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abstract | A melting apparatus for melt-decontaminating radioactive metal waste includes a melting furnace, a high frequency generator, a ladle, a bogie, a cooling unit and a dust collector. In detail, the melting furnace includes a crucible into which the metal waste is input, and an induction coil which is wound around the crucible to melt the metal waste. The induction coil has a hollow hole in which cooling fluid flows. The high frequency generator applies high-frequency current to the induction coil. The ladle supplies molten metal, from which slag has been removed in the crucible, into molds. The bogie is disposed adjacent to the ladle and is provided with the molds, each of which forms an ingot using the molten metal supplied thereinto. The cooling unit cools the cooling fluid and circulates it along the induction coil. The dust collector filters out dust and purifies gas. |
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abstract | A method for manufacturing a collimator module and/or a collimator bridge is disclosed, as well as a collimator module, a collimator bridge, a collimator and a tomography device. A collimator module for a radiation detector includes a plurality of collimator layers. These collimator layers each have a flat lattice structure. In an embodiment, a first collimator layer has a holder structure and the collimator layers are aligned relative to one another by the holder structure on a first holder tool. With such a holder structure it is possible to glue the aligned collimator layers to one another such that the glued collimator layers form the collimator module with absorber walls disposed in a lattice shape. In such cases, the collimator layers can be aligned to one another in an especially simple and yet precise manner. Through this the actual lattice shape corresponds especially accurately to a prespecified lattice shape. |
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060524316 | abstract | An X-ray converging mirror that can be positioned adjacent an X-ray source for reflecting X-ray beams from the X-ray source includes an X-ray converging mirror having a reflecting surface of a cross-sectional profile expressed by a curve of the following equation: EQU x=y tan .theta.[1-ln(y/b)]. wherein x and y denote a coordinate system, .theta. is equal to or less than a Bragg critical angle of reflection for the X-ray beams, and b denotes a point on the y-axis when dx/dy is 0. |
046997539 | summary | CROSS-REFERENCE TO RELATED APPLICATION Commonly owned U.S. patent application Ser. No. 382,269 filed May 26, 1982 in the names of John Kaufmann, Kenneth J. Swida and Leonard P. Hornak and entitled "Refueling of Nuclear Reactor". BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a simulator which is used in combination with a detachable control unit for a nuclear reactor refueling machine to simulate inputs to the control unit without it actually being installed on the machine, and is useful for operator training and testing. 2. Prior Art A reactor refueling machine is a device used to remove and replace, or rearrange, fuel assemblies and other components in the core of a shutdown nuclear reactor. Typically such a machine comprises a bridge which moves reciprocally on horizontal tracks straddling the water filled pit in which the reactor vessel is housed. A trolley is mounted on the bridge for reciprocal horizontal movement along the bridge so that by appropriate movement of the bridge and trolley, a mast assembly mounted vertically on the trolley can be positioned over any desired location in the pit. The mast assembly includes an inner mast telescopically mounted inside a fixed mast. A hoist mounted on the trolley raises and lowers the inner mast which carries on its lower end grippers for engaging and lifting fuel assemblies. When a fuel assembly has been lifted clear of the reactor vessel by the hoist, the bridge and trolley are repositioned to locate the fuel assembly over a new location in the core, or to move the fuel assembly to a storage area in the pit or to a transfer system which removes the fuel assembly from the pit. New fuel assemblies supplied through the transfer system are inserted in the core by reverse operation of the refueling machine. Some of the newer refueling machines also have mechanisms for transferring separately from the fuel assemblies other reactor components, such as fuel rod clusters and control rod thimble plugs. An example of such a machine is described in U.S. Pat. No. 4,511,531. In this machine, a rod telescoped inside the inner mast carries grippers adapted to engage these other reactor components. The hoist is connected to this rod, which in turn is selectively coupled to the inner mast by lugs on the rod which engage a pivotable stop plate on the inner mast. With the stop plate raised, the inner mast is raised and lowered with the rod for servicing fuel assemblies. With the stop plate lowered, the rod moves independently of the inner mast for servicing the other reactor components. The bridge, trolley and hoist of a refueling machine are positioned independently by separate motors. These motors are controlled by an operator from a control console mounted on the trolley. Signal generators generate feedback signals indicative of movement of each of these components in response to operation of the respective motors. The control console uses these signals in a control loop to accurately position these components and to generate indications to the operator of their respective locations. In the refueling machine disclosed in the above cross-referenced application, the feedback signal generators produce pulses representative of incremental movement of the respective components. The control console includes a programmed digital computer which counts the pulses to track movement and generate a visual display of component position on a cathode ray tube. The earlier control consoles for reactor refueling machines utilized relay logic which is relatively immune to the harsh conditions inside containment, and therefore these units were left in place on the trolley during operation of the reactor. The digital computer and its associated interfaces are less tolerant of the high temperature, humidity and radiation levels found within containment during reactor operation. Since the refueling machine has no function during reactor operation, it has become the practice to remove the control console from containment during plant operation and to place it in storage until the next refueling cycle. SUMMARY OF THE INVENTION It has been recognized by us, that since the detachable refueling machine control console is accessible and available during plant operation it would be desirable to test it and use it for operator training at that time, rather than during a refueling operation when there are competing demands for access to the reactor and any extension of down time is very costly. Accordingly, we have developed a simulator that can be used with the detachable control console to simulate the signals that would be generated by the refueling machine. All commands to the control console actually send signals to the simulator which responds to them as a refueling machine would and feeds responses back to the console. The invention embraces a combination which includes a detachable refueling machine control console which generates, one at a time, motor signals for the drive motors of a plurality of refueling machine components, and in particular the bridge, trolley, and hoist motors. Separate output leads from the control console apply each of the motor signals to the simulator. The simulator includes only one simulator motor which is connected to the output leads from the control console such that it is driven when any of the motor signals is generated. The simulator also includes only one feedback signal generator which is connected to the simulator motor and generates a simulator feedback signal representative of rotation of the simulator motor. The control console also includes a separate input lead for receiving a feedback signal associated with each of the drive motors. These input leads are also connected to the simulator. Switching means within the simulator, which is responsive to the motor drive signals received from the control console over the output leads, connects the single pulse generator to the console input lead associated with the motor drive signal received from the control console. Thus, the single motor and pulse generator in the simulator selectively simulate each of the refueling machine drive motors in response to the particular drive motor signal generated by the control console, and send back a feedback signal representative of operation of that motor over the appropriate dedicated console input lead. The motor signals generated by the control console include a motor drive signal and a control signal for each motor and separate output leads are provided for each signal. All of the motor drive signals are connected to the single simulator motor while the control signals are connected to the switching means to route the feedback signal to the appropriate console input lead. The separate control signals generated by the console are brake signals which are used to release the brake on the appropriate motor on the refueling machine. In the preferred embodiment of the invention, the one simulator motor is provided with a brake and all of the brake signals are applied to it so that the brake is released when any of these signals is generated. The brake signals are also connected to the switching means to effect routing of the feedback signal to the proper console input lead. The invention also embraces the simulator as described which is designed to be used in combination with a detachable control console. The invention permits the operation of the detachable refueling machine control console to be verified without being installed on the refueling machine, which minimizes the potential for critical path down time problems. It is also useful for training operators without requiring any reactor down time. While the invention is primarily intended for use while the control console is physically removed from the refueling machine and from containment, it can also be connected to the console when the latter is on the machine to assist in identifying the source of electrical problems during refueling operations. |
055747590 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is seen a sub-region of a reactor pressure vessel 1 with a particularly bulky part of pressure-vessel fittings 2. The method according to the invention is to be described with reference to this bulky part, which is formed of upper and lower core grids 3, 4 and a core shroud 5. As a rule, between the core grids 3, 4 and the core shroud 5 there is a screw connection which is released as early as during removal from the reactor pressure vessel, so that three individual parts are available for dismantling. However, the method can also be employed when, for example, a welded structure is present and the core grids 3, 4 and the core shroud 5 form a single part. After being removed from the reactor pressure vessel 1, the core grids 3 and 4 and the core shroud 5 are set down on a bottom 6 of a water tank 7, as is indicated by the core shroud 5 in dot-dash lines in FIGS. 2 to 4. According to FIG. 2, a bottom part 8a of a dismantling container 8 is set down on the bottom 6 and one of the core grids 3, 4 is laid onto the bottom part 8 a. A casing 8 b of the dismantling container which is set down on a tank edge 9 is moved into the water tank 7 through the use of a non-illustrated lifting appliance and is connected to the bottom part 8a to form the dismantling container 8, as is also seen in FIGS. 3 and 4. A receiving container 11 for receiving parts obtained during subsequent dismantling is disposed on the core grid. A dismantling manipulator 12 that is likewise set down on the tank edge 9 is set down on a flange 13 of the dismantling container 8 through the use of the non-illustrated lifting appliance or through a likewise non-illustrated rail connection and is fixed relative to the dismantling container, as is shown in FIG. 4. When this phase for dismantling a core grid 3, 4 according to FIG. 2 is reached, a separation of the core grid into transportable parts is carried out by the dismantling manipulator, for example by plasma cutting, with the parts being deposited in the receiving container 11 through the use of an auxiliary lifting appliance 14 that is seen in FIG. 4 and is assigned to the dismantling manipulator 12. After the receiving container 11 is filled, the dismantling manipulator 12 is brought into its set-down position on the tank edge 9. According to FIG. 3, a shielding container 15 is introduced into the water tank 7, its bottom part 15 a is removed, the receiving container 11 is drawn into the shielding container 15 and the bottom part 15 a is reattached. The shielding container 15 that is loaded with the receiving container 11 is brought to a transfer station 16 stationed on a tank edge 9 a. A transport container 17, which is constructed as an ultimate-storage container and has a cover 18 that is removed, is already disposed there. The shielding container 15 is set down on the transport container 17 in alignment in the axial direction, and its bottom part 15 a is moved away laterally, so that the receiving container 11 is lowered into the transport container 17 by a lifting device 20. The shielding container 15 is closed through the use of its bottom part 15 a and is set down at a suitable point until it is next used. After the receiving container 11 has been loaded several times, as soon as the core grids 3, 4 are dismantled, extracted and stored in a radiation-proof manner, the dismantling of the core shroud 5 is dealt with according to FIG. 4. In this case as well, the procedure according to FIG. 2 is carried out analogously, with the core-container shroud 5 and a receiving container 11a being set down on the bottom part 8a after the bottom part 8a has been put in place. The dismantling-container casing 8 b is then lowered in a sleeve-like manner over the core shroud 5 and is connected to the bottom part 8a to form the dismantling container 8. The dismantling manipulator is then supported on the flange of the dismantling container 8 and the dismantling of the core shroud 5 commences according to FIG. 4. Segments which are detached in each case during this dismantling are inserted into the container 11 a through the use of the auxiliary lifting appliance. After the container 11 a is filled, the dismantling manipulator is brought to its set-down point on the tank edge 9 and the load of the receiving container 11 a is transferred to a transport container 17 correspondingly to FIG. 3. In another embodiment, the receiving container 11 a, together with its load, can also be placed directly into a transport container. The water of the dismantling container 8 is purified through the use of a circulating system 21. |
051805413 | claims | 1. A handling flask for handling a load, comprising a hollow body having a vertical channel in a central part of said hollow body and a device for vertical displacement of said load along an axis of said channel, comprising at least two sets of two drums which are driven by two motor means and on which are wound two cables for suspension and displacement of a grab movable in said channel and in an axial extension of said channel and comprising attachment means for said load and a support equipped with pulleys over which said cables pass, wherein each of said sets of two drums driven by a motor means and constituting a winch is fastened to an outer surface of said hollow body, in such a way that said drums of each said winch are each located opposite one of said drums of the other said winch in relation to the vertical axis of said channel, said device for vertical displacement of said load further comprising (a) a first cable having ends wound on a first and a second drum situated at opposite locations on said hollow body and, on a run of said cable between said first and second drums, on a set of deflecting pulleys and at least one pulley mounted on said support for supporting said grab; and (b) a second cable having ends wound on a third and a fourth drum situated at opposite locations on said hollow body and, on a run of said cable between said third and fourth drums, on a set of deflecting pulleys and at least one pulley mounted on said support for supporting said grab. 2. Handling flask according to claim 1, wherein said drums of said winches are arranged around said hollow body in a crosswise arrangement, positions of the four drums being offset angularly by 90.degree. relative to one another about said axis of said channel corresponding to an axis of displacement of said load. 3. Handling flask according to claim 1, wherein each of said drums is adapted to wind a length of cable greater than a length necessary for carrying out displacement of said load to a highest position of said load. 4. Handling flask according to claim 1, wherein said first and second cables have length greater than a length of cable necessary for displacing said load to a lowest position of said load. 5. Handling flask according to claim 1, further comprising a unit for rebalancing said load between said two cables, said unit being connected to driving means of each of said two drums of one of said winches. 6. Handling flask according to claim 5, wherein said driving means of each of said drums of one of said winches consist of reducers of a floating-body type, and said load-rebalancing unit consists of a rocker mounted pivotally on a central part of said hollow body and carrying, at ends of said rocker, damping devices comprising a piston rod up against elastic return devices and connected to a body of a corresponding floating reducer by means of a lever. 7. Handling flask according to claim 1, wherein said motor means for driving each of said winches is in the form of an assembly comprising an electric motor in a position remote from said drums driven by said motor means. 8. Handling flask according to claim 7, wherein said motor assembly comprises, in addition to said electric motor, a bevel-gear transmission device and, for each of said drums driven by said motor assembly, a main reducer and a secondary reducer driven by means of a bevel-gear device and connected to said main reducer by means of a shaft comprising at least one cardan joint. 9. Handling flask according to claim 8, wherein said main reducers are floating-body reducers mounted on a rotary axle of a corresponding drum. 10. Handling flask according to claim 1, wherein each of said first and second cables pass successively over a first deflecting pulley, over a supporting pulley and over a second deflecting pulley on a run of said pulleys between said drums arranged opposite one another, said deflecting pulleys being mounted rotatably on said hollow body and said supporting pulley on said support of said grab by means of horizontal axles, bottoms of grooves of said two deflecting pulleys and of said supporting pulley associated with each of said cables being arranged in a vertical plane passing through said axis of said channel. |
claims | 1. A method for generating an X-ray, comprising the steps of:irradiating an energy beam onto a target from an energy beam source, thereby generating an X-ray with an irradiating area to be irradiated onto an object; andintroducing said X-ray into a spectrometer including a first reflective crystal plate and a second reflective crystal plate which are subsequently arranged at a relative angle twice as large as an incident angle of said X-ray onto said first reflective crystal plate, thereby generating an X-ray with parallelism through the selection of wavelength and wavelength range. 2. The generating method as defined in claim 1, wherein said first reflective crystal plate and said second reflective crystal plate are made of a material selected from the group consisting of silicon, lithium fluoride (LiF), graphite, germanium and quartz. 3. The generating method as defined in claim 1, further comprising the step of, before introducing said X-ray into said spectrometer, transmitting said X-ray through at least one of an absorptive plate and a slit so as to remove components with unnecessary wavelength of said X-ray. 4. The generating method as defined in claim 3, wherein said absorptive plate is an aluminum plate. 5. The generating method as defined in claim 1, wherein said target is a stationary type target. 6. The generating method as defined in claim 1, wherein said energy beam source is an electron beam source so that said energy beam can be an electron beam. 7. The generating method as defined in claim 6, wherein said electron beam source is a diode or a triode type electron beam source. 8. The generating method as defined in claim 1, wherein said X-ray with parallelism is usable for medical use. 9. An apparatus for generating an X-ray, comprising:a target for generating an X-ray through the irradiation of an energy beam;an energy beam source for generating said energy beam to generate said X-ray so as to have an irradiating area to be irradiated onto an object; anda spectrometer for selecting wavelength and wavelength range of said X-ray through the introduction of said X-ray so as to generate an X-ray with parallelism from said X-ray,wherein said spectrometer includes a first reflective crystal plate and a second reflective crystal plate which are subsequently arranged at a relative angle twice as large as an incident angle of said X-ray onto said first reflective crystal plate. 10. The generating apparatus as defined in claim 9, wherein said first reflective crystal plate and said second reflective crystal plate are made of a material selected from the group consisting of silicon, lithium fluoride (LiF), graphite, germanium and quartz. 11. The generating apparatus as defined in claim 9, further comprising at least one of an absorptive plate and a slit so as to remove components with unnecessary wavelength of said X-ray by transmitting said X-ray through said at least one before said X-ray is introduced into said spectrometer. 12. The generating apparatus as defined in claim 11, wherein said absorptive plate is an aluminum plate. 13. The generating apparatus as defined in claim 9, wherein said energy beam source is an electron beam source so that said energy beam can be an electron beam. 14. The generating apparatus as defined in claim 13, wherein said electron beam source is a diode or a triode type electron beam source. 15. The generating apparatus as defined in claim 9, wherein said X-ray with parallelism is usable for medical use. 16. A method for generating an X-ray, comprising the steps of:irradiating an energy beam onto a target from an energy beam source, thereby generating an X-ray with an irradiating area to be irradiated onto an object; andintroducing said X-ray into a spectrometer including a first transmission crystal plate, a second reflective crystal plate and a third transmission crystal plate, which are subsequently arranged so that a reflection plane of said second crystal plate is perpendicular to reflection planes of said first crystal plate and third crystal plate, thereby generating an X-ray with parallelism through the selection of wavelength and wavelength range. 17. The generating method as defined in claim 16, wherein said first reflective crystal plate, said second transmission crystal plate and said third reflective crystal plate are made of a material selected from the group consisting of silicon, lithium fluoride (LiF), graphite, germanium and quartz. 18. The generating method as defined in claim 16, further comprising the step of, before introducing said X-ray into said spectrometer, transmitting said X-ray through at least one of an absorptive plate and a slit so as to remove components with unnecessary wavelength of said X-ray. 19. The generating method as defined in claim 18, wherein said absorptive plate is an aluminum plate. 20. The generating method as defined in claim 16, wherein said target is a stationary type target. 21. The generating method as defined in claim 16, wherein said energy beam source is an electron beam source so that said energy beam can be an electron beam. 22. The generating method as defined in claim 21, wherein said electron beam source is a diode or a triode type electron beam source. 23. The generating method as defined in claim 16, wherein said X-ray with parallelism is usable for medical use. 24. An apparatus for generating an X-ray, comprising:a target for generating an X-ray through the irradiation of an energy beam;an energy beam source for generating said energy beam to generate said X-ray so as to have an irradiating area to be irradiated onto an object; anda spectrometer for selecting wavelength and wavelength range of said X-ray through the introduction of said X-ray so as to generate an X-ray with parallelism from said X-ray, said spectrometer including a first transmission crystal plate, a second reflective crystal plate and a third transmission crystal plate which are subsequently arranged so that a reflection plane of said second crystal plate is perpendicular to reflection planes of said first crystal plate and said third crystal plate. 25. The generating apparatus as defined in claim 24, wherein said first reflective crystal plate, said second transmission crystal plate and said third reflective crystal plate are made of a material selected from the group consisting of silicon, lithium fluoride (LiF), graphite, germanium and quartz. 26. The generating apparatus as defined in claim 24, further comprising at least one of an absorptive plate and a slit so as to remove components with unnecessary wavelength of said X-ray by transmitting said X-ray through said at least one before said X-ray is introduced into said spectrometer. 27. The generating apparatus as defined in claim 26, wherein said absorptive plate is an aluminum plate. 28. The generating apparatus as defined in claim 24, wherein said energy beam source is an electron beam source so that said energy beam can be an electron beam. 29. The generating apparatus as defined in claim 28, wherein said electron beam source is a diode or triode type electron beam source. 30. The generating apparatus as defined in claim 24, wherein said X-ray with parallelism is usable for medical use. |
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claims | 1. A particle-beam treatment system in which, in the case where, during particle-beam irradiation, multi-layer conformal irradiation is performed while setting of the shape of a multileaf collimator in an irradiation head is changed, the shape of the multileaf collimator is detected by a leaf-position detection mechanism, the particle-beam treatment system comprising:an optical shape-monitoring unit mounted attachably and detachably in the snout portion at the downstream side of the multileaf collimator, the optical shape-monitoring unit having a shape-monitoring mirror, opposing the multileaf collimator, for monitoring the shape of the multileaf collimator;a video camera for shooting the shape, of the multileaf collimator, which is reflected by the shape-monitoring mirror; andan image monitor for displaying an image of the video camera that shoots the shape of the multileaf collimator, the shape of the multileaf collimator being able to be monitored during particle-beam irradiation. 2. The particle-beam treatment system according to claim 1, wherein a gradient of the shape-monitoring mirror opposing the multileaf collimator is made close to 90°, rather than 45°, from a traveling direction of a particle beam so as to reduce the space, in the traveling direction of a particle beam, of the optical shape-monitoring unit; an aspect-ratio distortion in an image of the video camera that shoots the multileaf-collimator shape reflected by the shape-monitoring mirror is corrected through image processing; and the image of the video camera is displayed on the image monitor, as an image equivalent to the image of the multileaf-collimator shape as directly viewed in the beam-axis direction. 3. The particle-beam treatment system according to claim 1, the particle-beam treatment system comprising:an optical patient-position monitoring unit mounted attachably and detachably at the downstream side of the multileaf collimator, the optical shape-monitoring unit having a patient-position monitoring mirror, opposing a patient, for monitoring a patient position;a video camera for shooting the patient position reflected by the patient-position monitoring mirror; andan image monitor for displaying the respective images of the video camera that shoots the shape of the multileaf collimator and the video camera that shoots the patient position, the shape of the multileaf collimator and the patient position being able to be monitored during particle-beam irradiation. 4. The particle-beam treatment system according to claim 3, wherein the one side of the monitoring mirror serves as the shape-monitoring mirror and the other side serves as the patient-position monitoring mirror, and the optical shape-monitoring unit includes the optical patient-position monitoring unit. 5. The particle-beam treatment system according to claim 3, further comprising an image-processing means for extracting by use of a binarization method respective outlines or characteristic points from signals for images of the video camera that shoots the shape of the multileaf collimator and the video camera that shoots the patient position, wherein the multi leaf-collimator shape and the patient position are enabled to be monitored based on the respective extracted outlines or characteristic points of monitoring subjects. 6. A particle-beam treatment system in which, in the case where, during particle-beam irradiation, multi-layer conformal irradiation is performed while setting of the shape of a multileaf collimator in an irradiation head is changed, the shape of the multileaf collimator is detected by a leaf-position detection mechanism, the particle-beam treatment system comprising:an optical shape-monitoring unit mounted attachably and detachably in the snout portion at the downstream side of a multileaf collimator, the optical shape-monitoring unit having a shape-monitoring mirror, opposing the multileaf collimator, for monitoring the shape of the multileaf collimator;a video camera for shooting the multileaf-collimator shape reflected by the shape-monitoring mirror; anda comparison means for comparing an image of the video camera with multileaf-collimator-shape information in a treatment plan and determining whether or not the comparison result is appropriate,particle-beam irradiation or particle-beam cutoff processing being performed depending on whether or not the comparison result is appropriate. 7. The particle-beam treatment system according to claim 6, the particle-beam treatment system comprising:an optical patient-position monitoring unit mounted attachably and detachably at the downstream side of the multileaf collimator, the optical shape-monitoring unit having a patient-position monitoring mirror, opposing a patient, for monitoring a patient position;a video camera for shooting the patient position reflected by the patient-position monitoring mirror; anda comparison means for comparing an image of the video camera with patient-position information in a treatment plan and determining whether or not the comparison result is appropriate,particle-beam irradiation or particle-beam cutoff processing being performed depending on whether or not the comparison result is appropriate. 8. The particle-beam treatment system according to claim 7, wherein a gradient of the patient-position monitoring mirror opposing the patient is made close to 90°, rather than 45°, from a traveling direction of a particle beam so as to reduce the space, in the traveling direction of a particle beam, of the optical patient-position monitoring unit; an aspect-ratio distortion in an image of the video camera that shoots the patient position reflected by the patient-position monitoring mirror is corrected through image processing; and the image of the video camera is displayed on the image monitor, as an image equivalent to the image of the patient position as directly viewed in the traveling direction of a particle beam. 9. The particle-beam treatment system according to claim 7, wherein, in the case where the result of the comparison, performed by the comparison means for comparing an image of the video camera that shoots the patient position reflected by the patient-position monitoring mirror with patient-position information in a treatment plan, is inappropriate and particle-beam irradiation is interrupted, information, during the interruption, on settings for devices in the irradiation-head is stored and conditions, when particle-beam irradiation is resumed, for the devices in the irradiation-head are set by use of the information on settings for the devices, so that planned particle-beam irradiation is compensated. |
