. 4. The method of claim 1, wherein the non-directional dithers include dithering along a second direction. 5. The method of claim 1, wherein multiple non-directional dithers are applied to the first exposure grid. 6. The method of claim 1, wherein Floyd-Steinberg dithering is applied to the first exposure grid. 7. The method of claim 1, wherein multiple grid shifts are applied to the first exposure grid. 8. The method of claim 1, wherein the grid shift comprises shifting along a first direction. 9. The method of claim 1, wherein the grid shift comprises shifting along a second direction. 10. The method of claim 1, wherein the grid shift comprises shifting along two directions. 11. The method of claim 1, wherein a direction of the grid shift is independent of a direction of dithering. 12. A method for providing a modified exposure grid, comprising:providing an integrated circuit (IC) layout design in a graphic database system (GDS) grid;converting the IC design layout GDS grid to a first exposure grid and using k bits for a grey level;dithering the first exposure grid and using less than k bits for grey level;applying a grid shift to the first exposure grid to generate a grid-shifted exposure grid and using less than k bits for grey level and applying a dither to the grid-shifted exposure grid; andafter dithering the first exposure grid and after applying the dither to the grid-shifted exposure grid, adding, by a computer, the first exposure grid to the grid-shifted exposure grid to generate a modified exposure grid. 13. The method of claim 12, wherein after dithering the first exposure grid the first exposure grid uses k−1 bits for a grey level. 14. The method of claim 12, wherein after dithering the first exposure grid the pixel size of the first exposure grid is not larger than the first exposure grid. 15. The method of claim 12, wherein after applying the dither to the grid-shifted exposure grid the grid-shifted exposure grid uses k−1 bits for a grey level. 16. The method of claim 12, wherein after applying the dither to the grid-shifted exposure grid the pixel size of the grid-shifted exposure grid is less than the first exposure grid. 17. The method of claim 12, wherein the pixel size of the modified exposure grid is less than the first exposure grid. 18. The method of claim 12, further comprising performing multiple non-directional dithers to the first exposure grid. 19. The method of claim 12, further comprising performing multiple grid shifts to the first exposure grid. 20. A method of providing a grid for use in a lithography process, comprising:providing an integrated circuit (IC) layout design in a graphic database system (GDS) grid with a plurality of polygons in a two-dimensional array of pixels coordinate system;applying a proximity correction process to the IC layout design GDS grid;converting the IC layout design GDS grid to a first exposure grid with a plurality of polygons in a two-dimensional array of pixels coordinate system, using a pixel size larger than the IC layout design GDS grid, and using k bits for a grey level;applying dithering to the first exposure grid, wherein after applying dithering to the first exposure grid the first exposure grid uses less than k bits for a grey level;applying a grid shift to the first exposure grid, wherein the grid-shifted exposure grid uses less than k bits for a grey level and applying dither to the grid-shifted exposure grid; andafter applying the dithering to the first exposure grid and after applying the dither to the grid-shifted exposure grid, adding, by a computer, the first exposure grid to the grid-shifted exposure grid to generate a second exposure grid, wherein the second exposure grid contains a same or less data volume than the first exposure grid. |
|
abstract | A multilevel MLC includes a first set and a second set of a plurality of pairs of beam blocking leaves arranged adjacent one another. Leaves of each pair in the first set are disposed in an opposed relationship and longitudinally movable relative to each other in a first direction. Leaves of each pair in the second set are disposed in an opposed relationship and longitudinally movable relative to each other in a second direction generally parallel to the first direction. The first and second sets of pairs of leaves are disposed in different planes. |
|
description | The present invention relates generally to diagnostic imaging and, more particularly, to an integrated scintillator and collimator and method of manufacturing same. Typically, in computed tomography (CT) imaging systems, an x-ray source emits a fan-shaped beam toward a subject or object, such as a patient or a piece of luggage. Hereinafter, the terms “subject” and “object” shall include anything capable of being imaged. The beam, after being attenuated by the subject, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is typically dependent upon the attenuation of the x-ray beam by the subject. Each detector element of the detector array produces a separate electrical signal indicative of the attenuated beam received by each detector element. The electrical signals are transmitted to a data processing system for analysis which ultimately produces an image. Generally, the x-ray source and the detector array are rotated about the gantry within an imaging plane and around the subject. X-ray sources typically include x-ray tubes, which emit the x-ray beam at a focal point. X-ray detectors typically include a collimator for collimating x-ray beams received at the detector, a scintillator for converting x-rays to light energy adjacent the collimator, and photodiodes for receiving the light energy from the adjacent scintillator and producing electrical signals therefrom. As stated above, typical x-ray detectors include a collimator for collimating x-ray beams such that collection of scattered x-rays is minimized. As such, the collimators operate to attenuate off-angle scattered x-rays from being detected by a scintillator cell. Reducing this scattering reduces noise in the signal and improves the final reconstructed image. Therefore, it is necessary that the scintillator array and the collimator, typically plates extending along one dimension above the scintillator array, are uniformly aligned. That is, exact mechanical alignment is required between the collimator plates and the cast reflector lines in the array of scintillators. Known manufacturing processes attempt this exact alignment by constructing a continuous collimator that is sized to dimensionally match the width and length of the entire detector array. That is, the collimator plates are arranged or arrayed in a continuous consistent pattern or pitch that spans the entire detector length and is placed and attached to the detector rail structure. As such, individual scintillator arrays or packs are must then be exactly aligned to the continuous collimator to ensure that all scintillator cells and collimator cells are aligned exactly; otherwise the collimator must be discarded or repaired, or the scintillator packs must be discarded. This process requires excessively tight tolerancing and requires great operator skill and patience to assemble. Accordingly, these known processes are susceptible to waste of parts, material, and labor. Additionally, as CT detectors grow in the z-direction, alignment requirements will tighten and the number of cells requiring alignment will increase. Therefore, the low process yields and high-end process scrap and re-work associated with these known manufacturing processes will increase the cost and time associated with CT detector assembly. Notwithstanding the advances made in CT detector manufacturing, these known detector assemblies and assembly processes result in a detector with less than optimal collimation. Referring to FIG. 10, a known CT detector 1 fabricated according to known manufacturing processes is shown. The CT detector 1 includes a series of tungsten collimator plates 2 that collimate x-rays projected toward scintillator cells 3 of a scintillator array 4. As shown, each of the collimator plates 2 is generally aligned with a reflector line 5 disposed between adjacent scintillators 3. The reflector lines 5 prevent light from being emitted between adjacent scintillators. The scintillator array is coupled to a photodiode array 6 that detects light emissions from the scintillator array and transmits corresponding electrical signals to a data acquisition system for signal processing. As readily shown, the collimator plates are not integrated with the individual scintillator elements 3. That is, an air gap 7 exists between the collimator plates and the scintillator cells 3. The air gap 7 typically results in a separation between the collimator plates and the scintillator array of approximately two to four thousands of an inch. This air gap occurs as a result of the manufacturing process whereupon the collimator plates are formed as a single collimator assembly that accepts and aligns an array of scintillators. The air gap, however, makes the CT detector susceptible to x-rays received between two collimator plates impinging upon an adjacent scintillator thereby resulting in undesirable anomalies in the final reconstructed CT image. Therefore, it would be desirable to design an integrated scintillator and collimator absent the aforementioned air gap as well as a method of manufacturing such an integrated scintillator and collimator. The present invention is directed to an integrated scintillator and collimator and method of manufacturing same that overcome the aforementioned drawbacks. The integrated scintillator and collimator reduces x-ray cross-talk between adjacent detector cells and improves dimensional alignment between collimator septum and scintillator reflector walls by integrating collimator plates with a top reflector surface of a scintillator. A pixilated array of scintillators is placed on a tooling base whereupon a mold having a series of parallel aligned air cavities is positioned atop the array of scintillators. The air cavities within the mold are positioned such that each aligns with a reflector line in the scintillator array. Using high precision tooling, the mold and the scintillator array are precisely aligned relative to one another. Upon proper alignment, a vacuum pump is used to remove the air cavities from within the mold. Thereafter, an injector is used to dispose collimator mixture within the mold and which is allowed to cure. Once the collimator mixture has cured, the integrated scintillator/collimator is formed. Therefore, in accordance with one aspect of the present invention, a method of manufacturing a detector having an integrated scintillator and collimator is provided. The method includes the steps of positioning an array of scintillator elements or pack on a tooling base and positioning a collimator mold housing having a collimator mold cavity therein on the block. As a result, the mold cavity will be very accurately aligned to the scintillator array pattern. A collimator mixture is then disposed into the mold cavity and allowed to cure to form an integrated scintillator and collimator. In accordance with another aspect of the present invention, a detector for a CT system includes an array of scintillation elements arranged to convert received x-rays to light. A plurality of collimator elements is integrally formed in a top surface of the array of scintillation elements and operates to attenuate off-angle scattered x-rays from being detected by scintillator elements. The detector further includes an array of photodiode elements arranged to receive light emissions from the array of scintillation elements. According to another aspect of the present invention, an integrated scintillator and collimator array is formed by the steps of placing an array of pixilated scintillators on a tooling base and positioning a collimator mold defining a plurality of cavities that extend to a top surface of the array adjacent the array. A collimator material is then disposed within the plurality of cavities and cured so as to form the integrated scintillator and collimator array. In accordance with yet another aspect of the present invention, an apparatus for manufacturing an integrated scintillator and collimator includes a tooling base designed to support a block of scintillating material and a mold to be positioned on the block of scintillating material. An alignment mechanism is provided to align the block in the mold in an aligned arrangement as well as a mold evacuator designed to remove air cavities within the mold. A collimator mixture supply is also provided to supply collimator material to the mold. According to yet another aspect of the present invention, a system to manufacture an integrated scintillator/collimator includes means for positioning a block of scintillator pack on a tooling base as well as means for positioning a collimator mold over the block. Means for aligning the block and the collimator mold is provided as well as means for removing air cavities from the mold. The system also includes means for disposing collimator material into a volume previously occupied by the removed air cavities and means for curing the collimator material to form an integrated scintillator and collimator. Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings. The operating environment of the present invention is described with respect to a four-slice computed tomography (CT) system. However, it will be appreciated by those skilled in the art that the present invention is equally applicable for use with single-slice or other multi-slice configurations. Moreover, the present invention will be described with respect to the detection and conversion of x-rays. However, one skilled in the art will further appreciate that the present invention is equally applicable for the detection and conversion of other high frequency electromagnetic energy. The present invention will be described with respect to a “third generation” CT scanner, but is equally applicable with other CT systems. Referring to FIGS. 1 and 2, a computed tomography (CT) imaging system 10 is shown as including a gantry 12 representative of a “third generation” CT scanner. Gantry 12 has an x-ray source 14 that projects a beam of x-rays 16 toward a detector array 18 on the opposite side of the gantry 12. Detector array 18 is formed by a plurality of detectors 20 which together sense the projected x-rays that pass through a medical patient 22. Each detector 20 produces an electrical signal that represents the intensity of an impinging x-ray beam and hence the attenuated beam as it passes through the patient 22. During a scan to acquire x-ray projection data, gantry 12 and the components mounted thereon rotate about a center of rotation 24. Rotation of gantry 12 and the operation of x-ray source 14 are governed by a control mechanism 26 of CT system 10. Control mechanism 26 includes an x-ray controller 28 that provides power and timing signals to an x-ray source 14 and a gantry motor controller 30 that controls the rotational speed and position of gantry 12. A data acquisition system (DAS) 32 in control mechanism 26 samples analog data from detectors 20 and converts the data to digital signals for subsequent processing. An image reconstructor 34 receives sampled and digitized x-ray data from DAS 32 and performs high speed reconstruction. The reconstructed image is applied as an input to a computer 36 which stores the image in a mass storage device 38. Computer 36 also receives commands and scanning parameters from an operator via console 40 that has a keyboard. An associated cathode ray tube display 42 allows the operator to observe the reconstructed image and other data from computer 36. The operator supplied commands and parameters are used by computer 36 to provide control signals and information to DAS 32, x-ray controller 28 and gantry motor controller 30. In addition, computer 36 operates a table motor controller 44 which controls a motorized table 46 to position patient 22 and gantry 12. Particularly, table 46 moves portions of patient 22 through a gantry opening 48. As shown in FIGS. 3 and 4, detector array 18 includes a plurality of scintillators 57 forming a scintillator array 56. A collimator (not shown) is positioned above scintillator array 56 to collimate x-ray beams 16 before such beams impinge upon scintillator array 56. In one embodiment, shown in FIG. 3, detector array 18 includes 57 detectors 20, each detector 20 having an array size of 16×16. As a result, array 18 has 16 rows and 912 columns (16×57 detectors) which allows 16 simultaneous slices of data to be collected with each rotation of gantry 12. Switch arrays 80 and 82, FIG. 4, are multi-dimensional semiconductor arrays coupled between scintillator array 56 and DAS 32. Switch arrays 80 and 82 include a plurality of field effect transistors (FET) (not shown) arranged as multi-dimensional array. The FET array includes a number of electrical leads connected to each of the respective photodiodes 60 and a number of output leads electrically connected to DAS 32 via a flexible electrical interface 84. Particularly, about one-half of photodiode outputs are electrically connected to switch 80 with the other one-half of photodiode outputs electrically connected to switch 82. Additionally, a reflector layer (not shown) may be interposed between each scintillator 57 to reduce light scattering from adjacent scintillators. Each detector 20 is secured to a detector frame 77, FIG. 3, by mounting brackets 79. Switch arrays 80 and 82 further include a decoder (not shown) that enables, disables, or combines photodiode outputs in accordance with a desired number of slices and slice resolutions for each slice. Decoder, in one embodiment, is a decoder chip or a FET controller as known in the art. Decoder includes a plurality of output and control lines coupled to switch arrays 80 and 82 and DAS 32. In one embodiment defined as a 16 slice mode, decoder enables switch arrays 80 and 82 so that all rows of the photodiode array 52 are activated, resulting in 16 simultaneous slices of data for processing by DAS 32. Of course, many other slice combinations are possible. For example, decoder may also select from other slice modes, including one, two, and four-slice modes. As shown in FIG. 5, by transmitting the appropriate decoder instructions, switch arrays 80 and 82 can be configured in the four-slice mode so that the data is collected from four slices of one or more rows of photodiode array 52. Depending upon the specific configuration of switch arrays 80 and 82, various combinations of photodiodes 60 can be enabled, disabled, or combined so that the slice thickness may consist of one, two, three, or four rows of scintillator array elements 57. Additional examples include, a single slice mode including one slice with slices ranging from 1.25 mm thick to 20 mm thick, and a two slice mode including two slices with slices ranging from 1.25 mm thick to 10 mm thick. Additional modes beyond those described are contemplated. Referring now to FIG. 6, a CT detector having an integrated scintillator and collimator is schematically shown. The detector 20 includes a photodiode array 52 coupled to receive light emissions from a scintillator array 56 of scintillation elements 57. Cast directly onto the scintillation array or pack is a plurality of collimator plates 86. The collimator plates 86 are precisionally aligned with reflector lines 88 disposed between the scintillator elements 57. By casting the collimator plates directly onto the scintillator pack, the air gap discussed with reference to FIG. 10 is eliminated thereby improving the collimation achieved by collimator plates 86. As will be described in greater detail below, each of the collimator plates is formed by a combination or mixture of tungsten and epoxy. Casting the collimator plates directly onto a top reflective surface 90 of the scintillator pack improves the rigidity of the scintillator/collimator structure thereby improving the detector's response to loads induced by a rotating gantry during CT data acquisition. That is, the collimator plates of a CT detector 1 similar to that shown in FIG. 10 are susceptible to gravitational and rotational forces induced movement as a result of the collimator plates being separated from the scintillator array by the previously discussed air gap. The CT detector illustrated in FIG. 6, however, has reduced susceptibility to the aforementioned gravitational forces as a result of the collimator plates being directly cast onto the scintillator pack. Referring now to FIG. 7, a tooling assembly 92 for manufacturing an array of integrated scintillators and collimators is shown. The tooling assembly includes a tooling base 94 designed to support a scintillator array cast pack 96 that is positioned within the lower mold cavity 98. The lower mold cavity 98 is aligned with an upper mold housing 100 such that the pack 96 and mold 102 are properly aligned with respect to one another. To ensure proper and precisioned alignment, tooling assembly 92 includes a dowel pin alignment assembly 104. Other dowel pins and alignment tools such as bore datums (not shown) are contemplated and applicable with the illustrated assembly. In the illustrated embodiment, mold 102 includes a series of cavities 106 that is uniformly aligned in parallel relative to cast pack 96. Further, each cavity 106 has a height equal to the desired height of a collimator plate and extends to the top surface 108 of scintillator array cast pack 96. Assembly 92 further includes an evacuation gate 110 that is connected to a vacuum pump 112. The vacuum pump is controlled by a CPU 114 to remove air from each cavity 106. When the mold is positioned atop the scintillator pack, air fills cavities 106. This air must be removed for proper formation of the collimator, as will be described hereinafter. As such, pump 112 is used to remove air from cavities 106. After a vacuum is formed within the mold housing 100, a collimator mixture is injected by injector 116 through fill gate 118 such that each of the cavities 106 is filled with collimator mixture. The collimator mixture may directly injected by injector 116 or drawn into the mold cavity by the vacuum created in the cavity upon removal of air from within the cavity. The collimator mixture is preferably a combination of tungsten and epoxy. Additionally, the collimation is preferably a powder. However, other combinations, mixtures, and combinations and in non-powder forms may be equivalently used. The collimator mixture is cured at room temperature or elevated temperatures within the mold housing 100. Once cured, the mold housing is removed thereby leaving a series of collimator plates integrally formed with a top surface of the scintillator pack. Referring now to FIG. 8, a manufacturing process 120 for manufacturing an integrated scintillator and collimator array begins at 122 with a series of diced slices of scintillator material undergoing a hot setting process at 124. After undergoing the hot setting process 124, a mold or fence is installed at 126. The mold is used to properly dispose reflector material between each scintillation element. The material used to form the reflector layer is allowed to cast and cure 128 whereupon the mold is removed at 130. The resulting scintillator array cast pack having the reflector lines integrated therewith is milled at 132. Following milling of the top reflective layer of the cast pack, a collimator cavity is positioned about the milled scintillator pack at 134. As stated above, the mold cavity is used during aligning of the scintillator pack relative to the collimator mold. Once the mold cavity and scintillator pack are properly positioned on a tooling base, a collimator mold is positioned or installed relative to the scintillator pack and mold cavity at 136. The collimator mold cavity and scintillator pack are properly aligned using a dowel pin alignment assembly and a series of bore datums, as was previously described. Once the mold, cavity, and block are properly aligned, the air contained in each of the cavities, as a result of the positioning of the mold on the scintillator pack, is removed using a vacuum pump. Once a vacuum is created within the mold, the collimator mixture or powder is introduced into each of the cavities 138. The injected mixture is then allowed to cure 140 thereby resulting in a series of collimator plates being formed integrally with a top surface of the scintillator pack. The mold assembly is then disassembled at 142 resulting in an array of integrated scintillators and collimators. The resulting assembly then undergoes a grinding, inspection, and testing stage 144 to ensure proper alignment and fabrication of the integrated scintillator and collimator array 144. The present invention has been described with respect to fabrication of integrated scintillator and collimator for a CT detector of a CT imaging system. CT detectors incorporating an integrated scintillator and collimator in accordance with the present invention may be used in medical imaging systems as well as parcel inspections systems similar to those illustrated in FIG. 9. Referring to FIG. 9, package/baggage inspection system 150 includes a rotatable gantry 152 having an opening 154 therein through which packages or pieces of baggage may pass. The rotatable gantry 152 houses a high frequency electromagnetic energy source 156 as well as a detector assembly 158 having arrays of integrated scintillator/collimator cells similar to that shown in FIG. 6 and fabricated using an assembly apparatus similar to that described with respect to FIG. 7. A conveyor system 160 is also provided and includes a conveyor belt 162 supported by structure 164 to automatically and continuously pass packages or baggage pieces 166 through opening 154 to be scanned. Objects 166 are fed through opening 154 by conveyor belt 162, imaging data is then acquired, and the conveyor belt 162 removes the packages 166 from opening 164 in a controlled and continuous manner. As a result, postal inspectors, baggage handlers, and other security personnel may non-invasively inspect the contents of packages 166 for explosives, knives, guns, contraband, etc. The present invention has been described with respect to fabricating an integrated scintillator and collimator for a CT based imaging system. Further, fabrication of a rectangular shaped scintillator/collimator combination has been described. However, the present invention contemplates additional patterns or shaped cells being fabricated. Additionally, the present invention envisions numerous collimator material combinations beyond the tungsten/epoxy mixture previously described. Additionally, the high precision alignment and tooling aspects of the present invention may be used to support different “molding” processes such as extrusion, injection molding, and the like. The high precision alignment and tooling aspects could be also applied to electronics packaging application to provide x-ray shielding of sensitive components. Additionally, the present invention has been described with respect to an integrated scintillator whereupon the collimator plates are cast along one dimensional, i.e., the z-axis. However, integrated scintillators and collimators may be formed using the aforementioned methods of manufacturing along an x and z axis thereby rendering a “checkerboard” full two-dimensional (2D) arrangement of integrated scintillators and collimators. The present invention may be implemented to create a partial 2D array of integrated scintillator and collimators. That is, the collimator mold may be constructed such that the collimator cavities have different heights when filled with the collimator mixture. As a result, the collimator plates along one axis, i.e., the z-axis, may have a greater height than collimator plates along another axis, i.e., the x-axis. Therefore, in accordance with one embodiment of the present invention, a method of manufacturing a detector having an integrated scintillator and collimator is provided. The method includes the steps of positioning an array of scintillator elements or pack on a tooling base and positioning a collimator mold housing having a collimator mold cavity therein on the block. As a result, the mold cavity will be very accurately aligned to the scintillator array pattern. A collimator mixture is then disposed into the mold cavity and allowed to cure to form an integrated scintillator and collimator. In accordance with another embodiment of the present invention, a detector for a CT system includes an array of scintillation elements arranged to convert received x-rays to light. A plurality of collimator elements is integrally formed in a top surface of the array of scintillation elements and operates to attenuate off-angle scattered x-rays from being detected by scintillator elements. The detector further includes an array of photodiode elements arranged to receive light emissions from the array of scintillation elements. According to another embodiment of the present invention, an integrated scintillator and collimator array is formed by the steps of placing an array of pixilated scintillators on a tooling base and positioning a collimator mold defining a plurality of cavities that extend to a top surface of the array adjacent the array. A collimator material is then disposed within the plurality of cavities and cured so as to form the integrated scintillator and collimator array. In accordance with yet another embodiment of the present invention, an apparatus for manufacturing an integrated scintillator and collimator includes a tooling base designed to support a block of scintillating material and a mold to be positioned on the block of scintillating material. An alignment mechanism is provided to align the block in the mold in an aligned arrangement as well as a mold evacuator designed to remove air cavities within the mold. A collimator mixture supply is also provided to supply collimator material to the mold. According to yet another embodiment of the present invention, a system to manufacture an integrated scintillator/collimator includes means for positioning a block of scintillator pack on a tooling base as well as means for positioning a collimator mold over the block. Means for aligning the block and the collimator mold is provided as well as means for removing air cavities from the mold. The system also includes means for disposing collimator material into a volume previously occupied by the removed air cavities and means for curing the collimator material to form an integrated scintillator and collimator. The present invention has been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims. |
|
051329948 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT Prior to the description of the embodiments according to the present invention, filter means used in the present invention will be explained in detail below. When a substance layer with a thickness of d is provided in an optical path of light of high energy such as X rays, a spectral transmittance t (E) of the substance layer, with an absorption coefficient of the substance taken as .mu. [F. Biggs, "Analytical Approximations for X-ray Cross Sections II", Sandia Lab. Research Report SC-PRT-710507 (1971)], is given by EQU t(E)=exp(-d.multidot..mu.) (1) The absorption coefficient .mu. is the amount depending on the kind of substance and the energy (namely, the wavelength) of incident light and has a general trend to diminish as the energy of radiation increases. Accordingly, the substance layer of this kind has the function of a high-pass filter and can behave as the high-pass filter (X-ray filter) with a desired spectral characteristic by selecting the material and thickness of the substance layer. FIG. 6 shows the spectral transmittance characteristic of an Fe filter of d=0.5 .mu.m calculated according to Equation (1). As is apparent from this figure, the X-ray filter suppresses the transmittance of radiation on the low energy side to a small value and therefore fulfils the function of the high-pass filter with respect to photon energy. Further, by varying the material and thickness of the filter, cutoff energy can be selected. Next, when a ray of light is incident at a particular grazing angle on a plane mirror, its reflectance is given by EQU R={(.theta.-a).sup.2 +b.sup.2 }/{(.theta.+a).sup.2 +b.sup.2 }(2) where ##EQU1## Here, the complex index of refraction of the substance constituting the mirror surface can be expressed as n.sub.c =1-.delta.-i.beta.. Further, EQU .delta.=(N.sub.a .multidot.r.sub.e .multidot..lambda..sup.2 .multidot.f.sub.1)/2.pi. EQU .beta.=(N.sub.a .multidot.r.sub.e .multidot..lambda..sup.2 .multidot.f.sub.2)/2.pi. where N.sub.a is the number of atoms per unit volume, r.sub.e the classical electron radius, .lambda. the wavelength of light, and f.sub.1 and f.sub.2 the scattering and absorption factors in the table of Henke [ATOMIC DATA AND NUCLEAR DATA TABLES, Vol. 27, No. 1, p. 1-144 (1982)]. Also, .theta. denotes the grazing angle of light. The grazing incidence mirror, as shown in FIG. 7 [the dependence of the wavelength .lambda. of the reflectance on a Pt reflecting surface at the grazing angle .theta. which is calculated from Equation (2)], has the effect that when radiation with various wavelengths is incident at particular grazing angles (2.degree., 3.degree., 5.degree. and 7.degree.), the reflectance of the radiation on the short wavelength side is suppressed to a small value. That is, it fulfills the function of the low-pass filter suppressing the radiation of high energy. Further, by changing the material of the mirror surface and the grazing angle, the cutoff energy can be selected. As such, if the X-ray filter is used in combination with the grazing incidence mirror, a band-pass filter can be constructed. In particular, a proper selection of characteristics of the filter makes it possible to secure the filter transmitting selectively the radiation of the region of wavelengths of 10-100 .ANG. called "water window" in which the following absorption edges of substances governing a living phenomenon exist. ______________________________________ Substance Absorption edge Wavelength (.ANG.) ______________________________________ P L2, 3 94 S L3** 75.1 Na K 11.569 C K 43.68 N K 30.99 Ca L2 35.13 L3 35.49 ______________________________________ [From: L. Henke, Atomic Data and Nuclear Data Tables 27, p. 1-144 (1982) Also, as the filter for this wavelength region, its thickness is moderate to range from nearly 5 to several .mu.m (although it depends on substances as a matter of course). The filter of larger thickness will cut even the soft X rays and, with smaller thickness, the long wavelength light such as vacuum ultraviolet rays cannot be blocked. Furthermore, the filter of smaller thickness has difficulties in respect of the latest manufacturing technology and the strength. In accordance with the embodiments shown, the present invention will be described in detail below. However, the substances constituting the filter means used in the present invention is not necessarily limited to those shown in individual embodiments. FIRST EMBODIMENT FIG. 8 is a schematic view showing the construction of a scanning X-ray microscope equipped with the Walter optical system. In this figure, the Walter optical system, though shown in regard to only the one side of the optical axis, has the arrangement in which an annular ellipsoidal mirror 1 and a hyperboloidal mirror 2 are coaxially connected with each other. Further, an X-ray source O is disposed at a focal point F.sub.1 of the ellipsoidal mirror 1 and radiation emitted from the X-ray source O is reflected from the order of the ellipsoidal mirror 1 and the hyperboloidal mirror 2 and converged at a focal point F.sub.2 of the hyperboloidal mirror 2. At this position is provided a stage on which a specimen is placed. The radiation transmitted through the specimen is conducted to a detector 5 through an X-ray filter 4. The stage 3 is such that a two-dimensional movement, which is possible in a plane normal to the optical axis, enables the specimen to be scanned by a radiation spot. Here, the laser plasma source having the characteristic such as is shown in FIG. 1B is used as the X-ray source O, the Fe filter of the characteristic shown in FIG. 6 as the X-ray filter 4, and the MCP shown in FIG. 3 as the detector. Also, the entire system is contained in a vacuum vessel, although not shown. For a scanning technique, there is a method of providing a movable grazing incidence mirror on the optical axis, instead of changing the position of the stage, to move the radiation spot by turning the grazing incidence mirror. In this embodiment, a detecting efficiency G(.lambda.) of the radiation with the particular wavelength .lambda. emitted from the radiation source is given by ##EQU2## where I(.lambda.) is the spectrum of the radiation emitted from the plasma radiation source, I max the maximum of I(.lambda.), .alpha.(.lambda.) the convergent efficiency =.intg.R.sub.1 R.sub.2 d.omega. (the integration covers the range of an effective solid angle at which the radiation can be incident on the optical system) of the Walter optical system, R.sub.1 the reflectance at the ellipsoidal mirror 1, R.sub.2 the reflectance at the hyperboloidal mirror 2, t(.lambda.) the spectral transmittance of the X-ray filter 4, and QE(.lambda.) the quantum detecting efficiency of the detector 5. FIG. 9 shows the Walter optical system comprising a Pt reflecting mirror which is favorable for the embodiment and FIG. 10 depicts the wavelength dependence of the convergent efficiency .alpha.(.lambda.) thereof. FIG. 11 diagrams the detecting efficiency G(.lambda.) calculated from Equation (3) with respect to the X-ray microscope constructed by the combination in which the Walter optical system such as is shown in FIG. 9 is adopted as a converging optical system, the laser plasma source radiating radiation with the spectrum shown in FIG. 1B as the X-ray source O, the filter having the spectral transmittance shown in FIG. 6, namely, the Fe filter with a thickness of 0.5 .mu.m, as the X-ray filter 4, and the MCP of the characteristic shown in FIG. 4A as the detector 5. FIG. 12, on the other hand, shows the detecting efficiency G(.lambda.) of an arrangement in which the X-ray filter 4 is removed from the preceding X-ray microscope. In FIG. 11, energy where the detecting efficiency becomes about 10% of the maximum on the low energy side is approximately 230 eV, which is equivalent to 55 .ANG. more or less in terms of the wavelength. Accordingly, the radiation of longer wavelength is cut by the X-ray filter. In FIG. 12, although the diagram may be rather hard to read because the peak of the detecting efficiency G(.lambda.) is cut, the energy where the detecting efficiency G(.lambda.) becomes about 10% of the peak is 100 eV more or less. It will thus be seen that the radiation of longer wavelengths is cut by the X-ray filter 4. SECOND EMBODIMENT FIG. 13 is a view showing an outline of the arrangement of a Walter type soft X-ray scanning microscope which is designed so that in the optical system of FIG. 8, a grazing incidence mirror 6 is disposed on the emergence side of the specimen and the radiation transmitted through the specimen, after being reflected from the grazing incidence mirror 6, is incident on the detector 5 though the X-ray filter 4. The detecting efficiency G(.lambda.) relative to the light of the wavelength .lambda. of this embodiment is given by ##EQU3## where R(.lambda.) is the spectral reflectance of the grazing incidence mirror, which is as shown in FIG. 7. FIG. 14 shows the detecting efficiency G(.lambda.) calculated according to Equation (4) by adding a Pt grazing incidence mirror with a grazing angle of 5.degree. to the example of FIG. 11. As is evident from this diagram, the photon energy where the value of the detecting efficiency G(.lambda.) becomes about 10% of the peak is less than 700 eV and consequently the short wavelength region is cut to the extent of 18 .ANG.. It will thus be seen that the use of the grazing incidence mirror makes it possible to cut the radiation of the short wavelength region compared with the example in FIG. 11. THIRD EMBODIMENT FIG. 15 shows the detecting efficiency G(.lambda.) calculated from Equation (3) in regard to the X-ray microscope constructed by the combination in which the Walter optical system such as is shown in FIG. 9 is adopted as the converging optical system, the synchrotron radiation source emitting the radiation with the spectrum shown in FIG. 1A as the X-ray source O, the filter having the spectral transmittance shown in FIG. 16, namely, an Ni filter with a thickness of 0.4 .mu.m, as the X-ray filter 4, and the MCP of the characteristic shown in FIG. 4A as the detector 5. FIG. 17 depicts the detecting efficiency of the X-ray microscope devoid of the X-ray filter. As is evident from these diagrams, it is noted that the photon energy such that the S/N ratio of the detecting efficiency is held to nearly 10% (that is, such that the detecting efficiency becomes nearly 10% of the peak) comes to more than 300 eV and thus the long wavelength radiation is cut to the extent of 41 .ANG.. FOURTH EMBODIMENT FIG. 18 is a view showing an outline of the arrangement of a soft X-ray scanning microscope for microscopy of biological specimens. The radiation emitted from the X-ray source O and converged through an optical system 7 traverses a window member 9 of a vacuum chamber 8 to be incident on and transmitted through the specimen located in the atmosphere and after passing through a window member 11 of a vacuum chamber 10, is detected by the detector 5. At this time, the detecting efficiency G(.lambda.) of the radiation with the wavelength .lambda. is ##EQU4## where t.sub.1 (.lambda.) is the X-ray transmittance of the window member 9, t.sub.2 (.lambda.) the X-ray transmittance of the window member 11, and AIR(.lambda.) the X-ray transmittance of an atmospheric layer in which the specimen and the stage 3 are located. In this way, where a living body is observed in vivo, it is required that the specimen and the stage 3 are disposed in the atmosphere and, as illustrated in FIG. 19, a microscope body and a detecting section positioned in the vacuum chambers 8 and 10, respectively, are separated somehow from each other by windows. If the X-ray filters are used as the windows, the window members 9 and 11 separating the vacuum from the atmosphere will be secured and unnecessary radiation with low energy can be cut. Moreover, the atmosphere between the microscope body and the detecting section serves as a high-pass filter such that the radiation with low energy is attenuated by the atmosphere per se, as seen from, for example, the spectral transmittance [of N.sub.2 (d=650 .mu.m) constituting principally the atmosphere which is calculated from Equation (1)] shown in FIG. 20. Hence, even if the atmospheric layer exists, the high-pass filter with good performance can be designed. FIG. 21 shows the detecting efficiency G(.lambda.) calculated from Equation (5) in relation to the X-ray microscope constructed by the combination in which the Walter optical system such as is shown in FIG. 9 is adopted as the converging optical system 7, the synchrotron radiation source emitting the radiation with the spectrum shown in FIG. 1A as the X-ray source O, Be filters each having a thickness of 0.3 .mu.m (the spectral transmittance of a 0.6-.mu.m-thick Be filter is as shown in FIG. 22) as the window members (X-ray filters) 9 and 11, a layer with a thickness of 650 .mu.m (whose spectral transmittance is as shown in FIG. 20) as the atmospheric layer, and the MCP of the characteristic shown in FIG. 4A as the detector 5. As is evident from this diagram, it is seen that the region of wavelengths detected with the S/N ratio of more than 10% is reduced to less than nearly 60 .ANG.. FIFTH EMBODIMENT FIG. 23 shows the detecting efficiency G(.lambda.) of the radiation with the wavelength .lambda. in the case where the Pt grazing incidence mirror with a grazing angle of 2.degree. is disposed on the emergence side of the specimen in the X-ray microscope of FIG. 18. As is apparent from this diagram, it is seen that the radiation of the short wavelength region is cut to the extent of 15 .ANG. compared with FIG. 21. SIXTH EMBODIMENT FIG. 24 shows the detecting efficiency G(.lambda.) calculated from Equation (5) with respect to the X-ray microscope in which in FIG. 18, the Walter optical system such as is shown in FIG. 9 is adopted as the converging optical system 7, the synchrotron radiation source emitting the radiation of the spectrum shown in FIG. 1A as the X-ray source O, a 0.3-.mu.m-thick Ni filter (whose spectral transmittance is as shown in FIG. 25) and a 0.3-.mu.m-thick Al filter (whose spectral transmittance is as shown in FIG. 26) as the windows members (X-ray filters) 9 and 11, respectively, a layer with a thickness of 50 .mu.m (whose spectral transmittance is as shown in FIG. 27) as the atmospheric layer, and the MCP of the characteristic shown in FIG. 4A as the detector 5. As is apparent from this diagram, by combining substances different from each other as in the foregoing to construct the window members, the substance transmitting the X-rays to some extent in the low energy region (namely, on the long wavelength side) can also be utilized as the window member if the Al filter with such a thickness is used alone. That is, it will be noted from FIG. 24 that the wavelength region detected with the S/N ratio of more than 10% is reduced to the extent of less than 41 .ANG.. SEVENTH EMBODIMENT FIG. 28 is a schematic view showing the arrangement of a Schwarzschild type soft X-ray scanning microscope. In this case, the radiation radiating from the X-ray source O and converged by a Schwarzschild optical system 12 is incident on and transmitted through the specimen placed on the stage 3 and after passing through the X-ray filter 4, is detected by the detector 5. The Schwarzschild optical system, as depicted in FIG. 29, possesses per se remarkable properties of wavelength dispersion in a soft X-ray region due to the effect of multilayer films applied to the mirror surfaces of individual reflecting mirrors [FIG. 29 indicates the property of wavelength dispersion of the multilayer film alternately laminated with 201 Ni-Si layers which is optimally designed under the conditions of a wavelength of 39.8 .ANG. and an incident angle of 6.degree.]. For the radiation of the long wavelength beyond the vacuum ultraviolet rays, however, the reflectance increases again, so that the X-ray filter 4 is effective to cut such radiation. FIG. 30 depicts the Schwarzschild optical system with a numerical aperture of 0.25 on the specimen side and a magnification of 100.times. which is favorable for this embodiment, and a concave mirror 12.sub.1 and a convex mirror 12.sub.2 constituting the optical system are coated with the multilayer films of the following specification: ______________________________________ 201 Ni--Si layers ______________________________________ Film thickness Concave mirror 12.sub.1 Ni = 9.1 .ANG. Si = 11.1 .ANG. Convex mirror 12.sub.2 Ni = 9.2 .ANG. Si = 11.3 .ANG. ______________________________________ FIG. 31 shows the wavelength (that is, energy) dependence of the convergent efficiency .alpha.(.lambda.) in the Schwarzschild optical system. FIG. 32 shows the detecting efficiency G(.lambda.) calculated from Equation (3) in regard to the X-ray microscope constructed by the combination in which the multilayer film Schwarzschild optical system such as is shown in FIG. 30 is adopted as the converging optical system, the synchrotron radiation source emitting the radiation with the spectrum shown in FIG. 1A as the X-ray source, the filter having the spectral transmittance shown in FIG. 6, namely, a 0.5-.mu.m-thick Fe filter, as the X-ray filter 4, and the MCP of the characteristic shown in FIG. 4A as the detector 5. As is obvious from the diagram, it is noted that the long wavelength radiation such as vacuum ultraviolet rays is cut in comparison with the characteristic of the example (comparison example) making no use of the X-ray filter 4. EIGHTH EMBODIMENT FIG. 34 is a view showing an outline of the arrangement of a zone plate type soft X-ray scanning microscope. In such an instance, the radiation emitted from the X-ray source O and converged by a zone plate 13 (refer to FIG. 2C) traverses a pinhole 14 to be incident on and transmitted through the specimen on the stage 3 and after passing through the X-ray filter 4, is detected by the detector 5. Also in this embodiment, since the long wavelength radiation diffracted by the pinhole 14 and the short wavelength radiation transmitted therethrough adversely affect image formation, the X-ray filter 4 is available. NINTH EMBODIMENT FIG. 35 is a schematic view showing the arrangement of an imaging mode X-ray microscope. The imaging mode, unlike the scanning mode, is such that by forming an image of an object of predetermined size, the image of certain size can be observed without moving the object. This embodiment is designed so that the specimen on the stage 3 is irradiated with the radiation emitted from the X-ray source O and the radiation transmitted through the specimen is imaged by an imaging optical system 15, thereby causing the image of the specimen to be formed through the X-ray filter 4 at the position of the detector 5. A condenser lens may be disposed between the X-ray source O and the specimen, as necessary. TENTH EMBODIMENT FIG. 36 shows a schematic arrangement of the imaging mode X-ray microscope constructed so that in the optical system of FIG. 35, the grazing incidence mirror 6 is disposed at the imaging position of the specimen secured by the imaging optical system and the radiation transmitted through the specimen is reflected from the grazing incidence mirror 6 to enter the detector 5 through the X-ray filter 4. ELEVENTH EMBODIMENT FIG. 37 shows a schematic arrangement of an imaging mode X-ray microscope for microscopy of biological specimens which comprises the optical system of FIG. 35 or 36 incorporated in the vacuum chambers 8 and 10, except for the stage 3. |
claims | 1. A radioprotective unwoven fabric, which isa sheet in which metal fibers are three-dimensionally and randomly stacked, the metal fibers each comprising a metal material having a specific gravity higher than a specific gravity of lead,wherein the metal fibers make up the radioprotective unwoven fabric, and each of the metal fibers consists of metal wire. 2. The radioprotective unwoven fabric according to claim 1,wherein the metal fibers comprise a tungsten wire. 3. The radioprotective unwoven fabric according to claim 2,wherein the metal fibers further comprise a molybdenum wire. 4. The radioprotective unwoven fabric according to claim 1,wherein the metal fibers are only tungsten wires. 5. The radioprotective unwoven fabric according to claim 1, which isfelt. 6. The radioprotective unwoven fabric according to claim 1,wherein each of the metal fibers is not a monofilament. 7. The radioprotective unwoven fabric according to claim 1,wherein each of the metal fibers has a diameter of at most 1 mm and a length of at least 20 mm and at most 80 mm. 8. A fiber product, which isobtained by sewing the radioprotective unwoven fabric according to claim 1. 9. A radioprotective product, which isa quilt including a front cloth, a back cloth, and padding including metal fibers and disposed between the front cloth and the back cloth,wherein the metal fibers are three-dimensionally and randomly stacked,the metal fibers each comprise a metal material having a specific gravity higher than a specific gravity of lead, andthe metal fibers are woolly and make up the radioprotective unwoven fabric, and each of the metal fibers consists of metal wire. 10. The radioprotective product according to claim 9,wherein the metal fibers comprise a tungsten wire. 11. The radioprotective product according to claim 10,wherein the metal fibers further comprise a molybdenum wire. 12. The radioprotective product according to claim 9,wherein the metal fibers are only tungsten wires. 13. The radioprotective product according to claim 9,wherein each of the metal fibers is not a monofilament. 14. The radioprotective product according to claim 9,wherein each of the metal fibers has a diameter of at most 1 mm and a length of at least 20 mm and at most 80 mm. |
|
abstract | A communication network for nuclear plant protection systems includes monitoring and control channels, including a first pair of channels having first and second channels, the first pair of channels communicating through fiber optic data paths with a second pair of channels having third and fourth channels; a plurality of engineered safety feature trains, including first and second trains, the first train communicating directly with the first pair of channels and the second train, the second train communicating directly with the second pair of channels and the first train; a first vital power bus powering the first channel; a second vital power bus powering the second channel, and redundantly powering the first train and first vital power bus; a third vital power bus powering the third channel; and a fourth vital power bus powering the fourth channel, and redundantly powering the second train together with the third vital power bus. |
|
description | 1. Field of the Invention The present invention relates generally to a method and apparatus for testing the steam system of a boiling water reactor (BWR), and more particularly, to a method and apparatus for performing tests on a scale model of the steam system of a scale BWR. 2. Description of the Related Art A reactor pressure vessel (RPV) of a nuclear reactor such as a boiling water reactor (BWR) typically has a generally cylindrical shape and is closed at both ends, e.g., by a bottom head and a removable top head. A top guide typically is spaced above a core plate within the RPV. A core shroud, or shroud, typically surrounds the reactor core and is supported by a shroud support structure. The shroud has a generally cylindrical shape and surrounds both the core plate and the top guide. There is a space or annulus located between the cylindrical reactor pressure vessel and the cylindrically-shaped shroud. Heat is generated within the core and water circulated up through the core is at least partially converted to steam. Steam separators separate the steam and the water. Residual water is removed from the steam by steam dryers located above the core. The de-watered steam exits the RPV through a steam outlet near the vessel top head. Conventional BWRs can experience damage resulting from aero-acoustic loading of the steam dryer during operation. Some conventional BWRs have experienced significant degradation of the steam dryer after operating at power levels in excess of the original licensed thermal power. For example, the aero-acoustic loading of the steam dryer can result in vibration of the steam dryer during operation, which may manifest as unusual wear or in some cases cracking of steam dryer components. Steam dryer damage can prevent the plant from operating at a desired power level. Further, costs (time, money, etc.) associated with repairs to the steam dryer can be significant. Accordingly, it is desirable to be able to predict the nature of acoustic loads expected on a BWR steam dryer. Conventionally, there are several methods used to predict the nature of the acoustic loads expected on BWR steam dryers. These methods include (1) empirical generic load estimates based on in plant operating data from different BWR configurations and different operating conditions; (2) plant specific in-vessel instrumentation programs to measure acoustic loads at various power levels; (3) acoustic circuit models of a plant configuration driven by in-plant data obtained at desired power level from instrument lines or main steam line strain gauges; and (4) Computational Fluid Dynamics (CFD) analyses performed for a plant specific configuration. The empirical generic load estimate is inaccurate and hampered by the fact that the data is obtained from reactor plants other than the plant considered. Thus, no plant-specific information is used to determine if the load estimate is conservative or non-conservative for the plant being considered. This method uses all information available from a BWR steam system in an attempt to produce an acoustic load definition for any plant. The suitability of this method for plant specific applications is difficult to demonstrate. Many utilities complain that the load prediction is too conservative. The Nuclear Regulatory Commission (NRC) complains that the empirical method is not sufficient to differentiate between plants that have experienced steam dryer failures and plants which have not. In some cases, utilities have decided to pursue in-vessel instrumentation programs to measure actual loads on the steam dryer. However, this method is expensive, which makes it an undesirable approach for many utilities. Further, this method is channel limited, meaning that a limited number of instruments may be placed on the steam dryer to obtain operating data. This number is typically around 40 instrument locations. Use of in-vessel instrumentation also requires that the critical regions of the steam dryer be known prior to the time that the in-vessel tests are performed. Further, there is no opportunity to relocate instruments once the reactor is back online and operational. Further, some organizations have created acoustic circuit approximations of a plant specific steam system. These analytical models are effectively transfer functions used to predict acoustic loads on the steam dryer from unsteady pressure data obtained from instrumentation lines attached to the RPV, main steam lines or main steam line strain gauges. The acoustic circuit models and methods cannot be used to predict plant-specific loads unless data is obtained from the plant at the operating conditions of the desired acoustic load conditions. The unsteady pressure data is obtained at the end of instrumentation lines containing both liquid water and steam, and thus exhibits significant thermal gradients. The condition of the instrument lines makes an accurate prediction of the unsteady pressure in the steam lines difficult to verify. Additionally, use of main steam line strain gauges provides data that contains mechanical signals introduced into the desired acoustic pressures by main steam line vibration; thus a large number of strain gauges and significant signal processing care must be taken to apply this method. In other words, prediction of the system response in one portion of the system using the response from another portion of the system, without a complete understanding of the location and characteristics of all acoustic sources, makes it difficult to verify the load predictions obtained with this method. Some CFD analyses have been performed in an effort to understand the loading expected on the steam dryer. However, the lack of empirical data to benchmark this approach, the physical size of the model required to approximate the steam system, and the computational resources required to make an accurate prediction of unsteady pressure oscillations on the steam dryer prevent this approach from being practical. This technology is not yet mature enough to be used for an industrial problem of the complexity exhibited by the BWR steam system. An example embodiment of the present invention is directed to a system for predicting acoustic loads expected on a BWR and components thereof. The system may include a BWR scale model, a test fixture configured to generate air flow in the scale model, and one or more measurement devices for monitoring the behavior of the system. Another example embodiment of the present invention is directed to a method of predicting acoustic loads expected on a BWR steam dryer. The method includes providing a scale model of the BWR to be evaluated, generating airflow through the scale model, and monitoring system behavior of the scale model to predict how acoustic loads affect plant operation at the BWR being evaluated. Another example embodiment of the present invention is directed to a method of predicting acoustic loads expected on BWRs. The method includes using scaling relationships derived from dimensional analysis to convert data obtained from a BWR scale model to plant conditions. Example embodiments of the present invention as will be described in further detail hereafter are directed to a system and method for determining acoustic loads in the main steam system of a BWR. More specifically, example embodiments of the present invention are directed to performing tests on a scale model of the steam system of a BWR to determine acoustic loads which may occur during operation. FIG. 1 is a schematic of an example BWR scale model acoustic test system 100. FIG. 2 illustrates an example test fixture 110, and FIG. 3 illustrates an example of model main steam lines 190 connected to the BWR scale model 120 of the BWR scale model acoustic test system 100 (as depicted in FIG. 1). The BWR scale model acoustic test system 100 is based in part on a premise that the system acoustics are governed by system geometry and fluid properties. Accordingly, characteristic modes of the scale model acoustic test system 100 can be related to those of a reactor plant to be evaluated through appropriate scaling relationships derived using dimensional analysis of the governing fluid equations. These relationships are obtained from an engineering first principles approach. Significant factors to be considered in design and operation of the scale model include preservation of the fluid Mach number in the model and plant and maintaining a consistent geometric scale. In other words, if all aspects of the BWR and main steam line scale models 120 and 190 are built to the same arbitrary scale and the model air flow Mach number is the same as the plant steam flow Mach number, then the normal acoustic modes in the BWR and main steam line scale models 120 and 190 will be proportionately related to the normal acoustic modes in the plant being evaluated through the following relationship in expression (1): f Plant f Test = ( d Test D Plant ) ( C Plant C Test ) ( 1 ) Similarly, the model pressures may be related to the plant pressures by expression (2): P Plant P Test = ( P Plant P Test ) ( C Plant C Test ) 2 ( 2 ) Accordingly, scaling relationships derived from dimensional analysis may be used to convert data obtained from a model to plant conditions. The BWR scale model acoustic test system 100 may include a test fixture 110 and a BWR and main steam line scale model 120 and 190. The test fixture 110 may include components for generating air flow and routing the air flow to the BWR scale model 120. As shown in FIG. 2, test fixture 110 may include a blower 130, inlet piping 140, a flow meter 150 and a muffler 160. The blower 130 is configured to provide air flow, which may be routed through the inlet piping 140 into the BWR scale model 120. The air flow generated by the blower 130 is used to simulate flow in the BWR scale model 120 (as depicted in FIGS. 1 and 3) similar to the flow generated in an operating BWR that results in acoustic loads, which as discussed above could result in a variety of problems. An example blower 130 could be an electrical centrifugal blower such as a Sonic 70 Centrifugal Blower The inlet piping 140 connects the blower 130 to the BWR scale model 120 (as depicted in FIGS. 1 and 3). The inlet piping 140 may be composed of various sections that may be tailored (e.g. the size and material may vary) depending on the environment and characteristics of the components (e.g., blower 130, flow meter 150, BWR scale model 120, muffler 160, etc.) that the inlet piping 140 connects together. The flow meter 150, which may be embodied as a venturi flow measurement device, and muffler 160 may be located between the blower 130 and the BWR scale model 120. The flow meter 150 may be used to measure the system air flow. The flow meter 150 measurements may be monitored, recorded, and/or used as part of a control mechanism for the BWR scale model test system 100. For example, measurements from the flow meter 150 may be used to control the blower 130. Further examples of measurement devices, locations thereof, and uses thereof will be described later. The muffler 160 may be used to substantially isolate the BWR model 120 from noise introduced into the system by the test fixture 110. For example, noise generated by the test fixture 110 may include the blower 130 Vane Passing Frequency (VPF), organ pipe modes associated with inlet piping 140, etc. The muffler 160 may be an absorptive muffler such as used in Heating Ventilation and Air Conditioning systems, for example. A method of predicting acoustic loads expected on a BWR steam dryer may include providing a BWR scale model 120 to be evaluated and generating airflow through the BWR scale model 120. System behavior of the BWR scale model 120 may be monitored to predict how acoustic loads affect plant operation at the BWR being evaluated. Monitoring may further include monitoring one or more of pressure oscillations in the BWR scale model test system 100, total air flow of the BWR scale model test system 100, absolute static air pressure in the BWR scale model test system 100, and air temperature in the BWR scale model test system 100, and/or adjusting one or more adjustable components (e.g., pipe length adjuster 200, relief valve inlet length adjuster 300, etc.) recording measurements, and/or further adjusting one or more adjustable components and recording additional measurements, thereby obtaining parametric data for the BWR scale model test system 100. As shown in FIG. 4, the BWR scale model 120 may include a scale version of a RPV 170, a steam dryer 180 and RPV top head 175. The scale to be used for the BWR scale model 120 may be determined by the flange diameter at the outlet of the muffler 160, for example. The material selected to fabricate the BWR scale model 120 should prevent air from leaking through the steam dryer 180 surfaces, the RPV 170 and the top head 175. Accordingly, any material capable of withstanding about two to five pounds per square inch of internal pressure (gauge) may be suitable for fabricating the BWR scale model 120. Example materials for the BWR scale model 120 include acrylic for the RPV 170 and nickel plated polymer for the steam dryer 180. The top head 175 of RPV 170 may be stainless steel. The model main steam lines 190 may also be stainless steel. These are merely illustrative of the different components of the BWR scale model 120 and model main steam lines 190 and should not limit the invention in any way. FIG. 5 is an example BWR scale model 120 including model main steam lines 190 attached to the BWR scale model 120. The model main steam lines 190 may connect the one or more turbine inlets 500 to the BWR scale model 120. The model main steam lines 190 may include turbine valves 400 (e.g., turbine stop valves, turbine control valves, etc.) pipe length adjusters 200, equalizing header 900, main steam isolation valves 800, flow meters 150, and safety and relief valves 700. The example model components described above may function to control the characteristics of the steam system. However, the model valves (e.g., turbine valves 400, pipe length adjusters 200, equalizing header 900, main steam isolation valves 800, flow meters 150, and safety and relief valves 700) may or may not have the same function as valves included in an operational BWR. For example, the model safety and relief valves 700 may be used only to model an acoustic cavity of an operational BWR and not designed to fulfill an overpressure protection function in a BWR scale model acoustic test system 100. The model main steam lines may be designed with unions such that the system may be disassembled at various locations in the model main steam lines 190. This allows various components to be removed from the system enabling the model to be used for identification of the aero-acoustic sources. Further, the system may be designed so that any valve in the model main steam lines 190 (e.g., main steam isolation valves, turbine stop valves, turbine control valves, etc.) may be included with an adjustable component to investigate its effect on the system behavior. The pipe length adjusters (e.g., pipe length adjusters 200, relief valve inlet adjusters 300, etc.) may be used to adjust the characteristics of the steam system connected to the BWR scale model 120. FIG. 6 illustrates an example embodiment of a pipe length adjuster 200 that may be used in the present invention. In FIG. 6, the pipe length adjuster 200 is configured to increase and/or reduce the overall path length of the steam lines connected to the scale model BWR 120. As shown in FIG. 6, pipe length adjuster 200 may include a first pipe section 210, a second pipe section 220, a pipe length adjusting device 230, a length adjustment setting device 240, a first bracket 260, second bracket 270, and O-rings. The first pipe section 210 may be configured for insertion into the second pipe section 220 of the pipe length adjuster 200 or vice versa. The pipe length adjusting device 230 may be connected to the first pipe section 210 and the second pipe section 220. Pipe length adjusting device 230 is configured to insert and retract the first pipe section 210 to and from second pipe section 220, thereby changing the path length from point A to point B pipe length adjuster 200, as shown in FIG. 6. The length adjustment setting device 240 may provide a read out to the user representing the length adjustment. The length adjustment setting device 240 includes reference lines 250 used to determine the length to be adjusted by the pipe length adjusting device 230. As the pipe length adjusting device 230 is adjusted to increase the distance between first bracket 260 and second bracket 270, the amount of first pipe section 210 that is inserted into the second pipe section 220 is reduced, thereby increasing the path length between point A and point B. As shown in FIG. 6, the reference lines 250 included on the length adjustment setting device 240 may be used in connection with first bracket 260 to determine the amount that path length between points A and B is increased. O-rings may be used to seal the interface between 210 and 220 to prevent air from leaking out of the system during operation. FIG. 7 is an example of a model valve adjuster according to an example embodiment of the present invention. In FIG. 7, the model relief valve inlet length adjuster 300 is illustrated in both a fully inserted and fully retracted position. The relief valve inlet length adjuster 300 may include a valve pipe 310, valve insert 320, valve insert top 330, valve length setting device 340, valve housing 350, and valve seat 360. The relief valve inlet length adjuster 300 may be configured to adjust the effective length of the relief valve inlets. For example, the valve insert 320 may be configured to be adjustably inserted into the valve pipe 310, thereby varying the effective length of the relief valve. Length adjustment is obtained by turning valve insert top 330 which is attached to a threaded shaft 320 and valve seat 360. As 330 is turned, 320 threads either up or down into the model valve housing 350 which causes the valve seat 360 to move into or out of the valve pipe 310. An O-ring seal 370 may prevent air from leaking between the valve pipe 310 and the valve seat 360. Valve length adjustment setting device 340 may be used in connection with the valve insert top 330 to determine the effective length of the relief valve. As the valve insert top 330 is turned and the valve seat 360 moves into or out of the valve pipe 310, the length of the valve cavity is read from a scale on the valve length setting device 340. FIG. 8 is an example scale model steam dryer with measurement devices 50 mounted thereon. The measurement devices 50 may be embodied as one or more of pressure, temperature, flow, etc. to measure a variety of characteristics. While the measurement devices 50 are illustrated as being located on the steam dryer 180, it should be noted that measurement devices 50 may located on various components of the BWR scale model 120, main steam lines 190, and locations on the test fixture 110. The measurement devices 50 can be located anywhere in BWR scale model acoustic test system 100 where it is desirable to obtain data. Further, because ambient air is used as the test fluid it is easy to add and remove sensors because a sensor location can be easily added or removed by adding or plugging a sensor hole. It will be evident to one of ordinary skill in the art that the measurement devices could be embodied by any suitable device configured to measure one or more desired characteristics. For example, one or more of the measurement devices 50 may be configured to measure pressure oscillations of the steam dryer model; and/or one or more of the measurement devices 50 may be a microphone (not shown) mounted such that a sensor diaphragm (not shown) of the microphone is flush with the outer surface of the steam dryer 180 to measure unsteady pressure oscillations; one or more of the measurement devices 50 may be a pressure transducer configured to monitor the absolute static air pressure in the steam dryer 180; and one or more of the measurement devices 50 may be a temperature sensor configured to monitor the air temperature of the steam dryer 180. Further, the measurements of the measurement devices may be recorded, monitored, and used to control the BWR scale model acoustic test system 100. A data acquisition system may be used to record, monitor and analyze time history data acquired from one or more of the measurement devices. For example, the time history data measured from the model steam dryer may be used to form steam dryer fluctuating loads. Further, time history data measured from other locations in the model steam system can be used to identify aero-acoustic source locations and excitation mechanisms. The example apparatus and methodology may allow utilities to obtain plant-specific data, may be designed and fabricated for less money than conventional plant-specific test programs, and may allow more sensor locations than are possible for existing in-vessel test. Further, use of the example BWR scale model acoustic test system 100 may prevent a plant from operating at a power level for which loads are not currently known. This is because the test can be completed using the BWR scale model acoustic test system 100. Using the conventional acoustic circuit model approach, the plant power level must be raised to obtain data. Therefore, if damaging loads exist at the adjusted power level, structural fatigue of the actual BWR may occur resulting in necessary repairs and/or replacement of components. The example BWR scale model acoustic test system 100 may also permit parametric studies to be performed, thus enabling a utility to predict possible problems and then design acceptable repairs, if necessary, prior to operating a plant associated with the scale model at potentially damaging power levels. The example embodiments of the present invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as departure from the spirit and scope of the example embodiments of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. |
