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abstract | An apparatus comprises an ionization chamber for providing ions during a process of ion implantation, and an electron beam source device inside the ionization chamber. The electron beam source device comprises a field emission array having a plurality of emitters for generating electrons in vacuum under an electric field. |
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055725597 | claims | 1. Radiography apparatus for determining the composition and/or thickness of a solid object, said apparatus comprising: a circulating system of water; a source of energetic neutrons located adjacent a first portion of said circulating water system for directing said energetic neutrons onto the water and activating oxygen in the water to a radioactive state, followed by decay of the activated water by the emission of substantially monoenergetic gamma rays; collimator means disposed adjacent a second, remote portion of said circulating water system for directing a beam of said gamma rays onto an object; and photodetector means disposed adjacent said second, remote portion of said circulating system of water for receiving said gamma rays after transitting the object for analyzing the composition and/or thickness of the object. circulating water in a closed loop; generating and directing energetic neutrons onto the circulating water in a first portion of said closed loop for activating oxygen in the water to a radioactive state, followed by decay of the activated oxygen by the emission of substantially monoenergetic gamma rays; forming the emitted gamma rays into a beam at a second, remote location in said closed loop; directing the gamma ray beam onto the solid object; and detecting the gamma rays after transitting the object for analyzing the composition and/or thickness of the object. 2. The apparatus of claim 1 wherein said source of energetic neutrons includes a tritium target responsive to energetic deuterons incident thereon. 3. The apparatus of claim 2 wherein said tritium target is of a titanium-tritide composition. 4. The apparatus of claim 2 further comprising a source of energetic deuterons including a deuterium-tritium fusion reactor. 5. The apparatus of claim i wherein the oxygen in the water is activated by the reaction .sup.16 O(n,p).sup.16 N reaction for providing 14-MeV neutrons. 6. The apparatus of claim 1 wherein said circulating system of water includes a variable pump for varying the intensity of the gamma rays. 7. The apparatus of claim 6 wherein said circulating system is in the form of a closed loop and includes a flow meter for measuring water flow rate. 8. The apparatus of claim 1 further comprising a lead shield disposed about the second, remote portion of said circulating system of water, and wherein said collimator means includes a rectangular slot disposed in said lead shield in facing relation to the object. 9. The apparatus of claim 1 further comprising displacement means coupled to the object for moving the object relative to said source of energetic gamma rays and scanning said energetic gamma rays over the object. 10. The apparatus of claim 1 wherein said photodetector means includes a shielded sodium iodide scintillator. 11. The apparatus of claim 1 wherein said circulating system of water includes plastic tubing for passing water adjacent to said source of energetic neutrons. 12. The apparatus of claim 1 further comprising means for rendering said photodetector means insensitive to gamma rays less than a predetermined threshold energy level for reducing background noise and improving signal-to-noise ratio. 13. A method for analyzing the composition and/or thickness of a solid object, said method comprising the steps of: 14. The method of claim 13 wherein the step of generating and directing energetic neutrons onto the circulating water includes generating and directing energetic deuterons onto a tritium target. 15. The method of claim 14 wherein the step of generating and directing energetic deuterons onto a tritium target includes directing the deuterons from a deuterium-tritium fusion reactor onto tritium in a D-T plasma environment. 16. The method of claim 13 wherein the step of forming the emitted gamma rays into a beam includes directing the emitted gamma rays through a rectangular slot. 17. The method of claim 13 further comprising the step of displacing the object while the gamma ray beam is incident thereon for scanning the gamma ray beam over the object. 18. The method of claim 13 further comprising the step of varying the flow rate of the circulating water in the closed loop for changing the intensity of the gamma ray beam. 19. The method of claim 13 further comprising the step of cutting off gamma rays having less than a predetermined threshold energy level from detection for reducing background noise and improving signal-to-noise ratio. |
claims | 1. A specimen temperature adjusting apparatus that adjusts a temperature of an observation specimen contained in a culture container having a leg and a transparent member at a bottom of the culture container, said specimen temperature adjusting apparatus comprising:a specimen stage on which the culture container containing the observation specimen is to be placed, the specimen stage having a groove surrounding a portion where the culture container containing the observation specimen is to be placed, and the specimen stage further having a recess to receive the leg of the culture container such that a bottom surface of the transparent member at the bottom of the culture container contacts the specimen stage when the culture container is placed on the specimen stage; anda temperature adjustment element that is attached to the specimen stage, the temperature adjustment element being located in the groove of the specimen stage. 2. A specimen temperature adjusting apparatus according to claim 1, wherein the transparent member comprises a glass plate. 3. A specimen temperature adjusting apparatus according to claim 1, wherein the temperature adjustment element comprises a heater. 4. A specimen temperature adjusting apparatus according to claim 1, wherein the temperature adjustment element is configured to perform heating and cooling. 5. A specimen temperature adjusting apparatus according to claim 4, wherein the temperature adjustment element comprises a Peltier element. 6. A specimen temperature adjusting apparatus according to claim 1, further comprising a temperature sensor that measures a temperature of at least one of the observation specimen and the specimen stage, and a temperature controller that controls the temperature adjustment element based on the temperature measured by the temperature sensor. 7. A manipulation device to manipulate an electric stage comprising:a base member; andan X-movement coaxial handle, a Y-movement coaxial handle, and a Z-movement coaxial handle provided on the base member,wherein the X-movement coaxial handle is assigned with X coarse movement and X fine movement, the Y-movement coaxial handle is assigned with Y coarse movement and Y fine movement, and the Z-movement coaxial handle is assigned with Z coarse movement and Z fine movement, and wherein each of the X-, Y- and Z-movement coaxial handles comprises first and second rotary knobs,wherein the base member is shaped such that an observer who places his or her elbows on a table on which the manipulation device is provided can manipulate the first and second rotary knobs of each of at least the X- and Y-movement coaxial handles with either a left or right hand. 8. A manipulation device according to claim 7, wherein each of the X-, Y-, and Z-movement coaxial handles includes a rotary resistance adjustment member. 9. A manipulation device according to claim 7, wherein the base member includes an X-Y base member and a Z base member which are spatially separated, and wherein the X-movement coaxial handle and the Y-movement coaxial handle are provided on the X-Y base member, and the Z-movement coaxial handle is provided on the Z base member. 10. A manipulation device according to claim 7, wherein the base member comprises an inclined upper surface and at least the X- and Y-movement coaxial handles are provided on the inclined upper surface of the base member. 11. A manipulation device according to claim 10, wherein the X- and Y-movement coaxial handles are longitudinally arranged on the inclined upper surface of the base member. |
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047284790 | abstract | A high pressure seal fitting with a built-in low pressure seal arrangement for sealing a space defined by an inner diameter of a pipe and a rod slidably disposed within the first pipe and extending beyond and end of the first pipe. The fitting includes a fitting body provided with an axial passage for slidably accommodating the rod and having a first end region constructed for engaging the end of the pipe for forming a high pressure seal between the pipe and the fitting body, and a second end region opposite the first end region and including an outer circumferential protrusion having the shape of a ferrule for cooperating with components utilized to form a compression seal to form a releasable high pressure seal. The fitting body further includes a low pressure sealing device disposed in the axial passage at the second end region of the fitting body for maintaining a low pressure seal between the fitting body and the rod when the releasable high pressure seal is disconnected. |
claims | 1. An X-ray imaging system for displaying an image on a monitor comprising means for selecting an area of interest in said image and exposing said area of interest to a higher radiation level than the rest of the image, wherein said higher radiation is a result of a higher image updating rate, and wherein the area of interest is automatically selected by the system. 2. A system as in claim 1 comprising an automatically variable mask capable of limiting the radiation pattern in two dimensions and wherein said mask is operable to repeatedly switch between two or more positions during imaging. 3. A system as in claim 2 wherein said variable mask is formed by overlapping at least two X-ray shields mounted on rotary actuators. 4. A system as in claim 2 wherein said variable mask is formed by overlapping at least two X-ray shields mounted on linear actuators. 5. A system as in claim 2 wherein said mask widens periodically to stop limiting the radiation pattern. 6. A system as in claim 2 wherein firing of an X-ray source is synchronized to the position of the variable mask. 7. A system as in claim 1 wherein said higher radiation level is created by a variable aperture in an X-Ray blocking mask. 8. A system as in claim 1 wherein said higher radiation level is created by a variable aperture in an X-Ray attenuating mask. 9. A system as in claim 1 wherein said higher radiation level is created by a variable aperture in an X-Ray blocking mask, said mask created by overlapping at least two X-ray shields. 10. A system as in claim 1 wherein the area of interest is automatically selected by the system based on rates of changes in the image. 11. A system as in claim 1 wherein both the location and shape of the area of interest are automatically selected. 12. An X-ray imaging system for displaying an image on a monitor wherein part of said image is created at a higher radiation level than the rest of the image, wherein said higher radiation is a result of a higher image updating rate, and wherein an area of interest is automatically selected by the system. 13. A system as in claim 12 wherein the area of interest is automatically selected by the system based on rates of changes in the image. 14. A method for X-ray imaging comprising the following steps:selecting an area of interest in an image by using a variable X-ray mask and updating the image of the area of interest at full rate;updating the rest of the image at a lower rate by periodically opening up said mask during imaging; anddisplaying the image that is a combination of the area of interest and the rest of the image. 15. A method as in claim 14 wherein selecting the area of interest comprises manually selecting the area of interest. 16. A method as in claim 14 wherein selecting the area of interest comprises automatically selecting the area of interest. |
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053176103 | summary | BACKGROUND OF THE INVENTION The present invention relates to a device, such as pipes and various valves used with such pipes, which is made of carbon steel and constitutes the wet steam system, the feedwater and condensate system, and the drain system in thermal and nuclear power plants and which is protected from reduction of its wall thickness due to erosion-corrosion, a special and rapid form of damage to metal parts. Carbon steel, such as forged steel and cast steel, is widely used as a material suitable for compositional parts, such as piping and various valves including gate valves, globe valves and check valves, used in the wet steam system, feedwater and the condensate system and the drain system of a thermal or nuclear power plant. When these parts are made of carbon steel and exposed to a flow of a fluid, erosion-corrosion occurs at the surface on which the flow touches the parts. Because such power plants tend to be operated for longer periods of time, the thickness of part walls may reduce to such an extent as to cause various problems. Therefore, the devices used in the wet steam system, the feedwater and condensate system and the drain system of a thermal or nuclear power plant have to be regularly overhauled and inspected to confirm that their wall thickness has not, due to erosion-corrosion, progressively reduced and no interference with the operation of the plant would occur. If such development of reduced thickness appears to possibly exceed the allowable design limit, portions with developing reduced thickness are overlaid by welding, or affected parts are replaced. Also, when the progress of thickness reduction is fast and incidental repairs by the overlaying or by the replacement of parts are frequently needed, these parts are generally produced anew using a CrMo steel or an austenitic stainless steel which has higher resistance against erosion-corrosion than carbon steel. Here, the devices made of carbon steel constituting the wet steam system, the feedwater and condensate system and the drain system of a thermal or nuclear power plant amount to a voluminous quantity; therefore, it is very expensive to inspect each device regularly with UT (ultrasonic testing) and repair thickness-reduced portions by overlaying or replacing affected parts. Also, if each device is to be made of austenitic stainless steel having a higher erosion-corrosion resistance than carbon steel, the cost of material would be several times as much as that of carbon steel, and therefore is uneconomical. SUMMARY OF THE INVENTION In view of the state of the art described above, it is an object of the present invention to provide a device for thermal and nuclear power plants which is protected from reduction of wall thickness caused by erosion-corrosion. For achieving this object, the present invention provides: 1) a device for thermal or nuclear power plants which constitutes a wet steam system, a feedwater and condensate system, or a drain system of a thermal or nuclear power plant and which is exposed to a fluid flowing inside these systems, which device is characterized in that a coating of a metal or a ceramic which is chemically stable against the fluid flowing through the device and which functions as resistance against the efflux of Fe.sup.2+, or a boundary film is formed on a parent metal of the device, so as to prevent the erosion-corrosion of the device; 2) a device for a thermal or nuclear power plant according to 1) above which is characterized in that the above-mentioned coating consists of a lower layer coating made of Ni--Cr and an upper layer coating made of WC (tungsten carbide) and Ni--Cr, each formed by atmospheric plasma thermal spraying; 3) a device for a thermal or nuclear power plant according to 1) above which is characterized in that the above-mentioned coating is made of a single layer of WC and Co, or WC, Ni and Cr formed by jet kote spraying which belongs to the high energy gas spray coating method; and 4) a device for a thermal or nuclear power plant according to the item 1) above which is characterized in that the above-mentioned coating is made of a single layer of austenitic stainless steel formed by diamond jet spraying which belongs to the high energy gas spray coating method. |
abstract | An improved compact searchlight utilizing the merging of multiple single beams to a concentrated light. This provides or light beam that is nearly constant illumination intensity across the beam of light. This reduces or eliminates bight and dim areas that are created from previous light systems that use desecrate lighting elements. The lighting elements includes an a power supply a light source and a lens projection system, wherein the lens projection system including a collecting lens, a negative lens, and a collimating lens such that the illuminance of an area illuminated by a beam and searchlight is projected by the improved light is homogeneous throughout the whole of the illuminated area. |
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claims | 1. An anode for an X-ray tube comprisingan electron aperture through which electrons emitted from an electron source travel subject to substantially no electrical field; anda target, wherein said target comprises more than one target segment, wherein each of said target segments is in a non-parallel relationship to said electron aperture and arranged to produce X-rays when electrons are incident upon a first side of at least one of said target segments, wherein each of said target segments further comprises a cooling channel located on a second side of the target segment. 2. The anode of claim 1 wherein the cooling channel comprises a conduit having coolant contained therein. 3. The anode of claim 2 wherein the coolant is at least one of water, oil, or refrigerant. 4. The anode of claim 1 wherein said second sides of each of said target segments are attached to a backbone. 5. The anode of claim 4 wherein the backbone is a rigid, single piece of metal. 6. The anode of claim 5 wherein the backbone comprises stainless steel. 7. The anode of claim 6 wherein at least one of said target segments is connected to said backbone using a bolt. 8. The anode of claim 7 wherein at least one of said target segments is connected to said backbone by placing said backbone within crimped protrusions formed on the second side of said target segment. 9. The anode of claim 1 wherein each of the target segments is held at a high voltage positive electrical potential with respect to said electron source. 10. The anode of claim 1 wherein the first side of each of the target segments is coated with a target metal, wherein said target metal is at least one of molybdenum, tungsten, silver, metal foil, or uranium. 11. The anode of claim 4 wherein the backbone is made of stainless steel and said target segments are made of copper. 12. The anode of claim 2 wherein the conduit is electrically insulated and the cooling channel has at least one of a square, rectangular, semi-circular, or flattened semi-circular cross-section. 13. An X-ray tube comprising:an anode further comprisingat least one electron aperture through which electrons emitted from an electron source travel subject to substantially no electrical field;a target, wherein said target comprises more than one target segment, wherein each of said target segments is in a non-parallel relationship to said electron aperture and arranged to produce X-rays when electrons are incident upon a first side of at least one of said target segments, wherein each of said target segments further comprises a cooling channel located on a second side of the target segment; andan X-ray aperture through which X-rays from the target pass through and are at least partially collimated by the X-ray aperture. 14. The anode of claim 13 wherein the cooling channel comprises a conduit having coolant contained therein. 15. The anode of claim 14 wherein the coolant is at least one of water, oil, or refrigerant. 16. The anode of claim 13 wherein said second sides of each of said target segments are attached to a backbone. 17. The anode of claim 16 wherein at least one of said target segments is connected to said backbone by a bolt or by placing said backbone within crimped protrusions formed on the second side of said target segment. 18. The anode of claim 13 wherein each of the target segments is held at a high voltage positive electrical potential with respect to said electron source. |
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054830648 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is related in general to scanning tunneling and scanning force microscopy. In particular, it describes a method and a mechanism for always operating the scanning means of such microscopes in coaxial alignment with the instrument's probe irrespective of the portion of sample being scanned. 2. Description of the Related Art During the last decade scanning tunneling microscopes (STM's) and scanning force microscope (SFM's; also known as atomic force microscopes) have evolved into powerful tools in science and technology for measuring microscopic features and physical properties of materials. Scanning tunneling microscopy is based on the principle of quantum mechanical tunneling of electrons between two electrodes, such as an atomically sharp metal tip and a sample, under an applied electric field. A potential is applied through a feedback control system that maintains a constant current between the tip and the sample by controlling the vertical distance between the two. In one configuration, the tip is held stationary while the sample is mounted on piezoelectric ceramic material that is capable of moving the sample in the x, y and z directions with respect to the tip by the application of electric fields to the ceramic. In another configuration, the sample is stationary and the tip is mounted on a scanning piezoelectric ceramic. In either case, the accurate positioning of the tip in the x, y and z directions relative to a target point on the sample allows high-resolution point measurements of surface topography, electrical conductivity, electronic and atomic structure, and chemical composition. Scanning force microscopy functions on the principle of a conventional stylus profilometer having a sharp point mounted on a flexible cantilever and moved across the surface of a sample. The motion of the stylus is correlated to a property being observed as a target point in the sample is being scanned by means equivalent to the ones used by STM's. Scanning force microscopy is used to study various interactions between a probe and a surface, such as interatomic, frictional, magnetic, electrostatic, and adhesion forces In addition, SFM's are used to produce high-resolution images for both conductive and insulating materials. As in the case of STM's, either the probe or the sample is mounted on a scanning mechanism that allows the relative motion of the two along the surface of the sample. Scanning is conducted under one of three modes of operation. In the first mode, the deflection of the cantilever is held constant by adjusting the vertical position of the probe or the sample with a feedback control loop (constant force mode). In the second mode, the sample is kept at a constant height and the variation of the deflection of the cantilever during scanning is used to produce a topography of the surface. In the third mode, the cantilever is modulated near its resonance frequency, such as by a piezoelectric unit, and the amplitude or phase change of the vibration is monitored to produce a measurement of the distance between the probe and the surface of the sample. Scanning tunneling and atomic force microscopes based on these principles are well known in the art and are described in detail in the literature. See, for example, Jahanmir, J. et al., "Scanning Microscopy, " Vol. 6 No. 3, 1992 (pp. 625-660). The present invention is directed to the class of scanning tunneling and atomic force microscopes that utilize a fixed probe interacting with a sample mounted on a piezoelectric mechanism that provides the scanning action required for the operation of the system. A typical such system for an STM is shown schematically in FIG. 1 for illustration. A fixed probe 10 mounted on a rigid support block 12 is kept within tunneling distance of the surface 14 of a sample 16 mounted on a piezoelectric element or tube 18 by a conventional feedback mechanism. The tunnel current I resulting from a tunnel voltage P applied between the probe and the sample is converted to an output voltage V by a current detection circuit 20. The output voltage V is compared to a setpoint reference value S to produce an error signal E, which in turn is converted to a control voltage by control circuitry 22 that adjusts the z position of the ceramic to minimize the error. The control voltage is stored as a function of x and y positions and related to the topography of the surface 14. Motion of the sample in the x and y directions is provided, usually in raster fashion, by scanning voltages applied to the piezoelectric element 18 (not illustrated in the FIGURE). Thus, the piezoelectric element 18 provides the vertical motion as well as the scanning motion of the sample 16 with respect to the fixed probe 10. Typically, piezoelectric ceramics are either mounted in an orthogonal tripod arrangement for independently scanning the x, y and z directions or consist of a single-tube ceramic sectioned into four equal parts parallel to the axis of the tube. Different voltage potentials applied to the various sections cause different degrees of expansion of the ceramic sections that result in x-, y- and z-directional movement of a sample stage connected to the top of piezoelectric element. The movement so produced in the x-y plane provides the scanning of the surface of the sample 14 by the tip of the stationary probe 10 (see FIG. 1). One of the design specifications for a typical STM system is that the tip-to-sample position control be better than the resolution desired for the application of interest. Thus, for example, for atomic imaging the tip position has to be resolved 0.1 angstrom vertically and 1 angstrom laterally and the dynamic range required is a few thousand angstroms in the x, y and z directions. Piezoelectric ceramics, which are capable of position control within 0.1.ANG. and have a dynamic range of several micrometers, satisfy the scanning requirements of most systems once the target of interest in a sample is positioned directly under the point of the probe. Between scanning operations, coarse positioning of the tip with respect to the sample is provided by translational mechanisms that move either the probe or the piezoelectric/sample assembly and permit the precise positioning of the tip of the probe on the target area on the surface of the sample, typically with the aid of optical instrumentation. The target area is then scanned by the piezoelectric action described above. During horizontal scanning, the piezoelectric tube 18 of typical STM or SFM apparatus provides lateral movement of the sample stage connected to it by bending in the direction of motion as a result of the net effect of the voltages applied to the ceramic's various sections. Therefore, such bending introduces a tilt .alpha. in the position of the sample 16 that becomes progressively pronounced as the limits of the scanning range of the piezoelectric element 18 are approached, as illustrated in FIG. 2 (in exaggerated fashion for clarity). This tilt, which is typically in the order of seconds of a degree, is the source of several problems that the present invention is directed at solving. The first problem is a material reduction of the vertical operating range between the probe 10 and the sample 16 when the probe is aligned with a peripheral portion of the sample, as illustrated in FIG. 3. Since the probe 10 is positioned over the target area by the translational mechanism 24 (FIG. 2) but is stationary during scanning, its distance d from the sample is obviously affected by any tilt .alpha. in the plane of the sample and the variation is progressively increased as the probe is further removed from the vertical axis A of the piezoelectric element (in its relaxed state). Thus, for example, when the sample is raised toward the probe by the tilting action resulting from scanning toward the left of the sample (requiring-the piezoelectric tube to bend toward the right), the probe may press against the sample and produce highly distorted images (FIG. 3). When the sample is lowered away from the probe by the tilting action, as illustrated in phantom line in FIG. 3, the probe may be outside the vertical range of the piezoelectric element and again produce highly distorted images or no images at all. The second problem associated with the prior art is related to the hysteresis that all piezoelectric elements show during the electromechanical cycles that produce scanning. In order to position the probe at the appropriate distance from the sample, because of the tilt .alpha. in the plane of the sample, the vertical motion required of the piezoelectric element is greater when the probe is not aligned with the vertical axis A of the scanning piezoelectric element. Accordingly, all hysteresis effects experienced between scanning operations become more pronounced as the target point is moved away from the axis A of the piezoelectric element and are more difficult to correct by means of standard electronic circuitry. A third problem is related to the nonlinear response of piezoelectric elements to applied voltages. As in the case of hysteresis, the tilt of the sample also causes the piezoelectric element to operated in less linear regions when the scanning is performed over a target located away from the vertical axis A of the piezoelectric ceramic. This higher degree of nonlinearity distorts the voltage readings and introduces an additional source of error that must be corrected by numerical or other means. This invention provides simple solutions that materially improve the effects of these problems in the operation of STM's and SFM's. BRIEF SUMMARY OF THE INVENTION One general objective of this invention is a scanning approach that minimizes the effects of the sample tilt that is necessarily introduced by scanning with piezoelectric-actuated mechanisms. A specific goal of the invention is a method and apparatus for scanning that avoid the vertical-range problem encountered when a sample is scanned at a point out of alignment with the main axis of the piezoelectric element used to produce the scanning motion. Another goal is a method and apparatus that ensure scanning with minimal effects from the hysteresis of the piezoelectric element. Yet another goal is a method and apparatus that ensure scanning with minimal effects from the nonlinearity of response of the piezoelectric element. Another objective of the invention is a mechanism for positioning the sample that, consistently with these goals, provides a take-up gap around the sample to ensure its free movement during scanning. Still another objective is a sample-positioning mechanism that provides a take-up gap around the sample automatically and independently of a user's visual response and manual dexterity. A final objective is a design for STM's and SFM's that can be implemented easily and economically according to the above stated criteria. Therefore, according to these and other objectives, the present invention consists of scanning tunneling and atomic force microscopes wherein the probe operates at all times in alignment with the piezoelectric element providing the scanning motion. The sample is slidably connected to the piezoelectric element and the target area on the sample is positioned substantially coaxially with the probe and the scanning element prior to commencement of the scanning operation. A particular embodiment of a sample positioner is provided that eliminates any interference by the positioner with the sample during scanning. Various other purposes and advantages of the invention will become clear from its description in the specification that follows and from the novel features particularly pointed out in the appended claims. Therefore, to the accomplishment of the objectives described above, this invention consists of the features hereinafter illustrated in the drawings, fully described in the detailed description of the preferred embodiment and particularly pointed out in the claims. However, such drawings and description disclose but one of the various ways in which the invention may be practiced. |
claims | 1. A neutron absorber system for a cell of a nuclear fuel storage rack, comprising: a neutron absorber having a first longitudinal portion and a second longitudinal portion, said first longitudinal portion and said second longitudinal portion having an angle therebetween greater than an angle between adjacent cell walls of the cell of the nuclear fuel storage rack, said first longitudinal portion and said second longitudinal portion being elastically deformable toward each other in response to a stress being placed thereon; an installation tool configured to provide the stress to the neutron absorber to elastically deform said first longitudinal portion and said second longitudinal portion; said installation tool configured to insert said neutron absorber into the nuclear fuel storage rack; and said installation tool configured to release the stress on the neutron absorber said first longitudinal portion and said second longitudinal portion configured to abut the adjacent walls of the cell in response to the release of the stress to cause a frictional fit between the first longitudinal portion and the second longitudinal portion and the adjacent walls of the cell to attach the neutron absorber to the adjacent walls of the cell of the nuclear fuel storage rack. 2. The system of claim 1 wherein said neutron absorber comprises a chevron shape. claim 1 3. The system of claim 1 wherein the cell angle is about ninety degrees. claim 1 4. The system of claim 1 wherein the cell walls are vertical walls of the nuclear fuel storage rack. claim 1 5. The system of claim 1 wherein said neutron absorber further comprises a plurality of notches configured to engage said installation tool. claim 1 6. The system of claim 1 wherein said plurality of notches is configured to receive the stress from said installation tool to cause the elastically deforming of the first longitudinal portion and the second longitudinal portion. claim 1 7. The system of claim 5 wherein at least one of said plurality of notches is cooperatively engageable with the plurality of cell walls. claim 5 |
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claims | 1. A method of producing uranium nitride (UN), the method comprising:reacting a reaction mixture comprising uranium carbide with a gas comprising hydrogen and nitrogen;cooling the reaction mixture to a temperature below a phase transition temperature between a phase comprising UN and a phase comprising U2N3, wherein such temperature ranging from 1352° C. to 1132° C., to thereby produce a phase comprising U2N3; andheating the reaction mixture to a temperature above the phase transition temperature between the phase comprising UN and the phase comprising U2N3, wherein such temperature is greater than 1352° C., to thereby convert the phase comprising U2N3 to the phase comprising UN. 2. The method of claim 1, the method further comprising:reacting UO2 with at least three molar equivalents of carbon to form the reaction mixture comprising uranium carbide. 3. The method of claim 2, wherein the at least three molar equivalents of carbon comprises an excess of three molar equivalents of carbon. 4. The method of claim 2, the method further comprising:granulating the reaction mixture comprising uranium carbide prior to reaction with the gas comprising hydrogen and nitrogen. 5. The method of claim 1, the method further comprising:repeating the cooling the reaction mixture and heating the reaction mixture to purify the UN. 6. The method of claim 2, wherein the reacting UO2 with at least three molar equivalents of carbon is accomplished under an active vacuum. 7. The method of claim 2, wherein the reacting UO2 with at least three molar equivalents of carbon is accomplished under an inert atmosphere comprising N2, Ar, He, H2, or a mixture thereof. 8. The method of claim 1, the method being a continuous process wherein the reaction mixture comprising uranium carbide is continuously moved through a series of at least first, second, and third reaction zones arranged in a sequence, wherein:the first reaction zone has a temperature corresponding to the reacting the reaction mixture comprising uranium carbide with the gas comprising hydrogen and nitrogen;the second reaction zone has a temperature corresponding to the cooling the reaction mixture to the temperature below the phase transition temperature between the phase comprising UN and the phase comprising U2N3, wherein such temperature ranging from 1352° C. to 1132° C., to produce the phase comprising U2N3; andthe third reaction zone has a temperature corresponding to the heating the reaction mixture to the temperature above the phase transition temperature between the phase comprising UN and the phase comprising U2N3, wherein such temperature is greater than 1352° C., suitable to convert the phase comprising U2N3 to the phase comprising UN. 9. The method of claim 1, wherein the heating the reaction mixture to the temperature above the phase transition temperature between the phase comprising UN and the phase comprising U2N3 to convert the phase comprising U2N3 to the phase comprising UN comprises heating the reaction mixture to a temperature of 1375° C. to 2000° C. |
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description | This application claims the benefit under 35 U.S.C. § 119(e) of the priority of the following U.S. Provisional Applications filed on Apr. 3, 2013, the entire disclosures of which are hereby incorporated by reference: U.S. Provisional Application No. 61/808,136, entitled “MAGNETIC FIELD PLASMA CONFINEMENT FOR COMPACT FUSION POWER”; U.S. Provisional Application No. 61/808,122, entitled “MAGNETIC FIELD PLASMA CONFINEMENT FOR COMPACT FUSION POWER”; U.S. Provisional Application No. 61/808,131, entitled “ENCAPSULATION AS A METHOD TO ENHANCE MAGNETIC FIELD PLASMA CONFINEMENT”; U.S. Provisional Application No. 61/807,932, entitled “SUPPORTS FOR STRUCTURES IMMERSED IN PLASMA”; U.S. Provisional Application No. 61/808,110, entitled “RESONANT HEATING OF PLASMA WITH HELICON ANTENNAS”; U.S. Provisional Application No. 61/808,066, entitled “PLASMA HEATING WITH RADIO FREQUENCY WAVES”; U.S. Provisional Application No. 61/808,093, entitled “PLASMA HEATING WITH NEUTRAL BEAMS”; U.S. Provisional Application No. 61/808,089, entitled “ACTIVE COOLING OF STRUCTURES IMMERSED IN PLASMA”; U.S. Provisional Application No. 61/808,101, entitled “PLASMA HEATING VIA FIELD OSCILLATIONS”; and U.S. Provisional Application No. 61/808,154, entitled “DIRECT ENERGY CONVERSION OF FUSION PLASMA ENERGY VIA CYCLED ADIABATIC COMPRESSION AND EXPANSION”. This disclosure generally relates to fusion reactors and more specifically to encapsulating magnetic fields for plasma confinement. Fusion power is power that is generated by a nuclear fusion process in which two or more atomic nuclei collide at very high speed and join to form a new type of atomic nucleus. A fusion reactor is a device that produces fusion power by confining and controlling plasma. Typical fusion reactors are large, complex, and cannot be mounted on a vehicle. According to one embodiment, a fusion reactor includes an enclosure, an open-field magnetic system comprising one or more internal magnetic coils suspended within the enclosure, and one or more encapsulating magnetic coils coaxial with the one or more internal magnetic coils of the open-field magnetic system. The one or more encapsulating magnetic coils form a magnetosphere around the open-field magnetic system. The open-field magnetic system and the one or more encapsulating magnetic coils, when supplied with electrical currents, form magnetic fields for confining plasma within the enclosure. Technical advantages of certain embodiments may include providing a compact fusion reactor that is less complex and less expensive to build than typical fusion reactors. Some embodiments may provide a fusion reactor that is compact enough to be mounted on or in a vehicle such as a truck, aircraft, ship, train, spacecraft, or submarine. Some embodiments may provide a fusion reactor that may be utilized in desalination plants or electrical power plants. Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages. Fusion reactors generate power by confining and controlling plasma that is used in a nuclear fusion process. Magnetic fields are one of the main methods of confining plasma for the purposes of harnessing nuclear fusion energy. Open field line versions of confining plasma may suffer from particle streaming losses. Some reactors may utilize recirculation to return exiting particles along the field lines by containing the expansive field lines in a much larger device than would be otherwise used. However, these fields become weaker farther away from the device and thus become susceptible to plasma detachment and instability. Additionally, typical fusion reactors are extremely large and complex devices. Because of their prohibitively large plant sizes, it is not feasible to mount typical fusion reactors on vehicles. As a result, the usefulness of typical fusion reactors is limited. The teachings of the disclosure recognize that it is desirable to provide a compact fusion reactor that is small enough to mount on vehicles such as trucks, trains, airplanes, ships, submarines, and the like. For example, it is desirable to provide truck-mounted compact fusion reactors that may provide a decentralized power system. As another example, it is desirable to provide a compact fusion reactor for an aircraft that greatly expands the range and operating time of the aircraft. The following describes an encapsulated fusion reactor for providing these and other desired benefits associated with compact fusion reactors. The encapsulation fields of the disclosed devices allow recirculating field lines to be compressed and contained. The disclosed embodiments contain the fields within a much smaller volume, completely containing the plasma within a magnetosphere much like the magnetosphere surrounding the Earth. The encapsulated fields of the disclosed embodiments are higher strength and less susceptible to instability as well as more compact—a great improvement over typical systems. FIG. 1 illustrates applications of a fusion reactor 110, according to certain embodiments. As one example, one or more embodiments of fusion reactor 110 are utilized by aircraft 101 to supply heat to one or more engines (e.g., turbines) of aircraft 101. A specific example of utilizing one or more fusion reactors 110 in an aircraft is discussed in more detail below in reference to FIG. 2. In another example, one or more embodiments of fusion reactor 110 are utilized by ship 102 to supply electricity and propulsion power. While an aircraft carrier is illustrated for ship 102 in FIG. 1, any type of ship (e.g., a cargo ship, a cruise ship, etc.) may utilize one or more embodiments of fusion reactor 110. As another example, one or more embodiments of fusion reactor 110 may be mounted to a flat-bed truck 103 in order to provide decentralized power or for supplying power to remote areas in need of electricity. As another example, one or more embodiments of fusion reactor 110 may be utilized by an electrical power plant 104 in order to provide electricity to a power grid. While specific applications for fusion reactor 110 are illustrated in FIG. 1, the disclosure is not limited to the illustrated applications. For example, fusion reactor 110 may be utilized in other applications such as trains, desalination plants, spacecraft, submarines, and the like. In general, fusion reactor 110 is a device that generates power by confining and controlling plasma that is used in a nuclear fusion process. Fusion reactor 110 generates a large amount of heat from the nuclear fusion process that may be converted into various forms of power. For example, the heat generated by fusion reactor 110 may be utilized to produce steam for driving a turbine and an electrical generator, thereby producing electricity. As another example, as discussed further below in reference to FIG. 2, the heat generated by fusion reactor 110 may be utilized directly by a turbine of a turbofan or fanjet engine of an aircraft instead of a combustor. Fusion reactor 110 may be scaled to have any desired output for any desired application. For example, one embodiment of fusion reactor 110 may be approximately 10 m×7 m and may have a gross heat output of approximately 100 MW. In other embodiments, fusion reactor 110 may be larger or smaller depending on the application and may have a greater or smaller heat output. For example, fusion reactor 110 may be scaled in size in order to have a gross heat output of over 200 MW. FIG. 2 illustrates an example aircraft system 200 that utilizes one or more fusion reactors 110, according to certain embodiments. Aircraft system 200 includes one or more fusion reactors 110, a fuel processor 210, one or more auxiliary power units (APUs) 220, and one or more turbofans 230. Fusion reactors 110 supply hot coolant 240 to turbofans 230 (e.g., either directly or via fuel processor 210) using one or more heat transfer lines. In some embodiments, hot coolant 240 is FLiBe (i.e., a mixture of lithium fluoride (LiF) and beryllium fluoride (BeF2)) or LiPb. In some embodiments, hot coolant 240 is additionally supplied to APUs 220. Once used by turbofans 240, return coolant 250 is fed back to fusion reactors 110 to be heated and used again. In some embodiments, return coolant 250 is fed directly to fusion reactors 110. In some embodiments, return coolant 250 may additionally be supplied to fusion reactors 110 from APUs 220. In general, aircraft system 200 utilizes one or more fusion reactors 110 in order to provide heat via hot coolant 240 to turbofans 230. Typically, a turbofan utilizes a combustor that burns jet fuel in order to heat intake air, thereby producing thrust. In aircraft system 200, however, the combustors of turbofans 230 have been replaced by heat exchangers that utilize hot coolant 240 provided by one or more fusion reactors 110 in order to heat the intake air. This may provide numerous advantages over typical turbofans. For example, by allowing turbofans 230 to operate without combustors that burn jet fuel, the range of aircraft 101 may be greatly extended. In addition, by greatly reducing or eliminating the need for jet fuel, the operating cost of aircraft 101 may be significantly reduced. FIGS. 3A and 3B illustrate a fusion reactor 110 that may be utilized in the example applications of FIG. 1, according to certain embodiments. In general, fusion reactor 110 utilizes any open-field magnetic system in order to control plasma 310 within enclosure 120. In some embodiments, fusion reactor 110 is an encapsulated linear ring cusp fusion reactor in which encapsulating magnetic coils 150 are used to prevent plasma that is generated using internal cusp magnetic coils from expanding. In some embodiments, fusion reactor 110 includes an enclosure 120 with a center line 115 running down the center of enclosure 120 as shown. In some embodiments, enclosure 120 includes a vacuum chamber and has a cross-section as discussed below in reference to FIG. 7. Fusion reactor 100 includes internal coils 140 (e.g., internal coils 140a and 140, also known as “cusp” coils), encapsulating coils 150, and mirror coils 160 (e.g., mirror coils 160a and 160b). Internal coils 140 are suspended within enclosure 120 by any appropriate means and are centered on center line 115. Encapsulating coils 150 are also centered on center line 115 and may be either internal or external to enclosure 120. For example, encapsulating coils 150 may be suspended within enclosure 120 in some embodiments. In other embodiments, encapsulating coils 150 may be external to enclosure 120 as illustrated in FIGS. 3A and 3B. In general, fusion reactor 100 provides power by controlling and confining plasma 310 within enclosure 120 for a nuclear fusion process. Internal coils 140, encapsulating coils 150, and mirror coils 160 are energized to form magnetic fields which confine plasma 310 into a shape such as the shape shown in FIGS. 3B and 5. Certain gases, such as deuterium and tritium gases, may then be reacted to make energetic particles which heat plasma 310 and the walls of enclosure 120. The generated heat may then be used, for example, to power vehicles. For example, a liquid metal coolant such as FLiBe or LiPb may carry heat from the walls of fusion reactor 110 out to engines of an aircraft. In some embodiments, combustors in gas turbine engines may be replaced with heat exchangers that utilize the generated heat from fusion reactor 110. In some embodiments, electrical power may also be extracted from fusion reactor 110 via magnetohydrodynamic (MHD) processes. In embodiments of fusion reactor 110, one or more encapsulating coils 150 provide encapsulation fields that allow recirculating field lines of an open-field magnetic system within fusion reactor 110 to be compressed and contained. This configuration of encapsulating coils 150 that encapsulate the magnetic fields of the open-field magnetic system within fusion reactor 110 provides a system that contains all the fields within a much smaller volume, completely containing the plasma within a magnetosphere much like the one surrounding the Earth. The encapsulated fields are higher strength and less susceptible to instability as well as more compact—a substantial benefit for compact reactor concepts. The general technique of providing one or more encapsulating coils 150 that surround an open-field magnetic system within fusion rector 110 may be applied to any recirculating open field line device. For example, the open-field magnetic system within fusion reactor 110 may be any linear ring cusp device, a Polywell device, any spindle cusp device, any mirror device, any of the linear-ring cusp devices described herein, or any other magnetic system having open magnetic field lines. The general technique of providing one or more encapsulating coils 150 that surround an open-field magnetic system within fusion reactor 110 allows recirculating plasma flow to follow much stronger magnetic field lines. This eliminates the chances for plasma detachment and instabilities. Additionally, encapsulation greatly reduces the size of recirculating field line devices. This may permit compact fusion reactors that may mounted on any vehicle. Encapsulation is generally the process of adding additional external fields (e.g., by using one or more encapsulating coils 150) to an open field line geometry (i.e., an open-field magnetic system within fusion reactor 110). The magnetic fields of the one or more encapsulating coils 150 close the original magnetic lines formed by the open-field magnetic system inside a magnetosphere. Closing the magnetic lines can reduce the extent of open field lines and reduce losses via recirculation. All types of dipoles, mirrors, and cusp devices can be encapsulated. As discussed above, encapsulating coils 150 may be utilized with any open-field magnetic system to confine plasma for the purposes of harnessing nuclear fusion energy. The following figures illustrate various embodiments of fusion reactor 110 that utilize different open-field magnetic systems to confine plasma 310. For example, FIG. 3A below illustrates an embodiment of fusion reactor 110 that utilizes encapsulating coils 150 in conjunction with an open-field magnetic system that includes a central linear ring cusp (i.e., center coil 130), two spindle cusps (i.e., internal coils 140) that are located axially on either side of the central linear ring cusp, and two mirror coils located axially at the ends (i.e., mirror coils 160). While particular embodiments of an open-field magnetic system within fusion reactor. 110 are illustrated, it should be understood that encapsulating coils 150 may be utilized with any appropriate open-field magnetic system. In some embodiments, fusion reactor 110 is an encapsulated linear ring cusp fusion device. The main plasma confinement is accomplished in some embodiments by a central linear ring cusp (e.g., center coil 130) with two spindle cusps located axially on either side (e.g., internal coils 140). These confinement regions are then encapsulated (e.g., with encapsulating coils 150) within a coaxial mirror field provided by mirror coils 160. The magnetic fields of fusion reactor 110 are provided by coaxially located magnetic field coils of varying sizes and currents. The ring cusp losses of the central region are mitigated by recirculation into the spindle cusps. This recirculating flow is made stable and compact by the encapsulating fields provided by encapsulating coils 150. The outward diffusion losses and axial losses from the main confinement zones are mitigated by the strong mirror fields of the encapsulating field provided by encapsulating coils 150. To function as a fusion energy producing device, heat is added to the confined plasma 310, causing it to undergo fusion reactions and produce heat. This heat can then be harvested to produce useful heat, work, and/or electrical power. In some embodiments, additional coils may be utilized to alter the shape of the confinement zones for the purposes of creating confinement zones more suitable for specific purposes. For example, the central confinement well can be expanded into a more spherical shape, increasing its volume and suitability for non-thermal fusion schemes. Another example is the stretching of the central region into a more elongated cigar shape, perhaps for easier integration into aerospace vehicles or for easier power conversion or surface wall effects such as breeding. In certain embodiments, additional central cells may be utilized to expand the fusing volume without increasing losses as the whole stack would still be capped by two spindle cusps on the axis. This serves as a way to modularize the system and tailor the output of a given installation to the power needs. Fusion reactor 110 is an improvement over existing systems in part because global MHD stability can be preserved and the losses through successive confinement zones are more isolated due to the scattering of particles moving along the null lines. This feature means that particles moving along the center line are not likely to pass immediately out of the system, but will take many scattering events to leave the system. This increases their lifetime in the device, increasing the ability of the reactor to produce useful fusion power. Fusion reactor 110 has novel magnetic field configurations that exhibit global MHD stability, has a minimum of particle losses via open field lines, uses all of the available magnetic field energy, and has a greatly simplified engineering design. The efficient use of magnetic fields means the disclosed embodiments may be an order of magnitude smaller than typical systems, which greatly reduces capital costs for power plants. In addition, the reduced costs allow the concept to be developed faster as each design cycle may be completed much quicker than typical system. In general, the disclosed embodiments have a simpler, more stable design with far less physics risk than existing systems. Enclosure 120 is any appropriate chamber or device for containing a fusion reaction. In some embodiments, enclosure 120 is a vacuum chamber that is generally cylindrical in shape. In other embodiments, enclosure 120 may be a shape other than cylindrical. In some embodiments, enclosure 120 has a centerline 115 running down a center axis of enclosure 120 as illustrated. In some embodiments, enclosure 120 has a first end 320 and a second end 330 that is opposite from first end 320. In some embodiments, enclosure 120 has a midpoint 340 that is substantially equidistant between first end 320 and second end 330. A cross-section of a particular embodiment of enclosure 120 is discussed below in reference to FIG. 8. Some embodiments of fusion reactor 110 may include a center coil 130. Center coil 130 is generally located proximate to midpoint 340 of enclosure 120. In some embodiments, center coil 130 is centered on center line 115 and is coaxial with internal coils 140. Center coil 130 may be either internal or external to enclosure 120, may be located at any appropriate axial position with respect to midpoint 340, may have any appropriate radius, may carry any appropriate current, and may have any appropriate ampturns. Internal coils 140 are any appropriate magnetic coils that are suspended or otherwise positioned within enclosure 120. In some embodiments, internal coils 140 are superconducting magnetic coils. In some embodiments, internal coils 140 are toroidal in shape as shown in FIG. 3B. In some embodiments, internal coils 140 are centered on centerline 115. In some embodiments, internal coils 140 include two coils: a first internal coil 140a that is located between midpoint 340 and first end 320 of enclosure 120, and a second internal coil 140b that is located between midpoint 340 and second end 330 of enclosure 120. Internal coils 140 may be located at any appropriate axial position with respect to midpoint 340, may have any appropriate radius, may carry any appropriate current, and may have any appropriate ampturns. A particular embodiment of an internal coil 140 is discussed in more detail below in reference to FIG. 7. Encapsulating coils 150 are any appropriate magnetic coils and generally have larger diameters than internal coils 140. In some embodiments, encapsulating coils 150 are centered on centerline 115 and are coaxial with internal coils 140. In general, encapsulating coils 150 encapsulate internal coils 140 and operate to close the original magnetic lines of internal coils 140 inside a magnetosphere. Closing these lines may reduce the extent of open field lines and reduce losses via recirculation. Encapsulating coils 150 also preserve the MHD stability of fusion reactor 110 by maintaining a magnetic wall that prevents plasma 310 from expanding. Encapsulating coils 150 have any appropriate cross-section, such as square or round. In some embodiments, encapsulating coils 150 are suspended within enclosure 120. In other embodiments, encapsulating coils 150 may be external to enclosure 120 as illustrated in FIGS. 3A and 3B. Encapsulating coils 150 may be located at any appropriate axial position with respect to midpoint 340, may have any appropriate radius, may carry any appropriate current, and may have any appropriate ampturns. Fusion reactor 110 may include any number and arrangement of encapsulating coils 150. In some embodiments, encapsulating coils 150 include at least one encapsulating coil 150 positioned on each side of midpoint 340 of enclosure 120. For example, fusion reactor 110 may include two encapsulating coils 150: a first encapsulating coil 150 located between midpoint 340 and first end 320 of enclosure 120, and a second encapsulating coil 150 located between midpoint 340 and second end 330 of enclosure 120. In some embodiments, fusion reactor 110 includes a total of two, four, six, eight, or any other even number of encapsulating coils 150. In certain embodiments, fusion reactor 110 includes a first set of two encapsulating coils 150 located between internal coil 140a and first end 320 of enclosure 120, and a second set of two encapsulating coils 150 located between internal coil 140b and second end 330 of enclosure 120. While particular numbers and arrangements of encapsulating coils 150 have been disclosed, any appropriate number and arrangement of encapsulating coils 150 may be utilized by fusion reactor 110. Mirror coils 160 are magnetic coils that are generally located close to the ends of enclosure 120 (i.e., first end 320 and second end 330). In some embodiments, mirror coils 160 are centered on center line 115 and are coaxial with internal coils 140. In general, mirror coils 160 serve to decrease the axial cusp losses and make all the recirculating field lines satisfy an average minimum-β, a condition that is not satisfied by other existing recirculating schemes. In some embodiments, mirror coils 160 include two mirror coils 160: a first mirror coil 160a located proximate to first end 320 of enclosure 120, and a second mirror coil 160b located proximate to second end 330 of enclosure 120. Mirror coils 160 may be either internal or external to enclosure 120, may be located at any appropriate axial position with respect to midpoint 340, may have any appropriate radius, may carry any appropriate current, and may have any appropriate ampturns. In some embodiments, coils 130, 140, 150, and 160 are designed or chosen according to certain constraints. For example, coils 130, 140, 150, and 160 may be designed according to constraints including: high required currents (maximum in some embodiments of approx. 10 MegaAmp-turns); steady-state continuous operation; vacuum design (protected from plasma impingement), toroidal shape, limit outgassing; materials compatible with 150C bakeout; thermal build-up; and cooling between shots. Fusion reactor 110 may include one or more heat injectors 170. Heat injectors 170 are generally operable to allow any appropriate heat to be added to fusion reactor 110 in order to heat plasma 310. In some embodiments, for example, heat injectors 170 may be utilized to add neutral beams in order to heat plasma 310 within fusion reactor 110. In operation, fusion reactor 110 generates fusion power by controlling the shape of plasma 310 for a nuclear fusion process using at least internal coils 140, encapsulating coils 150, and mirror coils 160. Internal coils 140 and encapsulating coils 150 are energized to form magnetic fields which confine plasma 310 into a shape such as the shape shown in FIGS. 3B and 5. Gases such as deuterium and tritium may then be reacted to make energetic particles which heat plasma 310 and the walls of enclosure 120. The generated heat may then be used for power. For example, a liquid metal coolant may carry heat from the walls of the reactor out to engines of an aircraft. In some embodiments, electrical power may also be extracted from fusion reactor 110 via MHD. In order to expand the volume of plasma 310 and create a more favorable minimum-P geometry, the number of internal coils can be increased to make a cusp. In some embodiments of fusion reactor 110, the sum of internal coils 140, center coil 130, and mirror coils 160 is an odd number in order to obtain the encapsulation by the outer ‘solenoid’ field (i.e., the magnetic field provided by encapsulating coils 150). This avoids making a ring cusp field and therefor ruining the encapsulating separatrix. Two internal coils 140 and center coil 130 with alternating polarizations give a magnetic well with minimum-β characteristics within the cusp and a quasi-spherical core plasma volume. The addition of two axial ‘mirror’ coils (i.e., mirror coils 160) serves to decrease the axial cusp losses and more importantly makes the recirculating field lines satisfy average minimum-R, a condition not satisfied by other existing recirculating schemes. In some embodiments, additional pairs of internal coils 140 could be added to create more plasma volume in the well. However, such additions may increase the cost and complexity of fusion reactor 110 and may require additional supports for coils internal to plasma 310. In the illustrated embodiments of fusion reactor 110, only internal coils 140 are within plasma 310. In some embodiments, internal coils 140 are suspending within enclosure 120 by one or more supports, such as support 750 illustrated in FIG. 7. While the supports sit outside the central core plasma well, they may still experience high plasma fluxes. Alternatively, internal coils 140 of some embodiments may be amenable to levitation, which would remove the risk and complexity of having support structures within plasma 310. FIG. 4A illustrates a simplified view of the coils of one embodiment of fusion reactor 110 and example systems for energizing the coils. In this embodiment, the field geometry is sized to be the minimum size necessary to achieve adequate ion magnetization with fields that can be produced by simple magnet technology. Adequate ion magnetization was considered to be −5 ion gyro radii at design average ion energy with respect to the width of the recirculation zone. At the design energy of 100 eV plasma temperature there are 13 ion diffusion jumps and at full 20 KeV plasma energy there are 6.5 ion jumps. This is the lowest to maintain a reasonable magnetic field of 2.2 T in the cusps and keep a modest device size. As illustrated in FIG. 4A, certain embodiments of fusion reactor 110 include two mirror coils 160: a first mirror coil 160a located proximate to first end 320 of the enclosure and a second magnetic coil 160b located proximate to second end 330 of enclosure 120. Certain embodiments of fusion reactor 110 also include a center coil 130 that is located proximate to midpoint 340 of enclosure 120. Certain embodiments of fusion reactor 110 also include two internal coils 140: a first internal coil 140a located between center coil 130 and first end 320 of enclosure 120, and a second internal coil 140b located between center coil 130 and second end 330 of enclosure 120. In addition, certain embodiments of fusion reactor 110 may include two or more encapsulating coils 150. For example, fusion reactor 110 may include a first set of two encapsulating coils 150 located between first internal coil 140a and first end 320 of enclosure 120, and a second set of two encapsulating coils 150 located between second internal coil 140b and second end 330 of enclosure 120. In some embodiments, fusion reactor 110 may include any even number of encapsulating coils 150. In some embodiments, encapsulating coils 150 may be located at any appropriate position along center line 115 other than what is illustrated in FIG. 4A. In general, encapsulating coils 150, as well as internal coils 140 and mirror coils 160, may be located at any appropriate position along center line 115 in order to maintain magnetic fields in the correct shape to achieve the desired shape of plasma 310. In some embodiments, electrical currents are supplied to coils 130, 140, 150, and 160 as illustrated in FIGS. 4A-4E. In these figures, each coil has been split along center line 115 and is represented by a rectangle with either an “X” or an “O” at each end. An “X” represents electrical current that is flowing into the plane of the paper, and an “O” represents electrical current that is flowing out the plane of the paper. Using this nomenclature, FIGS. 4A-4E illustrate how in these embodiments of fusion reactor 110, electrical currents flow in the same direction through encapsulating coils 150, center coil 130, and mirror coils 160 (i.e., into the plane of the paper at the top of the coils), but flow in the opposite direction through internal coils 140 (i.e., into the plane of the paper at the bottom of the coils). In some embodiments, the field geometry of fusion reactor 110 may be sensitive to the relative currents in the coils, but the problem can be adequately decoupled to allow for control. First, the currents to opposing pairs of coils can be driven in series to guarantee that no asymmetries exist in the axial direction. The field in some embodiments is most sensitive to the center three coils (e.g., internal coils 140 and center coil 130). With the currents of internal coil 140 fixed, the current in center coil 130 can be adjusted to tweak the shape of the central magnetic well. This region can be altered into an axial-oriented ‘bar-bell’ shape by increasing the current on center coil 130 as the increase in flux ‘squeezes’ the sphere into the axial shape. Alternatively, the current on center coil 130 can be reduced, resulting in a ring-shaped magnetic well at midpoint 340. The radius of center coil 130 also sets how close the ring cusp null-line comes to internal coils 140 and may be chosen in order to have this null line close to the middle of the gap between center coil 130 and internal coils 140 to improve confinement. The radius of internal coils 140 serves to set the balance of the relative field strength between the point cusps and the ring cusps for the central well. The baseline sizes may be chosen such that these field values are roughly equal. While it would be favorable to reduce the ring cusp losses by increasing the relative flux in this area, a balanced approach may be more desirable. In some embodiments, the magnetic field is not as sensitive to mirror coils 160 and encapsulating coils 150, but their dimensions should be chosen to achieve the desired shape of plasma 310. In some embodiments, mirror coils 160 may be chosen to be as strong as possible without requiring more complex magnets, and the radius of mirror coils 160 may be chosen to maintain good diagnostic access to the device center. Some embodiments may benefit from shrinking mirror coils 160, thereby achieving higher mirror ratios for less current but at the price of reduced axial diagnostic access. In general, encapsulating coils 150 have weaker magnetic fields than the other coils within fusion reactor 110. Thus, the positioning of encapsulating coils 150 is less critical than the other coils. In some embodiments, the positions of encapsulating coils 150 are defined such that un-interrupted access to the device core is maintained for diagnostics. In some embodiments, an even number of encapsulating coils 150 may be chosen to accommodate supports for internal coils 140. The diameters of encapsulating coils 150 are generally greater than those of internal coils 140, and may be all equal for ease of manufacture and common mounting on or in a cylindrical enclosure 120. In some embodiments, encapsulating coils 150 may be moved inward to the plasma boundary, but this may impact manufacturability and heat transfer characteristics of fusion reactor 110. In some embodiments, fusion reactor 110 includes various systems for energizing center coil 130, internal coils 140, encapsulating coils 150, and mirror coils 160. For example, a center coil system 410, an encapsulating coil system 420, a mirror coil system 430, and an internal coil system 440 may be utilized in some embodiments. Coil systems 410-440 and coils 130-160 may be coupled as illustrated in FIG. 4A. Coil systems 410-440 may be any appropriate systems for driving any appropriate amount of electrical currents through coils 130-160. Center coil system 410 may be utilized to drive center coil 130, encapsulating coil system 420 may be utilized to drive encapsulating coils 150, mirror coil system 430 may be utilized to drive mirror coils 160, and internal coil system 440 may be utilized to drive internal coils 140. In other embodiments, more or fewer coil systems may be utilized than those illustrated in FIG. 4A. In general, coil systems 410-440 may include any appropriate power sources such as battery banks. FIG. 4B illustrates coils 130-160 of another embodiment of fusion reactor 110. In this embodiment, fusion reactor 110 includes a center coil 130, two internal coils 140, and two mirror coils 160. In addition, this embodiment of fusion reactor 110 includes six encapsulating coils 150. While specific locations of coils 130-160 are illustrated, coils 140-160 may be located in any appropriate positions along center line 115 in order to maintain a desired shape of plasma 310 within enclosure 120. FIG. 4C illustrates coils 130-160 of another embodiment of fusion reactor 110. In this embodiment, fusion reactor 110 includes two center coils 130, three internal coils 140, and two mirror coils 160. In addition, this embodiment of fusion reactor 110 includes six encapsulating coils 150. While specific locations of coils 130-160 are illustrated, coils 140-160 may be located in any appropriate positions along center line 115 in order to maintain a desired shape of plasma 310 within enclosure 120. FIG. 4D illustrates coils 130-160 of another embodiment of fusion reactor 110. In this embodiment, fusion reactor 110 includes two center coils 130, four internal coils 140, and four mirror coils 160. In addition, this embodiment of fusion reactor 110 includes eight encapsulating coils 150. While specific locations of coils 130-160 are illustrated, coils 140-160 may be located in any appropriate positions along center line 115 in order to maintain a desired shape of plasma 310 within enclosure 120. FIG. 4E illustrates coils 130-160 of another embodiment of fusion reactor 110. In this embodiment, fusion reactor 110 includes a center coil 130, four internal coils 140, and four mirror coils 160. In addition, this embodiment of fusion reactor 110 includes four encapsulating coils 150. While specific locations of coils 130-160 are illustrated, coils 140-160 may be located in any appropriate positions along center line 115 in order to maintain a desired shape of plasma 310 within enclosure 120. As illustrated in the various embodiments of FIGS. 4A-4E above, embodiments of fusion reactor 110 may have any appropriate number, combination, and spacing of internal coils 140, encapsulating coils 150, and mirror coils 160. In general, fusion reactor 110 has a center coil 130, two or more internal coils 140 (e.g., two, four, six, etc.), two or more mirror coils 160 (e.g., two, four, six, etc.), and one or more encapsulating coils 150 that provide a magnetic field that encapsulates internal coils 140. This disclosure anticipates any number, combination, and spacing of internal coils 140, encapsulating coils 150, and mirror coils 160 and is not limited to the illustrated embodiments. FIG. 5 illustrates plasma 310 within enclosure 120 that is shaped and confined by center coil 130, internal coils 140, encapsulating coils 150, and mirror coils 160. As illustrated, an external mirror field is provided by mirror coils 160. The ring cusp flow is contained inside the mirror. A trapped magnetized sheath 510 that is provided by encapsulating coils 150 prevents detachment of plasma 310. Trapped magnetized sheath 510 is a magnetic wall that causes plasma 310 to recirculate and prevents plasma 310 from expanding outward. The recirculating flow is thus forced to stay in a stronger magnetic field. This provides complete stability in a compact and efficient cylindrical geometry. Furthermore, the only losses from plasma exiting fusion reactor 110 are at two small point cusps at the ends of fusion reactor 110 along center line 115. This is an improvement over typical designs in which plasma detaches and exits at other locations. The losses of certain embodiments of fusion reactor 110 are also illustrated in FIG. 5. As mentioned above, the only losses from plasma exiting fusion reactor 110 are at two small point cusps at the ends of fusion reactor 110 along center line 115. Other losses may include diffusion losses due to internal coils 140 and axial cusp losses. In addition, in embodiments in which internal coils 140 are suspended within enclosure 120 with one or more supports (e.g., “stalks”), fusion reactor 110 may include ring cusp losses due to the supports. In some embodiments, internal coils 140 may be designed in such a way as to reduce diffusion losses. For example, certain embodiments of fusion reactor 110 may include internal coils 140 that are configured to conform to the shape of the magnetic field. This may allow plasma 310, which follows the magnetic field lines, to avoid touching internal coils 140, thereby reducing or eliminating losses. An example embodiment of internal coils 140 illustrating a conformal shape is discussed below in reference to FIG. 7. FIG. 6 illustrates a magnetic field of certain embodiments of fusion reactor 110. In general, fusion reactor 110 is designed to have a central magnetic well that is desired for high beta operation and to achieve higher plasma densities. As illustrated in FIG. 6, the magnetic field may include three magnetic wells. The central magnetic well can expand with high Beta, and fusion occurs in all three magnetic wells. Another desired feature is the suppression of ring cusp losses. As illustrated in FIG. 6, the ring cusps connect to each other and recirculate. In addition, good MHD stability is desired in all regions. As illustrated in FIG. 6, only two field penetrations are needed and MHD interchange is satisfied everywhere. In some embodiments, the magnetic fields can be altered without any relocation of the coils by reducing the currents, creating for example weaker cusps and changing the balance between the ring and point cusps. The polarity of the currents could also be reversed to make a mirror-type field and even an encapsulated mirror. In addition, the physical locations of the coils could be altered. FIG. 7 illustrates an example embodiment of an internal coil 140 of fusion reactor 110. In this embodiment, internal coil 140 includes coil windings 710, inner shield 720, layer 730, and outer shield 740. In some embodiments, internal coil 140 may be suspending within enclosure 120 with one or more supports 750. Coil windings 710 may have a width 715 and may be covered in whole or in part by inner shield 720. Inner shield 720 may have a thickness 725 and may be covered in whole or in part by layer 730. Layer 730 may have a thickness 735 and may be covered in whole or in part by outer shield 740. Outer shield may have a thickness 745 and may have a shape that is conformal to the magnetic field within enclosure 120. In some embodiments, internal coil 140 may have an overall diameter of approximately 1.04 m. Coil windings 710 form a superconducting coil and carry an electric current that is typically in an opposite direction from encapsulating coils 150, center coil 130, and mirror coils 160. In some embodiments, width 715 of coils winding is approximately 20 cm. Coil windings 710 may be surrounded by inner shield 720. Inner shield 720 provides structural support, reduces residual neutron flux, and shields against gamma rays due to impurities. Inner shield 720 may be made of Tungsten or any other material that is capable of stopping neutrons and gamma rays. In some embodiments, thickness 725 of inner shield 720 is approximately 11.5 cm. In some embodiments, inner shield 720 is surrounded by layer 730. Layer 730 may be made of lithium (e.g., lithium-6) and may have thickness 735 of approximately 5 mm. Layer 730 may be surrounded by outer shield 740. Outer shield 740 may be made of FLiBe and may have thickness 745 of approximately 30 cm. In some embodiments, outer shield may be conformal to magnetic fields within enclosure 120 in order to reduce losses. For example, outer shield 740 may form a toroid. FIG. 8 illustrates a cut-away view of enclosure 120 of certain embodiments of fusion reactor 110. In some embodiments, enclosure 120 includes one or more inner blanket portions 810, an outer blanket 820, and one or more layers 730 described above. In the illustrated embodiment, enclosure 120 includes three inner blanket portions 810 that are separated by three layers 730. Other embodiments may have any number or configuration of inner blanket portions 810, layers 730, and outer blanket 820. In some embodiments, enclosure 120 may have a total thickness 125 of approximately 80 cm in many locations. In other embodiments, enclosure 120 may have a total thickness 125 of approximately 1.50 m in many locations. However, thickness 125 may vary over the length of enclosure 120 depending on the shape of the magnetic field within enclosure 120 (i.e., the internal shape of enclosure 120 may conform to the magnetic field as illustrated in FIG. 3b and thus many not be a uniform thickness 125). In some embodiments, inner blanket portions 810 have a combined thickness 815 of approximately 70 cm. In other embodiments, inner blanket portions 810 have a combined thickness 815 of approximately 126 cm. In some embodiments, inner blanket portions are made of materials such as Be, FLiBe, and the like. Outer blanket 820 is any low activation material that does not tend to become radioactive under irradiation. For example, outer blanket 820 may be iron or steel. In some embodiments, outer blanket 820 may have a thickness 825 of approximately 10 cm. FIG. 9 illustrates an example computer system 900. In particular embodiments, one or more computer systems 900 are utilized by fusion reactor 110 for any aspects requiring computerized control. Particular embodiments include one or more portions of one or more computer systems 900. Herein, reference to a computer system may encompass a computing device, and vice versa, where appropriate. Moreover, reference to a computer system may encompass one or more computer systems, where appropriate. This disclosure contemplates any suitable number of computer systems 900. This disclosure contemplates computer system 900 taking any suitable physical form. As example and not by way of limitation, computer system 900 may be an embedded computer system, a system-on-chip (SOC), a single-board computer system (SBC) (such as, for example, a computer-on-module (COM) or system-on-module (SOM)), a desktop computer system, a laptop or notebook computer system, an interactive kiosk, a mainframe, a mesh of computer systems, a mobile telephone, a personal digital assistant (PDA), a server, a tablet computer system, or a combination of two or more of these. Where appropriate, computer system 900 may include one or more computer systems 900; be unitary or distributed; span multiple locations; span multiple machines; span multiple data centers; or reside in a cloud, which may include one or more cloud components in one or more networks. Where appropriate, one or more computer systems 900 may perform without substantial spatial or temporal limitation one or more steps of one or more methods described or illustrated herein. As an example and not by way of limitation, one or more computer systems 900 may perform in real time or in batch mode one or more steps of one or more methods described or illustrated herein. One or more computer systems 900 may perform at different times or at different locations one or more steps of one or more methods described or illustrated herein, where appropriate. In particular embodiments, computer system 900 includes a processor 902, memory 904, storage 906, an input/output (I/O) interface 908, a communication interface 910, and a bus 912. Although this disclosure describes and illustrates a particular computer system having a particular number of particular components in a particular arrangement, this disclosure contemplates any suitable computer system having any suitable number of any suitable components in any suitable arrangement. In particular embodiments, processor 902 includes hardware for executing instructions, such as those making up a computer program. As an example and not by way of limitation, to execute instructions, processor 902 may retrieve (or fetch) the instructions from an internal register, an internal cache, memory 904, or storage 906; decode and execute them; and then write one or more results to an internal register, an internal cache, memory 904, or storage 906. In particular embodiments, processor 902 may include one or more internal caches for data, instructions, or addresses. This disclosure contemplates processor 902 including any suitable number of any suitable internal caches, where appropriate. As an example and not by way of limitation, processor 902 may include one or more instruction caches, one or more data caches, and one or more translation lookaside buffers (TLBs). Instructions in the instruction caches may be copies of instructions in memory 904 or storage 906, and the instruction caches may speed up retrieval of those instructions by processor 902. Data in the data caches may be copies of data in memory 904 or storage 906 for instructions executing at processor 902 to operate on; the results of previous instructions executed at processor 902 for access by subsequent instructions executing at processor 902 or for writing to memory 904 or storage 906; or other suitable data. The data caches may speed up read or write operations by processor 902. The TLBs may speed up virtual-address translation for processor 902. In particular embodiments, processor 902 may include one or more internal registers for data, instructions, or addresses. This disclosure contemplates processor 902 including any suitable number of any suitable internal registers, where appropriate. Where appropriate, processor 902 may include one or more arithmetic logic units (ALUs); be a multi-core processor; or include one or more processors 902. Although this disclosure describes and illustrates a particular processor, this disclosure contemplates any suitable processor. In particular embodiments, memory 904 includes main memory for storing instructions for processor 902 to execute or data for processor 902 to operate on. As an example and not by way of limitation, computer system 900 may load instructions from storage 906 or another source (such as, for example, another computer system 900) to memory 904. Processor 902 may then load the instructions from memory 904 to an internal register or internal cache. To execute the instructions, processor 902 may retrieve the instructions from the internal register or internal cache and decode them. During or after execution of the instructions, processor 902 may write one or more results (which may be intermediate or final results) to the internal register or internal cache. Processor 902 may then write one or more of those results to memory 904. In particular embodiments, processor 902 executes only instructions in one or more internal registers or internal caches or in memory 904 (as opposed to storage 906 or elsewhere) and operates only on data in one or more internal registers or internal caches or in memory 904 (as opposed to storage 906 or elsewhere). One or more memory buses (which may each include an address bus and a data bus) may couple processor 902 to memory 904. Bus 912 may include one or more memory buses, as described below. In particular embodiments, one or more memory management units (MMUs) reside between processor 902 and memory 904 and facilitate accesses to memory 904 requested by processor 902. In particular embodiments, memory 904 includes random access memory (RAM). This RAM may be volatile memory, where appropriate. Where appropriate, this RAM may be dynamic RAM (DRAM) or static RAM (SRAM). Moreover, where appropriate, this RAM may be single-ported or multi-ported RAM. This disclosure contemplates any suitable RAM. Memory 904 may include one or more memories 904, where appropriate. Although this disclosure describes and illustrates particular memory, this disclosure contemplates any suitable memory. In particular embodiments, storage 906 includes mass storage for data or instructions. As an example and not by way of limitation, storage 906 may include a hard disk drive (HDD), a floppy disk drive, flash memory, an optical disc, a magneto-optical disc, magnetic tape, or a Universal Serial Bus (USB) drive or a combination of two or more of these. Storage 906 may include removable or non-removable (or fixed) media, where appropriate. Storage 906 may be internal or external to computer system 900, where appropriate. In particular embodiments, storage 906 is non-volatile, solid-state memory. In particular embodiments, storage 906 includes read-only memory (ROM). Where appropriate, this ROM may be mask-programmed ROM, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), electrically alterable ROM (EAROM), or flash memory or a combination of two or more of these. This disclosure contemplates mass storage 906 taking any suitable physical form. Storage 906 may include one or more storage control units facilitating communication between processor 902 and storage 906, where appropriate. Where appropriate, storage 906 may include one or more storages 906. Although this disclosure describes and illustrates particular storage, this disclosure contemplates any suitable storage. In particular embodiments, I/O interface 908 includes hardware, software, or both, providing one or more interfaces for communication between computer system 900 and one or more I/O devices. Computer system 900 may include one or more of these I/O devices, where appropriate. One or more of these I/O devices may enable communication between a person and computer system 900. As an example and not by way of limitation, an I/O device may include a keyboard, keypad, microphone, monitor, mouse, printer, scanner, speaker, still camera, stylus, tablet, touch screen, trackball, video camera, another suitable I/O device or a combination of two or more of these. An I/O device may include one or more sensors. This disclosure contemplates any suitable I/O devices and any suitable I/O interfaces 908 for them. Where appropriate, I/O interface 908 may include one or more device or software drivers enabling processor 902 to drive one or more of these I/O devices. I/O interface 908 may include one or more I/O interfaces 908, where appropriate. Although this disclosure describes and illustrates a particular I/O interface, this disclosure contemplates any suitable I/O interface. In particular embodiments, communication interface 910 includes hardware, software, or both providing one or more interfaces for communication (such as, for example, packet-based communication) between computer system 900 and one or more other computer systems 900 or one or more networks. As an example and not by way of limitation, communication interface 910 may include a network interface controller (NIC) or network adapter for communicating with an Ethernet or other wire-based network or a wireless NIC (WNIC) or wireless adapter for communicating with a wireless network, such as a WI-FI network. This disclosure contemplates any suitable network and any suitable communication interface 910 for it. As an example and not by way of limitation, computer system 900 may communicate with an ad hoc network, a personal area network (PAN), a local area network (LAN), a wide area network (WAN), a metropolitan area network (MAN), or one or more portions of the Internet or a combination of two or more of these. One or more portions of one or more of these networks may be wired or wireless. As an example, computer system 900 may communicate with a wireless PAN (WPAN) (such as, for example, a BLUETOOTH WPAN), a WI-FI network, a WI-MAX network, a cellular telephone network (such as, for example, a Global System for Mobile Communications (GSM) network), or other suitable wireless network or a combination of two or more of these. Computer system 900 may include any suitable communication interface 910 for any of these networks, where appropriate. Communication interface 910 may include one or more communication interfaces 910, where appropriate. Although this disclosure describes and illustrates a particular communication interface, this disclosure contemplates any suitable communication interface. In particular embodiments, bus 912 includes hardware, software, or both coupling components of computer system 900 to each other. As an example and not by way of limitation, bus 912 may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a front-side bus (FSB), a HYPERTRANSPORT (HT) interconnect, an Industry Standard Architecture (ISA) bus, an INFINIBAND interconnect, a low-pin-count (LPC) bus, a memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCIe) bus, a serial advanced technology attachment (SATA) bus, a Video Electronics Standards Association local (VLB) bus, or another suitable bus or a combination of two or more of these. Bus 912 may include one or more buses 912, where appropriate. Although this disclosure describes and illustrates a particular bus, this disclosure contemplates any suitable bus or interconnect. Herein, a computer-readable non-transitory storage medium or media may include one or more semiconductor-based or other integrated circuits (ICs) (such, as for example, field-programmable gate arrays (FPGAs) or application-specific ICs (ASICs)), hard disk drives (HDDs), hybrid hard drives (HHDs), optical discs, optical disc drives (ODDs), magneto-optical discs, magneto-optical drives, floppy diskettes, floppy disk drives (FDDs), magnetic tapes, solid-state drives (SSDs), RAM-drives, SECURE DIGITAL cards or drives, any other suitable computer-readable non-transitory storage media, or any suitable combination of two or more of these, where appropriate. A computer-readable non-transitory storage medium may be volatile, non-volatile, or a combination of volatile and non-volatile, where appropriate. Herein, “or” is inclusive and not exclusive, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A or B” means “A, B, or both,” unless expressly indicated otherwise or indicated otherwise by context. Moreover, “and” is both joint and several, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A and B” means “A and B, jointly or severally,” unless expressly indicated otherwise or indicated otherwise by context. The scope of this disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments described or illustrated herein that a person having ordinary skill in the art would comprehend. The scope of this disclosure is not limited to the example embodiments described or illustrated herein. Moreover, although this disclosure describes and illustrates respective embodiments herein as including particular components, elements, functions, operations, or steps, any of these embodiments may include any combination or permutation of any of the components, elements, functions, operations, or steps described or illustrated anywhere herein that a person having ordinary skill in the art would comprehend. Furthermore, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. |
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claims | 1. An X-ray imaging apparatus comprising:a splitting element configured to spatially split an X-ray into multiple X-ray beams;a shielding unit including a shielding elements configured to block part of an X-ray acquired by the splitting element;a detecting unit including a pixel group, the pixel group including a first detection pixel and a second detection pixel, the pixels being configured to detect the intensity of the X-ray beam transmitted through the shielding unit; anda computing unit configured to compute X-ray transmittance of a test object on the basis of the intensity of the X-ray detected by the second detection pixel,wherein part of the X-ray beam detected at the first detection pixel is blocked by the shielding elements and the X-ray beam detected at the second detection pixel adjoining the first detection pixel is not blocked by the shielding element. 2. The X-ray imaging apparatus according to claim 1, wherein the shielding element is not disposed on the boundary between the first detection pixel and the second detection pixel. 3. The X-ray imaging apparatus according to claim 1, wherein the X-ray beam incident on the first detection pixel and the X-ray beam incident on the second detection pixel are split. 4. The X-ray imaging apparatus according to claim 1, wherein the X-ray beam incident on the first detection pixel and the X-ray beam incident on the second detection pixel are not split. 5. The X-ray imaging apparatus according to claim 1, wherein,the detection pixels not blocked by the shielding elements are linearly aligned in a first direction and a second direction orthogonal to the first direction, andtransmitting parts of the splitting element are linearly aligned in the first direction and disposed in a zigzag pattern in the second direction. 6. An X-ray imaging apparatus according to claim 1,wherein the positions of X-ray beams incident on the first detection pixels differ from the positions X-ray beams incident on the second detection pixels, and part of the X-ray beams incident on the first detection pixels is blocked by the shielding elements. 7. The X-ray imaging apparatus according to claim 1, wherein the first detection pixels include a region that is shielded from the X-ray beams by the shielding elements and a region that the X-ray beams are allowed to enter, and a dividing line between the region that is shielded from the X-ray beams and the region that the X-ray beams are allowed to enter is arranged not obliquely. 8. The X-ray imaging apparatus according to claim 1, wherein the detecting unit includes a plurality of pixel groups. 9. The X-ray imaging apparatus according to claim 8, wherein the computing unit computes an image of the test object associated with a phase shift of the X-ray beams based intensities of the X-ray beams detected at the first detection pixel and the second detection pixel. 10. An imaging method for an X-ray imaging apparatus, comprising the steps of:blocking part of spatially split X-ray beams by a shielding unit having a shielding elements;detecting the intensity of the X-ray beams transmitted through the shielding unit by a detecting unit including a pixel group, the pixel group including a first detection pixel and a second detection pixel;detecting an X-ray beam of which part is blocked by the shielding elements by the first detection pixel and detecting an X-ray beam of which part is not blocked by the shielding elements by the second detection pixel adjoining the first detection pixel; andcalculating X-ray transmittance of a test object on the basis of the intensity an X-ray beam detected by the second detection pixel. 11. The imaging method according to claim 10, further comprising a step of:computing a differential phase contrast image or a phase contrast image of the test object on the basis of the intensities of X-ray beam detected by the first detection pixel and the second detection pixel. 12. The imaging method according to claim 10, wherein the first detection pixels include a region that is shielded from the X-ray beams by the shielding elements and a region that the X-ray beams are allowed to enter, and a dividing line between the region that is shielded from the X-ray beams and the region that the X-ray beams are allowed to enter is arranged not obliquely. 13. The imaging method according to claim 10, wherein the detecting unit includes a plurality of pixel groups. 14. An X-ray imaging apparatus comprising:a splitting element configured to spatially split an X-ray;a shielding unit including a plurality of shielding element configured to block part of X-ray beams acquired by the splitting element; anda detecting unit including a plurality of pixel groups, each pixel group including a first detection pixel and a second detection pixel, the pixels being configured to detect the intensity of the X-ray beam transmitted through the shielding unit; anda computing unit configured to compute X-ray transmittance of a test object on the basis of the intensity of the X-ray detected by the second detection pixel,wherein the shielding elements are disposed on the first detection pixel and are not disposed on the second detection pixel. 15. The X-ray imaging apparatus according to claim 14, wherein the first detection pixels include a region that is shielded from the X-ray beams by the shielding elements and a region that the X-ray beams are allowed to enter, and a dividing line between the region that is shielded from the X-ray beams and the region that the X-ray beams are allowed to enter is arranged not obliquely. 16. An X-ray imaging apparatus comprising:a splitting element configured to spatially split an X-ray into multiple X-ray beams;a shielding unit including a plurality of shielding elements configured to block part of an X-ray acquired by the splitting element; anda detecting unit including a plurality of pixel groups, each pixel group including a first detection pixel and a second detection pixel, the pixels being configured to detect the intensity of the X-ray beam transmitted through the shielding unit,wherein part of the X-ray beam detected at the first detection pixel is blocked by the shielding elements and the X-ray beam detected at the second detection pixel adjoining the first detection pixel is not blocked by the shielding elements, andwherein, among the plurality of pixel groups, a first detection pixel and a second detection pixel included in each pixel group are alternately arranged in the detecting unit in one or more directions. |
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description | This application claims priority to U.S. provisional patent application 61/512,988, filed Jul. 29, 2011, hereby fully incorporated by reference. The United States Government has rights in this invention pursuant to Contract No. DE-AC07-051D14517, between the U.S. Department of Energy (DOE) and Contractor. The present invention relates to nuclear fuel and to methods for fabricating the same. Traditional reactor fuel efficiencies are limited by design. In traditional reactors, neutrons interact with the fissile material creating fission-products that cannot be transmuted. This expedites fission product buildup and causes swelling. Consequently, substantial fission product poisoning negatively affects nuclear fuel longevity and efficiency. Compared to traditional reactors, fast reactors are more immune to fission product poisoning. The fission-products created can be further transmuted, using more fuel, more efficiently. However, more fission-products and helium gas are created due to the increased number of transmutations that occur. Additionally, the extra fission-products and fission gases cause fuel swelling because current fuel designs cannot accommodate fission product buildup within the fuel. This causes accelerated damage of the nuclear fuel and cladding due to the excessive swelling. Therefore, there is a need for a nuclear fuel, and a process for fabricating it, that limits fuel swelling by accommodating fission-products and gases, and, as a result, facilitating higher burnup rates. A method of fabricating a nuclear fuel comprising providing a fissile material, one or more hollow microballoons, and a phenolic resin. The one or more hollow microballoons comprising carbon. The fissile material, phenolic resin and the one or more hollow microballoons are combined. The combined fissile material, phenolic resin and the one or more hollow microballoons are heated sufficiently to form at least some fissile material carbides creating a nuclear fuel particle. The resulting nuclear fuel particle comprises one or more fission product collection spaces. In a preferred embodiment, the fissile material, phenolic resin and the one or more hollow microballoons are combined by forming the fissile material into microspheres. The fissile material microspheres are then overcoated with a microballon mixture of the phenolic resin and microballoons. In another preferred embodiment, the fissile material, phenolic resin and the one or more hollow microballoons are combined by particle spheronization. In an another preferred embodiment the microballoons and phenolic resin are spheronized and then overcoated with the fissile material. A method of fabricating a nuclear fuel comprising providing a fissile material, one or more hollow microballoons, and a phenolic resin. The one or more hollow microballoons comprising carbon. The fissile material, phenolic resin and the one or more hollow microballoons are combined. The combined fissile material, phenolic resin and the one or more hollow microballoons are heated sufficiently to form at least some fissile material carbides creating a nuclear fuel particle. The resulting nuclear fuel particle comprises one or more fission product collection spaces. In a preferred embodiment, the fissile material, phenolic resin and the one or more hollow microballoons are combined by forming the fissile material into microspheres. The fissile material microspheres are then overcoated with a microballon mixture of the phenolic resin and microballoon. In another preferred embodiment, the fissile material, phenolic resin and the one or more hollow microballoons are combined by spheronizing the microballoons and phenolic resin and then overcoating with the fissile material. In another preferred embodiment, the fissile material, phenolic resin and the one or more hollow microballoons are all combined by spheronizing the mixture. Fissile material comprises any fissile, or combination of fissile materials, that is capable of undergoing fission or is fissionable. The fissile material preferably comprises transuranics including, but not limited to: U metal, UO2, UN, UC, Pu metal, and PuO2, or a combination thereof. In a preferred embodiment, the fissile material is a fissile material oxide. Preferably, the fissile material is eventually thermally treated in a carbothermic reduction of the oxide to form fissile material carbides. Preferably, the fissile material is melted and electrochemically separated to remove residual salts, or dissolved and aqueously separated to remove fission products and undesirable elements. In a preferred embodiment, the fissile material is first atomized into solid microspheres. Preferably, the fissile material is gelation precipitated, formed using the Wurster Process, atomized by shot tower, gas atomization, or rotating electrode atomization, or spheronized from powder. Preferably, the solid microspheres of fissile material have a representative diameter between approximately 2-500 microns. A representative diameter is the average distance across a cross-section of any shape, for example cubes, cuboids, spheres, cylinders, cone, triangular prism, hexagonal prism, square-based pyramid, hexagonal pyramid, spheroids, etc, The one or more hollow microballoons each comprises a hollow shell. The shell of each microballon comprises carbon. Preferably, each hollow microballon has a representative diameter of approximately 2 to 60 μm and a spherical or spheroid geometry. Preferably, each hollow microballon has a partial vacuum. In one preferred embodiment, each hollow microballoons has a tap density of approximately 0.146 g/cm3 or approximately 6% of the density of graphite. In another preferred embodiment, each hollow microballon has a tap density of approximately 0.265 g/cm3 or approximately 12% of the density of graphite. In one preferred embodiment, the one or more hollow microballoons are made using the method discussed in U.S. Pat. No. 7,749,456, hereby fully incorporated by reference. Briefly, in this embodiment, a cured phenolic resin microballoon is heated using a heat dissipation reactor in a furnace. The phenolic resin microballoons are preferably carbonized by subjecting the phenolic resin microballoons to a stepped heating cycle that incrementally heats the phenolic resin microballoons over several hours, and then cools the phenolic resin microballoons over several hours until the phenolic resin microballoons are completely converted into carbon microballoons. The resulting one or more hollow microballoons are then preferably sized using a cyclone separation. Preferably, the one or more hollow microballoons are thermally treated to over 2,400° C. in a vacuum. The Phenolic resin is capable of bonding with the fissile material and the one or more microballoons. The phenolic resin is preferably a synthetic thermosetting resin such as obtained by the reaction of hydroxybenzine with formaldehyde. Preferably, the phenolic resin is formed by a step-growth polymerization reaction that can be either acid-catalyzed or alkaline-catalyzed. Preferably, the phenolic resin is cured sufficiently to remove volatile organic and preferably from the resin and preferably form the resin into a glassy carbon structure. In a preferred embodiment, the phenolic resin is an acid catalyzed resin using Hexamethylenetetramine as the hardening agent (formaldehyde donor). The fissile material, phenolic resin and one or more microballoons are combined, preferably into a plurality of granules. In a preferred embodiment, the combination of fissile material, phenolic resin and one or more microballoons is combined by overcoating one or more of the fissile material, phenolic resin and microballoons using a process such as the GRANUREX process trademarked by VECTOR Corporation. In this process, the interior of a conical rotor chamber is maintained at a slight vacuum, and pressurized air is allowed to flow around the interior to fluidize the starting particles. The coating particles are also vacuum inducted into the interior of the conical chamber, thereby coating the particles. In one embodiment, the microballoons are overcoated with a fissile matrix of the resin and fissile material. More preferably, fissile material granules are overcoated with a microballon mixture of the resin and microballoons. Preferably, the combination of fissile material, phenolic resin and the one or more hollow microballoons has excess carbon, thereby enhancing the production of fissile carbides during heating. The combined fissile material, phenolic resin and the one or more hollow microballoons are heated sufficiently to form at least some fissile material carbides creating a nuclear fuel particle with one or more fission product collection spaces. Preferably, the combined fissile material, phenolic resin and the one or more hollow microballoons are heated to a temperature greater than 1,400° C. to form fissile material carbides. In a preferred embodiment, the heating is conducted in a vacuum, soaking the agglomerated microballoons and fissile material at approximately 1,800° C. for four hours or until complete bonding between the one or more microballoons and fissile material has occurred for densification. In a preferred embodiment the one or more microballoons form a bonded honeycomb structure when the carbon from the phenolic resin reacts with the fissile material. Preferably, the resulting nuclear fuel particle is substantially carbides of the fissile material. Preferably, the resin is cured at a temperature up to 200° C., thereby holding the nuclear fuel particle together during any future carbonization and heat treatments of the nuclear fuel particle. In a preferred embodiment, the resin is an uncured, solid powder during overcoating, heated to a viscous liquid and then cured at a temperature up to 200° C., thereby holding the nuclear fuel particle together during any future carbonization and heat treatments of the nuclear fuel particle. The one or more fission product collection spaces are capable of capturing fission products during the fission of the nuclear fuel particle. Preferably, the one or more fission product collection spaces are generated from the one or more hollow microballoons. Preferably, the one or more hollow microballoons are heated in the fissile material thereby creating voids. In one preferred embodiment, the one or more fission product collection spaces are voids generated from heating and reacting the one or more hollow microspheres and glassy carbon from the resin with the fissile material, preferably generating fissile material carbides. The one or more fission product collection spaces reduce fuel swelling that compromises nuclear fuel particle cladding integrity. As the internal pressure of the fuel increases as the buildup of solid and gaseous fission-products occurs, the fission-products are isolated from the fuel in the fission product collection spaces, eliminating fuel swelling. Consequently, damage due to fuel swelling to any surrounding cladding at the fuel interface due to swelling is reduced, or more preferably eliminated. Fabricating fuel with fission product collection spaces substantially reduces the risk of a breach of the cladding, lengthens the life of the nuclear fuel particle and increases efficiency. The fission product collection spaces prevent the corrosion and swelling of the resulting nuclear fuel particle by isolating fission-products away from any fuel cladding. In addition, because the fission product collection spaces are contained within the nuclear fuel particle, the need for plenum space at either end of the fuel rod is eliminated. Eliminating the need for plenum space at either end of the fuel rod shortens the length of the fuel rod or allows for more fuel to be used in one fuel rod. Additionally, because the fission-products are fully contained within the one or more fission product collection spaces of nuclear fuel particle, one more barrier is added to the physical barriers that prevent the escape of the fission-products in case of a reactor breach. Preferably, the fission product collection spaces account for greater than 5%, but less than 50% of the resulting fuel particle by volume. Preferably, the resulting combination of fissile material, phenolic resin, and microballon is overcoated with a metal, preferably a powder, forming a metal matrix. In a preferred embodiment, the resulting combination of fissile material, phenolic resin, and microballon is overcoated with Zirconium (Zr), Titanium (Ti), Niobium (Nb), Ferritic or marensitic chromium steel (based on HT-9 or Mod 9Cr-1 Mo), ODS powder, Intermetallics (e.g., NiAl3), or a combination thereof. In a preferred embodiment, the resulting combination of fissile material, phenolic resin, and microballon is overcoated with zirconium, as zirconium materials have good neutronics characteristics, irradiation behavior with alpha microstructure, high temperature strength. The broad working range of temperatures of zirconium makes it a preferred candidate to be coupled with other metals, allowing a greater variety of materials to be used for nuclear fuel particles. In another preferred embodiment, the resulting combination of fissile material, phenolic resin, and microballon is overcoated with titanium materials as they have good high temperature properties and formability characteristics. Titanium is also fully miscible with zirconium, niobium, and tantalum (Ta). In yet another preferred embodiment, the resulting combination of fissile material, phenolic resin, and microballon is overcoated with niobium materials, as they have high melting points with good high temperature properties. A plurality of the nuclear fuel particle formed using one of the discussed methods herein is preferably compacted and extruded forming one or more fuel rods. Preferably, a plurality of the nuclear fuel particle formed using one of the discussed methods herein is preferably compacted and extruded forming one or more fuel rods at a temperature at least approximately 1,100° C., but less than the reaction temperature of the particles, preferably less than approximately 1,400° C. Preferably, the resulting fuel has a fissile material by volume fraction optimized for extrusion and the resulting rod fuel density, depending on various factors, for example, matrix metal, extrusion temperature, sodium bond barrier (if used), fissile material, cladding used etc. Preferably, the resulting fuel has less than approximately 30% fissile material by volume fraction, more preferably approximately 10 percent. The fuel rods are formed after the nuclear fuel particle is heated sufficiently to form at least some fissile material carbides, thereby maintaining the fission product collection spaces during the formation of the fuel rods. In a preferred embodiment, one or more fuel rods formed using one of the above discussed methods, is encapsulated in a cladding. The cladding is preferably made of zirconium alloy. Preferably, the cladding is metallurgically bonded or sodium bonded with the fuel rod. Preferably, the fuel rods are cooled after they are formed and subsequently heated for alignment of microstructures of the, at a temperature less than the reaction temperature of the particles, more preferably less than approximately 1400° C. FIG. 6 shows a preferred embodiment of a nuclear fuel rod comprising a plurality of nuclear fuel particles. FIG. 6 shows a preferred embodiment of a nuclear fuel rod 40 that comprising a plurality of nuclear fuel particles 30 each comprising one or more fission product collection spaces as described above. The plurality of nuclear fuel particles 30 are mixed with a metal matrix, compacted, extruded to fuel core dimensions, sheared to core lengths, encapsulated in fuel cladding, and finished with a sodium bond. In a preferred embodiment the plurality of nuclear fuel particles 30 are extruded to form one or more fuel rods 40. The one or more fuel rods 40 are preferably chemically cleaned to remove any exposed fuel from the sectioned ends, and then enclosed in a cladding 42. The cladding 42 ends are preferably welded closed. Preferably, the fuel rods are cooled after they are formed and subsequently heated for alignment of microstructures of the cladding, at a temperature less than the reaction temperature of the particles, more preferably less than approximately 1,400° C. Each fission product collection space 24 is defined within the fissile material 22 and each fission product collection space 24 is capable of capturing fission-products produced from the fissions of the fissile material 22. In a preferred embodiment, the nuclear fuel particle 20 will have less than approximately 50 vol % fission-collection space 24 content. In one preferred embodiment, each fission product collection space 24 comprises a partial vacuum. In another preferred embodiment, when the fission product collection spaces 24 are created in a fluidized bed of a partial pressure, the fission product collection spaces 24 comprise fluidizing gas. The fission product collection spaces 24 are distinctly separate and from each other and are not connected to each other. Preferably, the location of the fission products collection spaces 24 is optimized for use in a nuclear reactor, preferably by distributing the fission product collection spaces 24 evenly across the nuclear fuel particle 20. Preferably, the fission product collection spaces 24 are spheroid in shape, including, but not limited to, both spheroids (ovals) and spheres (circles). Additionally, because the fission product collection spaces 24 are incorporated into the nuclear fuel particle 20 design, less fissile material 22 is necessary for fabrication of the nuclear fuel particle 20. This allows higher fuel fissile densities to be used when fabricating the nuclear fuel particle 20, and, higher burn-up efficiency is achieved because burn-up is limited to using the fissile material 22. The simplified composition of the nuclear fuel particle 20 not only allows for simplified manufacture but also allows the nuclear fuel particle 20 to be readily separated for fuel recycle. In one preferred embodiment, a plurality of nuclear particles 30 is mixed with a metal matrix forming a metal/particle matrix. Preferably, the metal/particle matrix is combined in a preformed canister. In a preferred embodiment, the metal comprises zirconium (Zr), titanium (Ti), niobium (Nb), and the preformed canister comprises zirconium alloy, ferritic or marensitic chromium steel (based on HT-9 or Mod 9Cr-1 Mo), or an ODS alloy. The plurality of nuclear fuel particles 30 mixed with a metal are preferably compacted in the preformed canister, the can is seal welded in vacuum, and enclosed in copper and a lubricant. Preferably, the plurality of nuclear fuel particles 30 mixed with a metal is coextruded and sectioned into one or more fuel rods 40. The one or more fuel rods 40 are preferably chemically cleaned to remove any exposed fuel from the sectioned ends, encapsulated in fuel cladding and finished with a sodium bond. Preferably, the fuel rods are cooled after they are formed and subsequently heated for alignment of microstructures of the cladding and metal matrix, at a temperature less than the reaction temperature of the particles, more preferably less than approximately 1,400° C. In one embodiment, a plurality of nuclear particles 30 is mixed with a metal forming a metal matrix. Preferably, the metal/particle matrix is combined in a preformed canister. In a preferred embodiment, the metal comprises Zirconium (Zr), Titanium (Ti), Niobium (Nb), and the preformed canister is zirconium alloy, ferritic or marensitic chromium steel (based on HT-9 or Mod 9Cr-1 Mo), or an ODS alloy. The plurality of nuclear fuel particles 30 mixed with a metal are is coextruded with the cladding material to form one or more fuel rods 40. In this embodiment, the plurality of plurality of nuclear fuel particles 30 mixed with a metal are compacted in a cladding 42 preform can, the can is seal welded in vacuum, and enclosed in copper and a lubricant. Then the plurality of nuclear fuel particles 30 mixed with a metal are coextruded and sectioned into one or more fuel rods 40. The one or more fuel rods 40 are each chemically cleaned to remove the copper and any exposed fissile material from the sectioned ends, and then the ends are hot swaged in preparation for the end cap. Preferably, hot swaging is completed by a tool that heats and deforms the end of each fuel rod 40, locally reducing the fuel rod diameter. After another chemical cleaning, end caps are brazed and welded, resistance welded, or friction-welded to each end of the fuel rods 40 to provide a fully hermetic fuel rod that prevents all attack of the fuel particles by reactor coolant. Preferably, the fuel rods are cooled after they are formed and subsequently heated for alignment of microstructures of the cladding and metal matrix, at a temperature less than the reaction temperature of the particles, more preferably less than approximately 1,400° C. It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present invention. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present invention and the appended claims are intended to cover such modifications and arrangements. All publications and patent documents cited in this application are incorporated by reference in their entirety for all purposes to the same extent as if each individual publication or patent document were so individually denoted. Any element in a claim that does not explicitly state “means for” performing a specified function, or “step for” performing a specific function, is not to be interpreted as a “means” or “step” clause as specified in 35 U.S.C.§112, ¶ 6. In particular, the use of “step of” in the claims herein is not intended to invoke the provisions of 35 U.S.C.§112, ¶ 6. |
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abstract | A neutron beam controlling apparatus includes a plurality of multilayered plate members, each having on one or both of its surfaces, one or more minute protruding portions. Each of the protruding portions is a long and narrow protrusion extending in an area-wise direction and having both an inclined surface that is inclined against the beam axis of neutron beam and serves as an incident plane or an outgoing plane for the neutron beam and a surface approximately normal to the plate member. |
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summary | ||
abstract | We disclose a gripper and associated apparatus and methods for delivering nano-manipulator probe tips inside a vacuum chamber. The gripper includes a tube; a compression cylinder inside of and coaxial with the tube; and at least one elastic ring adjacent to the compression cylinder. There is a vacuum seal coaxial with the compression cylinder for receiving and sealing against a probe tip. An actuator is connected to the compression cylinder for compressing the elastic ring and causing it to grip the probe tip. Thus the probe tip can be gripped, transferred to a different location in the vacuum chamber, and released there. |
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abstract | According to an embodiment, a core catcher has: a main body including: a distributor arranged on a part of a base mat in the lower dry well, a basin arranged on the distributor, cooling channels arranged on a lower surface of the basin connected to the distributor and extending in radial directions, and a riser connected to the cooling channels and extending upward; a lid connected to an upper end of the riser and covering the main body; a cooling water injection pipe open, at one end, to the suppression pool, connected at another end to the distributor; and chimney pipes connected, at one end, to the riser, another end being located above the upper end of the riser and submerged and open in the pool water. |
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summary | ||
abstract | A nuclear fuel includes a volume of a nuclear fuel material defined by a surface, the nuclear fuel material including a plurality of grains, some of the plurality of grains having a characteristic length along at least one dimension that is smaller than or equal to a selected distance, wherein the selected distance is suitable for maintaining adequate diffusion of a fission product from a grain interior to a grain boundary in some of the grains, the nuclear fuel material including a boundary network configured to transport the fission product from at least one grain boundary of some of the grains to the surface of the volume of the nuclear fuel material. |