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claims | 1. An apparatus removeably attachable to a steam dam of a core shroud of a nuclear power plant for inspecting an upper section of the core shroud for flaws or defects therein, said core shroud having lug pairs around its outer surface and being located within a reactor pressure vessel, the apparatus being operable from above the core shroud and comprising:a pair of flanges consisting of an outside flange and an inside flange, said pair of flanges forming an arc of approximately 30° on either side of the steam dam;a pair of flange clamps for securing the distal ends of the pair of flanges to the steam dam;a gear rack attached to the outside flange;a Y-car having a Y-car motor with a gear that meshes with the gear rack;a lug clamp on said Y-car to clamp said Y-car in between the lugs of one of the lug pairs;the Y-car being moveable back and forth along the arc formed by the pair of flanges by (a) securing the pair of flange clamps to the steam dam, (b) releasing the lug clamp from the lug pair, and (c) actuating the Y-car motor to move the Y-car via the gear meshing with the gear rack;the pair of flanges being moveable to a neighboring arcuate segment of the core shroud by (d) moving the lug clamp to a neighboring one of the lug pairs and securing it thereto, (e) releasing the pair of flange clamps from the steam dam, and (f) actuating the Y-car motor to move the pair of flanges and the gear rack via the gear meshing with the gear rack;an upper transducer mounted on the Y-car adjacent to the outer surface of the core shroud;a vertical arm extending downwardly from the Y-car into a space between the reactor pressure vessel and the core shroud;the Y-car having a pivot arm base extending radially outwardly therefrom, said vertical arm being pivotally attached to said arm base;a plurality of transducers being mounted on said vertical arm, including at least an upper moveable transducer and a lower moveable transducer, the upper moveable transducer being threadably attached to an upper lead screw and the lower moveable transducer being threadably attached to a lower lead screw, the upper and lower lead screws independently allowing up and down movement of their respective upper and lower moveable transducers along said vertical arm, said up and down movement provided by a shared transducer motor;said plurality of transducers capable to simultaneously inspect axially spaced apart sections of the outer surface of the core shroud;a bottom transducer arm pivotally attached to a bottom of the vertical arm by a pivot pin, at least one lower transducer being mounted on said bottom transducer arm;the bottom transducer arm pivotal to a position adjacent the outer surface, but under a lower lip of, the core shroud by actuation of an air cylinder during insertion or removal of the apparatus;said air cylinder connected between a radially extending portion of a roller bracket and the bottom transducer arm, said roller bracket having a roller that sets the distance between the vertical arm and the outer surface of the core shroud. |
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description | The present invention relates to a method for disposal of radioactive waste. More specifically, the invention relates to the disposal of intermediate and low level radioactive waste (especially, contaminated soil) that is generated at the time of a nuclear power plant accident around a nuclear power plant such as the Fukushima nuclear power plant accident. In the following descriptions, the amount of an additive (mixture) will be measured in units of mass unless otherwise specified. When a nuclear power plant accident like the one mentioned above occurs, a large quantity of contaminated soil (intermediate and low level radioactive waste) may be found on houses, schools, agricultural land, and forest roads in an area 20 to 30 km around the nuclear power plant. Since the Fukushima nuclear power plant accident, there has been a stronger need than ever before for a method for disposal of radioactive waste which enables a large quantity of intermediate and low level radioactive waste to be safely transported and stored and which enables final disposal of waste after the radiation level is reduced to a natural radiation level or national predetermined reference value (e.g., ICRP recommendation: a yearly radiation dose of 20 mSv). The fission product 137Cs (55) contained in radioactive waste is turned by the β decay into 137Ba (56) which emits gamma rays. In this regard, Cs has a half-life of 30.17 years, thus requiring a long-term storage. Furthermore, the gamma rays emitted from 137Ba (56) themselves have an exceptionally high transmittance when compared with other α rays or β rays. Typically, as a shield for gamma rays, heavy concrete (having a specific gravity of 3.5 to 4.3; up to 2.3 for ordinary concrete) which has aggregates of iron ore and iron scrap in concrete have been used (see Encyclopaedia Chimica Editing Committee (ed.) (Jul. 31, 1962) “Encyclopaedia Chimica 8”, p.617, Kyoritsu Shuppan). However, the storage container or capsule that employs the heavy concrete as a shield increases in weight, and thus had problems in transportation and storage. Furthermore, the concrete is fundamentally porous, thus completely preventing leakage of radioactive nuclides is difficult. Thus, radioactive nuclides had to be covered with a closely packed shield or buried deep in the ground, making it difficult to ensure storage sites or the like. In this context, the development of a method for disposal of radioactive waste has been desired, the method enabling the intermediate and low level radioactive waste to be reduced in radiation level until the waste can be reused as landfill or the like and preventing the leakage of radiation nuclides in the ground. However, the inventors of the prevent invention have not heard of known techniques for such a method for disposal of radioactive waste. Although having no effects on the patentability of the present invention, the following prior art documents exist. Disclosed in Patent Documents 1 and 2 is “a radioactive waste storage container (radiation shielding structure) composed of constituents including calcium silicate and magnesium oxide, or oxidation calcium and acid phosphate.” Disclosed in Patent Document 3 is “a radioactive waste disposal container characterized by including: a body material wall constituting skeleton of the container; a corrosion-resistant barrier material wall for covering the outer surface of the body material wall so as to prevent the same from an external corrosive environment; and an insulating material wall which is assembled between the body material wall and the corrosion-resistant barrier material wall and which electrically insulates between the body material wall and the corrosion-resistant barrier material wall. Patent Literature 1: JP-2012-504774A Patent Literature 2: JP-2012-504773 A Patent Literature 3: JP-2006-132976 A In view of the aforementioned problems, it is an object of the present invention to provide a method for disposal of radioactive waste which is capable of reducing the radiation dose of radioactive waste down to a reference value at which the radioactive waste can be readily handled and the storage site is not strictly limited particularly, the method being further capable of reducing the radiation dose to a level at which the waste is reusable as final disposal site landfill and preventing the leakage of radiation nuclides in the ground. In the course of intensive studies and development to solve the aforementioned problems, the inventors have reached the idea of the present invention adapted as stated below on the basis of the findings that a primary treatment step adapted as stated below enables the radiation level to be reduced to a predetermined value or less and allows storage and transportation, and a secondary treatment step adapted as stated below enables the radiation level to be reduced to a level at which the waste can be buried in the ground and also enables the leakage of most of the radiation nuclides in the ground to be prevented. A method for disposal of intermediate and low level radioactive waste, the method including: a primary treatment step of turning the radioactive waste into a radioactive waste (hereafter referred to as the “primary treated waste”) which has a radiation level equal to or less than a reference value via a shielding agent composed of or predominantly composed of a Ca-based inorganic compound; and a secondary treatment step of heating to melt the primary treated waste and thereafter cooling the same to glass granules, and then sealing radioactive nuclides in the glass granules, the method being characterized in that in the secondary treatment step, the primary treated waste to which a fusing agent (melting point depressant) and/or glass powder having an upper slow cooling temperature of 550° C. or less is added is heated and melted at a temperature setting in the range from 750 to 1050° C. The primary treatment step is capable of reducing the radiation level of the radioactive waste to a reference value or less, thereby facilitating transportation to storage. Furthermore, the secondary treatment step (glass granule forming step) implements glass granule forming by melting and cooling the primary treated waste at a temperature setting of 750 to 1050° C., thereby making it possible to seal most of the radioactive nuclides Cs in a body of glass granules. That is, in the secondary treatment step, the melting temperature of 750 to 1050° C. is lower by 200° C. or more than the boiling point of the radioactive nuclides Cs (the lowest 1250° C. (CsF)). It is thus possible to seal most of the radioactive nuclides Cs in the glass without being vaporized. At this time, low melting temperatures decrease productivity; but radioactive nuclides Cs in the secondary treatment step can be prevented with reliability from being emitted into the atmosphere, thus eliminating the need for a special radioactive nuclide capturing facility. Now, description will be made to the present invention with reference to FIGS. 1 and 2. (1) A primary treatment step: radioactive waste is turned with a radiation shielding agent (hereafter referred to as “the shielding agent”) into a radioactive waste having a radiation level that is equal to or less than a reference value (hereafter referred to as a “primary treated waste”). As used herein, the radioactive waste is defined to have a intermediate and low radiation level (0.1 to 1 mSv/h). The radioactive waste may include, for example, removed contaminants by decontamination that are generated from radioactive decontamination areas designated due to a nuclear power plant accident, sewage sludge incinerated ash, and general waste incinerated ash. The removed contaminants by decontamination may include, for example, soil on playgrounds and agricultural land, sludge in gutters, trees and grasses, and fallen leaves. The aforementioned shielding agent to be employed may be a Ca-based inorganic compound, that is, one composed of Ca salt and/or Ca oxide. The Ca salt may preferably be (a) discarded pulverized seashells mentioned below, and the Ca oxide may be (b) Ca-based inorganic binders mentioned below. (a) Discarded pulverized seashells (seashell powder obtained by burning and pulverizing seashells): seashells may include, for example, scallops, oysters, and clams. These seashells are industrial waste that is generated in large quantities by the food industry. Thus, the seashells will contribute to effective use of industrial waste. (b) Ca-based inorganic binders, which may include, for example, lime (CaO, hydrated lime (Ca(OH)2, magnesium lime), gypsum (CaSO4.2H2O, burnt plaster (CaSO4), anhydrite plaster), and alumina cement ((CaO)x.(Al2O3)y). These raw materials are available at low costs. (c) Non-Ca-based binders: [organic type] natural polymer (such as polynucleotide, polypeptide, polysaccharide, and gum arabic), nonionic polymer (such as polyacrylamide, polyacrylic acid, polyethylene oxide, polyvinyl alcohol, and poly N-Vinyl-pyrrolidone); [inorganic type] water glass and the like. Then, the radioactive waste (such as contaminated soil) and a shielding agent containing a binder are kneaded with water added thereto and thereafter solidified to yield a primary treated waste (hereafter the “primary treated waste single type”) 13, which has a radiation level equal to or less than a reference value. Here, the primary treated waste single type is not limited to a particular form, and can be a block (compact) or granule body. Furthermore, the ratio between the radioactive waste and the Ca-based inorganic compound of the shielding agent (the (a) component and the (b) component) is set, as appropriate, depending on the radiation level of the radioactive waste. Typically, the ratio is set as appropriate in the range of the radioactive waste/the Ca-based inorganic compound=1/9 to 5/5 (preferably, 2/8 to 4/6). The ratio between the radiation shielding agent and the radioactive waste is limited to those of the Ca-based component because non-Ca-based binders have almost no radiation shielding effects (effects of reducing the radiation level). Furthermore, with respect to a total 100 parts of the radioactive waste and the Ca-based inorganic compound of the shielding agent, the amount of water added is 50 to 100 parts. This varies depending on the moisture content of the radioactive waste and the type of the Ca-based inorganic compound. The primary treated waste single type 13 is typically charged into a storage container 11. Here, the storage container 11 is desirably a radiation shielded container (hereafter referred to as the “shielded container”) formed by kneading a shielding agent (discarded seashells component +a binder) with water. This is to doubly shield the radioactive waste. In this case, the waste is of a primary treated waste complex type (I) (the primary treated waste single type+the shielded container). The primary treated waste complex type (I) can be readily adapted to a radioactive waste of a relatively high radiation level among intermediate and low level radioactive waste. The primary treated waste complex type may be obtained by covering the primary treated waste single type or the radioactive waste with a radiation shield, to which a kneaded product of the shielding agent with water is solidified, in place of the shielded container. Furthermore, if the radioactive waste is not in a bulky form, not a kneadable powdery, mud-like, or chip-like form, required pre-processing, for example, pulverization or incineration is performed. If the pulverization or incineration may possibly cause radioactive nuclides (especially, Cs) to be emitted into the atmosphere via dust particles or ash particles, the radioactive waste is directly stored in a radiation shielded container 11 or covered with a radiation shield. That is, the radioactive waste is turned into the primary treated waste complex type (II) (the radiation shield+the radioactive waste). The radiation shielded container 11 is to be made up of a container body (cylindrical type, box type) and a lid assembly, each having a predetermined thickness. The container body and the lid assembly may be preferably obtained by kneading the shielding agent with water added thereto and then molding the resulting mixture. The thickness varies depending on the radiation level of the radioactive waste to be charged and the required capacity. For example, for the storage container 11 having a size of a drum (with a capacity of 200 L), an appropriate value may be selected from the range of thicknesses of 50 to 100 mm (preferably, 80 mm or greater). In the case of an insufficient strength, iron bars or iron nets are buried. As described later, the shielded container 11 can also be molded from a mixture of a shielding agent and a radioactive waste (such as contaminated soil) kneadable with the shielding agent, the radioactive waste measuring about ½ or less in total composition. The primary treated waste complex type 15 that is formed by charging a primary treated waste single type 13 into the radiation shielded container 11 or by charging the radioactive waste into the radiation shielded container 11 is transported to a local temporary storage site, an intermediate storage facility, or a final disposal facility. At this time, the level of radiation from the radiation shielded container 11 is equal to or less than a reference value at which the waste can be handled, thus allowing the waste to be transported and stored at each site or facility without requiring high-level radiation protective measures. When the primary treated waste single type (aggregate-shaped waste) has a low radiation level, the waste may be charged into a general-purpose storage container, for example, an iron drum or plastic container and then stored at a temporary storage site within the premises. (2) The aforementioned primary treated waste single type and complex type (I) and (II) are heated to melt and then cooled to a glass body in a waste melting disposer 20 as follows. At this time, typically, a fusing agent (freezing point depressant) and/or glass powder of an upper slow cooling temperature of 550° C. or less is added to the waste. This is to heat and melt the waste at 1050° C. or less. The fusing agents may include, for example, boric acid, borax, or frit. The fusing agent may be added in advance to the shielding agent. The aforementioned glass of an upper slow cooling temperature of 550° C. or less may be borosilicate glass of 518 to 550° C., soda lime glass of 472 to 523° C., and lead glass of 419 to 451° C. (cited from Encyclopaedia Chimica Editing Committee (ed.) (Jul. 31, 1962) “Encyclopaedia Chimica 9”, p. 858, Kyoritsu Shuppan). The glass powder can be obtained by pulverizing glass waste (especially, waste such as TV cathode-ray tubes or window glass). Thus, this contributes to effective use of industrial waste. When the aforementioned glass waste is lead glass like TV cathode-ray tube glass or soda lime glass like window glass, effects of increasing the radiation shielding capacity can be preferably expected. Silica glass powder has high slow cooling temperatures of 910 to 1140° C. for silica glass and is composed of only silica. Thus, each of the effects of decreasing the freezing point and increasing the radiation shielding cannot be expected; however, the silica glass powder, which is a waste, can be used as an extending agent. Furthermore, the amount of fusing agent and glass powder added to 100 parts of primary treated waste (the radioactive waste+the shielding agent) varies depending on the melting temperature setting, the composition of the shielding agent, and the type of the fusing agent or the glass powder. Typically, an appropriate value is chosen from the range of 15 to 300 parts. The waste melting disposer 20 is made up of a stir pulverize step unit (stirring pulverizer 21), a melting step unit (a melting furnace 23), and a cooling step unit (a cooler 25). Here, for example, the stirring pulverizer 21 can be any of a screw type or propeller type. That is, it is sufficient as long as it has a capability of pulverizing the storage container composed of the Ca-based shielding agent. The melting furnace 23 can be, for example, of any of a burner type or electric furnace type. That is, the melting furnace 23 may serve sufficiently as long as it has a capacity of turning the primary treated waste single type and complex type into molten glass (at 750 to 1050° C.). Furthermore, the cooler 25 is provided with a heat exchanger, an air cooling means, or a water cooling means. Now, description will be made to a secondary disposal method for the primary treated waste (single type and complex type) using the waste melting disposer 20 mentioned above. The primary treated waste is charged into the stir pulverize unit, and then a fusing agent and/or glass powder of an upper slow cooling temperature of 550° C. or less is added thereto so as to stir and pulverize the primary treated waste. At this time, typically, the waste is preferably pulverized to medium sizes from 1 to 10 mm. Then, the stirred and pulverized waste is charged into a melting furnace so as to be heated and melted at a temperature setting within the range of 750 to 1050° C. The temperature setting is preferably lower from the viewpoint of preventing radioactive nuclides Cs from being emitted into the atmosphere, but is preferably higher from the viewpoint of shortening the processing time of the melting treatment (productivity). To keep the balance between the two, the temperature setting may be preferably 800 to 1000° C. Also, the melting treatment time is, for example, about two hours at 800° C. and about one hour at 1000° C. Also, when a temperature setting is less than 750° C., it is difficult to melt the waste into a glass body even if the fusing agent or glass powder is added thereto, causing the treatment time for heating and melting to be elongated thus degrading productivity. Then, the molten waste is cooled to be glass granules. The cooling method may be performed either slowly or rapidly depending on the type of the binder and the size required for the glass granules. The slow cooling may tend to lead to relatively large granules, while providing a low glass rate (density). The rapid cooling may tend to be difficult to obtain large granules, while providing a high glass rate (density). Unlike a hydrate hardened product such as cement, the glass body is so dense so that radioactive nuclides (Cs) are sealed (encapsulated) almost perfectly, allowing little possibility of leakage of radioactive nuclides. Here, the glass granules are typically produced by dropping (rapidly cooling) molten waste into water. The typical size thereof at this time is 0.1 to 5 mm. For the fusing agent or powder glass not containing the radiation shielding component (Ca or Pb), the secondary treated waste (glass granules) has the same radiation dose as that of the primary treated waste, but has been turned into a glass body, thus having no possibility of leakage of the radioactive nuclides from the secondary treated waste. Thus, regardless of place, the secondary treated waste can serve as landfill material and can be used as asphalt subgrade material or concrete aggregate. Furthermore, for the fusing agent or the powder glass containing the radiation shielding component (Ca or Pb), further increased effects of shielding radiation can be expected. That is, the radiation dose of the secondary treated waste can be reduced. When the radiation dose of the secondary treated waste has not reached a final disposal reference at which disposal is allowed, the shielding agent (Ca-based inorganic compound) or glass powder having a shielding capacity is added again to the secondary treated waste by one to two times the previous amount and then turned into the glass granules in the same manner as above. This step of forming glass granules is repeated until the radiation dose reaches the final disposal reference value. When the primary treated waste single type has been stored in a storage container such as the aforementioned iron container, only the primary treated waste single type 13 is charged into the stirring pulverizer 21 of the waste melting disposer 20. This test example compares the radiation shielding capacities of each radiation shield. Prepared were plate-shaped radiation shields with each having a thickness of 60 mm and sides of 100 mm. The material of the present invention: 20 parts of binder (gum arabic) was added and then 70 parts of water was further added to 100 parts of calcined scallop shells (condition: 1000° C.×60 min) and pulverized material (median diameter: 0.1 μm) so as to be kneaded and formed into the plate-shaped material as specified above. Concrete material: 150 parts of water was added to 100 parts of constituent of cement/sand=1/2 so as to be kneaded and formed into the plate-shaped material as specified above. Lead plate: a commercially available lead plate was cut so as to be stacked one by one, and thereby the plate-shaped material was prepared as specified above. Then, the contaminated soil collected at Namie-machi in Fukushima prefecture that is located within the 20 to 30 km range of the Fukushima nuclear power plant was charged into a petri dish (having an inner volume of 1000 cc). Then, the aforementioned each plate-shaped shield place on top of the petri dish was measured three times for the radiation dose. Measurements were also made in the same manner on the petri dish with no shield placed on the top thereof. A radiation meter (“RADIATION ALERT Inspector” (trade mark) (available from Sowa Trading Co., Ltd.) was used. TABLE 1SeashellPowderShieldNot AvailableCompactLead PlateConcreteRadiation Dose3.8 μSv/h0.42 μSv/h0.28 μSv/h0.53 μSv/hShielding Rate (%)0.088.992.686.0 From Table 1 indicating the aforementioned results (arithmetic average values), it was confirmed that the compact (radiation shield) with seashell powder employed as the shielding agent has a higher shielding effect than the concrete. This is due to a high CaO component content. Thus, the compact of only gypsum or lime can provide the effects of the present invention. Furthermore, the waste that has been heated to melt and then cooled into glass granules can be expected to increase effects of shielding radiation and preventing leakage of radioactive nuclides by the glass body made denser. For the contaminated soil to be mixed with a radiation shielding agent, a mixing ratio that makes a radiation shield (container) available was studied. It was confirmed that a high radiation shielding rate was achieved when the entire composition ratio of the contaminated soil was about 1/2 or less, preferably about 1/3 or less. Used as the contaminated soil (radioactive waste) was the sewage sludge incinerated ash from a sewage sludge disposal site at a city in Kanto area. The shielding component (shielding agent): the one having the same composition as that of the present invention was used. Then, the shielding component and the contaminated soil were each weighed and prepared at the ratio shown in Table 2 and then charged into a beaker (see FIG. 3). After that, 60 g of water was added to a total amount of 100 g of the mixture (90 g for 150 g). Subsequently, after kneading, the mixture was left until it was solidified so as to prepare a radiation shield (plate-shaped compact) that is a primary treated waste single type. The thus prepared radiation shield (samples a and b) or the contaminated soil compact (sample c) was measured for the radiation dose for 5 minutes by the radiation meter set at the opening surface of the beaker. From Table 2 indicating the results, it can be seen that composition of the contaminated soil being ½ to ⅓ or less in the entire amount, the radiation dose of the contaminated soil (compact) is reduced by 20 to 40%. TABLE 2Sample aSample bSample cShielded Component/50 g/50 g100 g/50 g0 g/100 gContaminated SoilThickness (t)13 mm20 mm20 mm(Shielded) Compact0.263-0.2130.236-0.1370.347-0.257Radiation Dose(μSv/h)Reduction Rate (%)75-8268-53— Next, to check the shielding effect of each radiation shield prepared in this manner, the contaminated soil (radioactive waste) was placed on the lower surface of each beaker in which the radiation shield is held, so that the radiation dose was measured on the upper surface of the beaker (at a distance of 60 mm from the radioactive waste) in the same manner as above. From Table 3 indicating the results, it was confirmed that the radiation shield of the present invention prepared by mixing the contaminated soil exhibits a radiation shielding rate of 93 to 95%. TABLE 3RadioactiveSample aSample bWasteThickness (t)13 mm20 mm—Radiation Dose60 mm from the60 mm from the60 mm from theMeasurementUpper Surface ofUpper Surface ofUpper Surface ofPositionRadiation WasteRadiation WasteRadiation WasteMeasured18.93-17.9513.1-11.1270.1-248.7Radiation Dose(μSv/h)Shielding Rate93.0-92.895.5-95.2—(%) Next, three beakers (FIG. 3), each having a height of 800 mm×a diameter of 100 mm, were prepared, and sample a and sample b were each charged into a beaker, and a mixture of 250 g with the shielding agent/the contaminated soil=2/1 was charged into the remaining beaker so as to prepare the radiation shield (of a thickness of 33 mm) b′ in the same manner. Then, the contaminated soil (radioactive waste) was placed on the lower surface of each beaker which held the radiation shield, and the radiation meter was placed on the upper surface to measure the radiation dose. From Table 4 indicating the results, it was confirmed that an increase in thickness lead to a further increase in shielding rate of 93 to 98%. TABLE 4Sample a +RadioactiveSample bSample b′WasteThickness (t)13 mm +33 mm—20 mm = 33 mmMeasurement80 mm from the80 mm from the80 mm from thePositionUpper Surface ofUpper Surface ofUpper Surface ofRadiation WasteRadiation WasteRadiation WasteMeasurement14.6-16.85.57-5.13249.3-240.9Dose (μSV/h)Shielding Rate93-9597-98—(%) Finally, a formwork was used to form a shielded container (radiation shield) 33l which includes a storage hole 27 (side lengths of 80 cm×a depth of 80 cm) for the radioactive waste shown in FIG. 4 and which is made up of a cubic container body 31 and a lid assembly 29. At this time, the composition and the kneading and solidifying of the shielding agent was the same as those of the present invention. Then, the radioactive waste was charged into the radioactive waste storage hole 27 of the storage container 33, and the radiation dose at the opening of the storage hole 27 before being closed with the lid assembly 31 and the radiation dose after being closed with the lid assembly 31 were measured. From Table 5 indicating the results, it was confirmed that the radiation shielded container 33 predominantly composed of the shielding agent had a thickness of 90 mm showing a radiation shielding rate of 99% or greater. It was also confirmed that the measured radiation dose at that time was about 1 μSv/h (8.76 mSv/y) and thus reduced below the reference value 20 μSv of the yearly radiation dose, so that the radiation level was reduced to such a level that allows the resulting waste to be brought into or taken out of a temporary storage site. TABLE 5LidSidewallRadiation WasteShielding Compact0.197-0.1330.197-0.133—(μSV/h)Radiation DoseThickness (t)90 mm100 mm—Measured Radiation1.162-1.0420.559-0.419558.9-532.6Dose (μSV/h)Shielding Rate (%)99.79-99.8 99.89-99.92— As described above, the aforementioned radiation shielded container 33 having a thickness of 90 to 100 mm can store and retain the radioactive waste (contaminated substance). That is, the radiation shielded container 33 can be used as the aforementioned storage container 11 allowing safe storage in a temporary storage site (intermediate storage site). The primary treated waste single type having the same composition as that of sample b (the shielding component/the contaminated soil=2/1) in Table 2 above was hammered into intermediate pulverized material of a size of 1 to 2 cm. Then prepared was the waste to be disposed that was obtained by adding 1 kg of lead glass powder (TV cathode-ray tube pulverized material) and 1 kg of boric acid were added to 1 kg of the intermediate pulverized material (the primary treated waste). The waste to be disposed was charged into a heating and melting furnace (“KYN-6N” by KYOEI ELECTRIC KILNS CO., LTD., Specifications: 200V and 6 kW, maximum service temperature of 1300° C.) and then heated and melted for two hours at a temperature setting of 800° C., thereafter allowed to flow into water (at room temperature). In this manner, provided was glass granules of 1 to 2 mm (the secondary treated waste). The volume of the secondary treated waste was about ⅓ the volume of the waste to be disposed. The surface radiation dose of the secondary treated waste was about 80% of the surface radiation dose of the primary treated waste. That is, it was confirmed that the lead glass powder added had an effect (of reducing the radiation dose and increasing the radiation shielding rate). 11 Radioactive waste storage container (radiation shielded container) 13 Primary treated waste single type 15 Primary treated waste complex type 20 Waste melting disposer 21 Stirring pulverizer 23 Melting furnace 25 Cooler (Cinder notch) |