|
claims | 1. An apparatus comprising:a post that intersects an ion beam to create a shadow;one or more camera systems to capture at least one image of the ion beam including the shadow; anda control system coupled to the one or more camera systems to control an angular uniformity of the ion beam in response to the at least one image of the ion beam including the shadow. 2. The apparatus of claim 1, wherein the one or more camera systems comprises one or more moveable minors. 3. The apparatus of claim 1, wherein the one or more camera systems are positioned at various positions along an ion beam path. 4. The apparatus of claim 1, wherein the one or more camera systems comprise at least one swivel camera. 5. The apparatus of claim 1, wherein the control system further comprises a dose profiler to provide information to one or more ion implantation components in at least one of a feedback loop and a feedforward loop. 6. The apparatus of claim 1, wherein the one or more camera systems comprises at least one color filter to enhance the image of the ion beam. 7. The apparatus of claim 6, wherein the enhanced image of the ion beam provides at least one of the following additional information about ions in the beam: type, density, and charge. 8. The apparatus of claim 1, further comprising one or more gases to enhance the image of the ion beam. 9. A method comprising:driving a post to intersect an ion beam to create a shadow;capturing at least one image of the ion beam including the shadow with one or more camera systems; andcoupling a control system to the one or more camera systems to control an angular uniformity of the ion beam based on the at least one image of the ion beam including the shadow. 10. The method of claim 9, wherein the one or more camera systems comprises one or more moveable mirrors. 11. The method of claim 9, wherein the one or more camera systems are positioned at various positions along an ion beam path. 12. The method of claim 9, wherein the one or more camera systems comprise at least one swivel camera. 13. The method of claim 9, wherein the control system further comprises a dose profiler to provide information to one or more ion implantation components in at least one of a feedback loop and a feedforward loop. 14. The method of claim 9, wherein the one or more camera systems comprises at least one color filter to enhance the image of the ion beam. 15. The method of claim 14, wherein the enhanced image of the ion beam provides at least one of the following additional information about ions in the beam: type, density, and charge. 16. The method of claim 9, further comprising inserting one or more gases to enhance the image of the ion beam. 17. A downloadable, computer-readable media comprising code to perform the acts of the method of claim 9. |
|
description | This application claims priority of U.S. Provisional Application Ser. No. 60/569,798, filed on May 10, 2004, the disclosure of which is herein incorporated by reference. 1. Field of the Invention This invention deals with materials and techniques for shielding of neutron and gamma radiation emitting together from radioactive waste sources such as transuranic and high-level wastes. It is based on specially formulated composite materials and techniques. In particular, this invention relates to different composite materials and admixtures, and their multifaceted application to safe handling, containerization and management of neutron and gamma emitting high-level, transuranic and low-level radioactive wastes and materials, as well as to decontamination and decommissioning of radioactively contaminated facilities. Owing to their significant capacity for attenuation of neutron and gamma radiation, these technologies relates to protecting health and environment from exposure to harmful radiation emitted by nuclear wastes and materials. 2. Description of the Related Art Radioactive wastes, owing to temporal decay and fission of radionuclides, emit alpha, beta, gamma and neutron radiation, of which neutron and gamma radiation are extremely harmful. Radioactive wastes can be solids, liquids and sludge, and these are of three types: A) High-level radioactive wastes contain gamma emitting long-half life radionuclides, such as plutonium (Pu-238, Pu-239, Pu-240 and Pu-242) and uranium (U-234, U-235, and U-236). High-level wastes include spent (or used up) nuclear fuel and wastes from commercial and defense related nuclear reactors resulting from reprocessing of spent nuclear fuel. Most spent nuclear fuel in the United States is currently located in pools of water, at nuclear generating plants across the country, to protect workers from radiation. Spent fuel also is stored in large concrete casks. High-level wastes are also generated from reprocessing of fuel from weapons production reactors to obtain materials to make nuclear weapons. These wastes are primarily in liquid and sludge forms. B) Transuranic (TRU) wastes contain such radionuclides as californium Cf-249-252), americium (Am-241, 242 and 243), curium (Cm-242-250), neptunium (Np-235 and 236), plutonium (Pu-236-242) and berkelium (Bk-247 and 250). Generally, TRU wastes are made up of solids or liquids and contain radionuclides that have more than 20-year half-lives. TRU wastes are generated by defense nuclear research and development activities, such as development and fabrication of nuclear weapons. TRU wastes are usually classified as “contact-handled” (CH) and “remote-handled” (RH) wastes. These are highly radioactive with high radiation flux of neutrons and gamma rays, as well as alpha rays. Often, these wastes are mixed with hazardous organic and inorganic wastes, and therefore, they are also called as transuranic mixed wastes. C) Low-Level radioactive wastes do not include either high-level or transuranic waste materials. Most low-level wastes (classified by the NRC as A, B or C) emit relatively low-levels of radiation from radioactive decay of short half-life radionuclides, such as strontium-90, cesium-137, krypton-85, barium-133 and beryllium-7 and 10. Generally, these wastes have radioactivity that decays to background levels in less than 500 years and about 95 percent of the waste decays to background levels in about 100 years. Low-level radioactive wastes are generated by commercial and university laboratories, pharmaceutical industries and hospitals, as well as nuclear power plants. Low-level wastes include both solid and liquid wastes. High-level wastes are very radioactive, which emit extremely harmful gamma (like x-rays) and neutron radiation. RH-TRU wastes are primarily neutron and secondary gamma radiation emitters, CH-TRU wastes are also very radioactive, which emit harmful alpha radiation, as well as neutron radiation. In order to handle these wastes, heavy concrete and/or lead shielding materials are required and high energy flux energy radioactive wastes, such as RH-TRU wastes, are robotically handled despite the concrete/lead shielding. One of the main radiation hazards posed by this waste is through exposure and inhalation or ingestion. During handling and management, inhalation of or exposure to certain transuranic wastes, such as plutonium in very small quantities, could deliver significant internal radiation doses. Exposure to gamma and neutron radiation, as well as alpha and beta radiation, associated with these wastes can induce chronic, carcinogenic and mutagenic health effects that lead to cancer, birth defects and death. However, thousands of tons of both solid and liquid, as well as sludge radioactive wastes have been generated in the past and they will continue to be generated in the future by commercial/private industries and government agencies. Unless they are safely and cost-effectively shielded, managed and disposed, these wastes may pose serious health and economic consequences. Generally, alpha radiation can be easily shielded by paper, skin or clothes, where as beta radiation can easily pass through paper, skin or clothes but it will be blocked by a thin layer of plastic, aluminum foil or wood. In contrast, gamma and neutron radiation is very penetrating, and neutron radiation is more penetrating than gamma. Gamma radiation can be blocked by heavy shielding materials such as thick-concrete, lead, steel and Ducrete (depleted uranium mixed with concrete); whereas neutron radiation can penetrate through heavy metal shielding, only specially engineered and chemically formulated high density concrete blocks and lead can shield penetration of neutron radiation from its source. High-level radioactive wastes are currently stored at nuclear power plants and DOE facilities across the country. Similar wastes have been generated by the Department of Defense also. Department of Energy's Office of Civilian Radioactive Waste Management (OCRWM) is charged with identifying and developing a suitable site for deep geologic disposal of these wastes. The OCRWM is currently conducting research and testing to determine the suitability of the Yucca Mountain, Nev. site for long-term safe disposal of these wastes. Transuranic wastes are destined to be disposed into an already established geologic repository at WIPP site in Carlsbad, N. Mex. Class A and B low-level radioactive wastes are currently disposed in isolated shallow burial ground; whereas greater than class C waste low-level waste use deep geologic disposal in specially licensed facilities. Management and disposal of high-level, transuranic and low-level radioactive wastes are very risky. Radioactive waste management also includes decontamination and decommissioning of contaminated sites. Management activities, prior to disposal, include handling, solidification of liquid wastes, loading, storage, radiation monitoring, reloading of wastes into transportable containers, and transport of waste containers to long-time safe disposal sites. Storage, transportation and disposal of radioactive wastes are a growing problem in the United States and abroad. Many U.S. commercial power plants do not have sufficient existing capacity to accommodate future spent nuclear fuel wastes, and much of the DOE's HLW and TRU wastes are currently located in unlicensed storage structures that need to be upgraded or replaced. Therefore, there is a strong need for improved radiation shielding materials and techniques for waste container systems so that the wastes can be safely stored, transported and disposed. Currently, two main methods are used for storage of commercial power plant nuclear waste: wet and dry. In wet storage, the waste is immersed in a lined, water-filled pool, which shields the radiation and removes radioactive heat aided by an active system. Wet storage is intended for a period of five years after waste immersion, and thereafter, it is stored in dry storage casks or vaults constructed out of concrete, which shield the radiation. Generally, the design and manufacturing of waste containment systems for the dry storage are governed by a number of governing factors, such as 1) shielding effectiveness, 2) structural integrity and durability, 3) thermal performance, 4) ease of handling and transportation, 5) high volume waste loading, 6) cost-effectiveness, and 7) health and environmental protection. Current radiation shielding and waste containment technologies are based on low or high density concrete, lead, carbon and stainless steel, borated resins, polymers and other additives, as well as glass vitrification and ceramic calcinations. However, these materials and processes have limitations and they do not fully satisfy the above-mentioned governing factors of waste containment systems. Some examples of these limitations are as follows: The above mentioned shielding materials or additives and technologies do not meet the shielding requirements of radiation waste sources consisting of a flux of mixed radiation types of various energy levels and the secondary radiation effects (e.g., emission of secondary gamma radiation due to inelastic collision or capture of emitted neutrons) that are induced within the shields as a result of interaction of the initial flux with certain atoms in the shield itself. While thin liners of lead, used in waste storage casks and containers, are effective for shielding gamma radiation, they are not very effective in shielding neutron radiation. When applied as a part of a neutron particle shielding, lead has an extremely low level of neutron absorption, and hence, practically no absorption of secondary gamma radiation. For neutron shielding, thicker lead liners are required, which not only reduces the space for waste loading in the containment systems but also makes the containment systems heavy for handling and transport. Consequently, lead technology can be costly. If the shield material has a high rate of neutron capture, it will over time become radioactive, and sharply reduce its effectiveness as a shield material, consequently, their subsequent handling and disposal will be a problem. In addition, lead can be leached and will contaminate the environment, potentially posing toxic health effects. Although some containment systems have used concrete liners, castings or grouts as safe storage of radioactive wastes, they are not very effective in shielding high energy flux of neutron and gamma radiation, unless significantly thick high density concrete liners in conjunction with metal liners are used. Generally, concrete liners are not very efficient in shielding neutron radiation because, concrete products have low hydrogen atomic density, which is the measure of a materials ability to shield neutron radiation. In addition, concrete-based containment systems generally lack mobility, and therefore, limit the volume of radioactive wastes that can be stored in a given limited space due to the high density and volume concrete required to obtain the necessary shielding properties. As a result, the application of this technology to waste containment systems can be uneconomical. In addition, chemical and mechanical properties of concrete can be degraded due to alkali-silica-reaction (at <5 pH) and at elevated radioactive temperatures, resulting in shrinkage and cracking and consequential attenuation of its shielding capacity. Similarly, the bonded water in cement grouts tends to decrease with time due to radioactive heat, causing increase in porosity and reduction in shielding capacity. Traditionally, Portland cement-based grouts have been used for solidification/encapsulation of hazardous and low level radioactive wastes. However, this technology has shown to be effective only in situations where the salt loading is relatively low (i.e. <10%) and when the total organic content of the waste is below 3%. Given the above limitations, use of concrete based technology for solidification of liquid wastes and storage of high-level and transuranic wastes may be inappropriate. Borated stainless steel has been used in the radioactive waste storage containers; however, this material, owing to its weak mechanical/metallurgical properties, has the potential for cracking and breaking, rendering weak shielding capacity over a long period of time. Further, the bombardment of borated stainless steel by the neutrons emitted by the wastes can reduce the steel's shielding efficacy, making it an unsuitable material for long term safe storage of high-level and transuranic wastes. In the case of vitrification technology, there is significant uncertainty in effectiveness of in-situ or ex situ vitrification technology for solidification of liquid wastes with variable compositions and pH conditions, as well as for volatile components. In addition, glass production and chemical durability of vitrified glass is unknown. In glass production, the largest uncertainties are related to the reliability and safety of the high-temperature melting process behavior of the glass during the first and second glass pours, such as the effects of glass fracturing on chemical and physical durability, and the significance of mixed waste-constituents crystallization. Owing to rapid cooling rate and high viscosity of oxide and silicate, waste constituents/molecules cannot move sufficiently to be uniformly incorporated into crystalline structure of the glass. Furthermore, vitrification may produce secondary wastes and management of such wastes would be an issue to contend with. In terms of chemical durability of glass, very little is known about the type and conditions of formation of colloids and less about their ability to bind up and transport the waste constituents. Corrosion of vitrification melt materials from acidic wastes is a key issue that must be dealt with. In an attempt to reducing the thickness of concrete shield while maintaining the desired long-life of the waste containers, Suzuki et al (U.S. Pat. No. 4,687,614) taught a three layered structure comprising a metallic vessel with a reinforced concrete lining as an inner layer, and polymerized and cured impregnated layer as intermediate layer between the inner concrete layer and the outer metallic layer. However, this and similar other attempts have been unsuccessful in achieving the desired reduction in thickness. In addition, this three layered system was found to be not very effective in shielding high energy flux of neutron and gamma radiation. Kronberg (U.S. Pat. No. 5,334,847) teaches an alternate shielding system using depleted uranium core for absorbing gamma rays with a bismuth coating for preventing corrosion, and alternatively having a gadolinium sheet positioned between the depleted uranium core and the bismuth coating for absorbing neutrons. However, this shielding system does not reduce the undesirable density and thickness of the shielding to maintain the desired capacity for shielding of high flux neutron and gamma radiation. In addition, this shielding system is neither efficient in avoiding the depleted uranium corrosion nor assuring the durability of the shielding system over desired long-life, particularly at elevated temperatures. Owing to the uranium corrosion, this system is considered inefficient for shielding of neutron and gamma radiation fluxes. In addition, corrosion can cause leaching and release of uranium from the concrete in the form of uranium bicarbonate and uranium tri-carbonate complexes, causing health and environmental problems. Furthermore, this system is relatively expensive. Yoshihisa, in Japanese Patent Document No. 61-091598, teaches utilization of depleted uranium and uranium oxide aggregate containing concrete for radiation shielding. While this system has the potential for reducing the thickness of radiation shielding for gamma rays, it has serious problems of concrete degradation and maintaining the desired long-life of the system, particularly at elevated radioactive temperatures. Tensile and compressive strengths of concrete are seriously compromised by addition of the uranium aggregate to the concrete. Quapp et al. (U.S. Pat. Nos. 5,786,611 and 6,166,390) disclose radiation shielding of containers for storing spent nuclear fuel waste. These containers are formed from concrete product with stable uranium oxide aggregate and a neutron absorbing material. The neutron absorbing materials described are B2O3, HfO2 and Gd2O3. In addition, the concrete shielding composition of this invention requires including reinforcing materials. These may include, steel bars, fillers and strengthening impregnates, such as steel fiber, glass fiber, polymer fiber, lath or steel mesh, creating a complex system of shielding. However, owing to the uranium corrosion problem, this concrete shielding products along with their additives are not efficient for radiation shielding and they do not contribute to the long-time durability of waste containers, especially at elevated temperature. Corrosion can cause leaching and release of uranium from the concrete in the form of uranium bicarbonate and uranium tricarbonate complexes, causing health and environmental problems. Further, this type of shielding containers does not reduce the undesirable density and thickness of the shielding to maintain the desired capacity for shielding of high flux neutron and gamma radiation. In addition, cooling of concrete surfaces is required during radioactive waste storage to further the length of the concrete to avoid high radioactive temperature, without which, the concrete system could degrade and allow for emission of radiation. Generally, concrete systems lack mobility and limit the volume of radioactive wastes to be stored in a given space due to great concrete thickness and density required to obtain the necessary shielding properties. The above mentioned shielding materials and systems, using single component or dual component materials provide only limited shielding capacity under a given set of density, thickness and configuration of shielding materials and containers. Generally, they do not offer the desired shielding of both neutron and gamma emitted from the same waste source, particularly the transuranic waste source or its containers. These materials and techniques suffer from the problems of offering desired shielding efficiency, long-term durability, health and environmentally safety. In addition, the systems are complex and made up of multilayered dense and thick layers of concrete admixed with depleted uranium, lead and stainless steel, which reduce the volume of containers/casks for radioactive waste loading. Consequently, more containers/casks have to be built to store or transport a given volume of radioactive wastes; therefore, those containment systems are not cost-effective. Furthermore, high density containment systems are not be easily mobile and are very difficult to handle, in addition to being unsafe. In general, the prior art uses many kinds of additives to meet the shielding requirements of a particular radiation spectrum and energy flux involved, but they are not effective in meeting the desired shielding requirements of radiation fluxes of different energy levels arising from complex, uncharacterized radioactive waste sources. This situation may be further complicated when secondary radiation effects are induced as a result of interaction of initial radiation flux with certain atoms in the waste materials, as well as within a given shielding material. Therefore, it is necessary to formulate admixture composite materials that offer optimal total radiation shielding capacity to cater to the needs of such complexities. Accordingly, it is desirable and advantageous to provide improved materials and simple techniques that offer a better, more durable and cost-effective radiation shielding and waste containment systems than those mentioned above. Improved materials and techniques shall enhance the safety of handling, storage, transportation, long-time containment of radioactive wastes, as well as protect human health and environment. In addition, it is desirable for such materials and techniques to have such attributes as a) applicable to shield multi spectral and energy flux radiation, b) ease of application, c) easy to handle variations in waste characteristics without the need for separation of incompatible wastes that do not generate secondary waste streams, d) will not expose workers to any significant and unnecessary amount of radiation and e) exhibit superior performance over regulatory long times. This invention pertains to multi-component composite materials and techniques that provide improved capabilities for shielding highly penetrating, harmful neutron and gamma radiation, as well as alpha and beta radiation emitted by high-level, transuranic and low level radioactive wastes. These radiation shielding composite materials offer better and more cost-effective shielding capabilities than those of the conventional concrete, lead and steel shields. This invention is drawn to a combination of elements that uses selected naturally occurring minerals and materials which result in this combination of elements producing synergistic and unexpected shielding effects, which is exclusively a result of such use. The objectives of this invention are as follows: a) It is the intent and premise of this invention to formulate and offer multi-component composite materials in different permutations and combinations, as well as in various proportions and grain size to provide a total cumulative capacity for shielding of neutron and associated gamma radiation of variable fluxes and energies, and which exceeds the capacity of conventionally used shielding materials or the materials known in the prior art. b) To provide combinatorial radiation shielding compositions admixed with different carrier grout matrices, which will provide a significantly improved radiation attenuation. These radiation attenuation compositions are designed for use in various management aspects of radioactive solid, liquid and sludge wastes, as well as radioactive wastes mixed with hazardous organic and inorganic wastes. The multifaceted use includes such applications as inner and over packs and liners of radioactive waste containment systems, as corrosion-resistant coatings on the surfaces of casks and containers used for storage, transport and permanent disposal of radioactive wastes, as well as coatings on the drip shields in radioactive waste repositories, as prefabricated structures and liners for waste storage vaults and as decontamination of radioactively contaminated equipment/facilities. c) To provide formulated materials and compositions in a predetermined proportion for use in waste containment systems that will allow for minimum thickness of liners or inner and over packs of the waste containment systems while achieving desired shielding of both neutron and gamma radiations, wherein the reduction in thickness of shielding liners or inner and over packs will allow for enhanced container volume for more waste loading. d) To provide significant improvements over conventional or known art materials and techniques by offering effective radiation shielding, safe radioactive waste management, ease of implementation or application, cost-effectiveness, and durability. e) To provide specially designed materials and compositions for water tight grouting and coating of underground storage metal tanks, containers and radioactive beryllium blocks for eliminating water infiltration and metal corrosion, diffusion of radioactive gases such as radon and iodine, and for resisting the damage from high energy flux of neutron and gamma radiation. f) To provide improved materials and techniques that can be used for solidification, encapsulation and immobilization of radioactive liquid and sludge wastes. g) To improve materials and techniques that can be cost-effectively applied to safe management of decontamination and decommissioning of radioactively contaminated facilities and equipment. h) To formulate materials and techniques for safe and cost-effective management of uranium and thorium mine tailings and mill wastes. This invention deals with materials and techniques for improved shielding of neutron and gamma radiation emitting together from radioactive waste sources such as transuranic and high-level wastes. It is based on specially formulated multi-component composite materials and techniques. This invention is drawn to a combination of elements that uses selected naturally occurring minerals and materials which results in this combination of elements producing a synergistic and expected shielding effects, which is exclusively a result of such use. In particular, this invention relates to various composite materials and modified carrier grout admixtures and techniques for formulating and producing final Admixture Composite Materials, which will provide enhanced radiation shielding capacity and multifaceted application to safe handling, containerization and management of neutron, gamma, beta and alpha emitting high-level, transuranic and low-level radioactive wastes and materials, as well as to decontamination and decommissioning of radioactively contaminated facilities. The shielding materials and techniques of this invention provide more desirable and advantageous attributes than those available in the prior art. These attributes include a) unparalleled radiation shielding capacity for both neutron and gamma radiation, b) shielding of multi-spectral and fluxes of different radiation energy levels, c) easy to handle variations in waste characteristics without a need for segregation of incompatible wastes or without generation of secondary wastes, d) enhance the safety of handling, storage, transportation and long-time containment of radioactive wastes, without workers' exposure to any unsafe amount of radiation, e) durability, f) ease of application and f) cost-effectiveness. Description of this invention is provided below to enable those of ordinary skill in the art to practice this invention for using the formulated multi-component composite materials and techniques for shielding neutron and gamma radiation, as well as alpha and beta radiation emitted from complex radioactive waste sources. Since the relative penetration capacity of alpha and beta radiation is significantly lower than that of gamma and neutron, any composite materials formulated and engineered for shielding of neutron and gamma radiation will undoubtedly shield alpha and beta radiation fluxes. Generally, the selection of shielding materials is depended upon many factors, such as desired shielding of radiation levels, ease of heat dissipation, resistance to chemical degradation and radiation damage, desired thickness, density and engineering properties, uniformity of shielding capability, ease of application, multifaceted application, cost-effectiveness and long time durability. Depending on the type of application, selected multi-component composites are formulated by using combinatorial percent proportions of mineralogical compounds and materials for providing effective shielding of the full spectrum and flux of neutron and gamma radiation, as well as alpha and beta radiation. Neutron attenuation is accomplished by the selected composite materials mainly through elastic and inelastic scatter by reducing the energy of the neutrons until they are absorbed (neutron capture) in the shielding materials. During the inelastic scattering, secondary gamma radiation is generated, which is also attenuated by certain components of the formulated composite materials. The embodiments of multi-component shielding materials, as well as the carrier grout matrices for attenuation or shielding of both neutron and gamma radiations are described below. The scope of this invention encompasses the full ambit of the claims and all available equivalents. For combined shielding of neutron and gamma radiation of different energies and fluxes, desired naturally occurring minerals and materials are selected and proportionately combined to form a multi-component composite material that will synergistically provide a desired optimal radiation shielding capacity. The proportions may vary from 0-100 weight percent. These are made up of exclusive groups of naturally occurring raw minerals and materials. These groups include: lead mineral and material compounds, boron mineral and material compounds, aluminum mineral and material compounds, coaliferous mineral and material compounds, titanium mineral and material compounds, hydrides, sulfate mineral and material compounds, iron mineral and material compounds, lithium mineral and material compounds and cadmium mineral and material compounds, and combinations thereof. In addition, leaded glass and hydrides can also be used alternatively. The use of naturally occurring minerals in a synergistic combination with modified cement, modified asphaltenes/maltenes or modified polyurethane foam carrier grout matrices is hitherto unknown in the prior art, and as can be seen in FIG. 8 and FIG. 9, provides unexpected and unobvious radiation shielding results. Leaded-glass materials useful for this invention include glasses with 20 percent, 30 percent, 40 percent and 50 percent lead. In addition and depending on percent lead contents, these leaded-glasses indigenously contain silicon dioxide (40 to 68%), sodium oxide (about 5%), barium oxide (about 2.4%), aluminum oxide (about 1.8%), calcium oxide (about 1.5%), strontium oxide (about 1.5%), potassium oxide (about 1.0%) and antimony oxide (about 0.3%). These materials may be recovered from glass waste streams, such as CRT (Cathode Ray Tube) scraps from computer monitors, television screens and the like. Such recycled materials to be used herein are processed to remove any leachable hazardous constituents, which may be present in or on the particles of the recycled glass materials, as described in U.S. Pat. Nos. 6,666,904 and 6,669,757 disclosures, of which are herein incorporated by reference. Lead-bearing minerals and materials useful for this invention include naturally occurring lead-bearing hydrated minerals (cerussite and linarite), silicates (larsenite and other complex lead-silicates), sulfides (galena and other lead-sulfides), and sulfates (anglesite and other lead-sulfates), oxides (wulfenite and other lead-oxides), as well as other lead-bearing compounds, such as but not limited to lead-bearing refractory ceramics, lead-chromates, tetraethyl lead, lead acetate or combinations thereof. The boron minerals and materials useful for this invention include naturally occurring oxy-hydroxide minerals, such as but not limited to tincal, datolite, hydroboracite, kernite, priceite, probertite, sassolite, szaibelyite, tincalconite and ulexite, in addition to other compounds, such as but not limited to borides such as aluminum dodecaboride, magnesium tetraboride, barium hexaboride, calcium hexaboride, iron boride, magnesium tetraboride, manganese tetraboride, and silicon hexa- and tetraborides and other boride compounds or combinations thereof. The mineralogical materials of aluminum useful for this invention include naturally occurring hydrated and silicate minerals, such as but not limited to bauxite, cryolite, boehmite, gibbsite, diaspore, heulandite, clinoptilite, stilbite, barrerite as well as other aluminum bearing compounds or combinations thereof. The coaliferous minerals considered useful for this invention include naturally occurring bituminous and anthracite coal materials (90-95% carbon) with variable amounts of associated minerals (5-10%) such as quartz (SiO2), mullite (AlgSi2O13), tricalcium aluminate (Ca3Al2O6), melilite [(Ca2 (Mg,Al)(AlSi)2O7)], merwinite [(Ca3Mg(SiO4)2)], ferrite spine 1((Mg,Fe)(Fe.A1)2)], pyrite (FeS2), magnetite (Fe3O4), hematite (Fe2O3), lime (CaO), anhydrite (CaSO4), periclase (MgO), and alkali sulfates ((Na,K)2SO4) or combinations thereof. Titanium minerals and materials of this invention include naturally occurring oxide minerals, such as but not limited to ilmenite, rutile, brookite, anatase, titano-magnetite, as well as other titanium compounds or combinations thereof. Hydride materials considered useful for this invention include materials such as but not limited to ditantalum hydride, lithium hydride, titanium dihydride, and other hydrides or combinations thereof. In the case of sulfate-bearing minerals and materials, naturally occurring hydrated sulfate minerals, such as but not limited to gypsum, anhydrite, jarosite, barite, melanterite, as well as compounds such as but not limited to magnesium sulfate heptahydrate and lithium hydrazinium sulfate, sodium thiosulfate or combinations thereof are considered useful for this invention. The iron-bearing minerals and materials useful for this invention include naturally occurring minerals, such as but not limited to oxides, hydrated oxides, carbonates and sulfates of iron (hematite, magnetite, siderite, goethite, limonite, ferberite, foresterite, melanterite, lepidocrocite and ferrihydrite), as well as other iron compounds or combinations thereof. The minerals and materials of lithium useful for this invention include naturally occurring silicate, phosphate and sulfate minerals, such as but not limited to lepidolite, spodumene, petalite, amblygonite and others like, as well as other compounds, such as but not limited to lithium sulfate, hydrated lithium hydrazinium sulfate and lithium hydride and other lithium compounds or combinations thereof. Among the cadmium minerals and materials useful for this invention are naturally occurring minerals, such as but not limited to cadmium sulfide (greenockite and cadmium ocher), cadmium selenite (cadmoselite), cadmium chloride, cadmium sulfate, cadmium fluroborate, cadmium carbonate and cadmium oxides, and other cadmium compounds, such as but not limited to cadmium nitrates, cadmium acetates and others like or combinations thereof. For radiation shielding purposes, selective minerals and materials from the above-mentioned groups are selected in various proportions and combined to form multi-component composites. These are then grinded to desired grain size and mixed with different types of selected grout matrix, which act as a medium for carrying the composite material and provide desired structural engineering and thermal properties for application of radiation shielding composites to various radioactive waste containment systems, management of decontamination of radioactively contaminated facilities and equipment, as well as for other shielding needs. In addition, the components of carrier grout matrix will augment the radiation shielding capacity. Three types of primary carrier grout matrices/admixtures are considered useful for this invention. These are described as follows: Type-A—modified cement carrier grout matrix: For this type of grout matrix, various types of Portland cements are considered. These include Type I or II Portland cements or their modified forms, with various additives, to meet the specific engineering requirements (e.g. compressive strength, tensile strength and shear-bond strength) of a given application. The modified cements include hydrated calcium-alumina silicate cements with iron (Ciment Fondu®), alumina-hydrated calcium sulfate cement, magnesium oxychloride-phosphate cements, plaster of Paris cements, silica-gel and clay cements. To these cements, additives such as but not limited to polyethylene fibers, steel fibers, polymeric graphite, ground blast furnace slag and cement-kiln dust are added to reinforce the cements for structural integrity and durability. Similarly, Class N pozzolan fly ash is added to eliminate any Alkali-Silica-Reaction (ASR) problem and enhance the mechanical integrity of cement carrier grout. Alternatively, the Type B or Type C carrier grout matrix, described below, can be also admixed with modified cement in different proportions to achieve desired mechanical and thermal properties of the carrier grout matrix. Overall, these modified cement carrier grout matrix is compatible for mixing with and hosting various combinations and proportions of the above mentioned minerals and materials to form Admixture Composite Materials to provide an augmented radiation shielding capacity with desirable engineering and thermal properties, durability and attributes for a specific application. Type-B—polymer modified asphaltenes and maltenes carrier grout matrix: For this type of admixture, polymer modified asphaltenes and maltenes, with special additives, such as but not limited to emulsifiers, dispersants, gallants, stabilizers (antioxidants), aromatic solvents, plasticizers, fire retardants, and curing and cross-linking agents are used to meet the specific functional requirements (e.g. resistant to impact, shock, leaching and high temperatures; non-pyrophoric; low permeability and density; and desirable engineering strength and durability) of a specific application. Depending on the requirements of a specific application, these additives may also include materials such as but not limited to thermoplastic elastomers and polymers, thermosetting modifiers, chemical modifiers, fibers, adhesion improvers, natural asphalts or fillers or combinations thereof. Alternatively, the Type A or Type C carrier grout matrix (described below) can also be admixed with modified asphaltenes and maltenes in different proportions to achieve desired mechanical and thermal properties. Overall, these types of carrier grout matrices are compatible for mixing with and hosting various combinations of the above mentioned minerals and materials to provide an augmented radiation shielding capacity with desirable engineering and thermal properties, and durability, as well as attributes for a specific application. Type-C—polymer modified polyurethane foam carrier grout matrix: For this type of grout matrix, different types of commercially available polyurethane raw materials, such as but not limited to aromatic isocynates [diphenylmethane 4, 4′ diisocyanate (MDI)] and aromatic isocyanurate [toluene 2, 4 and 2, 6 diisocyanates (TDI)], aromatic isocynates and polyols are used. These are modified by additives such as but not limited to cross-linkers (triols and tetrols), catalysts (amines, metal salts and organometallic compounds), surfactants and blowing agents (silicones). A two component system is used to generate an appropriate carrier grout matrix for mixing with the composited minerals and materials, mentioned above. Alternatively, commercially available polymer/resin modified polyurethane foams such as but not limited to ethylene bis-tetrabromophthalimide, chlorinated phosphonate ester, neutral phosphorus-based polyol, hexabromocyclododecane, tetrabromocuclooctane, hexabromododecane, bisphenol-A type epoxy or others, including combinations thereof can be also used as carrier grout matrix. These modified polyurethane foams are relatively less dense (about 2.0 lbs/c.ft or 0.032 g/cm2) resistant to high temperature, high impact and chemical leaching, non-pyrophoric or flame retardant, and exhibit desirable adhesive and coating properties, as well as desirable engineering properties. Alternatively, the Type A or Type B carrier grout matrix (described above) can be also admixed with modified polyurethane carrier grout matrix in different proportions to achieve desired mechanical and thermal properties, as well as attributes for a specific application. Overall, these modified foam matrices are compatible for mixing with and hosting various combinations of the above mentioned neutron-gamma shielding composite materials to provide an augmented radiation shielding capacity with engineering and thermal properties, and durability. Depending on the type of application, the formulated composite radiation shielding materials are ground to desired grain size (see 703 in FIG. 7) and mixed with a selected carrier grout matrix or their combinations thereof, in various weight percentages and grain-size (see 704 in FIG. 7), to form a “final admixture composite materials” for a specific application (see 705 in FIG. 7). Effective radiation shielding results from the use of exclusive admixture composite materials of this invention, which are enriched with the atoms that provide a substantial cumulative absorptive cross-section, measured in barns (a measure of probability of absorption) and elastic scattering capacity for attenuation of neutrons and gamma rays. Generally, fast neutrons have a low probability of capture by the nuclei of shielding materials; however, they are attenuated through elastic scattering in the shielding materials containing such atoms as hydrogen and lithium. In contrast, slow or thermal neutrons have high probability of capture, via inelastic scattering, by the desired atoms or isotope of atomic nuclei of components in the shielding materials used, and the probability varies depending on the type and concentration of the radioactive isotopes and the desired atomic nuclei or atoms. Upon capture of neutrons, most nuclei emit gamma rays (capture gamma, also called secondary gamma) of an energy characteristic of that type of nuclei. Examples of the thermal neutron capture cross-sections of nuclei of shielding materials and the resulting capture-gamma energies are given in Table 1 below. TABLE 1Absorption cross sections of atomsand isotopes of shielding materialsAbsorp-tiveAtoms ofNuclei ofAbsorptioncaptureshieldingisotopes ofcross-gammacomponentsAbsorptiveshieldingsectionenergiesin naturalcross-sectioncomponents(barns)(MeV)abundance(barns)H10.33 2.23Hydrogen332 ± 2 Li6 9500.0Lithium71 ± 1 B10 38400.478Boron750 ± 10 C120.00344.95Carbon0.0032 ± 0.0002Cd11320,0009.05Cadmium2500 ± 100 From the data in the above table, it is obvious that while cadmium concentrated shielding material has 5.2 times more capacity for capturing neutrons than boron concentrated material, they have the disadvantage of generating about 19 times more capture gamma than boron material. It is also obvious from the table that the advantage of using boron containing shielding material is that the probability of capturing neutrons is roughly 10,000 better than hydrogen containing material, and such material can also reduce the energy of capture gamma rays from 2.23 Mev to 0.478 Mev. However, hydrogen has the capacity to slow down the fast neutrons, through elastic scattering, which results in slow thermal neutrons. In contrast to cadmium and boron materials, lithium materials have the advantage of not generating any capture gamma radiation, although they have relatively low capacity for capturing neutrons. Therefore, it is advantage to combine lithium, hydrogen and boron bearing minerals and materials for use in radiation shielding. The results of the above mentioned paragraphs are summarized as follows, which form a basis for formulating a multi-component composite materials using naturally occurring raw minerals: 1) When dealing with fluxes of mixed radiation types of various energy levels, it is essential to have multi-component materials, consisting of naturally occurring minerals, in different combinations and proportions to create a balanced and enhanced radiation shielding capacity, 2) In multi-component composite materials, while one component of a mineral significantly attenuates neutron radiation, by capture, and generates more capture gamma, the other mineral component(s) can significantly attenuate the gamma radiation in addition to neutron attenuation. Thus a balance is created for achieving a desired optimal radiation shielding, 3) Certain isotopes of atoms are effective in radiation shielding, but hydrogen, boron, lithium, cadmium and others in their natural state (viz. in natural occurring minerals and materials) have adequate quantities of the desired isotopes for providing required shielding capacity, and therefore, processing to enrich the amount of desired isotopes is neither necessary nor desired from an economic point of view, 4) The overall effectiveness of shielding materials in arresting thermal neutrons and gamma rays is based on the total cumulative shielding capacity of a multi-component system or composite, derived out of combining different types of naturally occurring minerals and materials, which exclusively offer higher total cumulative absorption cross-section, than a commercially created single component and 5) The multi-component composite minerals and materials of this invention can form one single layer/liner to provide a total cumulative capacity to adequately shield radiation of different fluxes and energy levels, thus, providing the safety of workers, and health and environment protection, as well as economic benefits. Based on the above-mentioned, it is the intent and premise of this invention to formulate and offer various composite materials, made up of multi-component minerals and materials and admixed with carrier grout matrices in different combinations, proportions and grain sizes to form final Admixture Composite Materials. These materials will significantly enhance the capacity for shielding various fluxes of mixed radiation types and energy levels, emanating from complex, interactive radioactive waste sources. Depending on the needs of a radiation flux and energy level, the minerals from the aforementioned groups of minerals and materials are preferentially selected and combined in various combinations and permutations, in weight percentages to formulate the multi-component composite materials. In the formulation of the composite materials, the weight percentage of a group of minerals and materials can vary from 0.0 percent to 100.0 percent. For example, in one radiation shielding case, if lead, boron and lithium containing groups of minerals and materials are considered, then in the first step, a number of preferred minerals and materials from those groups are selected. In the second step, 40 weight percent of the boron group of minerals/materials, 30 weight percent of the lithium group of minerals/compounds and 30 weight percent of the lead group are considered for formulating a required batch of composite materials. The selection and proportions of preferred minerals and compounds from those groups may be different in a second radiation shielding case, and the preferred weight percentages may be 30, 50 and 20 weight percentages for boron group, lithium group and lead group of minerals respectively. Such proportional combinations, designed to provide a synergistic material composites for effective radiation shielding of combined neutron and gamma radiation are hitherto not known in the prior art, and as can be seen in FIG. 8 and FIG. 9, provides unexpected and unobvious results. Grain size is one of the variables that affect the physical make up and engineering properties of the final admixture composite materials. Generally, voids and in-homogeneities in the admixture composite materials are created if proper grain size of formulated composite materials is not achieved for homogenously mixing with carrier grout matrices. Voids and in-homogeneities can compromise the integrity, desired engineering and thermal properties and durability of final admixture composite materials for use in radiation shielding. These problems can be easily avoided by selecting proper grain size of the composite materials based on the type of carrier grout matrix and nature of application. For example, in constructing liners or prefabricated structures for radioactive waste storage casks or vaults, Type-A carrier grout based admixture composite materials are required. For preparing formable mortar mixture and slurry, using modified cement carrier grout, it is necessary to select fine to coarse grain size composite materials to fill the voids. These grain sizes will promote tightly and homogenously packed density and structural integrity. In addition, the grain size has to be compatible with all phases or components of carrier grout matrices so that proper bonding can be created for setting the mortar mix. In contrast, for applying the shielding products by spraying to coat waste containers, radioactively contaminated equipment and facilities for decontamination and decommission, micron to fine grain size particles of composite materials are preferred with Type-B or Type-C carrier grout matrix. Generally, particle size and size distribution, in addition to material density, are closely related to shielding thickness. Selection of particle size of the formulated multi-component composites appropriate for a specific carrier grout matrix will significantly increase the homogeneity of the final admixture composite materials, and reduce the porosity of the shielding media and provide effective shielding of radiation emitted by all kinds of radioactive materials and wastes. Furthermore, such reduction in porosity of admixture composites, especially the Type-B carrier grout based composite materials, will significantly reduce the diffusion of radioactive gases such as radon and iodine. Therefore, it is necessary to maintain the desired grain size of the formulated composite materials when formulating various admixture composite materials for radiation shielding. The stepwise method for selection of shielding material (701), and techniques for formulating composite materials (702) and carrier grout matrices (704), as well as the processes leading to the development of the final Admixture Composite Material (705) for various types of applications (706) are shown in FIG. 7. In formulating the composite materials of this invention, naturally occurring raw mineral materials are preferred over manufactured materials. One of the main advantages of using only naturally occurring raw mineral materials is that they contain major and minor elements/atoms that are vital for enhancing shielding of both neutron and gamma radiations for safe radioactive waste containment. In addition, the multi-component atoms of these naturally occurring mineral materials, when combined will have a synergistic effect to augment the radiation shielding capacity. For example, boron mineral—Priceite (CaB10O197H2O) provides 10 atoms of boron and 14 atoms of hydrogen, which will have more neutron attenuation capacity (about 12048 barns of absorption cross section) than a commercially produced Boron oxide (B2O3) with only two boron atoms, not hydrogen. Similarly, when Priceite (CaB10O197H2O) is combined with mineral Lepidolite mica [(K2Li3Al4Si7(OH, F)3)], the combined composition provides 10 atoms of boron, 17 atoms of hydrogen, 3 atoms of lithium and 4 atoms of aluminum for shielding. Thus, this combination cumulatively provides much more neutron attenuation capacity (about 13258 barns of absorption cross-section) than a single mineral component or a commercially produced compound. Since neutron inelastic scattering interaction with lithium does not produce capture gamma, its presence in mineral composite material will undoubtedly help to reduce overall gamma radiation. Similarly, presence of calcium minerals, such as Priceite (CaB10O197H2O) and Gypsum (CaSO4.0.5H2O) in composite mineral material will also reduce gamma radiation by absorption. Aluminum and silica in Lepidolite mica are refractory components that have the capacity to contain the radioactive temperatures in the shield. The other advantage is that the cost of these naturally occurring mineral materials is generally lower than that of the industrially produced shielding materials or components. Therefore, naturally occurring multi-component minerals and materials are preferred over commercially produced single component compounds In formulating and preparing the final admixture composite materials for radiation shielding, naturally occurring raw mineral materials that offer optimal radiation absorption and radioactive heat containment are selected (see 701 in FIG. 7), along with an application based modified carrier grout matrix (see 704 in FIG. 7). The selected raw mineral materials are formulated into multi-component composite material by using their different combinations and weight percent proportions (see 702 in FIG. 7), and are subjected to grinding for achieving desired particle size(s) (see 703 in FIG. 7), which will be compatible for mixing with a selected carrier grout matrix. This ground material is then admixed with a preferred carrier grout matrix (see 704 in FIG. 7) to produce the final Admixture Composite Material (see 705 in FIG. 7). In formulating and preparing the final admixture composite materials for radiation shielding, the weight percentages of composite materials and the modified carrier grout matrices can vary from 5-75 and 25-95, respectively to make up 100 weight percent of the final material product. These aforementioned proportions do not significantly compromise the properties of the final Admixture Composite Materials. Examples of embodiments of the final Admixture Composite Materials are illustrated below. Although the embodiments of the formulated composites and carrier grout matrices can be comprehensively illustrated in different component combinations and permutations, along with their corresponding application to different aspects of radiation shielding management, only a summary of some specific, representative example illustrations are presented below and in the corresponding FIGS. 1, 2, 3, 4, 5 and 6. The respective numbers given in these figures represent the proportions (in weight percentages) of the multi-components used in a particular admixture composite material, and these numbers are assigned in parenthesis next to each component of an embodiment illustrated below. It should be understood that the radiation shielding admixture composites of the invention are necessarily limited thereto since alternative embodiments and applicability of embodiments will become apparent to those skilled in the art in view of the disclosure. 1. Admixture Composite Material—A (see FIG. 1): Leaded glass with 40% lead—30 weight percent—LG4030 (10) Boron oxide and hydroxide minerals: boracite (Mg10B14O26C12), hydroborocite (CaMgB6O115H2O), kernite (Na2B4O74H2O), priceite (CaB10O197H2O sassolite (H3BO3), tincalconite (Na2B4O75H2O), tincal (Na2B4O710H2O)—10 weight percent—BO—OH10 (13) Aluminum hydroxide minerals: bauxite (hydrated aluminum and iron silicate), gibbsite [Al(OH)3], diaspore [AlO(OH)], heulandite [(Na, Ca)2Al13(Al, Si)2 Si13O3612H2O ], clinoptilite [(Na, K, Ca)2 Al13 (Al,Si)2 Si13O3612H2O] and stilbite [Na3Ca3(Al8 Si28O72)30 H2O]—10 weight percent—AlO—OH10 (12) Lithium minerals: lepidolite mica [(K2Li3Al4Si7(OH, F)3)], spodumene (LiAlSi2O6), petalite (LiAlSi4O10), amblygonite [LiAl(F, OH)PO4] and lithium hydrazinium sulfate [(Li (N2H5SO4)]—10 weight percent—LiM10 (11) Type-A carrier grout matrix: 20 weight percent of I or II Portland cement, 5 weight percent Class N Pozzolan fly ash and 15 weight percent polyethylene fibers.—40 weight percent (14) Alternatively, lead-bearing mineral material, in the same weight percentage, can easily be substituted for leaded glass. Similarly, Type-B—polymer modified asphaltenes and maltenes carrier grout matrix, Type-C—polymer modified polyurethane foam carrier grout matrix/admixture or combinations thereof, in the same overall weight percentage, can be substituted for Type-A carrier grout matrix. Other embodiments not specifically described herein will be apparent to one of ordinary skill in the art upon reviewing the above description. 2. Admixture Composite Material—B (see FIG. 2): Leaded glass with 50% lead—20 weight percent—LG5020 (22) Boron oxide and hydroxide minerals: boracite (Mg10B14O26C12), hydroborocite (CaMgB6O115H2O), kernite (Na2B4O74H2O), priceite (CaB10O197H2O), sassolite (H3BO3), tincalconite (Na2B4O75H2O), and tincal (Na2 B4O710H2O)—15 weight percent—BO—OH15 (23) Aluminum hydroxide minerals: bauxite (hydrated aluminum and iron silicate), gibbsite [Al(OH)3], diaspore [AlO(OH)], heulandite [(Na, Ca)2 Al13(Al, Si)2Si13O3612H2O ], clinoptilite [(Na, K, Ca)2 Al13(Al,Si)2 Si13O3612H2O] and stilbite [Na3Ca3(Al8Si28O72)30H2O]—10 weight percent—AlO—OH10 (20) Coaliferous materials/compounds: bituminous and anthracite coals containing 90-95% carbon and 5-10% of variable amounts of associated minerals, such as quartz (SiO2), mullite (AlgSi2 O13), tricalcium aluminate (Ca3Al2 O6), melilite [(Ca2(Mg,Al)(AlSi)2O7)], merwinite [(Ca3Mg(SiO4)2)], ferrite spinel [(Mg,Fe)(Fe.A1)2)], pyrite (FeS2), magnetite (Fe3O4), hematite (Fe2O3), lime (CaO), anhydrite (CaSO4), periclase (MgO), and alkali sulfates [(Na,K)2SO4)]—10 weight percent—CM10 (21) Type-A carrier grout matrix: 30 weight percent of I or II Portland cement, 3 weight percent Class N Pozzolan fly ash and 12 weight percent polyethylene fibers—45 weight percent (24) Alternatively, lead-bearing minerals, in the same weight percentage, can easily be substituted for leaded glass. Similarly, Type-B—polymer modified asphaltenes and maltenes carrier grout matrix, Type-C—polymer modified polyurethane foam carrier grout matrix or combinations thereof, in the same weight percentage, can easily be substituted for Type-A carrier grout matrix. Other embodiments not specifically described herein will be apparent to one of ordinary skill in the art upon reviewing the above description. 3. Admixture Composite Material—C (see FIG. 3): Leaded glass with 40% lead—20 weight percent—LG4020 (32) Boron hydroxide minerals: hydroborocite (CaMgB6 O115H2O), kernite (Na2 B4O74H2O), priceite (CaB10O197H2O), tincalconite (Na2B4O7 5H2O) and tincal (Na2B4O710H2O)—20 weight percent—BO—OH20 (30) Lithium minerals: lepidolite mica [(K2Li3Al4Si7(OH, F)3)], spodumene (LiAlSi2O6), petalite (LiAlSi4O10) and amblygonite (LiAl(F, OH)PO4)—10 weight percent—LiM10 (31) Type-A carrier grout matrix: 30 weight percent of I or II Portland cement, 3 weight percent Class N Pozzolan fly ash and 12 weight percent polyethylene fibers—30 weight percent and Type-B—polymer modified asphaltenes and maltenes carrier grout matrix—20 weight percent (33) Alternatively, lead-bearing mineral material, in the same weight percentage, can easily be substituted for leaded glass. Similarly, Type-A carrier grout matrix, Type-C—carrier grout matrix alone or combinations thereof can easily be substituted, in the same weight percentage, for Type-B carrier grout matrix. Other embodiments not specifically described herein will be apparent to one of ordinary skill in the art upon reviewing the above description. 4. Admixture Composite Material—D (see FIG. 4): Boron oxide, hydroxide and boride minerals: boracite (Mg10B14O26C12), hydroborocite (CaMgB6O115H2O), kernite (Na2B4O74H2O), priceite (CaB10O197H2O), tincalconite (Na2B4O75H2O), tincal (Na2 B4O710H2O) and silicon hexaboride (SiB6)—30 weight percent—BO—OH30 (40) Iron hydroxide, silicate and carbonate minerals: hematite (Fe2O3), magnetite (Fe3O4), siderite (FeCO3), goethite (Fe OOH), limonite [(Fe2O3), nH2O)], melanterite [Fe2+(SO4).7(H2O)], lepidocrocite (Fe OOH), iron biotite mica [K(Mg, Fe) 3AlSi3O10 (OH)2] and ferrihydrite (5Fe2O3O.9H2O)—15 weight percent—FeM15 (41) Titanium minerals: ilmenite (FeTiO3), rutile (TiO2) and titano-magnetite (TiO. Fe3O4)—5 weight percent—TiM5 (42) Lithium minerals: lepidolite mica [(K2Li3Al4Si7(OH, F)3)], spodumene (LiAlSi2O6), petalite (LiAlSi4O10), amblygonite (LiAl(F, OH)PO4), lithium hydrazinium sulfate [(Li (N2H5SO4)], and lithium hydride (LiH)—10 weight percent—LiM10 (43) Type-C—polymer modified polyurethane foam carrier grout matrix—40 weight percent (44) Type-A carrier grout matrix, Type-B—polymer modified asphaltenes and maltenes carrier grout matrix or combinations thereof can easily be substituted, in the same 40 weight percentage, for Type-C carrier grout matrix. Other embodiments not specifically described herein will be apparent to one of ordinary skill in the art upon reviewing the above description. 