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description | For purposes of the USPTO extra-statutory requirements, the present application constitutes a continuation-in-part of U.S. patent application Ser. No. 12/800,400, entitled LIQUID FUEL NUCLEAR FISSION REACTOR, naming Roderick A. Hyde and Jon D. McWhirter as inventors, filed May 25, 2010, now U.S. Pat. No. 9,183,953 which is currently co-pending, or is an application of which a currently co-pending application is entitled to the benefit of the filing date. The present application is related to and claims the benefit of the earliest available effective filing date(s) from the following listed application(s) (the “Related Applications”) (e.g., claims earliest available priority dates for other than provisional patent applications or claims benefits under 35 USC § 119(e) for provisional patent applications, for any and all parent, grandparent, great-grandparent, etc. applications of the Related Application(s)). All subject matter of the Related Applications and of any and all parent, grandparent, great-grandparent, etc. applications of the Related Applications is incorporated herein by reference to the extent such subject matter is not inconsistent herewith. The United States Patent Office (USPTO) has published a notice to the effect that the USPTO's computer programs require that patent applicants reference both a serial number and indicate whether an application is a continuation or continuation-in-part. Stephen G. Kunin, Benefit of Prior-Filed Application, USPTO Official Gazette Mar. 18, 2003, available at http://www.uspto.gov/web/offices/com/sol/og/2003/week 11/patbene.htm. The present Applicant Entity (hereinafter “Applicant”) has provided above a specific reference to the application(s) from which priority is being claimed as recited by statute. Applicant understands that the statute is unambiguous in its specific reference language and does not require either a serial number or any characterization, such as “continuation” or “continuation-in-part,” for claiming priority to U.S. patent applications. Notwithstanding the foregoing, Applicant understands that the USPTO's computer programs have certain data entry requirements, and hence Applicant is designating the present application as a continuation-in-part of its parent applications as set forth above, but expressly points out that such designations are not to be construed in any way as any type of commentary and/or admission as to whether or not the present application contains any new matter in addition to the matter of its parent application(s). This patent application relates to nuclear fission reactors. Disclosed embodiments include nuclear fission reactors, nuclear fission fuel pins, methods of operating a nuclear fission reactor, methods of fueling a nuclear fission reactor, and methods of fabricating a nuclear fission fuel pin. The foregoing is a summary and thus may contain simplifications. generalizations, inclusions, and/or omissions of detail; consequently, those skilled in the art will appreciate that the summary is illustrative only and is NOT intended to be in any way limiting. Other aspects, features, and advantages of the devices and/or processes and/or other subject matter described herein will become apparent in the teachings set forth herein. In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. The present application uses formal outline headings for clarity of presentation. However, it is to be understood that the outline headings are for presentation purposes, and that different types of subject matter may be discussed throughout the application (e.g., devices/structures may be described under processes/operations headings and/or processes/operations may be discussed under structures/processes headings; and/or descriptions of single topics may span two or more topic headings). Hence, the use of the formal outline headings is not intended to be in any way limiting. Illustrative Nuclear Fission Reactors Given by way of overview and referring to FIG. 1A, in a non-limiting embodiment an illustrative nuclear fission reactor 10 includes a reactor vessel 12. A solution 14 of fissile nuclear fission fuel material dissolved in neutronically translucent liquid carrier material is received in the reactor vessel 12. Undissolved fertile nuclear fission fuel material 16 is disposed in contact with the solution 14. The fertile nuclear fission fuel material 16 is transmutable into the fissile nuclear fission fuel material. Still by way of overview, in operation a portion of the undissolved fertile nuclear fission fuel material 16 is transmuted into the fissile nuclear fission fuel material. The transmuted fissile nuclear fission fuel material is diffused to the solution 14. Thus, in some embodiments diffusion of transmuted fissile nuclear fission fuel material to the solution 14 could help replenish a portion of the fissile nuclear fission fuel material that is consumed during fissioning of the fissile nuclear fission fuel material. Non-limiting, illustrative details will be set forth below by way of example and not of limitation. Still referring to FIG. 1A, solubility of the fissile nuclear fission fuel material in the neutronically translucent liquid carrier material is greater than solubility of the fertile nuclear fission fuel material 16 in the neutronically translucent liquid carrier material. In some embodiments and as mentioned above, the fissile nuclear fission fuel material is solvable in the neutronically translucent liquid carrier material, thereby making the solution 14. In some embodiments, the fertile nuclear fission fuel material 16 is substantially insoluble in the neutronically translucent liquid carrier material. The liquid carrier material, the fissile nuclear fission fuel material, and the fertile nuclear fission fuel material 16 may be selected among as desired according to the above solubility and neutronic translucency relationships. For example, in various embodiments the neutronically translucent liquid carrier material may include liquid materials such as Mg, Ag, Ca, Ni, and the like. In some embodiments the fissile nuclear fission fuel material may include 239Pu. Also, in some embodiments the fertile nuclear fission fuel material 16 may include 238U. An example will be explained by way of illustration and not of limitation. In one illustrative embodiment, the liquid carrier material may include liquid Mg, the fissile nuclear fission fuel material may include 239Pu, and the fertile nuclear fission fuel material 16 may include 238U. In such an illustrative case, Mg has a melting point around 650° C. The liquid Mg carrier material is a solvent for the 239Pu fissile nuclear fission fuel material, and the plutonium lowers the melting point of the magnesium. Given by way of non-limiting example, at around 5 atom percent Pu, a eutectic composition is formed with a melting temperature of around 600° C. The liquid Mg carrier material is not a solvent for the 238U fertile nuclear fission fuel material 16 (and is substantially immiscible in solid and liquid form). Also, Mg has a neutron absorption cross section in the fast spectrum on the order of around 1 mb. Such a low neutron cross section in the fast spectrum thus makes the liquid Mg carrier material neutronically translucent to the 239Pu fissile nuclear fission fuel material. It will be appreciated that mass transfer diffusion coefficients affect diffusion of the transmuted fissile nuclear fission fuel material. For the non-limiting combination of materials discussed above, the mass transfer diffusion coefficient for Pu through liquid Mg is approximately 1E-05 cm2/s. As will be discussed further below, the transmuted fissile nuclear fission fuel material first diffuses through the fertile nuclear fission fuel material 16 to get to the solution 14. With that in mind, the mass transfer diffusion coefficient for Pu through U is approximately 1E-12 cm2/s. As mentioned above, the undissolved fertile nuclear fission fuel material 16 is disposed in contact with the solution 14. In some embodiments, the fertile nuclear fission fuel material 16 may be in direct physical contact with the neutronically translucent liquid carrier material. Moreover, in some embodiments the fertile nuclear fission fuel material 16 may be suspended in the neutronically translucent liquid carrier material. To that end, in some embodiments the fertile nuclear fission fuel material 16 may be provided in solid form. In various embodiments, the fertile nuclear fission fuel material may be provided in various forms such as granular form, wire form, plate form, foam form, and the like. Regardless of form in which the fertile nuclear fission fuel material is provided and as mentioned above, the transmuted fissile nuclear fission fuel material first diffuses through the fertile nuclear fission fuel material 16 to get to the solution 14. It will be appreciated that the larger the specific surface area provided by the form of the fertile nuclear fission fuel material, the greater the rate of diffusion of transmuted fissile nuclear fission fuel material through the fertile nuclear fission fuel material to the liquid carrier material. It will also be appreciated that, when the fertile nuclear fission fuel material is provided in granular form, a small particle size can help introduce a large concentration gradient (of transmuted fissile nuclear fission fuel material) without large differences in concentration (between transmuted fissile nuclear fission fuel material distributed in the fertile nuclear fission fuel material and fissile nuclear fission fuel material dissolved in the neutronically translucent liquid carrier material). Thus, a concentration of the fissile nuclear fission fuel material in the fertile nuclear fission fuel material 16 is established that is greater than a concentration of the fissile nuclear fission fuel material in the neutronically translucent liquid carrier material. It is this concentration gradient that causes the transmuted fissile nuclear fission fuel material to diffuse through the fertile nuclear fission fuel material 16 to the solution 14. Still referring to FIG. 1A, the solution 14 and the fertile nuclear fission fuel material 16 may be distributed in the reactor vessel 12 in any manner as desired. To that end, no limitation is implied, and is not to be inferred, from the illustration shown in FIG. 1A. Referring now to FIG. 1B, in some embodiments the solution 14 and the fertile nuclear fission fuel material 16 may be distributed homogeneously in the reactor vessel 12. For example, the fertile nuclear fission fuel material 16 may be provided in any format that may lend itself to homogeneous distribution within the solution 14, such as without limitation any one or more format like pellets, rods, particle suspension, foam, and the like. Given by way of nonlimiting example of a homogeneous distribution, for depleted U in the 60 v/o range, 8-9 v/o of Pu in Mg is entailed in order to attain a potentially critical configuration (that is, k∞>1). Too much depleted U by volume results in k∞<1, which is not useable as a fuel (that is, it does not become self-sustaining). At about 9 v/o Pu in Mg (around 50 w/o Pu), liquid Pu comes out of solution from the Mg and forms a two liquid system, so this is another constraint on the level of Pu from the high end. The effect of the depleted U on k∞ can be reduced in any one or more of several ways, such as by: (i) suspending the U at a reduced concentration in the Pu—Mg solution, thereby resulting in a higher k∞; or (ii) diluting the U with a solid, insoluble, neutronically translucent material such as MgO; or (iii) providing the U in a foam form with much higher porosity and hence lower concentration, thereby resulting in a higher k∞. In any of these cases, if the U content is reduced to below about 50 v/o, then a lower Pu concentration, such as on the order of around 3-5 v/o, can result in k∞>1. In some other embodiments and referring to FIGS. 1C and 1D, the solution 14 and the fertile nuclear fission fuel material 16 may be distributed heterogeneously in the reactor vessel 12. The heterogeneous distribution may be any heterogeneous distribution as desired and is not intended to be limited to heterogeneous distributions shown in the drawings. Given by way of non-limiting example and as shown in FIG. 1C, in some embodiments a portion 18 of the solution 14 may be received in a fission region 20 of the reactor vessel 12. The fertile nuclear fission fuel material 16 and a portion 22 of the solution 14 may be received in a fertile blanket region 24 of the reactor vessel 12. In such embodiments, the fertile blanket region 24 is in hydraulic communication with the fission region 20 (because the liquid carrier material occupies the fission region 20 and the fertile blanket region 24) and neutronic communication with the fission region 20 (because the solution 14 of the fissile nuclear fission fuel material dissolved in the neutronically translucent liquid carrier material occupies the fission region 20 and the fertile blanket region 24). In other embodiments and referring now to FIG. 1E, nuclear fission fuel pins 26 may be received in the reactor vessel 12. Each nuclear fission fuel pin 26 has an axial end 28 and an axial end 30. Referring additionally to FIG. 1F, in some embodiments a portion 32 of at least one of the nuclear fission fuel pins 26 may be disposed in the fission region 20 and at least a portion 34 of the at least one nuclear fission fuel pin 26 may be disposed in a fertile blanket region 24. Referring additionally to FIG. 1G, in some embodiments the solution 14 is distributed throughout each of the plurality of nuclear fission fuel pins 26 and the fertile nuclear fission fuel material 16 may be received in fertile blanket zones 36 and 38 disposed toward the axial ends 28 and 30. Thus, it will be appreciated that in some embodiments a fertile blanket region 24 (FIG. 1F) could be located toward the axial ends 28 of the nuclear fission fuel pins 26 and another fertile blanket region 24 (FIG. 1F) could be located toward the axial ends 30 of the nuclear fission fuel pins 26. Referring now to FIGS. 1H and 1J, in some embodiments fertile blanket modules 40 may be disposed in the fertile blanket region 20. In such embodiments the fertile nuclear fission fuel material 16 is received in the fertile blanket modules 40. Referring now to FIGS. 1I and 1J, in some embodiments at least one heat exchanger element 42 may be disposed in thermal communication with the solution 14. FIG. 1I represents a general depiction of an embodiment in partial schematic form while FIG. 1J represents a more detailed view of an embodiment that includes the fertile blanket modules 40. In some cases, the heat exchanger element 42 may be immersed in the solution 14. Also, in some cases an annulus 44 may be disposed in the reactor vessel 12 adjacent the heat exchanger element 42 such that natural circulation of the solution may be established through the heat exchanger element 42 and around the annulus 44. To that end, the reactor vessel 12 is filled with the solution 14 up to a level 45 that is above the heat exchanger element 42 and the annulus 44. In such an arrangement, heat from fission in the fission region 20 causes the fissile solution 14 to rise, as indicated by arrow 46. The rising solution 14 flows around the annulus 44 into the heat exchanger element 42, as indicated by arrows 47. The heat exchanger element 42 cools the solution 14 that flows therethrough. The solution 14 that has been cooled by the heat exchanger element 42 moves downwardly as indicated by arrows 48. The downwardly-flowing solution 14 flows around the annulus 44 and into the fission region 20, as indicated by arrows 49, thereby establishing a natural circulation loop. It will be appreciated that reactivity may be controlled in any manner as desired. For example, given by way of illustration and not of limitation, reactivity may be controlled by way of any one or more illustrative reactivity control methodologies, such as without limitation: dissolving neutron absorbing poisons in the liquid carrier material; inserting and extracting control rods (not shown) of neutron absorbing material into and out of the solution 14; redistributing the fertile nuclear fission fuel material 16 and the fissile nuclear fission fuel material as desired; adding neutronically translucent liquid carrier material to reduce concentration of fissile nuclear fission fuel material in the neutronically translucent liquid carrier material; inserting neutronically translucent material to displace the solution 14 (that contains fissile nuclear fission fuel material); and/or the like. Reactivity may be controlled in similar manners in all embodiments disclosed herein. As such, for the sake of brevity, details of reactivity control need not be repeated in all embodiments for an understanding of the disclosed embodiments. Now that an overview of embodiments and aspects has been set forth, additional embodiments, aspects, and illustrative details will be described. In the interest of brevity, details for components that are common to previously-described embodiments need not and will not be repeated, and the same reference numbers will be re-used. Referring now to FIGS. 2A and 2B, a nuclear fission reactor 210 includes a reactor vessel 12 having a solution 14 of fissile nuclear fission material dissolved in neutronically translucent liquid carrier material. The reactor vessel 12 defines a fission region 20 toward a centralized region 221 of the reactor vessel 12 and a fertile blanket region 24 toward a peripheral region 225 of the reactor vessel 12. Undissolved fertile nuclear fission fuel material 16 is disposed in the fertile blanket region 24 in contact with the solution. The fertile nuclear fission fuel material 16 is transmutable into the fissile nuclear fission material. In some embodiments the reactor vessel 12 may be cylindrical. In such cases and as shown in FIG. 2A, the peripheral region 225 may include a radially peripheral region. However, the reactor vessel 12 need not be cylindrical, and may have any shape as desired. Regardless of shape of the reactor vessel 12 and as shown in FIG. 2B, in some embodiments the peripheral region 225 may include an axially peripheral region. As also shown in FIG. 2B, it will be appreciated that fertile blanket regions 24 may be established at both axially peripheral regions 225. However, it will also be appreciated that fertile blanket regions 24 need not be established at both axially peripheral regions 225. To that end and in some embodiments, a fertile blanket region 24 may be established at either one but not both of the axially peripheral regions 225. Some aspects that previously have been explained in detail will be mentioned briefly below. As discussed above, solubility of the fissile nuclear fission fuel material in the neutronically translucent liquid carrier material is greater than solubility of the fertile nuclear fission fuel material 16 in the neutronically translucent liquid carrier material. In some embodiments and as mentioned above, the fissile nuclear fission fuel material is solvable in the neutronically translucent liquid carrier material, thereby making the solution 14. In some embodiments, the fertile nuclear fission fuel material 16 is substantially insoluble in the neutronically translucent liquid carrier material. In various embodiments, the neutronically translucent liquid carrier material may include liquid materials such as Mg, Ag, Ca, Ni, and the like. In some embodiments the fissile nuclear fission fuel material may include 239Pu. Also, in some embodiments the fertile nuclear fission fuel material 16 may include 238U. As mentioned above, the undissolved fertile nuclear fission fuel material 16 is disposed in contact with the solution 14. In some embodiments, the fertile nuclear fission fuel material 16 may be in direct physical contact with the neutronically translucent liquid carrier material. Moreover, in some embodiments the fertile nuclear fission fuel material 16 may be suspended in the neutronically translucent liquid carrier material. In some embodiments the fertile nuclear fission fuel material 16 may be provided in solid form. In various embodiments, the fertile nuclear fission fuel material may be provided various forms such as granular form, wire form, plate form, foam form, and the like. Referring now to FIGS. 2C and 2E, in some embodiments fertile blanket modules 40 may be disposed in the fertile blanket region 20 toward the peripheral region 225. In such embodiments the fertile nuclear fission fuel material 16 is received in the fertile blanket modules 40. Referring now to FIGS. 2D and 2E, in some embodiments at least one heat exchanger element 42 may be disposed in thermal communication with the solution 14. FIG. 2D represents a general depiction of an embodiment in partial schematic form while FIG. 2E represents a more detailed view of an embodiment that includes the fertile blanket modules 40 disposed toward the peripheral region 225. In some cases, the heat exchanger element 42 may be immersed in the solution 14. Also, in some cases an annulus 44 may be disposed in the reactor vessel 12 adjacent the heat exchanger element 42 such that natural circulation of the solution may be established through the heat exchanger element 42 and around the annulus 44. Details are similar to those described above with reference to FIGS. 1H-1J and need not be repeated. Referring now to FIG. 3A, in another illustrative embodiment a nuclear fission reactor 300 includes a reactor vessel 12 and nuclear fission fuel pins 26 received in the reactor vessel 12. Each nuclear fission fuel pin has an axial end 28 and an axial end 30. A solution 14 of fissile nuclear fission material is dissolved in neutronically translucent liquid carrier material, and the solution 14 is distributed throughout each nuclear fission fuel pin 26. A centralized axial region 321 of the nuclear fission fuel pins 26 defines a fission region 20 of the reactor vessel 12. Undissolved fertile nuclear fission fuel material 16 is disposed in contact with the solution in fertile blanket zones 36 and 38 disposed toward the axial ends 28 and 30, respectively, of each nuclear fission fuel pin 26. The fertile nuclear fission fuel material 16 is transmutable into the fissile nuclear fission material. The fertile blanket zones 36 and 38 of the nuclear fission fuel pins 26 define the fertile blanket regions 24. An illustrative nuclear fission fuel pin 26 has been discussed above with reference to FIG. 1G, and its details need not be repeated. Some aspects that previously have been explained in detail will be mentioned briefly below. As discussed above, solubility of the fissile nuclear fission fuel material in the neutronically translucent liquid carrier material is greater than solubility of the fertile nuclear fission fuel material 16 in the neutronically translucent liquid carrier material. In some embodiments and as mentioned above, the fissile nuclear fission fuel material is solvable in the neutronically translucent liquid carrier material, thereby making the solution 14. In some embodiments, the fertile nuclear fission fuel material 16 is substantially insoluble in the neutronically translucent liquid carrier material. In various embodiments, the neutronically translucent liquid carrier material may include liquid materials such as Mg, Ag, Ca, Ni, and the like. In some embodiments the fissile nuclear fission fuel material may include 239Pu. Also, in some embodiments the fertile nuclear fission fuel material 16 may include 238U. As mentioned above, the undissolved fertile nuclear fission fuel material 16 is disposed in contact with the solution 14. In some embodiments, the fertile nuclear fission fuel material 16 may be in direct physical contact with the neutronically translucent liquid carrier material: Moreover, in some embodiments the fertile nuclear fission fuel material 16 may be suspended in the neutronically translucent liquid carrier material. In some embodiments the fertile nuclear fission fuel material 16 may be provided in solid form. In various embodiments, the fertile nuclear fission fuel material may be provided various forms such as granular form, wire form, plate form, foam form, and the like. Illustrative Nuclear Fission Fuel Pins Referring now to FIG. 4A, in another illustrative embodiment a nuclear fission fuel pin 426 includes cladding 450 that defines an elongated enclosure 452. A solution 14 of fissile nuclear fission fuel material is dissolved in neutronically translucent liquid carrier material. The solution 14 is distributed throughout the elongated enclosure 452. Undissolved fertile nuclear fission fuel material 16 is disposed in contact with the solution 14 in the elongated enclosure 452. The fertile nuclear fission fuel material 16 is transmutable into the fissile nuclear fission fuel material. In some embodiments the elongated enclosure 452 has axial ends 28 and 30 and a centralized axial region 29 between the axial ends 28 and 30. Still referring to FIG. 4A, the solution 14 and the fertile nuclear fission fuel material 16 may be distributed in the elongated enclosure 452 in any manner as desired. To that end, no limitation is implied, and is not to be inferred, from the illustration shown in FIG. 4A. In some embodiments the solution 14 and the fertile nuclear fission fuel material 16 may be distributed homogeneously in the elongated enclosure 452. Referring now to FIG. 4B, in some other embodiments the solution 14 and the fertile nuclear fission fuel material 16 may be distributed heterogeneously in the elongated enclosure 452. The heterogeneous distribution may be any heterogeneous distribution as desired and is not intended to be limited to heterogeneous distributions shown in the drawings. Still referring to FIG. 4B, in some embodiments the centralized axial region 29 defines a fission region 20 of the nuclear fission fuel pin 426. In some embodiments the fertile nuclear fission fuel material 16 may be disposed toward the axial ends 28 and 30. In such cases, the axial ends 28 and 30 may define fertile blanket zones 36 and 38, respectively, of the nuclear fission fuel pin 426. Some aspects that previously have been explained in detail will be mentioned briefly below. Referring now to FIGS. 4A and 4B and as discussed above, solubility of the fissile nuclear fission fuel material in the neutronically translucent liquid carrier material is greater than solubility of the fertile nuclear fission fuel material 16 in the neutronically translucent liquid carrier material. In some embodiments and as mentioned above, the fissile nuclear fission fuel material is solvable in the neutronically translucent liquid carrier material, thereby making the solution 14. In some embodiments, the fertile nuclear fission fuel material 16 is substantially insoluble in the neutronically translucent liquid carrier material. In various embodiments, the neutronically translucent liquid carrier material may include liquid materials such as Mg, Ag, Ca, Ni, and the like. In some embodiments the fissile nuclear fission fuel material may include 239Pu. Also, in some embodiments the fertile nuclear fission fuel material 16 may include 238U. As mentioned above, the undissolved fertile nuclear fission fuel material 16 is disposed in contact with the solution 14. In some embodiments, the fertile nuclear fission fuel material 16 may be in direct physical contact with the neutronically translucent liquid carrier material. Moreover, in some embodiments the fertile nuclear fission fuel material 16 may be suspended in the neutronically translucent liquid carrier material. In some embodiments the fertile nuclear fission fuel material 16 may be provided in solid form. In various embodiments, the fertile nuclear fission fuel material may be provided various forms such as granular form, wire form, plate form, foam form, and the like. Referring now to FIG. 4C, in some embodiments the fertile nuclear fission fuel material 16 may disposed in contact with a wall of the elongated enclosure 452. Given by way of non-limiting example, the fertile nuclear fission fuel material 16 may be disposed in contact with an inner surface 456 of the wall 454. Now that various embodiments including nuclear fission reactors and nuclear fission fuel pins have been discussed, other embodiments including various methods will be discussed below. Further illustrative details regarding neutronics and mass transfer will be set forth by way of non-limiting examples. Illustrative Methods Following are a series of flowcharts depicting implementations. For ease of understanding, the flowcharts are organized such that the initial flowcharts present implementations via an example implementation and thereafter the following flowcharts present alternate implementations and/or expansions of the initial flowchart as either sub-component operations or additional component operations building on one or more earlier-presented flowcharts. Those having skill in the art will appreciate that the style of presentation utilized herein (e.g., beginning with a presentation of a flowchart presenting an example implementation and thereafter providing additions to and/or further details in subsequent flowcharts) generally allows for a rapid and easy understanding of the various process implementations. In addition, those skilled in the art will further appreciate that the style of presentation used herein also lends itself well to modular and/or object-oriented program design paradigms. Illustrative details regarding the fissile nuclear fission fuel material, the neutronically translucent carrier material, the solution of the fissile nuclear fission fuel material dissolved in the neutronically translucent carrier material, and the fertile nuclear fission fuel material have been discussed above and need not be repeated in the context of the following illustrative, non-limiting methods. Referring, now to FIG. 5A, in an embodiment an illustrative method 500 is provided for operating a nuclear fission reactor. The method 500 starts at a block 502. At a block 504 a portion of undissolved fertile nuclear fission fuel material is transmuted into fissile nuclear fission fuel material, with the undissolved fertile nuclear fission fuel material being disposed in contact with a solution of the fissile nuclear fission fuel material dissolved in neutronically translucent liquid carrier material. Given by way of example and not of limitation, when 238U is exposed to a neutron flux, the 238U will be transmuted to 239Pu. More particularly, when an atom of 238U is exposed to a neutron flux, its nucleus will capture a neutron, thereby changing it to 239U. The 239U then rapidly undergoes two beta decays. After the 238U absorbs a neutron to become 239U it then emits an electron and an anti-neutrino (υϵ) by β− decay to become 239Np and then emits another electron and anti-neutrino by a second β− decay to become 239Pu. At a block 506 the transmuted fissile nuclear fission fuel material is diffused to the solution. The method 500 stops at a block 508. Referring additionally to FIG. 5B, in some embodiments at a block 510 intermediate transmuted material may be diffused to the solution. Given by way of non-limiting examples, as discussed above the intermediate transmuted material may include without limitation 239U and 239Np. Referring additionally to FIG. 5C, in some embodiments at a block 512 a portion of the fissile nuclear fission fuel material fissions. In such cases, fissioning of the fissile nuclear fission fuel material can provide the neutron flux to which the fertile nuclear fission fuel material is exposed, thereby causing transmuting of a portion of undissolved fertile nuclear fission fuel material at the block 504 (FIG. 5A). Referring additionally to FIG. 5D, in some embodiments diffusing the transmuted fissile nuclear fission fuel material to the solution at the block 506 may include diffusing the transmuted fissile nuclear fission fuel material through the undissolved fertile nuclear fission fuel material at a block 514. For example and as discussed above, regardless of form in which the fertile nuclear fission fuel material is provided, the larger the specific surface area provided by the form of the fertile nuclear fission fuel material, the greater the rate of diffusion of transmuted fissile nuclear fission fuel material through the fertile nuclear fission fuel material to the liquid carrier material. It will also be appreciated that, when the fertile nuclear fission fuel material is provided in granular form, a small particle size can help introduce a large concentration gradient (of dissolved fissile nuclear fission fuel material) without large differences in concentration (between transmuted fissile nuclear fission fuel material dissolved in the fertile nuclear fission fuel material and fissile nuclear fission fuel material dissolved in the neutronically translucent liquid carrier material). Thus, a concentration of the fissile nuclear fission fuel material in the fertile nuclear fission fuel material is established that is greater than a concentration of the fissile nuclear fission fuel material in the neutronically translucent liquid carrier material. It is this concentration gradient that causes the transmuted fissile nuclear fission fuel material to diffuse through the fertile nuclear fission fuel material to the solution. Referring now to FIG. 6A, in another illustrative embodiment a method 600 is provided for operating a nuclear fission reactor. The method 600 starts at a block 602. At a block 604 a first concentration is established of fissile nuclear fission fuel material in a solution of the fissile nuclear fission fuel material dissolved in neutronically translucent liquid carrier material. At a block 606 a second concentration is established of the fissile nuclear fission fuel material in undissolved fertile nuclear fission fuel material disposed in contact with the solution, with the second concentration being greater than the first concentration. At a block 608 fissile nuclear fission fuel material is diffused through the undissolved fertile nuclear fission fuel material toward the solution. The method 600 stops at a block 610. Referring additionally to FIG. 6B, in some embodiments establishing a first concentration of fissile nuclear fission fuel material in a solution of the fissile nuclear fission fuel material dissolved in neutronically translucent liquid carrier material at the block 604 may include consuming a portion of the fissile nuclear fission fuel material in the solution of the fissile nuclear fission fuel material dissolved in neutronically translucent liquid carrier material at a block 612. Referring additionally to FIG. 6C and given by way of non-limiting example, consuming a portion of the fissile nuclear fission fuel material in the solution of the fissile nuclear fission fuel material dissolved in neutronically translucent liquid carrier material at the block 612 may include fissioning a portion of the fissile nuclear fission fuel material in the solution of the fissile nuclear fission fuel material dissolved in neutronically translucent liquid carrier material at a block 614. Referring additionally to FIG. 6D, in some embodiments establishing a second concentration of the fissile nuclear fission fuel material in undissolved fertile nuclear fission fuel material disposed in the solution, the second concentration being greater than the first concentration, at the block 606 may include transmuting a portion of the fertile nuclear fission fuel material into the fissile nuclear fission fuel material at a block 616. Given by way of example and not of limitation, in some embodiments as discussed above when 238U is exposed to a neutron flux, the 238U will be transmuted to 239Pu. More particularly, when an atom of 238U is exposed to a neutron flux, its nucleus will capture a neutron, thereby changing it to 239U. The 239U then rapidly undergoes two beta decays. After the 238U absorbs a neutron to become 239U it then emits an electron and an anti-neutrino (υϵ) by β− decay to become 239Np and then emits another electron and anti-neutrino by a second β− decay to become 239Pu. Referring additionally to FIG. 6E, in some embodiments at a block 618 intermediate transmuted material may be diffused to the solution. Given by way of non-limiting examples, as discussed above the intermediate transmuted material may include without limitation 239U and 239Np. Referring now to FIG. 7A, in another embodiment a method 700 is provided for operating a nuclear fission reactor. The method 700 starts at a block 702. At a block 704, in a fission region of a reactor core of a nuclear fission reactor, a portion of fissile nuclear fission fuel material, in a solution of the fissile nuclear fission fuel material dissolved in neutronically translucent liquid carrier material, is fissioned. At a block 706, in a fertile blanket region of the reactor core, material a portion of undissolved fertile nuclear fission fuel material disposed in contact with the solution is transmuted into the fissile nuclear fission fuel. Given by way of example and not of limitation, in some embodiments as discussed above when 238U is exposed to a neutron flux (such as may be caused by leakage from the fission region of neutrons from fissioning of the fissile nuclear fission fuel material at the block 704), the 238U will be transmuted to 239Pu. More particularly and as discussed above, when an atom of 238U is exposed to a neutron flux, its nucleus will capture a neutron, thereby changing it to 239U. The 239U then rapidly undergoes two beta decays. After the 238U absorbs a neutron to become 239U it then emits an electron and an anti-neutrino (υϵ) by β− decay to become 239Np and then emits another electron and anti-neutrino by a second β− decay to become 239Pu. At a block 708 the transmuted fissile nuclear fission fuel is diffused. The method 700 stops at a block 710. Referring additionally to FIG. 7B, diffusing the transmuted fissile nuclear fission fuel material at the block 708 may include diffusing the transmuted fissile nuclear fission fuel material through the fertile nuclear fission fuel material at a block 712. For example and referring additionally to FIG. 7C, diffusing the transmuted fissile nuclear fission fuel material through the fertile nuclear fission fuel material at the block 714 may include diffusing the transmuted fissile nuclear fission fuel material through the fertile nuclear fission fuel material to the solution at a block 714. Referring now to FIGS. 7A and 7D, in some embodiments, in a fission region of a reactor core of a nuclear fission reactor, fissioning a portion of fissile nuclear fission fuel material in a solution of the fissile nuclear fission fuel material dissolved in neutronically translucent liquid carrier material at the block 704 may include, in a fission region of a reactor core of a nuclear fission reactor, consuming a portion of fissile nuclear fission fuel material in the solution of the fissile nuclear fission fuel material dissolved in neutronically translucent liquid carrier material at a block 716. Referring additionally to FIG. 7E, it will be appreciated that, in a fission region of a reactor core of a nuclear fission reactor, consuming a portion of fissile nuclear fission fuel material in the solution of the fissile nuclear fission fuel material dissolved in neutronically translucent liquid carrier material at the block 716 may include establishing in the fissile region a first concentration of the fissile nuclear fission fuel material in the solution at a block 718. Referring additionally to FIG. 7F, it will also be appreciated that, in a fertile blanket region of the reactor core, transmuting into the fissile nuclear fission fuel material a portion of undissolved fertile nuclear fission fuel material disposed in the solution at the block 706 may include establishing, in the fertile blanket region, a second concentration of the fissile nuclear fission fuel material in the fertile nuclear fission fuel material, the second concentration being greater than the first concentration at a block 720. Referring additionally to FIG. 7G, in some embodiments at a block 722 intermediate transmuted material may be diffused to the solution. Given by way of non-limiting examples, as discussed above the intermediate transmuted material may include without limitation 239U and 239Np. It will be appreciated that blocks of the methods 500 (FIGS. 5A-5D), 600 (FIGS. 6A-6E), and 700 (FIGS. 7A-7G) may occur in any suitable host environment. Given by way of non-limiting examples, the blocks may occur in any suitable reactor vessel, such as without limitation reactor vessels described above. In some embodiments, the blocks may occur in suitable nuclear fission fuel pins, such as without limitation nuclear fission fuel pins described above. Referring now to FIG. 8A, in an embodiment an illustrative method 800 is provided for fueling a nuclear fission reactor. The method 800 starts at a block 802. At a block 804 liquid carrier material is received in a reactor core of a nuclear fission reactor. At a block 806 insoluble fertile nuclear fission fuel material and soluble fissile nuclear fission fuel material are disposed in the liquid carrier material. The liquid carrier material is neutronically translucent to the soluble fissile nuclear fission fuel material, and the fertile nuclear fission fuel material is transmutable into the fissile nuclear fission fuel material. The method 800 stops at a block 808. Referring additionally to FIG. 8B, in some embodiments the fissile nuclear fission fuel material may be dissolved in the neutronically translucent liquid carrier material at a block 810. Referring additionally to FIG. 8C, at a block 812 the fertile nuclear fission fuel material may be disposed in contact with a solution of the fissile nuclear fission fuel material dissolved in the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material remaining undissolved in the solution. Referring additionally to FIG. 8D, in some embodiments disposing the fertile nuclear fission fuel material in contact with a solution of the fissile nuclear fission fuel material dissolved in the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material remaining undissolved in the solution, at the block 812 may include disposing undissolved fertile nuclear fission fuel material in direct physical contact with the solution at a block 814. For example and referring additionally to FIG. 8E, in some embodiments disposing the fertile nuclear fission fuel material in direct physical contact with a solution of the fissile nuclear fission fuel material dissolved in the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material remaining undissolved in the solution, at the block 814 may include suspending fertile nuclear fission fuel material in the solution at a block 816. Referring additionally to FIG. 8F, in some embodiments disposing the fertile nuclear fission fuel material in contact with a solution of the fissile nuclear fission fuel material dissolved in the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material remaining undissolved in the solution, at the block 812 may include disposing, homogeneously in the reactor core, fertile nuclear fission fuel material in contact with a solution of the fissile nuclear fission fuel material dissolved in the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material remaining undissolved in the solution, at a block 818. In some other embodiments and referring additionally to FIG. 8G, disposing the fertile nuclear fission fuel material in contact with a solution of the fissile nuclear fission fuel material dissolved in the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material remaining undissolved in the solution, at the block 812 may include disposing, heterogeneously in the reactor core, the fertile nuclear fission fuel material in contact with a solution of the fissile nuclear fission fuel material dissolved in the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material remaining undissolved in the solution, at a block 820. Given by way of non-limiting example and referring additionally to FIG. 8H, in some embodiments disposing, heterogeneously in the reactor core, the fertile nuclear fission fuel material in contact with a solution of the fissile nuclear fission fuel material dissolved in the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material remaining undissolved in the solution, at the block 820 may include disposing undissolved fertile nuclear fission fuel material in contact with a solution of the fissile nuclear fission fuel material dissolved in the neutronically translucent liquid carrier material in a fertile blanket region of the reactor core at a block 822. In another embodiment and referring now to FIG. 9A, an illustrative method 900 is provided for fabricating a nuclear fission fuel pin. The method 900 starts at a block 902. At a block 904 liquid carrier material is received in an elongated enclosure of cladding. At a block 906 insoluble fertile nuclear fission fuel material and soluble fissile nuclear fission fuel material are disposed in the liquid carrier material. The liquid carrier material is neutronically translucent to the soluble fissile nuclear fission fuel material, and the fertile nuclear fission fuel material is transmutable into the fissile nuclear fission fuel material. The method 900 stops at a block 908. Referring additionally to FIG. 9B, in some embodiments at a block 910 the fissile nuclear fission fuel material may be dissolved in the neutronically translucent liquid carrier material. Referring additionally to FIG. 9C, in some embodiments at a block 912 the fertile nuclear fission fuel material may be disposed in contact with a solution of the fissile nuclear fission fuel material dissolved in the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material remaining undissolved in the solution. Referring additionally to FIG. 9D, in some embodiments the fertile nuclear fission fuel material may be disposed in contact with a wall of the elongated enclosure of cladding at a block 914. Referring now to FIGS. 9A-9C and 9E, in some embodiments at a block 916 an elongated enclosure of cladding may be defined, the elongated enclosure having a first axial end, a second axial end, and a centralized axial region between the first and second axial ends. Referring additionally to FIG. 9F, in some embodiments disposing in the elongated enclosure undissolved fertile nuclear fission fuel material in contact with the solution, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at the block 912 may includes disposing homogeneously in the elongated enclosure undissolved fertile nuclear fission fuel material in contact with the solution, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at a block 918. In some other embodiments and referring now to FIGS. 9A-9C, 9E, and 9G, disposing in the elongated enclosure undissolved fertile nuclear fission fuel material in contact with the solution, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at the block 912 may include disposing heterogeneously in the elongated enclosure undissolved fertile nuclear fission fuel material in contact with the solution, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at a block 920. For example and referring additionally to FIG. 9H, in some embodiments disposing heterogeneously in the elongated enclosure undissolved fertile nuclear fission fuel material in contact the solution, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at the block 920 may include, at a block 922, disposing toward first and second axial ends of the elongated enclosure undissolved fertile nuclear fission fuel material in contact with the solution, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material. Referring additionally to FIG. 9I, in some embodiments disposing in the elongated enclosure undissolved fertile nuclear fission fuel material in contact with the solution, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at the block 912 may include disposing in the elongated enclosure undissolved fertile nuclear fission fuel material in direct physical contact with the solution, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at a block 924. Given by way of non-limiting example and referring additionally to FIG. 9J, in some embodiments disposing in the elongated enclosure undissolved fertile nuclear fission fuel material in direct physical contact with the solution, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at the block 924 may include suspending fertile nuclear fission fuel material in the solution, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at a block 926. Referring now to FIG. 10A, in another embodiment an illustrative method 1000 is provided for fabricating a nuclear fission fuel pin. The method 1000 starts at a block 1002. At a block 1004 liquid carrier material that is a solvent for fissile nuclear fission fuel material and that is neutronically translucent to the fissile nuclear fission fuel material is disposed in an elongated enclosure of cladding. At a block 1006 undissolved fertile nuclear fission fuel material is disposed in contact with the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material. The method 1000 stops at a block 1008. Referring additionally to FIG. 10B, in some embodiments fissile nuclear fission fuel material may be dissolved in the neutronically translucent liquid carrier material at a block 1010. Referring additionally to FIG. 10C, in some embodiments disposing undissolved fertile nuclear fission fuel material in contact with the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at the block 1006 may include disposing, homogeneously in the elongated enclosure, undissolved fertile nuclear fission fuel material in contact with the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at a block 1012. In some other embodiments and referring to FIGS. 10A, 10B and 10D, disposing undissolved fertile nuclear fission fuel material in contact with the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at the block 1006 may include disposing, heterogeneously in the elongated enclosure, undissolved fertile nuclear fission fuel material in contact with the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at a block 1014. Given by way of non-limiting example and referring additionally to FIG. 10E, in some embodiments disposing, heterogeneously in the elongated enclosure, undissolved fertile nuclear fission fuel material in contact with the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at the block 1014 may include disposing toward first and second axial ends of the elongated enclosure undissolved fertile nuclear fission fuel material in contact with the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at a block 1016. Referring additionally to FIG. 10F, in some embodiments at a block 1018 an elongated enclosure of cladding may be defined, the elongated enclosure having a first axial end, a second axial end, and a centralized axial region between the first and second axial ends. Referring additionally to FIG. 10G, in some embodiments disposing undissolved fertile nuclear fission fuel material in contact with the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at the block 1006 may include disposing in the elongated enclosure undissolved fertile nuclear fission fuel material in direct physical contact with the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material at a block 1020. For example and referring additionally to FIG. 10H, in some embodiments disposing undissolved fertile nuclear fission fuel material in direct physical contact with the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at the block 1020 may includes suspending fertile nuclear fission fuel material in the neutronically translucent liquid carrier material, the fertile nuclear fission fuel material being transmutable into the fissile nuclear fission fuel material, at a block 1022. Referring now to FIGS. 10A and 10I, in some embodiments the fertile nuclear fission fuel material may be disposed in contact with a wall of the elongated enclosure of cladding at a block 1024. Those skilled in the art will appreciate that the foregoing specific illustrative processes and/or devices and/or technologies are representative of more general processes and/or devices and/or technologies taught elsewhere herein, such as in the claims filed herewith and/or elsewhere in the present application. Those skilled in the art will recognize that it is common within the art to implement devices and/or processes and/or systems, and thereafter use engineering and/or other practices to integrate such implemented devices and/or processes and/or systems into more comprehensive devices and/or processes and/or systems. That is, at least a portion of the devices and/or processes and/or systems described herein can be integrated into other devices and/or processes and/or systems via a reasonable amount of experimentation. Those having skill in the art will recognize that examples of such other devices and/or processes and/or systems might include—as appropriate to context and application—all or part of devices and/or processes and/or systems of (a) an air conveyance (e.g., an airplane, rocket, helicopter, etc.), (b) a ground conveyance (e.g., a car, truck, locomotive, tank, armored personnel carrier, etc.), (c) a building (e.g., a home, warehouse, office, etc.), (d) an appliance (e.g., a refrigerator, a washing machine, a dryer, etc.), (e) a communications system (e.g., a networked system, a telephone system, a Voice over IP system, etc.), (f) a business entity (e.g., an Internet Service Provider (ISP) entity such as Comcast Cable, Qwest, Southwestern Bell, etc.), or (g) a wired/wireless services entity (e.g., Sprint, Cingular, Nextel, etc.), etc. In certain cases, use of a system or method may occur in a territory even if components are located outside the territory. For example, in a distributed computing context, use of a distributed computing system may occur in a territory even though parts of the system may be located outside of the territory (e.g., relay, server, processor, signal-bearing medium, transmitting computer, receiving computer, etc. located outside the territory). A sale of a system or method may likewise occur in a territory even if components of the system or method are located and/or used outside the territory. Further, implementation of at least part of a system for performing a method in one territory does not preclude use of the system in another territory. With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations are not expressly set forth herein for sake of clarity. The herein described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures may be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected”, or “operably coupled,” to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “operably couplable,” to each other to achieve the desired functionality. Specific examples of operably couplable include but are not limited to physically mateable and/or physically interacting, components, and/or wirelessly interactable, and/or wirelessly interacting components, and/or logically interacting, and/or logically interactable components. One skilled in the art will recognize that the herein described components (e.g., operations), devices, objects, and the discussion accompanying them are used as examples for the sake of conceptual clarity and that various configuration modifications are contemplated. Consequently, as used herein, the specific exemplars set forth and the accompanying discussion are intended to be representative of their more general classes. In general, use of any specific exemplar is intended to be representative of its class, and the non-inclusion of specific components (e.g., operations), devices, and objects should not be taken limiting. While particular aspects of the present subject matter described herein have been shown and described, it will be apparent to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from the subject matter described herein and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of the subject matter described herein. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to claims containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that typically a disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms unless context dictates otherwise. For example, the phrase “A or B” will be typically understood to include the possibilities of “A” or “B” or “A and B.” With respect to the appended claims, those skilled in the art will appreciate that recited operations therein may generally be performed in any order. Also, although various operational flows are presented in a sequence(s), it should be understood that the various operations may be performed in other orders than those which are illustrated, or may be performed concurrently. Examples of such alternate orderings may include overlapping, interleaved, interrupted, reordered, incremental, preparatory, supplemental, simultaneous, reverse, or other variant orderings, unless context dictates otherwise. Furthermore, terms like “responsive to,” “related to,” or other past-tense adjectives are generally not intended to exclude such variants, unless context dictates otherwise. While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims. |
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041566580 | description | DESCRIPTION OF THE INVENTION The present invention provides an improved method for fixing radioactive ions in soils. Generally, the present method comprises injecting a chemical grout into the soil which contains the ions, such as radioactive ions, whose mobility is desired to be limited and fixing the ions in place in the soil. The chemical grout contains water-soluble organic monomers which are polymerizable to gel structures with ion exchange sites. Water-soluble monomers are used, as they have proven very satisfactory, whereas water-insoluble monomers are not acceptable due to inconsistent setting characteristics and difficulty in polymerizing these materials in soil. Particular types of ion exchange sites which have been found to be effective are carboxyl groups or carboxyl salts. An initiator and a catalyst for the polymerization of the monomer are injected into the soil to cause polymerization and the formation of the ion exchange gel in the soil. The soil and ions are physically fixed in place by the gel structure which surrounds the soil particles, thereby encapsulating the material and preventing mobility of the radioactive contamination through the open soil. In addition, the ion exchange properties of the gel chemically fix the ions onto the ion exchange sites, further preventing leaching and diffusion of the radioactive ions through the gel. Strontium and cesium ions are of particular concern both because the radioisotopes of these elements are very common in radioactive wastes and radioisotopes of these elements have extremely long half-lives which render them particularly hazardous. Strontium and cesium ions are readily exchanged onto and retained by the ion exchange gels. Water-soluble organic monomers which have been found to be particularly useful in the practice of the present invention include acrylic acid, acrylates, methacrylic acid, and methacrylates. N,N' methylene bisacrylamide has been found to be a particularly good agent for cross linking with these monomers to form gel structures with ion exchange sites. N,N' methylene bisacrylamide has proven particularly useful because it has a relatively high solubility in water. The high solubility of this material and the water-solubility of the other organic monomers is extremely important, as it has been found that water-soluble materials are particularly effective for in situ polymerization and fixation of soils. Dispersion of these water-soluble materials from the point of injection through the soil containing the contamination is far better than with water-insoluble materials; and it has also been found that the water-soluble organic monomers are far more readily polymerized in soil than the water-insoluble materials. The effectiveness of the particular method for fixing ions and the effect of the ion exchange properties of the material in reducing the mobility of ions through the gel is illustrated by the following examples: A chemical grout which forms an ion exchange gel was prepared by dissolving sufficient AM-9 (a product of American Cyanamid Company containing acrylamide and N,N' methylene bisacrylamide, and which, based on solubility tests, is believed to contain less than 10% N,N' methylene bisacrylamide and mostly acrylamide), sodium acrylate and N,N' methylene bisacrylamide to give a solution containing 9% AM-9, 1% acrylate as sodium acrylate, and 1.8% N,N' methylene bisacrylamide. Radioactive strontium was added to give a concentration of 0.0007 microcurie of .sup.85 Sr per liter of grout. The grout was then treated while mixing with 1.5% of catalyst, .beta.-dimethylaminopropionitrile (DMAPN) followed by 1% of initiator, ammonium persulfate (AP), to begin the polymerization process. The acrylamide and sodium acrylate cross-links with the N,N' methylene bisacrylamide to produce a stable gel. The sodium acrylate forms ion exchange sites (carboxyl group) on the gel structure. The solution was divided into 75 ml portions placed in polyethylene containers and allowed to gel. A grout which produces a gel without ion exchange properties was prepared by repeating the above steps with the exception that 10% AM-9 was used and no sodium acrylate was added. When gelation was complete, the gel surface was leached with a 50 ml aliquot of tap water to determine the .sup.85 Sr leach rate as a function of time. After various time intervals, the supernatant liquid was decanted and replaced with a fresh 50 ml aliquot of tap water. The leach water was not agitated or stirred during contact with the gel except during addition and removal. Measured portions of the leach water were analyzed to determine the .sup.85 Sr concentrations. The leach rate, which is a function of the diffusion rate, is computed from the following equation: ##EQU1## The leach rate as shown above is an apparent dissolution rate of the gel which does not actually take place. Only soluble substances (i.e., ions) are removed from the gel. Appropriate corrections were included in the computation to account for the decay of .sup.85 Sr which has a half-life of 65 days. The .sup.85 Sr leach rate for the ion exchange gel is compared with that of the gel without ion exchange properties in FIG. 1, which is a graph of the leach rate in grams/cm.sup.2 /day versus time in days. As is apparent from the graph, the strontium leach rate from the ion exchange gel was only 10% or less than that for the gel without ion exchange sites. The cesium leach rate from soil-gel mixtures was also determined using soil based with cesium traced with .sup.134 Cs. Chemical grout solutions were prepared as above except no .sup.85 Sr tracer was added and the amount of AP was double to promote gelation in the presence of soil. 100 cm.sup.3 of packed soil was mixed with 50 ml of catalyzed grout, separated into two portions, and placed in polyethylene containers to gel. The surfaces of the soil-gel mixtures were scraped to remove a very small excess of gel and were then leached with successive volumes (33 ml) of tap water over a two-month period. The results of these soil-gel leaching experiments are illustrated in FIG. 2, which is a graph of the leach rate in grams/cm.sup.2 /day versus time in days. It can be seen from this graph that the cesium leach rate from the ion exchange gel is only about half that from the gel without ion exchange properties. The ion exchange gels are expected to be more effective for reducing the leaching rate of divalent ions, such as strontium, than of univalent ions, such as cesium, because of the high attractive forces in the gel for the divalent ions where in contact with low ionic strength solutions, such as tap water. Consequently, it can be seen that, while present techniques exist for polymerizing material in soil to immobilize radioactive materials, the present technique of using water-soluble monomers which are polymerizable to gel structures with ion exchange sites provides advantages of improved dispersion and polymerization in the soils and improved immobilizing ability by the chemical retention of radioactive ions over and above the physical fixation. |
051270307 | abstract | Tomographic imaging is implemented by providing a source of penetrating radiation, means for forming a pencil beam and sweeping the pencil beam over a line in space, a radiation detector and a beam length collimator. The beam length collimator lies outside of the sweep plane defined by the sweeping motion of the pencil beam and has a plane of symmetry which intersects the sweep plane at an angle which may or may not be a right angle. The beam length collimator defines a sensitive volume which has a dimension along the length of the pencil beam where the selected slice is defined by (or partly by) a dimension of the pencil beam. The combination of the beam length collimator and the pencil beam define a sensitive volume from which scattered energy can pass the collimator and be detected. The beam length collimator preferentially detects energy scattered by the sensitive volume. The sweep of the pencil beam allows a line image representing a plurality of sensitive volumes within the sweep plane at a focal distance from the beam length collimator. By providing relative motion between the object and the source/detector/collimator arrangement, a tomographic image of the selected slice can be created. The beam length collimator allows the sensitivity of the imaging arrangement to be tailored to anomalies or cracks lying parallel to a surface of a longitudinally extending object or parallel to a circumference of a cylindrical object. |
063234998 | abstract | An electron beam exposure apparatus which minimizes the influence of the space charge effect and aberrations of a reduction electron optical system, and simultaneously, increases the exposure area which can be exposed at once, thereby increasing the throughput. An electron beam exposure apparatus having a source for emitting an electron beam and a reduction electron optical system for reducing and projecting, on a target exposure surface, an image of the source, includes a correction electron optical system which is arranged between the source and the reduction electron optical system to form a plurality of intermediate images of the source along a direction perpendicular to the optical axis of the reduction electron optical system, and corrects in advance aberrations generated when the intermediate images are reduced and projected on the target exposure surface by the reduction electron optical system. |
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abstract | An apparatus for measuring an image of a pattern to be formed on a semiconductor by scanning the pattern using a scanner, the apparatus including an EUV mask including the pattern, a zoneplate lens on a first side of the EUV mask and adapted to focus EUV light on a portion of the EUV mask at a same angle as an angle at which the scanner will be disposed with respect to a normal line of the EUV mask, and a detector arranged on another side of the EUV mask and adapted to sense energy of the EUV light from the EUV mask, wherein NAzoneplate=NAscanner/n and NAdetector=NAscanner/n*σ, where NAzoneplate denotes a NA of the zoneplate lens, NAdetector denotes a NA of the detector, and NAscanner denotes a NA of the scanner, σ denotes an off-axis degree of the scanner, and n denotes a reduction magnification of the scanner. |
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description | This application is a National Stage Application of PCT/CN2012/088089, filed Dec. 31, 2012, which claims benefit of Chinese Patent Application No. 201210003988.8 filed on Jan. 6, 2012 in China and which applications are incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications. 1. Field of the Invention The present disclosure belongs to the technical field of X-ray generator. In particular, the present disclosure relates to an installation case for a radiation device, an oil-cooling circulation system based on the installation case for a radiation device, and an X-ray generator with the oil-cooling circulation system. 2. Description of the Related Art The kernel components of a safety inspection apparatus, which employs an X-ray imaging technique, are an X-ray source and an image capturing and processing system. Imaging quality and detection effect of the safety inspection apparatus, to a great extent, depend on performance of the X-ray source. Therefore, the quality of the X-ray source plays an important role. At present, an X-ray source of a safety inspection apparatus, which employs an X-ray imaging technique, mainly uses an X-ray generator. The conventional X-ray generator comprises an X-ray tube assembly, a high frequency and high voltage generator, a filament power supplying module, a cooling system, and a case body. The X-ray tube assembly comprises an X-ray tube and a collimator (also referred to as a front collimator) fixedly connected with anode and cathode sheaths of the X-ray tube. The X-ray tube assembly is provided inside the case body. The case body is made by jointing sheet materials together using welding and bolts. The collimator and the case body are two separate components fixedly connected with each other. The collimator is provided with a beam exit aperture, and the case body is provided with a beam exit opening. The portion, except the beam exit opening, of the inner wall of the case body is fixedly provided with an X-ray shielding layer for shielding the X-ray in the non-main beam direction. The high frequency and high voltage generator is electrically connected with the anode and cathode of the X-ray tube to provide direct current voltage for the anode and cathode of the X-ray tube. The filament power-supplying module is electrically connected with the cathode of the X-ray tube to provide high frequency pulse voltage for the cathode of the X-ray tube. When the filament power-supplying module provides high frequency pulse voltage for the cathode of the X-ray tube, the cathode of the X-ray tube emits electron streams under the action of a high voltage electric field to bombard the anode of the X-ray tube, such that the X-ray is excited, and the X-ray can in turn pass through the beam exit aperture and the beam exit opening to the outside of the case body. The cooling system is used for dissipating the heat accumulated in the X-ray tube to avoid burning-out of the X-ray tube. The case body and the collimator form an enclosed space. This enclosed space is filled with a cooling liquid and is an important component part of the cooling system. During operating of the X-ray generator, the main beam of the X-ray will pass through a beam exit channel constituted by the beam exit aperture and the beam exit opening to the outside of the case body, while the X-ray in the non-main beam direction will be shielded inside the shielding layer. There are the following problems in the prior art. The conventional case body is made by jointing sheet materials together using welding and bolts. However, there will be some gaps at corners and edges of the case body jointed through welding and bolts, due to welding deformation of material, insufficiently screwing-in of bolts, offsetting of screwing-in angle, or like. This causes the conventional case body to have a poor sealing, and the cooling liquid in the case body is likely to leak. Furthermore, the X-ray generated by the X-ray tube has great penetrating power. If the X-ray shielding layer is inappropriately provided, the case body will be weighty, or leakage of the X-ray will worsen, even beyond safety standard of X-ray leakage dose regulated by various industries. Therefore, an object of the present disclosure is to provide an installation case for a radiation device, an oil-cooling circulation system based on the installation case for a radiation device, and an X-ray generator provided with the above oil-cooling circulation system, so that the technical problems of the weight of the case body of the conventional X-ray generator being heavy and leakage amount of the X-ray in the conventional X-ray generator being large can be solved. In order to achieve the above object, the present disclosure provides the following solutions. the installation case for a radiation device comprises a case body and a collimator fixedly connected with the case body, the collimator being provided with a beam exit aperture and the case body being provided with a beam exit opening; the installation case for a radiation device further comprises a layer or layers of shielding devices provided within the case body, the shielding device is made of a material that can shield a radioactive ray, and between the shielding device and the case body, there is a space in which liquid can flow and parts can be installed; the collimator and the shielding device are integrally formed, or the collimator and the shielding device are two separate parts and are fixedly connected with each other; each layer of the shielding device is provided with a ray exit aperture, and the ray exit aperture, the beam exit aperture and the beam exit opening are coaxial. The above solution according to the present invention has the following advantages. Since the case body is provided therein with a layer or layers of shielding devices, the shielding device is made of a material that can shield the X-ray, the shielding device is provided in the case body and between the shielding device and the case body, there is a space in which liquid can flow and parts can be installed, when the X-ray tube is located in the shielding device, the X-ray emitted from the X-ray tube will orderly pass through the ray exit aperture, the beam exit aperture and the beam exit opening which are coaxial and be emitted out of the case body. Before the X-ray that is not emitted out of the case body from the beam exit opening provided in the case body reaches outside of the case body, it has to be subjected to at least double shielding of a layer or layers of shielding devices and the case body. Compared with the case body of the conventional installation case for a radiation device, the above structure of the installation case for a radiation device according to the present disclosure remarkably reduces the amount of the ray leaking out of the case body of the X-ray generator to the environment around the case body, so that the technical problem of amount of the ray leaking out of the case body to the environment around the case body being large can be solved. Meanwhile, the arrangement of the shielding device being provided in the case body enables the shielding device to be reasonably and effectively used, so that amount of shielding material can be reduced and hence the weight of the whole case body is reduced. Preferable solutions of this disclosure are provided as follows. Preferably, the radioactive ray is an X-ray; and/or the shielding device is made of insulation material; and/or the shielding device is in a cylindrical or prismatic shape and comprises a cylindrical body, a first end cover and a second end cover, wherein the first end cover and the second end cover are fixedly connected with the two end openings of the cylindrical body, respectively, and at least one of the first end cover, the second end cover and the cylindrical body are provided with a fluid channel and/or a circuit channel; and/or the case body is provided therein with multiple layers of shielding device of which the inner layer of shielding device is located inwardly of the outer layer of shielding device, and between the inner layer of shielding device and the outer layer of shielding device and between the case body and the outermost layer of shielding device, there are spaces for flowing of liquid and mounting of parts. Preferably, the circuit channel and/or the fluid channel is a through hole in a bent shape or an oblique hole provided in at least one of the first end cover, the second end cover and the cylindrical body; or at least one of the first end cover, the second end cover and the cylindrical body is in a dual-layer structure that is formed by superimposing an outer plate and an inner plate, and wherein a liquid flowing cavity is provided between the outer plate and the inner plate, and both of the outer plate and the inner plate are provided with a flow guiding orifice communicating with the liquid flowing cavity, and the fluid channel is constituted by the flow guiding orifices and the liquid flowing cavity, and the orthographic projection of the flow guiding orifice in the outer plate in the axial direction thereof and the flow guiding orifice provided in the inner plate are entirely staggered. Preferably, the bent shape is a right-angle polygonal-line shape; and/or both of the first and second end covers are provided with the fluid channels and the circuit channels; and/or a plurality of flow guiding orifices are distributed on the outer plate and/or the inner plate of the first end cover and/or the second end cover along the circumferential direction of the cylindrical body at equal angle intervals, and the distances between the respective flow guiding orifices and the axis of the cylindrical body are equal with each other; and/or the cylindrical body is provided with inner screw threaded tubes embedded therein, and the inner screw threaded tubes each are provided with inner screw thread, and the portion of a connection bolt having outer screw thread passes through the outer plate and engages with the inner screw thread of the inner screw threaded tube; and/or the inner plate is fixedly provided with a positioning pole which is embedded into a positioning counter bore in the outer plate and is tightly fitted with the positioning counter bore; and/or a step portion in a step shape is provided at the inside end edge of the cylindrical body, and the step portion bears against the edge of the inner plate. Preferably, the shielding device is made of lead oxide; and/or the beam exit opening is filled with a blocking window, and the blocking window is made of a material through which the radioactive ray can transmit, and the blocking window functions to realize liquid and gas seal between the inside of the case body and the outside of the case body; and/or the case body comprises a main body portion, a first case cover and a second case cover, wherein: the first case cover and the second case cover are fixedly provided at the two end openings of the main body portion, respectively, the main body portion is integrally formed, and the material for the first case cover and the second case cover is the same as that for the main body portion. Preferably, the shielding device is made of trilead tetroxide; and/or the main body portion is made of aluminum or aluminum alloy material and is formed by using a stretch forming process or a wire electrode cutting process; and/or sealing strips are provided between the first case cover and the main body portion and/or between the second case cover and the main body portion, wherein: the end face of the main body portion is provided with a step face or a groove, and the sealing strip is provided on the step face or provided in the groove and extends beyond the end face of the main body portion, and the first case cover and/or the second case cover are close to the surface of the main body portion and press against the portions of the sealing strips extending beyond the end face of the main body portion, or a step face or groove is provided on an edge of the first case cover and/or the second case cover, the sealing strip is provided on the step face or provided in the groove and extends beyond the edge of the first case cover and/or the second case cover, and the main body portion is close to the surface of the first case cover and/or the second case cover and presses against the portions of the sealing strips extending beyond the edge of the first case cover and/or the second case cover. The oil-cooling circulation system according to this disclosure comprises a liquid-filled box, an insulation liquid filled in the liquid-filled box and a cooling device for reducing the temperature of the insulation liquid, and the cooling device comprises an oil pump, a heat radiator and a cooling fan, wherein: the liquid-filled box is constituted by the installation case for a radiation device according to any one of the foregoing technical schemes; the heat radiator is located outside of the liquid-filled box, a liquid inlet of the heat radiator is communicated with a liquid outlet of the liquid-filled box, and a liquid outlet of the heat radiator is communicated with a liquid inlet of the liquid-filled box; the oil pump provides a motive power for circulation between the insulation liquid in the liquid-filled box and the insulation liquid in the heat radiator; the cooling fan dissipates the heat from the heat radiator in such a way that the flow of ambient air around the heat radiator is expedited. Preferably, the cooling device further comprises a frame-shaped bracket hooding the heat radiator and the cooling fan, and the bracket is fixedly connected with the liquid-filled box; and/or the oil pump is a DC brushless submersible pump; and/or the oil pump is fixedly provided on the inner wall of the liquid-filled box and is located between the liquid-filled box and the shielding device, or the oil pump is fixedly provided in the heat radiator; and/or the shielding device is provided with a fluid channel, wherein: a liquid outlet and a liquid inlet of the shielding device are located in the fluid channel; a liquid suction port of the oil pump faces toward the liquid outlet of the shielding device, or the liquid suction port of the oil pump is communicated with the liquid outlet of the shielding device via a conduit; the liquid inlet of the shielding device is communicated with a liquid inputting pipe, the liquid outlet of the liquid-filled box is communicated with a liquid introducing pipe, and a liquid outputting port of the liquid introducing pipe faces toward a liquid inputting port of the liquid inputting pipe, or the liquid inlet of the shielding device is communicated with the liquid outlet of the liquid-filled box via a conduit. The X-ray generator according to the present disclosure comprises an X-ray tube, a high frequency and high voltage generator, a filament power supplying module and the oil-cooling circulation system according to the present disclosure, wherein: the X-ray tube is mounted within the shielding device, and the X-ray emitted from the X-ray tube passes through the ray exit aperture, the beam exit aperture and the beam exit opening in this order and radiates out of the case body of the installation case for a radiation device; the high frequency and high voltage generator is electrically connected with a cathode and an anode of the X-ray tube; the filament power supplying module is electrically connected with the cathode of the X-ray tube. Preferably, the shielding device is further provided with a circuit channel, the high frequency and high voltage generator is electrically connected with the cathode and anode of the X-ray tube via wires or interfaces passing through the circuit channel, and the filament power supplying module is electrically connected with the cathode of the X-ray tube via wires or interfaces passing through the circuit channel; at least some of modules constituting the high frequency and high voltage generator are located between the case body and the shielding device, and a power supply external to the case body and the rest of the modules constituting the high frequency and high voltage generator are located outside of the case body; the case body is provided with a wire exit channel, and those of the modules constituting the high frequency and high voltage generator located in the case body are electrically connected with those modules located outside of the case body via wires or interfaces passing through the wire exit channel, or the high frequency and high voltage generator is electrically connected with the external power supply via wires or interfaces passing through the wire exit channel; the shielding device comprises a cylindrical body, a first end cover and a second end cover, and the first end cover and the second end cover are fixedly connected with two end openings of the cylindrical body, respectively; at least one of the first end cover, the second end cover and the cylindrical body is provided with a fluid channel and the circuit channel. Preferably, both of the first end cover and the second end cover are a dual-layer structure constituted by laminating an outer plate and an inner plate, and both of the first end cover and the second end cover are provided with the circuit channel, wherein: the circuit channel provided in the first end cover comprises a cathode positioning aperture provided in the inner plate of the first end cover and a wire routing aperture provided in the outer plate of the second end cover, and in the X-ray tube, a sheath for protecting the cathode is embedded in the cathode positioning hole, and the wire routing aperture comprises a longitudinal aperture coincident with/parallel to the axial direction of the X-ray tube and a transverse aperture communicating with the longitudinal aperture, the axial direction of the transverse aperture being perpendicular to the axial direction of the longitudinal aperture, and the cathode of the X-ray tube is led out from the wire routing aperture from an inside of the sheath by two wires; the circuit channel provided in the second end cover comprises anode positioning apertures provided in the inner plate and the outer plate of the second end cover, a conductive stud orderly passes through the anode positioning apertures provided in the outer plate and the inner plate of the second end cover, and the conductive stud is provided with an outer screw threaded portion which is engaged with an anode screw hole provided in the anode, the portion of the conductive stud far away from the anode is provided with a positioning screw hole, a conductive screw is provided with an outer screw threaded portion which is engaged with the positioning screw hole, and a wire electrically connected with the anode of the high frequency and high voltage generator is sandwiched between a head of the conductive screw and the conductive stud; and/or the inner plate of the second end cover is provided with at least one anode position-limit hole, the anode is provided with a position-limit screw hole, a positioning stud is provided with an outer screw threaded portion which is engaged with the position-limit screw hole, and the end of the positioning stud far away from the position-limit screw hole is inserted in the anode position-limit hole; and/or both of the first end cover and the second end cover are provided with the fluid channels, both of the first end cover and the second end cover are the dual-layer structure constituted by the laminated outer plate and inner plate, there is a liquid flowing cavity between the outer plate and the inner plate, and both of the inner plate and the outer plate are provided with flow guiding orifices communicated with the liquid flowing cavity, and the fluid channel is constituted by the flow guiding orifices and the liquid flowing cavity; the anode is in a hood shape and covers the end of a glass hood of the X-ray tube far away from the cathode, a liquid flowing space is provided between the anode and the outer circumferential surface of the glass hood of the X-ray tube, and the anode is provided with liquid circulating holes respectively communicating with the liquid flowing space and the flow guiding orifice provided in the inner plate of the second end cover. Preferably, the bent shape is a right-angle polygonal-line shape; and/or the case body comprises a main body portion, a first case cover and a second case cover, wherein: the first case cover and the second case cover are fixedly provided at the two end openings of the main body portion, respectively; constituent modules of the high frequency and high voltage generator comprise a first rectification and voltage regulation module, a high frequency inverter, a high voltage transformer and a voltage-doubling rectification module which are electrically connected with each other in this order, wherein: the first rectification and voltage regulation module is electrically connected with the external power supply and is configured to take electrical energy required for loading a DC high voltage to the cathode and the anode of the X-ray tube from the external power supply; the voltage-doubling rectification module is electrically connected with the cathode and the anode of the X-ray tube; among the constituent modules of the high frequency and high voltage generator, at least the high voltage transformer and the voltage-doubling rectification module are fixedly provided between the case body and the shielding device; the high voltage transformer is fixedly provided on the collimator, the first case cover, the second case cover or the shielding device, and the voltage-doubling rectification module is fixedly provided on a circuit board, wherein: at least one of two ends of the circuit board bears against a position-limit protruding piece fixedly provided on the first case cover or the second case cover, and the circuit board is fixed on the position-limit protruding pieces by fasteners, or at least one of the two ends of the circuit board is inserted in a groove provided on the first case cover or the second case cover, and the middle region of the circuit board is fixed on the main body portion by fasteners. Preferably, the X-ray generator further comprises a monitor system, and the monitor system comprises a signal sampling module, a sampled-signal processing module, a logic decision and control module, and an auxiliary power supply module configured to supply power for the logic decision and control module, wherein: the signal sampling module is located between the case body and the shielding device or is located within the shielding device; the signal sampling module is used for detecting electric signals on the cathode and/or the anode of the X-ray tube, the temperature of the insulation liquid and the flow rate of the insulation liquid flowing into or flowing out of the case body, and sends the detected electric signals to the sampled-signal processing module; the sampled-signal processing module is electrically connected with the signal sampling module and the logic decision and control module; the sampled-signal processing module is configured for processing the electric signals such as filtering the electric signals and/or converting the electric signals into the detection result in a digital form through analog-digital conversion and sending the detection result in a digital form to the logic decision and control module; the logic decision and control module is also electrically connected with at least one of the high frequency and high voltage generator, the filament power supply module, and the cooling device; the logic decision and control module automatically calls previously-stored control instructions according to the detection result based on predetermined correspondence rules between the detection result and the control instructions, and controls at least the output voltage and/or current of the high frequency and high voltage generator or the filament power supply module according to the control instructions, or controls power consumption of the cooling device according to the control instructions. Preferably, the filament power supply module comprises a second rectification and voltage regulation module electrically connected with the logic decision and control module, a filament inverter and a filament transformer electrically connected with the filament inverter and the cathode of the X-ray tube; the filament transformer is fixedly provided in the case body, and is configured to convert the voltage output from the filament inverter into a high frequency pulse voltage required for the cathode of the X-ray tube and to output the high frequency pulse voltage to the cathode of the X-ray tube; the first rectification and voltage regulation module, the high frequency inverter, the logic decision and control module, the second rectification and voltage regulation module, the filament inverter and the auxiliary power supply module are fixedly provided on the outer surface of the case body or in a control box provided outside of the case body; the wires or interfaces passing through the wire exit channel provided in the case body are aviation plugs that provide liquid and gas seal between the inside of the case body and the outside of the case body, wherein the high voltage transformer and the high frequency inverter are electrically connected with each other via the aviation plugs, the signal sampling module and the sampled-signal processing module are electrically connected with each other via the aviation plugs and/or the filament inverter and the filament transformer are electrically connected with each other via the aviation plugs. The above respective preferable technical solutions can also achieve the following technical effects. Since the main body portion in the embodiments is formed by using a stretch forming process or a wire electrode cutting process causing a small deformation, and arrangement of sealing strips improves sealing of the case body, leakage of the insulation liquid from the case body can be reduced. Since a layer or layers of shielding devices provided in the case body according to the embodiments are made of light material and have a small volume, the technical problem of the weight of the case body being heavy is overcome. Further, since the end covers of the shielding device are in a double-layer structure in which the two layers are superimposed with each other, requirements for liquid flowing in the cooling system can be met and good X-ray shielding can be ensured. Next, the technical scheme of the present disclosure will be described in details with reference to the accompanying drawings and embodiments. The embodiments of the present disclosure provide an installation case for a radiation device, an oil-cooling circulation system based on the installation case for a radiation device, and an X-ray generator provided with the oil-cooling circulation system. The installation case can effectively avoid leakage of an X-ray, emitted from an X-ray tube, out of the case body to surroundings of the case body. In addition, the installation case is light in weight and occupies small space. As shown in FIGS. 1-3, the installation case for a radiation device proposed by the embodiments of the present disclosure comprises a case body 1, a collimator 2 as shown in FIG. 2, and a layer of shielding device 3 provided inside the case body 1. The shielding device 3 is made of material that can shield an X-rays. Between the shielding device 3 and the case body 1, there is a space in which liquid can flow and parts can be installed. The collimator 2 and the shielding device 3 are integrally formed. The collimator 2 and the case body 1 are two separate parts and they are detachably and fixedly connected with each other. The shielding device 3 is provided with a ray exit aperture 36 as shown in FIG. 5, the collimator 2 is provided with a beam exit aperture (coinciding with the ray exit aperture 36 shown in FIG. 5), and the case body 1 is provided with a beam exit opening 11. The ray exit aperture 36, the beam exit aperture and the beam exit opening 11 are coaxial. The case body 1 according to the embodiment of the present disclosure is provided therein with a layer of shielding device 3. It is appreciated that multiple layers of shielding device 3 can be provided. The shielding device 3 is made of material, e.g., lead oxide, that can shield the X-rays. The shielding device 3 is located inside the case body 1. When the X-ray tube 4 shown in FIG. 5 is provided inside the shielding device 3, the X-rays emitted by the X-ray tube 4 passes through the ray exit aperture 36, the beam exit aperture and the beam exit opening 11 shown in FIG. 5, which are coaxial, to outside the case body 1 in this order. In this embodiment, the ray exit aperture 36, the beam exit aperture and the beam exit opening 11 being coaxial may mean that they are entirely coaxial, that is, their orthographic projections in the respective axial directions are entirely coincident, or that they are partially coaxial, that is, their orthographic projections in the respective axial directions are partially coincident, as long as the X-rays can in turn pass through the ray exit aperture 36, the beam exit aperture and the beam exit opening 11 to outside the case body 1 finally. In this embodiment, between the shielding device 3 and the case body 1, there is a space in which liquid can flow and parts can be installed, as shown in FIG. 2. The size of the space may be appropriately arranged according to requirements. On one hand, the presence of the space for flowing of liquid and mounting of components allows electric elements to be mounted and insulation liquid to be filled, in which the insulation liquid is used for enhancing insulation properties and heat dispersion between the electric elements; but on the other hand, the shielding device 3 can be made in a smaller size, without adversely affecting heat dispersion and shielding effect, so that the material for the case body can be saved and the volume and weight of the case body can be reduced. When the X-ray tube 4 shown in FIG. 5 is mounted in the shielding device 3 provided in the case body 1, the thickness of the shielding device 3 and the number of the layer of shielding device 3 can be determined according to the intensity of the X-rays emitted from the X-ray tube 4. When multiple layers of shielding device 3 are provided in the case body 1, each layer of shielding device 3 may be made of the material that can shield the X-ray, or some layers of the multiple layers of shielding device 3 may be made of the material that can shield the X-rays. Every layer of shielding device 3 is located in the case body 1. The inner layer of shielding device 3 is located inwardly of the outer layer of shielding device 3. The space for flowing of liquid and mounting of components is between the case body 1 and the outermost layer of shielding device 3. The X-ray tube 4 is mounted inwardly of the innermost layer of shielding device 3. Further, in this embodiment, the collimator 2 and the case body 1 may be integrally formed. In this case, the collimator 2 and the shielding device 3 are two separate parts and are detachably and fixedly connected with each other, e.g., by screws or bolts. However, in a case where manufacture accuracy is high, the collimator 2, the case body 1 and the shielding device 3 or the bodies thereof may be integrally formed. As shown in FIGS. 2, 3, 5 and 9, in this embodiment, the shielding device 3 is in a cylindrical shape and comprises a cylindrical body 30, a first end cover 31 and a second end cover 32. The first end cover 31 and the second end cover 32 are fixedly connected to the two end openings of the cylindrical body 30, respectively. Both of the first end cover 31 and the second end cover 32 are provided with a fluid channel 312 and a circuit channel 311, as shown in FIG. 5. With the above simple structure, the assembly of the shielding device 3 is facilitated and the manufacture of the respective parts of the shielding device 3 is facilitated. Furthermore, the smooth flowing of the insulation liquid and the connection of wires and interfaces are facilitated. Since the smooth flowing of the insulation liquid is facilitated, the heat of the X-ray tube 4 mounted in the shielding device 3 can be easily dispersed, so that the efficiency of cooling the X-ray tube 4 is enhanced. Alternatively, instead of in a cylindrical shape, the shielding device 3 may be in a prismatic shape (including rectangular parallelepiped and square parallelepiped), in a circular stage shape, or the like. In this embodiment, as shown in FIG. 5, one or both of the circuit channel 311 and the fluid channel 312 may only be provided in the cylindrical body 30. Alternatively, the circuit channel 311 and the fluid channel 312 may be formed in the cylindrical body 30 and the first end cover 31 or second end cover 32, respectively. As shown in FIG. 5, in this embodiment, both of the first end cover 31 and the second end cover 32 are in a dual-layer structure that is formed by superimposing an outer plate 331 and an inner plate 332. A liquid flowing cavity 333 is provided between the outer plate 331 and the inner plate 332. The outer plate 331 is provided with flow guiding orifices 334 communicating with the liquid flowing cavity 333. The inner plate 332 is provided with flow guiding orifices 335 communicating with the liquid flowing cavity 333. The fluid channel 312 is constituted by the flow guiding orifices 334, the flow guiding orifices 335 and the liquid flowing cavity 333. The orthographic projection of the flow guiding orifices 334 in the outer plate 331 in the axial direction thereof and the flow guiding orifices 335 provided in the inner plate 332 are entirely staggered. In this embodiment, the circuit channel 311 provided in the first end cover 31 comprises a cathode positioning aperture 313 provided in the inner plate 332 of the first end cover 31 and a wire routing aperture 340 provided in the outer plate 331 of the first end cover 32. The wire routing aperture 340 is a bent through hole. The wire routing aperture 340 preferably comprises a longitudinal aperture 342 coincident with/parallel to the axial direction of the shielding device 3 and a transverse aperture 341 communicating with the longitudinal aperture 342. The axial direction of the transverse aperture 341 is perpendicular to the axial direction of the longitudinal aperture 342. When the case body 1 is filled with the insulation liquid, the first end cover 31 and the second end cover 32 in the above structure can ensure that the insulation liquid can not only flow into the cylindrical body 30 via the fluid channel 312 in the second end cover 32, but can also flow out of the shielding device 3 via the fluid channel 312 the first end cover 31. What is more important is that: When the X-ray tube 4 is mounted in the shielding device 3, the orthographic projections of the flow guiding orifices 334 in the outer plate 331 in the axial direction thereof and the flow guiding orifices 335 in the inner plate 332 are entirely staggered. The fluid channel 312 forms a labyrinth structure. In this way, even if the X-rays emitted from the X-ray tube 4 passes through the flow guiding orifices 335 in the inner plate 332, the X-rays will not pass through the flow guiding orifice 334 in the outer plate 331, and hence will not pass through the shielding device 3. Similarly, the circuit channel 311 in the above structure also forms a labyrinth structure, and the circuit channel 311 can efficiently prevent the X-rays from straightly passing through the shielding device 3 without adversely affecting connection of interfaces and wires. In the present disclosure, in a case where the first end cover 31 and the second end cover 32 are not provided in a dual-layer structure, the circuit channel 311 and/or the fluid channel 312 may also form the above labyrinth structure. In this case, the circuit channel 311 and/or the fluid channel 312 may be through holes in a bent shape, such as a right-angle polygonal-line shape, or may be an oblique hole (such as a through hole, the axial direction of which is at an acute or obtuse angle to the axial direction of the shielding device 3, preferably at an acute angle with a smaller angle value or an obtuse angle with a larger angle value to the axial direction of the shielding device 3). Further, one of the flow guiding orifice 334 in the outer plate 331 and the flow guiding orifice 335 in the inner plate 332 and/or one of the wire routing aperture 340 in the outer plate 331 and the cathode positioning aperture 313 in the inner plate 332 may be a through hole in a bent shape (e.g., a right-angle polygonal-line shape) or an oblique hole. In this case, the first end cover 31 and the second end cover 32 also can form the circuit channel 311 and/or the fluid channel 312 in a labyrinth structure. Since the orthographic projections of the two end openings of the oblique hole in the radial direction of the shielding device 3 are entirely or partially staggered, the oblique hole can also partially or entirely prevent the X-rays irradiating one of the two end openings of the oblique hole from passing through the other of the two end openings while leading out the wires or allowing the insulation liquid to flow therethrough, especially in a case where the ratio of the thickness of the shielding device 3, the first end cover 31 and the second end cover 32 to the size of the end openings of the circuit channel 311 and/or the fluid channel 312 is great. As shown in FIG. 5, in this embodiment, a plurality of (more than two) flow guiding orifices 335 are distributed in the inner plate 332 (as shown in FIGS. 6 and 7) of the first end cover 31 along the circumferential direction of the cylindrical body 30 shown in FIG. 5 at equal angle intervals, and the distances between the respective flow guiding orifices 335 and the axis of the cylindrical body 30 (the axis of the cylindrical body 30 is also the axis of the shielding device 3) are equal with each other. Further, the outer plate 331 of the first end cover 31 also can be provided with a plurality of (more than two) flow guiding orifices 334 along the circumferential direction of the cylindrical body 30 at equal angle intervals. The flow guiding orifices 335 may be distributed in the first end cover 31 in other distribution manners. Also, the flow guiding orifices 334 in the first end cover 31 can be distributed in the above-described manner. Further, the flow guiding orifices 334 or the flow guiding orifices 335 may be distributed only in the outer plate 331 or the inner plate 332 of the first end cover 31 in the above described manner. In this embodiment, the wire routing aperture 340 in the outer plate 331 of the first end cover 31 comprises a longitudinal aperture 342 coincident with the axial direction of the cylindrical body 30 (the axial direction of the cylindrical body 30 is also the axial direction of the shielding device 3) and a transverse aperture 341 communicating with the longitudinal aperture 342 and the axial direction of which is perpendicular to the axial direction of the longitudinal aperture 342. The transverse aperture 341 and the longitudinal aperture 342 form the wire routing aperture 340 in a shape of right-angle polyline. Such structure can ensure that the X-ray emitted from the X-ray tube 4 does not come out of the wire routing aperture 340 while the wire electrically connected with a cathode 41 of the X-ray tube 4 (which can be regarded as a part of the cathode) is led out from the wire routing aperture 340. In an embodiment, the longitudinal aperture 342 may be parallel to the axial direction of the cylindrical body 30, and the wire routing aperture 340 may be an oblique through hole or a through hole in other bent shapes, such as a sharp-angle polyline shape or an obtuse-angle polyline shape. In the X-ray tube 4, a sheath 315 for protecting the cathode 41 is embedded in the cathode positioning hole 313 of the inner plate 332 of the first end cover 31, and the wire sheath 315 (usually made of copper material) electrically connected with the cathode 41 is led out from the shielding device 3. An inner anode (or anode base) 42 of the X-ray tube 4 is fixed to the second end cover 32 by using fasteners made of conductive material (in this embodiment, the fasteners are a conductive stud 317 and a conductive screw 318 shown in FIG. 5), and the anode 42 of the X-ray tube 4 is electrically connected with an anode of an voltage-doubling rectification module 54 (the anode of the voltage-doubling rectification module 54 is also the anode of a high frequency and high voltage generator 5 shown in FIG. 1) provided outside the shielding device 3 by using fasteners and wires electrically connected with the fasteners. The fasteners made of conductive material themselves also provide conducting function. The anode 42 of the X-ray tube 4 is in a shape of hood and is hooded on an end of a glass hood of the X-ray tube 4 far away from the cathode 41, and a liquid flowing space 422 is provided between the anode 42 and the outer circumferential surface of the glass hood of the X-ray tube 4, and the anode 42 is provided with liquid circulating holes 423 communicating with the liquid flowing space 422. In this structure, the insulation liquid outside the shielding device 3 flows into/flows out of the shielding device 3 through the liquid circulating holes 423 shown in FIG. 12 or 13. In this embodiment, the axial direction of the liquid circulating holes 423 is preferably parallel to the axial direction of the X-ray tube 4. In order to position the anode 42 more effectively, the outer circumferential surface of the anode 42 may also be provided with one, two or plural circumferential screw holes 420. The screws passing through the cylindrical body 30 and embedded in the circumferential screw holes 420 fix the anode 42 in the shielding device 3 in the circumferential direction of the anode 42. The above structure can be mounted easily and conveniently and can also provide reliable connection. Preferably, the number of the flow guiding orifices 335 distributed in the inner plate 332 of the second end cover 32 is the same as that of the liquid circulating holes 423 of the anode 42 of the X-ray tube 4. In an embodiment, the number of the flow guiding orifices 335 is different from that of the liquid circulating holes 423. The advantage of the above structure is that the insulation liquid with a lower temperature can first flow to the vicinity of the inner anode 42 of the X-ray tube 4, so that a target embedded onto the anode 42 of the X-ray tube 4 can be prevented from burning out due to a too high temperature. In this embodiment, the shielding device 3 is made of material having protection and insulation properties. When the X-ray tube 4 is mounted within the shielding device 3, the above structure not only can effectively avoid leakage of the X-ray, but also can prevent the X-ray tube 4 loaded with high voltage and electric elements or modules for supplying the high voltage to the X-ray tube 4 (e.g., as shown in FIG. 1, a high voltage transformer 53 and the voltage-doubling rectification module 54 in the high frequency and high voltage generator 5) from suffering electric arc or short circuit within the case body 1. In this embodiment, the cylindrical body 30 is provided with inner screw threaded tubes 301 embedded therein. The inner screw threaded tubes 301 each is provided with inner screw thread, and the portion of a connection bolt 302 having outer screw thread passes through the outer plate 331 and engages with the inner screw thread of the inner screw threaded tube 301, so that the cylindrical body 30 and the first and second end covers 31 and 32 are connected and fixed together. The screw thread connection structure constituted by the connection bolts 302 and the inner screw threaded tubes 301 connects the cylindrical body 30 with the first and second end covers 31 and 32 and fix them together. Since the cylindrical body 30 is made of lead oxide and therefore is very fragile, it is very difficult to form inner screw thread in the cylindrical body 30 by cutting processing. Preferably, the embedded inner screw threaded tube 301 is made of high temperature-resistant metal material. The inner screw threaded tube 301 can be embedded into the cylindrical body 30 before the cylindrical body 30 is not completely formed. In this embodiment, as shown in FIG. 6, the inner plate 332 is fixedly provided with a positioning pole 321 which is embedded in a positioning counter bore (not shown) in the outer plate 331 and is tightly fitted with the positioning counter bore. Preferably, the positioning pole 321 is integrally formed with the inner plate 332. In this embodiment, a step portion 304 in a step shape is provided at the inside end edge of the cylindrical body 30, and the step portion 304 bears against the edge of the inner plate 332. With the above structure, easiness of installation and assembly and compact structure can be achieved. As shown in FIG. 5, in this embodiment, the beam exit opening 11 is filled with a blocking window 12 shown in FIG. 3 or FIG. 10. The blocking window 12 is made of a material through which the X-ray can transmit, and the blocking window 12 has a function of realizing liquid and gas seal between the inside of the case body 1 and the outside of the case body 1. The blocking window 12 seals the beam exit opening 11. On one hand, environment air and dust can be prevented from entering into the case body 1, and on the other hand, when the inside of the shielding device 3 and/or the space for flowing of liquid and mounting of components between the shielding device 3 and the case body 1 is filled with the insulation liquid, the blocking window 12 also can prevent the insulation liquid from flowing out of the case body 1 from the beam exit opening 11. When the inside of the shielding device 3 is filled with the insulation liquid, the X-ray emitted from the X-ray tube 4 will penetrate the insulation liquid and radiate the environment outside of the case body 1 from the blocking window 12. Since the X-ray emitted from the X-ray tub 4 has a high intensity, loss of the X-ray caused by the insulation liquid is slight and usually can be omitted. It should be noted that, in this embodiment, there is a possibility that no blocking window 12 is provided. When the glass hood of the X-ray tube 4 shown in FIG. 5 tightly bears against the end opening of the ray exit aperture 36 at the inside of the shielding device 3, and the ray exit aperture 36, the beam exit aperture (coincident with the ray exit aperture 36), the beam exit opening 11 and the glass hood of the X-ray tube 4 constitute an insulation liquid sealing chamber, the insulation liquid cannot leak from a gap between the X-ray tube 4 and the shielding device 3 to the ray exit aperture 36, the beam exit aperture and the beam exit opening 11. In this embodiment, the insulation material preferably is trilead tetroxide. Plates or containers made of trilead tetroxide remarkably shield the X-ray. In an embodiment, the insulation material may be other lead oxides than trilead tetroxide. Compared with other material, such as lead or lead-antimony alloy, that also can remarkably shield the X-ray, the lead oxides have a lower density, a higher strength and excellent performances of electrical insulation and radiation protection. As shown in FIG. 5 and FIG. 10, in this embodiment, the case body 1 comprises a main body portion 13, a first case cover 14 and a second case cover 15. The first case cover 14 and the second case cover 15 are fixedly provided at the two end openings of the main body portion 13, respectively. The main body portion 13 is integrally formed. The material for the first case cover 14 and the second case cover 15 is the same as that for the main body portion 13. The integrally-formed main body portion 13 has a simple structure, a higher connection strength between respective portions and can be formed by a one-step molding process. Compared with a main body portion 13 formed by jointing plates (usually using screws or through a welding process), the integrally-formed main body portion 13 provides a good sealing effect and an improved leakage protection of the insulation liquid and the X-ray. Furthermore, during operation of the X-ray generator, and especially when the insulation liquid is injected into the case body 1 by using vacuum oil injection (after the insulation liquid is injected from an oil injection orifice 112 shown in FIG. 3 by using vacuum oil injection, a gasket and a sealing bolt 113 are used to seal the oil injection orifice 112), the air outside of the case body 1 will not penetrate the main body portion 13 into the case body 1, and thus negative influence of the air on heat dissipation and insulation effect of the insulation liquid can be avoided. In an embodiment, the main body portion 13 may be formed by jointing and splicing separate structures through welding or screw threaded connection. In that case, the first case cover 14, the second case cover 15 and the main body portion 13 may be made of different materials. As shown in FIGS. 3-5, in this embodiment, sealing strips 345 as shown in FIG. 4 are provided between the first case cover 14 and the main body portion 13 and between the second case cover 15 and the main body portion 13 shown in FIG. 8. The sealing strips 345 are made of rubber material. Specifically, as shown in FIG. 4, the end face of the main body portion 13 is provided with a step face 346 or a groove, and the sealing strip 345 is provided on the step face 346 or provided in the groove and extends beyond the end face of the main body portion 13. The first case cover 14 and the second case cover 15 are close to the surface of the main body portion 13 and press against the sealing strips 345. In such structure, since the sealing strips 345 are pressed when being interposed between the first case cover 14 and the main body portion 13 and between the second case cover 15 and the main body portion 13, the sealing strip 345 can more tightly press against the first case cover 14 and the main body portion 13, an improved sealing effect can be achieved. In the above structure, the sealing strips 345 may be made of other elastic material than rubber material. The sealing strip may be provided only between the first case cover 14 and the main body portion 13 or only between the second case cover 15 and the main body portion 13. In an embodiment, as shown in FIG. 4, the step face 346 or groove may be provided on the edge of the first case cover 14, and/or as shown in FIG. 5, the step face 346 or groove may be provided on the edge of the second case cover 15. In that case, the sealing strip 345 is provided on the step face 346 or provided in the groove and extends beyond the edge of the first case cover 14 and/or the second case cover 15, and the main body portion 13 is close to the surface of the first case cover 14 and/or the second case cover 15 and presses against the sealing strip 345. In this embodiment, as shown in FIG. 5, the main body portion 13 is made of aluminum or aluminum alloy with a high strength and a light weight and is formed by using a stretch forming process. The stretch forming process has a higher manufacture efficiency and can avoid leakage caused by deformation and defect of a welding structure. It should be noted that the case body may be formed by using wire electrode cutting or like and may be made of other material. All in a word, the case 1 of aluminum alloy material formed by a stretch forming process and the shielding device 3 according to this embodiment have advantages over those in the prior art in volume and weight. Hence, the installation case for a radiation device according to this embodiment has an advantage of light weight and can be more easily processed, assembled, and conveyed. As shown in FIGS. 9 and 11, the oil-cooling circulation system according the embodiment comprises a liquid-filled box, the insulation liquid filled in the liquid-filled box and a cooling device 72 for reducing the temperature of the insulation liquid. The cooling device 72 comprises an oil pump 721, a heat radiator 722 and a cooling fan 723. The liquid-filled box is constituted by the installation case for a radiation device according to the above-mentioned embodiment. The heat radiator 722 is located outside of the liquid-filled box. The liquid inlet of the heat radiator 722 is communicated with a liquid outlet of the liquid-filled box, and the liquid outlet of the heat radiator 722 is communicated with a liquid inlet of the liquid-filled box. The oil pump 721 provides a motive power for circulation between the insulation liquid in the liquid-filled box and the insulation liquid in the heat radiator 722. The cooling fan 723 dissipates the heat from the heat radiator 722 in such a way that the flow of ambient air around the heat radiator 722 is expedited. In this embodiment, the insulation liquid is a 25# transformer insulation oil. The insulation liquid not only can, as an insulation medium, prevent respective elements or modules loaded with high voltage from breakdown or short circuit, but also can function as a heat dissipation medium. In an embodiment, the insulation liquid may use other insulation oils than the 25# transformer insulation oil. The X-ray tube 4 can convert only about 1% of energy into the X-ray, and the rest of, about 99%, energy is converted into heat energy and acts on the anode 42 of the X-ray tube 4. Thus, in order to prevent the anode 42 of the X-ray tube 4 from being overheated and hence to prevent a target from being melted and damaged, it is necessary to externally connect with the oil pump 721 and the heat radiator 722 so as to perform circulated oil-cooling heat dissipation. Then, the cooled insulation liquid is returned back to the anode 42 of the X-ray 4, so that heat dissipation can be achieved. In this embodiment, as shown in FIG. 1, an external power supply 8 coming from outside of the case body is 220V AC commercial power. It should be noted that the external power supply 8 may be a secondary battery or an industrial power. By using the fluid channel 312 shown in FIG. 5, the insulation liquid freely flowing within the shielding device 3 and between the case body 1 and the shielding device 3 will transfer the heat generated by the X-ray tube 4 (mainly generated by the anode 42 of the X-ray tube 4) within the shielding device 3 and the case body 1, as shown in FIG. 5, to the heat radiator 722 under the driving provided by the oil pump 721 shown in FIG. 3 or 9, and then the transferred heat is dissipated by the flowing air. Hereafter, the insulation liquid cooled by the heat radiator 722 is input into the shielding device 3 and in between the case body 1 and the shielding device 3 again, and absorbs the heat generated by the X-ray tube 4 again. When the cooling system is designed, not only the efficiencies of heat dissipation of the case body 1, the shielding device 3, the heat radiator 722 and the insulation liquid, but also the power consumption of the oil pump 721 shown in FIG. 3 or FIG. 9 should be synthetically considered, so that a cooling system, in which the heat dissipation performance thus designed can meet the whole heat dissipation requirements of the X-ray generator, can be achieved. In an embodiment, the oil pump 721 may provide a motive power only for circulation between the insulation liquid in the shielding device 3 or the case body 1 and the insulation liquid in the heat radiator 722. As shown in FIGS. 3 and 9, in this embodiment, the oil pump 721 is fixedly provided on the inner wall of the case body 1 (preferably, being fixedly provided on the first case cover 14 using screws or bolts), and is located between the case body 1 and the shielding device 3. The installation space between the case body 1 and the shielding device 3 is large and is suitable for installation of the oil pump 721. In this embodiment, as shown in FIG. 3, a liquid suction port of the oil pump 721 faces toward a liquid outlet of the shielding device 3. A liquid inlet of the shielding device 3 is communicated with a liquid inputting pipe 35. A liquid inlet 111 of the case body 1 is communicated with a liquid introducing pipe 17. A liquid outputting port 170 of the liquid introducing pipe 17 faces toward a liquid inputting port 350 of the liquid inputting pipe 35. In such structure, the oil pump 721 will pump the heat-carried insulation liquid from the liquid outlet of the shielding device 3 and output the heat-carried insulation liquid from a liquid outlet 110 of the case body 1 shown in FIG. 3 to the heat radiator 722. Arrangement of the liquid inputting pipe 35 and the liquid introducing pipe 17 can smoothen flowing of the insulation liquid. In an embodiment, communication of the liquid suction port of the oil pump 721 with the liquid outlet of the shielding device 3 and/or communication of the liquid outputting port 170 of the liquid introducing pipe 17 with the liquid inputting port 350 of the liquid inputting pipe 35 can be achieved by using conduits. The oil pump 721 may be fixedly provided in the heat radiator 722, or may be, in part, fixedly provided between the liquid-filled box and the shielding device 3 and, in part, fixedly provided in the heat radiator 722. In a case where the number of the oil pump 721 is two or more, one or more of the oil pumps may be provided in the heat radiator 722 and the other one or more of the oil pumps may be located between the liquid-filled box and the shielding device 3. As shown in FIG. 3 or 9, in this embodiment, the oil pump 721 is a DC brushless submersible pump which has a good seal, a reduced noise, a low power consumption, a stable performance and a long life span. In an embodiment, the cooling fan 723 shown in FIG. 9 may employ other refrigeration devices, such as a refrigeration device used by a refrigerator or a refrigerating cabinet, to directly refrigerate the heat radiator 722 instead of using air flow to dissipate heat. As shown in FIGS. 9 and 10, in