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abstract | An alumino-borosilicate glass for the confinement, isolation of a radioactive liquid effluent of medium activity, and a method for treating a radioactive liquid effluent of medium activity, wherein calcination of said effluent is carried out in order to obtain a calcinate, and a vitrification adjuvant is added to said calcinate. |
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abstract | Disclosed are methods and apparatus for cleaning heat exchangers and similar vessels by introducing chemical cleaning solutions and/or solvents while maintaining a target temperature range by direct steam injection into the cleaning solution. The steam may be injected directly into the heat exchanger or into a temporary side stream loop for recirculating the cleaning solution or admixed with fluids being injected to the heat exchanger. The disclosed methods are suitable for removing metallic oxides from a heat exchanger under chemically reducing conditions or metallic species such as copper under chemically oxidizing conditions. In order to further enhance the heat transfer efficiency of heating cleaning solvents by direct steam injection, mixing on the secondary side of the heat exchanger can be enhanced by gas sparging or by transferring liquid between heat exchangers when more than one heat exchanger is being cleaned at the same time. |
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056174578 | claims | 1. A pressurized-water reactor, comprising: a pressure vessel having a bottom, an inlet, a lateral outlet, and an interior; a core support disposed at said bottom of said pressure vessel; a grid plate having apertures formed therein and having an upper surface, said grid plate defining a plenum above said grid plate in said interior of said pressure vessel, said plenum leading to said lateral outlet; plenum attachments protruding into said plenum at said upper surface of said grid plate; a multiplicity of mutually adjacent fuel assemblies disposed in said interior of said pressure vessel on said core support, each of said fuel assembled containing a bundle of fuel rods and a top carrying a top plate covering said bundle and having passage openings formed therein, and each of said fuel assemblies being disposed around control-rod guide tubes and being supported at said apertures in said grid plate by said top; a device disposed in said pressure vessel for deflecting a coolant flow from said inlet, into said pressure vessel and through said core support, for distributing the coolant flow over said individual fuel assemblies and for guiding the coolant flow along said fuel rods, through said passage openings in said top plates of the fuel assemblies, through said apertures in said grid plate and into said plenum; and throttle plates each being attached in said top of a respective one of a plurality of said fuel assemblies, said throttle plates having throttle openings formed therein for an individual adaptation of pressure in the coolant flowing through said top of said respective fuel assembly, said throttle openings in said throttle plate having a smaller cross section than said passage openings in said top plate, said throttle openings having a cross-sectional area, and the greatest part of said cross-sectional area of said throttle openings being disposed above said passage openings in said top plate. a pressure vessel having a bottom, an inlet, a lateral outlet, and an interior; a core support disposed at said bottom of said pressure vessel; a grid plate having apertures formed therein and having an upper surface, said grid plate defining a plenum above said grid plate in said interior of said pressure vessel, said plenum leading to said lateral outlet; plenum attachments protruding into said plenum at said upper surface of said grid plate; a multiplicity of mutually adjacent fuel assemblies disposed in said interior of said pressure vessel on said core support, each of said fuel assemblies containing a bundle of fuel rods and a top and being supported by said top at said apertures in said grid plate; a device disposed in said pressure vessel for deflecting a coolant flow from said inlet into said pressure vessel, for distributing the coolant flow through said core support over said individual fuel assemblies and for guiding the coolant flow along said fuel rods, through said tops of said fuel assemblies and said apertures in said grid plate and into said plenum; and throttle elements associated with a plurality of said apertures in said grid plate, said throttle elements each having at least one passage opening formed therein for an individual adaptation of pressure in the coolant emerging from said tops of said fuel assemblies, said throttle elements being supported at said apertures in said grid plate above said tops of said fuel assemblies. a pressure vessel having a bottom, an inlet, a lateral outlet, and an interior; a core support disposed at said bottom of said pressure vessel; a grid plate having apertures formed therein and having an upper surface, said grid plate defining a plenum above said grid plate in said interior of said pressure vessel, said plenum leading to said lateral outlet; plenum attachments protruding into said plenum at said upper surface of said grid plate; a multiplicity of mutually adjacent fuel assemblies disposed in said interior of said pressure vessel on said core support, each of said fuel assembled, containing a bundle of fuel rods and a top carrying a top plate covering said bundle and having passage openings formed therein, and each of said fuel assemblies being disposed around control-rod guide tubes and being supported at said apertures in said grid plate by said top; a device disposed in said pressure vessel for deflecting a coolant flow from said inlet into said pressure vessel and through said core support, for distributing the coolant flow over said individual fuel assemblies and for guiding the coolant flow along said fuel rods, through said passage openings in said top plates of the fuel assemblies, through said apertures in said grid plate and into said plenum; and throttle plates each being attached in said top of a respective one of a plurality of said fuel assemblies, said throttle plates having throttle openings formed therein defining a flow cross section for coolant flowing through said top of said respective fuel assembly; and said flow cross section of one respective fuel assembly being greater than said flow cross section of a respective other fuel assembly. 2. The reactor according to claim 1, wherein said throttle plate is attached releasably in said top of said fuel assembly. 3. The reactor according to claim 1, wherein said throttle plate and said top plate are bolted together to an upper end of said control-rod guide tubes. 4. The reactor according to claim 1, including common holding-down devices holding said top plate and said throttle plate in said top of said fuel assembly. 5. The reactor according to claim 1, wherein each of said throttle plates is disposed above a respective one of said top plates. 6. A pressurized-water reactor, comprising: 7. The reactor according to claim 6, wherein said throttle inserts are inserted in said apertures in said grid plate. 8. A pressurized-water reactor, comprising: |
description | The present patent application is a non-provisional application of International Application No. PCT/IB02/001965, filed May 30, 2002. The invention relates to an X-ray optical element, a collimator for high-energy electromagnetic radiation, an alternative X-ray optical element, alternative collimator, an X-ray detector as well as a spectrometer. Notably the detection of X-rays, but also of other high-energy electromagnetic radiation, gives rise to the problem that an examination result concerning information contained in such radiation, for example, spectrometric information or images of regions of different absorption, is falsified by background radiation. It is inevitable, notably in the X-ray range in which X-ray optical elements operate essentially in reflection only and not in transmission, that reflected radiation as produced by the incidence of photos on the reflecting material as well as secondary radiation, such as characteristic radiation of the material used in the relevant optical system, are also detected and hence falsify the result. In order to reduce scattered radiation, for example, use is made of diaphragms, that is, components which leave only a small opening for the passage of radiation. However, secondary radiation or reflected radiation can also pass through this opening. Such disturbing radiation is reduced when a succession of diaphragms is arranged along the optical path at a distance from one another. However, it is to be noted that secondary radiation is also produced at the area of the opening for the radiation; this is due to the interaction of the radiation with the edge zone of the passage opening, for example, of the diaphragm aperture. This again yields radiation which falsifies a measuring result and is mixed with the measuring signal. The more diaphragms or the like are arranged in succession, the larger the surface area of interaction will be. Therefore, the occurrence of disturbing radiation cannot be effectively counteracted by simply increasing the number of diaphragms. It is an object of the invention to remove disturbing radiation of the described kind as much as possible from a measuring beam. This object is achieved in accordance with the invention by means of an X-ray optical diaphragm as disclosed herein, a collimator and an X-ray optical element as well as by means of a collimators, an X-ray detector and a spectrometer. Advantageous embodiments are also disclosed. Because of the angulation of the edge zone, radiation incident thereon is reflected at an angle which is more inclined, relative to the direction of propagation of the rays, notably X-rays, than in the absence of the angulation. Both the reflected radiation and the secondary radiation are thus removed from the radiation containing the actual information. The disturbance component is thus reduced. However, the construction of the diaphragm overall may still be very thin, thus enabling only slight interaction with the diaphragm material. The angulation advantageously is such that the passage opening becomes narrower in the beam direction. The rays interacting with the edge zone of the passage opening, therefore, are incident on a surface which is inclined towards the rays in the case of a parallel beam path and hence are very thoroughly deflected away from the propagation direction followed thus far upon incidence on this surface. The risk that deflected rays or secondary rays are also detected, therefore, is small. It is particularly advantageous, and of a special importance for trace analysis, to arrange several of such diaphragms one behind the other and at a distance from one another, the angulation being particularly advantageous if, in the case of grazing incidence of a light beam along the angulated surface, a first diaphragm does not conduct this light beam to the next diaphragm which is transparent thereto, but against walls of a tube which is arranged between these diaphragms so that beams which are incident on the edge surface at an angle of incidence larger than 0 instead of at a grazing angle are indeed reflected against said walls and not against the next diaphragm. This is important notably for characteristic and hence material-specific X-rays, because the diaphragms are often made of the same material, so that the second diaphragm would be transparent as if it were for such characteristic radiation. A material mix between the diaphragms or similar X-ray optical components would also be of assistance. Such an arrangement with suitably chosen distances between the diaphragms offers a significant improvement of the suppression of the background. The measuring accuracy can thus be significantly increased. X-ray optical elements of this kind can be used in various devices, notably in collimators in X-ray spectrometers and X-ray detectors for the examination of information originating from an X-ray beam. Trace analysis represents one possible field of application. An alternative embodiment of an X-ray optical element is provided with a graduation different zones are formed in the direction of propagation of the beam, so that rays which are incident on a wall surface in the elongate zone and are reflected or scattered thereby or cause secondary radiation are kept away from the beam path by reflection or absorption by the step in the subsequent, constricted zone. A collimator may also be provided with such an element; a combination of the abovementioned elements and the graduated elements is also feasible. In any case, an adequate distance should again be maintained between the element at the entrance side and the element at the exit side in the collimator. Elements may also be ranged therebetween. The collimator 1 shown in FIG. 1 forms part of an X-ray spectrometer (not completely shown) or an X-ray detector in which the X-rays 7 are conducted to a detection surface 2. The collimator 1 serves as an imaging element which operates purely in the transmission mode for high-energy electromagnetic rays, for example, for X-rays. To this end, the collimator 1 includes an entrance diaphragm 3 and an exit diaphragm 4 as well as a tube 5 which is situated therebetween and on the inner walls 6 of which reflection, scattering or other formation of secondary radiation of the electromagnetic rays propagating along the optical path 8 can take place. The diaphragms 3, 4 are provided with respective passage openings 3a, 4a which are constructed, for example, as a slit or as a passage opening bounded by a round contour. The edge zones 3b, 4b are angulated relative to the direction of propagation of the rays which in this case coincides with the optical axis 8. The X-ray optical elements 3, 4 may be provided with different angulations in their edge zones 9, 10 as shown in FIG. 3. The angle α of the edge zone 9 of the diaphragm 3 at the entrance side relative to the optical is chosen to be such that a light beam 7a which is incident at a grazing angle would not be incident on the diaphragm 4 at the exit side, but on the zones 6 of the walls of the collimator. It is thus ensured that all rays which are not incident at a grazing angle but are reflected at an angle γ relative to the surface of the edge zone 9 will be in on the inner wall zone 6. The same hold for secondary rays emanating at an angle γ. This is of importance notably for characteristic X-rays in which defined, intense peaks arise from the diaphragm material. When the diaphragm 4 at the exit side is mad of the same material as the diaphragm 3 at the entrance side, it will be transparent to such characteristic radiation. Characteristic radiation of this kind would then remain in the beam path without being affected by the diaphragm 4 at the exit side or other diaphragms of the same material. The walls 6, however, are customarily made of a different material, so that absorption of such characteristic radiation can be achieved. Moreover, the angle β of the edge zones 10 around the passage opening 4a of the X-ray optical element 4 at the exit side is such that a grazing ray 7b thereon just has to originate from the inner walls 6. The distance L between the entrance diaphragm 3 and the exit diaphragm 4 is chosen accordingly. In the present construction in the form of hole diaphragms 3, 4, the edge zones 9, 10 are angulated each time on the full circle surrounding the passage zone 3a, 4a. However, depending on the shape of the passage opening 3a, 4a for example, in the case of a slit-shaped diaphragm, this is not absolutely necessary. It is not absolutely necessary either that the passage openings 3a, 4a are constructed in the direction of propagation 7 of the rays as is shown in FIG. 4. The cross-section of the diaphragm opening 3a or 4a of the diaphragms 3 or 4 is shown in detail in FIG. 2. It appears that a ray 11 penetrates the material of the diaphragm because it enters near the edge zone and hence cannot be completely absorbed by the locally remaining effective diaphragm thickness D. A similar situation occurs in the reverse circumstances as shown in FIG. 3. The shortest 12 shown therein however, will emanate approximately perpendicularly to the angulated surface 9, 10; this path, however, is shorter than the path of the ray 11 in the reverse orientation of the diaphragm. This gives rise to more fluorescence and more scattering which could disturb the measurement. As opposed to the arrangement shown in FIG. 4, the collimator 1 may also be provided with a total of more than one diaphragm 3 at the entrance side and one diaphragm 4 at the exit side, that is, an arrangement of a plurality of diaphragms may be provided in the beam path 7; in that case each of said diaphragms or some of said diaphragms may be provided with angulated edge zones 9, 10. The X-ray optical elements 3, 4 together lead to a stronger enlargement of the emission angle γ of scattered radiation and fluorescent radiation, emanating as secondary rays in the case of interaction between hip-energy electromagnetic waves and matter, from the beam path 7 relative to the propagation direction 7 of the rays to be measured on the detector 2. Consequently, fewer of such disturbing rays appear on the detector window 2. The FIGS. 5 and 6 show X-ray optical elements 103, 104 which can be used as an alternative for the X-ray optical elements 3, 4. A combination of diaphragms 103, 104 and diaphragms 3, 4, for example, within a collimator 1, is also feasible. The diaphragms 3, 4 as well as 103, 104 can be selected and used also in an X-ray detector or spectrometer, as desired. FIG. 5 shows a diaphragm 103 which is composed of two assembled plate members 111, 112; such plate member 111, 112 may contain materials. When a diverging ray 113 is incident on the edge zone 109 and is reflected or scattered therefrom or generate secondary rays so that a ray 113b is obtained which emanates from the edge surface 109 at the angle ε, this ray 113b is incident on the constricted zone of the diaphragm 103 or 104. At that area it can either be scattered back or reflected, so that it is removed from the beam path 7. Absorption in the material at the area of the shorter edge zone 110 is also possible. The absorption is particularly effective when the second plate 112 is made of a material other than that of the first plate member 111, because characteristic radiation of the material as produced in the edge zone 109 can then also be absorbed in the plate member 112. A construction of the diaphragm 104 as a single piece, as shown in FIG. 6, is also possible. Because the effect of the absorption process taking place in the constricted part of the edge zone 110 is comparatively insignificant, such a diaphragm 104, or a diaphragm 103 which comprises two plate members 111, 112 of the same material is also suitable for suppressing scattered or reflected rays or secondary rays in the edge zone 109. X-ray optical elements 3, 4, 103, 104 of this kind are generally known for use in spectrometers for example for trace analysis, or in X-ray detectors, for example, for the acquisition of information concerning different absorption behaviors of X-rays in a spatially resolved manner. A special application is found in X-ray detectors or spectrometers or spectrometers utilizing similar high-energy radiation. |
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052689417 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, and particularly to FIG. 1, the reactor 1 shown therein comprises a pressure vessel 2 having a removable closure head 4 attached to the pressure vessel 2 by a plurality of bolts (not shown). The pressure vessel 2 may be of a well known type suitable for containing a fluid coolant at a relatively high pressure. In the present case the coolant utilized is water; however, other suitable fluids may be utilized as a coolant if desired. The pressure vessel 2 has an inlet nozzle 6 and outlet nozzle 8. The coolant is circulated through the reactor vessel in a manner well known in the art. Fuel assemblies 10 are mounted within the pressure vessel 2 between a lower core plate 12 and an upper core plate 14 which constitutes the reactor core. The lower core plate 12 is attached by welding to a core barrel 16 having an upper flange 18 which rest on a ledge 20 of the pressure vessel 2. The upper core plate 14 is supported from a deep-beamed upper support plate 22 by means of a plurality of support tubes 24. The reactor is provided with control rod drive mechanisms 26 that may be of any conventional type including electromagnetic linear motion drive type devices or hydraulic drive type devices which move the control rods in incremental steps into and out of the reactor core. As was noted previously, of the control rod drive mechanisms 26 are attached to the closure head 4 by way of adapter tubes 28 with the control rod drive mechanism 26 being sealed to a respective adapter tube 28 by way of an omega seal 30 as shown in FIG. 2. As can be seen from FIG. 2 the omega seal 30 is the original seal between the adapter tube 28 and the control rod drive mechanism 26. Further, as can be noted from FIG. 2, a canopy seal 32 having a semi-circular cross-section is positioned and secured so as to enclose the entire periphery of the omega seal 30. It is the proper positioning and securing of a canopy seal 32 which constitutes the preferred embodiment of the present invention. Generally speaking, the process of welding the canopy seal 32 in place about the omega seal 30 is done remotely by means of a control rod drive canopy seal weld head illustrated in FIGS. 8 and 9 of the drawings. Canopy seal 32 is sealed about the omega seal 30 in order to contain any leakage at the omega seal site. The control rod drive mechanism canopy seal weld system is composed of three individual tools each performing a particular function with the primary goal of being to remotely weld the canopy seal 32 to contain any leakage at the omega seal site. The three component tools are a stalk measuring device 34 shown in FIGS. 3 and 4, a split canopy installation fixture 36 shown in FIGS. 5, 6 and 7 and a robotic weld arm 108 shown in FIGS. 8 and 9. Additionally, a carousel for positioning and maneuvering the stalk measuring device 34 and the robotic weld arm 108 is illustrated in FIGS. 12, 13 and 14. These individual devices are used in conjunction with one another in order to properly position and weld the canopy seal 32 about the omega seal site. The stalk measuring device 34 is used initially to determine the precise diameter of the adapter tube 28 such that the split canopy installation fixture 36 may properly position the canopy seal 32 about the omega seal site. Once the diameter of the adapter tube 28 is determined, adjustments can be made to the split canopy seal installation fixture 36 so that this fixture will properly engage the adapter tube 28 in order to hold the canopy seal in its proper position for welding. The stalk measuring device 34 is anchored to the carousel 38 by any conventional means; however, because the stalk measuring device 34 is only temporarily mounted to the carousel 38 it is preferred that a mating dovetail structure 40 be utilized. Mounted to the dovetail structure 40 is an extension beam 42 to which an air cylinder 44 is pivotally secured. The air cylinder 44 is pivotally mounted within bracket 46 by way of pivot 48. The extension and retraction of the air cylinder 44 is controlled by compressed air which is fed to, and exhausted from the air cylinder 44 through tube fittings 50 and 51. Pivotally mounted to the extension beam 42, through pivot shaft 52, is a caliper support structure 54, with the caliper support structure 54 being adapted to be displaced in an angular direction by the air cylinder 44. The air cylinder 44 is further pivotally attached to the caliper support structure through pivot 56, this pivotal action to be described in greater detail hereinafter. The caliper support structure 54 supports an air cylinder 58 which is provided between a pair of caliper arms 60 and 62. A plate 64 is provided to extend from the rearward end of the caliper arm 62 and is contacted by a displacement sensor 66. The output generated by the displacement sensor 66 is forwarded to a control center (not shown) by way of cable 68 whereby any movement of the caliper arm 62 is transmitted to the control center which digitally displays the resultant displacement. The caliper arms 60 and 62 are initially calibrated to a known predetermined diameter prior the positioning of the stalk measuring device 34 adjacent the control rod drive mechanism 26. The stalk measuring device 34 is then anchored to the carousel 38 and lowered down the housing of the control rod drive mechanism 26 to a position adjacent the adapter tube 28. By actuation of the air cylinder 44, the caliper support structure 54 is pivoted to a position normal to the extension beam 42. In doing so, the caliper arms 60 and 62 will be positioned adjacent diametrically opposed sides of the adapter tube 28. Once the stalk measuring device 34 has reached this position the air cylinder 58 is actuated in order to draw the caliper arms 60 and 62 towards one another. This displacement is sensed by the sensor 66 through contact with the plate 64 with the data being forwarded to the control center which provides a digital read out of the actual diameter of the adapter tube 28. Once this actual diameter of the adapter tube 28 has been determined, the air cylinder 58 reverses the action on the caliper arms 60 and 62 which move away from one another. The air cylinder 44 then retracts in order to return the caliper support structure 54 to its original position. Once this position is reached, the stalk measuring device 34 is disconnected from the carousel 38 and removed. As mentioned previously, this measurement is used to properly adjust the split canopy installation fixture 36 in order to properly position the installation fixture 36 about the