5. Admixture Composite Material—E (see FIG. 5): Lead-bearing minerals: cerussite [PbCO3.Pb(OH)], linarite [PbCu(SO4)(OH)2], larsenite [PbZnSiO4OH (FeO, MgO, CaO)], lead-silicates (PbO2SiO2), galena (PbS), anglesite (PbSO4), wulfenite (PbMoO4), leaded refractory ceramics, lead-chromates (PbCrO4), tetraethyl lead [Pb(C2H5)4 and lead acetate [Pb(CH3COO)2]—10 weight percent—PbM10 (52) Boron oxide, hydroxide and boride minerals: boracite (Mg10B14O26C12), hydroborocite (CaMgB6O115H2O), kernite (Na2B4O74H2O), priceite (CaB10O197H2O), sassolite (H3BO3), tincalconite (Na2B4O75H2O), tincal (Na2 B4O710H2O), Iron boride (Fe2B) and silicon hexaboride (SiB6)—15 weight percent—BO—OH15 (51) Aluminum hydroxide minerals: bauxite (hydrated aluminum and iron silicate), gibbsite [Al (OH)3], heulandite [(Na, Ca)2 Al13(Al, Si)2 Si13O36 12H2O], stilbite [Na3Ca3(Al8Si28O72)30 H2O] and and diaspore [AlO(OH)]—10 weight percent—AlO—OH10 (50) Lithium minerals: lepidolite mica [(K2Li3Al4Si7(OH, F)3)], spodumene (LiAlSi2O6), petalite (LiAlSi4O10), amblygonite (LiAl(F, OH)PO4) and lithium hydride (LiH)—10 weight percent—LiM10 (54) Cadmium minerals: cadmium sulfide (greenockite and cadmium ocher), cadmium selenite (cadmoselite), cadmium fluroborate, cadmium carbonate and cadmium oxides—10 weight percent—CdM10 (53) Type-B—polymer modified asphaltenes and maltenes carrier grout matrix—45 weight percent (55) Alternatively, Type-A carrier grout matrix, Type-C carrier grout matrix or their combinations thereof can easily be substituted in the same proportion (i.e. 45 weight percentage) for Type-B grout matrix. Other embodiments not specifically described herein will be apparent to one of ordinary skill in the art upon reviewing the above description. 6. Admixture Composite Material—F (see FIG. 6): Boron oxide, hydroxide and boride minerals: boracite (Mg10B14O26C12), colemanite (Ca2B6O115H2O), hydroborocite (CaMgB6O115H2O), kernite (Na2B4O74H2O), priceite (CaB10O19 7H2O), sassolite (H3BO3), tincalconite (Na2B4O75H2O), tincal (Na2B4O710H2O), Iron boride (Fe2B), silicon hexaboride (SiB6), magnesium tetraboride (MgB4), aluminum dodecaboride (AlB12) and strontium hexaboride (SrB6)—15 weight percent—BO—OH15 (60) Lead minerals: cerussite [PbCO3.Pb(OH)], linarite [PbCu(SO4) (OH)2], larsenite [PbZnSiO4OH (FeO, MgO, CaO)], lead-silicates (PbO 2SiO2), Galena (PbS), anglesite (PbSO4), Wulfenite (PbMoO4), leaded refractory ceramics and lead-chromates (PbCrO4)—9 weight percent—PbM9 (62) Leaded glass with 40% lead—6 weight percent—LG406 (64) Hydride material: ditantalum hydride (Ta2H), lithium hydride (LiH) and titanium dihydride (TiH2)—10 weight percent—HydM10 (61) Lithium minerals: lepidolite mica [(K2Li3Al4Si7 (OH, F)3)], spodumene (LiAlSi2O6), petalite (LiAlSi4O10), amblygonite (LiAl(F, OH)PO4), lithium hydrazinium sulfate [(Li (N2H5SO4)], and lithium hydride (LiH)—10 weight percent—LiM10 (63) Hydrated sulfate minerals: gypsum (CaSO4.0.5H2O), jarosite [KFe3+3(SO4)2(OH)6], barite [BaSO4.0.5(H2O)], melanterite [Fe2+(SO4).7(H2O)], magnesium sulfate heptahydrate (MgSO4.7H2O), and other similar compounds—5 weight percent—HSlf5 (65) Type-C—polymer modified polyurethane foam carrier grout matrix—45 weight percent (66) Alternatively, Type-B—carrier grout matrix, Type-A carrier grout matrix or combinations thereof can easily be used, in the same 45 weight percentage proportion, as an alternative to Type-C carrier grout matrix. Other embodiments not specifically described herein will be apparent to one of ordinary skill in the art upon reviewing the above description. For demonstrating the efficacy of the invention materials for neutron-gamma radiation shielding, admixture composite material A, B and C were lab tested and compared with other prior art/conventional shielding admixture materials, which are concrete-based and denoted as “Hudson Admixture”, “Mix #1 composite”, Mix #2 composite” and “SNS admixture”. In the admixture composite materials A and B, Type-A carrier grout matrix is used and in the admixture composite material C, Type-A and Type-B carrier grout matrices are used for testing. The test results have shown unexpected and unobvious capacities for shielding both neutron and gamma radiation. The test results are presented in Table 2 below, and illustrated in FIG. 8 and FIG. 9. TABLE 2Test results of radiation shielding capacities of AdmixtureComposite Material A, B and C of the invention as compared withthe other admixtures (testing is based on MCNP4C model)Neutrondose afterCapture gamma doseAdmixture Compositesexposureafter exposureof the Invention(mrem/hr)(mrem/hr)Admixture Composite26.20.3Material - AAdmixture Composite23.50.3Material - BAdmixture Composite2.80.2Material - COther AdmixturesHudson admixture85.03.3Mix #1 composite206.07.0Mix #2 composite207.06.6SNS admixture118.02.5Input Parameters: Initial exposure dose of 100 micrograms Cf-252 source (about 800 mrem/hr). Cylindrical waste cask with inner length of 73 inches, inner diameter of 42 inches, wall thickness of 6 inches, bottom thickness of 6 inches and top thickness of 4 inches. Dose rates measured at the outer surface cylinder. These test results show that the Admixture Composite Materials A, B and C provide up to 74 times more neutron radiation shielding capacity and up to 35 times more gamma radiation shielding capacity than the other admixture composite materials. Admixture Composite materials-C show significantly higher neutron radiation shielding than the admixture composites A and B. However, their capacity for shielding of gamma radiation is not significantly different. It is obvious that the test results of the formulated multi-component admixture composites of the invention demonstrate unexpected and unobvious enhanced shielding of relatively high flux and energy neutron and gamma radiation. From these unexpected and unobvious results, it is apparent that these formulated shielding products of the invention when applied or used for management of deleterious radiation can provide unexpected benefits that are not otherwise obvious. The multi-component admixture composites of this invention demonstrate a significant improvement over conventional shielding materials or the materials known in the art. These multi-component composites will provide a better radiation shielding technology than the conventional single or dual component technologies for enhancing the safety of handling, storage, transport, management and disposal of solid and liquid or mixed radioactive wastes. In addition, the multi-component based technology provides greater ease and flexibility of application for radiation shielding, and solidification and immobilization of liquid and sludge radioactive wastes than the conventional/prior art technology. Usage of admixture composite materials as inner packs or liners of waste containers can accommodate more container space for loading of additional waste by significantly reducing the thickness, dimensions and mass of radiation shielding inner packs or liners. The relative thickness of the shielding liner (container wall) made out of Admixture Composite Material—C of this invention was compared with the thicknesses of other conventionally used or prior art material liners for shielding of 10 mR/h energy flux of neutron and gamma radiation. The results are represented in histograms and presented in FIG. 10. The histograms show that for neutron radiation shielding, the thickness of Admixture Composite Material—C shielding liner/wall is roughly 4.5 times thinner than that of concrete, 6 times thinner than that of lead, 7 times thinner than that of steel and 4 times thinner than that of Ducrete. For gamma radiation shielding, the thickness of Admixture Composite Material—C shielding liner/wall is roughly 12 times thinner than that of concrete, 2.5 times thinner than that of lead, 3.6 times thinner than that of steel and 3 times thinner than that of Ducrete. These demonstrate that the liner made out of formulated Admixture Composite Material—C of this invention is better than those made out of conventional or prior art shielding materials by providing technological superiority, and environmental and economic benefits. Technologically, the composite material of this invention has superior radiation shielding capacity (see FIG. 8 and FIG. 9), and as a result only a thinner liner is required for shielding the given flux of radiation. Usage of thinner liner made out relatively low density composite material will accommodate loading of additional waste in the same container. Consequently, usage of the composite material of this invention with superior radiation shielding capacity renders safe handling and storage, ease of handling and retrieval, transportation, management and disposal of containerized radioactive wastes of variable radiation fluxes and energies, as well as economic benefits. There are a wide variety of applications of radiation-shielding admixture composites of the present invention to various aspects of high-level, transuranic and low-level radioactive waste management, as well as to management of decontamination of radioactively contaminated facilities and equipment, and uranium-thorium mill and mine tailings. Depending on the type of application and the conditions, various multi-component mixtures (composites) of minerals and materials are preferred for formulating the composites. Admixture composite materials are formulated using the specific mineral composites and mixing them in various proportions with selected carrier grout matrix of this invention. For various radiation shielding applications (see 706 in FIG. 7), slurries, solids, liquids or viscous material of admixture composite materials are produced (see 705 in FIG. 7). Table 3 lists the formulated admixture composite materials, their physical form and relative densities required for a given type of application, as well as the corresponding application methods. TABLE 3Admixture compositeType of ApplicationmaterialPhysical formRelative DensityApplication methodOver and inner packsAdmixture compositeSlurry,Lighter thanPouring oror liners for storagematerial: A, B or Cviscousconventionalinjection, pre-and transport casksmaterials orconcrete andfabrication ofand containers as ansolidslead or Ducretestructures or moldsalternative to lead andlinersconcrete shielding orfor partial substitutionCoatings for corrosionAdmixture compositeLiquids orLighter thanSprayingand radiationmaterial: D, E or Fviscousconventionalprotection of wastematerialsconcretecontainers andpackages, drip shieldsVaults for storage ofAdmixture compositeSlurry or solidLighter thanPrefabrication ofnuclear wastes,material: D, E or Fconventionalstructuresmaterials and war-concreteheads, and structuresfor linear acceleratorfacilitiesImpact limitingAdmixture compositeViscousLighter thanPrefabrication ofstructures and paddingmaterial: D, E or Fmaterialsconventionalstructures andliners for wasteconcretepadding linerstransportcontainers/casksEncapsulation of spentAdmixture compositeViscousLighter thanSprayingfuel, radioactivematerial: A, B, C ormaterials orconventionalwastes, tank wastescombinationsliquidsconcrete andand contaminated soilsDucreteLiquid/sludge wasteAdmixture compositeSolidsLighter thanPouring, mixingsolidification andmaterial: C, D, E, F orconventionaland sprayingimmobilizationcombinationsconcreteShielding radioactiveAdmixture compositeViscousLighter thanSprayingBeryllium blocksmaterial: C, D, E, F ormaterialsconventionalcombinationsconcreteCoating of thermalAdmixture compositeLiquids andLighter thanSprayingneutron facilities andmaterial: A, B or CviscousconventionalequipmentmaterialsconcreteRadioactiveAdmixture compositeViscousLighter thanSprayingdecontamination ofmaterial: D, E, F ormaterialsconventionalfacilities andcombinationsconcreteequipment fordecommissioningRadioactive dustAdmixture compositeLiquids andLighter thanSprayingsuppressantmaterial: D, E or FviscousconventionalapplicationmaterialsconcreteStructures for x-rayAdmixture compositeSlurry orLighter thanPrefabrication ofroomsmaterial: A, D, E or FsolidsconventionalstructuresconcreteImpeding diffusion ofAdmixture compositeViscousLighter thanPrefabrication ofgases-radon or iodinematerial: C, B or Ematerials orconcretestructures/linerssolids Although specific embodiments of the formulated admixture composite materials of the invention are illustrated and described herein, this disclosure is intended to cover any and all combinations and permutations of various embodiments of the invention. Furthermore, it is to be understood that the description of the embodiments given above has been made in an illustrative fashion, and not a restrictive one. Combination of the illustrated composite embodiments, and other embodiments not specifically described herein will be apparent to one of ordinary skill in the art upon reviewing the above-mentioned descriptions and illustrations. The scope of variations in the embodiments of this invention includes any other applications in which the materials and techniques of this invention, as well as their permutations and combinations, can be used. Therefore, the scope of various embodiments and their application of this invention should be determined with reference to the appended claims, along with the full range of equivalents to which such claims are entitled. |
|
summary | ||
052251462 | claims | 1. A method of improving confinement properties of a plasma of a tokamak having a toroidal magnetic field direction comprising: (a) providing a ripple field region in the plasma; (b) injecting electrons having predominantly perpendicular energy with respect to the toroidal magnetic field direction of the plasma into the ripple field region for trapping the electrons into the plasma; and, (c) negatively charging the plasma center with respect to the edge by allowing the electrons to grad-B drift vertically toward the plasma interior until they are detrapped, thereby creating a radial electric field at the edge of the plasma. (a) an external cathode adjacent to the tokamak for emitting electrons into the plasma; (b) means for accelerating the electrons by radiofrequency waves at the electron cyclotron frequency; (c) a plurality of magnetic coils located around the torus of the tokamak creating a local magnetic field ripple for trapping the electrons; whereby the electrons drift and move toward the interior of the plasma until they are detrapped, thereby creating a radial electric field at the edge of the plasma. 2. The method of claim 1 wherein the electrons are injected from an electron source exterior of the plasma. 3. The method of claim 2 wherein the electrons are injected by a flat cathode containing an electrocyclotron-heating cavity. 4. The method of claim 3 wherein the trapping of electrons in the plasma is governed by: EQU v.sub..perp. v.sub..vertline. .gtoreq.(2.delta.).sup.1/2 5. The method of claim 4 wherein the ripple field is created by poloidal bending magnets locally placed around the torus of the takamak. 6. The method of claim 5 wherein the cathode has an electron emitting faceplate of LaB.sub.6. 7. An electron injector for improving confinement properties in a tokamak plasma direction comprising: 8. The electron injector of claim 7 wherein the means for accelerating the electrons by radio frequency waves includes an electro cyclotron heating waveguide cavity and an electro cyclotron heating acceleration region adjacent to the cathode. 9. The electron injector of claim 8 wherein the electrode includes a carbon heater and an electron emitting faceplate of LaB.sub.6. |
description | 1. Technical Field The present application relates generally to apparatus and methods for automated inspection in semiconductor manufacturing and the like. 2. Description of the Background Art Semiconductor wafer inspection apparatus typically image the wafer surface by either one of two techniques. A first technique involves scanning a square area of a stationary wafer. After that area is scanned, the wafer is moved over by the width of that square to acquire the next image. A second technique involves continuously scanning the wafer surface while, at the same time, moving the stage on which the wafer is mounted. The wafer surface often has repeating patterns. In order to detect defects, the following method may be used. Image sections of repeating patterns on the wafer surface, displaced by one or multiple cell widths in the direction of the stage movement, are subtracted from each other to form a difference image. Such a difference image may be used as the basis for the defect detection. One embodiment relates to an apparatus for automated inspection of a semiconductor substrate. Processor-executable code is configured to control the stage electronics to move the substrate using a continuous motion in a substrate-translation direction and is configured to control the beam to scan it across the surface of the substrate and collect corresponding image data, scan lines being along a scan-line direction perpendicular to the substrate-translation direction. Processor-executable code is also configured to select from the image data two cells of the repeating pattern on the surface of the substrate, the two cells being displaced from each other by one or multiple cell heights in the scan-line direction. Finally, processor-executable code is configured to generate a difference image by subtracting image data from said two cells on a pixel-by-pixel basis. Other embodiments, aspects, and features are also disclosed. A substantial fraction of semiconductor wafer inspections are conducted on wafer patterns that repeat themselves in cells. These cells, such as a unit cell in a memory array, repeat themselves in both (x and y) directions. For example, the x-direction may be in the direction of the stage or substrate translation, and the y-direction may be the scan-line direction. To compare images of two neighboring cells, the images are generally shifted by one or multiple cell widths in the direction of the stage movement (i.e. the x-direction), and the shifted image is then subtracted from the original image on a pixel-by-pixel basis to form a difference image for defect detection. As discussed above, individual pixels that are subtracted from each other are acquired a time period, Δt, apart, where Δt is equal to the scan speed (in units of scan lines per second) times the cell width (in units of scan lines). For electron beam apparatus, Δt typically ranges from about 100 microseconds to 10 milliseconds. However, applicants note that the longer Δt is, the more time for the inspector to accumulate systematic errors, such as beam deflection noise and stage motion uncertainty. Applicants further note that small perturbations to the beam and/or the continuous stage movement introduces positional distortion into the images that can only be partially corrected by image alignment. This additional noise makes the inspection tool less sensitive to the smallest physical defects and/or the weakest voltage-contrast defects. This is because the defect detection threshold has to be raised to avoid the flagging of false defects due to these misalignments. The above-described problems and disadvantages may be overcome by utilizing apparatus and methods disclosed in the present application. As described below, the present application discloses apparatus and methods which can reduce positional distortion in difference data. With this reduced distortion, the defect detection threshold may be lowered without resulting in an overabundance of false-positive defect detections. FIG. 1A is a schematic diagram of an electron beam apparatus 100 in accordance with an embodiment of the invention. The apparatus 100 includes, but is not limited to, a vacuum chamber 102 of an electron beam column, a controller 130, and an image processor 140. Within the vacuum chamber 102 of the column are various components, including an electron source 104, a condenser electron lens 106, a controllable deflector 108, an objective electron lens 110, a substrate specimen 112, a movable stage 114, and an electron detector 118. The electron source 104 generates electrons which are used to form an electron beam 105. The condenser lenses 106 may be utilized to focus the beam 105 into a smaller diameter beam. The deflectors 108 may comprise a magnetic or an electrostatic deflector. The objective lens 110 may be utilized to focus the beam 105 onto a spot on a surface of the substrate 112. The substrate 112 is held under the beam 105 by the stage 114. The stage 114 may be moved the substrate 112 under the beam 105 using a controllable stage-moving mechanism 116. The detector 118 may be configured to detect secondary and/or scattered electrons resulting from the impingement of the primary electron beam 105 onto the substrate 112. The controller 130 may include a processor 132, a memory 134, and input/output (I/O) circuitry 138. The memory 134 may include processor-executable code 136 and other data. The I/O circuitry 138 may be used by the controller to communicate with external electronic devices. The I/O circuitry 138 may be coupled to stage control circuitry 122, deflector control circuitry 124, and other column control circuitry 126. The stage-moving mechanism 116 may be controlled by the controller 130 by way of the stage control circuitry 122. The beam deflectors 108 may be controlled by the controller 130 by way of the deflector control circuitry 124. The deflector 108 may be controlled so as to scan the beam spot over different locations on the surface of the substrate 112. The other column control circuitry 126 may be coupled to circuitry for the electron source 104 so as to control beam current and/or beam voltage. The other column control circuitry 126 may also be coupled to the lenses 106 and/or 110 to control the field of view of the column. Detection electronics 128 may be coupled to the detector 118. The image processor 140 may be configured to receive data from the detection electronics 128. The image processor 140 may also be communicatively coupled to the controller 130. In accordance with an embodiment of the invention, the apparatus 100 may be configured such that a user may select a swath scanning mode. In the swath scanning mode, the stage 114 may be moved in a relatively slow and continuous (or nearly continuous) linear motion under the electron beam column. Meanwhile, the electron beam 105 may be scanned linearly back-and-forth along scan lines in a raster pattern so as to cover the moving substrate in swath-like segments. Alternatively, instead of raster scanning of an electron beam 105 that is focused onto a spot, the electron beam apparatus 100 may be configured to focus the electron beam 105 such that it is spread out in one dimension so as to form a linear-shaped electron beam. Such a linear-shaped electron beam may illuminate an entire area of a scan line for line-by-line image acquisition. In such a configuration, all the pixels of a scan line may be acquired simultaneously, for example, using a time-delay integration (TDI) detector. Image data collected during the swath-like scanning may then be processed by the image processor 140. This image data may be processed in accordance to the methods disclosed herein to detect and verify defects in a relatively rapid and efficient manner which allows for high-throughput inspection of substrates. The image processor 140 may include a processor 142, a memory 144, and input/output (I/O) circuitry 148. The memory 144 may include processor-executable code 146 and other data. The I/O circuitry 148 may be used by the controller to communicate with external electronic devices. The I/O circuitry 148 may be coupled to detection electronics 128 and the controller 130. FIG. 1B is a schematic diagram of an optical beam apparatus 150 in accordance with an embodiment of the invention. The apparatus 150 includes, but is not limited to, a controllable source 152 for an optical beam 153, an optical detector 156, a controller 130, and an image processor 140. The controllable source 152 generates an optical beam 153 which is scanned across a surface of the substrate 112. The substrate 112 is held under the optical beam 153 by the stage 114. The stage 114 may be moved the substrate 112 under the beam 152 using a controllable stage-moving mechanism 116. The optical detector 156 may be configured to detect scattered photons resulting from the impingement of the optical beam 153 onto the substrate 112. The controller 130 may include a processor 132, a memory 134, and input/output (I/O) circuitry 138. The memory 134 may include processor-executable code 136 and other data. The I/O circuitry 138 may be used by the controller to communicate with external electronic devices. The I/O circuitry 138 may be coupled to stage control circuitry 122, and scan control circuitry 154. The stage-moving mechanism 116 may be controlled by the controller 130 by way of the stage control circuitry 122. The scanning of the optical beam 153 may be controlled by the controller 130 by way of the scan control circuitry 154. Detection electronics 158 may be coupled to the optical detector 156. The image processor 140 may be configured to receive data from the detection electronics 158. The image processor 140 may also be communicatively coupled to the controller 130. In accordance with an embodiment of the invention, the apparatus 150 may be configured such that a user may select a scanning mode wherein the stage 114 may be moved in a relatively slow and continuous (or nearly continuous) linear motion which is perpendicular to the scan line. Meanwhile, the optical beam 153 may be configured to illuminate an entire scan line such that all the pixels of a scan line may be acquired simultaneously using a time-delay integration (TDI) detector. Image data collected during the scanning may then be processed by the image processor 140. This image data may be processed in accordance to the methods disclosed herein to detect and verify defects in a relatively rapid and efficient manner which allows for high-throughput inspection of substrates. The image processor 140 may include a processor 142, a memory 144, and input/output (I/O) circuitry 148. The memory 144 may include processor-executable code 146 and other data. The I/O circuitry 148 may be used by the controller to communicate with external electronic devices. The I/O circuitry 148 may be coupled to detection electronics 158 and the controller 130. FIG. 2 is a flow chart of a method to detect a defect in a substrate in accordance with an embodiment of the invention. A semiconductor wafer or other similar substrate is provided 202 to be inspected. The wafer is translated or moved 204 in a “swath” (wafer translation) direction under a beam. The beam may be an electron beam generated by an electron column, for example, as shown in FIG. 1A, or the beam may be an optical beam generated by the optical source, for example, as shown in FIG. 1B. As the wafer is being translated under the beam in the swath direction, the beam is scanned 206 with the scan-line direction being perpendicular to the swath (wafer translation) direction. The combination of the wafer translation and scanning results in parallelogram-shaped (or rectangularly-shaped) regions (called “swaths”) of the wafer surface being imaged. Image data may be detected and collected 207, for example, by the electron detector 118 and detection electronics 128 shown in FIG. 1A, or by the optical detector 156 and detection electronics 158 shown in FIG. 1B. The image data may then be processed by the image processor 140. In accordance with an embodiment of the invention, the processing of the image data may include the following steps. Reference and candidate cells within the image data are selected 208, where each pixel of one cell in the pair is displaced from a corresponding pixel of the other cell in the pair by one or multiple cell “heights” in the scan-line direction 304. In the absence of defects, the images of reference and candidate cells are expected to be substantially similar due to the repeating nature of the pattern on the semiconductor wafer. An example of one such first pair of reference and candidate cells, displaced by one cell “height” in the scan-line direction, is depicted in FIG. 3. The image data of one of the pair of cells is subtracted from the image data of the other cell of the pair. In other words, a difference image is generated 210, where the difference image may be generated by taking an intensity value for each image pixel in the candidate cell and subtracting the intensity value for the corresponding image pixel in the reference cell. Defects in the candidate cell may then be detected 212 by applying a threshold to the difference image. For example, if the difference image indicates that certain pixels have differences in intensity values higher than the threshold, those pixels may be considered to be indicative of a defect. Note that using cells displaced in the scan-line direction to generate a difference image per the above-discussed method 200 is not normally done in conventional practice. This is because the conventional wisdom is that using cells displaced in the swath (wafer translation) direction avoids aberrations in the difference image due to lens distortions. In contrast, by using the above-discussed method 200, the aberrations due to lens distortions are avoided because corresponding pixels in both cells would experience the same distortion, and so the distortion would cancel out in generating the difference image. Applicants have found that the above-discussed method 200 provides a substantial and unexpectedly useful advantage in that Δt is much shorter than in the conventional method. In other words, pixels subtracted from each other to create the difference image have a much smaller difference in acquisition times than in the conventional technique. More particularly, applicants have found Δt to be in the range from 10 nanoseconds to 1 microsecond by using the above-discussed technique with an electron beam apparatus. This is orders of magnitude shorter than the conventional technique with an electron beam apparatus which typically results in Δt ranging from 100 microseconds to 10 milliseconds. Applicants have further found that the substantially shorter Δt of the above-discussed method 200 results in much less time for the inspection tool to accumulate systematic errors distorting the image. This lower distortion noise yields a difference image with less noise for subsequent defect detection. The above-discussed method 200 has the further advantage of being much less sensitive to image aliasing that can occur when an image is under-sampled from one scan line to the next. Furthermore, noise from beam current fluctuations and small glitches is much more likely to affect the conventionally-generated difference image (between cells displaced in the wafer translation direction) than the difference image generated using the above-discussed method 200. In another embodiment, the above-discussed method 200 may be extended by modifying block 208 to select multiple reference cells and by modifying block 210 to generate multiple difference images, each difference image being between the candidate cell and one of the reference cells. Advantageously, the multiple difference images may be used for arbitration purposes to make the defect detection more robust. For example, if three difference images are generated using three reference cells, then the algorithm may require that a defect be detected only if the defect passes the threshold application (in a modified block 212) in at least two of the three difference images. FIG. 3 is an illustrative diagram depicting a first pair of reference and candidate cells in accordance with an embodiment of the invention. This illustrative diagram shows example image data and further shows the swath (wafer or substrate translation) direction 302 and the scan-line direction 304. As seen, the swath and scan-line directions are perpendicular to each other. A reference cell 306 and a candidate cell 308 are also shown. In this instance, each pixel of one cell in the pair is displaced from a corresponding pixel of the other cell in the pair by one cell “height” in the scan-line direction 304. (In other instances, the displacement between the cells may be multiple cell “heights”.) In the absence of defects, the images of reference and candidate cells are expected to be substantially similar due to the repeating nature of the pattern on the semiconductor wafer. FIGS. 4A and 4B depict steps in a method to detect and verify a defect in a substrate in accordance with an embodiment of the invention. The method starts with the process 400 shown in FIG. 4A. A semiconductor wafer or other similar substrate is provided 402 to be inspected, and the wafer is translated or moved 404 in a “swath” (wafer translation) direction under a beam, for example, such as the electron beam of the apparatus 100 discussed above in relation to FIG. 1A, or the optical beam of the apparatus 150 discussed above in relation to FIG. 1B. As the wafer is being translated under the beam in the swath direction, the beam is scanned 406 with the scan-line direction being perpendicular to the swath (wafer translation) direction. The combination of the wafer translation and scanning results in parallelogram-shaped (or rectangularly-shaped) regions (called “swaths”) of the wafer surface being imaged. Image data may be detected and collected 407 by the electron detector 118 and detection electronics 120. The image data may then be processed by the image processor 140. In accordance with an embodiment of the invention, the processing of the image data may include the following steps. A first pair of reference and candidate cells within the image data is selected 408, where each pixel of one cell in the pair is displaced from a corresponding pixel of the other cell in the pair by one or multiple cell “heights” in the scan-line direction 304. In the absence of defects, the images of reference and candidate cells are expected to be substantially similar due to the repeating nature of the pattern on the semiconductor wafer. An example of one such first pair of reference and candidate cells, displaced by one cell “height” in the scan-line direction, is depicted in FIG. 3. The image data of one of the first pair of cells is subtracted from the image data of the other cell of the first pair. In other words, difference data is generated 410, where the difference data may be generated by taking an intensity value for each image pixel in the candidate cell of the first pair and subtracting the intensity value for the corresponding image pixel in the reference cell of the first pair. Defects in the candidate cell of the first pair may then be detected 412 by applying a threshold to the difference data. For example, if the difference data indicates that certain pixels have differences in intensity values higher than the threshold, those pixels may be considered to be indicative of a defect. The method continues with the process 420 shown in FIG. 4B. A second pair of reference and candidate cells within the image data is selected 422, where each pixel of one cell in the pair is displaced from a corresponding pixel of the other cell in the pair by one or multiple cell “widths” in the swath (wafer translation) direction 302. In the absence of defects, the images of reference and candidate cells are expected to be substantially similar due to the repeating nature of the pattern on the semiconductor wafer. An example of one such first pair of reference and candidate cells, displaced by one cell “width” in the scan-line direction, is depicted in FIG. 5. (Note that, while the example candidate cells 308 and 508 in FIGS. 3 and 5 are depicted as having different shapes and covering different regions, one embodiment of the invention may select candidate cells 308 and 508 to be of the same shape and cover the same region. In other words, the candidate cells 308 and 508 may be the same cell.) The image data of one of the second pair of cells is subtracted from the image data of the other cell of the second pair. In other words, difference data is generated 424, where the difference data may be generated by taking an intensity value for each image pixel in the candidate cell of the second pair and subtracting the intensity value for the corresponding image pixel in the reference cell of the second pair. Defects in the candidate cell of the second pair may then be detected 426 by applying a threshold to the difference data. For example, if the difference data indicates that certain pixels have differences in intensity values higher than the threshold, those pixels may be considered to be indicative of a defect. By comparing the pixels indicative of a defect found in step 412 to the pixels indicative of a defect found in step 426, any such defects may be verified 428. In particular, if the difference data from both the first and second pairs of cells indicates a defect, then the defect may be deemed as verified. On the other hand, if one set of difference data (for example, from the first pair of cells) indicates a defect, but the other set of difference data (for example, from the second pair of cells) does not, then the defect would remain unverified and may be deemed a false defect or undergo further analysis. FIG. 5 is an illustrative diagram depicting a second pair of reference and candidate cells in accordance with an embodiment of the invention. This illustrative diagram shows example electron image data and further shows the swath (wafer translation) direction 302 and the scan-line direction 304. As seen, the swath and scan-line directions are perpendicular to each other. An example cell pair, including a reference cell 506 and a candidate cell 508, is also shown. In this instance, each pixel of one cell in the pair is displaced from a corresponding pixel of the other cell in the pair by one cell “width” in the swath (wafer translation) direction 302. (In other instances, the displacement between the cells may be multiple cell “widths”.) In the absence of defects, the images of reference and candidate cells are expected to be substantially similar due to the repeating nature of the pattern on the semiconductor wafer. In the above description, numerous specific details are given to provide a thorough understanding of embodiments of the invention. However, the above description of illustrated embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise forms disclosed. One skilled in the relevant art will recognize that the invention can be practiced without one or more of the specific details, or with other methods, components, etc. In other instances, well-known structures or operations are not shown or described in detail to avoid obscuring aspects of the invention. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims. Rather, the scope of the invention is to be determined by the following claims, which are to be construed in accordance with established doctrines of claim interpretation. |
|
051494957 | abstract | Water rod configurations, such as for a boiling water nuclear reactor, are provided. An efficiency parameter is defined which relate to how well-used the sacrificed fuel rod positions are. Four particular water rod configurations are described, which produce high efficiency, such as having a water rod efficiency greater than about 0.6, preferably greater than about 0.7. Desired moderation is achieved by providing for sacrifice of more than four and less than nine lattice positions. The first "peanut" configuration has a cross-section with two round-cornered triangular regions, integrally connected by a constricted portion. The second configuration has a substantially rectangular cross-section. The third "clover" configuration has a four-lobed shape. The fourth "figure 8" configuration has two substantially circular cross-sectional portions. A method for analysis and design, using a new efficiency parameter, is provided. An apparatus and method for maintaining the water rod and associated fuel rods in the desired spaced configuration is effected by devices for engagement. The engagement devices use resilient deflection to produce engagement of the water rods with spacer apparatus. |
description | This application is a continuation-in-part of U.S. patent application Ser. No. 11/197,707, filed Aug. 4, 2005 now U.S. Pat. No. 7,194,383, which in turn claims benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 60/633,481, entitled “Vibration Analysis System and Method for a Machine”, filed Dec. 6, 2004. This invention relates generally to a system and method for analyzing vibration related data for a machine and, more particularly, to a system and method for testing and analyzing vibration relevant data for a rotating machine using traditional vibration analysis techniques in cooperation with artificial intelligence. Rotating machinery is used in many applications. For example, machines such as mobile machines, e.g., on and off road vehicles, construction machines, earthworking machines, and the like, employ principles of rotation to function. Engines, motors, drive trains, ground engaging components such as wheels or tracks, and the like rotate to enable the machines to perform work tasks. The efficiency and life expectancy of rotating machinery may be analyzed and determined by resort to a study of vibrations present in the machine components. Friction forces between moving parts, compounded by irregularities in component tolerances, serve to cause vibrations in the machines. An analysis of the vibrations may aid in determining, in real time and non-intrusively, the health of the machines, even to the point of predicting component life and potential breakdowns. Vibration analysis, including related concepts of sound and ultrasonic analysis, has long been of interest in monitoring and diagnosing machine health. However, vibration analysis techniques have typically proven to be lacking by either providing questionable results or providing data that cannot be readily interpreted and understood. Efforts have been made to use artificial intelligence techniques to test and analyze vibration of machines. For example, U.S. Pat. Nos. 5,566,092, 5,566,273, 5,602,761, 5,854,993, 6,236,950 and 6,539,319, all assigned to the present assignee, disclose variations in techniques for using neural networks to perform testing and analysis of machines, particularly with respect to vibration characteristics of the machines. Although the techniques embodied in the above patents have resulted in some degree of success, it is desired that further techniques be developed which offer greater reliability, robustness and precision in testing and analysis. The present invention is directed to overcoming one or more of the problems as set forth above. In one aspect of the present invention a system for detecting and analyzing anomalies in a machine during operation is disclosed. The system includes at least one sensor associated with a component on the machine, a transducer configured to be positioned about the component, and a test station for receiving signals from the at least one sensor and the transducer, and correlating the signals to determine a source of an anomaly. In another aspect of the present invention a method for detecting and analyzing anomalies in a machine during operation is disclosed. The method includes the steps of receiving sensed signals from the machine, receiving audio signals from a transducer positioned about components on the machine, correlating audio signals received with respect to each component with corresponding sensed signals associated with each component, cross-correlating all correlated signals, and determining a location of an anomaly based on the cross-correlation. Referring to the drawings in general, a system 100 and method for detecting and analyzing anomalies in a machine 10 during operation is shown. Anomalies may refer to vibration related characteristics of the machine 10, in particular to vibration related characteristics of rotating components of the machine 10. Referring to FIG. 1 in particular, a machine 10 is embodied as a wheel loader, typically used for earthworking and construction purposes. The wheel loader depiction is merely for exemplary purposes, in that machines of a variety of types, mobile and stationary, may be used with the present invention. For example, other types of wheeled machines and vehicles, tracked machines, power generators, machines for manufacturing, assembly, and storage, and various other types of machines, may all benefit from use of the present invention. The exemplary machine 10 of FIG. 1 may include an engine 12, a transmission 14, a transfer unit 16 of some type, e.g., a transfer case, and a drive train 18, all of which are well understood in the art. A common feature of the above listed components of the machine 10 is that all embody rotating movement of component parts, that may be prone to vibration within or outside of acceptable tolerances. At least one vibration sensor 20 may be used to sense, either directly or through derivation, vibrations in the machine 10. Vibration sensors 20 may include such devices as rotational speed sensors, accelerometers, and the like, and may be connected at various desired locations on the machine 10 to sense parameters indicative of vibration. At least one other, non-vibration sensor 22 may be used to detect, either directly or indirectly, characteristics associated with the machine 10 that are not vibration related. Examples of non-vibration sensors 22 may include temperature sensors, humidity sensors, barometric pressure sensors, fluid level sensors, and the like. Referring to FIG. 2, a block diagram illustrating an aspect of the system 100 is shown. The system 100 is depicted as having a remote test station 102 for on-site testing of the machine 10, and a processing hub 118 that may be located at a central point away from the test station 102. For example, there may be many remote test stations 102 located at sites in which machines are also located, and a single processing hub 118 located at a central station away from the machine sites. Although the present disclosure describes the exemplary situation in which the test station 102 and the hub 118 are at separate locations, it is conceivable that the test station 102 and the hub 118 may be located at one site, perhaps even housed as one unit. The test station 102 may include a plurality of sensed inputs 104, for example from a variety of vibration and non-vibration sensors 20,22. The sensed inputs 104 may be input to a signal conditioner 106. The signal conditioner 106 may be used to perform functions such as providing proper biasing currents. The conditioned signals may then be routed through analog filters 107 for anti-aliasing. The signals may then be delivered to an I/O connector 108, and then to an A/D converter card 109 for conversion from analog to digital. Sensed inputs 104a–m represent signals that are processed by the above steps. Alternatively, signals, as depicted by sensed inputs 104n–z, may not require the above conditioning and filtering and may be delivered directly to the I/O connector 108. A processor 110 may receive the conditioned data signals and perform additional processing. For example, a memory 112 may be accessed to store and retrieve data. The processor 110 may also prepare the data for delivery to the hub 118, e.g., by selecting certain data, categorizing data, tabulating and partially analyzing raw data, and the like. The remote test station 102 is powered by a power supply 114, which may be an uninterruptible power supply (UPS) to protect the equipment and the received and compiled data from corruption caused by power interruptions. A communications link 116 provides communications between the test station 102 and the hub 118. The communications link 116 may be wired or wireless, depending on the overall system configuration and needs. Preferably, communications may be made by way of an Internet protocol for web access. However, other methods of communication may be used. For example, the communications link 116 may be wireless such as radio, microwave, or satellite, or may be wired such as via telephone line, coaxial cable, power transmission lines, and the like. In addition, the communications link 116 may be hard wired by way of dedicated wiring connections, or the test station 102 and the hub 118 may be connected together as one integrated unit. Associated transmit and receive equipment (not shown) is used to enable communications over the communications link 116. By whatever medium used for communicating, the communications link 116 may be secured from access, such as by an encrypted Internet protocol, for example. The processing hub 118 is enabled to receive data from one or more test stations 102, process and analyze the data, and deliver the results of the analysis to the test stations 102, or to other designated locations, e.g., to other sites which may be designated to receive out of tolerance or alarm condition messages by way of text messaging or email. Details of operation of the hub 118 may best be described with reference to FIG. 3. The hub 118 may represent software within a computer. In this embodiment, the blocks in FIG. 3 represent various software functions. In FIG. 3, a block indicated as time signal 302 represents the test signal that is delivered to the hub 118 by way of the communications link 116. The time signal 302 is processed prior to delivery by the test station 102 and may be analog to digital converted, encrypted, and delivered as a compacted test message, for example in Internet protocol. The time signal 302 may have many channels and many test steps for each channel. For example, the time signal 302 may have channels representative of each sensed signal being analyzed, and each channel may have test steps for multiple operating conditions of the machine 10. More specifically, the machine 10 may be a transmission, the channels may represent signals received from a multitude of sensors which are configured to sense a corresponding multitude of characteristics of the transmission, e.g., vibrations, temperature, pressure, environmental conditions, and the like, and the test steps may be indicative of various operating modes of the transmission, e.g., first gear forward, second gear forward, and the like. At least one virtual channel 304 is set up to receive the time signals 302 for delivery to at least one algorithm 306. The virtual channels 304 may be compared in function to signal splitters, thus providing distinct routes for the time signals 302 to be sent. However, the virtual channels 304 have no physical connection to the world outside of the hub 118. The time signals 302 may pass unaltered through each virtual channel 304 or, alternatively, one or more virtual channels 304 may be used to select desired components of the time signals 302. The algorithms 306 may be used to process the time signals 302 for analysis using techniques such as correlation, co-variance, wavelet analysis, and the like. A multiple channel selector 308 provides for selection of multiple channels for processing and analysis. The multiple channel selector 308 may provide more than one channel of the time signal 302 to an algorithm, such as a correlation algorithm 310, to analyze the channels, in particular the results of interactions between the channels. For example, a channel indicative of a vibration signal of a sensor located on a component under test may be analyzed with consideration given to a channel indicative of a vibration signal of a sensor located elsewhere on the machine 10. The multiple channel selector 308 may also process the time signals 302, e.g., for each of multiple channels, to prepare the signals for a neural network, such as neural network number three 312. In particular, the multiple channel selector 308 may average values, e.g., peak amplitude or power, of the signals to provide points to neural network number three 312. The time signals 302 may also be delivered to an autoregression (AR) algorithm 314 for conversion to the frequency domain. The AR algorithm 314, as is well known in the art, is a computationally efficient method for transferring signals from the time domain to the frequency domain. The transferred signals may then be delivered to a neural network, such as neural network number one 316 for analysis. Various channels of the time signal 302 may represent ancillary sensors, i.e., signals from non-vibration sensors 22. These ancillary sensor signals may be sent to a compensatory neural network, i.e., neural network number five 318, for comparison of the influence of the ancillary characteristics on the analysis of vibration related signals. For example, ancillary characteristics such as temperature, pressure, fluid levels, ambient conditions, and the like, have an effect on machine vibrations. As such, an analysis of vibration signals may be made at a higher confidence level if these ancillary characteristics are taken into account. The time signals 302 may also be sent to an FFT (Fast Fourier Transform) control 320, which may provide options such as the use of a truncated FFT, a decimated time waveform FFT, and the like. FFTs, such as FFT number one 322 and FFT number two 324, convert the time domain signals to the frequency domain and may or may not condense the number of frequency domain points to simplify the work of the neural networks. The use of an FFT algorithm allows for processing of a time domain signal to produce a frequency domain signal which represents all frequency components present in the provided time-domain signal. Given the large number of data points in the frequency spectrum, it may take a significant amount of time to determine which frequencies are significant, and to determine what a normal level for these frequencies should be. The present invention may use an autostencil algorithm to automatically create a set of spectral divisions, based on the given frequency domain signal. Based on the dimensions of the division, new data signals may be passed through the divisions to perform diagnostic functions upon their content, such as the absolute maximum value of any frequency component contained therein, or the power, e.g., RMS value, of the data contained within the division. A preferred algorithm may work by identifying key component frequency elements in the signal, creating a spectral division around the signal, scaling the height of the division as appropriate, and repeating until a series of divisions are created. The algorithm may first identify the highest amplitude frequency component that is not already part of an existing spectral division. The algorithm may then use a predefined or user configurable transfer function to create a spectral division around this frequency component. The transfer function serves to identify the width of the spectral division. The transfer function is typically an exponential curve. As variations in environmental variables, e.g., RPM, temperature, humidity, and the like, may cause a shift in frequencies, higher frequency components will typically be more greatly affected than lower frequency components. The exponential transfer function may serve to widen those spectral divisions at upper frequencies so that their content remains relatively stable. A similar exponential transfer function may exist to scale the height, e.g., thresholds, of the spectral division. This transfer function may then serve to scale down the thresholds of any spectral divisions present in higher frequency ranges as it takes a much higher force at higher frequencies to cause a significant change in amplitude of a frequency component than it would take at lower frequencies. The process of identifying frequency components may repeat until certain criteria have been met. In a first embodiment, a fixed number of divisions, i.e., N number, may be requested, to identify the top N major components of the signal. In a second embodiment, the algorithm may run with the number of divisions N set to infinity to saturate the signal with divisions, thus ensuring that substantially all of the signal is covered by at least one division. A third embodiment may involve calculating a signal-to-noise ratio and a total power in the signal, and then a process begins of identifying divisions until all non-noise power in the signal is contained within defined spectral divisions. The FFT points from FFT number one may be applied directly to a neural network such as neural network number two for vibration analysis. The FFT points from FFT number two 324 may then be sent through a series of band pass filters (BPF) 326 configured in parallel so that the frequency domain may be split into bands of frequency packets. Each packet then may undergo further processing by way of frequency packet processors 328. For example, a root mean square (RMS) value of each packet may be determined or a peak value (PK) of each packet may be determined. Alternatively, a power spectral density (PSD) or some other such value may be determined. The points from the frequency packet processors 328 may then be applied to a neural network such as neural network number four 332 to analyze vibration characteristics of the machine 10 under test. Furthermore, the points may, in addition or alternatively, be applied to neural network number five 318, i.e., the compensatory neural network, for inclusion of the influence of ancillary characteristics in the vibration analysis of the machine 10 under test. Preferably, the results of the compensatory neural network will have a higher confidence level due to the inclusion of factors that may have an effect on machine vibrations, that are not considered by typical vibration analysis techniques. Each of the neural networks and algorithms used may be assigned an adjustable weighting factor during initial setup of the hub 118, and during subsequent sessions in which the hub 118 is fine tuned for optimal performance. The process for setting up the hub 118 may employ the use of wizards which prompt for certain inputs, such as number and types of neural networks, BPF specifics, virtual channels and algorithms to be used, and the like. The resultant hub configuration may thus be customized for specific vibration analysis situations, and also may be altered periodically as desired. The hub 118 may be based on software which provides for drag and drop user configurability. For example, various selectable features such as BPFs, algorithms, neural networks, and the like, may be selected by dragging icons representative of such features to a portion of a display and dropping the icons to select them. By this technique, any desired number of features may be chosen. The selection of features may be made for each test step of each channel in the time signal 302. The above described algorithm, and other algorithms that may be used as well, may be used to identify a series of inputs that are applicable to a neural network. Part of the configuration process involves taking collected data, identifying it as a normal pattern, and training this normal pattern to all the neural networks contained within the processing hub 118. When a new test plan is set up, or an existing test plan is updated or modified, each neural network present must potentially be reconfigured based on the most recent data collected. As a part of this process, each neural network present must be re-initialized, created, and trained. Subsequently, the normal pattern for each neural network must be identified, and each neural network must be trained with a new pattern. The use of wizards may be used to fully automate this process, thus eliminating operator error, and significantly reducing the time required to get the processing hub 118 into operation. The wizards may identify each neural network present, regardless of the previous state of any neural network. Furthermore, the use of wizards may allow for test identification of normal samples, i.e., a sample being the full result of one test performed by the processing hub 118. This may include the identification of multiple samples, having patterns which may then be combined to form a single input pattern. Once an input pattern is identified for each unique neural network, the network is blanked if necessary, initialized, and then trained to the normal pattern identified by the above procedure. The process may then be repeated for each neural network present, regardless of the size of the pattern, e.g., number of points. An expert system 334 receives the weighted outputs from the chosen neural networks and algorithms, and responsively sums the weights for a final vibration analysis of the machine 10. If desired, conditioned packets from the BPFs 326, e.g., RMS conditioned, may be sent directly to the expert system 334 to help establish confidence in the neural networks, in particular neural network number four 332, and neural network number five 318. Referring to FIG. 4, a block diagram illustrating another embodiment of the present invention is shown. Machine 10 has a number of components 402a–e, such as pumps, drive train components, and the like. The components 402 may be connected together or may be separately located, for example adjacent each other. The components 402 may be rotating or non-rotating components, and may be a combination thereof. For example, components 402b and 402d may be rotating components, and components 402a, 402c and 402e may be non-rotating. A plurality of sensors 404a–e may be located with respect to corresponding components 402a–e. The sensors 404 may be transducers, such as pressure transducers, having analog outputs. In one embodiment, one or more sensors 404 may be accelerometers. Each sensor 404 is configured and located to sense vibration anomalies from a corresponding component 402. However, since vibrations generated by one component, e.g., component 402b, may induce further vibrations in other components, e.g., 402a and 402c, it is conceivable that all of sensors 404a–c may pick up vibration anomalies from their corresponding components 402a–c, even though only one component 402b is creating the vibrations. Thus, it is difficult to determine the concise origin of the vibrations. A transducer 406 is configured to be movably positioned adjacent selected individual components. Since vibrations typically may generate audible sound signals which then travel through space, the transducer 406 may be a sound transducer, such as a microphone. In particular, a directional microphone may be used. The transducer 406 may be configured to pick up audio signals caused by vibrations, and then deliver electrical signals representative of the audio to the remote test station 102. For discussion purposes, the remote test station 102 may be referred to as the test station 102. A method of operation of the embodiment of FIG. 4 is shown in the flow diagram of FIG. 5. In a first control block 502, signals are sensed from the machine 10 and received by the test station 102. The signals may originate from sensors 404. In a second control block 504, the test station 102 determines the presence of vibrations from the sensed signals. In a third control block 506, a transducer 406, for example a microphone, is positioned near a component 402, for example component 402a. A user may be prompted by the test station 102 to position the microphone or, alternatively, the user may position the microphone and then provide input to the test station 102 that component 402a is being monitored. In a fourth control block 508, an audio signal is delivered from the transducer 406 to the test station 102. In a fifth control block 510, the received audio signal is correlated with the sensed signals to determine the strongest correlation found between the transducer 406 and the sensor locations. Preferably, the transducer 406 is moved about the component 402 with respect to the location of the associated sensor 404 to find the strongest correlation between the audio signal and the sensed vibration signal. A first decision block 512 indicates that the processes of control blocks 506–510 are repeated for each desired component, for example components 502b, 502c, and so forth. In a sixth control block 514, the test station 102 cross-correlates all of the correlated signals to find the strongest cross-correlation. In a seventh control block 516, the test station 102 determines from the cross-correlation which component is most likely to be the source of vibration. In an alternate embodiment, the data gathered by the test station 102 may be delivered to the processing hub 118 for further processing, and the cross-correlation function may be performed by the processing hub 118. The system 100 may be selected to operate in any one of several modes. For example, a first mode may be chosen in which the system 100 monitors the results of all configured test plan parameters, and outputs an alarm if a threshold of any selected parameter is exceeded. Notifications may be sent to any desired location by any desired means. A second mode may include the features of the above described first mode, and further include alarm functions based on the outputs of any neural networks if preset confidence levels are exceeded. A third mode may include features of the first and second modes, and may further include the ability for a test engineer to elect to have the system 100 make an intelligent prognosis based on the weighted results of any selected parameters, as well as any of the neural network confidence levels. The results, based on a combination of weights in any desired category, may be provided to an operator of the machine 10, a test engineer at the hub 118, a database for recordation, another specified location, or any combination thereof. The use of the above described techniques and components in the hub 118 allows for greater confidence levels in the results and also enables vibration analysis with the use of neural networks which have no need for past historical data to achieve a reasonable level of reliability certainty. Other aspects can be obtained from a study of the drawings, the disclosure, and the appended claims. |
|
claims | 1. A collimator, for high-energy electromagnetic radiation, comprising a plurality of X-ray optical elements which bound an opening arranged in a beam path including an X-ray optical element at an entrance side and an X-ray optical element at an exit side of the collimator, and a tube having inner walls between the X-ray optical elements at the entrance side and the exit side; wherein the X-ray optical elements are slit or hole diaphragms provided with at least one passage opening for rays; and wherein an edge zone of the X-ray optical element at the entrance side is angled at least partly relative to a direction of propagation of the rays; and the inner walls are of a different material than the diaphragms, wherein at least one of the X-ray optical elements is provided with at least one passage opening for rays, and the edge zone of the X-ray optical element which faces the passage opening is graduated and comprises a zone which is longer in the propagation direction of the rays and has a larger opening and also a subsequent zone in the direction of propagation which is shorter and has a smaller opening. 2. A collimator according to claim 1, wherein the angle of the element at the entrance side is such that a ray which travels at a grazing angle along the angled edge zone of the X-ray optical element at the entrance side is not incident directly on the X-ray optical element at the exit side. 3. A collimator as claimed in claim 1, wherein the X-ray optical elements are arranged at a distance from one another and are provided with respective angulated edge zones. 4. A collimator as claimed in claim 1, wherein the X-ray optical diaphragms enclose the rays in a segment and the collimator is provided on an inner side with walls which reflect or scatter or produce secondary radiation. 5. A collimator as claimed in claim 4, wherein in the collimator there are arranged further diaphragms which bound a beam diameter in order to filter out radiation reflected or scattered by the walls or secondary radiation. 6. A collimator as claimed in claim 1, wherein the X-ray optical diaphragms at the entrance side and the exit side are provided with an angulation of the same orientation. 7. A collimator as claimed in claim 1, wherein an angulation of the element at the exit side is such that a ray which travels at a grazing angle along an angulated edge of the X-ray optical element at the exit side does not originate directly from the X-ray optical element at the entrance side. 8. A collimator as claimed in claim 1 which includes said X-ray optical elements having edge zones at the entrance side and at the exit side. |
|
046817328 | abstract | A method of operating a gas-cooled nuclear reactor having graphite fuel elements in which, to reduce the reactor, a quenching element is introduced which takes a particle of a reaction-reducing substance in a sheath which will melt or release the substance in vapor form so that the substance can penetrate in gaseous form through the surrounding graphite body and deposit upon fuel elements. |