this embodiment, the cooling device 72 further comprises a frame-shaped bracket 724 hooding the heat radiator 722 and the cooling fan 723. The bracket 724 is fixedly connected with two separate components of the case body 1. The bracket 724 is formed by welding pipes of aluminum alloy material with a low density together. Such structure uses less material, and not only can protect the heat radiator 722 and the cooling fan 723, but also can be used as a handle for grasping of a user. In an embodiment, the bracket 724 may be made of other material, may be formed by welding solid rods together, or may be formed by connection structure of screws or bolts with screw holes of rods. The bracket 724 may be replaced with other protection hoods with good ventilation. As shown in FIGS. 1 and 2, the X-ray generator according to the embodiment comprises the X-ray tube 4, the high frequency and high voltage generator 5, a filament power supplying module 6 and the oil-cooling circulation system according to any one of the above embodiments of the present disclosure. The X-ray tube 4 is mounted within the shielding device 3 in the installation case for a radiation device. The X-ray emitted from the X-ray tube 4 passes through the ray exit aperture 36, the beam exit aperture (coincident with the ray exit aperture 36) and the beam exit opening 11 in this order, as shown in FIG. 5, and radiates out of the case body 1 of the installation case for a radiation device. The high frequency and high voltage generator 5 is electrically connected with the cathode 41 and the anode 42 of the X-ray tube 4. The high frequency and high voltage generator 5 is used for providing a DC voltage to the anode 42 and the cathode 41 of the X-ray tube 4. The filament power supplying module 6 is electrically connected with the cathode 41 of the X-ray tube 4, and is used to provide the cathode 41 of the X-ray tube 4 with a high frequency pulse voltage which is sufficiently high for the cathode 41 of the X-ray tube 4 under its high voltage electric field to emit electron flow that can bombard the anode 42. In this embodiment, the shielding device 3 is also provided with the circuit channel 311 as shown in FIG. 5. As shown in FIG. 1, the cathode of the high frequency and high voltage generator 5 is electrically connected with the cathode 41 of the X-ray tube 4 via wires passing through the circuit channel 311. The anode of the high frequency and high voltage generator 5 is electrically connected with the anode 42 of the X-ray tube 4 via wires that are electrically connected with the conductive screw 318 and the conductive stud 317. The filament power supplying module 6 is electrically connected with the cathode 41 of the X-ray tube 4 via wires passing through the circuit channel 311. Parts of the modules constituting the high frequency and high voltage generator 5 are located between the case body 1 and the shielding device 3, and the external power supply 8 and the rest of the modules constituting the high frequency and high voltage generator 5 are located outside of the case body 1. The case body 1 is provided with a wire exit channel 16 shown in FIG. 3. The modules located in the case body 1 are electrically connected with the modules located outside of the case body 1 via interfaces passing through the wire exit channel 16. In an embodiment, all modules constituting the high frequency and high voltage generator 5, that is, the entire high frequency and high voltage generator 5, a sampled-signal processing module 92 and a logic decision and control module 93 may be provided between the case body 1 and the shielding device 3. In that case, the above mentioned electric devices are electrically connected with external power supply circuits and signal transmitting circuits for telecommunication required for operation of these electric devices via interfaces passing through the wire exit channel 16. The above mentioned wires for electric connections may be replaced with interfaces, and vice versa. Further, in this embodiment, parts of the modules constituting the high frequency and high voltage generator 5 shown in FIG. 1 may be located within the shielding device 3. In that case, those, located within the shielding device 3, of the modules constituting the high frequency and high voltage generator 5 shown in FIG. 1 are electrically connected with those, located between the case body 1 and the shielding device 3, of the modules constituting the high frequency and high voltage generator 5 shown in FIG. 1 or with the modules located outside of the case body 1 via wires or interfaces passing through the circuit channel 311 or the circuit channel 311 and the wire exit channel 16. In this embodiment, both of the first end cover 31 and the second end cover 32 are provided with a dual-layer structure constituted by laminating the outer plate 331 and inner plate 332. Both of the first end cover 31 and the second end cover 32 are provided with the circuit channel 311. The circuit channel 311 provided in the first end cover 31 comprises the cathode positioning aperture 313 provided in the inner plate 332 of the first end cover 31 and the wire routing aperture 340 provided in the outer plate 331 of the second end cover 32. In the X-ray tube 4, the sheath 315 for protecting the cathode 41 is embedded in the cathode positioning hole 313, and the wire routing aperture 340 comprises the longitudinal aperture 342 coincident with/parallel to the axial direction of the shielding device 3 and the transverse aperture 341 communicating with the longitudinal aperture 342. The axial direction of the transverse aperture 341 is perpendicular to the axial direction of the longitudinal aperture 342. In the X-ray tube 4, the sheath 315 for protecting the cathode 41 is embedded in the longitudinal aperture 342. The cathode 41 of the X-ray tube 4 is two wires extending beyond the transverse aperture 341 from the sheath 315. The circuit channel 311 provided in the second end cover 32 comprises anode positioning apertures 316 provided in the inner plate 332 and the outer plate 331 of the second end cover 32. The conductive stud 317 orderly passes through the anode positioning apertures 316 provided in the inner plate 332 and the outer plate 331 of the second end cover 32. The conductive stud 317 is provided with an outer screw threaded portion which is engaged with an anode screw hole disposed in the anode 42. The portion of the conductive stud 317 far away from the anode 42 is provided with a positioning screw hole. The conductive screw 318 is provided with an outer screw threaded portion which is engaged with the positioning screw hole. Wires electrically connected with the anode of the high frequency and high voltage generator 5 are sandwiched between the head of the conductive screw 318 and the conductive stud 317. An annular spacer is provided between the conductive screw 318 and the conductive stud 317. The wires electrically connected with the anode of the high frequency and high voltage generator 5 are sandwiched between the spacer and the head of the conductive screw 318. In the present embodiment, as shown in FIG. 6, the inner plate 332 of the second end cover 32 is provided with at least one anode position-limit hole 320. As shown in FIGS. 12 and 13, the anode 42 is provided with a position-limit screw hole 424. A positioning stud 421 is provided with an outer screw threaded portion which is engaged with the position-limit screw hole 424. The end of the positioning stud 421 far away from the position-limit screw hole 424 is inserted into the anode position-limit hole 320. The number of the positioning stud 421 is the same as that of the anode position-limit hole 320 and is two. It should be noted that the number of the positioning stud 421 and the anode position-limit hole 320 may be one or three or more. In this embodiment, the first end cover 31 and the second end cover 32 are provided with fluid channels 312. Both of the first end cover 31 and the second end cover 32 are a dual-layer structure constituted by laminating the outer plate 331 and inner plate 332. There is the liquid flowing cavity 333 between the outer plate 331 and the inner plate 332. The inner plate 332 is provided with the flow guiding orifices 335 communicated with the liquid flowing cavity 333, and the outer plate 331 is provided with the flow guiding orifice 334 communicating with the liquid flowing cavity 333. The fluid channel 312 is constituted by the flow guiding orifice 334, the flow guiding orifices 335 and the liquid flowing cavity 333. As shown in FIG. 12, the anode 42 is in a hood shape and covers the end of the glass hood of the X-ray tube 4 far away from the cathode 41. The liquid flowing space 422 is provided between the anode 42 and the outer circumferential surface of the glass hood of the X-ray tube 4, and the anode 42 is provided with the liquid circulating holes 423 communicating with the liquid flowing space 422. In the present embodiment, the axial direction of the liquid circulating hole 423 is preferably parallel to the axial direction of the X-ray tube 4. The insulation liquid outside the shielding device 3 flows into/flows out of the shielding device 3 through the fluid channel 312 of the second end cover 32, the liquid circulating holes 423 and the liquid flowing space 422. In order to more effectively position the anode 42, one, two or more circumferential screw holes 420 are provided in the outer circumferential surface of the anode 42. The anode 42 is fixed in the shielding device 3 in the circumferential direction by passing screws through the cylindrical body 30 and inserting the screws into the circumferential screw holes 420. For the sake of simplicity, FIG. 12 does not show holes for positioning the anode 42, i.e., the position-limit screw holes 424, and the circumferential screw holes 420 which are visible in FIG. 13. This structure can be easily assembled. The transverse hole 341 and the longitudinal hole 342 form the wire routing aperture 340 in a shape of right-angle polyline. Such structure can ensure that the X-ray emitted from the X-ray tube 4 does not come out of the wire routing aperture 340 while the wire is led out from the wire routing aperture 340. In an embodiment, the wire routing aperture 340 may be an oblique through hole or a through hole in other bent shapes, such as a sharp-angle polyline shape or an obtuse-angle polyline shape. In the present embodiment, as shown in FIG. 5, the liquid outlet of the shielding device 3 is located in the fluid channel 312 of the first end cover 31, and the liquid inlet of the shielding device 3 is located in the fluid channel 312 of the second end cover 32. Since the heat emitted by the X-ray tube 4 mainly comes from the anode 42 of the X-ray tube 4, when the liquid inlet of the shielding device 3 is located in the second end cover 32, the liquid inlet is closer to the anode 42 of the X-ray tube 4, and the insulation liquid with a lower temperature will contact with the anode 42 of the X-ray tube 4 first and take the heat from the anode 42 of the X-ray tube 4 away. In this way, the target of the anode of the X-ray tube 4 can be prevented from being burned out due to excessive heat. The target is located at a position where the X-ray is emitted from the right side in the glass hood (at the center line), as shown in FIG. 12. In this embodiment, constituent modules of the high frequency and high voltage generator 5 shown in FIG. 1 are a first rectification and voltage regulation module 51, a high frequency inverter 52, a high voltage transformer 53 and a voltage-doubling rectification module 54 which are electrically connected with each other in this order. The first rectification and voltage regulation module 51 is electrically connected with the external power supply 8, and takes electrical energy required for loading a DC high voltage on the cathode 41 and the anode 42 of the X-ray tube 4 from the external power supply 8. The voltage-doubling rectification module 54 is electrically connected with the cathode 41 and the anode 42 of the X-ray tube 4. In the constituent modules of the high frequency and high voltage generator 5, the high voltage transformer 53 and the voltage-doubling rectification module 54 are fixedly provided between the case body 1 and the shielding device 3 shown in FIG. 2. The high voltage transformer 53 shown in FIG. 2 is fixedly provided on the collimator 2. It should be noted that the high voltage transformer 53 may be fixedly provided on a PCB board, the first case cover 14 or the second case cover 15. The voltage-doubling rectification module 54 is fixedly provided on a circuit board. At least one of the two ends of the circuit board (FIG. 3 shows the end the height of the position of which is higher.) bears against a position-limit protruding piece 145 fixedly provided on the first case cover 14 or a position-limit protruding piece 145 fixedly provided on the second case cover 15 (FIG. 3 only shows the position-limit protruding piece 145 fixedly provided on the first case cover 14.). The circuit board is fixed on the position-limit protruding pieces 145 by fasteners (preferably made of nylon material). In this embodiment, there are many ways for fixedly connecting the circuit board fixedly provided with the voltage-doubling rectification module 54 with the case body 1. For instance, at least one of the two ends of the circuit board may be inserted into a groove provided on the first case cover 14 or the second case cover 15, and the middle region of the circuit board may be fixed on the main body portion 13 by fasteners. The fasteners are used for preventing vibration or deformation of the circuit board, so that the voltage-doubling rectification module 54 can be prevented from being damaged due to vibration. The above fixing and assembling arrangement of the constituent modules of the high frequency and high voltage generator 5 shown in FIG. 1 provides a compact structure, and the space within the case body 1 can be adequately used. In an embodiment, the voltage-doubling rectification module 54 may be fixedly provided on the surface of the shielding device 3, and the high voltage transformer 53 may be fixedly provided on the side of the first case cover 14 or the second case cover 15 contacting with the insulation liquid. In this embodiment, the first rectification and voltage regulation module 51 is fixedly provided outside of the case body 1, and comprises a full bridge rectification module and a BUCK chopping voltage regulation module. The full bridge rectification module converts the AC supplied by the external power supply 8 into DC. The BUCK chopping voltage regulation module is used for converting a fixed DC voltage into a variable DC voltage, i.e., DC/DC convert. Then the converted DC voltage is input into the high frequency inverter 52. The high frequency inverter 52 is also fixedly provided outside of the case body 1 and employs a full bridge series-parallel resonance high-frequency inverter circuit to inversely convert a low voltage DC into a high frequency and low voltage AC. The high voltage transformer 53 is used for boosting the voltage output from the high frequency inverter 52 and then inputting the boosted voltage into the voltage-doubling rectification module 54. The voltage-doubling rectification module 54 employs a multi-stage (more than two stages) voltage-doubling rectification circuit, and provides boosting and rectifying (AC to DC) functions. Since the high voltage transformer 53 and the voltage-doubling rectification module 54 are usually loaded with a high voltage of about 1 kV or more, when the high voltage transformer 53 and the voltage-doubling rectification module 54 are fixedly provided between the case body 1 and the shielding device 3 and are immersed in the insulation liquid, the insulation liquid can avoid breakdown caused by the high voltage loaded on the high voltage transformer 53 and the voltage-doubling rectification module 54, and the heat generated in the high voltage transformer 53 and the voltage-doubling rectification module 54 can be taken away by the flowing insulation liquid. As shown in FIGS. 1 and 3, in the present embodiment, the X-ray generator also comprises a monitor system. As shown in FIG. 1, the monitor system comprises a signal sampling module 91, the sampled-signal processing module 92, the logic decision and control module 93, and an auxiliary power supply module 94 configured to supply power for the logic decision and control module 93. The signal sampling module 91 is located between the case body 1 and the shielding device 3. The installation space between the case body 1 and the shielding device 3 is large and is suitable for installation of the signal sampling module 91. In an embodiment, the signal sampling module 91 may be mounted within the shielding device 3. The signal sampling module 91 is used for detecting electric signals on the cathode 41 and the anode 42 of the X-ray tube 4, the temperature of the insulation liquid and the flow rate of the insulation liquid flowing into the case body 1, and sends the detected electric signals to the sampled-signal processing module 92. The sampled-signal processing module 92 is electrically connected with the signal sampling module 91 and the logic decision and control module 93. The sampled-signal processing module 92 is configured for processing, such as filtering, the electric signals received from the signal sampling module 91 and eliminating related interference signals, and converting the electric signals into the detection result in a digital form (e.g., in a binary form) through analog-digital conversion and then sending the detection result in a digital form to the logic decision and control module 93. In the present embodiment, the logic decision and control module 93 realizes external data interaction through a series communication interface 95 shown in FIG. 1. It should be noted that the external data interaction may be realized through other communication interfaces or wires, or even may be realized by sending or receiving wireless signals. The logic decision and control module 93 may not output the detection result, but automatically call previously-stored control instructions according to the detection result based on predetermined correspondence rules between the detection result and the control instructions, and control parts or all of the output voltage and/or current of the high frequency and high voltage generator 5, the output voltage and/or current of the filament power supply module 6 and the power consumption of the oil pump 721 according to the corresponding control instructions. In this way, a high degree of automatization can be realized. As shown in FIG. 1, the signal sampling module 91 comprises a kV/mA sampling circuit 911, a temperature sensor 912 and a flow sensor 913. The kV/mA sampling circuit 911 is configured for detecting voltage and/or current on a high voltage loop constituted by the cathode 41 and the anode 42 of the X-ray tube 4. The kV/mA sampling circuit 911 mainly comprises a kV high voltage voltage-divider, a mA sampling resistor and a flashover mutual-inductor. The kV/mA sampling circuit 911 is integrally formed with the voltage-doubling rectification module 54 shown in FIG. 2. It should be noted that the kV/mA sampling circuit 911 and the voltage-doubling rectification module 54 may be formed separately and be electrically connected with each other. The temperature sensor 912 is used for detecting the temperature of the insulation liquid. The flow sensor 913 is used for detecting the flow rate of the insulation liquid passing through the fluid channel 312 shown in FIG. 5. In this embodiment, the electric signals output by the temperature sensor 912 and the flow sensor 913 are in the form of on-off value (in a binary form), and no analog-to-digital conversion is needed. In this way, workload of the sampled-signal processing module 92 is reduced. It should be noted that the electric signals output by the temperature sensor 912 and the flow sensor 913 may be in an analog form. The types of fault signals sampled by the signal sampling module 91 comprise a flow rate fault signal, a temperature fault signal and a flashover fault signal. When the flow rate is not within a predetermined range, the electric signal fed back to the sampled-signal processing module 92 and representative of the out-of-limit flow rate is regarded as the flow rate fault signal. As such, when the temperature goes beyond the predetermined value, the electric signal fed back to the sampled-signal processing module 92 and representative of excess temperature is regarded as the temperature fault signal. In a case where the sampled voltage and/or current values are abnormal, whether a flashover failure is present or not can be determined according to the abnormal voltage and/or current values, and thus the abnormal voltage and/or current values can be regarded as the flashover fault signal. As shown in FIG. 3, the flow sensor 913 is fixedly provided on the liquid introducing pipe 17 of the case body 1. The insulation liquid entering the case body 1 from the heat radiator 722 will pass through the liquid introducing pipe 17. Therefore, the arrangement of the flow sensor 913 being provided on the liquid introducing pipe 17 can precisely detect the flow rate of the insulation liquid entering the case body 1. It should be noted that the flow sensor 913 may be fixedly provided on the liquid outlet 110 of the case body 1. In that case, the flow rate of the insulation liquid flowing out of the case body 1 can be detected. Since the amount of the insulation liquid in the case body 1 is constant, the flow rate of the insulation liquid entering the case body 1 can be inversely derived by detecting the flow rate of all of the insulation liquid flowing out of the case body 1. As shown in FIG. 3, the temperature sensor 912 is fixedly provided in the vicinity of the wire exit channel 16 provided in the case body 1. In this way, the temperature sensor 912 can be led out from the wire exit channel 16 more easily. In this embodiment, as shown in FIG. 1, the filament power supply module 6 comprises a second rectification and voltage regulation module 61 electrically connected with the logic decision and control module 93, a filament inverter 62 and a filament transformer 63 electrically connected with the filament inverter 62 and the cathode 41 of the X-ray tube 4. The filament inverter 62 has a half bridge structure. The filament transformer 63 is fixedly provided at a portion of the inner wall of the main body portion 13 (shown in FIG. 2) which is close to the first case cover 14. The filament transformer 63 is a step-down transformer which is configured to convert the voltage output from the filament inverter 62 into a high frequency pulse voltage required for the cathode 41 of the X-ray tube 4 and to output the high frequency pulse voltage to the cathode 41 of the X-ray tube 4. An interface passing through the wire exit channel 16 provided in the case body 1 shown in FIG. 3 is an aviation plug 161 that provides liquid and gas seal between the inside of the case body 1 and the outside of the case body 1. The high voltage transformer 53 and the high frequency inverter 52, the signal sampling module 91 and the sampled-signal processing module 92, and the filament inverter 62 and the filament transformer 63 are electrically connected with each other via aviation plugs 161, respectively. The voltages applied to the first rectification and voltage regulation module 51, the high frequency inverter 52 and the logic decision and control module 93 are lower. In this embodiment, in order to save the volume of the case body 1 and facilitate installation, detachment, electrical connection and/or parameter setting, the first rectification and voltage regulation module 51, the high frequency inverter 52, the logic decision and control module 93, the second rectification and voltage regulation module 61, the filament inverter 62 and the auxiliary power supply module 94 all are fixedly provided on the outer surface of the case body 1. It should be noted that the first rectification and voltage regulation module 51, the high frequency inverter 52, the second rectification and voltage regulation module 61, the filament inverter 62 and the logic decision and control module 93 may be fixedly provided in a control box provided outside of the case body 1. The control box may be fixedly provided on the outer surface of the case body 1, or may be separately provided on a shelf or a machine case. Related electric signals coming from the control box may be electrically connected with the aviation plug 161 (shown in FIG. 3) via wires passing through the control box. As shown in FIGS. 3 and 10, the aviation plug 161 has a good seal, can be easily mounted and can provide stable electric signal transmission. The interfaces may be combination of wires and sealing members, such as a sealing ring. It should be noted that the high voltage transformer 53 and the high frequency inverter 52, the signal sampling module 91 and the sampled-signal processing module 92, and the filament inverter 62 and the filament transformer 63 may be, in part, electrically connected with each other via the aviation plugs 161, and may be, in part, electrically connected with each other via wires or other interfaces, respectively. In this embodiment, as shown in FIG. 2, the collimator 2 is provided with a plurality of screw holes 21 the number of which is more than two, and the case body 1 is provided with mounting holes that are coaxial with the screw holes 21. The case body 1 (the main body portion 13, as shown in FIG. 5) is fixedly connected with the collimator 2 via screws orderly passing through the mounting holes and the screw holes 21. The connection structure constituted by the screw holes 21 and the screws can be easily assembled and detached. When the X-ray tube 4 according to the present embodiment is mounted, the oil pump 721, the filament transformer 63, the circuit board provided with the voltage-doubling rectification module 54 and the aviation plug 161 are integrally mounted on the first case cover 14 first, and then the X-ray tube 4 is mounted between the first end cover 31 and the second end cover 32 of the shielding device 3. After related electrical connections are completed, the whole structure is pushed into the case body 1. Then, the shielding device 3 (including the collimator 2) is fixed on the main body portion 13 shown in FIG. 5 through screws, and the oil introducing pipe 17 and the oil outlet 110 are connected with each other. Finally, the first case cover 14 and the second case cover 15 are hermetically fixed on the main body portion 13. It should be noted that the screws may be replaced with other fasteners, such as bolts or studs, which are provided with screw threads. As shown in FIG. 2, the number of the screw holes 21 may be one, one row or a plurality of rows (two rows or more). The specific number of the screw holes 21 can be set according to practical requirements (e.g., the size of the screws or bolts suitable for an installation site). As shown in FIGS. 5 and 8, in this embodiment, the installation case for a radiation device comprises the case body 1 as described above, a protrusion edge 18 fixedly provided on the inner wall of the case body 1 and in a ring shape, and a compensation device which is liquid-hermetically and fixedly connected or liquid-hermetically and movably connected with the protrusion edge 18. One of two sides of the compensation device, the inner wall of the case body 1 and the protrusion edge 18 form a liquid receiving chamber for receiving the insulation liquid. The inner wall of the case body 1 opposite to the other one of the two sides of the compensation device and the inner wall of the protrusion edge 18 form a compensation device moving space configured to allow the compensation device to deform or move along a direction approaching to or away from the insulation liquid. In the present disclosure, since the protrusion edge 18 is provided on the inner wall of the case body 1, the compensation device is liquid-hermetically and fixedly connected or liquid-hermetically and movably connected with the protrusion edge 18. When the case body 1 comprises the main body portion 13, the first case cover 14 and the second case cover 15 shown in FIG. 5, the components can be assembled into the complete case body after the compensation device has been separately mounted on the protrusion edge 18 on the second case cover 15. Thus, assembly of the compensation device and assembly of the case body can be separately carried out. Such separate assemblies are laborsaving and convenient and can reduce installation errors. Furthermore, since the height of the protrusion edge 18 can be designed according to practical requirements, the depth and size of the compensation device moving space also can be designed according to practical requirements. The protrusion edge 18 not only can provide a function of fixing the compensation device, but also can guide the orientation of deformation or movement of the compensation device, and thus the orientation of deformation or movement of the compensation device will be more regular. Besides, since the inner diameter of the protrusion edge 18 is less than that of the second case cover 15, the required area of the compensation device will be less than that of the second case cover 15 in this embodiment, and the material used for the compensation device will be less. Further, the operation of connection of the protrusion edge 18 with the compensation device is performed in the case body 1, and good liquid seal can be achieved. In this embodiment, as shown in FIG. 5 or 8, the compensation device is an elastic diaphragm 19 that is fixedly connected with an opening of the protrusion edge 18 away from the inner wall of the case body 1 and covers the opening of the protrusion edge 18 away from the inner wall of the case body 1. The elastic diaphragm 19 can deform along the direction approaching to or away from the insulation liquid within the compensation device moving space. When the insulation liquid is subject to an thermal expansion phenomenon, the volume of the insulation liquid will expand and will press the elastic diaphragm 19 to deform along the direction away from the insulation liquid, i.e., the direction approaching to the second case cover 15; when the insulation liquid is subject to a cold contraction phenomenon, the volume of the insulation liquid will contract, and the elastic diaphragm 19 will deform along the direction approaching to the insulation liquid, i.e., the direction away from the second case cover 15, and press the insulation liquid, so that the thermal expansion and cold contraction of the insulation liquid can be compensated by elastic deformation of the elastic diaphragm 19. In this way, the case body 1 can be ensured to be filled with the insulation liquid throughout, and the pressure applied to everywhere in the case body 1 and respective electric elements by the insulation liquid will be substantially constant. Thus, the case body 1 and the electric elements within the case body 1 will not be damaged due to excess pressure from the insulation liquid. Meanwhile, when the oil is injected into the case body 1 by using vacuum oil injection, the elastic diaphragm 19 will press the insulation liquid in an elastic deformation manner after the injection operation of the insulation liquid into the case body 1 is finished. In this way, it can be ensured that the insulation liquid fills the entire case body 1, and hence the oil amount in the case body 1 can meet the requirements. It should be noted that the compensation device may be a piston (not shown in Figs.) provided in the protrusion edge 18 shown in FIG. 2. The piston can slideably move in the compensation device moving space along the direction approaching to or away from the insulation liquid. In that case, a dropping-out preventing structure for preventing the piston from getting out of the protrusion edge 18 can be provided between the piston and the inner wall of the protrusion edge 18. The dropping-out preventing structure may be a protruding side edge fixedly provided on the inner wall of the protrusion edge 18 away from the insulation liquid. The protruding side edge may be integrally formed with the inner wall of the case body. In this embodiment, as shown in FIG. 5, the case body 1 is further provided with an air guiding aperture 114 communicating with the ambient air (outside of the case body 1) and the compensation device moving space. The elastic diaphragm 19 will press the air in the compensation device moving space when the elastic diaphragm 19 deforms along the direction approaching to the second case cover 15, so that the air in the compensation device moving space will be discharged from the air guiding aperture 114; when the elastic diaphragm 19 deforms along the direction away from the second case cover 15, the air outside of the case body 1 will flow into the compensation device moving space, so that the elastic diaphragm 19 is ensured to deform in the compensation device moving space more easily. The size of the diameter of the air guiding aperture 114 can be designed according to practical requirements. The arrangement of the compensation device moving space enlarges the space for elastic deformation of the elastic diaphragm 19. It should be noted that in order to realize function of the elastic diaphragm 19, other elastic structures or elastic members may be provided in the case body 1 to replace the above structure. Further, relevant movement and protection design is needed. For instance, an inflatable bag communicating with the air guiding aperture 114 and having an elasticity is fixedly provided in the case body 1, and the joint portion of the inflatable bag with the air guiding aperture 114 is liquid-hermetical, so that the insulation liquid can be prevented from leaking out of the case body 1 from the joint portion of the inflatable bag with the air guiding aperture 114. The inflatable bag communicates with the ambient air via the air guiding aperture 114. The inflatable bag follows the same principle of compensating thermal expansion and cold contraction of the insulation liquid in an elastic deformation manner as acted by the elastic diaphragm 19. However, when the oil is injected into the case body 1 by using an external vacuum oil injection, if there is no protection measure for the inflatable gas, then the inflatable gas should be ensured to be filled with an appropriate amount of the air all the time, so that it can be ensured that the inflatable bag can always apply a certain elastic pressure to the insulation liquid, or at the same time the inflatable bag is evacuated, so that it can prevent the inflatable bag from being broken due to expansion. Further, sealing problem also exists in the technical scheme including the inflatable bag. In this embodiment, as shown in FIG. 5, the side of the elastic diaphragm 19 away from the inner wall of the case body 1 is provided with a pressing plate 20. The edge of the pressing plate 20 bears the edge of the elastic diaphragm 19 against the protrusion edge 18, and the edge of the pressing plate 20 is fixedly connected with the protrusion edge 18 via fasteners 201. A plurality of through holes 202 (more than two) through which the insulation liquid can freely pass are provided in the middle region of the pressing plate 20, as shown in FIG. 5. In this embodiment, the side of the elastic diaphragm 19 close to the protrusion edge 18 or the side of the elastic diaphragm 19 close to the pressing plate 20 is fixedly provided with at least one protrusion portions 191 in a convex shape, and the protrusion edge 18 or the pressing plate 20 is provided with recesses in a concave shape. The protrusion portions 191 are engaged in the recesses. The engagement structure of the protrusion portion 191 and the recesses provides a more reliable seal. Preferably, the protrusion portion 191 and the recesses are interference-fitted to each other. In this embodiment, the protrusion portion 191 is in an annular shape. The axis of the protrusion portion is coincident with that of the protrusion edge 18. With such structure, sealing between the entire protrusion edge 18 and the elastic diaphragm 19 is more reliable. The pressing plate 20 functions to reliably fix the elastic diaphragm 19 and to prevent damage of the elastic diaphragm 19 caused by the elastic diaphragm 19 excessively extending beyond the protrusion edge 18 due to deformation. At the same time, the plurality of through holes 202 in the pressing plate 20 can ensure that the insulation liquid can contact with the elastic diaphragm 19, so that the elastic diaphragm 19 can play a role. The design of the pressing plate 20 enables the X-ray generator to be adapted to oil injection conducted outside of a vacuum apparatus and oil injection conducted inside of a vacuum apparatus. In an embodiment, the pressing plate 20 may be replaced with a sieve or other fixing structures. In this embodiment, as shown in FIGS. 5 and 8, the middle region of the side of the elastic diaphragm 19 close to the pressing plate 20 is in a folded shape. The elastic diaphragm 19 in the folded shape has a better elasticity. Since the side edge region of the elastic diaphragm 19 is relatively flat, once the portion of the elastic diaphragm 19 in the folded shape is directly placed on the middle portion of the protrusion edge 18, the elastic diaphragm 19 can be aligned with the protrusion edge 18 and the elastic diaphragm 19 can be easily mounted. In this embodiment, as shown in FIG. 5, the side edge of the pressing plate 20 is fixedly connected with the protrusion edge 18 via the fasteners 201. The fasteners 201 are screws or other fasteners. As shown in FIG. 5, in this embodiment, the protrusion edge 18 is integrally formed with the second case cover 15. Such structure facilitates formation in a one-step molding process, and compared with the structure formed by assembling separate components, connection strength between respective components of such structure is stronger. In an embodiment, the protrusion edge 18 may be integrally formed with one of the first case cover 14 and the main body portion 13, or the protrusion edge 18 and one of the first case cover 14, the second case cover 15 and the main body portion 13 may be separately formed and are fixedly connected with each other. The number of the protrusion edge 18 in the case body 1 may be one or two or more, depending on the amount of thermal expansion and cold contraction of the insulation liquid. In this embodiment, as shown in FIGS. 5 and 10, on the outer surface of the main body portion 13, there is provided a plurality of reinforcement ribs 22 (more than two) that are integrally formed with the main body portion 13. The reinforcement ribs 22 are provided with screw holes 21 and are symmetrically provided on the main body portion 13. On one hand, the reinforcement ribs 22 can reinforce the strength of the main body portion 13, and on the other hand, the screw holes 21 of the reinforcement ribs can be detachably connected with other external devices or frames. In an embodiment, the reinforcement ribs 22 may be provided on the first case cover 14 or the second case cover 15, and the number of the reinforcement rib may be one. As shown in FIGS. 2, 3 and 5, in this embodiment, the protrusion edge 18 is in a circular annular shape. The profile of the cross-section of the protrusion edge 18 is a circle. The pressing plate 20 is in a circular disk shape. The fasteners 201 are distributed on the pressing plate 20, the elastic diaphragm 19 and the protrusion edge 18 at equal angle intervals in the circumferential direction of the pressing plate 20. With such structure, the pressing forces to which the pressing plate 20, the elastic diaphragm 19 and the protrusion edge 18 are subject and applied by the fasteners 201 are more even. The pressing plate 20, the elastic diaphragm 19 and the protrusion edge 18 (especially the elastic diaphragm 19) are unlikely to be damaged, and fixed connections between them are more reliable. It should be noted that the cross-section of the protrusion edge 18 may be in an elliptical shape, a triangular shape, a rectangular shape (including an oblong shape and a square shape) or one of other polygons than the triangular shape and the rectangular shape. In a case where the cross-section of the protrusion edge 18 is rectangular, the pressing plate 20 is a rectangular plate. The protrusion edge 18 and the pressing plate 20, the elastic diaphragm 19 and the like provided on it can be provided on the shielding device 3. For instance, these components can be provided on the cylindrical body 30, the first end cover 31 or the second end cover 32. In that case, the shielding device 3 may be substantively regarded as an installation case for a radiation device which is also within the scope of the present disclosure. In this embodiment, the material for the elastic diaphragm 19 is nitrile-butadiene rubber. It should be noted that the elastic diaphragm 19 may be made of other oil-resistant elastic material, such as fluoro-rubber material. It should be noted that the above embodiments only are examples for explaining the present disclosure and are not intended to limit the present disclosure. Although preferred embodiments for the general concept of the present disclosure have been shown and explained in details, the skilled person in the art will appreciate that modifications to the above embodiments or equivalent replacement to part of the technical features can be carried out without departing from the spirit and principle of the present general inventive concept. The scope of the present disclosure should be defined by the appended claims and equivalents thereof. |
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description | This application is a continuation of, and claims the benefit of the earlier filing date of, U.S. patent application Ser. No. 11/124,776, entitled “System and Method for Preparing Trace Data in Analysis,” filed on May 9, 2005, now U.S. Pat. No. 7,243,046. A portion of the disclosure of this patent document contains command formats and other computer language listings, all of which are subject to copyright protection. The copyright owner, EMC Corporation, has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. This invention relates generally to systems and methods for preparation of workload data from a data storage environment for analysis, and more particularly to a system and method that may access trace data of workload activity produced in a data storage system, prepare it, and then analyze the trace data in the same or a different environment for benchmark testing or other reasons. This application is related to co-pending U.S. patent application Ser. No. 11/124,875 entitled “System And Method For Handling Trace Data for Analysis” by Sahin, et al, filed on May 9, 2005, and is assigned to EMC Corporation, the same assignee as this invention. It is well known to capture workload data from a data storage system for different reasons including analysis for troubleshooting or performance-related issues. A problem encountered in trace processing and analysis is caused by the huge amount of information contained in a captured trace. The longer the trace duration and more complex the box configuration the bigger the trace size. The typical trace size for several minutes of data collection may reach hundreds of megabytes. Because of the size constraint, the analysis program cannot hold all relevant data in computer memory. It would be an advancement in the art to solve these and other trace-related analysis programs associated with captured trace data. To overcome the problems of the prior art mentioned above and to provide advantages also described above, this invention in one embodiment is a method for preparing captured traces of workload data in a data storage environment for analysis. The traces are prepared by categorizing information from the capture trace into categories. The categories are related to (i) components in the data storage system experiencing the traced workload activity and (ii) information type including response times and task events. The categories are used for access to trace-related information for trace analysis by the computerized trace analysis process. In another embodiment the invention is an apparatus enabled for performing method steps of the method embodiment. In another embodiment the invention is a system enabled for performing method steps of the method embodiment. In still another embodiment the invention is a computer program product including a computer-readable medium having program logic encoded thereon that enables performance of method steps of the method embodiment. Embodiments of the present invention provide a unique system, method, and program product for understanding, analyzing and troubleshooting performance issues in a data storage environment. Overview The invention is directed toward preparing and handling trace information to be used for understanding, analyzing and troubleshooting performance issues in a data storage system. So the first step of the overall embodiment of the method is to access a workload. Such accessed data is typically in the form of trace data accessed form I/Os operating on data volumes or logical devices on one or more data storage systems. Logical devices are sometimes interchangeably referred to as data volumes and generally refer to logical representations of physical volumes of data on a physical storage device. A workload trace data accessing system useful with the present invention is described in U.S. Pat. No. 6,813,731 entitled “METHODS AND APPARATUS FOR ACCESSING TRACE DATA” to Zahavi et al. issued Nov. 2, 2004 and assigned to EMC Corporation the assignee of the present application and which is hereby incorporated by reference. A system and method for trace data capture are also described in U.S. Pat. No. 6,769,054 “System and method for Preparation of Workload Data for Replaying in a Data Storage Environment” to Sahin, et al. issued Jul. 27, 2004 and also assigned to EMC Corporation the assignee of the present application and which is hereby incorporated by reference. In general, and preferably, for the accessing of data it is extracted to a binary file for processing. The size of the trace file depends on the events being traced, the number of IOs traced and the trace duration. Once data is accessed in the form of a trace file it can be made ready for being analyzed, and analyzed as described in more detail below. The trace file contains information about I/O activity also referred to as workload data on the data storage system from which the trace was accessed. Such a data storage system may be the preferred EMC Symmetrix Data Storage System or CLARiiON Data Storage System available from EMC Corporation of Hopkinton, Mass. In a preferred embodiment the exemplary data storage system for which workload data is to be captured and analyzed in accordance with methodology described herein is a Symmetrix Integrated Cache Disk Arrays available from EMC Corporation of Hopkinton, Mass. However, it will be apparent to those with skill in the art that there this invention is useful with any data storage system. Nevertheless, regarding the preferred embodiment, such a data storage system and its implementation is fully described in U.S. Pat. No. 6,101,497 issued Aug. 8, 2000, and also in U.S. Pat. No. 5,206,939 issued Apr. 27, 1993, each of which is assigned to EMC the assignee of this invention and each of which is hereby incorporated by reference. Consequently, the following discussion makes only general references to the operation of such systems. Overview of Trace Creation or Access Step The data storage system is equipped with an event trace routine configured according to embodiments of the invention which is able to access trace data and/or trace buffer pointer information for a trace buffer when called upon to do so by the Trace Capture Process. Using the event trace routine, the Trace Capture Process can determine when new trace data is available in the trace buffer in the data storage system, for example, by detecting advancement of a trace buffer pointer. The Trace Capture Process can then use the event trace routine to access (i.e., to read) the trace data in the trace buffer and to obtain an update on the current value of the trace buffer pointer. By keeping track of previous and current trace buffer pointer locations and how frequently the trace buffer pointer changes, the Trace Capture Process can determine exactly how much, and how frequently, trace data is written to or added to the trace buffer during operation (e.g., execution) of a software program in trace mode in the data storage system. Embodiments of the Trace Capture Process can adjust the frequency or timing between calls to the event trace routine to obtain trace data from the trace buffer at a rate sufficient enough to avoid trace data being overwritten in the trace buffer. The timing between calls to the event trace routine can be adjusted dynamically according to an adaptive timing algorithm which can take into account such factors as the number of events being traced, the amount of trace data created during the occurrence of trace events, and the speed and length of time during which the software program operating in trace mode is allowed to perform. Embodiments of the invention can thus remotely capture trace data over prolonged periods of performance of software programs that operate in trace mode in a data storage system without software developers having to interrupt the software programs in order to manually capture the trace data. Overview of Preparation and Handling for Analysis Process Based on a critical recognition by the inventor that a problem encountered in trace processing and analysis is caused by the huge amount of information contained in the trace, the inventors include modules for functionality to achieve the following methodology (reference is made to a Trace Analysis Process and Trace File which are explained further below): 1. Handling/categorizing of trace data in multiple files organized by components and by the information they contain (IO rate, event tasks or response time). This provides quick access to component data when necessary. 2. Creating a relatively small file that contains the summary information about the trace. Since the trace files are large, it is very difficult to share them with others. With the summary files, field personnel can share interesting cases with their peers and performance experts in corporate headquarters. 3. A server program that listens for client analysis programs. When a Trace Analysis Process session starts, it connects to the server and reports who is using the program and for how long. Also, the client Trace Analysis Process can transfer summary trace file into the server. This enables a. Further analysis by using the summary data b. A database of summary file examples showing customer performance problems, symptoms and potential solutions. 4. A multipass operation for a Microsoft Windows operating system, which has a limit on the number of open files. When trace data is rearranged into multiple component files, the program needs to open many more files than this limit. The Trace Analysis Process overcomes this limitation by passing through the Trace File multiple times.System Architecture of an Embodiment Useful for Capturing and Replaying Trace Data FIG. 1 illustrates an example of a computing system environment 100 configured in accordance with embodiments of the invention. The computing system environment 100 includes a host computer system 110-1 and 110-2 coupled via data interface lines 130, 131, 133 and 137, respectively as shown, to data storage system 150. The host computer system 110-1 includes an interconnection mechanism 112 coupling a memory 114, a processor with clock 116, a host interface 118. The memory 114 is encoded with program logic instructions such as software application code and/or data which collectively form A Trace Capture Application 120-1 configured in accordance with embodiments of the invention. The I/O activity from the hosts is directed over respective host interfaces 118 and 119 and their respective host bus adapters (HBA's), network interface cards (NIC's) or any other contemporary interconnectivity adapters 118A-B, and 119A-B to respective host channel directors 155 and 157 and their respective ports 155A-B and 157A-B. The processor 116 can access the logic instructions that form the trace capture application 120-1 via the interconnection mechanism 112 to the memory 114 in order to perform (e.g., execute, run, interpret or otherwise operate) such logic instructions. When this happens, a Trace Capture Process 120-2 is formed via the combination of the logic instructions of the trace capture application 120-1 operating on the processor 116. In other words, the trace capture application 120-1 represents an embodiment of the invention in a computer readable medium such as the memory 114, which includes logic instructions that when performed on the processor 116, provide an embodiment of the invention referred to herein as the Trace Capture Process 120-2. During operation, the Trace Capture Process 120-2 can access a trace database 122 in order to store trace data, as will be explained. The host computer system 110-2 includes an interconnection mechanism 112 coupling a memory 115, a processor with clock 117, and a host interface 119. The memory is encoded with logic instructions such as software application code and/or data that collectively form a Trace Analysis Application 121-1. The processor can access the logic instructions that form the workload via the interconnection mechanism 121 to the memory in order to perform (e.g., execute, run, interpret or otherwise operate) such logic instructions. When this happens, a Trace Analysis Process 121-2 is formed via the combination of the logic instructions of the application operating on the processor. In other words, the Trace Analysis Application represents an embodiment of the invention in a computer readable medium such as the memory, which includes logic instructions that when performed on the processor, provide an embodiment of the invention referred to herein as the Trace Analysis Process. The methods and apparatus of this invention may take the form, at least partially, of program code (i.e., instructions) embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, random access or read only-memory, or any other machine-readable storage medium forming a computer program product. FIG. 22 shows such a computer program product 700 including a computer readable medium 704 including (Trace Analysis) Program Logic 710 that when executed by a CPU becomes all or part of the Trace Analysis Process 121-2 for carrying out the methodology described herein. When the Program Logic or program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. The methods and apparatus of the present invention may also be embodied in the form of program code that is transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via any other form of transmission. And may be implemented such that herein, when the program code is received and loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. When implemented on one or more general-purpose processors, the program code combines with such a processor to provide a unique apparatus that operate analogously to specific logic circuits. Returning to the aspect of capturing the trace data, reference is once again made to FIG. 1. The data storage system 150 includes an interconnection mechanism 152 which couples a trace enabled front end interface 154, a trace enabled back end interface 156 and a cache 158 (e.g., a cache memory system). In this example embodiment, the cache 158 is encoded with a trace buffer 160 (e.g., a data structure) which is able to store trace data 190. The trace enabled back end interface 156 includes a coupling 170 to one or more storage devices 172 which may be disk drives, tape drives, or any other storage media. According to the general operation of the data storage system 150, the trace enabled front end interface 154 couples to the data interface 130 to process data access requests (not specifically shown) on behalf of host computer systems (e.g., 110 and others, not specifically shown) for access to data stored within the data storage system 150. The trace enabled back end interface 156 handles data access operations related to data stored within the storage devices 172. An example implementation of the data storage system 150 is a Symmetrix data storage system manufactured by EMC Corporation of Hopkinton, Mass., USA. The trace enabled front end interface 154 and the trace enabled back end interface 156 are called “trace enabled” interfaces since each represents at least one processor which can perform a respective software program 153-1, 153-2 that can each operate in trace mode to produce the trace data 190 within the trace buffer 160. For purposes of the descriptions of embodiments of this invention, it is not particularly important which processor (one or more) operating a software program 153 (e.g., 153-1 or 153-2) within the data storage system 150 produces the trace data 190 in a trace buffer 160. To this end, the software programs 153-1 and 153-2 may be different and may operate separately or together to produce trace data 190 separately or concurrently. In this example then, such trace data 190 may be produced and placed into the trace buffer 160 from either the front end or back end interfaces 154 or 156. It is to be understood that these processors 154, 156 operating the software programs 153-1, 153-2 are illustrative only and that any processor within any component (e.g., a processor operating perhaps within a storage device 172) in the data storage system 150 may produce the trace data 190 in the trace buffer 160. The incorporated '731 and '054 patents show techniques for capturing traces, so not much more detail is given here regarding trace capturing for the sake of simplicity. Also, while the example explanations of preferred embodiments presented herein explain certain techniques for accessing trace data and reconfiguring it prior to trace analyzing, it is to be understood by those skilled in the art that variations on these mechanisms and techniques are possible and are intended to be within the scope of embodiments of the invention. For example, the host computer systems may be any type of general purpose or dedicated (e.g., specific purpose) computer system and it is to be understood that the host computer system shown in the figures is shown by way of example only. Likewise, the data storage system can be any type of data storage system, large or small, and may contain any number of processors that operate to produce trace data 190 in a manner such as that explained above, and analysis it as described below. Referring to FIG. 1 an operational feature of the Trace Capture Process is shown. The feature provides exchanging data storage system configuration and project files. A Trace Analysis Server Program 300-1 runs on host computer 110-2 and when executing becomes Trace Analysis Server Process 300-2. Another program which is Client Program 302-1 when executing as Client Process 302-2 is embedded into every Trace Capture Process. The computers 110-1 and 110-2 are connected with Ethernet running TCP/IP. The connection type and communication protocol can be any contemporary protocols available. The Client Process finds the Server and sends it different statistics about users, session duration and such information. Also, the Client can transfer (upload) project summary trace files directly to the server (project files are discussed in detail below. This enables further analysis by the engineering using the summary data and a creation of a database (not shown) of summary file examples showing customer performance problems, symptoms and potential solutions. This server communication is conceptualized as the Server Communication Module. FIG. 2 shows a schematic of the cooperative interaction of the Trace Capture Process 120-2 and Trace Analysis Process including the following modules: Handling and Categorizing Module 150; Trace File Summarizing Module 152; Server Communication Module 154; and Multipass Module 156. Characteristics of these modules are described below; however the module functions are explained herein as a conceptual model for explaining the major types of functions performed with the Trace Analysis Process rather than necessarily indicating that there are specific program code parsed into such modules (although that could be the case). FIG. 3 shows an example of information in Trace File 160 including I/O timestamp information 162 including several information fields. A time stamp field records when the IO is issued by the host system or received by the storage system, it is a floating point number, the unit is seconds. For example, in FIG. 3, a time stamp field reads 318.161743 seconds. The operation IO type shows the direction of the IO relative to the storage system, i.e., whether a Read or Write command is issued to disk, preferably a text string. A port identifier field yields a record of either the Source port id (e.g. 16a) that indicates which HBA (host-based adapter: the fibre channel or SCSI card on the host) initiated the IO, on a preferred EMC Symmetrix system. Other IO information is also presented, but for the sake of simplicity it will not be described further. Initial processing of the trace is made on the component level, i.e. for each active component in the preferred Cache Disk Array Data Storage System the corresponding file is created containing the trace information pertinent for this component only. For easier identification it is a good choice to choose a file name that is meaningful containing component name, for example lv—008D.txt—for logical volume 008D, disk_data08B-D8.txt and disk_prot08B-D8.txt—for disk 08B-D8, cpu—14B.txt—for cpu 14B. This is one of the functions of the Categorizing Module, and other functions are described below. Due to the fact that a large data storage system such as a preferred Symmetrix may contain thousands of components of one type, to overcome operational system number of simultaneously open files limit multiple scanning of trace is done. Important to note that this time consuming procedure should best be done only once during the first trace processing and created component files may be used in later sessions. Also, these component files may be used for extracting detailed trace information at any timestamp. The typical statistics is collected in the table presented on user screen 200 in the FIG. 5A. As discussed above, the original trace information contains real timestamps of all IO's, which are not convenient for understandable presentation in a table or graphical form of IO rates. Therefore, during the first trace processing the default compartmenting of trace statistics is done. The default bucket size is 1 sec. In parallel, during the first trace processing, the main trace statistics is estimated for sub-bucket 0.1 sec. The difference in IO rates between bucket and sub-bucket gives information about bursts in the trace. Referring to FIG. 4, schematics are shown for illustrating that the Trace File 160 and Configuration File 163 are key inputs for the Trace Analysis Process 121-2. In the preferred Symmetrix system, the configuration is gathered from an internal configuration file. The configuration file provides mapping of the devices in the front end (host-adapter) and in the back end (disk-adapter). Furthermore, it includes how logical volumes are mapped to physical drives, as well as mirror and parity locations. The Trace Analysis Process uses the information in the configuration file to separately analyze each of the components in the system. The components are the front end and back end CPUs, logical volumes (a.k.a. LUNs—logical unit numbers), and physical drives. Event traces includes multiple (tens) of events for every IO in the system. Each trace event contains specific information about particular action taken by the system at a particular time instant. The time resolution of events in the system is in the order of microseconds. For example there are events, such as Command Descriptor Block (CDB) events in the open systems emulations and Command and Command Parameters events in the mainframe emulations that indicate start of an IO with details about the IO: logical volume, director/controller, IO type (read, write, etc), IO size, and IO address. There is also another event that indicates the end of the IO. Using the events showing the start and end of IO it is possible to calculate the response time of an IO inside Symmetrix. In addition, there are events that give information about specific phases of IO's. For example, the task events provide information about the duration of emulation tasks. Traces show the workload profile one IO at a time. The Trace Analysis process then singles out individual IO's if for example it takes too long to complete it. The Trace Analysis Process also allows compartmentalizing the information in traces to get averaged values at any time resolution, including coarse time resolutions that conventional analysis programs provide. The users can load multiple segmented and compressed trace files directly into the Trace Analysis Process which then un-compresses and merges them. The trace events that are recognized and analyzed include: CDB (OS emulation) and Command and Command Parameters (Mainframe computer emulation) events DV TASK event: is event that shows the duration of emulation tasks. Several other events to determine end of an IO in order to calculate the response time. The traces collected from front end and back end directors are processed and analyzed. FIG. 5B shows a dialog presented on user screen 202, wherein the user may control the bucket size to make more or less dense trace processing. The information about component trace information is stored in a specially designated format for this file (for example, lv_buck—00DA.txt.—contains information for logical volume 00DA). It gives opportunity to plot IO rates in a very fast manner for any component (for selected compartment or bucket size) and for the whole data storage systems or box level as discussed presented in FIG. 16 discussed below. FIGS. 6A-6B show event types that are included in Trace Events. FIG. 6A shows in information box 206 CDB trace in the inline format received in the Trace Capture Process. On the other hand, FIG. 6B shows in information box 208 the CDB trace event in a text format converted by the Trace Analysis Process and which can be presented to a user on a user screen for better understanding. FIG. 7 shows that the Trace File 160 including Events 164 are handled by the Trace Analysis Process as shown in Functional box 210 that includes the operations of Splitting Information into many files by Components or by Information Type. Trace files may be quite large. The size of the trace file depends on the duration of trace collected and the number of events collected. The more events collected, and the longer the trace, the larger the file is. It is possible to collect several gigabytes of traces. But typically 30-300 MB traces are collected from data storage systems operating in the field. The Trace Analysis Program should have access to information in the traces. There are two approaches: 1) Store the trace file and all possible information combinations in the trace in the computer's RAM. The computer referred to here is the computer analyzing the trace, i.e. running the Trace Analysis Process. This provides quick access to information; however, due to size requirements it is nearly impossible to fit everything into the RAM available in contemporary computers. Once the RAM is full, the computers starts swapping in and out of local disk drive. This slows down the processing since page swaps are not controlled by the analysis program. 2) The alternative is to keep all relevant information in files in the local disk drive arranged specifically by the analysis program so that access to them will be relatively quick. It is preferred to implement this second approach, but one skilled in the art will recognize that the first approach may be used. When a user loads a new Trace File, the Trace Analysis Process splits the information in the trace by the components (front end LV, back end LV, front end director, back end director, disk, etc), and by the information type (IO rate, alignment, sequentiality, task events, response time). The split information is placed in many files in the same location as the trace file. Thus, the program requires file access very frequently. As accessing network shares is costlier (time, bandwidth etc) than accessing local hard drive(s), it may be preferable to avoid loading files from network shares. FIG. 8 shows information presented on user screen 212 including the directory structure, input files, task events and other information. Importantly, one may note that the original trace file size (uncompressed) is 64 MB, but the summary (.smt) file is only 93 KB, a significant decrease in size yet critical information for the Trace Analysis Process is available in the .smt file. An important feature of the Trace Analysis Process is a creation of a project summary (.smt) file. Despite a usually very large size of the Trace File, the project .smt file is only a fraction of its size. Yet, the .smt file contains about 90% of trace statistical information such as rates, misalignment parameters, sequences. In .smt-only session rates, misalignment and sequentiality plots as well as troubleshooting results may be restored without any access neither to original trace file not to split component files. In such a way, field personnel can share interesting cases with their peers and performance experts in corporate headquarters (sending project files by, for example, email). The structure of these Trace Files are described in the project file (.smt file). This way, when a user wants to continue analysis at a later time, s/he can just load the smt file and avoid time consuming re-splitting process. Two functions of the project file include (1) providing quick and easy access to split file structure; and (2) sharing among analysts. Depending on the trace file size and strength of computer CPU/hard disk, it could take a few minutes to half an hour to load and split the trace file. But once the trace is loaded and split, it is just a fraction of a second to load the project or .smt file and continue with the analysis. As mentioned above, there is a significant size difference between trace file (64 MB) and the .smt file (93 KB). This example shows how important it could be to summarize the trace file and share the summary file rather than extremely detailed trace file. Such a summary file may include a summary of task events and response time information. This is a function of the Summarizing Module. Since loading and splitting the trace file takes a long time and consumes computer resources heavily, the Trace Analysis Process can include a command line mode in which users can load and process the trace files in batch mode. Also it is possible to start the Process at low priority mode so that it will not compete with computer resources when a user is interacting with the computer. FIG. 9 shows four different analysis modes presented for activating for use on user screen 218. The analysis modes include Stat Analysis; Task Viewer; Troubleshooter; and Response Time modes. The screen capture shows these 4 modes in 4 tabs. This Stat Analysis tab includes sub-analysis functions now described. Rate Analysis provides throughput (IO's/s and MB/s) and IO size information at different components. The default bucket size is 1 seconds, but users have the option of selecting smaller or larger time buckets to view the rates. Also, double-clicking the charts shows finer granularity buckets as well as individual IO's. Sequentiality Analysis shows the sequentiality pattern of the workload as well as the percent of IO's present in sequences. The sequences of IO's (i.e. IO's with consecutive addresses) are special in that storage systems exploit their sequential pattern by prefetching (reading-ahead) thereby increasing the chances of cache hits. For workloads with high read sequential components, one expects the performance level comparable to cache hits. Alignment also has some performance implications. Those IO's spanning multiple cache pages (cache slots or tracks) may cause contention for cache page locks. Similarly, there is a CRC calculation penalty for write IO's resulting in partial sector operations. By looking at the alignment of the IO's in the system, the Trace Capture Process may identify performance issues caused by the misalignment of IO's. FIG. 10 shows on screen 220 the Event Viewer that analyzes task events, and presents task durations in the trace. Duration of these tasks indicate potential performance problems. For example if the task associated with access to a disk through a disk adapter is too high, it may indicate that there is a problem with the physical disk. FIG. 11 shows a troubleshooter tab presentation on user screen 224 that contains the critical performance thresholds for certain performance metrics. The “rules” are user editable. In this tab, the user can pass the information through the rules and Trace Analysis Process flags and reports violations. Also, Trace Analysis Process provides a color-coded “critical values” map that shows violations of throughput figures at components (shown in black and white distinctive patterns in FIG. 11). FIG. 12 shows a response time histogram presented on a user screen 226 that is viewable at a component or data storage system level. This chart shows the response time histogram at the LV, director and the system level. It shows the number of IO's at each response time bucket shown in the x-axis (horizontal axis). This histogram may also be called as relative frequency chart. When normalized by the number of IO's, these charts are called probability density functions (PDF). The area under PDF is always 1 (or 100%). The users may change this chart to show: all IO types (read, write etc); only Reads; and/or only Writes. Also, users may select different LVs and directors from the pull down boxes. FIG. 13 shows a chart presented on a user screen 228 for analysis at component or data storage system level. This chart shows the percent cumulative distributions at the LV, director and the system level. For any given response time value in the x-axis, it shows the percent of IO's with response times with that value or less. In mathematical terms, this chart is the cumulative distribution function (CDF). CDF is the integral (cumulative sum) of PDF. Hence, the CDF charts always end up at 100%. The users may change this chart to show: all IO types (read, write etc); only Reads; and/or only Writes. Also, users may select different LVs and directors from the pull down boxes. FIG. 14 shows another chart presented on a user screen 230 for analysis of response times of IO activity at component or data storage system level. This chart shows the response time of individual IO's versus elapsed time at the LV, director and the system level. Every dot in the chart is an IO, reads and writes are each marked differently. The users may change this chart to show: all IO types (read, write etc); only Reads; and/or only Writes. Also, users may select different LVs and directors from the pull down boxes. FIG. 15 shows a chart on user screen 232 of active IO's in a data storage system presented on a user screen. This chart shows the number of active IO's in the system when a new IO arrives. The larger this number is, the more chance that an IO will take complete. Every dot in the chart shows arrival time of an IO in x-axis, and the number of IO's in progress at LV or director in y-axis. Reads and writes are marked differently. Users may select different LVs and directors from the pull down boxes. FIG. 16 shows on user screen 234 IO rates for a data storage system, short handedly referred to as a box. The information about component trace information is stored in a specially designated for this file (for example, lv_buck—00DA.txt.—contains information for logical volume 00DA). It gives opportunity to plot IO rates in a very fast manner for any component for selected bucket size and for the whole box level as presented in FIG. 3. FIG. 17 shows on user screen 236 a split view by components of raw captured trace data. Keeping the information divided by components raw data from original trace gives a user an opportunity to access law level raw information for any timestamp. It is implemented in the following way: selecting a timestamp of interest and obtaining the corresponding raw data that maybe previewed in a table form and compartmentalized for any bucket size different from the original one Such approach provides very convenient way to investigate bursts. FIGS. 18-21 are discussed below. The similar approaches of multiple scanning and component file splitting can be used for investigation of trace misalignment, forward and backward sequentialities, analyzing task events, and also analyzing response times. The corresponding analysis data is kept in designated buckets for component level files. FIG. 18 shows on user screen 238 misalignment data by component. FIG. 19 shows on user screen 240 sequentiality data by component. FIG. 20 shows on user screen 242 task events by box and components and FIG. 21 shows on user screen 244 response times, also by box or component. Having described a preferred embodiment of the present invention, it may occur to skilled artisans to incorporate these concepts into other embodiments. Nevertheless, this invention should not be limited to the disclosed embodiment, but rather only by the spirit and scope of the following claims and their equivalents. |
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claims | 1. A nuclear fuel cell repair tool, comprising:a main body;a jack depending from said main body, said jack being adapted for applying a force to a structural deformation of a nuclear fuel cell;a support member depending from said main body, said support member being adapted for supporting said tool on the nuclear fuel cell; anda force reacting member depending from said main body, said force reacting member being adapted for engagement with the nuclear fuel cell and being aligned with and spaced apart from said jack. 2. The nuclear fuel cell repair tool of claim 1 further comprising an optical element positionable so as to provide an image of the structural deformation. 3. The nuclear fuel cell repair tool of claim 2 wherein said optical element is selected from a fiber optic cable, a laser, and a photodetector. 4. The nuclear fuel cell repair tool of claim 1 further comprising an extension extending from said main body, wherein said extension is adaptable for attachment to a lifting device. 5. The nuclear fuel cell repair tool of claim 1 wherein said support member comprises a groove adapted for receiving a portion of the nuclear fuel cell. 6. The nuclear fuel cell repair tool of claim 1 further comprising an attachment means for attaching said tool to the nuclear fuel cell. 7. The nuclear fuel cell repair tool of claim 1 wherein said jack is mounted to said main body with a joint. 8. The nuclear fuel cell repair tool of claim 7 wherein said joint permits translation and rotation of said jack. 9. The nuclear fuel cell repair tool of claim 1 further comprising an actuator adaptable for activating said jack. 10. The nuclear fuel cell repair tool of claim 1 wherein said jack comprises a contact surface adapted for linear translation toward said force reacting member. 11. A method of repairing a structural deformation of a nuclear fuel cell wall, comprising:positioning a repair tool having a jack and a force reacting member on a nuclear fuel cell;aligning said jack and said force reacting member with the structural deformation such that the structural deformation is disposed between said jack and said force reacting member; andapplying a force to the structural deformation using said jack. 12. The method of claim 11 wherein:said positioning is accomplished by an operator located at a remote location from the nuclear fuel cell. 13. The method of claim 11 wherein:said aligning is accomplished using one or more actuators. 14. The method of claim 11 further comprising:inspecting the structural deformation. 15. The method of claim 14 wherein said inspecting comprises direct visual inspection. 16. The method of claim 14 wherein said inspecting comprises inspection via an optical element. 17. A nuclear fuel cell repair tool comprising:a main body and an arm element depending from said main body, each of said main body and said arm element comprising a groove adapted for supporting said tool on a nuclear fuel cell;a jack mounted to said main body with at least one joint, said jack comprising a contact surface adapted for engagement with a structural deformation of the nuclear fuel cell, said at least one joint adapted to orient said contact surface at various angles;a first post depending from said main body and being spaced apart from said jack;a first actuator operably connected to said jack and adapted for causing said contact surface of said jack to apply a force to said structural deformation; anda fiber optic cable positioned on said tool so as to provide an image of said structural deformation. 18. The nuclear fuel cell repair tool of claim 17 further comprising a second post and a clamping actuator depending from said arm element, said clamping actuator comprising a clamping actuator surface adapted for pressing a wall of the nuclear fuel cell against said second post. 19. The nuclear fuel cell repair tool of claim 17 wherein said first actuator is connected to said jack with a joint. 20. The nuclear fuel cell repair tool of claim 17 wherein said at least one joint permits said jack to be rotated or translated in any direction. |
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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. |
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042809223 | description | Referring now to the drawing and first, particularly, to FIG. 1 thereof, there are shown four chambers 5, 6, 7 and 8 separated from one another by intermediate walls or partitions 2, 3 and 4 in a concrete building 1, the chambers 5, 6, 7 and 8 serving as a drumming station for radiant synthetic wastes. Waste storage or drumming in a condition affording ultimate disposal is effected with the aid of a kneader 10 which is essentially disposed in the chamber 7. The kneader 10 is constructed, for example, as disclosed in U.S. Pat. No. 3,971,732. It has one or more worm shafts that are set in motion by a non-illustrated electric motor through a drive shaft 11. The worm shafts advance or convey the radiant wastes and bitumin employed as matrix or embedding material in direction of the arrow 12 through the kneader 10 to a discharge opening 13. The kneaded mixture is delivered thereat into socalled standard drums 14 having a 200 liter capacity which, after having been filled and closed, are transported to an ultimate storage facility, such as abandoned salt mines, for example. The kneader 10 has three degassing domes 16, 17 and 18 serially disposed in direction toward the discharge opening 13 and serving for removal of gases or vapors, as is disclosed in the hereinaforementioned German Published Nonprosecuted Application DE-OS No. 25 31 584. The degassing domes 16, 17 and 18 have respective ends thereof facing away from the kneader 10 which extend into the chamber 6. In the illustrated embodiment of the invention, the radiant wastes are accumulated in a rocking bin or bunker 20. These wastes are in essence dried residues from filters for purifying gas or liquid flows of a pressurized water reactor. The size of particles thereof is from about 1 to 300.mu.. The synthetic substance contained therein is primarily resins having a styrene base. In addition thereto, the residues include filtering aids or auxiliaries such as kieselguhr or diatomaceous or infusorial earth. From the rocking bunker 20, the wastes can be conveyed by a conveyor tube 21 to a downcomer or gravity tube 22 which extends out of the chamber 5 through the wall or partition 2 into the chamber 6. A gate-type shut-off valve 23 is provided thereat which is connected by means of a flexible collar 24, preferably formed of rubber or rubber-like material, to a section of pipe 25. The pipe section 25 is the outer extension or elongation of a metering tube which is shown in greater detail in FIGS. 2 to 4. The pipe section 25 is sealed by means of a corrugated tube 26 with respect to a cover 27 of the vapor or steam dome 18 and is set into vibratory motion above all transversely to the longitudinal axis thereof by a vibrator 30. The vibration frequency may be 50 Hz at an amplitude of 0.7 mm. As is seen in FIGS. 2 to 4, the steam dome 18 seated on the kneader 10 constitutes a tube 31 having a rectangular cross section. The tube 31 is surrounded with clearance by a cylindrical tube 32, so that an annular or ring chamber 33 for receiving superheated steam therein is formed. Another annular or ring chamber 34 which is defined by concentric or coaxial tube sections 35 and 36, can contain a non-illustrated condenser therein. A metering tube 38 having a wedge-shaped squeezed-together end 39 projects therewith, as an extension or elongation of the tube section 25, into the dome 18 up to the screws or worms of the kneader 10 which are indicated by center lines 40. The longitudinal direction of the wedge-shaped end 39 extends transversely to the longitudinal direction of the kneader worms 40, so that the entire width of the bitumin flow displaced by the worms 40 is covered. The metering tube 38 is provided with an outer casing 41 so that an intermediate space 42 is defined therebetween which can receive steam therein. A union 43 for the supersaturated steam is shown in FIG. 2. At an oppositely disposed union location 44, scavenging air can be blown into the tube 38 and can flow therethrough to the kneader 10 and simultaneously ensure that the tube 38 is not wetted by condensing vapors and covered by dried-up bitumin splashes or by waste. In addition, the conveyance or delivery of the waste particles is improved. At the cover 27 of the degassing dome 18, wherein the metering tube 38 is disposed, tightly sealed with the corrugated tube 26, a lead-glass window 45 is provided for observation, for example, by means of a television camera. The supersaturated steam flows from the union 43 through the annular space 42 in direction toward the kneader 10. At the lower end 39 of the metering tube 38, the supersaturated steam discharges from nozzles 46. Thereby, clogging or obstructing of the lower region of the dome 18 with bitumin is prevented. Similar discharge openings can also be distributed over the height or length of the metering tube 38. |
abstract | A pressurized water reactor (PWR) includes a cylindrical pressure vessel defining a sealed volume, a nuclear reactor core disposed in a lower portion of the cylindrical pressure vessel, one or more control rod drive mechanisms (CRDMs) disposed in the cylindrical pressure vessel above the nuclear reactor core, and an annular steam generator surrounding the nuclear reactor core and the CRDM. In some such PWR, a cylindrical riser is disposed coaxially inside the pressure vessel and inside the annular steam generator and surrounds the nuclear reactor core and the CRDM, and the steam generator is disposed coaxially inside the cylindrical pressure vessel in an annular volume defined by the cylindrical pressure vessel and the cylindrical riser. In other such PWR, the steam generator is disposed coaxially outside of and secured with the cylindrical pressure vessel. |
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description | Referring to FIGS. 1 and 2, electron beam irradiation apparatus 30 is suitable for irradiating a continuously moving 3-dimensional profiled article 28 with electrons along a manufacturing line, for example, tubing, structural profiles, etc. Article 28 may be metal, plastic, etc. and is shown in FIG. 1 as a continuously extruded H-shaped cross section as an example. Irradiation apparatus 30 is typically employed for curing electron beam curable coatings on article 28 such as ink, protective coatings, paint, etc., applied by a coating station 35 (FIG. 2). Coating station 35 typically sprays the coating on article 28, but alternatively, may apply the coating by other suitable methods. Irradiation apparatus 30 includes an electron beam emitter system 31 having multiple (more than one) electron beam emitters 26 which are positioned around an irradiation region or zone 32. Each electron beam emitter 26 includes a vacuum chamber 26b within which an electron gun is positioned for generating electrons exe2x88x92. The electrons exe2x88x92 are accelerated out from the vacuum chamber 26b through a thin foil exit window 26a in an electron beam 25 into irradiation region 32. Electron beam emitters 26 may be similar to those described in U.S. application Ser. No. 09/209,024, filed Dec. 10, 1998, and Ser. No. 09/349,592, filed Jul. 9, 1999, the contents of which are incorporated herein by reference in their entirety. The electron beam emitters 26 are positioned relative to each other so that the beams 25 of electrons exe2x88x92 generated by emitters 26 through exit windows 26a are able to irradiate the outwardly exposed surfaces of article 28 while article 28 moves through irradiation region 32 to provide about 360xc2x0 of electron beam coverage around article 28. In the embodiment depicted in FIGS. 1 and 2, electron beam emitter system 31 includes four electron beam emitters 26 for irradiating article 28 with beams 25 of electrons exe2x88x92 from four different directions. For articles 28 having right angled corners, adjacent emitters 26 are usually oriented at right angles to each other as shown in FIG. 1. In the embodiment shown in FIG. 1, electron beam emitters 26 are positioned around irradiation region 32 along a common plane and in two opposed pairs which are at right angles to each other. Each electron beam emitter 26 is capable of being moved towards or away from irradiation region 32 in the direction of arrows 34 with an adjustable linear mechanism in order to adjust to varying sizes, orientations and shapes of article 28. In addition, each electron beam emitter 26 may be rotated about the center C of irradiation region 32 in the direction of arrows 36 (FIG. 1) with an adjustable rotating mechanism to provide further adjustment. In one embodiment, each electron beam emitter 26 is rotated independently from the other. In another embodiment, the electron beam emitters 26 can be rotated in unison. The electron beam emitters 26 can be rotated by a single mechanism or each by a separate mechanism. Article 28 is moved through irradiation region 32 in the direction of arrows A by a conveyance system 39 having upstream 39a and downstream 39b portions which typically includes a series of rollers 38 (FIG. 2) for driving and/or guiding article 28. The rollers 38 may be paired as shown or can consist of a single bottom support roller 38 at the upstream 39a and downstream 39b portions of conveyance system 39. The conveyance system 39 can also include tractor belts. In use, referring to FIG. 2, after article 28 is formed, article 28 is continuously guided and/or driven through the irradiation region 32 of irradiation apparatus 30 by conveyance system 39. Coating station 35 is positioned between irradiation region 32 and the upstream portion 39a of conveyance system 39 for continuously coating the outer surfaces of article 28 with the desired coating. Since the coating station 35 is downstream from the upstream portion 39a of conveyance system 39, the coated article 28 does not come in contact with the conveyance system 39 before reaching the irradiation region 32. This allows the article 28 to reach the irradiation region 32 with a consistent coating. When the coated article 28 passes through irradiation region 32, the beams 25 of electrons exe2x88x92 (FIG. 1) generated by electron beam emitters 26 treat the coated outwardly exposed surfaces of article 28. The electron beam emitters 26 of electron emitter system 31 are adjusted inwardly or outwardly relative to article 28 and irradiation region 32 in the direction of arrows 34 so that the coated surfaces of article 28 are the proper distance from electron beam emitters 26 for receiving sufficient electron exe2x88x92 radiation (for example, 0.75 to 1.25 inches when operating at 120 kV). If required, the electron beam emitters 26 are also adjusted rotationally around article 28 about center C to better orient the electron beam emitters 26 relative to the outer surfaces of article 28. When the electrons exe2x88x92 treat the coated surfaces of article 28 continuously passing through irradiation region 32, the electrons exe2x88x92 cause the cross linking or polymerization of the coating which rapidly cures and hardens the coating on the article 28. Consequently, by the time article 28 passes through the downstream portion 39b of conveyance system 39, the coating on article 28 typically does not experience damage from the downstream portion 39b. In an alternate use, irradiation apparatus 30 can be employed for sterilizing article 28 where the beams 25 of electrons kill or disable microorganisms on article 28. In such a case, coating station 35 is either omitted or is not operated. Additionally, irradiation apparatus 30 can be employed for surface modification of the outer surfaces of article 28 in order to obtain, for example, oxidation, passivation, nitriding, etc. Referring to FIG. 3, electron beam irradiation apparatus 48 is another embodiment of the present invention which differs from the irradiation apparatus 30 in that irradiation apparatus 48 has two opposed pairs of electron beam emitters 26 which are offset from each other along the longitudinal direction of article 28. This allows the electron beam emitters 26 to be brought further into irradiation region 32 and closer to the surfaces of article 28, thereby providing better adjustability. An article 28 passing through irradiation region 32 is irradiated on two opposed sides when passing between the first pair of opposed electron beam emitters 26 and then irradiated on two more opposed sides when passing between the second pair of opposed electron beam emitters 26. Consequently, instead of simultaneously irradiating all surfaces of article 28, irradiation region 32 progressively sequentially irradiates the surfaces of article 28. Electron beam emitters 26 may be provided with adjustability in the direction of arrows 40 (longitudinally relative to article 28). Alternatively, electron beam emitters 26 can also be provided with adjustability laterally relative to article 28, as shown by arrow 40a for centering emitters 26 relative to article 28. Referring to FIGS. 4 and 5, irradiation apparatus 50 is another embodiment of the present invention. Irradiation apparatus 50 includes an outer housing 44. When employed for curing coatings on an article 28, housing 44 is positioned downstream from a coating station 35. An electron beam emitter system 31 having four electron beam emitters 26 is positioned within the interior 44a of housing 44. The housing 44 provides shielding from radiation from the electron beam emitters 26. The radiation can include both electron beam radiation as well as X-ray radiation formed from the electrons exe2x88x92. The four electron beam emitters 26 of electron beam emitter system 31 are positioned within the interior 44a of housing 44 in two opposed pairs that are mounted to a tunnel 43 extending through the housing 44. Article 28 is able to continuously pass through housing 44 by entering housing 44 through the upstream portion 43a of tunnel 43 and exiting through downstream portion 43b. The irradiation region 32 is contained within the tunnel 43 between the electron beam emitters 26. The two opposed pairs of electron beam emitters 26 are offset from or adjacent to each other along the longitudinal direction of tunnel 43. The longitudinal axes of the opposed pairs of the electron beam emitters 26 are shown positioned at inclined angles, for example, 45xc2x0, with the two pairs being at right angles to each other. Alternatively, the two pairs of electron beam emitters 26 can be oriented at other angles, such as horizontally and vertically, respectively. Tunnel 43 includes two end plates 56a with openings 56b therethrough located at the upstream 43a and downstream 43b portions for allowing the passage of article 28. The combination of tunnel 43 and end plates 56a provides further radiation shielding as well as allows an inert gas such as nitrogen to be introduced and contained within the irradiation region 32 to aid in the curing process during irradiation. Openings 56b are preferably sized to be only slightly larger than the cross section of article 28 so that maximum radiation shielding and nitrogen gas retention can be provided. Housing 44 includes a series of feet 41 for raising and lowering housing 44 in order to accommodate height variations of different sized articles 28. A motor 52 and a drive transmission 54 are located at the bottom of housing 44 for driving a series of bushings 53 that are secured to the housing 44. This raises and lowers the bushings 53 relative to a series of respective threaded foot columns 55 that are vertically fixed to the floor or ground below housing 44, which in turn raises and lowers housing 44. A conveyance assembly 68 having a roller assembly 70 with a guide/idler roller extending into the downstream portion 43b of tunnel 43 contacts the article 28 after leaving irradiation region 32. The conveyance assembly 68 has a vertical member 68a in contact with the ground or floor for maintaining the guide/idler roller at the same height regardless of the height of housing 44. Consequently, the bottom surface of different sized articles 28 can always pass through housing 44 at the same height from the floor, while the amount of elevation of the housing 44 is adjusted to accommodate the height of the top part of the different sized articles 28. The electron beam emitter system 31 also includes two adjustment fixtures 46. The electron beam emitters 26 are mounted to the adjustment fixtures 46 which provide linear adjustment or movement of the emitters 26 in the direction of arrows 34, towards or away from irradiation region 32 in order to accommodate articles 28 of different shapes, orientations and sizes, as well as different heights of housing 44. Referring to FIG. 6, each adjustment fixture 46 includes a frame 46a having a pair of mounting plates 62 to which the vacuum chambers 26b of an opposed pair of electron beam emitters 26 are mounted. The mounting plates 62 are connected to each other and to one end of frame 46a by two threaded adjusting rods 60 located on opposite sides of the electron beam emitters 26. The adjusting rods 60 are driven by a motor 58 and a drive system 72. The drive system 72 includes two drive portions 72a that are connected together by a drive pulley or chain (not shown), each for driving or rotating a separate adjusting rod 60. Rotation of the adjusting rods 60 in one direction moves the electron beam emitters 26 closer together and, in the other direction, farther apart. An encoder 57 determines the relative positions of electron beam emitters 26. The frame 46a also includes mounting brackets 66 for mounting the adjustment fixture 46 and electron beam emitters 26 to the tunnel 43. The tunnel 43 is configured to be open in the regions corresponding to the exit windows 26a of the electron beam emitters 26 in order to allow the entrance of the beams 25 of electrons exe2x88x92 into the irradiation region 32. If the exit windows 26a are designed to emit electrons exe2x88x92 in a rectangular configuration, the exit windows 26a are typically oriented so that the long direction of the rectangular configuration extends in the longitudinal direction of the tunnel 43 so that the length of irradiation region 32 is maximized. A series of shields 64 are mounted to each mounting plate 62 for engaging the openings into the tunnel 43 for radiation shielding as well as preventing inert gases from escaping tunnel 43 when inert gases are employed. The shields 64 extend forwardly relative to the exit window 26a to allow for adjustment of the electron beam emitters 26 towards or away from irradiation region 32 while continuing to provide shielding. Although FIG. 6 depicts a single motor 58 for simultaneously moving two electron beam emitters 26, alternatively, each electron beam emitter 26 can be provided with a motor and moved independently of each other. In addition, adjustment fixture 46 can include features to provide some or all of the other adjustments contemplated for irradiation apparatuses 30 and 48. Curing of coatings at high speed can be performed with irradiation apparatus 50, with 300-1000 feet per minute being a typical speed. In one embodiment, the width or height of article 28 can range between xc2xd to 3xc2xc inches. It is understood that the dimensions of article 28 can vary, and that the dimensions of irradiation apparatus 50 are sized to accommodate the dimensions of article 28. The size and power of electron beam emitters 26 for irradiation apparatuses 30, 48 and 50 can be chosen to suit the particular application at hand (speed, size, type of coating, etc.). Article 28 does not have to be generally rectangular in shape and can be curved, round, triangular, polygonal, complex combinations thereof, etc. Article 28 can be either hollow or solid and can be made by typical continuous processes involving, for example, extrusion, continuous casting, bending, bending and welding, etc. In addition, the electron beam emitter system 31 can have less than or more than four electron beam emitters 26 depending upon the application at hand. Furthermore, the emitters 26 do not have to be at right angles to each other. This most often occurs when fewer than four or more than four electron beam emitters 26 are employed. When irradiating articles 28 that have round or triangular cross sections, three electron beam emitters 26 can be employed. Opposed electron beam emitters 26 in some situations can be in axial or angular misalignment. Although the embodiments of FIGS. 1-6 have been mainly described for curing coatings on 3-dimensional articles, alternatively, such embodiments can be employed for irradiating a moving 2-dimension web, as well as be employed for sterilization or surface modification purposes. When employed for sterilization or surface modification purposes, the coating station 35 can be omitted. Also, when irradiating a 2-dimensional web, only two opposed electron beam emitters 26 need to be operating. Referring to FIG. 7, electron beam irradiation apparatus 10 is still another embodiment of the present invention that is suitable for sterilizing 3-dimensionally shaped articles 16, for example, medical instruments such as dental or surgical instruments. Irradiation apparatus 10 includes an electron beam emitter system 13 having two electron beam emitters 12. The electron beam exit windows 12a of electron beam emitters 12 face each other and are axially aligned with each other on opposite sides of a gap forming an irradiation/sterilization region or zone 20 therebetween. The electron beam emitters 12 direct opposing beams 25 of electrons exe2x88x92 into the irradiation region 20 (FIG. 8). Power to the electron beam emitters 12 is provided through cables 16. A conveyance system 18 conveys articles 16 through the irradiation region 20 and through the opposing beams 25 of electrons exe2x88x92 for sterilization. The conveyance system 18 includes first 22a and second 22b conveyors, each having an endless belt 14 that is driven around rollers or pulleys 24 (FIG. 9) in the direction of the arrows 13 by the rotation of the pulleys 24 in the direction of arrows 11. The conveyors 22a/22b are spaced apart from each other in the region of irradiation region 20 so as not to block the beams 25 of electrons exe2x88x92. This allows articles 16 to be fully sterilized while passing through sterilization region 20. In use, the power to electron beam emitters 12 is turned on and two opposing beams 25 of electrons exe2x88x92 are directed into irradiation region 20 by the electron beam emitters 12. The conveyance system 18 is turned on and the belts 14 of conveyors 22a/22b are driven around pulleys 24. An article 16 to be sterilized is placed upon the belt 14 of the first conveyor 22a (FIG. 9). The first conveyor 22a moves article 16 into the sterilization region 20. As the tip 16a of article 16 reaches the end of the first conveyor 22a, the tip 16a extends off the end of the first conveyor 22a into the irradiation region 20 (FIG. 10). Since the tip 16a is no longer resting on a belt 14 which could block some of the sterilizing electrons exe2x88x92, the beams 25 of electrons exe2x88x92 are able to fully sterilize all surfaces of tip 16a. After the tip 16a passes through the irradiation region 20, the tip 16a reaches the second conveyor 22b. The mid-section 16b and rear end 16c of article 16 follow tip 16a and pass from the first conveyor 22a through irradiation region 20, thereby becoming sterilized before reaching the second conveyor 22b (FIG. 11). The second conveyor 22b then conveys article 16 away from irradiation region 20. In most cases, the articles 16 are typically instruments that are relatively small in cross section so that electron beam emitters 12 which provide a 2-inch diameter beam 25 of electrons exe2x88x92 is usually sufficient. Alternatively, larger or smaller electron beam emitters 12 may be employed depending upon the application at hand. In addition, if required, more than two electron beam emitters 12 can be employed. Such an arrangement can direct a beam 25 of electrons exe2x88x92 from multiple directions. The electron beam emitters 12 can be angled forwardly or rearwardly, or axially offset. Furthermore, each electron beam emitter 12 can be adjustable up or down, towards or away from the irradiation region 20, rotatably about irradiation region 20, or at angles. Although irradiation apparatus 10 is typically employed for sterilizing articles 16 that are relatively short in length, alternatively, irradiation apparatus 10 can be employed for sterilizing a single continuously moving article, or can be employed for curing coatings or obtaining surface modification. The conveyance system 18 can be modified to suit the application at hand. For example, the conveyors 22a/22b can be moved farther apart from each other or replaced with rollers. While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims. For example, features of the various embodiments disclosed may be combined or omitted. In addition, although conveyance systems with rollers or conveyor belts have been described, alternatively, the conveyance systems can include components for dropping articles through the irradiation zone by gravity. In such a case, the electron beam system would be configured appropriately. Reflectors can be employed for reflecting electrons exe2x88x92 to aid in the irradiation of articles in the irradiation region. In some cases, some of the electron beam emitters can be replaced with reflectors. Furthermore, the configuration, size and dimensions of various components of the irradiation apparatuses of the present invention are understood to vary depending upon the size and shape of the article to be irradiated. The articles can have varying surfaces or structures, and do not need to be smooth. |
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summary | ||
abstract | Potentials at a plurality of points on a diameter of a semiconductor wafer 13 are measured actually. Then, a potential distribution on the diameter is obtained by spline interpolation of potentials between the actually-measured points adjacent in the diameter direction. Thereafter, a two-dimensional interpolation function regarding a potential distribution in the semiconductor wafer 13 is obtained by spline interpolation of potentials between points adjacent in the circumferential direction around the center of the semiconductor wafer 13. Then, a potential at a observation point on the semiconductor wafer 13 is obtained by substituting the coordinate value of this observation point into the two-dimensional interpolation function. As a result, a potential distribution due to electrification of the wafer can be estimated accurately, and the retarding potential can be set to a suitable value. |
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054935920 | claims | 1. A fuel rod of a pressurized-water-cooled fuel assembly, comprising a fuel filling, a cladding tube enclosing said fuel filling and including a first thicker inner layer facing toward said fuel filling and being formed of a first zirconium alloy, and a second thinner outer layer being metallurgically bound to said inner layer and being formed of a second zirconium alloy, said two zirconium alloys each containing at least the metals tin, iron and chromium as alloying constituents, and: a) said first alloy containing 1-2% by weight of Sn, 0.05-0.25% by weight of Fe and 0.05-0.2% by weight of Cr; b) said second alloy having a content of 0.5-1.3% by weight of Sn, 0.15-0.5% by weight of Fe and 0.05-0.4% by weight of Cr; c) said second alloy having a total content of tin, iron and chromium of more than 1.0% by weight, a ratio of the content of tin in said second alloy to the content of tin in said first alloy being between 0.35 and 0.7; and d) a ratio of the content of iron and chromium in said second alloy to the tin content of said first alloy being between 0.2 and 0.5. a) said first alloy containing 1-2% by weight of Sn, 0.05-0.25% by weight of Fe and 0.05-0.2% by weight of Cr; b) said second alloy having a content of 0.5-1.3% by weight of Sn, 0.15-0.5% by weight of Fe and 0.05-0.4% by weight of Cr; c) said second alloy having a total content of tin, iron and chromium of more than 1.0% by weight, a ratio of content of tin in said second alloy to the content of tin in said first alloy being between 0.35 and 0.7; and d) a ratio of the content of iron and chromium in said second alloy to the tin content of said first alloy being between 0.2 and 0.5. 2. The fuel rod according to claim 1, wherein each of said layers contains only further alloying constituents permitted for Zircaloy 2 and Zircaloy 4 in addition to Sn, Fe and Cr, said further alloying constituents having amounts being substantially within limits permitted for one of Zircaloy 2 and Zircaloy 4. 3. The fuel rod according to claim 1, wherein all of said constituents of said first layer have amounts being within limits permitted for one of Zircaloy 2 and Zircaloy 4. 4. The fuel rod according to claim 1, wherein at least said second alloy has a nickel content of less than about 0.007% by weight. 5. The fuel rod according to claim 1, wherein said cladding tube has a silicon content of more than 0.005% by weight and less than 0.02% by weight. 6. The fuel rod according to claim 1, wherein said cladding tube has a silicon content of more than 0.007% by weight and less than 0.012% by weight. 7. The fuel rod according to claim 1, wherein each of said two alloys of said cladding tube has a silicon content of more than 0.005 by weight and less than 0.02% by weight. 8. The fuel rod according to claim 1, wherein each of said two alloys of said cladding tube has a silicon content of more than 0.007% by weight and less than 0.012% by weight. 9. The fuel rod according to claim 1, wherein said cladding tube has an oxygen content of less than 0.2% by weight and more than 0.05% by weight. 10. The fuel rod according to claim 1, wherein said cladding tube has an oxygen content of less than about 0.16% by weight and more than 0.12% by weight. 11. The fuel rod according to claim 1, wherein the tin content of said first alloy is more than 1.2% by weight and less than 1.6% by weight. 12. The fuel rod according to claim 1, wherein the tin content of said first alloy is more than 1.4% by weight and less than 1.6% by weight. 13. The fuel rod according to claim 1, wherein the tin content of said second alloy is more than 0.7 and less than 1.1 by weight. 14. The fuel rod according to claim 1, wherein the tin content of said second alloy is more than 0.7 and less than 0.9% by weight. 15. The fuel rod according to claim 1, wherein the iron content of said first alloy is more than 0.1% by weight and less than 0.24% by weight. 16. The fuel rod according to claim 1, wherein the iron content of said first alloy is more than 0.18% by weight and less than 0.24% by weight. 17. The fuel rod according to claim 1, wherein the iron content of said second alloy is more than 0.18% by weight and less than 0.4% by weight. 18. The fuel rod according to claim 1, wherein the iron content of said second alloy is more than 0.24% by weight and less than 0.35% by weight. 19. The fuel rod according to claim 1, wherein the chromium content of said first alloy is more than 0.07 and less than 0.13% by weight. 20. The fuel rod according to claim 1, wherein the chromium content of said second alloy is more than 0.07% by weight. 21. The fuel rod according to claim 1, wherein the chromium content of said second alloy is more than 0.13% by weight. 22. The fuel rod according to claim 1, wherein the chromium content of said second alloy is less than 0.25% by weight. 23. The fuel rod according to claim 1, wherein the chromium content of said second alloy is less than 0.21% by weight. 24. The fuel rod according to claim 1, wherein the total content of chromium, iron and tin of said second alloy is between 1.1 and 1.5% by weight. 25. The fuel rod according to claim 1, wherein said first zirconium alloy has a content of (1.5.+-.0.1) % by weight of Sn; said second alloy has a content of (0.8.+-.0.1) % by weight of Sn; and each of said zirconium alloys has (0.21.+-.0.03) % by weight of Fe, (0.1.+-.0.03) % by weight of Cr, (0.14.+-.0.02) % by weight of O.sub.2, (0.01.+-.0.003) % by weight of Si and at most 0.007% by weight of Ni. 26. The fuel rod according to claim 1, wherein said first zirconium alloy has a content of (1.5.+-.0.1) % by weight of Sn, (0.21.+-.0.03) % by weight of Fe and (0.1.+-.0.03) % by weight of Cr; said second zirconium alloy has a content of (0.8.+-.0.1) % by weight of Sn, (0.28.+-.0.04) % by weight of Fe and (0.17.+-.0.04) % by weight of Cr; and each of said zirconium alloys has a content of (0.14.+-.0.02) % by weight of O, (0.01.+-.0.003) % by weight of Si and not more than 0.007% by weight of Ni. 27. A fuel assembly of a pressurized-water reactor, comprising fuel rods each including a fuel filling, a cladding tube enclosing said fuel filling and having a first thicker inner layer facing toward said fuel filling and being formed of a first zirconium alloy, and a second thinner outer layer being metallurgically bound to said inner layer and being formed of a second zirconium alloy, said two zirconium alloys each containing at least the metals tin, iron and chromium as alloying constituents, and: |