adapter tube 28. Turning now to FIGS. 5, 6 and 7, the split canopy installation fixture 36 will be discussed in greater detail. As can be seen from FIGS. 6 and 7, the split canopy installation fixture 36 includes a pair of semi-circular buckets 70 and 72 for accommodating the two piece canopy seal 32. Each of the buckets 70 and 72 includes a plurality of canopy seal retaining clips 74 which aid in maintaining the canopy seal 32 in position within the buckets 70 and 72 during their positioning. Each of the buckets 70 and 72 are reciprocably mounted on elevating air cylinders 76 for elevating the buckets 70 and 72 for properly positioning the canopy seal beneath the control rod drive mechanism 26. Each of the elevating air cylinders are mounted to the two-piece adapter tube clamp 78a and 78b which are hingedly connected to one another by way of hinge 80. The hinge 80 is pivotable about the pivot pin 82 such that the two-piece adapter tube clamp 78a, 78b may be opened and positioned about the adapter tube 28 and subsequently closed and camlocked tightly to the adapter tube 28. An air cylinder 84 which is pivotally mounted to one of the elevating air cylinders 76 by way of bracket 86 and pin 88 is provided for displacing the hinge 80 in order to open and close the two-piece adapter tube clamp 78a, 78b along the split line 90. An additional dual air cylinder construction is further pivotally mounted to the same elevating air cylinder as that of air cylinder 84. The dual air cylinder consist of a first air cylinder 92 which is pivotally secured to the elevating air cylinder 76 and a second air cylinder 94 which is pivotally mounted at a first end to the first air cylinder 92 by way of pivot pin 96 and is pivotally mounted at a second end to a hinge 98 and a lever arm 100. The hinge 98 includes a camlock 102 which may be forced about the lock lug 104 in order to fixedly clamp the two-piece adapter tube clamp 78a, 78b about the adapter tube 28. In order to maneuver the split canopy installation fixture 36 to a position below control rod drive mechanism 26 and adjacent to the adapter tube 28, lift flanges 106 are provided and secured to a respective one of the buckets 70 and 72. These flanges allow the split canopy installation fixture 36 to be lowered by way of a rope or pole to the desired position. The purpose of the split canopy installation fixture 36 is to transport the two-piece canopy seal 32 to the omega seal site and properly position the canopy seal 32 about the adapter tube 28. The split canopy installation fixture 36 and the canopy seal 32 are lowered to a position adjacent the adapter tube 28 by using ropes or a pole connected to the lift flanges 106. The two halves of the canopy seal rest in the buckets 70 and 72 as the fixture 36 is lowered. While not shown in the figures, each half of the canopy seal includes locator pins while each of the buckets 70 and 72 include pin holes for accommodating the locator pins of the canopy seal 32 in order to maintain the canopy seal 32 in place during the lowering of the split canopy installation fixture 32. Once in a position adjacent the adapter tube 28, air cylinder 84 is activated so as to close the two-piece adapter tube clamp 78a and 78b about the adapter tube 28. Once the two-piece adapter tube clamp has been closed around the adapter tube 28, the first air cylinder 92 is activated in order to pivot the hinge 98 to an initial position about the lock lug 104. After this position is reached, the second air cylinder 94 is actuated in order to further push the camlock 102 over a lock lug 104 and firmly secure the adapter tube clamp 78a, 78b to the adapter tube 28. Upon completion of the clamping process, the elevating air cylinders 76 are actuated in unison so as to elevate the canopy seal 32 to the proper position below the control rod drive mechanism 26. The canopy seal 32 is then held in place while the robotic weld arm 108, to be discussed in greater detail below, descends and temporarily tacks the seal in this position. Once the canopy seal 32 has been properly tacked, the buckets 70 and 72 of the installation fixture 36 are lowered and the camlock 102 is released so that the installation fixture 36 may be removed. Removal of the installation fixture 36 facilitates the robotic weld arm's access to all necessary weld areas of the canopy seal 32. The robotic weld arm 108 is illustrated in detail in FIGS. 8 and 9. The robotic weld arm 108 includes an upper housing 110, an intermediate housing 112 and a lower housing 114. The upper housing 110 accommodates a first magnetic induction motor 116 which when actuated rotates gear 118 which is meshed with gear 120 which is capable of rotating the intermediate housing 112 about an elbow axis 122 in a desired direction. The upper housing 110 further accommodates the weld wire spool mount bracket 124 which is secured to the upper housing 110 by bolts 126. The spool mount bracket 124 carries a pair of weld wire spools 128 with the wire from a first spool being used for the vertical C-shaped welds between the two-piece canopy seal structure and the weld wire of a second spool being used to perform the upper and lower radial welds about the canopy seal 32. A weld wire drive mechanism 130 is secured to the intermediate housing 112. The weld wire drive mechanism 130 includes a pair of wire feed drive motors 132 and 134 which rotate the drive shafts 133 and 135 respectively. As shown in FIG. 11, each of the drive shafts 133 and 135 drive respective wire feed drive rollers 136 and 138 which drive the weld wires 137 and 139. Counter wire feed rollers 140 and 142 are provided for pressing the respective weld wire against the drive rollers. The force in which the counter rollers 140 and 142 contact the weld wire may be readily adjusted by the tension adjustment screws 141 and 143. Springs 144 and 146 assure the continuous contact between the counter rollers 140 and 142 and the respective weld wire. As can be further noted from FIG. 11, wire feed guide tubes 145 and 147 are provided in order to guide the weld wire through the weld wire drive mechanism 130 to the weld head 148. Intermediate housing 112 further accommodates a second magnetic induction motor 150 as shown in FIG. 10. The second magnetic inductor motor 150 includes a drive shaft 152 which drives gear 154 which mates with gear 156 which rotates the shaft 158 and subsequently the gear 160 mounted within the gear housing 162. Gear 160 is meshed with a cooperating gear 164 within the gear housing 162 which rotates the shaft 166 within the bearings 168 which ultimately pivots the lower housing 114 about a wrist axis which is constituted by the shaft 166. Cameras 170 and 172 are provided for inspecting both the leading and trailing edges of the weld as it is being formed by the weld head 148. The weld head 148 includes a gas torch 174 and a tungsten weld wire wire 176. An additional weld wire guide 178 is provided at a position near the end portion of the weld head 148 so as to appropriately guide the weld wire to a position adjacent the weld head 148. The cameras 170 and 172 are additionally provided with lens covers 180 for protecting the cameras during the welding process. The robotic weld arm 108 is provided with five degrees of freedom, one being the rotation about the wrist axis, the second being the rotation about the elbow axis 122. A third degree of movement is the vertical movement of the weld head 148 which is performed by piston cylinder assembly 182 which is accommodated in the lower housing 114. The piston cylinder assembly 182 is composed of a piston 184 having a shaft 186 secured to the weld head 148. Hydraulic fluid is provided to the piston cylinder assembly through the hydraulic fittings 187 and 188. By varying the flow of fluid through the hydraulic fittings 187 and 188, the vertical positioning of the weld head may be varied. This feature will be discussed in greater detail hereinafter. Two additional degrees of freedom are provided to the robotic weld arm 108 by way of the carousel 38 shown in FIGS. 12-14. The carousel 38 is adapted to be positioned about an upper portion of the control rod drive mechanism 26. As shown in FIG. 13 the carousel 38 includes a chuck housing 192 and an inner housing 194 with the chuck housing including a reciprocable resilient pad 196 which may be readily displaced by the pin 198. Once the carousel 38 is positioned about the control rod drive mechanism 26, the pin 198 is driven forwardly so as to displace and press the resilient pad 196 against an upper portion of the control rod drive mechanism 26. This will maintain the carousel in a stable position relative to the control rod drive mechanism 26. A magnetic induction motor 200 is supported on a top hat plate 202 above the inner housing 194. The magnetic induction motor 200 includes a drive shaft 204 having a gear 206 fixedly secured thereto. The gear 206 is meshed with a ring gear 208 which is secured to an outer housing 210 by way of a flange 212. The outer housing 210 is permitted to rotate about the inner housing 194 by way of bearings 214. As can be seen from FIGS. 12 and 14, a mount 216 is fixedly secured to an outer portion of the outer housing 210 which supports the robotic weld arm 108 as well as a mechanism for vertically displacing the robotic weld arm. As shown in FIG. 14, the mount 216 is secured to the outer housing 210 by way of bolts 218, and accommodates a magnetic induction motor 220. A telescopic tubular construction 222 is suspended from the mount 216 and includes an outer tubular member 224 and an inner displaceable tubular member 226. As noted in FIG. 8, this inner tubular member 226 is also attached to the robotic weld arm and surrounds the screw shaft 228. The screw shaft 228 is connected to the output drive shaft 230 of the magnetic induction motor 220. Rotation of the output drive shaft 230 and consequently the rotation of the screw shaft 228 causes of the displacement of the inner tubular member 226 relative to the outer tubular member 224 which subsequently results in the vertical displacement of robotic weld arm 108. Additionally, mounted to an outer portion of the outer tubular member 224 is a spacer which includes rollers 234 and 235 which contact an outer portion of the control rod drive mechanism 26 so as to aid in the stabilization of the robotic weld arm 108. As can be seen from the foregoing, it is the carousel 190 in conjunction with the robotic weld arm 108 which provides the necessary five degrees of freedom such that the robotic weld arm 108 can perform both the upper and lower radial welds as well as the C-shape vertical welds in a narrowly confined space. The motion of the robotic weld arm is controlled by a central computer system which has been programmed with preset data for controlling the positioning of the robotic weld arm 108 as well as the speed of the welding process. The welding process is controlled by an ARC machine (not shown) the ARC machine provides the necessary power to the robotic arm for performing the welding process. The central computer which controls the positioning of the robotic weld arm also controls the positioning of the torch and the speed of the torch movement. As noted previously, the weld head 148 may be manipulated in a direction parallel to the direction in which the weld head 148 is positioned by the wrist axis by way of the piston cylinder assembly 182. This allows for an instantaneous movement of the tungsten weld wire 176 so as to maintain a constant ARC between the tungsten weld wire 176 and the surface being welded. The entire welding process is carried in the following manner. Initially, the carousel 38 is positioned about the control rod drive mechanism 26 and secured thereto by the resilient pad 196. Once in this position, the stalk measuring device 34 can be secured thereto and suspended adjacent the control rod drive mechanism 26 and the adapter tube 28. Upon actuation of the air cylinder 44, the caliper support structure will pivot and position the caliper arms 60 and 62 on diametrically opposite sides of the adapter tube 28. Air cylinder 58 is then actuated to displace the caliper arms 60 and 62 towards one another with this displacement being sensed by the displacement sensor 66. The displacement sensed by the sensor 66 is transmitted by way of the cable 68 to a control center where the actual diameter of the adapter tube 28 is provided. Once the actual diameter of the adapter tube 28 has been determined, the stalk measuring device 34 is removed from its position adjacent control rod drive mechanism 26. The split canopy installation fixture 36 is then adjusted such that it may be securely fixed to the adapter tube 28. The two-piece canopy seal is next positioned within the buckets 70 and 72 of the split canopy installation fixture 36 with this fixture then being lowered to a position adjacent the adapter tube 28. Next, the hydraulic air cylinder 84 is activated such that the hinge 80 is displaced to open the two-piece adapter tube clamp 78a, 78b. The split canopy installation fixture is then positioned about the adapter tube 28 with the air cylinder 84 then being actuated in a reverse manner to close the two-piece adapter tube clamp 78a, 78b about the adapter tube 28. Once the installation fixture 36 is closed around the adapter tube, it is camlocked in place by the cooperating movement of the first and second air cylinders 92 and 94 which positions the camlock 102 about the lock lug 104. After the fixture has been secured about the adapter tube 28, the elevating air cylinders 76 are actuated so as raise the buckets 70 and 72 to properly position the canopy seal 32 as shown in FIG. 2. The canopy seal is held in place by the split canopy installation fixture 36 while the robotic weld arm 108 descends to a position adjacent the seal and temporarily tacks the canopy seal in place. When the canopy seal 32 has been properly tacked in place, the buckets 70 and 72 of the installation fixture 36 are retracked, the camlock is released and the fixture is removed. Removal of the split canopy installation fixture 36 facilitates the robotic weld arm's access to all necessary weld areas of the canopy seal 32. The robotic weld arm 108 with its previously mentioned five degrees of freedom is capable of following the C-shaped vertical welds between the two-piece canopy seal as well as the upper and lower radial welds in the confined space between adjacent control rod drive mechanisms 26. After the split canopy installation fixture 36 has been removed, an argon gas purge is inserted in the canopy seal 28 to a evacuate any oxygen at the omega seal site. The preset data contained in the control center directs the robotic weld arm 108 to complete an initial tacking of the seal in place. The robotic weld arm 108 then begins the vertical C-shape welds and subsequently completes the top and bottom radial welds except for a vent opening which is provided for the purge gas insertion. The purge gas insertion is then removed and the robotic weld arm applies a final hot pass weld which closes the argon gas purge vent opening. As stated previously, the welding process is controlled by an ARC machine which provides the necessary power to the robotic weld arm 108 for welding. During the welding process data is continuously presented to the control center which is used to manipulate the robotic weld arm 108 and particularly the tungsten weld wire 176. |
description | The present invention relates to a jet pump disposed in a reactor pressure vessel of a boiling water reactor to cause a forced circulation of coolant water in the reactor pressure vessel, and in particular to a technique for restraining vibration of the jet pump. Conventionally, an inlet mixer pipe and a diffuser pipe for jet pumps used in boiling water reactors are connected to each other by inserting the inlet mixer pipe into an upper end opening of the diffuser pipe with a clearance left therebetween. This is known as a slip joint structure. The slip joint structure has a clearance which accommodates a structural deformation due to thermal expansion, and acts as an adjusting allowance in connection of members. The clearance provided in the slip joint structure forms a clearance flow path for coolant through which pumped coolant transferred from the inlet mixer pipe to the diffuser pipe is trying to overflow from the clearance. It is known that when a clearance flow flowing through the clearance flow path reaches a certain flow rate, a vibration having a large amplitude, referred to as self-excited vibration, occurs which may lead to a damage to the jet pump. Note that even in the case of a minute vibration which does not lead to the self-excited vibration, when the minute vibration continues for a long time, e.g., sliding wear of an interconnection portion between a wedge and a riser bracket may cause reduction or loss of support performance of the inlet mixer pipe. Such degradation of the support performance results in an increase of the clearance of the slip joint structure, i.e., an increase in a flow rate of the clearance flow, this eventually increasing possibility of the self-excited vibration. Conventionally, vibration restraining techniques for jet pumps listed below have been known. (1) A reinforcing hardware for restraining vibration and wear is provided in an interconnection portion between a wedge and a riser bracket (for example, see Patent Document 1). (2) A clearance adjuster is provided which eliminates a clearance defined by a riser bracket and an inlet mixer pipe to restrain vibration (for example, see Patent Documents 2 and 3). (3) A fastener is provided, by which an inlet mixer pipe and a diffuser pipe are press-contacted to each other to restrain vibration (for example, see Patent Document 4). (4) A member for eliminating a clearance flow is interposed in a clearance between an inlet mixer pipe and a slip joint structure connecting the inlet mixer pipe with a diffuser pipe (see Patent Document 5). (Patent Document 1) U.S. Pat. No. 6,052,425 (Patent Document 2) Japanese Patent Laid-Open No. 2001-249196 (Patent Document 3) Japanese Patent Laid-Open No. 2003-161795 (Patent Document 4) U.S. Pat. No. 6,394,765 (Patent Document 5) U.S. Pat. No. 6,438,192 Each of the vibration restraining techniques described in Patent Documents 1 to 3 includes a vibration restraining structure at a location away from the connection portion between the inlet mixer pipe and the diffuser pipe. Each of such vibration restraining structures is not intended to directly restrain the self-excited vibration due to the clearance flow described above, so that a restraint effect of the self-excited vibration decreases with distance between the vibration restraining structure and the connection portion between the inlet mixer pipe and the diffuser pipe. In the vibration restraining technique described in Patent Document 4, the inlet mixer pipe and the diffuser pipe are press-contacted to each other by an external force applied thereto. In the vibration restraining technique described in Patent Document 5, the clearance defined by the inlet mixer pipe and the diffuser pipe is eliminated. Therefore, in each of the vibration restraining techniques, a function of the clearance for accommodating a structural deformation due to e.g. thermal expansion of the inlet mixer or the diffuser pipe is inhibited, as well as mechanical deterioration is caused. The present invention is made in view of the above circumstances, and has an object to provide a jet pump, and a method for restraining vibration of the jet pump, which can restrain self-excited vibration in a connection portion between an inlet mixer pipe and a diffuser pipe without inhibiting a structural deformation due to thermal expansion and the like. According to one embodiment, a jet pump disposed in a reactor pressure vessel of a boiling water reactor, the jet pump including an inlet mixer pipe connected to a riser pipe, and a diffuser pipe connected to the inlet mixer pipe to cause a forced circulation of coolant water in the reactor pressure vessel, the jet pump includes: a slip joint structure connecting the inlet mixer pipe and the diffuser pipe to each other by inserting the inlet mixer pipe into an upper end opening of the diffuser pipe with a clearance left therebetween; and a self vibration damping structure configured such that when the clearance defined by an outer pipe wall of the inlet mixer pipe and an inner pipe wall of the diffuser pipe is widening or narrowing due to vibration of the inlet mixer pipe or the diffuser pipe, a flow path resistance inside a clearance flow path for pumped coolant water defined by the clearance is not smaller than a fluid inertia force all over the clearance flow path. According to another embodiment, a jet pump disposed in a reactor pressure vessel of a boiling water reactor, the jet pump including an inlet mixer pipe connected to a riser pipe, and a diffuser pipe connected to the inlet mixer pipe to cause a forced circulation of coolant water in the reactor pressure vessel, the jet pump includes: a slip joint structure connecting the inlet mixer pipe and the diffuser pipe to each other by inserting the inlet mixer pipe into an upper end opening of the diffuser pipe with a clearance left therebetween; and a self vibration damping structure including a groove portion provided on any one side of an outer pipe wall of the inlet mixer pipe and an inner pipe wall of the diffuser pipe, and a convex portion provided on the other side and being fit into the groove portion with a minute clearance left therebetween. According to another embodiment, a jet pump disposed in a reactor pressure vessel of a boiling water reactor, the jet pump including an inlet mixer pipe connected to a riser pipe, and a diffuser pipe connected to the inlet mixer pipe to cause a forced circulation of coolant water in the reactor pressure vessel, the jet pump includes: a non-slip joint structure connecting the inlet mixer pipe and the diffuser pipe to each other by abutting an opening edge of the inlet mixer pipe against an opening edge of the diffuser pipe. According to another embodiment, A method for restraining vibration of a jet pump disposed in a reactor pressure vessel of a boiling water reactor, in which an inlet mixer pipe and a diffuser pipe are connected to each other by inserting the inlet mixer pipe into an upper end opening of the diffuser pipe with a clearance left therebetween, to cause a forced circulation of coolant water in the reactor pressure vessel, the method including: controlling a flow of a clearance flow such that when the clearance defined by an outer pipe wall of the inlet mixer pipe and an inner pipe wall of the diffuser pipe is widening or narrowing due to vibration of the inlet mixer pipe or the diffuser pipe, a flow path resistance inside a clearance flow path for pumped coolant water defined by the clearance is not smaller than a fluid inertia force all over the clearance flow path. These embodiments of present invention can restrain self-excited vibration in a connection portion between an inlet mixer pipe and a diffuser pipe without inhibiting a structural deformation due to thermal expansion and the like. Embodiments of a jet pump according to the present invention and methods for restraining vibration of the jet pump will be described with reference to the accompanying drawings. FIGS. 1 and 2 are views showing a first embodiment of a jet pump according to the present invention. FIG. 1 is a view showing an arrangement of the jet pump, and FIG. 2 is a view showing a structure of the jet pump. A jet pump 10 of this embodiment, as shown in FIG. 1, is disposed in a clearance (a so-called downcomer region 50) defined by an inner reactor wall of a reactor pressure vessel 20 and a shroud 40 surrounding a reactor core 30 in a boiling water reactor 1. The jet pump 10 takes in coolant water from a recirculation inlet nozzle 70 via a recirculation pump 60 and discharges the coolant water to a lower plenum 80, thereby causing a forced circulation of the coolant water within the reactor pressure vessel 20. Note that outline arrows in FIG. 1 indicates a direction of coolant flow. The jet pump 10, as shown in FIG. 2, comprises a riser pipe 11 through which the coolant water fed from the recirculation inlet nozzle 70 (FIG. 1) is raised, an elbow pipe 19 directing the raised coolant water downward, an inlet mixer pipe 12 conducting the coolant water, fed from a nozzle port of the elbow pipe 19, downward while involving reactor water, and a diffuser pipe 13 ejecting the coolant water into the lower plenum 80 (FIG. 1). Referring to reference numerals in FIG. 2, the numeral 14 denotes a riser bracket fixing the riser pipe 11 and the inlet mixer pipe 12 relative to each other; the numeral 15 denotes a wedge; and the numeral 17 denotes a connection portion between the inlet mixer pipe 12 and the diffuser pipe 13. The jet pump 10 includes a slip joint structure and a self vibration damping structure in the connection portion 17 between the inlet mixer pipe 12 and the diffuser pipe 13. FIG. 3 is a view showing the slip joint structure and the self vibration damping structure in the jet pump 10 (longitudinal sectional layout view of the connection portion 17 shown in FIG. 1). The slip joint structure is a structure in which the inlet mixer pipe 12 is inserted into an upper end opening of the diffuser pipe 13 with a clearance S left therebetween. The clearance S is provided in order to accommodate thermal expansion of the inlet mixer pipe 12 or the diffuser pipe 13, and leave adjusting allowance for use in installation. The self vibration damping structure, as show in FIG. 3, includes a narrowing clearance flow path configured to gradually narrow the clearance S of the slip joint structure toward an upper end of the diffuser pipe 13. In other word, a clearance flow path defined by an outer pipe wall 101 of the inlet mixer pipe 12 and an inner pipe wall 102 of the diffuser pipe 13 is configured to be gradually narrow toward the upper end of the diffuser pipe 13. The narrowing clearance flow path may be provided throughout the entire region where the clearance S is formed, or otherwise may be formed in a region which extends upward from a midpoint along a vertical direction within the region where the clearance S is formed. The narrowing clearance flow path of this embodiment is defined by the outer pipe wall 101 of the inlet mixer pipe 12 configured to gradually increase an outer diameter thereof with distance away from a lower end of the inlet mixer pipe 12, and the inner pipe wall 102 of the diffuser pipe 13 configured such that an inner diameter thereof is uniform. An operation of the jet pump 10 will now be described. FIGS. 4 and 5 are views illustrating an operation of the jet pump. As shown in FIG. 4A, in a conventional jet pump 10a, a slip joint structure in a connection portion 17a between an inlet mixer pipe 12a and a diffuser pipe 13a is configured to gradually widen a clearance Sa thereof toward an upper end of the diffuser pipe 13a. In a clearance flow path for pumped coolant water defined by such clearance Sa (hereinafter, it is called a widening clearance flow path), both a flow path resistance and a fluid inertia force decrease toward an outlet, but the fluid inertia force is larger than the flow path resistance in a vicinity of the outlet, as shown in FIG. 5. When the clearance Sa is widening, a flow rate increases since the flow path resistance decreases, and however the flow rate is not easily increase in the vicinity of the outlet since the fluid inertia force is relatively large compared to the flow path resistance. Thus, this result in the same effect as a fluid being forced into an inlet while an outlet being closed, thereby increasing a pressure within the clearance Sa. On the other hand, when the clearance Sa is narrowing, the flow rate decreases since the flow path resistance increase, and however the flow rate does not easily decrease in the vicinity of the outlet since the fluid inertia force is relatively large compared to the flow path resistance. Thus, this result in the same effect as a fluid being sucked from an outlet while an inlet being closed, thereby reducing a pressure within the clearance Sa. Therefore, in the case of the widening clearance flow path, the pressure within the clearance Sa rises when the clearance Sa is widening, and the pressure within the clearance Sa drops when the clearance Sa is narrowing. For this reason, so to speak, a negative damping force acts on vibrations of the inlet mixer pipe 12a and the diffuser pipe 13a. As an actual phenomenon, a vibration having a large amplitude, referred to as self-excited vibration, may occur, which appears at the time when a clearance flow 202a exceeds a certain limiting value. It is noted that reference numeral 201a in FIG. 4A denotes a main flow of pumped coolant. In contrast, in the jet pump 10 of this embodiment, as shown in FIG. 4B, the slip joint structure in the connection portion 17 between the inlet mixer pipe 12 and the diffuser pipe 13 is configured to gradually narrow the clearance S thereof toward the upper end of the diffuser pipe 13. In the clearance flow path, or the narrowing clearance flow path, for pumped coolant water defined by such clearance S, both a flow path resistance and a fluid inertia force increase toward an outlet, but the fluid inertia force is smaller than the flow path resistance in a vicinity of the outlet, as shown in FIG. 5. When the clearance S is widening, a flow rate increases since the flow path resistance decreases, and however the flow rate easily increases in the vicinity of the outlet since the fluid inertia force is relatively small compared to the flow path resistance. Thus, this result in the same effect as a fluid being sucked from an outlet while an inlet being closed, thereby decreasing a pressure within the clearance S. On the other hand, when the clearance S is narrowing, the flow rate decreases since the flow path resistance increase, and the flow rate easily decreases in the vicinity of the outlet since the fluid inertia force is relatively small compared to the flow path resistance. Thus, this result in the same effect as a fluid being forced into the inlet while an outlet being closed, thereby increasing a pressure within the clearance S. Therefore, in the narrowing clearance flow path, the pressure within the clearance S drops when the clearance S is widening, and the pressure within the clearance S rises when the clearance S is narrowing. For this reason, so to speak, a positive damping force