description | This application is a divisional of and claims priority to U.S. application Ser. No. 12/966,350, filed Dec. 13, 2010, which is a continuation-in-part of U.S. application Ser. No. 12/966,315, filed Dec. 13, 2010, the entire contents of each are hereby incorporated by reference. Embodiments of the present disclosure relate generally to methods and devices for shielding an area from radiation and, more particularly, to a cryogenically cooled radiation shield device and an associated method. The sun occasionally releases significant amounts of charged particles during events known as coronal mass ejectas (“CMEs”). The charged particles released during CMEs include electrons, protons, and heavy ions. Each CME may last for about one or two days in the vicinity of earth, but their effects may linger for up to a week. Such proton and heavy ion radiation can cause cell damage to humans exposed to such radiation. Additionally, sensitive electronic components and other devices may be adversely affected by such radiation. Therefore, even though CMEs are relatively uncommon occurrences, the amounts of radiation they could potentially inflict upon a crew and equipment of a spacecraft suggests that consideration be given to shielding part or all of a spacecraft from such radiation. Similarly, comparable radiation protection may be desirable in other environments as well, such as habitats for celestial bodies such as the moon and Mars. Shielding from proton and heavy ion radiation may generally be accomplished by either absorbing the particles or by deflecting the particles. To absorb the radiation, materials of a thickness sufficient for the amount of energy expected from the radiation, can be provided around an area that houses the crew and/or sensitive equipment during a CME. However, because of the significant amount of weight such a housing would require, the use of radiation absorbing material is not practical for space exploration and other applications. Additionally, the absorption of high energy particles may release a different form of radiation such as gamma rays and X-rays that pass through the shielding material and create other difficulties for the crew and/or equipment. It may therefore be preferable to deflect the particles of radiation rather than absorb them. In order to deflect particles of radiation, active radiation shield devices have been proposed. An active radiation shield device may include one or more coils that extend about an area to be shielded, such as about a spacecraft or the like. By passing current through the coil(s) of the radiation shield device, a magnetic field may be generated that deflects particles of radiation that may otherwise impinge upon the spacecraft. In order to facilitate the generation of the protective magnetic field, a radiation shield device may include coils formed of a superconductive material. The coils formed of the superconductive material must therefore be maintained at a temperature below its critical superconducting temperature onset level and as close to absolute zero as practical. As such, the coils formed of a superconductive material may be initially cooled from an ambient temperature and then maintained at a temperature below its critical superconducting temperature onset level by electrical refrigeration units. However, the electrical refrigeration units may be relatively heavy and may consume a substantial amount of electrical power. In addition, the electrical refrigeration unit may require electrical power generation and distribution, which also disadvantageously adds to the overall weight of the system. As it is often desirable to reduce the weight of a spacecraft, it may therefore be undesirable to include an electrical refrigeration unit and the associated electrical power generation distribution system in order to cool the coils formed of a superconducting material to a temperature near absolute zero. As such, radiation shield devices, including coils formed of a superconductive material, may alternatively immerse the coils in liquid helium, which lowers the temperature of the coils from an ambient temperature, such as about 23° C., to a temperature required for superconducting operations, such as −269° C., as a result of the boil-off vaporization of the liquid helium. Since the latent heat of the liquid helium is relatively low, however, an excessive amount of liquid helium, as measured in terms of the weight and volume of the liquid helium, may need to be boiled off in order to cool the coils. As such, a substantial quantity of liquid helium may be required to be provided in order to sufficiently cool the coils formed of a superconductive material, thereby disadvantageously increasing the weight of the spacecraft or the like. A cryogenically cooled radiation shield device as well as an associated method are provided according to embodiments of the present disclosure in order to shield an area, such as the capsule of a space vehicle, from radiation, such as the charged particles released during CMEs. In this regard, the cryogenically cooled radiation shield device and associated method of one embodiment are configured to deflect the particles of radiation in a manner that is lighter and/or consumes less cryogen liquid than some prior approaches. In one embodiment, a cryogenically cooled radiation shield device is provided that includes at least one first coil comprised of a superconducting material extending about an area to be shielded from radiation. The cryogenically cooled radiation shield device also includes a first conduit extending about the area to be shielded from radiation. The at least one first coil is disposed within the first conduit. The cryogenically cooled radiation shield device also includes a second conduit extending about the area to be shielded from radiation. The first conduit is disposed within the second conduit. The cryogenically cooled radiation shield device also includes a first cryogen liquid disposed within the first conduit and a second cryogen liquid, different than the first cryogen liquid, disposed within the second conduit exterior of the first conduit. In one embodiment, the cryogenically cooled radiation shield device may also include thermal insulation surrounding the second conduit. The first cryogen liquid may have a lower boiling point than the second cryogen liquid. For example, the first cryogen liquid may comprise liquid helium, and the second cryogen liquid may be liquid oxygen, liquid nitrogen or liquid hydrogen. In one embodiment, the cryogenically cooled radiation shield device also includes at least one second coil comprised of a superconductive material and extending about the area to be shielded from radiation, third and fourth conduits extending about the area to be shielded from radiation with the at least one second coil being disposed within the third conduit and the third conduit being disposed within the fourth conduit, and first and third cryogen liquids disposed within the third and fourth conduits, respectively, with the third cryogen liquid being different than the first and second cryogen liquids. In this embodiment, the second cryogen liquid may comprise liquid hydrogen, and the third cryogen liquid may comprise liquid oxygen. Further, the cryogenically cooled radiation shield device of this embodiment may also include a fuel cell configured to receive boil-off of the second and third cryogen liquids. In another embodiment, a space vehicle is provided that includes a capsule and a radiation shield device. The radiation shield device includes at least one first coil comprised of a superconductive material extending about the capsule. The radiation shield device also includes first and second conduits extending about the capsule. The at least one first coil is disposed within the first conduit. The first conduit is, in turn, disposed within the second conduit. The radiation shield device of this embodiment also includes first and second cryogen liquids disposed within the first and second conduits, respectively. In one embodiment, the radiation shield device may also include thermal insulation surrounding the second conduit. The first cryogen liquid of one embodiment has a lower boiling point than the second cryogen liquid. For example, the first cryogenic liquid may be liquid helium, and the second cryogen liquid may be liquid oxygen, liquid nitrogen, or liquid hydrogen. The radiation shield device of one embodiment may also include at least one second coil comprised of a superconductive material and extending about the capsule, third and fourth conduits extending about the capsule with the at least one second coil disposed within the third conduit, and the third conduit disposed within the fourth conduit. The radiation shield device of this embodiment also includes first and third cryogen liquids disposed within the third and fourth conduits, respectively, with the third cryogen liquid being different than the first and second cryogen liquids. In this regard, the second cryogen liquid may be liquid hydrogen, and the third cryogen liquid may be liquid oxygen. The space vehicle of one embodiment may also include a fuel cell configured to receive boil-off of the second and third cryogen liquids. In a further embodiment, a method of cryogenically cooling a radiation shield device is provided that includes cryogenically cooling at least one first coil comprised of a superconductive material. The cryogenic cooling includes circulating a first cryogen liquid through a first conduit in which at least one first coil is disposed and circulating a second cryogen liquid, different than the first cryogen liquid, through a second conduit in which the first conduit is disposed. The method of this embodiment also generates a protective magnetic field by providing current flow through the at least one first coil while the at least one first coil is cryogenically cooled. In one embodiment, the at least one first coil may be pre-cooled prior to commencement of the mission, thereby reducing the quantity of cryogen liquid that must be carried during the mission. The first cryogen liquid may have a lower boiling point than the second cryogen liquid. For example, the first cryogen liquid may be liquid helium, and the second cryogen liquid may be liquid oxygen, liquid nitrogen, or liquid hydrogen. In one embodiment, the circulation of a second cryogen liquid may include the sequential circulation of a plurality of different cryogen liquids through the second conduit. In this embodiment, the plurality of different cryogen liquids may be sequentially circulated through the second conduit in order of descending boiling point. Accordingly, the circulation of the first cryogen liquid through the first conduit may commence following the sequential circulation of a plurality of different cryogen liquids through the second conduit. In accordance with embodiments of the present disclosure, a cryogenically cooled radiation shield device and an associated method are provided in order to deflect particles of radiation in a manner that is conservative in terms of its weight and its consumption of liquid cryogen. However, the features, functions and advantages that have been discussed may be achieved independently and the various embodiments of the present disclosure may be combined in the other embodiments, further details of which may be seen with reference to the detailed description and drawings. Embodiments of the present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments are shown. Indeed, these embodiments 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. Referring now to FIG. 1, the radiation shield device 10 in accordance with one embodiment of the present disclosure is illustrated. The radiation shield device 10 is generally described herein as providing protection from radiation for a manned space vehicle or a habitat for celestial bodies, particularly during CME events. However, further embodiments of the present disclosure may include radiation shield devices for any situation in which protection from particle radiation is desired beyond the earth's magnetosphere. The radiation shield device 10 of the illustrated embodiment includes first and second shells 12, 14 that at least partially surround an area 16 to be shielded from radiation. In the illustrated embodiment, a space vehicle defines the area 16 to be shielded from radiation. A space vehicle may have various configurations, but the space vehicle of the illustrated embodiment has a cylindrical center portion and tapered end portions. A space vehicle may house one or more crew members as well as equipment, such as electronics, that may be sensitive to particle radiation. As shown in the illustrated embodiment, the first and second shells 12, 14 at least partially surround the space vehicle. As such, the first and second shells may somewhat follow the shape of the space vehicle. In this regard, the first and second shells 12, 14 of the illustrated embodiment have a medial cylindrical portion that encircles the cylindrical central portion of the space vehicle and opposed end portions that are tapered radially inward from the medial cylindrical portion so as to generally follow the tapered end portions of the space vehicle. The tapered end portions of the first and second shells 12, 14 may taper in a curved fashion as shown in the embodiment of FIG. 1. Alternatively, the end portions of the first and second shells 12, 14 may taper linearly or otherwise so as to more closely follow or conform to the tapered end portions of the space vehicle. As shown in FIG. 1, the second shell 14 is spaced apart from the first shell 12 in such a manner that the second shell is further away from the area 16 to be shielded, such as the space vehicle, than the first shell. In this regard, the first shell 12 may be adjacent to the area 16 to be shielded and, in one embodiment, is attached or connected thereto, while the second shell 14 is spaced further from the area to be protected. As such, the radiation shield device 10 may include a truss network 18 between the first and second shells 12, 14 for connecting the second shell to the first shell and positioning the second shell relative to the first shell. In one embodiment, the truss network 18 is formed of a plurality of truss members extending between and connected to the first and second shells 12, 14. Although the truss network 18 may be formed of various materials, the truss elements of one embodiment may be formed of a composite material, such as a carbon reinforced matrix material in order to provide sufficient strength while limiting the weight of the truss network. The second shell 14 may be larger than the first shell 12 as a result of the second shell being spaced further from the area 16 to be shielded and having, for example, a larger effective radius from the central axis 20 of the area to be shielded. However, the second shell 14 of one embodiment has the same or a comparable shape to that of the first shell 12, as shown in FIG. 1. The first shell 12 includes a plurality of conductive coils that encircle the area 16 to be shielded. With respect to the embodiment of FIG. 1, the circles that graphically represent the first shell 12 are intended to be generally representative of one or more of the coils that encircle the area 16 to be shielded. Likewise, the second shell 14 includes a plurality of conductive coils that encircle the area 16 to be shielded from radiation as well as encircling the first shell 12. Again, the circles that graphically represent the second shell 14 in FIG. 1 are intended to be generally representative of one or more of the coils that encircle the area 16 to be shielded. Indeed, in one embodiment, both the first and second shells 12, 14 may include a substantially greater number of coils than the number of circles shown in FIG. 1. As described below in conjunction with the thermal control system, the coils of each of the first and second shells 12, 14 may be arranged in coil groupings. In one embodiment, the coil groupings of the first shell 12 are paired with respective coil groupings of the second shell 14. Additionally, while the coil planes of the first and second shells 12, 14 of the illustrated embodiment are shown to be parallel and offset form one another, the coil planes of the first and second shells of other embodiments may be rotated with respect to one another, either with or without an offset. The coils of one embodiment are formed of superconductive material. For example, the coils may be formed of a niobium titanium (NbTi) copper matrix multifilament superconducting wire winding. However, other embodiments of the present disclosure may include coils formed of alternative superconductive materials. In order to have superconductive properties, the superconductive material must be maintained at a temperature below its critical superconducting temperature onset level and as close to absolute zero as practical, preferably 36b K or lower, more preferably less than 25 K and most preferably less than 10 K. As such, the radiation shield device 10 may include a thermal control system in thermal communication with the superconductive material of the coils to lower the temperature of the superconductive material to a desired temperature below its critical superconducting temperature onset level. In operation, current is flowed through the coil groupings of the first shell 12 in one direction, such as a counterclockwise direction when looking down on the area 16 to be shielded from above. Conversely, current is flowed through the coil groupings of the second shell 14 in the opposite direction, such as in a clockwise direction when viewed down on the area 16 to be shielded from above. As a result of the current flow through the coils, a magnetic field is generated by each of the first and second shells 12, 14 which function as first and second solenoids, respectively. As a result of the current flowing through the first and second shells 12, 14 being in opposite directions, however, the north and south poles of the coil groupings of the first shell are correspondingly oriented opposite the north and south poles of the paired coil groupings of the second shell. With reference to the illustrated embodiment, for example, the north pole of the coil groupings of the first shell 12 may be at the upper end of the area 16 to be shielded and the south pole of the coil groupings of the first shell may be at the lower end of the area to be shielded, while the north pole of the coil groupings of the second shell 14 may be at the lower end of the area to be shielded and the south pole of the paired coil groupings of the second shell may be at the upper end of the area to be shielded. Representative magnetic flux lines generated by the first and second shells 12, 14 are shown in FIG. 1. As a result of the opposite direction of the current flow through the coils of the first and second shells 12, 14, the magnetic fields generated by the current flow through the coils of the first and second shells offset one another within the area 16 to be shielded such that little or no magnetic field is generated therewithin. Thus, the radiation shield device 10 need not include an internal magnetic shield device to protect the interior of the area to be shielded from the magnetic fields generated by the radiation shield device itself. Accordingly, the weight of a space vehicle or the like may be reduced relative to space vehicles that require such an internal magnetic shield device. In the region between the first and second shells 12, 14, the magnetic fields generated by the current flowing in opposite directions through the coils are directed in the same direction and are additive, thereby resulting in a stronger magnetic field between the first and second shells than that generated by either the first or the second shell individually. Further details regarding the radiation shield device 10 and the resulting magnetic field are provided by U.S. patent application Ser. No. 12/966,315 entitled “Radiation Shield Device and Associated Method”, filed Dec. 13, 2010, the entire contents of which are incorporated by reference herein. As noted above, the radiation shield device 10 includes a thermal control system for establishing and maintaining the temperature required for superconducting operation of the coils. In this regard, FIG. 2 illustrates one example embodiment of aspects of the thermal control system for controlling the temperature of the coils. It is noted, however, that the truss network is not shown in FIG. 2 so as to more clearly illustrate aspects of the thermal control system. Although each shell 12, 14 could be treated as a single unit for thermal control purposes, the plurality of coils of each shell may be broken into a plurality of groupings, such as the three groupings depicted in FIG. 2. Each grouping may, in turn, be separately cooled to temperatures sufficient to allow for superconducting operations. Although three groupings are shown for each shell in the embodiment of FIG. 2, a shell may include more or fewer coil groupings in other embodiments. The thermal control system includes a first conduit 24 that extends about the area 16 to be shielded from radiation. In an embodiment in which the coils of a shell include two or more coil groupings, the thermal control system may include a first conduit, a third conduit, a fifth conduit, etc. (hereinafter generally referenced as “a first conduit” and designated as 24), one of which is associated with each coil grouping. As shown in FIG. 2 and, in more detail, in FIG. 3, the first conduit 24 houses the coils 22 for the respective coil grouping. The first conduit 24 is generally slightly larger than the coils 22 disposed therein such that a cryogen liquid may be circulated therethrough as described below. The first conduit 24 may be formed of various materials but, in one embodiment, is formed of material that does not react with the cryogen liquid, such as aluminum. A first conduit 24 may also have various shapes and configurations but, in the illustrated embodiment, has a length in the axial direction that is greater than its radial width such that the coils 22 housed within the first conduit may relatively uniformly encircle that portion of the area 16 to be shielded from radiation about which the first conduit extends. As shown in FIG. 2 and, in more detail, in FIG. 3, the thermal control system also includes a second conduit 26 extending about the area 16 to be shielded from radiation. In an embodiment in which the coils of a shell include two or more coil groupings, the thermal control system may include a second conduit, a fourth conduit, a sixth conduit, etc. (hereinafter generally referenced as “a second conduit” and designated as 26), one of which is associated with each coil grouping. As shown, each first conduit 24 is disposed within a respective second conduit 26. As such, the second conduit 26 is generally larger than the first conduit 24, such as by having a greater length in the axial direction and a greater radial width, so that a cryogen liquid may be flowed therethrough. Although not necessary, the second conduit 26 may also have a shape that is consistent with or, in one embodiment, identical to that of the first conduit 24. The second conduit 26 may also be formed of various materials but, in one embodiment, is formed of a material that does not react with the cryogen liquid, such as the same material as the first conduit 24, e.g., aluminum. The thermal control system may also include thermal insulation 28 surrounding each second conduit 26 for limiting thermal transfer between the second conduit and the environment. Although the thermal insulation 28 may be formed of various materials, the thermal insulation of one embodiment is formed of a layered composite insulation with paper. With the exception of predefined inlets and outlets for controllably introducing and removing cryogen liquids, the first and second conduits 24, 26 are watertight such that a cryogen liquid circulated through the first conduit remains within the first conduit and does not leak into the second conduit. Likewise, a cryogen liquid circulated within the second conduit 26 exterior of the first conduit 24 does not leak into the first conduit and, instead, remains within the second conduit. In operation, cryogen liquids may be circulated through the first and second conduits 24, 26 in order to lower the temperature of the superconductive material of the coils 22 to a temperature below the critical superconducting temperature onset level and to thereafter maintain the temperature of the superconductive material of the coils at that relatively low temperature. As a result of the thermal control system and associated method of operation of embodiments of the present disclosure, the coils 22 may be efficiently cryogenically cooled in a manner that is sensitive to the weight that is required to be carried by the space vehicle. As described above in conjunction with the embodiment of FIGS. 2 and 3, the thermal control system may include two nested conduits, with each first conduit 24 disposed within a respective second conduit 26. However, other embodiments of the thermal control system of the present disclosure may include additional conduits arranged in a nested fashion such that interior conduit(s) are disposed within exterior conduit(s). By way of example, FIG. 4 illustrates another embodiment of a thermal control system that has three nested conduits, namely, a first conduit 24 in which the coils 22 are disposed, a second conduit 26 within which the first conduit is disposed and an outer conduit 30 within which both the first and second conduits are disposed. The outer conduit 30 may, in turn, be surrounded by insulation 32, such as a layered composite insulation with paper. In the illustrated embodiment, the second conduit 26 is also surrounded by insulation 28 such that the second and outer conduits are spaced apart from one another by the insulation. As described below, cryogen liquids may be circulated through each of the conduits in order to efficiently cool the coils 22 to a temperature sufficiently low for superconducting operations. Although any additional conduits may be formed to have different shapes and to be formed of different materials, the outer conduit 30 of the embodiment illustrated in FIG. 4 has a common shape with those of the first and second conduits 24, 26 and is formed of the same material as the first and second conduits, such as a material that does not react with the cryogen liquid, e.g., aluminum. Although the radiation shield device 10 may be configured in various fashions, the radiation shield device of one embodiment includes a power source 34 as shown in FIG. 5. The power source 34 is in communication with the first and second shells 12, 14, such as the plurality of coils of the first and second shells such that actuation of the power source causes current to flow through the coils of the first and second shells in the desired directions. The radiation shield device 10 of one embodiment is an active device such that the power supply 34 may alternately cause current to flow through the coils of the first and second shells 12, 14 in order to generate a protective magnetic field or cease the current flow through the coils of the first and second shells in order to no longer generate the protective magnetic field. As such, the power supply 34 may be configured to be actuated in instances in which approaching particle radiation is detected such that current flow is initiated and the protective magnetic field is generated prior to the particle radiation impinging upon the area 16 to be protected, such as a space vehicle. Once the particle radiation has dissipated, however, the power source 22 may be deactuated, thereby conserving energy until the next time that a protective magnetic field is to be generated. The radiation shield device 10 of the embodiment of FIG. 5 may also include a source 36 of the cryogen liquids, the controlled circulation of which lowers the temperature of the superconductive material of the coils to a temperature below its critical superconducting temperature onset level prior to or concurrent with the flow of current therethrough. In one embodiment, a separate source, such as a tank, is provided for each cryogen liquid. In one embodiment, however, the sources of the cryogen liquids are combined. In this regard, the cryogen liquids are maintained separate from one another, but the tanks that store and supply the different cryogen liquids are nested in a comparable fashion to the conduits. In this regard, the cryogen liquid having the lowest boiling point, such as liquid helium, may be stored in an innermost tank 36a. The innermost tank 36a may be disposed within a second tank 36b that stores the cryogen liquid having the next lowest boiling point, such as liquid hydrogen. The source 36 of this embodiment would generally have the same number of nested tanks as the number of different cryogen liquids. Thus, while the source 36 of cryogen liquids of the embodiment of FIG. 5 has two nested tanks 36a, 36b, the source may include three or more nested tanks in other embodiments such that the first and second tanks may, in turn, be disposed within a third tank that stores the cryogen liquid having the third lowest boiling point, such as liquid nitrogen. If additional cryogen liquids are utilized by the thermal control system, the source 36 may have additional tanks for storing the cryogen liquids with the sequence or nesting of the tanks based upon the relative boiling points of the cryogen liquids with the tanks ranging from an innermost tank 36a storing the cryogen liquid having the lowest boiling point to an outermost tank storing the cryogen liquid having the highest boiling point. Each tank may be individually connected to the conduit(s) through which the respective cryogen liquid is to circulate. The radiation shield device 10 may also include a controller 38 for controlling the valves or other control devices that selectively allow the flow of cryogen liquids through the different conduits. In one embodiment, the thermal control system is active in that the thermal control system is alternately activated and inactivated with the thermal control system being activated in response to predefined events, such as the detection of approaching particle radiation. In this regard, the thermal control system may be activated so as to lower the temperature of the coils 22 to enable superconducting operation and the generation of a protective magnetic field about the area 16 to be protected prior to the arrival of the particle radiation. Once the particle radiation has dissipated, the thermal control system may be deactivated, thereby conserving energy and reducing the quantity and, therefore, the weight of the cryogen liquid required to cool the coils 22. As shown in FIG. 2, the thermal control system of one embodiment may divide the coils into two or more groupings, each of which is surrounded by two or more conduits carrying cryogen liquids. Although each coil grouping may be cooled in the same fashion utilizing the same cryogen liquids in each respective conduit, different coil groupings may be cooled utilizing different cryogen liquids in some embodiments. For example, the thermal control system of one embodiment may circulate a second cryogen liquid, e.g., liquid hydrogen, through the second conduit 26 associated with one coil grouping and a third cryogen liquid, e.g., liquid oxygen, through the second conduit associated with another coil grouping. While the circulation of either liquid hydrogen or liquid oxygen reduces the temperature of the coils 22 within the respective first conduit 24, the boil-off of the liquid hydrogen and the liquid oxygen that it caused as a result of the absorption of heat from the coils may be combined and utilized productively, as shown in the embodiment of FIG. 5. In this regard, the boil-off of the liquid oxygen from one coil grouping of the thermal control system and the boil-off of the liquid hydrogen from another coil grouping of the thermal control system may be provided to a fuel cell 40. The fuel cell 40, in turn, may combine the boil-off of the liquid oxygen and the boil-off of the liquid hydrogen to generate electricity and/or to generate drinking water which may be utilized to facilitate operation and habitation of the space vehicle. A radiation shield device 30 of another embodiment is shown in FIGS. 6 and 7. In this embodiment, the radiation shield device 10 does not include first and second shells. Instead, the radiation shield device 10 includes two or more cylindrical coils 42 extending about and encircling the center cylindrical portion of an area 16 to be shielded, such as a space vehicle, and a pair of trapezoidal coils 44 extending about and encircling portions of the opposed trapezoidal end portions of the area to be shielded. Each of the coils may include a plurality of coils formed of a superconductive material. In operation, current may be caused to flow and through the coils in the same direction and a magnetic field may be generated as shown by the magnetic flux lines of FIG. 6. The magnetic field generated by the radiation shield device 10 of this embodiment also protects against particle radiation. However, the magnetic field generated by the radiation shield device 10 of this embodiment extends through and creates a magnetic field within the area 16 to be shielded, such as within the space vehicle. As shown in cross-section FIG. 7, the radiation shield device 10 of this embodiment may also include a thermal control system with the windings that comprise each respective coil being disposed within a respective first conduit 24. As before, each of the first conduits 24 is disposed within a respective second conduit 26 which, in turn, is surrounded by thermal insulation 28. By circulating cryogen liquids through the respective conduits, the coils may be cooled so as to facilitate superconducting operation. Referring now to FIG. 8 and, in particular, to operation 50, a method of cryogenically cooling a radiation shield device 10 is illustrated. In one embodiment, the coils of the radiation shield device 10 may be pre-cooled, such as to a temperature capable of supporting a superconducting operation or to a temperature at least cooler than ambient, prior to commencement of a mission, such as prior to launch of the space vehicle. Although the coils need not be pre-cooled in all embodiments, pre-cooling the coils reduces the cooling that is subsequently required during the mission and may therefore reduce the amount of cryogen liquids that are required to be carried onboard the space vehicle, thereby advantageously reducing the weight. Once the mission has begun, and regardless of whether the coils were pre-cooled prior to the mission, a determination may be made, such as by the controller 38, that the coils are to be cooled to a sufficiently low temperature to support superconducting operation. For example, the controller 38 may detect or otherwise determine that particle radiation is approaching the space vehicle and may desire to generate a protective magnetic field. Thus, prior to the arrival of the particle radiation, the controller 38 may issue instructions to the thermal control system regarding the circulation of a cryogen liquid required to cryogenically cool the coils. In the embodiment illustrated in FIG. 8, one or more second cryogen liquids are initially circulated through the second conduit 26. See operation 52. Although the second cryogen liquid circulated through the second conduit 26 may be the same as the first cryogen liquid circulated through the first conduit 24, the second cryogen liquids circulated through the second conduit in one embodiment have a higher boiling point than the first cryogen liquid circulated through the first conduit. While a variety of second cryogen liquids may be circulated through the second conduit 26, examples of cryogen liquids that may be circulated through the second conduit include liquid oxygen, liquid nitrogen and liquid hydrogen. In order to increase the efficiency with which the coils are cooled, the thermal control system may be configured to sequentially circulate different cryogen liquids through the second conduit 26. In this embodiment, the cryogen liquids that are sequentially circulated through the second conduit 26 may be sequenced based upon the respective boiling points of the cryogen liquids and, in particular, in order of descending boiling point. As such, from among the cryogen liquids to be circulated through the second conduit 26, the cryogen liquid having the highest boiling point is initially circulated through the second conduit, the cryogen liquid having the next highest boiling point is next circulated through the second conduit, and so on until the cryogen liquid having the lowest boiling point is circulated through the second conduit. In one example in which liquid oxygen, liquid nitrogen, and liquid hydrogen are circulated through the second conduit 26, liquid oxygen having a boiling point of −183° C. may initially be circulated through the second conduit. Once the liquid oxygen has lowered the temperature of the coils to about −183° C., the liquid oxygen may be replaced with liquid nitrogen having a boiling point of about −198° C. Once the liquid nitrogen has lowered the temperature of the coils to about −198° C., the liquid nitrogen may be replaced with liquid hydrogen having a boiling point of about −253° C., with the circulation of the liquid hydrogen continuing until the temperature of the coils has been lowered to about −253° C. As shown in operation 54 of FIG. 8, a first cryogen liquid may also be circulated through the first conduit 24 in which the coils 22 are disposed. Although the first cryogen liquid may be circulated through the first conduit 24 concurrent with the circulation of a second cryogen liquid through the second conduit 26, the circulation of the first cryogen liquid through the first conduit is initiated, in one embodiment, once the circulation of the second cryogen liquids through the second conduit has lowered the temperature of the coils 22, such as to or near the boiling point of the second cryogen liquid, e.g., to at or near the lowest boiling point of the second cryogen liquids, such as −253° C. in an instance in which liquid hydrogen is circulated through the second conduit. By initially lowering the temperature of the coils 22 by circulation of the second cryogen liquid through the second conduit 26 prior to introducing the first cryogen liquid into the first conduit 24, the coils more efficiently cooled. In this regard, although the second cryogen liquids circulated through the second conduit 26 may have higher boiling points than the first cryogen liquid, such as liquid helium, circulating through the first conduit 24, the latent heat of the second cryogen liquids circulated through the second conduit may be larger than the latent heat of the first cryogen liquid circulated through the first conduit such that the second cryogen liquids may absorb more heat from the coils and cool the coils more efficiently and more rapidly than the first cryogen liquid. In this regard, the latent heat of second cryogen liquids such as liquid oxygen, liquid nitrogen, and liquid hydrogen are 213 kJ/kg-K, 200 kJ/kg-K, and 455 kJ/kg-K, respectively, while the latent heat of a first cryogen liquid such as liquid hydrogen is about 21 kJ/kg-K. Thus, the bulk of the cooling may be performed with the second cryogen liquids that can efficiently lower the temperature of the coils 22 a substantial amount, even though the second cryogen liquids may not be able to completely lower the temperature of the coils to the desired temperature for superconducting operations. Once the second cryogen liquids have lowered the temperature of the coils 22 a substantial amount, such as to or near the lowest boiling point of the second cryogen liquids, such as −253° C. in one embodiment, the first cryogen liquid may be circulated through the first conduit 24 in order to further reduce the temperature of the coils to a temperature sufficient for superconducting operations, such as to −269° C. in an instance in which the first cryogen liquid is liquid helium. This efficient multi-stage cooling of the coils to the desired temperature for superconducting operations also permits the coils to be cooled in a manner that requires less coolant in terms of weight and/or volume, thereby reducing the quantity of coolant that the space vehicle, for example, must transport. Once the temperature of the coils 22 has been lowered so as to support superconducting operation, current may be provided to the coils by the power source 34 as shown in operation 56 with the direction of the current through the coils being controlled as described above. Based upon the flow of current through the coils and the direction of the current flow, a protective magnetic field may be generated about the space vehicle. See operation 58 of FIG. 8. In order to maintain the coils 22 at a temperature that is sufficiently low to support superconducting operations, the first and second cryogen liquids may continue to be circulated with the boil-off of the first cryogen liquid serving to overcome the internal heat or the heat transported in the first cryogen liquid through the insulation 28 external to the first conduit 24, while the boil-off of the second cryogen liquid serves to overcome the heat absorbed from the ambient atmosphere. As such, the area 16, such as a space vehicle, may be shielded from radiation utilizing coils formed of a superconductive material that are efficiently cooled in a manner that limits the quantity of coolant that is required. Further, the method may shield an area 16 from radiation without requiring substantial energy for operation. In this regard, the method of shielding an area 16 from radiation may be activated in response to detection of approaching particle radiation, but may be deactuated, thereby conserving energy, in instances in which particle radiation is not imminent. Many modifications and other embodiments of the present disclosure set forth herein will come to mind to one skilled in the art to which these embodiments pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the present disclosure 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 a generic and descriptive sense only and not for purposes of limitation. |
|
claims | 1. A liquid-metal cooled fast reactor core having a fuel reactor core comprising:a first nuclear fuel assembly in an inner reactor core region at a center of the fuel reactor core,a second nuclear fuel assembly in a middle reactor core region surrounding the first nuclear fuel assembly of the inner reactor core region, anda third nuclear fuel assembly in an outer reactor core region surrounding the second nuclear fuel assembly of the middle reactor core region,wherein the fuel reactor core is installed in a hexagonal duct,wherein each of the first, the second and the third nuclear fuel assembly respectively includes a plurality of first nuclear fuel rods in the inner reactor core region, a plurality of second nuclear fuel rods in the middle reactor core region and a plurality of third nuclear fuel rods in the outer reactor core region,wherein each of the plurality of first nuclear rods includes a first nuclear fuel material surrounded by a first cladding,wherein each of the plurality of second nuclear rods includes a second nuclear fuel material surrounded by a second cladding,wherein each of the plurality of third nuclear rods includes a third nuclear fuel material surrounded by a third cladding,wherein diameters of each of the plurality of first, each of the plurality of second and each of the plurality of third nuclear fuel rods are the same,wherein a thickness of the first cladding is thicker than a thickness of the second cladding and a thickness of the second cladding is thicker than a thickness of the third cladding,wherein each of the plurality of first, the plurality of second and the plurality third nuclear rods maintains an interval with one another by wire wrap located among the each of the plurality of first, the plurality of second and the plurality of third nuclear rods. 2. The liquid-metal cooled fast reactor core as set forth in claim 1, wherein the first cladding of each of the plurality of first nuclear fuel rods in the inner reactor core region has a thickness of 1.02 mm. 3. The liquid-metal cooled fast reactor core as set forth in claim 1 or 2, wherein the first nuclear fuel material of each of the plurality of first nuclear fuel rods in the inner reactor core region has a diameter of 6.03 mm. 4. The liquid-metal cooled fast reactor core as set forth in claim 1, wherein the second cladding of each of the second nuclear fuel rods in the middle reactor core region has a thickness of 0.74 mm. 5. The liquid-metal cooled fast reactor core as set forth in claim 1 or 4, wherein the second nuclear fuel material of each of the second nuclear fuel rods in the middle reactor core region has a diameter of 6.51 mm. 6. The liquid-metal cooled fast reactor core as set forth in claim 1, wherein the third cladding of each of the plurality of third nuclear fuel rods in the outer reactor core region has a thickness of 0.59 mm. 7. The liquid-metal cooled fast reactor core as set forth in claim 1 or 6, wherein the third nuclear fuel material of each of the plurality of third nuclear fuel rod in the outer reactor core region has a diameter of 6.77 mm. |
|
summary | ||
description | This application is a national stage entry of PCT/IN2009/000393, filed Jul. 9, 2009. The present invention relates to a polymer composite for the extraction of cesium from high level acidic nuclear waste that is particularly useful to nuclear industry. Specifically, the invention is directed to a AMP blended polymer composite for the separation of active Cesium. More specifically, the polymer composite material of this invention with superior granulometric properties open up a possibility wherein the void volume of the composite material can be varied to obtain the desired Cs ion exchange capacity, is radiation resistant and stable in highly acidic and alkaline medium. Also, the composite material is helpful for the separation of non-active Cesium from other inorganic wastes/solution. The operation of nuclear power plants, reprocessing plants research facilities and the use of radioisotopes in industry and diagnostic medicine produces a wide variety of radioactive wastes. Many of these wastes need to be treated in order to reduce the radioisotopes concentration to levels acceptable for discharge to the environment. One of the most conventional processes used for the treatment process is ion exchange. Nuclear power reactors use fuel rods containing uranium. Cesium is a by product of nuclear fission process of 235U. The spent fuel contains cesium along with several other radioactive elements. These rods are dissolved in concentrated nitric acid and the solution thus obtained is processed for removal of radioactive elements. It is thus highly desirable to remove cesium from this waste solution to make waste handling easy as well as for possible use of separated cesium as radiation source. These sources can be used for blood irradiation, food preservation, hygeinization of sewage sludge and for radiation sterilization of medical products. To be useful as a Cesium on exchanger in acidic nuclear waste streams, an inorganic compound must exhibit a number of unique properties. The waste streams to be treated have very high levels of Na, K, Ca, Al, Fe, Zr and H+ concentrations relative to Cs. The candidate ion exchange material must have high Cs capacity in presence of these other cations which are up to five orders of magnitude greater in concentration. The HNO3 concentration in each of the waste streams is ˜3-5 M which demands the exchange material to be stable to acidic and oxidizing environments. The compounds must also be highly resistant to radiolytic degradation and elevated temperatures resulting from decay heat generation. Finally the compound must be amenable to fixation by a suitable binding agent or support that will allow the formation of a bead or grain with good mechanical and hydraulic properties. The binding agent must also possess the same qualities of stability in high acid, oxidizing and radiation environments. The use of inorganic ion-exchangers and related composites for treating liquid radioactive wastes has recently gained prospect due to greater safety and lower cost of such exchangers in addition to thermal and radiation stability and high selection for the capture of certain ions. The ion exchange mechanism of AMP or ammonium phosphomolybdate that exists in microcrystalline powder form was first reported by Buchwald and Thistlewaite (1957) and according to Smit and Van (1958), the phosphomolybdate complex ion [PMo12O40]3− consists of a hollow sphere formed by 12 MoO6 octahedra with the PO4 group in the centre of the crystal structure of the ammonium salt of this ion. The ammonium ions with the associated water molecules are probably fitted in between these spheres of negative ions thus accounting for the cohesion of these ions. They also report that the exchange of NH4+ ions for the monovalent ions Na+, K+, Rb+, Cs+, with Cs being much preferred over the others. Thus AMP is a selective ion exchanger for cesium. AMP is available in fine powder form and hence unsuitable for column operations. To make it suitable for intended practical application like the ones to be used in column operations in nuclear plants involved in handling nuclear wastes, it has to be converted into granular forms for use. To create a composite absorber out of AMP, it must be fixed with a binding agent, substrate or support that will allow it to be used in a packed bed column for the separation of Cesium from highly acidic nuclear wastes with reasonable flow rate and pressure. To improve on the granulometric property, AMP is often mixed with asbestos, paper, silica gel, alumina, macro porous organic resin, polyvinyl acetate or polystyrene etc. These modified AMP containing exchanger could not be used for technological application because of lower amount of active AMP loaded on these support and poor granulomertic property. Because of their disadvantage in possessing unsuitable granulometric and mechanical properties, many methods have been proposed for improving such properties of this inorganic ion-exchanger. Various ammonium molybdophosphate (NH4)3[(MoO3)12PO4] or AMP bound polymers and polymer composites became well known in the art to separate cesium wherein the polymer and polymer composites comprise of poly methylmethacrylate (PMMA), polyacrylonitrile (PAN) and natural polymers like alginates that showed improvement in granulometric properties. V, Stoy et. al, in Czech Patent A.O. 181605 achieved improvement in granulomertic properties of the powdered AMP inorganic exchanger in using organic hydrophilic or macro porous polymer and copolymer based on polyacrylonitrile (PAN). H. Mimura et. al. in Journal of Nuclear Science and Technology, 38, 2001, pp 872-878, teaches the immobilizing ability of prominent biopolymer like aliginic acids and alginates in effective granulation or blending of fine crystals of AMP ion-exchanger that offer a number of advantages such as simplicity of preparation, loading of high content of the active component (AMP), high porosity, high mechanical strength and high acid resistance. However, there remains a technological limitation in recovery of loaded Cesium from this substrate because of its deformation in alkaline media wherein the exchange kinetics is also slow due to rigid polymer/AMP composite structures. T. J. Tranter et. al, in Advances in Environmental Research 6, 2002, pp 107-121 illustrates polyacrylonitrile matrix immobilized AMP, an engineered form of cesium selective sorbent material but with high equilibrium contact time. Nilchi et. al, in Applied Radiation and Isotopes, 65, 2007, pp 482-487, teaches the removal of Cs and Co ions from medium active nuclear waste solutions containing granular hexacyanoferrate-based ion exchanger and their PAN (polyacrylonitrile) based composites that were chemically and thermally stable and stable in strong acidic solutions such as ≦5M but the amount of Cs and Co adsorbed decreases with increase in nitric acid concentration. However, PAN (polyacrylonitrile) itself is not stable in required highly acidic and basic conditions (3-5 M HNO3, 1M and above NaOH, 8M HNO3 dissolves PAN). Under these conditions, PAN gets hydrolyzed to polyacrylate and swells thereby increasing bed volume and thus unsuitable for large scale column operations. Due to said swelling and hydrolysis, mechanical properties also reduce wherein said PAN binder is excellent for neutral to weakly acidic solutions. U.S. Pat. No. 4,714,482 teaches on the formation of thin film polymer blend membranes made by blending organic polymers and inorganic chemicals for gas sensing applications wherein said thin film polymer blend membranes are composited on solid porous beads comprising of polysulfone to impart increased structural strength to the membrane. Moreover, the polymers employed in forming the said thin film polymer blend membranes do not use polysulfone as the polymer in the said blend. WO 02/35581 discloses a PAN-AMP composite wherein said PAN (polyacrylonitrile) forming the composite is itself not stable in required highly acidic and basic conditions such as 3-5 M HNO3, 1M and above NaOH, 8M HNO3 that dissolves the said PAN wherein under the said conditions PAN gets hydrolyzed to polyacrylate and swells and thus increasing bed volume, and hence undesirable for large scale column operations. It is thus apparent from the discussions hereinbefore that the granular forms of known polymer-AMP composites of the above mentioned prior arts have technological deficiencies and suffer from one or many of the following drawbacks: i. hard; ii. lower available surface area; ii. low accessibility; iv. Deformation or swelling in alkaline solutions (acrylates); v. Decreased adsorption from highly acidic nuclear wastes; vi. low radiation stability; vii. slow exchange kinetics (longer equilibrium time) viii. labor intensive manufacturing and ix. use of significant quantities of organic solvents, cross-linkers etc. Therefore it is imperative to develop and provide for alternatives that would be cost effective in requiring small volume of organic solvent in its process of preparation, has high AMP to polymer loading, is stable to radiation, has fast exchange kinetics (short equilibrium time) and shows increased stability in acidic and alkaline medium with no significant deformation of the polymer structure. It is thus the basic object of the present invention to provide for a selective blend of high AMP to polymer loaded engineered composite material directed to aid in the rapid extraction of active and non-active Cesium from high level acidic nuclear waste and/or from other inorganic wastes/solutions. Another object of the present invention is to provide for a AMP blended polymer composite that would have faster kinetics (shorter equilibrium time) to result in improved and high Cesium ion exchange capacity. Yet another object of the present invention is to provide for a AMP blended polymer composite with a flexible composite structure such that the void volume can be varied to attain the desired exchange kinetics. Yet further object of the present invention is to provide for a AMP blended polymer composite that would be thermally stable, stable in highly acidic and alkaline medium and radiation resistant. Still another object of the present invention is to provide for a AMP blended polymer composite that would possess improved granulometric properties in spite of high AMP loading on the polymer support. Another object of the present invention is directed to provide for a AMP blended polymer composite with improved granulometric properties and sufficient mechanical strength that would be amenable for column operation. Yet further object of the present invention is to provide for a AMP blended polymer composite with improved granulometric properties in the form of beads, fibers, films etc. that are economic, easy to make and involves lesser quantities of organic solvents in its process of manufacturing. Yet another object of the present invention is to provide for a AMP blended polymer composite with desired exchange kinetics that would lead to the desired Cesium ion extraction characteristics from high level acidic and radioactive nuclear waste. This according to the basic aspect of the present invention there is provided a polymer composite for extracting active and non-active Cesium from high level acidic radioactive nuclear waste and/or other inorganic wastes/solutions comprising a blended composite of at least one of polysulfone or its derivatives, or mixtures thereof and Ammonium molybdophosphate (AMP) in the blend ratio of 1:2 to 1:6 providing a composite of highly inner porous structure and an outer structured layer having surface pores which together provide a void volume of 15 to 70% and skeleton density 1.1 to 1.6 gm/cc adapted for equilibrium time of 30-100 minutes and a Cesium ion exchange capacity of 0.4-1.0 meg/gm. It is the finding of the present invention that a blend of AMP with a selective polymer with high AMP to polymer loading provide for obtaining the desired engineered composite material involving desired void volume and density of the composite structure which can also be varied to obtain desired exchange kinetics thereby aiding rapid extraction of active and non-active Cesium from high level acidic nuclear waste and/or from other inorganic wastes/solutions. In accordance with a preferred aspect of the invention there is provided a polymer composite comprising an outer structured layer varying of from 20 to 25 μm with surface pores in the range of 100-300 nm together providing a void volume of 45 to 50% and density of 1.2 g/cc adapted for equilibrium time of 35-40 minutes and a Cesium ion exchange capacity of 0.75-0.8 meq/gm. Preferably, there is provided a polymer composite wherein the said polymer substrates comprise polysulfone and its derivatives, preferably polyether sulfone or its derivatives. More preferably, a polymer composite is provided wherein the said derivatives of polysulfone comprise derivatives in the form of different substituents attached to the benzene ring of the unit. Advantageously, a polymer composite is provided in the present invention wherein the various forms of the said composite comprises of film, bead or fiber preferably bead. Importantly, a polymer composite is provided wherein the polymer substrate of molecular weight between 60,000 to 200,000 comprise Glass Transition Temperatures (Tg) between 170 to 250° C. In another preferred aspect of the invention a polymer composite is provided wherein the molecular weight of 150,000 has of a Glass Transition Temperature (Tg) 210° C. and molecular weight of 60,000 has a Glass Transition Temperature (Tg) 180° C. In yet another preferred aspect of the present invention there is provided a polymer composite comprising void volume of 20-22%, density 1.6 (g/cc), equilibrium time 90-100 minutes has a cesium ion exchange capacity of 0.7 meq/gm. Significantly, a polymer composite is provided comprising improved granulometric properties which is thermally stable up to 200° C., radiation resistant and stable in highly acidic and alkaline medium without any significant change in ion exchange capacity of AMP. Still another aspect of the present invention there is provided a process for the preparation of the above said polymer composite comprising of the following steps (a) reacting the polymer substrate comprising at least one of polysulfone or its derivatives, or mixtures thereof dissolved in a suitable solvent with AMP in required amount in the temperature range of 20 to 50° C. and (b) obtaining therefrom the said polymer composite. Advantageously the above said polymer composite finds effective use for the extraction of active and non-active Cesium from high level acidic radioactive nuclear waste and/or other inorganic wastes/solutions. The details of the invention, its objects and advantages are explained hereunder in greater detail in relation to non-limiting exemplary illustrations as per the following exemplary illustrations: As discussed herein before, the present invention provides a polymer composite of polysulfone, polysulfone derivative, preferably polyether sulfone and its derivatives or their mixture with AMP having highly inner porous structure and an outer structured layer (FIG. 3a, marked as OSL) that control the exchange kinetics wherein the pore diameter varies from 100 to 300 nm (pore sizes are determined from SEM surface photograph, FIG. 3d wherein it is also revealed that the AMP density in the outer layer is much higher than AMP present inside the bead wherein the crystals of AMP are uniformly distributed through out the said surface layer). The polysulfone derivative in the embodiment of the present invention strictly means different substituents attached to the benzene ring of the unit. The various forms of the composite such as film, bead or fiber have higher kinetics of exchange of cesium, are stable to radiation, thermally stable and stable in acidic and alkaline medium. The bead form is the preferred form for column operation. About 90% percent of exchange capacity of AMP was achieved. Importantly, the void volume and density of the composite structure was varied to obtain the desired exchange kinetics. It was achieved in a simple way by selecting a suitable polymer which is radiation stable and inert to acidic or alkaline medium; dispersing the said polymer and AMP in a suitable and common organic solvent wherein the polymer is soluble in the solvent but AMP is finely dispersed (not soluble) and both polymer and AMP are insoluble in water; introducing this solution dropwise into water whereby beads are formed entrapping the AMP. The above said polymer forms a highly porous structure in the presence of AMP in the process of formation of such composite. The polymer forms a highly porous structure in the presence of AMP and in the process of formation of the composite. In the above said polymer-AMP composite of the invention, the AMP granules are dispersed and encaged inside the porous beads wherein the beads have enough mechanical strength for normal column operations for extraction of cesium from high level acidic nuclear waste. Interestingly, the new composite of the present invention obtained by using known ingredients efficiently extracts Cesium from high level acidic nuclear waste overcoming all the limitations known so far and as discussed in the Background Art Section. A typical polymer composite preferably comprising of AMP in the range of 60-90% and polymer in the range of 10-40% with void volume in the range of 15-70 percent and polymer density between 1.1-1.6, extracts Cesium with equilibrium time ranging from 30-100 min and Cesium ion exchange capacity of 0.4-1.0 m equivalent/gm. The invention is illustrated further in greater detail in relation to the following non-limiting exemplary illustrations: In a typical procedure, polymer substrate is dissolved in a suitable solvent including di-chloromethane, n-methyl pyrrolidone and N—N dimethylacetamide, N—N dimethyl formamide and/or their mixtures and ammonium molybdophosphate or AMP in required amount is added slowly at 35° C. and stirred for 30 minutes. The resulting solution is syringed out and added drop wise in distilled or de-ionized water. Different sized beads are obtained by wet phase separation process by varying the bore size of the needle. The beads are washed extensively with water. The wet beads are put in a stainless steel column. Simulated, acidic radioactive waste is passed through the column. Input and output counts are recorded using gamma detector. The thermal stability of the polymer and the resulting AMP-polymer composite bead is demonstrated by the TGA-DTA curves in FIGS. 1a and 1b. FIG. 1a reveal that there is a weight loss in the TGA/DTG curve at 516° C. indicating decomposition of pure polymer. The TGA/DTG curve of FIG. 1b reveals that the composite contains water. It reveals three prominent weight loss peaks, one at around 100° C. and the second at around 450° C. are particularly notable. First peak shows void volume in the bead which is equal to volume of the water lost (weight loss/density of water). FIG. 1c reveals a typical DSC glass transition temperature (Tg) of the polymer used in the present invention. The optical microscopy photographs of the composite beads are demonstrated in FIG. 2a and its cross section revealed in FIG. 2b wherein the characteristic features of the composite beads include: Particle Size: 300 μm-850 μm sulk Density (Dry): 0.6 g/cc sulk Density (wet, immersed in water)=1.2 g/cc pH stability: Stable in acidic and alkaline medium Radiation Stability: Excellent Thermal stability: TGA/DTG profile of pure AMP gives decomposition steps at about 50-80° C. (due to moisture loss), 180° C., 450° C. and at 780° C. TGA/DTG profile of bead (FIG. 1b) shows steps at 100° C. (due to water loss), 450° C. and 780° C. Since the bead contains dispersed crystals of pure AMP, the thermal stability of functional bead is taken as about 180° C., whereas the polymer itself is stable up to 500° C. The fine powders of AMP with high Cs+ ion selectivity were granulated by using polymers of polysulfone and its derivatives and their mixtures used as immobilizing matrices. The SEM images of the AMP-polymer composite and the magnification of its surface are illustrated in FIGS. 3a, 3b, 3c and 3d respectively wherein FIG. 3a shows the magnification of its cross section and revealing 25 μm thick OSL containing AMP crystals, FIG. 3b shows that fine AMP crystals are immobilized in the polymer matrices. Further magnification as seen in FIG. 3c reflects that the AMP crystal size of about 1 to 3 μm is embedded in the polymer matrix and FIG. 3d shows uniform distribution of AMP crystal in OSL. a. 15 gm of polyether sulfone is dissolved in 85 gm of N-methyl pyrrolidone. 80 gm of AMP was dispersed in the solution and bead was made following the procedure illustrated in Example I. b. 25 gm of polyether sulfone is dissolved in 75 gm of N-methyl pyrrolidone. 80 gm of AMP was dispersed in the solution and bead was made following the procedure illustrated in Example I. c. 15 gm of polyether sulfone is dissolved in 85 gm of N-methyl pyrrolidone. 40 gm of AMP was dispersed in the solution and bead was made following the procedure illustrated in Example I. d. 7.5 gm of polyether sulfone (Molecular weight 1, 50, 000) and 7.5 gm of polysulfone (Molecular weight 60, 000) is dissolved in 85 gm of N-methyl pyrrolidone. 20 gm of AMP was dispersed in the solution and bead was made following the procedure illustrated in Example I. In order to assess the applicability and efficiency of the AMP-blended polymer composite in the form of beads for Cs+ removal that is amenable to fixed bed column operation, the void volume of the beads packing the column was analyzed to elucidate the kinetic parameters such as equilibrium time and Cs+ ion exchange capacity. Void volume, equilibrium time and cesium ion exchange capacity of the resulting beads of the above described comparative processes (a-d) was measured and the values obtained is tabulated below in Table 1. TABLE 1Sl.Void VolumeEquilibrium timeCesium ion exchange capacityNo.(%)(min)(meq/gm)a20-22 90-1000.68b30-4050-700.70c45-4935-400.75-0.8 d6230-320.71 Values in Table 1 reveal that the void volume of the composite structure is flexible whereupon the void volume could be varied by varying the stoichiometry of the added ingredients. Also, it is reflected in the above table that a void volume of 45-49% gives the desirable equilibrium time to obtain maximum Cs+ ion exchange capacity of 0.75-0.8 meq/gm. The bound cesium on the AMP-polymer composite after acidic nuclear waste treatment (of acidity of 3-4 M HNO3 solution) was further treated in alkaline medium preferably with 1M NaOH solution to download the Cs-bound AMP for further separation and reuse Cesium. The following observable features during the dissolution process as demonstrated in FIG. 4 are highlighted below pointwise: Complete dissolution of Cs-bound AMP was achieved after passing 11 liters of 1 M NaOH. There was no bed expansion during dissolution. No reduction of AMP (blue colour formation) as seen in the other acrylates based materials. No formation of white precipitate in the solution obtained after dissolution. Dissolution process is fast and smooth. Production process is easy and environment friendly as water is used as solvent for the product Large scale manufacturing can be done from locally available ingredients. The above mentioned FIG. 4 also demonstrates that the white coloured portion in the column of the AMP-polymer composite bead is due to the absence of AMP from those regions of the composite beads structure because of the dissolution of AMP by NaOH whereas the yellow coloured portion as seen in the column is due to the undissolved fraction of the AMP in the AMP-polymer composite bead that is waiting to be dissolved as is normally seen in column operations. The collecting chamber below shows a yellow coloured solution which is the alkaline Cs-AMP solution as extracted by 1M NaOH. Advantageously, the AMP blended polymer composite is technically advanced comprising up to 90% AMP loaded onto it which still remains suitable for column operations. The composite of the invention is thermally stable, stable in acidic and alkaline medium and has high radiation resistance. Additionally, the ion exchange utilization capacity of the bound AMP in the polymer composite of the present invention is 90-95%. Most importantly, the void volume of the AMP-polymer composite structure can be varied to obtain the desired exchange kinetics. It is thus possible by way of the present invention to provide for an AMP blended polymer composite with high Cesium ion exchange capacity adapted for the extraction of Cesium from high level acidic nuclear waste. Also, the invention is directed towards the further downloading of the Cesium-AMP from the bound Cs-AMP blended polymer composite by treating the polymer-AMP-Cs composite with an alkali that finally yields the Cesium. The separated Cesium thus becomes useful in radiation processing application as well as makes nuclear waste handling easier. |