054065976 | description | MODE(S) FOR CARRYING OUT THE INVENTION Illustrated schematically in FIG. 1 is an exemplary boiling water reactor (BWR) 10 including a cylindrical pressure vessel 12 having a longitudinal centerline axis 14. The vessel 12 includes a conventionally removable upper head 12a, and a lower head 12b. Disposed inside the vessel 12 is a conventional annular reactor core 16 containing a plurality of elongate, laterally spaced apart, conventional nuclear fuel bundles 18 additionally shown in FIG. 2. The core 16 is disposed in the vessel 12 above the lower head 12b to define a lower plenum 20 therebetween. In accordance with one embodiment of the present invention, an annular or cylindrical chimney 22 extends upwardly from the core 16 in the vessel 12 in flow communication with the core 16. Surrounding the core 16 is a conventional annular shroud 24 which extends downwardly from the chimney 22 to the lower head 12b. The core 16 and the chimney 22 are spaced radially inwardly from the inner surface of the vessel 12 to define a conventional annular downcomer 26 in flow communication with the lower plenum 20. The chimney 22 includes a lower grid 28 disposed at the top of the core 16, an upper grid 30 spaced upwardly from the lower grid 28, and a top manifold 32 defining an open plenum above the upper grid 30. A conventional steam separator assembly 34 includes conventional standpipes and steam separators which extend upwardly from the chimney 22 in flow communication with the chimney top manifold 32. A conventional steam dryer assembly 36 is spaced upwardly above the steam separator assembly 34 and below the vessel upper head 12a in flow communication with the steam separator assembly 34. The vessel 12 is filled with a reactor water 38 to a nominal or normal vertical water level L measured from the vessel lower head 12b. The reactor water 38 acts as both a coolant and moderator for the core 16. The normal water level L is preferably disposed at an elevation through the steam separator assembly 34 at about half its height as is conventionally known. A plurality of conventional recirculation pumps 40 extend through the vessel lower head 12b and into the downcomer 26 for conventionally pumping the water 38 downwardly from the downcomer 26 and into the lower plenum 20 for flow upwardly through the reactor core 16. The core 16 therefore receives the water 38 recirculated downwardly through the downcomer 26, through the lower plenum 20 and upwardly therein, with the core 16 being conventionally effective for boiling the water 38 to generate a steam-water mixture 38a which flows upwardly from the core 16 and through the chimney lower grid 28, chimney 22, and upper grid 30 into the chimney top manifold 32. From the chimney top manifold 32 the steam-water mixture 38a flows conventionally upwardly into the steam separator assembly 34 and in turn through the steam dryer assembly 36 for removing water therefrom for discharging primarily steam 38b from the vessel 12 through a conventional outlet nozzle 42. The outlet nozzle 42 is conventionally joined to a conventional steam turbine, for example, for powering a conventional electrical generator to produce electrical power for an electrical utility grid (not shown). A plurality of conventional nuclear control rods 44 are selectively positionable in the core 16 in accordance with one embodiment of the present invention between the fuel bundles 18 for conventionally controlling reactivity in the core 16. Only two control rods 44 are illustrated in FIG. 1 for clarity of presentation, with it being understood that a suitable number thereof, for example several hundred, are actually used in a conventional reactor core. Also in accordance with one embodiment of the present invention, a plurality of control rod drives (CRDs) 46 extend at least downwardly from the vessel lower head 12b and are operatively joined to respective ones of the control reds 44 for selectively translating the control rods 44 upwardly out of the core 16 and downwardly into the core 16. In the preferred embodiment, one CRD 46 is provided for each of the control rods 44. In a conventional BWR, control rod drives extend downwardly from the vessel lower head and include conventional control rod guide tubes extending between the vessel lower head and the bottom of the core (not shown). The guide tubes have a length approximately equal to the length of the control rods themselves so that the control rods may be fully withdrawn downwardly from the core and into the guide tubes within the pressure vessel. By utilizing the split CRD arrangement disclosed above, with the CRDs 46 extending downwardly from the vessel lower head 12b and the control rods 44 being withdrawn upwardly from the core 16 into the chimney 22, the conventional, relatively long control rod guide tubes between the bottom of the core and the vessel lower head may be eliminated. Since the control rods 44 in accordance with the present invention are withdrawn upwardly above the core 16, no guide tubes are necessary below the core 16 for suitably guiding translation of the control rods 44 or for providing a vertical space for storing the control rods 44 when they are fully withdrawn from the core 16. Instead, the CRDs 46 are effective for raising the control rods 44 upwardly into the chimney 22 for their withdrawal from the core 16, and for lowering the control rods 44 from the chimney 22 and into the core 16. FIG. 1 illustrates one exemplary control rod 44 on the left side of the core 16 in its fully inserted position in the core 16, and a second exemplary control rod 44 on the right side of the core 16 in its fully withdrawn position disposed within the chimney 22. In this way, the chimney 22 may itself provide for an increase in the normal water level L above the core 16 without a corresponding increase in the overall height of the pressure vessel 12 since the core 16 may be positioned more closely adjacent to the vessel lower head 12b upon elimination of the conventional control rod guide tubes therebetween as described in more detail below. And, the chimney 22 may be used additionally for guiding upwardly the control rods 44 as well as providing flow channels for confining the flow of the steam-water mixture 38a from the core 16 upwardly toward the steam separator assembly 34 for improved performance. More specifically, since the flow of the steam-water mixture 38a upwardly from the core 16 is turbulent, a plurality of removable chimney channels or tubes 48 are disposed in the chimney 22 above the core 16 and are laterally spaced apart from each other as shown in more particularity in FIG. 2 to define therebetween guide slots 50 for slidably receiving respective ones of the control rods 44 translated upwardly out of the core 16 by the CRDs 46. As shown in FIG. 2, the channels 48 are preferably vertically aligned above and with the fuel bundles 18 for receiving and channeling upwardly therefrom to the steam separator assembly 34 the steam-water mixture 38a. Not only do the chimney channels 48 provide guides for the translation of the control rods 44 upwardly, but they provide partitions to separate the upward flow of the steam-water mixture 38a to ensure predictability of the pressure drop therethrough and the two-phase (liquid and vapor) flow distributions of the steam-water mixture 38a laterally across the chimney 22. Chimneys including partitioned risers are conventional for providing these benefits. However, the chimney channels 48 provide an improved, more simple configuration for additionally allowing the control rods 44 to be withdrawn upwardly above the core 16 instead of downwardly therefrom, as well as providing the guide slots 50 for guiding the withdrawal of the control rods 44 from the core 16 in addition to allowing an increase in the normal water level L above the core 16 by a reduction in the height of the vessel 12 between the bottom of the core 16 and the vessel lower head 12b by the elimination of conventional control rod guide tubes. As illustrated in FIG. 2, each of the control rods 44 preferably has a cruciform transverse configuration or section, and each of the chimney channels 48 has a preferably square configuration and is imperforate. Four adjacent ones of the chimney channels 48 are disposed together so that the guide slots 50 defined therebetween collectively have a cruciform configuration for receiving and guiding a respective one of the control rods 44. Referring to both FIGS. 1 and 2, the chimney upper grid 30 is in the exemplary form of a square lattice and the chimney channels 48 are supported therefrom by hanging downwardly into the chimney 22. For example, the tops of the chimney channels 48 may include radially outwardly extending flanges which are simply supported in complementary recesses defined in the upper grid 30 so that they may be easily inserted therein or removed therefrom during assembly and disassembly. The chimney channels 48 may otherwise be conventionally supported from the upper grid 30 by conventional gimbals for example. The chimney channels 48 may additionally or alternatively be supported by the lower grid 28 by being simply rested thereon, for example, in a complementary recess therein. In the preferred embodiment of the invention illustrated in FIG. 2, each of the fuel bundles 18 has a conventional square configuration and each includes a plurality of conventional elongate, tubular fuel rods 52 as shown in one, exemplary fuel bundle 18 in FIG. 2. Each fuel bundle 18 includes a conventional handle 54 extending upwardly from its top for conventionally inserting and withdrawing the fuel bundle 18 from the core 16. In the preferred embodiment illustrated in FIG. 2, each of the chimney channels 48 is vertically disposed above and aligned with, and is sized for covering four of the fuel bundles 18 in a square array for channeling the steam-water mixture 38a upwardly therefrom and through the chimney channel 48. Each of the fuel bundles 18 may therefore be inserted or withdrawn directly through the chimney channel 48 without the removal thereof if desired. In other embodiments of the invention, the chimney channels 48 may be first removed upwardly from the chimney 22 for allowing access to the fuel bundles 18 disposed therebelow so that the fuel bundles 18 may be removed and replaced with new fuel bundles 18. This preferred alignment also allows the control rods 44 to be withdrawn upwardly between the fuel bundles 18 and between the chimney channels 48 in the guide slots 50 while leaving the interior of the chimney channels 48 open to prevent obstruction of the primary upward flow of the steam-water mixture 38a therein directly from the fuel bundles 18. The secondary upward flow of the steam-water mixture 38a through the guide slots 50 is therefore distinct from the primary flow. Accordingly, the chimney 22 partitioned by the chimney channels 48 serves several functions by providing a space for housing the control rods 44, which therefore allows the control rods 44 to be withdrawn upwardly from the core 16, with the channels 48 also providing the guide slots 50 for guiding upwardly the control rods 44 without the need for additional guiding structure. The chimney channels 48 also effectively channel upwardly the steam-water mixture 38a to prevent crossflow transversely across the chimney 22 for obtaining improved flow distributions from the core 16 with predictable pressure drops thereof through the chimney 22. Furthermore, the chimney 22 also allows for an increase in the normal water lever L as described above. More specifically, the reactor 10 as illustrated in FIG. 1 preferably further includes a gravity-driven cooling system (GDCS) 56 which has a pool 58 of makeup water 60 disposed vertically above the normal water level L of the vessel 12 at a vertical height H.sub.1. The pool 58 is conventionally joined in flow communication with an inlet nozzle 62 of the vessel 12 by a conventional conduit 64 in which is disposed in serial flow communication a conventional valve 66. The valve 66 is normally closed for preventing flow of the makeup water 60 into the vessel 12, and is conventionally openable in response to a LOCA situation, for example, for selectively draining by gravity the makeup water 60 into the vessel 12. The makeup water 60 will be drained into the vessel 12 by its pressure head due to being elevated above the water level L at the height H.sub.1. However, since that pressure head is substantially below the normal pressure within the pressure vessel 12, the pressure vessel 12 must first be suitably depressurized to a sufficiently low pressure for allowing the pressure head of the makeup water 60 in the pool 58 to drain the makeup water 60 into the vessel 12. Accordingly, a conventional automatic depressurization system 68 is joined in flow communication with the pressure vessel 12, through a conventional venting nozzle 70 for example, for initially venting the pressure within the vessel 12 to about atmospheric pressure so that the valve 66 may then be opened to allow draining of the makeup water 60 by gravity into the vessel 12. In order to provide a normal water level L at a height H.sub.2 above the top of the reactor core 16 which is greater than a conventional level, the chimney 22 is provided as described above and has a height H.sub.3 between the lower and upper grids 28 and 30 which is approximately the height of the control blades 44 for allowing the control blades 44 to be fully withdrawn from the core 16 and into the chimney 22. The core 16 has a height H.sub.4 which is equal to the height of the fuel bundles 18, and which is also about the height of the control blades 44, so that the control blades 44 may be fully inserted into the core 16. Since conventional control rod guide tubes are not required between the bottom of the core 16 and the vessel lower head 12b, the lower plenum 20 has a height H.sub.5 which is less than the height H.sub.4 of the core 16 for reducing the overall height H.sub.6 of the pressure vessel 12 measured between the upper and lower heads 12a and 12b. The height of the vessel 12 which would conventionally be provided between the core 16 and the lower head 12b for the control rod guide tubes may be reduced since the guide tubes are no longer required, with the vessel 12 being instead lengthened between the core 16 and the steam separator assembly 34 by incorporating the chimney 22 having the height H.sub.3. In this way, the overall height H.sub.6 of the pressure vessel 12 may remain about the same as a conventional pressure vessel, for example at about 21 meters, with more length being provided between the core 16 and the separator assembly 34 instead of between the vessel lower head 12b and the core 16. Accordingly, the normal water level above the core 16, i.e. height H.sub.2, may be increased over that contained in a conventional boiling water reactor for providing improved performance of the vessel 12 with the gravity-driven cooling system 56 in a LOCA situation, as well as providing improved performance in an all pump trip of the recirculation pumps 40. Furthermore, the conventional skirt surrounding the steam separator assembly 34 may be vertically lengthened by about 1.5 meters in order to improve the capability to recover from swings of the water level L resulting from other conventional upset conditions in the BWR 10. Illustrated in FIGS. 3-5 is an exemplary CRD 46 for translating a respective control rod 44, shown in phantom in FIG. 3 for clarity of presentation. Referring first to FIG. 3, a support tube 72 preferably extends upwardly from the vessel lower head 12b to a bottom plate 16a of the core 16 for supporting the core 16 in this exemplary embodiment. Each of the CRDs 46 includes a tubular CRD housing 74 conventionally fixedly and sealingly joined through the vessel lower head 12b for forming a portion of the pressure boundary for containing the pressurized reactor water 38 within the vessel 12. The CRD housing 74 includes a top portion which extends upwardly from the vessel lower head 12b to the core bottom plate 16a, and a lower portion which extends downwardly from and through the lower head 12b. An elongate drive rod 76 in the exemplary form of a drive screw extends upwardly from the CRD housing 74 and is conventionally releasably coupled to a respective one of the control rods 44 by a conventional bayonet coupling 78 for example. Alternatively, the coupling 78 may be in the form of a screw extending upwardly from the drive rod 76 which threadingly engages a complementary receptacle in the bottom of the control rod 44 for reducing the diameter of the coupling 78 to improve clearance between the channels 48. The CRD 46 in the exemplary embodiment illustrated in FIG. 3 preferably includes means for selectively translating the drive rod 76 upwardly for withdrawing the control rod 44 upwardly from the core 16 and into the chimney 22, and for selectively translating the drive rod 76 downwardly for inserting the control rod 44 into the core 16 from the chimney 22. Means are also provided for selectively releasing the drive rod 76 for allowing gravity to insert the control rod 44 into the core 16 without obstruction from the CRD 46 itself. More specifically, in a conventional bottom-mounted control rod drive, quick insertion upwardly into the core, during a SCRAM occurrence for example, is effected by providing a pressurized fluid over a piston for lifting the piston and the control rod vertically upwardly against the force of gravity. However, with the bottom-mounted CRDs 46 in accordance with the present invention which withdraw the control rods 44 upwardly above the core 16 into the chimney 22, suitable means must be provided for inserting the control rods 44 downwardly during a SCRAM occurrence without obstruction from the CRDs 46 since the SCRAM insertion direction is toward the CRDs 46 instead of away from the CRDs 46 as typically found in a conventional bottom mounted control rod drive. Referring again to FIG. 3, the translating means for the drive rod 76 in the form of a drive screw include a drive tube 80 disposed inside the CRD housing 74, which includes a top endplate 82 having a central top aperture 82a therein through which the drive screw 76 extends upwardly into the core 16. A segmented drive nut 84 is operatively joined to and inside the drive tube 80 as shown in FIG. 3, and in more particularity in FIG. 4, and is selectively engageable and retractable from the drive screw 76 by the releasing means. As shown in FIG. 3, a conventional stepper motor 86 is operatively joined to the drive tube 80 for selectively rotating the drive tube 80, and in turn the drive nut 84, in a first, or clockwise, direction for translating downwardly the drive screw 76, and in a second, opposite, direction, i.e. counterclockwise, for translating upwardly the drive screw 76 when the drive nut 84 is engaged with the drive screw 76. The drive screw 76 is prevented from rotating by being joined to the control rod 44, which is prevented from rotating by the adjacent chimney channels 48 as shown in FIG. 2. By instead rotating the drive nut 84, the drive screw 76 must itself translate upwardly or downwardly depending upon the direction of rotation of the drive nut 84. More specifically, the drive tube 80 further includes a bottom endplate 88 having a central drive shaft 90 extending downwardly through a lower manifold 74a of the CRD housing 74 which is conventionally operatively joined to the motor 86 for rotating the drive tube 80. The drive shaft 90 is preferably an integral portion of the bottom endplate 88 and has a splined end which conventionally slides into the motor 86 for being conventionally rotated thereby. This preferred connection of the drive shaft 90 to the motor 86 allows for easy removal of the drive tube 80 upwardly through the core as described in more detail below. Disposed inside the drive tube 80 and around the drive screw 76 is a central core tube 92 extending upwardly from the drive tube bottom endplate 88 and integral therewith. The central core tube 92 is spaced radially inwardly from the inner surface of the drive tube 80 to define an annular core channel 94 therebetween which extends upwardly to the drive nut 84. A piston 96 in the form of an annulus is slidably disposed in the core channel 94 and is operatively coupled to the drive nut 84 for selectively engaging and releasing the drive nut 84 from the drive screw 76. The drive tube bottom endplate 88 preferably includes a plurality of fluid ports 88a disposed therethrough in flow communication between the lower manifold 74a and the core channel 94 inside the drive tube 80 for channeling a pressurized fluid 98, such as water, into the core channel 94 to generate a pressure force F bearing upwardly against the bottom of the piston 96 for engaging drive nut 84 with drive screw 76. The fluid ports 88a are also effective for venting the pressurized fluid 98 from the core channel 94 to release the pressure force F from the piston 96 for releasing the drive nut 94 from the drive screw 76. The pressurized fluid 98 is conventionally selectively provided to the lower manifold 74a through a supply port 100 extending through the lower end of the CRD housing 74 in flow communication with the lower manifold 74a. A conventional fluid supply 102 is joined to the supply port 100 by a suitable conduit and is effective for selectively providing to the lower manifold 74a the pressurized fluid 98. The fluid supply 102 may be a conventional pump or a conventional accumulator providing the pressurized fluid 98 to the CRD housing 74 through a conventional valve. The fluid supply 102 is also effective for venting the pressurized fluid 98 from the lower manifold 74a. More specifically, the outer diameter of the cylindrical drive tube 80 is suitably less than the inner diameter of the cylindrical CRD housing 74 for providing a relatively close fit therebetween so that the bottom endplate 88 forms an effective flow barrier to reduce or prevent leakage of the pressurized fluid 98 upwardly past the endplate 88a and between the drive tube 80 and the CRD housing 74, to maintain an effective pressure of the pressurized fluid 98 in the lower manifold 74a. The circumference of the bottom endplate 88 may include conventional labyrinth teeth as shown, or piston rings (not shown), cooperating with the inner surface of the CRD housing 74 to provide an effective fluid seal therebetween. In this way, the pressurized fluid 98 channeled into the lower manifold 74a is channeled to flow upwardly through the fluid ports 88a, the core channel 94, and against the bottom of the piston 96 for engaging the drive nut 84 with the drive screw 76. And, upon venting of the pressurized fluid 98 from the lower manifold 74a, the pressure thereof is released for disengaging the drive nut 84 from the drive screw 76 to release and allow gravity to insert the control rod 44 into the core 16. Illustrated in more particularity in FIG. 4 is the top of the CRD housing 74 with the piston 96 effecting the engagement of the drive nut 84 with the drive screw 76. The drive nut 84 has at least two complementary segments, for example each being about 180.degree. in extent, with each segment including screw threads 84a for engaging the drive screw 76 as shown, and a first shank 84b extending radially outwardly through a complementary aperture of the core tube 92. The first shank 84b has an enlarged head and includes an inclined first cam surface 84c facing downwardly toward the piston 96. A first compression spring 104 is disposed between the core tube 92 and the head of the first shank 84b for biasing the drive nut 84 away from the drive screw 76 for allowing unobstructed travel of the drive screw 76 either upwardly or downwardly through the core tube 92. Each segment of the drive nut 84 is identical, with corresponding springs 104 for separately biasing each segment. Referring again to FIG. 4, the piston 96 has an inner diameter larger than the outer diameter of the core tube 92, and an outer diameter smaller than the inner diameter of the drive tube 80 for allowing the piston 96 to sealingly slide upwardly and downwardly within the core channel 94. The outer and inner diameters of the piston 96 may include suitable grooves and piston rings 106 to reduce leakage of the pressurized fluid 98 upwardly past the piston 96 for maintaining the pressure force F when desired. Extending upwardly from the piston 96 is an annular second shank 96a having an inclined, or conical second cam surface 96b being complementary in angle of inclination with the first cam surface 84c in abutting slidable contact therewith. For example, the first and second cam surfaces 84c, 96b are preferably inclined at about 45.degree. from the longitudinal axis of the drive screw 76 so that the upwardly directed pressure force F acting on the piston 96 urges the piston 96 upwardly as shown in FIG. 4, so that the second cam surface 96b slides against the first cam surface 84c for exerting a lateral force to engage the nut threads 84a with the drive screw 76 and overcome the biasing force of the first spring 104. A second compression spring 108 is disposed between the top endplate 82 and the top of the piston 96 for biasing the piston 96 downwardly away from the drive nut 84 for allowing the first spring 104 to release the drive nut 84 from the drive screw 76 as shown in FIG. 5. When the pressure force F is removed from the piston 96, the second spring 108 urges the piston 96 downwardly in the direction D.sub.1 illustrated in FIG. 5, and the first spring 104 urges the drive nut 84 radially outwardly away from the drive screw 76 into a retracted position. The first and second springs 104 and 108 are preferably sized so that the pressure force F generated against the piston 96 by the pressurized fluid 98 is effective for lifting upwardly the piston 96 against the second spring 108 to allow the second cam surface 96b to slide against the first cam surface 84c to urge the drive nut 84 radially inwardly toward the drive screw 76 and against the first spring 104 to engage the drive nut 84 with the drive screw 76. In this way, when the drive nut 84 engages the drive screw 76 as shown in FIGS. 3 and 4, the motor 86 may be selectively operated for rotating the drive tube 80 either clockwise or counterclockwise, which in turn rotates the drive nut 84 therewith for translating the drive screw 76 upwardly or downwardly for either withdrawing or inserting the control rod 44. When the pressure fluid 98 is vented through the supply port 100, the pressurize force F is removed from the piston 96, the drive nut 84 is disengaged from the drive screw 76, and gravity will cause the control rod 44 to drop for insertion into the core 16 without obstruction. By retracting the segmented drive nut 84, the drive screw 76 is allowed to freely fall within the core tube 92 without obstruction. The fluid supply 102 may vent the lower manifold 74a to a pressure suitably less than that found in the core 16 so that the control rod 44 may be inserted more quickly with the assistance of the resulting differential pressure between the core 16 and the vented lower manifold 74a. As shown in FIG. 3, the core tube 92 preferably includes a plurality of vent ports 92a adjacent to the fluid ports 88a in the drive tube bottom end 88 for allowing the fluid in the core tube 92 to be vented in turn through the vent ports 92a, the core channel 94, and the fluid ports 88a, into the lower manifold 74a and out the CRD housing 74 through the supply port 100 as the drive screw 76 is translated downwardly inside the core tube 92. During a SCRAM insertion of the control rod 44 into the core 16, the drive nut 84 is disengaged from the drive screw 76 as shown in FIG. 5 and the drive screw 76 is allowed to drop downwardly inside the core tube 92 in the direction D.sub.2 also shown in FIG. 5. As shown in dashed line in FIG. 3, fluid 110 is displaced by the downwardly moving drive screw 76 in the core tube 92 and is channeled downwardly through the vent ports 92a and in turn out of the CRD housing 74. The fluid 110 may either be portions of the reactor water 38 or the pressurized fluid 98, or both, which find their way into the core tube 92. The size of the vent ports 92a and the clearance between the top aperture 82a and the drive screw 76 are suitably selected to ensure that a suitable pressure force F may be maintained against the piston 96 to selectively engage the drive nut 84 with the drive screw 76, as well as for allowing release of the fluid 110 from inside the core tube 92 during insertion of the drive screw 76 therein. In a preferred embodiment of the present invention, the CRD housing 74 includes an open top end 74b facing upwardly toward the core 16 and preferably extending to the core bottom plate 16a. The drive tube 80 is predeterminedly sized smaller in diameter than the CRD housing top end 74b for being upwardly removable from the CRD housing 74 without obstruction. In a conventional boiling water reactor, bottom-mounted control rod drives are typically removed from the pressure vessel downwardly below the pressure vessel lower head. This requires that suitable access space be provided below the pressure vessel, and suitable means must be provided for preventing leakage of the reactor coolant during disassembly and assembly of the control rod drives. However, in accordance with one feature of the present invention, the entire drive tube 80, including the structures therein, may be conveniently removed from within the CRD housing 74 upwardly through the core 16 by a conventional hoist contained in the power plant. Referring again to FIG. 1, the vessel upper head 12a may be conventionally removed during a maintenance operation to allow access inside the vessel 12 with conventional removal of the steam dryer and separator assemblies 36 and 34 in turn. The chimney top manifold 32 is then conventionally removed, followed in turn by removal of the fuel bundles 18 either through the chimney channels 48 as described above or after removal of the chimney channels 48. The drive tubes 80 are then accessible through the core 16 and may be simply removed upwardly from within the CRD housing 74. By utilizing the conventional spline joint between the drive shaft 90 and the motor 86 (FIG. 3), the motor 86 may remain behind as part of the pressure boundary when the drive tube 80 is lifted from the CRD housing 74. Accordingly, the improved BWR 10 disclosed above provides a new configuration having bottom-mounted, upwardly retractable, and top-removable fine motion control rod drives 46 in combination with the partitioned chimney 22. An increased normal water level L may therefore be obtained for improving natural circulation flow and softening the effects of transient operation, with the ability to apply gravity-driven core cooling through an adequate inventory of in-vessel coolant during depressurization of the vessel 12 in the event of a LOCA. The configuration is compact and utilizes the common space provided by the chimney 22 for multiple purposes, including the elimination of conventional control rod guide tubes between the core 16 and the vessel lower head 12b while providing a space for retraction of the control rods 44 upwardly from the core 16; the chimney channels 48 provide the guide slots 50 for guiding the upward and downward translation of the control rods 44; the chimney channels 48 prevent crossflow within the chimney 22 for controlling the upward rise of the steam-water mixture 38; and, the chimney 22 itself allows for an increased normal water level L above the core 16 with a corresponding reduction below the core 16 without requiring a substantial increase in the height of the pressure vessel 12. Furthermore, although the space between the core 16 and the vessel lower head 12b is reduced, bottom-mounted CRDs 46 may still be used. The control rods 44 and the CRDs 46 are split in space vertically by the core 16, with the chimney channels 48 providing a space for retracting upwardly the control rods 44 while guiding the vertical translation thereof. The preferred chimney channels 48 are discrete members each separately supported by the upper grid 30 and separately removable therefrom. Each chimney channel 48 is relatively simple in structure and may simply be a four-sided imperforate tube, with adjacent channels 48 defining therebetween the guide slots 50. The CRDs 46 themselves may utilize a drive rod in the form of the drive screw 76 for providing fine motion control of the control rods 44 at precise intermediate positions within the reactor core 16 as well as providing fast, SCRAM insertion of the control rods 44 downwardly toward the CRDs 46 without obstruction therefrom. The segmented drive nut 84 is selectively disengaged as described above to allow the drive screw 76 and the control rod 44 joined thereto to drop by gravity downwardly toward the CRD 46 without obstruction. The above arrangement also allows for upward removal of the CRD drive tube 80 for improved maintenance of the CRDs 46 without requiring access below the vessel lower head 12b for that purpose and without requiring additional means for preventing leakage of the reactor water 38 during such a maintenance operation. While there have been described herein what are considered to be preferred embodiments of the present invention, other modifications of the invention shall be apparent to those skilled in the art from the teachings herein, and it is, therefore, desired to be secured in the appended claims all such modifications as fall within the true spirit and scope of the invention. Accordingly, what is desired to be secured by Letters Patent of the United States is the invention as defined and differentiated in the following claims. |
abstract | A 17×17 jacketless fuel assembly for a PWR-type light-water reactor uses thorium as the fuel. The fuel assembly has a square shape in the plan view, a seed region, a blanket region that encircles it, an upper nozzle, and a lower nozzle. The fuel elements of the seed region re arranged in the rows and columns of a square coordinate grid and have a four-lobed profile that forms spiral spacer ribs along the length of a fuel element. The blanket region contains a frame structure within which a bundle of fuel elements made from thorium with the addition of enriched uranium is positioned. The blanket region fuel elements are arranged in the two or three rows and columns of a square coordinate grid. |
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046541713 | abstract | Process and apparatus for confining the pollution of an isostatic pressing enclosure.. At the end of an isostatic pressing operation, a glove box is sealingly fixed above the enclosure, the plug is removed from the latter and deposited within the glove box, after which the sampling and inspection operations necessary for detecting any contamination are performed.. Application to the compression of radioactive waste by isostatic pressing. |
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summary | ||
abstract | A storage phosphor plate for the storage of X-ray information, including a storage phosphor layer which stores the X-ray information and can be stimulated by stimulation light into emitting emission light, and a support layer on which the storage phosphor layer is located, the support layer being partially transparent for the stimulation light, and having a thickness d and an absorption coefficient for the stimulation light, where (k times d)≧0.2. |
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description | 1. Field of the Invention The present invention relates generally to a process for adding an organic compound to coolant water in a pressurized water reactor, and more particularly, for adding the organic compound to coolant water passing through a primary circuit of the pressurized water reactor. 2. Background of the Invention Crud is the result of corrosion products formed when structural materials in the primary circuit, e.g., Reactor Coolant System (RCS), are exposed to coolant water, e.g., reactor coolant, during plant operation. These corrosion products are subsequently released into the coolant and can then deposit on the fuel in the reactor core. As core crud deposit thickness increases, heat transfer decreases as compared to the heat transfer of a clean surface. The temperature at the heat transfer surface will rise, increasing cladding corrosion. Minimizing fuel cladding corrosion is important to assure cladding integrity for all periods of plant operation. It is also an important consideration in fuel rod and reactor core design. Historically, significant effort has been expended in selection of corrosion resistant materials and in development of chemistry control additives and plant operating practices to minimize crud formation and crud deposition in the reactor core. Crud induced power shift (CIPS) can occur when boron, which is present as boric acid, a reactor coolant additive used to control reactivity in a commercial nuclear power plant, such as, a pressurized water reactor (PWR), accumulates to sufficiently high concentrations within core crud deposits to suppress local neutron flux. This results in a shift in axial power distribution away from the boron deposits. The occurrence of CIPS during power operation at various commercial PWRs has been attributed to sufficiently thick, localized corrosion product deposits in the upper spans of a PWR core coincident with locations where the highest reaction steaming rates are predicted to occur. Locally thick crud deposits can also reduce heat transfer and increase fuel cladding temperatures which can lead to crud induced localized corrosion (CILC) and possibly fuel failures. The injection of a soluble zinc additive to the reactor coolant of PWRs has been used for the purpose of radiation field reduction, general corrosion control, and primary water stress corrosion cracking (PWSCC) mitigation. In the PWR system, water is used as the reactor coolant. The water is circulated by pumps through-out a primary circuit, i.e., the RCS, that includes a pressure vessel which houses the heat generating reactor core, and a plurality of flow loops. The water in the primary circuit normally contains boric acid to control reactivity, hydrogen to provide reducing conditions, and an additive to maintain pH in a target control band. When “zinc addition” has been employed at a PWR, zinc acetate has been the preferred additive that is added to the reactor coolant. The use of zinc acetate was desirable because the acetate anion allowed for the zinc to be provided in a soluble form, and the anion and its decomposition products exhibited minimal or no detrimental effect on materials of construction in the RCS. The addition of zinc in the form of soluble zinc acetate has been utilized at a number of commercial PWR power plants. As a result of adding zinc acetate to the reactor coolant of PWRs, desirable changes have been observed in ex-core shutdown radiation fields and various characteristics of core crud deposits. However, zinc acetate addition may result in various operation and/or design challenges. There is a desire to find a reactor coolant additive that can be added to the coolant water to produce elemental carbon. Further, there is a desire to find a reactor coolant additive that can condition core crud deposits. Moreover, there is a desire to find a reactor coolant additive to produce beneficial changes in the deposition and morphology of crud deposits without the potential challenges of known additives. Such an additive would be desirable for use in a wide variety of power plants, worldwide that utilize water reactor core designs. Thus, it is further desired to develop a process for conditioning core crud deposits that results in core crud deposits having at least one of the following features: (i) a change in morphology, e.g., crud is finer grained and/or less well-crystallized, (ii) a change in deposition pattern, e.g., the crud is thinner and/or more uniformly distributed, (iii) a decrease in residence time, e.g., the crud has a shorter residence time on the core, and (iv) a change in composition, e.g., the crud has a higher carbon content. Furthermore, it is desired to develop a process that can inhibit CIPS, and/or CILC, and/or general cladding corrosion and/or fuel failures in water reactors. In one aspect of the invention, a process for a pressurized water reactor having a primary circuit and reactor core is provided. The process includes adding a sufficient amount of an organic compound to coolant water passing through the primary circuit of the pressurized water reactor, the organic compound including elements of carbon and hydrogen, for producing elemental carbon. The organic compound can further include elements selected from the group consisting of oxygen, nitrogen, and mixtures thereof. The equivalent elemental carbon addition rate can be maintained in a range of from about 1 mg/hour to about 10 g/hour. The water reactor can be a nuclear reactor. The coolant water can be in a reactor coolant system of a nuclear reactor. The organic compound can be selected from the group consisting of organic acids, alcohols, amines, aldehydes, ketones, and mixtures thereof. The organic compound can be selected from the group consisting of acetic acid, methanol, ethanol, ethylamine, ethanolamine, and mixtures thereof. The organic compound can be substantially soluble. The process can further include producing corrosion product deposits in the reactor core including elemental carbon in a range of from about 15 to about 20 percent by weight of the deposits. The radiation level in the reactor core can be up to about 4000 Mrad/hour from gamma and neutrons. The hydrogen concentration in the reactor core can be greater than 0 cc/kg, or from about 25 to about 50 cc/kg. The organic compound can be added on a continuous or batch basis. The organic compound can be in a high purity form. The process can further include producing corrosion product deposits in the reactor core wherein the elemental carbon is produced in an amount effective to change at least one of the morphology, deposition pattern, residence time and carbon content of crud deposits in the reactor core as a result of adding the organic compound. The process can further include producing corrosion product deposits in the reactor core wherein the elemental carbon is produced in an amount effective to inhibit at least one of crud induced power shift, crud induced localized corrosion, cladding corrosion in the reactor core, and fuel failures as a result of adding the organic compound. In another aspect of the invention, a process for a nuclear reactor having a primary circuit is provided. The process includes adding a sufficient amount of an organic compound to coolant water passing through the primary circuit of the nuclear reactor, the organic compound including elements of carbon and hydrogen, for producing elemental carbon. The organic compound can further include elements selected from the group consisting of oxygen, nitrogen, and mixtures thereof. The equivalent elemental carbon addition rate can be maintained in a range of from about 1 mg/hour to about 10 g/hour. The nuclear reactor can be a pressurized water reactor. In yet another aspect of the invention, a nuclear reactor having a reactor coolant system wherein the reactor coolant system contains reactor coolant circulating therethrough is provided. The reactor coolant includes an organic additive, the organic additive includes elements of carbon and hydrogen, and the organic additive being present in the reactor coolant in an amount sufficient to produce elemental carbon. The organic compound can further include elements selected from the group consisting of oxygen, nitrogen, and mixtures thereof. As used herein and the claims, CIPS refers to a shift in core axial power which is greater than or equal to three percent (3%) of the predicted core axial power as a result of concentration/deposition of boron in corrosion product deposits in regions of the fuel undergoing sub-cooled nucleate boiling. Boron, which accumulates in thick corrosion product deposits in the reactor core, can cause local depressions in neutron flux that shifts power axially. This complicates control by the reactor operators, and in cases where CIPS is severe, may limit the plant to less than 100% rated power output. As core crud deposit thickness increases, the temperature at the heat transfer surface will rise, increasing general cladding corrosion. Locally thick crud deposits can lead to CILC and possibly fuel failures. The process of the present invention relates to the addition of an organic compound to the coolant water of a pressurized water reactor. The coolant water passes through the primary circuit of the pressurized water reactor. The process may serve to modify the corrosion products (i.e., crud) that circulate in the coolant water and/or form films or deposits in the reactor core. Further, addition of the organic compound to the coolant water results in the production of elemental carbon (e.g., in the reactor core, primary coolant, and/or corrosion products therein). Without intending to be bound by any particular theory, it is believed that elemental carbon is produced from the additive by the combined effect of the high radiation levels in a reactor core when criticality is achieved and the dissolved hydrogen concentration in the reactor coolant. In an embodiment, the radiation levels in the core and the dissolved hydrogen concentration in the reactor coolant are each maintained in a range within industry standards for PWR operation. In another embodiment, the radiation level in an operating reactor core can be up to about 4000 Mrad/hour from both gamma and neutrons. In other embodiments, the dissolved hydrogen concentration in the reactor core can be greater than zero (0) cc/kg, or from about 25 to about 50 cc/kg. It is further believed that the in-core radiation fields radiolytically decompose the organic molecule, and the reducing conditions produced by the hydrogen, present as an integral component of the nominal PWR chemistry control specifications, result in a portion of the free radical species arising from the organically bound carbon being deposited as elemental carbon. The addition of zinc acetate to the reactor coolant can lower ex-core radiation fields, slow both initiation and propagation of PWSCC in Alloy 600, and result in thinner, finer grained, more uniformly distributed core crud deposits with shorter core residence times and higher carbon content. In the present invention, the addition of an organic additive to the reactor coolant, e.g., in a sufficient amount to produce elemental carbon, can modify the morphology and deposition pattern of the core crud deposits to result in thinner, finer grained, less well-crystallized, more uniformly distributed core crud deposits with shorter core residence times and higher carbon content, with minimal or no impact on ex-core oxide films and without the addition of zinc. In accordance with the present invention, an organic compound is added to the coolant water, such as reactor coolant, of a pressurized water reactor. Suitable organic compounds include those organic compounds known in the art which are made up of at least carbon and hydrogen. In an embodiment, the organic compound may also include nitrogen, oxygen, and mixtures thereof. Thus, in alternate embodiments, organic compounds for use in the present invention can include those containing at least carbon and hydrogen, or at least carbon, hydrogen, and oxygen, or at least carbon, hydrogen, and nitrogen, or at least carbon, hydrogen, oxygen, and nitrogen. In a preferred embodiment, the additive is miscible with, or substantially soluble in, the coolant water. However, even immiscible or only slightly soluble organic additives can be used wherein less control of the addition rate is acceptable. Non-limiting examples of suitable organic compounds for use in the present invention can include organic acids such as, but not limited to, acetic acid, alcohols such as, but not limited to, methanol and ethanol, aldehydes, amines, ketones, and mixtures thereof. Other non-limiting examples can include soluble or slightly soluble organic compounds that contain at least carbon and hydrogen, and optionally oxygen, such as but not limited to, ethylacetate, and/or optionally nitrogen, including organic amines such as, but not limited to ethylamine and ethanolamine. In an embodiment, high purity forms of the organic compound are used consistent with standard industry practice of limiting impurities to as low as reasonably achievable (ALARA) in any additive to the reactor coolant of a PWR. The organic compound can be added to the coolant water using a variety of conventional mechanisms known, such as, for example but not limited to, injection. The addition can be conducted, for example, on a batch or a continuous basis. In a non-limiting embodiment, the organic compound is continuously injected into the reactor coolant. Further, in a non-limiting embodiment, the injection can be employed during power operation. The organic compound is injected into the reactor coolant at a rate sufficient to produce elemental carbon. In an embodiment, the rate of injection of the organic compound is sufficient to produce elemental carbon in an amount that is effective to change the morphology and deposition pattern of the core crud deposits as previously described herein. In one embodiment, the organic compound is injected into the reactor coolant at a rate sufficient to provide an equivalent elemental carbon addition rate maintained in the range of from about 1 mg/hour to about 10 g/hour. Injection of the organic compound at a rate within this specified range can be sufficient to produce corrosion product deposits in the reactor core that contain elemental carbon in the range of from about 15 to about 20 percent by weight of the deposits. Without intending to be bound by any particular theory, it is believed that the deposition of elemental carbon on the reactor core cladding and on developing core crud deposits favorably affects the morphology and deposition pattern of the core crud deposits such as to reduce the risk of CIPS/CILC occurring and/or to reduce general fuel cladding corrosion and fuel failures. It is further believed that the presence of the organic additive serves to condition and control the core crud retention and release to minimize the potential for CIPS/CILC and to reduce general fuel cladding corrosion and fuel failures. For example, during power operation, the injection of an organic compound into the reactor coolant at a rate that is effective to to produce elemental carbon in an effective amount, or at an effective rate, or in a predetermined specified range, can produce core corrosion product deposits having at least one desirable characteristic such as, for example but not limited to, (i) a change in morphology, e.g., crud is finer grained and/or less well-crystallized, (ii) a change in deposition pattern, e.g., the crud is thinner and/or more uniformly distributed, (iii) a decrease in residence time, e.g., the crud has a shorter residence time on the core, and (iv) a change in composition, e.g., the crud has a higher carbon content. These changes are as compared to core corrosion product deposits produced under nominal PWR reactor coolant chemistry operating conditions. Zinc Acetate Addition Evaluations Zinc acetate addition has been employed at an increasing number of PWRs to lower ex-core radiation fields and to provide PWSCC protection to austenitic stainless steel and nickel based alloys that are used both in construction of the pressure boundary of the RCS and structural components within the RCS as discussed in Pressurized Water Reactor Primary Water Zinc Application Guidelines. EPRI, Palo Alto, Calif.: 2006. 1013420. Following the initial use of zinc addition at Plant A during Cycle 10, visual examination of the core during the refueling outage showed a uniform-appearing black deposit over the full height of the fuel assemblies as described in Evaluation of Zinc Addition to the Primary Coolant of PWRs. EPRI, Palo Alto, Calif.: October 1996. TR-106358, Vol. 1. Measurements made on samples of crud removed from these fuel assemblies by scraping showed that the crud deposits were extremely thin (<0.5 μm) compared to previous operating cycles at this plant, even in the hottest spans where maximum sub-cooled nucleate boiling was predicted and maximum crud thickness was normally observed. The visual appearance of this crud was described as highly unusual. The Plant A Cycle 10 fuel deposits were also described as different from fuel crud deposits formed on cores where zinc acetate addition had not been used. It was noted that the sooty-looking deposits could be easily removed by the sampling tool and were not nearly as tenacious as crud on cores where zinc acetate addition was not used. Residence time calculations for this crud showed that these deposits remained on the core about half as long as crud from this plant in the previous cycle of operation when zinc acetate was not added. A study was conducted as described in Evaluation of Fuel Clad Corrosion Product Deposits and Circulating Corrosion Deposits in PWRS, EPRI, Palo Alto, Calif., and Westinghouse Electric Company, Pittsburgh, Pa.: 2004. 1009951, where core crud deposits from nine operating commercial PWRs were removed, analyzed, and compared. One of the nine PWRs, Cycle 11 at Plant B, was operating with zinc acetate addition to the RCS. The core crud deposits for this plant were found to contain carbon and were described as thinner, less crystalline, and more mobile when compared to core crud for plants not adding zinc acetate. The morphology of the core crud deposits at Plant B after Cycle 11 was further described as sub-micron in size and having no display of distinct crystal faces. This observation was in marked contrast to the morphology of core crud deposits at the plants that did not add zinc acetate. The morphology of core crud at the plants not adding zinc acetate was described as consisting of well-crystallized micron-sized particles. As described in Evaluation of Fuel Cladding Corrosion and Corrosion Product Deposits from Callaway Cycle 13: Results of Poolside Examinations Following One Cycle of Zinc Addition. EPRI, Palo Alto Calif.: 2005. 1011088, core crud examinations at Plant C after Cycle 13, the initial cycle of operation with zinc acetate addition to the RCS, were also conducted. The post-zinc acetate addition core crud deposits were compared to pre-zinc acetate core deposits at this same plant and were described as being different in chemical composition and deposit morphology, thinner, more widely distributed over the core, less activated, and more easily released upon shutdown. The following results of the second cycle of zinc acetate addition at Plant C were described in Evaluation of Fuel Cladding Corrosion and Corrosion Product Deposits from Callaway Cycle 14: Results of Poolside Measurements Following Two Cycles of Zinc Addition. EPRI, Palo Alto, Calif., 2006. 1013425. In the core crud examination after Cycle 14, it was noted that carbon was an elemental component of the core crud deposits. The transition to crud that was less activated (i.e., lower specific activity and lower residence time) during Cycle 13 had continued in Cycle 14. In addition to examination of fuel crud deposits, cladding corrosion measurements were also performed at a number of plants before and after implementing zinc acetate addition. Plants operating with zinc acetate addition had lower oxide thickness measurements, on average, than plants operating without zinc acetate addition. The actual measured values could also be compared to the oxide thickness as predicted based on corrosion models. Plant D experienced corrosion consistent with the predictions prior to adding zinc acetate, whereas fuel rods which had been exposed to zinc acetate experienced less corrosion than predicted. Thus, examination of fuel from PWR power plants which add zinc acetate has shown beneficial changes in crud such as, for example but not limited to, thinner core crud deposits, shorter residence time of core crud deposits, higher carbon content of core crud deposits, and finer grained, less well-crystallized core crud deposits. In accordance with the present invention, beneficial changes in crud can be attained by adding to the coolant water of a pressurized water reactor an organic compound which is made up of at least carbon and hydrogen, but optionally may also include oxygen, nitrogen, and mixtures thereof. In an embodiment, the pressurized water reactor is a nuclear reactor. In a further embodiment, the nuclear reactor includes reactor coolant circulating through the Reactor Coolant System (RCS). Addition of the organic compound additive can condition core crud deposits. Further, the organic additive can produce beneficial changes in the deposition and morphology of crud deposits. The resultant core crud deposits can have at least one of the following features: (i) a change in morphology, e.g., crud is finer grained and/or less well-crystallized, (ii) a change in deposition pattern, e.g., the crud is thinner and/or more uniformly distributed, (iii) a decrease in residence time, e.g., the crud has a shorter residence time on the core, and (iv) a change in composition, e.g., the crud has a higher carbon content. It is believed that these beneficial changes in core crud are effective to inhibit CIPS, and/or CILC, and/or general fuel cladding corrosion, and/or fuel failures. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof. |
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description | The present application is a continuation-in-part of U.S. application Ser. No. 15/584,684, titled MOLTEN FUEL NUCLEAR REACTOR WITH NEUTRON REFLECTING COOLANT, filed May 2, 2017, now U.S. Pat. No. 10,665,356. U.S. application Ser. No. 15/584,684 claims the benefit of U.S. Provisional Patent Application No. 62/330,726, titled “IMPROVED MOLTEN FUEL REACTOR CONFIGURATIONS”, filed May 2, 2016. U.S. application Ser. No. 15/584,684 also is a continuation-in-part of U.S. application Ser. No. 15/282,814, titled NEUTRON REFLECTOR ASSEMBLY FOR DYNAMIC SPECTRUM SHIFTING, filed Sep. 30, 2016, now U.S. Pat. No. 10,734,235. U.S. application Ser. No. 15/282,814 claims the benefit of U.S. Provisional Patent Application No. 62/337,235, titled “NEUTRON REFLECTOR ASSEMBLY FOR DYNAMIC SPECTRUM SHIFTING”, filed May 5, 2016; and U.S. Provisional Patent Application No. 62/234,889, entitled “MOLTEN CHLORIDE FAST REACTOR AND FUEL” and filed on Sep. 30, 2015. A particular classification of fast nuclear reactor, referred to as a “breed-and-burn” fast reactor, includes a nuclear reactor capable of generating more fissile nuclear fuel than it consumes. That is, the neutron economy is high enough to breed more fissile nuclear fuel (e.g., plutonium-239) from fertile nuclear reactor fuel (e.g., uranium-238) than it burns in a fission reaction. In principle, a breed-and-burn reactor may approach an energy extraction rate of 100% of the fertile materials. To initiate the breeding process, a breed-and-burn reactor must first be fed with an amount of fissile fuel, such as enriched uranium. Thereafter, breed-and-burn reactors may be able to sustain energy production over a timespan of decades without requiring refueling and without the attendant proliferation risks of conventional nuclear reactors. One type of breed-and-burn reactor is a molten salt reactor (MSR). Molten salt reactors are a class of fast spectrum nuclear fission reactors wherein the fuel is a molten salt fluid containing mixed or dissolved nuclear fuel, such as uranium or other fissionable elements. In an MSR system, the unmoderated, fast neutron spectrum provided by fuel salts enables good breed performance using the uranium-plutonium fuel cycle. In contrast to the fast spectrum neutrons that dominate breeding of fissile fuel from fertile fuel, thermal neutrons dominate the fission reaction of fissile fuel. A fission reaction resulting from a collision of a thermal neutron with a nuclide can consume the fissile fuel in a fission reaction, releasing fast spectrum neutrons, gamma rays, large amounts of heat energy and expelling fission products, such as smaller nuclei elements. Consuming nuclear fuel is referred to as burnup or fuel utilization. Higher burnup typically reduces the amount of nuclear waste remaining after the nuclear fission reaction terminates. The fast neutron spectrum also mitigates fission product poisoning to provide exceptional performance without online reprocessing and the attendant proliferation risks. The design and operating parameters (e.g., compact design, low pressures, high temperatures, high power density) of a breed-and-burn MSR, therefore, offer the potential for a cost-effective, globally-scalable solution to zero carbon energy. During operation of an MSR system, molten fuel salt exchange can allow some control over reactivity and breeding in the reactor core within desired operational bounds by altering the composition of the circulating molten fuel salt. In some implementations, the reactor core is wholly or partially enclosed in a neutron reflector assembly containing a neutron reflector material. The disclosed dynamic neutron reflector assembly allows additional dynamic and/or incremental control over reactivity and breed rate by adjusting reflectivity characteristics of a neutron reflector assembly to manage the neutron spectrum in the reactor core. Such control manages the reactivity and the breed rate in the reactor core. The composition of materials in the dynamic neutron reflector assembly may be altered by selectively inserting or removing neutron-spectrum-influencing materials, such as neutron reflectors, moderators or absorbers, to dynamically manage the dynamic neutron reflector assembly's neutron-spectrum-influencing characteristics (“reflectivity characteristics”). Alternatively, these reflectivity characteristics may be adjusted by varying the temperature, density, or volume of the material in the dynamic neutron reflector assembly. In some implementations, the dynamic neutron reflector assembly may include a flowing neutron reflector material that is in thermal contact with the fuel (e.g., molten fuel salt). The flowing neutron reflector material may be in any appropriate form including, without limitation, fluids like lead bismuth, slurry of suspended particulates, solids such as a powder, and/or pebbles such as carbon pebbles. The dynamic neutron reflector assembly may selectively circulate or flow through the assembly one or more neutron absorbing materials, such that it is possible to selectively add or remove reflector material therefrom. In other implementations, the flowing neutron reflector material can extract heat from the molten fuel salt in a heat exchanger via a primary or secondary coolant circuit. FIG. 1 is a schematic view of an example molten salt reactor (MSR) system 100 enabling an open breed-and-burn fuel cycle with fuel feed 102 and fuel outlet 104. The fuel outlet 104 flows molten fuel salt 108 from a reactor vessel 107 through a primary coolant loop to an external heat exchanger (not shown), which extracts heat (e.g., for use in a steam turbine) and cools the molten fuel salt 108 for return to the reactor vessel 107 via the fuel feed 102. The molten fuel salt 108 flows into the reactor vessel 107 through a molten fuel salt input 111 and flows out of the reactor vessel 107 through a molten fuel salt output 113. The reactor core section 106 is enclosed by the reactor vessel 107, which may be formed from any material suitable for use in molten salt nuclear reactors. For example, the bulk portion of the reactor core section 106 may be formed from one or more molybdenum alloys, one or more zirconium alloys (e.g., Zircaloy), one or more niobium alloys, one or more nickel alloys (e.g., Hastelloy N) or high temperature steel and other similar materials. The internal surface 109 of the reactor core section 106 may be coated, plated or lined with one or more additional material in order to provide resistance to corrosion and/or radiation damage. Reactor core section 106 is designed to maintain a flow of a molten fuel salt 108, wherein such flow is indicated by hollow tip thin arrows as in FIG. 1. In one implementation, the reactor vessel 107 enclosing the reactor core section 106 may have a circular cross-section when cut along a vertical or Z-axis (i.e., yielding a circular cross-section in the XY plane), although other cross-sectional shapes are contemplated including without limitation ellipsoidal cross-sections and polygonal cross-sections. As part of the reactor startup operation, the MSR system 100 is loaded with an enriched fuel charge of initial molten fuel, such as uranium-233, uranium-235, or plutonium-239. In one implementation, uranium-235 is used as a startup fuel in the form of PuCl3, UCl4, UCl3, and/or UF6 along with a carrier salt (e.g., NaCl, NaF, etc.). In one example, the initial molten fuel mixture contains enriched uranium at 12.5 w %, although other compositions may be employed. The initial molten fuel circulates through the reactor core section 106 of the MSR system 100, ignited by the criticality or reactivity of thermal neutrons of the enriched uranium. During operation, the initial molten fuel may be augmented by the breed-and-burn processes and by extraction and supplementation of molten fuel salt in varying compositions and amounts, in one approach, to managing the reactivity in the reactor core section 106. A neutron reflector assembly 110 is disposed at or near the exterior of the reactor core section 106, such that the neutron reflector assembly 110 surrounds at least a portion of the nuclear fission region within the reactor core section 106. The neutron reflector assembly 110 may be designed in a single contiguous piece or may be composed of multiple segmented reflectors as explained in more detail below. The neutron reflector assembly 110 may be formed from and/or include any material suitable for neutron reflection, neutron moderation and/or neutron absorption, such as, for example, one or more of zirconium, steel, iron, graphite, beryllium, tungsten carbide, lead, lead-bismuth, etc. Among other characteristics, the neutron reflector assembly 110 is suitable for reflecting neutrons emanating from the reactor core section 106 back into the molten fuel salt 108, according to dynamic incrementally adjustable reflectivity characteristics. One type of a dynamic incrementally adjustable reflection characteristic is neutron reflection, an elastic scattering of neutrons as they collide with reflector nuclei. Colliding neutrons are scattered at substantially the same energy with which they arrived but in a different direction. In this manner, a high percentage of fast spectrum neutrons can be reflected back into the reactor core section 106 as fast spectrum neutrons, where they can collide with fertile nuclear material to breed new fissile nuclear material. Accordingly, neutron reflector material in the neutron reflector assembly 110 can enhance the breed operation of a breed-and-burn fast reactor. Additionally, or alternatively, another dynamically adjustable reflection characteristic is neutron moderation, an inelastic scattering of neutrons as they collide with moderator nuclei. Colliding neutrons are scattered at a lower energy than that with which they arrived (e.g., a fast spectrum neutron scatters as a thermal spectrum neutron) and with a different direction. In this manner, a high percentage of fast spectrum neutrons can be reflected back into the reactor core section 106 as thermal neutrons, where they can collide with fissile nuclear material and result in a fission reaction. Accordingly, neutron moderator material in the neutron reflector assembly 110 can enhance the burn-up operation of a breed-and-burn fast reactor. Additionally or alternatively, another dynamically adjustable reflection characteristic is neutron absorption, also known as neutron capture: a nuclear reaction in which an atomic nucleus and one or more neutrons collide and merge to form a heavier nucleus. Absorbed neutrons are not scattered but remain part of the merged nuclei unless released at a later time, such as part of a beta particle. Neutron absorption provides the reflectivity characteristic of zero or minimal reflection. In this manner, fast and thermal neutrons emanating from the reactor core may be prevented from scattering back into the reactor core section 106 to collide with fissile or fertile material. Accordingly, neutron absorbing material in the neutron reflector assembly 110 can diminish the breed operation and burn operation of a breed-and-burn fast reactor. Dynamic control over neutron reflectivity characteristics of the neutron reflection assembly 110 permits selection of a desired reactivity level in reactor core section 106. For example, molten fuel salt 108 requires a minimum level of thermal neutron contact to remain critical in reactor core section 106. The dynamic neutron reflector assembly 110 may be adjusted to provide the reflectivity characteristics for maintaining or contributing to the criticality in the molten fuel salt 108 within the reactor core section 106. As another example, it may be desired to operate the MSR system 100 at full power, which would motivate an increased thermalization of neutrons in the reactor core section 106 to increase the fission rate. The reflectivity characteristics of dynamic neutron reflector assembly 110 could be therefore increased to provide more moderation until a desired reactivity level representing full power for the reactor core section 106 has been reached. In contrast, as MSR system 100 is a breed-and-burn reactor, it may be desired to dynamically control breed rate at various points over the lifecycle of the reactor. For example, early in the reactor's lifecycle, a high breed rate may be desired to increase the availability of fissile material in reactor core section 106. The reflectivity characteristics of dynamic neutron reflector 110 may therefore be adjusted to provide increased reflection of fast neutrons into reactor core section 106 to breed more fertile material into fissile fuel. As more fast neutrons are reflected into reactor core section 106 over time, the fast neutrons may breed fertile material into fissile material until a desired concentration of fissile material has been reached. Later in the reactor's lifecycle, it may be desirable to increase burnup to provide increased power through increased burnup. The reflectivity characteristics of dynamic neutron reflector assembly 110 may therefore be adjusted to increase moderation of fast neutrons into thermal neutrons to maintain the desired burn rate. In this way, the core reactivity and the ratio of breeding to burning may be accurately controlled over time by adjusting the reflectivity characteristics of dynamic neutron reflector assembly 110. For example, an operator of the MSR system 100 may wish to maintain a high and consistent burn profile over time. In some implementations, a desired burn profile is a burn profile that remains near maximum burn rate of the MSR system 100 over an extended period of time, such as over a period of years or decades. Reflectivity characteristics of dynamic neutron reflector assembly 110 may be chosen at various intervals over the extended period of time to obtain such a burn profile. As in the example above, early in the life cycle of the MSR system 100, reflectivity characteristics may be chosen to reflect more fast neutrons into reactor core section 106 to breed fertile material into fissile material until a desired concentration of fissile material has been reached. Reflectivity characteristics may be again adjusted for increased thermalization appropriate to the concentration of fissile material. Over time, as the fissile material is burned, reflectivity characteristics of dynamic neutron reflector assembly 110 may again be adjusted to introduce more breeding through fast neutron reflection, by reducing moderation and/or increasing fast neutron reflection. These adjustments may continue such that the burn profile of MSR system 100 remains high, and fertile material is bred into fissile material at a rate sufficient to supply the MSR system 100 with fuel over the extended period. FIG. 2 is a plot 200 of reactivity against time of a fast spectrum MSR with one or more dynamic reflector assemblies against two other assembly configurations with static neutron influencing characteristics. A plot line 202 shows reactivity over time for a fast spectrum MSR reactor with static lead neutron reflector assembly surrounding a reactor core, wherein the lead neutron reflector assembly tends to elastically scatter fast neutrons into the reactor core. After a time T0, when the reactor is started with an initial fuel charge, breeding of fertile fuel may occur rapidly due to reflection of fast neutrons into the reactor core. After T1, reactivity on the plot line 202 gradually increases over time as the breeding increases the amount of available fissile material to burn, reaching a maximum at a time near T4. Breeding may slow over time with increasing burnup as fertile fuel previously present in the reactor core is converted to fissile material or fissioned due to increased competition for neutrons with products of fission. The plot line 202 does not show a constant reactivity level over time because, near the beginning of the period, there are not sufficient fast neutrons in the fuel region to breed enough fissile material to support a high burn rate. Over time, the larger number of fast neutrons breeds fertile material into fissile material, and reactivity increases but remains below the maximum burn rate of which the reactor is capable. Near the end of the period, around time T5, reactivity reaches a local maximum and begins to decline as the supply of fertile material begins to decline. A plot line 204 shows reactivity over time for a fast MSR with a static graphite moderator configuration, wherein the moderating neutron reflector assembly tends to provision the reactor core with thermalized neutrons. On the plot line 204, reactivity begins around time T0 at a relatively higher level than plot line 202 due in part to thermalization caused by the graphite moderator increasing the probability of fission. Plot line 204 may drop significantly near time T0 due to thermal spectrum multiplication adjacent to the graphite reflector. Reactivity may then gradually reduce over time in a generally linear manner as the thermal neutrons burn fissile fuel in the reactor core. The plot line 204 is similar to plot line 202 in the respect that neither plot line reaches or maintains a maximized burn rate achievable within the reactor core. The plot line 204 does not reach the reactor's maximum burn rate because there are not enough fast neutrons to maintain a breeding rate high enough to support the burn rate as time progresses though the period T0-T5. In the plot lines 202 and 204, the burn rate is not optimized over the time period T0-T5. Instead, each plot has a period of relatively higher burn rate and a period of relatively lower burn rate over the course of the graph. The plot lines 202 and 204 are shown in contrast to plot line 206. The plot line 206 illustrates reactivity over time for a fast MSR system with a dynamic neutron reflector assembly, starting with a high moderator configuration and changing to a high reflector configuration, thereafter being dynamically controlled to achieve desired reactivity conditions within the reactor core. Reactivity over time on the plot line 206 starts relatively high after an initial fuel charge is loaded around time T0, and remains high due to the dynamically controllable nature of the reflection and thermalization of neutrons. Around time T0, the composition of material in the neutron reflection assembly is adjusted for a moderation rate that correlates with the concentration of fissile material available in the fuel region at that time. As the burn up progresses, the composition of material in the neutron reflection assembly is adjusted to increase fast neutron reflection and decrease moderation to continue supplying the fuel region with newly bred fissile material while, at the same time, maintaining an appropriate amount of thermalization to match the current conditions in the fuel region. The adjustments may be performed continuously or as a batch process, and continue over time towards T5. An effect of these dynamic neutron reflector assembly adjustments is to maintain a relatively stable and high reactivity rate over the entire period T0-T5 that is not feasible with static moderators and neutron reflectors, such as those represented by the plot lines 202 and 204, respectively. Nevertheless, the same dynamic neutron reflector assembly may be used to control reactivity in other ways (e.g., to reduce reactivity, etc.). It should also be noted that inclusion of a neutron absorber within the neutron reflector assembly can also impact the reactivity within the reactor core. Dynamic adjustments among neutron reflector, moderator, and absorber materials within the neutron reflector assembly can provide richer control options than static neutron reflector assemblies alone. FIG. 3 is a schematic view of a segmented dynamic neutron reflector assembly 300 surrounding an MSR core 301. The MSR core 301 is equipped with a fuel feed 308 and a fuel outlet 310. The fuel outlet 310 flows molten fuel salt from a reactor vessel 303 through a primary coolant loop to an external heat exchanger (not shown), which extracts heat (e.g., for use in a steam turbine) and cools the molten fuel salt for return to the reactor vessel 303 via the fuel feed 308. The molten fuel salt flows into the reactor vessel 303 through a molten fuel salt input 312 and flows out of the reactor vessel 303 through a molten fuel salt output 314. Segmented dynamic neutron reflector 300 may partially or substantially surround the MSR core 301. For example, there may be gaps between the segments 302, 304, 306 or the segments 302, 304, 306 may encircle the MSR core contiguously. Although three segments of the dynamic reflector assembly 300 are shown in FIG. 3, it should be understood that the dynamic reflector assembly may comprise any number of segments. The segments of the dynamic reflector assembly 300 may surround the core by completely or partially encircling the core radially. Segments of the dynamic reflector assembly 300 may be optionally positioned above and/or below the reactor core in combination with, or instead of, radial reflector segments. It should be understood that in some cases it may not be possible for the segmented dynamic neutron reflector to completely surround the reactor core in an uninterrupted or completely contiguous manner. For example, it may be appropriate to dispose various structures and instruments around the fast MSR core 301 with supporting elements such as input/output piping, power supply conduits, data conduits, and/or other instrumentation, controls, and supporting hardware. These structures and instruments may require direct or indirect access to the reactor core such that the segments of the dynamic reflector assembly 300 may need to be shaped or positioned to accommodate access. Accordingly, in some implementations, it may be appropriate to permit gaps between the segments or arrangements wherein portions of the area surrounding the reactor core are not covered by segments of the dynamic reflector assembly 300. Some or each segment 302, 304, 306 of the dynamic reflector assembly 300 may contain one or more channels (not shown in FIG. 3) for conducting a flowing reflector material. As used in this application, the term channels refers not only to a tubular enclosed passage, but to any volume suitable for flowing a reflector material. A flowing reflector material may include materials that may not necessarily be fluids, but materials that can circulate or flow through the assembly, such that it is possible to selectively add or remove reflector material therefrom. Examples of suitable neutron reflector materials include fluids, slurry of suspended particulates, and/or solids such as a powder, and/or pebbles, such as carbon pebbles, etc. The segments 302, 304, 306 may contain one or more first channels for conducting a flowing reflector material in a first direction, such as, for example, down along the periphery of the respective segments, and one or more second channels for conducting a flowing reflector material in a second direction, such as, for example, back up to the top of dynamic neutron reflector assembly 300. The channels of the various reflector segments may be fluidically coupled such that the flowing neutron reflector material flows between the segments. In another implementation, the reflector segments may be fluidically separate from one another such that flowing reflector material flows into and out of only a single segment. In an implementation, one or more of the fluid channels in the reflector segments may be in thermal communication with a heat exchanger and/or the molten fuel salt, acting as a coolant. The flowing reflector material may thus exchange heat with the molten fuel salt, and transfer the heat via the heat exchangers to a secondary coolant circuit to supply heat from the reactor to a turbine or other electricity generating equipment. As the flowing reflector material exchanges heat with the reactor core through a primary and/or a secondary coolant circuit, the flowing reflector material temperature may fluctuate. As the flowing reflector material's temperature fluctuates, its density may vary. For example, in an implementation, the flowing reflector material is molten lead-bismuth, and the molten lead-bismuth will experience a higher density at lower temperatures. As the temperature of the molten lead-bismuth lowers and its density rises, the number of molecules per unit volume of the lead-bismuth will increase. As the number of molecules per unit volume increases (i.e., higher density), the likelihood of reflecting a fast spectrum neutron emanating from the reactor core increases, thus increasing the effective reflectivity of the flowing reflector material without changing the volume of the material. In another implementation, the density of the flowing reflector material may be adjusted by introducing a non-reflective material (such as non-reflective material particulates, fluids gas bubbles, etc.) into the flowing reflector material. In yet another implementation, the density of the flowing reflector material may be adjusted by adjusting environmental characteristics to vaporize the flowing reflector material into a low density vapor phase. In this way, the material composition of the dynamic neutron reflector assemblies, and thus its reflectivity, may be altered. FIG. 4 illustrates an MSR system 400 with a dynamic flowing neutron reflector assembly 406 equipped with a spillover reservoir 408. A molten fuel salt 402 flows in an upward direction as it is heated by the fission reaction in the internal central reactor core section and flows downward as it cools around the internal periphery of the reactor vessel 401. In FIG. 4, hollow tip arrows indicate the flow of molten fuel salt through MSR system 400. The constituent components of the molten fuel may be well-mixed by the fast fuel circulation flow (e.g., one full circulation loop per second). In one implementation, one or more heat exchangers 404 are positioned at the internal periphery of the reactor vessel 401 to extract heat from the molten fuel flow, further cooling the downward flow, although heat exchangers may additionally or alternatively be positioned outside the reactor vessel 401. MSR system 400 includes dynamic neutron reflector assemblies 406. Operating temperatures of MSR system 400 may be high enough to liquefy a variety of suitable neutron reflector materials. For example, lead and lead-bismuth melt at approximately 327° C. and 200° C., respectively, temperatures within the operating range of the reactor. In an implementation, dynamic neutron reflector assemblies 406 are configured to contain a flowing and/or circulating fluid-phase of the selected neutron reflector materials (e.g., lead, lead-bismuth, etc.). In FIG. 4, solid tip arrows indicate the flow of neutron reflector material. Dynamic neutron reflector assemblies 406 may be formed from any suitable temperature and radiation resistant material, such as from one or more refractory alloys, including without limitation one or more nickel alloys, molybdenum alloys (e.g., a TZM alloy), tungsten alloys, tantalum alloys, niobium alloys, rhenium alloys, silicon carbide, or one or more other carbides. In an implementation, dynamic neutron reflector assemblies 406 are positioned on, and distributed across, the external surface of the reactor core section. In implementations, the dynamic neutron reflector assemblies 406 may be segmented, as explained above with reference to FIG. 3. In an implementation, dynamic neutron reflector assemblies 406 are arranged radially across the external surface of the reactor core section. Dynamic neutron reflector assemblies 406 may be arranged to form a contiguous volume of neutron reflector material around the reactor core section. Any geometrical arrangement and number of dynamic neutron reflector assemblies 406 is suitable for the technology described herein. For example, dynamic neutron reflector assemblies 406 may be arranged in a stacked ring configuration, with each module filled with a flow of neutron reflector material to form a cylindrical neutron reflecting volume around the reactor core section. Dynamic neutron reflector assemblies 406 may also be arranged above and below the reactor core section. The composition of the dynamic neutron reflector assemblies 406 may be adjusted to change reflectivity characteristics, such as, for example, by adjusting the volume of the flowing reflector material in reflectors 406. One way of adjusting the volume of the flowing reflector material in reflectors 406 is to pump the material into or out of dynamic reflectors 406 into spillover reservoir 408 via piping assembly 410 and pump 414. To decrease the volume of the flowing neutron reflector material, and thus to decrease the reflectivity characteristics of reflectors 406, a portion of the flowing neutron reflector material may be pumped or displaced into spillover reservoir 408 via piping assembly 410. A valve 412 and pump 414 may cooperate to regulate the flow of the flowing neutron reflector material through piping assembly 410. To increase the volume of the flowing neutron reflector material, valve 412 and pump 414 may cooperate to flow the flowing neutron reflector material out of overflow tank 408 and back into reflectors 406 via piping assembly 410. In another implementation, the reflectivity of dynamic neutron reflector assemblies 406 may be adjusted by regulating the temperature, and thus the density, of the flowing neutron reflector material. Changes in the density of the flowing neutron reflector material alter its neutron reflective characteristics as denser materials have a higher mass per unit volume. Denser materials will contain more molecules per unit volume, and are therefore more likely to reflect neutrons because any neutron travelling through the denser material will be more likely to strike a molecule of the flowing neutron reflector material and thus be reflected. Pump 414 and valve 412 may cooperate to increase or decrease the flow rate of the flowing neutron reflector material into or out of dynamic neutron reflectors 406 to regulate the temperature of the reflecting flowing neutron reflector material. In other implementations, spillover reservoir 408 may be replaced with other configurations, such as a closed circuit loop. The MSR system 400 may include a flowing neutron reflector material cleaning assembly 416. The flowing neutron reflector material cleaning assembly 416 is in fluid communication with the piping assembly 410, and may be located on either side of valve 412 and pump 414. The flowing neutron reflector material cleaning assembly 416 may filter and/or control the chemistry of the neutron reflector material. For example, the flowing neutron reflector cleaning assembly 416 may remove oxygen, nitrites, and other impurities from the neutron reflector material. In an implementation, a zircon nitrite coating in the neutron reflector cleaning assembly 416 is configured to control the chemistry of the flowing neutron reflector material. In another implementation, the flowing neutron reflector cleaning assembly 416 may perform a “slagging” technique wherein the flowing neutron reflector cleaning assembly 416 captures oxygen as an oxide material. If the oxide material is molten, it may phase separate and the flowing neutron reflector cleaning assembly 416 may remove the oxide material from the neutron reflector material by, for example, scraping the oxide material. In another implementation, the flowing neutron reflector cleaning assembly 416 is configured for a hydrogen treatment of the neutron reflector material to remove oxygen contained therein. The composition of dynamic neutron reflectors 406 may also be adjusted by introducing a flowing moderator material. The flowing moderator material may be held in a reserve tank (not shown) and introduced into dynamic neutron reflectors 406 via piping assembly 410 and pump 414 in fluid communication with the fluid moderator reserve tank. The flowing moderator material may circulate in dynamic reflectors 406, and may be removed by pump 414 into the reserve tank via piping assembly 410. In an implementation, water or heavy water may be used as a flowing moderating liquid in dynamic neutron reflectors 406. In another implementation, beryllium may be used as a flowing moderating material in dynamic neutron reflectors 406. In yet another implementation, LiF—BeF2 may be used a flowing moderating material in dynamic neutron reflectors 406 and/or in the fuel salt itself. The pump 414 may pump the flowing moderator liquid and/or the flowing neutron reflector material into and out of the dynamic reflectors 406 continuously and/or in a batch process. As previously described, neutron absorbing material can also be incorporated into dynamic neutron reflector assemblies 406, individually or in combination with various compositions and/or configurations of neutron reflector materials and neutron moderator materials. FIG. 5 is a top-down schematic view of a dynamic neutron reflector assembly 500 with a plurality of refractory clad sleeves 502 to conduct a flowing neutron reflector material therethrough. In an implementation, flowing neutron reflector assembly 500 substantially surrounds a nuclear fuel region 504 from which fast spectrum neutrons 506 emanate. In FIG. 5, example paths of fast spectrum neutrons 506 are indicated by lines terminating in double arrows, such as lines 508. The example fast spectrum neutrons 506 are inelastically scattered (or reflected) from the flowing reflector material and back into the nuclear fuel region 504. The reflector configuration of FIG. 5 may be used to incrementally shift neutron spectrum in nuclear fuel region 504 by selectively filling each of the channels 502 with a volume of neutron reflector material. In FIG. 5, the neutron reflector material flows upward through a refractory clad channel 502 toward the viewer. In an implementation, neutron reflector material may circulate in channels 502 (e.g., cells, sleeves, conduits, etc.) with input and output ports above the nuclear fuel region 504 such that no fixtures or ports are needed beneath the reactor. In other implementations, the neutron reflector material may flow in only one direction, either in an upward or downward direction, through the channels 502 with one port above the nuclear fuel region 504 and another port below fuel region 504. In yet other implementations, the neutron reflector material may comprise a semi-stagnant or creeping flow through the channels 502. In yet other implementations, the neutron reflector material may flow through radial input and output ports. The dynamic neutron reflector assembly 500 is in thermal communication with heat exchanger 510 disposed on the opposite side from fuel region 504. The heat exchanger 510 may contain one or more types of liquid coolant circulating therethrough. As neutron reflector 500 exchanges heat with the heat exchanger 510, the heat exchanger 510 may transport the heat away from the dynamic neutron reflector assembly 500 as part of a secondary coolant circuit. The secondary coolant circuit may supply heat to electricity generation equipment, such as, for example, a steam-driven turbine. In an implementation, molten fuel salt may flow upward through the nuclear fuel region 504 and downward through the heat exchanger 510, thus exchanging heat as part of a primary coolant circuit. In other words, the heat exchangers may exchange heat with both the molten fuel salt and exchange heat with the flowing neutron reflector in the channels 502. The flow rate of neutron reflector material may be adjusted to vary contact time with the heat exchangers to vary the temperature of reflector material flowing in the channels 502. As the temperature of reflector material varies, its density changes accordingly. Changes in the density of the reflector material alter its neutron reflective characteristics as denser materials have a higher mass per unit volume and are therefore more likely to reflect neutrons. The channels 502 may be formed in geometric shapes including without limitation square, rectangular, round, circular, polygonal, etc. FIG. 6 is a top-down schematic view of a dynamic neutron reflector assembly 600 with a plurality of sleeves 602 conducting a flowing neutron reflector material and a plurality of sleeves 604 including neutron moderating members 606 selectively inserted into sleeves 602, 604 in any desired configuration with respect to which and how many sleeves 602 may receive a neutron moderating member 606. Dynamic neutron reflector assembly 600 substantially surrounds a fuel region 608 from which fast spectrum neutrons 610 emanate. In FIG. 6, lines terminating in double arrows such as lines 612 indicate fast spectrum neutrons. Upon insertion, neutron moderating members 606 displace a volume of flowing neutron reflector material, thus altering the neutron reflectivity characteristics of dynamic neutron reflection assembly 600. Since dynamic neutron reflector assembly 600 contains neutron reflecting and neutron moderating materials, some of the fast spectrum neutrons are reflected back into fuel region 608, and other fast spectrum neutrons 610 strike neutron moderating members 606 and are converted into thermal neutrons. In FIG. 6, example paths of thermal neutrons are indicated by lines terminating in single arrows, such as line 614. Example paths of fast spectrum neutrons are indicated by lines terminating in double arrows. As dynamic reflector assembly 600 converts fast spectrum neutrons into thermal neutrons, the thermal neutrons may be reflected back into fuel region 608 by the flowing neutron reflector material in the channels 602, 604, or reflected by another neutron reflector disposed behind dynamic reflector 600 (not shown). By displacing some of the volume of flowing neutron reflector material, the overall reflectivity characteristics of reflector 600 are changed, thus reducing the breed rate in fuel region 608 due to a reduced reflection of fast spectrum neutrons compared to a configuration without neutron moderating volumetric displacement members 606. The displacement member configuration shown in FIG. 6 also increases the burn rate in fuel region 608 due to an increase in thermal spectrum neutrons compared to a configuration without displacement members. By selectively inserting neutron moderating volumetric displacement members 606 into reflector 600, the breed and burn rates, as well as the neutron spectrum, in fuel region 608 may be dynamically adjusted. The volumetric displacement members 606 may be formed in geometric shapes including without limitation square, round, rectangular, circular, polygonal, etc. In an embodiment, the overall reflectivity characteristics of the reflector 600 are changed by draining one or more of the channels 602, 604 of the flowing neutron reflector material, thus leaving empty space in one or more of the channels 602, 604. Active cooling can be provided to the reflector 600 can provide active cooling by providing thermal communication with the fuel salt and/or with a secondary coolant. In FIG. 6, the neutron reflector material flowing in channels 602 flows upward toward the viewer. In an implementation, neutron reflector material flowing in channels 602 may circulate in channels 602 with input and output ports above fuel region 608 such that no fixtures or ports are needed beneath the reactor. In other implementations, neutron reflector material flowing in channels 602 may flow in only one direction, either in an upward or downward direction, through channels 602 with one port above fuel region 608 and another port below fuel region 608. In yet other implementations, the neutron reflector material may comprise a semi-stagnant or creeping flow through channels 602. In yet other implementations, the neutron reflector material may flow through radial input and output ports. Heat exchanger 614 may be in thermal communication with dynamic reflection assembly 600 for exchanging heat from fuel region 608. In an implementation, the heat exchanger 614 is disposed adjacent on the opposite side of dynamic reflector assembly 600 from fuel region 608. As the neutron reflector material flows through the sleeves of dynamic reflector assembly 600, it may transfer heat emanating from fuel region 608 to the heat exchanger 614 to form a secondary coolant circuit. The secondary coolant circuit may include one or more secondary coolant loops formed from piping. The secondary coolant circuit may include any secondary coolant system arrangement known in the art to be suitable for implementation in a molten fuel salt reactor. The secondary coolant system may circulate a secondary coolant through one or more pipes and/or fluid transfer assemblies of the one or more secondary coolant looks in order to transfer heat generated by the reactor core and received by the heat exchanger 614 to downstream thermally driven electrical generation devices and systems. The secondary coolant system may include multiple parallel secondary coolant loops (e.g., 2-5 parallel loops), each carrying a selected portion of the secondary coolant through the secondary coolant circuit. The secondary coolant may include, but is not limited to, liquid sodium. In an implementation, the heat exchanger 614 is protected by one or more materials effective as a poison or neutron absorber to capture neutrons emanating from the fuel region 608 before the neutrons interact with, and cause radiation damage to, the heat exchanger 614. In an implementation, the heat exchanger 614 includes the one or more materials effective as a poison or neutron absorber. In another implementation, the one or more materials effective as a poison or neutron absorber are included in the dynamic reflector assembly 600. FIG. 7 is a top-down schematic view of a molten nuclear fuel salt fast reactor core with fuel region 702 surrounded by a neutron reflector assembly 700. Neutron reflector assembly 700 contains a neutron reflector material 704 flowing through channels 712. In FIG. 7, neutron reflector material 704 flows upward toward the viewer. In an implementation, neutron reflector material 704 may circulate in channels 712 with input and output ports above fuel region 702 such that no fixtures or ports are needed beneath the reactor. In other implementations, neutron reflector material 704 may flow in only one direction, either in an upward or downward direction, through channels 712 with one port above fuel region 702 and another port below fuel region 702. In yet other implementations, neutron reflector material 704 may comprise a semi-stagnant or creeping flow through channels 712. In yet other implementations, neutron reflector material 704 may flow through radial input and output ports disposed between heat exchangers 706. Flowing dynamic neutron reflector material 704 is in thermal communication with heat exchangers 706. Heat exchangers 706 may contain one or more types of liquid coolant circulating therethrough. As neutron reflector material 704 exchanges heat with heat exchangers 706, heat exchangers 706 may transport the heat away from neutron reflector assembly 700 as part of a secondary coolant circuit. The secondary coolant circuit may supply heat to electricity generation equipment, such as, for example, a steam-driven turbine. In an implementation, molten fuel salt may flow upward through fuel region 702 and downward through heat exchangers 706, thus exchanging heat as part of a primary coolant circuit. In other words, heat exchangers 706 may exchange heat with both the molten fuel salt and exchange heat with the flowing neutron reflector material 704. The flow rate of neutron reflector material 704 may be adjusted to vary contact time with heat exchangers 706 to vary the temperature of the neutron reflector material 704. As the temperature of the neutron reflector material 704 varies, its density changes accordingly. Changes in the density of neutron reflector material 704 alter its neutron reflective characteristics as denser materials have a higher mass per unit volume and are therefore more likely to reflect neutrons. FIG. 7 shows example fast neutrons 710 emanating from a fuel region 702. Fast neutrons are indicated by lines terminating in double arrows. Example fast neutrons 710 may originate in fuel region 702 and be reflected by a neutron reflector material 704 and travel back into fuel region 702. Example fast neutrons 710 reflected back into fuel region 702 may increase the fissile material in fuel region 702 upon contact with fertile materials. Similarly, FIG. 7 shows example thermal neutrons 714. Example thermal neutrons 714 are indicated by lines terminating in single arrows. Example thermal neutrons 714 may be reflected by neutron reflector material 704 and travel back into fuel region 702. Example thermal neutrons reflected into fuel region 702 may increase the reactivity in fuel region 702 upon contact with fissile material located therein. FIG. 8 is a top-down schematic view of a molten nuclear fuel salt fast reactor core with a fuel region 802 surrounded by a neutron reflector assembly 800 with a neutron reflector material 804 in thermal communication with heat exchangers 806. In FIG. 8, neutron reflector material 804 flows upward toward the viewer. In an implementation, neutron reflector material 804 may circulate in channels 808 with input and output ports above fuel region 802 such that no fixtures or ports are needed beneath the reactor. In other implementations, neutron reflector material 804 may flow in only one direction, either in an upward or downward direction, through channels 808 with one port above fuel region 802 and another port below fuel region 802. In yet other implementations, neutron reflector material 804 may comprise a semi-stagnant or creeping flow through channels 808. In yet other implementations, neutron reflector material 804 may flow through radial input and output ports disposed between heat exchangers 806. Flowing neutron reflector material 804 is in thermal communication with heat exchangers 806. Heat exchangers 806 may contain one or more types of liquid coolant circulating therethrough. As flowing neutron reflector material 804 exchanges heat with heat exchangers 806, heat exchangers 806 may transport the heat away from the neutron reflector assembly 800 as part of a secondary coolant circuit. The secondary coolant circuit may supply heat to electricity generation equipment, such as, for example, a steam-driven turbine. In an implementation, molten fuel salt may flow upward through fuel region 802 and downward through heat exchangers 806, thus exchanging heat as part of a primary coolant circuit. In other words, heat exchangers 806 may exchange heat with both the molten fuel salt and exchange heat with the flowing neutron reflector material 804. The flow rate of neutron reflector material 804 may be adjusted to vary contact time with heat exchangers 806 to vary the temperature of neutron reflector material 804. The reflector assembly 800 includes neutron moderating volumetric displacement members 812 inserted into fluid channels 808. Upon insertion of moderating members 812, the volume of the reflecting liquid 804 in the channel is reduced. With reduced volume, the remaining neutron reflector material 804 in the channel has an altered neutron reflectivity characteristic, and is therefore less likely to reflect neutrons than before the moderating member 812 was inserted. The presence of moderating member 812 in the area surrounding fuel region 802 makes thermalization of neutrons more likely, such as, for example, thermalized neutron 810. Increased thermalization will tend to increase burnup of fissile material in the fuel region 802. The moderating volumetric displacement members 812 may be inserted into channels 808 singly or in any plurality of members. Moderating volumetric displacement members 812 may take on a cylindrical shape, a square or rectangular prism shape, a triangular prism shape, a polygonal prism shape and the like. In another implementation, moderating volumetric displacement members 812 may include a set of members (not shown). Selection of the geometric shape and number of moderating volumetric displacement members 812 per channel 808 will determine the ratio of moderating material to reflector material in channels 808. Selectively inserting moderating volumetric displacement members 812 permits adjustment of breed rate and reactivity in fuel region 802 and allows maintenance of a desired burnup level. In an implementation, a burnup rate is maintained within a desired upper and lower bound by selectively inserting and removing at least a subset of moderating volumetric displacement members 812. FIG. 9 is a top-down schematic view of a molten nuclear fuel salt fast reactor core with a fuel region 902 surrounded by a neutron reflector assembly 900 with a flowing neutron reflector material 904 through channels 908. In FIG. 9, neutron reflector material 904 flows upward toward the viewer. In an implementation, neutron reflector material 904 may circulate in channels 908 with input and output ports above fuel region 902 such that no fixtures or ports are needed beneath the reactor. In other implementations, liquid neutron reflector 904 may flow in only one direction, either in an upward or downward direction, through channels 908 with one port above the fuel region 902 and another port below the fuel region 902. In yet other implementations, liquid neutron reflector 904 may comprise a semi-stagnant or creeping flow through channels 908. In yet other implementations, liquid neutron reflector 904 may flow through radial input and output ports disposed between heat exchangers 914. Flowing neutron reflector material 904 is in thermal communication with heat exchangers 914. Heat exchangers 914 may contain one or more types of liquid coolant circulating therethrough. As flowing neutron reflector material 904 exchanges heat with heat exchangers 914, heat exchangers 914 may transport the heat away from neutron reflector assembly 900 as part of a secondary coolant circuit. The secondary coolant circuit may supply heat to electricity generation equipment, such as, for example, a steam-driven turbine. In an implementation, molten fuel salt may flow upward through fuel region 902 and downward through heat exchangers 914, thus exchanging heat as part of a primary coolant circuit. In other words, heat exchangers 914 may exchange heat with both the molten fuel salt and exchange heat with the flowing neutron reflector material 904. The flow rate of neutron reflector material 904 may be adjusted to vary contact time with heat exchangers 914 to vary the temperature of neutron reflector material 904. As the temperature of neutron reflector material 904 varies, its density changes accordingly. Changes in the density of neutron reflector material 904 alter its neutron reflective characteristics as denser liquids have a higher mass per unit volume and are therefore more likely to reflect neutrons. Reflector assembly 900 includes selectively inserted neutron absorbing members 906 and selectively inserted volumetric displacement members 910. Neutron absorbing members 906 and volumetric displacement members 910 may be of any geometric shape compatible with the shape of channels 908. Neutron absorbing members 906 and volumetric displacement members 910 displace a volume of flowing neutron reflector material 904 in the channel 908 into which they are inserted, thus lowering the neutron reflectivity of that channel. Selectively inserting neutron absorbing members 906 and volumetric displacement members 910 adjusts the neutron reflectivity in the nuclear reactor core by altering the composition of the material in the neutron reflection assembly. Several scenarios are possible for fast neutrons travelling into volumetric displacement members 910, such as example fast neutron 910. Fast neutron 912 may pass through the member 910 (not shown in FIG. 9), fast neutron 912 may be reflected by the remaining flowing neutron reflector material 904 in the channel, or fast neutron 912 may be reflected by another surface (not shown). Example fast neutron 912 is less likely to reflect back into fuel region 902 when a volumetric displacement member 910 is inserted than when the channel is full of the flowing neutron reflector material 904. Inserting neutron absorption member 906 is another way of adjusting neutron reflectivity in the nuclear reactor core by altering the composition of the material in the neutron reflection assembly. When neutron absorption member 906 is inserted into a channel 908, example fast neutron 912 may strike and be absorbed by the absorption member 906. Other scenarios are also possible. Example fast neutrons may be reflected by flowing neutron reflector material 904 that was not displaced by absorption member 906, or it may exit the core region where it may be reflected or absorbed by other material (not shown). In another implementation, neutron absorption members 906 may be inserted into a channel 908 while flowing neutron reflector material 904 is removed from the channel. It should be understood that volumetric displacement members 910 and neutron absorption members 906 may be selectively inserted into channels 908 in any desired configuration and in any combination with other members not shown in FIG. 9, such as neutron moderating members. Any number of volumetric displacement members 910 and neutron absorption members 906 may be inserted into a single channel, alone or in combination with other insertable members. Volumetric displacement members 910 and neutron absorption members 906 may be inserted into only some of the channels 908, or only into channels on a portion of dynamic reflector 900. It may be desirable to focus the location of breeding or burning in fuel region 902 by choosing an insertion configuration that concentrates the desired neutron activity in a desired location. For example, an increased breed may be induced in the upper half of fuel region 902 by selectively removing members inserted in the upper half of reflector assembly 900 to allow the neutron reflector material 904 to fill channels 908 on the upper half of the reflector assembly 900. In another example, an increased burn may be induced in the lower half of fuel region 902 by selectively inserting neutron moderating members into the channels 908 on the lower half of reflector assembly 900. In yet another example, reactivity in a portion of fuel region 902 may be reduced by selectively inserting neutron absorbing members 906 into the channels 908 located on the desired side of reflector assembly 900. In the implementation of FIG. 9, flowing neutron reflector material 904 in the channels 908 are in thermal communication with heat exchangers 914. Varying the flow rate of flowing neutron reflector material 904 in channels 908 may alter the flowing reflecting liquid's temperature, and thus its density and thus its neutron reflection characteristics. Altering the density of the flowing neutron reflector material 904 is another way of adjusting the neutron reflectivity in the nuclear reactor core by altering the composition of the material in the neutron reflection assembly. By way of the heat exchangers 914, flowing neutron reflector material 904 in the channels 908 is a secondary coolant for the fuel region 902 because it may operate to exchange heat with the molten fuel salt in the fuel region 902 to the outside of the reactor core via the heat exchangers 914. FIG. 10 is a side schematic view of a molten nuclear fuel salt fast reactor core surrounded by a dynamic neutron reflector assembly 1000 with a neutron reflector material 1002 in thermal communication with a molten nuclear fuel salt 1004 in a tube and shell heat exchanger. Flowing reflecting liquid 1002 flows through inlets 1006 and into outer channels 1008. Outer channels 1008 provide a neutron reflecting layer from which fast neutrons emanating from fuel region 1004 may be reflected back into the fuel region 1004. After leaving outer channels 1012, flowing reflecting liquid 1002 flows through lower channels 1012. Lower channels 1012 provide a neutron reflecting layer from which fast neutrons emanating from fuel salt 1004 may be reflected back into the fuel salt 1004. After leaving lower channels 1012, flowing neutron reflector material 1002 flows upwards through tubes 1014. Tubes 1014 are in thermal communication with molten fuel salt 1004 flowing downward in channels 1016 surrounding tubes 1014 in a shell-and-tube configuration, and therefore function as a secondary coolant for the reactor core. Tubes 1014 may be configured as any number of tubes of any diameter and cross-sectional geometry. Configuration of tubes 1014 may be chosen for a desired surface area contact with flowing molten fuel salt 1004 in the region 1016 for a desired thermal exchange between the flowing neutron reflector material 1002 and the molten fuel salt 1004. After leaving tubes 1014, flowing neutron reflector material 1002 enters upper channel 1020. Upper channel 1020 provides a reflecting layer from which neutrons emanating from fuel region 1004 may be reflected back into fuel region 1004. Heat exchangers (not shown) may be in thermal communication with flowing neutron reflector material 1002. In an implementation, heat exchangers may be disposed outside channel 1008. In another implementation, heat exchangers may be disposed above flowing neutron reflector material inlet 1006 or outlet 1022. By way of the heat exchangers, flowing neutron reflector material 1002 is a secondary coolant for fuel region 1004 because it may operate to exchange heat with the molten fuel salt to the outside of the reactor core. Neutron reflectivity in the nuclear reactor core may be adjusted by altering the composition of the reflecting liquid in channels 1008, 1012, 1020. For example, the volume of flowing neutron reflector material 1002 may be adjusted by pumping an amount of the flowing neutron reflector material 1002 into or out of overflow tank 1010, thus increasing or decreasing the reflectivity, respectively. In another example, the density of flowing neutron reflector material 1002 through channels 1008, 1012, 1020 may be adjusted. A higher density of flowing neutron reflector material 1002 may lead to an increased neutron reflectivity while a lower density of flowing neutron reflector material 1002 may lead to a decreased neutron reflectivity. The density of flowing neutron reflector material 1002 may be adjusted by varying temperature. Temperature of flowing neutron reflector material 1002 may be adjusted by varying flow rate, and thus thermal contact time with the molten fuel salt 1004. Alternatively, or additionally, the direction of flow of the flowing neutron reflector material 1002 may be reversed. As such, the flowing neutron reflector material 1002 may flow in a downward direction through tubes 1014 and up through channels 1008 into overflow tank 1010. The direction of flow of the molten nuclear fuel salt 1004 may also be reversed. As such, the molten nuclear fuel salt 1004 may flow in a downward direction in the center of the fission region and flow in an upward direction around tubes 1014. FIG. 11 is a top-down schematic view of a molten nuclear fuel salt fast reactor core with fuel region 1102 surrounded by a neutron reflector assembly 1100 with a neutron reflector material 1104 flowing through channels 1110, and flowing through tubes 1108 in channels 1112, tubes 1108 being in thermal communication with a molten nuclear fuel salt flowing through fuel region 1102 and through channels 1112 in a tube and shell style heat exchanger. From the viewpoint of FIG. 11, the molten fuel salt flows upward through fuel region 1102 and downward through channels 1112. The flowing reflecting liquid flows downward through channels 1110 and upward through tubes 1108. In this implementation, the flowing reflecting liquid 1104 is also a secondary coolant for the fuel in fuel region 1102. Tubes 1108 may take a variety of configurations, including without limitation any number of tubes in each channel 1112 or tubes of any geometric shape. Selection of the number of tubes 1108 per channel 1112 and the shape of tubes 1108 will determine the surface area in contact with molten fuel salt flowing upward in channel 1112, and alter the amount of heat exchanged between flowing reflecting liquid 1104 and molten fuel salt 1102. Although pairs of tubes 1108 per channel 1112 are shown in FIG. 11, a variety of configurations are possible. For example, tubes 1108 may take a meandering path through channels 1112 to increase surface area thermally exposed to the molten fuel salt. In another implementation, channels 1112 may contain a series of baffles around which the molten fuel salt must flow in an indirect pattern between the inlet and outlet ports. The indirect flow pattern increases the thermal contact between the molten fuel salt and the tubes, and increases the angle between the tubes and the molten fuel salt flow to increase thermal communication. In an embodiment, example fast neutrons 1114 emanating from fuel region 1102 may be reflected by flowing reflecting liquid 1104 contained in tubes 1008 or be reflected by flowing reflecting liquid 1104 contained in channels 1110, and back into fuel region 1102. Fast neutrons such as example fast neutron 1116 emanating from molten fuel salt flowing in channels 1112 may also be reflected by flowing reflector material 1104 in tubes 1108 or in channels 1110, and back into fuel region 1102. FIG. 12 depicts a flow diagram of example operations 1200 of dynamic spectrum shifting in a molten nuclear fuel salt fast reactor. A sustaining operation 1202 sustains a nuclear fission reaction in a nuclear reactor core surrounded by a dynamic neutron reflector assembly. The neutron reflector assembly may have at least one neutron reflector material. A neutron reflection assembly may surround a nuclear reactor core by being disposed radially around, above, and/or below the reactor core. The neutron reflection assembly may be formed in one contiguous piece, formed into discrete pieces distributed around the reactor core, disposed around the core in discrete pieces with gaps in between, and/or segmented into regular or irregular sections. The reflection assembly may contain one or more channels for conducting a flowing reflector material. The reflection assembly may contain one or more levels of channels, such that a flowing reflector material flows in one direction in one level, and flows in another direction in one or more other levels. For example, the reflection assembly may contain an outer channel with flowing reflector material flowing downward, and another inner channel with flowing reflector material flowing upward to avoid any inlet or outlet plumbing underneath the reactor core. The reflection assembly may further be in thermal communication with one or more heat exchangers, and therefore function as a secondary coolant for the reactor core. In one implementation, heat exchangers are thermally coupled to channels for conducting the flowing reflector material. Another implementation may utilize a tube-and-shell heat exchanger wherein a first channel conducts a flowing reflector material in a first direction, and one or more additional channels conduct the flowing reflector material in a second direction through one or more tubes surrounded by flowing molten fuel salt. An adjusting operation 1204 adjusts fast neutron flux and thermal neutron flux within the nuclear reactor core during the sustained nuclear fission reaction by altering reflectivity characteristics of reflector material in the neutron reflector assembly. Altering reflectivity characteristics of reflector material in the neutron reflector assembly may include: any one or more of modifying the volume of reflector material in the reflector assembly, modifying the density of reflector material in the reflector assembly, modifying the composition of reflector material in the reflector assembly, inserting and/or removing neutron moderating members into the reflector assembly, inserting and/or removing neutron absorbing members into the reflector assembly, and/or inserting and/or removing volumetric displacement members into the reflector assembly. FIG. 13 depicts a flow diagram of other example operations 1300 of dynamic spectrum shifting in a molten nuclear fuel salt fast reactor. A sustaining operation 1302 sustains a nuclear fission reaction in a nuclear reactor core surrounded by a neutron reflector assembly. The neutron reflector assembly may have at least one neutron reflector material. A neutron reflection assembly may surround a nuclear reactor core by being disposed radially around, above, and/or below the reactor core. The neutron reflection assembly may be formed in one contiguous piece, formed into discrete pieces distributed around the reactor core, disposed around the core in discrete pieces with gaps in between, and/or segmented into regular or irregular sections. The reflection assembly may contain one or more channels for conducting a flowing reflector material. The reflection assembly may contain one or more levels of channels, such that a flowing reflector material flows in one direction in one level, and flows in another direction in one or more other levels. For example, the reflection assembly may contain an outer channel with flowing reflector material flowing downward, and another inner channel with flowing reflector material flowing upward to avoid any inlet or outlet plumbing underneath the reactor core. The reflection assembly may further be in thermal communication with one or more heat exchangers, and therefore function as a secondary coolant for the reactor core. In one implementation, heat exchangers are thermally coupled to channels for conducting the flowing reflector material. Another implementation may utilize a tube-and-shell heat exchanger wherein a first channel conducts a flowing reflector material in a first direction, and one or more additional channels conduct the flowing reflector material in a second direction through one or more tubes surrounded by flowing molten fuel salt. An adjusting operation 1304 adjusts fast neutron flux and thermal neutron flux within the reactor core during the sustained nuclear fission reaction by modifying the volume of reflector material in the neutron reflector assembly. In an implementation, volume of a flowing reflector material may be altered by a pump and valve fluidically coupled to a spillover reservoir. A volume of flowing reflector material may be pumped through the valve and into the spillover reservoir to reduce volume of reflector material in the reflection assembly, and thus reduce the flux of fast and/or thermal neutrons scattered into the reactor core. Conversely, a volume of flowing material may be pumped though the valve out of the spillover reservoir to increase volume in the reflector assembly, and thus increase reflectivity of neutrons into the reactor core. In another implementation, altering the composition of material in the neutron reflector assembly may include selectively inserting or removing a volumetric displacement member into one or more channels conducting a flowing reflector material. In implementations, a volumetric displacement member may be a neutron moderating member, a neutron absorbing member, or a volumetric displacement member that does not influence neutron flux (e.g., a hollow member or a member formed of non-neutron influencing materials). Insertion of a volumetric displacement member into a channel conducting flowing reflector material surrounding a reactor core reduces the volume of the reflector material in a channel, and thus alters the reflectivity characteristics of the reflector assembly by reducing the scattering of neutrons because fewer neutrons are likely to be scattered due to a reduced volume of reflector material. Removing a volumetric displacement member from a channel conducting a flowing reflector material surrounding a nuclear reactor core may increase the volume of the flowing reflector material, and thus alters the reflectivity characteristics of the reflector assembly by increasing the scattering of neutrons because flowing reflector material may return to the reflector assembly into the space vacated by the withdrawn volumetric displacement member, thus increasing the likelihood that neutrons emanating from a reactor core will be scattered due to increased volume of reflector material. FIG. 14 depicts a flow diagram of other example operations 1400 of dynamic spectrum shifting in a molten nuclear fuel salt fast reactor. A sustaining operation 1402 sustains a nuclear fission reaction in a nuclear reactor core surrounded by a neutron reflector assembly. The neutron reflector assembly may have at least one neutron reflector material. A neutron reflection assembly may surround a nuclear reactor core by being disposed radially around, above, and/or below the reactor core. The neutron reflection assembly may be formed in one contiguous piece, formed into discrete pieces distributed around the reactor core, disposed around the core in discrete pieces with gaps in between, and/or segmented into regular or irregular sections. The reflection assembly may contain one or more channels for conducting a flowing reflector material. The reflection assembly may contain one or more levels of channels, such that a flowing reflector material flows in one direction in one level, and flows in another direction in one or more other levels. For example, the reflection assembly may contain an outer channel with flowing reflector material flowing downward, and another inner channel with flowing reflector material flowing upward to avoid any inlet or outlet plumbing underneath the reactor core. The reflection assembly may further be in thermal communication with one or more heat exchangers, and therefore function as a secondary coolant for the reactor core. In one implementation, heat exchangers are thermally coupled to channels for conducting the flowing reflector material. Another implementation may utilize a tube-and-shell heat exchanger wherein a first channel conducts a flowing reflector material in a first direction, and one or more additional channels conduct the flowing reflector material in a second direction through one or more tubes surrounded by flowing molten fuel salt. An adjusting operation 1404 adjusts fast neutron flux and thermal neutron flux within the reactor core during the sustained nuclear fission reaction by modifying the density of reflector material in the neutron reflector assembly. Density of reflector material in the neutron reflector assembly may be modified by altering the temperature of a flowing neutron reflector material in the reflector assembly. At higher temperatures, a flowing neutron reflector material tends to have lower density, and, at lower temperatures, a flowing neutron reflector material tends to have higher density. Changes in density will alter the alter the reflectivity characteristics of the reflector assembly because fast and thermal neutrons emanating from the reactor core will be more or less likely to be scattered by the reflector material depending on the likelihood of a collision with the nuclei of the reflector material in the reflector assembly. One way of altering the temperature of a flowing neutron reflector material is to alter its flow rate, and thus the thermal contact time the flowing reflector material has with a molten fuel salt. A higher flow rate may reduce contact time with a hot fuel salt, thus lowering the flowing reflector material's temperature and increasing the flowing reflector material's density. A lower flow rate may leave the flowing reflector material in thermal contact with the hot fuel salt for a relatively longer period of time, thus increasing its temperature and lowering the flowing reflector material's density. In another embodiment, a tube and shell heat exchanger may be employed to exchange heat between the flowing reflector material and the molten fuel salt. The tube and shell heat exchanger may be configured with baffles to route the molten fuel salt in a meandering path around tubes carrying the flowing reflector material. Movable baffles may increase or decrease the thermal contact time between the flowing reflector material and the molten fuel salt. As described above, a change in thermal contact time between the flowing reflector material and the molten fuel salt may tend to alter the temperature, and thus density, of the flowing reflector material. FIG. 15 depicts a flow diagram of other example operations 1500 of dynamic spectrum shifting in a molten nuclear fuel salt fast reactor. A sustaining operation 1502 sustains a nuclear fission reaction in a nuclear reactor core surrounded by a dynamic neutron reflector assembly. The neutron reflector assembly may have at least one neutron reflector material. A neutron reflection assembly may surround a nuclear reactor core by being disposed radially around, above, and/or below the reactor core. The neutron reflection assembly may be formed in one contiguous piece, formed into discrete pieces distributed around the reactor core, disposed around the core in discrete pieces with gaps in between, and/or segmented into regular or irregular sections. The reflection assembly may contain one or more channels for conducting a flowing reflector material. The reflection assembly may contain one or more levels of channels, such that a flowing reflector material flows in one direction in one level, and flows in another direction in one or more other levels. For example, the reflection assembly may contain an outer channel with flowing reflector material flowing downward, and another inner channel with flowing reflector material flowing upward to avoid any inlet or outlet plumbing underneath the reactor core. The reflection assembly may further be in thermal communication with one or more heat exchangers, and therefore function as a secondary coolant for the reactor core. In one implementation, heat exchangers are thermally coupled to channels for conducting the flowing reflector material. Another implementation may utilize a tube-and-shell heat exchanger wherein a first channel conducts a flowing reflector material in a first direction, and one or more additional channels conduct the flowing reflector material in a second direction through one or more tubes surrounded by flowing molten fuel salt. An adjusting operation 1504 adjusts fast neutron flux and thermal neutron flux within the reactor core during the sustained nuclear fission reaction by inserting a neutron moderating member into the neutron reflector assembly. Insertion of a neutron moderating member may introduce nuclei into the reflector assembly that may tend to cause elastic collisions with fast neutrons. The presence of these nuclei may scatter thermal neutrons back into the nuclear reactor core, thus increasing burnup. Adjusting operation 1504 may also have an effect on the neutron reflectivity characteristics of the neutron reflection assembly because the neutron moderating member will displace a volume of flowing neutron reflector material from the neutron reflector assembly. The decrease in volume of flowing neutron reflector material will tend to decrease the amount of elastic collisions with neutrons emanating from the nuclear reactor core, thus reducing the likelihood of scattering fast neutrons emanating from the nuclear reactor core back into the reactor core to breed fertile material into fissile material. FIG. 16 depicts a flow diagram of other example operations 1600 of dynamic spectrum shifting in a molten nuclear fuel salt fast reactor. A sustaining operation 1602 sustains a nuclear fission reaction in a nuclear reactor core surrounded by a dynamic neutron reflector assembly. The neutron reflector assembly may have at least one neutron reflector material. A neutron reflection assembly may surround a nuclear reactor core by being disposed radially around, above, and/or below the reactor core. The neutron reflection assembly may be formed in one contiguous piece, formed into discrete pieces distributed around the reactor core, disposed around the core in discrete pieces with gaps in between, and/or segmented into regular or irregular sections. The reflection assembly may contain one or more channels for conducting a flowing reflector material. The reflection assembly may contain one or more levels of channels, such that a flowing reflector material flows in one direction in one level, and flows in another direction in one or more other levels. For example, the reflection assembly may contain an outer channel with flowing reflector material flowing downward, and another inner channel with flowing reflector material flowing upward to avoid any inlet or outlet plumbing underneath the reactor core. The reflection assembly may further be in thermal communication with one or more heat exchangers, and therefore function as a secondary coolant for the reactor core. In one implementation, heat exchangers are thermally coupled to channels for conducting the flowing reflector material. Another implementation may utilize a tube-and-shell heat exchanger wherein a first channel conducts a flowing reflector material in a first direction, and one or more additional channels conduct the flowing reflector material in a second direction through one or more tubes surrounded by flowing molten fuel salt. An adjusting operation 1604 adjusts fast neutron flux and thermal neutron flux within the reactor core during the sustained nuclear fission reaction by removing a neutron moderating member out of the neutron reflector assembly. Removal of a neutron moderating member will reduce available nuclei in the reflector assembly that may tend to cause elastic collisions with fast neutrons. The reduced presence of these nuclei will scatter fewer thermal neutrons back into the nuclear reactor core, thus decreasing burnup. Adjusting operation 1504 may also have an effect on the neutron reflectivity characteristics of the neutron reflection assembly because the removed neutron moderating member may have displaced a volume of flowing neutron reflector material when it had been inserted in the neutron reflector assembly. An increase in volume of flowing neutron reflector material may tend to increase the amount of elastic collisions with neutrons emanating from the nuclear