acts on vibrations of the inlet mixer pipe 12 and the diffuser pipe 13. As an actual phenomenon, self-excited vibration is restrained, which appears at the time when a clearance flow 202 exceeds a certain limiting value. It is noted that reference numeral 201 in FIG. 4B denotes a main flow of pumped coolant. Advantages of the jet pump 10 will then be described. The jet pump 10 has the following advantages. (1) The jet pump 10 includes: the slip joint structure connecting the inlet mixer pipe 12 and the diffuser pipe 13 to each other by inserting the inlet mixer pipe 12 into the upper end opening of the diffuser pipe 13 with the clearance S left therebetween; and the self vibration damping structure configured such that when the clearance S defined by the outer pipe wall 101 of the inlet mixer pipe 12 and the inner pipe wall 102 of the diffuser pipe 13 is widening or narrowing due to vibration of the inlet mixer pipe 12 or the diffuser pipe 13, the flow path resistance inside the clearance flow path for pumped coolant water defined by the clearance S is not smaller than the fluid inertia force all over the clearance flow path. Therefore, the self-excited vibration in a connection portion 17 between the inlet mixer pipe 12 and the diffuser pipe 13 may be restrained without inhibiting a structural deformation due to thermal expansion and the like. (2) The self vibration damping structure includes the narrowing clearance flow path configured to gradually narrow the clearance S toward the upper end of the diffuser pipe 13. The narrowing clearance flow path is defined by the outer pipe wall 101 of the inlet mixer pipe 12 configured to gradually increase the outer diameter thereof with distance away from a lower end of the inlet mixer pipe 12, and the inner pipe wall 102 of the diffuser pipe 13 configured such that the inner diameter thereof is uniform. Therefore, it is possible to obtain the advantage (1), while simplifying the structure of the jet pump 10. FIG. 6 is a view showing a second embodiment of the jet pump according to the present invention (a longitudinal sectional layout view of the connection portion 17 shown in FIG. 1). This embodiment is a modification of the self vibration damping structure in the jet pump 10 of the first embodiment. Hereinafter, the same elements as those of the first embodiment are referred to the same reference numerals to omit descriptions thereof. Elements obtained by modifying the elements of the first embodiment or adding a new element thereto are described by adding “A” at the end of the reference numerals. A self vibration damping structure of this embodiment, like the first embodiment, includes a narrowing clearance flow path configured to gradually narrow a clearance S defined by an inlet mixer pipe 12 and a diffuser pipe 13 toward an upper end of the diffuser pipe 13. The narrowing clearance flow path of this embodiment, as shown in FIG. 6, is constituted using a slip joint clamp 18A. The slip joint clamp 18A is provided so as to cover an opening edge of the diffuser pipe, and inserted into a clearance flow path for pumped coolant water. The narrowing clearance flow path is defined by an inner wall 103A of the slip joint clamp configured to gradually decrease an inner diameter thereof with distance away from a lower end of the slip joint clamp 18A, and an inner pipe wall 102 of the diffuser pipe 13. The narrowing clearance flow path may be provided throughout the entire region where the clearance S is formed, or otherwise may be formed in a region which extends upward from a midpoint along a vertical direction within the region where the clearance S is formed. FIGS. 7A and 7B is a view illustrating an exemplary fixation of the slip joint clamp 18A, wherein FIG. 7A is a view showing a state of the slip joint clamp 18A being fixed, and FIG. 7B is a view showing a structure of an attachment of the slip joint clamp 18A. The slip joint clamp 18A is fixed to the jet pump 10, e.g., to the riser pipe 11, as shown in FIG. 7A. Note that when the slip joint clamp 18A is fixed to the riser pipe 11, for example, the slip joint clamp 18A may be fixed in place using a fixing plate 181A, one side of which is fixed to the slip joint clamp 18A and the other side of which is fixed to the riser pipe 11, as shown in FIG. 7B. The slip joint clamp 18A and the fixing plate 181A may be fixed to each other using a fixing bolt 182A. An attachment and an attaching method are not specifically limited. Advantages of a jet pump 10A will then be described. The jet pump 10A may obtain the following advantage in addition to the advantage (1) of the first embodiment. (3) The narrowing clearance flow path is defined by the inner wall 103A of the slip joint clamp configured to gradually decrease the inner diameter thereof with distance away from the lower end of the slip joint clamp 18A, and the inner pipe wall 102 of the diffuser pipe 13. Therefore, it is possible to obtain the advantage (1) of the first embodiment even in the case of a widening clearance flow path configured to gradually widen the clearance flow path for pumped coolant water defined by an outer pipe wall 101 of the inlet mixer pipe 12 and the inner pipe wall 102 of the diffuser pipe 13, toward an upper end of a diffuser pipe 13. FIGS. 8A and 8B is a view showing a third embodiment of the jet pump according to the present invention, wherein FIG. 8A is a longitudinal sectional layout view of the connection portion 17 shown in FIG. 1, and FIG. 8B is an enlarged view of P area in FIG. 8A. This embodiment is a modification of the self vibration damping structure in the jet pump 10 of the first embodiment. Hereinafter, the same elements as those of the first embodiment are referred to by the same reference numerals to omit descriptions thereof. Elements obtained by modifying the elements of the first embodiment or adding a new element thereto are described by adding “B” at the end of the reference numerals. As shown in FIG. 8B, in a self vibration damping structure of this embodiment, a clearance flow path for pumped coolant water defined by an outer pipe wall 101 of an inlet mixer pipe 12 and an inner pipe wall 102 of a diffuser pipe 13 has a minimum clearance flow path width H0 on a downstream side in a coolant water pumping direction D, and a maximum clearance flow path width H1 on an upstream side in the coolant water pumping direction D. Further, when a (a flow path magnification factor) is defined as follows: α=(H1−H0)÷H0, the clearance flow path is configured to meet α≦1. It is noted that this embodiment illustrates an exemplary configuration of a widening clearance flow path designed to gradually widen a clearance S toward an upper end of the diffuser pipe 13. An operation of a jet pump 10B will now be described. FIG. 9 is a view illustrating an operation of the jet pump 10B, which is a graph showing a critical flow rate through the clearance, at which the self-excited vibration occurs, in the widening clearance flow path, predicted by analysis using the flow path magnification factor α as a parameter. In FIG. 9, a horizontal axis shows the flow path magnification factor α plotted as logarithm, and a vertical axis shows the critical flow rate through the clearance. The critical flow rate through the clearance is a flow rate at which the self-excited vibration easily occurs. As is obvious from an analysis result shown in FIG. 9, when the flow path magnification factor α is not more than 1, the critical flow rate through the clearance is extremely increased, and it is found that the self-excited vibration does not easily occur even when the clearance flow path for pumped coolant water is the widening clearance flow path. Advantages of the jet pump 10B will then be described. The jet pump 10B may obtain the following advantage in addition to the advantage (1) of the first embodiment. (4) The self vibration damping structure has a configuration in which the clearance flow path for pumped coolant water defined by the outer pipe wall 101 of the inlet mixer pipe 12 and the inner pipe wall 102 of the diffuser pipe 13 has the minimum clearance flow path width H0 on the downstream side in the coolant water pumping direction D, and the maximum clearance flow path width H1 on the upstream side in the coolant water pumping direction D, as well as is configured to meet (H1−H0)÷H0≦1. Therefore, it is possible to obtain the advantage (1) of the first embodiment even in the case of a widening clearance flow path configured to gradually widen the clearance flow path for pumped coolant water defined by the outer pipe wall 101 of the inlet mixer pipe 12 and the inner pipe wall 102 of the diffuser pipe 13 toward the upper end of the diffuser pipe 13. FIGS. 10A and 10B is a view showing a fourth embodiment of the jet pump according to the present invention, wherein FIG. 10A is a longitudinal sectional layout view of the connection portion 17 shown in FIG. 1, and FIG. 10B is an enlarged view of P area in FIG. 10A. This embodiment is a modification of the self vibration damping structure in the jet pump 10 of the first embodiment. Hereinafter, the same elements as those of the first embodiment are referred to by the same reference numerals to omit descriptions thereof. Elements obtained by modifying the elements of the first embodiment or adding a new element thereto are described by adding “C” at the end of the reference numerals. A self vibration damping structure of this embodiment, as shown in FIG. 10B, comprises a labyrinth structure 104C provided on an outer pipe wall 101 of an inlet mixer pipe 12 and to form a turbulent flow in a clearance flow 202 flowing through a clearance S between the inlet mixer pipe 12 and a diffuser pipe 13. It is noted that this embodiment illustrates an exemplary configuration of a widening clearance flow path designed to gradually widen the clearance S toward an upper end of the diffuser pipe 13. The labyrinth structure 104C has a lot of grooves which are formed on a periphery of the outer pipe wall 101 of the inlet mixer pipe 12. Note that it is only necessary for the grooves of the labyrinth structure 104C to be designed to turn the clearance flow 202 into the turbulent flow, and a shape and the number of the labyrinth structure 104C are not specifically limited. In addition, depths of the grooves are not specifically limited, and not required to be equal. Advantages of a jet pump 10C will then be described. The jet pump 10C may obtain the following advantage in addition to the advantage (1) of the first embodiment. (5) The self vibration damping structure comprises the labyrinth structure 104C provided on the outer pipe wall 101 of the inlet mixer pipe 12. Therefore, when the clearance S is repeatedly widened and narrowed due to vibration of the inlet mixer pipe 12 and the like, the clearance flow 202 efficiently changes into a turbulent flow, resulting in a flow which does not easily cause self-excited vibration. Thus, it is possible to obtain the advantage (1) of the first embodiment even in the case of a widening clearance flow path configured to gradually widen a clearance flow path for pumped coolant water defined by the outer pipe wall 101 of the inlet mixer pipe 12 and an inner pipe wall 102 of the diffuser pipe 13 toward the upper end of the diffuser pipe 13. FIGS. 11A and 11B is a view showing a fifth embodiment of the jet pump according to the present invention, wherein FIG. 11A is a longitudinal sectional layout view of the connection portion 17 shown in FIG. 1, and FIG. 11B is an enlarged view of P area in FIG. 11A. This embodiment is a modification of the self vibration damping structure in the jet pump 10C of the fourth embodiment. Hereinafter, the same elements as those of the fourth embodiment are referred to by the same reference numerals to omit descriptions thereof. Elements obtained by modifying the elements of the fourth embodiment or adding a new element thereto are described by adding “D” at the end of the reference numerals. A self vibration damping structure of this embodiment, as shown in FIG. 11B, comprises a ridge structure 105D. The ridge structure 105D is provided around a perimeter of an outer pipe wall 101 of an inlet mixer pipe 12, and is a structure that projects so as to block a clearance flow 202 flowing through a clearance flow path for pumped coolant water. Note that a shape, the number, and a size of the ridge structure 105D are not specifically limited. The ridge structure 105D may be partially provided on the outer pipe wall 101 of the inlet mixer pipe 12. Advantages of a jet pump 10D will then be described. The jet pump 10D may obtain the following advantage in addition to the advantage (1) of the first embodiment. (6) The self vibration damping structure comprises the ridge structure 105D that protrudes into the clearance flow path for pumped coolant water so as to block the clearance flow 202 flowing through the flow path, and thus increases pressure loss in the clearance flow 202 in a vicinity of an outlet. Therefore, it is possible to obtain the advantage (1) of the first embodiment even in the case of a widening clearance flow path configured to gradually widen the clearance flow path for pumped coolant water toward an upper end of a diffuser pipe 13. FIG. 12 is a view showing a sixth embodiment of the jet pump according to the present invention (a cross sectional layout view of the connection portion 17 shown in FIG. 1). This embodiment is a modification of the self vibration damping structure in the jet pump 10 of the first embodiment. Hereinafter, the same elements as those of the first embodiment are referred to by the same reference numerals to omit descriptions thereof. Elements obtained by modifying the elements of the first embodiment or adding a new element thereto are described by adding “E” at the end of the reference numerals. As shown in FIG. 12, a self vibration damping structure of this embodiment comprises groove portions 106E provided on an outer pipe wall 101 of an inlet mixer pipe 12, and convex portions 107E provided on an inner pipe wall 102 of a diffuser pipe 13, each convex portion 107E being fit into each groove portion 106E with a minute clearance 108E left therebetween. Note that a shape, the number, and a size of the groove portions 106E and the convex portions 107E are not specifically limited. Advantages of a jet pump 10E will then be described. In the jet pump 10E, (7) The self vibration damping structure is configured such that the inlet mixer pipe 12 and the diffuser pipe 13 fit into each other with the minute clearance 108E maintained, and therefore vibration displacements of the inlet mixer pipe 12 and the diffuser pipe 13 are permitted only within the minute clearance 108E. Therefore, self-excited vibration in the connection portion 17 between the inlet mixer pipe 12 and the diffuser pipe 13 can be restrained without inhibiting a structural deformation due to thermal expansion, and the like. FIG. 13 is a view showing a seventh embodiment of the jet pump according to the present invention (a longitudinal sectional layout view of the connection portion 17 shown in FIG. 1). This embodiment is a modification of the connection structure between the inlet mixer pipe 12 and the diffuser pipe 13 in the jet pump 10 of the first embodiment. Hereinafter, the same elements as those of the first embodiment are referred to by the same reference numerals to omit descriptions thereof. Elements obtained by modifying the elements of the first embodiment or adding a new element thereto are described by adding “F” at the end of the reference numerals. A connection structure between an inlet mixer pipe 12 and a diffuser pipe 13 in a jet pump 10F of this embodiment is a non-slip joint structure. Thus, as shown in FIG. 13, an opening edge of the inlet mixer pipe 12 abuts with an opening edge of the diffuser pipe 13 to connect the inlet mixer pipe 12 and the diffuser pipe 13 to each other. Further, the opening edge of the inlet mixer pipe 12 is formed into a concave sphere 109F, and the opening edge of the diffuser pipe 13 is formed into a convex sphere 110F which receives the opening edge of the inlet mixer pipe 12. Advantages of the jet pump 10F will then be described. In the jet pump 10F, (8) the inlet mixer pipe 12 and the diffuser pipe 13 are connected using the non-slip joint structure, so that the clearance flow 202 as described in the first embodiment is not generated. Moreover, the opening edges of the inlet mixer pipe 12 and the diffuser pipe 13 have a so-called spherical seat structure, so that structural displacements thereof in radial and longitudinal directions due to thermal expansion are less limited. Therefore, self-excited vibration in the connection portion 17 between the inlet mixer pipe 12 and the diffuser pipe 13 can be can restrained without inhibiting a structural deformation due to thermal expansion, and the like. FIG. 14 is a view showing an eighth embodiment of the jet pump according to the present invention (a longitudinal sectional layout view of the connection portion 17 shown in FIG. 1). This embodiment is a modification of the connection structure between the inlet mixer pipe 12 and the diffuser pipe 13 in the jet pump 10F of the seventh embodiment. Hereinafter, the same elements as those of the seventh embodiment are referred to by the same reference numerals to omit descriptions thereof. Elements obtained by modifying the elements of the seventh embodiment or adding a new element thereto are described by adding “G” at the end of the reference numerals. In a connection structure between the inlet mixer pipe 12 and the diffuser pipe 13 in a jet pump 10G of this embodiment, a metal seal portion 111G is interposed between opening edges of the inlet mixer pipe 12 and the diffuser pipe 13, as shown in FIG. 14. Further, the opening edges of the inlet mixer pipe 12 and the diffuser pipe 13, between which the metal seal portion 111G is interposed, are inclined. The metal seal portion 111G is made of a material having hardness that is lower than hardness of the inlet mixer pipe 12 or the diffuser pipe 13. It is noted that the metal seal portion 111G may be integrated with the structure of the inlet mixer pipe 12 or the diffuser pipe 13. Advantages of the jet pump 10G will then be described. The jet pump 10G may obtain the following advantage in addition to the advantage (8) of the seventh embodiment. (9) The metal seal portion 111G is interposed between an opening edge 109F of the inlet mixer pipe 12 and the opening edge of the diffuser pipe 13, and such both opening edges are inclined. Therefore, it is possible to obtain the advantage (8) of the seventh embodiment, while effectively ensuring adjusting allowance, in thermal expansion and interconnection, in radial and longitudinal directions. The jet pump of the present invention has been described above based upon first to eighth embodiments. Specific constitutions thereof are not limited to these embodiments, but design change, addition and the like may be made without departing from the spirit and scope of the invention. For example, the narrowing clearance flow path of the first embodiment, as shown in FIG. 15, may be defined by an inner pipe wall 102 of the diffuser pipe 13 configured to gradually increase an inner diameter thereof with distance away from an upper end of the diffuser pipe 13, and an outer pipe wall 101 of the inlet mixer pipe 12 configured such that an outer diameter thereof is uniform. Also, the narrowing clearance flow path of the first embodiment, as shown in FIG. 16, may be defined by the outer pipe wall 101 of the inlet mixer pipe 12 configured to gradually increase an outer diameter thereof with distance away from the lower end of the inlet mixer pipe 12, and an inner pipe wall 102 of the diffuser pipe 13 configured to gradually increase an inner diameter thereof with distance away from an upper end of the diffuser pipe 13. Alternatively, the narrowing clearance flow path may be defined by an outer pipe wall 101 of the inlet mixer pipe 12 configured such that an outer diameter thereof is uniform, and the inner pipe wall 102 of the diffuser pipe 13 configured such that an inner diameter thereof is uniform. In any form, when the clearance S defined by the inlet mixer pipe 12 and the diffuser pipe 13 is widening or narrowing due to vibration, the flow path resistance within the clearance flow path for pumped coolant water defined by the clearance S is not smaller than the fluid inertia force all over the clearance flow path. Therefore, it is possible to obtain the same advantage as the advantage (1) of the first embodiment. In the second embodiment, as shown in FIG. 17, a slip joint clamp 18A may be provided, which is mounted so as to surround the outer pipe wall 101 of the inlet mixer pipe 12 and inserted into the clearance flow path for pumped coolant water defined by the outer pipe wall 101 of the inlet mixer pipe 12 and the inner pipe wall 102 of the diffuser pipe 13, wherein a narrowing clearance flow path may be defined by an outer wall 112A of the slip joint clamp configured to gradually increase an outer diameter thereof with distance away from a lower end of the slip joint clamp 18A, and the inner pipe wall 102 of the diffuser pipe 13. In the fourth embodiment, as shown in FIG. 18, the labyrinth structure 104C may be provided on the inner pipe wall 102 of the diffuser pipe 13. In the fifth embodiment, the ridge structure 105D may be provided on the inner pipe wall 102 of the diffuser pipe 13. In the sixth embodiment, as shown in FIG. 19, the groove portions 106E may be provided on the inner pipe wall 102 of the diffuser pipe 13, and the convex portions 107E may be provided on the outer pipe wall 101 of the inlet mixer pipe 12. Alternatively, a groove portion 106E and a convex portion 107E may be alternately provided on either the inner pipe wall 102 of the diffuser pipe 13 or the outer pipe wall 101 of the inlet mixer pipe 12. In the seventh embodiment, as shown in FIG. 20, the convex sphere 110F may be formed on the opening edge of the inlet mixer pipe 12, and the concave sphere 109F may be formed on the opening edge of the diffuser pipe 13. |
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summary | ||
description | FIG. 1 shows a first embodiment of the apparatus 1 for radiation treatment for personal care according to the invention, with a housing 2 in which a UV source 3 is present which in this embodiment comprises two compact UV lamps 33. The apparatus 1 further comprises a wall 4 manufactured from a light-transmitting material and closing off the housing 2. In this embodiment, the wall 4 is made from an inorganic glass, but the wall may alternatively be made from any other known type of UV-transmitting material. The wall 4 has a central area 7 and side areas 8 adjoining the central area, as viewed in longitudinal direction. The wall 4 has a lower transmission to radiation having a wavelength less than 320 nm adjacent the central area 7 than adjacent the side areas 8. This is realized in this embodiment in that the wall has a greater thickness adjacent the central area than adjacent the side areas, as is apparent from FIG. 2a. It is advantageous if this greater thickness adjacent the central area is realized by means of a coating 21 on the wall, which coating is provided in a greater number of layers adjacent the central area 7 than adjacent the side areas 8. The coating in this embodiment comprises a sol-gel material, but the coating may alternatively comprise any other known type of material. The radiation originating from the UV source 3 is thus better transmitted adjacent the side areas 8 of the wall than adjacent the central area 7 of the wall 4. As a result, a distribution of effective radiation energy resulting from radiation with a wavelength less than 320 nm over an irradiation plane 9 is realized as indicated with the curve UVBinv. in FIG. 2b. The value of the effective radiation energy is plotted on the vertical axis in FIG. 2b, and the longitudinal direction of the irradiation plane 9 is plotted on the horizontal axis. Compared with the curve UVBnorm, which indicates the distribution of effective radiation energy resulting from radiation with a wavelength less than 320 nm in a known apparatus, it is apparent that the distribution realized over the longitudinal direction of the irradiation plane 9 by means of the apparatus according to the invention is substantially homogeneous. The problem of an uneven distribution of the effective radiation energy solved by the invention arises in particular in the longitudinal direction of the irradiation plane, which is why the distribution in lateral direction is not pictured here. It is furthermore visible in FIG. 2b that the distribution UVTotinv. of the total effective radiation energy resulting from radiation from the UV source with a wavelength less than 320 nm and with a wavelength in the range from 320 to 400 nm taken together is also more homogeneous in an apparatus according to the invention than the corresponding distribution UVTotnorm realized in a known apparatus. FIG. 3a shows a second embodiment of an apparatus 1xe2x80x2 for radiation treatment for personal care according to the invention. In this embodiment, the wall 4xe2x80x2 is manufactured from a first material 10 with a comparatively high transmissivity to radiation having a wavelength less than 320 nm, and a second material 11 is provided adjacent the central area having a comparatively low transmissivity to radiation with a wavelength less than 320 nm. The first material in this embodiment comprises inorganic glass, but the first material may alternatively comprise some other known type of material with a comparatively high transmissivity to radiation with a wavelength less than 320 nm. The second material in this embodiment comprises a sol-gel material, but the second material may alternatively comprise some other known types of material with a comparatively low transmissivity to radiation with a wavelength less than 320 nm. The distribution of effective radiation energy over an irradiation plane in this embodiment approximates the distribution as pictured in the graph of FIG. 2b. It is furthermore advantageous if the material 11 has not only a comparatively low transmissivity to radiation with a wavelength less than 320 nm but also a comparatively high transmissivity to radiation with a wavelength in the range from 320 to 400 nm. The UV source 3 produces a small quantity of radiation in this range, which quantity if transmitted fully by the wall 4xe2x80x2 will not be of any risk to the user. Since the second material 11 has a comparatively high transmissivity to radiation with a wavelength in the range from 320 to 400 nm, this radiation is transmitted for a major portion to the central portion of the irradiation plane 9. The comparatively small quantity of radiation produced by the UV source in this range is thus optimally utilized. FIG. 3b shows the wall 4xe2x80x2 viewed from a direction A in FIG. 3a. It is apparent here that the second material 11 is provided in a predetermined pattern of dots. It is noted that the shape of the material elements to be provided and the configuration in which this is done may be freely chosen in dependence on the desired embodiment of the apparatus for radiation treatment. It is also possible for the second material 11 to be provided on the wall 4xe2x80x2 in shapes other than in dots, and in configurations other than the pattern shown in FIG. 3b. FIG. 4 shows a third embodiment of an apparatus 1xe2x80x3 for radiation treatment for personal care according to the invention, in which intermediate areas 5 are present between the central area 7xe2x80x3 and the side areas 8xe2x80x3, in which areas 5 the wall 4xe2x80x3 has a transmission to radiation with a wavelength less than 320 nm which lies between the transmission of the central area 7xe2x80x3 and the transmission of the side areas 8xe2x80x3. In this embodiment, the wall 4xe2x80x3 comprises not only the coating 21, which is provided in a number of layers adjacent the central area as described with reference to FIG. 2a, but also further coating layers 31 provided adjacent to the intermediate areas 5 in a smaller number than the coating adjacent the central area. The wall 4xe2x80x3 thus has a transmission to radiation with a wavelength less than 320 adjacent the intermediate areas 5 which lies between the transmission of the central area 7xe2x80x3 and that of the side areas 8xe2x80x3. The intermediate areas 5 thus contribute further to the realization of a substantially homogeneous distribution of effective radiation energy of radiation having a wavelength less than 320 nm over the irradiation plane. It is noted that the transmission of the intermediate areas may be realized in alternative manners such as, for example, by means of a further material which is provided adjacent the intermediate areas in the embodiment as described with reference to FIG. 3a. FIG. 5 shows a fourth embodiment of an apparatus 1xe2x80x2xe2x80x3 for radiation treatment for personal care according to the invention in which the housing 2 has a base wall 14 which extends substantially parallel to the UV-transmitting wall 4, which housing has at least one, in this embodiment two reflecting side walls 15 which extend from the base wall 14 but alongside the UV source 3 at an angle to said base wall. The reflecting side wall 15 comprises a material which has a comparatively low reflectivity for radiation with a wavelength less than 320 nm at a side facing the UV source. In this embodiment, this material 16 comprises an aluminum alloy, but the material may alternatively comprise any other known type of material with a comparatively low reflectivity to radiation with a wavelength less than 320 nm. This radiation is thus reflected towards the central portion of the irradiation plane to a low degree only. Furthermore, the wall 4xe2x80x2xe2x80x3 has a lower transmission to radiation with a wavelength less than 320 nm adjacent the central area 7xe2x80x2xe2x80x3 than adjacent the side areas 8xe2x80x2xe2x80x3, which is realized in this embodiment in that the wall 4xe2x80x2xe2x80x3 has a coating of greater thickness adjacent the central area 7xe2x80x2xe2x80x3 than adjacent the side areas 8xe2x80x2xe2x80x3. It is noted that the lower transmission adjacent the central area 7xe2x80x2xe2x80x3 of the wall 4xe2x80x2xe2x80x3 may be realized in alternative ways, for example as described for the second embodiment of the apparatus according to the invention. The combination of the wall 4xe2x80x2xe2x80x3 with the reflecting side wall 15 comprising the material 16 of comparatively low reflectivity to radiation with a wavelength less than 320 nm contributes to an even more homogeneous distribution of the effective radiation energy over the entire irradiation plane. It is advantageous here, furthermore, if said material 16 has a comparatively high reflectivity to radiation with a wavelength in the range from 320 to 400 nm, so that the radiation in this range is optimally utilized. It is noted that an apparatus for radiation treatment for personal care according to the invention also relates to types of such apparatuses other than the apparatus pictured in FIG. 1 such as, for example, a suntanning couch with a collapsible housing. It is further noted that besides the embodiments mentioned above alternative embodiments are equally possible, in which the wall adjacent the central area has a lower transmission to radiation with a wavelength less than 320 nm than adjacent the side areas such as, for example, an embodiment in which the UV-transmitting wall is built up from materials with a varying transmissivity to radiation with a wavelength less than 320 nm. |