|
summary | ||
061852686 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, the embodiments of this invention will be described below. A main steam pressure disturbance preventing apparatus of a nuclear power plant according to a first embodiment of the present invention will be described referring to FIG. 1. The same component elements in FIG. 1 as those shown in FIG. 11 will be assigned with the same reference numerals and the explanations of duplicated portions will be omitted here. That is, in FIG. 1, in an instrumentation pipe of the steam system or the drain system with detection pipe 10, main instrumentation valve 11, upward detection pipe 12 and downstream side detection pipe 10 sequentially connected in series to main steam pipe 2, a catalyst 14 is installed in the inner surface at the top of upward detection pipe 12. Hydrogen and oxygen produced as a result of radiolysis of core cooling water flow into the top of upward detection pipe 12 together with steam. As steam is condensed to drain and returned to main steam pipe 2, hydrogen and oxygen are accumulated in upward detection pipe 12. But the accumulated hydrogen and oxygen are recombined by catalyst 14 installed in detection pipe 12 and removed, and therefore, their densities do not increase to the levels to generate the disturbance of main steam pressure. Further, although the example of pressure detector 13 is used for the explanation in FIG. 1, it is needless to say that this invention can be applied to an instrumentation pipe connected to a water level detector for pressure detector 13 in the same manner as described above. Next, a second embodiment of the present invention will be described referring to FIG. 2. FIG. 2 shows an example of the present invention applied to a water level detector that is generally used in the main steam system or the drain system. In FIG. 2, an upper detection pipe 15 is branched and connected to main steam pipe 2, and a water level detector 17 is connected to this upper detection pipe 15 via an inlet valve 16. Water level detector 17 has a built-in float 18 to measure the water level of drain 19. At the bottom of water level detector 17, a lower detection pipe 20 is connected, and this lower detection pipe 20 is connected to the drain side of main steam pipe 2 via an outlet valve 21. Main steam from reactor 1 flows into the top of main steam pipe 2 and the downstream side of main steam pipe 2 is connected to the drain side. At the top in water level detector 17, that is, in the inner surface of an upper lid 17a of water level detector 17, catalyst 14 is installed. Steam along with hydrogen and oxygen flow into water level detector 17 from main steam pipe 2 via upper detection pipe 15. In water level detector 17, steam is condensed to drain 19 which is then accumulated in the lower portion of water level detector 17 and hydrogen and oxygen are accumulated in the upper part of water level detector 17. However, the accumulated hydrogen and oxygen are recombined by catalyst 14 provided in water level detector 17 and are removed, and therefore, densities of hydrogen and oxygen will not increase. In water level detector 17, float 18 moves upward with the increase of the water level of drain 19, a stem 18a connected to float 18 thereby moves upward to actuate a microswitch (not shown) that is set at a prescribed position, and thus, detects that drain 19 arrives at a specified water level. Further, although the example of water level detector 17 is used for the explanation in FIG. 2, it is needless to say that this invention can be applied to a pressure detector for water level detector 17. In the embodiments illustrated in FIG. 1 and FIG. 2, it is described that catalyst 14 is installed in the instrumentation pipe and the inner surface of the detector. As a means to install catalyst 14 in the detector or the instrumentation pipe, it is coated or welded. Thus, catalyst 14 can be installed easily and certainly. Next, a third embodiment of the present invention will be described. In the first and the second embodiment shown in FIG. 1 and FIG. 2, if hydrogen and oxygen are accumulated in the steam inflow portion of the instrumentation pipe or the detector while a nuclear power plant is in operation, the surface temperature of the instrumentation pipe or the detector becomes lower than the main steam temperature. Therefore, in this embodiment, a pressure detector or a water level detector is provided to the instrumentation pipe at a point where the surface temperature of the steam inflow portion drops to below a specified temperature after the plant operation and a catalyst is installed in the instrumentation pipe or the detector at that point from the economical viewpoint. The specified temperature is below 100.degree. C. Next, a fourth embodiment of the present invention will be described. In the embodiments shown in FIGS. 1 and 2, examples of the means to install catalyst 14 in the inner surface of the instrumentation pipe or the detector through the coating or welding are explained. In this embodiment, catalyst 14 is formed in a meshed or granular shape in order to make the contact areas of hydrogen, oxygen and catalyst large for the purpose of increasing the effect of catalyst 14 for accelerating the recombination. Further, as for catalyst 14 used in the embodiments described above, it will be described later in detail. Next, a main steam pressure disturbance preventing apparatus of a nuclear power plant according to a fifth embodiment of the present invention will be described referring to FIG. 3. The same component elements used in FIG. 3 as those shown in FIG. 11 will be assigned with the same reference numerals and the explanations of the duplicated portions will be omitted. That is, in FIG. 3, in a piping system shown in FIG. 3(a) composed of detection pipe 10, main instrumentation valve 11, upward detection pipe 12 and detection pipe 10 sequentially connected in series to main steam pipe 2, a cylindrical thin plate 22 is installed in upward detection pipe 12. In the inner surface of cylindrical thin plate 22, a catalyst plated layer 23 plated with catalyst such as platinum, palladium, etc. is formed as shown in FIG. 3(b). Plated catalyst layer 23 is formed in a thickness of about 1 .mu.m around the overall inner surface as shown by the partial hatching. Hydrogen and oxygen flow into the top of upward detection pipe 12 along with steam. As steam is condensed to drain and returned to main steam pipe 2, hydrogen and oxygen are accumulated in upward detection pipe 12. However, they are recombined by catalyst plated layer 23 and therefore, it becomes possible to avoid the accumulation of hydrogen and oxygen. Next, a sixth embodiment of the present invention will be described referring to FIG. 3(c). In FIG. 3(c), a notched portion 24 is provided by notching the lower part of cylindrical thin plate 22, and catalyst plated layer 23 plated with platinum, palladium, etc. for use as a catalyst is provided in the inner surface of cylindrical thin plate 22. Notched portion 24 having a certain notched width will be sufficiently usable. When hydrogen and oxygen are recombined by the catalyst and condensed to water, and the water is then accumulated in the lower part of the pipe, the catalyst becomes disable to display its performance by the water adhered to the surface of the catalyst. To avoid this, the present embodiment features that notched portion 24 is provided at the lower part of cylindrical thin plate 22. Further, when installing cylindrical thin plate 22 having catalyst plated layer 23 to the instrumentation pipe by welding, in consideration of the difference in thermal expansion between the instrumentation pipe and cylindrical thin plate 22, there is much flexibility against the circumferential elongation in this embodiment as notched portion 24 is provided at the lower part of cylindrical thin plate 22. Accordingly, this embodiment is more excellent in mountability when compared with the fifth embodiment with cylindrical thin plate 22 without notched portion 24 shown in FIG. 3(b). Next, a seventh embodiment of the present invention will be described referring to FIG. 3(d). As shown in FIG. 3(d), this embodiment features that unplated layer (the blank portions) 25 are provided at both ends of cylindrical thin plate 22 and catalyst plated layer 23 is provided only at the central portion. According to this embodiment, it becomes possible to avoid adverse effects such as separation of the plate by the thermal effect when welding cylindrical thin plate 22 to the instrumentation pipe by avoiding the plating to both ends of cylindrical thin plate 22. As an example, it is desirable to leave the portions of about 50 mm from both ends of a 300 mm long cylindrical thin plate 22 as unplated layers 25 and make the plate thickness to about 1 .mu.m in catalyst plated layer 23. Then, an eighth embodiment of the present invention will be described. This embodiment features that it is devised to avoid electrolytic corrosion of detection pipe 15 by using the same material as that of detection pipe 12 for cylindrical thin plate 22 provided with, along its inner surface, catalyst plated layer 23 plated by platinum, palladium, etc. As an example, a SUS 304L (JIS) made thin plate is used for cylindrical thin plate 22 for inserting into a SUS 316L (JIS) made instrumentation pipe. A main steam pressure disturbance preventing apparatus of a nuclear power plant according to a ninth embodiment of this invention will be described referring to FIG. 4. In FIG. 4, the same component elements as those shown in FIGS. 2 and 11 will be assigned with the same reference numerals and the explanations of the duplicated portions will be omitted. This embodiment shows an example of the main steam pressure disturbance preventing apparatus applied to a water level detector that is generally used in a main steam system or a drain system of a boiling water nuclear power plant. In FIG. 4(a), upper detection pipe 15 is branched and connected to main steam pipe 2, and a detection container 17A of water level detector 17 is connected to this upper detection pipe 15 via inlet valve 16. Float 18 is provided in detection container 17A to measure the water level of drain 19. Float stem 18a is connected to float 18. Float stem 18a is connected to a switch (not shown) by penetrating upper lid 17a. Lower detection pipe 20 is connected to detection container 17A at its bottom. Lower detection pipe 20 is further connected to the drain side of main steam pipe 2 via outlet valve 21. Main steam from reactor 1 flows into main steam pipe 2 through its top, and the lower side of main steam pipe 2 is connected to the drain side. A catalyst plated thin disc plate 14A is provided at the inner top portion of detection container 17A of water level detector 17, that is, the inner surface of upper lid 17a, plated with a catalyst, such as platinum, for recombining hydrogen and oxygen. Hydrogen and oxygen flow into detection container 17A along with steam from main steam pipe 2 via upper detection pipe 15. Steam is condensed to drain 19 and accumulated in the lower portion of detection container 17A, and hydrogen and oxygen are accumulated in the upper part of detection container 17A. However, when hydrogen and oxygen are accumulated, they are recombined by the catalyst in catalyst plated thin disc plate 14A provided in detection container 17A and removed. Accordingly, the densities of hydrogen and oxygen do not increase. When the water level of drain 19 in detection container 17A increases, float 18 moves upward, and float stem 18a connected to float 18 moves upward and actuates a microswitch (not shown) that is set at a specified position, and it is thus detected that a specified water level is reached. Thin disc plate 14A has a center hole 22A and a small cylindrical projection 23A rising from the circumference of this center hole 22A, and a rising portion 24A of this projection 23 has a curved surface R, as shown in FIG. 4(b). The surface of thin disc place 14A is provided with a catalyst plated layer of platinum, etc. for recombining hydrogen and oxygen. Next, taking platinum (Pt) as an example of the catalyst for the catalyst plated layer provided on the surface of thin disc plate 14A, an example to provide a Pt catalyst plated layer on thin disc plate 14A according to an electrolytic plating method will be described. That is, when providing a Pt plated layer to thin disc plate 14A according to the electrolytic plating method, after masking all portions of thin disc plate 14A except the portion on which platinum is plated, the plating is performed under the conditions shown below, out of general plating, using a solution close to neutral in order to prevent oxidation of material of thin disc plate 14A. Platinum salt: (NH.sub.4).sub.2 PtCl.sub.2, PA1 Conductive salt: Phosphate of ammonium PA1 pH: 4, Temperature: 80.degree. C., PA1 Current density: 1.5 A/cm.sup.2 It is desirable that the catalyst plated layer is sufficiently thick enough to remain on the surface and the amount of Pt is preferred as small as possible from the viewpoint of cost. Accordingly, a desirable thickness of Pt plated layer is about 1 .mu.m. According to this embodiment, as rising portion 24A of small cylindrical projection 23A provided at center hole 22A of thin disc plate 14A is formed to curved surface R, it is possible to avoid the drain dropped from the upper part of detection container 17A of water level detector 17 from adhering to the catalyst plated layer provided on the surface of thin disc plate 14A. As a result, it is possible to avoid the separation of such metals as chrome, etc. on the catalyst plated layer caused by the drain containing such metals adhered to the catalyst plated layer and thereby to avoid the drop of performance of catalyst resulting from decrease in the surface area of the catalyst plated layer. Next, a tenth embodiment of the present invention will be described referring to FIG. 5. This tenth embodiment differs from the ninth embodiment in that the catalyst plated layer is provided on the surface of thin disc plate 14A except curved surface R of rising portion 24A of small cylindrical projection 23A rising from the circumference of center hole 22A of thin disc plate 14A. In FIGS. 5, (a) and (b) show a longitudinal sectional view of thin disc plate 14A and an under surface view thereof, respectively. That is, in this embodiment the catalyst plated layer is not provided on curved surface R formed on rising portion 24A of small cylindrical projection 23A projecting from the circumference of center hole 22A on thin disc plate 14A but is provided on other surface of thin disc plate 14A (the hatched portion in FIG. 5(b)). According to this embodiment, likewise the ninth embodiment, it is possible to prevent the drain from adhering to the catalyst plated layer. Due to the drop in the adherence state of the catalyst in the catalyst plated layer caused by the effect of the stress, etc. in the processing of the curved surface, the separation of the catalyst plated layer occurs during the subsequent use of a nuclear power plant. As the catalyst plated layer is not provided on curved surface R on thin disc plate 14A in this embodiment, it is possible to avoid the above-described adverse effects and thereby is possible to avoid the separated catalyst layer from being brought for the further process. Next, an eleventh embodiment of the present invention will be described referring to FIG. 6. This embodiment differs from the ninth embodiment in that a disc plate 25A having a short cylindrical portion 25a is directly installed at the center on the inner surface of upper lid 17a of detection container 17A, and a thin ring plate 26A having the catalyst plated layer on the under surface is provided on the under surface of this disc plate 25A except short cylindrical portion 25a. This thin ring plate 26A has a hole provided to fit it into the outside of short cylindrical portion 25a. According to this embodiment, disc plate 25A having the cylinder is provided between thin ring plate 26A having the catalyst plated layer on its inner surface and upper lid 17a at the upper part of detection container 17A. As the drain drops along the inner surface of short cylindrical portion 25a from the upper part of detection container 17A by providing this disc plate 25A having the cylinder, it is possible to avoid the drain from adhering to the catalyst plated layer provided on the surface of thin ring plate 26A. Further, the electrolytic corrosion caused by dissimilar metals contact can be prevented by using the same material for disc plate 25A with the cylinder and thin ring plate 26A. Next, a twelfth embodiment of the present invention will be described referring to FIG. 7. This embodiment differs from the ninth embodiment in that a tapered thin plate 27 is provided for thin disc plate 14A. As shown in FIG. 7, tapered thin plate 27 has center hole 22A likewise thin disc plate 14A and has a dish shaped tapered surface 28 which becomes thinner toward the circumferential edge from the lower surface of center hole 22A. There is a catalyst plated layer 29 provided on tapered surface 28 plated with catalyst for recombining hydrogen and oxygen. Tapered thin plate 27 is thick at its center and thin at the circumferential edge. According to this embodiment, it is possible to prevent the drain from adhering to catalyst plated layer 29 of tapered thin plate 27, because the drain flowing from the upper part of detection container 17A of water level detector 17 drops directly from center hole 22A, as tapered thin plate 27 provided with catalyst plated layer 29 at tapered surface 28 is installed on the lower surface of upper lid 17a of detection container 17A. Next, a thirteenth embodiment of the present invention will be described referring to FIG. 8. This embodiment differs from the ninth embodiment in that a thin disc plate 30 having a ring 31 for preventing drain adherence on the under surface is provided for thin disc plate 14A. That is, as shown in FIG. 8(a) showing a longitudinal sectional view of thin disc plate 30, thin disc plate 30 has center hole 22A and is provided with catalyst plated layer 29 at the under surface. On the under surface of thin disc plate 30, ring 31 for preventing drain adherence shown in FIG. 8(b) which shows a perspective view of ring 31 is installed by welding and this ring 31 has center hole 22A in the same diameter as that of center hole 22A of thin disc plate 30. According to this embodiment, as ring 31 for preventing drain adherence is installed to the under surface of thin disc plate 30, the drain from the upper portion of detection container 17A of water level detector 17 drops along ring 31. Accordingly, it is possible to prevent the drain from adhering to catalyst plated layer 29 provided on thin disc plate 30. Further, the electrolytic corrosion caused by contact of dissimilar materials can be prevented by using the same material for ring 31 as that for thin disc plate 30. Next, a fourteenth embodiment of the present invention will be described referring to FIG. 9. This embodiment differs from the ninth embodiment in that catalyst plated layer 29 is provided to float stem 18a for thin disc plate 14A. That is, as shown in FIG. 9, catalyst plated layer 29 is provided to float stem 18a, and the tip of float stem 18a is connected to a switch 32. Float stem 18a is enclosed by cylinder 17c erected from upper lid 17a. According to this embodiment, as float 18a provided with catalyst plated layer 29 is inserted in detection container 17A at its top, catalyst plated layer 29 is set vertically, and as a result, the drain can be prevented from adhering to the surface of catalyst plated layer 29. Further, although the present invention has been explained taking a water level detector as an example in the ninth through the fourteenth embodiments, this invention can also be applied to a pressure detector likewise to the water level detector. According to this invention, it is possible to provide a main steam pressure disturbance preventing apparatus of a nuclear power plant, which is capable of recombining hydrogen and oxygen gradually by catalyst and removing them in a pressure detector or a water level detector connected to a steam system or a drain system, preventing thereby pressure disturbance, and thus maintaining the pressure and water level measurements in a satisfactory state. Further according to this invention, it is possible to provide a main steam pressure disturbance preventing apparatus of a nuclear power plant, which is capable of recombining hydrogen and oxygen gradually by catalyst and removing them in an instrumentation pipe for connecting a pressure detector or a water level detector to a steam system or a drain system, preventing thereby pressure disturbance, and thus maintaining the pressure and water level measurements in a satisfactory state. According to the present invention, it is possible to provide a main steam pressure disturbance preventing apparatus of a nuclear power plant which is capable of maintaining the performance of catalyst for a long period and the measurements of pressure, water level, etc. in a satisfactory state, by preventing the drop of performance of catalyst by metals contained in drain and separated when the drain is adhered to the surface of a catalyst inserted for preventing hydrogen and oxygen to accumulate in a detection container of a water level detector or a pressure detector of a main steam system or a drain system of a nuclear power plant. Obviously, numerous 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 therein. |
048866350 | claims | 1. Gripping tool for a device for the remote-controlled removal of samples in housings with heads from a container, comprising a rigid mast having a first coupling part, a second coupling part opposite and associated with said first coupling part, a guide bar elastically bearing on said second coupling part in a telescoping manner, pivots disposed on said guide bar, at least two catches of a two-armed lever being disposed on said pivots and having a guide grooves formed therein, a bushing surrounding said guide bar having guide pins each engaging a respective one of said guide grooves, and at least one remotely controlled linear pressure medium drive moving said bushing in the direction of the longitudinal axis of said bushing for surrounding the head of the sample housing with said catches like tongs, said at least one drive including at least one cylinder disposed on said guide bar having a piston with a piston rod connected to said bushing. 2. Gripping tool according to claim 1, wherein said first coupling part is an existing element provided for pulling fuel assemblies, and said second coupling part is adapted to and connected with said first coupling part. |
description | This application claims the benefit of priority from U.S. Provisional Patent Application No. 62/340,543, filed on May 24, 2016, and entitled “AUTOMATIC PORTABLE IRRADIATION SYSTEM,” which is incorporated herein by reference in its entirety. The present disclosure generally relates to methods and devices for sample transfer, particularly to methods and devices for automatic sample transfer, and more particularly to methods and devices for automatic sample transfer for nuclear irradiation. Nuclear irradiation is a process in which an object or a sample may be exposed to nuclear radiation. The radiation source may be a neutron source, such as a nuclear reactor or a nuclear accelerator. Nuclear irradiation may have different applications, one such example including Neutron Capture Therapy (NCT), and in particular Boron Neutron Capture Therapy (BNCT), which has been used in cancer treatment. Boron Neutron Capture Therapy (BNCT) may be performed at a facility with a specially designed nuclear reactor or at, hospitals that have an accelerator-based neutron source. A beam of epithermal neutrons is provided by the nuclear reactor or the accelerator-based neutron source and may penetrate the samples that are placed in front of the neutron source. Traditionally, placing the samples in front of a nuclear reactor in, order to be exposed to a specific dose of nuclear radiation may be done manually by operators. However, there are problems associated with the manual transfer and placement of the samples, including but not limited to the threat of being exposed to the nuclear radiations, as well as unstable irradiation due to stability issues associated with nuclear reactors. There is a need in the art for methods and devices to improve the transfer process of the samples to be irradiated. There is further a need in the art for an automatic and portable transfer system for transferring the samples in front of nuclear radiation automatically, which is capable of exposing the samples to a homogeneous dose of nuclear radiation. This summary is intended to provide an overview of the subject matter of this patent, and is not intended to identify essential elements or key elements of the subject matter, nor is it intended to be used to determine the scope of the claimed implementations. The proper scope of this patent may be ascertained from the claims set forth below in view of the detailed description below and the drawings. In one general aspect, the present disclosure is directed to a method of irradiating samples using an irradiation system. The method includes releasing at least a first sample container from an initial position, receiving the first sample container in an irradiation position, the irradiation position being disposed below the initial position, and exposing the first sample container to a radiation source, thereby irradiating the first sample container. The above general aspect may include one or more of the following features. For example, the method may further include rotating the first sample container while the first sample container is being irradiated and/or releasing a second sample container from the initial position. In some cases, the initial position and the irradiation position may be linked together by a substantially vertical conduit, where the first sample container moves from the initial position to the irradiation position through the conduit. The method may also include releasing a second sample container from the initial position; and moving a first gate into a first slit, the first slit being formed in a first portion of the conduit, the first gate blocking the passage of the second sample container through, the first portion of the conduit. In addition, the method may involve removing the first gate from the first slit, thereby permitting the second sample container passage through the first portion of the conduit. The method may also include moving a second gate into a second slit, the second slit being formed in a second portion of the conduit, the second portion being disposed below the first portion, the second gate blocking the passage of the second sample container through the second portion of the conduit. In some cases, the second gate may be removed from the second slit, thereby permitting the second sample container passage through the second portion of the conduit. The method may include releasing the irradiated sample container from the irradiation position; and receiving the irradiated sample container in a sample storage area, the sample storage area being disposed lower relative to the irradiation position. In addition, the method may include using a controller associated with the irradiation system to adjust a number of sample containers to be received by the irradiation position. In another general aspect, the present disclosure is directed to a sample transfer system for nuclear irradiation. The sample transfer system includes a conduit defining a passage for transfer of at least a first sample container from at least an initial position to an irradiation position, an input assembly configured to allow the first sample container to pass through the conduit in a predefined order, and an exposure assembly configured to receive the first sample container via the conduit and rotate the sample containers during exposure to a radiation source. The above general aspect may include one or more of the following features. For example, the system may be configured to close and open a first portion of the passage in the conduit. In addition, the input assembly may include a first gate configured to open and close the conduit; and a second gate disposed above the first gate, the second gate being configured to hold one or more sample containers while the first gate is opened. The input assembly may further include a motor; an actuator coupled to the motor, where the actuator is configured to convert a rotational motion of the motor to a linear motion of the first gate; and a mechanism connected to the actuator, wherein the mechanism is configured to transfer motion of the actuator to the second gate and thereby close the conduit while the first gate is opened. The mechanism may be further configured to transfer motion of the actuator to the second gate and thereby open the conduit while the first gate closes. In some cases, the exposure assembly rotates each received sample container for a predetermined amount of time. In addition, each sample container may be attached to an engagement member. The exposure assembly may further comprise a first mechanism configured to engage and rotate the sample container, the first mechanism including a first motor and at least one gear coupled to the first motor, where the at least one gear is configured to engage with the engagement member of the sample container. The exposure assembly may further comprise a second mechanism configured to displace the first mechanism, the second mechanism including a second motor and an actuator coupled to the second motor, where the actuator is configured to actuate the first mechanism to be displaced thereby to be engaged with the engagement member. The system may further comprise a sample storage area, where the sample storage area comprises a lead-coated chamber. Other systems, methods, features and advantages of the implementations will be, or will become, apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description and this summary, be within the scope of the implementations, and be protected by the following claims. In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant teachings. However, it should be apparent that the present teachings may be practiced without such details. In other instances, well known methods, procedures, components, and/or circuitry have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present teachings. Disclosed methods and devices herein are directed to a sample transfer system configured to transfer a number of samples from a distant first position to an irradiation position in front of a radiation source, such as a neutron source, or other radiation sources. The samples to be irradiated (i.e., exposed to the radiation emitted by the radiation source) may be placed inside sample containers or vials. The sample transfer system may be capable of rotating the sample containers in front of the radiation source in order for the samples to receive a substantially homogeneous amount of nuclear radiation for a predefined amount of exposure time. In some implementations, the sample transfer system may be portable and automatic. In one implementation, the sample transfer system may include a conduit, an input assembly, an exposure assembly and a controller. The conduit provides the sample containers with a vertical or substantially vertical passage to facilitate the transfer of samples from the first position defined by the input assembly to the irradiation position defined by the exposure assembly by the force of gravity. In some implementations, the input assembly may be configured to open and close a path defined by the conduit in order to send the sample containers to the irradiation position in a predefined order. In one implementation, the input assembly may send a second sample container to the irradiation position after a first sample has received irradiation for a predetermined amount of time. Alternatively, the input assembly may send a set of predefined number of sample containers to the irradiation position. The time of irradiation for each sample may be specified by a user. The input assembly may be disposed at an adjustable distant first position from the exposure assembly, and the input assembly may be configured to receive a number of samples with a predefined order and sending the samples to the exposure assembly utilizing the force of gravity. The samples inside the sample containers, once placed in the irradiation position, may be rotated in front of the radiation source by the exposure assembly in order for each sample to receive substantially uniform radiation from the radiation source. After a predefined period of time, the sample containers may be allowed to exit the exposure assembly towards a lead-coated chamber in order to be stored. In some implementations, the sample containers are automatically removed from the irradiation position and placed at a distant position after the predefined period of time has passed. The methods and system described herein provide an automatic and portable transfer system for transferring the samples in front of nuclear radiation, as well as a system that is capable of exposing the samples to a homogeneous dose of nuclear radiation. FIG. 1 illustrates a flowchart of an implementation of a transfer method 100 for transferring a number of samples from a distant initial position to an irradiation position near a radiation source, such as a nuclear reactor, accelerators, or other radiation sources. Method 100 includes a first step 101 of releasing at least a first sample container from an initial position, a second step 102 of receiving the first sample container in an irradiation position, the irradiation position being disposed below the initial position, and a third step 103 of exposing the first sample container to a radiation source, thereby irradiating the first sample container. In other implementations, there may be optional further steps, as represented by a fourth step 104 in which the first sample container is rotated while in the irradiation position, and, a fifth step 105 where the first sample container is moved to a storage unit. In other implementations, the method can include additional steps or features. For example, the method can further comprise rotating the first sample container while the first sample container is being irradiated, releasing a second sample container from the initial position, releasing a second sample container from the initial position, and/or moving a first gate into a first slit, the first slit being formed in a first portion of the conduit, the first gate blocking the passage of the second sample container through the first portion of the conduit. Still other implementations can include removing the first gate from the first slit, thereby permitting the second sample container passage through the first portion of the conduit, moving a second gate into a second slit, the second slit being formed in a second portion of the conduit, the second portion being disposed below the first portion, the second gate blocking the passage of the second sample container through the second portion of the conduit, and/or removing the second gate from the second slit, thereby permitting the second sample container passage through the second portion of the conduit. In some implementations, the method can involve releasing the irradiated sample container from the irradiation position and receiving the irradiated sample container in a sample storage area, the sample storage area being disposed lower relative to the irradiation position, and/or using a controller associated with the irradiation system to adjust a number of sample containers to be received by the irradiation position. Furthermore, in different implementations, the method can comprise first step of sending a number of sample containers from the initial position to the irradiation position via a substantially vertical path, utilizing the force of gravity (where the initial position is higher relative to the irradiation position); a second step of exposing the sample containers to radiations received from the radiation source in the irradiation position for a predetermined amount of time; a third step of concurrently rotating the sample containers in the irradiation position; and an optional fourth step of storing irradiated sample containers in a storage unit. It should be understood that in an exemplary implementation, the third step can describe the ongoing rotation of the sample container while the radiation exposure of the second step is occurring (e.g., the rotation occurs concurrently with the exposure of the sample container to the irradiation). This can optimize the uniform exposure of the contents of the sample container to the radiation in some cases. However, in other implementations, the third step can describe one or more rotation(s) of the sample container that occur during the period the sample container is in the irradiation position (whether or not the radiation source is active/on or off). In other words, in different implementations, the rotation can be substantially continuous during the irradiation of the sample container, while in some other implementations, there may be multiple partial rotations, where the sample container is turned partway, paused, and turned partway again. In some cases, the partial rotation may occur when the sample container is in the irradiation position, but is not being irradiated. In this case, once the sample container is rotated to the desired position, the radiation source can irradiate the sample. In other implementations, the partial rotation may occur while the sample container is being irradiated. In addition, in some implementations, the first step may include sending the sample containers to the irradiation position in a predefined order, for example one sample at a time, or a set of predefined number of samples at a time. Furthermore, in some implementations of the second step, each sample may be exposed to radiation for a specific amount of time for that sample. Referring now to FIG. 2, an illustration of a sample transfer apparatus 200 that may be configured for use with one or more methods described herein is presented. In one implementation, the sample transfer apparatus 200 may include a substantially vertical conduit (“conduit”) 201, an input assembly 202, an exposure assembly 203, a controller 204, and optionally a sample storage unit 299. As shown in FIG. 2, conduit 201 may provide a substantially vertical path through which one or more sample containers, such as sample container 205, may be sent to the irradiation position defined by exposure assembly 203. The sample to be irradiated may be placed inside a sample container 205. Sample container 205 may be placed inside conduit 201. In one implementation, a number of sample containers may be placed or inserted, one on top of another, inside of conduit 201 (see for example FIG. 4B below). Input assembly 202 may intercept the path defined by conduit 201. Input assembly 202 may be configured for allowing sample containers to pass through conduit 201 in a predefined order. In one implementation, input assembly 202 may be configured to allow a predefined number of sample containers to pass through conduit 201 while holding any remaining sample containers that have been placed in conduit 201. In some implementations, input assembly 202 may be configured to allow a predefined number of sample containers to pass through conduit 201 by opening the path (“open state”) defined by conduit 201. Similarly, input assembly 202 may be configured to hold or store the remaining sample containers by closing or blocking a portion of the path (“closed state”) defined by conduit 201. According to an implementation, after placing the sample containers inside conduit 201, the exposure time for each sample may be specified via controller 204. Controller 204 may be configured to communicate, transmit commands, or otherwise cause input assembly 202 to allow the passage of each sample container based on the specified exposure time for each sample container. As noted above, once sample containers are allowed to pass through conduit 201 (where the conduit is in the open state), the sample containers may fall or drop towards exposure assembly 203 due to the force of gravity. It should be understood that while in some implementations the sample containers can fall in a substantially free manner, with little or no friction or other hindrance, in other implementations, the passage define by conduit 201 can include a diameter that snugly receives and conducts the sample container at a speed slower than that of a free fall. Similarly, in some implementations, the passage defined by conduit 201 can include bumps, irregularities, texturing, protuberances, cushioning, or other features that interact with the exterior of the sample container and can facilitate a smooth, stable, and/or secure pathway for the sample container. With further reference to FIG. 2, in different implementations, a sample container conducted from input assembly 202 to exposure assembly 203 via conduit 201 may be received in the irradiation position defined inside exposure assembly 203. In one implementation, the irradiation position is associated with a position near an opening 206 in exposure assembly 203. In some implementations, the opening 206 can be directly in front of or otherwise proximal to a radiation source 207. In one implementation, once a sample container is received or otherwise disposed in the irradiation position, controller 204 may receive a signal from a touch, pressure, force, motion or other type of sensor that may indicate the presence of a sample container in the irradiation position. Upon receiving the signal, controller 204 may communicate, command, or otherwise cause exposure assembly 203 to rotate the sample container while the sample container is in the irradiation position. A benefit from this feature may include but is not limited to a substantially homogeneous dose of radiation being received by the sample inside the sample container. The irradiation of each sample may be carried out for a predetermined exposure time. In some implementations, the predetermined exposure time can be the same for each sample container in a series, while in other implementations, the predetermined exposure time can vary for two or more sample containers. In some implementations, once each sample container has received radiation from radiation source 207 for the predetermined exposure time, exposure assembly 203 may allow or facilitate the transfer of the irradiated sample container towards sample storage unit 299. In some implementations, sample storage unit 299 can comprise, for example, a lead-coated chamber that may be a preserving container coated with a shield of lead. In other implementations, sample storage unit 299 can comprise any protective container or holding area configured to provide radiation shielding. Referring now to FIGS. 3 and 4A, conduit 201 may define a path 208 with rectangular or circular cross sections or other shapes that may be sized for allowing a generally free movement of sample container 205 through path 208. In one implementation, the conduit 201 may be constructed in separate sections that may then be connected to one another to form the passage. In some cases, the separate sections can be integrally joined, while in other cases, one or more of the sections can be modular, and removably attached or connected for ease of assembly and disassembly. Furthermore, in some implementations, the length of the conduit 201 may be adjustable. For example, a user may extend the length of the conduit 201 to use the system 200 from a preferred safe distance from the nuclear radiation source 207. In addition, a user may adjust the length of the conduit 201 to provide a shorter or longer passageway for receiving a smaller or larger set of sample containers in some implementations. As shown in FIG. 4A, sample containers may initially be conducted down path 208 from a position immediately above input assembly 202, adjacent to or above a first gate 218. Conduit 201 may be mounted or arranged vertically or include a vertical component, with an orientation that allows for movement of the sample container 205 by the force of gravity. Referring to FIGS. 3 and 4A, there may be a second slit 231 and a first slit 233 defined and provided on the wall of conduit 201 in front of the input assembly 202. The first slit 233 may be defined for the movements of the first gate 218 and the second slit 231 may be defined for the movements of the second gate 229. Referring to FIGS. 2 and 3, in one example implementation, radiation from the irradiation source 207 may reach the sample container 205 through opening 209, which may be defined on the wall of conduit 201 in a position in front of the irradiation source 207. The sample container 205 may be placed inside the conduit 201 in front of the opening 209 during the simultaneous process of rotation and irradiation. The opening 209 may be aligned with the opening 206 in order to make a window and allow the neutron beam of the irradiation source 207 to pass through and reach the sample container 205 placed in an irradiation position 301 near opening 209. Referring to FIG. 3, in one example implementation, the conduit 201 may be mounted as an adjustable passage with some portions to be connected. The input assembly 202 may be constructed as a portable unit mounted in front of a portion of the conduit 201. The input assembly 202 may be placed in a safe distance from the radiation source 207. In another implementation the conduit 201 may be mounted in front of the radiation source 207 while the input assembly 202 and the exposure assembly 203 may be mounted thereon. Referring now to FIG. 4A, an isolated view of a portion of the system including the input assembly 202 is provided for purposes of clarity. In some implementations, input assembly 202 may be activated to allow a predetermined number of the sample containers 205 to pass through the conduit 201 by displacing the first gate 218. In addition, a mechanism 226 may be activated during this time which is configured to hold remaining sample containers (if any) in their places in a vertical queue (shown in FIG. 4B) within the conduit 201. As shown in FIG. 4A, in one implementation, the input assembly 202 may include: a first gate 218 aligned with a first slit 233, the first gate 218 being configured to be displaced, thereby opening or closing path 208; a second gate 229 disposed above the first gate 218, the second gate 229 being configured to hold the remaining sample containers 205 during periods in which the first gate 218 is opened; a motor 222 configured to provide required power and torque; an actuator 220 coupled with the motor 222, the actuator 220 configured to convert the rotational movement of the motor 222 to the linear movement of the first gate 218; and a mechanism 226 connected with the actuator 220, wherein the mechanism 226 may be configured to transfer the movement of the actuator 220 to the second gate 229. This can allow the second gate 229 to hold the remaining sample containers 205 in their queue while the first gate 218 is opened and also allow the second gate 229 to release the remaining samples while the first gate 218 is closed. FIG. 4A can be understood to depict one example implementation of the input assembly 202 as it is configured to transfer a predefined number of the sample containers in a predefined order, while holding any remaining samples in place. With reference back to FIG. 2, in some implementations, the controller 204 may activate the input assembly 202 and trigger a displacement of the first gate 218, in order to allow the movement of the sample containers 205 through the passageway in the conduit. Referring to FIG. 4B, it can be seen that the mechanism 226 may be linked with the actuator 220. Therefore the mechanism 226 may transfer the linear movement of the actuator 220 to the second gate 229 to allow the second gate 229 to hold the remaining sample containers 205, while the first gate 218 is opened to permit a predefined number of sample containers 205 to pass through the first gate 218 (lower figure in FIG. 4B). As shown in the upper figure of FIG. 4B, when the first gate 218 closes the conduit 201, the second gate 229 may rotate, slide, or otherwise move away from the conduit 201, thereby releasing any remaining sample containers 205. As a result, a predefined number of the sample containers 205 may be allowed to pass the second gate 229 and rest upon or be placed on the first gate 218 in a type of vertical queue. In this state a first sample container may fall on the first gate 218 while a predefined number of additional sample containers 205 are positioned upon or directly above the first sample container. In this state there may be no engagement of the second gate 229 with the sample containers 205. In different implementations, the timing of the movements of the first gate 218 and the second gate 229 may be adjusted by regulating the displacement course of the actuator 220. In one implementation, the movement of the actuator 220 may be regulated at least in part by a sensor system and the controller 204. As shown in FIG. 4B, in some implementations, the mechanism 226 may be connected to an actuator 220 of the input assembly 202 and may be configured to move in a substantially synchronous way relative to the actuator 220. The mechanism 226 may also be configured to help hold an adjacent sample container 205 in place, such that any remaining sample containers 205 in the queue above are held in place and prevented from further downward movement. When the first gate 218 has moved and the conduit 201 is in the open state, a predefined number of the sample containers 205 may be passed towards the next position. In the implementation shown in FIG. 4B, one sample container 205 may pass at a time. The sample containers 205 which pass through the first gate 218 may subsequently drop towards the exposure assembly 203. Thus, as the sample container(s) fall downward, the exposure assembly 208 may receive each of the sample containers 205. Once received, the sample containers 205 may be rotated in front of the opening 207 in order to be uniformly exposed to a predetermined amount of nuclear irradiation. In some implementations, the input assembly 202 may facilitate the order and timing of transfer of the sample containers 205, and the exposure assembly 203 may provide the sample containers 205 with a position to be simultaneously rotated and exposed to the radiation. For purposes of clarity, additional details regarding the operation of the first gate 218 is provided with reference again to FIG. 4A. In some implementations of the current disclosure, a mounting plate 224 may be placed in front of the conduit 201, the mounting plate 224 extending in a plane that is in alignment with the first slit 233, and providing a mounting base for different parts of the input assembly 202. The mounting plate 224 may be placed in front of or adjacent to the first slit 233 in order to allow the movements of the first gate 218 inside or through the first slit 233. In some implementations, a set of two parallel rails 232 may be disposed or mounted on the mounting plate 224 in substantial alignment with the first slit 233, thereby defining a linear track for displacements of the first gate 218. The first gate 218 may be disposed on or associated with the two rails 232, and be capable of movement along the defined linear track. Thus, the two rails 232 can provide a mechanism by which the first gate 218 may slide in to and out of the first slit 233 in order to open or block the path 208. The motor 222 is mounted on the mounting plate 218 and may be activated by the controller 204 to provide the power for the movement of the first gate 218. The actuator 220 may be considered a type of converting mechanism, which may convert the rotational power of the motor 222 to the linear movement of the first gate 218. In different implementations, the actuator 220 may comprise various structures. For example, actuator 220 can comprise a ball screw mechanism, a threaded rod-nut set, or other types of mechanical actuators, hydraulic actuators, pneumatic actuators, piezoelectric actuators, electro-mechanical actuators, linear motors, telescoping linear actuators, or other type of actuator. In the implementation of FIG. 4A, the actuator 220 comprises a rack and pinion mechanism, wherein the pinion 221 may be coupled with the output shaft of the motor 224 and the rack 219 may be attached to the first gate 218. The rotational movements of the motor 222 may be transferred to the rotation of the pinion 221 as a driver gear which is meshed with the rack gear 219. As a result, the rack gear 219 may be linearly moved, and as the rack 219 is attached to the first gate 218, the rack 219 and the first gate 218 may be moved along the defined track by the rails 232. Consequently the first gate 218 may either be moved through the opening provided by the first slit 233 to block the path 208 or move out of the first slit 233 and open the path 208. In some implementations, as shown in FIGS. 4A and 4B, the mechanism 226 may be mounted on the mounting plate 224, connected to the actuator 220, and configured to transfer the movement of the first gate 218 to the second gate 229. In other words, the mechanism 226 may adjust the movement of the second gate 229 in accordance with the movement of the first gate 218. The movement of the second gate 229 may be substantially synchronous with the movement of the first gate 218. This can allow the second gate 229 to close the upper portion of the path 208 and hold the remaining sample containers 205 while the lower section of the path 208 is opened by the first gate 218, allowing a predefined number of samples to pass through the conduit 201. Similarly, when the first gate 218 is closed, the second gate 229 may release the sample containers 205. Therefore, in some implementations, the position of the second gate 229 may be determined relative to the position of the first gate 218. Thus, as the first gate 218 moves, the mechanism 226 can ensure that the second gate 229 slides in to or out of the second slit 231 in accordance with the position of the first gate 218 in the system. Further details on the mechanism 226 are provided, with reference again to FIG. 4A. As shown in FIG. 4A, in one implementation, the mechanism 226 may include a first link 225 and a second link 227. The second link 227 may be rotatably mounted on the mounting plate 224 making a pivot 235 around which the mechanism 226 may be rotated. The first link 225 may be attached to the second link 227 and rotatable therewith around the pivot 235. The second link 227 may be mounted vertically with respect to the mounting plate 224 and parallel to the axis of the conduit 201. The first link 225 may be placed in a plane parallel to that of the mounting plate 224 and attached to the second link 227. It can be seen that the linear movement of the first gate 218 may be transferred to the first link 225 when an appendage 238 engages with the first link 225. The appendage 238 may be attached to the first gate 218 and can be forced to move into contact with the first link 225 during the linear movement of the first gate 218. The interaction of the appendage 238 and the first link 225 may cause the first link 225 to rotate around the pivot 235, in turn causing the second link 227 to rotate around an axis of rotation 236. The second gate 229 may be in alignment with the second slit 231 and attached to the second link 227 perpendicularly from one end and may rotate therewith around the axis 236 in order to open or close the path 208 associated with the second slit 231. Furthermore, a spring 228 may be attached to the mechanism 226 that is configured to produce the required restoring force for the mechanism 226 to return to its initial position during the reverse displacement of the first gate 218. The spring 228 may cause the second link 227 to rotate in the opposite direction around the axis 236 in order to reverse the opening or closing action of the second gate 229. Referring now to FIG. 5A, a schematic view of an implementation of the exposure assembly 203 is presented. As noted earlier, the exposure assembly 203 may be configured to receive a predefined number of the sample containers 205 via the conduit 201 and rotate the received sample containers 205 in front of the irradiation source 216. In FIG. 5A, it can be seen that associated, with, a portion of the conduit 201 placed in front of or near the exposure assembly 203, two additional slits (a fourth slit 237 and a third slit 251) are formed. The fourth slit 237 permits a first mechanism 260 to engage or disengage the sample container 205. Furthermore, a third gate 242 may move into and out of the third slit 251 in order to open or close the path 208. In some implementations, the exposure assembly 203 is configured to rotate the sample containers 205 in front of the opening 209 and simultaneously expose the sample containers 205 to the nuclear radiation. As best represented in the depictions of FIGS. 5A-5C, in different implementations, the exposure assembly 203 may include: a third gate 242 configured to move into and out of the third slit 251, allowing the path 208 to be opened or closed, a first mechanism 260 configured to engage and disengage with sample containers and rotate one or more sample containers during irradiation, a second mechanism 270 configured to displace the first mechanism 260 to allow engagement with an engagement member 223 of the sample containers 205 (see FIG. 5C), as well as a third mechanism 240 configured to displace the third gate 242. Further details regarding the operation of the exposure assembly are provided now with reference to FIGS. 5A, 5B, and 5C. In one implementation, the first mechanism 260 may be displaced to contact the head of the sample container 205 and rotate the sample container 205 around an axis 278. In some implementations, the first mechanism 260 may be engaged and disengaged to the sample containers 205. The engagement member 223 may be placed on the head of the sample containers 205 and facilitate engagement with the first mechanism 260. The controller 204 (see FIG. 2) may then activate the second mechanism 270 to displace the first mechanism 260 and move the first mechanism 260 into alignment with the fourth slit 237, where it can engage or disengage with the head of the sample containers 205. In some implementations, the first mechanism 260 may be mounted in front of the fourth slit 237 on a mounting plate 261. The mounting plate 261 may be attached to the housing of the assembly in one implementation. The third slit 251 may be provided on the wall of the conduit 202 below the fourth slit 237. The third gate 242 may be placed in front of the third slit 251 and aligned therewith on a mounting plate 250. The third gate 242 may displace in and out of the fourth slit 237 crossing the conduit 202 to open or close the path 208. The third mechanism 240 may be mounted on the mounting plate 250. The mounting plate 250 may be placed in front of the third slit 251 and attached to the housing of the assembly. The distance between the fourth slit 237 and third slit 251 may be adjusted according to the dimensions and number of the samples to be exposed in each interval. Referring again to FIGS. 5A-5C, various samples may be placed inside the sample containers 205. The sample containers 205 may be in a shape to facilitate substantially free or smooth movement along the path 208 of the conduit 201. Therefore the shape of the sample containers 205 may be dependent on the shape of the conduit 201. In one example implementation, for the cylindrical conduit 201, the sample containers 205 may comprise a cylindrical or spherical shape with a head or cover. The head of the sample containers 205 may be disposed near the top portion of the container. The engagement member 223 may be disposed upon or above the head of the sample containers 205. The exposure assembly 203 may be engaged to the sample containers 205 through the engagement member 223 and rotate the sample containers 205 around the vertical axis of rotation 278. In, one example implementation, the head of the sample container 205 comprises the engagement member 223. In another example the engagement member 223 may be a gear placed on a head of the sample container 205. Referring to FIGS. 5A, 5B and 5C, in different implementations, the first mechanism 260 may include: a movable plate 262 configured to provide the mounting places for parts of the first mechanism 260, a first motor 263 (visible in FIG. 5A) mounted on the movable plate 262 and configured to provide the required rotational power; a gear set 266 which may include at least a pinion gear 267, coupled with the first motor 263 and configured to transfer the rotational power of the first motor 263 to the rotation of the sample containers 205; and a spring 269 attached to the movable plate 262 from one side and to the mounting plate 261 from the other side, the spring 269 being configured to provide the restoring force for the movable plate 261 to return to its initial position. The pinion 267 may be coupled with the output shaft of the first motor 263 and may also be engaged with the gear 268. The motor 263 and the gear set 266 may be mounted on the movable plate 262. In one implementation, the movable plate 262 may be mounted on the mounting plate 261 by a pivoting pin 265. The pin 262 may provide a pivot around which the whole set, including the first motor 263, the gear set 266 and the movable plate 262, may be rotated. Through the rotation of the movable plate 262, the first mechanism 260 becomes engaged with the head of the sample containers 205 (or the engagement member 223). In other implementations, the movable plate 262 may be moved along a linear track defined by a set of two rails 248 by an actuator, such as the actuators described herein with respect to FIGS. 4A and 4B. This system provides a means of rotating the sample containers 205. Due to the pivoting of the movable plate 262, the gear 268 can engage with the engagement member 223. The sensor system 205 may adjust the amount of the pivoting and sense the engagement of the gear 268 with the engagement member 223. The controller 204 may force the first motor 263 to rotate the pinion 267. The rotation may be transferred to the sample containers 205 through the gear 268 subsequently in an adjustable rotational speed. As a result the sample container 205 may rotate around the axis 278 in front of the opening 207. Referring to FIGS. 5A and 5C, in one implementation, the second mechanism 270 may be configured to displace the first mechanism 260 to engage with and rotate the sample containers 205. An example of the third mechanism 270 is shown in FIG. 5C. As depicted in FIG. 5C, third mechanism 270 may include: a second motor 272 configured to provide the rotational power; an actuator 274 configured to convert the rotational movement of the motor 272 to a linear movement; and a base plate 271 configured to provide the mounting places for different parts of the third mechanism 270. In some implementations, the actuator 274 may comprise a linear actuator, such as a rack-pinion set, including at least a pinion 275 and a rack gear 276. The pinion 275 may be coupled with the output shall of the motor 272 and engage, either directly or through intermediary gears, with the rack gear 276. The rack gear 276 may be movable linearly on a slotted guide 277. The slotted guide 277 may be attached to the base plate 271 and the rack gear 276 may be movable thereon inside the slot. The rotational movement of the second motor 272 may be converted to the linear movement of the rack gear 276 through the rotation of the pinion 275. The rack gear 276 may then linearly displace in the slotted guide 277. An appendage 279 may be attached to the front side of the rack gear 276. During the movement of the rack gear 276 the appendage 279 may contact the movable plate 262 of the first mechanism 260 and exert a force in order to displace the first mechanism 260. Other implementations of the actuator 274 may include a ball screw mechanism, a thread-nut mechanism, or other actuators as described herein with respect to FIGS. 4A and 4B. Some implementations of the third mechanism 270 may include an embedded motor and actuator set which may be placed inside the first mechanism 260, replacing the pivoting pin 265. Through the activation of the motor-actuator by the controller 204 the displacement of the first mechanism 260 may be possible. In different implementations the controller 204 may activate the second mechanism 270 to displace the first mechanism 260. The second mechanism 270 may hold the first mechanism 260 that is engaged with the sample container 205 during the irradiation process. Upon completion of irradiation, the controller 204 can direct the second mechanism 270 to return to its initial position. As a result, the exerted force may be removed and the first mechanism 260 may be pulled back by the spring 269. The spring 269 may provide the restoring force for the first mechanism 260 to return to its initial position through the rotation of the movable plate 262 around the pivoting pin 265. Following irradiation, the irradiated sample containers 205 may be transferred or otherwise moved to the lead-coated chamber of the sample storage unit due to their weight. The controller 204 may cause the third mechanism 240 to displace the third gate 242 in order to open the lower portion of path 208 leading towards the lead-coated chamber. Further detail regarding the third mechanism 240 is also provided with reference to FIGS. 5A and 5B. In different implementations, the third mechanism 240 may be activated by the controller 204 to displace the third gate 242 in or out of the third slit 251 in order to open or close the path 208. Referring to FIGS. 5A and 5B, the third mechanism 240, in one implementation, may include: a mounting plate 250 mounted in front of the third slit 251 and attached to the housing of the assembly and configured to provide a mounting area or region; a third motor 244 which may be mounted on the mounting plate 250 and provide rotational power; an actuator 246 which may be connected to the third motor 244 and is configured to convert the rotational movement of the third motor 244 to the linear movement of the third gate 242; and a set of two parallel rails 248 which may be mounted on the mounting plate 250 and be configured to define a track for displacing the third gate 242. The actuator 246 may be implemented by different mechanisms like a ball screw actuator, thread-nut mechanism and so on, or any of the actuators described herein. Referring to FIGS. 5A and 5B, in one implementation, the actuator 246 may include a rack-pinion gear set 246, where the pinion 245 is coupled with the output shaft of the third motor 244 and engaged with the rack gear 247. The rack gear 247 may be attached to the third gate 242 and configured to receive the rotational power of the third motor 244 through the pinion 245 and translate along the track defined by the rails 248 in order to move the third gate 242 linearly in or out of the third slit 251. In other implementations, a touch sensor may also be embedded on the third gate 242. This sensor may be associated with the sensor system 205, and can be configured to sense the receipt of the sample container 205 and inform the controller 204 when the sample container is in the designated position. In addition, in some implementations, the third gate 242 may include a lower plate 241 and an upper plate 243. The lower plate 241 may be placed on the rails 248 and the upper plate 243 may be placed at an angle with respect to the lower plate 241, attaching to the lower plate 241 from its proximal end and capable of rotating around the proximal end. The touch sensor may be disposed between the two plates (lower plate 241 and upper plate 243). The sensor system 205 may inform the control system 204 when the samples are received on the third gate 242. Upon receiving the signal from the sensor system 205, the controller 204 may cause the second mechanism 270 to displace the first mechanism 260, such that the first mechanism 260 is engaged to the respective sample container 205 through the engagement member 223 and initiate rotation of the sample container 205. Following the irradiation process, the sensor system 205 may inform the controller 204 that irradiation has been completed. The controller 204 may then cause the second mechanism 270 to displace the first mechanism 260 and disengage the first mechanism 260 from the sample container 205. At this time the rotation of the sample container 205 can be discontinued, and the sample container 205 may be ready to move to the lead-coated chamber. The sensor system 205 may then inform the controller 204 that the rotation has ceased, and the controller 204 can activate the third mechanism 240. The controller 204 may cause the third mechanism 240 to displace the third gate 242 along the track defined by the rails 248. The controller 204 may further activate the motor 243 to rotate the pinion 245. The pinion 245 may then drive the rack gear 247 linearly to open the path 208. Subsequently the path 208 may be opened and the irradiated sample container 205 or a predefined number of the irradiated sample containers 205 may move or slide downward as a result of their respective weights towards the lead-coated chamber. The third gate 242 may then be driven by the rack gear 247 to return to its initial position in the third slit 251 and close the path 208 again. The system may be ready for use again with new sample containers. While the foregoing has described what are considered to be the best mode and/or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that the teachings may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all applications, modifications and variations that fall within the true scope of the present teachings. Unless otherwise stated, all measurements, values, ratings, positions, magnitudes, sizes, and other specifications that are set forth in this specification, including in the claims that follow, are approximate, not exact. They are intended to have a reasonable range that is consistent with the functions to which they relate and with what is customary in the art to which they pertain. The scope of protection is limited solely by the claims that now follow. That scope is intended and should be interpreted to be as broad as is consistent with the ordinary meaning of the language that is used in the claims when interpreted in light of this specification and the prosecution history that follows and to encompass all structural and functional equivalents. Notwithstanding, none of the claims are intended to embrace subject matter that fails to satisfy the requirement of Sections 101, 102, or 103 of the Patent Act, nor should they be interpreted in such a way. Any unintended embracement of such subject matter is hereby disclaimed. Except as stated immediately above, nothing that has been stated or illustrated is intended or should be interpreted to cause a dedication of any component, step, feature, object, benefit, advantage, or equivalent to the public, regardless of whether it is or is not recited in the claims. It will be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein. Relational terms such as first and second and the like may be used solely to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “a” or “an” does not, without further constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in various implementations. This is for purposes of streamlining the disclosure, and is not to be interpreted as reflecting an intention that the claimed implementations require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed implementation. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter. While various implementations have been described, the description is intended to be exemplary, rather than limiting and it will be apparent to those of ordinary skill in the art that many more implementations and implementations are possible that are within the scope of the implementations. Although many possible combinations of features are shown in the accompanying figures and discussed in this detailed description, many other combinations of the disclosed features are possible. Any feature of any implementation may be used in combination with or substituted for any other feature or element in any other implementation unless specifically restricted. Therefore, it will be understood that any of the features shown and/or discussed in the present disclosure may be implemented together in any suitable combination. Accordingly, the implementations are not to be restricted except in light of the attached claims and their equivalents. Also, various modifications and changes may be made within the scope of the attached claims. |