reactor core, thus increasing the likelihood of scattering fast neutrons emanating from the nuclear reactor core back into the reactor core to breed fertile material into fissile material. FIG. 17 depicts a top-down schematic view of an example neutron reflector assembly 1700. Neutron reflector assembly 1700 includes two sub-assemblies, a primary static neutron reflector sub-assembly 1712 and a secondary dynamic neutron reflector sub-assembly 1716. In FIG. 17, example paths of fast spectrum neutrons 1706, 1714 are indicated by lines terminating in double arrows, such as lines 1708 indicate example fast spectrum neutrons. In an implementation, flowing neutron reflector assembly 1700 substantially surrounds a nuclear fuel region 1704 from which fast spectrum neutrons 1706, 1714 emanate. Primary static neutron reflector sub-assembly 1712 may contain a neutron reflector material. The neutron reflector material contained in primary static neutron reflector sub-assembly 1712 may be a solid, liquid, or fluid neutron reflector material, or a combination thereof. The primary static neutron reflector sub-assembly 1712 may substantially surround a fuel region 1704. In another implementation, primary static neutron reflector sub-assembly 1712 may partially surround the fuel region 1704 in a continuous, segmented, and/or modular manner. The example fast spectrum neutrons 1714 emanating from nuclear fuel region 1704 are inelastically scattered (or reflected) from the primary static neutron sub-assembly 1716 and back into the nuclear fuel region 1704, thus increasing a breed rate of fertile fuel in the fuel region 1704. Other example fast spectrum neutrons, such as example neutrons 1706 may pass through primary static neutron reflector sub-assembly 1712, and be inelastically scattered (or reflected) from secondary dynamic neutron reflector sub-assembly 1716, as explained in more detail below. The primary static neutron reflector sub-assembly 1712 may be disposed adjacent to, and/or in thermal contact with, the nuclear fuel region 1704. Due to the positioning of primary static neutron sub-assembly 1712 with respect to the nuclear fuel region 1704, the primary static neutron reflector sub-assembly 1712 may experience high levels of exposure to forces that may cause damage or wear. For example, the primary static neutron reflector sub-assembly may be exposed to high levels of heat and various types of radiation emanating from the nuclear fuel region 1704, including without limitation, alpha particles, beta particles, and/or gamma rays. Prolonged exposure to heat and/or radiation may cause the primary static neutron reflector sub-assembly 1712 to suffer excessive structural degrading over a period of time. The primary static neutron reflector sub-assembly 1712 may therefore be removable from flowing neutron reflector assembly 1700. In other words, the primary static neutron reflector sub-assembly may, or modular parts thereof, may be slidably fitted to a housing (not shown) to permit selective replacement of the sub-assembly, which may be carried out according to a periodic maintenance schedule or based on periodic inspection of the primary static neutron reflector sub-assembly 1712. FIG. 17 also illustrates a secondary dynamic neutron reflector sub-assembly 1716. Secondary dynamic neutron reflector sub-assembly 1716 may be used to incrementally shift neutron spectrum in nuclear fuel region 1704 by selectively filling each of the channels 1702 with a volume of neutron reflector material. Secondary dynamic neutron reflector assembly 1716 may include a plurality of refractory-clad sleeves 1702 to conduct a flowing neutron reflector material therethrough. In FIG. 17, the neutron reflector material flows upward through a refractory clad channel 1702 toward the viewer. In an implementation, neutron reflector material may circulate in channels 1702 (e.g., cells, sleeves, conduits, etc.) with input and output ports above the nuclear fuel region 1704 such that no fixtures or ports are needed beneath the reactor. In other implementations, the neutron reflector material may flow in only one direction, either in an upward or downward direction, through the channels 1702 with one port above the nuclear fuel region 1704 and another port below fuel region 1704. In yet other implementations, the neutron reflector material may comprise a semi-stagnant or creeping flow through the channels 1702. In yet other implementations, the neutron reflector material may flow through radial input and output ports. The secondary dynamineutron reflector sub-assembly 1716 is in thermal communication with heat exchanger 1710 disposed on the opposite side from fuel region 1704. It is to be appreciated that the dynamic neutron reflector assembly and/or the heat exchanger could be inside, or disposed among the static reflector sub-assembly. The heat exchanger 1710 may contain one or more types of liquid coolant circulating therethrough. As secondary dynamic neutron reflector sub-assembly 1716 exchanges heat with the heat exchanger 1710, the heat exchanger 1710 may transport the heat away from the secondary dynamic neutron reflector sub-assembly 1716 as part of a secondary coolant circuit. The secondary coolant circuit may supply heat to electricity generation equipment, such as, for example, a steam-driven turbine. In an implementation, molten fuel salt may flow upward through the nuclear fuel region 1704 and downward through the heat exchanger 1710, thus exchanging heat as part of a primary coolant circuit. In other words, the heat exchangers may exchange heat with both the molten fuel salt and exchange heat with the flowing neutron reflector in the channels 1702. The flow rate of neutron reflector material may be adjusted to vary contact time with the heat exchangers to vary the temperature of reflector material flowing in the channels 1702. As the temperature of reflector material varies, its density changes accordingly. Changes in the density of the reflector material alter its neutron reflective characteristics as denser materials have a higher mass per unit volume and are therefore more likely to reflect neutrons. FIG. 18 is a top-down schematic view of a molten nuclear fuel salt fast reactor core with a fuel region 1802 surrounded by a neutron reflector assembly 1800. The neutron reflector assembly includes an inner annular channel 1808 and outer annular channel 1810 surrounding fuel region 1802. The inner and outer annular channels 1808, 1810 may contain neutron reflector materials 1804 and 1806, respectively. The neutron reflector materials 1804, 1806 may be the same or differ from one another in terms of their respective neutron-reflecting properties or other properties that may affect performance of the neutron reflector assembly (viscosity, density, specific heat value, etc.). Neutron reflector materials 1804, 1806 may tend to reflect example fast neutrons 1812 back into fuel region 1802. Neutron reflector materials 1804, 1806 may be selectively added, removed, and/or replaced in channels 1808, 1810 to dynamically alter the neutron reflecting characteristics of the neutron reflector assembly 1800 over time. In one implementation, one or both of the neutron reflector materials 1804, 1806 may be completely removed from their respective channels 1808, 1810 to alter the neutron reflecting characteristics of the neutron reflector assembly 1800. In another implementation, the neutron reflector materials 1804, 1806 may be the same material. In yet another implementation, the neutron reflector materials 1804, 1806 may be selectively added, removed, and/or replaced to provide lower neutron reflection near the beginning of the life of the reactor when there is greater breeding of fertile fuel, and selectively added, removed, and/or replaced to provide greater neutron reflection as the reactor ages and burnup begins to dominates in the fuel region 1802. In another implementation, neutron reflector materials 1804, 1806 may mix inside one or both of channels 1808, 1810. In yet another implementation, one or both of neutron reflector materials 1804, 1806 may be added over time to channels 1808, 1810 to alter the ratio between the two materials and thus the neutron reflectivity of the assembly. If more than two neutron reflector materials 1804, 1806 are mixed inside channels 1808, 1810, a separator component (not shown) may operate to separate the materials if desired and may operate in any suitable manner to separate the two or more neutron reflector materials including one or more suitable chemical, mechanical, magnetic, electrical, time-bases processes based on the chemical and physical properties of the two or more neutron reflector materials. In another embodiment, mixed neutron reflector materials 1804, 1806 may be separated via a flush operation. Alternatively, the neutron reflector materials 1804, 1806 may be held in separate reservoirs (not shown) to selectively source the flows into one or both of channels 1808, 1810. In an implementation, neutron reflector materials 1804, 1806 may circulate in channels 1808, 1810 with input and output ports above fuel region 1802 such that no fixtures or ports are needed beneath the reactor. In other implementations, neutron reflector materials 1804, 1806 may flow in only one direction, either in an upward or downward direction, through channels 1808, 1810 with one port above fuel region 1802 and another port below fuel region 1802. In yet other implementations, neutron reflector materials 1804, 1806 may comprise a semi-stagnant or creeping flow through channels 1808, 1810. In yet other implementations, neutron reflector materials 1804, 1806 may flow through radial input and output ports. In another implementation, the channels 1808, 1810 may be selectively filled with materials that are not neutron reflectors. In one example, the channels 1808, 1810 may be filled with neutron moderating materials, neutron absorbing materials, or neutronically translucent materials. In another implementation, one or both of the channels 1808, 1810 may include selectively insertable volumetric displacement members 1814. Volumetric displacement members 1814 may contain neutron moderating materials, neutron absorbing materials, or neutronically translucent materials. Upon insertion of volumetric displacement members 1814, the volume of the reflecting liquid 1804, 1806 in the channel into which the volumetric displacement member has been inserted is reduced. With reduced volume, the remaining neutron reflector material 1804, 1806 in the channel has an altered neutron reflectivity characteristic, and is therefore less likely to reflect neutrons than before the volumetric displacement member 1814 was inserted. FIG. 19 is a top-down schematic view of a molten nuclear fuel salt fast reactor core with a fuel region 1902 surrounded by a neutron reflector assembly 1900. The neutron reflector assembly includes an inner annular channel 1908 and outer annular channel 1910 surrounding fuel region 1902. The inner and outer annular channels 1908, 1910 may contain a neutron reflector material 1904. In an implementation, neutron reflector material 1904 may circulate in channels 1908, 1910 with input and output ports above fuel region 1902 such that no fixtures or ports are needed beneath the reactor. In other implementations, neutron reflector material 1904 may flow in only one direction, either in an upward or downward direction, through channels 1908, 1910 with one port above fuel region 1902 and another port below fuel region 1902. In yet other implementations, neutron reflector material 1904 may comprise a semi-stagnant or creeping flow through channels 1908, 1910. In yet other implementations, neutron reflector material 1904 may flow through radial input and output ports. In one implementation, neutron reflector material 1904 may flow through channels 1908, 1910 at time periods near the beginning of the life of the reactor with fuel region 1902. As the reactor breeds fertile fuel over time, the effectiveness of the neutron reflector assembly 1900 may decrease because the inventory of bred nuclear fuel may exceed the amount needed to fuel the reactor. It may be desirable to therefore replace a portion of the neutron reflector material in part of the neutron reflector assembly as shown in FIG. 20 to alter the shape of the neutron reflector assembly 1900 over time. FIG. 20 is a top-down schematic view of a molten nuclear fuel salt fast reactor core with a fuel region 2002 surrounded by a neutron reflector assembly 2000. In FIG. 20 the neutron reflector material contents of inner annular channels 2008 are selectively replaced with additional fuel salt from fuel region 2002. As a result, the reactor will experience less neutron “leak.” Example fast neutrons 2012 may continue to experience reflection against neutron reflection material 2006 in channel 2010. It is therefore possible to start a fission reaction in the reactor core with a smaller volume of fuel salt near the beginning of the life of the reactor because more fissile fuel materials may be bred as the reactor operates. The additional bred fuel may replace a volume of neutron reflector material in the channels 2008. This may lower the upfront cost of operating the reactor and enhance the breeding of the reactor later in life when breeding is more challenging due at least in part to built-up fission products. Neutron reflector materials 2006 may tend to reflect example fast neutrons 2012 back into the fuel salt, whether the example fast neutrons 2012 emanate from fuel region 2002 or from inner annular channels 2008. FIG. 21 is a top-down schematic view of a molten nuclear fuel salt fast reactor core with a fuel region 2102 surrounded by a neutron reflector assembly 2100. The neutron reflector assembly includes a plurality of annular channels 2104 surrounding the fuel region 2102. The annular channels 2104 may contain a plurality of tubes 2108 containing a flowing neutron reflector material 2106 in neutronic communication with the fuel region 2102. In an implementation, the plurality of tubes 2108 are cylindrical tubes. The flowing neutron reflector material 2106 may be circulated in the tubes 2108 with input and output ports above fuel region 2102 such that no fixtures or ports are needed beneath the reactor. In other implementations, neutron reflector material 2106 may flow in only one direction, either in an upward or downward direction, through the tubes 2108 with one port above fuel region 2102 and another port below fuel region 2102. In yet other implementations, neutron reflector material 2106 may comprise a semi-stagnant or creeping flow through tubes 2108. The tubes 2108 are arranged such that the radius of all tubes 2108 is not equal. As such, a plurality of tubes 2108 with varying radius values may be disposed in a channel 2104. In an implementation, tubes 2108 of varying radius may flow neutron reflector material in a volume that occupies a cross-sectional area of 80% of the cross-sectional area of the channels 2104. Numerals have not been assigned to every tube to improve readability due to the large number of tubes 2108 depicted in FIG. 21. This disclosure should be understood as indicating that each tube shown in channels 2104 is a tube 2108 containing neutron reflector material 2106, even those that are not so numbered therein. As discussed above, in some embodiments reflectors or portions of reflectors may be completely solid at operating temperatures, e.g., between 300-350° C. and 800° C., or could be a liquid reflector material encased in an enclosed container in which the container walls are solid at operating temperature. Examples of solid reflector materials include uranium, uranium-tungsten, carbides of uranium or uranium-tungsten, and magnesium oxide. Examples of reflector materials that could be used as a liquid coolant include lead, lead alloys, PbBi eutectic, PbO, iron-uranium alloys including iron-uranium eutectic, graphite, tungsten carbide, densalloy, titanium carbide, depleted uranium alloys, tantalum tungsten, and tungsten alloys. In yet another embodiment fuel salt may be used as reflector material. In an embodiment, liquid coolant includes materials that are liquid at the reactor operating temperature and that have a density greater than 10 grams/cm3. In an alternative embodiment, liquid coolant includes materials that are liquid at the reactor operating temperature and that exhibit an elastic cross section of 0.1 barns or greater for 0.001 MeV neutrons. As discussed above, examples of liquid nuclear fuels include salts containing one or more of PuCl3, UCl4, UCl3F, UCl3, UCl2F2, UClF3, bromide fuel salts such as UBr3 or UBr4, and thorium chloride (e.g., ThCl4) fuel salts. Furthermore, a fuel salt may include one or more non-fissile salts such as, but not limited to, NaCl, MgCl2, CaCl2, BaCl2, KCl, SrCl2, VCl3, CrCl3, TiCl4, ZrCl4, ThCl4, AcCl3, NpCl4, AmCl3, LaCl3, CeCl3, PrCl3 and/or NdCl3. Note that the minimum and maximum operational temperatures of fuel within a reactor may vary depending on the fuel salt used in order to maintain the salt within the liquid phase throughout the reactor. Minimum temperatures may be as low as 300-350° C. and maximum temperatures may be as high as 1400° C. or higher. Similarly, except were explicitly discussed otherwise, heat exchangers will be generally presented in this disclosure in terms of simple, single pass, shell-and-tube heat exchangers having a set of tubes and with tube sheets at either end. However, it will be understood that, in general, any design of heat exchanger may be used, although some designs may be more suitable than others. For example, in addition to shell and tube heat exchangers, plate, plate and shell, printed circuit, and plate fin heat exchangers may be suitable. FIG. 22 illustrates a cross-section view of an embodiment of a reactor 2200 utilizing a circulating reflector material. The illustration shows the half of the reactor 2200 from the center to the left edge of the containment vessel 2218. The reactor 2200 includes a reactor core 2204 defined by an upper reflector 2208A, a lower reflector 2208B and an inner reflector 2208C. In the embodiment shown, the lower reflector 2208B also extends laterally and up the sides of the containment vessel 2218 for added protection to the vessel head 2238. The primary heat exchanger 2210 configured to have shell-side coolant flow (illustrated by dotted lines 2214), the coolant entering through a coolant inlet channel 2230 and heated coolant exiting from coolant outlet channel 2236. In the embodiment shown, fuel flows (illustrated by dashed lines 2206) from the reactor core 2204, via an upper channel through the inner reflector 2208C, and into the heat exchanger 2210 through the inlet tube sheet 2232. After passing through the tube set, the now-cooled fuel exits the lower tube sheet 2231 and flows back into the reactor core 2204 via a lower channel through the inner reflector 2208C. Flow of the fuel is driven by a pump assembly 2212 that includes an impeller in the fuel circuit (in this embodiment illustrated below the lower tube sheet 2231) connected by a shaft to a motor (in this embodiment located above the upper reflector 2208A). In FIG. 22, the reflectors 2208A, 2208B, 2208C are in fluid communication allowing liquid reflector material to be circulated around the reactor core 2204. Flow of the reflector material is illustrated in FIG. 22 by the large, gray arrows 2234. In the embodiment shown, reflector material flows through an inlet in the vessel head 2238 into reactor 2200 along the interior surface of the containment vessel 2218 and then along the bottom of the containment vessel 2218 before rising and making a U-turn to flow adjacent to the bottom of the reactor core 2204. The reflector material then flows up through the inner reflector 2208C then into the upper reflector 2208A from which it can be removed via an outlet in the vessel head 2238 or recirculated to the interior surface of the containment vessel 2218. The circulating reflector material in FIG. 22 may be used to assist in the cooling of the reactor core 2204. In this configuration, the heated reflector material may be removed from the containment vessel 2218 and passed through a heat exchanger (not shown) external to the reactor 2200. In an embodiment, the same primary coolant loop that removes heat directly from the fuel via heat exchanger 2210 may also be used to remove heat from the reflector material. In an alternative embodiment, a separate and independent cooling system may be used to remove the heat from the reflector material which may use the same type of coolant as the primary coolant or a different type of coolant. In yet another embodiment, the reflector material cooling may be incorporated into an auxiliary cooling system that provides emergency cooling to the reflector material in the event of a loss of flow in the primary cooling loop. In the embodiment shown, when the reflector material is part of a cooling loop, a benefit of the configuration illustrated in FIG. 22 is that the containment vessel is both actively cooled and protected from excessive neutron flux. Because cooled reflective material is first flowed along the interior surfaces of the containment vessel 2218 prior to flowing to locations near the reactor core 2204, the initial temperature of the cooled reflective material can be used control the temperature of the containment vessel 2218. In yet another embodiment, a cooling jacket (not shown) can be provided on the exterior surface of the containment vessel 2218, which serves to remove heat from the circulating reflective material on the interior surface of the containment vessel 2218. This may be done in addition to or instead of an exterior reflective material cooling circuit. As described above, the overall reflectivity of the reflector configuration of FIG. 22 may be controlled by controlling the flow rate of reflective material through the reflectors as well as by inserting or removing rods or other components containing moderating materials or materials of different reflectivity from that of the circulating reflective material. FIG. 23 illustrates an embodiment of a reactor with a shell-side fuel/tube-side primary coolant heat exchanger configuration using the same cross-section view of half of the reactor as in FIG. 22. The reactor core 2304 is surrounded by an upper reflector 2308A, a lower reflector 2308B, and an inner reflector 2308C that separates the reactor core from the primary heat exchanger 2310. The channels are provided through the reflectors 2308A, 2308B, 2308C allowing the circulation of fuel salt (illustrated by a dashed line 2306) from the reactor core 2304 through the inner reflector 2308C, into the shell of the primary heat exchanger 2310. The fuel flows through the shell around the tube set, thus transferring heat to the primary coolant. Cooled fuel then exits the shell and passes through the inner reflector 2308C back into the bottom of the reactor core 2304. Baffles 2312 are provided in the shell to force the fuel salt to follow a circuitous path around the tubes of the heat exchanger for more efficient heat transfer. Coolant flows through the tube-side of the heat exchanger 2310, but before entering the bottom of the heat exchanger first flows through an inlet in the vessel head 2338, down the length of a coolant inlet channel 2330 adjacent to a portion of the lower reflector 2308B. The primary coolant enters the tubes of the heat exchanger 2310 by flowing through the lower tube sheet 2331, which is illustrated as being level with the bottom of the reactor core. The lower tube sheet 2331 may be at or below the level of the lower reflector 2308B depending on the embodiment. The coolant exits the tubes of the heat exchanger at the upper tube sheet 2332, which is located in FIG. 23 some distance above the reactor core 2304 and containment vessel 2318. The flow of the coolant is also illustrated by a dashed line 2314. FIG. 23 illustrates a region 2334 within the shell of the heat exchanger that is above the level of salt in the reactor core 2304. This region may either be solid, except for the penetrating tubes, or may be a headspace filled with inert gas. One or more pumps (not shown) may be provided to assist in the fuel salt circulation, the primary coolant circulation or both. For example, an impeller may be provided in one or both of the heated fuel salt inlet channel at the top of the reactor core 2304 or (as discussed in greater detail below) the cooled fuel outlet channels at the bottom of the reactor core 2304. Likewise, an impeller may be provided in the coolant inlet channel 2330 to assist in control of the primary coolant flow. In FIG. 23, the reflectors 2308A, 2308B, 2308C are in fluid communication allowing liquid reflector material to be circulated around the reactor core 2304. Flow of the reflector material is illustrated in FIG. 23 by the large, gray arrows 2334. In the embodiment shown, reflector material flows into reactor 2300 through an inlet in the vessel head 2338 and then along the interior surface of the side of the containment vessel 2318 in a reflector channel. The reflector channel then follows the bottom of the containment vessel 2318 before making a U-turn and rising to flow adjacent to the bottom of the reactor core 2304. The reflector material then flows up through the inner reflector 2308C and into the upper reflector 2308A from which it can be removed at a central location via an outlet in the vessel head 2338, as shown, or recirculated to the interior surface of the containment vessel 2318. As discussed with reference to FIG. 22, the circulating reflector material in FIG. 23 may be used to assist in the cooling of the reactor core 2304. In this configuration, the heated reflector material may be removed from the containment vessel 2318 and passed through a heat exchanger (not shown) external to the reactor 2300. When the reflector material is part of a cooling loop, a benefit of the configuration illustrated in FIG. 23 is that the containment vessel is both actively cooled and protected from excessive neutron flux. Because cooled reflective material is first flowed along the interior surfaces of the containment vessel 2318 prior to flowing to locations near the reactor core 2304, the initial temperature of the cooled reflective material can be used control the temperature of the containment vessel 2318. As described above, the overall reflectivity of the reflector configuration of FIG. 23 may be controlled by controlling the flow rate of reflective material through the reflectors as well as by inserting or removing rods or other components containing moderating materials or materials of different reflectivity from that of the circulating reflective material. As discussed above, yet another approach to cooling the reactor is to utilize a liquid reflector as the primary coolant. In this design, the primary coolant performs both the function of the reflectors and the primary cooling functions. In an embodiment, a reflector material will be liquid at the minimum operational fuel salt temperature (for example, between 300° C. and 800° C.) and have a density greater than 10 grams/cm3. In an alternative embodiment, a reflector material may be a material having a low neutron absorption cross section and a high scattering cross section and that may undergo (n,2n) reactions. FIG. 24 illustrates such an embodiment of a reflector cooled reactor. In the embodiment, half of the reactor 2400 is illustrated in cross-section as in FIGS. 22 and 23. The reactor core 2404 is surrounded by an upper reflector 2408A, a lower reflector 2408B. Molten reflector material, such as lead, flowing through the coolant inlet channel as illustrated by gray arrow 2414 acts as the inner reflector 2408C as well as the primary coolant. Any type of system may be used to circulate the reflector material. In the embodiment in FIG. 24, for example, a pump 2413 as described with reference to FIG. 22 is provided in the cooled material inlet channel. Such a pump 2413 may be located so that the impeller is at any convenient location in the neutron-reflecting coolant loop to assist or drive the circulation of the liquid neutron-reflecting coolant. In the embodiment shown, the fuel is shell-side and the reflector material which is also the coolant is tube-side. The shell and tubes are made of some structural material that is solid at the operating temperatures. The circulation of fuel salt (illustrated by a dashed line 2406) from the reactor core 2404 into and through the shell side of the primary heat exchanger 2410 and back into the bottom of the reactor core 2404. Baffles 2412 are provided in the shell to force the fuel salt to follow a circuitous path around the tubes of the heat exchanger. Reflector/coolant flows through the tube-side of the heat exchanger 2410, but before entering the bottom of the heat exchanger first flows down the length of a coolant inlet channel adjacent to the sides and bottom of the containment vessel 2418. In an embodiment, a solid layer of reflector material may form on the inner surface of the containment vessel, especially if the exterior of containment vessel 2418 is cooled. This is acceptable as long as it does not interfere with the flow of the reflector/coolant. The reflector/coolant then enters the tubes of the heat exchanger by flowing through the lower tube sheet 2431, which is illustrated as being level with the bottom of the reactor core 2404. The reflector/coolant exits the tubes of the heat exchanger at the upper tube sheet 2432, which is located in FIG. 24 some distance above the reactor core 2404 and containment vessel 2418. FIG. 24 illustrates a region 2434 within the shell of the heat exchanger that is above the level of fuel salt in the reactor core 2404. This region may be filled, except for the penetrating tubes, with any reflecting or moderating material, for example filled with a different or the same reflector material as the reflector/coolant. In FIG. 24, the upper reflector 2408A and lower reflector 2408B are illustrated as distinct from the circulating reflector/coolant material. In an alternative embodiment, the upper reflector 2408A, lower reflector 2408B, and inner reflector 2408C may all be in fluid communication as shown in FIGS. 22 and 23. For example, reflector material may be routed into reactor 2400 along the interior surface of the side of the containment vessel 2418, as shown, but then routed along the bottom of the containment vessel 2418 before rising and making a U-turn to flow adjacent to the bottom of the reactor core 2404, as shown in FIG. 23. The reflector material may also be routed into the upper reflector 2308A from which it can be removed at a central location, also as shown in FIG. 23. A pump (not shown), or at least the impeller of a pump, may be provided to assist in fuel salt circulation or reflector/coolant circulation. For example, an impeller may be provided in one or both of the heated fuel salt inlet to the primary heat exchanger at the top of the reactor core 2404 or (as discussed in greater detail below) the cooled fuel outlet of the shell of the primary heat exchanger at the bottom of the reactor core 2404. In yet another embodiment, reflective coolant may be flowed through upper and lower axial reflectors to advect away any heat generated in these reflectors in a circulation loop that is separate from the primary cooling loop. In yet another embodiment of a reflector design, a ‘breed and burn blanket’ may be provided surrounding the main core. In this embodiment, a reflector ‘blanket’ containing uranium could be provided, either as the only reflector or as a second reflector located inside (between the core and the primary reflector) or outside of the primary reflector. The uranium in the reflector could be either liquid or solid, and could be uranium metal, a uranium oxide, a uranium salt or any other uranium compound. The uranium in the reflector will reflect neutrons but will also breed plutonium over time, thus becoming a source of fuel. FIGS. 7-11, among others, illustrate a separator between the reflector material and the reactor core. This separator, referred to as the “core barrel”, is illustrated in FIGS. 7-9 and 11 as a white ring (750, 850, 950, 1150, respectively) and in FIG. 10 as a thick, black solid line 1050. In an embodiment, the core barrel forms a continuous inner surface between the reactor core (e.g., reactor core 702 of FIG. 7) and the reflector channels (e.g., reflector channels 704). For example, in the embodiment shown in FIG. 7 in which the reflector channels 704 are completely filled with reflector material, the core barrel may serve simply to prevent mixing of fuel salt in the core 702 with reflector material in the reflector channels 704. The core barrel may be a structural or non-structural element depending on the design. For example, a non-structural core barrel could be provided between the reactor core 702 and the cells, sleeves, conduits, etc. described above that define each reactor channel 704 and hold the reactor material. Alternatively, the cells, sleeves, conduits, etc. that define each reactor channel 704 could be integrated or physically connected (e.g., welded) so that they are connected to form the core barrel. For molten nuclear fuel salt fast reactors in which fuel salt is between individual reflector tubes/channels, such as those reactors shown, for example, in FIGS. 10, 11, 21 and 24, the core barrel may provide a separator that prevents mixing and directs flow of the fuel salt between the reactor core and the region around the individual reflector channels. For example, with reference to FIGS. 10 and 11, the core barrel serves to promote the circulation of the fuel in a loop around the circuit formed by the reactor core (e.g., 1102 in FIG. 11) and the shell side of the heat exchanger region around the individual reflector tubes (e.g., 1014 in FIGS. 10 and 1108 in FIG. 11). In an embodiment, the core barrel may also be used to separate materials other than the fuel salt and reflector material. For example, in FIG. 21 multiple, individual reflector tubes 2108 are shown in the reflector channels 2104. The core barrel may be used to separate material in the interstitial region of the channels 2104 between the individual reflector tubes 2108 from the fuel salt in the fuel region 2102. As discussed above, in one embodiment, this interstitial material may be fuel salt (be it flowing or stagnant). In an alternative embodiment, the interstitial material may be a vacuum, an inert gas such as argon, a primary coolant, or some inert gaseous, liquid, or solid material or any appropriate combination of the foregoing (e.g., solid and fluid (liquid and/or gas)). In an embodiment the primary coolant may be another salt, such as NaCl, MgCl or a mixture of salts such as NaCl—MgCl2. For example, in an embodiment, the primary coolant is 42MgCl2+58NaCl salt. Other coolants are also possible including Na, NaK, supercritical CO2, lead, and lead bismuth eutectic. If the primary coolant is or includes a chloride salt, some or all of the chlorine may be enriched with the 37-Cl isotope so that some amount of the chloride ion in any one or more of the chloride compounds contain a specific percentage of 37Cl. Chlorine has many isotopes with various mass numbers. Of these, there are two stable isotopes, 35Cl (which forms 76% of naturally-occurring chlorine) and 37Cl (24% in naturally-occurring chlorine). The most common isotope, 35Cl, is a neutron moderator, that is, 35Cl reduces the speed of fast neutrons, thereby turning them into thermal neutrons. The isotope 35Cl is also a strong neutron absorber, and leads to formation of corrosive sulfur and long lived radioactive 36Cl. The isotope 37Cl, on the other hand, is relatively transparent to fast neutrons. One aspect of the present technology is to adjust the 37Cl content of any chloride-containing compounds to be used as primary coolant. As discussed above, use of naturally occurring chloride ions to create a chloride compound would result in roughly 76% of the chloride ions being 35Cl and 24% being 37Cl. However, in the embodiments described herein any ratio of 37Cl to total Cl may be used in any particular chloride primary coolant salt embodiment, and in some cases may meet or exceed a selected ratio of 37Cl to total Cl. It is to be appreciated that any known or to be developed enrichment techniques may be used to ensure the desired and/or selected 37Cl ratio concentration including but not limited to centrifuges, ion exchange columns, etc. In an embodiment all chloride-containing compounds may be created from as pure a feed of 37Cl as possible. For example, chloride-based primary coolant salt compounds may be created so that greater than 90%, 95%, 98%, 99% or even 99.9% of the chloride ions in the fuel salt are 37Cl. Alternatively, a chloride-based primary coolant may be developed to achieve any target or selected percentage amount of 37Cl to other chloride ions in the fuel or in different components of the fuel. For example, for a coolant designed for thermal reactions, the chloride-based primary coolant may be created so that less than 10%, 5%, 2%, 1% or even 0.1% of the chloride ions in the fuel salt are 35Cl, the remaining being 37Cl. For coolants tailored to fast reactions, the chloride-based fuel salt compounds may be created so that greater than 10%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or more up to 100% as described above of the chloride ions in the fuel salt are 37Cl. Furthermore, the use of enriched chlorine reduces both neutron parasitic absorption and production of 36Cl, which is a long-lived activation product. As described above, heterogeneous reflector configurations may be used in which different reflector materials are in different reflector channels. For example, in an embodiment some reflector channels may be filled with lead while other channels may be filed with a different material such as zirconium, steel, iron, graphite, beryllium, tungsten carbide, lead-bismuth, or graphite. By filling different channels with different materials (e.g., lead in a first channel and graphite in a second), different material compositions (e.g., lead in a first channel and lead-bismuth in a second), and/or different composition ratios (e.g., lead-bismuth eutectic (44.5% lead/55.5% bismuth) in a first channel and a 37% lead/63% bismuth lead-bismuth composition in a second), the reflection characteristics of the molten nuclear fuel salt reactor may be tailored to obtain desired effects. One illustrative embodiment is filling reflector channels closest to the reactor core with graphite and reflector channels further away from the reactor core with lead, lead-bismuth, or alternating between the two. For example, with reference to FIG. 18, the interior reflector channels 1804 may be filled with graphite while the exterior channels 1806 are filled with lead. FIG. 25 illustrates an embodiment of a reflector tube, such as those 2108 shown in FIG. 21, provided with a layer of a more absorbent material on one side of the tube, which is otherwise filled with another material that is either less of a neutron absorber or a reflective material. In the embodiment shown, the reflector tube 2500 has an absorbent layer 2502, or partial liner, on one side of the tube 2500. The partial liner may be on the inside of the reflector tube 2500, as shown, or the outside surface of the reflector tube. The absorbent material may be any neutron absorber such as graphite or boron carbide (B4C). The majority of the tube is filled with a reflective material 2504, such as lead. The shape of the reflector tube may have any appropriate cross-sectional polygonal, circular, or other shape as appropriate, which may differ or be consistent along the length of the reflector tube. The tube 2500 further may be provided with a structural sleeve, casing, conduit or other structural element 2506 to hold the lead and graphite. The layer 2502 may be crescent shaped, as illustrated or any other appropriate shape or form as appropriate for the reactor design, or may be a layer of constant or variable thickness that extends partially around the interior or exterior of the casing 2506. For example, in an embodiment tube 2500 may be a structural sleeve filled with half graphite and the other half may be lead. Such absorbent-lined tubes 2500 may be provided in all reflector tubes or in just some reflector tubes of a reactor. For example, in an embodiment graphite-lined tubes 2500 may be provided only in tubes that are adjacent the reactor core, such as the five tubes 2108 in FIG. 21 that abut the core barrel in each reflector channel 2104. In yet another embodiment, only the largest tubes are lined tubes 2500. Depending on the embodiment, the layer 2502 may be installed in the reactor so that it is core-facing or outside-facing. In another embodiment, the lined tubes 2500 may be rotatable about an axis, e.g., the vertical axis, to provide additional adjustment to the reactivity. By rotating the tubes 2500 in place around their center, vertical axis, given sides of the tubes 2500 may be moved between a core-facing position and an outside-facing position the reactivity can be tuned during operation. For example, the absorbant-lined tubes 2500 may be placed in one position during startup and then rotated as the operational conditions are met to maintain the reactor in criticality, modify thermal and/or power generation of the reactor and/or adjust the local neutron environment for components to extend its lifetime in the core. The rotation may also be used to shut down the reactor by rotating the drums so that the absorber is in the core-facing position. In this embodiment, one or more drive mechanisms are provided to rotate the drums. FIG. 26 illustrates another embodiment of a heterogeneous reflector configuration for a molten nuclear fuel salt reactor. FIG. 26 illustrates a reactor 2600 with a graphite-backing configuration in which a relatively thin graphite layer 2602 is provided outside of a lead reflector 2604 which surrounds the reactor core 2606. FIG. 27 illustrates yet another embodiment of a heterogeneous reflector configuration for a molten nuclear fuel salt reactor. FIG. 27 illustrates a reactor 2700 with a graphite-fronting configuration in which a relatively thin graphite layer 2702 is provided next to the reactor core 2706 and between the core and the lead reflector 2704. FIG. 28 illustrates a comparison of the modeled effect on reactivity of graphite-fronting and graphite-backing embodiments similar to those shown in FIGS. 26 and 27. In the modeling, graphite-fronting and graphite-backing embodiments of a reactor are modeled and the only variable changed besides the location of graphite layer is the thickness of the graphite layer relative to the thickness of the lead reflector layer. As can be seen, there is a significant difference in reactivity between the two embodiments. This means that each configuration has different reactivity characteristics, which allows other aspects of the reactor to be optimized such as reactor core size and, thus, the volume of fuel salt required for criticality. For example, graphite-fronting embodiments have generally higher reactivity, which allows a smaller reactor core to be used. In yet another embodiment, one or more removable core barrel inserts may also be provided. In this embodiment, the core barrel inserts may be installed into or removed, individually or as a group, from the reactor core to adjust the reactivity of the reactor. Installation of core barrel inserts acts to increase the effective thickness of the core barrel and reduces the volume of the core by reducing the cross-sectional area. Removal of the inserts has the opposite effect. Such adjustability allows the mean velocity of the neutrons to be increased or decreased without otherwise changing the reactor design or components. FIG. 29 illustrates a simplified reactor design showing multiple removable core barrel inserts installed in the reactor core. FIG. 29 is a top-down schematic view of a molten nuclear fuel salt fast reactor core with a fuel region 2902 surrounded by a neutron reflector assembly 2900. In FIG. 29 the neutron reflector material 2906 is provided in the inner annular channels 2908 and the outer annular channels 2910. The core barrel 2912 is shown surrounding the fuel region 2902 with three, removable, concentric core barrel inserts 2914, 2916, 2918 installed. By removing and inserting the core barrel inserts the cross-sectional area of the fuel region 2902 can be adjusted as needed to maintain or change the reactivity of the reactor. Note that although this and other top-down views illustrate a cylindrical reactor core configuration with annular channels, this is but one possible geometry and channel layout. For example, prisms, pyramidal, conical and other shapes are other geometries that may be used with appropriate channel or other layouts in addition to cylindrical geometries. FIGS. 30A-30C illustrate a reconfigurable reactor design that can be operated as either a fast neutron reactor or a thermal neutron reactor. In the embodiment shown, the MCFR reactor begins operating with a large core diameter and fast reflectors, which may comprise any fast spectrum reflector including, without limitation, lead, lead bismuth, etc. Thermal reflectors may be provided and which comprise any thermal reflector material including, without limitation, graphite, etc. Then, thermal reflectors may be inserted directly into the core, inside the fast reflectors, to reduce the critical core diameter and increase the power density. In this way, the MCFR reactor is capable of operating in multiple phases, where the first phase operates in a fast-reflected fast neutron spectrum and the second phase operates in a thermal-reflected thermal neutron spectrum. Additionally or alternatively, the reactor may be operated with both the thermal and fast reflectors in place for a later transition from a thermal reactor after removal of the thermal reflectors which would then modify the reactor to a fast spectrum with only the fast reflectors in place. Thus, the reactor is reconfigurable so that can be operated as either a fast neutron reactor or a thermal neutron reactor as needed. The same heat exchanger circuits are used in either configuration and/or additional heat circuits may be provided when the inner (thermal) reflectors are removed. In the simplified embodiment shown, a set of lead reflectors 3004 surround a fuel region 3002 as shown in FIG. 30A. The upper lead reflector may be removed and a set of graphite reflectors 3008 may be installed in the fuel region 3002 as shown in FIG. 30B. The graphite reflectors 3008 define a smaller fuel region 3006 as shown in FIG. 30C in which thermal neutrons are generated. The graphite reflectors may be provided with channels 3010 (illustrated by dashed lines in FIG. 30C) that connect to the fuel inlet and outlet channels through the lead reflectors 3004 to allow heated fuel to circulate between the smaller fuel region 3006 and the external heat exchangers through the channels in the reflectors. Notwithstanding the appended claims, the disclosure is also defined by the following clauses: 1. A molten fuel salt nuclear reactor core assembly configurable to operate in either the thermal spectrum or the fast spectrum comprising: a set of neutron reflectors, the set of neutron reflectors defining a fast spectrum fuel volume and at least one reflector fuel inlet channel and at least one reflector fuel outlet channel through which cooled molten fuel salt can enter and heated molten fuel salt can exit the fast spectrum fuel volume; and a set of neutron absorbers sized to fit within the fast spectrum fuel volume, the set of neutron absorbers, when installed in the fast spectrum fuel volume defined by the set of neutron reflectors, defining a thermal spectrum fuel volume and at least one absorber fuel inlet channel and at least one absorber fuel outlet channel through which cooled molten fuel salt can enter and heated molten fuel salt can exit the thermal spectrum fuel volume. 2. The molten fuel salt nuclear reactor core assembly of clause 1 further comprising; a heat exchanger fluidly connected to at least one reflector fuel inlet channel and at least one reflector fuel outlet channel. 3. The molten fuel salt nuclear reactor core assembly of clause 1 and/or 2 wherein each absorber fuel inlet channel is fluidly connected to an associated reflector fuel inlet channel. 4. The molten fuel salt nuclear reactor core assembly of any of clauses 1, 2, or 3 wherein each absorber fuel outlet channel is fluidly connected to the associated reflector fuel outlet channel. 5. The molten fuel salt nuclear reactor core assembly of any of clauses 1-4 wherein the set of neutron reflectors includes a removable neutron reflector and removal of the removable neutron reflector provides access to the fast spectrum fuel volume. 6. A nuclear reactor comprising: a neutron reflector assembly configured to surround a nuclear reactor core volume during a sustained nuclear fission reaction; a fixed core barrel between the nuclear reactor core volume and the neutron reflector assembly; and the neutron reflector assembly being further configured to adjust fast neutron flux and thermal neutron flux within the reactor core by altering reflectivity characteristics of reflector material in the neutron reflector assembly. 7. The nuclear reactor of clause 6 wherein the neutron reflector assembly includes a plurality of reflector tubes separated by an interstitial space, each reflector tube containing at least some neutron reflecting material and the interstitial space separated from the nuclear reactor core by the fixed core barrel. 8. The nuclear reactor of clause 7 wherein the interstitial space contains one of an inert gas, a primary coolant salt, or a fuel salt. 9. The nuclear reactor of clause 8 wherein the interstitial space contains a chloride salt. 10. The nuclear reactor of clause 9 wherein the chloride salt has an enriched amount of the 37Cl isotope. 11. The nuclear reactor of any of clauses 7-10 wherein at least one of the plurality of reflector tubes is rotatable. 12. The nuclear reactor of any of clauses 7-11 wherein at least one of the plurality of reflector tubes includes a neutron absorbing element in addition to the reflecting material. 13. The nuclear reactor of clause 12 wherein the neutron absorbing element is a partial liner inside a casing of the reflector tube. 14. The nuclear reactor of clause 12 wherein the neutron absorbing element is a partial liner outside the casing of the reflector tube. 15. The nuclear reactor of any of clauses 6-14 wherein the neutron reflector assembly further comprises at least one insertable core barrels sized to fit within and adjacent to the fixed core barrel and, thereby, reducing the nuclear reactor core volume. 16. The nuclear reactor of any of clauses 7-15 wherein the nuclear reactor core volume, as defined by the core barrel, is in the shape of a prism, a cube, a pyramid, a cone, a frustum, or a cylinder. It will be clear that the systems and methods described herein are well adapted to attain the ends and advantages mentioned as well as those inherent therein. Those skilled in the art will recognize that the methods and systems within this specification may be implemented in many manners and as such is not to be limited by the foregoing exemplified embodiments and examples. In this regard, any number of the features of the different embodiments described herein may be combined into one single embodiment and alternate embodiments having fewer than or more than all of the features herein described are possible. While various embodiments have been described for purposes of this disclosure, various changes and modifications may be made which are well within the scope contemplated by the present disclosure. Numerous other changes may be made which will readily suggest themselves to those skilled in the art and which are encompassed in the spirit of the disclosure. |
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053316746 | abstract | A nozzle dam has a valve controlled passage through the nozzle dam wall for releasing trapped gas from the nozzle in the region below the nozzle dam. The gas is released while the reactor coolant system water general level is above the level of the nozzle dam. |
claims | 1. A radiation shielding device, mounted on a vehicle, for meteorological observation with internal air circulation, the radiation shielding device comprising:a body for allowing one or more meteorological sensors to be mounted therein;a cover for covering the body by engaging with the body; anda modified Venturi tube which is physically formed while the body and the cover are engaged with each other;wherein, while the body and the cover are engaged with each other, the modified Venturi tube is configured as a first opening for receiving external air from an exterior of the body, a second opening for receiving internal air from an interior of the body, and a third opening for releasing the received external air and the received internal air, andwherein a size of a cross-section of the first opening and a size of a cross-section of the third opening are increased along directions from a central portion of the modified Venturi tube to both ends of the modified Venturi tube, andwherein the modified Venturi tube performs a function of a conventional Venturi tube by using the first opening and the third opening, and allows the internal air in the interior of the body to flow into the modified Venturi tube through the second opening, andwherein, the first opening, the second opening and the third opening are configured such that, while the vehicle on which the radiation shielding device is mounted is moved, the external air gets into the modified Venturi tube through the first opening, the internal air gets into the modified Venturi tube through the second opening, and the external air and the internal air are released from the modified Venturi tube through the third opening to thereby allow the internal air therein to be circulated, andwherein a fourth opening is formed on a bottom portion of the body, to allow the internal air to be circulated according to (i) a first airflow vector including a 1-1 sub-vector representing that the external air is received by the bottom portion of the body through the fourth opening, a 1-2 sub-vector representing that the received external air is transmitted to the central portion of the modified Venturi tube via the second opening and a 1-3 sub-vector representing that the transmitted external air is released through the third opening, which is much facilitated by an aid of (ii) a second airflow vector including a 2-1 sub-vector representing that the external air is received through the first opening and a 2-2 sub-vector representing that the received external air is released through the third opening to be added together, to thereby promote the internal air circulation of the body, andwherein each of the size of the cross section of the first opening, the size of the cross section of the second opening, and a size of a cross section of the third opening is controlled to be increased or decreased to adjust an intensity of an airflow in the body by referring to a total vector, which is obtained by adding the first airflow vector and the second airflow vector. 2. The radiation shielding device of claim 1, wherein an internal supporting structure for allowing the one or more meteorological sensors to be mounted is installed on a predetermined portion within the body, andwherein the one or more meteorological sensors are mounted on the internal supporting structure. 3. The radiation shielding device of claim 1, wherein the body and the cover are engaged with each other by using a first fastening mechanism formed on the body and a second fastening mechanism formed on the cover, and wherein a minimum size of the cross-section of the first opening and a minimum size of the cross-section of the third opening are adjusted to be equal to or less than a predetermined threshold by controlling the first fastening mechanism and the second fastening mechanism while the first fastening mechanism and the second fastening mechanism are in alignment. |
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053393422 | description | Referring now to the figures of the drawing in detail, and first, particularly, to FIG. 1 thereof, there is seen a preferred exemplary embodiment of a fuel assembly which includes a support element in the form of a central coolant tube (water tube) WR, that forms a flow channel for liquid coolant and has openings 1, 2 at the bottom and the top and extends from a lower tie plate LTP to an upper tie plate UTP. The bottom plate or lower tie plate LTP is screwed to a lower end piece of the water tube WR. An upper end piece also has a screw fastening, and in this case a bolt 3 of the tube WR reaches through an opening in the cover plate or upper tie plate UTP and in a handle H mounted on it. A protruding end of the bolt 3 has a thread on which a nut is mounted that forms a stop for the handle and the upper tie plate UTP. In FIG. 1, this nut does not become visible until the handle and the upper tie plate are pressed against a compressed tension spring 4 inserted between the water tube and the upper tie plate. Once this spring is relieved, the nut vanishes in a profiled recess in the handle H in which this nut is secured against being unintentionally turned and loosened. At various axial positions of the water tube, spacers SP are held between stops 5 and 6. Ribs of this spacer SP form voids in which fuel rods FR are supported. Upper end caps of these fuel rods are constructed as bolts and are loosely guided in bores 7 in the upper tie plate UTP. The coolant tube, spacer, lower and upper tie plates and fuel rods accordingly form an insert, which can be held at the handle H and inserted from above or below into a fuel assembly box or case or water channel WC that is open at the bottom and top. In the process this insert with the lower tie plate LTP comes to rest on an upper edge of a base part FT on which the lower tie plate can be set or even welded. A skeleton for the bundle of fuel rods includes the handle H, the upper tie plate UTP, the lower tie plate LTP and the support element or water tube WR. If the lower tie plate LTP is welded to the base plate FT, then it also forms part of the skeleton onto which the water channel WC can be slid from above. The entire, fully installed fuel assembly can be lifted with the handle. A distance d between the upper surface of the upper tie plate UTP and the bottom of the lower tie plate LTP is substantially constant with this construction of the load-bearing skeleton. In other words, the distance d varies only as a result of the thermal expansion of the water tube WR, and this construction also enables a thermal expansion of the fuel rods FR to take place. If the load-bearing skeleton is destroyed, for example if the water tube WR breaks or if one of the screw fasteners that keep the handle H on the upper tie plate and keep the lower tie plate LTP on the water tube WR (or load-bearing fuel rods if applicable) tears, then the lower tie plate held by the base part FT and the fuel rods resting on it can no longer be removed from the core by lifting the handle H. The distance d accordingly increases to the extent by which the handle H is lifted. The invention therefore provides a redundant support structure that, in addition to the support means of the skeleton, assures that the distance d will not drop below a specific maximum value. This redundant support structure may be formed in a simple manner by the water channel WC and by corresponding stops or retaining means between the water channel and the two plates UTP and LTP, with these stops defining the maximum value d. To that end, suitable fastening means for the water channel and the lower tie plate, or for the base part FT carrying the lower tie plate, are provided on a lower edge of the cluster or bundle of fuel rods. These fastening means may be a stop retained in the channel wall, which laterally engages the inside of the lower tie plate LTP or fits over this lower tie plate at its lower surface. By way of example, this stop may be a spring clip, for instance, that is secured to the base part and initially engages only a bore oriented toward the water channel, so that the lower edge of the water channel resting on the base part and on the lower tie plate can be slipped onto the base part and the lower tie plate. In that case, the lower edge of the water channel has a corresponding bore as well, into which the spring clip snaps due to its spring force once the water channel has been slipped on, so that the spring clip then forms a stop that engages recesses in the base part (or the lower tie plate) and in the water channel and so that when the water channel is lifted, a maximum value for the distance d between the lower tie plate and the upper edge of the water channel that rests on the upper tie plate UTP is defined. Naturally, a corresponding spring clip may be secured to the outside of the base part FT or to the outer surface of the side of the water channel, so that once the water channel has been slipped on it will engage corresponding recesses in the water channel and in the base part FT (or in the lower tie plate LTP) and be held in that position. In FIG. 1, a screw SCR is provided as the lower stop. Once the case has been installed, this screw SCR is screwed into a threaded bore 8 in the base part FT, through a corresponding hole 9 that is shaped for receiving the head of the screw and is provided in the lower edge of the case. Since this screw is seated at a point of the fuel assembly that is virtually unstrained thermally, and mechanically as well if the supporting skeleton is intact, then it is sufficient for retention of this stop to adapt the threaded bore 8 to the screw profile with adequate play, so that the screw can be inserted into the threaded bore 8 with only a little exertion of force, and the resultant frictional forces can hold this screw. Since the lateral position of the lower tie plate LTP resting on the base part is also fixed because of the retention of the water channel on the base part, it is possible in this construction to dispense with a weld connection between the lower tie plate and the base part. Unless it is necessary to make the fuel rods inserted into the skeleton laterally accessible for inspection purposes, the lower tie plate can be fixed to the water channel and to the base part by welding them together, instead of having to provide a screw or a corresponding stop. A stop disposed between the water channel and the plate and retained by a spring clip in the described way is shown in FIG. 1 as a retainer for the upper tie plate UTP. Typically, the handle and the upper tie plate have a frame that on one hand fits over the upper edge of the water channel WC for retaining it and on the other hand serves as a bearing surface for fuel assemblies adjacent the frame in the reactor core. According to FIG. 1, a spring clip or locking spring SG, having a free end which reaches through a recess 11 in the water channel and rests with a locking element in the form of a profiled part 13 on a stop surface 12 of the upper tie plate UTP, is secured to the outer surface of a frame or laterally protruding distance piece FM by lock means 10. Through the use of the compressed tension spring 4, the upper tie plate UTP has been pushed so far upward that the profiled part 13 of the spring clip SG is retained captive between the stop surface 12 and the case wall even if the spring clip SG itself should break. Alternatively or in addition, FIG. 1 shows a screw 14, with which the frame FM, water channel WC and handle H are screwed together in this position, in the manner already described for the screw SCR serving as a lower stop. This construction assures that even if the load-bearing parts of the supporting skeleton break (for instance if there is a broken water tube WR), a maximum value for the distance d between the upper tie plate UTP and the lower edge of the water channel WC itself (and therefore the bearing of the lower tie plate LTP resting there) will not be exceeded even if the fuel assembly is lifted at the handle H. In order to remove the coolant tube, the upper tie plate UTP is pressed against the tension spring 4, so that the profiled part 13 of the spring clip and the recess 11 in the fuel assembly case adapted to it face one another, the profiled part 13 can be bent outward by a tool through the recess 11, and the fuel assembly case WC can be pulled off. The screws SCR and 14 are loosened in the process. When the fuel assembly is installed, the procedure is correspondingly the reverse. The spring clip is first bent outward far enough by a suitable tool that the fuel element case can be slipped into the skeleton until, when the spring clip is released, with the upper tie plate pressed downward, the profiled part can snap through the opening 11 into its terminal position and lock in the terminal position specified by the profiled part 12 when the spring 4 is relaxed. A corresponding spring clip that locks into place in a recess in the fuel assembly case can naturally be secured to the upper tie plate UTP or to the top of the frame FM instead of to the side of the frame. It is equally possible to provide a stop that is held on the fuel assembly case by spring forces or frictional forces, which engages a corresponding opening in the frame and/or in the handle and/or in the upper tie plate. Accordingly, while the profiled part 13 forms an upper stop for the fuel assembly case, with the stop being resiliently held on the skeleton and reaching transversely to the fuel assembly axis through a window (recess 11) in the case, the lower stop is advantageously constructed as a screw that reaches through the fuel assembly case and the base part. As is seen in FIG. 2, this screw is approximately transverse to the fuel assembly axis and has a head SCH that is countersunk from the outside into the fuel assembly case, while a threaded part has a bore SCB that is oriented toward the screw head SCH and is accessible from the interior of the base part. This bore SCB is slightly flared open once the screw has been screwed into the base part. As a result, the threaded part of the screw is firmly pressed into the contrary thread of the base part, producing a connection between the case and the base part that is releasable only by damaging the screw. In this way, the screw itself is secured against being lost. It is practical to reinforce the base part in the region of the screw, and FIG. 2 shows that bypass bores BP, through which coolant can be introduced into the region of the fuel rods, can be disposed inside this reinforced part. A locking element that locks resiliently in detent fashion into corresponding receiving points of the fuel assembly case and of the upper part (upper end of the skeleton), and that is therefore simple to release but is secured in captive fashion on the fuel assembly, can advantageously be used as the upper stop that keeps the fuel assembly case supportingly on the upper part. This kind of locking means can also be used if the fuel assembly does not include any skeleton that would form an integrated insert which would be removable from the fuel assembly case along with the fuel rods. The invention therefore relates to fuel assemblies for a boiling water reactor that contain a cluster or bundle of fuel rods FR that are approximately parallel to one another, spacers SP for lateral fixation of the fuel rods, a lower end with a base part FT and a lower tie plate LTP as a stop for the fuel rods FR, an upper end with an upper tie plate UTP as a stop for the fuel assembly and a handle H connected to the upper tie plate and to the frame or distance piece FM, and a fuel assembly case WC laterally surrounding the cluster or bundle along with the spacers SP, the lower tie plate and the upper tie plate. Through the use of screw fasteners or other retaining means, the lower end is held on the fuel assembly in the installed state, and the lower tie plate serves as a lower stop for the fuel rods. The upper tie plate on the upper end correspondingly acts as an upper stop for the fuel rods, and this upper end includes a handle that is connected to the upper tie plate and to a distance piece laterally protruding beyond it. FIGS. 3 and 4 show two longitudinal sections through an exemplary embodiment, in which a spring with a locking element reaching through a window of the fuel assembly case is held on the upper end. In FIG. 3, the fuel assembly case WC, which has a polygonal and in particular a square cross section, and the handle H, can be seen. The handle forms a component that is cast in one piece with the upper tie plate UTP and a frame having a distance piece DP, or is held together in some other way. The distance piece DP fits over the upper edge of the fuel assembly case WC on at least two sides and forms a bearing surface on which adjacent fuel assemblies rest, in the core structure. It may be advantageous to hold a distance spring DS on the head by means of a fastening screw HS, in order to support the fuel assembly against adjacent fuel assemblies. In the case of assembly and disassembly, the upper end with the upper tie plate and the distance piece can be displaced toward the lower end, counter to the restoring force of the tension spring 4 that was already shown in FIG. 1, into a position 15 that is represented by a phantom line. As a result, a locking element 17 that reaches through a window 16 can be moved out of the window 16. This locking element 17 is retained on the upper part of the fuel assembly by a locking spring or spring element 18. It can therefore be bent out of the window counter to the restoring force of this locking spring. As FIG. 4 shows, the locking spring is secured on the upper part due to the fact that one end of the spring is screwed to the distance piece DP by a retaining screw 19. The locking spring 18 has a spring part 20 resting flatly on the upper part of the water channel WC in the direction of the lower end, and the locking spring 18 has a lower hook-like end 21 which engages the window 16 in hook-like fashion from above as an upper stop. Accordingly, if the upper end of the fuel assembly case is lifted at the handle H, then the case is suspended in the hook-like end 21 of the locking spring. Advantageously, this kind of locking spring 18 that is constructed as a leaf spring has an engagement surface in the form of a strap 22 which may be disposed laterally, for instance, so that the spring can be bent out of the window 16. FIG. 3 shows that the frame of the upper part also has disassembly bores 23 leading to this engagement surface 22, and a pin for moving the spring could be introduced through these bores. An advantageous spring shape is also shown in FIG. 5, wherein a spring has a middle part 24 bent into a U and it has a flat spring part 25 pointing upward, with a locking element 26. Ends 27 of legs of the spring may be suspended from or screwed or welded to the upper part, while the locking element 26 engages the window of the fuel assembly case. Instead of leaf springs, which sometimes tend to break, helical springs can also be used as the locking springs- in particular, a locking bar that is held by the upper part, is displaceable counter to the restoring force of the helical locking spring, and protrudes into the window of the fuel assembly case can be used as the locking element. FIG. 6 shows this kind of structure, in which the distance piece DP forming the frame of the upper part has a window or recess 28 formed therein, in which a helical locking spring 29 is supported in such a way that one end 30 of a locking element in the form of a bar that is located in the recess, is pressed outward. In this outwardly pressed position, another end 31 of the locking bar engages the inside of the window 16 of the water channel WC. Once again, a disassembly bore 32 makes it possible to press the locking bar back by the insertion of a pin, thereby compressing the spring 29 and freeing the window 16 in the water channel. In the preferred embodiment, the locking element is constructed as a latch that is held by the upper part and is pivotable approximately perpendicularly to the fuel assembly axis, counter to the restoring force of the locking spring. Such an embodiment is shown in FIG. 7 in a plan view of the upper part of the fuel assembly, in FIG. 8 in a cross section through the handle, and in FIG. 9 in a longitudinal section through the upper part. In this case, the upper part is provided in multiple parts and includes a hoop of the handle H extending diagonally across the rectangular cross section of the fuel assembly and merging with frame parts that rest on opposite corners of the water channel WC from the inside and through which frame parts another frame part that fits over the upper edge of the fuel assembly case is screwed on by means of fastening screws HS. This other frame part carries the distance springs DS, acting as the distance piece DP, on which the upper parts of adjacent fuel assemblies are supported. The upper tie plate UTP has through-flow openings 40 for the coolant and guide openings 41 for the upper cap pieces of the fuel rods and is secured to a slightly eccentric central case CC, which is cast onto the handle. It can be seen from FIG. 8 that a frame part 42 which rests from the inside on one corner of the fuel assembly case, has a recess 43 formed therein, in which a joint element 44 of a latch and a locking spring 45 are supported. In the case of installation, the locking spring 45 can be inserted through a bore 46 and compressed enough to permit the locking element, of which only the joint part 44 is visible in FIG. 8, to be inserted into the recess 43 from the side. This type of recess, support and installation may also be provided for the locking bar of FIG. 6. The locking element may then include a tongue that reaches through the opening 46 diametrically into a corresponding window in the corner of the fuel assembly case. However, FIG. 9 shows that the locking element has a forked tongue 47, so that it can engage corresponding windows of abutting case walls in the corner of the fuel assembly case. The recess 43 has a lower part which forms an approximately hemispherical or partially cylindrical joint socket 48. The joint part 48 accordingly likewise has a hemispherical or partially cylindrical end, with the radius of curvature of the joint part being less than the radius of curvature of the socket. Upon a pivoting motion of the locking element, this half-round profile of the joint part accordingly rolls along the socket. It can be seen from FIGS. 6 and 8 that the locking element can be seated in the recess 43 with considerable play to all sides, because its final position is fixed once the locking spring presses the locking element outward and the locking bars or tongues engage the inside of the window. This makes installation easier and lessens the danger of the locking element sticking to the frame part after the fuel assembly has been in use for a relatively long period in a nuclear reactor because of corrosion or soiling, which would prevent it from being pushed back counter to the restoring force of the locking spring when the fuel assembly is being dismantled. In particular, such factors are virtually no threat to the pivoting motion of the latch of FIGS. 7 through 9, because the generous play means that it can easily be broken loose and can roll along the joint socket even over layers of corrosion and dirt. When the fuel assembly is installed, the resilient locking parts automatically snap into the windows and openings that are provided for retaining the fuel assembly case on the upper part of the fuel assembly, as soon as the upper part is inserted into the case. In the case of disassembly, the screws 19 in FIG. 4 and HS in FIGS. 3 and 7 that are involved in this fastening, need not be loosened. If the connection is constructed as a resiliently supported locking bar or latch, then there is also no danger that leaf springs might break or that parts of the lock might loosen and be lost in the flow of coolant, where they could cause considerable disruption to the system. Naturally, corresponding resilient locking means may also be provided as a releasable connection between the lower end of the fuel assembly case and the lower end of the fuel assembly, but in this region of the fuel assembly they are unnecessary in many cases because of the low thermal and mechanical strain. |
claims | 1. A method of manufacturing a device using a lithographic apparatus, comprising:providing a substrate which is at least partially covered by a layer of energy-sensitive material; generating an electromagnetic field to act upon a projection beam generated by said lithographic apparatus, wherein an optical axis of said electromagnetic field is displaced by an action of a multipole magnetic field in at least one direction perpendicular to said optical axis in synchronism with a scanning motion of the lithographic apparatus; and irradiating portions of said layer of energy-sensitive material with a projection beam of radiation which has been affected by said displaced optical axis of said electromagnetic field. 2. A method in accordance with claim 1, wherein said optical axis of said electromagnetic field is displaced by an action of at least one quadrupole magnetic field which acts substantially perpendicularly to a stationary magnetic field. 3. A method in accordance with claim 1, wherein an array of selectable coils are provided, arranged in pairs on opposite sides of a space through which a projection beam is scanned, to generate at least one quadrupole field, and where individual pairs of said selectable coils are selectively energized to displace said optical axis. 4. A method in accordance with claim 3, wherein two groups of selectable coils, each group comprising at least one pair of coils, are simultaneously energized to form a field having an axis at a position between two pairs of coils. 5. A method in accordance with claim 1, wherein an electron-optical element comprising two arrays of selectable coils, arranged in lines on opposite sides of space through which a projection beam is scanned, are used in combination with conductors to generate a magnetic field in a plane perpendicular to a direction of propagation of said projection beam, and wherein said coils are selectively energized to form the multipole field at an arbitrary position in space, which multipole field acts as a beam deflector. 6. A method of manufacturing a device by employing a lithographic apparatus including a sliding electron-optical element, said method comprising:providing a projection beam of radiation; generating a multipole electromagnetic field using said sliding electron-optical element, to displace an optical axis of said projection beam by acting upon said projection beam from at least one direction perpendicular to said optical axis of said beam, in synchronism with a scanning action of said lithographic apparatus; and projecting at least a portion of said beam which has passed through said electromagnetic field onto a target portion of a substrate. 7. A method in accordance with claim 6, wherein said sliding electron-optical element employs a magnetic lens formed by a sum of a magnetic field operating substantially parallel to said optical axis and a quadrupole magnetic field operating substantially perpendicular to said optical axis. 8. A method in accordance with claim 7 wherein said magnetic field substantially parallel to said axis is stationary and said quadrupole magnetic field is displaced in synchronism with said scanning action. 9. A method in accordance with claim 8, wherein said sliding electron-optical element employs a pair of slit coils provided with yokes to generate said magnetic field substantially parallel to said axis, and employs an array of selectable coils, arranged in pairs on opposite sides of the space through which said projection beam is scanned, to generate said quadrupole field, said pair of slit coils being static and individual pairs of said selectable coils being selectively energized to displace an axis of said magnetic lens. 10. A method in accordance with claim 9, wherein two groups of said selectable coils, each group comprising at least one pair of coils, are simultaneously energized to form a field having an axis at a position between two pairs of coils. 11. A method in accordance with claim 9, wherein each of said selectable coils comprise first and second parts spaced apart in a direction parallel to the direction of propagation of said projection beam, and wherein said first and second parts are energized separately. 12. A method in accordance with claim 6, wherein said electron-optical element comprises two arrays of selectable coils arranged in lines on opposite sides of a space through which said projection beam is scanned and having conductors which generate a magnetic field in a plane perpendicular to a direction of propagation of said projection beam, wherein said coils are selectively energized to form a deflector, the multipole field, or both, at an arbitrary position in space. 13. A method in accordance with claim 6, wherein said electron-optical element is displaced physically in synchronism with said scanning action. 14. A method in accordance with claim 6, wherein said electron-optical element is displaced electronically in synchronism with said scanning action. 15. A method in accordance with claim 6, wherein said projection system comprises two sliding electron-optical elements functioning as lenses. 16. A method in accordance with claim 15, wherein one of said sliding electron-optical elements is arranged on an object side and another of said sliding electron-optical elements is arranged on a image side of a beam cross-over. 17. A method in accordance with claim 6, wherein said sliding electron-optical element is arranged to displace said optical axis along a substantially linear path substantially perpendicular to the axis of said projection beam. 18. A method in accordance with claim 6, wherein said sliding electron-optical element is arranged to displace said optical axis along a substantially arcuate path. 19. A method in accordance with claim 18, further comprising additional electromagnets before and after said sliding optical element to deflect said projection beam. 20. A method according to claim 6, comprising generating a plurality of projection beams which are spaced apart and scanned simultaneously. 21. A method according to claim 20, wherein one or more of said projection beams is scanned along each of a plurality of substantially parallel slots. |
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abstract | A nuclear reactor power regulator adjusts reactor output based on a reactor output target value and a reactor output change rate. The regulator includes a reactor output calculating device that performs computation based on a thermal equilibrium from power signals of plant parameters to calculate a reactor output signal. A correcting device corrects a continuously obtained reactor output equivalent signal that is considered to be equivalent to a reactor output at a calculation interval of the output signal, so that the output equivalent signal coincides with the output signal. The correcting device calculates a continuous corrected output equivalent signal. A reactor output controlling device calculates a reactor output control signal for controlling the output of the reactor, using the corrected reactor output equivalent signal, the reactor output target value, and the reactor output change rate. A reactor output controller is operated based on the reactor output control signal. |
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summary | ||
description | This application is a continuation of U.S. application Ser. No. 10/903,657, filed July 30, 2004 now U.S. Pat. No. 7,132,673. The present invention relates to an apparatus for the controlled removal of material from surface science technology or electron microscopy specimens as part of a specimen preparation technique. More specifically, the invention relates to a device including both high and low energy ion milling capabilities within a closely controlled environment, including, but not limited to, the parameters of specimen temperature, specimen location and vacuum. The invention further relates to a method for utilizing the disclosed device for the preparation of surface science technology or electron microscopy specimens. A charged particle instrument uses electrons that interact with a specimen to gain information from the specimen. Examples of such instruments are transmission electron microscope, atomic force microscopes, atom probe field ion microscopes and devices incorporating other scanned probe and x-ray technology for high magnification and imaging. Additionally, high angle annular dark field detections may be utilized in conjunction with such devices for high resolution scanning or transmission electron microscopy. In order for a specimen to be viewed using these devices, and more particularly, a transmission electron microscope, or TEM, it must have a portion or area that is electron transparent and atomically clean, meaning it is on the order of one atomic layer to 5 microns thick, depending on the material and the accelerating voltage of the TEM. One method of creating an electron transparent area in a specimen involves first mechanically reducing the size of the specimen in a gross fashion utilizing cutting, cleaving, thinning or polishing techniques, such as with a dimpling grinder or wedge polisher, and then ion milling the specimen. In ion milling, one, or preferably two, ion beams comprised of an inert gas, such as argon, are generated by an ion beam source or sources, otherwise known as ion guns, and are aimed at the mechanically reduced portion of the specimen. In some instances, corrosive beams may also be utilized for specific reduction or modification of the specimen material. Preferably, one ion beam is aimed at the top of the specimen at an angle of approximately 5-10° from horizontal, and a second ion beam is aimed at the bottom of the specimen at an angle of approximately 5-10° from horizontal. The ion beams remove material from the specimen by momentum transfer. Typically, ion milling is used to create a small hole in the center of the already mechanically thinned portion of the specimen such that the portions of the specimen adjacent to the hole are electron transparent. The ion beams used in conventional ion milling are on the order of 250 μm-2 mm in diameter, and have ion energies on the order of 0.5-10 keV, accomplishing material removal, or milling rates on the order of 20 μm/hr. Conventional ion milling has been accomplished utilizing lower energy devices, typically in the 50-100 eV range, but devices designed for this low energy utilization are frequently incapable of developing higher energies with appropriate current. Additionally, devices capable of higher energy, higher current milling cannot maintain a small beam diameter. These devices typically achieve a beam diameter as low as 1 mm, such as the Technoorg Linda Gentle Mill, manufactured by Technoorg Linda, Budapest, Hungary. Another device used to prepare specimens is a focused ion beam, or FIB. FIB milling was originally developed for circuit editing in the semiconductor industry to cut and weld traces. In FIB milling, a small diameter, high energy ion beam is generated from a liquid metal source. Typically, the diameter of the ion beam is on the nanometer scale and the energy of the beam is on the order of 5-30 keV. In light of its small beam diameter, FIB milling may be used for very fine cutting applications. Additionally, because of this fine cutting capability, focused ion beam etching has also been used for other specimen preparation to create the electron transparent area. For example, FIB milling is often used to create TEM specimens from processed microelectronic wafers. One common example of such use of the FIB technique is known as an H-Bar sample. In an H-Bar sample, two trenches, approximately 20 micron wide, are cut into the top and bottom of a cleaved or ground section of a wafer, leaving an electron transparent area between the trenches. One problem with focused ion beam etching as used in TEM specimen preparation is, because of the high ion energy and/or mass, the FIB processes often damage the crystalline structure of the specimen, thereby causing amorphization. In addition, the metal ions tend to penetrate the specimen substrate, a condition known as implantation. Amorphization and implantation both adversely affect the quality of the TEM image that may be obtained from the specimen. Conventional ion milling may be used to remove or remedy some of this amorphization and implantation. However, because the ion beam used in conventional ion milling is typically on the order of 1 mm and the trenches in an H-Bar sample are on the order of 20 microns, the ion beam will often remove some specimen material from the edges surrounding a trench and deposit that material in the trench. This problem, known as redeposition, also adversely affects the quality of the TEM image obtained from the specimen. A variety of other methodologies are utilized either with or without the use of a FIB. These include grinding and polishing a specimen into a relatively thin, wedge shaped orientation, which may then be viewed at the thin edge of the wedge or carved directly from the face of a substrate utilizing the FIB. In one particular methodology, a thin slice of material is removed from a solid substrate by removing a trench of material immediately adjacent the thin slice or section of the substrate material to be viewed. The thin slice is protected during the milling of the trench and is subsequently removed once the area around it has been cleared by cutting the thin, roughly rectangular section away from the surrounding substrate walls. In any of the previous examples of specimen preparation, the use of mechanical grinding and cutting techniques, as well as cutting and thinning through the use of the FIB, results in relatively localized amorphous damage to the specimen as described above. A number of techniques have been utilized in the prior art to alleviate both the creation of the damage to the specimen during its initial preparation, as well as remove the damage created by that preparation. Such techniques include the use of gas plasma, as disclosed in Fischione, U.S. Pat. No. 5,633,502. Various alternative preparation techniques, as described above, have further been developed for the purpose of exposing an appropriate area of interest of the specimen in such a manner that the physical separation of the sample section containing the area of interest from the surrounding substrate layer and the thinning of the sample take place in an area spatially removed from the particular area of interest. As will be apparent to those skilled in the art, the use of lower energy ions for less abrasive mechanical techniques would minimize specimen damage, however, the ability to solely utilize these techniques while retaining a reasonable preparation time and treating a given area of the specimen without redeposition has not been resolved. The requirement of electron transparency therefore necessitates the utilization of some electrical, chemical, thermal or mechanical preparation methodology before the exposure of the surface at the precise area of interest. Prior ion milling devices have been utilized in a variety of ways to achieve these same purposes. Typical ion milling energies and prior art devices, however, range from 0.5 to 10 keV. Alternative methodologies for reducing the impact damage of such traditional ion sources include the use of milling at low angles in order to reduce the direct impact of the ions utilized for milling on the specimen surface and for the more careful and controlled removal of specimen material from that surface. Ion Mill Model No. 1010, currently manufactured by E. A. Fischione Instruments, Inc. of Export, Pa., is a typical example of the prior art mill. It incorporates the use of hollow anode discharge, or HAD, ion sources, which are mounted adjacent to a tilting and rotating specimen stage. The use of the tilting and rotating specimen stage allows for the manipulation of the specimen relative to the HAD ion sources and for projecting and moving the ion beam across the surface of the specimen. While ion mills of the prior design have been effective, new developments in nanotechnology, electron microscopy and the continued sub-miniaturization of the specimen areas of interest have necessitated further improvements in both the magnification power of the transmission electron microscopes as well as the need for reduction of specimen damage during preparation. At higher levels of magnification, the damage from prior art preparation techniques threatens not only to overwhelm the field of view in specimen imaging, but also to produce a variable and unpredictable modification of the specimen structure. What is lacking in the art, therefore, is a methodology of thinning a specimen to electron transparency which provides both time efficient gross specimen preparation and thinning capability, and finely controlled finishing capability, while minimizing damage to the specimen through the use of both high and low energy ion beams having a relatively small beam diameter. What is further lacking in the art, moreover, is the ability to prepare the specimens with minimal damage utilizing a variety of techniques or devices under carefully controlled conditions of temperature and vacuum. A number of devices are currently identified in the prior art which provide many of the features identified above, but which are provided only in discreet implementations or devices without regard to the condition of the specimen being transferred between such preparation devices or intermediate such techniques. An ion mill is described which provides the capability of preparing a specimen utilizing a variety of low and high ion beam energies, while maintaining a relatively small beam spot size or diameter. The use of a small beam spot size minimizes the amount of sputtered material which may be re-deposited on the specimen surface and further promotes the ability to raster the beam across the surface of the specimen. Moreover, the operations are conducted within a single vacuum space, minimizing the effects of exposure of the specimen to ambient environmental conditions and contaminants. The device includes computing capabilities, which permit both centralized control of the various components of the device, as well as the programmatic control of those components for automated processing, both locally and over a network. While a Windows-based PC is preferably utilized for this function, any computing device may be utilized, including customized solutions. Alternative input and output functionality may be incorporated such as touch screens or dedicated display panels. Additionally, if purely manual operation is deemed appropriate, the computing device can be eliminated and the controls and outputs of the various components may be individually controlled through appropriate discrete components, as will be evident to those skilled in the art. A chamber housing forms the primary structural component of the operable device. This chamber housing may be mounted on any type of suitable support, with a transportable cabinet being preferred. The operative sections of the milling device may, however, be mounted on a bench or any other support with the requisite stability. The chamber block is itself comprised of a number of component structural parts, and may be subdivided for ease of manufacture, service or assembly. It is constructed of such material, preferably aluminum with requisite strength and other mechanical and chemical properties to support the components mounted thereon, as well as the milling activities within. The chamber block is the locus of the milling functions of the ion milling device and is provided with imaging capability for the purpose of observing the progress of the milling and beam targeting operation conducted therein. While a variety of imaging devices may be utilized in conjunction with the milling operations, including optical, thermal, electro-optical, scanning, or other microscopic capabilities, the high energy function is preferably observed utilizing a CCD camera, while the low energy operation is observed utilizing a secondary electron detector or SED, imaging module. The high energy milling function includes at least one and preferably a plurality of HAD ion sources, which may be utilized individually or in combination. Although the HAD devices are preferred at this time, it is specifically contemplated that other high energy milling devices might be incorporated directly within the milling device, including, but not limited to a FIB or other liquid metal source device. The HAD or other high energy devices are supplied utilizing a gas, which may be inert for providing a cleaning function, or corrosive, for providing a selective etching function. In the preferred embodiment, the inert gas is preferably argon. In addition to the high energy milling capability of the device, the combined ion milling device further includes low energy milling capability, which is utilized for the more controlled removal of specimen material. The low energy source is designed as a self-contained unit which incorporates rods to support and space a filament assembly in an appropriate orientation for interface with the remaining components of the low energy source. The lens assembly is positioned directly adjacent to the filament assembly at the lower portion of the filament section and is separately supported thereby in this fashion. Optionally, the filament assembly may be removed alone, or the lens assembly may be removed in conjunction with the filament assembly and the two assemblies may be separated external to the ion milling device for service and access to the various component parts. The elements of the ion source and lens include a gas fitting for the insertion of inert gas to a point adjacent to the filament element. A series of electrodes is disposed circumferentially about the base of the filament and contains a bore for the electrons originating from the filament to pass therethrough, as well as to provide for the acceleration of the ions to the lens device. Once the ions emerge from the aperture of the source, they are directed into a lens which is preferably provided with a conical bore. The lens includes rastering or deflecting segments at its terminal end to permit scanning of the ion beam across the surface of the specimen. Specimen induced current for endpoint detection—use faraday cup adjacent beam to measure transmitted current far side of specimen to sense presence The milling device is also provided with a plurality of methods for end point detection and observation during the milling process, primarily provided by the use of a light source positioned for direct impingement on the specimen. The detection of the light source through the specimen during the milling process indicates that a milling endpoint is anticipated, if not already achieved. Other forms of endpoint detection may also be incorporated which do not utilize direct impingement of a beam through the specimen. These include methods and devices which utilize a sensor, such as a Faraday cup, mounted adjacent the path of the ion beam passing through the specimen to detect the presence of the beam on the opposite side of the specimen from the beam source. A specimen positioning module, or carriage, provides a stable cradle for the support and positioning of a dewar for retaining liquid nitrogen or other cooling media, together with an armature for supporting the specimen holder and heat transfer. Although a dewar-based system is preferred, other cooling systems may be interchanged with similar results, such as a Peltier cooler module. Mechanically, these alternative modules would be interchangeable with the dewar system, other than the adaptation of the specimen positioning module to support the alternative device, which would be well within the ability of those skilled in the art. The positioning module controls and supports the movement of the specimen with respect to the ion milling sources, together with the attendant accessories necessary to support and monitor the specimen during the operations. The positioning module is displaced laterally utilizing a motor-driven lead screw assembly. The positioning module is guided by support rods and engages the lead screw drive. Control of the drive motor converts lead screw rotation into module translation. The positioning module is displaced rotationally about the lateral module axis for tilting of the specimen into the ion beam paths. A motor fixed to the chamber, engages a gear which is attached to the module and provides complete module tilt. All motion limits of the positioning module are defined using sensors which indicate both the ends of travel for translation, and a center-of-rotation home position for tilt. All intermediate positions are defined in software relative to the limits and controlled by stepper or encoder based motor drives. While the preferred embodiment allows for the lateral positioning of the specimen, together with the ability to tilt and rotate the specimen with respect to the ion beam, it is to be specifically understood that additional manipulations of the specimen may become useful or necessary in future embodiments, including, but not limited to tilting of the specimen along a second, front-to-back axis, normal to the side-to-side tilting function described above, as well as the ability to raise and lower the stage from the plane containing the lateral movement and side-to-side tilt axis of rotation. A vacuum pump module provides vacuum pumping functionality for the vacuum chamber. The vacuum pump module may be of any conventional design, and is typically constructed of commercially available devices. The primary pumping capability is preferably provided by a turbomolecular pump. As will be apparent to those skilled in the art, appropriate seals are provided between each of the modules and components associated with or mounted on the chamber block in order to facilitate the maintenance of a vacuum therebetween. The specimen stage is both structurally and thermally affixed to the dewar containing the cooling media. The specimen is typically milled under cooling conditions, so as to prevent degradation from the heat caused by the impingement of the ion beam. A thermally conductive support extends from the positioning module support structure, which is located outside of the chamber block to the vacuum chamber contained therein, which is the site of all milling and imaging activity. The specimen stage assembly is, however, able to be temporarily disengaged from its thermal connection to the cooling system. The thermally conductive support receives the specimen stage in a slidable engagement which is resiliently biased toward engagement with the cooling system, preferably by a spring. When loading or unloading specimens, however, the stage is forced against the spring and moved into a disengaged position, allowing the specimen and holder to return to an ambient temperature. This process may also be facilitated by a heater built into the stage. The device is further provided with the ability to insert and remove specimens into the vacuum chamber without need of releasing and recreating the high vacuum state of the chamber. A load lock is utilized to introduce the specimen to the vacuum chamber. It is also specifically contemplated that the device may be utilized in conjunction with a vacuum-based specimen transfer device which may externally mate directly to the load lock. The specimen may be removed from the holder to the transfer device under vacuum and transported to the microscope or other imaging device without exposure to the atmosphere or other environmental contaminants. The load lock vacuum, as described more fully herein, may also be utilized to maintain or support the vacuum within such transfer device. When the specimen stage is moved into a load/unload position, it extends from within the vacuum chamber into the load lock. The stage is designed to seal off its sample holder extending into the load lock from the vacuum chamber. The engagement of the stage with the load lock in this position also disengages the thermal connection between the stage and the cooling system. The load lock may then be vented and opened, exposing the end of the specimen stage while maintaining the vacuum within the chamber. After sample exchange, the load lock may then be pumped down and the stage retracted into the primary chamber. Retraction into the chamber automatically re-engages the thermal coupling to the cooling system. The specimen stage itself contains, in addition to the heater described above, a temperature sensor for monitoring the temperature of the specimen stage. The specimen stage supports the specimen itself in a clamping, rotational holder, which can be rotated upon remote command through the use of a small motor within the stage. Additionally, the motor or a pump device may be mounted external to the stage and provide mechanical energy to the stage or holder through mechanical or pneumatic communication. The holder is removable to allow for multiple holders, of potentially differing geometries or design, to be utilized in conjunction with the device. The preferred embodiment, adapted for TEM specimen milling, utilizes a riser which suspends the specimen over a gap which permits the milling of the underside of the specimen. Additionally, the specimen holder permits the passage of end detection illumination therethrough. Additionally, the stage may be adapted for receiving and supporting multiple specimens, typically in a carousel arrangement rotated through the use of an additional motor supporting a turntable-like support which would, in turn, support the various holders mounted thereon. A computing device, which is preferably a Windows-based PC, may be provided to control and monitor the operational aspects of the milling device. This includes the location and manipulation of the specimen through the various positioning devices, the vacuum systems, the imaging systems and the ion milling devices. It is also anticipated that all functions may be independently controlled and monitored through the use of discrete manual devices. The computing device, if present, may also be utilized to create and execute programs for the automated control and sequencing of the device processes. A graphical input/output interface is preferably utilized in conjunction with the computing device to simplify the operability of the device and further provides a convenient and compact locus for all control and output, typically in conjunction with a keyboard and/or pointing device. The various screens and menus provided in conjunction with the interface permit the full control of all mechanical and milling operations of the device, together with graphical, pictorial or other data output from the various sensors and imaging devices. As is customary with such computing devices, connection to a network may be utilized to exchange data, images or operational controls between interconnected computing devices. Remote operation of the computing device, including the ability to perform diagnostic functions, is also anticipated in such an embodiment, as would be well known to those skilled in the art. A feature of the device is the ability to perform pre-defined automated milling sequences. A specimen may be grossly thinned utilizing the high energy ion mill module and then finished utilizing the low energy ion mill module. The milling parameters are defined by the user, and may be manually or programmatically controlled, including movement of the specimen with respect to the ion beams during the milling operations. At the initiation and conclusion of milling operations, the specimen stage is returned to the load/unload position and the load lock mechanism is engaged. In this manner, a sequence of specimens may be processed through combined milling mechanism without the need to recreate the vacuum conditions within the vacuum chamber. These and other advantages and features of the present invention will be more fully understood upon reference to the presently preferred embodiments thereof and to the appended drawings. Referring now to FIGS. 1 and 2, an ion mill 1 is shown having a base cabinet 5, which is utilized to support the operable equipment and to enclose the power supply, vacuum system and circuitry utilized in the device. Base cabinet 5 includes a plurality of removable or openable panels to provide access to the internal components and storage spaces. The cabinet includes a counter top 10, which is made of an inert and durable material, which will withstand both physical and chemical abuse or attack while in use in a laboratory setting. In operation, the combined milling mechanism 15 is provided with covers 20A through 20D, which are utilized to provide both an aesthetically pleasing exterior surface, as well as protection for the relatively delicate device components. Each of the covers 20A through 20D provides removable access to these components for repair or inspection. A dewar access panel 25 is provided as a readily openable or removable cover to permit easy access to the internal mechanism for replenishment of the liquid nitrogen cooling media utilized within the device, as will be described later. A computing device, including processor, memory and data storage means, is incorporated within the device for all logic control and data output as will be more fully described with reference to FIGS. 14 and 15. A Windows-based PC is preferably utilized for this function. The primary components of which are mounted inside cabinet 5. Keyboard 30, pointing device 35 and screen 40 are positioned exterior to cabinet 5 in order to provide user input and data output. While data input and output are necessary for the utilization of the device in an effective manner, it should be specifically noted that the methodologies of input and output are to be considered optional within the scope of the art and the utilization of alternative input and output methods are clearly contemplated. The cabinet 5 is optionally provided with casters 45 or other alternative cabinet support devices in order to position the cabinet 5. Referring now to FIGS. 3, 4 and 5, the main chamber block 50 is provided, which in conjunction with low energy ion source mounting block 260 provides the majority of the vacuum chamber of the combined device. Chamber block 50 is preferably constructed of milled aluminum but may optionally be constructed of any material comprising similar strength and compatibility with the ion milling function contained therein. Additionally, the materials utilized in the device may need to be modified in the event that corrosive gasses are utilized, as would be apparent to those skilled in the art. Chamber block 50 contains vacuum chamber 55 in which specimen positioning module 60 is utilized to introduce and position specimen stage module 140. Vacuum chamber 55 is provided with such size and dimensions as will permit the free introduction of the various componentry while maintaining a sufficient wall thickness within chamber block 50 to permit the necessary vacuum conditions specified herein. Chamber block 50 is further the locus of the high energy milling function of the ion milling device and is provided with CCD imaging module 65 for the purpose of observing the progress of the high energy milling conducted within chamber block 50. The high energy milling function is provided utilizing high energy ion milling module 70, which includes at least one and preferably a plurality of preferably hollow anode discharge ion sources. These conventional HAD devices are generally identical in function and similar in construction to those found on the Model 1010 Ion Mill produced by E. A. Fischione Instruments, Inc. of Export, Pa. The high energy ion mill module preferably comprises two fixed position HAD ion sources having ion beam energy variably and continuously adjustable within the range of 0.5 to 6.0 keV. This energy level is derived from an ion source current, which is also continuously variable and adjustable between 3 mA and 10 mA. The HAD sources may be utilized individually or in combination, and can develop a beam current of up to 400 uA/cm2 with a spot size of as low as 1 mm, achieving material removal rates of approximately 20 μm/hr. The HAD devices are typically supplied utilizing an argon gas supply which should be well-known to those skilled in the art. In the event that corrosive gasses are utilized, it is contemplated that supply components would typically include the use of stainless steel and PTFE. In normal use, the HAD devices consume approximately 0.4 sccm of gas. As with the prior art devices, the high energy ion mill module 70 is held in a fixed position while the specimen is manipulated within the field of the fixed beam while some other prior art devices hold the specimen in a fixed position while manipulating the ion sources In addition to the high energy milling capability of the device, the combined ion milling device further includes low energy ion mill module 75, which is utilized for the more controlled removal of specimen material, as will be described more fully herein. As with the high energy module, the low energy module is provided with imaging capability so that the specimen may be observed during the milling procedure. Provided for this functionality is secondary electron detector or SED, imaging module 80, which, like the low energy ion mill module 75, is fixed in a position extending into the low energy ion source mounting block 260. It is to be specifically noted that any optical, thermal, electro-optical or electronic imaging device, may be substituted for the SED, dependent upon the application. Low energy ion source mounting block 260 is further provided with low energy milling chamber 265, which, similar to vacuum chamber 55, is sized and positioned within low energy mounting block 260 such that an appropriate vacuum may be maintained therein, while preserving enough operating space for the equipment and specimen holders inserted therein. Chamber structure assembly 228 is further provided to separate and screen the components of vacuum chamber 55 and low energy milling chamber 265. A motorized divider, best viewed in FIG. 4, is selectively positioned to extend into and divide the two chambers during operation of high energy ion mill module 70. Low energy ion source mounting block 260 is further provided with an endplate 262 which closes and seals the low energy milling chamber 265 and further supports load lock 85. Load lock 85 is utilized to introduce the specimen to the specimen stage module 140 when in the appropriate load position, as will be described more fully herein. Load lock 85 provides controlled ingress and egress of the specimen stage module 140 and access thereto from the outside environment. Specimen stage module 140 is supported by specimen positioning module 60, which in itself is comprised of a number of support elements. Specimen positioning support rods 95, of which there are preferably at least three, are mounted in conjunction with specimen positioning support flange 100 to provide a stable cradle for the support and positioning of dewar 155 and its attendant mechanisms. Lateral displacement motor 105 is mounted on specimen positioning support flange 100 and is engaged with threaded drive rod 110, which runs parallel to specimen positioning support rods 95. Lateral displacement motor 105 is preferably a stepper- or servo-type motor having movement control on the order of ±1 degree. A rotational support housing 115 is provided in conjunction with specimen positioning support rods 95 and specimen positioning support flange 100 to form the complete cradle, which will support dewar 155 and its attendant mechanism. In operation, the lateral movement of dewar 155 is controlled by the interface between threaded drive rod 110 and dewar support housing 150. Dewar 155 is provided with a removable dewar cover 160 and is encased in dewar support housing 150. Dewar support housing 150 is supported by and is slidably mounted upon specimen positioning support rods 95 and threadably engages threaded drive rod 110. The controlled rotation of lateral displacement motor 105 rotates threaded drive rod 110, thus laterally displacing, through the threaded engagement between threaded drive rod 110 and dewar support housing 150, the movement of dewar 155, as will be discussed subsequently. The movement of dewar 155 further controls the movement of specimen stage module 140 through primary specimen support 130. Specimen positioning module 60, including dewar 155 and specimen stage module 140, is axially or rotationally displaced for tilting of the specimen positioning module 60, as well as the specimen itself, within the various ion sources, by the use of rotational displacement motor 120, as will be described more fully herein. Rotational displacement motor 120 engages rotational gear 125, which is mounted at the periphery of rotational support housing 115. Rotational displacement motor 120 is preferably a stepper motor or servo motor having movement control of approximately ±0.1 degree, within an operable range of 0 to 45 degrees. In operation, the movement of rotational displacement motor 120 engages rotational gear 125 which accomplishes the tilting of the entire specimen positioning module 60 as a unit, in accordance with the gear ratio of their coupling. A more precise description of the operation and tilting of specimen positioning module 60 will be described further with references to FIGS. 6, 7 and 8. Referring now to FIGS. 3, 4, 5 and 14, a vacuum pump module 90 provides vacuum pumping functionality for vacuum chamber 55 and low energy milling chamber 265. Vacuum pump module 90 is preferably a turbomolecular pump 91 such as the Model No. TMPO71 manufactured by Pfeiffer Vacuum Technology AG, of Asslar, Germany, backed by a roughing pump 92 which may be of any known type, as will be apparent to those skilled in the art. Pumping systems of this type are similar, if not identical, to those systems found in the Model 1010 Ion Mill and Model 1020 Plasma Cleaner manufactured by E. A. Fischione Instruments, Inc. of Export, Pa. While the vacuum pumping system may be of any type suitable to develop a vacuum of 10−5 torr, the vacuum system is preferably of an oil-free design in order to minimize any potential oil contamination of the specimen. In certain circumstances, however, the use of an oil based system may be incorporated. The precise application of the combined ion mill will dictate to those skilled in the art, which vacuum system should be applied. Also apparent to those skilled in the art, are the appropriate seals to be provided between each of the modules described above in order to facilitate the maintenance of a vacuum between the various mounting blocks and components. While such seals are preferably of an O-ring construction, it is to be specifically contemplated that a variety of other sealing devices or techniques may be applied. Referring again to FIGS. 3, 4 and 5, imaging of the specimen during high energy milling is accomplished using CCD camera 210, which is supported by CCD lens adapter 220, which is itself supported by CCD camera support block 205. CCD lens 215 provides zoom capabilities for adjustable imaging of the specimen. The focus of CCD camera 210 is accomplished by vertical movement of camera 210, as will be described herein. CCD camera 210 and CCD zoom lens 215 are preferably manufactured by Mitutoyo of Kanagawa, Japan. CCD objective lens 225 is utilized to create the image for CCD camera 210 through CCD zoom lens 215. Objective lens 225 is vertically displaceable with respect to the specimen for focus of the image, while CCD zoom lens 215 is utilized to adjust the magnification of the specimen's image on the CCD element within camera 210. Protective window 226, preferably constructed of sapphire, is utilized to separate the vacuum chamber 55 from the lens 225 and camera. A motorized lens shutter assembly 227, of conventional design, may be utilized to cover protective window 226 during milling processes when imaging is not necessary, in order to prevent build-up of sputtered material on the face of protective window 226. CCD camera 210 is positioned laterally through the use of a multipart mounting block system. CCD imager mounting block 175 is directly positioned on chamber block 50 and is provided with a sliding track on base block 185, which is adjustable utilizing adjustment knob 195 for the controlled movement thereof in a first dimension along the longitudinal axis of the entire device. CCD imager positioning block 180 is a multipart section which includes a sliding block 190 which is adjustable in a second dimension normal to the movement of CCD imager positioning block 180. The combination of blocks 180, 185 and 190 permit the positioning of CCD camera support rod 200 in any one of a number of infinitely variable fixed positions for the ultimate positioning of CCD camera 210 within the optical field necessitated by the movement of specimen holder module 140 during operation. CCD camera support block 205 is slidably and lockably mounted on CCD camera support rod 200 to permit the appropriate height and focus adjustment of CCD camera 210, utilizing height and focus adjustment knob 207. The milling device, in conjunction with the high energy milling section, also provides a plurality of methods for end point detection and observation during the milling process. This is primarily provided by end point detection module 230. End point detection module 230 comprises a light source mounting block 235, which is affixed directly to chamber block 50. Light sources may be positioned for either direct impingement on the specimen as shown with end point detector light source 240, which is preferably a laser, or axially, for impingement utilizing a mirror 245. Either will project light through lens 255 and be focused upon the underside of the specimen by passing through specimen holder module 140 as will be further described. End point detection is achieved by the passage of the laser beam of light source 240 through the nearly perforated specimen by CCD camera 210. Referring now to FIGS. 4 and 14, a secondary axial visual light source 241 may be positioned external to the device, with access through light port 246 to impinge upon mirror 245. Spring 250 is utilized to support lens 255 within the bore of end point light source mounting block 235. Such secondary visual light sources 241 are typically utilized for assisting in the visual inspection of the milling progress upon the specimen. A chamber vacuum gauge 118 is provided for monitoring of vacuum conditions within vacuum chamber 55. Referring now to FIGS. 4 and 6, specimen position device 60 is mounted directly in an appropriate bore contained in chamber block 50, which is adapted to receive and restrain the tilting motion of specimen position module 60 through rotational support housing 115. Support housing 115 is supported within the bore on bearings 127 and vacuum is preserved within vacuum chamber 55 through the use of seal 129 interposed between rotational support housing 115 and the bore provided within chamber block 50. Rotational support housing 115, in conjunction with rotational displacement motor 120, are provided with center position detection means not shown, which conventionally identify an home zero point of tilt and provide a means for determining the tilt position of specimen positioning module 60 relative to that home zero point. As previously stated, dewar 155 is positioned and affixed within dewar support housing 150. Primary specimen support 130 is affixed to dewar support housing 150 to provide thermal conductivity and cooling of specimen stage module 140, as will be described further herein. Primary specimen support 130 is itself comprised of thermally conductive support 131 extending spaced apart and axially within primary specimen support housing 132, separated by vacuum. Thermally conductive support 131 extends to a point immediately adjacent the inner chamber 154 of dewar 155 and is thermally isolated from dewar support housing 150 by dewar mounting bushing 165. Dewar heat transfer rod 170 extends inwardly into the dewar chamber 154 and is positioned for direct impingement with the liquid nitrogen media to be contained therein. Dewar heat transfer rod 170 is mounted within thermally conductive support 131 and is in direct thermal communication therewith. Thermally conductive support 131 extends axially from dewar 155 to an internal point of vacuum chamber 55, where it receives and restrains specimen stage module 140, providing both physical support for specimen stage module 140 as well as the heat transfer mechanism for the cooling of the relevant components of specimen stage module 140. Thermally conductive support 131 is supported at the chamber end by rotational support bushing 168. Rotational support bushing 168 is further drilled to permit the vacuum of vacuum chamber 55 to extend into the space between thermally conductive support 131 and specimen support housing 132 within primary specimen support 130. Thermally