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048620050 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference now to FIGS. 1, 2A and 2B, wherein like numerals designate like components throughout all of the several figures, the radiation detector apparatus 1 of the invention comprises a radiation detector assembly 3 that includes a primary radiation detector 5 having a top side 7 where the objects to be tested are placed, and a spare detector 9 that is structurally identical to the primary detector 5 and stacked directly below it. As will be discussed in more detail hereinafter, both the primary and spare detectors 5 and 9 are preferably gas-flow proportional type detectors whose topsides 7 have five mutually overlapping zones, each of which is independently sensitive to radiation. To maximize the sensitivity of the detector 5, both the primary and the spare detectors 5, 7 are positioned on top of a one-half inch thick plate of lead shielding material 10 as is indicated in FIG. 2B. Such lead shielding material 10 reflects back some of the gamma radiation emitted toward it from a radioactive tool or other hand-held object, thereby giving the detector 5 two opportunities to count the reflected gamma ray. The particular radiation circuitry and pneumatic components which are connected to the detector 5 and which form the balance of the radiation detector assembly 3 are illustrated in schematic form in FIG. 7. These components will be described in detail hereinafter. The primary and spare detectors 5 and 9 are housed at the bottom of a shielding cabinet 11 having an access opening 13 for depositing and withdrawing the objects being tested. The shielding cabinet 11 overlies a support cabinet 15. The purpose of the shielding cabinet 11 is to substantially attenuate the amount of the background gamma radiation which impinges upon the detector 5, while the purpose of the support cabinet 15 is to raise the access opening 13 of the shielding cabinet 11 to a convenient height for the system operator, as well as to prevent airborne debris and other dust from entering the components of the radiation detector assembly contained therein. Both the shielding cabinet 11 and the support cabinet 15 are formed from a frame of angular support members 17, 18 which is covered with smooth, easily decontaminable stainless steel sheet material 19, 20. In the shielding cabinet 11, inner sheets of stainless steel 21 are provided to form flat, rectangular support pockets capable of holding one or more lead sheets for shielding purposes, as will be described presently. The shielding cabinet 11 includes a pair of opposing side walls 23a, 23b, a top wall 25, a short front wall 27 which is bordered by two opposing U-shaped brackets 28a, 28b and which defines the bottom edge of the access opening 13, and a back wall 29. Each of the side walls 23a, 23b includes a cabinet door 32a, 32b which is capable of pivoting downwardly 90 degrees and forming a support shelf as is best seen in FIG. 1. With reference now to FIG. 3, each of the cabinet doors 32a, 32b is formed from an outer sheet of stainless steel having an L bend 35 at its bottom edge, as well as spaced apart inner sheet of stainless steel 37 have an L bend 39 along its top edge. The outer and inner sheets 33, 37 of the cabinet door 32a form a flat, rectangular sheet-holding pocket 41 into which one or more sheets of lead or other shielding material may be placed. In the preferred embodiment, the sheet-holding pocket 41 is approximately 0.6 inches wide so that either one or two sheets of lead 0.25 inches thick may be slid therein. In one embodiment of the invention, a plate of 0.50 inch thick lead is welded within the doors 32a, 32b. However, in the alternative, an edge cap 43 may be provided that is detachably connected over an open side edge of the doors to allow the amount of lead shielding in the doors 32a, 32b to be adjusted. In the preferred embodiment, the edge cap 43 includes a pair of parallel, shallow flanges on either side that are insertable within and engagable against the inside surfaces of the sheets 33 and 37. The edge cap 43 is secured in place by a plurality of screws 44 (only one of which is shown) that extend through mutually registering bores in the flanges of the edge cap 43. Such edge caps 43 are preferably used along the upper edges of the side walls 23a, 23b, the top wall 25, front wall 27 and back wall 29 to secure one or two lead sheets in the pockets that exist in these walls. A continuous hinge 45 connects the bottom edge of each of the cabinet doors 32a, 32b to the top edge of a cap member 47 that connects and spaces apart sheets 19 and 21 at the bottom portion of the side wall 23a. This bottom portion of the side wall 23a in turn rests on a lower floor panel 49 as shown. Disposed in the center portion of the cabinet door 32a is a shallow, U-shaped handle 51. This handle 51 is secured onto the door 32a by means of a pair of screws 53a, 53b which are threadedly engaged in bores 55 present at the ends of the handle 51. Disposed at the top edges of each of the doors 32a, 32b are opposing door support assemblies 57. The purpose of the support assemblies 57 is to prevent the doors 32a, 32b from pivoting any further than 90 degrees when the handle 51 of each is drawn downwardly, thereby rendering the doors 32a, 32b into shelves (as may best be seen in FIG. 1). The rendering of the cabinet doors 32a, 32b into shelves not only provides additionally access to the top surface 7 of the radiation detector 5; it further helps to support elongated objects (such as the long handles of certain tools, scaffolding members, etc.) that are longer than the width of the shielding cabinet 11 as they are drawn over the top surface 7 of the detector 5. Each door support assembly 57 includes an elongated link member 59 which is pivotally connected to the upper inside edge of each of the doors 32a, 32b by means of a pin 61 supported by a bracket 63. A rivet 64 is disposed within the slot defined along the center of the elongated link member 59. As is best seen in FIG. 2B, the shank of the rivet 64 is rigidly affixed to the frame 17 of the shielding cabinet 11. The head 65 of the rivet 64 prevents the link member 59 from sliding off of the shank of the rivet 64. With reference again to FIGS. 1, 2B and 2A, the top wall 25 of the shielding cabinet 11 includes an instrument panel support frame 67 for supporting the instrument panel 69 and detector readout 71 of the detector circuitry. With specific reference to FIG. 4, a continuous hinge 73 forms a pivotal connection between the bottom edge of the instrument panel support frame 67 and an upper floor panel 75. Under normal circumstances, the instrument panel support frame 67 lies on top of the outer sheet of stainless steel sheet 19 that forms the outer surface of the cabinet 11. However, if access is desired to the back of the instrument panel 69, the hinge 73 allows the instrument panel support frame 67 to be pivoted clockwise. To afford clearance for the display components which project off of the back side of the instrument panel 69, the central portion of the sheet 19 is removed along the tapered portion of the top wall 25. With references now to FIGS. 2B and 5, the front wall 27 of the shielding cabinet 11 includes an outer sheet 79 as shown, and an inner sheet 81 having an L bend 83 along its upper edge. The resulting flat, rectangular pocket 84 defined within the wall 27 can accommodate two sheets 85, 87 of lead shielding material, each of which is 0.25 inches thick. A continuous hinge 89 pivotally connects protective cover 91 to the upper edge of the top wall 27. The protective cover 91 protects the delicate gas fittings and cables (not shown) extending out of both the main and spare detectors 5 and 9. Because the distal edge of the protective cover 91 terminates along the outer edge of the top side 7 of the detector 5, protective cover 91 further advantageously provides a lead-in ramp to help the operator smoothly slide objects on to or off of the top surface 7. Protective cover 91 is preferably formed from stainless steel sheet metal due to the strength and corrosion resistance of this material. As is most evident in FIGS. 2B and 3, the entire shielding cabinet 11 is supported by the frame 18 of the support cabinet 15. As has been previously indicated, the primary function of the support cabinet 15 is to raise the access opening 13 of the shielding cabinet 11 at an ergonometrically optimal height, as well as to house various components of the radiation detector assembly which are electrically and pneumatically connected to the detectors 5 and 9. However, to provide the access that is necessary for these components, the front side of the support cabinet 15 includes an access drawer 97. A handle is centrally connected to the front face of the drawer 97 as shown. To provide for an adequate amount of air cooling for the electronic components disposed within the cabinet 15, the back wall of this cabinet includes louvers 101. Although not specifically shown in any of the several figures, a thin sheet of filter material may be disposed over the inside surface of the louvers 101 to prevent the intrusion of dust and debris within the cabinet 15. To provide mobility for the apparatus 1, locking casters (shown in FIG. 8) may be connected to the bottom of the support cabinet 15. Such casters, if used, should be height adjustable so that the apparatus 1 may be easily rendered level if used on an unlevel surface. With reference now to both FIGS. 6A and 6B, both the primary and spare detectors 5 and 9 include a platform screen assembly 111 disposed over their top sides 7. This component includes a screen member 113 formed from 22 gauge stainless steel having hexagonally shaped apertures as shown, each of which is about 0.25 inches across. The hexagonal cut-out pattern of the screen 113 maximizes the ratio of shear strength to open area. At least 60 percent and preferably 70 percent of the screen member 113 is open so that beta radiation can easily travel without significant impediment from a tool or other object placed on top of the assembly 111 to the radiation-sensitive zones of the detector 5 disposed therebelow. The screen member 113 of the platform screen assembly 11 is circumscribed by a rigidifying frame 114 which is preferably formed from sixteen gauge stainless steel crimped around the edge of the screen 113 in the manner illustrated both in FIGS. 6A and 6C. The platform screen assembly 111 advantageously includes a clear sheet of 0.25 mil thick Mylar.RTM. 115 which is affixed by a strip of tape 116 disposed around the inner perimeter of the frame 114. The screen member 113 effectively prevents sharp corners of the tools or other objects deposited over the detector 5 from penetrating the aluminized sheet of Mylar.RTM. 118 that seals the aluminum housing 119 of the detector 5 from the ambient atmosphere. The clear sheet of Mylar.RTM. 115 disposed immediately beneath the screen member 113 keeps dirt and debris from accumulating on top of the aluminized Mylar.RTM. 118. Immediately disposed beneath the platform screen assembly 111 is a support grid 117 that is preferably made from milled aluminum approximately one-fourth of an inch thick. This support grid 117 performs three functions. First, the reinforcement it offers to the platform screen assembly 111 greatly increases the amount of compressive load that can be borne by the screen member 113. Secondly, it coacts with the platform screen assembly 111 to space the side of a tool or other object being inspected a uniform distance from the top side 7 of the detector 5. Thirdly, it provides "windowpane" type support for the sheet of aluminized Mylar.RTM. 118 disposed directly underneath it. The support grid 117 is supported around its edges by the previously mentioned aluminum housing 119 of the detector 5. In the preferred embodiment, the aluminum housing 119 forms the cathode of detector 5, which is a gas-flow proportional radiation detector. Five, fork-shaped stainless steel electrodes form parallel and independent anodes 121a-121e within the enclosure defined by the interior of the aluminum housing 119 and the aluminized Mylar.RTM. 118 sealingly disposed thereover. Small tubular manifolds 123a, 123b are disposed inside the aluminum housing 119 along its edges for uniformly distributing a counting gas which, in the preferred embodiment, is a mixture of 90 percent argon and 10 percent methane known as P-10 counting gas. Gas tight fittings 125a, 125b are provided at either end of the aluminum housing for connecting cathode lead wires 127a, 127b to the inside of the aluminum housing 119. Similarly, gas-tight fittings 129a-129e are provided in the housing 119 as shown for anode lead wires 131a-131e, each of which is connected at one end to one of the five, fork-shaped stainless steel electrodes 121a-121e. In the preferred embodiment, both the primary and spare detectors 5 and 9 are Model 43-67 gas proportional probes manufactured by Ludlum Measurements, Inc. located in Sweetwater, Tex. The independently charged, fork-shaped electrodes 121a-121e in combination with the oppositely charged aluminum housing 119 creates a gas proportional flow type radiation detector 5 having a plurality of mutually overlapping radiation sensitive zones 132a-132e (of which only 132a and 132b are indicated). As will be better appreciated hereinafter, each of the zones 132a-132e is advantageously independently sensitive to any gamma or beta radiation which traverses it. FIG. 7 illustrates the radiation detection circuitry and pneumatic components 133 which form the balance of the radiation detection assembly 3. These components include a source of pressurized counting gas which, as previously mentioned, is a mixture of 90 percent argon and and 10 percent methane. After flowing through a gas regulator 39, this gas enters a primary outlet line 141. A Y joint 143 bifurcates the flow of gas from the primary outlet line 141 into two inlet lines 145a and 145b, each of which is connected to the inlet of a flow meter 137a, 137b. The outlets of these flow meters 137a, 137b are in turn connected to the primary and the spare detectors 5 and 9, respectively. It should be noted that in operation, P-10 gas from the pressurized gas source 135 continuously flows through the spare detector 9 during the use of the primary detector 5, thereby obviating the need for completely purging the spare detector 9 if a malfunction of the primary detector 5 necessitates the use of the spare detector 9, thus minimizing downtime. Turning now to the electrical components of the radiation detector assembly 3, an input cable 151 individually connects in parallel the anode lead wires 131a-131e to separate power and amplifier circuits of the radiation detector circuitry 149. This circuitry 149 is adjusted by a means of switching controls 152. The circuitry 149 includes a microprocessor whose output is transmitted along an output cable 153 to the previously discussed display panel 169 of the apparatus 1. In the preferred embodiment, circuitry 149 is a Model RM-22 Radiation Monitor by Eberline, a subsidiary of Thermo Instrument Systems, Inc., located in Santa Fe, N.M. This monitor includes a Model 8085 microprocessor with four 2K byte No. 2716EPROMVIC boards, three 256-8 bit bytes Model 8155RAMVIC boards, a NVRAM module to retain memory in case of a power failure, as well as a 15 channel counterboard to interface TTL level pulses into the microprocessor. The cable 151 connects each of the anodes 121a-121e to its own separate amplifier-discriminator board and card cage. These anodes are each individually powered by a P-21B HV power supply also manufactured by Eberline. Separate power lines 155a and 155b provide power from a surge suppressor 156 to hood lights 159 and a Sonalert 161 located in the upper portion of the shielding cabinet 11, and to the detector circuitry 149 respectively. The input end of the surge suppressor 156 is in turn connected to a source of electrical power 157. In the preferred embodiment, surge suppressor 156 is a Model 1A815 transient surge suppressor manufactured by Dayton Electric Manufacturing Company of Chicago, Ill. Finally, a mat switch 164 is electrically connected to the radiation detector 149 for automatically actuating both the detector 149 and the hood lights 159 when a potential user stands thereon. The use of a mat switch 164 to actuate the apparatus 1 advantageously eliminates the need for manual buttom controls which are apt to accumulate radioactive dust. The apparatus may be operated in one of two modes. In the first mode, the mat switch 164 is placed on the floor in front of the apparatus 1 just in front of the access opening 13 so that the detector monitor 149 and hood lights 159 will automatically be actuated as soon as a potential user steps up to the apparatus adjacent to the axis opening 13. The user then stands on the mat switch 164, thereby actuating the radiation detection circuitry 149 and hood lights 159. He then inserts the tool or other object to be scanned through access opening 13 and onto the platform screen assembly 111 on the top side of the detector 7. He then waits for the circuitry to render a radiation count on the display 71 of the panel 69. This should take only 2 to 5 seconds, as the detector 7 is highly sensitive to beta radiation. After the count has been completed, he turns the tool onto its opposite side and again waits for a reading. He repeats the process until a reading is taken on every side of the tool. In the second mode of operation illustrated in FIG. 8, the operator places the mat switch 164 beside one of the sides 28a, 28b of the apparatus 1. He then opens side doors 32a, 32b into the shelf position as shown. He next places a shallow support table 165 through access opening 13. Another gas-flow proportional detector 167 is laid on the top surface of the table 165. The operator then stands onto mat switch 164, thereby actuating the radiation detection circuitry 149 and hood lights 159. The apparatus 1 is now ready to receive elongated objects, such as scaffold members, which are drawn between the detectors 5 and 167, which simultaneously scan both the upper and lower surfaces of such members, thereby allowing all necessary readings to be taken on a single passthrough. This second mode of operation is well suited for tools or scaffold members having uniform thickness. Before the commencement of either mode of operation, the amount of lead shielding slid into the pockets defined with the walls 23a, 23b, 25, 27 and 29 will have been adjusted in accordance with the amount of background radiation present in the area where the apparatus 1 is set up. |
050776851 | abstract | Radioactivity exposure amount of workcraftmen is obtained through simulation by using an operation processor when the workcraftmen carry out work operation within an area under controlled radioactivity. The movement of the workcraftmen carrying out work operation in the area under controlled radioactivity is simulated by making use of layout graphic data relating to the area. The radioactivity exposure amount of the workcraftmen is calculated in response to the simulated movement of the workcraftmen. The operation procedures of the target work operation for radioactivity exposure amount calculation is outputted from the operation processor, when the calculated radioactivity exposure amount satisfies a predetermined value. |
061309265 | summary | CROSS-REFERENCES TO RELATED APPLICATION Not Applicable. FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT Not Applicable. REFERENCE TO A MICROFICHE APPENDIX Not Applicable. BACKGROUND OF THE INVENTION The present invention relates generally to producing a nuclear particle beam of narrow energy spectrum and more specifically to producing a neutron beam for Boron Neutron Capture Therapy (BNCT). The present invention also relates to increasing the production rate of an accelerator based radionuclide provided that the target nuclide from which the radionuclide is generated has a high melting point and can be made into thin foil. Specific example is generation of palladium 103 from a beam of energetic proton bombarding a rhodium 103 target. BNCT is potentially the most advanced cancer treatment which presently is at clinical stage for inoperable brain tumors and melanoma. Since this technique can selectively target and destroy tumor cells without injuring adjacent cells, future research will apply to many other types of cancer. The success of BNCT as an idealized form of therapy is dependent on two processes: the delivery of sufficient Boron 10 to a cancer tumor followed by bombardment of the tumor by low energy neutrons. The neutron flux on the tumor for a reasonable treatment time should exceed 10.sup.9 neutrons per cm.sup.2 per second. The only available source for this high intensity neutron remained to be a reactor based neutron source which is currently used for clinical trial. However, the neutron energy spectrum obtained from a reactor is not optimum and to provide sufficient neutrons at the treatment area a reactor has to operate at a very high operating power, on the order of several megawatts. This is a result of very large neutron spectrum in the core which requires a relatively long distance to slow down high energy neutrons using suitable moderators. The other drawbacks of a reactor are its very high price and the fact that it cannot be installed in hospitals for safety reasons. In contrast to the reactor based neutron sources, accelerator based neutron sources for BNCT appear to have attractive features such as lower cost, reduced residual reactivity, much lower operating power, reduced safety concerns, and better neutron energy spectrum. Many designs have been proposed for using a beam of proton impacting lithium or beryllium targets and producing neutron through (p, n) reaction. In this reaction a proton collides with the nucleus of the target nuclide and causes emission of a neutron. With a proton beam of 2 to 4 MeV the calculated beam current to achieve adequate neutron flux in the treatment area varies somewhat and is estimated between 20 to 50 mA. Many complex issues in these designs remain to be solved. First, production of 20 to 50 mA beam of 2 to 4 MeV proton is technically challenging and remains to be unsolved. A potential solution to this problem is very costly as well. The other unsolved issue is in relation to the usage of lithium as a target which has a melting point of only about 181.degree. C. For example, a beam of 20 mA and 2.5 MeV proton produces 50 kW heat in the target. There is no practical solution for removal of this heat from a solid lithium target of acceptable area. Beryllium, on the other hand, has a much higher melting point, about 1250.degree. C. But a beryllium target has a lower neutron yield than a lithium target. The neutron yield of (p, n) reaction from beryllium target at 4 MeV becomes comparable to a lithium target at 2.5 MeV. Therefore, for producing the same amount of neutrons and by using the conventional method, a beryllium target needs higher power beam than a lithium target, by about a factor of 4/2.5=1.6. With the present invention, however, the differences between power consumption for producing a 2.5 and a 4 MeV proton of the same current becomes insignificant. But the main objects of the present invention are to solve the production of high current beam for generation of neutrons and to provide an easy solution for dissipating the heat load from the beam in the target. The neutron utilization efficiency is the ratio of the rate of useful neutrons in the treatment zone to the rate of total neutrons generated in the target or the reactor core. The useful neutrons are those with energy of several keV. Suitable moderators should be used to degrade the fast neutrons generated in the target to useful neutrons in the treatment zone. When the neutron energy spread where they are born is large a relatively large distance between their birthplace and the treatment zone should be filled with moderators to degrade the fast neutrons to the treatment regime. This in turn lowers the neutron utilization efficiency, since moderators that slow down the fast neutrons inevitably causes scattering and loss of other neutrons. When all neutrons born in the target have approximately the same energy they respond similarly to a moderator. With suitable choice of moderators they can be brought to the treatment zone with high utilization efficiency. Neutrons generated with the present invention have approximately the same energy. Subsequently, a relatively high neutron utilization efficiency can be obtained with the present invention. As has been mentioned at the beginning of this section, another object of the invention relates to increasing the production rate of an accelerator based radionuclide. In nuclear medicine certain types of radionuclides are used as therapeutic seeds. For example, palladium 103 is an x-ray emitting radionuclide that has a half life of 17 days. It is used for interstitial implantation as small seeds in tumors. The x-ray emitted from palladium 103 has a short range in tissues and subsequently is absorbed locally by tumors which results in gradual destruction of tumors. Palladium 103 can be produced either by neutron activation of palladium 102. Pd-102(n, .gamma.)Pd-103, by using neutrons from a reactor, or through a beam of proton from an accelerator, which is mostly a cyclotron, bombarding a rhodium 103 target. Rh-103(p, n)Pd-103. The energy of the proton beam for production of palladium 103 ranges from 12 to 16 MeV. The accelerator route has many clear advantages over the neutron route. For example, the accelerator route can provide a carrier free palladium 103 (free from other palladium isotopes) and with much higher specific activity than the neutron route. One of the objects of the present invention is to increase the yield of palladium 103 from the rhodium by using the target system of the present invention and by keeping the proton beam at an energy where the excitation function of palladium 103 from rhodium 103 is maximum. This method may also be applied for production of other radionuclides provided that the target nuclides from which they are generated meet the requirements mentioned earlier in this section. SUMMARY OF THE INVENTION An apparatus for recirculating charged particles through a single target location. The apparatus comprising: a cyclic particle accelerator, such as a cyclotron, having a center and which acts upon charged particles drawn into the accelerator at the center thereof so that the charged particles increase in energy and are moved along a path which spirals radially outward from the center of the accelerator in conjunction with the increase in energy of the charged particles; and target means positionable in the radially-outward spiral path of the charged particles so that the charged particles strike the target means and wherein the target means permits the charged particles to pass therethrough following an absorption by the target of a small portion of the energy of the charged particles so that upon passing through the target means, the charged particles possess a reduced amount of energy and begin to spiral radially-inwardly of the accelerator whereupon the accelerator acts upon the reduced-energy charged particles so that the charged particles of reduced-energy again increase in energy and thereby re-establish movement along a path which spirals radially outward from the center of the accelerator toward the target means. In one embodiment the present invention provide solutions to the two technically challenging and unsolved issues in developing an accelerator-based neutron source for boron neutron capture therapy being generation of tens of mA of 2 to 4 MeV protons and removal of heat from the target of a reasonable size. The present invention may also be used to increase production of accelerator based radionuclides. |
summary | ||
abstract | A containment vessel of a boiling-water nuclear power plant and a method of operating a condenser in a nuclear power plant, include a drain pipe which connects a top region of the containment vessel to a condensing chamber disposed in the containment vessel. The drain pipe draws off noncondensible gases from the surroundings of a building condenser in the containment vessel and thus maintains reliability of performance of the building condenser. The noncondensible gases flow automatically into the condensing chamber through the drain pipe. As a result, the building condenser may have a simple and cost-effective structure. |