|
claims | 1. A construction layout for caverns of an underground nuclear power plant, the construction layout comprising:a) two nuclear island powerhouse cavern groups, each nuclear island powerhouse cavern group comprising:a1) a primary cavern accommodating nuclear reactor powerhouse;a2) an electric powerhouse cavern;a3) a safe powerhouse cavern;a4) an auxiliary powerhouse cavern;a5) a nuclear fuel powerhouse cavern; anda6) a connecting powerhouse cavern;b) a first primary traffic tunnel;c) a second primary traffic tunnel;d) a third primary traffic tunnel;e) a fourth primary traffic tunnel;f) two primary steam channels;g) a bottom adit system; andh) a top adit system comprising:h1) a first primary adit;h2) a second primary adit;h3) a third primary adit; andh4) a fourth primary adit;wherein:the electric powerhouse cavern, the safe powerhouse cavern, the nuclear auxiliary powerhouse cavern, the nuclear fuel powerhouse cavern, and the connecting powerhouse cavern are disposed around the corresponding primary cavern;a connecting line of centers of cross-sections of the two primary caverns at a horizontal plane is perpendicular to a longitudinal direction of a mountain in which the underground nuclear power plant is constructed, wherein the horizontal plane is parallel to a ground surface and the longitudinal direction of the mountain;each of the electric powerhouse cavern, the safe powerhouse cavern, the nuclear auxiliary powerhouse cavern, the nuclear fuel powerhouse cavern, and the connecting powerhouse cavern comprises a rectangular cross-section having a longitudinal axis at the horizontal plane;the longitudinal axes of the electric powerhouse cavern, the safe powerhouse cavern, and the nuclear fuel powerhouse cavern are arranged along the longitudinal direction of the mountain; the longitudinal axes of the auxiliary powerhouse cavern and the connecting powerhouse cavern are arranged perpendicular to the longitudinal direction of the mountain and parallel to the ground surface;the safe powerhouse cavern and the nuclear fuel powerhouse cavern are disposed on two sides of the primary cavern, respectively; the electric powerhouse cavern and the safe powerhouse cavern are located on a same side of the primary cavern; the auxiliary powerhouse cavern and the connecting powerhouse cavern are disposed on two sides of the primary cavern, respectively;two primary caverns are disposed between the first primary traffic tunnel and the third primary traffic tunnel; the second primary traffic tunnel is disposed between the two primary caverns;the fourth primary traffic tunnel is disposed perpendicular to the longitudinal direction of the mountain and parallel to the ground surface;the fourth primary traffic tunnel is connected to the first primary traffic tunnel, the second primary traffic tunnel, and the third primary traffic tunnel;one of the two nuclear island powerhouse cavern groups is surrounded by the fourth primary traffic tunnel together with the first primary traffic tunnel and the second primary traffic tunnel, and the other of the two nuclear island powerhouse cavern groups is surrounded by the fourth primary traffic tunnel together with the second primary traffic tunnel and the third primary traffic tunnel;the primary cavern communicates with the corresponding connecting powerhouse cavern via one of the two primary steam channels;the first primary adit, the second primary adit, the third primary adit, and the fourth primary adit of the top adit system are disposed along the longitudinal direction of the mountain, and are connected to the ground surface;skewbacks or endwalls of top arches of the caverns of each nuclear island powerhouse cavern group communicate with the ground surface via the first primary adit, the second primary adit, the third primary adit, and the fourth primary adit of the top adit system;the first primary traffic tunnel, the second primary traffic tunnel, the third primary traffic tunnel, and the two primary steam channels are disposed along the longitudinal direction of the mountain, and are connected to the ground surface;bottoms of sidewalls of the caverns of each nuclear island powerhouse cavern group communicate with the first primary traffic tunnel, the second primary traffic tunnel, the third primary traffic tunnel, the fourth primary traffic tunnel, and the primary steam channel via the bottom adit system, and the bottoms of sidewalls of the caverns of each nuclear island powerhouse cavern group communicate with the ground surface via the first primary traffic tunnel, the second primary traffic tunnel, the third primary traffic tunnel, and the primary steam channel;the first primary adit, the second primary adit, the third primary adit, and the fourth primary adit are disposed at a higher elevation with respect to the first primary traffic tunnel, the second primary traffic tunnel, the third primary traffic tunnel, and the two primary steam channels;the first primary adit, the second primary adit, the third primary adit, and the fourth primary adit are adapted for construction; andthe first primary traffic tunnel, the second primary traffic tunnel, the third primary traffic tunnel, and the two primary steam channels are adapted for slag discharge. 2. The construction layout of claim 1, wherein the top adit system further comprises: a first top adit of a first primary cavern, a second top adit of a second primary cavern, third top adits of the nuclear fuel powerhouse caverns, fourth top adits of the connecting powerhouse caverns, fifth top adits of the electric powerhouse caverns, seventh top adits of the safe powerhouse caverns, an eighth top adit of the auxiliary powerhouse caverns, and ninth top adits of the safe powerhouse caverns;an elevation of the first primary adit is higher than an elevation of the second primary adit, an elevation of the third primary adit, and an elevation of the fourth primary adit; the first primary adit is connected to skewbacks of top arches of the two primary caverns;the second primary adit and the fourth primary adit are respectively connected to endwalls of top arches of outer end faces of the auxiliary powerhouse caverns; two ends of the eighth top adit are respectively connected to endwalls of top arches of inner end faces of the two nuclear auxiliary powerhouse cavern; one end of the third primary adit is connected to a middle section of the eighth top adit;the second primary adit is connected to an endwall of a top arch of a first nuclear fuel powerhouse cavern via one of the third top adits; the third primary adit is connected to an endwall of a top arch of a second nuclear fuel powerhouse cavern via the other of the third top adits;the third primary adit is connected to an endwall of a top arch of a first connecting powerhouse cavern via one of the fourth top adits; the fourth primary adit is connected to an endwall of a top arch of a second connecting powerhouse cavern via the other of the fourth top adits; the fourth top adits are connected to endwalls of top arches of the electric powerhouse caverns via the fifth top adits, respectively; andthe third primary adit is connected to an endwall of a top arch of one end of a first safe powerhouse cavern via one of the seventh top adits; the eighth top adit is branched to form one of the ninth top adits connected to an endwall of a top arch of the other end of the first safe powerhouse cavern; one of the ninth top adits is disposed between an inner end face of a first nuclear auxiliary powerhouse cavern and the third primary adit; the fourth primary adit is branched to form the other of the seventh top adits; and the other of the seventh top adits and the other of the ninth top adits are connected to endwalls of top arches of two ends of a second safe powerhouse cavern. 3. The construction layout of claim 1, wherein the two primary caverns are provided with first apparatus conveying channels for communicating with corresponding connecting powerhouse caverns; and a bottom of a sidewall of each of the connecting powerhouse caverns communicates with the ground surface via a second apparatus conveying channel. 4. The construction layout of claim 2, wherein, each top adit of the top adit system has a longitudinal slope smaller than 12%. 5. The construction layout of claim 2, whereinthe bottom adit system comprises: first bottom adits of the two primary caverns, second bottom adits of the electric powerhouse caverns, third bottom adits of the safe powerhouse caverns, fourth bottom adits of the auxiliary powerhouse caverns, fifth bottom adits of the nuclear fuel powerhouse caverns, and sixth bottom adits of the auxiliary powerhouse caverns;the first primary traffic tunnel is connected to a bottom of a sidewall of a first primary cavern via one of the first bottom adits; the second primary traffic tunnel is connected to a bottom of a sidewall of a second primary cavern via the other of the first bottom adits;each primary steam channel is connected to a bottom of a sidewall of corresponding electric powerhouse cavern via each second bottom adit;the two third bottom adits are disposed on the fourth primary traffic tunnel and are connected to bottoms of endwalls of corresponding safe powerhouse caverns; the two fifth bottom adit are disposed on the fourth primary traffic tunnel and are connected to bottoms of endwalls of corresponding nuclear fuel powerhouse caverns;the two fifth bottom adit are connected to bottoms of endwalls of one ends of corresponding auxiliary powerhouse caverns via sixth bottom adits of the auxiliary powerhouse caverns; andthe two third bottom adit are connected to bottoms of endwalls of the other ends of corresponding auxiliary powerhouse caverns via fourth bottom adits of the auxiliary powerhouse caverns. 6. The construction layout of claim 2, wherein the two primary caverns are provided with first apparatus conveying channels for communicating with corresponding connecting powerhouse caverns; and a bottom of a sidewall of each of the connecting powerhouse caverns communicates with the ground surface via a second apparatus conveying channel. 7. The construction layout of claim 4, wherein the two primary caverns are provided with first apparatus conveying channels for communicating with corresponding connecting powerhouse caverns; and a bottom of a sidewall of each of the connecting powerhouse caverns communicates with the ground surface via a second apparatus conveying channel. 8. The construction layout of claim 5, wherein each bottom adit of the bottom adit system has a longitudinal slope smaller than 15%. 9. The construction layout of claim 5, wherein the two primary caverns are provided with first apparatus conveying channels for communicating with corresponding connecting powerhouse caverns; and a bottom of a sidewall of each of the connecting powerhouse caverns communicates with the ground surface via a second apparatus conveying channel. 10. The construction layout of claim 8, wherein the two primary caverns are provided with first apparatus conveying channels for communicating with corresponding connecting powerhouse caverns; and a bottom of a sidewall of each of the connecting powerhouse caverns communicates with the ground surface via a second apparatus conveying channel. |
|
description | 1. Field of the Invention The present invention relates to a method for X-ray wavelength measurement and X-ray wavelength measurement apparatus for carrying out X-ray wavelength measurement with high precision. 2. Description of the Related Art Such an X-ray wavelength measurement apparatus for carrying out X-ray wavelength measurement with high precision by using a slit to narrow down the incident direction of X-ray, or by arranging two analyzing crystals has been conventionally known. In addition, there is such an instrument as allowing four analyzing crystals to be interlocked with gears in order to obtain high resolution (for example, JP-A-2005-140719). An X-ray wavelength measurement apparatus as disclosed in JP-A-2005-140719 irradiates radiation light as primary X-ray to a sample, and spectrally reflects fluorescent X-ray generated from the sample with four analyzing crystals in (+, −, −, +) arrangement to measure the intensity with a detector. Then, while changing the wavelength of the fluorescent X-ray spectrally reflected with the analyzing crystals by an interlocking means for interlocking the analyzing crystals and the detector, the apparatus guides the fluorescent X-ray into the detector. In this way, the resolution of the fluorescent X-ray spectrum is improved. However, when such an X-ray wavelength measurement apparatus as described above is used, a slit is separately used to adjust strictly a diffraction angle θ for the purpose of determining absolute wavelength. Consequently, for the alignment to adjust a standard position, a special technique is required, and the measurement can not be carried out simply. Further, an X-ray wavelength measurement apparatus of two-crystal arrangement, which utilizes the arrangement of two planar analyzing crystals, needs an interlocking mechanism and results in a complex structure. The present invention is achieved with the view of such circumstances, and aims to provide a method for X-ray wavelength measurement and an X-ray wavelength measurement apparatus for easily determining absolute wavelength and carrying out precise wavelength measurement with a simple structure. The present invention relates to an X-ray absolute angle spectroscopic instrument that uses the halved value of added measurement values of angles in plus and minus directions of two channel-cut crystals. (1) In order to attain the above objects, the method for X-ray wavelength measurement according to the present invention is a method for X-ray wavelength measurement carried out by using a channel-cut crystal for wavelength measurement on which two opposing cut planes are formed and the lattice constant of which is known, and the method is characterized by comprising the steps of: diffracting X-ray in respective arrangements of (−, +) and (+, −) with the channel-cut crystal for wavelength measurement; and determining the absolute wavelength of X-ray from the difference between crystal rotation angles in the respective arrangements. As described above, in the Method for X-ray wavelength measurement of the present invention, by diffracting and spectrally reflecting X-ray in respective arrangements (−, +) and (+, −) of the channel-cut crystal for wavelength measurement, it is possible to determine the zero point of the crystal rotation angle. Consequently, as compared with the conventional method which requires precise position adjustment by using a slit, the alignment becomes simpler. As the result, when only a channel-cut crystal suitable for measurement can be prepared, the measurement can be carried out easily with high precision. (2) The Method for X-ray wavelength measurement according to the present invention is the Method for X-ray wavelength measurement, carried out by using a channel-cut crystal for collimator which is arranged on an X-ray incident side of the channel-cut crystal for wavelength measurement and in which two opposing cut planes are formed, and the method is further characterized by comprising the steps of: diffracting X-ray at a crystal plane having the same index as that of a crystal plane at which the channel-cut crystal for wavelength measurement diffracts X-ray at respective cut planes of the channel-cut crystal for collimator; and guiding the diffracted X-ray into the channel-cut crystal for wavelength measurement to carry out wavelength measurement. Consequently, when X-ray to be spectrally reflected is divergent light, the X-ray is diffracted in different angles for respective wavelengths by the channel-cut crystal for collimator to enter a channel-cut crystal for wavelength measurement. As the result, it is possible to carry out X-ray wavelength measurement without interlocking the rotation of the channel-cut crystal for collimator with the channel-cut crystal for wavelength measurement. (3) The X-ray wavelength measurement apparatus according to the present invention comprises: a channel-cut crystal for wavelength measurement in which two opposing cut planes are so formed that at least a part of mutual projections thereof overlap with the cut planes; and a detector for detecting the intensity of X-ray spectrally reflected by the channel-cut crystal for wavelength measurement, wherein a rotation center of the channel-cut crystal for wavelength measurement is set to be capable of diffracting X-ray in respective arrangements of (−, +) and (+, −). As described above, in the X-ray wavelength measurement apparatus of the present invention, the channel-cut crystal for wavelength measurement has a rotation center so set that it can diffract X-ray in the arrangement of (−, +) and (+, −). Consequently, it is possible to carry out wavelength measurement in above two arrangements to determine precisely the diffraction angle from the difference of crystal rotation angles, and therefore the alignment becomes simpler as compared with the conventional method that requires precise position adjustment by using a slit. Further, since it is not necessary to interlock the channel-cut crystal upon carrying out X-ray wavelength measurement, the mechanism can be made simple. In addition, the X-ray wavelength measurement apparatus for wavelength measurement with setting two planer analyzing crystals in (+, +) arrangement have limitation on the diffraction angle of the analyzing crystal due to the interference of respective parts of the instrument, but in the X-ray wavelength measurement apparatus of the present invention, the position of the X-ray detector does not need to be largely moved, and, by preparing analyzing crystals suitable for respective diffraction angles, the diffraction angle is not limited. (4) The X-ray wavelength measurement apparatus according to the present invention is characterized by further comprising a channel-cut crystal for collimator which is arranged on the incident side of the channel-cut crystal for wavelength measurement and in which two opposing cut planes are formed, wherein the channel-cut crystal for collimator diffracts X-ray at a crystal plane having the same index as that of a crystal plane at which the channel-cut crystal for wavelength measurement diffracts X-ray, to guide the diffracted X-ray into the channel-cut crystal for wavelength measurement. Consequently, when X-ray to be spectrally reflected is divergent light, the X-ray is diffracted in different angles for respective wavelengths by the channel-cut crystal for collimator to enter the channel-cut crystal for wavelength measurement. As the result, it is possible to carry out X-ray wavelength measurement without interlocking the rotation of the channel-cut crystal for collimator with the channel-cut crystal for wavelength measurement, and to make the structure of the instrument simple. (5) The X-ray wavelength measurement apparatus according to the present invention is characterized in that the channel-cut crystal for collimator is placed so that the rotation can be fixed for the incident X-ray upon carrying out wavelength measurement. As described above, it is possible to carry out X-ray wavelength measurement, for a divergent light source, only by adjusting the rotation of the channel-cut crystal for wavelength measurement without interlocking the rotation of the channel-cut crystal for collimator with the channel-cut crystal for wavelength measurement. Consequently, the structure of the instrument can be made simple. (6) The X-ray wavelength measurement apparatus according to the present invention is characterized in that the rotation center of the channel-cut crystal for wavelength measurement is set between two cut planes of the channel-cut crystal for wavelength measurement or between extended planes thereof; and a cut plane on which X-ray is incident when the channel-cut crystal for wavelength measurement diffracts the X-ray in the arrangement of (−, +) differs from that on which X-ray is incident when the channel-cut crystal for wavelength measurement diffracts the X-ray in the arrangement of (+, −). As described above, in the X-ray wavelength measurement apparatus of the present invention, the rotation center of the channel-cut crystal for wavelength measurement is set between two cut planes of the channel-cut crystal for wavelength measurement or between extended planes thereof. Consequently, when X-ray is made diffracted in the arrangements (−, +) and (+, −) of the channel-cut crystal for wavelength measurement, it is possible to guide X-ray into different cut planes in the respective arrangements for wavelength measurement, and to measure absolute wavelength with high precision from the difference between respective crystal rotation angles even for a small diffraction angle. (7) The X-ray wavelength measurement apparatus according to the present invention is characterized in that the rotation center of the channel-cut crystal for wavelength measurement is set in a position allowing X-ray to enter the identical cut plane when the channel-cut crystal for wavelength measurement diffracts the X-ray in either arrangement of (−, +) or (+, −). As described above, in the X-ray wavelength measurement apparatus of the present invention, the rotation center of the channel-cut crystal for wavelength measurement is so set that X-ray can enter the identical cut plane when the crystal diffracts the X-ray in either arrangement (−, +) or (+, −), therefore, even for high diffraction angles, absolute wavelength can be measured with high precision from the difference between respective crystal rotation angles. In addition, for a high diffraction angle, δλ/λ (=δθ/tan θ) becomes small, therefore wavelength resolution can be improved. (8) The X-ray wavelength measurement apparatus according to the present invention is characterized by further comprising a rotation control mechanism for controlling the rotation of the channel-cut crystal for wavelength measurement, wherein the rotation control mechanism includes an angle detector having self-calibration function for detecting the displacement of the scale position of the rotation angle. As described above, since the X-ray wavelength measurement apparatus of the present invention is provided with an angle detector having self-calibration function, it can detect the displacement of the scale position of the rotation angle of the channel-cut crystal for wavelength measurement and calibrate absolute wavelength. Further, it can also evaluate how much degree of inaccuracy exists in the obtained absolute wavelength. According to the Method for X-ray wavelength measurement of the present invention, since the zero point of the crystal rotation angle can be determined by rotating the channel-cut crystal for wavelength measurement to diffract and spectrally reflect X-ray in respective arrangements of (−, +) and (+, −), the alignment becomes simpler as compared with the conventional method which requires precise position adjustment by using a slit. As the result, when only a channel-cut crystal suitable for measurement is prepared, the measurement can be carried out easily with high precision. According to the X-ray wavelength measurement apparatus of the present invention, since the zero point of the crystal rotation angle can be determined by diffracting and spectrally reflecting X-ray in the arrangements where the channel-cut crystal for wavelength measurement is set in (−, +) and (+, −) respectively, the alignment becomes simple. Further, there is no necessity to interlock the channel-cut crystal for collimator, thus making the mechanism simple. Furthermore, an X-ray wavelength measurement apparatus with two planer analyzing crystals that carries out wavelength measurement in an arrangement of (+, +) has limitation on the diffraction angle of the analyzing crystal due to the position of the X-ray detector, but the X-ray wavelength measurement apparatus of the invention does not need large movement of the position of the detector and is not limited by diffraction angles by preparing analyzing crystals suitable for respective diffraction angles. Next, embodiments of the present invention will be described with reference to the drawings. To facilitate understanding of the description, the same reference numeral is given to the same constituent and overlapping description is omitted. FIG. 1 is a plan view showing the outline of the configuration of an X-ray wavelength measurement apparatus 1 according to the present invention. As shown in FIG. 1, the X-ray wavelength measurement apparatus 1 includes a channel-cut crystal for collimator 10, a channel-cut crystal for wavelength measurement 20, a rotatable platform 50, an angle detector 60 and an X-ray detector 100. The channel-cut crystal is prepared by carving grooves to a unitary crystal block, and the parallel walls on both sides thereof are utilized for reflection, that is, diffraction. For the channel-cut crystal, the whole is composed of unitary crystal, and therefore all X-rays Bragg-reflected by one crystal wall cause Bragg reflection by the other crystal wall. The X-ray wavelength measurement apparatus 1 spectrally reflects X-ray having a specified wavelength out of incident X-ray having a continuous spectrum, and measures the intensity thereof with the X-ray detector 100. The X-ray wavelength measurement apparatus 1 can be applied to, for example, a state analysis instrument by spectroscopy and an X-ray wavelength precise measuring instrument. The channel-cut crystal for collimator 10 is arranged on the X-ray incident side of the channel-cut crystal for wavelength measurement 20, and has a first crystal wall 11 and a second crystal wall 12. At respective crystal walls, a first cut plane 11a and a second cut plane 12a facing each other are formed. The channel-cut crystal for collimator 10 is fixed on a platform (not shown) at a position where X-ray being an object to be spectrally reflected enters to be diffracted. When X-ray to be spectrally reflected is divergent light, the X-ray is diffracted in different angles for respective wavelength by the fixed channel-cut crystal for collimator to enter the channel-cut crystal for wavelength measurement. Accordingly, in the X-ray wavelength measurement apparatus 1, it is possible to carry out X-ray wavelength measurement without interlocking the rotation of the channel-cut crystal for collimator 10 with the channel-cut crystal for wavelength measurement 20. Accordingly, the structure of the instrument can be made simple. Further, when X-ray to be spectrally reflected is parallel light such as radiation from synchrotron source, the channel-cut crystal for collimator may be omitted to make the configuration simpler. The Bragg angle of the channel-cut crystal for collimator 10 is represented as θ1 in FIG. 1. The channel-cut crystal for collimator is so arranged that X-ray having been diffracted by the channel-cut crystal for collimator 10 enters the channel-cut crystal for wavelength measurement 20. The channel-cut crystal for collimator 10 may have such figure and arrangement that allow X-ray to be diffracted at a crystal plane having the same index as that of a crystal plane at which the channel-cut crystal for wavelength measurement 20 allows X-ray to be diffracted, so that the X-ray may enter the channel-cut crystal for wavelength measurement 20. The number of diffraction at the channel-cut crystal is at least two, may be four or six, and there is no particular limitation on it. By increasing the number of the diffraction, a sharp peak having a cut tail can be detected. On the other hand, when emphasizing the assurance of intensity, the number of the diffraction may be decreased. Incidentally, although the channel-cut crystal for collimator 10 is fixed on the platform during the spectrum measurement, it is so designed that the adjustment of the angle prior to the measurement is possible. The adjustment may be practiced either manually or automatically. In any event, the channel-cut crystal for collimator 10 is independent of the rotation control of the channel-cut crystal for wavelength measurement 20 to be described. The channel-cut crystal for wavelength measurement 20 has a third crystal wall 21 and a fourth crystal wall 22. At respective crystal walls, a third cut plane 21a and a fourth cut plane 22a facing each other are formed. In addition, the projection of the cut plane 21a to the cut plane 22a and the cut plane 22a are so formed that at least a part of these overlap with each other. That is, when the channel-cut crystal for wavelength measurement is viewed from the side, the crystal walls 21 and 22 overlap with no interspace. This makes it possible to rotate the channel-cut crystal for wavelength measurement 20 to diffract X-ray in respective arrangements of (−, +) and (+, −). The arrangement of (+) or (−) indicates an arrangement of a crystal that diffracts X-ray in the bending direction determined by regarding the bending direction of the first diffraction as (+). Accordingly, an arrangement of a crystal that diffracts X-ray in the same bending direction as that in the first diffraction is (+), and an arrangement of a crystal that diffracts X-ray in the bending direction reverse to that of the first diffraction is (−). The channel-cut crystal for spectroscopy 20 is provided at a position where X-ray having been diffracted by the channel-cut crystal for collimator 10 on the turn table 50 can enter. The channel-cut crystal for spectroscopy 20 has the rotation center C1 that is set so as to be capable of diffracting X-rays in an arrangement of (−, +) and (+, −) relative to the incident X-ray. That is, the rotation center C1 is set at a position where X-rays are not intercepted by the crystal wall 21 or 22 when either one of the above arrangements is taken, and X-rays are not prevented from reaching the cut plane in either one of the arrangements. As described above, the rotation center C1 thereof is set in the channel-cut crystal for wavelength measurement 20 so as to make it possible to diffract X-ray in arrangements of (−, +) and (+, −). As described above, since it is possible to carryout the spectral reflection in the arrangement to determine the zero point of the crystal rotation angle, the alignment becomes simpler as compared with the conventional method that requires precise position adjustment by using a slit. In an example in FIG. 1, the rotation center C1 is set between the cut planes 21a and 22a. The cut plane 21a on which X-ray is incident when the channel-cut crystal for wavelength measurement 20 takes the (−, +) arrangement, and the cut plane 22a on which X-ray is incident when the channel-cut crystal for wavelength measurement 20 takes the (+, −) arrangement are different from each other. In other words, for the cut plane 21a, (−) diffraction occurs in either arrangement, and for the cut plane 22a, (+) diffraction occurs in either arrangement. Here, the rotation center C1 may be set between the extended planes of respective cut planes. The Bragg angle of the channel-cut crystal for wavelength measurement 20 is represented by θ2 in FIG. 1. Analyzing crystals that can be used for the channel-cut crystal for collimator 10 or the channel-cut crystal for wavelength measurement 20 include Si and Ge, but are not limited to these. As to crystal planes for use in spectral reflection, for example, Si (400), Si (220), Si (440), Si (111), Si (333) and Si (444) can be mentioned. The rotatable platform 50 is connected to a rotary driving instrument (not shown) capable of rotating at intervals of a minute angle. The rotary driving instrument uses a servo motor, a stepping motor or the like. The angle detector 60 is a detector for measuring the rotation angle of the channel-cut crystal for wavelength measurement 20 by counting the scale carved to a circular disc with a reading head. The angle detector 60 uses, for example, a common rotary encoder. The rotatable platform 50, the angle detector 60 and the X-ray detector 100 are controlled by a controlling section (not shown). The X-ray detector 100 is arranged at a position on which the X-ray diffracted by the channel-cut crystal for wavelength measurement 20 is incident. In the present invention, there is no need to move largely the position of the X-ray detector to eliminate the limitation on the angle caused by the interference of respective sections. The X-ray detector 100 detects the intensity of the X-ray spectrally reflected by the channel-cut crystal. The position of the X-ray detector 100 can be moved corresponding to the incident position of the X-ray. Incidentally, the X-ray detector 100 may use the one having a large detection range, being fixed and used at a predetermined position. Next, a method for X-ray wavelength measurement by using the aforementioned X-ray wavelength measurement apparatus 1 will be described. Firstly, from a crystal having a known lattice constant, two channel-cut crystals are prepared in which a cut plane is formed so as to diffract X-ray at the identical crystal plane. One of these is set on a platform as the channel-cut crystal for collimator 10, and the other is set on the rotatable platform 50 as the channel-cut crystal for wavelength measurement 20. Then, the channel-cut crystal for collimator 10 is adjusted and fixed so as to diffract X-ray having required range of wavelength in the direction of channel-cut crystal for wavelength measurement 20. On the other hand, the channel-cut crystal for wavelength measurement 20 is fixed on the rotatable platform 50 so that the rotation center C1 lies between the cut planes 21a and 22a. Then, the rotatable platform 50 is rotated to set the channel-cut crystal for wavelength measurement 20 in such arrangement that causes (+, −) diffraction as shown in FIG. 2A. Subsequently, by guiding X-ray for spectral reflection, firstly, wavelength measurement is carried out in such setting that the channel-cut crystal for wavelength measurement 20 has an arrangement of (+, −) to diffract X-ray. That is, the arrangement is set so that the diffraction by respective channel-cut crystals is (+, −, +, −), and the X-ray is diffracted in the order of cut planes 11a, 12a, 22a and 21a. On this occasion, in case where diffraction is carried out by using the identical crystal plane for the channel-cut crystal for collimator and for the channel-cut crystal for wavelength measurement, a sharp peak can be obtained when two crystal planes become strictly parallel to each other. As described above, the peak angle position ω0 of the X-ray intensity having been detected with the X-ray detector 100 is detected with the angle detector 60. The peak angle position ω0 is the origin position of the channel-cut crystal for wavelength measurement. Next, the channel-cut crystal for wavelength measurement 20 is set to an arrangement that diffracts X-ray in (−, +) as shown in FIG. 2B. That is, respective channel-cut crystals are arranged so as to give (+, −, −, +) diffractions, respectively, and the X-ray is diffracted in the order of cut planes 11a, 12a, 21a and 22a. Then, from the X-ray intensity detected by the X-ray detector 100 and the angle ω detected by the angle detector 60, an X-ray spectrum with high resolution is obtained. Incidentally, the angle detected by the angle detector 60 can be obtained by measuring the rotation amount of the rotation platform or the rotation axis (shaft) from the reference rotation position with the angle detector 60, which corresponds to the crystal rotation angle. The method for determining angles ω and ω0 as shown in the drawing is an example, and there is no particular limitation on the method for determining the angle when the angle represents the rotation angle of the crystal. The origin of the angle ω detected by the angle detector 60 in the measured spectrum is the above-described ω0. Accordingly, the difference between both angles ω−ω0 is the rotation angle of the channel-cut crystal for wavelength measurement, and Bragg angle θ of the channel-cut crystal for wavelength measurement on this occasion is represented by θ=(ω−ω0)/2. When representing the lattice spacing of the channel-cut crystal for wavelength measurement by d, the angle θ on the horizontal axis of a measured spectrum can be converted to the wavelength λ of X-ray according to the formula of λ=2d·sin θ. Further, the wavelength λ (Å) of X-ray is converted to energy E (eV) according to the formula of E=12398.419/λ. In this way, the absolute wavelength of spectrally reflected X-ray can be detected. As described above, X-ray is diffracted in respective arrangements in which two channel-cut crystals are set to (+, −, −, +) and (+, −, +, −) by rotating the channel-cut crystal for wavelength measurement 20 to carry out spectral reflection and determine the origin of the crystal rotation angle, therefore the alignment becomes simpler as compared with conventional method that requires precise position adjustment by using a slit. As the result, when only suitable channel-cut crystals are prepared, X-ray wavelength measurement can be carried out easily with high precision. In the above-described Embodiment 1, the rotation center C1 is so provided that X-ray enters different cut planes when the channel-cut crystal for wavelength measurement 20 is set to respective arrangements of (+, −) and (−, +), but the rotation center may be provided so that X-ray may enter the identical cut plane. FIG. 3 is a schematic drawing showing the X-ray wavelength measurement apparatus 1 in which the channel-cut crystal for wavelength measurement is so arranged that X-ray enters the identical cut plane. A channel-cut crystal for collimator 30 has a first crystal wall 31 and a second crystal wall 32, and, at respective crystal walls, a first cut plane 31a and a second cut plane 32a facing each other are formed. The lengths of respective crystal walls are shortened in different directions in accordance with the passing channels of X-ray beams so that a large diffraction angle can be obtained. For a scheme to obtain a large diffraction angle, as shown in FIG. 4, crystals, in which mutual distance is enlarged relative to the length thereof without shortening the lengths of the crystal wall 31 and the crystal wall 32, may be employed. A channel-cut crystal for wavelength measurement 40 has a third crystal wall 41 and a fourth crystal wall 42, and, at respective crystal walls, a third cut plane 41a and a fourth cut plane 42a facing each other are formed. In the channel-cut crystal for wavelength measurement 40, a crystal, in which the mutual distances of respective crystal walls 31 and 32 are enlarged relative to the lengths of these, is employed so as to obtain a large diffraction angle. These two opposing cut planes 41a and 42a are so formed that at least a part of respective projections overlap with the cut planes. This makes it possible to rotate the channel-cut crystal for wavelength measurement 40 to diffract X-ray in respective arrangements of (−, +) and (+, −). In the example in FIG. 3, a rotation center C2 of the channel-cut crystal for wavelength measurement is set outside the cut plane 41a. Then, the rotation center C2 is set at a position where X-ray is not shielded by the crystal wall 42 when either of the above arrangements occurs and X-ray reaches the cut plane 41a in either arrangement. The cut plane 41a on which X-ray enters when the channel-cut crystal for wavelength measurement 40 diffracts the X-ray in an arrangement of (−, +), and the cut plane 41a on which X-ray enters when the channel-cut crystal for wavelength measurement 40 diffracts the X-ray in an arrangement of (+, −) are identical. As described above, the rotation center of the channel-cut crystal for wavelength measurement 40 is set at a position that allows X-ray to enter the identical cut plane 41a in both cases where X-ray is diffracted in either arrangement of (−, +) or (+, −), therefore absolute wavelength can be measured for high diffraction angles with high precision. For high diffraction angles, δλ/λ becomes small, therefore high wavelength resolution can be obtained. On this occasion, the cut plane 41a leads to carry out the diffraction in (−) direction in one arrangement, and the diffraction in (+) direction in the other arrangement. Next, a method for carrying out X-ray wavelength measurement in the above-described crystal arrangement will be described. Firstly, two channel-cut crystals, in which a cut plane has been formed so as to be capable of diffracting X-ray at the identical crystal plane, are prepared from a crystal having a known lattice constant, and these are set on a platform and on the rotatable platform 50 as a channel-cut crystal for collimator and a channel-cut crystal for wavelength measurement, respectively. The channel-cut crystal for wavelength measurement 40 is so fixed on the rotatable platform 50 that the rotation center C2 lies near the crystal wall 41. Firstly, the channel-cut crystal for wavelength measurement 40 is set to an arrangement for causing (+, −) diffraction, as shown in FIG. 5A. Then, by guiding X-ray for spectral reflection, firstly, the channel-cut crystal for wavelength measurement 40 diffracts the X-ray in the arrangement of (+, −) to carry out wavelength measurement. That is, respective channel-cut crystals are arranged so as to be (+, −, +, −) to allow X-ray to be diffracted in the order of cut planes 31a, 32a, 41a and 42a. On this occasion, in case where the diffraction is carried out by using the identical crystal plane for the channel-cut crystal for collimator and for the channel-cut crystal for wavelength measurement, a sharp peak is obtained when two crystal planes become strictly parallel to each other. As described above, the peak angle position ω0 of X-ray intensity detected by the X-ray detector 100 is detected with the angle detector 60. The angle position ω0 is the origin point of the channel-cut crystal for wavelength measurement. Next, the channel-cut crystal for wavelength measurement 40 is so arranged as to cause (−, +) diffraction as shown in FIG. 5B. That is, respective channel-cut crystals are so arranged as to cause (+, −, −, +) diffraction, and allow X-ray to be diffracted in the order of cut planes 31a, 32a, 41a and 42a. Then, from the X-ray intensity detected by the X-ray detector 100 and the angle ω detected by the angle detector 60, an X-ray spectrum with high resolution is obtained. The origin of the angle ω detected by the angle detector 60 in the measured spectrum is above-described ω0. Accordingly, the difference in respective angles ω−ω0 is the rotation angle of the channel-cut crystal for wavelength measurement, and Bragg angle θ of the channel-cut crystal for wavelength measurement on this occasion is represented by θ=π/2−(ω−ω0)/2. When representing the lattice spacing of the channel-cut crystal for wavelength measurement by d, the angle θ on the horizontal axis of a spectrum can be converted to the wavelength λ of X-ray according to the formula of λ=2d·sin θ. Further, the wavelength λ (Å) of X-ray is converted to energy E (eV) according to the formula of E=12398.419/λ. The above is described for the case where X-ray to be spectrally reflected is divergent light, but in case where a spectrum of X-ray having been spectrally reflected to some extent or of such parallel light as synchrotron radiation source is measured, the channel-cut crystal for collimator may be omitted. On this occasion also, by measuring ω0 while arranging the channel-cut crystal for wavelength measurement in (−, +) followed by measuring ω while arranging it in (+, −), as is the case for the above, Bragg angle θ can be calculated correctly. The above-described X-ray wavelength measurement apparatus 1 of the Embodiment 1 can measure absolute wavelength with high precision, but it is also possible to carry out precise calibration by giving additional self-calibration function to the angle detector. FIG. 6 is a side view showing an X-ray wavelength measurement apparatus 2 provided with an angle detector having self-calibration function. As shown in FIG. 6, the X-ray wavelength measurement apparatus 2 includes a channel-cut crystal for collimator 10, a channel-cut crystal for wavelength measurement 20, a fixed platform 49, a rotatable platform 50, a rotary driving instrument 55, an angle detector 60, a controlling section 70 and a detector 100. The rotary driving instrument 55, the angle detector 60 and the controlling section 70 constitute a rotation control mechanism. The rotatable platform 50 is connected to the rotary driving instrument 55 capable of rotation at intervals of a minute angle. The rotary driving instrument 55 uses a servo motor, a stepping motor or the like. The angle detector 60 is a detector for measuring a rotation angle by counting scales carved to a circular disc 61 with a reading head 63. The angle detector 60 uses a rotary encoder or the like. FIG. 7 is a perspective view of the angle detector 60 in the present invention. As shown in FIG. 7, the angle detector 60 includes a circular disc 61 to which scales are carved, a shaft 62 to which the circular disc 61 is fixed, and a reading head 63 set around the disc at even intervals. The reading head 63 is arranged around the circular disc 61 at even intervals. The rotatable platform 50, the angle detector 60 and the X-ray detector 100 are controlled by the controlling section 70. The controlling section 70 is constituted of CPU and main memory, and, mainly, carries out the control of instruments and the calculation of numerical values. Hereinafter, a method for obtaining the displacement of the scale position is described. The displacement of the angle signal of the scale i to be detected by the reading head 63 can be represented as bi. Further, the displacement of the angle signal of the scale i+j·N/n at jth reading head 63 can be represented as bi+j·N/n. On this occasion, it is intended to indicate the number of reading heads arranged at even intervals by n, and the number of scales of the encoder by N. When determining the 0th reading head 63 as the reference head, difference δi,j between the angle signal bi+j·N/n of the jth head and the angle signal bi of the reference head, and the average value μi,n of these can be represented as follows. δ i , j = b i + j · N / n - b i ( formula I ) μ i , n = 1 n ∑ j = 0 n - 1 δ i , j = 1 n ∑ j = 0 n - 1 b i + j · N / n - b i ( formula II ) The amount resulted from eliminating Fourier components of multiple number of n from bi can be obtained as follows. b ~ i , j = b i - 1 n ∑ j = 0 n - 1 b i + j · N / n = - μ i , n ( formula III ) The above-described −μi,n is the displacement of the scale position of the scale i. In this way, by seeking the measurement difference between the reference reading head 63 and respective reading heads and by obtaining the average value thereof, it is possible to calculate the displacement of the scale position and to carry out self-calibration. As described above, it is possible to calibrate the error of such angle information as the decentering of an attaching axis under use environments and the secular change of the angle detector. In addition, it is also possible to evaluate how much uncertainness is there in obtained absolute wavelength. An experiment of wavelength measurement was practiced by using the X-ray wavelength measurement apparatus of the Embodiment 1. The experimental method and the experimental results are described below as Experimental Example. As an X-ray source, CuKα line was used, and as a channel-cut crystal, a Si analyzing crystal was used and Si (400) was used as the crystal plane. Firstly, since the Bragg angle θ is approximately 34.5°, two channel-cut crystals having a suitable size and figure for the angle were prepared. One of these was fixed on a platform as the channel-cut crystal for collimator so that diffracted X-ray became approximately parallel to the incident X-ray, and the other was set on a rotatable platform as the channel-cut crystal for wavelength measurement. The rotation center of the channel-cut crystal for wavelength measurement was set so as to lie between two cut planes. Then, by setting the channel-cut crystal for wavelength measurement to an arrangement of (+, −) and diffracting X-ray as shown in FIG. 2A, the profile of the CuKα peak of the X-ray was detected. When an identical crystal plane is used for the channel-cut crystal for collimator and for the channel-cut crystal for wavelength measurement to carry out the diffraction, a sharp peak is obtained when respective crystal planes become strictly parallel to each other. The peak angle poison of the channel-cut crystal for wavelength measurement on this occasion is indicated by ω0. Next, by setting the channel-cut crystal for wavelength measurement to an arrangement of (−, +) and diffracting X-ray as shown in FIG. 2B, X-ray wavelength measurement profile with a high resolution was measured. On this occasion, the channel-cut crystal was set to an arrangement of (+, −, −, +) to cause the diffraction. The origin of the angle ω detected by the angle detector 60 in the measured spectrum is the above-described ω0. Therefore, the difference between both angles ω−ω0 was calculated to obtain the rotation angle of the channel-cut crystal for wavelength measurement. Bragg angle θ of the channel-cut crystal for wavelength measurement on this occasion is θ=(ω−ω0)/2. When representing the lattice spacing of the channel-cut crystal for wavelength measurement by d, the angle θ on the horizontal axis of a spectrum is represented by a formula of λ=2d·sin θ. According to the formula, the angle θ was converted to the wavelength λ of the X-ray. Further, the wavelength λ (Å) of X-ray was converted to energy E (eV) according to the formula of E=12398.419/λ. FIG. 8 is a profile showing the result of the above-described X-ray wavelength measurement. In the graph, a shows the X-ray intensity obtained by the experiment. Each of peaks P1 to P4 shows curve of Lorenz function representing peaks of Cukα1 and Cukα2 obtained by calculation, respectively. When subjecting these curves of Lorenz functions to fitting treatment, they coincided with the profile obtained by the experiment. Parameters of respective Lorenz functions thus obtained are shown in FIG. 9. The full width of Half Maximum 2.286 eV at the peak P1 is the highest resolution among those historically obtained. On this occasion, δE is considered to be 0.2 eV or less. Further, precise absolute wavelength of X-ray could be measured. |
|
description | This application is the National Stage of International Application No. PCT/EP2013/054064 having International filing date 28 Feb. 2013, which designated the United States of America, and which International Application was published under PCT Article 21 (s) as WO Publication 2013/127935 A1 and which claims priority from, and benefit of, French Application No. 1350149 filed on 8 Jan. 2013 and French Application No. 1251872 filed on 29 Feb. 2012, the disclosures of which are incorporated herein by reference in their entireties. 1. Field The presently disclosed embodiment relates to a method and a device for monitoring the dynamic confinement of a confinement enclosure that is at a raised or at a reduced pressure in relation to the exterior surroundings. The presently disclosed embodiment also relates to an enclosure equipped with such a confinement control device. 2. Brief Description of Related Developments It is known practice within the nuclear industry to use a confinement enclosure in order to clean up and/or to dismantle radioactive equipment of a nuclear installation, for example if this equipment has become obsolete or if the installation itself is being shut down. FIG. 1 shows such a confinement enclosure 1 of the prior art. This confinement enclosure 1 comprises a set of vinyl air locks comprising a personnel entrance and exit air lock 2, a materials entrance and exit air lock 3 and an intervention air lock 4. It is inside this latter air lock 4 that one or more operators carry out the operations of cleaning up and/or of dismantling the contaminated equipment. The first two air locks 2, 3 each have access to the exterior and direct access to the intervention air lock 4. These two air locks 2, 3 do not communicate with one another such that the first air lock 2 is reserved exclusively for personnel, the second air lock 3 being intended only for the removal of the materials resulting for example from the dismantling of the radioactive equipment. Each air lock 2-4 is typically formed of a metal structure with flexible vinyl walls. Access to the air locks 2-4 is had via two vinyl sheets 5. These vinyl walls prevent contaminated substances from being dispersed into the environment during cleanup operations. Such a confinement enclosure 1 intended for dismantling and/or cleanup operations is kept at a reduced pressure in relation to the host space in which this enclosure is situated by means of a ventilation system which may be autonomous or may be connected to the network that exists within the host space. The materials and personnel entrance/exit air locks 2, 3 are ventilated by air transfer. Only the intervention air lock 4 has forced air extraction (not depicted). During cleanup and/or dismantling operations, the air flows through the intervention air lock 4 are extracted by a fan preceded by high efficiency particulate air filters (HEPA filters) capable of trapping the particles carried in the air thus extracted. This creation of a reduced pressure therefore allows contaminated dust generated for example when cutting up radioactive equipment to be confined and sucked up. The safety of operations relies on the combination of static confinement (airtightness of the walls) of the confinement enclosure and dynamic confinement (ventilation) that allows this enclosure to be kept at a reduced pressure. The French Nuclear Safety Authority (ASN) recommends that such a confinement enclosure be kept at a reduced pressure by maintaining a pressure differential of the order of −40 Pa to −80 Pa with respect to the host space. This reduced pressure is currently measured at the start of each working shift, but it is not possible from this to deduce with certainty that this level of reduced pressure is being maintained throughout the cleanup operations and/or the operations of dismantling contaminated material. Specifically, this reduced pressure may, for example, vary suddenly as a result of a break in the static confinement or alternatively as a result of the filtration system becoming plugged, leading to a drop in the extraction flow rate. When this happens, the amount of reduced pressure no longer falls within the range of recommended values, causing the cleanup work and/or dismantling work to have to stop until the target reduced pressure can be re-established. Now, such work stoppages lead to additional costs and significant extensions of deadlines which are incompatible with the economic requirements of the companies involved. Conversely, there are confinement enclosures which require a raised pressure in order to keep the dust outside such an enclosure. Maintaining a raised pressure makes it possible to maintain a healthy atmosphere inside the enclosure, namely an atmosphere that is devoid of the kind of dust that would hamper the operations performed in this enclosure. The safety of operations relies on the combination of static confinement (airtightness of the walls) of the confinement enclosure and dynamic confinement (ventilation) that allows this enclosure to be kept at a raised pressure. The presently disclosed embodiment seeks to alleviate these various disadvantages by proposing a method and a device for monitoring the confinement of an enclosure that is at a reduced pressure or at a raised pressure in relation to the exterior surroundings in which this enclosure is placed, being simple in their design and mode of operation and guaranteeing that these operations can be carried out safely. Another object of the presently disclosed embodiment is such a method and such a device for monitoring the dynamic confinement of an enclosure that makes it possible to continuously monitor the quality of the dynamic confinement of this enclosure. In the remainder of this document, the term “confinement” will refer to dynamic confinement or containment. The term “enclosure” will refer to a confinement space. To this end, the presently disclosed embodiment relates to a method for monitoring the confinement of an enclosure, said enclosure comprising walls delimiting an interior volume and exterior surroundings outside said enclosure, whereby a differential pressure (ΔP) is continuously maintained between the interior volume of the enclosure and said exterior surroundings. According to the presently disclosed embodiment, with the enclosure comprising an orifice in one of its walls establishing fluidic communication between said interior volume and said exterior surroundings, said orifice has passing through it a flow of gas at a speed (V) at least equal to a reference speed Vref, under the effect of said differential pressure (ΔP), according to which method the following steps are carried out: the speed (V) of said gas flow is measured at predetermined time intervals or continuously and this speed measurement (V) is compared with the reference speed Vreference, when the speed measurement (V) is lower than the reference speed Vreference, at least one alarm signal is emitted. This monitoring method therefore comprises a step of monitoring over time the speed of the flow of gas entering the enclosure when the enclosure is at a reduced pressure in relation to the exterior surroundings, or leaving the enclosure when the latter is at a raised pressure in relation to the exterior surroundings, by measuring the speed of this gas flow either continuously or at predetermined time intervals, for example periodically. Advantageously, this speed measurement is performed at the orifice of predetermined dimensions. The speed of the flow of gas entering or leaving the confinement enclosure through the orifice is directly connected to the extraction or, respectively, inlet flow rate (Q) of the ventilation system that ventilates this enclosure. By way of example, the flow of gas entering or leaving the confinement enclosure is air or a neutral gas. The method of monitoring the confinement of an enclosure at a reduced pressure in relation to the exterior surroundings ensures, through measuring a simple parameter throughout the cleanup and/or dismantling operations, that the quality of confinement can be guaranteed and any risk of contamination outside the enclosure can be avoided. The method of monitoring the confinement of an enclosure at a raised pressure in relation to the exterior surroundings ensures, through measuring a simple parameter throughout the operations performed inside the enclosure, that the quality of confinement can be guaranteed and any risk of contamination outside the enclosure can be avoided. This speed criterion is simple to: retain, obtain, measure, monitor over time. This reference speed: guarantees correct operation of the containment confinement system, eliminates the constraints associated with creating a reduced pressure in the enclosure thus reducing the cost of carrying out the work, or eliminates the constraints associated with placing the enclosure at a raised pressure. In various aspects of the disclosed embodiment of this confinement monitoring method, each having its own particular advantages and capable of being combined in many possible technical combinations: said differential pressure (ΔP) between the interior volume of the enclosure and said exterior surroundings is established by at least one ventilation system of said enclosure. Having determined a reference flow rate (Qref) at which said enclosure is ventilated by said at least one ventilation system, the following steps are carried out: the flow rate (Q) at which said enclosure is ventilated is measured, the ventilation flow rate measurement (Q) thus obtained is compared with the reference flow rate (Qref) to determine whether the ventilation flow rate has dropped, and if appropriate, the ventilation flow rate (Q) is adjusted to generate a gas flow passing through said orifice at a speed at least equal to said reference speed Vreference. The “ventilation flow rate” means the rate at which a flow of gas such as air is extracted or admitted depending on whether said at least one ventilation system operates in an extraction mode or in an admission mode. The ventilation flow rate (Q) of said enclosure is advantageously measured periodically. Purely by way of illustration, the ventilation flow rate is measured at a frequency of one measurement per day, and better still, one measurement per hour. By way of example, the ventilation flow rate may have dropped as a result of one or more enclosure filtration stages becoming plugged. The reference ventilation flow rate (Qref) is advantageously recorded in a storage unit. Alternatively, with the ventilation flow rate (Q) of said enclosure being equal or substantially equal to the reference flow rate (Qref), the leak or leaks in said enclosure is or are located and said leak or leaks is or are plugged. Purely by way of illustration, this locating of the leak or leaks causing a loss in the static confinement of the enclosure may be performed by sweeping the enclosure with a tracer gas and using one or more analyzers distributed outside the enclosure to detect the presence and concentration of the tracer gas. For preference, the gas with which the enclosure is thus swept is a neutral gas. Said at least one ventilation system is chosen from the group comprising: a gas flow extraction system, a gas flow inlet system, a reversible system capable of switching between a gas flow extraction mode and a gas flow inlet mode and combinations of these elements. said differential pressure (ΔP) between the interior volume of the enclosure and said exterior surroundings is established by at least one gas flow supply source that has an inlet flow rate (Q). Purely by way of illustration, this at least one gas flow supply source comprises at least one pressurized container of a flow of gas. This or these pressurized containers may be connected to a feed circuit supplying the enclosure with a flow of gas. Of course, as need be, it is possible to introduce one or more different gas flows. Having determined a reference inlet flow rate (Qref) at which said at least one supply source supplies said enclosure with a flow of gas, the following steps are carried out: the inlet flow rate (Q) to said enclosure is measured, the inlet flow rate measurement (Q) thus obtained is compared with the reference flow rate (Qref) in order to determine whether the inlet flow rate (Q) has dropped, and where appropriate, the inlet flow rate (Q) is adjusted in order to generate a flow of gas passing through said orifice at a speed at least equal to said reference speed Vreference. Advantageously, with the inlet flow rate (Q) of said enclosure being equal or substantially equal to the reference flow rate (Qref), the leak or leaks in said enclosure is or are located and said leak or leaks is or are plugged. said reference speed Vreference is at least equal to 1 m·s−1. The invention also relates to a device for implementing the confinement monitoring method as described hereinabove. According to the presently disclosed embodiment, this device comprises: a pipe of diameter D intended to be mounted on an orifice of a wall of said enclosure, said pipe comprising a nonreturn valve which closes off said pipe to prevent the passage of a flow of gas from inside the enclosure toward the exterior surroundings when said enclosure is at a reduced pressure with respect to the exterior surroundings, or from the exterior surroundings toward the interior volume of said enclosure when said enclosure is at a raised pressure with respect to the exterior surroundings, and a means of measuring the speed of the gas flow passing along said pipe. For example, this means of measuring speed is a hot-wire anemometer or a vane anemometer. With the anemometer being a hot-wire anemometer, this anemometer is advantageously positioned a distance of at least five (5)×D from the ends of said pipe in order to guarantee the most reliable possible measurement. For preference, the device additionally comprises an audible and/or luminous alarm for emitting at least one alarm signal when the speed (V) measured by the speed measuring means is below a threshold speed value such as the reference speed Vreference. Advantageously, with the speed measuring means being connected to a processing unit that processes the signal emitted by this measurement means, this or these alarms may be connected to the processing unit and controlled thereby. Alternatively, the processing unit itself emits the alarm. The presently disclosed embodiment also relates to an enclosure comprising at least one interior volume delimited by walls and at least one device for placing this interior volume of said enclosure at a reduced pressure or at a raised pressure in relation to the exterior surroundings in which said enclosure is placed. According to the presently disclosed embodiment, this enclosure comprises a device for implementing the confinement monitoring method as described hereinabove, this device being mounted on an orifice of one of said walls of the enclosure delimiting said interior volume. First of all, it should be noted that the figures are not to scale. FIG. 2 shows an enclosure 10 which is at a reduced pressure in relation to the exterior surroundings according to one aspect of the presently disclosed embodiment. This enclosure 10 comprises a metallic structure covered with sheets of vinyl delimiting a first airlock 11 for the circulation of one or more operator(s) and a second air lock 12 intended to accommodate and allow the removal of structural materials resulting from the cleaning up and/or the dismantling of contaminated elements, equipment or installations. The first and second air locks 11, 12 are separate from one another and not interconnected. Purely by way of example, the volume of the first air lock 11 is 5 m3 while the volume of the second air lock 12 is 15 m3. These vinyl walls also delimit a third air lock 13, referred to as the intervention air lock and having a greater volume than the other two, for example 40 m3. Of course, an enclosure 10 may have varying volumes depending on the size of the contaminated elements, equipment or installations to be processed. It is within this intervention air lock 13 that the actual cleanup and/or dismantling operations proper are carried out. This third air lock 13 comprises an air extraction installation that allows the enclosure to be placed at a reduced pressure in relation to the exterior surroundings in which this enclosure is situated. These exterior surroundings in this instance are the hall of a building housing the enclosure 10. Advantageously, this air extraction installation that sucks air out of the third volume 13 comprises an extraction device 14 such as a fan, the extraction flow rate of which is adjustable. The installation also comprises an extraction circuit 15 to which the air extraction device 14 is connected, this circuit comprising an installation for filtering the extracted air. Advantageously, this extraction circuit 15 also comprises a flow meter 16 for accurately measuring the flow rate Q of the extraction device. By way of example, this flow meter 16 comprises an anemometer connected to a processing unit for calculating the extraction flow rate from the extraction speed measured by the anemometer. Alternatively, a Pitot tube would also be suitable for measuring the extraction speed. One of the walls 17 of this third volume comprises an opening housing a pipe 18. A first end 19 of this pipe opens to the interior of the third air lock 13 of the enclosure while its other end 20 opens to outside this enclosure. This pipe 18 therefore establishes fluidic communication between the exterior surroundings outside the enclosure and the interior volume of this enclosure. As the enclosure is at a reduced pressure in relation to the exterior surroundings, an incoming flow of air is generated in this pipe 18. This pipe 18 which, in the embodiment being considered, has a diameter of 100 mm, is preferably made of a rigid plastic such as polyvinyl chloride (PVC), and is assembled in an airtight manner with the vinyl wall 17 of the third air lock. Advantageously, the pipe 18 is lightweight so that it does not weaken the vinyl wall 17 on which it is mounted. For preference, this pipe 18 is fixed to the wall of the enclosure using fixing tabs 21, the assembly being rendered airtight in this instance by sticking, for example using an adhesive tape. The end 19 of the pipe that opens to the interior of the enclosure preferably comprises a nonreturn valve 22 that allows air to pass from the exterior surroundings toward the inside of the enclosure 10 but blocks the flow of air in the other direction in order to prevent any risk of contamination outside the enclosure. A vane anemometer 23 for continuously measuring the speed of the incoming air flow is placed in this pipe 18. Advantageously, the axis about which the vane rotates is kept parallel, or substantially parallel, to the stream line of the incoming air flow passing along the pipe 18. The assembly is connected to a signal processing unit 24 that processes the signal emitted by the anemometer 23, such as an electronic unit, by a connecting element 25 such as a cable. The electronic unit allows the measured speed to be read and supports the visible and/or audible alarm 26 that is perceived when the measured speed is below a setpoint speed Vreference here taken to be equal to 1 ms−1 by way of example. Thus, in order to obtain the confinement enclosure 10 as described hereinabove for dismantling and/or cleanup work, the following steps will have been carried out: creating an orifice of calibrated diameter equal to 100 mm, likewise by way of example, in a wall of this enclosure, adjusting the enclosure extraction flow rate so as to obtain a speed at least equal to 1 ms−1 measured at the calibrated orifice using the vane anemometer, this speed of 1 ms−1 being referred to as Vreference, measuring the enclosure extraction flow rate for this speed and the pressure drop for the filtration with the pressure drop of the damper compensating for filter plugging (the setpoint for the filtration). More generally, depending on the dimensions of the orifice and of the enclosure at a reduced pressure, the value Vreference of the reference speed of the incoming or outgoing flow of gas used for setting off the alarm will have been determined beforehand. In order to do so and in one particular aspect of the presently disclosed embodiment, a tracer gas is introduced into the enclosure. This tracer gas is preferably an inert gas such as sulfur hexafluoride (SF6) or helium (He). The chief benefit of these tracer gases lies in their high level of chemical inertia even at high temperatures and in their properties of being detectable continuously and in real time, using mass spectrometry in the case of helium and infrared analysis in the case of SF6. This tracer gas is swept into the enclosure, for example using a fan attached to and positioned at the center of the third air lock 13. The presence and concentration of this tracer gas outside the enclosure 10 are detected and measured using one or more analysis apparatuses for various values of the speed of the flow of gas such as air, entering or leaving via the fixed-diameter orifice and under various operating conditions of this enclosure. The data thus obtained are compared and the smallest of these speed values for which the detected concentration of tracer gas outside the enclosure 10 under the various envisioned operating conditions is below or equal to a threshold value is retained. This threshold value here corresponds to a negligible transfer of the tracer gas to the outside. Purely by way of illustration, the various operating conditions may be simulated by intervention air lock entrance/exit scenarios such as those described hereafter. Scenario 1: an operator enters the personnel entrance/exit air lock 11 and then the intervention air lock 13. The personnel leaves the intervention air lock 13 via the personnel entrance/exit air lock 11, waiting time of one minute to simulate the time taken for the operator to undress and then exit to outside the enclosure 10; Scenario 2: as per scenario 1 but “downgraded” version. The operator does not wait around in the personnel air lock for one minute but exits directly to the outside; Scenario 3: simulation of materials entering the materials air lock 12 without materials, operator exits, operator enters the personnel entrance/exit air lock 11 and then the intervention air lock 13. Simulation of the recovery of materials from the materials air lock 12, leaving the intervention air lock via the personnel entrance/exit air lock 11, waiting time of one minute to simulate the time taken by the operator to undress, then exit to outside the enclosure 10; Scenario 4: material entrance/exit in “degraded” version without passing via the personnel entrance/exit air lock 11 and without waiting around for one minute; Scenario 3′: as per scenario 3 but with a material transport device such as a trolley or barrow; Scenario 4′: as per scenario 4 but with a trolley or barrow; Scenario 5: as per scenario 1 but via the materials air lock; Scenario 6: no simulation of operator movements but vinyl doors between the personnel entrance/exit air lock and the materials entrance/exit air lock 12 and the outside open and then, in a second phase, with the opening of the vinyl door between the intervention air lock 13 and the materials air lock 12. It should be noted that scenarios 1 and 3 are the scenarios usually applied in a monitored zone. The benefit of carrying out scenarios 2, 4, 5 and 6 is that they test other situations which are in theory more penalizing and likely to occur during use. |