conductive support 131 is further located at the axis of rotation of specimen positioning module 60. Bellows 145 is provided as the primary translation vacuum seal to the chamber along primary specimen support 130. Referring now to FIG. 6, as previously described the rotation of rotational support housing 115 causes the entire specimen positioning module 60 to tilt, which in turn provides the tilting function for the positioning of the specimen relative to the ion beams in either of the two ion milling positions. The lateral positioning of the specimen within the ion beams is controlled, as previously described, by the longitudinal displacement of primary specimen support 130, specimen stage module 140 and dewar support housing 150 by the rotation of the lead screw, or threaded drive rod 110 and is previously described in conjunction with rotational displacement motor 120. Dewar support housing 150 and lateral displacement motor 105 are further provided with locational detection means (not shown), which identify points of lateral movement of specimen positioning module 60, including a travel limit detector at each extreme end of travel of primary specimen support 130 as well as the ability to locate within approximately 0.1 mm the lateral movement of primary specimen support 130 as well as the specimen itself within the range of travel. Referring now to FIGS. 4 and 6, primary specimen support 130 is provided with a hollow bore end 133 in which secondary specimen support 135 is slideably mounted which is further restrained in said bore by specimen holder restraint flange 325. Secondary specimen support 135 is urged to an extreme outward and leftward position, as shown in FIGS. 4 and 6, by specimen holder engagement spring 295. Secondary specimen support 135 when urged into this outward and leftward positioning directly against and adjacent specimen holder restraint flange 325 and is in thermal engagement with thermally conductive support 131 at specimen holder temperature transfer engagement surface 300. To the extent that secondary specimen support 135 is caused to compress specimen holder engagement spring 295, as will be further described herein, and urged away from engagement with specimen holder restraint flange 325 and specimen holder temperature transfer engagement surface 300, then secondary specimen support 135 is no longer within thermally conductive engagement with thermally conductive support 131 and will assume the ambient temperature of its surrounding environment. Secondary specimen support 135 has been provided with the ability to thermally engage and disengage from thermally conductive support 131 for the purpose of selecting either the temperature of thermally conductive support 131 or ambient temperature based upon the position of secondary specimen support and, therefore, specimen stage module 140 within the device. This functionality is directly related to the operation of the load lock as will now be described. Referring now to FIGS. 4 and 6, a primary functionality of the combined ion mill is the ability to rapidly thin or otherwise mill the specimen utilizing the high energy mill module 70 and subsequently finish the preparation of the specimen, utilizing the low energy ion mill module 75, all within a single vacuum chamber. As previously discussed, the ability to perform both operations without the attendant loss of time related to pumping down a vacuum chamber to achieve the appropriate vacuum in a second device, as well as exposing the specimen to ambient air and temperature, is extremely important. One of the primary timesaving functionalities of the device is the ability to minimize the number of cycles of creating and releasing the vacuum in the vacuum chamber. Consequently, the device is further provided with the ability to insert and remove specimens into the vacuum chamber without need of releasing and recreating the high vacuum state of the vacuum chamber. This is achieved through the use of the load lock 85. Load lock 85 is further provided with load lock cap 280, which is constructed of stainless steel or other material which is sufficient to withstand the presence of the vacuum on the chamber side and ambient air pressure on the external surface. Load lock cap 280 is provided with a hollow center chamber which permits the extension of the relevant portion of specimen stage module 140 to be extended therein when primary specimen support 130 is extended to its leftmost extreme in point, designated as the load/unload position. Load lock cap 280 is supported on load lock cap support rod 285 in a pivotal manner, such that load lock cap 280 maintains some degree of freedom of movement relative to load lock cap support rod 285 and further permitting load lock cap 280 to remain in a precise parallel engagement with endplate 262 at the time of engagement so as to exert even and uniform support on the sealing mechanism material therebetween (not shown). Load lock cap support rod 285 is pivotally attached to endplate 262 and is urged into an engagement position by load lock spring 290. In operation, load lock cap 280 is retained in an engaged position by load lock spring 290 and the presence of a vacuum inside, directly adjacent to low energy milling chamber 265. When primary specimen support 130 and specimen stage module 140 are moved to the extreme left, as shown in FIG. 4, the load/unload position, specimen stage module 140 will extend exterior to low energy milling chamber 265 and into the load lock cap 280. After venting the load lock cap 280, the user may disengage load lock cap 280 from endplate 262 and gain access to specimen stage module 140. At this position, the vacuum inside vacuum chamber 55 and low energy milling chamber 265 is maintained by the engagement of specimen stage engagement surface 311 provided on specimen stage module 140 with the inner wall of endplate 262 immediately adjacent to load lock cap 280 at a point designated as load lock engagement surface 310. Specimen stage engagement surface 311 is provided as a ring collar with a radial seal, provided circumferentially on the exterior surface of specimen stage module 140 and is urged in the load/unload position against load lock engagement surface 310 by the action of specimen stage engagement spring 295. In this manner, the vacuum is maintained within the chambers of the device and the load lock cap 280 may be opened and the specimen exchanged. When the load lock cap 280 is replaced in the operative position and primary specimen support 130 and specimen stage module 140 are moved away from the load/unload or extreme left position, as shown in FIGS. 4 and 6, the vacuum within vacuum chamber 55 and low energy milling chamber 265 may drop slightly, based upon the volume of air contained within the interior of load lock cap 280, but the vacuum within the chambers is normalized more quickly to the target level than would be necessary for the return of vacuum chamber 55 and low energy milling chamber 265 from ambient air pressure. Additional vacuum is preferably applied directly to the load lock cap 280. Referring to FIGS. 4 and 14, load lock vacuum port 86 communicates directly into the chamber area inside load lock cap 280 when specimen stage module 140 is in the load/unload position and vacuum is provided by roughing pump 93, as will be further described with reference to FIG. 14. Evacuation of the space inside load lock cap 280 by roughing pump 93 alone, prior to the withdrawal of specimen stage module 140 from load lock engagement surface 310, removes a large fraction of the entrapped air and thus minimizes the temporary pressure increase occurring on the retraction of specimen stage module 140 into low energy milling chamber 265. It is further necessary to thermally disengage secondary specimen support 135 from thermally conductive support 131 during the load/unload operation. If the secondary specimen support 135 were to remain at the cooling temperatures provided by thermally conductive support 131 and the liquid nitrogen media within dewar 155 at the time that the specimen and specimen stage module 140 were introduced to the ambient temperature, then the ambient water vapor, together with all airborne contaminants, such as hydrocarbons in the surrounding laboratory atmosphere would immediately condense and freeze on both the specimen and the equipment, which is undesirable. The combined ion milling device, therefore, provides that at the point of engagement of secondary specimen support 135 with load lock engagement surface 310, secondary specimen support 135 is urged against specimen stage engagement spring 295 and is displaced inwardly within primary specimen support bore 133, disengaging secondary specimen support from specimen stage temperature transfer engagement surface 300 within the bore. This allows the specimen stage module 140 to return to an ambient temperature and reduce condensation and contamination of the specimen upon the opening of load lock cap 280. This process may be assisted by the use of a supplementary heating system within the specimen holder base 305 of specimen stage module 140, as will be more fully described herein. Referring now to FIG. 8, the operation of specimen stage module 140 is described in further detail. It is to be specifically noted that the orientation of specimen stage module 140 in FIG. 8 is reversed from that shown in FIGS. 4, 5 and 6. As previously described, thermally conductive support 131 is provided with bore 133 into which secondary specimen support 135 is slidably located. In normal operation, specimen stage engagement spring 295 urges second specimen support 135 into an outward position. Secondary specimen support 135 is restrained within primary specimen support bore 133 by specimen stage restraint flange 325. Specimen stage restraint flange 325 is restrained as the end cap of thermally conductive support 131 by bolts 330. Specimen holder base 305 is affixed by bolts 340 to the end of secondary specimen support 135 in an offset manner so as to maintain the location of the specimen at the axis of rotation of thermally conductive support 131, being the tilting of specimen positioning module 60. Contained within specimen holder base 305 is specimen mounting block 315, which itself contains the mechanism for the rotation of the specimen relative to the impingement of the ion milling beam. Specimen holder rotation motor 345 is affixed by a series of rotational drive gears 350 within specimen holder 335. The operation of specimen holder rotation motor 345 is controlled through electrical impulses through electrical connection 320, as previously described, in conjunction with rotational displacement motor 120 and lateral displacement motor 105. Specimen holder rotation motor 345 is provided with an arbitrary end point detection module (not shown) which allows for the precise positioning of the specimen within the 360° of rotational freedom of the specimen stage 335. Specimen holder gear 350A, which directly supports specimen holder 335, is further provided with specimen observation bore 351, which permits the passage of light from end point detection module 230 to reach the underside of the specimen through specimen holder 335. Referring now to FIG. 8A, specimen holder 335 is further provided with specimen holder base 336, which is circular in shape for easy rotation within holder bore 335A provided in specimen mounting block 315. Specimen holder base 336 is integrally formed with mounting bore boss 354, which extends upwardly therefrom in order to support specimen holder mounting bore 353, which extends axially therethrough. Mounting bore 353 is provided for the insertion of any conventional locking means (not shown) for the temporary and removable affixation of specimen holder 335 to the upper shaft of specimen holder gear 350A, as shown in FIG. 8. Referring again to FIG. 8A, integrally formed with mounting bore boss 354 is specimen holder riser 356, which is divided into two sections by specimen holder milling gap 352. Specimen holder riser 356 is intended to space the actual mounting surface for the specimen some distance away from specimen holder base 336 and mounting bore boss 354 to permit access to the underside of the specimen mounted within specimen mounting recess 358. The specimen is inserted in specimen mounting recess 358, which is sized and curved to accept specimens which are typically on the order of 3 mm in diameter. The specimen is retained in place through the exertion of a downward force thereon by restraining tines 363 of specimen restraining clips 359 against the upper surface of specimen mounting recess 358. Specimen restraining clips 359 are slidably mounted on the upper surface of specimen holder riser 356 for adjustable interaction of the restraining tines 363 with the upper surface of the specimen, such that the specimen is securely restrained, but the tines 363 do not interfere with the regular viewing of the area of interest of the specimen. Each of the specimen restraining clips 359 is provided with a clip adjustment slot 357, which is in turn mounted upon specimen restraining clip mounting pin 361 in each case. In operation, specimen restraining clips 359 may be laterally positioned within the limitation of movement of clip adjustment slot 357 about mounting pin 361. When an appropriate location is identified, mounting screws 362 are tightened, which fixes specimen restraining clips 359 in place. Additional embodiments of specimen restraining clips 359 may include the use of electronic or pneumatic motion systems which would mechanically raise and lower such specimen restraining clips 359 into contact with the specimen. As previously described during the milling phases of operation of the device, it may be necessary to either view or impinge a beam upon the underside of the specimen. During the two-sided high energy milling process, the underside of the specimen is impinged by the output of one of the high energy ion mill modules 70 as shown in FIG. 4, which passes through specimen holder milling gap 352 to reach the underside of the specimen. Additionally, during such high energy milling, the underside of the specimen may be illuminated by end point detector primary light source 240 and/or visual light source 241 which is utilized for visualization of the specimen during the milling operation. In either instance, the light is passed from lens 255, as shown in FIG. 4, upwardly through the base of specimen holder gear 350A through specimen observation bore 351 as shown in FIGS. 4 and 8 in order to emerge from specimen observation bore 351 at the base of specimen holder milling gap 352 and be projected unto the lower surface of the specimen. As previously described, specimen stage module 140 is adapted to engage and disengage from thermally conductive support 131 to allow specimen stage module 140 to return to ambient temperature prior to exposure to the atmosphere when engaged with the load lock module. It is therefore necessary to ascertain the temperature of the specimen stage module 140 to determine the time point at which the specimen stage module 140 reaches a temperature which is appropriate for the opening of load lock cap 280 when specimen stage module 140 is in the load/unload position. Referring now to FIG. 8B, specimen holder base 305 is provided with heater block cavity 304 which contains heat transfer media 306. Provided within heat transfer media 306 is sensor bore 308 which is adapted to receive and restrain temperature sensor 309 which communicates with the central processor through heater connector 313. Temperature sensor 309 is intended for the detection and relay of an appropriate electrical output, which indicates to the central processor the temperature of specimen stage base 305 as well as specimen holder 335. In many situations, it is advantageous to accelerate the return of specimen holder base 305 to ambient or near ambient temperatures and for that purpose, heater rod 307 is provided embedded within heat transfer media 306. Heater connector 313 provides an electrical connection in an appropriate interface to the central processor, which will activate heater rod 307 and enable the more rapid warming of specimen holder base 305. Referring now to FIGS. 9, 10 and 11, low energy ion mill module 75 comprises a carrier assembly, which is comprised of low energy source carrier top flange 385, low energy source carrier 390 and low energy source carrier retaining lugs 395. Referring specifically to FIG. 10, carrier top flange 385 is bolted to low energy source carrier 390 by a series of bolts 392, which are also illustrated with respect to FIG. 5. The assembled carrier is inserted into low energy ion source mounting block 260 and is received and restrained by low energy source carrier restraining lugs 395 which are held in place by bolts. It is to be specifically noted that the design of low energy ion mill module 75 is specifically directed toward the ease of removal and replacement as a self-contained unit, as shown in FIG. 10, for ease of access and maintenance through the engagement of restraining lugs 395 in low energy ion source mounting block 260. Referring now to FIGS. 9, 10 and 11, but most particularly to FIG. 11, all electrical connections for low energy ion mill module 75 are made through internal electric connector 372 and low energy lens connector 440 while the gas connection is made through gas port 365. Removal of low energy ion mill module 75 is therefore facilitated by the quick removal of the electrical and gas connections and the restraining lugs. Referring now to FIG. 9, the core section of the low energy ion mill module is displayed having low energy source housing 355, which supports the majority of the internal components. Flange 355 is indexed so that it may be inserted directly, without adjustment, into low energy source carrier top flange 385 and is restrained by low energy source housing restraint block 360, which is visible with respect to FIGS. 5 and 10. Low energy source electrical connector 370 is affixed to the top of housing 355 to allow the passage of electronic signals therethrough and is shown, with particular reference to FIG. 11, to comprise a quick release connector, which is electrically connected with internal electric connector 372. Internal electric connector 372 allows for the wiring of electrical contact block 400, which transmits electrical impulses from connector 370 to the various components of the low energy ion source, as will be described herein. Referring now to FIG. 9, it is apparent that the low energy source is designed as a self-contained unit which incorporates low energy housing support rods 375 to support and space a filament contained within a filament of support block 415 in an appropriate orientation for interface with the remaining components of the low energy source. Appropriate electrical connection wiring (not shown) provides electrical communication between internal electrical connector 372, filament support block 415 and electrical contact block 400. Referring now to FIGS. 10 and 11, the interface between the low energy milling module and the surrounding housing supporting the lens assembly is apparent. Low energy source housing 355, which supports the filament assembly, is affixed to low energy source carrier top flange 385, which comprises the topmost element of the lens assembly and carrier. The lens assembly is positioned directly adjacent the filament assembly at the lower portion of the filament section and is separately supported in this fashion. Optionally, the filament assembly may be removed alone, or the lens assembly may be removed in conjunction with the filament assembly and the two assemblies may be separated external to the ion milling device for service and access to the various component parts. Both assemblies are further intended to be electrically self-sufficient, in that the removal of each subassembly does not necessitate the removal of additional internal electrical connections to the remaining components of the device as a whole. External low energy lens connector 440 is located within low energy source carrier top flange 385 and provides for easily removable electrical communication between the ion milling device and the central processor and the elements of the lens by conventional wiring (not illustrated for clarity). Referring now to FIG. 10, the elements of the ion source and lens are described with more particularity. Gas feed line 405 passes from gas port 365 through insulating support rod 410, which is preferably constructed of an insulating material such as Vespel manufactured by DuPont. Gas feed line 405 passes internally of ionization chamber block 380. The filament, which is preferably constructed of tantalum, thoriated iridium or thorium oxide is positioned in a conventional manner within filament block 415. A wehnelt electrode 420 is disposed circumferentially about the base of filament block 415 and contains a bore or passageway for the electrons emitted from the filament to pass therethrough and is to provide for guidance of the emitted electrons into the ionization region at the center of ionization chamber block 380. A pair of intermediate electrodes identified as G2 electrode 425 and G3 electrode 430 are similarly disposed circumferentially about the path of the electrons emitted by the filament element. The gas, preferably argon, is supplied from a conventional gas reservoir 795, the flow of which is controlled and maintained by mass flow controller 790 and computing device 550, as more fully illustrated in FIG. 14. G2 and G3 electrodes 425 and 430, respectively, are utilized to guide the electrons from the filament into the ionization region in the hollow bore of the ionization chamber block 380. An electric field is established within the ionization region by applying a suitable voltage difference, preferably between 1V and 20V, between G3 electrode 430 and exit aperture 435. A portion of the electrons from the filament enter into the ionization region and collide with gas atoms introduced into the ionization region through gas delivery tube 405. A portion of the resultant collisions produce ionized gas atoms, as is well known to those skilled in the art, which are directed toward exit aperture 435 by virtue of the aforementioned electric field. A portion of the ions strike the metal surrounding exit aperture 435 and are neutralized by transfer of electrons with the metal parts, but some of the ions pass through the exit aperture 435 and are therefore directed into the lens. As is also well known to those skilled in the art, this electrode geometry is of a type utilized to produce ions having uniform kinetic energy within a range of plus or minus 2 eV, with a mean energy that is closely related to the bias voltage on the ionization chamber block 380 with respect to the specimen, typically in the range of 10 eV to 6 keV. Voltages are applied to each of the electrodes through connectors 370 and electrical contact block 400, as determined by the user, through the processor interface, as will be described herein. Once the ions emerge from exit aperture 435, they are directed into lens entrance electrode 450, which is provided with a conical bore therein and is electrically grounded. Lens entrance electrode 450 is supported by lens support flange 445, which is in turn supported by low energy housing support rods 375 directly from low energy source carrier top flange 385. The lens elements, including lens entrance electrode 450, lens ground segment 460, lens active segment 465 and deflection segments 470 are all contained within lens housing 475, which is also affixed to lens support flange 455, creating a self-contained unit. Lens active segment 465 is electrically connected through external low energy lens connector 440 to an external power source which is under the control of the central processor, as will be described herein. A voltage is applied to lens active segment 465, proportional to the ion beam energy and generally in the range of approximately 200 to 1000 V, creating an image with ions of exit aperture 435 on the specimen, with a magnification range of approximately 1, i.e., a range of 0.1 to 10. With a suitably sized exit aperture 435, an image or spot size of approximately 1 μm-100 μm is achieved on the specimen surface. The beam passes through the bore of the lens elements to the final section of the lens, deflection segments 470 which provide a rastering function. Deflection segments 470 are a plurality of electrically isolated segments forming a circumferential ring about the path of the beam. Differential voltages are selectively applied to the different electrically isolated deflection segments 470 in order to cause the beam emerging from the lens to be deflected by a desired angle, which is proportional to the differential voltage and generally in the range of 0 to 10 degrees. Angular deflection of the beam at the output of the lens results in a change in the position of the image or spot on the specimen surface. Appropriate electrical controls from the central processor will thus cause the beam to be directed in a pattern across the surface of the specimen, which is located directly below deflection segments 470. Referring now to FIGS. 4 and 12, a Faraday cup mounting flange 480 is located in low energy ion source mounting block 260, opposite the low energy ion mill module 75. Faraday cup mounting flange 480 supports Faraday cup 270 and Faraday cup connector 275, which permits the communication of current flow from Faraday cup 270 to the outside environment. Faraday cup 270 is utilized to measure the output of low energy ion mill module 75 in a testing mode when no specimen is present in order to determine the output current of low energy ion mill module 75. Referring now to FIGS. 5 and 13, a secondary electron detector imaging module 80, or SED, is provided for the imaging of the specimen during low energy milling. During the low energy milling process, secondary electrons will be ejected from the surface of the specimen upon the impingement of the ions constituting the low energy milling beam. SED imaging module 80 is mounted with the collection electrode 510 internal to low energy mounting source block 260 within low energy milling chamber 265 immediately adjacent specimen holder module 140 when in the operative position for low energy milling. The secondary electrons are attracted and deflected into SED imaging module 80 by electrode 510 and impinge upon scintillator surface 505 of SED light guide 500. Scintillator surface 505 is held at a high positive potential such as 10 kV with respect to the chamber 265 so that electrons will strike the scintillator 505 with high kinetic energy such as 10 keV. SED mounting flange 520 comprises a housing which receives and supports electrode 510 and light guide 500 to SED housing 515. SED housing 515 supports photomultiplier tube 495 which is powered through electrical connector 485 in electrical communication with the processing and imaging modules described herein. In operation, the secondary electrons impinge upon SED scintillator 505, causing the emission or generation of light signals in proportion to the quantity of secondary electrons impinging thereon. The light signals pass through the SED light guide 500 to photomultiplier tube 495, which converts the light signals into electrical current, proportional to the intensity of incident light. Voltage divider 490 provides a necessary distribution of potentials to the electrodes within the photomultiplier tube 495, as is described and implemented by Hammamatsu Company, Japan. Electrical output of the photomultiplier tube 495, which is substantially proportional to the incident light intensity and therefore substantially proportional to the quantity of collected secondary electrons, is transmitted to the processor through connector 485. A signal processing device, such as a PC or oscilloscope, records the instantaneous position of the incident ion beam on the specimen and also the received SED signal amplitude. If the sample is not homogeneous, the relative production of secondary electrons may differ for different locations of the ion beam image on the sample. In the extreme case, for example, if the sample does not cover the entire deflection area of the incident ion beam, a secondary electron signal will be received when the beam impinges on the sample, and will not be received when the ion beam is positioned on a location at which no sample material is present. In this way a graphical representation or image of the sample represented by the quantity of secondary electrons received by scintillator 505 as a function of beam or the spot position on the sample surface, may be displayed upon screen display 40. Referring now to FIGS. 4, 14 and 15, a computing device 550, which is preferably a Windows-based PC, is provided mounted within cabinet 5. It is constructed having the typical components of processor, memory, data storage and input/output or I/O functions. It is considered well within the skill of those in the art to establish appropriate communications protocols between the commercially available interface cards and circuitry and the various electronic components according to the specific parameters set by the component manufacturers. Computing device 500, as is typical for such devices, may also contain an ethernet or other networking port or connection (not shown) for electronic data communication with other devices on a local or global network. Such communication may be utilized for interchange of data or images, remote operation of the device and remote diagnostic functions, among others. As is customary with such devices, peripheral control section 555 is provided for communicating with peripheral devices. An RS-232 serial connection 560 is provided for interface and data communication with high energy milling circuit board 590. High energy milling circuit board 590 is utilized to route and translate electronic communication with high energy module interface cards 600 provided for each of high energy ion mill modules 70. Electrical connections 600A and 70A, respectively, provide electronic communication between these components. High energy module interface card 600 is utilized to translate operational instructions from computing device 550 to the hollow anode discharge guns provided within high energy ion mill module 70, which instructions typically take the form of the application or discontinuation of operation, as well as the precise electrical parameters to develop the user pre-selected output. Also controlled is the delivery of the process gas, through the activation of mass flow controller 790. Computing device peripheral control section 555 further provides a serial bus connection 565 which is preferably comprised of a USB port. Serial bus connection 565 may be utilized to communicate with any number of serial devices, but is preferably utilized to communicate with CCD camera 210 for operational control thereof, as well as the receipt of image information from CCD camera 210. Also provided are keypad input connection 575, pointer input connection 580 and power connection 585 which are provided in a conventional manner, as is found on the majority of personal computing devices for user input and machine control. Video output connection 570 is utilized to provide graphical information to screen display 40, also in a conventional manner. Operational control of combined milling mechanism 15 is provided through the use of a series of interface circuit boards which are typically commercially available, and I/O expansion cards for use with the particular model of computing device 550 selected. The preferred embodiment utilizes PCI bus-based interface cards contained in I/O control section 615. Motor control circuit 620 is provided to translate and generate the appropriate motor control signals from computing device 550 to the various motors identified and utilized within the combined ion milling mechanism 15. The signal path includes direct communication through motor control circuit connection 620A to signal breakout circuit board 645. Signal breakout circuit board 645 is provided as the locus for a variety intermediate circuits within cabinet 5 in order to facilitate the location and mounting of various electronic and mechanical components therein. Signal breakout circuit board 645 also provides operational power to the various motors and peripheral devices utilized in the combined milling mechanism 15. Signal breakout circuit board 645 further contains various discrete circuits with are utilized to route the various identified inputs to the appropriate downstream interface circuitry or mechanical devices, as will be further described herein. With respect to motor control circuit 620, motor control circuit connection 620A provides electronic communication between the appropriate segment of signal breakout circuit board 645 and stage/vacuum circuit 655, shutter driver circuit 660 and rotation motor driver circuit 665, as well as direct communication to rotational displacement motor 120, specimen positioning device location sensor 675, lateral displacement motor 105 and specimen positioning device tilt sensor 680. More specifically, motor control circuit 620, in conjunction with the appropriate segments of signal breakout circuit board 645, provide electronic communication with shutter driver circuit 660, which interprets and translates electronic communication and instructions to shutter motor 670 contained within chamber shutter assembly 228. Motor control circuit 620 and signal breakout circuit board 645 directly communicate with rotational displacement motor 120 through rotational motor displacement connection 120A for control and operation of the tilting function of the specimen stage. As previously described, specimen positional device location sensor 675 is utilized to detect and identify an arbitrary zero or end point of that tilting movement and communicates such locational information to motor control circuit 620 and computing device 550 through specimen positioning device location sensor connection 675. Likewise, motor control circuit 620 controls and receives communication from lateral displacement motor 105 and specimen positioning device location sensor 675 in a similar manner. Utilizing this circuitry, motor control circuit 620 and computing device 550 control the lateral movement of the specimen stage module and translocate the same through the various milling positions and the load/unload position. Digital I/O control circuit 625, digital to analog control circuit 630, slow analog to digital control circuit 635 and fast analog to digital control circuit 640, like motor control circuit 620, are provided in the form of PCI-based interface cards in conjunction with computing device 550. These commercially available devices are utilized in conjunction with the appropriate sections of signal breakout circuit board 645 in the passage and translation of electronic data and power to and from the various electronic components. In this manner, computing device 550 through signal breakout control circuit 645 and stage/vacuum interface circuit 655, can receive electronic output signals from temperature sensor 309, convert the data output of temperature sensor 309 into an appropriate temperature measurement scale, and display such output on screen display 40, as will be described further herein. Stage/vacuum interface circuit 655 further provides an actuation circuit for heater rod 307 located within specimen stage module 140 for the adjustment of the specimen temperature during the load/unload sequence as previous described. The utilization of this circuitry further permits computing device 550 to allow the user to preset or program certain conditions based upon the achievement of a certain target temperature or to initiate certain conditions such as activation of the heater rod 307 when certain temperature conditions are not met. Stage/vacuum interface circuit 655 also controls the operation of turbomolecular pump 91, roughing pump 93 and associated vacuum valves 92, as will be more fully described herein with particular reference to FIG. 14. Under normal operating circumstances, vacuum chamber 55 is evacuated through the use of vacuum pump module 90, which is itself comprised of turbomolecular pump 91 and roughing pump 93. Roughing pump 93 is necessary to create an initial base vacuum from which turbo molecular pump 91 may begin operation. Turbomolecular pump 91 is typically not capable of drawing a vacuum from ambient air pressure. Vacuum valve 92 is disposed between turbomolecular pump 91 and roughing pump 93 to permit roughing pump 93 to be operated independently of turbomolecular pump 91. As previously described in conjunction with the load lock 85, roughing pump 93 may be utilized to evacuate the chamber created in load lock 85 during the load/unload sequence. In this situation, the vacuum valve between turbomolecular pump 91 and roughing pump 93 is closed while vacuum valve 92 located between load lock 85 and roughing pump 93 is open. During all other operation of the combined milling mechanism 15, this load lock vacuum valve 92 remains closed. Load lock vacuum sensor 119 is provided to determine when the appropriate vacuum has been achieved within load lock cap 280. With respect to both the load lock operation as well as the normal pumping of vacuum chamber 55, appropriate vacuum valves 92 are provided to permit the venting of the chambers and the exhaust of pumped air in conjunction with appropriate valves. Returning to FIGS. 4, 14 and 15, computing device 500, through I/O control section 615, further controls the operation of low energy ion mill module 75 and the associated SED imaging module 80. Computing device 550, through signal breakout circuit board 645, is in operational communication with low energy ion mill module interface circuit 685, which is utilized to control low energy ion module 75 and, more particularly, the ion source contained therein. Low energy ion mill module interface circuit connections 685A provide for the routing of electronic communications thereto and permit the control of power being applied to the filament support block 415, the wehnelt electrode 420, the G2 and G3 electrodes 425 and 430, respectively, and exit aperture 435. Control of the device is maintained through the transmission of user preset signals which monitor the current flow to the various components. Similarly, low energy ion mill lens interface circuit 690, in conjunction with connection 690A, provides similar control for the various components of the low energy source. Electronic communication is provided through external low energy lens connector 440 and electronic signals from computing device 550 are utilized to control electronic current flow and deflection through signal breakout control circuit 645 to lens active segment 465 and deflection segment 470. Also controlled is the delivery of the process gas, through the activation of mass flow controller 790. Computing device 550 utilizes I/O control section 615 in order to operate and receive graphic images from SED imaging module 80 through the use of SED imaging module interface circuit 695. The interface 695 provides the ability for computing device 550 to initiate operation of SED imaging module 80, as well as receive the output therefrom, which has been amplified by SED amplifier 800 before returning for interpretation by computing device 550 and the projection of a graphical representation thereof on screen display 40. Referring now to FIG. 16, a graphical representation is made of a typical main screen display 700 which is utilized to provide an interface between the user and device. Main screen display 700 is intended to permit the user to select various functions of the combined milling mechanism 15 as well as observe a variety of images and data output in order to monitor the progress of the milling functions. Main screen display 700 is provided with status bar display 705 which contains a series of sections which report the status of the various operational devices utilized in conjunction with the combined milling mechanism 15. It is to be specifically understood that main screen display 700 may be utilized in a variety of formats as is well known in the art, and may be oriented in any fashion suitable to the designer. Status bar display 705 contains error indicator section 710 which may utilize a series of indicator icons or other textual output which may indicate an error or fault condition. Specimen stage temperature status section 715 displays the current temperature of specimen holder block 305, and consequently, the specimen, as determined from temperature sensor 309 as well as the activation status of heater rod 307. Additionally, specimen stage temperature status section 715 may contain information relating to the engagement of thermally conductive support 131 with specimen stage module 140, indicating that the cooling capacity of the liquid nitrogen media contained in dewar 155 is being applied to specimen stage module 140, as appropriate. VacuumAoad lock status section 720 typically provides a boolean output indicating the condition of presence or absence of appropriate vacuum in the load lock, the chamber, and the open or closed status of load lock 85. This information is detected from chamber vacuum gauge 118, load lock vacuum sensor 119, and an interface switch (not shown) which is activated upon the engagement of load lock cap 280 with end plate 262. Activity status section 725 indicates the position and activity of specimen holder module 140 with respect to either high energy ion mill module 70, low energy ion mill module 75, load lock 85, or in a resting position. Activity status section 725 further indicates whether high energy ion mill module 70 or low energy mill module 75 is in an active condition. Message section 730 may be utilized for communication of a variety of messages including status, help, or other conditions of the device. Main screen display 700 further contains and displays activity buttons 740 which are utilized to access additional menus and command dialog boxes from which certain operations or sequences may be initiated or tracked. These may include maintenance, calibration, and other functions utilizing a series of screen displays which are purely factual in nature and within the ambit of those skilled in the art. The activity buttons 740 are typically contained within an activity bar display 735 which is utilized to provide a degree of organization to main screen display 700. With respect to screen displays, of particular interest are activity scheduler screen 745 and motion control display 765 as shown in FIG. 17. Referring now to activity scheduler screen 745 as shown in FIG. 16, this screen provides the ability to program a series of algorithmic steps into the device to allow the user to program and initiate a sequence of events which will be automatically carried out by the device without additional user input or supervision. These protocols may be saved and stored as necessary for repeated operation or modification. Activity scheduler screen 745 is provided having an activity list screen 750 in which the various steps of the procedure are displayed after selection and addition by the user. The various operations that may be included in the activity list screen 750 are contained as buttons in activity selector display 755. These include the selection of high energy milling, low energy milling, movement of the specimen between the various stations and load lock, imaging of the specimen at the two milling stations, the operation of the vacuum components as well as the ability to set certain end points and conditions for each operation. These end points and conditions include end point detection for high energy milling as described with reference to end point detector primary light source 240, a preset time duration for any milling operation, and certain temperature parameters as detected by temperature sensor 309. Each of these commands and parameters may be input in any order, although it should be obvious to one skilled in the art that certain activities may take place only after the completion of other prerequisite steps. Main screen display 700 is further provided with vacuum control bar 760 which permits manual control of the various pumping activities of vacuum pump module 90, the component turbomolecular pump 91 and component roughing pump 93, as well as the initiation of the load/unload sequence. Referring now to FIG. 17, precise manual control of specimen stage module 140 is obtained through the use of motion control display 765, which is one of activity buttons 740 selectable from main screen display 700. Motion control display 765 includes motion control status display 770 which provides a graphical representation of the location and condition of the various components of combined milling mechanism 15. Actual control of the device is provided through holder rotation control bar 775 for the circular rotation of specimen holder 335. Specimen holder 335 may be rotated either clockwise or counterclockwise through the use of appropriate controls within holder rotation control bar 775, as well as returning specimen holder 335 to the arbitrary zero point as provided through the end detection means described previously. Stage tilt control bar 780 allows for manual control of the tilt of specimen stage module 140 through the rotation of specimen positioning module 60, as previously described. The use of appropriate buttons or icons allow the user to engage the rotation of specimen positioning module 60 in either of two arbitrarily identified directions. The translocation or lateral movement of specimen positioning module 60 is controlled through the buttons contained within stage lateral displacement control bar 785, which engages lateral displacement motor 105 for the appropriate movement of specimen holder module 140 between the various stations, a rest position and the load/unload position. It is to be specifically noted that one skilled in the art might select any one of a number of different graphical representations to engage and monitor the electrical and mechanical operation of the various components of the device. In operation, the device is initiated by powering up computing device 550 and ensuring that appropriate liquid nitrogen media is placed within dewar 155 through dewar access panel 25. The operation of computing device 550 is observed and initiated through the use of screen display 40, keyboard 30 and pointing device 35 in a conventional manner well known within the skill of those in the art in the utilization of PC-based computing devices. Main screen display 700 is utilized to initiate and/or access the appropriate operational parameters of the device. A vacuum condition within chamber 55 and low energy milling chamber 265 must be established, although this may take place before or after the loading of the initial specimen. In either event, the appropriate control is selected from vacuum control bar 760 to initiate the pumping sequence. The vacuum status is indicated by vacuum/load lock status section 720, and when appropriately indicated, the remaining steps of the procedure may be initiated. In single operation, which is provided as an exemplar of all operations, both manual and programmed, specimen stage module 140 is laterally transferred into the appropriate load/unload position through stage lateral displacement control bar 785. As previously described, the initiation of this sequence causes lateral displacement motor 105 to move specimen positioning module 60 into the load/unload position. The movement of specimen stage module 140 into the load/unload position further causes the disengagement of secondary specimen support 135 from thermally conductive support 131 at specimen holder temperature transfer engagement surface 300, allowing specimen holder stage 140 to return to ambient temperature. As necessary, the operation of heater rod 307 may be initiated through the appropriate commands (not shown) to cause specimen stage module 140 to more quickly return to an ambient temperature. The status of such temperature change is indicated in specimen stage temperature status section 715 of main screen display 700. Once specimen stage module 140 has engaged in the load/unload position and the temperature of specimen stage module 140 has achieved ambient temperature, the chamber within load lock cap 280 is vented to the use of the appropriate command on vacuum control bar 760. As previously described, the operation of the vacuum and venting processes include the initiation of a base vacuum by roughing pump 93 and the utilization of turbomolecular pump 91 to establish a more significant vacuum as set by the operating parameters. The established vacuum within load lock cap 280 is vented through the opening of the appropriate valve, and an indication of ambient pressure within load lock cap 280 is displayed within vacuum/load lock status section 720. Load lock cap 280 may then be disengaged from end plate 262 and the specimen inserted within specimen mounting recess 358 and restrained by specimen restraining clips 359. It is to be specifically noted that specimen holder 335 may require modification for the use of alternatively shaped specimens, but such modifications are within the ambit of those skilled in the art. Additionally, interchangeable specimen holders 335 may be utilized by alternative mounting upon specimen stage gear 350A through the use of appropriate mounting devices. Having affixed the specimen in an appropriate position on specimen holder 335, load lock cap 280 is replaced in parallel engagement with end plate 262, and an appropriate command is issued through vacuum control bar section 760 to evacuate load lock cap 280 to an appropriate vacuum level. Once this is achieved, as indicated in vacuum/load lock status section 720, and the pump has established the appropriate vacuum, specimen positioning module 60 may be laterally displaced to place the specimen in an appropriate position within combined milling mechanism 15 for one of the two available milling operations. Movement of specimen positioning module 60 is initiated through the use of stage lateral displacement control bar 785 on motion control display 765. The displacement of specimen positioning module 60 away from engagement in the load/unload position allows secondary specimen support 135 to re-engage thermally conductive support 131 at specimen holder temperature transfer engagement surface 300. The interface of secondary specimen support 135 with thermally conductive support 131 causes specimen stage module 140 to be cooled by the liquid nitrogen media contained within dewar 155. The status of the temperature of specimen holder module 140 is illustrated within the specimen stage temperature status section 715 of main screen display 700, along with an indicator identifying the cooling function. Under normal conditions, a specimen is first grossly thinned utilizing high energy ion mill module 70, and then finished utilizing low energy ion mill module 75. In that situation, specimen positioning module 60 is activated through stage lateral displacement control bar 785 to the appropriate position as displayed in motion control status display 770 within high energy ion mill module 70. The milling parameters are defined by the user, and may be manually or programmatically controlled. These include time of milling, tilt and rotation of the specimen during the milling operation, the intensity of the ion impingement beam, temperature parameters for the specimen, selection of the process gas and the intensity of the end point detection illumination which will discontinue the operation of the milling procedure. These parameters are all identified and set through the use of main screen display 700, motion control display 765, or additional parameter displays (not shown) which would be conventional numeric displays. With respect to the rotation of the specimen, control of specimen holder 335 is initiated through stage rotation control bar 775, as previously described. The tilt function is also controlled by stage tilt control bar 780 while operation electrical parameters are controlled through activity selector display 755. In the event that a multiplicity of procedures are contemplated to be conducted under programmatic control, each step of the algorithm is input into activity list screen 750 through the use of appropriate commands and parameters selected through activity selector display 755 and the appropriate submenus contained therein. The operation of such a programmed algorithm may be initiated manually or may be saved to a data file for repeated or later use. The operation of low energy ion mill module 75 is analogous to the operation of high energy ion mill module 70 other than the need to laterally translocate specimen stage module 140 to the appropriate position through the use of stage lateral displacement control bar 785. As with high energy milling, low energy milling may be conducted in conjunction with a variety of motion parameters including tilt and rotation of the specimen. It is also contemplated that either module may be separately applied, as necessitated by circumstances. In either sequence, images of the milling operations may be viewed in real time on screen display 40, as well as stored in appropriate data files, as either still or full motion images, according to conventional imaging storage techniques and formats. Selection of the various screen displays related to imaging and motion are controlled through the use of activity button 740 in activity bar display 735. At the conclusion of milling operations, specimen holder module 140 is returned to the load/unload position and the procedure detailed previously regarding the loading of the specimen is repeated. In this manner, a sequence of specimens may be processed through combined milling mechanism 15 without the need to recreate the vacuum conditions within vacuum chamber 55 and low energy milling chamber 265. While a present preferred embodiment of the invention is described, it is to be distinctly understood that the invention is not limited thereto, but may be otherwise embodied and practiced with the scope of the following claims. |
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abstract | A carousel and first and second members have common axes in a first direction. The carousel, preferably cylindrical, has a ring-shaped configuration defined by inner and outer diameters. The first member has an outer diameter preferably contiguous to the carousel inner diameter. The second member has an inner diameter preferably contiguous to the carousel outer diameter. The carousel is divided into compartments by vanes. The carousel rotates at a substantially constant speed past radiation directed by an accelerator in the first direction. When a fault occurs in the system operation, (1) the carousel and radiation stop and (2) the carousel reverses in direction. When the fault is resolved, the carousel moves in the forward direction at the substantially constant speed and the radiation resumes at the position where the article was being irradiated at the time that the fault occurred. Each article is transferred from a first conveyor into one of the compartments from a position above the compartment and, after being irradiated, is transferred to a second conveyor from the position above the compartment. A cover at the top of the compartment normally covers the compartment. The cover becomes opened to provide for the article transfer into the compartment, remains open during the article irradiation in the compartment and becomes closed after the article transfer to the second conveyor. The leading edge of the article in the compartment is determined to facilitate the article transfer from the compartment after the article irradiation. |
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abstract | Collimator apparatus is provided for an X-ray imaging system comprising an X-ray tube disposed to project an X-ray beam, and a detector spaced apart from the X-ray tube for receiving X-rays of the beam within an Active Imaging Area (AIA). The apparatus comprises a first collimator positioned along the path of the beam, the first collimator being vertically adjustable, and being operable to symmetrically collimate the beam. The apparatus further comprises a second collimating device positioned between the first collimator and the detector. The second collimating device limits the uppermost rays of the symmetrically collimated beam which reach the detector to a predetermined upper boundary. Thus, the second collimating device serves to fix the upper edge of the AIA on the detector. At the same time, the second collimating device allows the lowermost rays of the symmetrically collimated beam reaching the detector, which define the lower edge of the AIA, to have a lower boundary which is determined by selective adjustment of the first collimator. |
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063234971 | claims | 1. An ion implantation system comprising: means for generating an ion beam; means for determining an ion beam current reference level; means for measuring an ion beam current during implantation; and means for adjusting an ion implantation parameter to compensate for vacuum fluctuations during implantation based on the reference level and the measured ion beam current, and not based on a detected pressure. a beam generator that generates an energetic ion beam and directs the beam toward a semiconductor wafer; a detector that detects an ion beam current; a wafer drive that moves the semiconductor wafer in a direction transverse to the ion beam path; and a controller that receives signals from the detector representative of a detected ion beam current, detects a vacuum fluctuation based on the detected ion beam current, and controls the wafer drive to adjust a wafer scan rate to compensate for the vacuum fluctuation during implantation. 2. An ion implantation system comprising: 3. The apparatus of claim 2, wherein the controller scales the difference value to account for non-line of sight and line of sight charge exchanging collisions experienced by ions in the beam along the ion beam path. 4. The apparatus of claim 3, wherein the difference value is scaled based on a ratio of line of sight collisions to non-line of sight collisions. 5. The apparatus of claim 2, further comprising a vacuum system, and wherein the controller controls the vacuum system to begin evacuation based on the determined difference value. 6. The apparatus of claim 2, wherein the detector is a Faraday cup positioned adjacent a semiconductor wafer. 7. The apparatus of claim 2, wherein the beam generator includes an angle corrector magnet. 8. The apparatus of claim 2, wherein the ion beam current reference value is determined based on an ion beam current measured while a vacuum level along the ion beam path is stable. 9. The apparatus of claim 2, wherein the ion beam current reference value is retrieved by the controller from a memory. 10. The apparatus of claim 2, wherein the controller detects a vacuum fluctuation based on a difference value between an ion beam current reference value, which corresponds to an ion beam current in the absence of vacuum fluctuations along an ion beam path, and an ion beam current measured in the presence of vacuum fluctuations along the ion beam path. 11. The apparatus of claim 2, wherein the controller adjusts an ion implantation parameter in addition to the wafer scan rate to adjust for wafer dosing non-uniformity in two dimensions. 12. The apparatus of claim 2, wherein the controller adjusts a wafer scan rate and a beam scan rate. 13. The apparatus of claim 12, wherein the controller adjusts the wafer scan rate and beam scan rate based on two scale factors. 14. The apparatus of claim 2, wherein the controller adjusts the wafer scan rate using a scale factor that is mathematically derived by modeling the implantation system. 15. The apparatus of claim 14, wherein the controller uses a scale factor that has been determined based on calculated beam path length neutral particle density products that are obtained, at least in part, from a model of an ion beam path and a vacuum system in the implantation system. |
claims | 1. A method for catalytic recombination of hydrogen, being carried in a gas flow, with oxygen, which comprises the steps of:adding steam to the gas flow before the gas flow enters a reaction zone;passing the gas flow through the reaction zone having a number of catalytic converter elements; andadjusting a feed rate of the steam to be added in dependence on a measured value being characteristic of a current actual temperature in the reaction zone. 2. The method according to claim 1, which further comprises adjusting the feed rate of the steam to be added such that the gas flow has a steam content of at least 70% by volume when the gas flow enters the reaction zone. 3. The method according to claim 1, which further comprises adjusting the feed rate of the steam to be added such that the gas flow has a hydrogen content of between 3 and 8% by volume when the gas flow enters the reaction zone. 4. The method according to claim 1, which further comprises adjusting the feed rate of the steam to be added in dependence on measured values which are characteristic of a plurality of current actual temperatures in the reaction zone. 5. The method according to claim 4, which further comprises adjusting the feed rate of the steam to be added in dependence on a development of the measured values over time. 6. The method according to claim 4, which further comprises providing at least one current actual inlet temperature and one current actual outlet temperature of the reaction zone as the measured values. 7. The method according to claim 1, which further comprises adjusting the feed rate of the steam to be added in dependence on a further measured value being characteristic of a current pressure loss in the reaction zone. 8. The method according to claim 1, which further comprises taking the gas flow from a turbine condenser of a nuclear power station. 9. A recombination system for catalytic recombination of hydrogen being carried in a gas flow, with oxygen, the recombination system comprising:a reaction zone having a number of catalytic converter elements;a steam supply line;an inlet line for supplying the gas flow into said reaction zone and connected to said steam supply line for adding steam as required;a metering valve connected in said steam supply line;a number of temperature sensors associated with said reaction zone; anda control unit controlling said metering valve and having a data input side connected to said number of temperature sensors, said control unit controlling said metering valve for adjusting a flow of the steam in dependence on values derived from said temperature sensors. 10. The recombination system according to claim 9, wherein said control unit is a regulator unit with a temperature value of said reaction zone as a reference variable. 11. The recombination system according to claim 9, wherein said control unit has a data memory. 12. The recombination system according to claim 9, wherein said inlet line has an inlet side connected to a turbine condenser of a nuclear power station. 13. The recombination system according to claim 12, wherein said inlet line has a branch line connected to a safety vessel of the nuclear power station. 14. The recombination system according to claim 9, further comprising:a compressor disposed along said steam supply; anda steam jet pump disposed along said inlet line, said steam supply line is connected to said steam jet pump for providing a propellant steam pressure that can be regulated, and, after said compressor the propellant steam pressure is more than five to ten times a steam jet pump outlet pressure. |
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abstract | An apparatus for control of a procedure, comprising: a communications interface; a control console, wherein the control console is adapted to provide control commands via the communications interface to at least one of: at least one imaging device or at least one medical instrument used to perform the procedure; and, at least one radiation shield attached to the control console and positioned between the control console and a patient on which the procedure is being performed, wherein the apparatus is separately movable from at least one of the at least one imaging device, the patient or the at least one medical instrument. |
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060977906 | abstract | A pressure partition includes a thin film for dividing a predetermined space into two spatial zones and a supporting device for supporting the film at an outside peripheral portion thereof. The supporting device has a curved surface for producing curvature in the outside peripheral portion of the film. The curved surface is disposed at one of the two spatial zones having a lower pressure as compared with the other, and the curved surface has a convex shape with respect to a plane intersecting the film. |
description | This is a continuation in part of U.S. Ser. No. 12/072,851 filed on Feb. 28, 2008, which claims priority of German application No. 10 2007 010 132.7 filed Feb. 28, 2007 and claims priority of German application No. 10 2008 007 245.1 filed Feb. 1, 2008. All of the applications are incorporated by reference herein in their entirety. The invention relates to a combined radiation therapy and magnetic resonance unit. Generally in radiation therapy the aim is to irradiate a target within the human body in order to combat diseases, in particular cancer. For this purpose a high dose of radiation is specifically generated in an irradiation center (isocenter) of an irradiation apparatus. During irradiation the problem often arises that the irradiation target in the body can move. For instance, a tumor in the abdomen can move during breathing. On the other hand, in the period between radiation treatment planning and actual radiation treatment a tumor may have grown or have already shrunk. It was therefore proposed to check the position of the irradiation target in the body during radiation treatment by imaging, in order to control the beam or if necessary discontinue the irradiation, and thus increase the success of the therapy. This is in particular relevant for irradiation targets in the upper and lower abdomen as well as in the pelvic area, for example the prostate. To minimize the dose of radiation outside the target volume and thus protect healthy tissue, the entire radiation generation is moved around the patient. This concentrates the radiation dose in the beam in the area of the rotational axis. Both X-ray and ultrasound systems were proposed as the imaging medium for monitoring the therapy. These, however, provide only a limited solution to the problem. In the case of ultrasound imaging the necessary penetration depth is lacking for many applications. In X-ray imaging the X-ray sensors can be disrupted or damaged by the gamma radiation of the accelerator. Furthermore, the quality of the tissue images is often unsatisfactory. For this reason, at present mainly positioning aids and fixing devices or markings made on the skin of the patient are used to ensure that the patient is in the same position in the irradiation apparatus as decided in the radiation treatment planning and that the irradiation center of the irradiation apparatus is actually consistent with the irradiation target. These positioning aids and fixing devices are, however, expensive and in most cases they are also uncomfortable for the patient. In addition, they conceal the risk of irradiation errors because as a rule no further check of the actual position of the irradiation center is carried out during irradiation. Magnetic resonance is a known technique which permits both particularly good soft-tissue imaging as well as spectroscopic analysis of the area being examined. As a result this technique is fundamentally suitable for monitoring radiation therapy. In U.S. Pat. No. 6,366,798 a radiation therapy device is combined with various magnetic resonance imaging systems. In all the different versions mentioned here the magnet arrangement of the magnetic resonance imaging system is divided into two parts. In addition, in some versions key parts of the magnetic resonance imaging system rotate with the radiation source of the radiation therapy device. In each case the radiation source is outside the magnetic resonance imaging system and must be protected by means of shields from the stray field of the magnetic resonance imaging system. A division of the magnet, a rotatable magnet and shielding of the radiation source represent elaborate technical solutions and increase the cost. In GB 2 427 479 A, U.S. Pat. No. 6,925,319 B2, GB 2 247 478 A, US 2005/0197564 A1 and US 2006/0273795 A1 further devices are described in which a radiation therapy device or an X-ray imaging system are combined with a magnetic resonance imaging system. GB 2 393 373 A describes a linear accelerator with an integrated magnetic resonance imaging system. In one exemplary embodiment the magnetic resonance imaging system comprises means for compensation of a magnetic field in order to minimize the field strength of the magnetic field of the magnetic resonance imaging system at the location of the accelerator. In another exemplary embodiment a filter is used in order to compensate for possible heterogeneity caused in a therapy beam by the magnetic field of the magnetic resonance imaging system. The object underlying the invention is therefore to provide a combined radiation therapy and magnetic resonance unit which with little constructional expense permits high-quality image monitoring by means of magnetic resonance during radiation therapy. This object is achieved by the subject matter of the independent claim. Advantageous embodiments are described in the dependent claims. In accordance with the invention a combined radiation therapy and magnetic resonance unit is provided comprising a magnetic resonance diagnosis part with an interior which is limited in radial direction by a main magnet, and a radiation therapy part for irradiation of an irradiation area within the interior, whereby at least parts of the radiation therapy part are located within the interior. The magnetic diagnosis part permits a movement analysis of the irradiation target in real time and thus optimal monitoring and control of radiation therapy. The integration of the radiation therapy part in a magnetic resonance device and the resultant proximity of the radiation therapy part to the irradiation target permit a high radiation luminance as well as high accuracy in controlling the beam path. The use of a conventional main magnet is possible. Advantageously, the radiation therapy part comprises an electron accelerator. Electrons are simple to generate and the accelerated electrons can easily generate a therapy beam. In a particularly advantageous embodiment an electron beam direction runs essentially parallel to the axis of the main magnetic field in the electron accelerator. Electrons which move parallel to a magnetic field are not influenced by it in their flight path. It is therefore easier to determine their flight direction and speed compared with electrons influenced or accelerated by magnetic fields. Advantageously, the radiation therapy part comprises a beam deflection arrangement which in particular comprises an electromagnet which deflects the electron beam inward into the interior. In this way the accelerated electrons are directed into the desired therapy beam direction. In a particularly advantageous embodiment the beam deflection arrangement comprises a pulsed magnet. This can (briefly) generate a magnetic field as big as the main magnetic field or bigger without any particular expense. Moreover, by using particularly short pulses, disruption of the magnetic resonance device is minimized. Expediently, the radiation therapy part comprises a target anode to produce an X-ray beam along an X-ray beam path. X-ray radiation, in particular high-energy X-ray radiation, is particularly suitable for radiation therapy and is not influenced by the electromagnetic fields prevailing in a magnetic resonance device. In a particularly advantageous embodiment the target anode is a transmission anode. A transmission anode is particularly suitable for generating high-energy X-ray radiation. In a further embodiment a homogenizing body is arranged in the X-ray beam path after the target anode. The homogenizing body for example weakens the beam core and homogenizes the X-ray beam distribution in the beam cross-section. Advantageously, a collimator is arranged in the X-ray beam path after the target anode. The collimator enables the direction of the X-ray beam and the cross-section of the X-ray beam to be regulated. In a particularly advantageous embodiment the collimator is arranged at least partially between two axially distanced partial gradient coils of the magnetic resonance device. This represents a particularly space-saving arrangement and at the same time provides for advantageous proximity to the irradiation target. In a further advantageous embodiment the collimator comprises adjusters for changing the cross-section of the X-ray beam. As a result, the cross-section of the X-ray beam can be ideally adapted to the shape of the irradiation target. At least partial gradient coils of the gradient coil system are advantageously shielded against the radiation therapy part. This permits independent, in particular also simultaneous, operation of the radiation therapy part, which rotates in operation, and of the magnetic resonance diagnosis part as the changing gradient fields of the gradient coils in this way do not influence the rotating radiation therapy part. If the radiation therapy part is rotatable around the axis of the main magnetic field the further advantage results that the applied dose of radiation outside the target volume, i.e. outside the irradiation center, can be minimized. This means that adverse effects on healthy tissue during radiation therapy are reduced. FIG. 1 shows a schematic representation (not to scale) of a combined radiation therapy and magnetic resonance unit 1 with a magnetic resonance diagnosis part 3 and a radiation therapy part 5. The magnetic resonance diagnosis part 3 comprises a main magnet 10, a gradient coil system comprising two in this case symmetrical partial gradient coils 21A,21B, high-frequency coils 14, for example two parts of a body coil 14A,14B, and a patient bed 6. All these components of the magnetic resonance part are connected to a control unit 31 and an operating and display console 32. In the example presented, both the main magnet 10 and the partial gradient coils 21A,21B are essentially shaped like a hollow cylinder and arranged coaxially around the horizontal axis 15. The inner shell of the main magnet 10 limits in radial direction (facing away vertically from the axis 15) a cylinder-shaped interior 7, in which the radiation therapy part 5, the gradient system, high-frequency coils 14 and the patient bed 6 are arranged. More precisely the radiation therapy part 5 is located in the interior 7 between the outer side of the gradient coil system 21A and 21B and the inwardly facing shell surface of the main magnet 10. In addition to the magnet coils the main magnet 10 comprises further structural elements, such as supports, housing etc., and generates the homogenous main magnetic field necessary for the magnetic resonance examination. In the example shown the direction of the main magnetic field is parallel to the horizontal axis 15. High-frequency excitation pulses which are irradiated by means of high-frequency coils 14 are used to excite the nuclear spins of the patient. The signals emitted by the excited nuclear spins are also received by high-frequency coils 14. The axially distanced partial gradient coils 21A,21B in each case comprise gradient coils 20, which are in each case completely enclosed by a shield 27. The gradient coil 20 comprises supports and individual gradient coils which irradiate magnetic gradient fields for selective layer excitation and for location-coding of the magnetic resonance signals in three spatial directions. The radiation therapy part 5 is arranged on a gantry 8 and comprises an electron accelerator 9, which here is configured as a linear accelerator, a beam deflection arrangement 17, a target anode 19, a homogenizing body 22 and a collimator 23. The gantry 8 can feature a recess (broken lines), by which access to the magnetic resonance diagnosis part remains possible also from this side. The electron accelerator 9 of the radiation therapy part 5 comprises an electron source 11, for example a tungsten cathode, which generates an electron beam 13, which is accelerated by the electron accelerator 9 preferably pulsed parallel to the main magnetic field of the main magnet 10. The electron accelerator 9 for example generates electron beam pulses with a length of 5 μs every 5 ms. If the electron accelerator 9 generates pulsed electron beams 13, it can be built more compactly, e.g. with a length of about half a meter, and still withstand the impact of the high-energy electron beams 13. The electrons of the electron beam 13 are accelerated by electric alternating fields in cylinder-shaped hollow conductors of the electron accelerator 9. The electrons of the electron beam 13 are accelerated to energies up to a magnitude of several MeV. The electron accelerator 9 is connected to an accelerator control unit 12 to control the alternating fields and the electron source 11. The electron beam 13 leaves the electron accelerator 9 at the end opposite the electron source and is deflected by the beam deflection arrangement 17 through 90° radially inward in the direction of axis 15. For this purpose the beam deflection arrangement 17 comprises a magnet which generates a suitable magnetic field. The magnet is configured as an electromagnet made of non-ferromagnetic materials to prevent undesired interaction with the surrounding magnetic fields. As the beam deflection arrangement 17 has to work in a strong, outer magnetic field, it has been modified compared with conventional beam deflection arrangements. To be able to deflect the pulsed electron beam 13 in a small space, the beam deflection arrangement 17 must generate strong magnetic fields. To reduce the power loss, the magnetic field of the beam deflection arrangement 17 is a pulsed magnetic field which is synchronized with the pulsed electron beam 13. For this purpose the beam deflection arrangement 17 is connected to a beam deflection control unit 18 which is also connected to the accelerator control unit 12. The deflected electron beam 13 hits the target anode 19 and generates an X-ray beam that emerges from the target anode in the beam elongation along an X-ray beam path. The X-ray beam is homogenized by the homogenizing body 22. The collimator 23 is arranged in an annular slot between the distanced partial gradient coils 21A,21B in the X-ray beam after the target anode 19. The proximity to the irradiation target thus achieved improves the radiation luminance and also the effectiveness of the collimator 23. The collimator 23 enables the direction of the X-ray beam and the cross-section of the X-ray beam to be influenced. For this purpose the collimator 23 incorporates moveable adjusters 24, which permit the X-ray beam to pass only in a certain direction, e.g. only parallel to the radial axis 26 or up to at most in one direction through an angle α away from the axis 26, and only with a certain cross-section. It is also possible to set the adjusters 24 of the collimator 23 in such a way that no X-ray beams can pass parallel to the axis 26 and only angled X-ray beams in one direction through certain angles away from the axis 26 can pass through. To control the adjusters 24 the collimator 23 is connected to a collimator control unit 25. Such collimators are adequately known. By way of example reference can be made to multi-leaf collimators. They make it possible to perform intensity modulated radiation therapy (IMRT), in which the size, shape and intensity of the X-ray beam can be optimally adapted to the irradiation target. In particular IMRT also enables the irradiation center to be positioned outside the rotational axis of the radiation therapy device. The X-ray beam penetrates the examination subject, in this case the patient P, and the X-ray beam path runs through a diagnosis volume D of the magnetic resonance diagnosis part 3. To minimize the local dose of radiation outside the irradiation target volume, the radiation therapy part rotates around the axis of the main magnetic field. As a result, the full dose is applied only in the irradiation center B. The collimator 23 constantly adapts the cross-section of the X-ray beam to the actual outline of the irradiation target even during rotation. The gantry 8 is configured for rotation of the radiation therapy part. A gantry control unit 29 controls the movement of the radiation therapy part 5. As an example the radiation therapy part 5 is shown as radiation therapy part 5′ after rotation through 180°. The gantry control unit 29, the collimator control unit 25, the beam deflection control unit 18, the accelerator control unit 12 and the control unit 31 are connected to each other so that the diagnosis data collected by the magnetic resonance diagnosis part, for example the three-dimensional shape of the irradiation target, the rotational position of the radiation therapy part, as well as the collimator settings with regard to cross-section and direction of the X-ray beam and the generation of pulsed beams described above can be coordinated with each other. The patient bed 6 is preferably moveable in three spatial directions so that the target area of the irradiation can be positioned precisely in the irradiation center B. For this purpose the control unit 31 is expediently configured for controlling a movement of the patient bed. FIGS. 2 to 4 show segments of further exemplary configurations of a combined radiation therapy and magnetic resonance unit in accordance with the invention. In the exemplary configurations shown in particular the arrangement of a respective radiation therapy part 5,105,205,305 varies from the exemplary embodiment in FIG. 1. For the sake of clarity, therefore, only the upper section of a main magnet 110,210,310 of the combined radiation therapy and magnetic resonance unit up to about one high-frequency coil 114,214,314 of the combined radiation therapy and magnetic resonance unit is shown. The rest of the configuration and its mode of operation are, unless otherwise described, essentially the same as in the example shown in FIG. 1, to which reference is hereby made. FIG. 2 shows a main magnet 110 of the combined radiation therapy and magnetic resonance unit on whose side facing an interior 107 of the combined radiation therapy and magnetic resonance unit a gradient coil system 120 is arranged. The gradient coil system 120 comprises in particular primary coils 121 and secondary coils 122. Between primary coils 121 and secondary coils 122 a free space is located in which the radiation therapy part 105 of the combined radiation therapy and magnetic resonance unit is arranged. Such a distanced arrangement of the primary and secondary coils 121 and 122 increases the efficiency of the gradient coil system 120. In addition, high-frequency coils 114 are arranged on the side of the gradient coil system facing the interior 107. The gradient coil system 120 or at least the primary coils 121 as shown in the example in FIG. 1 can be divided into two partial gradient coils 121A,121B and arranged in such a way that at least parts of the radiation therapy part 105 can move in an annular space between the parts in a rotation of the radiation therapy part 105 around the axis of the main magnetic field. In this case the high-frequency coils 114 are also advantageously divided correspondingly into two partial high-frequency coils 114A and 114B. Alternatively it is conceivable for the gradient coil system 120 to be configured in such a way that together with the radiation therapy part 105 it can rotate around the axis of the main magnetic field. In this case a division of the gradient coil system 120 or of the primary coils is not absolutely appropriate. It suffices to configure the primary coil 121 in such a way that it can let the radiation therapy part 105 penetrate into the interior 107 at one point in order to emit the therapy beams onto an irradiation center B. The same applies to the high-frequency coils 114. It may be necessary here to compensate for the mechanical turning of the gradient coil system 120 by suitable activation of the gradient currents. Such an electric rotation of gradient fields is, however, a usual capability of standard magnetic resonance systems. Nevertheless, high requirements should be imposed on the accuracy and reproducibility of the rotation. Thanks to its particularly compact design this exemplary embodiment gives the patient an exceptional amount of room in the interior 107. Advantageously, a collimator of the radiation therapy part 105 is incorporated in a particularly flat configuration in the exemplary embodiment shown in FIG. 2 in order to give the patient even more room in the interior 107 of the combined radiation therapy and magnetic resonance unit. FIG. 3 presents a segment of a further exemplary embodiment of a combined radiation therapy and magnetic resonance unit. In this exemplary embodiment a gradient coil system 220 as in a standard magnetic resonance device is arranged on the side of a main magnet 210 facing an interior 207 of the combined radiation therapy and magnetic resonance unit. Standard components can be used for the main magnet 210 and the gradient system 220, which among other things reduces cost. Again on the side of the gradient system 220 facing the interior 207 high-frequency coils 214 are arranged. Between the gradient system 220 and the high-frequency coils 214, however, adequate space is left in order to arrange a radiation therapy part 205 of the combined radiation therapy and magnetic resonance unit between the gradient system 220 and the high-frequency coils 214. During irradiation of an irradiation center B the radiation therapy part 205 rotates around the main magnetic field axis of the combined radiation therapy and magnetic resonance unit. In a similar way as in the exemplary embodiment of FIG. 2 the high-frequency coils 214 can here too either be divided into two partial high-frequency coils 214A and 214B in such a way that at least parts of the radiation therapy part 205 can move in an annular gap between the partial high-frequency coils 214A and 214B. Or the high-frequency coils 214 can be rotated with the radiation therapy part 205. FIG. 4 shows schematically a segment of a further exemplary embodiment of a combined radiation therapy and magnetic resonance unit. In this case, as in a conventional design of a magnetic resonance unit, high-frequency coils 314 are arranged within a gradient system 320 which itself is arranged within a main magnet 310. A radiation therapy part 305 is arranged on the side facing an interior 307 of the combined radiation therapy and magnetic resonance unit. As in the exemplary embodiments presented above the radiation therapy part 305 rotates during irradiation around the main magnetic field axis of the combined radiation therapy and magnetic resonance unit. In this exemplary embodiment no particular structural measures are necessary with regard to the gradient system 320 and the high-frequency coils 314 to make this rotational movement of the radiation therapy part possible. Advantageously the inner radius of the high-frequency coils 314 is as big as possible and the radiation therapy part is as flat as possible so that the patient is not cramped in the interior 307. The radiation therapy part 105,205,305 of the exemplary embodiments in FIGS. 2 to 4 in each case incorporates essentially the same construction as the radiotherapy part 5 from the exemplary embodiment in FIG. 1. For the sake of clarity the individual components are not shown again. The rotational movement of the radiation therapy parts 105,205,305 and/or the gradient coil system 120,220,320 and/or the high-frequency coils 114,214 is indicated in each case by a broken-line arrow. If necessary, in the exemplary embodiments of FIGS. 2, 3 and 4 the radiation therapy part 105,205,305 and the magnetic resonance part, in particular the gradient system 120,220,320 and/or the high-frequency coils 114,214,314, are not operated at the same time but are alternated in order to exclude possible disruptive interaction, in particular between moving parts of the radiation therapy part 105,205,305 and electromagnetic alternating fields of the magnetic resonance part. FIGS. 5 to 8 show three examples of possible configurations of beam deflection arrangements 17 which can be used in a radiation therapy part 5,105,205,305. FIG. 5 shows a beam deflection arrangement 17′ which consists of two annular deflection coils 17A′ and 17B′. The deflection coils 17A′,17B′ are arranged in a combined radiation therapy and magnetic resonance unit essentially vertically to the main magnetic field of the main magnet of the combined radiation therapy and magnetic resonance unit. The field direction of the deflection coils 17A′,17B′ runs essentially parallel to a radial axis 26 of the combined radiation therapy and magnetic resonance unit, i.e. in the direction of exit desired for a therapy beam. Through the combination of the main magnetic field and the magnetic field of the deflection coils 17A′,17B′ an electron beam 13′ is deflected in the desired direction. The current density in the deflection coils 17A′,17B′ must be determined among other things according to the main magnetic field strength of the combined radiation therapy and magnetic resonance unit and energy of the electron beam. For example, with an electron beam of 6 MeV and a main magnetic field of 1.5 T the deflection coils 17A′,17B′ can deflect the beam in the desired direction if the current density in the deflection coils 17A′,17B′ amounts to approx. 500 MA/m2. FIGS. 6 to 8 show beam deflection arrangements 17″ and 17′″, whose configurations were calculated by means of computer simulation programs, for example based on a finite elements method or a finite differences method. In each case the underlying problem was the question as to how an electron beam which enters a main magnetic field in a parallel direction can be deflected in a direction which is vertical to the main magnetic field in order to hit a target. For this purpose, the field necessary for such deflection and how it can be produced were calculated. FIG. 6 shows an active coil pair 17″ as the beam deflection arrangement which is shaped in such a way that it solves the problem posed. An electron beam 13″ arriving parallel to a horizontal axis 15, and therefore in the direction of a main magnetic field of a combined radiation therapy and magnetic resonance system, enters between the coil pair 17″ at the position “I” and is guided in such a way that it leaves the coil pair 17″ parallel to a radial axis 26 of the combined radiation therapy and magnetic resonance unit at the position “O”. The strength of the field strength of the coil pair 17″ can be varied according to the energy of the electron beam. An exemplary coil pair 17″ generates a quadrature-axis field of approx. 0.3 T. As a result, e.g. an electron beam of 6 MeV can be deflected in a combined radiation therapy and magnetic resonance unit of 1.5 T field strength in the desired way. FIGS. 7 and 8 present a further possible solution of the above-mentioned problem, this time using a passive beam deflection arrangement. As shown in FIG. 7, the beam deflection arrangement 17′″, which generates the quadrature-axis field necessary for solving the problem, comprises four deflection units 117A,B,C,D. The arrangement of the deflection units 117A,B,C,D was determined by iteration in such a way that an electron beam 13′″ entering parallel to a main magnetic field as shown in FIG. 7 from the right into the deflection unit 117A is deflected in such a way by deflection unit 117A to deflection unit 117B that the electron beam 13′″ is deflected upward through deflection unit 117B. From deflection unit 117B the electron beam 13′″ is deflected by deflection unit 117C, whereby the electron beam 13″ leaves the deflection unit 117C in such a way that it is deflected downward to deflection unit 117D, so that it leaves deflection unit 117D vertically to the main magnetic field. References such as “upward”, “downward”, “right” and “left” relate in each case to the example shown in FIG. 7. FIG. 8 shows more precisely a deflection unit 117. The deflection unit 117 comprises several permanent magnets 118A,B,C,D,E,F,G,H, which are preferably made of rare earths, e.g. NdFeB or SmCo. FIGS. 7 and 8 present a further possible solution of the above-mentioned problem, this time using a passive beam deflection arrangement. As shown in FIG. 7, the beam deflection arrangement 17′″, comprises four deflection units 117A,B,C,D. Each of these deflection units is a magnetic dipole generating a magnetic field which is substantially perpendicular to the direction of the charged particle beam as it passes through the dipole. The angle of rotation of the dipole's magnetic field about the direction of the charged particle beam is selected to provide the desired deflection of the charged particle path. It is the interaction of the dipole magnetic field and the charged particles flowing in a direction perpendicular to the dipole magnetic field which causes a force to act upon the charged particles as they travel through the dipole magnetic field and causes deflection of their path. The direction of the deflection is perpendicular to the dipole magnetic field and perpendicular to the direction of travel of the charged particle beam as it arrives at the dipole magnetic field. For this reason, each of the dipoles 117A,B,C,D are arranged with their dipole magnetic fields substantially perpendicular to the particle beam as it passes through the corresponding dipole magnetic field. The arrangement of the deflection units 117A,B,C,D may be determined by iteration or modeling in such a way that an electron beam 13′″ entering the first deflection unit in a direction parallel to a main magnetic field, as shown in FIG. 7 from the right into the deflection unit 117A, is deflected in such a way by deflection unit 117A to deflection unit 117B that the electron beam 13′″ is deflected upward through deflection unit 117B. From deflection unit 117B the electron beam 13′″ is deflected by deflection unit 117C, whereby the electron beam 13″ leaves the deflection unit 117C in such a way that it is deflected downward to deflection unit 117D, so that it leaves deflection unit 117D vertically to the main magnetic field. References such as “upward”, “downward”, “right” and “left” relate in each case to the example shown in FIG. 7. The degree and direction of deflection caused by each deflection unit will vary according to the angle of rotation about the beam path of the dipole magnetic field, and the orthogonality of the dipole magnetic field to the beam path. The deflection effects if each deflection unit may be controlled by selecting the angle of rotation of the dipole field about the direction of the charged particle beam, and suitable selecting the strength of the dipole magnetic field. FIG. 8 shows more precisely an example of a deflection unit 117. The deflection unit 117 comprises several permanent magnets 118A,B,C,D,E,F,G,H, which are preferably made of rare earths, e.g. NdFeB or SmCo. For example, to deflect a 6 MeV electron beam in a main magnetic field of 1.4 T in the desired way, six permanent magnets 118A,B,C,D,E,F with dimensions of approx. 10×4×4 mm and two permanent magnets 118G,H with dimensions of 10×8×4 mm are arranged as shown. In each case three of the permanent magnets of the smaller size 118A,B,C,D,E,F are stacked on top of each other with alternating direction of the respective magnetic fields of the permanent magnets 118A,B,C,D,E,F. The two larger permanent magnets 118G,H are arranged between this stack. The arrows indicate the respective magnetic field directions in the permanent magnets 118A,B,C,D,E,F,G,H. This configuration is particularly easy to produce and, furthermore, forms a particularly compact solution. In addition, only low static forces are exerted here, so that no particular fastening measures are needed. Furthermore, initial results show that the beam deflection arrangement 17′″ produces only a very small stray field. However, permanent magnets are sensitive to changes in the ambient temperature or the surrounding main magnetic field. The resulting dipole magnetic field of the deflection unit 117 of FIG. 8 will be in a direction from magnet 118G to magnet 118H, perpendicular to the path of a charged particle beam passing through the deflection unit. By arranging such deflection units with their magnetic dipoles substantially perpendicular to the charged particle beam, and at desired angles of rotation about the charged particle beam, a desired deflection path may be obtained in three dimensions, such as shown in FIG. 7, even in the presence of a background magnetic field. Further examples of suitable deflection units, each producing a dipole magnetic field and each suitable for use in an arrangement such as shown in FIG. 7 are shown in FIGS. 9A to 9D. The arrangement of 9A has the advantage of low stray fields, which may be important when placed within an MRI system, so as not to interfere with the magnetic fields used for imaging. However, it does require the production of several different orientations of magnetized trapezium cross-section pieces. A similar arrangement, but with even lower stray field losses, is shown in FIG. 9B, where arc-shaped cross-section magnetized pieces are assembled into a cylindrical deflection unit. FIG. 9C shows a deflection unit made up of an arrangement of identical magnetized octagonal cross-section pieces. This arrangement has the advantage that only one type of magnetized piece is required, and has been found to have a tolerable stray magnetic field. The arrangement of FIG. 9D is further simplified, requiring only four identical magnetized pieces. In the illustrated example, these are of square cross-section. While simple, light and cost-effective, this arrangement has a significant stray field and a correspondingly low dipole magnetic field at the centre of the deflection unit. In the following description, arrangements such as shown in FIG. 9C, employing magnetized pieces of octagonal cross-section, will be referred to. While arrangements such as shown in FIG. 7 have been found to deflect the charged particle beams satisfactorily, some degradation of beam focus and beam quality has been observed. Prior to entering the first deflection unit 117A, the charged particle beam 13′″ is travelling parallel to the background magnetic field of the main magnet 10. This helps to maintain beam focus and quality, as any divergence of charged particles from the direction of the main beam path will interact with the background magnetic field and cause a force to act on the diverging particles which acts to return them to the main beam path. However, once the particle beam has diverged from its path parallel to the background magnetic field, for example as a result of the interaction with a first deflection unit 117A, the beam focus degrades, resulting in a loss of quality of the beam. The beam becomes wider and less intense. The effect continues with further deflections and with increasing path length. According to an aspect of the invention, a multipole magnetic field unit is introduced, along with the dipole deflection units discussed above. The multipole magnetic field unit may be a quadrupole of higher polar magnetic field unit, as will be discussed further below. FIGS. 10A-10E show examples of quadrupole magnetic field units, similar to the dipole deflection units of FIGS. 8, 9A-9D respectively. Representative magnetic fields are also shown within the central cavity of each quadrupole. As can be seen, the magnetic field strength at the centre of the quadrupole is essentially zero, with magnetic fields in alternating directions around the periphery of the cavity. Quadrupole magnetic field units similar to those shown in FIGS. 10A-10E are known in themselves, for use in the field of high-energy physics, for example in relation to particle beams operating with energies of several GeV. Their use in relation to linear accelerators for medical particle beam therapy, where beam energies of 6 MeV are typical, is believed to be hitherto unknown. There has previously been no issue of beam defocus and beam quality reduction in medical particle beam therapy apparatus due to the very different equipment conventionally used for beam steering. Conventionally, the particle beams were filtered, for example by bending the beam through 270°, to remove particles of unusually low or high energies. This filtering generated a lot of heat which required cooling, and the equipment was large, expensive and heavy. Use of quadrupole magnetic field units and presently proposed dispenses with these cooling requirements. That part of a particle beam which passes through the centre of the cavity of the quadrupole passes through a region of zero magnetic field from the quadrupole, and its trajectory is unchanged by the quadrupole, although it may still be influenced by the background magnetic field. For diverging parts of the beam, caused by the loss of focus and reduction in beam quality, these will encounter one of the magnetic fields which extend in alternating directions around the periphery of the cavity. When a part of the beam encounters one of these fields, it will experience a force tending to deflect it back towards the centre of the beam, radially re-focusing the beam and compensating for dispersion introduced by the steering. In this way, the quadrupole will tend to refocus the particle beam, but will not deflect it from its trajectory. The refocusing performed by a quadrupole is not perfect, and there is a tendency for the refocused beam to have a somewhat cruciform cross-section. In alternative embodiments, higher-polar arrangements, such as sextupole or octupole and so on may be used instead of, or in conjunction with, a quadrupole magnetic field unit. The higher-polar arrangements will be less powerful at focusing for a given size and field strength of it components, but will not deform the cross-section of the beam as much as a quadrupole. FIG. 11 shows an embodiment of a beam deflection apparatus according to an embodiment of the present invention, using dipole deflection units 210 and a quadrupole magnetic field unit 220. In this embodiment, the dipole deflection units 210 and quadrupole magnetic field unit 220 are constructed from magnetized octagonal cross-section pieces as shown in FIGS. 9C and 10D. FIGS. 12 and 13A-13D show further views of the same arrangement. This embodiment resembles the arrangement of FIG. 7 in that it includes a sequence of four dipole deflection units 210, with a quadrupole magnetic field unit 220 placed in the middle of the sequence. Each of the dipole deflection units functions to deflect the charged particle beam 13 as in the arrangement of FIG. 7, and the quadrupole magnetic field unit acts to refocus the beam. The quadrupole magnetic field unit 220 may be replaced with a higher polar arrangement such as a sextupole or octupole of similar construction, if preferred. The quadrupole or higher polar arrangement may be positioned in the path of the particle beam amongst the steering dipoles, for example in a DDQDD arrangement as shown in FIGS. 11-13D. Alternatively, the quadrupole or higher polar arrangement may be positioned in the path of the particle beam after all of the dipole deflection units, which may be referred to as a DDDDQ arrangement, if four dipoles are used as in the arrangement of FIG. 7. In further embodiments, more than one quadrupole or higher polar arrangement may be used, for example in a DDQDDQ arrangement. In embodiments using only a single quadrupole or higher polar arrangement, it may be preferred to place the quadrupole or higher polar arrangement after the last dipole in the direction of the particle beam, so that the refocusing and beam quality improvement may correct the distortions introduced by the beam deflection at all dipoles. Alternatively, use of two or more quadrupole or higher polar arrangements allows partial correction of defocus and loss of beam quality before the beam spreads so far that it can no longer be corrected by a single final quadrupole or higher polar arrangement. Two or more quadrupoles or higher polar arrangements may be used in sequence, such as in a DDDDQQ arrangement, which will allow a desired focusing and beam quality restoration effect while allowing a lower field strength in each quadrupole or higher polar arrangement. This may help to minimize distortion of the magnetic fields of the imaging system. A computer modeling step may be performed to determine the necessary positions, orientations and magnetic field strengths of the dipoles and quadrupoles or higher polar arrangements so as to achieve the desired beam steering with an acceptable final beam quality. While the dipoles, quadrupoles and higher polar arrangements have been described above in terms of permanent magnets, alternative embodiments of the present invention provide such structures in the form of electromagnets, preferably using coils of non-magnetic wire such as copper or aluminum to minimize distortion of the magnetic fields of the imaging system. If required, control may be exercised over the final beam quality by variation of a parameter of the quadrupole(s) or higher polar arrangement(s), for example by repositioning of a permanent magnet quadrupole, or electrical control of electromagnet quadrupoles. Further improvements in final beam quality may be achieved by using edge focusing. |
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claims | 1. An extreme ultraviolet (EUV) radiation source, comprising:a fuel droplet generator configured to provide a plurality of fuel droplets to an EUV source vessel along a first trajectory;a primary laser configured to generate a primary laser beam along a second trajectory that intersects the first trajectory at a non-perpendicular angle, wherein the primary laser beam has a sufficient energy to ignite a plasma that emits extreme ultraviolet radiation from the plurality of fuel droplets; anda collector mirror located between the primary laser and the first trajectory and having a concave curvature configured to focus the extreme ultraviolet radiation to an exit aperture of the EUV source vessel that is not linearly aligned with the second trajectory of the primary laser beam. 2. The EUV radiation source of claim 1, further comprising:a protection element linearly aligned with the primary laser beam and configured to absorb remnants of the primary laser beam passing through the first trajectory of the plurality of fuel droplets. 3. The EUV radiation source of claim 2, wherein the protection element is located outside of a path of the EUV radiation focused by the collector mirror to the exit aperture. 4. The EUV radiation source of claim 2, wherein the collector mirror has an opening extending through the collector mirror at a location that is offset from a center of the collector mirror. 5. The EUV radiation source of claim 2, further comprising:a second fuel droplet generator configured to provide a second plurality of fuel droplets to the EUV source vessel along a third trajectory;a second primary laser configured to generate a second primary laser beam along a fourth trajectory that intersects the third trajectory at a second non-perpendicular angle; anda second protection element linearly aligned with the second primary laser beam on an opposite side of the second trajectory as the second primary laser. 6. The EUV radiation source of claim 5, wherein the second trajectory and the fourth trajectory are not parallel. 7. The EUV radiation source of claim 5, wherein the protection element and the second protection element are disposed onto opposite sides of the exit aperture of the EUV source vessel. 8. The EUV radiation source of claim 1, wherein the collector mirror is configured to focus the EUV radiation a downstream scanner comprising a plurality of mirrors configured to convey the extreme ultraviolet radiation to a semiconductor workpiece. 9. The EUV radiation source of claim 8, further comprising:an intermediate focus unit comprising a cone shaped aperture arranged within the exit aperture between the EUV source vessel and the scanner. 10. The EUV radiation source of claim 1, further comprising:a pre-pulse laser configured to generate a pre-pulse laser beam, having a lower energy than the primary laser beam, along a fifth trajectory that is not perpendicular to the first trajectory, wherein the pre-pulse laser is arranged so that the pre-pulse laser beam deforms the plurality of fuel droplets prior to the primary laser beam hitting the plurality of fuel droplets. 11. An EUV radiation source, comprising:a tin droplet generator configured to provide a plurality of tin droplets to an EUV source vessel along a first trajectory extending in a first direction;a collector mirror having a concave curvature and an opening that extends through the collector mirror at a location offset from a center of the collector mirror;a carbon dioxide (CO2) laser configured to generate a primary laser beam along a second trajectory extending through the opening in a second direction that is not perpendicular to the first direction; anda protection element linearly aligned with the primary laser beam and configured to absorb remnants of the primary laser beam passing through the first trajectory of the plurality of tin droplets. 12. The EUV radiation source of claim 11, wherein the protection element is located outside a path of the EUV radiation focused by the collector mirror to a focal point of the collector mirror. 13. The EUV radiation source of claim 11, further comprising:a second fuel droplet generator configured to provide a second plurality of tin droplets to the EUV source vessel along a third trajectory extending in a third direction;a second primary laser configured to generate a second primary laser beam along a fourth trajectory extending in a fourth direction that is not perpendicular to the third direction; anda second protection element linearly aligned with the second primary laser beam on an opposite side of the second trajectory as the second primary laser. 14. The EUV radiation source of claim 13, further comprising:an intermediate focus unit comprising a cone shaped aperture arranged within an exit aperture of the EUV source vessel at a location between the EUV source vessel and a downstream scanner. 15. The EUV radiation source of claim 14, wherein the protection element and the second protection element are disposed onto opposite sides of an exit aperture of the EUV source vessel. 16. The EUV radiation source of claim 11, further comprising:a pre-pulse laser configured to generate a pre-pulse laser beam, having a lower energy than the primary laser beam, along a fifth trajectory extending in a fifth direction that is not perpendicular to the first direction, wherein the pre-pulse laser is arranged so that the pre-pulse laser beam deforms the plurality of tin droplets prior to the primary laser beam hitting the plurality of tin droplets. 17. The EUV radiation source of claim 11, wherein the first direction and the second direction are separated by an obtuse angle. 18. A method of generating extreme ultraviolet (EUV) radiation, comprising:providing a plurality of fuel droplets along a first trajectory extending in a first direction; andstriking the fuel droplets with a primary laser beam following a second trajectory extending in a second direction and intersecting the first trajectory at a non-perpendicular angle, wherein the primary laser beam ignite a plasma that emits EUV radiation. 19. The method of claim 18, further comprising:focusing the EUV radiation at a focal point separated from the plasma along a third direction different than the second direction. 20. The method of claim 19, further comprising:providing a second plurality of tin droplets along a third trajectory extending in a third direction; andstriking the fuel droplets with a second primary laser beam along a fourth trajectory extending in a fourth direction that is not perpendicular to the third direction. |
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summary | ||
abstract | A lithography system and method for operating the same. The lithography system may include a cathode adapted to emit an electron beam, a beam-homogenizing structure, capable of increasing at least one of the uniformity and energetic of the electron beam, and a mask adapted to accelerate the electron beam to form a pattern on a wafer. |
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041586034 | summary | The invention relates to a blow-off device for limiting excess pressure in nuclear power plants, especially in boiling water nuclear power plants, and more particularly wherein the blow-off device has at least one condensation tube disposed so that a lower outlet end thereof is immersed in a volume of water (condensate) in a condensation chamber having a gas cushion located in a space above the volume of water, and the upper inlet end of the condensation tube extending out of the volume of water and being connected to a source of steam that is to be condensed or a steam-air mixture, the outlet end of the condensation tube, for smoothing the condensation, being provided with wall parts forming passages extending in axial direction, delimited from one another and terminating in the water volume, the wall parts serving to subdivide steam flow from the source thereof and bubbles produced in the water volume. Such a blow-off device has become known heretofore from German Published Prosecuted Application DT-AS 2 212 761; especially in FIG. 5 thereof. In this heretofore known device, the passages terminating in the water condensate are formed by annular channels of telescoping tube sections. It has also become known heretofore from German Published Non-Prosecuted Application DT-OS 2 457 901 to subdivide more finely the outlet cross section of the condensation tube. The interior of the outlet of the condensation tube is provided with a framework of wall parts. Even if a relatively fine subdivision of the steam flow and the bubbles can be effected by means of the last-mentioned heretofore known device, the cooling and wetting of the partial flows of steam, especially for high-quantity flows of steam, are relatively slight, because all of the passages are then filled with saturated steam, the partial flows of steam being able to be reunited as bubbles as they exit from the tube outlet end. It is accordingly an object of the invention to provide a blow-off device for limiting excess pressure in nuclear power plants that is of such improved and perfected construction and operation that good cooling and wetting of the partial steam flows and partial bubbles are produced during the blow-off process, and wherein the production and attachment of the wall parts to the condensation tube is much simplified over those of the aforementioned prior art. With the foregoing and other objects in view, there is provided, in accordance with the invention, in a blow-off device for limiting excess pressure in nuclear power plants, at least one condensation tube disposed so that a lower outlet end therof is immersed in a volume of water in a condensation chamber having a gas cushion located in a space above the volume of water, and the upper inlet end thereof extending out of the volume of water and being connectible to a source of steam that is to be condensed or a steam-air mixture, the outlet end of the condensation tube, for smoothing the condensation, being provided with wall parts forming passages extending in axial direction, delimited from one another and terminating in the water volume, the wall parts serving to subdivide steam flow from the source thereof and bubbles produced thereby in the water volume, the wall parts being constructed as a tube attachment and being formed with an opening corresponding to the outlet end of the condensation tube and by means of which the tube attachment is mounted on the outlet end of the condensation tube, a first group of the wall parts in the tube attachment being disposed in alignment with the outlet end of the condensation tube, and a second group of the wall parts surrounding the first group thereof, the passages formed by the second group of the wall parts communicating laterally with the passages formed by the first group of the wall parts, the passages formed by the second group of the wall parts, at least at the upper ends thereof, communicating with the water volume. The advantages attainable with the invention are that the central steam flow through the passages formed by the wall parts of the tube attachment are not only finely subdivided, but also that the partial steam flows and the subdivided condensation bubbles are wetted and cooled inwardly from the outer periphery. In accordance with another feature of the invention, the second group of wall parts overlap the outlet end of the condensation tube in axial direction. This has advantages of providing strength and stability and, moreover, a greater cooling and wetting surface or area is afforded thereby. In accordance with a further feature of the invention, the first and the second groups of wall parts are formed of axially and radially extending plates defining sector-shaped passage cross sections. The central partial steam flows can thereby fan radially outwardly, thereby further increasing the cooling and wetting surface or area. In accordance with alternate additional features of the invention, whereby the cooling surface or area can be increased even further yet, the first and the second group of wall parts extend axially to the tube attachment, and wave-shaped metal sheets or plates are included which extend transversely to the axially extending wall parts and form zig-zag or serpentine passage cross sections. For reasons of strength and stability and for the purpose of attaining a definite axial inlet or entry of the cooling water from the water condensate of the condensation chamber into the tube attachment, there is provided, in accordance with an added feature of the invention, a tube attachment having a jacket tube enveloping the wall parts thereof. For reasons of strength and stability, it is advantageous, moreover, for the tube attachment to have a slide-on tube section which is connected to the wall parts and has an inner diameter corresponding to the outer diameter of the condensation tube per se. Thus, in accordance with a concomitant feature of the invention, a first group of wall parts is surrounded by a slide-on tube having an inner diameter corresponding to the outer diameter of the condensation tube at the outlet end thereof and being slidable onto the outlet end of the condensation tube, the second group of wall parts being secured to the slide-on tube at the outer peripheral surface thereof, the slide-on tube being formed with openings in the surface thereof through which the passages formed by the first and second groups of wall parts are in communication with one another. The tube attachment is thereby formed of two coaxial tubes, a slide-on tube, and a jacket tube, the inner space of the slide-on tube, disregarding the insertion opening for the condensation tube, being filled-in with the wall parts, and the peripheral space between the slide-on tube and the wall surface of the jacket tube being also filled in with wall parts. Although the invention is illustrated and described as embodied in blow-off device for limiting excess pressure in nuclear power plants, especially in boiling water- nuclear plants, 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. |
056617666 | claims | 1. An apparatus for measuring dimensional characteristics of a nuclear fuel assembly having at its lower end a lower alignment pin extending downward from a lower tie plate, the lower alignment pin being positioned and oriented for engaging a corresponding alignment hole in a lower core support plate of a nuclear reactor, the fuel assembly having at its upper end an upper alignment hole located in the upper tie plate, the upper alignment hole being positioned and oriented for receiving an alignment pin extending downward from the underside of an upper core support plate; the apparatus comprising: (a) an elongated fixture defining an internal volume for a nuclear fuel assembly, the fixture mounted in an upright position and having an opening disposed towards an upper end of the fixture, the opening adapted to receive the fuel assembly therethrough, the fixture further including a removable top adapted to fit into the opening and having a locating pin with a longitudinal axis extending from an underside for engaging the upper alignment hole in the upper tie plate of the fuel assembly, the fixture further including at a lower end a bottom reference plate adapted to form a locating hole having a second longitudinal axis for receiving the lower alignment pin of the fuel assembly, the locating pin and the locating hole being adapted to engage the fuel assembly lower alignment pin and the fuel assembly upper alignment hole so as to constrain the fuel assembly as if the fuel assembly was positioned in the reactor, at least one of the first longitudinal axis and the second longitudinal axis defining a predetermined longitudinal axis of the fixture; (b) at least one reference wire extending from the upper end of the fixture to the lower end of the fixture, the at least one reference wire being disposed parallel to the predetermined longitudinal axis of the fixture; (c) an ultrasonic measuring device comprising: (d) transmission means which transmits from the transponder the signal of the first reflected wave and signal of the second reflected wave to the ultrasonic flaw detector. 2. The apparatus as in claim 1 wherein the fixture is adapted to have slots extending longitudinally therethrough. |
045227829 | claims | 1. Fuel assembly for a nuclear reactor constituted by a bundle of parallel fuel rods whose spacing is maintained by spacer grids which are transverse with respect to said rods, two transverse end plates and supporting guide tubes which replace some fuel rods and which are longer than said fuel rods, rigidly fixed to said end plates and to said spacer grids for assuring retention of said spacer grids, rigidity of the assembly and taking up of axial forces as well as guiding control rods of said reactor, said end plates being made of stainless steel, wherein at least two supporting guide tubes made of material which is metallurgically compatible with the material of said spacer grids are welded to the latter, while other guide tubes which also guide control rods of said reactor constituting the majority of the guide tubes of said assembly are made of zirconium alloy and are secured to only one of said end plates and slip-fitted on the cells of said spacer grids so as to be movable with respect thereto under the effect of expansion and assuring only the guidance of said control rods. 2. Fuel assembly according to claim 1, wherein said spacer grids are made of a material in the group comprising stainless steel and nickel alloys, and said supporting guide tubes are made of stainless steel and are directly welded to said spacer grids. 3. Fuel assembly according to claim 2, wherein said supporting guide tubes made of stainless steel are directly welded to said end plates. 4. Fuel assembly according to claim 2, wherein said supporting guide tubes made of stainless steel are welded to an upper end plate of said assembly through sleeves assuring joining between said upper end plate and an upper spacer grid of said assembly to which said sleeves are welded. 5. Fuel assembly according to claim 2 or 3, wherein said guide tubes made of zirconium alloy are engaged at their upper part in sleeves assuring joining between said upper end plate and said upper spacer grid of said assembly. 6. Fuel assembly according to claim 2, comprising twenty-four guide tubes, including four supporting guide tubes made of stainless steel and twenty guide tubes made of zirconium alloy. 7. Fuel assembly according to claim 1, wherein said spacer grids are made of zirconium alloy and said supporting guide tubes made of zirconium alloy are welded to said spacer grids and mechanically fixed to said end plates. |