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048662810 | description | FIGS. 1a and 1b represent an irradiation plant according to the invention comprising a wall-shaped radiation source 2 in an irradiation chamber 1 and a conveyor system comprising four irradiation tracks 3 symmetrical with the chamber 1 and disposed between two transverse tracks 4 and 4A. A number of conveyor units 5 carried and guided by tracks 3 and transverse tracks 4, 4A and each loaded with two superposed pallets 6 containing material for irradiation are driven by chain drives 7 along the various tracks. The transverse track 4 is connected to an entry section 15 and an exit section 16. Each conveyor unit 5 has control elements which act on control-system sensors disposed along the tracks and thus guide units 5 on individual paths along the irradiation tracks 3 and transverse tracks 4, 4a. A shift device 8, 8a moves along each of the transverse tracks 4, 4a from and to the ends of the various irradiation tracks 3, parking tracks 31, and the entry section 10, 15 and exit section 11, 16. A drive 100 drives the shift carriages 8, 8a always together and in the same direction, so that they are always facing one another. Controlled locking devices (not shown in FIGS. 1a and 1b) prevent the shift devices 8, 8A from being both loaded with a conveyor unit 5 at the end of the process of loading or unloading a shift device 8 or 8A. The irradiation chamber 1 is surrounded by a concrete casing which protects the environment e.g. from radioactive .alpha., .beta. or .gamma. rays from wall 2 and is connected to the wall by an entry labyrinth 10 and an exit labyrinth 11. Outside the irradiation chamber 1, the conveyor system 12 travels through an unloading station 13 where the pallets 6 and irradiated material are unloaded from conveyor units 5, and a loading station 14 where the conveyor units 5 and pallets 6 of material for irradiation are loaded on to units 5. Units 5 travel along the entry section 10 and connecting track 15 to the shift carriage and the irradiation tracks 3. The exit section 16 extends through a change station 17 in which pallets 6 superposed on conveyor surfaces can be changed . . . a lift 18 and a lift shaft 19 are disposed underneath. The entry and exit sections 15, 16 have the same construction as the irradiation tracks 3. A container 20 filled with water is provided under the radiating wall 2 and the radiation source 2 can be lowered by a hoist 21 into chamber 20, to provide a screen against radiation. This is necessary if maintenance staff have to enter the irradiation chamber. Drive motors 7', 7" are disposed on the concrete casing 9 for the chain drives 7 near the irradiation tracks 3 and near the entry and exit sections 15 and 16. The two drive motors 8' for the shift devices 8, 8A drive their chain drives. The motor 18' for lift 8 and the drive 21' for the hoisting unit 21 of radiation source 2 are likewise disposed on the roof of concrete casing 9 outside the radiation area of source 2, thus greatly facilitating maintenance. Each conveyor unit 5 in the irradiation chamber can travel e.g. along a path shown in FIGS. 2a to 2f along the irradiation tracks 3 and transverse tracks 4, 4A on the shift devices 8. The path is chosen in dependence on the desired intensity, duration and dose of radiation. Combinations of the illustrated paths are also possible. Advantageously, units 5 are driven at a constant average speed. FIGS. 3a, 3b and 3c show the construction and arrangement of the radiation source 2. In the example shown, it comprises two substantially this parallelepipedal walls movable vertically along two rails 23, individual radiation sources being enclosed in modular manner in the walls 22. The height of wall 22 is less than half the conveyor unit 5 (FIG. 1b), so that the vertical position of walls 22 can be varied to obtain an optimum distribution of radiation on the article to be irradiated. A horizontal shaft 25 rotatable in two rolling bearings 24 is disposed along the top end face of each wall 22 and pinions 27 are secured by pins 26 (FIG. 3c) to each end of shaft 25 and engage chains 28 disposed on the inside of rails 23. This prevents the radiation source 22 from tilting or jamming. The guidance of radiation source 22 is further improved by two pairs of wheels 29 moving on the inner surface of rails 23 and rotatably secured near the bottom of radiation source 22. Hoist 21 is connected by a steel cable 30 to the radiation sources 22. In their lowest positions (FIG. 3b) inside basin 20, the two radiation sources 22 are disposed side by side, thus greatly reducing the dimensions of container 20. Alternatively, racks can be used instead of chains 28. The construction of the conveyor units 5 is shown in FIG. 4. Each conveyor unit 5 substantially comprises an aluminium box 50 which defines two approximately cubical chambers disposed one above the other, i.e. a bottom chamber 51 and a top chamber 52, the chambers having conveyor surfaces 57 and two sides open to the tracks. A coupling member 53 is secured to the top of box 50 and two pairs of rollers 54 are secured to member 53. Member 53 has two upwardly open grooves 55 separated by a space z. Track 3 comprises two "U"-shaped bearers 3' having their open sides facing one another and separated by a space somewhat greater than the thickness of coupling members 53. Rollers 54 run on the inside of bearers 3'. Conveyor units 50 are suspended by coupling member 53 and run on rollers 54 on tracks 3. Cams of the drive system engage in slots 55. On the floors or conveyor surfaces 57 of each chamber 51, 52 there are two rows of rollers 56 on which the pallets 6, mounted on an aluminium or steel undercarriage 58, are moved. A braking and holding device 60 for retaining the pallets 6 and undercarriages 58 is disposed between rollers 56, e.g. in the middle of conveyor surfaces 57. A rod 61 for actuating the brake 60 is movably disposed in a wall of box 50 and projects from the wall in the upper part of the box. At its top end, rod 61 has a pressure plate 62. A compression spring 63 operates between plate 62 and the roof of box 50 and presses the rod 61 upwards. A rotatable round rod 64 is mounted in each conveyor surface 57 and is permanently connected at one end to a lever 65 and at the other end to a gearwheel 66. Lever 65 is pivotably connected to rod 61, and gearwheel 66 cooperate with a rack 67 permanently connected to the brake 60. If rod 61 is pressed downwards against spring 63, brake 60 is lowered and pallets 6 can be unloaded or loaded. In the example shown, the brakes are released by one of the pressure rollers 68 secured to one of the "U" bearers 3' and acting on the pressure plates 62. Each conveyor unit 5 has control elements which in the present example are in the form of engageable and disengageable levers 70 secured at the top of box 50 and optionally act on the control means via switches 71 secured to the "U" bearers 3'. As shown in FIGS. 5a and 5b, levers 70 are rotatably disposed in a bearing structure 72 permanently connected to box 50, and in which a spring-loaded push rod 73 acts on each lever 70 so that the lever 70 is firmly held in one or the other of two stable positions. In the disengaged position, levers 70 act on the associated switches 71 (FIG. 5a) whereas in the engaged position they move past the corresponding switches 71, which are the sensors of the control means. In the conveyor system, therefore, switches or sensors 17 of the control means are disposed e.g. along the tracks at each junction. In the loading station 14, the individually selectable irradiation path for each conveyor unit 50 is set by the operators, using levers 70. Levers 70 and/or switches 71 can be multiple, thus further improving safety. The grooves 55 of the coupling members 53 co-operate with cams 79 of drive chains 75 for the conveyor units 5. FIG. 6 shows four pinions 76 of the drive system 7. The drive chain 75 has five cams 79 which engage in grooves 55 of the coupling members 53 of the conveyor units 50. Chain 75 and cams 79 are designed and disposed so that at least one of them always engages in a groove 55, so that unit 5 is always guided via the coupling member 53. Chain 75 is driven e.g. via a bevel gear on a shaft 76' driven by a drive bevel gear which is driven by the shaft of a drive motor extending through the roof of the concrete casing 9. Each pair of adjacent drive chains 75 are separated by the same spacing z as between the grooves 55 of the coupling member. Drive chains 75' in FIG. 7a are constructed so that a single chain can simultaneously drive a number of conveyor units 5 on a track. FIG. 7a also shows the shift device 8, which can bear a single conveyor unit 5. Each shift device 8, 8A contains a track 3 made up of "U" bearers 3'. The top ends of bearers 3' are held together by two reinforced sheet-metal walls 80. Two wheels 81 are secured to each wall 80 and run on rails 4' of the transverse track 4 or 4A. The shift device 8, 8A is guided so that the ends of bearers 3' reach near enough to the irradiation tracks 3, parking tracks 31 and entry and exit sections 15, 16 for the conveyor units to be able to change over from one track to another. Each shift device 8, 8a e.g. has a chain drive 7 for conveying the units 5 to the respective tracks. Walls 80 each have a passage 82 for the coupling members 53 of units 5. The drive 100 (FIG. 1) of the shift devices 8, 8a is e.g. via tension chains 83, 84 guided on wheels 85. In the case both of tension chain 83 and drive chain 84, one of the wheels 85 is secured to a tension spring 86 on the wall of the concrete casing 9. The other wheel 85 of chain 83 is connected to a shaft portion 88' and the other wheel 85 of chain 84 is connected to a drive shaft 88. Shaft portion 88' and drive shaft 88 are interconnected via a coupling 90, and shaft 88 is driven via bevel gears 91 by the shaft 108 of motor 8' extending through the roof of the concrete casing 9. All the wheels 85 can have the same construction. The drive chain 84 bears another wheel 93 secured to the shift device 8, 8A and is guided on two pinions 94. As FIG. 7b shows, a wheel 93 secured to the shift device 8, 8A drives the drive chain 7 via a transmission 95, a pinion 96, an auxiliary chain 97 and a pinion 98. As FIG. 7c shows, each coupling 90 comprises two similar bevel gears 91, one permanently connected to the drive shaft 108 and the other to the shaft portion 88, and a movable double bevel gear 87' which, in the coupled position, engages the two bevel gears 92. The double bevel gears 87' of the two couplings 90 are rotatably mounted on a connecting shaft 87 which is connected to a piston rod 103 and a piston 102 movable in a cylinder 101. Piston rod 103 extends through piston 102 to a switch 104. Switch 104 connects an electric power source 105 optionally to one out of two electric lines 106 or 107. Each line 106, 107 has a junction 110 and leads to the drive motors 8' of the two shift devices 8, 8A. One line 106 has a switch 106' between the junction 110 and each drive motor 8', whereas the other line 107 only has a switch 107' between switch 104 and junction 110. Cylinder 101 has two connections 109 for actuating the e.g. pneumatic pressure switch via piston 2. Instead of having the connecting shaft 87 and the piston rod 103, the couplings 90 and switch 104 could be actuated in synchronism by purely electric or pneumatic or hydraulic means or combinations thereof. The drive of the conveyor system shown in FIGS. 7a, 7b and 7c operates as follows: When coupling 90 is disengaged, the drive motor 8' (not shown in FIG. 7a) drives the shafts 88 via bevel gears 91. Each shaft 88 drives chain 7 via one of the sprockets 85, one of the drive chains 84, sprocket 93, transmission 95, pinion 96, auxiliary chain 97 and pinion 98, and thus drives the conveyor unit 5 in shift device 8, 8A. When the couplings 90 are engaged, the tension chains 83 are driven via sprockets 85 and consequently the two shift devices 8 and 8A are moved along the transverse tracks 4, 4A. Since the tension and drive chains 83, 84 are now running at the same speed and in the same direction, the speed of each drive chain 84 relative to the sprocket wheel 93 connected to the shift carriages 8, 8A is zero, so that wheel 93 remains effectively braked. Consequently, unit 5 cannot move. This automatically prevents the conveyor units 5 extending out of a moving shift carriage 8, 8A. It is only after the coupling 90 has disengaged that carriages 8, 8A are stopped and units 5 can be moved. In FIG. 7c, coupling 90 is engaged and piston 102 and consequently piston rod 103 and the shaft 87 connected thereto are in an end position. Consequently the two double bevel gears 87' are in engagement with the associated two bevel gears 92. Switch 104, which is likewise connected to piston rod 103, is switched so that the current source 105 is connected to line 107' and switch 107. Consequently, the two drive motors 8' can be switched on or off only in synchronism. In order to disengage the couplings 90, piston 102 is brought into the other end position, when the double bevel gears 87' are no longer in engagement with bevel gears 92. Switch 104 is simultaneously changed over and now connects the current source 105 to the line 106 having two switches 106', so that the drive motors 8' can be individually actuated in order optionally to load a conveyor unit 5 on to one or the other shift device 8, 8A. FIG. 7c shows only a simple form of a suitable circuit, but there are a number of other circuits equally suitably for the conveyor system. Advantageously the circuit should be constructed so that coupling 90 can be released only if the shift devices 8, 8A are in line with an irradiation track 3 or parking track 31. To prevent accidental movement of devices 8, 8A, the devices can be fitted with brakes which can be released only when coupling 90 is engaged and motors 8' are switched on. Reversing switches must also be available for enabling motors 8' to run in both directions of rotation. To ensure that the conveyor system is operating efficiently, a control means of the conveyor system overriding the aforementioned electromechanical system must ensure that after every loading or unloading process, not more than one of the facing shift devices 8, 8A is loaded with a unit 5. This can be done by means of locking devices which prevent a shift device 8, 8A from being loaded or unloaded as soon as the aforementioned condition is not fulfilled. To this end, the conveyor system can have a network of sensors which are disposed on the track junctions and the various shift devices 8, 8A and constantly report the loading situation of the tracks and shift carriages e.g. to a monitoring unit which can be a computer. The control unit can operate on devices for locking the conveyor units, which can be disposed along the tracks and on the shift devices 8, 8A. One possible arrangement of locking means is diagrammatically shown in FIG. 7d. In this embodiment, locking is brought about in that some drive chains 75, 75' are not operated when the shift devices 8, 8A are loaded in a certain manner of, if the tracks and shift devices 8, 8A are loaded differently, a conveyor unit 5 first has to be unloaded by a shift device 8, 8A, depending on the path to be followed by units 5. The locking device comprises signal generators 36 disposed as near as possible to the irradiation tracks 3 and which can be acted upon e.g. by rollers 35' of units 5 secured to rods 35. Signal generator 36 is connected by a signal line 37 to a monitoring and control unit 38 which in the case shown prevents device 8 from being loaded as long as device 8A is loaded with a conveyor unit. To prevent the cams 79 meeting the coupling members 53 outside slots 55, the drive motors 7', 7", 8' should operate in synchronism or a sequence control system must be provided. The conveyor system can also have horizontally or obliquely disposed chains which co-operate with coupling members 53 mounted at other places on units 5. Slots 55 may also be sloping or curved, to avoid jerky movements. In order to irradiate the articles in units 5 as uniformly as possible, it may be necessary not only to vary the vertical position of radiation source 22 when chamber 1 is closed, but also to change over the pallets 6 superposed on the conveyor surfaces. This purpose is served by the change station 17 and lift 18, which are explained with reference to FIGS. 8a to 8e. As FIG. 1b shows, lift 18 is suspended from a steel cable 30 extending through the roof of concrete casing 9. Motor 18" drives the winch 18' of the lift. Lift 18 is guided on rails and is movable upwards and downwards in a separate lift shaft 19. Lift 18 is substantially an aluminium box similar to units 5 and can also have rollers and a brake for the pallets. Pressure rollers 68 for adjusting the brake are disposed in the lift rails and operate via a lever system on the rod 62 of brake 60. Lift 18 is so designed so that e.g. conveyor units travelling on the exit section 16 can be driven very close so that the two chambers 51, 52 of the lift are opposite the chambers of the conveyor unit. The change station 17 also comprises e.g. three double-acting hydraulic cylinders 40 having piston chambers 41, 42 which can be optionally pressurized. Each piston 43 is connected to on end of a spindle 44, at the other end of which one or more slides 45 are disposed. Two functionally independent superposed cylinders 40 are disposed so that units 5 come to rest between them and lift 18. The change station 17 operates as follows: First, a conveyor unit 5 loaded with pallets 6 is driven to lift 18. A pressure roller 68 is disposed at the entry section 16 in station 17 and, as described, releases the brakes 60 of unit 5 for pallets 6. Slide 45 is then driven against the pallets 6 (FIG. 8b), after which the pallets 6 and undercarriages 58 are pushed by slide 45 from unit 5 on to lift 18 (FIG. 8c). The two slides 45, which reload a pallet 6 in co-operation, prevent the loads from tipping over. Slides 45 are the brought back to their starting position, so that lift 18 is raised and the bottom pallet 6 can be pushed by two slides 45 from lift 18 into the top chamber of unit 6 (FIG. 8d). Slides 45 are then returned to their starting position. Lift 18 is then driven downwards and the top pallet 6 is moved by slides 45 from lift 18 to the bottom chamber 51 of unit 5 (FIG. 8e). Finally, slides 45 are returned to their starting position and unit 5 returns to the irradiation tracks in order to continue the irradiation. In short, the irradiation unit according to the invention operates as follows: Units 5 in the loading station 14 are loaded preferably each with two pallets 6 and travel in the conveyor system 12 along the entry labyrinth 10 to the irradiation chamber 1, where units 5 are conveyed by system 12 to the beginning of the entry section 15, from where they are conveyed by the chain drive 7 to the shift device 8 and thence to the transverse tracks 4, 4A and the irradiation tracks 3. In the process each unit 5 travels along the path preset in the loading station 14 by engaging and disengaging the levers 70. In the case of articles which have to be heavily irradiated or for a long time, an intermediate stop in station 17 can be prescribed for changing the pallets 6 and moving the radiation sources 22. At the end of the preset irradiation program, unit 5 is conveyed to the exit section 16 and exit labyrinth 11 towards the outlet and the discharge station 13. The example shown here relates to a preferred embodiment of the invention, but other embodiments are also possible. More particularly the number of irradiation tracks 3 can be chosen in adaptation to the required irradiation. Also, the drive for the conveyor units and the shift devices can be different, e.g. hydraulic or pneumatic. Instead of suspended rail tracks, other rail systems can be used as guides, e.g. floor rails, moving carpets, or air, gas or liquid cushion tracks. The conveyor units can also be designed for a number other than two pallets, and the pallets can be other than superposed. More particularly, hydraulic lifting blocks can be used as a hoist for the lift (18) and for the radiating wall (2). The switches and sensors can be electric, electronic, hydraulic or pneumatic. They should if possible be disposed outside the radiation area or be protected against radiation, which is particularly damaging to electric and electronic components. Alternatively the control system can operate on a synchronously operating model of the conveyor system disposed outside the radiation chamber. In the embodiments, the shift devices 8, 8A are moved only in common and in the same direction and therefore always facing one another. This embodiment is very simple and clear and is therefore frequently preferred. However, in some imaginable embodiments of the plant according to the invention the shift devices 8, 8A can also run independently of one another, in which case the control means must be designed so that a conveyor unit is not pushed to or from one of the radiation tracks 3 unless a shift carriage 8, 8A is a both ends. In addition, in order to irradiate very long articles, it is possible to use a conveyor unit 5 from which the top conveyor surface can be removed. |
044302762 | description | The following examples further illustrate this invention. EXAMPLE I This example describes the addition of dopant oxides or salts to highly sinterable UO.sub.2 (whose characteristics were defined previously). In the case of the dopant being introduced as a salt, the addition was made by mortar and pestle mixing of the salts with the UO.sub.2 powder for 30 minutes in aqueous media. These slurries were then dried in a vacuum oven at 60.degree. C., with the resultant cake being granulated and "slugged" and pressed into pellets as given below. Salts, e.g., nitrates, of Ti, V, Al, Ca, Mg, Nb, and mixtures of Ca and Ti, in the range of 0.05 to 0.15 mole% cation produced the proper density, thermal stability, and tailored microstructure. In the case of the oxide dopants, these were added to the UO.sub.2 powder by roll blending for 15 minutes before slugging to 4.5 g/cm.sup.3. The slugs were granulated through a 14 mesh screen and roll blended with 0.2 wt.% zinc stearate (die lubricant) for 10 minutes prior to pressing pellets to a green density of 5.8 g/cm.sup.3. Oxide additions including Ti, V, Al, Ca, Mg, Nb, and mixtures of Ca plus Ti, in the approximate ranges 0.05 to 1.7 mole% with respect to the UO.sub.2, were found to produce the aforementioned special pellet features upon sintering. The pellets were sintered at 1780.degree. C. for 1 hour in H.sub.2 saturated with room temperature water vapor. The density, thermal stability (or change in density on resintering for extended times up to 33 hours at 1780.degree. C.), associated grain size, and quantitative porosity were measured. Undoped UO.sub.2 pellets had an as-sintered density of 97.8% of theoretical, a grain size of 7.9 .mu.m and contained fine porosity, primarily <1 .mu.m, and little or none >5 .mu.m. On resintering, the density increased to greater than 99% of theoretical. In contrast, the doped UO.sub.2 pellets had a controlled density of .about.95% of theoretical, which satisfies current LWR fuel specifications. Importantly, these pellets were stable on resintering, showing less than a 1% increase in density. This stability, crucial for good in-reactor fuel performance, is attributable to the relatively large grain size (.about.15-30 .mu.m) and large porosity (generally, >5 .mu.m size) produced in the doped pellets. Furthermore, these microstructural features are known to be valuable for good fission gas retention during reactor operation. If an excessive amount of dopant is added, evidence of a second phase begins to be apparent primarily as a grain boundary phase. This situation is to be avoided since enhanced grain boundary mobility due to a liquid phase would result in excessive deformation during reactor operation due to creep. EXAMPLE II This example describes the addition of the soluble dopant compound as an aqueous solution dissolved in the liquid uranyl fluoride. An intimate co-mix of ADU incorporating the dopant is then precipitated. Titanium nitrate in an amount corresponding to 0.15 mole% with respect to the uranyl fluoride was added to the uranyl fluoride while stirring. The concentration of uranium in the starting uranyl fluoride solution was 159 g/l, and it contained 2 moles of HF and 2 moles of NH.sub.4 F for each mole of UO.sub.2 F.sub.2. A dispersant, Tamol 731, manufactured by Rohm and Haas, was also added at a concentration of 0.24 g/l to minimize agglomeration during precipitation. Subsequent co-precipitation from this solution of the ADU containing the dopant was effected by adding an excess of ammonium hydroxide. The conditions of precipitation included a pH of 10.2 obtained with a NH.sub.3 /U molar ratio of 26/1, a temperature of .about.29.degree. C., and a residence time of about 8 minutes. The co-precipitate was filtered from the reaction mixture and rinsed with deionized water. The washed filter cake was calcined at 550.degree. C. for 3 hours in a steam/hydrogen mixture of 50:1 ratio. The resulting UO.sub.2 powder containing the dopant was fabricated into pellets as described previously. Sintering was performed at 1780.degree. C. for 8 hours in H.sub.2 saturated with water vapor. Undoped (control) pellets had an average sintered density of approximately 97% of theoretical and a grain size of about 15-20 .mu.m. Most of the porosity appeared to be less than 1 .mu.m in size and practically none was greater than 5 .mu.m. The pellets containing the additive(s) were notably superior. A controlled density of nearly 94% of theoretical, which meets the density criterium in light water reactors, was measured. Furthermore, the grain size was considerably larger, falling in the range 30 to 40 .mu.m, and the porosity appeared to be relatively large and primarily greater than 5 .mu.m in size. Limited resintering studies suggested that these microstructural characteristics would lead to excellent thermal stability in the pellets as would be expected and was the case in Example I. EXAMPLE III Example II was repeated using vanadium fluoride at a 0.05 mole% concentration instead of titanium nitrate. EXAMPLE IV Example II was repeated using 0.15 mole% niobium chloride instead of titanium nitrate. EXAMPLE V Example II was repeated using 0.15 mole% aluminum nitrate instead of titanium nitrate. EXAMPLE VI Examples, II, III, IV and V were repeated using uranyl nitrate instead of uranyl fluoride. In this case the same amount of the dopant cited in Examples II, III, IV and V was added. The uranium concentration in the uranyl nitrate starting solution was 160 g/l and it had a specific gravity of 1.298. Precipitation was performed at about 34.degree. C. and using a NH.sub.3 /U molar ratio of 28 to give a pH of .about.9.5. The residence time for the co-precipitate was approximately 4 minutes. EXAMPLE VII Examples I and II were repeated using less or greater concentrations of dopants. In the case of too little dopant the LWR density specification range (93.5 to 96% of theoretical was not achieved), but rather an excessive density was reached. Furthermore, the pellets were not thermally stable due to their relatively small grain size (.about.10-15 .mu.m) and their fine porosity (.about.1 .mu.m) which persisted as in the undoped fuel. When excess dopant was used, the density suppression generally was excessive to the extent that the pellets did not meet the minimum LWR requirement. Moreover, the grain size can be non-uniform or can exhibit discontinuous growth during sintering. EXAMPLE VIII This example describes the addition of dopant(s) as insoluble compounds to the wet ADU filter cake obtained from either the uranyl fluoride or the uranyl nitrate as recounted above. In one case niobium oxide in an amount equal to 0.20 mole% relative to the ADU was uniformly distributed in the ADU filter cake in a blending operation. The dopant-ADU mixture was then calclined as before to leave the dopant in intimate and uniform contact with the resultant UO.sub.2. Pelleting and sintering followed with the same results as described in Example II. EXAMPLE IX Example VIII was repeated using 0.05 to 1.50 mole% titanium oxide (relative to the ADU) instead of the niobium oxide. EXAMPLE X Example IX was repeated using calcium oxide instead of titanium oxide in the same amount. EXAMPLE XI Example VIII was repeated using a mixture of calcium and titanium oxide in equal proportions and totaling from 1.0 to 2.0 mole% instead of the niobium oxide. EXAMPLE XII Example XI was repeated using calcium nitrate instead of calcium oxide. EXAMPLE XIII In the event these dopant levels are not reached or are exceeded, then the undesirable pellet properties described in Examples I and VII will be obtained causing the UO.sub.2 fuel to be unacceptable. |
summary | ||
abstract | According to one embodiment, each of driving mechanisms is differently connected to one of control rods located in a nuclear reactor. A driving mechanism drives a connected control rod to be inserted and withdrawn with a high-pressure driving water by opening and closing control valves thereof. Driving time data of unlatch, insertion, withdrawal and settle of each control rod, is stored. The driving time data is measured by a test of insertion and withdrawal at a periodical inspection before starting operation of the nuclear reactor. At least one is selected from the control rods, based on a command to select and drive a control rod. A timing table that prescribes timings to open and close each control valve to unlatch, insert, withdraw and settle the selected control rod, is created based on the driving time data thereof. The selected control rod is driven based on the timing table. |