|
abstract | A system for analyzing a film and detecting a defect associated therewith includes a scanning probe microscope having a nanotube tip with a material associated therewith which exhibits a characteristic that varies with respect to a film composition at a location corresponding to the nanotube tip. The system also includes a detection system for detecting the material characteristic and a controller operatively coupled to the detection system and the scanning probe microscope. The controller configured to receive information associated with the detected characteristic and use the information to determine whether the film contains a defect at the location corresponding to the nanotube tip. The invention also includes a method of detecting a film composition at a particular location of a film or substrate. The method includes associating a material exhibiting a characteristic which varies with respect to a film composition with a nanotube tip of a scanning probe microscope and detecting the characteristic. The method then includes the step of determining a composition of a portion of the film using the detected characteristic. |
|
052672859 | abstract | An apparatus and method are provided for suppressing the formation of vortices in circulating coolant fluid of a nuclear reactor. A vortex-suppressing plate having a plurality of openings therein is suspended within the lower plenum of a reactor vessel below and generally parallel to the main core support of the reactor. The plate is positioned so as to intersect vortices which may form in the circulating reactor coolant fluid. The intersection of the plate with such vortices disrupts the rotational flow pattern of the vortices, thereby disrupting the formation thereof. |
description | Most problems encountered in engineering design are nonlinear by nature and involve the determination of system parameters that satisfy certain goals for the problem being solved. Such problems can be cast in the form of a mathematical optimization problem where a solution is desired that minimizes a system function or parameter subject to limitations or constraints on the system. Both the system function and constraints are comprised of system inputs (control variables) and system outputs, which may be either discrete or continuous. Furthermore, constraints may be equalities or inequalities. The solution to a given optimization problem has either or both of the following characteristics: 1) minimizes or maximizes a desired condition or conditions, thus satisfying the optimality condition and 2) satisfies the set of constraint equations imposed on the system. With the above definitions, several categories of optimization problems may be defined. A Free Optimization Problem (FOP) is one for which no constraints exist. A Constraint Optimization Problem (COP) includes both, constraints and a “minimize” (or “maximize”) condition(s) requirement. In contrast, a Constraint Satisfaction Problem (CSP) contains only constraints. Solving a CSP means finding feasible solution(s) within the search space that satisfies the constraint conditions. Solving a COP means finding a solution that is both feasible and optimal in the sense that a minimum (or maximum) value for the desired condition(s) is realized. The solution to such a problem typically involves a mathematical search algorithm, whereby successively improved solutions are obtained over the course of a number of algorithm iterations. Each iteration, which can be thought of as a proposed solution, results in improvement of an objective function. An objective function is a mathematical expression having parameter values of a proposed solution as inputs. The objective function produces a figure of merit for the proposed solution. Comparison of objective function values provides a measure as to the relative strength of one solution versus another. Numerous search algorithms exist and differ in the manner by which the control variables for a particular problem are modified, whether a population of solutions or a single solution is tracked during the improvement process, and the assessment of convergence. However, these search algorithms rely on the results of an objective function in deciding a path of convergence. Examples of optimization algorithms include Genetic Algorithms, Simulated Annealing, and Tabu Search. Within optimization algorithms, the critical issue of handling constraints for COPs and CSPs must be addressed. Several classes of methods exist for dealing with constraints. The most widespread method is the use of the penalty approach for modifying the objective function, which has the effect of converting a COP or CSP into a FOP. In this method, a penalty function, representing violations in the set of constraint equations, is added to an objective function characterizing the desired optimal condition. When the penalty function is positive, the solution is infeasible. When the penalty function is zero, all constraints are satisfied. Minimizing the modified objective function thus seeks not only optimality but also satisfaction of the constraints. Objective functions take application specific forms, and therefore, each new problem or modification to a problem requires the construction of a new objective function. Furthermore, the objective function plays the important role of guiding an optimization algorithm to a possible best solution. Presumably, the better the objective function, the better the optimization result and/or the more efficient the optimization operation. Accordingly, a constant demand exists in the field of constraint-based problems for improved objective functions. The invention provides a systematic and general method and apparatus for defining an objective function for Constrained Optimization Problems (COPs), Constraint Satisfaction Problems (CSPs) and Free Optimization Problems (FOPs), independent of the optimization search employed. The invention provides a generic definition of an objective function. Given the particular optimization problem (e.g., boiling water nuclear reactor core design, transportation scheduling, pressure water reactor core design, or any large scale, combinatorial optimization problem in discrete or continuous space), the objective function is configured following the generic definition. Specifically, the generic definition of the objective function according to the present invention is a sum of credit components plus a sum of penalty components. Each credit component includes a credit term times an associated credit weight. Each penalty term includes a penalty term times an associated penalty weight. A credit term is a mathematical expression representing an optimization parameter, and a penalty term is a mathematical expression representing an optimization constraint. Configuring an objective function involves establishing the number of credit and penalty components, establishing the mathematical expressions for the credit and penalty terms and establishing the initial weights of the credit and penalty weights. At least one of the penalty terms is based on a channel deformation criteria. This is accomplished through user input or by accessing a previously stored configured objective function. The configured objective function may then be usable as part of an optimization process, or may be usable as a tool when a user assesses a candidate solution to an optimization problem. Because of the flexibility of the invention, changes in optimality conditions, constraint term definitions, and weight factors are readily accommodated. The present invention provides a generic definition of an objective function, which is applicable across a wide variety of constraint and optimization problems. Namely, the generic objective function is applicable to any large scale, combinatorial optimization problem in discrete or continuous space such as boiling water reactor core design, pressurized water reactor core design, transportation scheduling, resource allocation, etc. The generic objective function is defined as a sum of credit and penalty components. A penalty component includes a penalty term multiplied by an associated penalty weight. A credit component includes a credit term multiplied by an associated credit weight. The credit terms represent the optimality conditions for the problem. The penalty terms represent the constraints for the problem. Each credit term is a mathematical expression that quantifies an optimality condition. Each penalty term is a mathematical expression that quantifies a constraint. Mathematically, this can be expressed as follows: F obj = ∑ m λ m credit C m + ∑ n λ n penalty P n where, Fobj=objective function Cm=credit term m Pn=penalty term n λmcredit=weight factor credit term m λnpenalty=weight factor penalty term n Credit and penalty terms may be defined by maximum (i.e. upper bounded) or minimum (i.e. lower bounded) values and can represent scalar or multi-dimensional values. The only requirements are: 1) the penalty terms must be positive for constraint violations and zero otherwise, and 2) in the absence of constraint violations, the credit terms are consistent with a minimization problem. Thus, minimizing the modified objective function solves the optimization problem. As an example, consider an air-conditioning system where the optimization problem is to minimize the average air temperature within a room, yet assure that no region within the room exceeds a certain temperature. For this example, the credit would be the average air temperature within the room volume. The constraint would be a limit on the point-wise temperature distribution within the room, which, in the form of a penalty term, would be calculated as the average temperature violation. To obtain the average temperature violation one would sum the differences of actual and limiting temperature values for those points within the room that violate and divide by the total number of points. Alternatively, one could calculate the penalty term as the maximum value of the point-wise temperature violations within the room. The form of the generic objective function thus allows any number of credit and penalty terms to be defined in a general manner for the problem being solved. Forms for the credit or penalty terms include, but are not limited to: The maximum value within a data array; The minimum value within a data array; The average of values within a data array; The integral of values within a data array; The maximum of calculated differences between elements of a data array and the corresponding constraint limit, restricted to elements that violate; The minimum of calculated differences between elements of a data array and the corresponding constraint limit, restricted to elements that violate; The average of calculated differences between elements of a data array and the corresponding constraint limit, restricted to elements that violate; and The integral of calculated differences between elements of a data array and the corresponding constraint limit, restricted to elements that violate. FIG. 1 illustrates an embodiment of an architecture according to the present invention for implementing the method of evaluating a proposed solution according to the present invention. As shown, a server 10 includes a graphical user interface 12 connected to a processor 14. The processor 14 is connected to a memory 16. The server 10 is directly accessible by a user input device 18 (e.g., a display, keyboard and mouse). The server 10 is also accessible by computers 22 and 26 over an intranet 20 and the Internet 24, respectively. The operation of the architecture shown in FIG. 1 will be discussed in detail below. According to one embodiment, a configured objective function satisfying the above-described generic definition is already stored in the memory 16 of the server 10. For example, the configured objective function could have been configured according to one of the embodiments described below. In this embodiment, the user instructs the server 10 to provide a list of the configured objective functions stored in the memory 16, and instructs the server 10 to use one of the listed configured objective functions. In another embodiment, a user via input 18, computer 26 or computer 22 accesses the server 10 over the graphical user interface 12. The user supplies the server 10 with a configured objective function meeting the definition of the above-described generic definition. In this embodiment, the user supplies the configured objective function using any well known programming language or program for expressing mathematical expressions. Specifically, the user instructs the processor 14 via the graphical user interface 12 to upload a file containing the configured objective function. The processor 14 then uploads the file, and stores the file in memory 16. In still another embodiment, configuring the objective function is interactive between the user and the server 10. Here, the user instructs the processor 14 to start the process for configuring an objective function. The processor 14 then requests the user to identify the number of credit components and the number of penalty components. For each credit component, the processor 14 requests that the user provide a mathematical expression for the credit term and an initial weight for the associated credit weight. For each penalty component, the processor 14 requests that the user provide a mathematical expression for the penalty term and an initial weight for the associated penalty weight. In supplying the mathematical expression, the processor 14 via the graphical user interface 12 accepts definitions of mathematical expressions according to any well known programming language or program. In another embodiment, the server 10 is preprogrammed for use on a particular constraint or optimization-based problem. In this embodiment, the server 10 stores possible optimization parameters and possible constraint parameters associated with the particular optimization or constraint problem. When a user instructs the processor 14 via the graphical user interface 12 to configure an objective function, the processor 14 accesses the possible optimization parameters already stored in the memory 16, and provides the user with the option of selecting one or more of the optimization parameters for optimization. FIG. 2 illustrates a screen shot of an optimization configuration page used in selecting one or more optimization parameters associated with the optimization problem of boiling water reactor core design according to this embodiment of the present invention. As shown, the optimization parameters 40 of optimize rod patterns, optimize core flow, optimize sequence intervals, and optimize channel deformation criteria are available for selection by the user as optimization parameters. As is known, control blade (sometimes also referred to as control rods) positions affect the local power as well as the nuclear reaction rate within the fuel bundles. Optimize rod patterns means making an optimal determination of individual control rod or blade positions and rates of movement within a control blade grouping, for the duration of time during the operating cycle when a given sequence is being used to control the reactor. Sequences are time intervals during the reactor's cycle of operation. Generally, sequences may be a period of approximately 120 days, but the duration of sequences may be any period less than or equal to the nuclear reactor's cycle of operation. Optimize core flow means making an optimal determination of reactor coolant flow rate through the reactor as a function of time during the operating cycle. Flow rate affects global reactor power as well as the nuclear reaction rate. Optimize sequence intervals means making an optimal determination of the time duration a given sequence is used to control the reactor during the operating cycle. Sequence intervals affect local power as well as the nuclear reaction rate. Optimize channel deformation criteria means accounting for channel deformation (e.g., bow, bulge, or twist in the channel walls) for a next cycle of operation based on at least one of a proposed operational plan, a current operational plan, and current conditions (e.g., channel deformation conditions) within the core. Channel bow is the bowing of the channel walls, which surround a fuel bundle. A control blade moves between adjacent channel walls of adjacent fuel bundles and this movement may become obstructed by the channel walls. The channel bow phenomenon will be described in greater detail below with respect to FIG. 5. Using the data input device 18, computer 22 or computer 26, each of which includes a display and a computer mouse, the user selects one or more of the optimization parameters by clicking in the selection box 42 associated with an optimization parameter 40. When selected, a check appears in the selection box 42 of the selected optimization parameter. Clicking in the selection box 42 again de-selects the optimization parameter. The memory 16 also stores constraint parameters associated with the optimization problem. The constraint parameters are parameters of the optimization problem that must or should satisfy a constraint or constraints. FIG. 3 illustrates a screen shot of an optimization constraints page listing optimization constraints associated with the optimization problem of boiling water reactor core design according to this embodiment of the present invention. As shown, each optimization constraint 50 has a design value 52 associated therewith. Optimization constraints may be below the specified design value if maximum valued or, alternatively, may be above the specified design value if minimum valued. The user has the ability to select optimization parameters for consideration in configuring the objective function. Using the data input device 18, computer 22 or computer 26, each of which includes a display and a computer mouse, the user selects an optimization constraint by clicking in the selection box 54 associated with an optimization constraint 50. When selected, a check appears in the selection box 54 of the selected optimization constraint 50. Clicking in the selection box 54 again de-selects the optimization constraint. Each optimization parameter has a predetermined credit term and credit weight associated therewith that is stored in memory 16. Similarly, each optimization constraint has a predetermined penalty term and penalty weight associated therewith that is stored in memory 16. In the embodiment shown in FIG. 3, the penalty term incorporates the design value, and the user can change (i.e., configure) this value as desired. Additionally, the embodiment of FIG. 3 allows the user to set an importance 56 for each optimization constraint 50. In the importance field 58 for an optimization constraint, the user has pull-down options of minute, low, nominal, high and extreme. Each option correlates to an empirically predetermined penalty weight such that the greater the importance, the greater the predetermined penalty weight. In this manner, the user selects from among a set of predetermined penalty weights. Once the above-selections have been completed, the processor 14 configures the objective function according to the generic definition discussed above and the selections made during the selection process. The resulting configured objective function equals the sum of credit components associated with the selected optimization parameters plus the sum of penalty components associated with the selected optimization constraints. Additionally, the embodiment provides for the user to select a method of handling the credit and penalty weights. For example, the user is supplied with the possible methodologies of static, death penalty, dynamic, and adaptive for the penalty weights; is supplied with the possible methodologies of static, dynamic and adaptive for the credit weights; and the methodology of relative adaptive for both the penalty and credit weights. The well-known static methodology maintains the weights at their initially set values. The well-known death methodology sets each penalty weight to infinity. The well-known dynamic methodology adjusts the initial weight value during the course of the objective function's use in an optimization search based on a mathematical expression that determines the amount and/or frequency of the weight change. The well-known adaptive methodology is also applied during the course of an optimization search. In this method, penalty weight values are adjusted periodically for each constraint parameter that violates the design value. The relative adaptive methodology is disclosed in U.S. application Ser. No. 10/246,718, titled METHOD AND APPARATUS FOR ADAPTIVELY DETERMINING WEIGHT FACTORS WITHIN THE CONTEXT OF AN OBJECTIVE FUNCTION, by the inventors of the subject application. FIG. 4 illustrates a flow chart showing one of the many uses for the objective function of the present invention. Specifically, FIG. 4 illustrates a flow chart of an optimization process employing the objective function of the present invention. For the purposes of explanation only, the optimization process of FIG. 4 will be described as being implemented by the architecture illustrated in FIG. 1. As shown, in step S10 the objective function is configured as discussed above in the preceding section, and then the optimization process begins. In step S12, the processor 14 retrieves from memory 16 or generates one or more sets of values for input parameters (i.e., system inputs) of the optimization problem based on the optimization algorithm in use. For example, for the optimization problem of boiling water reactor core design, some of the input parameters would be placement of fresh and exposed fuel bundles within the reactor, selection of the rod groups (sequences) and placement of the control rod positions within the groups as a function of time during the cycle, core flow as a function of time during a cycle, reactor coolant inlet pressure, etc. Each input parameter set of values is a candidate solution of the optimization problem. The processor 14 runs a simulated operation and generates a simulation result for each input parameter set of values. For example, for boiling water reactor core design, a well-known simulation program for boiling water reactor operation is run using an input parameter set. The simulation result includes values (i.e., system outputs) for the optimization parameters and optimization constraints. These values, or a subset of these values, are values of the variables in the mathematical expressions of the objective function. Then, in step S14, the processor 14 uses the objective function and the system outputs to generate an objective function value for each candidate solution. In step S16, the processor 14 assesses whether the optimization process has converged upon a solution using the objective function values generated in step S14. If no convergence is reached, then in step S18, the input parameter sets are modified, the optimization iteration count is increased and processing returns to step S12. The generation, convergence assessment and modification operations of steps S12, S16 and S18 are performed according to any well-known optimization algorithm such as Genetic Algorithms, Simulated Annealing, and Tabu Search. When the optimization problem is boiling water reactor core design, the optimization algorithm can be, for example, one of the optimization processes as disclosed in U.S. patent Ser. No. 09/475,309, titled SYSTEM AND METHOD FOR OPTIMIZATION OF MULTIPLE OPERATIONAL CONTROL VARIABLES FOR A NUCLEAR REACTOR or U.S. application Ser. No. 09/683,004, tilted SYSTEM AND METHOD FOR CONTINUOUS OPTIMIZATION OF CONTROL-VARIABLES DURING OPERATION OF A NUCLEAR REACTOR, filed Nov. 7, 2001. Before the advent of fairly successful optimization tools, generating viable solutions to an optimization problem fell on the shoulders of highly experienced individuals, who through years of practice and experience in a particular field, developed a set of skills for generating possible solutions to the optimization problem. Even today such practices continue. However, these individuals still need a reliable method for assessing their solutions. The objective function of the present invention provides such a tool. Referring again to FIG. 1 for the purposes of explanation only, an individual desiring to apply an objective function according to the present invention accesses the server 10 via input 18, computer 26 or computer 22. The user then configures an objective function as described above; for example, the user accesses a previously stored configured objective function or configures the objective function through data entry. The user then supplies the values for the input variables of the objective function, and receives an objective function result. The user can perform this operation for different candidate solutions to obtain figures of merit regarding the solutions. In this manner, the user treats the objective function as a tool in determining a solution to the optimization problem. The invention provides a systematic and general method for defining an objective function for Constrained Optimization Problems (COPs), Constraint Satisfaction Problems (CSPs) and Free Optimization Problems (FOPs), independent of the optimization search employed. The invention provides a mechanism within the context of the penalty function approach for addressing: 1) any number of constraints and optimality conditions, 2) different mathematical forms for the credit and penalty terms and 3) any number of dimensions in the candidate solution data and constraints. The invention provides a prescription for encoding objective function definitions within an optimization search through a software data module. Because of the flexibility of the invention, changes in optimality conditions, constraint term definitions, and weight factors are readily accommodated within the calling program simply by changing the data passed to the software data module. The technical effort of the invention is a computer system that provides for configuring an objective function for a given optimization problem; a computer system that generates a possible solution for a particular optimization problem; and a computer system that allows internal and external users to measure the performance of their possible solutions to an optimization problem. FIG. 5 illustrates a portion of a fuel bundle arrangement within a core. The fuel bundles 100 within a core contain a plurality of fuel rods 102. Fuel rods 102 deliver fuel for the nuclear reaction during the operation or cycle of the reactor. The fuel bundles 100 may be analyzed using a loading map. The loading map sets forth the placement of fuel bundles 100 and their attributes (e.g., type, location, depth, serial number, etc. . . . ). During the operation of the reactor, it is desirable to maintain a stable reactivity level to achieve a desired level of reactor performance. Accordingly, the reactor may include a plurality of control blades 110 positioned between fuel bundles. Control blades 110 may control the reactivity of the core (e.g., changing a position of a control blade 110 changes the reactivity of the core by slowing the nuclear reactions in a given proximity of the control blade 110). Generally, the control blades 110 may be moved mechanically to a deeper position within the core in order to decrease the core reactivity. Alternatively, the control blades 110 may be moved to a position further removed from the core in order to increase the core reactivity. Each control blade 110 within the core may be positioned within a given range, the given range including a position furthest into the core at one extreme and a position furthest out of the core at another extreme. Within the range of control blade positioning, the control blade 110 may be moved to positions (referred to as “notches”) that are a fixed interval from one another. For example, notches may be spaced apart from each other at a given interval of 3″, 1.5″, etc., with each control blade 110 within the core including the same notch intervals. For example, assume that a control blade 110 has notch positions ranging from “0” to “48”. The control blade 110 is in a position deepest in the core when at the notch position “0”, and the control blade 110 is in a position furthest out of the core when at the notch position “48”. The notch positions between “0” and “48” correspond to varying degrees or depths of control blade insertion, wherein the given interval between adjacent notches is uniform throughout the notches in each of the plurality of control blades 10. For example, if the given notch interval is 3″, then changing a control blade 110 from a position of notch “4” to notch “8” moves the control blade further out of the core by 12″. For each sequence, each of the plurality of control blades 110 within the core may move to a lower notch position (i.e., further into the core), a higher notch position (i.e., further out from the core), or the control blade 110 may maintain its position. The determined direction of movement to a higher or lower notch position or non-movement for each of the plurality of control blades 110 may be maintained throughout the duration of the sequence, and generally is not changed until a next sequence. The movements of the control blades 10 may be controlled individually (e.g., each of the control blades 110 may move at a unique notch rate and direction) or in groups (e.g., each control blade 110 in a group of control blades may move at a same notch rate and direction). In addition to the direction of movement for each of the plurality of control blades 110, a rate at which each of the plurality of control blades 110 may move, referred to as a notch rate, typically remains below a threshold rate during the sequence (e.g., 4 notches per sequence, 5 notches per sequence, etc.). Also, similar to the direction of the control blade 110, the notch rate is generally constant throughout a sequence and may not change until a next sequence. Alternatively, the notch rate may change within a given sequence. Further, in one embodiment, the notch rate may become zero (e.g., the control blade 110 enters a period of non-movement during the sequence). However, in the above-described embodiments, the notch rate cannot reverse directions. In other words, if at any point during a given sequence a control blade 110 is moving into the core, the control blade 110 cannot move out of the core within the given sequence, and vise versa. As shown in FIG. 5, the channel walls 104, typically made of Zircaloy, may surround the fuel rods 102 of the fuel bundle 100. The channel walls 104 support the fuel bundle 100 as well as separate coolant flow between fuel bundles 100 in the core. The channel walls 104 may experience above-described channel deformation. Channel bow, which is one example of channel deformation, may be an obstruction to control blade movement in the core. Channel bow refers to an extension of the position of the channel walls 104 either from a bending of the channel walls 104 or a growth of a corrosion layer on the channel walls. Channel bow is typically caused by two factors; namely, fast neutron fluence and/or shadow corrosion. Fast neutron fluence is the striking of fast neutrons, typically above a given energy level, on the channel walls 104 for a given period of time. Over the period of time, an irradiation growth strain on the channel walls 104, referred to as the accumulated channel wall fast neutron fluence. Fluence may accumulate disproportionately on the channel walls 104. The differential in the fluence accumulated on the opposite faces of channel walls 104, may lead to bow. Shadow corrosion is where a layer of corrosion (i.e., shadow corrosion) develops on the channel walls 104 based on a proximity of the control blade 110 and the channel walls 104, thereby causing an extension of the channel walls 104 and a possible obstruction to the control blades 110. The corrosion layer increases in response to an increased rate of hydrogen absorption. Platelets (e.g., Zirconium hydride platelets) form when the hydrogen content exceeds a solubility limit (e.g., from the increased rate of hydrogen absorption). The difference in density between the platelets and the normal Zirconium may cause a volume expansion of the corrosion layer on the channel wall surfaces, while channel wall surfaces not in contact with the control blade (e.g., without the higher rate of hydrogen absorption) may not be affected. The increased hydrogen may also affect the normal dislocation density-induced irradiation growth normally experience by the channel walls 104 (e.g., as described above with respect to fast neutron fluence). The differential in the length of the channel (e.g., based on growth on sides in contact with the control blades 110 and no growth or less growth on sides not in contact with the control blades 110) may result in channel bow. As described above, channel bow is a physical, structural change of the fuel assembly or bundle 100, which may affect various operational factors of the core. For example, a control blade 110 may experience “no settle” conditions, where the control blade 110 cannot be inserted into the core at a required notch rate due to friction between the channel wall and the control blade 110 (e.g., caused by the channel bow). The channel bow may also affect safety thermal margins during operation of the core. Alternatively, the control blade 110 may not reach the “no settle” condition but may still be adversely affected by friction due to channel deformation (e.g., the channel bow) from at least one channel wall 104. These various degrees of friction between the control blade 10 and the channel walls 104 are undesirable during core operation. Control blade movements for a next cycle of operation may be designated in a proposed operational plan. The proposed operational plan may be generated according to any well-known method. For example, one method of generating the operational plan is through an experience based, trial and error, and iterative process performed by a core designer. An objective function may be configured for evaluating the new operational plan, as discussed in detail above. However, in this example, at least one of the penalty terms of the objective function takes the level of channel deformation into consideration (e.g., the number of control blades in the core affected by channel deformation). Methods of calculating the amount of channel deformation within a core during operation are well known in the art and will not be described further. These methods may include algorithms for fluence bow calculations, algorithms for shadow bow calculation, algorithms for channel bulge calculations, etc. . . . . Methods of calculating channel deformation at a next cycle of operation typically require the current operational plan, a proposed operational plan, and the current conditions (e.g., channel deformation levels) within the core. With respect to configuring the objective function, the user may select the penalty weight associated with the channel deformation constraint from among a set of predetermined penalty weights. For example, as above described with reference to the embodiment shown in FIG. 3, the user may set an importance 56 for each optimization constraint 50. In the importance field 58 for an optimization constraint, the user has an enumerated set of pull down options of minute, low, nominal, high and extreme. The enumerated list of options is mapped to a set of weighting factors, utilized in the objective function, that reflect the qualitative description. In this case, at least one of the optimization constraints may based on a channel deformation criteria (e.g., the number of control blades affected by channel deformation). In the example where the channel deformation criteria is a number of control blades affected by channel deformation, the calculation of this number may be performed manually by the core designer and/or may be automated with a processing device, such as a simulator. This number may then serve as a penalty term that is then multiplied with the selected penalty weight in the objective function. Once the above-selections have been completed, the processor 14 configures the objective function according to the generic definition discussed above and the selections made during the selection process. The resulting configured objective function equals the sum of credit components associated with the selected optimization parameters plus the sum of penalty components associated with the selected optimization constraints. Accordingly, the above-described process of constraint optimization, including a consideration of a channel deformation criteria, may be used as a tool. Referring again to FIG. 1 for the purposes of explanation only, an individual desiring to apply an objective function according to example embodiments of the present invention accesses the server 10 via input 18, computer 26 or computer 22. The user then configures an objective function as described above; for example, the user accesses a previously stored configured objective function or configures the objective function through data entry. The user then supplies the values for the input variables of the objective function, and receives an objective function result. The user can perform this operation for different candidate solutions to obtain figures of merit regarding the solutions. In this manner, the user treats the objective function as a tool in determining a solution to the optimization problem. Using the configured objective function, an optimization process such as described above with respect to FIG. 4 may be performed. Referring to FIG. 4, each candidate solution generated in S12 may result in a different operational plan. The optimization process may advance through steps S14, S16, S18 and back to S12 recursively until step S16 determines convergence for a generated candidate solution (i.e., operational plan). The invention being thus described, it will be obvious that the same may be varied in many ways. For example, while above-described example embodiments are directed to channel bow, it is understood that other example embodiments may be directed to any type of channel deformation constraint (e.g., bow, twist, bulge, etc. . . . ) Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. |
|
abstract | There is provided a compact charged particle beam apparatus with a non-evaporable getter pump which maintains high vacuum even during emission of an electron beam without generating foreign particles. The apparatus comprises: a charged particle source; a charged particle optics which focuses a charged particle beam emitted from the charged particle source on a sample and performs scanning; and means of vacuum pumping which evacuates the charged particle optics. The means of vacuum pumping has a differential pumping structure with two or more vacuum chambers connected through an opening in series. A pump made of non-evaporable getter alloy is placed in an upstream vacuum chamber with a high degree of vacuum, and a gas absorbing surface of the non-evaporable getter alloy is fixed without contact with another part. |
|
041697596 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT The part length rod design described herein is illustrated in the FIGURE. The nuclear reactor 10 generally includes nuclear reactor core 12 with length L, pressure vessel 14, control rod drive mechanisms 16 attached to nozzles 18 which penetrate the reactor pressure vessel 14 and part length rods 22 and 22' of length L connected to the control rod drive mechanisms 16 by means of connecting elements 20. The part length control rods 22, 22' of the invention have two neutron absorbing regions 24 and 26. Normal, full length control rods (an example of which shown at 23) constitute a first group of rods insertable into the core for normal control of reactor power, and the part length rods 22, 22' constitute a second group of control rods for control of power oscillations. Part length control rod 22 is shown in its normal control position approximately centrally positioned in the reactor core. Part length control rod 22' is shown in its scrammed or fully inserted position in which both poison sections 24 and 26 are positioned within the reactor core 12 at opposite ends of the core 12. Each part length control rod 22, 22' is translatable from a full out position to a full in position. As can be seen in the FIGURE, poison portions 24 and 26 are connected by an intermediate connecting portion 28. This intermediate connecting portion 28 acts as a poison section "follower". In the preferred embodiment the "follower" section 28 is a water filled Inconel tube designed to achieve the minimum reactivity control worth obtainable. Hence, by use of a water filled follower, the maximum effective control worth of the lower control portion 26 is obtained. On either part length control rod 22, 22' the first portion 24 appears at a first end of the part length rod 22, 22' and consists of a first neutron absorbing material. A second portion 26 appears at the second end of the part length rod 22, 22' and consists of a second neutron absorbing material. The second neutron absorbing material 26 preferably has a smaller macroscopic absorption cross-section than the first neutron absorbing material 24. For the purposes of this disclosure the terminology "macroscopic absorption cross-section" is defined to be the product of the number density of the particular element in question and the microscopic neutron absorption cross-section of the element in question. Accordingly, it is a desirable feature of the invention to provide the second portion 26 of the part length control rod 22, 22' with a macroscopic absorption cross-section that is smaller than the macroscopic absorption cross-section of the first portion 24 by providing a material with a high number density but with a low microscopic neutron absorption cross-section. This combination is desirable since it resists depletion of the neutron poison more readily than would a neutron poison resulting from the combination of a smaller number density but a larger microscopic neutron absorption cross-section. A well-known material in the science of nuclear reactor design which meets these requirements is the alloy Inconel 600. Inconel 600 is defined by the Standard Handbook For Mechanical Engineers by Baumeister and Marks, 7th Edition as having the following composition: (76Ni 0.04C--0.2MN--7.20Fe--0.2Si--0.1Cu--15.8Cr). An alternative and equally as acceptable material is Inconel 625 (61Ni--21Cr--9Mo). In the preferred embodiment of this disclosure the second neutron absorbing material located at the second end of the part length rod is preferably between 25 and 55 percent of the length of the active region of the nuclear core. Such a part length rod made from Inconel 600 has a longer and a weaker nuetron absorbing section than has previously been known in the prior art. This longer and weaker neutron absorbing section has many advantages. One positive advantage is that the longer weaker neutron absorbing section reduces the possibility of incurring nuclear fuel failure. Although the mechanism for nuclear fuel pin clad failure through fuel interaction has not been completely established, it is generally agreed that the magnitude and rate of change of local power density in a fuel pellet are important components of the failure mechanism. Since fuel pellets in the vicinity of control rods experience severe changes in local power density as the tip of the poison section moves past them, those pins are prime candiates for interaction induced clad failure. In modern larger nuclear cores the instabilities with respect to axial xenon oscillations are expected very early in the fuel life cycle. Although this presents no operational difficulties, it does require the presence, and continued motion of, the part length rods which have been provided to control axial power distribution. This control is accomplished by positioning the longer weaker portion of the part length control rod substantially in the center of the reactor core. When a neutron flux imbalance arises at either end of the core, the part length control rod is moved in the direction of higher neutron flux to reduce the neutron flux imbalance. Interaction as a result of part length rod motion is of concern under two separate conditions of operation. The first of these is motion of the part length rod out of a region in which they were formerly inserted, such as would occur during load follow maneuvering control or removal of the part length rod from the core. The second is the smaller motion of the part length rod required to control neutron flux imbalance or axial xenon oscillations. One benefit expected to be derived from the part length rod of the present invention is that the increase in the local power density as the part length rod is removed from the center of the core, is significantly less for the part length rod of the present invention as compared to the prior art part length rods. Removal of a previous prior art boron carbide part length rod bank is characterized by an increase in power of over 200 percent relative to the original power at the center of the rod. Removal of the part length rods of the invention results in a relative increase of in local power of only about 50 percent. For the smaller part length rod motion necessary to control axial xenon oscillation, the relative power increase at the rod tip is larger for the stronger prior art rods (150 percent for the B.sub.4 C rods versus 40 percent for the control rods of the present invention for a 5 percent motion of the part length rod). As a result of the significant differences between the reactivity worth of the prior art length rods and the present part length rod, an accidental drop of the new part length rod 22, 22' becomes an acceptable event as opposed to the accidental drop of a prior art part length rod which was an unacceptable event. As a result of these differences, the prior art part length rods had to be suspended from and controlled by control rod drive mechanisms which were of the non-scrammable type. This required each reactor to be outfitted with two different types of control rod drive mechanisms, one scrammable type for the regular control rods and one non-scrammable type for the part length control rods. As mentioned previously, the new part length control rods permit the use of a single type of control rod drive mechanism which is scrammable. In addition to the reduced cost necessary for outfitting the reactor with only one type of control rod drive mechanism, another advantage is to be gained from a scrammable part length rod. This second advantage is that the new part length rods are readily interchangable with regular control rods so that the positions of the part length control rods may readily be varied according to the requirements established by the management of the fuel cycle. This avoids the extreme difficulty of performing the difficult task of transposition of the drive mechanisms. A further advantage that may be derived from the use of the new part length rod is that, due to the lower effective worth of the new part length rod the effect on power peaking from either removing the part length rod from a core that has been depleted with the part length rods in place of inserting them into a core which has not had part length rods is reduced. This reduces the impact on thermal margin so that smaller thermal margins need be maintained for the purpose of accommodating these two types of part length rod movement. The upper portion 24 of the part length rod preferably consists of pellets of a strong poison, such as boron carbide (B.sub.4 C), contained within a clad or tube of Inconel. In addition the upper portion 24 preferably has a length up to 20 percent of the length of the active region of the core. By limiting the upper portion 24 to 20 percent of the active length of the core, the ability is retained to insert the part length rod 22, 22' up to 80 percent of its length for xenon power oscillation control without adversely effecting the power of the upper end of the core 12 by the insertion of the high worth poison 24. The provision of the upper portion 24 results in a part length control rod which may be scrammed upon the requirement for a rapid shutdown of the reactor. The net effect of scramming such a part length control rod is a contribution in shutdown reactivity rather than an effect which causes a decrease in net shutdown reactivity such as may have occurred upon the dropping of a prior art part length control rod. Accordingly, the available shutdown margin for the entire reactor is increased by the utilization of the part length rods of the present invention. |
description | This application is a continuation of PCT Application No. PCT/US14/57157, filed Sep. 24, 2014, which claims the benefit of U.S. Provisional Application No. 61/881,874, filed Sep. 24, 2013, and U.S. Provisional Application No. 62/001,583, filed May 21, 2014, which applications are incorporated by reference. The embodiments described herein relate generally to magnetic plasma confinement systems and, more particularly, to systems and methods that facilitate forming and maintaining Field Reversed Configurations with superior stability as well as particle, energy and flux confinement. The Field Reversed Configuration (FRC) belongs to the class of magnetic plasma confinement topologies known as compact toroids (CT). It exhibits predominantly poloidal magnetic fields and possesses zero or small self-generated toroidal fields (see M. Tuszewski, Nucl. Fusion 28, 2033 (1988)). The attractions of such a configuration are its simple geometry for ease of construction and maintenance, a natural unrestricted divertor for facilitating energy extraction and ash removal, and very high β (β is the ratio of the average plasma pressure to the average magnetic field pressure inside the FRC), i.e., high power density. The high β nature is advantageous for economic operation and for the use of advanced, aneutronic fuels such as D-He3 and p-B11. The traditional method of forming an FRC uses the field-reversed θ-pinch technology, producing hot, high-density plasmas (see A. L. Hoffman and J. T. Slough, Nucl. Fusion 33, 27 (1993)). A variation on this is the translation-trapping method in which the plasma created in a theta-pinch “source” is more-or-less immediately ejected out one end into a confinement chamber. The translating plasmoid is then trapped between two strong mirrors at the ends of the chamber (see, for instance, H. Himura, S. Okada, S. Sugimoto, and S. Goto, Phys. Plasmas 2, 191 (1995)). Once in the confinement chamber, various heating and current drive methods may be applied such as beam injection (neutral or neutralized), rotating magnetic fields, RF or ohmic heating, etc. This separation of source and confinement functions offers key engineering advantages for potential future fusion reactors. FRCs have proved to be extremely robust, resilient to dynamic formation, translation, and violent capture events. Moreover, they show a tendency to assume a preferred plasma state (see e.g. H. Y. Guo, A. L. Hoffman, K. E. Miller, and L. C. Steinhauer, Phys. Rev. Lett. 92, 245001 (2004)). Significant progress has been made in the last decade developing other FRC formation methods: merging spheromaks with oppositely-directed helicities (see e.g. Y. Ono, M. Inomoto, Y. Ueda, T. Matsuyama, and T. Okazaki, Nucl. Fusion 39, 2001 (1999)) and by driving current with rotating magnetic fields (RMF) (see e.g. I. R. Jones, Phys. Plasmas 6, 1950 (1999)) which also provides additional stability. Recently, the collision-merging technique, proposed long ago (see e.g. D. R. Wells, Phys. Fluids 9, 1010 (1966)) has been significantly developed further: two separate theta-pinches at opposite ends of a confinement chamber simultaneously generate two plasmoids and accelerate the plasmoids toward each other at high speed; they then collide at the center of the confinement chamber and merge to form a compound FRC. In the construction and successful operation of one of the largest FRC experiments to date, the conventional collision-merging method was shown to produce stable, long-lived, high-flux, high temperature FRCs (see e.g. M. Binderbauer, H.Y. Guo, M. Tuszewski et al., Phys. Rev. Lett. 105, 045003 (2010)). FRCs consist of a torus of closed field lines inside a separatrix, and of an annular edge layer on the open field lines just outside the separatrix. The edge layer coalesces into jets beyond the FRC length, providing a natural divertor. The FRC topology coincides with that of a Field-Reversed-Mirror plasma. However, a significant difference is that the FRC plasma has a β of about 10. The inherent low internal magnetic field provides for a certain indigenous kinetic particle population, i.e. particles with large larmor radii, comparable to the FRC minor radius. It is these strong kinetic effects that appear to at least partially contribute to the gross stability of past and present FRCs, such as those produced in the collision-merging experiment. Typical past FRC experiments have been dominated by convective losses with energy confinement largely determined by particle transport. Particles diffuse primarily radially out of the separatrix volume, and are then lost axially in the edge layer. Accordingly, FRC confinement depends on the properties of both closed and open field line regions. The particle diffusion time out of the separatrix scales as τ⊥˜a2/D⊥(a˜rs/4, where rs is the central separatrix radius), and D⊥ is a characteristic FRC diffusivity, such as D⊥˜12.5 ρie, with ρie representing the ion gyroradius, evaluated at an externally applied magnetic field. The edge layer particle confinement time τ81 is essentially an axial transit time in past FRC experiments. In steady-state, the balance between radial and axial particle losses yields a separatrix density gradient length δ˜(D⊥τ∥)1/2. The FRC particle confinement time scales as (τ⊥τ∥)1/2 for past FRCs that have substantial density at the separatrix (see e.g. M. TUSZEWSKI, “Field Reversed Configurations,” Nucl. Fusion 28, 2033 (1988)). Another drawback of prior FRC system designs was the need to use external multipoles to control rotational instabilities such as the fast growing n=2 interchange instabilities. In this way the typical externally applied quadrupole fields provided the required magnetic restoring pressure to dampen the growth of these unstable modes. While this technique is adequate for stability control of the thermal bulk plasma, it poses a severe problem for more kinetic FRCs or advanced hybrid FRCs, where a highly kinetic large orbit particle population is combined with the usual thermal plasma. In these systems, the distortions of the axisymmetric magnetic field due to such multipole fields leads to dramatic fast particle losses via collisionless stochastic diffusion, a consequence of the loss of conservation of canonical angular momentum. A novel solution to provide stability control without enhancing diffusion of any particles is, thus, important to take advantage of the higher performance potential of these never-before explored advanced FRC concepts. In light of the foregoing, it is, therefore, desirable to improve the confinement and stability of FRCs in order to use steady state FRCs as a pathway to a whole variety of applications from compact neutron sources (for medical isotope production and nuclear waste remediation), to mass separation and enrichment systems, and to a reactor core for fusion of light nuclei for the future generation of energy. The present embodiments provided herein are directed to systems and methods that facilitate the formation and maintenance of new High Performance Field Reversed Configurations (FRCs). In accordance with this new High Performance FRC paradigm, the present system combines a host of novel ideas and means to dramatically improve FRC confinement of particles, energy and flux as well as provide stability control without negative side-effects. An FRC system provided herein includes a central confinement vessel surrounded by two diametrically opposed reversed-field-theta-pinch formation sections and, beyond the formation sections, two divertor chambers to control neutral density and impurity contamination. A magnetic system includes a series of quasi-dc coils that are situated at axial positions along the components of the FRC system, quasi-dc mirror coils between either end of the confinement chamber and the adjacent formation sections, and mirror plugs comprising compact quasi-dc mirror coils between each of the formation sections and divertors that produce additional guide fields to focus the magnetic flux surfaces towards the divertor. The formation sections include modular pulsed power formation systems that enable FRCs to be formed in-situ and then accelerated and injected (=static formation) or formed and accelerated simultaneously (=dynamic formation). The FRC system includes neutral atom beam injectors and a pellet injector. In one embodiment, beam injectors are angled to inject neutral particles towards the mid-plane. Having the beam injectors angled towards the mid-plane and with axial beam positions close to the mid-plane improves beam-plasma coupling, even as the FRC plasma shrinks or otherwise axially contracts during the injection period. Gettering systems are also included as well as axial plasma guns. Biasing electrodes are also provided for electrical biasing of open flux surfaces. In operation, FRC global plasma parameters including plasma thermal energy, total particle numbers, plasma radius and length, as well as magnetic flux, are substantially sustainable without decay while neutral beams are injected into the plasma and pellets provide appropriate particle refueling. The systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. It is also intended that the invention is not limited to require the details of the example embodiments. It should be noted that the figures are not necessarily drawn to scale and that elements of similar structures or functions are generally represented by like reference numerals for illustrative purposes throughout the figures. It also should be noted that the figures are only intended to facilitate the description of the various embodiments described herein. The figures do not necessarily describe every aspect of the teachings disclosed herein and do not limit the scope of the claims. The present embodiments provided herein are directed to systems and methods that facilitate forming and maintaining High Performance Field Reversed Configurations (FRCs) with superior stability as well as superior particle, energy and flux confinement over conventional FRCs. Various ancillary systems and operating modes have been explored to assess whether there is a superior confinement regime in FRCs. These efforts have led to breakthrough discoveries and the development of a High Performance FRC paradigm described herein. In accordance with this new paradigm, the present systems and methods combine a host of novel ideas and means to dramatically improve FRC confinement as illustrated in FIG. 1 as well as provide stability control without negative side-effects. As discussed in greater detail below, FIG. 1 depicts particle confinement in an FRC system 10 described below (see FIGS. 2 and 3), operating in accordance with a High Performance FRC regime (HPF) for forming and maintaining an FRC versus operating in accordance with a conventional regime CR for forming and maintaining an FRC, and versus particle confinement in accordance with conventional regimes for forming and maintaining an FRC used in other