042773610 | description | DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 1, a reprocessing plant 210 includes a building 211 having side walls 212 and a roof 214 and a foundation 223. A vehicle access zone 215 permits mobile cranes 233 to move about on the covers 222 over compartments 221 arranged as an array of compartments 220, such as a rectangular array. A cover 222 is supported on a ledge 225 of a compartment wall 224. Openings 226 in vertical walls 224 permit communication lines 230 to extend from a compartment 221 to an appropriate zone. The compartment 221 has a support floor 227 on which processing equipment 232 can be mounted. A detection system in a sump 228 monitors for leaks. When desired, drainage systems can conduct liquids from sump to a remote storage system. It might sometimes be appropriate to provide an annular storage tank for emergency storage of liquid drained from the sump. As shown in FIG. 2, an air processing facility 240 includes a fan 241 and a series of specialized filters 242a, 242b, and heat exchangers 243 for cleaning and cooling the air supplied to fan 241. Air is withdrawn from compartments containing process equipment 232 through a return duct 245 and directed to filters 242a, 242b, and to heat exchanger 243 adapted to cool the air prior to supply to the fan 241. A recirculating air duct 246 directs the air from fan 241 to compartment 220. The covers 222 fit over compartments 221 in such a manner that some leakage is likely to occur even when the covers are not removed for a period of more than a year. The air pressure in the vehicle access zone 215 is greater than the pressure in compartment 221 whereby any air leakage that does occur tends to be from the vehicle access zone to the compartment rather than the other direction. The fan 241 maintains an air circulation of the air inventory of compartment 221 so that the air in compartment 221 can be treated as a quasi-hermetically sealed inventory of gas. The gas turnover rate is greater than one day but less than a year. Communication lines 230a, 230b, connect conduits 230c and 230d with process equipment 232. A system of interconnected conduits and manifolds 250 direct dirty air to a central air cleaner of the reprocessing plant 210. Air is discharged from recirculating duct 246 in each air processing facility 240 to the central air cleaner manifold system 250 through the exhaust line 251 for maintaining the quasi-hermetic seal of compartment 221 so that the air turnover rate is more than a day but less than a year. A turnover rate control 253 serves as a master control for maintaining the air circulation turnover rate within the range from about one day to about one year while also adjusting the pressure in compartment 221 so that often it is slightly less than the air pressure in the vehicle access zone 215. An air inlet 247 is connected to an air supply line 249 through a regulating valve 248 actuated by turnover rate control 253. A regulating valve 252 in exhaust line 251 (from facility 240 to manifold 250) is actuated by turnover rate control 253. The schematic showing of FIG. 2 is concerned with the quasi-hermatic sealing of a particular compartment 221 and its interrelationship with its air processing facility 240. It should be recognized that each of the compartments in which there is equipment 232 for the processing of the compositions derived from the depleted fuel rods has its own air processing facility 240. The total reprocessing plant 210 includes a considerable variety of such compartments 221 having their corresponding air processing facilities 240. As shown in FIG. 3, a reprocessing plant 310 can have a flow sheet in which there are communication lines 330 amongst compartments 320a, 320b, etc., 320m, each containing processing apparatus. An air processing facility 340a, 340b, etc., 340m is associated with corresponding compartments 320, containing processing equipment. As shown in connection with 320, a return duct 345c can direct the air from the compartment 320c to the air processing unit 340c and the cooled and/or filtered air can be returned to the compartment through recirculating air duct 346c. Fresh air through line 347 can be supplied to an air processing facility 340 in response to signals from control system 353. Each compartment is maintained at a controlled differential pressure less than that of the nearby zone, ordinarily the vehicle access zone. Moreover, each control 353 regulates the gas exhaust rate so that the gas turnover in its compartment is more than a day but less than a year. The stale air is discharged from the air processing unit 340 to a manifold 350 and thence to a central air cleaner 360. Clean air is discharged to the atmosphere through a vent 361. Various modifications of the invention are possible without departing from the scope of the appended claims. |
052934128 | claims | 1. An apparatus for dismantling an irradiated nuclear reactor component (1) having at least one tubular wall arranged with its axis in a vertical direction and fastened inside a vessel well (2) provided in a concrete structure (3), said apparatus comprising (a) a supporting structure (11) resting on part of said concrete structure vertically in alignment with said vessel well (2); (b) a device for lifting said component (1), said device comprising (c) cutting means (40, 70, 80, 90) arranged at an upper level of said vessel well (2); (d) means (23, 24, 25) for handling cut blocks of irradiated material (26) of the wall of said component; and (e) means (27, 27') for storing said cut blocks, said means being arranged at an upper lateral position in relation to said vessel well (2). 2. Apparatus according to claim 1, wherein said mast (13) comprises a toothing (13a) forming a rack directed longitudinally of said mast (13), and said means (20) for vertical displacement of said mast (13) and of said component (1) consist of pawl mechanisms (18a, 18b) each comprising a pawl (18a) mounted fixedly in a vertical direction and a pawl (18b) mounted movably in a vertical direction on a support (56) fixed to a rod (55) of a lifting jack (54), said pawls (18a, 18b) being mounted for pivoting movement through a limited angle about a horizontal axis and comprising an end part having a profile which corresponds to a profile of receptacles formed between successive teeth of said toothing (13a) of said mast (13). 3. Apparatus according to claim 1, wherein said means for fastening said lower part of said mast (13) to said lower part of said component (1) consist of a platen (32) carrying rods (37) to be engaged in orifices passing through a lower part of the wall of said component (1) and of means (36) for fastening the end of said rods underneath said lower part of said component (1). 4. Apparatus according to claim 1, further comprising a device (21) for setting said mast (13) in rotation about said axis of said mast and coinciding with the axis of said tubular part of said component (1). 5. Apparatus according to claim 1, comprising a tubular structure of vertical axis, along the axis of which the mast (13) is placed and which comprises a lower part adjacent said upper level of said vessel well (2), radially directed arms (15a) having ends at which are placed jacks (16) making it possible to carry out the positioning and retention of said component (1) with the axis of said component along the axis of said mast (13). 6. Apparatus according to claim 1, wherein said cutting means (40, 70) consist of band saws mounted on a support for rotation about the axis of said component (1) and of said vessel well (2), at a short vertical distance above the upper part of said vessel well (2). 7. Apparatus according to claim 6, wherein said cutting means comprise a device (40) for cutting in a substantially horizontal direction, said device having a support (42) which is mounted for rotation about the axis of said vessel well (2) and of said component (1) and pivotably about a horizontal axis, and a device (70) for cutting in a substantially vertical direction, mounted for rotation about the axis of said vessel well (2) coinciding with the axis of said component (1) and pivoting about a horizontal axis (73). 8. Apparatus according to claim 7, wherein said device (40) for cutting in a substantially horizontal direction comprises means (60) for guiding said support (42), comprising a helical groove (62), in which moves a roller (64) mounted rotatably on said support (42). 9. Apparatus according to claim 6, wherein said cutting means comprise a support (42, 72) mounted movably in rotation about the axis of said vessel well (2) and of the component (1) by means of a bearing (43, 75) fastened to a tubular vertical part (14) fastened to said supporting structure (11). |
claims | 1. A method of identifying an optimal landing energy of a probe current in a scanning electronic microscope for use in obtaining an optimal topographic image of a sample, comprising the steps of:(a) directing the probe current to the sample at a selected landing energy to produce a signal electron beam from the sample;(b) measuring the probe current;(c) providing a signal electron beam current detector;(d) receiving the signal electron beam at the signal electron beam current detector to obtain a signal electron beam current measurement;(e) calculating a ratio of the signal electron beam current measurement to the measured beam energy of the probe current;(f) repeating steps (a) through (e) at a landing energy other than the selected landing energy; and(g) comparing the calculated ratios at each landing energy to identify the optimal landing energy as a landing energy corresponding to a ratio having a value proximate “1”;(h) selecting the identified optimal landing energy; and(i) obtaining substantially the entire topographic image of the sample by directing the probe current to the sample at a single landing energy which is the optimal landing energy, and directing a resulting signal electron beam to an imaging detector. 2. The method of claim 1, wherein said providing step comprises applying to the sample a voltage having a value proximate a value of the voltage of the probe current, and using the signal electron beam to locate a desired position for the signal electron beam current detector. 3. The method of claim 1, wherein said measuring step (b) comprises disposing a probe current detector in a path of the probe current. 4. The method of claim 1, wherein said receiving step comprises directing the signal electron beam to said signal electron beam current detector. 5. The method of claim 4, wherein said step of directing the signal electron beam further comprises employing a Wein filter disposed in the path of the signal electron beam. 6. The method of claim 1, wherein said steps (d) and (h) are performed by employing a Wien filter disposed in the path of the signal electron beam for selectively directing the signal electron beam to one of said imaging detector and said signal electron beam current detector. 7. The method of claim 1, further comprising the step of selectively positioning said signal electron beam current detector within the path of the signal electron beam. 8. The method of claim 7, wherein said step (c) of providing a signal electron beam detector comprises the step of positioning the signal electron beam detector coplanar with, and at a 180° angle from, said imaging detector. 9. The method of claim 3, wherein said measuring step (b) further comprises using a Faraday cup as the probe current detector. 10. The method of claim 1, wherein said providing step (c) further comprises providing a Faraday cup as the signal electron current detector. 11. The method of claim 7, wherein said selectively positioning step further comprises applying a voltage to one of said signal electron beam and said imaging detector. 12. A system for identifying an optimal landing energy of a probe current in a scanning electronic microscope for use in obtaining an optimal topographic image of a sample, comprising:means for directing the probe current to the sample at a selected landing energy to produce a signal electron beam from the sample;a probe current detector for measuring the probe current;a signal electron beam current detector for obtaining a measurement of the signal electron beam;means for calculating a ratio of the signal electron beam current measurement to the measured beam energy of the probe current;means for obtaining a plurality of signal currents at different landing energies;means for comparing the calculated ratios at each landing energy to identify the optimal landing energy as a landing energy corresponding to a ratio having a value proximate “1”;means for selecting the identified optimal landing energymeans for obtaining substantially the entire topographic image of the sample by directing the probe current to the sample at a single landing energy which is the optimal landing energy, and directing a resulting signal electron beam to an imaging detector. |
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claims | 1. A method performed by a computer of rating a computer system's ability to run software applications, wherein the rating facilitates matching of software application requirements with computer system capabilities, the method comprising:performing an inventory of the computer system, wherein the performing an inventory yields a set of computer system features;testing performance of the computer system, wherein the testing yields performance results for the set of computer system features;comparing the set of computer system features and the performance results with capability rating requirements, wherein the capability rating requirements comprise a required set of features and required performance criteria;determining a capability rating for the computer system based on the comparing; andoutputting the capability rating. 2. The method of claim 1 wherein the performing an inventory includes performing an inventory of hardware components in the computer system. 3. The method of claim 2 wherein the performing an inventory further includes performing an inventory of features of the hardware components. 4. The method of claim 1 wherein the computer system comprises components, and wherein the capability rating is based on a lowest component rating among the components. 5. The method of claim 1 wherein the capability rating requirements are established by a board comprising voting members. 6. The method of claim 1 further comprising assigning the capability rating to the computer system. 7. The method of claim 6 further comprising presenting the capability rating in a standardized rating presentation. 8. The method of claim 1 wherein the capability rating is an integer number. 9. The method of claim 1 wherein the acts are performed in an operating system environment of the computer system as a feature of the operating system environment. 10. The method of claim 1 wherein the acts are performed by a capability tool. 11. The method of claim 10 wherein the capability tool is a software program obtained from a remote computer via a network. 12. The method of claim 10 wherein the capability tool is a software program run from a remote computer via a web browser interface. 13. The method of claim 1 wherein the capability rating requirements are obtained over a network from a database. 14. The method of claim 1 wherein the capability rating requirements are obtained from a storage medium in the computer system. 15. The method of claim 1 wherein the capability rating is further based on a category for the software applications, the category selected from a group comprising: entertainment software, computer-assisted drafting software, operating system software, image processing software. 16. The method of claim 1 wherein the capability rating is associated with a vendor identifier for the computer system. 17. A computer-readable medium having stored thereon computer-executable instructions for causing a computer to perform the method of claim 1. 18. A method performed by a computer of rating a computer hardware component, wherein the computer hardware component is operable to perform functions in a computer system, and wherein the functions are useful for running software applications on the computer system, the method comprising:performing an inventory of the computer hardware component, wherein the performing an inventory yields a set of computer hardware component features;testing performance of the computer hardware component, wherein the testing yields performance results for the set of computer hardware component features;comparing the set of computer hardware component features and the performance results with capability rating requirements;determining a capability rating for the computer hardware component based on the comparing; andoutputting the capability rating. 19. The method of claim 18 wherein the capability rating is based on a lowest feature rating among the set of computer hardware component features. 20. The method of claim 18 wherein the capability rating is an integer number. 21. The method of claim 18 wherein the capability rating requirements are established by a rating requirements decision-making organization. 22. The method of claim 18 further comprising assigning the capability rating to the computer hardware component. 23. The method of claim 22 further comprising presenting the capability rating in a standardized rating presentation. 24. The method of claim 18 wherein the acts are performed in an operating system environment of the computer system as a feature of the operating system environment. 25. The method of claim 18 wherein the acts are performed by a capability tool. 26. The method of claim 18 wherein the capability rating requirements are obtained from a device driver signature for the computer hardware component. 27. The method of claim 18 wherein the capability rating is associated with a vendor identifier for the computer hardware component. 28. A computer-readable medium having stored thereon computer-executable instructions for causing a computer to perform the method of claim 18. 29. A software system on one or more computer-readable media, the software system for rating a computer system's ability to run software applications, the software system comprising:means for performing an inventory of the computer system, to yield a set of computer system features;means for testing performance of the computer system, to yield performance results for the set of computer system features;means for comparing the set of computer system features and the performance results with capability rating level requirements; andmeans for determining a capability rating level for the computer system based on the comparing; andmeans for outputting the capability rating level. 30. A software system on one or more computer-readable media, the software system for rating a computer system's ability to run software applications, the software system comprising:means for performing an inventory of a computer hardware component, to yield a set of computer hardware component features;means for testing performance of the computer hardware component, to yield performance results for the set of computer hardware component features;means for comparing the set of computer hardware component features and the performance results with capability rating level requirements; andmeans for determining a capability rating level for the computer hardware component based on the comparing; andmeans for outputting the capability rating level. |
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abstract | An incore piping section maintenance system of a reactor comprises a maintenance system main body which is fixed to a maintenance target portion in a reactor pressure vessel or in the vicinity thereof to which a preventive-maintenance operation is executed, a support mechanism provided for the maintenance system main body so as to be movable in a reciprocal manner towards the maintenance target portion, a laser generator for generating a laser beam, a laser de-sensitization treatment apparatus which is rotatably supported around an axis of the support mechanism and which includes a laser irradiation section for irradiating the laser beam to the maintenance target portion, and an optical transmission element which guides the laser beam outputted from the laser generator to the laser de-sensitization treatment mechanism. |
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description | The present invention relates to magnetic data recording, and more particularly to a tool and method for manufacturing patterned magnetic recording media. The heart of a computer's long term memory is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider toward the surface of the disk, and when the disk rotates, air adjacent to the disk moves along with the surface of the disk. The slider flies over the surface of the disk on a cushion of this moving air. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic transitions to and reading magnetic transitions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions. In order to increase the data density of such magnetic data recording systems, the track-width of the system can be reduced while the linear density of the system can be increased. However, the data density of current and future recording systems is fast approaching the point that is has become very difficult to maintain good data resolution. One of the problems experienced at such high data densities is erasure of data due to thermal energy. When the track-width of the system is very small, media should have smaller grains with higher coercivity to minimize the superparamagnetic effect. However, there is a limit to scaling media grain size and coercivity. One way to minimize the superparamagnetic erasure of magnetic hits is to define a large, thermally stable bit on the magnetic medium Patterned magnetic recording media have been proposed to increase the data density in magnetic recording, data storage, such as hard disk drives. In bit patterned media (BPM), the magnetic material is patterned into small isolated blocks or islands such that there is a single magnetic domain in each island or “bit”. The single magnetic domains can be a single grain or can consist of a few strongly coupled grains that switch magnetic states in concert as a single magnetic volume. This is in contrast to conventional continuous media wherein a single “bit” may have multiple magnetic domains separated by domain walls. U.S. Pat. No. 5,820,769 is representative of various types of patterned media and their methods of fabrication. A description of magnetic recording systems with patterned media and their associated challenges is presented by R. L. White et al., “Patterned Media: A Viable Route to 50 Gbit/in2 and Up for Magnetic Recording?”, IEEE Transactions on Magnetics, Vol. 33, No 1. January 1997, 990-995. Similarly, discrete track media (DTM) consists of patterned isolated tracks where the magnetic storage layer of the media is removed between tracks. DTM creates a hybrid situation relative to BPM, where media in the downtrack direction is similar to conventional continuous media, but has patterned tracks in the cross-track direction. Patterned media with perpendicular magnetic anisotropy have the desirable property that the magnetic moments are oriented either into or out of plane, which represent the two possible magnetization states, it has been reported that these states are thermally stable and that the media show improved signal-to-noise ratio (SNR) compared to continuous (un-patterned) media. The present invention provides a tool for patterning a disk such as a magnetic media disk for use in a disk drive system, and can be used to treat other types of substrates as well. The tool includes a chamber and a first and second series of magnets, each appropriately spaced about the chamber wall. An ion beam source at an end of the chamber emits an ion beam toward the disk which is held within the chamber. The first series of magnets deflects the ion beam away from center and toward the chamber wall. The second series of magnets deflects the ion beam back toward the center so that the ion beam can strike the disk at an angle. In addition, to bending the ion beam, the magnets also rotate the bent ion beam so the bent ion beam rotates or revolves within the chamber. Furthermore, the path of the ions from the ion source to the media would gyrate about the axis of the chamber via a time varying magnetic field. Another magnet can be placed beneath the disk to focus or defocus the ion beam to alter the area of the disk to be patterned by the ion beam. In another possible embodiment of the invention a third and fourth series of magnets can be provided and another ion beam source can also be provided at an end of the chamber opposite the first ion beam source. With such an embodiment, two sides of the disk can be patterned simultaneously, thereby increasing throughput time and saving manufacturing cost. The second series of magnets (that series which is furthest from the ion source) preferably produces a stronger magnetic field than the first series of magnets (that which is closest to the ion beam source). In this way the ion beam is deflected back toward the center of the chamber, rattier than being deflected to a point that is just parallel with the axis of the chamber. This allows the ion beam to strike the surface of the disk at a desired angle. Varying the strength of the magnetic field produced by the first and second series of magnets can vary the angle at which the ion beam strikes the disk surface These and other features and advantages of the invention will be apparent upon reading of the following detailed description of preferred embodiments taken in conjunction with the figures in which like reference numerals indicate like elements throughout. The following description is of the best embodiments presently contemplated for carrying out this invention. This description is made for the purpose of illustrating the general principles of this invention and is not meant to limit the inventive concepts claimed herein. Referring now to FIG. 1, there is shown an example of a disk drive 100. The disk drive may include a disk 112 that has been manufactured using a tool that can be an embodiment of the present invention, as will be described below. As shown in FIG. 1, at least one rotatable magnetic disk 112 is supported on a spindle 114 and rotated by a disk drive motor 118. The magnetic recording on each disk is in the form of annular patterns of concentric data tracks (not shown) on the magnetic disk 112. At least one slider 113 is positioned near the magnetic disk 112, each slider 113 supporting one or more magnetic head assemblies 121. As the magnetic disk rotates, slider 113 moves radially in and out over the disk surface 122 so that the magnetic head assembly 121 may access different tracks of the magnetic disk where desired data are written. Each slider 113 is attached to an actuator arm 119 by way of a suspension 115. The suspension 115 provides a slight spring force which biases slider 113 against the disk surface 122. Each actuator arm 119 is attached to an actuator means 127. The actuator means 127 as shown in FIG. 1 may be a voice coil motor (VCM). The VCM comprises a coil movable within a fixed magnetic field, the direction and speed of the coil movements being controlled by the motor current signals supplied by controller 129. During operation of the disk storage system, the rotation of the magnetic disk 112 generates an air bearing between the slider 113 and the disk surface 122 which exerts an upward force or lift on the slider. The air bearing thus counter-balances die slight spring force of suspension 115 and supports slider 113 off and slightly above the disk surface by a small, substantially constant spacing during normal operation. The various components of the disk storage system are controlled in operation by control signals generated by control unit 129, such as access control signals and internal clock signals. Typically, the control unit 129 comprises logic control circuits, storage means and a microprocessor. The control unit 129 generates control signals to control various system operations such as drive motor control signals on line 123 and head position and seek control Signals on line 128. The control signals on line 128 provide the desired current profiles to optimally move and position slider 113 to the desired data track on disk 112. Write and read signals are communicated to and from write and read heads 121 by way of recording channel 125. FIG. 2 shows the magnetic disk (magnetic media) 112. As can be seen, the media 112 has a centrally located hole 202, for mounting the disk on a spindle 114 in a disk drive system 100. The disk has a surface 204 on which magnetic data signals can be written in concentric data tracks. The box area 206 shows a small area of the disk surface which is shown enlarged in FIG. 3. Therefore, FIG. 3A shows an enlarged view of a small portion of the surface of the disk. The surface of the disk 204 is formed with concentric ridges 302 that are formed to correspond with a data tracks formed thereon. The patterned media surface 204 may also be formed with patterned bits 312 as shown in FIG. 3B. The shape and packing of magnetic bits in FIG. 3B is only one example of BPM media 312. More generally, this patterned surface 204 can be seen more clearly with reference to FIG. 4, which shows a cross sectional view as taken from line 4-4 of FIG. 3A or FIG. 3B. The pitch of the patterned media tracks and/or bits may vary depending on head and media considerations. As seen in FIG. 4, the disk 112 can include a substrate 402, constructed of a material such as aluminum-magnesium alloy or glass. A magnetically soft under-layer 404 is formed over the substrate 402, and a magnetically hard top layer is formed over the under-layer 404. The magnetically hard top layer 406 is patterned to form the concentric ridges 302. The troughs 408 between the ridges can extend down into the magnetically soft under-layer 404 or can stop short of the magnetically soft under-layer 404, but are shown in FIG. 4 as extending to the upper surface of the under-layer as a possible preferred embodiment of the invention. Alternatively, one could also pattern the hard layer 406 for patterned bits 312. It should be pointed out that the media disk 204 can include other layers as well that are not shown for purposes of clarity. Such additional layers may include, but are not limited to, an exchange break layer and an overcoat layer. A patterned media can be formed by an ion milling process. However, forming such a patterned magnetic media in a traditional ion milling tool presents serious challenges. For example, as shown in FIG. 5, in order to pattern a magnetic media 502, the magnetic media (ie. disk 502) can be held within a tool 504 that includes an ion beam source 506. The media is held on a clamp 508 that is rotated by a motor or actuator 510. In order to form the necessary pattern, the ion milling must be performed at an angle relative to normal. This means that the disk 502 and clamp 508 must be held at an angle relative to the ion source 506. This is shown in FIG. 5. An ion beam 512 emits from the ion source 506 toward the disk 502, where the ion beam 506 strikes the disk 502 at a desired angle. Control of etching of the disk 502 may be improved with feedback from a metrology device (not shown) that could be incorporated with a chamber port 522 that would preferably have a line-of-sight to said disk 502. The use of such a tool requires the use of complex mechanisms for tilting and rotating the disk 502 (e.g. motor 510, clamp 508, and other mechanisms, not shown). In addition, many manufacturing processes such as etching for patterning of a disk are performed in a multi-station machine. Therefore, there is a need for a tool that can greatly simplify a process for angled ion milling of a disk surface, in order to reduce manufacturing complexity, time and cost in said multi-station machine. Preferably, the disk holder or carrier would be common to other stations in the multi-station machine. The present invention provides a tool that, can pattern a magnetic media with an angled ion milling without the need for complex mounting, rotation and tilting mechanisms, using a greatly simplified structure. FIG. 6 shows a tool 602 for patterning magnetic media or disk 604. The tool 602 includes a chamber 606. The disk 604 can be held on a clamp 608, for mounting within the chamber 606, and is patterned with a mask 605 that is formed with concentric rings and spaces in between, the rings and spaces coinciding with the width and spacing of data tracks on the disk. The mask 605 shown in FIG. 6, is, of course not to scale, as the rings and space (shown in cross section in FIG. 6) could be much smaller and much more numerous, hi addition, the shape of mask 605 could also comprise bit patterned media (BMP). It can be seen that the disk 604 does not have to be rotated, nor does it have to be tilted. Therefore, the disk 604 can be mounted on another structure such as by clamping to the outer periphery of the disk 604 or by holding the disk 604 on a platter or chuck (not shown). However, the disk 604 could rotate if needed. The tool 602 includes an ion source 610 that can emit an ion beam 612. A first series of electro-magnets 614 surround a first portion of the chamber 606, and a second series of electro-magnets 616 surrounds a second portion of the chamber 606. The arrangement of the magnets 614 can be seen more clearly with reference to FIG. 7, which shows a cross section of the tool 602 as viewed from line 7-7 of FIG. 6. As can be seen then, the series of magnets 614 include magnets 614(a), 614(b), 614(c) and 614(d). The magnets 614, 616 (FIG. 6) can be located within or outside of the chamber 606, and the arrangement of four such magnets 614 shown in FIG. 7 is by way of example. Other arrangements are also possible, such as three magnets, five magnets, etc. evenly spaced about the chamber 606. The magnets 614, 616 are controlled by circuitry that controls and varies the electrical current to and magnetic field produced by the magnets 614, 616. The magnets are electromagnets that are energized such that at least two of the magnets (e.g. 614(c) and 614(b)) in FIG. 7 deflect the ion beam 612 by producing a magnetic field perpendicular relative to the path of the ion beam 612. With reference again to FIG. 6, the other set of magnets 616 has the opposite polarity. Adjacent magnets (eg. 614, 616) are activated to produce a magnetic field that is either into or out of the plane of FIG. 6. Some field lines 624 produced with magnets including 614(c) and magnetic field lines 626 produced with magnets including 616(c) are shown in FIG. 6. Therefore, while the first set of magnets 614 deflects the ion beam outward toward the wall of the chamber 606, the other set of magnets 616 deflects the ion beam 612 back inward toward the center of the chamber 606. The second series of magnets 616 preferably produces a stronger magnetic field than the first series of electromagnets 614 to deflect the ion beam 616 not just parallel with the axis of the tool 602, but back inward as shown. This causes the ion beam to bend as shown in FIG. 6. As can be seen, this causes the ion beam 612 to strike the disk 604 at an angle without the need to tilt the disk 604. An approximation of the chamber dimensions and conditions can be made using the following equation v/r=qB/m, where v is the velocity of the ions exiting the ion source, q is the charge on the ion, m is the mass of the ion, B is the magnetic field, and r is the radius of curvature. Substituting an Ar ion mass of 6×10−26 kg with a velocity of 50,000 m/s (corresponding to an ion energy of about 500 eV), a magnetic field of 0.1 T yields a radius of curvature of the ion of 20 cm. With these conditions, it is preferable that the diameter of the chamber be greater than 40 cm. In general, it will be much larger to accommodate the volume of the magnets. With reference to both FIGS. 6 and 7, the activation of the individual magnets (i.e. 614(a), 614(b), 614(c), 614(d) is varied so that the curved path of the beam 612 to the disk 604 rotates about the central axis of the fool, resulting in a rotating angle of approach of the beam 612 to the disk 604 as indicated by arrow 618. Similarly, magnets (616a-d) would be varied to complete the curved, path of the ion beam to the disk 604. As can be seen, this causes the ion beam to rotate around the disk in order to pattern the surface of the disk 604 without the need to rotate the disk 604 and without the need to tilt the disk 604. As discussed above, this form of ion milling allows the disk 604 to be patterned without the need for any complex mounting, rotating or tilting mechanisms. Optionally, the strength of the magnetic field from the magnets 614, 616 can be varied in order to deflect the ion beam as it strikes the disk 604. As mentioned above, the configuration described with reference to FIGS. 6 and 7 (with four magnets in each set 614, 616) is by way of example only. For example, as shown in FIG. 8, each set of magnets could include three magnets 802(a), 802(b) and 802(c) arranged symmetrically about the chamber. FIG. 9 is a view of one of the magnets as viewed from line 9-9 of FIG. 7. As can be seen, the magnet can be formed as a coil wound into a doughnut shape, having an outer lead 902 and an inner lead 904 for supplying a current to the coil. This is by way of example, however, as other magnet configurations are possible as well. With reference to FIG. 10, another embodiment of the invention can be constructed to pattern both sides of a magnetic disk; simultaneously, thereby saving valuable time and cost. This patterning of both sides of the disk is made possible by the unique ion milling process of the present invention. This embodiment can include a tool 1002 including a chamber 1004. A disk 1006 is held within the chamber and may be held by a clamp the contacts the outer edges of the disk 1006, although other mechanisms could be configured for holding the disk 1006. The tool 1002 further includes first and second ion beam sources 1010, 1012 located at opposite ends of die chamber 1004. On a first half of the chamber 1004, first and second sets of magnets 1014, 1016 are provided for bending and rotating a first ion beam 1018 as discussed above to pattern a first side 1019 of the disk 1006. In addition, third and fourth sets of magnets 1020, 1022 are provided at a second half of the chamber 1004. These third and fourth sets of magnets bend and rotate a second ion beam 1024 in the manner discussed above to pattern a second side 1026 of the disk 1019. It should be noted that the disk holder 1008 can be electrically grounded or electrically biased to improve ion milling parameters. FIG. 11 illustrates yet another possible embodiment of the invention. This embodiment includes a tool 1102 that is similar to the tool 602 described above with reference to FIG. 6, except that this tool 1102 includes an additional magnet 1104. The additional magnet 1104 can be located directly beneath the disk 604, and when activated, can be used to focus or defocus the ion beam 612. This allows the ion beam to strike a larger area of the disk 604, thereby altering the speed and uniformity of the patterning of the disk 604. With reference now to FIGS. 12A and 12B, yet another embodiment of the invention is possible. This embodiment includes a first set 1202 of magnets nearer to the ion beam source and a second set of magnets 1204 further from the ion beam source 610. In this embodiment, the magnets 1202, 1204 can be mounted on structure 1206 that allows the magnets themselves to revolve about the chamber 606. This would produce a magnetic field that is perpendicular to the path of the ion beam 612. If the chamber is a non-magnetic metal such as aluminum, then the magnets 1202, 1204 can be mounted outside of the chamber 606. This embodiment allows for simplified electronics, because the magnets 1202, 1204 themselves revolve around the chamber 606 rather than requiring circuitry to activate various magnets at various times about the chamber. In addition, in this embodiment, the magnets 1202, 1204 can be hard, permanent magnets rather than electro-magnets, although electromagnets could be used as well. Also, with this embodiment, each set of magnets 1202, 1204 could include only two sets of magnets located outside of the chamber 606. As with the previously described embodiments, the second set of magnets would preferably produce a stronger magnetic field than the first set of magnets, in order to produce the desired angled ion milling. While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Other embodiments falling within the scope of the invention may also become apparent to those skilled in the art. Thus, the breadth and scope of the invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. |
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059498382 | claims | 1. A method of producing austenite steel for use in the radiation zone of a nuclear reactor, said method comprising the steps of: forming said austenite steel with about 17% by weight chromium, about 9 to 11.5% by weight nickel, about 0.04% by weight carbon, and iron impurities whose content of silicon is about 0.1% by weight and whose total content of sulfur and phosphorous is less than 0.03% by weight; and exposing said austenite steel to a temperature treatment at a temperature less than 1150.degree. C. to produce a fine grain lattice with grain diameter features under approximately 20, .mu.m. 2. The method of claim 1 further including the step of subjecting said austenite steel to rough deformation prior to said exposing step. 3. The method of claim 1 wherein said exposing step is performed at a temperature of approximately 850.degree. C. 4. The method of claim 1 wherein said forming step includes the step of using iron impurities whose total content of sulfur and phosphorous is less than 0.02% by weight. 5. The method of claim 1 wherein said forming step includes the step of using iron impurities whose total content of sulfur and phosphorous is less than 0.008% by weight. 6. The method of claim 1 wherein said forming step includes the step of forming said austenite steel with 2.0% by weight manganese. 7. The method of claim 1 wherein said forming step includes the step of forming said austenite steel with niobium in a niobium to carbon ratio of between about 10:1and 30:1. 8. The method of claim 1 wherein said forming step includes the step of forming said austenite steel with manganese. 9. Austenite steel formed by the method of claim 1. |
summary | ||
053012186 | claims | 1. In a fuel element for a nuclear reactor comprising an elongated body a metal alloy fissionable fuel housed within a sealed elongated cladding, said body of fuel having a smaller cross-sectional area than the cross-sectional of the internal space of said thereby providing an intermediate said body of fuel and said cladding, and a barrier of material arranged in said intermediate space to circumferentially surround said body of fuel, the improvement wherein said barrier comprises a multi-layer rolled foil held in a tubular shape by tack welding and having a section with an innermost layer, an outermost layer and an intermediate layer, said innermost layer lying between said body of fuel and said intermediate layer, said intermediate layer lying between said innermost and said outermost layers, and said outermost layer lying between said intermediate layer and said cladding, said outermost layer and said intermediate layer being tack welded to each other at points on said outermost layer which are removed from an outer longitudinal edge of said foil. 2. The fuel element as defined in claim 1, wherein said foil comprises metal. 3. The fuel element as defined in claim 1, wherein said foil comprises metal alloy. 4. The fuel element as defined in claim 2, wherein said metal is selected from the group consisting of zirconium, titanium, niobium, vanadium, chromium and molybdenum. 5. The fuel element as defined in claim 2, wherein said fuel comprises metallic uranium and plutonium and their alloys with elements taken from the group consisting of zirconium, titanium, niobium, vanadium, chromium and molybdenum, said cladding comprises stainless steel, and said metal is selected from the group consisting of zirconium, titanium, niobium, vanadium, chromium and molybdenum. 6. The fuel element as defined in claim 1, wherein said rolled foil has at least three layers at the point of tack welding and at least said outermost and said intermediate layers, but less than all of said layers are fused together by said tack welding from the outermost side. 7. The fuel element as defined in claim 6, wherein said fused material holding said outermost and said intermediate layers together fails at a level of stress due to expansion of said fuel body which is less than the level of stress at which the material of said foil would rupture. 8. The fuel element as defined in claim 1, wherein the geometric arrangement of said cladding and said barrier satisfies the relationship: EQU (C-2T-B).pi.+3S<L 9. A fuel/cladding barrier comprising a multi-layer rolled foil held in a tubular shape by tack welding and having a section with an innermost layer, an outermost layer and an intermediate layer, said intermediate layer lying between said innermost and said outermost layers, and said outermost layer and said intermediate layer being tack welded to each other at points on said outermost layer which are removed from an outer longitudinal edge of said foil. 10. The fuel/cladding barrier as defined in claim 9, wherein said foil comprises metal. 11. The fuel/cladding barrier as defined in claim 9, wherein said foil comprises metal alloy. 12. The fuel/cladding barrier as defined in claim 10, wherein said metal is selected from the group consisting of zirconium, titanium, niobium, vanadium, chromium and molybdenum. 13. The fuel/cladding barrier as defined in claim 9, wherein said rolled foil has at least three layers at the point or tack welding and at least two but less than all of said layers are fused together by said tack welding from the outermost side. 14. The fuel/cladding barrier as defined in claim 13, wherein said fused material holding said outermost and said intermediate layers together fails at a level of radial stress which is less than the level of radial stress at which the material of said foil would rupture. 15. A method of installing a barrier between an elongated body of a metal alloy fissionable fuel and the material of a sealed elongated container in which said fuel body is housed to inhibit an interaction whereby low-melting-point eutectic reaction products of components form the metal alloy fuel and container material are formed, said body of fuel having a smaller cross-sectional area than the cross-sectional of the internal space of said container, thereby providing an intermediate space between said body of fuel and said container, comprising the steps of: rolling foil into a multi-layer tubular configuration having a section with an innermost layer, an outermost layer and an intermediate layer, said intermediate layer lying between said innermost and said outermost layers; tack welding to hold said foil in said tubular configuration, said outermost layer and said intermediate layer being tack welded to each other at points on said outermost layer which are removed from an outer longitudinal edge of said foil; and installing said multi-layer rolled foil in said intermediate space so that said innermost layer circumferentially surrounds said body of fuel. 16. The method as defined in claim 15, wherein said foil comprises a metal selected from the group consisting of zirconium, titanium, niobium, vanadium, chromium and molybdenum. 17. The method as defined in claim 16, wherein said fuel comprises metallic uranium and plutonium and their alloys with elements taken from the group consisting of zirconium, titanium, niobium, vanadium, chromium and molybdenum, and said container comprises stainless steel. 18. The method as defined in claim 15, wherein said rolled foil has at least three layers at the point of tack welding and at least said outermost and said intermediate layers, but less than all of said layers are fused together by said tack welding from the outermost side. 19. The method as defined in claim 18, wherein said fused material holding said outermost and said intermediate layers together fails at a level of stress due to expansion of said fuel body which is less than the level of stress at which the material of said foil would rupture. 20. The method as defined in claim 15, wherein the geometric arrangement of said container and said barrier satisfies the following relationship: EQU (C-2T-B).pi.+3S<L |
claims | 1. A pH adjusting system comprising:an internal water storage tank that is disposed in a reactor container, which stores a nuclear reactor, and is capable of storing cooling water;a spraying unit that sprays the cooling water stored in the internal water storage tank into an inside of the reactor container; anda pH adjusting apparatus that is disposed above the internal water storage tank and below the spraying unit, the pH adjusting apparatus including a container that has an opened top side and stores a pH adjuster, and an overflow pipe, whereinthe overflow pipe is formed in a reversed U shape, an end of the overflow pipe is disposed in a lower portion of the container,a vent pipe with an opened end is provided to a top portion of the overflow pipe, andthe pH adjusting apparatus causes a pH-adjusted solution generated by dissolving or mixing the pH adjuster to flow out via the overflow pipe to the internal water storage tank below the pH adjusting apparatus. 2. The pH adjusting system according to claim 1, wherein the pH adjuster is prepared in a powder state. 3. The pH adjusting system according to claim 1, further comprising a solvent injecting unit that is capable of injecting a solvent for dissolving or diluting the pH adjuster into the pH adjusting apparatus, and further comprising an external water storage tank that is provided on an outside of the reactor container and is capable of storing the solvent, wherein the solvent injecting unit injects the solvent, which is stored in the external water storage tank, into the pH adjusting apparatus. 4. The pH adjusting system according to claim 1, whereinthe pH adjusting apparatus includes a basket containing the pH adjuster, and a basket housing container that houses the basket, andan inlet through which the solvent injected from the spraying unit flows in and an outlet from which the pH-adjusted solution generated by dissolving or mixing the pH adjuster in the solvent flows out to the internal water storage tank are formed in the basket housing container. |
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description | The present application is a continuation-in-part of U.S. patent application Ser. No. 29/383,507 filed Jan. 19, 2011, and having the title “Radiation Shielding Container Lid.” The present disclosure relates generally to a radioisotope elution system and tools for use therewith. Nuclear medicine uses radioactive material for diagnostic and therapeutic purposes by injecting a patient with a dose of the radioactive material, which concentrates in certain organs or biological regions of the patient. Radioactive materials typically used for nuclear medicine include Technetium-99m, Indium-111, and Thallium-201 among others. Some chemical forms of radioactive materials naturally concentrate in a particular tissue, for example, radioiodine (I-131) concentrates in the thyroid. Radioactive materials are often combined with a tagging or organ-seeking agent, which targets the radioactive material for the desired organ or biologic region of the patient. These radioactive materials alone or in combination with a tagging agent are typically referred to as radiopharmaceuticals in the field of nuclear medicine. At relatively low doses of radiation from a radiopharmaceutical, a radiation imaging system (e.g., a gamma camera) may be utilized to provide an image of the organ or biological region in which the radiopharmaceutical localizes. Irregularities in the image are often indicative of a pathology, such as cancer. Higher doses of a radiopharmaceutical may be used to deliver a therapeutic dose of radiation directly to the pathologic tissue, such as cancer cells. A variety of systems are used to generate, enclose, transport, dispense, and administer radiopharmaceuticals. One such system includes a radiopharmaceutical generator, including an elution column, and an input connector (e.g., an input needle) and an output connector (e.g., an output needle) in fluid communication with the elution column. Typically, a radiopharmacist or technician fluidly connects an eluant vial (e.g., a vial containing saline) to the input connector and fluidly connects an empty elution vial (e.g., a vial having at least a partial internal vacuum) to the output connector. The vacuum in the empty elution vial draws the eluant (e.g., saline) from the eluant vial through the elution column, and into the elution vial. The saline elutes radioisotopes as its flows through the elution column so that radioisotope-containing saline fills the elution vial. The elution vial is typically housed in its own radiation shielding container, sometimes referred to as pharmacy shield or an elution shield. This Background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. In one aspect, an elution tool for a radiopharmaceutical elution system includes an elution tool body having a top, an opposing bottom, and an opening in the top. The tool has a vial chamber that extends from the opening in the top toward the bottom and that is sized and shaped for receiving an elution vial through the opening in the top. An access opening extends through the bottom to the vial chamber and is aligned with a septum of the elution vial when the elution vial is received in the vial chamber. An elution tool lid is secured to the elution tool body by a hinged connection adjacent the top of the elution tool body. The elution tool lid is rotatable at the hinged connection and movable relative to the elution tool body between an occluded position, in which the elution tool lid occludes the opening in the top of the elution tool body, and an exposed position, in which the elution tool lid does not occlude the opening in the top of the elution tool body to allow the elution vial to be inserted into and removed from the vial chamber. The tool body and the lid include at least one of depleted uranium, tungsten, tungsten impregnated plastic, and lead. The tool also includes a latching mechanism for selectively and releasably locking the lid in the occluded position. In another aspect, an elution tool includes an elution tool body configured to be held in one hand of a user. A dispensing cap is removably securable to the bottom of the elution tool body. The dispensing cap includes a dispensing cap body having a dispensing access opening that is aligned with the access opening of the elution tool body when the dispensing cap is secured to the elution tool body. A dispensing lid is rotatably secured to the dispensing cap body for selectively occluding and exposing the dispensing access opening. Various refinements exist of the features noted in relation to the above-mentioned aspects of the present disclosure. Further features may be incorporated in the above-mentioned aspects of the present disclosure as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments of the present disclosure may be incorporated into any of the above-described aspects of the present disclosure, alone or in any combination. Referring to FIGS. 1A-4, one embodiment of a radioisotope elution system 10 includes a radioisotope generator 12 (FIGS. 3 and 4), which is removably receivable in an auxiliary shield assembly 14. As explained in more detail below, an elution tool 16, which houses an elution vial 17 (broadly, a container), and an eluant vial 18 (broadly, a container) are fluidly connectable to the radioisotope generator 12. Herein, “fluidly connectable” refers to the ability of first component and a second component to be connected (either directly or indirectly) or interface in a manner such that fluid (e.g., eluate, eluant) may flow therebetween in a substantially confined flow path. The auxiliary shield assembly 14 includes a radiation shielding body 20 that defines a cavity 22 in which the generator 12 is removably receivable, and a radiation shielding lid 24 that may be positioned on the body 20 toward a top thereof to substantially enclose the cavity 22 defined in the body 20. In general, the radiation shielding lid 24 facilitates proper alignment of the eluant vial 18 with the radioisotope generator 12 when fluidly connecting the eluant vial with the radioisotope generator. Additional disclosure of the radiation shielding lid 24 is set forth in detail below. The elution tool 16 illustrated in FIGS. 1-11 may be of any appropriate configuration (e.g., size, shape, design), as is known to one having ordinary skill in the art, and may include one or more suitable radiation shielding materials, such as depleted uranium, tungsten, tungsten impregnated plastic, or lead. A second embodiment of the elution tool is illustrated in FIGS. 22-33 and described in detail below. The illustrated elution vial 17 is a generally cylindrical container, made from glass or other material (e.g., plastic), which includes a septum 17a secured to a top portion thereof by a metal ring or cap 17b, as is generally known in the art. The elution vial 17 may be a different type of container suitably connectable to a radioisotope generator and/or may have a shape other than generally cylindrical. In one embodiment, the interior of the elution vial 17 is at least partially evacuated such that the elution vial has a reduced internal pressure (i.e., at least a partial vacuum). The eluant vial 18, like the elution vial 17, may be a generally cylindrical container, which includes a septum (not shown) secured to a top portion thereof by a metal ring or cap (not shown), as is generally known in the art. The eluant vial 18 may be a different type of container suitably connectable to a radioisotope generator and/or may have a shape other than generally cylindrical. The eluant vial 18 is filled with an eluant fluid, such as saline. In one embodiment, the volume of eluant fluid is less than the volume of the elution vial 17. In another embodiment, the interior volume of eluant vial 18 is less than the interior volume of the elution vial 17. For example, the eluant vial 18 may have an internal volume of about 26 milliliters, and the interior volume of the elution vial 17 may be about 36 milliliters. The elution vial 17 and/or the eluant vial 18 may be of other configurations without departing from the scope of the present disclosure. Referring to FIGS. 3-5, the radioisotope generator 12 includes: a housing 26; an elution column assembly 28 (FIG. 3) disposed within the housing; and input and output connectors 30, 32, respectively, in fluid communication with the elution column assembly 28; and a hood or cap 38 secured to the housing. The generator housing 26 is generally cylindrical and defines an axially extending cavity in which the elution column assembly 28 is received. The housing cap 38 may be snap-fit on the housing 26, or secured thereto in any other appropriate manner. The housing cap 38 has a recessed portion 40 extending downward from an upper surface of the cap. The cap 38 also has a generally U-shaped channel 42 extending downward from the upper surface and through a sidewall of the cap to the recessed portion 40. As explained in more detail below, the recessed portion 40 and the channel 42 together constitute an alignment structure, more specifically female alignment structure, for facilitating proper alignment of the radiation shielding lid 24 on the generator 12. The generator housing 26 and cap 38 may be formed from plastic (such as by molding) or from other suitable, preferably lightweight, material. Moreover, the generator housing 26 itself may be free from lead, tungsten, tungsten impregnated plastic, depleted uranium, or other radiation shielding material, such that the housing provides little or only nominal radiation shielding. The generator 12 includes a generator handle 44 pivotally secured to the cap 38. The handle 44 is pivotable between a stored position, in which the handle lies in a plane substantially transverse to the axis A1 of the housing 26 (FIG. 3) and below the upper surface of the cap 38, and a carrying position, in which the handle lies in a plane substantially parallel to the axis of the housing and above the upper surface of the cap. The generator handle 44 allows a radiopharmacist or technician to lift the generator 12 for placement of the generator in the auxiliary shield assembly 14 and removal of the generator from the auxiliary shield assembly. The generator handle 44 may be formed from plastic or any other appropriate material and may be pivotally connected to the generator housing 26 by pivot connectors 46 (FIG. 5) or in any other appropriate manner of connection. Referring to FIG. 3, the input and output connectors 30, 32 extend upward from the elution column assembly 28 and through respective input opening 50 and output opening 52 in a bottom surface 53 of the recessed portion 40 of the generator cap 38 such that respective terminal ends or tips 30a, 32a of the input and output connectors are disposed within the recessed portion. In the illustrated embodiment, the input and output connectors 30, 32 respectively include input and output needles or needles 30, 32 for piercing respective septums 17a of the elution vial 17 and the eluant vial 18, although it is contemplated that the connectors may be of other configurations/types. In addition to the input and output connectors 30, 32, a venting needle 54, in fluid communication with atmosphere, extends through the bottom surface 53 of the recessed portion 40 of the cap 38. The venting needle 54 is adjacent to the input connector 30 and extends through the same input opening 50 in the generator cap 38. In the illustrated embodiment, the venting needle 54 includes a needle having a terminal end or tip 54a disposed within the recessed portion 40 of the generator cap 38. The venting needle 54 pierces the septum 17a of the eluant vial 18, like the input needle 30, to vent the eluant vial 18 to atmosphere. As shown in FIGS. 12-13, in a non-use configuration of the generator—such as during shipping—the generator 12 may include needle covers 55a, 55b and a cap cover 56. In the illustrated embodiment, the needle covers include an input/venting needle cover 55a removably secured directly to the input needle 30 and the venting needle 54, and an output needle cover 55b removably secured directly to the output needle 32. The needle covers 55a, 55b protect the respective needles 30, 32, 54 and inhibit contaminants from entering the elution column assembly 28 via the needles. The illustrated needle covers 55a, 55b are solid, non-hollow, one-piece members made of a suitable material (e.g., silicone) that is pierceable by the needles 30, 32, 54. Before operating the elution system 10, a technician can remove the needle covers 55a, 55b using forceps or another suitable instrument. It is understood that the elution system 10 may not include the needles covers 55a, 55b, or the needle covers may be of other configurations without departing from the scope of the present invention. Referring still to FIGS. 12-13, the cap cover 56 is removably insertable in the recessed portion 40 of the generator cap 38 to cover and protect the input, output, and venting needles 30, 32, 54, respectively. The cap cover 56 has a top surface 56a that is disposed over and covers the needles 30, 32, 54 when the cap cover is secured to the generator 12, and a sidewall 56b depending downward from the top surface that frictionally engages the sidewall of the recessed portion 40 such that the cap cover is removably retained in the recessed portion by friction-fit connection. The cap cover 56 has two finger recesses 57 in the top surface 56a thereof, and a thumb recess 58 in the top surface and the sidewall 56b thereof. A technician can grip and remove the cap cover 56 using a single hand by inserting one or more of his/her fingers into each of the finger recesses 57 and inserting his/her thumb into the thumb recess 58, and then lifting the cap cover upward and out of the recessed portion 40. It is understood that a cap cover have other configurations and/or can be removably secured to the generator 12 in other ways without departing from the scope of the present invention. It is also understood that the elution system 10 may not include a cap cover without departing from the scope of the present invention. Referring to FIGS. 14-17, one embodiment of the elution column assembly 28 is shown in detail. As shown in FIGS. 16 and 17, an input conduit 59 extends from the input connector 30 and into a top 60a of an elution column 60 to fluidly connect the input connector to the elution column. An output conduit 61 extends from a bottom 60b of the elution column 60 to the output connector 32 to fluidly connect the elution column to the output connector. The input and output conduits 59, 61, respectively, can be made from suitable material, such as Inconel 625. The elution column 60 may include a source of radioactive material therein (e.g., molybdenum-99, adsorbed to the surfaces of beads of alumina or a resin exchange column). In the illustrated embodiment, a filter 62 (e.g., a conventional 0.2 micron filter) is fluidly connected to, and inline with, the output conduit 61. A fillport needle 63 is fluidly connected to conduit 64, which is in turn fluidly connected to the elution column 60 for loading the product (fillport needle is typically only accessed during loading and not accessed by the technician). A cover 63a, similar to the needle covers 55a, 55b described above, is removably attached to the needle 63. A venting conduit 65 (FIG. 17) fluidly connects the venting needle 54 with the atmosphere. The venting conduit 65 has a terminal end on which an air filter 66 is secured. As shown in FIGS. 14-16, a generally rigid U-shaped support 67, which may be formed from plastic or other suitable, generally rigid material, provides structural support to the input and output needles 30, 32, the venting needle 54, and the fillport needle 63, and portions of the respective conduits 59, 61, 64, 65. As shown in FIGS. 14 and 15, the elution column assembly 28 also includes a conduit shield 68 and a column shield 69. The conduit shield 68 covers the respective conduits 59, 61, 64, 65, or portions thereof, from adjacent the input, output, and venting needles, 30, 32, 54, respectively, to adjacent the top 60a of the elution column 60b. The conduit shield 68 also covers the fillport needle 63 and the output filter 62. The conduit shield 68 defines internal passages for receiving and covering the respective components, while leaving the input, output, and venting needles 30, 32, 54 and the air filter 66 exposed. The conduit shield 68 may be a two-piece construction and may include (e.g., be made from or have in their construct) lead, tungsten, tungsten impregnated plastic, depleted uranium and/or another suitable radiation shielding material. Referring to FIGS. 14 AND 15, the column shield 69 defines a chamber (not shown) for receiving the elution column 60 and a lower portion 71 of the conduit shield 68 therein. The column shield 64 may be a one-piece construction and may include (e.g., be made from or have in their construct) lead, tungsten, tungsten impregnated plastic, depleted uranium and/or another suitable radiation shielding material. Referring back to FIG. 1, the illustrated auxiliary shield assembly body 20 includes a top ring 72, a base 73, and a plurality of step-shaped or generally tiered, modular rings 74, which are disposed one over the other between the base 73 and the top ring 72. Substantially all or part of the illustrated auxiliary shield assembly body 20 may be made of one or more suitable radiation shielding materials, such as depleted uranium, tungsten, tungsten impregnated plastic, or lead. The modular aspect of the rings 74 may tend to enhance adjustment of the height of the auxiliary shield assembly body 20, and the step-shaped configuration may tend to contain some radiation that might otherwise escape through a linear interface between the modular rings. It is understood that the auxiliary shield assembly body 20 may be of other configurations. In one embodiment (FIG. 1B), an auxiliary shield cover 75 is receivable over the body 20. The cover 75 has a smooth exterior surface for ease of cleaning and to protect the outer surface of the body 20. The cover 75 may be formed from plastic (e.g., high-impact polypropylene) or other material. Referring now to FIGS. 6-11, the radiation shielding lid 24 includes: a generally cylindrical lid body 76 having upper and lower surfaces, 77, 78, respectively; an elution tool opening 79; and an eluant vial opening 80. In one example (of which an exemplary method of making is explained in more detail below), the lid body 76 includes a radiation shielding core 124 that is overmolded with a plastic material 126, 128. As an example, the radiation shielding core 124 may include depleted uranium, tungsten, tungsten impregnated plastic, or lead. The upper and lower surfaces 77, 78, respectively, are generally planar, although the surfaces may be other than generally planar. A male alignment structure, generally indicated at 81, is provided on the lower surface 78 of the lid body 76 to facilitate proper alignment of the lid 24 on the generator 12. More specifically, the male alignment structure 81 has a shape generally corresponding with the combined shape of the recessed portion 40 and the channel 42 of the generator 12 (together, these recessed portion 40 and the channel 42 constitute a female alignment structure) so that the male alignment structure mates with the generator in order to align the elution tool opening 79 with the output needle 32 and the eluant vial opening 80 with the input needle 30 and the venting needle 54. As such, it may be said that the lid 24 is keyed with the generator 12 (e.g., the cap 38 thereof) such that proper positioning of the lid 24 atop the generator 12 results in alignment of the respective openings 79, 80 with the corresponding needles 32, 30. The structure 81 enables only one position of the lid 24 relative to the generator 12. The illustrated male alignment structure 81 includes a wall 81a projecting outward from the bottom surface 78 and surrounding the elution tool opening 79 and the eluant vial opening 80. A plurality (e.g., a pair) of handles 82 on the upper surface 77 of the lid body 76 allows the radiopharmacist or technician to properly place the lid 24 on the generator 12 and remove the lid from the generator. The elution tool opening 79 extends through the lid body 76 from the upper surface 77 through the lower surface 78 thereof. The elution tool opening 79 is sized and shaped for removably receiving the elution tool 16 therein. For example, in the illustrated embodiment, the elution tool opening 79 has a generally circular circumference that is substantially uniform along its axis. In one embodiment, the elution tool opening 79 has a diameter slightly larger than an outer diameter of the elution tool 16 such that the opening effectively aligns the septum (not shown) of the elution vial 17 (FIG. 4) with the output needle 32 as the elution tool is inserted into the opening. For example, the elution tool opening 79 may have a diameter that is from about 0.25 mm (0.01 in) to about 1.0 mm (0.04 in) larger than the outer diameter of the elution tool 16. In one embodiment, the elution tool opening 79 may have a diameter from about 46 mm (1.8 in) to about 48 mm (1.9 in), although it may alternatively have a diameter falling outside this range. Other shapes and sizes of the elution tool opening 79 may be appropriate; however, it tends to be preferred that the shape and size of the elution tool opening 79 be at least generally complimentary to the shape and size of the elution tool 16 being used with the radiation shielding lid 24 to reduce the likelihood of misalignment between the elution vial 17 and the output needle 32. As shown in FIGS. 9 and 10, the eluant vial opening 80 is spaced apart and separate from the elution tool opening 79, and is sized and shaped for removably receiving an eluant vial 18 (FIG. 2), such as a vial containing saline or other eluants. In the illustrated embodiment (FIG. 10), the eluant vial opening 80 has a lower end 86 at the lower surface 78 of the lid body 76 and an upper end 88 intermediate the upper and lower surfaces 77, 78, respectively. In one example, the eluant vial opening 80 may have a diameter from about 34.0 mm (1.34 in) to about 34.5 mm (1.36 in), although it may alternatively have a diameter falling outside this range. As with the elution tool opening 79, other shapes and sizes of the eluant vial opening 80 may be appropriate; however, it tends to be preferred that the shape and size of the eluant vial opening 80 be at least generally complimentary to the shape and size of the eluant vial 18 being used with the radiation shielding lid 24 to reduce the likelihood of misalignment between the eluant vial 18 and the input needle 30 and venting needle 54. Referring to FIGS. 2, 6, 8, and 11, the illustrated lid 24 has two finger recesses 90 formed in the upper surface 77 of the lid body 76, which are diametrically opposite one another with respect to the eluant vial opening 80. The finger recesses 90 are defined by respective recessed surfaces extending downward from the upper surface 77 of the lid body 76 to the eluant vial opening 80, and are sized and shaped to allow at least distal portions of two fingers of a radiopharmacist or other appropriate technician to enter the finger recesses. Recessed surfaces defining illustrated finger recesses 90 are curved and generally in the shape of a half-bowl such that the recessed surfaces lead the radiopharmacist's or technician's fingers toward the eluant vial opening 80. It is understood that in other embodiments the lid 24 may have a single finger recess, such as a finger recess that completely or partially surrounds the eluant vial opening 80, or more than two finger recesses. Referring to FIG. 8, each illustrated finger recess 90 has an upper edge 92 adjacent the upper surface 77 of the lid body 76 and a lower edge 93 that is coextensive with a portion of the upper end 88 of the eluant vial opening 80. Referring to FIG. 11, the lid 24 of the auxiliary shield assembly 14 includes first and second alignment wings 100, each designated generally at reference numeral 100, extending upward from adjacent the upper end 88 of the eluant vial opening 80 within the finger recesses 90. Each of the first and second wings 100 has opposite sides 104, a top portion 106, and an inner surface 108 extending partially around a circumference of the upper end 88 of the eluant vial opening 80. In the illustrated embodiment, the top portion 106 of each of the wings 100 is disposed above the upper surface 77 of the lid body 76 (as seen best in FIGS. 7 and 10), and the inner surface 108 of each of the wings 100 is generally arcuate, although it is understood that the wings 100 may be of other shapes and relative dimensions. Together, the inner surfaces 108 of the wings 100 and the eluant vial opening 80 define a vial passageway 107 extending from the top portions 106 of the wings 100 through the lower surface 78 of the lid body 76. The wings 100 preferably enable alignment of the eluant vial septum with the input needle 30 and venting needle 54 as the eluant vial 18 is inserted into the vial passageway 107. As such, the wings 100 preferably make it is less likely that the input needle 30 or venting needle 54 will contact the metal ring or other hard part of the vial and damage the needle. In one example, the inner surface 108 of each wing 100 may extend at least 45 degrees and less than 180 degrees around the circumference of the upper end 88 of the eluant vial opening 80. In other examples, the inner surface 108 of each wing 100 may extend at least 60 degrees, or at least 90 degrees, and less than 180 degrees around the circumference of the upper end 88 of the eluant vial opening 80. Other configurations of the wings 100 do not depart from the scope of the present disclosure. To facilitate gripping of the eluant vial 18 during at least one of insertion of the vial into the vial passageway 107 and removal of the vial from the vial passageway, the respective adjacent sides 104 of the first and second wings 100 are spaced apart from one another about the eluant vial opening 80 to define gaps or first and second finger channels, each indicated at 112 (FIGS. 6 and 10), leading from the finger recesses 90 to the vial passageway. In the illustrated embodiment, the finger channels 112 are diametrically aligned, relative to the vial opening 80, with the finger recesses 90, and the respective sides 104 of the wings 100 extend into the associated finger recesses 90. Each of the first and second finger channels 112 are sized and shaped to allow at least the distal portion of one of the two fingers to enter the corresponding finger channel from the associated finger recess 90. For example, a minimum width of each of the finger channels 112 (i.e., the distance between the respective adjacent sides 104 of the first and second wings 100) may measure from about 19 mm (0.75 in) to about 21 mm (0.83 in), and more specifically, from about 19.0 mm (0.748 in) to about 19.6 mm (0.776 in), although the minimum width of each finger channel may fall outside this range. Thus, the finger channels 112 allow the radiopharmacist or technician to grip the eluant vial 18, such as by using his/her thumb and forefinger, during at least one of insertion of the vial in the vial passageway 107 and removal of the vial from the vial passageway. In the illustrated embodiment (FIGS. 8, 10, and 11), a diameter of a portion of the vial passageway 107 defined by the inner surfaces 108 of the wings 100 tapers from the top portions 106 of the wings toward the eluant vial opening 80. Tapering the inner surfaces 108 of the wings 100 facilitates molding of the wings when overmolding the lid 24 in one example, as described below. Although this diameter of the vial passageway 107, as defined by the inner surfaces 108, tapers along the length of the passageway, a plurality of alignment ribs 114 are provided on the inner surfaces to define an effective inner diameter of the vial passageway that is substantially uniform along the length of the passageway. The ribs 114 are spaced apart from one another between the sides 104 of the wings and extend longitudinally along the respective wings 100. The wings 100 project inwardly, generally toward a centerline of the passageway 107, such that each rib 114 has a terminal, guiding surface 115 (FIG. 11) generally facing the centerline of the passageway. Each guiding surface 115 is uniformly spaced from the centerline of the vial passageway 107 along its length. In other words, the guiding surface 115 of each rib 114 does not taper or flare with respect to the axis of the vial passageway 107. Through this configuration, the guiding surfaces 115 effectively align the elution vial 18 with the input needle 30 and venting needle 54 even though the inner surfaces 108 of the wings 100 are tapered. The ribs 114 have depths projecting into the vial passageway 107 relative to the respective inner surfaces 108. Because the diameter of the vial passageway 107 defined by the inner surfaces 108 of the wings 100 tapers, yet the guiding surfaces 115 do not taper or flare relative to the centerline of the vial passageway, the depths of the ribs relative to the respective inner surfaces 108 taper toward the eluant vial opening 80. The wings 100 may not include the ribs 114 without departing from the scope of the present disclosure. As illustrated in FIG. 3, a bottom 116 of the eluant vial 18 lies slightly below or at the top portions 106 of the wings 100 when the eluant vial is received in the vial passageway 107 and fluidly connected to the input needle 30. Notches 118 in the top portions 106 of the wings 100 allow the radiopharmacist or technician to view the eluant vial 18 in the passageway without having to position his/her head above the upper surface 77 of the lid 24. In one example, the auxiliary shield lid 24 may be formed by a two-step overmolding process. In such a process, a radiation shielding core 124 (FIG. 10)—which may include a suitable radiation shielding material such as depleted uranium, tungsten, tungsten impregnated plastic, or lead—is provided. The core 124 may be generally disk-shaped, having first and second openings, which will form the elution tool and eluant vial openings, 79, 80, respectively, and recesses, which will form the finger recesses 90. A first molded part is molded with a first thermoplastic material 126 to form the bottom surface 78, the male alignment structure 81, and the sidewall of the body 76, and at least lower portions of the elution tool opening 79 and the eluant vial opening 80. Next, the core 124 is placed into the first molded part. Finally, this assembly is overmolded with a second thermoplastic material 128 to form the top surface 77, the handles 82, the finger recesses 90, the wings 100, and an upper portion of at least the elution tool opening 79. The first and second thermoplastic materials 126, 128, respectively, may include polypropylene and polycarbonate, or other material, and the first and second thermoplastic materials may be of the same material. Other methods of making the auxiliary shield lid 24 may be used. Referring to FIGS. 18-21, an eluant shield 136 of the elution system 10 is positionable over the eluant vial 18 when the vial is received in the eluant vial opening 80 in the lid 24 and fluidly connected to the generator 12 to inhibit exposure of the radiopharmacist or technician to radiation when the eluant is fluidly connected to the generator (e.g., during and after an elution process). The eluant shield 136 has a top 138, an opposing bottom 140, and a cavity 142 extending from the bottom toward the top. A pair of shielding wings 144 at the bottom 140 of the eluant shield 136 partially surround the cavity 142. The shielding wings 144 are sized and shaped to fit snugly within the finger recesses 90 in the lid 24 so that the top portions 106 of the alignment wings 100 are received in the cavity 142 of the eluant shield 136 and the shielding wings 144 oppose the sides 104 of the alignment wings and the finger channels or gaps 112 between the sides of the alignment wings. As such, substantially an entirety of the eluant vial 18 is surrounded by radiation shielding material of either the lid 24 or the eluant shield 136. More specifically, when the eluant shield 136 is positioned on the lid 24, substantially the entirety of the eluant vial 18 is surrounded by a suitable radiation shielding material, such as depleted uranium, tungsten, tungsten impregnated plastic, or lead. In one example, the eluant shield 136 may be formed by a two-step overmolding process. In such a process, a radiation shielding core 124, which may include a suitable radiation shielding material such as depleted uranium, tungsten, tungsten impregnated plastic, or lead—is provided. The core is substantially the same shape as the eluant shield in finished form, including a pair of shielding wings and a cavity. A first molded part is molded with a first thermoplastic material to form the top 138. Next, the core is placed into the first molded part. Finally, this assembly is overmolded with a second thermoplastic material to form the bottom 140, the shielding wings 144, and the cavity 142. The first and second thermoplastic materials, respectively, may include polypropylene and polycarbonate, or other material, and the first and second thermoplastic materials may be of the same material. Other methods of making the eluant shield 136 may be used. Referring to FIGS. 22-33, a second embodiment of an elution tool 150 is generally indicated at reference numeral 150. This elution tool 150 includes a body, generally indicated at 152, having a top 154, and opposing bottom 156; and a lid, generally indicated at 158, hingedly secured to the top of the elution tool body. As explained in more detail below, a dispensing cap 160 (FIG. 22) is removably securable to the bottom 156 of the elution tool body 152 for configuring the elution tool in a dispensing tool configuration, and a storage cap 162 (FIG. 23) is removably securable to the bottom of the elution tool body for configuring the elution tool into a storage tool configuration. In generally, the dispensing cap 160 and the storage cap 162 are interchangeably securable to the elution tool body 152. In the illustrated embodiment, neither the dispensing cap 160 nor the storage cap 162 are secured to the elution tool body 152 when then elution tool 150 is inserted in the auxiliary shield and the elution vial 17 in the elution tool is fluidly connected to the generator 12. The elution tool body 152 is sized and shaped to be slidably receivable in the elution tool opening 79 in the auxiliary shield lid 24. The body 152 has an upper longitudinal portion 163 having first outer diameter that defines an annular stop surface 164 to inhibit the top 154 of the body from entering the elution tool opening 79 in the auxiliary shield lid 24. A lower longitudinal portion 166 of the body 152, having a second outer diameter that is less than the first outer diameter, is receivable in the dispensing and shielding caps 160, 162, respectively, as explained in more detail below. An intermediate longitudinal portion 168 of the body 152, having an outer diameter that is less than the first outer diameter and greater than the second outer diameter OD2, is sized and shaped to be slidably receivable in the elution tool opening 79. The elution tool body 152 may include (e.g., be made from or have in their construct) lead, tungsten, tungsten impregnated plastic, depleted uranium and/or another suitable radiation shielding material. The elution tool body 152 is configured to receive the elution vial 17 therein. In particular, the elution tool body 152 has a vial chamber 170 (FIG. 33) defined therein extending from an opening 172 in the top 154 of the elution tool body to an opposing access opening 174 in the bottom thereof. The top opening 172 is sized and shaped to allow the elution vial 17 to be inserted into and removed from the vial chamber 170, and the vial chamber has a size and shape generally corresponding to the size and shape of the elution vial such that the elution vial fits generally snugly within the chamber. The bottom 156 of the elution tool body 152 defines an annular internal surface 178 surrounding the access opening 174. When the elution vial 17 is received in the vial chamber 170, the metal ring 17b of the vial contacts the internal surface 176 so that the septum 17a is aligned with the access opening 174. Accordingly, when the elution tool 150 is inserted into the elution tool opening 79 in the lid 24, the output needle 32 enters the access opening 174 and pierces the septum 17a. The elution tool lid 158 is hingedly secured to the elution tool body 152 and configurable between an open or exposed position (FIG. 24), in which the top opening 172 is exposed and the elution vial 17 can be inserted into and removed from the vial chamber 170, and a closed or occluded position (FIGS. 25-28), in which the top opening is occluded and the elution vial is retained in the vial chamber. The elution tool lid 158 includes a generally planar or disk-shaped lid body 178 that is receivable in a lid recess 180 defined in the top 154 of the elution tool body 152 when the lid is in the closed position. The lid body 178 has a lower face 178a that seats on an inner annular flange or lid seat 182 of the lid recess 180, and an upper face 178b that is substantially coplanar with the top 154 of the elution tool body 152 when the lid 158 is in a closed position. The upper face 178b of the lid body 178 has a plurality of gripping slots 179 formed therein to provide a gripping region for the radiopharmacist or technician when opening and closing the lid, as explained in more detail below. For reasons which are apparent from the below description, the elution tool lid 158 has a generally circular periphery, and the lid recess 180 and the lid seat 182 have generally oblong peripheries. Moreover, the elution tool lid 158 is sized and shaped to allow for movement of the lid along the major axis of the lid recess 180 when the lid is seated on the lid seat 182. The elution tool lid body 178, may include (e.g., be made from or have in their construct) lead, tungsten, tungsten impregnated plastic, depleted uranium and/or another suitable radiation shielding material. Referring to FIGS. 22-28, the illustrated elution tool 150 includes a hinged lid connection, generally indicated 186, and a latching mechanism, generally indicated at 188, for releasable locking the lid 158 in the closed position. The hinged lid connection 186 includes a hinge connector 190 extending radially or laterally outward from the periphery of the lid body 178, and a hinge pin 192, adjacent the periphery of the top 154 of the elution tool body 152, to which the hinge connector is coupled. The hinge connector 190 defines a slot 194 in which the hinge pin 192 is received to allow both rotation of the hinge connector (and the lid 158) about the hinge pin, and limited transverse, linear movement of the hinge connector (and the lid) relative to the hinge pin. The latching mechanism 188 includes a latching member 194 extending radially or laterally outward from the periphery of the lid body 178, generally diametrically opposite the hinge connector 190. The latching member 194 includes a tongue 196 that is slidably receivable in a latching groove 198 adjacent the periphery of the top 154 of the elution tool body 152. A detent 200 (e.g., a ball detent) on the elution tool body 152 extends into the latching groove 198 and releasably engages the latching member 194 (e.g., an underside of the latching member) as the tongue 196 is slid into the latching groove to inhibit the latching member from inadvertently withdrawing (e.g., sliding back out) from the latching groove. To lock the lid 158 in the closed position (FIGS. 27 and 28), the radiopharmacist or technician can rotate the lid about the hinge pin 192 to the closed position such that the lid body 178 is seated on the lid seat 182 of the elution tool body 152. Once seated, the slot 194 in the hinge connector 190 allows the radiopharmacist or technician to move the lid 158 linearly toward the latching groove 198, whereby the tongue 196 can be slid into the latching groove 198. For example, while holding the elution tool 150 using one hand, the radiopharmacist or technician may contact the upper face 178b of the lid body 178 (more specifically, the region defined by the gripping slots 179) with his/her thumb to rotate the lid 158 to its closed position and then linearly slide the lid toward the latching groove 198. As the latching member 194 slides over the ball detent 200, the ball detent deflects and pushes against the latching member. Once the tongue 196 is received in the latching groove 198, the lid 158 is releasably locked in the closed position. The lid 158 may be unlocked (FIGS. 25 and 26) by the radiopharmacist or technician using his/her thumb to slide the lid away from the latching groove 198, against the pushing force of the ball detent, so that the tongue 196 is withdrawn from the latching groove 198. Once unlocked, the lid 158 can be rotated to the open position. It is understood that the lid 158 may be releasably lockable in the closed position in other ways, and other ways of retaining the elution vial 17 in the elution tool 150 do not depart from the scope of the present disclosure. As disclosed above, dispensing cap 160 is removably securable to the lower longitudinal portion 168 of the elution tool body 152, such as shown in FIG. 22, to configure the elution tool in the dispensing configuration. In the dispensing configuration, the elution tool 150 can be used as a dispensing tool, whereby the radiopharmacist or technician can hold the elution tool and withdrawal a quantity of radiopharmaceutical from the elution vial 17 housed in the elution tool without removing the dispensing cap 160. The dispensing cap 160 includes a body 204 (e.g., a generally cylindrical body) having a top 206 and a bottom 208. The dispensing cap body 204 defines a socket 210 extending from the top 206 toward the bottom 208 thereof that is sized and shape for receiving the lower longitudinal portion 166 of the elution tool body 152. The socket 210 has an open top end to allow insertion of the lower longitudinal portion 166 of the elution tool body 152 into the socket, and an access opening 212 at the bottom 208 of the dispensing cap body 204 that is alignable with the access opening 174 in the elution tool body 152 to provide access to the septum 17b of the elution vial 17 in the chamber 170 of the elution tool body 152. Referring to FIG. 22, the dispensing cap 160 includes a plurality of magnetic couplers 214 attached to dispensing cap body 204 and surrounding the socket 210 for releasably securing the dispensing cap to the elution tool body 152 when the lower longitudinal portion 166 of the elution tool body is received in the socket. The magnetic couplers 214 are magnetically attracted to an annular coupler surface 216 of the elution tool body 152 that is in opposing relationship with the magnetic couplers when the lower longitudinal portion 166 of the elution tool body is received in the socket 210 of the dispensing cap 160. In another embodiment, the elution tool body 152 may include magnetic couplers that are magnetically attracted to the magnetic couplers (or some other component or structure) of the dispensing cap body 204. The dispensing cap 160 also includes a locking pin 218 extending longitudinally outward from the top 206 of the dispensing cap body 204. The locking pin 218 is alignable with and receivable in a locking cavity 220 in the annular coupler surface 216 of the elution tool body 152 to inhibit the dispensing cap 160 from rotating about the elution tool body. In one example of securing the dispensing cap 160 to the elution tool body 152, the radiopharmacist or technician may insert the lower longitudinal portion 166 of the elution tool body 152 into the socket 210 of the dispensing cap 160 and then rotate the dispensing cap about the elution tool body (or vice versa) until the locking pin 218 aligns with and enters the locking cavity 220. The dispensing cap 160 may be removably securable to the elution tool body 152 in other ways. The dispensing cap 160 includes a dispensing lid 222 pivotably secured to the bottom 208 of the dispensing cap body 204 by a pivot pin 223 (e.g., a pivot bolt) for selectively opening and closing the access opening 212 of the socket 210 and for providing suitable radiation shielding when the elution vial 17 is received in the elution tool 150. More specifically, the dispensing lid 222 is received in a recess 224 formed in the bottom 208 of the dispensing cap body 204, and is pivotable about a pivot axis defined by the pivot pin 223 that is generally parallel to the longitudinal axis of the elution tool 150. The dispensing lid 222 is pivotable between a non-dispensing position (FIGS. 29 and 30), in which the dispensing lid is aligned with and opposing (i.e., covering) the access opening 212 of the socket 210, and a dispensing position (FIGS. 30 and 31), in which the dispensing lid is at least partially misaligned with the access opening (i.e., the access opening is at least partially uncovered) to allow access to the septum 17b of the elution vial 17. A detent 226 (e.g., a ball detent) on the bottom 208 of the dispensing cap body 204 releasable locks the dispensing lid 222 in the non-dispensing position. Moreover, when the dispensing lid 222 is moved to the dispensing position, the detent 226 is removably receivable in one of a plurality of slots (e.g., three slots, not shown) formed on an underside of the dispensing lid. Accordingly, the dispensing lid 222 is releasably lockable in a selected one of a plurality of dispensing positions, each providing a different degree to which the lid is open. To position the dispensing lid 222 in the dispensing position and provide access to the elution vial 17 in the elution tool 150 when the dispensing cap 160 is secured to the elution tool, a radiopharmacist or technician can hold the elution tool in one hand and use his/her thumb to grip the dispensing lid and swing (i.e., rotate) the dispensing lid about the pivot pin 223 and away from the access opening 212 in the dispensing cap. As the radiopharmacist or technician swings the dispensing lid 222 open, the detent 226 resiliently deflects to allow the dispensing lid to slide over the detent. The radiopharmacist or technician may continue to rotate the dispensing lid 222 until the lid is at a selected dispensing position and the detent 226 enters one of the slots (not shown) on the underside of the lid. With the dispensing lid 222 in a selected dispensing position, the radiopharmaceutical in the elution vial 17 is accessible to the radiopharmacist or technician, in that the radiopharmacist or technician can insert a dispensing needle of a syringe (not shown) through the access openings 212, 174 in the respective dispensing cap 160 and the elution tool body 150 and into the elution vial 17, by piercing the septum 17b, to withdraw a desired quantity of radiopharmaceutical from the elution vial. After withdrawing the desired quantity of radiopharmaceutical, the radiopharmacist or technician can position the dispensing lid 222 in the non-dispensing position by rotating or swinging the lid toward the access opening 212, whereby the detent 226 deflects as the lid slides toward the access opening. A wall 228 partially defining the recess 224 in the dispensing cap 160 acts as a stop for inhibiting the lid from sliding past the access opening 212 as the lid being closed. The dispensing lid 222 may include (e.g., be made from or have in their construct) lead, tungsten, tungsten impregnated plastic, depleted uranium and/or another suitable radiation shielding material. In contrast, the dispensing cap body 204 may be formed from a suitable material, such as aluminum, plastic or other corrosion-resistant, lightweight material, or other material that has a density less than the density of suitable radiation shielding, such as that provided by lead, tungsten, tungsten impregnated plastic, depleted uranium. The dispensing cap body 204 does not need to provide suitable radiation shielding, such as that provided by lead, tungsten, tungsten impregnated plastic, depleted uranium and/or another suitable radiation shielding material, because such suitable radiation shielding is provided by the elution tool body 152. Accordingly, the dispensing cap 160 does not add a significant amount of weight to the elution tool 150 so that the elution tool may be suitably used as a dispensing tool for the radiopharmacist or technician. Referring to FIG. 23, as disclosed above the storage cap 162 is removably securable to the elution tool body 152 to configure the elution tool in the storage configuration. In the storage configuration, the storage cap 162 must be removed from the elution tool body 152 in order for a radiopharmacist or technician to withdraw a quantity of radiopharmaceutical from the elution vial 17. The storage cap 162 includes a storage cap body 232 (e.g., a generally cylindrical body) having a top 234 and a bottom 236, and a radiation shield 238 secured to the bottom of the storage cap body. The storage cap body 232 defines a socket 240 extending from the top 234 toward the bottom 236 of the storage cap body that is sized and shape for receiving the lower longitudinal portion 166 of the elution tool body 152. The socket 240 has an open top end to allow insertion of the lower longitudinal portion 166 of the elution tool body 152 into the socket. The radiation shield 238 is secured to the bottom 236 of the storage cap body 232 such that the shield is aligned and in opposing relationship with the access opening 174 in the elution tool body 152 when the storage cap 162 is removably secured to the elution tool 150. In the illustrated embodiment, the radiation shield 238 is a press insert into the storage cap body 232. The radiation shield 238 may be secured to the storage cap body 232 in other ways without departing from the scope of the present disclosure. Referring to FIG. 23, the storage cap 162 is removably securable to the elution tool body 152 in substantially the same way as the dispensing cap 160, although the storage cap can be removably securable in other ways. More specifically, the storage cap 162 includes a plurality of magnetic couplers 244 secured to the storage cap body 232 and surrounding the socket 240. The magnetic couplers 244 are magnetically attracted to the annular coupler surface 216 of the elution tool body 152. It is understood that the elution tool body 152 may include magnetic couplers secured thereto, that are magnetically attracted to the magnetic couplers (or another component or structure) of the storage cap body. The dispensing cap 160 may be removably securable to the elution tool body 152 in other ways without departing from the scope of the present disclosure. Referring to FIGS. 34-37, the radioisotope elution system 10 may also include a sterile vial holder, generally indicated at 250, for a vial 252 of sterile fluid (e.g., TechneStat™) in which the output needle 32 is stored when the elution system 10 is not in use. As explained in more detail below, after the elution process, the elution tool 150 may be withdrawn from the elution tool opening 79 in the auxiliary shield lid 24, at which time the sterile vial holder 250 can be inserted into the elution tool opening so that the output needle 32 pierces a septum 252a of the sterile fluid vial. The sterile vial holder 250 includes a body, generally indicated at 254, for holding the sterile vial 252 therein, and a cap, generally indicated at 256, that is removably securable to the body. The holder body 254 has a generally cylindrical receptacle 258 having an open top 260, a bottom 262, and a vial chamber 264 sized and shaped for receiving and retaining the sterile vial 252 therein. As shown in FIG. 36, the bottom 262 of the receptacle 258 defines an access opening 266 that is aligned with the septum 252a of the sterile vial 252 when the vial is received in the chamber 264 so that the output needle 32 pierces the septum and enters the sterile vial when the sterile vial holder 250 is inserted into the elution tool opening 79. The holder body 254 includes a plurality of fins 268 (e.g., four fins) projecting radially outward from the receptacle 258 and spaced apart around the receptacle. The fins 268 define a diameter or cross-sectional dimension of the receptacle 258 that is sized and shaped to fit snugly within the elution tool opening 79 so that the access opening 266 (and the septum 252a) align with the output needle 32 when the holder 250 is inserted into the elution tool opening. The holder body 254 may be of other configurations without departing from the scope of the present disclosure. The cap 256 of the sterile vial holder 250 is removably securable to the body 254 by a twist-lock mechanism, generally indicated at 270. The body 254 includes an annular female twist-lock component 272 that receives a male twist-lock component 274 projecting outward from a bottom surface 276 of the cap 256. The female twist-lock component 272 defines slots or grooves 278 that are spaced apart around an interior surface 280 of the female twist-lock component to define gaps 281. The male twist-lock component 274 includes a plurality of tabs 282 that are receivable in the gaps 281 defined between the grooves 278 of the female twist-lock component, and that enter the grooves 278 when the cap 256 is rotated about its longitudinal axis relative to the holder body 254. When the tabs 282 are received in the grooves 278, the twist-lock mechanism inhibits relative longitudinal movement between the cap 256 and the holder body 254. In the illustrated embodiment, the male twist-lock component 274 also includes a longitudinal projection 284 that enters the vial chamber 264 of the receptacle 258 and abuts the bottom of the sterile vial 252 to limit or restrict longitudinal movement of the sterile vial in the chamber. It is understood that the cap 256 may be releasably securable to the body 254 in other ways without departing from the scope of the present disclosure. The holder body 254 may be a one-piece component formed (e.g., molded) from plastic or other material that has a density less than the density of material that provides suitable radiation shielding, such as that provided by lead, tungsten, tungsten impregnated plastic, depleted uranium. The cap 256, on the other hand, may include suitable radiation shielding material such as depleted uranium, tungsten, tungsten impregnated plastic, or lead. In one example, the cap may be formed by a two-step overmolding process. In such a process, a radiation shielding core—which may include a suitable radiation shielding material such as depleted uranium, tungsten, tungsten impregnated plastic, or lead—is provided. A first molded part is molded with a first thermoplastic material to form the top 260. Next, the core is placed into the first molded part. Finally, this assembly is overmolded with a second thermoplastic material to form the bottom 262, the male twist-lock component 274, and the longitudinal projection 284. The first and second thermoplastic materials, respectively, may include polypropylene and polycarbonate, or other material, and the first and second thermoplastic materials may be of the same material. Other methods of making the cap 256 may be used. Referring to FIGS. 38 and 39, the elution system 10 may also include a re-covering tool, generally indicated at 290, for reapplying the input/venting needle cover 55a and the output needle cover 55b on the respective input and venting needles 30, 54 and the output needle 32. The re-covering tool 290 has a first longitudinal portion 292, defining an output needle cover cavity 294 for snugly receiving the output needle cover 55b therein, and a second longitudinal portion 296, defining an input/venting needle cover cavity 298 for snugly receiving the input/venting needle cover 55a therein. The first longitudinal portion 292 has a size and shape such that it is snugly receivable in the elution tool opening 79 in the auxiliary shield lid 24, and the second longitudinal portion 296 has a size and shape such that it is snugly receivable in the eluant vial opening 80 in the auxiliary shield lid. The re-covering tool 290 may be formed from plastic, or other suitable material, and may be molded as a single, one-piece structure. To reapply the covers 55a, 55b, the radiopharmacist or technician inserts the covers into the respective cavities 294, 298. The covers 55a, 55b are held in the respective cavities 294, 298 by friction-fit engagement between the walls of the cavities and the covers. The radiopharmacist or technician can then insert the second longitudinal portion 296 into the eluant vial opening 80, whereupon the input and venting needles 30, 54 pierce the cover 55a. Upon withdrawing the second longitudinal portion 296 from the eluant vial opening 80, the cover 55a remains secured to the input and venting needles 30, 54. The radiopharmacist or technician can then insert the first longitudinal portion 292 into the elution tool opening 79 to reapply the cover 55b in a similar manner. It is understood that the covers 55a, 55b may be reapplied in any order without departing from the scope of the present disclosure. In a method of using the radioisotope elution system 10, the radiopharmacist or technician manually inserts the radioisotope generator 12 into the cavity 22 of the auxiliary shield body 20, the handle is folded down, and the cap cover 56 is removed in the manner set forth above. The auxiliary shield lid 24 is then manually placed in the cavity, on top of the radioisotope generator 12. The lid 24 may be rotated to thereby mate the male alignment structure 81 on the lid with the female alignment structure (i.e., the recessed portion 40 and the U-shaped channel 42) in the cap 38 of the generator 12. Upon mating, the eluant vial opening 80 is disposed over and generally vertically aligned with the input needle 30 and the venting needle 54, and elution tool opening 79 is disposed over and generally vertically aligned with the output needle 32. Using forceps (or another tool), the radiopharmacist or technician removes the two covers 55a and 55b. The eluant vial 17 is manually inserted into the passageway defined by the wings 100 and the eluant vial opening 80. The passageway guides the eluant vial 17 in a substantially vertical direction, such that the longitudinal axis of the eluant vial is generally aligned with the axes of the input needle 30 and the venting needle 54. More specifically, the passageway guides the eluant vial 17 such that the input needle 30 and the venting needle 54 pierce the septum of the vial to fluidly connect the interior of the eluant vial to the generator 12. The radiopharmacist or technician can view the bottom 116 of the eluant vial 18 through the notches 118 in the respective wings 100 when the vial is received in the passageway 107 to confirm that the eluant vial 18 is fully inserted onto the generator 12. Accordingly, the radiopharmacist or technician does not have to position his/her head directly above the lid 24 to confirm that the needles 30, 54 actually pierced the eluant vial septum. To this effect, the radiopharmacist or technician reduces any likelihood of radiation exposure from the generator 12 when positioning his/her head over the eluant vial opening 80. Once confirmation is made that the vial is properly placed, the eluant shield 136 may be placed over the bottom of the eluant vial in the manner set forth above. In this method, the elution vial 17 is inserted into the elution tool 150 and the lid 158 is closed in the manner set forth above. The elution tool, which does not have either the dispensing cap 160 or the storage cap 162 secured thereto, is manually inserted into the elution tool opening 79 such that the output needle 32 pierces the septum of the elution vial to fluidly connect the elution vial to the generator 12. The vacuum (or reduced pressure) in the elution vial 17 draws the saline from the vial 18 through the radioisotope column and into the elution vial 17. After the elution vial 17 is filled with the desired quantity of radioisotope-containing saline, the elution tool 150 can be manually removed from the lid 24, at which time the dispensing cap 160 or the storage cap 162 can be secured to the elution tool body 152 in the manner set forth above. With the dispensing cap 160 secured to the elution tool body 152, the radiopharmacist or technician can withdraw desired quantities of the radiopharmaceutical from the elution vial 17 in the manner set forth above. With the elution tool 150 removed from the lid 24, the sterile vial holder 250 can be inserted into the elution tool opening 79 so that the output needle 32 pierces the sterile vial 252. The now empty eluant vial 18 may remain on the radioisotope generator 12 until a subsequent elution in order to keep the needles 30, 54 sterile. When it is time for a subsequent elution, the eluant vial 18 can be manually removed from lid 24, such as by the radiopharmacist or technician inserting his/her thumb and forefinger into the respective finger recesses 90 and then into the respective finger channels 112 to grip (or pinch) the eluant vial. The radiopharmacist or technician can then lift the eluant vial 18 upward off the needles 30 and 54 and out of the lid 24. When introducing elements of the present invention or the embodiment(s) thereof, the articles “a”, “an”, the and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. As various changes could be made in the above apparatus and methods without departing from the scope of the disclosure, it is intended that all matter contained in the above description and shown in the accompanying figures shall be interpreted as illustrative and not in a limiting sense. |
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056132409 | description | DETAILED DESCRIPTION OF THE INVENTION The invention is based upon the discovery that sodalite can be produced from salt occluded zeolites by the use of heat or heat and pressure in the presence of glass contrary to prior teachings in the art. More specifically, it has been found that providing glass in the amount of about 5% to about 10% by weight and the presence of salt occluded zeolite while heating the material to a temperature of about 1000.degree. K. produces a material which, when tested by x-ray diffraction techniques, is sodalite. Because sodalite will absorb less waste salt than a corresponding amount of zeolite, it is required for the full appreciation of the method to provide excess amount of zeolite in the mixture prior to heating to accommodate the diminished capacity of sodalite to absorb the radionuclides. This prevents the resultant product from leaving a large amount of radioactive material not occluded by the sodalite. More specifically, zeolite in powder or pellet form may be initially dried by heating in a series of four steps to 800.degree. K. and flowing nitrogen or under a vacuum. This process removed nearly all the water from the zeolite and the zeolite was thereafter stored in an inert atmosphere such as in a glove box. In the protective atmosphere or in a glove box, the dry zeolite powder or pellets was loaded into a quartz test tube. The simulated waste salt was loaded into another quartz tube. The waste salt may be comprised of the following: ______________________________________ KI 0.3% NdCl.sub.3 1.04% LaCl.sub.3 1.06% CeCl.sub.3 0.74% YCl.sub.3 0.13% LiCl 32.9% NaCl 5.97% SrCl.sub.2 0.59% BaCl.sub.2 1.43% KCl 44.83% CsCl 3.73% ______________________________________ After the salt and zeolite are heated to about 700.degree. K. the salt is poured into the tube containing the zeolite and allowed to stand for 24 hours. In an ion exchange process, sufficient product chlorides are concentrated in the zeolite relative to the remainder of the salt. After the ion exchange, most of the excess salt is removed from the zeolite surface even though some of the free salt remains present. Thereafter, the salt loaded zeolite is combined with additional (up to 2 times) dehydrated zeolite in an alumina crucible. Because sodalite can occlude approximately 1/3 the volume of salt that a zeolite can occlude, generally twice the amount of occluded zeolite is added. In any event, enough dehydrated zeolite is added to reduce the total salt level to about 12wt % or less. Glass is added to this mixture in the range of between about 5% by weight to about 10% by weight of the zeolite and salt. Two hot pressing processes have been developed. In the one process, the zeolite powders/pellets are first converted to sodalite powders/pellets by heating to 1000.degree. K. for 24 hours or so. The sodalite powders/pellets are then densified using hot pressing at temperatures around 1200.degree. K. and 20-28 MPa. In a high pressure process, the zeolite powders and salt mixture is converted to sodalite directly during hot pressing at a temperature of 1000.degree. K. and pressures around 120 MPa. In a low pressure process, prior to hot pressing the zeolite and salt mixture is coverted to sodalite. If the glass is in frit form, the mixture is stirred and heated to 1000.degree. K. and held at that temperature for about 25 hours. After cooling, x-ray diffraction shows only sodalite. The sodalite powder with the occluded radionuclides is added to a graphite die and is initially cold pressed at 40 MPa. The cold pressed material is then heated to 1200 K. using a 20 K. per minute ramp rate and held at 28 MPa for approximately 30 minutes at maximum temperature. It is believed that a minimum pressure of 20 MPa will suffice. The measured gross pellet densities were between 2.1 and 2.4 grams per cubic centimeters (cc). Theoretical density of chlorosodalite is 2.31 grams per cc. In some cases, the salt loaded zeolite pellets were ground prior to conversion to the sodalite. When pellets were converted directly to sodalite, the preferred glass was aluminum 0.35 wt. %, calcium 13.1 wt %, sodium 7.6 wt %, magnesium 0.3 wt %, silicon 20.2 wt %, strontium 0.1 wt %, boron 6.7 wt %, potassium 0.06 wt %, zirconium 0.1 wt % with the balance oxygen. This glass was the only glass tested which provided full conversion of the zeolite pellets to sodalite. However, when the pellets were ground, a variety of glasses were useful to convert all of the zeolite to sodalite. Other glasses useful had the following compositions. ______________________________________ Best Others Worst ______________________________________ Al 0.35% 5.1 3.3 4.0 Ca 13.1% 9.61 7.9 0.37 Na 7.6% 4.9 2.4 4.1 Mg 0.3% 0.26 0.2 0.03 Si 22.2% 25.7 28.2 23 Sr 0.1% 0.06 6.8 0.8 B 6.7% 4.3 3.0 3.7 K 0.06% 0.66 1.0 0.17 Zr 0.06% balance O2 Ba 0.1 19.8 Balance O.sub.2 Zr.sub.x 0.35 ______________________________________ Another method of preparing the salt occluded sodalite is to dehydrate zeolite as stated above and to combine the dehydrated zeolite with a simulated waste salt of up to about 12% by weight or less and about 5 to about 10 weight % by glass. These materials were combined into a crucible and stirred for a short period of time on the order of less than one minute or about 10-30 seconds and then heated to about 1000.degree. K. and held at that temperature for about 24 hours. After cooling, x-ray diffraction showed only features consistent with sodalite. In order to produce sodalite of near theoretical density which is important for leach testing, the material has to be hot pressed as previously described. When zeolite is heated without the presence of glass, a mixture of nepheline and salt results and sodalite is not a major product. Nepheline has poor leach resistance and is not satisfactory for storing radioactive materials. However, when glass is added as described, then sodalite is the major product and is a significant improvement in leach testing compared to nepheline. Table 1 shows a comparison of normalized release rates for sodalite and nepheline using a salt such as that described above as a substitute for the radioactive chloride salt generally produced in the IFR process. TABLE 1 ______________________________________ Normalized Release Rates (g/m.sup.2 day)) Element Sodalite Nepheline ______________________________________ Cs 1.2 132 Sr 0.01 3.3 Ba 0.01 25 Na 0.4 6 K 0.6 9.4 Li 2.3 6.7 ______________________________________ In a high pressure process, the mixture of salt occluded zeolite, additional zeolite and glass is added to a graphite die and is initially cold pressed to 40 MPa. The cold pressed material is then heated to 1000.degree. K. with a ramp rate of 20 K. per minute. After the temperature is at least 700.degree. K., a pressure of about 120 MPa is applied. The pressure is maintained at 1000.degree. K. until densification is complete. The typical length of time required for a sample about 2.5 cm in diameter and about 0.3 cm thick is less than 30 minutes. In a twenty-eight day leach test, the sodalite prepared from and in accordance with the high pressure process set forth above provided the result set forth in Table 2. TABLE 2 ______________________________________ Normalized Release Rate Element 28 Day 90.degree. C. Test ______________________________________ Al 0.16 Ba 0.88 B 1.26 Ca 0.85 Cs 0.58 K 1.0 Li 0.83 Na 0.58 Si 0.23 Sr 1.22 Ce 0.013 Nd 0.009 La 0.009 Y .about.0 ______________________________________ Both Table 1 and Table 2 show results with deionized water maintained at 90.degree. C. It is preferred that a borosilicate glass is used and that it is present as glass frit. Moreover, while zeolites in general may be useful, the preferred zeolite is zeolite A and zeolite X otherwise known as faujasite. Mixtures of zeolite A and zeolite X are also useful. While there has been disclosed what is considered to be the preferred embodiment of the present invention, it is understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention. |