experiments. The present disclosure will outline and detail the innovative individual components of the FRC system 10 and methods as well as their collective effects. Description of the FRC System Vacuum System FIGS. 2 and 3 depict a schematic of the present FRC system 10. The FRC system 10 includes a central confinement vessel 100 surrounded by two diametrically opposed reversed-field-theta-pinch formation sections 200 and, beyond the formation sections 200, two divertor chambers 300 to control neutral density and impurity contamination. The present FRC system 10 was built to accommodate ultrahigh vacuum and operates at typical base pressures of 10−8 torr. Such vacuum pressures require the use of double-pumped mating flanges between mating components, metal O-rings, high purity interior walls, as well as careful initial surface conditioning of all parts prior to assembly, such as physical and chemical cleaning followed by a 24 hour 250° C. vacuum baking and Hydrogen glow discharge cleaning. The reversed-field-theta-pinch formation sections 200 are standard field-reversed-theta-pinches (FRTPs), albeit with an advanced pulsed power formation system discussed in detail below (see FIGS. 4 through 6). Each formation section 200 is made of standard opaque industrial grade quartz tubes that feature a 2 millimeter inner lining of ultrapure quartz. The confinement chamber 100 is made of stainless steel to allow a multitude of radial and tangential ports; it also serves as a flux conserver on the timescale of the experiments described below and limits fast magnetic transients. Vacuums are created and maintained within the FRC system 10 with a set of dry scroll roughing pumps, turbo molecular pumps and cryo pumps. Magnetic System The magnetic system 400 is illustrated in FIGS. 2 and 3. FIG. 2, amongst other features, illustrates an FRC magnetic flux and density contours (as functions of the radial and axial coordinates) pertaining to an FRC 450 producible by the FRC system 10. These contours were obtained by a 2-D resistive Hall-MHD numerical simulation using code developed to simulate systems and methods corresponding to the FRC system 10, and agree well with measured experimental data. As seen in FIG. 2, the FRC 450 consists of a torus of closed field lines at the interior 453 of the FRC 450 inside a separatrix 451, and of an annular edge layer 456 on the open field lines 452 just outside the separatrix 451. The edge layer 456 coalesces into jets 454 beyond the FRC length, providing a natural divertor. The main magnetic system 410 includes a series of quasi-dc coils 412, 414, and 416 that are situated at particular axial positions along the components, i.e., along the confinement chamber 100, the formation sections 200 and the divertors 300, of the FRC system 10. The quasi-dc coils 412, 414 and 416 are fed by quasi-dc switching power supplies and produce basic magnetic bias fields of about 0.1 T in the confinement chamber 100, the formation sections 200 and the divertors 300. In addition to the quasi-dc coils 412, 414 and 416, the main magnetic system 410 includes quasi-dc mirror coils 420 (fed by switching supplies) between either end of the confinement chamber 100 and the adjacent formation sections 200. The quasi-dc mirror coils 420 provide magnetic mirror ratios of up to 5 and can be independently energized for equilibrium shaping control. In addition, mirror plugs 440, are positioned between each of the formation sections 200 and divertors 300. The mirror plugs 440 comprise compact quasi-dc mirror coils 430 and mirror plug coils 444. The quasi-dc mirror coils 430 include three coils 432, 434 and 436 (fed by switching supplies) that produce additional guide fields to focus the magnetic flux surfaces 455 towards the small diameter passage 442 passing through the mirror plug coils 444. The mirror plug coils 444, which wrap around the small diameter passage 442 and are fed by LC pulsed power circuitry, produce strong magnetic mirror fields of up to 4 T. The purpose of this entire coil arrangement is to tightly bundle and guide the magnetic flux surfaces 455 and end-streaming plasma jets 454 into the remote chambers 310 of the divertors 300. Finally, a set of saddle-coil “antennas” 460 (see FIG. 15) are located outside the confinement chamber 100, two on each side of the mid-plane, and are fed by dc power supplies. The saddle-coil antennas 460 can be configured to provide a quasi-static magnetic dipole or quadrupole field of about 0.01 T for controlling rotational instabilities and/or electron current control. The saddle-coil antennas 460 can flexibly provide magnetic fields that are either symmetric or antisymmetric about the machine's midplane, depending on the direction of the applied currents. Pulsed Power Formation Systems The pulsed power formation systems 210 operate on a modified theta-pinch principle. There are two systems that each power one of the formation sections 200. FIGS. 4 through 6 illustrate the main building blocks and arrangement of the formation systems 210. The formation system 210 is composed of a modular pulsed power arrangement that consists of individual units (=skids) 220 that each energize a sub-set of coils 232 of a strap assembly 230 (=straps) that wrap around the formation quartz tubes 240. Each skid 220 is composed of capacitors 221, inductors 223, fast high current switches 225 and associated trigger 222 and dump circuitry 224. In total, each formation system 210 stores between 350-400 kJ of capacitive energy, which provides up to 35 GW of power to form and accelerate the FRCs. Coordinated operation of these components is achieved via a state-of-the-art trigger and control system 222 and 224 that allows synchronized timing between the formation systems 210 on each formation section 200 and minimizes switching jitter to tens of nanoseconds. The advantage of this modular design is its flexible operation: FRCs can be formed in-situ and then accelerated and injected (=static formation) or formed and accelerated at the same time (=dynamic formation). Neutral Beam Injectors Neutral atom beams 600 are deployed on the FRC system 10 to provide heating and current drive as well as to develop fast particle pressure. As shown in FIGS. 3A, 3B and 8, the individual beam lines comprising neutral atom beam injector systems 610 and 640 are located around the central confinement chamber 100 and inject fast particles tangentially to the FRC plasma (and perpendicular or at an angel normal to the major axis of symmetry in the central confinement vessel 100) with an impact parameter such that the target trapping zone lies well within the separatrix 451 (see FIG. 2). Each injector system 610 and 640 is capable of injecting up to 1 MW of neutral beam power into the FRC plasma with particle energies between 20 and 40 keV. The systems 610 and 640 are based on positive ion multi-aperture extraction sources and utilize geometric focusing, inertial cooling of the ion extraction grids and differential pumping. Apart from using different plasma sources, the systems 610 and 640 are primarily differentiated by their physical design to meet their respective mounting locations, yielding side and top injection capabilities. Typical components of these neutral beam injectors are specifically illustrated in FIG. 7 for the side injector systems 610. As shown in FIG. 7, each individual neutral beam system 610 includes an RF plasma source 612 at an input end (this is substituted with an arc source in systems 640) with a magnetic screen 614 covering the end. An ion optical source and acceleration grids 616 is coupled to the plasma source 612 and a gate valve 620 is positioned between the ion optical source and acceleration grids 616 and a neutralizer 622. A deflection magnet 624 and an ion dump 628 are located between the neutralizer 622 and an aiming device 630 at the exit end. A cooling system comprises two cryo-refrigerators 634, two cryopanels 636 and a LN2 shroud 638. This flexible design allows for operation over a broad range of FRC parameters. An alternative configuration for the neutral atom beam injectors 600 is that of injecting the fast particles tangentially to the FRC plasma, but with an angle A less than 90° relative to the major axis of symmetry in the central confinement vessel 100. These types of orientation of the beam injectors 615 are shown in FIG. 3C. In addition, the beam injectors 615 may be oriented such that the beam injectors 615 on either side of the mid-plane of the central confinement vessel 100 inject their particles towards the mid-plane. Finally, the axial position of these beam systems 600 may be chosen closer to the mid-plane. These alternative injection embodiments facilitate a more central fueling option, which provides for better coupling of the beams and higher trapping efficiency of the injected fast particles. Furthermore, depending on the angle and axial position, this arrangement of the beam injectors 615 allows more direct and independent control of the axial elongation and other characteristics of the FRC 450. For instance, injecting the beams at a shallow angle A relative to the vessel's major axis of symmetry will create an FRC plasma with longer axial extension and lower temperature while picking a more perpendicular angle A will lead to an axially shorter but hotter plasma. In this fashion the injection angle A and location of the beam injectors 615 can be optimized for different purposes. In addition, such angling and positioning of the beam injectors 615 can allow beams of higher energy (which is generally more favorable for depositing more power with less beam divergence) to be injected into lower magnetic fields than would otherwise be necessary to trap such beams. This is due to the fact that it is the azimuthal component of the energy that determines fast ion orbit scale (which becomes progressively smaller as the injection angle relative to the vessel's major axis of symmetry is reduced at constant beam energy). Furthermore, angled injection towards the mid-plane and with axial beam positions close to the mid-plane improves beam-plasma coupling, even as the FRC plasma shrinks or otherwise axially contracts during the injection period. Pellet Injector To provide a means to inject new particles and better control FRC particle inventory, a 12-barrel pellet injector 700 (see e.g. I. Vinyar et al., “Pellet Injectors Developed at PELIN for JET, TAE, and HL-2A,” Proceedings of the 26th Fusion Science and Technology Symposium, 09/27 to 10/01 (2010)) is utilized on FRC system 10. FIG. 3 illustrates the layout of the pellet injector 700 on the FRC system 10. The cylindrical pellets (D˜1 mm, L˜1-2 mm) are injected into the FRC with a velocity in the range of 150-250 km/s. Each individual pellet contains about 5×1019 hydrogen atoms, which is comparable to the FRC particle inventory. Gettering Systems It is well known that neutral halo gas is a serious problem in all confinement systems. The charge exchange and recycling (release of cold impurity material from the wall) processes can have a devastating effect on energy and particle confinement. In addition, any significant density of neutral gas at or near the edge will lead to prompt losses of or at least severely curtail the lifetime of injected large orbit (high energy) particles (large orbit refers to particles having orbits on the scale of the FRC topology or at least orbit radii much larger than the characteristic magnetic field gradient length scale)—a fact that is detrimental to all energetic plasma applications, including fusion via auxiliary beam heating. Surface conditioning is a means by which the detrimental effects of neutral gas and impurities can be controlled or reduced in a confinement system. To this end the FRC system 10 provided herein employs Titanium and Lithium deposition systems 810 and 820 that coat the plasma facing surfaces of the confinement chamber (or vessel) 100 and diverters 300 with films (tens of micrometers thick) of Ti and/or Li. The coatings are achieved via vapor deposition techniques. Solid Li and/or Ti are evaporated and/or sublimated and sprayed onto nearby surfaces to form the coatings. The sources are atomic ovens with guide nozzles (in case of Li) 822 or heated spheres of solid with guide shrouding (in case of Ti) 812. Li evaporator systems typically operate in a continuous mode while Ti sublimators are mostly operated intermittently in between plasma operation. Operating temperatures of these systems are above 600° C. to obtain fast deposition rates. To achieve good wall coverage, multiple strategically located evaporator/sublimator systems are necessary. FIG. 9 details a preferred arrangement of the gettering deposition systems 810 and 820 in the FRC system 10. The coatings act as gettering surfaces and effectively pump atomic and molecular hydrogenic species (H and D). The coatings also reduce other typical impurities such as Carbon and Oxygen to insignificant levels. Mirror Plugs As stated above, the FRC system 10 employs sets of mirror coils 420, 430, and 444 as shown in FIGS. 2 and 3. A first set of mirror coils 420 is located at the two axial ends of the confinement chamber 100 and is independently energized from the confinement coils 412, 414 and 416 of the main magnetic system 410. The first set of mirror coils 420 primarily helps to steer and axially contain the FRC 450 during merging and provides equilibrium shaping control during sustainment. The first mirror coil set 420 produces nominally higher magnetic fields (around 0.4 to 0.5 T) than the central confinement field produced by the central confinement coils 412. The second set of mirror coils 430, which includes three compact quasi-dc mirror coils 432, 434 and 436, is located between the formation sections 200 and the divertors 300 and are driven by a common switching power supply. The mirror coils 432, 434 and 436, together with the more compact pulsed mirror plug coils 444 (fed by a capacitive power supply) and the physical constriction 442 form the mirror plugs 440 that provide a narrow low gas conductance path with very high magnetic fields (between 2 to 4 T with risetimes of about 10 to 20 ms). The most compact pulsed mirror coils 444 are of compact radial dimensions, bore of 20 cm and similar length, compared to the meter-plus-scale bore and pancake design of the confinement coils 412, 414 and 416. The purpose of the mirror plugs 440 is multifold: (1) The coils 432, 434, 436 and 444 tightly bundle and guide the magnetic flux surfaces 452 and end-streaming plasma jets 454 into the remote divertor chambers 300. This assures that the exhaust particles reach the divertors 300 appropriately and that there are continuous flux surfaces 455 that trace from the open field line 452 region of the central FRC 450 all the way to the divertors 300. (2) The physical constrictions 442 in the FRC system 10, through which that the coils 432, 434, 436 and 444 enable passage of the magnetic flux surfaces 452 and plasma jets 454, provide an impediment to neutral gas flow from the plasma guns 350 that sit in the divertors 300. In the same vein, the constrictions 442 prevent back-streaming of gas from the formation sections 200 to the divertors 300 thereby reducing the number of neutral particles that has to be introduced into the entire FRC system 10 when commencing the start up of an FRC. (3) The strong axial mirrors produced by the coils 432, 434, 436 and 444 reduce axial particle losses and thereby reduce the parallel particle diffusivity on open field lines. Axial Plasma Guns Plasma streams from guns 350 mounted in the divertor chambers 310 of the divertors 300 are intended to improve stability and neutral beam performance. The guns 350 are mounted on axis inside the chamber 310 of the divertors 300 as illustrated in FIGS. 3 and 10 and produce plasma flowing along the open flux lines 452 in the divertor 300 and towards the center of the confinement chamber 100. The guns 350 operate at a high density gas discharge in a washer-stack channel and are designed to generate several kiloamperes of fully ionized plasma for 5 to 10 ms. The guns 350 include a pulsed magnetic coil that matches the output plasma stream with the desired size of the plasma in the confinement chamber 100. The technical parameters of the guns 350 are characterized by a channel having a 5 to 13 cm outer diameter and up to about 10 cm inner diameter and provide a discharge current of 10-15 kA at 400-600 V with a gun-internal magnetic field of between 0.5 to 2.3 T. The gun plasma streams can penetrate the magnetic fields of the mirror plugs 440 and flow into the formation section 200 and confinement chamber 100. The efficiency of plasma transfer through the mirror plug 440 increases with decreasing distance between the gun 350 and the plug 440 and by making the plug 440 wider and shorter. Under reasonable conditions, the guns 350 can each deliver approximately 1022 protons/s through the 2 to 4 T mirror plugs 440 with high ion and electron temperatures of about 150 to 300 eV and about 40 to 50 eV, respectively. The guns 350 provide significant refueling of the FRC edge layer 456, and an improved overall FRC particle confinement. To further increase the plasma density, a gas box could be utilized to puff additional gas into the plasma stream from the guns 350. This technique allows a several-fold increase in the injected plasma density. In the FRC system 10, a gas box installed on the divertor 300 side of the mirror plugs 440 improves the refueling of the FRC edge layer 456, formation of the FRC 450, and plasma line-tying. Given all the adjustment parameters discussed above and also taking into account that operation with just one or both guns is possible, it is readily apparent that a wide spectrum of operating modes is accessible. Biasing Electrodes Electrical biasing of open flux surfaces can provide radial potentials that give rise to azimuthal EXB motion that provides a control mechanism, analogous to turning a knob, to control rotation of the open field line plasma as well as the actual FRC core 450 via velocity shear. To accomplish this control, the FRC system 10 employs various electrodes strategically placed in various parts of the machine. FIG. 3 depicts biasing electrodes positioned at preferred locations within the FRC system 10. In principle, there are 4 classes of elctrodes: (1) point electrodes 905 in the confinement chamber 100 that make contact with particular open field lines 452 in the edge of the FRC 450 to provide local charging, (2) annular electrodes 900 between the confinement chamber 100 and the formation sections 200 to charge far-edge flux layers 456 in an azimuthally symmetric fashion, (3) stacks of concentric electrodes 910 in the divertors 300 to charge multiple concentric flux layers 455 (whereby the selection of layers is controllable by adjusting coils 416 to adjust the divertor magnetic field so as to terminate the desired flux layers 456 on the appropriate electrodes 910), and finally (4) the anodes 920 (see FIG. 10) of the plasma guns 350 themselves (which intercept inner open flux surfaces 455 near the separatrix of the FRC 450). FIGS. 10 and 11 show some typical designs for some of these. In all cases these electrodes are driven by pulsed or dc power sources at voltages up to about 800 V. Depending on electrode size and what flux surfaces are intersected, currents can be drawn in the kilo-ampere range. Un-Sustained Operation of FRC System—Conventional Regime The standard plasma formation on the FRC system 10 follows the well-developed reversed-field-theta-pinch technique. A typical process for starting up an FRC commences by driving the quasi-dc coils 412, 414, 416, 420, 432, 434 and 436 to steady state operation. The RFTP pulsed power circuits of the pulsed power formation systems 210 then drive the pulsed fast reversed magnet field coils 232 to create a temporary reversed bias of about −0.05 T in the formation sections 200. At this point a predetermined amount of neutral gas at 9-20 psi is injected into the two formation volumes defined by the quartz-tube chambers 240 of the (north and south) formation sections 200 via a set of azimuthally-oriented puff-vales at flanges located on the outer ends of the formation sections 200. Next a small RF (˜hundreds of kilo-hertz) field is generated from a set of antennas on the surface of the quartz tubes 240 to create pre-ionization in the form of local seed ionization regions within the neutral gas columns. This is followed by applying a theta-ringing modulation on the current driving the pulsed fast reversed magnet field coils 232, which leads to more global pre-ionization of the gas columns. Finally, the main pulsed power banks of the pulsed power formation systems 210 are fired to drive pulsed fast reversed magnet field coils 232 to create a forward-biased field of up to 0.4 T. This step can be time-sequenced such that the forward-biased field is generated uniformly throughout the length of the formation tubes 240 (static formation) or such that a consecutive peristaltic field modulation is achieved along the axis of the formation tubes 240 (dynamic formation). In this entire formation process, the actual field reversal in the plasma occurs rapidly, within about 5 μs. The multi-gigawatt pulsed power delivered to the forming plasma readily produces hot FRCs which are then ejected from the formation sections 200 via application of either a time-sequenced modulation of the forward magnetic field (magnetic peristalsis) or temporarily increased currents in the last coils of coil sets 232 near the axial outer ends of the formation tubes 210 (forming an axial magnetic field gradient that points axially towards the confinement chamber 100). The two (north and south) formation FRCs so formed and accelerated then expand into the larger diameter confinement chamber 100, where the quasi-dc coils 412 produce a forward-biased field to control radial expansion and provide the equilibrium external magnetic flux. Once the north and south formation FRCs arrive near the midplane of the confinement chamber 100, the FRCs collide. During the collision the axial kinetic energies of the north and south formation FRCs are largely thermalized as the FRCs merge ultimately into a single FRC 450. A large set of plasma diagnostics are available in the confinement chamber 100 to study the equilibria of the FRC 450. Typical operating conditions in the FRC system 10 produce compound FRCs with separatrix radii of about 0.4 m and about 3 m axial extend. Further characteristics are external magnetic fields of about 0.1 T, plasma densities around 5×1019 m3 and total plasma temperature of up to 1 keV. Without any sustainment, i.e., no heating and/or current drive via neutral beam injection or other auxiliary means, the lifetime of these FRCs is limited to about 1 ms, the indigenous characteristic configuration decay time. Experimental Data of Unsustained Operation—Conventional Regime FIG. 12 shows a typical time evolution of the excluded flux radius, rΔΦ, which approximates the separatrix radius, rs, to illustrate the dynamics of the theta-pinch merging process of the FRC 450. The two (north and south) individual plasmoids are produced simultaneously and then accelerated out of the respective formation sections 200 at a supersonic speed, vz˜250 km/s, and collide near the midplane at z=0. During the collision the plasmoids compress axially, followed by a rapid radial and axial expansion, before eventually merging to form an FRC 450. Both radial and axial dynamics of the merging FRC 450 are evidenced by detailed density profile measurements and bolometer-based tomography. Data from a representative un-sustained discharge of the FRC system 10 are shown as functions of time in FIGS. 13 A, 13B, 13C and 13D. The FRC is initiated at t=0. The excluded flux radius at the machine's axial mid-plane is shown in FIG. 13A. This data is obtained from an array of magnetic probes, located just inside the confinement chamber's stainless steel wall, that measure the axial magnetic field. The steel wall is a good flux conserver on the time scales of this discharge. Line-integrated densities are shown in FIG. 13B, from a 6-chord CO2/He-Ne interferometer located at z=0. Taking into account vertical (y) FRC displacement, as measured by bolometric tomography, Abel inversion yields the density contours of FIGS. 13C. After some axial and radial sloshing during the first 0.1 ms, the FRC settles with a hollow density profile. This profile is fairly flat, with substantial density on axis, as required by typical 2-D FRC equilibria. Total plasma temperature is shown in FIG. 13D, derived from pressure balance and fully consistent with Thomson scattering and spectroscopy measurements. Analysis from the entire excluded flux array indicates that the shape of the FRC separatrix (approximated by the excluded flux axial profiles) evolves gradually from racetrack to elliptical. This evolution, shown in FIG. 14, is consistent with a gradual magnetic reconnection from two to a single FRC. Indeed, rough estimates suggest that in this particular instant about 10% of the two initial FRC magnetic fluxes reconnects during the collision. The FRC length shrinks steadily from 3 down to about 1 m during the FRC lifetime. This shrinkage, visible in FIG. 14, suggests that mostly convective energy loss dominates the FRC confinement. As the plasma pressure inside the separatrix decreases faster than the external magnetic pressure, the magnetic field line tension in the end regions compresses the FRC axially, restoring axial and radial equilibrium. For the discharge discussed in FIGS. 13 and 14, the FRC magnetic flux, particle inventory, and thermal energy (about 10 mWb, 7×1019 particles, and 7 kJ, respectively) decrease by roughly an order of magnitude in the first millisecond, when the FRC equilibrium appears to subside. Sustained Operation —HPF Regime The examples in FIGS. 12 to 14 are characteristic of decaying FRCs without any sustainment. However, several techniques are deployed on the FRC system 10 to further improve FRC confinement (inner core and edge layer) to the HPF regime and sustain the configuration. Neutral Beams First, fast (H) neutrals are injected perpendicular to Bz in beams from the eight neutral beam injectors 600. The beams of fast neutrals are injected from the moment the north and south formation FRCs merge in the confinement chamber 100 into one FRC 450. The fast ions, created primarily by charge exchange, have betatron orbits (with primary radii on the scale of the FRC topology or at least much larger than the characteristic magnetic field gradient length scale) that add to the azimuthal current of the FRC 450. After some fraction of the discharge (after 0.5 to 0.8 ms into the shot), a sufficiently large fast ion population significantly improves the inner FRC's stability and confinement properties (see e.g. M. W. Binderbauer and N. Rostoker, Plasma Phys. 56, part 3, 451 (1996)). Furthermore, from a sustainment perspective, the beams from the neutral beam injectors 600 are also the primary means to drive current and heat the FRC plasma. In the plasma regime of the FRC system 10, the fast ions slow down primarily on plasma electrons. During the early part of a discharge, typical orbit-averaged slowing-down times of fast ions are 0.3-0.5 ms, which results in significant FRC heating, primarily of electrons. The fast ions make large radial excursions outside of the separatrix because the internal FRC magnetic field is inherently low (about 0.03 T on average for a 0.1 T external axial field). The fast ions would be vulnerable to charge exchange loss, if the neutral gas density were too high outside of the separatrix. Therefore, wall gettering and other techniques (such as the plasma gun 350 and mirror plugs 440 that contribute, amongst other things, to gas control) deployed on the FRC system 10 tend to minimize edge neutrals and enable the required build-up of fast ion current. Pellet Injection When a significant fast ion population is built up within the FRC 450, with higher electron temperatures and longer FRC lifetimes, frozen H or D pellets are injected into the FRC 450 from the pellet injector 700 to sustain the FRC particle inventory of the FRC 450. The anticipated ablation timescales are sufficiently short to provide a significant FRC particle source. This rate can also be increased by enlarging the surface area of the injected piece by breaking the individual pellet into smaller fragments while in the barrels or injection tubes of the pellet injector 700 and before entering the confinement chamber 100, a step that can be achieved by increasing the friction between the pellet and the walls of the injection tube by tightening the bend radius of the last segment of the injection tube right before entry into the confinement chamber 100. By virtue of varying the firing sequence and rate of the 12 barrels (injection tubes) as well as the fragmentation, it is possible to tune the pellet injection system 700 to provide just the desired level of particle inventory sustainment. In turn, this helps maintain the internal kinetic pressure in the FRC 450 and sustained operation and lifetime of the FRC 450. Once the ablated atoms encounter significant plasma in the FRC 450, they become fully ionized. The resultant cold plasma component is then collisionally heated by the indigenous FRC plasma. The energy necessary to maintain a desired FRC temperature is ultimately supplied by the beam injectors 600. In this sense the pellet injectors 700 together with the neutral beam injectors 600 form the system that maintains a steady state and sustains the FRC 450. Saddle Coils To achieve steady state current drive and maintain the required ion current it is desirable to prevent or significantly reduce electron spin up due to the electron-ion frictional force (resulting from collisional ion electron momentum transfer). The FRC system 10 utilizes an innovative technique to provide electron breaking via an externally applied static magnetic dipole or quadrupole field. This is accomplished via the external saddle coils 460 depicted in FIG. 15. The transverse applied radial magnetic field from the saddle coils 460 induces an axial electric field in the rotating FRC plasma. The resultant axial electron current interacts with the radial magnetic field to produce an azimuthal breaking force on the electrons, Fθ=−σVeθ<|Br|2>. For typical conditions in the FRC system 10, the required applied magnetic dipole (or quadrupole) field inside the plasma needs to be only of order 0.001 T to provide adequate electron breaking. The corresponding external field of about 0.015 T is small enough to not cause appreciable fast particle losses or otherwise negatively impact confinement. In fact, the applied magnetic dipole (or quadrupole) field contributes to suppress instabilities. In combination with tangential neutral beam injection and axial plasma injection, the saddle coils 460 provide an additional level of control with regards to current maintenance and stability. Mirror Plugs The design of the pulsed coils 444 within the mirror plugs 440 permits the local generation of high magnetic fields (2 to 4 T) with modest (about 100 kJ) capacitive energy. For formation of magnetic fields typical of the present operation of the FRC system 10, all field lines within the formation volume are passing through the constrictions 442 at the mirror plugs 440, as suggested by the magnetic field lines in FIG. 2 and plasma wall contact does not occur. Furthermore, the mirror plugs 440 in tandem with the quasi-dc divertor magnets 416 can be adjusted so to guide the field lines onto the divertor electrodes 910, or flare the field lines in an end cusp configuration (not shown). The latter improves stability and suppresses parallel electron thermal conduction. The mirror plugs 440 by themselves also contribute to neutral gas control. The mirror plugs 440 permit a better utilization of the deuterium gas puffed in to the quartz tubes during FRC formation, as gas back-streaming into the divertors 300 is significantly reduced by the small gas conductance of the plugs (a meager 500 L/s). Most of the residual puffed gas inside the formation tubes 210 is quickly ionized. In addition, the high-density plasma flowing through the mirror plugs 440 provides efficient neutral ionization hence an effective gas barrier. As a result, most of the neutrals recycled in the divertors 300 from the FRC edge layer 456 do not return to the confinement chamber 100. In addition, the neutrals associated with the operation of the plasma guns 350 (as discussed below) will be mostly confined to the divertors 300. Finally, the mirror plugs 440 tend to improve the FRC edge layer confinement. With mirror ratios (plug/confinement magnetic fields) in the range 20 to 40, and with a 15 m length between the north and south mirror plugs 440, the edge layer particle confinement time τ81 increases by up to an order of magnitude. Improving τ∥ readily increases the FRC particle confinement. Assuming radial diffusive (D) particle loss from the separatrix volume 453 balanced by axial loss (τ∥) from the edge layer 456, one obtains (2πrsLs)(Dns/δ)=(2πrsLsδ)(ns/τ∥), from which the separatrix density gradient length can be rewritten as δ=(Dτ∥)1/2. Here rs, Ls and ns are separatrix radius, separatrix length and separatrix density, respectively. The FRC particle confinement time is τN=[πrs2Ls<n>]/[(2πrsLs(Dns/δ)]=(<n>/ns(τ⊥τ∥)1/2, where τ⊥=a2/D with a=rs/4. Physcially, improving τ∥ leads to increased δ (reduced separatrix density gradient and drift parameter), and, therefore, reduced FRC particle loss. The overall improvement in FRC particle confinement is generally somewhat less than quadratic because ns increases with τ∥. A significant improvement in τ∥ also requires that the edge layer 456 remains grossly stable (i.e., no n=1 flute, firehose, or other MHD instability typical of open systems). Use of the plasma guns 350 provides for this preferred edge stability. In this sense, the mirror plugs 440 and plasma gun 350 form an effective edge control system. Plasma Guns The plasma guns 350 improve the stability of the FRC exhaust jets 454 by line-tying. The gun plasmas from the plasma guns 350 are generated without azimuthal angular momentum, which proves useful in controlling FRC rotational instabilities. As such the guns 350 are an effective means to control FRC stability without the need for the older quadrupole stabilization technique. As a result, the plasma guns 350 make it possible to take advantage of the beneficial effects of fast particles or access the advanced hybrid kinetic FRC regime as outlined in this disclosure. Therefore, the plasma guns 350 enable the FRC system 10 to be operated with saddle coil currents just adequate for electron breaking but below the threshold that would cause FRC instability and/or lead to dramatic fast particle diffusion. As mentioned in the Mirror Plug discussion above, if τ∥ can be significantly improved, the supplied gun plasma would be comparable to the edge layer particle loss rate (˜1022/s). The lifetime of the gun-produced plasma in the FRC system 10 is in the millisecond range. Indeed, consider the gun plasma with density ne˜1013 cm−3 and ion temperature of about 200 eV, confined between the end mirror plugs 440. The trap length L and mirror ratio R are about 15 m and 20, respectively. The ion mean free path due to Coulomb collisions is λii˜6×103 cm and, since λiilnR/R<L, the ions are confined in the gas-dynamic regime. The plasma confinement time in this regime is τgd˜RL/2Vs˜2 ms, where Vs is the ion sound speed. For comparison, the classical ion confinement time for these plasma parameters would be τc·0.5τii(lnR+(lnR)0.5)˜0.7 ms. The anomalous transverse diffusion may, in principle, shorten the plasma confinement time. However, in the FRC system 10, if we assume the Bohm diffusion rate, the estimated transverse confinement time for the gun plasma is τ⊥>τgd˜2 ms. Hence, the guns would provide significant refueling of the FRC edge layer 456, and an improved overall FRC particle confinement. Furthermore, the gun plasma streams can be turned on in about 150 to 200 microseconds, which permits use in FRC start-up, translation, and merging into the confinement chamber 100. If turned on around t˜0(FRC main bank initiation), the gun plasmas help to sustain the present dynamically formed and merged FRC 450. The combined particle inventories from the formation FRCs and from the guns is adequate for neutral beam capture, plasma heating, and long sustainment. If turned on at t in the range −1 to 0 ms, the gun plasmas can fill the quartz tubes 210 with plasma or ionize the gas puffed into the quartz tubes, thus permitting FRC formation with reduced or even perhaps zero puffed gas. The latter may require sufficiently cold formation plasma to permit fast diffusion of the reversed bias magnetic field. If turned on at t <−2 ms, the plasma streams could fill the about 1 to 3 m3 field line volume of the formation and confinement regions of the formation sections 200 and confinement chamber 100 with a target plasma density of a few 1013 cm−3, sufficient to allow neutral beam build-up prior to FRC arrival. The formation FRCs could then be formed and translated into the resulting confinement vessel plasma. In this way the plasma guns 350 enable a wide variety of operating conditions and parameter regimes. Electrical Biasing Control of the radial electric field profile in the edge layer 456 is beneficial in various ways to FRC stability and confinement. By virtue of the innovative biasing components deployed in the FRC system 10 it is possible to apply a variety of deliberate distributions of electric potentials to a group of open flux surfaces throughout the machine from areas well outside the central confinement region in the confinement chamber 100. In this way radial electric fields can be generated across the edge layer 456 just outside of the FRC 450. These radial electric fields then modify the azimuthal rotation of the edge layer 456 and effect its confinement via EXB velocity shear. Any differential rotation between the edge layer 456 and the FRC core 453 can then be transmitted to the inside of the FRC plasma by shear. As a result, controlling the edge layer 456 directly impacts the FRC core 453. Furthermore, since the free energy in the plasma rotation can also be responsible for instabilities, this technique provides a direct means to control the onset and growth of instabilities. In the FRC system 10, appropriate edge biasing provides an effective control of open field line transport and rotation as well as FRC core rotation. The location and shape of the various provided electrodes 900, 905, 910 and 920 allows for control of different groups of flux surfaces 455 and at different and independent potentials. In this way a wide array of different electric field configurations and strengths can be realized, each with different characteristic impact on plasma performance. A key advantage of all these innovative biasing techniques is the fact that core and edge plasma behavior can be effected from well outside the FRC plasma, i.e. there is no need to bring any physical components in touch with the central hot plasma (which would have severe implications for energy, flux and particle losses). This has a major beneficial impact on performance and all potential applications of the HPF concept. Experimental Data—HPF Operation Injection of fast particles via beams from the neutral beam guns 600 plays an important role in enabling the HPF regime. FIGS. 16A, 16B, 16C and 16D illustrate this fact. Depicted is a set of curves showing how the FRC lifetime correlates with the length of the beam pulses. All other operating conditions are held constant for all discharges comprising this study. The data is averaged over many shots and, therefore, represents typical behavior. It is clearly evident that longer beam duration produces longer lived FRCs. Looking at this evidence as well as other diagnostics during this study, it demonstrates that beams increase stability and reduce losses. The correlation between beam pulse length and FRC lifetime is not perfect as beam trapping becomes inefficient below a certain plasma size, i.e., as the FRC 450 shrinks in physical size not all of the injected beams are intercepted and trapped. Shrinkage of the FRC is primarily due to the fact that net energy loss (˜4 MW about midway through the discharge) from the FRC plasma during the discharge is somewhat larger than the total power fed into the FRC via the neutral beams (˜2.5 MW) for the particular experimental setup. Locating the beams at a location closer to the mid-plane of the vessel 100 would tend to reduce these losses and extend FRC lifetime. FIGS. 17A, 17B, 17C and 17D illustrate the effects of different components to achieve the HPF regime. It shows a family of typical curves depicting the lifetime of the FRC 450 as a function of time. In all cases a constant, modest amount of beam power (about 2.5 MW) is injected for the full duration of each discharge. Each curve is representative of a different combination of components. For example, operating the FRC system 10 without any mirror plugs 440, plasma guns 350 or gettering from the gettering systems 800 results in rapid onset of rotational instability and loss of the FRC topology. Adding only the mirror plugs 440 delays the onset of instabilities and increases confinement. Utilizing the combination of mirror plugs 440 and a plasma gun 350 further reduces instabilities and increases FRC lifetime. Finally adding gettering (Ti in this case) on top of the gun 350 and plugs 440 yields the best results—the resultant FRC is free of instabilities and exhibits the longest lifetime. It is clear from this experimental demonstration that the full combination of components produces the best effect and provides the beams with the best target conditions. As shown in FIG. 1, the newly discovered HPF regime exhibits dramatically improved transport behavior. FIG. 1 illustrates the change in particle confinement time in the FRC system 10 between the conventionally regime and the HPF regime. As can be seen, it has improved by well over a factor of 5 in the HPF regime. In addition, FIG. 1 details the particle confinement time in the FRC system 10 relative to the particle confinement time in prior conventional FRC experiments. With regards to these other machines, the HPF regime of the FRC system 10 has improved confinement by a factor of between 5 and close to 20. Finally and most importantly, the nature of the confinement scaling of the FRC system 10 in the HPF regime is dramatically different from all prior measurements. Before the establishment of the HPF regime in the FRC system 10, various empirical scaling laws were derived from data to predict confinement times in prior FRC experiments. All those scaling rules depend mostly on the ratio R2/ρi, where R is the radius of the magnetic field null (a loose measure of the physical scale of the machine) and ρi is the ion larmor radius evaluated in the externally applied field (a loose measure of the applied magnetic field). It is clear from FIG. 1 that long confinement in conventional FRCs is only possible at large machine size and/or high magnetic field. Operating the FRC system 10 in the conventional FRC regime CR tends to follow those scaling rules, as indicated in FIG. 1. However, the HPF regime is vastly superior and shows that much better confinement is attainable without large machine size or high magnetic fields. More importantly, it is also clear from FIG. 1 that the HPF regime results in improved confinement time with reduced plasma size as compared to the CR regime. Similar trends are also visible for flux and energy confinement times, as described below, which have increased by over a factor of 3-8 in the FRC system 10 as well. The breakthrough of the HPF regime, therefore, enables the use of modest beam power, lower magnetic fields and smaller size to sustain and maintain FRC equilibria in the FRC system 10 and future higher energy machines. Hand-in-hand with these improvements comes lower operating and construction costs as well as reduced engineering complexity. For further comparison, FIGS. 18A, 18B, 18C and 18D show data from a representative HPF regime discharge in the FRC system 10 as a function of time. FIG. 18A depicts the excluded flux radius at the mid-plane. For these longer timescales the conducting steel wall is no longer as good a flux conserver and the magnetic probes internal to the wall are augmented with probes outside the wall to properly account for magnetic flux diffusion through the steel. Compared to typical performance in the conventional regime CR, as shown in FIGS. 13A, 13B, 13C and 13D, the HPF regime operating mode exhibits over 400% longer lifetime. A representative cord of the line integrated density trace is shown in FIG. 18B with its Abel inverted complement, the density contours, in FIG. 18C. Compared to the conventional FRC regime CR, as shown in FIGS. 13A, 13B, 13C and 13D, the plasma is more quiescent throughout the pulse, indicative of very stable operation. The peak density is also slightly lower in HPF shots—this is a consequence of the hotter total plasma temperature (up to a factor of 2) as shown in FIG. 18D. For the respective discharge illustrated in FIGS. 18A, 18B, 18C and 18D, the energy, particle and flux confinement times are 0.5 ms, 1 ms and 1 ms, respectively. At a reference time of 1 ms into the discharge, the stored plasma energy is 2 kJ while the losses are about 4 MW, making this target very suitable for neutral beam sustainment. FIG. 19 summarizes all advantages of the HPF regime in the form of a newly established experimental HPF flux confinement scaling. As can be seen in FIG. 19, based on measurements taken before and after t=0.5 ms, i.e., t<0.5 ms and t>0.5 ms, the flux confinement (and similarly, particle confinement and energy confinement) scales with roughly the square of the electron Temperature (Te) for a given separatrix radius (rs). This strong scaling with a positive power of Te (and not a negative power) is completely opposite to that exhibited by conventional tokomaks, where confinement is typically inversely proportional to some power of the electron temperature. The manifestation of this scaling is a direct consequence of the HPF state and the large orbit (i.e. orbits on the scale of the FRC topology and/or at least the characteristic magnetic field gradient length scale) ion population. Fundamentally, this new scaling substantially favors high operating temperatures and enables relatively modest sized reactors. With the advantages the HPF regime presents, FRC sustainment or steady state driven by neutral beams and using appropriate pellet injection is achievable, meaning global plasma parameters such as plasma thermal energy, total particle numbers, plasma radius and length as well as magnetic flux are sustainable at reasonable levels without substantial decay. For comparison, FIG. 20 shows data in plot A from a representative HPF regime discharge in the FRC system 10 as a function of time and in plot B for a projected representative HPF regime discharge in the FRC system 10 as a function of time where the FRC 450 is sustained without decay through the duration of the neutral beam pulse. For plot A, neutral beams with total power in the range of about 2.5-2.9 MW were injected into the FRC 450 for an active beam pulse length of about 6 ms. The plasma diamagnetic lifetime depicted in plot A was about 5.2 ms. More recent data shows a plasma diamagnetic lifetime of about 7.2 ms is achievable with an active beam pulse length of about 7 ms. As noted above with regard to FIGS. 16A, 16B, 16C and 16D, the correlation between beam pulse length and FRC lifetime is not perfect as beam trapping becomes inefficient below a certain plasma size, i.e., as the FRC 450 shrinks in physical size not all of the injected beams are intercepted and trapped. Shrinkage or decay of the FRC is primarily due to the fact that net energy loss (−4 MW about midway through the discharge) from the FRC plasma during the discharge is somewhat larger than the total power fed into the FRC via the neutral beams (−2.5 MW) for the particular experimental setup. As noted with regard to FIG. 3C, angled beam injection from the neutral beam guns 600 towards the mid-plane improves beam-plasma coupling, even as the FRC plasma shrinks or otherwise axially contracts during the injection period. In addition, appropriate pellet fueling will maintain the requisite plasma density. Plot B is the result of simulations run using an active beam pulse length of about 6 ms and total beam power from the neutral beam guns 600 of slightly more than about 10 MW, where neutral beams shall inject H (or D) neutrals with particle energy of about 15 keV. The equivalent current injected by each of the beams is about 110 A. For plot B, the beam injection angle to the device axis was about 20° , target radius 0.19 m. Injection angle can be changed within the range 15°-25°. The beams are to be injected in the co-current direction azimuthally. The net side force as well as net axial force from the neutral beam momentum injection shall be minimized. As with plot A, fast (H) neutrals are injected from the neutral beam injectors 600 from the moment the north and south formation FRCs merge in the confinement chamber 100 into one FRC 450. The simulations that where the foundation for plot B use multi-dimensional hall-MHD solvers for the background plasma and equilibrium, fully kinetic Monte-Carlo based solvers for the energetic beam components and all scattering processes, as well as a host of coupled transport equations for all plasma species to model interactive loss processes. The transport components are empirically calibrated and extensively benchmarked against an experimental database. As shown by plot B, the steady state diamagnetic lifetime of the FRC 450 will be the length of the beam pulse. However, it is important to note that the key correlation plot B shows is that when the beams are turned off the plasma or FRC begins to decay at that time, but not before. The decay will be similar to that which is observed in discharges which are not beam-assisted—probably on order of 1 ms beyond the beam turn off time—and is simply a reflection of the characteristic decay time of the plasma driven by the intrinsic loss processes. While the invention is susceptible to various modifications, and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that the invention is not to be limited to the particular forms or methods disclosed, but to the contrary, the invention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the appended claims. In the description above, for purposes of explanation only, specific nomenclature is set forth to provide a thorough understanding of the present disclosure. However, it will be apparent to one skilled in the art that these specific details are not required to practice the teachings of the present disclosure. The various features of the representative examples and the dependent claims may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings. It is also expressly noted that all value ranges or indications of groups of entities disclose every possible intermediate value or intermediate entity for the purpose of original disclosure, as well as for the purpose of restricting the claimed subject matter. Systems and methods for generating and maintaining an HPF regime FRC have been disclosed. It is understood that the embodiments described herein are for the purpose of elucidation and should not be considered limiting the subject matter of the disclosure. Various modifications, uses, substitutions, combinations, improvements, methods of productions without departing from the scope or spirit of the present invention would be evident to a person skilled in the art. For example, the reader is to understand that the specific ordering and combination of process actions described herein is merely illustrative, unless otherwise stated, and the invention can be performed using different or additional process actions, or a different combination or ordering of process actions. As another example, each feature of one embodiment can be mixed and matched with other features shown in other embodiments. Features and processes known to those of ordinary skill may similarly be incorporated as desired. Additionally and obviously, features may be added or subtracted as desired. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents. |
|
abstract | An improved testing and data gathering method is described herein with reference to testing a new fuel, as an exemplary component to be tested for licensure purposes. The method includes generally: generating models for the new system; making samples and getting them accepted for a reactor; and testing the samples in a test or commercial reactor until the exposure time is reached for the expected cycle length of the fuel at final use. The method is preferably done concurrent to submitting a license application for commercial use of the new component to the relevant government body to expedite license testing review. |
|
045267430 | abstract | A containment vessel for a nuclear reactor having a dry well for mounting therein a pressure vessel for containing the nuclear reactor, a pressure suppressing chamber having a pool of coolant therein, and a vent pipe device for releasing therethrough into the pool of coolant within the pressure suppressing chamber steam which will be produced as a result of the occurrence of an accident and escape into the dry well. The vent pipe device includes a plurality of vent pipe members inserted in the pool of coolant within the pressure suppressing chamber and each having at least one exhaust port opening in the coolant. The vent pipe members are divided into a plurality of groups in such a manner that the vent pipe members of different groups differ from one another in the length of submerged portions of the vent pipe members interposed between the liquid of the coolant within the pressure suppressing chamber and the exhaust ports of the vent pipe members. |
abstract | In various embodiments, provided are ion optical assemblies, and systems for mounting and aligning ion optic components. In various embodiments, the present teachings provide ion optical assemblies with features that facilitate the alignment of ion optical elements. In various embodiments, the alignment of the ion optical elements by compressing them with securing members, as described in the present teachings, can simplify the alignment and assembly of ion optical elements. In the present teachings, no torque pattern is required to compress and align the ion optical elements. In various embodiments, the present teachings provide systems for mounting and aligning ion optic components that facilitate their alignment. |
|
description | The invention relates to head assemblies for nuclear reactor pressure vessels (“RPVs”) and more particularly to integrated head assemblies that can be transported as integral units. Commercial pressurized water nuclear power plants are operated to produce electric power during fuel cycles that extend for about one to two years and then are shutdown for scheduled refueling and maintenance outages that extend for up to about a month or more. At the beginning of these outages, removable RPV closure heads and overhead equipment and cooling air ductwork associated with the RPVs, including control rod drive mechanisms (“CRDMs”), CRDM cooling systems, CRDM seismic support platforms and missile shields (which collectively are known in the industry as the “head assemblies”) must be disconnected and/or removed in order to gain access to the fuel assemblies disposed in the interior portions of the RPVs. Then, at the end of the outages, the head assemblies must be re-assembled before starting the following fuel cycles. See, e.g., FIG. 1 of U.S. Pat. No. 4,678,623, which discloses a prior art assembly including a concrete missile shield. The many disassembly and re-assembly steps and sub-steps tend to be complex, costly to perform and require long times on critical path schedules in radioactive environments. Updated head assembly designs permit these structures to be transported as integral units to facilitate more efficient and safer outages. However, these newer designs include modified structures for redirecting the cooling air that completely or partially enclose the CRDMs and thereby hinder access to the CRDMs for repair and maintenance purposes. See, e.g., U.S. Pat. Nos. 4,678,623; 4,828,789; 5,742,652 and 6,061,414, which are incorporated herein for their disclosures of various modular, integrated and simplified head assemblies. While the development of integrated head assemblies and the other patented improvements have facilitated faster, safer outages, the nuclear industry is constantly searching for more efficient and safer ways of operating, refueling and maintaining their plants. Thus, it is an object of the present invention to provide an improved head assembly that provides both effective CRDM cooling during the fuel cycles and ready access to the CRDMs during the outages. It is a further object to provide a head assembly that facilitates the disassembly and re-assembly of the head assemblies during outages. Advantageously, the present invention can be employed in upgrades of existing plants and be employed in new construction. With these objects in view, the present invention resides in an improved head assembly for a reactor pressure vessel (“RPV”) having a removable closure head and a seismic support platform spaced from the RPV closure head. An array of CRDMs is disposed between the RPV closure head and the seismic support platform, each CRDM including an electro-magnetic coil stack assembly and having a lower end supported by the RPV and an upper end supported by the seismic support platform. A lower shroud surrounds the electro-magnetic coil stack assemblies and has an upper end spaced from the seismic support platform in air flow communication with the atmosphere around the CRDMs. A plurality of internal ducts are disposed within the array of CRDMs, each duct extending from a lower end disposed in air flow communication with the lower shroud to an upper end. An upper plenum is disposed above the seismic support platform in air flow communication with the internal ducts. A missile shield assembly is disposed within the upper plenum. A plurality of fan assemblies are disposed on the upper plenum in air flow communication with the upper plenum. Lift legs connected with the RPV closure head support the seismic support platform, the missile shield assembly and the upper plenum so that the head assembly (including CRDMs disposed between the RPV closure head and the seismic support platform and fan assemblies disposed on the upper plenum) can be removed and reinstalled as an integral assembly by a head assembly lift rig. Most preferably, each lift leg includes a lower leg member detachably connected with an upper leg member. The lower leg members connect with the RPV closure head and support the seismic support platform, thereby forming a lower subassembly (including the CRDMs). The upper leg members support the upper plenum and the missile shield assembly, thereby forming an upper subassembly (including the fan assemblies). When the upper leg members are detached from the lower leg members, the upper plenum, fan assemblies and missile shield assembly can be removed as a subassembly from above the RPV. Advantageously, the CRDMs and power and instrumentation cables and other appurtenances on the seismic support platform then may be readily inspected and serviced in place. Alternatively, when the upper leg members are attached to the lower leg members, the upper subassembly and the lower subassembly may be removed from the RPV as an integral unit. In one embodiment of the present invention, the internal ducts extend through the seismic support platform to the upper plenum. In this embodiment, the internal ducts preferably are supported by the upper plenum, the seismic support platform and the lower shroud. In another embodiment of the present invention, the internal ducts extend to a ring header duct disposed below the seismic support platform and at least one cross-over duct extends between the ring header duct and the upper plenum. In this embodiment, the internal ducts are supported by the ring header duct and the ring header duct is supported by the seismic support platform. Also, the cross-over duct extends around the seismic support platform and preferably has separable sections. FIG. 1 depicts a reactor pressure vessel (“RPV”) 10 in a reactor cavity 12 with a head assembly 14 embodying the present invention extending upwardly in one end of a refueling canal 16. The head assembly 14 embodying the present invention may be a new construction or a backfit in an existing plants. FIG. 1 depicts a backfitted RPV 10 in the course of a fuel cycle. At the beginning of the following outage, nuts on closure studs (depicted by stud 18) must be detensioned by devices known as “stud tensioners” so that the RPV closure head 20 and overhead equipment and ductwork can be removed in order to provide unhindered access to fuel assemblies (not shown) in the RPV 10. The head assembly 14 as depicted in FIG. 1 generally includes a RPV closure head 20 with a plurality of CRDM penetration nozzles 22. The nozzles 22 are embedded in insulation 24 in the course of fuel cycles. A seismic support platform 26 (supporting a stud tensioner rail 28) is spaced from the RPV closure head 20. An array of CRDMs 30 are disposed between the RPV closure head 20 and the seismic support platform 26. Each CRDM 30 has a lower end 32 supported by a CRDM penetration nozzle 22 and an upper end 34 supported by the seismic support platform 26. In addition, each CRDM 30 has an associated electromagnetic coil stack assembly 36 (each stack assembly depicted as three coil pairs), which generates a very substantial amount of heat that must be continuously removed during the fuel cycles. A missile shield assembly 40 having a heavy metal plate 42 is disposed over the upper ends 34 of the CRDMs 30 to absorb the energy of a failed CRDM 30. A CRDM cooling system is designed to remove the heat generated by the electromagnetic coil stack assemblies 36. The CRDM cooling system of the present invention generally includes a lower shroud 50, internal ducts 52 disposed within the array of CRDMs 30, an upper plenum 54 and a plurality of fan assemblies 56 for drawing air from the atmosphere surrounding the CRDMs 30 across the coil stack assemblies 36 and then exhausting the air into the general atmosphere either directly or through cooling air ductwork (not shown). The lower shroud 50 has an upper end 60 in air flow communication with the atmosphere and surrounds the coil stack assemblies 36. FIG. 1 depicts a lower shroud 50 like the shroud depicted by FIG. 1 of the above-referenced U.S. Pat. No. 4,678,623. Thus, the lower shroud 50 of a backfitted assembly may include a baffle 61 surrounding the coil stack assemblies 36 and extending to a CRDM plenum 62 having one or more duct connections 64 formerly connected with vertically extending elbow ducts. Advantageously, these elbow ducts are no longer necessary and may be removed. The connections 64 and other unused openings are preferably capped with covers 66 to prevent air from leaking into the cooling system. Each internal duct 52 extends from a lower end 70 disposed in air flow communication with the lower shroud 50 to an upper end 72. Each internal duct 52 may have any suitable cross-section. Thus, an internal duct 52 may have an “L” shape generally as depicted by FIG. 2, a rectangular shape or any other suitable shape. The lower end 70 is preferably supported against the coil stack assemblies 36 by a resilient spring, which may be a narrow deformed length of the internal duct 52 (not shown). This arrangement will accommodate differential thermal expansion between these members at high operating temperatures in addition to laterally supporting the lower end 70. The upper end 72 of each internal duct 52 is in air flow communication with the upper plenum 54. Preferably, the upper end 72 is supported by the upper plenum 54 by, e.g., bolts 73 extending through duct flanges 75. Preferably, each internal duct 52 has an internal seismic support structure, such as cruciform 76 shown in FIG. 2, disposed in the portion of the duct 52 extending through the seismic support platform 26 for transferring seismic loads to the seismic support platform 26. The fan assemblies 56 are disposed on the upper plenum 54 in air flow communication with the upper plenum 54 for drawing the cooling air through the CRDM cooling system. As is shown in FIG. 1, the missile shield assembly 40 is disposed in the upper plenum 54. Advantageously, the missile shield plate 42 can be cooled by the flowing air without needing ventilation holes. The head assemblies 14 are integrated assemblies. Thus, the components of a head assembly 14 are interconnected by lift legs 80 having connections 82 for connecting with a head assembly lift rig 84 so that a plant's polar crane may be connected with the lift rig 84 to transport the head assembly 84 as an integrated unit. Most preferably, each lift leg 80 has an upper leg member 86 and a detachably connected lower leg member 88. The upper leg members 86 support the missile shield 40 and the upper plenum 54. The lower leg members 88 are connected with the RPV head 20 (via vessel lugs) and support the seismic support platform 26. The detachable leg members 86, 88 of the lift leg 80 may be attached together in a clevis assembly 90 by bolts. The clevis assembly 90 may be unbolted and the missile shield 40 and upper plenum 54 may be removed as a subassembly. Advantageously, the seismic support platform 26 may then be readily accessed in order to inspect and service the CRDMs 30, power cables (not shown), rod position indicator cables (not shown) and other appurtenances (not shown). When the lower leg members 86 and the lower leg members 88 are attached, the entire head assembly 14 may be removed as an integral unit. FIG. 1 generally depicts a structural arrangement by which the upper leg members 86 may support the missile shield assembly 40, upper plenum 54 and fan assemblies 56 as a subassembly. The generally horizontal plate 42, which may be a two inches thick carbon steel plate, may be supported by horizontally extending support beams 92 that are bolted or welded to the top of the horizontal plate 42. The horizontal support beams 92 may be bolted or welded directly or via angles to vertical support columns 94, which in turn may be bolted or welded to upper and lower ring girders 96. FIG. 3 depicts such an arrangement by two orthogonal pair of beams 92. Advantageously, this-arrangement provides substantial area 98 for air flow around the carbon steel plate 42. The vertical support columns 94 may in turn be bolted or welded to the upper leg members 86 of the lift legs 80. Another missile shield support arrangement is illustrated by U.S. Pat. No. 6,061,415. The upper plenum 54 may be constructed of plates supported by the support columns 94 and ring girders 96 and/or upper leg members 86. FIG. 4 depicts another embodiment of the present invention wherein the internal ducts 52 do not extend through the seismic support platform 26. Rather, the internal ducts 52 extend upwardly to an outlet 102 communicating with a ring header duct 104. The ring header duct 104 may be supported by the stud tensioner rail 28 and may in turn support a second stud tensioner rail 106. A cross-over duct 108 may extend between the ring header duct 104 and the upper plenum 54 for providing air flow communication between the internal ducts 52 and the upper plenum 54. The cross-over duct 108 may have a flanged connection 110 that may be disconnected so that the missile shield 42/upper plenum 54 subassembly may readily be removed. While a present preferred embodiment of the present invention has been shown and described, it is to be understood that the invention may be otherwise variously embodied within the scope of the following claims of invention. |
|
abstract | A collimator taking the form of a prolate spheroid (40) comprising radiation attenuating material and featuring a twisted slit comprising radiation transmissive material. The twisted slit featuring first (43) and second (44) apertures arranged such that for each entrance point in one of the apertures there is a direct pathway through the major axis ‘B’ of the prolate spheroid (40), at a pre-determined angle, to a point in the other aperture, such that a compound aperture is formed. For each compound aperture the length of the direct pathway through the prolate spheroid (40) is constant. Rotation of the collimator about the major axis ‘B’, relative to a stationary point at the first aperture (43), steers in angle the compound aperture through the collimator from said stationary point. Such an arrangement allows radiation from a source positioned at said point to be collimated into a beam, the resultant beam being scanned in angle, and the resultant collimation effect being constant across the angular range of the scan. |
Subsets and Splits