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description | The present application is a continuation of U.S. patent application Ser. No. 12/426,769, filed Apr. 20, 2009 and entitled “Iron-Based Amorphous Alloys and Methods of Synthesizing Iron-Based Amorphous Alloys,” which is herein incorporated by reference. The United States Government has rights in this invention pursuant to Contract No. DE-AC52-07NA27344 between the United States Department of Energy and Lawrence Livermore National Security, LLC for the operation of Lawrence Livermore National Laboratory. The present invention relates to iron-based alloys, and more particularly to iron-based amorphous alloys and methods of synthesis thereof. Prevention of corrosion and methods and techniques of preventing corrosion are of great interest in many different industries and across many different fields. One such field is military applications, where corrosion resistant materials are applicable to the protection of military vehicles such as tanks, transports, helicopters, and airplanes, Perhaps more importantly, corrosion resistance is crucial in naval vessels and submarines, which come in contact with seawater. It is known that corrosion resistance can be improved by the used of structurally designed materials in the amorphous state where the atoms are arranged in a non-periodic fashion. In general, corrosion properties are attributed to both the atomic level and the microstructure level. At the atomic level, periodic defects exist which may create pathways for attack by ionic oxygen, nitrogen and/or hydrogen, which can travel through the crystal without significant obstruction. Grain boundaries and voids exist in crystalline materials, which are avenues for chemical attack into materials, substantially lowering their corrosion resistance. Crystalline materials often have anisotropic thermal expansion properties Thermal cycling can change microstructures, resulting in additional grain boundaries, dislocations, fractures and voids, which can initiate stress corrosion cracking. In amorphous metals, also called metallic glasses when prepared from the molten state, atomic arrangements are essentially random. Changes in the precise atomic locations do not significantly affect material properties. In these structures, thermal expansion can be highly isotropic, and grain boundaries and other defects can be eliminated. These structural changes mitigate stress corrosion cracking, and increase corrosion resistance. even though local short range chemical order does occur in amorphous materials. Amorphous materials can be elementally tailored to specific applications. Since amorphous materials do not have a sharply defined melting point, they can be heat-softened and mechanically shaped. Metallic glasses often exhibit extraordinary mechanical and thermal properties, magnetic behavior, and corrosion resistance. High-iron amorphous metal alloys containing minor amounts of other elements have been designed for corrosion resistant applications. The atomization process used to prepare large quantities of iron-based amorphous alloys is compositionally limited due to restraints on the cooling rate necessary to achieve an amorphous state. This is called the critical cooling rate (CCR). When the CCR is not achieved, some crystallization occurs. Only a particular compositional range can effectively yield amorphous solids using conventional fabrication techniques. Iron-based amorphous alloys have been produced by various techniques, for example, by atomization, melt spinning, and casting. The material mixtures are first melted and then quickly quenched to room temperature. The required CCRs are normally 104 to 1011 Kelvin per second in order to achieve an amorphous structure. Atomized powders are thermal spray coated onto substrates using the high-velocity oxy-fuel (HVOF) process. Melt-spun ribbon samples of the same materials have also been prepared for testing purposes. Corrosion testing of iron-based amorphous ribbons suggests that corrosion resistance can be improved by increasing the alloy molybdenum content. However, it has heretofore been impossible to create an amorphous alloy with an appropriately high molybdenum content due to the high CCRs that are required. Thus, current methods of amorphous alloy production are limited in what composition can be formed due to the process employed and the inherent requirement of high CCR. Therefore, it would be very beneficial to provide more flexibility in the composition of iron-based amorphous metal alloys by employing a more robust process of formation, resulting in more useful and previously unavailable coatings and/or structures with enhanced mechanical and/or thermal properties, magnetic behavior, and corrosion resistance. A method according to one embodiment includes combining an amorphous iron-based alloy and at least one metal selected from a group consisting of molybdenum, chromium, tungsten, boron, gadolinium, nickel phosphorous, yttrium, and alloys thereof to form a mixture, wherein the at least one metal is present in the mixture from about 5 atomic percent (at %) to about 55 at %; and ball milling the mixture at least until an amorphous alloy of the iron-based alloy and the at least one metal is formed. An amorphous iron-based metal alloy according to one embodiment includes between about 10 atomic percent (at %) and about 50 at % iron; between about 0 at % and about 25 at % of a metal selected from a group consisting of manganese, carbon, silicon, zirconium, and titanium; and at least one of the following constituents: between about 15 at % and about 30 at % of at least one metal selected from a group consisting of molybdenum, tungsten, gadolinium, nickel phosphorous, yttrium, and alloys thereof; between about 20 at % and about 55 at % chromium; and between about 20 at % and about 55 at % boron. A corrosion-resistant amorphous iron-based metal alloy according to another embodiment includes between about 10 atomic percent (at %) and about 50 at % iron; between about 15 at % and about 25 at % molybdenum; and between about 0 at % and about 25 at % of a metal selected from a group consisting of chromium, manganese, tungsten, carbon, boron, silicon, zirconium, and titanium. A radiation-shielding amorphous iron-based metal alloy according to one embodiment includes between about 10 atomic percent (at %) and about 50 at % iron; between about 20 at % and about 55 at % boron; and between about 0 at % and about 25 at % of a metal selected from a group consisting of chromium, manganese, molybdenum, tungsten, carbon, silicon, zirconium, and titanium. Other aspects, embodiments, and advantages of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the drawings, illustrate by way of example the principles of the invention. The following description is made for the purpose of illustrating the general principles of the present invention and is not meant to limit the inventive concepts claimed herein. Further, particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations. Unless otherwise specifically defined herein, all terms are to be given their broadest possible interpretation including meanings implied from the specification as well as meanings understood by those skilled in the art and/or as defined in dictionaries, treatises, etc. It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless otherwise specified. In one general embodiment, a method includes combining an amorphous iron-based alloy and at least one metal selected from a group consisting of molybdenum, chromium, tungsten, boron, gadolinium, nickel phosphorous, yttrium, and alloys thereof to form a mixture, wherein the at least one metal is present in the mixture from about 5 atomic percent (at %) to about 55 at %, and ball milling the mixture at least until an amorphous alloy of the iron-based alloy and the at least one metal is formed. In another general embodiment, an amorphous iron-based metal alloy comprises between about 10 at % and about 50 at % iron, between about 0 at % and about 25 at % of a metal selected from a group consisting of manganese, carbon, silicon, zirconium, and titanium, and at least one of the following constituents: between about 15 at % and about 30 at % of at least one metal selected from a group consisting of molybdenum, tungsten, gadolinium, nickel phosphorous, yttrium, and alloys thereof, between about 20 at % and about 55 at % chromium, and between about 20 at % and about 55 at % boron. In another general embodiment, a corrosion-resistant amorphous iron-based metal alloy comprises between about 10 at % and about 50 at % iron; between about 15 at % and about 25 at % molybdenum; and between about 0 at % and about 25 at % of a metal selected from a group consisting of chromium, manganese, tungsten, carbon, boron, silicon, zirconium, and titanium. In another general embodiment, a radiation-shielding amorphous iron-based metal alloy comprises between about 10 at % and about 50 at % iron; between about 20 at % and about 55 at % boron; and between about 0 at % and about 25 at % of a metal selected from a group consisting of chromium, manganese, molybdenum, tungsten, carbon, silicon, zirconium, and titanium. According to some embodiments, mechanical alloying techniques may be used to change the composition of iron-based amorphous alloys. This change is often very useful in many applications, because not only is there a need for the material to be amorphous; but also, the material may be tuned to enhance certain critical properties, for example corrosion resistance, neutron absorbance, hardness, etc. Iron-based alloys may include many elements, for example, iron (Fe), chromium (Cr), manganese (Mn), molybdenum (Mo), tungsten (W), carbon (C), silicon (Si), zirconium (Zr), titanium (Ti), and/or others. Other elements may be added at many occasions in the processing, possibly as a processing aid. In principle, using the techniques presented herein, the amorphous structure for a specific material may be produced. However, not all the amorphous materials are alike and not all the iron-based amorphous alloys are alike. The composition for each element may be a function of the desired defined properties. Similarly, the resultant material properties are in part controlled by the atomic compositions. These materials are of considerable interest because of the improvement in corrosion resistance for several reasons. One reason might be the lack of atomic ordering resulting in the absent of grain boundaries, which often are the weakest regions of the material. Possible applications for these materials are in areas of coatings to protect surfaces, pipes, tanks, components, vessels, etc. SAM2X5 which has the composition of Fe49.7Cr17.7Mn1.9Mo7.4W1.6C3.8Si2.4 and SAM1651 with the composition of Fe49.1Cr14.6Mo13.9B5.9C14.0Si0.3Y1.9Ni0.2, have been studied and the results of the studies have been included in the section called Experimental Results, below. Prior art materials which feature amorphous characteristics have been prepared by atomization and melt spinning. In these cases, the materials are initially physically mixed, thermally excited by heating to a completely molten (liquid) state, and quickly cooled down. It has been reported that the required CCR (critical cooling rate) has to be in the range of 104-106° K./sec, otherwise the amorphous structure will not be formed. Without the proper cooling rate, there is a tendency for the material to crystallize and hence the amorphous nature and the amorphous properties of the materials will not be achieved. At times, small amounts of other compounds, for example Yttrium, may be added to lower the CCR. The range of iron-based amorphous materials that can be produced by these methods are clearly defined by CCR and the ability of the elements not to crystallize. Unfortunately, the range of compositions that can be formed by these methods is very limited. The approaches presented herein overcome these limitations, thereby providing new methods and materials. According to some embodiments, the technique of mechanical alloying may be used to extend the compositional variations of the iron-based amorphous structure. In one embodiment, a high energy milling technique uses high energy ball collisions with the constituent materials in hardened steel vials to generate localized deformation and melting of the material particles. Standard commercial ball milling equipment may be used, but application specific ball milling equipment may be developed for use with the inventive processes. After impact-generated localized heating occurs, and because the particles are in contact with the mass of the vial and the balls, the material is quickly quenched to the vial temperature. The vial must be kept cool, e.g., at a temperature sufficient to impart the appropriate CCR. This technique ensures that the materials do not have enough time to crystallize. With continuing milling for an appropriate amount of time, the material may then be examined and verified that it is still amorphous. No crystallinity is developed during the mechanical alloying process described above. According to some embodiments, a method of forming amorphous alloys may employ the use of high energetic deformation via the use of ball milling to introduce different compositions of molybdenum into an atomized iron-based amorphous alloy. In one approach, molybdenum was chosen as a starting addition into SAM2X5 powders; however, this technique can be extended to the addition of chromium, tungsten, and/or other metals and alloys of chromium, tungsten, molybdenum, and/or other metals. With the addition of boron in high concentrations in some embodiments, or rather with high concentration of boron, the material will not only have better corrosion resistance, but it will also act as a good neutron absorber. To accomplish this, the elemental compositions of the alloy can be changed without changing the amorphous nature of the material. In one approach, boron powder may be mixed into a SAM1651 matrix with the goal of increasing the neutron absorption property and potential application in waste containers, such as those used in the Department of Energy's Yucca Mountain Project. According to one embodiment, a method includes combining an amorphous iron-based alloy and a metal or metals to form a mixture. The one or more metal is selected from a group consisting of molybdenum, chromium, tungsten, boron, gadolinium, nickel phosphorous, yttrium, and alloys thereof. Also, the one or more metal is present in the mixture from about 5 at % to about 55 at %. The method also includes ball milling the mixture for a period of time that is long enough for an amorphous alloy of the iron-based alloy and the one or more metal to be formed. Such amount of time may be readily determined by one practicing the invention and periodically examining the material in the mill for the desired composition and amorphous state. In further approaches, the length of time in which the ball milling is performed may be longer than the time it takes to form the amorphous alloy. In some embodiments, the iron-based alloy may be a product of atomization, e.g. SAM2X5 or SAM1651, etc. If the iron-based alloy is SAM1651, according to some approaches, the amorphous alloy of the iron-based alloy and the one or more metal may include boron, which may be present at greater than about 8 at %, or may be present at between about 10 at % and about 53 at %. Of course, boron may be present at higher and/or lower at % as well. In other embodiments, the amorphous alloy of the iron-based alloy and the one or more metal may be at least about 80 at % amorphous, more preferably at least about 90 at % amorphous, even more preferably at least about 95% amorphous. The more amorphous the alloy of the iron-based alloy and the one or more metal is, the more useful it can be in some applications. Therefore, it is desirable to achieve a high level of amorphousness in the alloy of the iron-based alloy and the one or more metal. In some approaches, an x-ray diffraction pattern of the amorphous alloy of the iron-based alloy and the one or more metal may show no sign of a crystalline form of the one or more metal. The x-ray diffraction pattern of the corrosion-resistant amorphous iron-based metal alloy may also show no sign of a crystalline form of other constituents. In further approaches, the amorphous alloy of the iron-based alloy and the one or more metal may comprise molybdenum which may be present at greater than about 9 at %; alternatively the molybdenum may be present at between about 12 at % and about 27 at %. In yet another embodiment, an amorphous iron-based metal alloy comprises between about 10 at % and about 50 at % iron, between about 0 at % and about 25 at % of a metal selected from a group consisting of manganese, carbon, silicon, zirconium, and titanium. The amorphous iron-based metal alloy also comprises at least one of the following constituents: between about 15 at % and about 30 at % of at least one metal selected from a group consisting of molybdenum, tungsten, gadolinium, nickel phosphorous, yttrium, and alloys thereof, between about 20 at % and about 55 at % chromium, and between about 20 at % and about 55 at % boron. In some embodiments, the at least one constituent may be molybdenum. The molybdenum may be present in the alloy at between about 15 at % and about 30 at %. Of course, other constituents may be used, and the constituents may be present in any atomic percent. Also, if the constituent is molybdenum, it may be present in atomic percentages of greater than 30 at % and 15 at %. In more embodiments, the at least one constituent may be boron, chromium, or some other element. A corrosion-resistant amorphous iron-based metal alloy, according to another embodiment, comprises between about 10 at % and about 50 at % iron, between about 15 at % and about 25 at % molybdenum, and between about 0 at % and about 25 at % of a metal selected from a group consisting of chromium, manganese, tungsten, carbon, boron, silicon, zirconium, titanium, and alloys thereof. According to some approaches, the iron may be present at between about 40 at % and about 50 at %. Of course, the iron may also be present at greater or less atomic percent. In some further approaches, the molybdenum may be present at between about 12 at % and about 27 at %. In more approaches, an x-ray diffraction pattern of the corrosion-resistant amorphous iron-based metal alloy may show no sign of a crystalline form of the molybdenum. The x-ray diffraction pattern of the corrosion-resistant amorphous iron-based metal alloy may also show no sign of a crystalline form of other constituents. A radiation-shielding amorphous iron-based metal alloy comprises, in some embodiments, between about 10 at % and about 50 at % iron, between about 20 at % and about 55 at % boron, and between about 0 at % and about 25 at % of a metal selected from a group consisting of chromium, manganese, molybdenum, tungsten, carbon, silicon, zirconium, and titanium. In further embodiments, the iron may be present at between about 25 at % and about 40 at %. Of course, the iron may be present in greater or less atomic percent in the radiation-shielding amorphous iron-based metal alloy. In addition, the boron may be present at between about 10 at % and about 53 at %. Of course, the boron may be present in greater or less atomic percent in the radiation-shielding amorphous iron-based metal alloy. Experiments The samples used for the experiments are listed in Table 1 in FIG. 5. For historical reasons, the SAM samples originated from SAM40. For example, SAM2X5 comprises 95 at % of SAM40 and 5 at % of Mo. Consequently, SAM2X10 comprises 90 at % of SAM40 and 10 at % of Mo and so forth. Table 1 also tabulates the atomic percentage of each element. To reduce the milling time, the starting matrix material of SAM2X5 and SAM1651 powders were prepared by the atomization technique. Two batches of molybdenum powder samples having a particle size of roughly 60 μm were used. The powder matrix samples of SAM2X5 and SAM1651 are amorphous as characterized by the x-ray diffraction technique. Table 2 in FIG. 6 shows the atomic composition for SAM1651 additions and the amount (in grams) of boron that was added into 2 grams of the matrix sample. The milling process was carried out using the Spex800D Mil/Mixer with 2 hardened steel vials. Various numbers of 316 and 440 stainless steel balls of different sizes were used in the ball miller. During processing, the vials were kept cool using an in-house air system. Three batches of 1, 1½, and 2 grams of SAM2X5 matrix powder were used and the amount of molybdenum by weight to be added was calculated and is listed in Table 2 in FIG. 6. The batches, the number of balls used, and the milling times were closely monitored, recorded, and optimized to achieve an amorphous mixture, to reduce the milling time, and to increase the quantity of the resulting powders. Typically, twelve 5/16″ balls (316SS and 440SS) with 2 grams of matrix powder and molybdenum or boron powders added. A milling time of about 16 hours resulted in total conversion of the mixture to a fully amorphous structure. The milling time can be shortened if the amount of matrix powders is reduced or the number of balls is changed. Typically, the powders are loaded into the vials in air. In situations where oxidation can easily occur, the loading should be carried out in a controlled inert atmosphere, such as in a glove box, clean room, etc. The resulting powders were then characterized using the XRD technique and crystalline metal oxides were not observed. The X-ray diffraction experiments were carried out using the conventional Philips vertical goniometer utilizing Cu Kα radiation. An analyzing diffracted beam monochromator was used for energy discrimination. The scans were performed from about 20° to about 80° (2θ) with a 0.02° (2θ) step size at 4 second counting intervals per step. The powder material was loaded onto a special glass holder to avoid any scattering effects. The amorphous peak from the glass holder was located at about 20° to about 25° (2θ). In most cases, there were sufficient amounts of sample such that the scattering signal from the holder was negligible. Experimental Results The results of molybdenum additions to SAM2X5 are discussed below. After milling, the powder samples were carefully monitored and unloaded to avoid contamination. Typically, the resulting powder is black in color and very fine. SAM2X5 has a rounded particle shape which is typical of materials prepared by an atomization technique. The resultant milled powder is much finer and has irregular particle sizes of a few microns compared to the coarser atomized sample. FIG. 1 shows the diffraction patterns of milled SAM2X10 powders at milling times of 0, 0.5, 5 and 7 hours. The curves are normalized for easy viewing. The starting physical mixture without milling is shown in the lowest pattern, indicating the presence of a crystalline component mixed with the amorphous SAM2X5. The three crystalline peaks can be indexed to cubic molybdenum. As it can be observed, the peak heights decrease as the milling time increases. The reduction in the peaks (and eventual disappearance) indicates that all of the components in the material, Mo and SAM2X5 are mixed at the atomic level and have become amorphous. It is interesting to note that the disappearance of Mo peaks is not totally due to the breakdown of the Mo crystals into nano-crystalline structures. This is because the Mo peaks diminish by losing intensity rather than by the increase in peak widths. The milling of SAM2X5 does not result in crystalline phases. Initial reduction of particle size can be observed by the peak broadening from the un-milled to the 0.5 hour milled sample. To ensure that there are no changes in SAM2X5, neat matrix materials were also milled and the results are shown in FIG. 2, indicating an absence of any change in crystallinity. Therefore, milling the amorphous SAM2X5 did not generate any crystallinity; however, the particle size has been changed as the result of ball milling. Similar curves are obtained for SAM2X15 and SAM2X20 after some milling time. As listed in Table 1, SAM2X10, SAM2X15, SAM2X20 and SAM2X25 have 12, 17, 22, and 27 atomic % (at %) of molybdenum at concentration. FIG. 3 shows the resulting diffraction pattern for SAM2X25 which has as much as 27 at % of Mo. Clearly, it can be observed that with increasing milling time, the intensity of Mo peaks is reduced significantly. During the initial milling period, the results suggest that the crystalline molybdenum particles break down into nano-crystallites, as evidenced by the broadening of the Mo peak. On continuing milling, these peaks diminish, suggesting that the crystalline Mo is incorporated into the SAM2X5 matrix, resulting in SAM2X25. Neat molybdenum powders were also processed using the mechanical alloying technique with the same processing parameters, that is, the same number of balls, amount of powder, and milling time. The result indicates the presence of crystalline Mo peaks, but the peaks are broader, suggesting that neat Mo cannot be made amorphous through the ball milling technique. The addition of boron into SAM1651 is discussed below. The addition is determined using the calculations in Table 2. The concentrations for each percentile are calculated based on atomic percent. As calculated, the amount by weight that may be added into 2 grams of SAM1651 is shown in the bottom row. Clearly, the addition of boron resulted in an amorphous structure even up to 25 at % of boron as shown in FIG. 4. Presently, the analysis cannot fully confirm that the boron atoms are incorporated into the SAM1651 matrix. This is because the X-ray scattering power of boron is significantly weaker than the other the elements used. The technique of mechanical alloying allows the addition of other elements into the amorphous matrix of SAM2X5 without developing crystallinity. This is not possible by the atomization technique used in the prior art because of the tendency of some elements to form crystalline phases. Mechanical alloying is a particle deformation technique that uses high energy ball collisions. In fact, it has also been argued that there is even instantaneous local melting with rapid quenching caused by the cold high mass sample vial. Since the temperature of the vials is kept below the alloy glass transition temperature, the materials will not have sufficient energy to crystallize. In some embodiments, as much as 27 at % molybdenum may be added to SAM2X5 and the material may still remain amorphous. Furthermore, the concentration of SAM2X5 amorphous alloy can now be tuned to enhance specific properties, through the addition of Cr, W, alloys of Cr, alloys of W, alloys of Mo, etc. The addition of boron to SAM1651 can be useful for controlling criticality and/or for providing radiation shielding in radioactive waste storage canisters. It appears that the incorporation of boron into SAM1651 yields amorphous alloys even up to the concentration of 50 at % boron. However, adding additional boron may be useful for some applications but may have negative impacts, on other alloy physical properties such as the corrosion resistance and hardness. Hence, this technique, in some embodiments, allows material synthesis with precise adjustment of the elemental compositions to fit a specific application while achieving an amorphous state. The resultant powders from the mechanical alloying process may be nanometers in size. According to some embodiments, this powder property may enhance the forming of high density amorphous bulk materials during consolation. Intuitively, the material may be conveniently pressed and annealed at an appropriately chosen temperature above the glass transition temperature to avoid pores and void formation. In other embodiments, sintering heat treatment may also be used because the particles have been brought much closer together during the pressing process. The embodiments described herein, and other embodiments not described but possible within the scope of the claims, may be useful for many different applications. For example, the amorphous powder may be fabricated to be used as a coating on components to enhance their corrosion resistance. Also, by adding neutron absorbing elements, the resulting materials may be used as a coating for nuclear storage baskets and/or waste containers, such as those used in the Yucca Mountain Project. There may be cost savings due to the use of the less expensive iron rather than a more expensive component. It is also possible that the material may be used to coat vessels and/or components used in saltwater or under harsh conditions, such as military applications, to prevent and/or reduce corrosion. The ability to tailor the elemental composition of the amorphous iron based alloy is not necessarily limited to coatings. Using advanced powder compaction technology, bulk parts can be molded using these amorphous powders. Amorphous materials which lack discreet melting points tend to soften over a wide range of temperatures. Unlike conventional crystalline materials, this unique property enables the materials to be conveniently molded and still retain their amorphous structure. Another property of amorphous materials is the formation of shear bands during impact. The shear band behavior allows for better absorption of high energy projectiles into bulk parts, such as armor plates. This is often described as a “self sharpening” phenomenon. The use of zirconium based amorphous metals with crystalline heavy metal wires has been described in U.S. Pat. No. 6,010,580, which is hereby incorporated by reference. Iron based alloys can also be used in a similar fashion. Consequently, armor plates made from amorphous materials can slow down the projectiles due to the shear band behavior. A successful employment of this material can replace the presently used depleted uranium armor plates, thus avoiding the toxicity issues associated with their production and disposal. While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. |
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051568039 | summary | BACKGROUND OF THE INVENTION The present invention relates to reactor vessels with a reactor core enclosed in a core shroud and more particularly, to an apparatus for inspection of a reactor vessel. Inspection of the interior of a reactor vessel typically includes the systematic inspection of weld joints in the reactor vessel and pipe sockets etc. Usually, an end effector comprising inspection members in the form of, for example, cameras, ultrasonic probes or the like is moved into the reactor vessel with the aid of special devices. These devices generally include a trolley, which is movable on the exposed upper flange of the vessel, provided with traversing wheels and a drive means. The trolley supports a support mast which is immersed into the reactor vessel substantially parallel to the vertical axis of the reactor vessel. The support mast supports the end effector which may be moved with the aid of a drive member. The device disclosed in U.S. Pat. No. 4,585,610, is well known in the art and includes a trolley with three or four wheels, which supports a support mast centrally insertable in the reactor vessel. Inspection of the vessel wall weld joints is accomplished by means of ultrasonic probes, which make contact with the vessel wall. However, the inspection depth is often limited by reactor components located at the wall of the vessel such as feed water spargers and/or core spray spargers which are not normally dismantled during inspection. Consequently, using this inspection technique weld joints and reactor components located towards the bottom portion of the reactor vessel are not accessible to inspection. It is also well known in the art to place the ultrasonic probes on an extension mast which is fixed to the lower part of the support mast and movable in the radial direction of the vessel. However, the support mast is lowered into the reactor vessel at such a large distance from the its wall that the support mast and the extension mast clear the feed water spargers. When the extension mast has cleared the spargers, the extension mast, by means of the trolley, is moved radially towards the vessel wall below the feed water spargers and also below any core spray spargers which may exist. Although this technique permits a certain increase in the available inspection depth, the inspection depth is limited by the fact that the extension mast cannot be made longer than the axial distance between the feed water spargers and the core shroud cover. In order for the extension mast of this conventional system to clear the feed water spargers, the extension mast must protrude within the annular space formed by the projection of the core shroud cover and the vessel wall. However, the extension mast can only be inserted into the reactor vessel to a point where it contacts the core shroud cover. Therefore, particularly in reactor vessels in which the distance between the core spargers and core shroud cover is relatively short, the space between the reactor vessel and the core shroud which is available for inspection is limited with use of the conventional inspection system. It is therefore an object of the present invention to provide an apparatus for inspection of a reactor vessel which is capable of being inserted into the lower portion of the annular space between the core shroud and the wall of the reactor vessel. It is also an object of the present invention to provide a reactor inspection apparatus which enables inspection of a greater area of the reactor vessel by providing for increased radial, tangential and axial movement of the end effector relative to the reactor vessel wall. SUMMARY OF THE INVENTION The aforementioned objects and advantages are achieved through use of the apparatus for inspection of a reactor vessel in accordance with the present invention. Compared with prior art devices, a device according to the present invention may increase the accessible part of the length of those weld joints which are positioned below the feed water spargers. The apparatus for inspection of a reactor vessel includes a support mast, a trolley for supporting the support mast to the wall flange of a reactor vessel and transporting the support mast along the inside side wall of the reactor vessel, an extension mast capable of vertically extending below the support mast, the extension mast being translated by means of a second trolley engaged between the extension mast and the support mast, an end effector means connected to the lower portion of the extension mast for inspecting the reactor vessel wall, and a tilting device connected to the support mast for varying the angle between the support mast and the reactor vessel wall. The tilting device may include an arm attached to the support mast, the arm being capable of being radially moved by a means for altering the angle between the support mast and the vessel wall. The means may include a compressed air cylinder. The tilting device may also include a support wheel connected to the arm for contacting the reactor vessel wall. The end effector may include a main frame, an upper drive device connected to the main frame, a lower drive device also connected to the main frame, a horizontal trolley affixed to a rack operatively connected to the upper drive device and capable of tangential movement relative to the main frame, a probe position trolley affixed to the horizontal trolley, and a probe holder capable of securing ultrasonic probes affixed to the probe position trolley by a shaft. The end effector may also comprise means for unlocking the probe holder from the probe position trolley to allow relative movement between the probe holder and probe position trolley. The means may include means for activating a spring loaded locking pin interfaced with the shaft, and a lower drive device adapted to rotate the probe position trolley around the shaft to unlock or lock the shaft from the horizontal trolley. The upper drive device may include an electric motor, a gear box operatively engaged with the motor, and a chain transmission means operationally engaged to the gear box and one or more gear wheels to displace the rack in the tangential direction. The apparatus may further include a support arm connecting the end effector means to the extension mast, a spring loaded bearing connecting the support arm to the extension mast for continuously applying a torque forcing the end effector means in a direction radially towards the reactor vessel wall, and means for forcing the end effector means in a direction radially opposite the reactor vessel wall. The means may be a compressed air cylinder. The apparatus may also include a locking pin affixed to the main frame and insertable into an aperture located on a front plate of the probe position trolley wherein the probe position trolley may be locked to the main frame when the pin is inserted into the aperture. Also, a rope affixed to the horizontal trolley and passing through a hole in an output shaft of the gear box of the upper drive device may be included, wherein applying a tension to the rope enables the horizontal trolley to be moved to a central position. The apparatus may further include a tangential direction fine positioning system and/or a radial direction fine positioning system comprising a rotatable member affixed to the trolley. The tangential direction fine positioning system may include a positioning arm pivotably affixed to the lower portion of the support mast, means for pivotably moving the position arm in an axial direction, and a distance measuring device affixed to the positioning arm for measuring the distance to a lug on the shroud of the reactor. The means may include a compressed air cylinder. The radial direction fine positioning system may include a nozzle within the member capable of radially displacing a beam relative to the member, the nozzle being affixed to the support mast. The apparatus may further include a simulation block located at the lower portion of the support mast for verifying the accuracy of probe on the probe holder. The apparatus, with the simulation block, may also include an arm pivotably affixed to the support mast, means for pivotably moving the arm from a retracted position to a verification position, and a simulation block holder located at the end of the arm for supporting the simulation block. The means may include a compressed air cylinder to cause the arm to extend into the verification position such that the simulation block will interface with the probes of the end effector for verification of the probes. The end effector may comprise a horizontal trolley for movement of the inspection members in a tangential direction in relation to the extension mast. This is particularly advantageous in those cases where, for example, jet pumps are placed in the gap between the reactor vessel and the core shroud since it makes possible inspection of at least parts of those weld joints which are situated between the jet pumps and the vessel wall. Other advantageous further developments of the invention will be clear from the following description and the appended claims. |
039500209 | description | The gripping device according to the present invention is characterized primarily in that the blocking member for delaying its movement into blocking position is automatically connected to an element of a displacement device located in the gripper housing which element will during an upward movement of the load receiving body relative to the gripper housing press a medium through a throttle means. The arrangement according to the present invention brings about the advantage that not only the fuel elements and the control bars or the like when being suspended on the grippers are reliably locked thereto but that also damages will be avoided which could occur when prior to the placing of the gripper housing upon a fuel element or the like or prior to the withdrawal of the gripper housing from such fuel element, the grippers would not be moved in time into their release positions. Referring now to the drawings in detail, a cable winch is mounted on a non-illustrated charging carriage while two cables extend from said drum. Suspended on said two cables by means of joint bolts 2 are two racks 3 the teeth of which face each other. A pinion 4 meshes with said teeth. The axles of said pinion 4 are located in a pot-shaped load receiving body 5 which receives the racks 3. The racks are by means of guiding rollers 6 guided in said load receiving bodies 5. The pinions 4 bring about a load equalization between the two cables 1. The gripper housing 7 is a longitudinally extending hollow body of for instance square shaped cross section which is displaceably vertically guided in a hollow (non-illustrated) post which from the charging carriage extends downwardly. At the upper end, the gripper housing 7 has an inwardly extending flange 8 which for instance in the position of FIG. 1 rests on the load receiving body 5 so that the gripper housing 7 is supported by the load receiving body 5. At the lower end, the gripper housing 7 has a bottom 9 with a downwardly extending pivot 10. This pivot fits into the bore of a sleeve 11 which extends upwardly from a head 12 for a plurality of control bars 13. This head is for instance in the position of FIG. 1 located on the head 14 of the fuel element which by means of bores receives the control bars 13 and in its turn is for instance in the position of FIG. 1 located in a position opening of the reactor core or of a bearing frame. The bore of sleeve 11 has an annular groove 15. Below this groove a piston 16 is guided, the piston rod of which extends downwardly and forms a control rod 17 which is slideably guided in a vertical bore of a head 12. A collar extending from the head 12 downwardly is provided with radial bores which contain supporting balls 18. In the position shown for instance in FIG. 1, the lower end of the control rod 17 is located ahead of the radial bores so that the supporting balls 18 project beyond the collar and engage an annular groove of a collar which extends upwardly from the fuel element head 14. In this way, the head 12 of the control bars 13 is coupled to the head 14 of the fuel element. The control rod 17 is above its lower end provided with an annular groove 19. When this groove 19 due to a downward movement of the piston 16 moves behind the radial bores, the supporting balls 18 can leave the annular groove 19 so that the head 12 of the control bars 13 are disengaged from the head 14 of the fuel element. A pressure spring 20 urges the piston 16 upwardly. A control rod 21 is displacebly guided in a bore of the pivot 10. This rod 21 is with the lowermost position shown in FIG. 1 located behind the radial bores which are provided in the pivot 10 and contain supporting balls 22 adapted to engage the annular groove 15 whereby the head 12 of the control bars 13 are coupled to the gripper housing 7. The control rod 21 has an annular groove 23 which when the control rod 21 moves upwardly, moves behind the radial bores of the pivot 10 so that the supporting balls 22 can leave the annular groove 15 as a result of which the gripper housing 7 is disengaged from the head 12 of the control rods. The control rod 21 is provided on a piston 24 of a pneumatic power system, the cylinder 25 of which is connected to the bottom 9. A compression spring 26 urges the piston 24 downwardly. Compressed air conveying conduits 27, 28 are connected to the cylinder chambers above and below the piston 24. These conduits 27, 28 may by means of a shift-over valve 29 be connected selectively to one of two compressed air conveying conduits 31, 32. Conduit 31 is connected to a compressed air source or bottle 33 (FIG. 10) in which a pressure of 6 atmospheric pressure prevails, whereas the other conduit 32 is connected to a compressed air supply or bottle 34 in which a pressure of 2 atmospheres above atmospheric pressure prevails. At the lower end of the gripper housing 7 on opposite sides thereof, gripper pawls 35 are pivotally mounted on horizontal joint bolts 36. From each gripper pawl at the level of the joint bolt 36 there is provided a short leg which is engaged by a bar 37. The bars pertaining to two gripper pawls are within the gripper housing 7 extending upwardly to a certain extent and are connected to the ends of a transverse head or beam 38 which is located at the lower end of a piston rod starting from a piston 39 of a further pneumatic power operable device. The cylinder 40 of this device is located on an intermediate bottom 41 of the gripper housing 7. A compression spring 42 rests on the upper cover of the cylinder 40 and on a cam piston 43 which is mounted on a bar extending from the piston 39 upwardly out of the cylinder 40. Compressed air conveying conduits 44, 45 are connected to the cylinder space located above and below the piston 39. The conduits 44 and 45 lead to a shift-over or reversing valve 46 by means of which the conduits 44, 45 can alternately be connected to one of the two conduits 31, 32. The gripper pawls 35 are adapted to engage openings of fingers 47 which extend upwardly from the fuel element head 14. The gripper housing 7 has an additional intermediate bottom arranged in spaced relationship to and above the cylinder 40. This intermediate bottom is provided with a cylinder 48 located thereon and closed at the top. Reciprocably mounted in said cylinder is a piston 49, the downwardly directed piston rod of which has a transverse head 50. From the ends of the transverse head 50 there extend downwardly feeler members 51 which extend through bores into the intermediate bottom 41 and pass with play through the lowermost bottom 9. In the lowermost position of the piston 49 for instance in the position as shown in FIG. 1, said feeler members 51 have their lower ends extended downwardly to a greater extent than the gripper pawls 35 while for instance in the position of FIG. 1, said feeler members 51 are located above the fingers 47. Connected to the cylinder 48 closely below its upper cover is a compressed air conveying conduit 52 which leads into a conduit 53 originating at the compressed air bottle 34. The compressed air conduit 52 comprises a throttling member 54. Parallel to the member 54 there is provided a check valve 55 which is located in a bypass line connected to the conduit 52. Valve 55 permits the air to pass through only in the direction toward the cylinder 48. The cylinder space below the piston 49 is through bores 56 in the intermediate bottom supporting the cylinder in communication with the atmosphere. Above the cylinder 48 and in spaced relationship thereto there is provided an intermediate bottom 57 of the gripper housing 7 while at the bottom side of said intermediate bottom 57 there is provided a cylinder 58 which opens in downward direction. Reciprocally mounted in said cylinder 58 is a piston 59 which by means of a bar 60 extending through a bore of the intermediate bottom 57 is connected to the rod receiving body 5. From the piston 59 downwardly extend two pairs of bars 61 which by means of a transverse head or beam are connected to the piston rod. These bars extend through bores in the cylinder bottom which support the cylinder 48 in the intermediate bottom 41. The bars extend below the intermediate bottom 41 to such an extent that a yoke 62 arranged in the lower ends engages from below an abutment 63 provided on the transverse head 38. Connected to the yoke 62 is one end of a cable 64 which in the form of a loop passes around a pulley 65 mounted on an extension of cylinder 25, and from here passes upwardly to a connecting area 66 on a bar which from the piston 24 extends upwardly out of the cylinder 25. Connected to the cylinder 58 closely below the intermediate bottom 57 is a compressed air conveying conduit 67 which leads into the conduit 53 and comprises a throttling member 68. In a bypass line connected to the conduit 67 and parallel to the throttling member 68, there is provided a check valve 69 which permits air to pass in one direction only namely in the direction toward the cylinder 58 in which it may be assumed that by means of the gripping device, it is intended to pull the fuel element with head 14 and control bars 13 out of the positioning bore for instance in the core of the reactor. To this end, according to FIG. 1, the gripper housing 7 which rests by means of flange 8 on the load receiving body suspended on the cables 11 is lowered coaxially with regard to the fuel element head 14. During this operation, first the piston 24 occupies its lower end position while the piston 39 is in its upper end position although according to FIG. 1, the reversing valves 29 and 46 are so set that the higher pressure from conduit 31 acts from below upon the piston 24 and from above upon the piston 39. The lower end position of the piston 24 corresponds to the closing position of the rod gripper comprising the supporting balls 22, whereas the upper end position of the piston 39 corresponds to the closing position of the fuel element gripper formed by the gripper pawls 35. However, the pistons 24 and 39 are against the air acting thereupon and having the higher pressure (6 atmospheres above atmospheric pressure) held in the mentioned position by the locking device which contains the yoke 62. It should be kept in mind that the gripper housing 7 with the parts located therein has such a high weight that due to the air pressure of two atmospheres above atmospheric pressure, which prevails in the cylinder 58 above the piston 59, the housing 7 is not lifted relative to the piston 59 but rests by means of its flange 8 on the load receiving body 5. Since thus the piston 49 --relative to the gripper housing 7-- occupies its uppermost position, the yoke 62 is held in its uppermost position in which it forces the transverse head 38 resting thereon by means of the abutment 63 to occupy the uppermost possible position. Consequently the piston 39 is against the resistance of the compressed air of 6 atmospheres above atmospheric pressure prevailing thereabove followed to stay in its uppermost end position. This, however, means that the bars 37 are pulled upwardly and consequently the gripper pawls 35 are with their lower ends pivoted into their closing position shown in FIG. 1. Furthermore, one end of the cable 64 is by the yoke 62 pulled upwardly as far as possible and consequently the other end of the cable at the connecting point 66 is pulled downwardly as far as possible. Consequently, the piston 24 is against the resistance asserted by the compressed air of 6 atmospheres above atmospheric pressure acting upon its lower side held in its lowermost position. This, however, means that the guiding bar 21 does not permit the supporting balls 22 to leave the radial bores in pivot 10. This corresponds to the closing position of the bar gripper. If, however, the gripper housing 7 is further lowered from the position of FIG. 1, the feeler member 51 has its lower ends hit upon the fingers 47 which in response to a further lowering of the gripper housing 7 are relative thereto moved upwardly. Consequently by means of the transverse head 50, the piston 49 is moved upwardly so that the piston 49 will press air from the cylinder 48 through the throttling member 54. Since in view of the throttling effect air will collect below the lower cover of the cylinder 48 and will increase the air pressure, the weight of the gripper housing 7 and the parts therein will to an ever increasing extent through the intervention of the air cushion above the piston 49 be supported by the feeler members 51 resting upon the fingers 47. Consequently, the cables 1 become slack as shown in FIG. 2. Therefore, the load receiving body 5 moves with its piston 59 in downward direction while in the upper portion of cylinder 58, compressed air of 2 atmospheres above atmospheric pressure flows from the conduits 53 and 67 through the check valve 69 without any material delay. Simultaneously, the transverse head 38 moves downwardly into the position shown in FIG. 2. Consequently, the piston 39 is no longer prevented by the abutment 63 from moving into the lower end position due to the air pressure of 6 atmospheres above atmospheric pressure, which prevails in the upper portion of the cylinder 40. As a result thereof, the gripper pawls 35 are through the intervention of the bars 37 likewise moving downwardly pivoted into their release position according to FIG. 2. Inasmuch as this occurs as long as the gripper housing 7 due to the delay of the escape of air from the cylinder through the throttling element 54 is prevented by the feeler members 51 which rest upon the fingers 47, from completely resting upon the fuel element head 14, the gripper pawls 35 reach their disengagement position prior to the time at which during a further lowering of the gripper housing 7 they would impact upon the fingers 47. Due to the downward movement of yoke 62, the cable 64 connected to said yoke 62 is slackened so that the connecting area 66 for the cable 64 on the rod extending upwardly from piston 24 can move in upward direction. Consequently the piston 24 will now no longer be prevented from moving under a pressure of 6 atmospheres above atmospheric pressure in the lower portion of the cylinder 25 to its upper end position according to FIG. 2 against the thrust of the pressure spring 26. Consequently, the control bar 21 will be lifted into that position of FIG. 2 in which the annular groove 23 occupies a position opposite to the radial bores which contain the supporting balls 22. Consequently, the supporting balls 22 will be able to escape into the annular groove 23 when the pivot 10 immerses into the bore of sleeve 11. FIG. 2 shows the condition in which the gripper housing 7 has been finally placed down onto the fuel element head 14 by means of forwardly extending fingers. The gripper pawls 35 will in this instance have been pivoted outwardly into their disengaging position, and the supporting balls 22 of the rod gripper will have entered the region of the annular groove 15. If now the fuel element together with the control bars therein is to be pulled out of the position bore, the switch-over valve 46 according to FIG. 3 is so changed that compressed air of 6 atmospheres above atmospheric pressure enters from conduit 44 into the lower portion of cylinder 40, whereas compressed air of 2 atmospheres above atmospheric pressure escapes from the upper portion of cylinder 40 through conduit 45. Accordingly, the piston 49 moves upwardly, and the gripper pawls 35 are through the intervention of bars 37 pivoted into closing position in which their hook shaped ends enter the recesses of the fingers 47 which extend upwardly from the fuel element head 14. Now, the lifting movement is initiated by turning on the winch drive motor so that the cables 1 become taut and the load receiving body 5 is lifted. According to FIG. 3, in this connection, the shift-over valve 29 is first so set that the air of 6 atmospheres above atmospheric pressure which prevails in the lower portion of the cylinder 25 has the tendency to keep the piston 24 in its upper end position. However, it would also be possible that the switch-over valve 29 is shifted immediately. In such an instance, the piston 24 would move downwardly in view of the compressed air of 6 atmospheres above atmospheric pressure acting upon the upper side of piston 24, aided by the spring 26. The cable 64 would become slack as long as yoke 62 has not reached its upper end position. This occurs only in the condition illustrated in FIG. 4. It will be appreciated that when lifting the load receiving body 5, the latter is followed by the gripper housing 7 only with delay. This is due to the fact that during the upward movement of the piston 59 provided on the load receiving body, the air in the cylinder 58 is only slowly pressed out through the throttle member 68. Only when piston 59 has reached its upper end position shown in FIG. 4, also the yoke 62 has reached its upper end position in which it engages the abutment 63 of the transverse head 38 located in its upper end position. Consequently, the yoke 62 blocks the fuel element gripper by preventing the transverse head 38 from moving downwardly. Consequently, the gripper pawls 35 are secured in their closing position. At the latest, when the yoke 62 has reached its uppermost end position, the piston 24 must have entered its lower end position. This is automatically brought about by the connection of the two parts by means of cable 64. This downward movement of the piston 24 is effected after the switch-over valve 29 has been moved into its position shown in FIG. 4 in which through conduit 28 compressed air of 6 atmospheres above atmospheric pressure enters the upper portion of the cylinder 25, whereas air of 2 atmospheres above atmospheric pressure escapes from the lower cylinder portion through conduit 27. Compressed spring 26 aids the effect of the compressed air in the upper cylinder portion. Due to the downward movement of the piston 24 the rod gripper has been brought into its closing position by the control rod 21 having forced the supporting balls 22 into the annular groove 15. Furthermore, the rod 21 has pressed the piston 16 downwardly against the thrust of spring 20 so that the annular groove 19 has moved into a position opposite the supporting balls 18 whereby the clutch connection between the head 12 and the control bars 13 and the fuel element head 14 is disengaged. Due to the described locking of the transverse head 38 it will be assured that the fuel element gripper remains in its engaging position so that an accidental dropping of the pulled-out fuel element from the gripper housing will for all practical purposes be impossible. FIG. 5 shows how subsequently the fuel element has been inserted into a position opening for instance in a bearing frame or in a reactor core. There is obtained the same setting as according to FIG 2. The cables 1 have again slackened and the piston 59 has moved downwardly together with the load receiving body 5 so that the yoke 62 simultaneously moved downwardly will permit the movement of the transverse head 38 in downward direction and via cable 64 will permit or free the movement of the piston 24 in upward direction. Accordingly, the gripper pawls 35 have been moved into releasing position. Also the rod gripper is released because the annular groove 23 of the control rod 21 has moved to a position opposite to the supporting balls 22. Simultaneously, the head 12 for the control bars 13 is coupled to the head 14 of the fuel element because due to the upward movement of the piston 16 under the influence of the pressure spring 20, the lower end of the control bar 17 has urged the supporting balls 18 into the annular groove 19. When subsequently, in conformity with FIG. 6, the gripper housing 7 is lifted off the fuel element head 14, first the cables 1 become taut and the load receiving body 5 is lifted with the piston 59. Due to the weight of the gripper housing 7 and the elements therein, air is only gradually pressed out of the upper portion of the cylnder 58 through the throttling member 68. Consequently, yoke 62 moves only slowly upwardly relative to the gripper housing 7, and sometime passes by before the yoke 62 moves into the position of FIG. 4. During the time period which passes by, the fuel element grippers and the rod grippers remain in release position because the switch-over valves 29 and 46 have not yet been switched over. Thus, the gripper pawls 35 are held in spread position and the control bar 21 is held in its upper end position. Consequently, the gripper pawls 35 and the pivot 10 of the rod gripper is lifted off the fuel element head 14 and out of the sleeve 11 of the rod head 12. Only thereafter, will the fuel element gripper and the rod gripper move to the closing positions because the piston 59 eventually moves to its upper end position in cylinder 58, and consequently the yoke 62 is lifted into its blocking position. When it is desired to pull the control bars 13 with head 12 out of the fuel elements, the gripper housing 7 is in the same manner as illustrated in FIG. 2, according to FIG. 7 placed upon the fuel elements head 14. In this condition, the cables 1 are slacked so that the load receiving body 5 with the piston 59 has moved downwardly relative to the gripper housing 7, and yoke 62 has moved to its releasing position. Since the reversing valve 46 remains further in its opening position, air of 6 atmospheres above atmospheric pressure acts from conduit 28 onto the top side of piston 39 so that the piston 39 has moved downwardly and the gripper pawls 35 are spread. However, the switch-over valve 29 has moved to its closing position so that the pressure of 6 atmospheres above atmospheric pressure acts upon the top side of the piston 24 of the rod gripper, and the control bar 21 is moved into closing position 7 in which the control bar 21 pressses the supporting balls 22 into the annular groove 15 of the sleeve 11 so that the coupling connection between the gripper housing 7 and the head 12 of the control bars 13 is established. Simultanaeously, the control bar 21 has pressed the piston 16 downwardly so that the annular groove 19 of the control bar 17 has moved into a position opposite the supporting balls 18. In this way, the coupling connection between the head 12 of the control bars 13 and the fuel element head 14 is disengaged. If now the load receiving body 5 is lifted by means of the cable 7, according to a certain delay, has been brought about by the flowing out of air from the cylinder 58 through the throttle valve 68, the gripper housing 7 is likewise lifted. In this way the head 12 is lifted which is coupled by the rod gripper to the gripper housing 7. As a result thereof, the control bars 13 are pulled out of the bores in the fuel element. In this connection it will be assured that the coupling connection of the rod gripper cannot accidentally be disengaged. It will be appreciated that in view of the relative movement of the load receiving body 5 and of the piston 59 relative to the gripper housing 7 in upward direction, the yoke 62 has moved to its upper end position, in which through the intervention of cable 64 it holds the piston 24 of the rod gripper automatically in its lower end position. In this connection, the transverse head 38 the abutment 63 of which is engaged by yoke 62 had to move to its uppermost end position which fact is inherent to a pivoting of the gripper pawls 35 to their closed position. This, however, happens only after the above mentioned delay which is caused by the escape of air from the cylinder 58 through the throttling member 68 so that the gripper pawls 35 will reach the position shown in FIG. 8 only when they have meen moved past the fingers 47 of the burner element head 14. The movement of the piston 39 of the burner element gripper in upward direction is brought about by the fact that the reversing valve 46 is brought into its closing position. This upward movement of piston 39 is aided by the compression spring 42. FIG. 9 shows how the control bars 13 suspended on the gripper housing 7 have moved to a major extent into position bores for instance of a fuel element mounted in a bearing frame or a reactor core. However, the gripper housing 7 has not yet finally desposited upon the fuel element head 14. Only the feelers 51 have abutted the fingers 47 and thus act as supports for the gripper housing so that the gripper housing can move downwardly only very slowly relative to the piston 49 which is supported by the elements 51. This is due to the fact that the exit of air from the upper portion of the cylinder 48 is delayed by the throttling member 54. This is due to the release of cables 1 brought about by the fact that the discharge of air from the upper portion of the cylinder 48 is delayed by the throttling member 54. Due to the thus effected release, the grippers become slack. Consequently, the load receiving body 5 with the piston 59 moves downwardly relative to the supported gripper housing 7 so that the yoke 62 moves into its releasing position. Shortly prior thereto, the switch-over valve 46 has been moved to its opening position so that now the piston 39 of the fuel element gripper is against the thrust of spring 42 moved downwardly by the pressure of 6 atmospheres in the upper portion of the cylinder 40. Consequently, the gripper pawls 35 are spread so that during the further lowering of the gripper housing they will not collide with the fingers 47. The switch-over valve 29 first remains in its closing position so that the head 12 for the control bars 13 remains in coupling engagement with the gripper housing 7. FIG. 10 shows finally the gripper housing 7 is completely places upon the burner head element 14 after the air in cylinder 48 was discharged in a delayed manner by the piston 49. Now also the switch over valve 29 is moved into its opening position so that the piston 24 of the rod gripper is moved upwardly while the previously slackened cable 64 again becomes taut. In this way the coupling connection between the head 12 and the gripper housing 7 is disengaged and simultaneously the coupling connection between the head 12 and the burner element head 14 is established because the supporting balls 18 are pressed by the lower end of the control rod 17 into the annular groove 19. Now the gripper housing can be lifted off the head 12 of the control bar 13 and of the fuel element head 14. It is, of course, to be understood that the present invention is, by no means, limited to the specific showing in the drawings but also comprises any modifications within the scope of the appended claims. |
abstract | A cylindrical gamma generator includes a coaxial RF-driven plasma ion source and target. A hydrogen plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical gamma generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which has many openings. The plasma generator emanates ions radially over 360° and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired. |
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summary | ||
description | This invention (Navy Case No. 102,478) is assigned to the United States Government and is available for licensing for commercial purposes. Licensing and technical inquiries may be directed to the Office of Research and Technical Applications, Space and Naval Warfare Systems Center, Pacific, Code 72120, San Diego, Calif., 92152; voice (619) 553-2778; email [email protected]. The present invention relates to a semiconductor diode, and more particularly to a beta voltaic semiconductor diode fabricated from a radioisotope. Beta voltaics convert the energy of radioactive decay products directly into electrical power. They operate much the same way as a solar cell except that the beta particles (high energy electrons) are used, rather than photons. The beta particles can produce many electron-hole pairs in the diode per incident particle. The accepted method of construction is to coat a diode with a beta emitter (i.e. a radioisotope that undergoes beta decay) such as Nickel 63, tritium (usually as a metal hydride), or promethium 147. Radiation damage is often an issue, therefore silicon carbide, (being more radiation hard than silicon) is primarily used. The high energy electrons (beta particles) do not penetrate very far into silicon. This presents issues for fabrication of the diodes and favors high surface to volume geometries (i.e., pillar or comb structures are employed). In one preferred embodiment, a semiconductor diode includes a first layer formed with a p-type semiconductor, a second layer formed with an n-type semiconductor, and a third active depletion layer contained between the first and second layers. The third layer is formed with a radioisotope of the p-type and n-type semiconductors (preferably Si 32) such that initial emission of beta particles begins in the active depletion region and substantially all of the emitted beta particles are contained within the first, second and third layers during operation. The p-type and n-type layers each have sufficient depth to contain substantially all of beta particles emitted from the depletion layer. The depth of each of the p-type and n-type layers is substantially equal to or greater than the maximum beta emission depth of the radioisotope. Incorporation of the isotope as the diode material overcomes the short range of the beta particles and simplifies the device fabrication geometry. The present invention relates to a semiconductor diode, and more particularly to a beta voltaic semiconductor diode fabricated from a radioisotope. Beta voltaics are generators of electrical current, in effect a form of a battery, which use energy from a radioactive source emitting beta particles (high energy electrons). Beta voltaics are particularly well-suited to low-power electrical applications where long life of the energy source is needed, such as implantable medical devices or military or space applications. Beta voltaics convert the energy of radioactive decay products directly into electrical power. In electronics, a diode is a two-terminal electronic component that conducts electric current in only one direction. A semiconductor diode is fabricated from a crystal of semiconductor such as silicon that has impurities added to it to create a region on one side of a junction that contains negative charge carriers (electrons), called n-type semiconductor, and a region on the other side of that junction that contains positive charge carriers (holes), called p-type semiconductor. The diode's terminals are attached to each of these regions, and the boundary within the diode between these two regions is called a PN junction, in which the action or operation of the diode takes place. There are many types of junction diodes, which either emphasize a different physical aspect of a diode often by geometric scaling, doping level, choosing the right electrodes, or just in the application of a diode in a special circuit. For example, a Schottky diode is typically fabricated from the contact between a metal and a semiconductor, rather than by a PN junction. A Schottky diode has a potential barrier formed at the metal-semiconductor junction which has rectifying characteristics, suitable for use as a semiconductor diode. Accordingly, the term “semiconductor diode” as used and claimed herein is intended to cover many types of semiconductor diodes, as will become apparent from the following description, when taken in conjunction with the accompanying drawings. In one preferred embodiment, the present invention relates to a beta voltaic or ‘nuclear battery” using an isotope of silicon (Si32) as the source (beta emitter), where the diode itself is made from the isotope. The present invention provides a long term power source for remote power generation of high efficiency and long term operation. In one embodiment, the present invention would make the diode out of an isotope of silicon (silicon-32 or Si32). The diode could be either silicon or silicon carbide. Silicon-32 is a pure beta emitter with no gamma radiation. It has a long half life of about 150 years and decays to phosphorus 32 (another strong beta emitter). Since the silicon-32 is internal to the diode structure, the short range of the beta particles is overcome and a simple planer geometry can be used. The use of silicon-32 vs. the naturally occurring (stable) isotopes of silicon should cause no material difference in the operation of the diode beyond the effects of radioactive decay. In a preferred embodiment, one aspect is to use a radioisotope (beta emitter) within the diode itself rather than applying it to the surface. The energy can be more efficiently harvested since the beta particles are emitted in the active region of the diode. Silicon-32 is one preferred candidate. Silicon-32 is a pure beta emitter, with no gamma rays. Silicon and silicon carbide diodes are made with silicon, therefore no “impurities” need to be added to the diode. Silicon has a 150 year half-life, ensuring commensurate long power output. The simple planer geometry with silicon-32 inside the device would be relatively straightforward to make, by using silicon-32 during manufacturing. The intended uses of such devices are for long missions, using low average power, where it would be difficult to change a traditional battery (such as deep sea, space probes, medical implant, remote location data collection etc.). FIG. 1 is a graph showing the range of high energy electrons in silicon carbide. Note the vertical axis (Y-axis) is shown on a log scale in FIG. 1 for clarity. For each isotope, the electrons are emitted at different energies. In FIG. 1, the average range is for the average-energy electron, the maximum range is the distance traveled for the maximum energy electron. The isotopes Pm147 and Si32 have equivalent emitted electron energies and therefore equivalent ranges. These ranges were calculated using data from NIST (National Institute of Standards and Technology), using the continuously slowing down approximation, which includes collisions and bremsstrahlung radiation (which can defined as electromagnetic radiation produced by the acceleration of a charged particle, such as an electron, when deflected by another charged particle, such as an atomic nucleus). Note that beta particle from tritium does not penetrate far into the silicon carbide. Also note the average and maximum ranges in depth shown in silicon carbide shown in FIG. 1 for Tritium, Nickel 63, and Pm 147/Si 32. In particular, the average-energy electron travel depths for Pm 147 and Si 32 shown in FIG. 1 are more than 20 microns (on the log scale) and the maximum-energy electron travel depth for Pm 147 and Si 32 shown in FIG. 1 (again on the log scale) are less than 200 microns in depth. FIG. 2 is a graph illustrating the general problems described above. FIG. 2 shows a diode 20 with various isotopes coated on the surface 22 (the top layer 22 in the graph of FIG. 2). The diode 20 in FIG. 2 includes a layer of a p-type region 24, a layer of an n-type region 25, and a depletion region 26. The depth (or width) of the p-type layer 24 and n-type layer 25 are each approximately 200 microns, or more than the maximum energy electron levels for Pm 147 and Si 32 shown in FIG. 1. In FIG. 2, the range of an average energy electron from each isotope is shown as the square hash pattern (not quite visible for tritium (H3) or nickel 63)—see the previous FIG. 1 for reference. The range of maximum penetration depth is shown in FIG. 2 as a diagonal hash mark 28. Note that for the geometry shown in FIG. 2, only promethium 147 penetrates into the depletion region 26 or the active layer of the diode. Also note that roughly half of the emitted electrons are not captured by this geometry shown in FIG. 2. FIG. 3 shows a view of a diode 50 of the present invention with the depletion region 52 made from silicon-32 (a radioisotope of silicon). In this geometry shown in FIG. 3, the layer 54 of the p-type region and the layer 56 of the n-type region act to slow the emitted electrons down. The square hatch regions 60, 62 are the respective stopping ranges for the average energy beta emitted by silicon-32, and the diagonal hatches 64, 66 show the range of the maximum energy beta emitted by silicon-32 from depletion region (or layer) 52. Note how the electrons emitted by silicon-32 are now mostly contained within the diode 50 shown in FIG. 3. One advantage of the present invention is that all the emitted electrons start in the active depletion region shown in FIG. 3. This means that most of the emitted electrons can be converted to electrical energy. In a standard geometry (isotope coated on a surface), half of the electrons are lost (emitted away from the diode), as seen in FIG. 2. Many more electrons do not make it into the active region. This eliminates the need to optimize the surface to volume ratio, as would be required for the structure shown in FIG. 2. Note in FIG. 3, the emitted electrons are now contained within the diode without extra shielding. For illustrative purposes, the depths (in microns) for the diode device shown in FIG. 3 are as follows: the p-type region (or layer) is approximately 200 microns in depth (again, more than the maximum energy electron level for Si 32 shown in FIG. 1); the n-type region (or layer) is also approximately 200 microns in depth (also more than the maximum energy electron level for Si 32 shown in FIG. 1); and the depletion region is approximately 100 microns in depth, as shown in FIG. 3. FIG. 4 shows another embodiment 70 of the present invention in which an energy converter on the surface of the diode that converts the high energy electrons into photons and with a mirror surface, sends them back into the diode 70 to get converted to electricity as well. A fluorescent coating 74, 76 can be added to all the sides of the diode 70, so that photons are returned into the diode structure 70, as shown in FIG. 4. The Si32 contained inside the diode 70 is a pure beta emitter with a half life of ˜150 years. It is also known that Si32=P32+e−+ve and that P32=S32+e−+ve (14.2 day half-life). FIG. 5 shows another embodiment of the present invention where the radioisotope is placed outside the depletion region. The semiconductor diode 80 shown in FIG. 2 includes a depletion region 82, a p-type layer 83, and an n-type layer 84. The depletion region 82 is critical for the functioning of the diode/betavoltaic cell. As shown in FIG. 5, one could place the isotope layers 86, 87 only outside the critical region 82, which could increase the operational life of the device. The resulting dimensions would be open to optimization. In the embodiment shown in FIG. 5, two isotope layers 86, 87 are placed above and below the depletion region 82. However, one isotope layer could be configured with the present invention (at least one isotope layer would be utilized in such an embodiment). FIG. 6 shows still another embodiment of a semiconductor diode 90 of the present invention, as a further variation of FIG. 5. The semiconductor diode 90 of FIG. 2 further includes scintillator/energy converter layers 91, 92, together with mirror coating layers 94, 96. In FIG. 6, the scintillator layers 91, 92 could be made from quantum dots, which have a high conversion efficiency. Any scintillator layer that converts the beta particles to light, matched to the band-gap of the diode (such as blue light for silicon carbide) would be suitable. The scintillator layers 91, 92 shown in FIG. 6 converts escaping high energy beta particles (electrons) into light, which is directed back into the depletion region 82, where it can be converted to an electron-hole pair and give rise to an electric current. A mirror surface layers 94, 96 (dielectric mirror tuned to the wavelength of the light emitted by the scintillator) shown in FIG. 6 reflects the light back into the depletion region 82. The scintillator, mirror, and p-type region act as radiation shielding as well. The entire device of the present invention could be made using a radioisotope such as silicon-32. Extra shielding for the electrons would be necessary. If a suitable isotope was available, the dopants added to make n or p-type could be radioisotopes. The surface could still be coated with an isotope. If the surface was coated with Pm 147, the device would have high power initially and decay with the 2.62 year half life of Pm 147, then remain powered at a low level for the half-life of silicon-32 (˜150 years). In general, the percent of silicon-32 relative to the stable isotope (silicon-28) could be tailored throughout the diode. The use of silicon-32 in p+n, junctions and Schottky diodes, etc would also be useful. Any diode junction used for generating electric power (photovoltaic) that contains silicon could be made with silicon-32. Note that the main dimensions shown in the figures above are somewhat arbitrary, and are not necessarily shown to scale. It should be understood that silicon-32 could be used as the power source and this would avoid the shallow range of the beta particles in the diode. This eliminates a surface to volume issue during design and manufacturing of such devices. Silicon-32 can be used in just the depletion region and the surrounding layers can then be used to contain the beta particles. FIG. 7 shows several views of a Schottky diode, which is a well known configuration, and with which the features of the present invention can be incorporated. FIG. 7A shows a side view of a Schottky diode, with an N-type silicon between a Schottky contact and ohmic contact. FIG. 7B shows a perspective view of a Schottky contact and an ohmic contact on a substrate. FIG. 7C shows a band diagram of a Schottky diode. FIG. 8 shows a beta voltaic Schottky diode 120 of the present invention, with radioisotope 126 (silicon 32) between Schottky contact 122 and ohmic contact 124. FIG. 9 shows a top view a metal-semiconductor-metal configuration 130 of radioisotope 136 between Schottky contact 132 and ohmic contact 134. In FIGS. 8 and 9, the energy of the beta particles would excite electrons in the semiconductor (N-type) into the conduction band, where they pass through the electric circuit, generating power. The depth should presumably be contained within the region defined as the depletion region, W, as shown in the energy band diagram of FIG. 7C. The contact is a Schottky contact if there exists an energy barrier (i.e. Schottky barrier) when the metal is deposited onto the semiconductor. Creating a Schottky barrier is actually much easier than creating an Ohmic contact. With an Ohmic contact the energy level of the metal is chosen to line up precisely with the conduction band or valence band energy levels for n-type and p-type semiconductors respectively. The Schottky contact creates a built-in depletion region just like the diode so they operate in a very similar fashion from that standpoint. From the above description, it is apparent that various techniques may be used for implementing the concepts of the present invention without departing from its scope. The described embodiments are to be considered in all respects as illustrative and not restrictive. The present invention is suitable for use with many types of semiconductor diodes, such as illustrated, for example, in “Diode-Wikipedia, the free encyclopedia”, which is readily accessible via the Internet at http://en.wikipedia.org/wiki/Diode, which shows many types of semiconductor diodes which could be utilized with the present invention. Also see S. M. Sze in “Physics of Semiconductor Devices”, Wiley 2007. It should also be understood that system is not limited to the particular embodiments described herein, but is capable of many embodiments without departing from the scope of the claims. |
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description | This application is a divisional of, and claims the benefit of, U.S. patent application Ser. No. 13/451,759, filed on Apr. 20, 2012, and entitled “Steam Generator for a Nuclear Reactor,” the entire contents of which are incorporated by reference herein. In a nuclear reactor, a core of nuclear material is confined to a small volume internal to the reactor so that a reaction may occur. In many instances, a controlled nuclear reaction may persist for an extended period of time, such as several years, before refueling of the reactor core is required. Accordingly, when used as a source of heat for converting water into steam, a properly designed nuclear reactor may provide a carbon-free, stable, and highly reliable source of energy. A nuclear reactor may make use of a working fluid, such as water, which may be converted to steam at a pressure significantly above atmospheric pressure. The pressurized steam may then be used to drive a turbine for converting mechanical energy to electric current. The steam may then be condensed back into water, and returned to the reactor. In many nuclear reactors, the cycle of vaporization, condensation, and vaporization of the working fluid may continue day after day and year after year. Thus, a significant feature of a nuclear reactor may be a steam generator that receives liquid coolant at an input side, vaporizes the coolant by way of exposure to the heat source of the nuclear reactor, and provides the vaporized coolant to the input of a turbine. Accordingly, the efficiency, ease of manufacture, performance, and the safety features of the steam generator represent areas of continued investigation, analysis, and evaluation. In some embodiments, a steam generator for a nuclear reactor comprises three or more plenums proximate with a first plane, wherein the first plane intersects a bottom portion of a column of a reactor vessel. The steam generator may further comprise three or more plenums proximate with a second plane, approximately parallel with the first plane, wherein the second plane intersects a top portion of the column. The steam generator may further include a plurality of steam-generating tubes from a flowpath that conveys coolant from one of the three or more plenums located proximate with the first plane to at least one of the three or more plenums proximate with the second plane. In other embodiments, a top portion of a steam generator includes three or more plenums disposed in a plane at approximately 90-degree intervals around a riser column, wherein at least one plenum of the three or more plenums includes an approximately flat tubesheet that faces a bottom portion of the steam generator, and wherein the approximately flat tubesheet of the at least one plenum includes a plurality of perforations, wherein the plurality of perforations changes in density between an area near an inner edge of the at least one plenum and an area near an outer edge of the at least one plenum. In other embodiments, a method of operating a nuclear reactor includes conveying a working fluid from a first group of three or more plenums to a plurality of flowpaths, vaporizing the working fluid in at least some of the plurality of flowpaths, wherein the vaporizing results, at least in part, from coupling thermal energy from a reactor coolant to the at least some of the plurality of flowpaths. The method may further include transferring the vaporized coolant to a second group of three or more plenums. Various systems and arrangements of a steam generator used in a nuclear reactor are described. In implementations, a group of plenums, wherein the group may include four plenums, may be arranged in a first plane at 90-degree increments around a bottom portion of an approximately cylindrical riser column of a nuclear reactor. A second group of plenums, wherein the second group may include four plenums, may be arranged in a second plane at 90-degree increments around a top portion of a cylindrical column of a nuclear reactor. Plenums located at both the top and bottom portions of the cylindrical riser column may include a substantially or approximately flat tubesheet having perforations that permit coupling to one of the plurality of steam generator tubes. In some embodiments, an orifice may be disposed within with at least some perforations of the plenums located proximate with the bottom portion of the cylindrical riser column. The presence of an orifice may result, at least in part, in a decrease in pressure as fluid flows upward from the plenum at the bottom portion of the riser. In certain other embodiments, three plenums may be arranged in a first plane at 120-degree around a bottom portion of an approximately cylindrical riser column of a nuclear reactor. A second group of plenums, wherein the second group may include three plenums, may be arranged in a second plane at 120-degrees around a top portion of a cylindrical riser column of a nuclear reactor. Plenums located at both the top and bottom portions of the cylindrical riser column may include substantially or approximately flat tubesheets having perforations that permit coupling to one or more of the plurality of steam generator tubes that form a flowpath between plenums located at the bottom and top portions of the cylindrical riser column. In some embodiments, an orifice may be disposed within at least some perforations of the plenums located proximate with the bottom portion of the cylindrical riser column. The presence of an orifice may result, at least in part, in a decrease in pressure as fluid flows upward from the plenum at the bottom portion of the riser. In certain embodiments, perforations in one or more of the approximately flat tubesheets of the plenums may be lower in density (for example, fewer in number per unit of area of the tubesheet) near an edge of the plenums closer to the cylindrical riser column and be of higher density (for example, greater in number per unit of area) nearby an outer wall of the reactor vessel enclosing the steam generator. Such a change in density of the perforations in the approximately flat tubesheet may result in an approximately uniform coupling of heat from a primary fluid within the reactor vessel to a secondary, working fluid within the steam generator tubes. As used herein and as described in greater detail in subsequent sections, embodiments of the invention may include various nuclear reactor technologies. Thus, some implementations may include nuclear reactors that employ uranium oxides, uranium hydrides, uranium nitrides, uranium carbides, mixed oxides, and/or other types of radioactive fuel. It should be noted that embodiments are not limited to any particular type of reactor cooling mechanism, nor to any particular type of fuel employed to produce heat within or associated with a nuclear reaction. FIG. 1 is a diagram of a nuclear reactor module employing a steam generator according to an example embodiment. In FIG. 1, reactor core 5 is positioned at a bottom portion of a cylinder-shaped or capsule-shaped reactor vessel 20. Reactor core 5 comprises a quantity of fissile material that generates a controlled reaction that may occur over a period of, for example, several years. Although not shown explicitly in FIG. 1, control rods may be employed to control the rate of fission within reactor core 5. Control rods may comprise silver, indium, cadmium, boron, cobalt, hafnium, dysprosium, gadolinium, samarium, erbium, and europium, or their alloys and compounds. However, these are merely a few of many possible control rod materials. In implementations, a cylinder-shaped or capsule-shaped containment vessel 10 surrounds reactor vessel 20 with the containment vessel being partially or completely submerged within a pool of water or other fluid coolant. The volume between reactor vessel 20 and containment vessel 10 may be partially or completely evacuated to reduce heat transfer from reactor vessel 20 to the external environment. However, in other embodiments, the volume between reactor vessel 20 and containment vessel 10 may be at least partially filled with a gas and/or a fluid that increases heat transfer between the reactor vessel and the containment vessel. In a particular implementation, reactor core 5 may be partially or completely submerged within a fluid, such as water, for example, which may include boron or other additive, which rises after making contact with a surface of the reactor core. In FIG. 1, the upward motion of heated coolant is represented by arrow 15 above reactor core 5. The coolant travels upward through riser column 30, which may be at least partially or approximately cylinder shaped, and over the top of steam generators 40 and 42 and is pulled downward by way of convection along the inner walls of reactor vessel 20, thus allowing the coolant to impart heat to steam generators 40 and 42. After reaching a bottom portion of the reactor vessel, contact with reactor core 5 results in heating the coolant as symbolized by arrow 15. Although steam generators are 40 and 42 are shown as comprising distinct elements in FIG. 1, steam generators 40 and 42 may represent a number of helical coils that wrap around riser column 30, which may comprise a cylindrical shape. In another implementation, another number of helical coils may wrap around an upper portion of riser column 30 in an opposite direction, in which, for example, a first helical coil wraps in a counterclockwise direction, while a second helical coil wraps in a clockwise direction. However, nothing prevents the use of differently configured and/or differently oriented heat exchangers and embodiments are not limited in this regard. Further, although fluid line 70 is shown as being positioned just above upper portions of steam generators 40 and 42, in other implementations, reactor vessel 20 may include a lesser or a greater amount of coolant. In FIG. 1, normal operation of the nuclear reactor proceeds in a manner wherein heated coolant rises through a channel defined by riser column 30 and makes contact with steam generators 40 and 42. After contacting steam generators 40 and 42, the coolant sinks towards the bottom of reactor vessel 20 in a manner that induces a thermal siphoning process as shown by arrows 25. In the example of FIG. 1, coolant within reactor vessel 20 remains at a pressure above atmospheric pressure, thus allowing the coolant to maintain a high temperature without vaporizing (i.e. boiling). As coolant within steam generators 40 and 42 increases in temperature, the coolant may begin to boil. As boiling commences, vaporized coolant is routed from a top portion of heat exchangers 40 and 42 to drive one or more of turbines 80 and 82 that convert the thermal potential energy of steam into electrical energy. After condensing, coolant is returned to a bottom portion of heat exchangers 40 and 42. Plenums 85 are located at input ports of steam generators 40 and 42 of FIG. 1. In some embodiments, plenums 85 include an approximately flat tubesheet that couples coolant from turbines 80/82 to steam generators 40/42. At least one of plenums 85, which may be located proximate with a first horizontal plane that intersects a lower portion of riser column 30, comprises an approximately flat tubesheet wherein the flat tubesheet faces upward in the direction of a plane intersecting an upper portion of riser column 30. At least one of plenums 87, which may be located proximate with a second horizontal plane intersecting an upper portion of riser column 30, comprises an approximately flat tubesheet wherein the flat tubesheet faces in the direction of a lower portion of the plane intersecting riser column 30. FIG. 2 shows a diametric view of a steam generator around an approximately cylindrical riser column according to an example embodiment. In FIG. 2, a flowpath comprising several layers of closely spaced tubes can be seen as extending helically between plenums 100 and plenums 120. In some embodiments, plenums 100 are spaced at 90-degree intervals in a first plane, such as plane 105, around an approximately cylindrical shape that surrounds a riser column. Both plenums 100 and plenums 120 include an approximately flat tubesheet that faces in the direction of plane 115, which intersects a midsection of steam generator 110. In FIG. 2, the tubes extending between plenums 100 and 120 may comprise lengths of approximately 24.0 to 30.0 meters. In certain implementations, the use of three or more plenums proximate with plane 105 and three or more plenums proximate with plane 125 may result, at least in part, in reducing variation in length to a predetermined threshold of each of the steam generator tubes that forms a flowpath between one of plenums 120 with one or more of plenums 100, for example. However, it should be noted that in other implementations, steam-generator tubes forming one more flowpaths between plenums 100 and 120 might comprise lengths of less than 24.0 meters, such as 22.0 meters, 20.0 meters, 18.0 meters, and other example lengths. In still other implementations, the tubes extending between plenums 100 and 120 comprise lengths greater than 30.0 meters, such as 32.0 meters, 35.0 meters, 40.0 meters, and other example lengths. Further, it should be understood that implementations and embodiments of the invention are not limited in this respect. Plenums 120, which may be approximately located in plane 125 near a bottom portion of a riser column, may also be spaced at 90-degree intervals. In FIG. 2, both plenums 100 and 120 comprise approximately flat tubesheets, wherein each tubesheet comprises perforations for coupling coolant from a plenum to the tubes of steam generator 110. In the embodiment of FIG. 2, each of plenums 100, which may be proximate with plane 105, is shown as being approximately or directly above a corresponding plenum of plenums 120 proximate with plane 125. However, nothing prevents one or more of plenums 100 from being rotated in plane 105 with respect to plenums 120. In some embodiments, tubesheets include perforations having a diameter of between 15.0 and 20.0 mm for coupling to the tubes of steam generator 110. However, other embodiments may make use of a tubesheet having perforations of less than 15.0 mm, such as 12.0 mm, 10.0 mm in diameter or smaller. Additionally, certain other embodiments may make use of a tubesheet having perforations greater than 20.0 mm in diameter, such as 25.0 mm, 30.0 mm, 35.0 mm, and other example diameters. FIG. 3 shows a bottom view of a steam generator around an approximately cylindrical riser column according to an example embodiment. In FIG. 3, plenums 220 may be spaced at approximately 90-degree intervals, for example, around an approximately circular shape, which may represent, for example, riser column 30 of FIG. 1. FIG. 3 also shows various concentric layers of steam generator tubes, which may surround a riser column. FIG. 4 shows a top view of a plenum used in a steam generator for a nuclear reactor according to an example embodiment. In FIG. 4, an approximately flat tubesheet having perforations suitable for coupling to individual tubes of a steam generator is shown. The perforations of FIG. 4 may be arranged in concentric arcs in which a larger number of perforations per unit area (e.g., higher density) may be present towards an outer edge, such as outer edge 260, than at inner edge 250 (e.g., lower density). In FIG. 5, edge 250 may correspond to a portion of the plenum closer to a cylindrical riser column, and outer edge 260 may correspond to a portion of the plenum closer to a wall of a reactor vessel, such as reactor vessel 20 of FIG. 1. FIG. 5 shows details of a plenum used in a steam generator for a nuclear reactor according to an example embodiment. In FIG. 5, tubesheet 330 is shown as being approximately flat and comprising an increasing density of perforations as the distance from riser column edge 335 increases. At a portion of plenum 320 closer to reactor vessel wall edge 340, a much larger density of perforations may be present than at a portion of the tubesheet closer to riser column edge 335. FIG. 6 shows an orifice used in a tubesheet perforation of a plenum used in a steam generator of a nuclear reactor according to an example embodiment. In some embodiments, an orifice may be used to reduce pressure of coolant 350, for example, perhaps by an amount of at least 15.0% of an overall pressure drop brought about by the length of a steam generator tube. In some embodiments, by reducing the pressure of coolant 350, pressure stability, which may be of particular concern during startup conditions, for example, may be enhanced. By stabilizing pressure, such as by way of an orifice of FIG. 6 placed within at least some of the perforations of tubesheet 330 of FIG. 5, for example, momentary oscillations between wet steam and dry steam, which may be particularly prevalent during low power operation of the nuclear reactor module of FIG. 1 may be reduced or eliminated. In turn, this may reduce the possibility of wet steam being coupled into turbines 80 and 82 of FIG. 1, for example, which may degrade the performance of one or more of turbines 80 and 82. In some embodiments, a method of operating a nuclear reactor may include conveying a working fluid from a first group of three or more plenums perhaps proximately located, for example, in a first plane of a reactor vessel, to a plurality of flowpaths. The conveying may include reducing pressure of the working fluid by an amount sufficient to preclude flow instability. In an embodiment, the percentage of pressure drop may comprise at least 15.0% of an overall pressure drop brought about by a length of steam generator tubing that may extend between a first plenum located at a first plane and a second plenum located at a second plane. The conveying may include coupling the working fluid to flowpaths through an approximately flat tubesheet of at least one plenum of the first group of three or more plenums. The method may further include vaporizing the working fluid in at least some of the plurality of flowpaths, wherein the vaporizing results, at least in part, from coupling thermal energy from a reactor coolant to at least some of the flowpaths. The method may further include transferring the vaporizing coolant to a second group of three or more plenums perhaps through an approximately flat tubesheet of at least one of the plenums. While several examples have been illustrated and described, it will be understood by those skilled in the art that various other modifications may be made, and equivalents may be substituted, without departing from the scope of the following claims. |
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060211709 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a nuclear reactor plant having a reactor pressure vessel with a core barrel and to a method for mounting a core barrel. A core barrel is disposed in a reactor pressure vessel of a nuclear reactor plant receiving a reactor core. During operation, particularly in the case of a boiling water reactor plant, a core barrel which is known, for example, from the AEG-Telefunken-Handbuch [AEG-Telefunken Manual], Volume 10, "Siedewasser-reaktoren fur Kernkraftwerke" ["Boiling water Reactors for Nuclear Power Stations"], Andrej Sauer, Berlin 1969, page 100, may suffer damage to weld seams located on its casing. It may then be necessary, in view of that damage, to remove the old core barrel from the reactor pressure vessel and replace it with a new core barrel. It is necessary, for that purpose, to separate the old core barrel mechanically from an essentially cylindrical lower part (core barrel residue) remaining in the reactor pressure vessel. The new core barrel then has to be placed onto that lower part, fitted into the reactor pressure vessel and fixed in the latter. SUMMARY OF THE INVENTION It is accordingly an object of the invention to provide a nuclear reactor plant having a reactor pressure vessel with a core barrel and a method for mounting the core barrel, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and in which the core barrel can be mounted simply and reliably on a holding structure that has remained in the reactor pressure vessel after the removal of the old core barrel. With the foregoing and other objects in view there is provided, in accordance with the invention, a nuclear reactor plant, comprising a reactor pressure vessel; a holding structure fixed to the reactor pressure vessel, the holding structure having a lower surface; a core barrel supported on the holding structure, the core barrel including a lower part having at least one elastically resilient segment with a projection engaging under the holding structure and defining a wedge-like gap between the lower surface of the holding structure and the projection; and a wedge braced in the gap. These structural features permit simple mounting. The new core barrel can simply be pushed onto the holding structure and fixed through the use of wedges by virtue of the elastically resilient segments. This is accomplished without further preliminary mechanical work being necessary, for example the machining of bores or threads for receiving screws. In accordance with another feature of the invention, the projection is beveled on its surface facing away from the gap in order to be led past the holding structure. In accordance with a further feature of the invention, the wedge is braced in the gap through the use of a screw disposed in the segment and acting on an end surface of the wedge. In accordance with an added feature of the invention, the wedge-like gap tapers in the radial direction toward the reactor pressure vessel, and the wedge is braced in the gap through the use of pressure force exerted by the screw. In accordance with an additional feature of the invention, the screw is secured by a device for securing against rotation. In accordance with yet another feature of the invention, a groove is provided on the outer periphery of the lower part, parallel to a longitudinal direction of the latter, and the lower part is pushed onto the holding structure through the use of the groove. With the objects of the invention in view there is also provided a method for mounting a core barrel in a reactor pressure vessel of a nuclear reactor plant, which comprises fixing a cylindrical holding structure to the reactor pressure vessel and providing the holding structure with a lower surface; providing the core barrel with a lower part having at least one elastically resilient segment with a projection; placing the lower part onto the cylindrical holding structure with the projection engaging under the holding structure and forming a wedge-like gap between the lower surface of the holding structure and the projection; and bracing a wedge in the gap. 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 nuclear reactor plant having a reactor pressure vessel with a core barrel and a method for mounting the core barrel, 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. |
summary | ||
abstract | Disclosed embodiments include nuclear fission reactors, nuclear fission fuel pins, methods of operating a nuclear fission reactor, methods of fueling a nuclear fission reactor, and methods of fabricating a nuclear fission fuel pin. |
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claims | 1. An irradiation field limiting device which shields radiation from a radiation source by driving a plurality of aperture leaves a specific amount to limit an irradiation field to a desired range, the irradiation field limiting device comprising:a plurality of aperture leaves each having a circumferential shape;a driver section; anda flexible linear member, one end thereof being secured to at least one aperture leaf and the other end being connected to the driver section, the driver section being configured to drive the flexible linear member in an axial direction of the flexible linear member to cause movement of the at least one aperture leaf,wherein the aperture leaves are arranged in a thickness direction thereof adjacent to each other, the one end of the flexible linear member is secured to an inner or outer circumferential surface of the at least one aperture leaf, and the driver section drives the flexible linear member while increasing or decreasing a contact portion between the flexible linear member and the inner or outer circumferential surface of the at least one aperture leaf by warping the flexible linear member, andwherein the driver section includes:a base;a drive shaft connected with a driving source through a connection portion and inserted into the base; anda slider which moves along an axial direction of the drive shaft accompanying rotation of the drive shaft and is connected with the linear member. 2. The irradiation field limiting device according to claim 1,wherein the connection portion includes a torque limiter section which limits transmission of torque equal to or greater than a specific torque. 3. The irradiation field limiting device according to claim 2,wherein the connection portion includes a clutch mechanism which transmits a driving force to the drive shaft or disconnects the driving force from the drive shaft; andwherein the irradiation field limiting device includes a control section which prevents the driving force from being transmitted to the drive shaft using the clutch mechanism when the torque limiter section has operated for a specific period of time. 4. The irradiation field limiting device according to claim 1,wherein the connection portion includes a clutch mechanism which transmits a driving force to the drive shaft or disconnects the driving force from the drive shaft; andwherein the irradiation field limiting device includes:a position detection section which detects a position of the aperture leaves; anda control section which prevents the driving force from being transmitted to the drive shaft using the clutch mechanism to stop movement of the aperture leaves when the position detection section has detected that the aperture leaves have moved to a target position. 5. The irradiation field limiting device according to claim 1, comprising:a driving force transmission section which transmits a driving force of the driving source to a plurality of the drive shafts;a plurality of clutch mechanisms which transmit the driving force to the drive shafts or disconnect the driving force from the drive shafts; anda control section configured to drive each of the aperture leaves by transmitting the driving force of the driving source in units of the drive shafts by controlling each of the clutch mechanisms. 6. The irradiation field limiting device according to claim 1,wherein the slider has a female thread portion; andwherein the drive shaft has a male thread portion which engages the female thread portion and moves the slider in the axial direction of the drive shaft by being rotated. 7. The irradiation field limiting device according to claim 1, wherein the aperture leaf is fan-shaped or approximately rectangular. 8. The irradiation field limiting device according to claim 1,wherein the linear member comprises a continuous metal wire, a wire rope formed by twisting metal wires, or a hollow pipe. 9. The irradiation field limiting device according to claim 1, comprising:a support shaft provided in the base and disposed approximately in parallel with the drive shaft at a specific interval from the drive shaft;at least one guide which is supported on the support shaft so that the guide moves in an axial direction of the support shaft and maintains a shape of the linear member; andan elastic member which is disposed between the guides and maintains an approximately identical interval between the guides. 10. The irradiation field limiting device according to claim 1, comprising:an absolute position sensor which measures an absolute position of at least one of the at least one aperture leaf and the slider; anda high-resolution relative position sensor which measures an amount of movement from a specific position of at least one of the at least one aperture leaf and the slider measured using the absolute position sensor. 11. The irradiation field limiting device according to claim 1,wherein the aperture leaves are arranged in the thickness direction so that the aperture leaves freely move through rolling elements; andwherein a side surface of each aperture leaf protrudes in the thickness direction to form a holding portion which holds each rolling element. 12. The irradiation field limiting device according to claim 11,wherein the holding portion forms at least one of a straight line and a curve to hold each rolling element. 13. The irradiation field limiting device according to claim 11,wherein one of adjacent rolling elements provided on either side of each aperture leaf is disposed at a position close to the radiation source, and the other is disposed at a position away from the radiation source. 14. The irradiation field limiting device according to claim 11,wherein holding portions are disposed at different positions with respect to the irradiation direction, and are repeatedly disposed at an identical position in units of a specific number of the aperture leaves. 15. The irradiation field limiting device according to claim 11,wherein the holding portion is a shielding portion which prevents radiation from passing through a space between the aperture leaves adjacent to each other. 16. The irradiation field limiting device according to claim 1, comprising:a shielding portion which shields radiation in an opening between the aperture leaves adjacent to each other. 17. The irradiation field limiting device according to claim 1,wherein linear members respectively secured to the aperture leaves adjacent in the thickness direction differ in axial direction. 18. The irradiation field limiting device according to claim 17,wherein the driver section drives the at least one aperture leaf of which the axial direction of the linear member is set to be identical in units of a specific number of the linear members. 19. The irradiation field limiting device according to claim 1,wherein linear members respectively secured to the aperture leaves adjacent in the thickness direction differ in axial direction and are identical in axial direction in units of a specific number of the linear members; andwherein the irradiation field limiting device includes a plurality of driver units each of which includes a plurality of driver sections which respectively drive the linear members of which the axial directions are set to be identical in units of a specific number of the linear members. 20. The irradiation field limiting device according to claim 1, comprising:a linear member holding portion which holds the linear member between the at least one aperture leaf and the driver section so that the linear member moves in the axial direction to prevent the linear member from buckling. 21. The irradiation field limiting device according to claim 1,wherein the linear member drives the at least one aperture leaf while contacting the thick portion, is preliminarily bent in a direction away from a contact portion between the linear member and the thick portion, and presses a portion in contact with the thick portion so that the linear member is prevented from buckling. |
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claims | 1. A magnetic jack type control element drive mechanism for precision position control of a control element assembly, wherein the magnetic jack type control element drive mechanism is a 4-coil type control element drive mechanism, the magnetic jack type control element drive mechanism comprisingan upper motor assembly and a lower motor assembly which drive a control element up and down along a control element drive shaft,wherein the magnetic jack type control element drive mechanism satisfies the following conditions:D1=D2=P+D5 (1)D3=P×2 (2)D4=D3×(N−½), wherein N is an arbitrary natural number, (3)whereinD1 represents a lift gap of the upper motor assembly;D2 represents a lift gap of the lower motor assembly;D3 represents a distance between tips of adjacent teeth of the control element drive shaft;D4 represents a gap between an upper latch constituting the upper motor assembly and a lower latch constituting the lower motor assembly;P represents a pitch indicating a distance the control element drive shaft ascends or descends when operating the upper motor assembly or the lower motor assembly; andD5 represents a margin which is a separation space between the teeth and the upper latch or the lower latch when the upper latch or the lower latch is inserted into the teeth of the control element drive shaft. 2. The magnetic jack type control element drive mechanism of claim 1, wherein P is 10 mm or smaller. 3. The magnetic jack type control element drive mechanism of claim 1, wherein D5 is equal to or greater than 0.1 mm and equal to or smaller than 1.0 mm. 4. The magnetic jack type control element drive mechanism of claim 1, wherein N is 10 or larger. |
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claims | 1. A heat removal system for the under vessel area of a nuclear reactor, the nuclear reactor comprising a reaction pressure vessel located in a primary containment, the primary containment having a floor and comprising a drywell, a suppression pool, and a passive containment cooling system, said heat removal system comprising: a glass matrix slab positioned adjacent the containment floor; and a plurality of heat tubes, each said heat tube comprising an evaporator portion and a condenser portion, said evaporator portion comprising a cylindrical tube, at least a portion of said evaporator tube substantially parallel to the containment floor and embedded in said glass matrix slab, one end of said evaporator tube extending through said glass matrix slab and into the area below the reactor pressure vessel, said condenser portion comprising a cylindrical tube in flow communications with said evaporator tube and extending away from the containment floor in the area below the reactor pressure vessel. 2. A heat removal system in accordance with claim 1 further comprising a plurality of header pipes, each said header pipe coupled to and in flow communication with at least one evaporator tube and at least one condenser tube. claim 1 3. A heat removal system in accordance with claim 2 wherein said plurality of header pipes are located around the perimeter of the containment floor. claim 2 4. A heat removal system in accordance with claim 3 wherein each said header pipe is configured to extend around a portion of the perimeter of the containment floor. claim 3 5. A heat removal system in accordance with claim 4 wherein each said header pipe forms an arc of a circle. claim 4 6. A heat removal system in accordance with claim 5 wherein said evaporator tubes extend from said header pipes in an inverted fan pattern so that a first end of said evaporator tubes is connected to said header pipes and said second end of said evaporator tubes extend toward a point located in the center of the containment floor. claim 5 7. A heat removal system in accordance with claim 1 wherein said glass matrix slab comprises a lead borate glass. claim 1 8. A heat removal system in accordance with claim 7 wherein said lead borate glass comprises lead oxide and boron oxide. claim 7 9. A heat removal system in accordance with claim 8 wherein said lead borate glass comprises at least two moles of lead oxide per mole of boron oxide. claim 8 10. A heat removal system in accordance with claim 1 wherein said plurality of evaporator tubes comprise tungsten or molybdenum. claim 1 11. A heat removal system in accordance with claim 1 wherein said plurality of condenser tubes comprise stainless steel, tungsten, or molybdenum. claim 1 12. A heat removal system in accordance with claim 1 further comprising vent tubes configured to connect the suppression pool with the drywell. claim 1 13. A nuclear reactor system comprising: a primary containment vessel, said primary containment vessel having a floor and comprising a drywell and a wetwell; a reaction pressure vessel located in said primary containment; a passive containment cooling system; a suppression pool located in said wetwell; a glass matrix slab positioned adjacent said containment floor; and a plurality of heat tubes, each said heat tube comprising an evaporator portion and a condenser portion, said evaporator portion comprising a cylindrical tube, at least a portion of said evaporator tube substantially parallel to said containment floor and embedded in said glass matrix slab, one end of said evaporator tube extending through said glass matrix slab and into the area below the reactor pressure vessel, said condenser portion comprising a cylindrical tube in flow communications with said evaporator tube and extending away from said containment floor in the area below the reactor pressure vessel. 14. A nuclear reactor system in accordance with claim 13 further comprising a plurality of header pipes, each said header pipe coupled to and in flow communication with at least one evaporator tube and at least one condenser tube. claim 13 15. A nuclear reactor system in accordance with claim 14 wherein said plurality of header pipes are located around the perimeter of said containment floor. claim 14 16. A nuclear reactor system in accordance with claim 15 wherein each said header pipe is configured to extend around a portion of the perimeter of said containment floor. claim 15 17. A nuclear reactor system in accordance with claim 16 wherein each said header pipe forms an arc of a circle. claim 16 18. A nuclear reactor system in accordance with claim 17 wherein said evaporator tubes extend from said header pipes in an inverted fan pattern so that a first end of said evaporator tubes is connected to said header pipes and said second end of said evaporator tubes extend toward a point located in the center of said containment floor. claim 17 19. A nuclear reactor system in accordance with claim 13 wherein said glass matrix slab comprises a lead borate glass. claim 13 20. A nuclear reactor system in accordance with claim 19 wherein said lead borate glass comprises lead oxide and boron oxide. claim 19 21. A nuclear reactor system in accordance with claim 20 wherein said lead borate glass comprises at least two moles of lead oxide per mole of boron oxide. claim 20 22. A nuclear reactor system in accordance with claim 13 wherein said plurality of evaporator tubes comprise tungsten or molybdenum. claim 13 23. A nuclear reactor system in accordance with claim 13 wherein said condenser tubes comprise stainless steel, tungsten, or molybdenum. claim 13 24. A nuclear reactor system in accordance with claim 13 further comprising vent tubes connecting said suppression pool with said the drywell. claim 13 |
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053176103 | description | Metals and ceramics that can be used in the present invention will now be described. A) A lower layer coating of Ni--Cr and an upper layer coating of WC and Ni--Cr [WC+(Ni--Cr)] (atmospheric plasma thermal spraying). For the lower layer coating of Ni--Cr, a coating with a composition of Ni:Cr=80:20 is preferable as an under layer because it is easy to melt upon heating during the thermal spraying and with which sufficient bonding strength is obtained through fusion with the parent metal. For the upper layer coating of WC+(Ni--Cr), WC is used because of its excellent corrosion-resistant and erosion-resistant properties and Ni--Cr is added as an intergranular bonding material to help bonding because WC is hard to melt. Generally, a composition in the vicinity of WC:Ni--Cr=1:2 is preferable because of its high strength. Also, when providing the lower and upper layer coatings, it is preferable to place a Ni--Cr lower layer coating whose thickness is about a third of the total thickness of the entire coating on the surface of the parent metal and a Ni--Cr coating which contains WC on the lower layer coating, so that sufficient bonding strength to the parent metal can be obtained. According to this, strong bonding is obtained between the parent metal and the lower layer coating and between the lower and upper layer coatings, and in particular, the corrosion and erosion resistant property which WC in the upper layer coating has against fluid can be utilized. Namely, the optimum thickness ratio of the lower layer coating to the upper layer coating is approximately 1:2. B) A single layer coating of WC and Co [WC+Co] or WC and Ni--Cr [WC+(Ni--Cr)1 (jet kote thermal spraying). Because WC does not easily melt upon heating during thermal spraying, Co or Ni--Cr is added as an intergranular bonding material. Because thermal spraying is performed by jet kote thermal spraying which can remarkably improve melting rate of WC as compared with atmospheric plasma thermal spraying, only a small amount of Co or Ni--Cr is needed to mix into WC and a composition of 88WC+12Co or 88WC+12(Ni--Cr) is preferred. The jet kote thermal spraying belongs to the high energy gas thermal spray coating method and is powder thermal spraying which can produce a very sharp and high density coating by making use of an ultrasupersonic jet of combustion gas having a velocity of about Mach 5. C) Austenitic stainless steel (diamond jet thermal spraying). In this case, the spraying of an austenitic stainless steel having a composition by weight percent of 10 to 14% Ni, 16 to 18% Cr, 2 to 3% Mo, and balance Fe, which corresponds to SUS316, is performed by means of so-called diamond jet thermal spraying which is one of the high energy gas thermal spraying methods. The diamond jet thermal spraying is a spraying method for producing a coating which is not porous and has a high density using high kinetic energy, and this method also allows control over the amount of heat, providing high bonding strength and a superb finished surface. According to the present invention, reductions of wall thickness due to erosion-corrosion occurring in devices and parts which are made of carbon steel, such as piping and various kinds of valves, and which are used in the wet steam system, the feedwater and condensate system and the drain system of thermal or nuclear power plants can be prevented at low costs. Diagrams of the embodiments are shown respectively for the case in which the present invention is applied to an elbow in FIG. 1, a branch pipe in FIG. 2 and a pipe disposed on the downstream side of a control valve in FIG. 3. In these drawings the hatched portions inside the pipes are where coating is applied according to the present invention. Reference numeral 6 indicates a control valve and 7 indicates piping. The reduction of wall thickness due to erosion-corrosion in the piping made of carbon steel used in the wet steam system, the feedwater and condensate system, and the drain system of a thermal or nuclear power plant is significant in parts of the piping where a curved flow is formed, such as an elbow, a bend, a branch pipe, a junction pipe, and also in portions of straight pipes installed on the downstream side of a curved pipe and located within a length which is approximately twice the pipe caliber from the pipe, and further in pipes provided on the downstream side of the parts forming a restricted flow, such as a control valve and an orifice. Therefore, to control development of thickness reductions due to erosion-corrosion in the piping for a new system to be built, it is effective and economical to form the coating of metal or ceramic of the present invention in advance only on the inner surface of various piping parts, such as those mentioned above, which are known to often undergo thickness reductions due to erosion-corrosion. Also, as for parts which are already in an existing system, it is possible to control the further progress of thickness reduction by forming the coating of metal or ceramic of the present invention on the surface of such parts where the thickness reduction has already occured to some extent. This can be done at a low cost because the existing parts are used further and not replaced in their entirety. According to the present invention, to the portions hatched inside the pipe walls in FIGS. 1 through 3, the following coatings, for example, are applied. a) A lower layer coating of Ni--Cr and an upper layer coating of WC+(Ni--Cr) can be applied by means of atmospheric plasma thermal spraying. The lower layer coating of Ni--Cr has a thickness of 0.2 mm with a composition of Ni:Cr=80:20, and the upper layer coating of WC+(Ni--Cr) has a thickness of 0.4 mm with a composition of WC:Ni--Cr=1:2 (Ni:Cr=80:20). b) A single layer coating of WC+Co or WC+(Ni--Cr) can be applied by means of jet kote thermal spraying. The single layer coating of WC+Co has a thickness of 0.15 mm with a composition of WC:Co 88:12. The single layer coating of WC+(Ni--Cr) has a thickness of 0.15 mm with a composition of WC:Ni--Cr=88:12 (Ni:Cr=80:20). c) A coating of SUS 316 can be applied with a thickness of 0.4 mm. Thickness reductions of the piping due to erosion-corrosion can be effectively prevented by forming any of the above-mentioned coatings. Next, other embodiments in which the present invention is applied to various kinds of valves for a thermal or nuclear power plant will be described. Diagrams of the embodiments are shown respectively for the case in which the present invention is applied to a gate valve in FIG. 4, a globe valve in FIG. 5, and a check valve in FIG. 6. In these drawings, the portions hatched inside the valve walls are where the coating of the present invention is applied. In FIGS. 4 through 6, reference numeral 1 denotes a valve casing, 2 a valve seat, 3 a valving element, 4 a connecting pipe and 5 an operation handle of the valving element. Additionally, when a coating is formed by thermal spraying according to the present invention, it is preferable to have the thermal spraying applied after finishing the assembly of parts by welding. For example, the welding of the valve casing 1 with the valve seat 2 and the welding of the valve casing 1 with the connecting pipe 5 correspond to this welding which should be done before spraying. This is to protect the coatings of metal or ceramic formed by spraying from being damaged by the heat during the welding. On the portions of the valve casing 1 and the valving element 3 shown in FIGS. 4 to 6 marked with hatching, any coating of the embodiments described in connection with FIGS. 1 through 3 can be formed to obtain similar effects as those of the described embodiments. |
summary | ||
claims | 1. A method of generating 124I comprising irradiating a target material comprising 124Te-enriched aluminum telluride with protons of an energy of at least about 11 MeV and releasing 124I from the target material, wherein the target material comprises the 124Te-enriched aluminum telluride prior to the step of irradiating. 2. The method of claim 1 wherein the target material is irradiated with protons of an energy from about 11 MeV to about 18 MeV. 3. The method of claim 1 wherein the 124I is distilled from the target material. 4. The method of claim 3 wherein a distillation temperature ranges from about 750° C. to about 900° C. 5. The method of claim 3 wherein a distillation temperature ranges from about 900° C. to about 1000° C. 6. The method of claim 3 wherein the distilled 124I is carried away from the target material by a noble gas flowing over the target material. 7. The method of claim 3 wherein the distilled 124I is carried away from the target material by air flowing over the target material. 8. The method of claim 1 wherein the method provides at least 80% release of 124I from the target material. 9. The method of claim 1 wherein the method provides at least 90% release of 124I from the target material. 10. The method of claim 1 wherein the method provides at least 95% release of 124I from the target material. 11. The method of claim 1 wherein the tellurium in the target material comprises at least about 95 atomic % 124Te. 12. A method of generating 124I comprising irradiating a target material comprising 124Te-enriched aluminum telluride with protons of an energy sufficient to generate 124I via the 124Te(p,n)124I reaction and releasing 124I from the target material, wherein the target material comprises the 124Te-enriched aluminum telluride prior to the step of irradiating. |
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