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051270307 | description | DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 is an isometric view, partially broken away, showing the major components of the invention. The components shown in FIG. 1 include a source of penetrating radiant energy, along with a means to form a flying pencil beam sweeping in a sweep plane, the apparatus collectively shown schematically at 130. The means used to form and sweep the pencil beam are well-known to those skilled in the art. The sweep plane is shown in dashed outline fashion, extreme rays 36.sub.U and 36.sub.D help to define the sweep plane WP. A radiation detector 40 is arranged to respond to radiant energy scattered from the pencil beam 36 by an object 20 which is located to be intercepted by the beam, in a selected slice. The slice of the object which will be imaged is identified as the slice 12. For this embodiment the slice 12 lies in or is defined by the sweep plane WP. The radiation detector 40 is any conventional radiation detector which, at any instant in time, forms a single valued signal which is determined by that portion of scattered energy passing a collimator 50 and thereafter detected. The signal generated by the detector 40 is coupled over the conductor 401 to digital processing and display electronics 70. Like the means to form and sweep the pencil beam, the digital processing and display electronics is also known to those skilled in the art. Located between the radiation detector 40 and the object 20 which is to be imaged is the collimator 50. The collimator has a plurality of radiation absorbing vanes 50-1 through 50-6. The form of the vanes is relatively arbitrary so long as they form radiation-transmitting channels, such as the channels C1 through C5. For reasons explained in the copending application, the vanes 50-1 etc. may be thin; the thickness of the vanes in FIG. 1 is exaggerated for purposes of illustration. The desire to maximize detected flux requires the " thickness" of the vanes to be reduced without compromising their function. The channels intersect the front face 50F of the collimator 50 in rectangular openings. In the direction X, each of the openings may be of identical width, and as will be described below in that case the width determines one dimension of the elementary volume element. It is not essential to use openings of either rectangular shape or of equal width. The channels C1-C5 are oriented so that theoretical extensions of the channels' planes of symmetry intersect each other in a "focal line" such as the line 11. The distance between the line 11 and the front face 50F of the collimator 50 (measured along the direction z) is referred to as the focal length F of the collimator 50. The collimator has a plane of symmetry SP, which is also shown in dashed outline in FIG. 1, and lies in the Y-Z plane as illustrated in FIG. 1. The plane of symmetry SP intersects the sweep plane WP to form the focal line 11. With the object 20 in the position shown, the scanning pencil beam 36 will at any instant in time illuminate one elementary volume element in the slice 12 lying along the line 11, such as the exemplary volume element VE. Depending on the material existing at the location of VE, more or less of the illuminating radiation will be scattered. Ideally, all of that portion of the radiation which is scattered from the elementary volume VE in the direction of the detector 40 will (as will be described below) pass through the channels C1-C5, be detected, recorded and contribute to a tomographic image of the slice 12. As the pencil beam 36 sweeps along the line 11 other, different volume elements lying along preferential line 11 will be illuminated and the radiation response of these different volume elements will also be detected and recorded in the same fashion. In this fashion the scattering characteristics of all volume elements lying along the line 11 in the slice 12 can be detected and recorded. The object 20 is supported on the conveyor 150 for motion in the direction of the arrow W. As the object 20 moves in that direction the line 11 will overlie different linear segments of the slice 12, and in the same fashion the radiation response of different linear segments of the slice 12 will also be detected and recorded. In this fashion the radiation response of all linear segments of the slice 12 can be detected and recorded so as to build up a tomographic image of the slice 12. It should also be apparent that at any instant the pencil beam 36 will also produce scattered energy from volume elements not along the line 11. It is the function of the beam length collimator 50 to reject such non-preferred, scattered energy. As will be described below the vanes lying between and defining the channels C1-C5 need not have the "thickness" shown in FIG. 1 and the number of channels may be different from the number shown in FIG. 1. The reasons for this statement and some further details of the collimator 50 are described in connection with FIGS. 2 and 3. FIG. 2 is a schematic cross-section of a collimator 51 in accordance with the invention and its relation to detector 40. FIG. 2 shows imaging an object 200 whose shape is different from that of the object 20 shown in FIG. 1, however FIG. 2 is useful to explain some of the geometrical considerations of the collimator 51. The collimator of FIG. 2 can also be used with objects such as the object 20 of FIG. 1. More particularly, as shown in FIG. 2 a cylindrical object 200 is shown being rotated about its center O. As is readily evident from FIG. 2, there is a portion of the object 200 which is located closer to the collimator 51 their is the sweep plane WP (which is seen on edge in FIG. 2). Any conventional turntable-like apparatus can be used to provide the motion in the direction R. As shown in FIG. 2 the pencil beam 36 of illuminating radiation intersects the object 200. Shown dotted in FIG. 2 is the "slice" 120 which will be imaged in accordance with this particular motion and several elementary volume elements VE.sub.1 -VE.sub.7. The cross-section of FIG. 2 is taken in a x-z plane, e.g. as shown in FIG. 2 the y direction is perpendicular to the plane of the illustration. The section of collimator 51 seen in FIG. 2 is representative of all parallel sections of the collimator. Since the sweep plane WP is an x-y plane, the sweeping motion of the pencil beam 36 is perpendicular to the plane of the illustration. The collimator 51 shown in FIG. 2 has a number of channels C1-C5 formed by the extremities of the collimator 51 and several vanes V.sub.1 through V.sub.4. The vanes, as will be described below, may be extremely thin, e.g. 10 to 20 thousandths (for relatively high density, high atomic number material) at illumination energies of about 120 KVp. Using tungsten for the vanes is preferable, although other materials (such as steel) may be suitable if the x-ray energy is sufficiently low. The openings of the channels C1-C5 in the front face 51F have equal dimensions in the x direction, each opening in the channels C1-C5 is of width a. It should be apparent to those skilled in the art that radiation may be scattered from the object 200 from any volume element of the object which lies along the pencil beam 36. However, the vanes of the collimator limit the scattered energy which can reach the detector 40 to that originating from a volume element of width a at a focal distance F from the front face 51F of the collimator 51. The slice thickness SL of the volume element which can be detected is determined by the dimension of the pencil beam 36 in the Z direction, e.g. SL. Sight lines from the outer extremities of the volume element are drawn dotted for illustration purposes. The collimator 50 or 51 is referred to as a beam length collimator since the spacing of the vanes, a, defines a length along the pencil beam which is one dimension of the elementary volume whose scatter is detected. Typically a is small compared to L and preferably the dimension F is minimized. As shown in FIG. 2 the plane of symmetry SP of the collimator 51 forms a right angle with the sweep plane WP. Of course it should be apparent that the important dimensions, such as the spacing a of the vanes, are selected in accordance with the particular imaging requirements. One typical imaging problem is to locate delaminations or cracks. In cylindrical bodies such as illustrated in FIG. 2, delaminations or cracks which typically are important are circumferential. For such imaging problems, the vane spacing a is selected generally to be much longer (for example three to ten times) than the slice thickness, SL. For example, while the slice thickness SL might be 0.5 mm, the vane spacing could be 3-10 mm. The beam length collimator as described herein has a further advantage over the collimator described in the copending application when imaging dense materials. Imaging dense materials requires higher beam energies than would be required for imaging less dense materials. The typical scattering characteristic becomes more and more forward peaked as the intensity of the beam energy increases. Since the beam length collimator may be sensitive to scatter in the range of .+-.60.degree. measured from a perpendicular to the beam direction, the beam length collimator tends to capture more of the forward scattered energy than would the collimator of the copending application. FIG. 8 illustrates the variation of relative number of scattered photons vs. scatter angle for energies of 100 KV and 400 KV. Focusing first on the region representing 135.degree. to 180.degree. (where 180.degree. represents scatter directly back toward the source) it will be apparent that as the incident energy increases, there is a reduction in the backscattered flux. FIG. 8 also makes clear the increase in scatter as the collimator is rotated from a position as described in the copending application (in the region 135.degree. to 180.degree. ) to the region described herein represented by the collimator positioned at 90.degree. (for acceptance in the region 30.degree. to 150.degree. ). Finally, the beam length collimator provides a unique view of the interior of the object being imaged as will be described. FIG. 3 is an illustration of another embodiment of the invention. FIG. 3 is a section taken under similar conditions to the section of FIG. 2. There are two substantial differences between the embodiments of FIGS. 2 and 3. In the embodiment of FIG. 3 the object 21 being imaged moves longitudinally in the direction of the arrow W, in the x direction. The sweep plane WP forms an angle with the direction W, and furthermore plane WP forms a non-right angle with the plane of symmetry SP of the collimator 51. The geometry shown in FIG. 3 is particularly useful for objects with flat surfaces or surfaces with a very large radius of curvature. FIG. 4 is similar to FIG. 3 but drawn to emphasize the physical relation between volume elements which are adjacent each other in the direction of motion W of the object 21. These different volume elements can be considered adjacent samples. In FIG. 4, the angle between the pencil beam 36 and a surface of the object is about 26.degree.. Successive views or samples are shown as 21-1 through 21-5. Each of the samples are "slanted" and the slice thickness is defined both by the cross-section of the beam 36 and the angle of incidence of the beam with respect to the object, 21. Because of the angle at which the pencil beam 36 enters the object 21, the volume of an elementary volume to which the detector 40 will respond is about three times larger than would be the case in accordance with the geometry described in the copending application for equal cross-section of the pencil beams and at the same collimator dimensions. In order to visually compare the size of the elementary volume, reference is made to FIGS. 5 and 6. FIG. 5 is a plan view drawn to illustrate imaging in accordance with the copending application. FIG. 5 also shows, relative thereto, the beam direction and direction of relative motion W. FIG. 5 represents the relationship between three different "views", each view representing an entire linear segment of the object. The different views are obtained by the relative motion between the object and the source and detector. The three views of FIG. 5 are labelled A, B and C, and the plan view of FIG. 5 is hatched (using the legends shown at A, B and C) to indicate the area encompassed in each "view". FIG. 6 is a similar view, using the same type hatching for views A', B' and C' in accordance with the present invention. FIG. 7 is drawn in the case the object 21 has the motion in the direction of the arrow W (see FIG. 3). Comparing FIGS. 5 and 6, it will be appreciated that: 1) There is more overlap in the different views in accordance with this invention than there was in the arrangement shown in the copending application. 2) The slice thickness is principally dependent on beam width and angle, and can be reduced without affecting the dimensions of the collimator and hence can be smaller than is the case in connection with the copending application. This results in a smaller "partial volume" effect. 3) The effect of items 1) and 2) produces more scattering per unit volume (neglecting absorption to which the beam is subjected on its way into the object). 4) And as a result the imaging is more effective for cracks parallel or nearly parallel to the surface of the object being imaged. 5) Conversely, for features which are perpendicular to the surface, or radial in the case of a cylinder, the imaging arrangement in the copending application is superior. FIGS. 7A-7C, similar to FIG. 2, are useful in illustrating the unique image which is created in accordance with the present invention. FIG. 7A illustrates an object 200 being imaged (cylindrical object, such as is also shown in FIG. 2) in which the slice being imaged is represented at 120. As illustrated in FIG. 7A, nine different views (V1-V19) are illustrated, where views V3-V7 include some portion of the crack or delamination SV. The image seen in FIG. 7B is broken down into a plurality of pixels which are identified as existing in one of several rows, including rows R3-R8 and several columns CL1-CL11. The relative motion (between object and source/detector) is again denoted by the arrow R, to indicate that the object 200 being imaged rotates. The pencil beam 36 intercepts the object and the selected slice 120. The pencil beam 36 sweeps perpendicular to the plane of the illustration, in the axial direction (which is represented by the circled dot in FIG. 7A) so that the sweep plane WP is seen edge on in FIG. 7A. As the pencil beam 36 sweeps in the axial direction, pixels for different columns in the image of FIG. 7B are generated. The rotation, R, generates pixels in different rows in the image. FIG. 7C relates the rotation R, the axial direction (AXIAL) and the extremes (36.sub.U, 36.sub.D) of the sweep. FIG. 7A illustrates (in a manner similar to FIGS. 5 and 6) sections of nine different views, V1-V9, which are presented sequentially to a detector, in that order. Finally, FIG. 7B correlates different pixels of an image with different views. A single view is determined by the collimator dimensions and thus for example at the instant in which the object 200 achieves the position shown in FIG. 7A, assuming that a single beam length collimator was employed, such a beam length collimator might define an extent of sampled volume or a view as that portion of the object intercepted by the pencil beam 36 within the limits of the view V5. Just prior to the time that the object rotated to the position shown in FIG. 7A, a view V4 would be effective. FIG. 7A is drawn for the condition in which successive views overlap in part. See for example the overlap between views V1 and V2, V2 and V3, etc. FIG. 7B is drawn on the assumption that the image is scanned left to right, hence time proceeds horizontally as in a conventional CRT with a Cartesian sweep wherein first one row is swept from left to right, the beam is stepped down to a succeeding for which is swept left to right, etc. The row R5 is drawn in FIG. 7B to represent the view V5. Row R3 has the pixels in columns CL4-CL8 strongly hatched to represent the extent of the delamination SV in the axial direction. Because, however, a portion of the material sampled in view V5 is also sampled in views V4 and V6, the corresponding rows (R4 and R6) of FIG. 7B are also hatched, although not as strongly as is R5. Likewise, since in the illustration of FIG. 7A the crack or delamination SV extends into the views V3 and V7, the corresponding rows (R3 and R7) are also hatched, although still more lightly than the rows R2 and R4. The illustration of FIG. 7B illustrates an advantage of the invention in imaging small cracks or delamination whose major dimension is circumferential. Because the beam traverses a path substantially parallel to the defect, the volume occupied by the defect is relatively large compared to the total pixel volume. This ratio is called the "partial volume" and may be increased by decreasing the beam width. Those skilled in the art will understand that this has the effect of increasing the sensitivity of the detected signal to the defect or anomaly. In this way, an imaging system in accordance with the invention is more sensitive to anomalies having a major dimension parallel to a surface of the object than the arrangement shown in the co-pending application. Furthermore, its sensitivity may be increased by making the beam width smaller or by adapting the geometry to have the beam more nearly parallel to the object's surface. FIG. 9 illustrates an example where the collimating system includes two separate collimators 51 and 52, one located on either side of the selected slice, each collimator associated with a corresponding detector component. More particularly, in the example shown in FIG. 9, a slice 120 within cylindrical object 200 is being imaged by the pencil beam 36 which sweeps in a plane perpendicular to the plane of the illustration. Similar to FIG. 2, a detector 51 is located to be responsive to energy scattered "outside" the cylinder. The collimator 51 is associated with the detector 41 producing, at any instant in time, a single valued signal representing the radiation passing the collimator 51 and which is detected. However, different from FIG. 2, FIG. 9 includes a second collimator 52 associated with a detector 42. The collimator 52 responds to energy scattered from the selected slice 120 "inside" the selected slice 120. The detector 42 responds to energy passing the collimator 52 and, like the detector 41, produces at any instant a single valued signal representing the energy passing the collimator 52 and which is detected. Both the collimators 51 and 52 each have a respective field of view, and each of those field of view, like the field of view of the collimators of FIGS. 1 and 2, intersects the sweep plane in a bounded line lying within the selected slice and along which the pencil beam 36 sweeps. Thus, at any instant in time, energy scattered from the selected slice passing the collimator 51 or the collimator 52 originates from the identical elementary volume. Accordingly, the output signals from detectors 41 and 42 can be summed (shown schematically in FIG. 9 by the summing element 43 to which the output of both the detectors 41 and 42 are connected). By placing a collimator/detector component on both "sides" of the selected slice, the collimating/detecting system as a whole subtends a larger angle at the elementary volume than would have been subtended by either the collimator 51/detector 41 or the collimator 52/detector 42. Of course the same advantages are available in the event the object being imaged is not cylindrical, i.e. a second collimator/detector could be used in the arrangements of FIGS. 1 and 3. It should be apparent from the foregoing that, in contrast to the imaging system shown in the copending application, the invention described herein, including the beam length collimator, can have its sensitivity shaped so as to be increased for anomalies or flaws lying generally along either an outer edge of a longitudinally extending object or circumferentially about a cylindrical object. While particular characteristics of various components of the invention have been emphasized, it should be understood that the arrangements described herein are exemplary and not limiting, and that many changes can be made within the spirit and scope of the invention. The scope of the invention is to be construed by the claims attached hereto. |
061920959 | summary | BACKGROUND OF THE INVENTION This invention relates to angioplasty as a means of treating arterioscleorosis of coronary arteries. More particularly, the invention relates to a radioactive stent capable of preventing restenosis of blood vessels and a process for producing it. Stated more specifically, the present invention relates to a radioactive cylindrical stent that has been ion injected with .sup.133 Xe and which will later emit .beta.-rays, .gamma.-rays and internal conversion electrons ejected by .gamma.-decay. The invention also relates to a process for producing the stent. The radioactive stent of the invention is placed within a blood vessel and prevents its restenosis by inhibiting abnormal growth of the smooth muscular cells in it. The advantage of the .sup.133 Xe radioactive stent of the invention is not limited to preventing blockage recurrence after angioplasy with a balloon or an ordinary non-radioactive stent; it can also replace the balloons and ordinary non-radioactive stents commonly used in angioplasy. To treat arteriosclerosis of coronary arteries, angioplasy is performed using balloons and stents; however, postoperative stenoses often occur and the frequency is 30 -40% in the case of using balloons and 10-30% with stents. Opened blood vessels are believed to occlude mainly from abnormal growth of smooth muscular cells and it has recently been found that intravascular exposure to radiations is an effective way to prevent postoperative restenoses (Waksman R. et al., Circulation, 91, (1995) 1533-1539). One of the ways to implement the intravascular exposure to radiations is by using a stent that has been rendered radioactive on its own and this technique is gaining increasing attention from researchers. However, the only case that has been reported on radioactive stents that are prepared by ion injection is about a .beta.-emitting radioactive stent that has been ion injected with .sup.32 p (Hehrlein C. et al., Circulation, 93, (1996) 641-645). A problem with this prior art technique is that due to the comparatively long half-life (14.3 days) of .sup.32 p, the time of exposure to the emitted .beta.-rays is unduly prolonged to interfere with the regeneration of vascular endothelia, potentially inducing thrombus formation. Therefore, it is necessary to develop a stent that has been rendered radioactive by means of a shorter-lived radioisotope and which is capable of preventing restenosis of blood vessels without interfering with the regeneration of vascular endothelia. In addition, in view of the fact that restenosis of a blood vessel occurs in that area of the vessel which is in contact with any surface of the inserted stent, it is required that the entire surface of the stent be uniformly ion injected with a radioactive isotope. Considering the number of patients with arteriosclerosis who are currently under treatment, mass production of radioactive stents is also an important factor. SUMMARY OF THE INVENTION According to the present invention, a radioactive stent is produced by injecting .sup.33 Xe as a nuclide that has a shorter half-life and emits a smaller maximum energy of .beta.-rays than .sup.32 p In the invention, a uniform irradiator is employed to enable uniform ion injection into the surface of a stent. Since .sup.133 Xe is a nuclear fission product, an ion injector may be connected to a nuclear reactor to achieve continuous ion injection of .sup.133 Xe, thereby enabling mass production of radioactive stents. Thus according to its first aspect, the present invention provides a .sup.133 Xe radioactive stent for preventing restenosis of blood vessels that is prepared by ion injecting .sup.133 Xe into the entire surface of a cylindrical stent and which retards the growth of the smooth muscles of blood vessels by means of .beta.-rays and internal conversion electrons emitted from the injected .sup.133 Xe. According to its second aspect, the present invention provides a process for producing .sup.133 Xe radioactive stent for preventing restenosis of blood vessels which comprises performing ion injection of .sup.133 Xe on a stent positioned in a uniform irradiating unit within an ion injector, whereby .sup.133 Xe is uniformly injected into the entire surface of the stent. According to its third aspect, the present invention provides a process for mass production of .sup.133 Xe radioactive stents for preventing restenosis of blood vessels, in which .sup.133 Xe that is a nuclear fission product generated upon irradiating .sup.235 U in fuel rods in a nuclear reactor with neutrons is supplied into an ion injector via a piping so that it is continuously ion injected into the surfaces of stents. |
description | Not Applicable. Not Applicable. Not Applicable. The present invention relates to flexible radiation shields and particularly to a flexible ionizing radiation shield for the protection of patients during ionizing radiation exposure, the flexible shield being attached to an X-ray machine component by a long retractable cable in a housing locked onto the X-ray machine component, the flexible shield having an elongated opening adjacent to a top edge for dual usage including a hand hold for manipulating the flexible shield during usage and a means to hang the flexible shield onto the housing by hanging the elongated opening over two adjacent hooks on the housing for storage to insure that the flexible shield is always available for use with the X-ray machine and further comprising sanitary disposable shield covers from a dispenser mounted on an X-ray machine component, the sanitary disposable shield covers used to enclose the shield for each usage to prevent exposure of patients to any infectious disease cross contamination from the flexible shield and to dispose of the shield cover after use. Description of Related Art including information disclosed under 37 CFR 1.97 and 1.98 X-rays are short wave electromagnetic energy sources which can penetrate solid matter, which are commonly used in medicine for diagnostic and therapeutic purposes. While X-rays serve as an important medical diagnostic and therapeutic tool, they are harmful to the living cells and tissues of the patient to whom the X-rays are directed and to the medical personnel who administer the X-rays. Many prior art devices have been made to shield patients or medical personnel from the harmful radiation. A flexible radiation shield intended for use with a portable or stationary X-ray machine to shield portions of a patient often becomes separated from the X-ray machine and may not be available for use when the patient is being X-rayed thereby endangering parts of the patient normally covered by the shield when being X-rayed. When used, the radiation shields are often just placed over a portion of a patient during an X-ray and then stored and used with each subsequent patient without cleaning or covering the shield so that patients may be exposed to infectious disease contamination from other patients using the shield. Prior art devices do not adequately address these problems. U.S. Pat. No. 5,379,332, issued Jan. 3, 1995 to Jacobson, concerns a launderable and replaceable lead blanket cover system for rehabilitating contaminated lead blankets. Lead blankets which can be removed from a nuclear facility or which are manufactured directly, include an outer cover which is heat sealed around the periphery to the inner lead blanket. The heat sealed periphery can include a plurality of blanket supporting metal grommets having a uniform predetermined spacing. A contaminated lead blanket which cannot be removed from a nuclear facility, has the contaminated cover removed in the nuclear facility and securing strips are secured to the inner cover. The contaminated lead blanket then is rehabilitated by adding a replaceable cover open on one end and having a heat sealed periphery and metal grommets in the other three sides. The open end with the lead blanket inside is then folded over and sealed, such as with an adhesive and then metal grommets can be secured through the sealed periphery to complete the lead blanket. A replaceable cover lead blanket can also be initially formed, if desired. Utilized with either type of lead blanket embodiment is a launderable and incinerable outer cover. The launderable cover includes two piece securing grommets having the same spacing as the metal grommets. The pieces are snapped together through the metal grommets to secure the launderable cover to the lead blanket and unsnapped to remove the cover for laundering or incineration. U.S. Pat. No. 6,974,961, issued Dec. 13, 2005 to George, illustrates a disposable cover for electromagnetic treatment applicators that prevents undesired exposure to potentially harmful radiation. The cover is a pouch-like structure having a back surface (which faces opposite, or away from, the treatment area) constructed from shielding material, such as metallized polyethylene. At least a portion of the cover which faces the treatment area is constructed solely from non-shielding material. Adhesive strips, ZIP-LOCK.®, or other interlocking edges, secure the applicator inside the cover and close off any leaks. The electromagnetic properties of the cover are integrated into the circuitry for the treatment applicator, such that the applicator is not functional in the absence of the cover. In use, an electromagnetic treatment applicator is inserted into the cover and positioned over the area to be treated, with the non-shielding, or “window”, portion of the cover overlying the treatment area. Once assembled, the applicator/cover combination forms a closely matched and tuned network for effecting a highly efficient RF output. When activated, the generated electromagnetic energy only exits the cover through the opening or “window”, thereby preventing exposure of the patient or caregiver to potentially harmful radiation. U.S. Pat. No. 5,523,581, issued Jun. 4, 1996 to Cadwalader, puts forth a slipcover or covering for containing a flexible radiation shield that allows the radiation shield to be reused without experiencing staining. The slipcover may be configured to cover the thyroid area, male gonadal areas, female gonadal areas, breast area, hands, and eyes. The radiation shield includes a radiation attenuating material and is inserted within a pocket or pouch in the slipcover. The slipcover includes a fastener for selectively opening and closing the pocket. The slipcover is preferably made of a surgical drape material such as a wood pulp or polyester material. The radiation shield may be coated in a fabric material to ease placement and removal of the radiation shield into and out of the pocket. U.S. Pat. No. 4,062,518, issued Dec. 13, 1977 to Stivender, discloses a diagnostic X-ray table, a first group of X-ray shielding panels are supported for rotation on a carrier and another group of panels are supported on a lever that is pivotally connected to the carrier. The lever may be aligned with the carrier to present the combined width of all panels across the front of a combination spot film and fluoroscopic device. Means responsive to pivoting the lever along the side of the apparatus rotate the first group of panels to substantial parallelism with second group to present the panels along the side of the apparatus when the spot film and fluoroscope device is angulated to put the patient being examined in an erect posture. U.S. Pat. No. 5,417,225, issued May 23, 1995 to Rubenstein, claims a radiation shield including an aperture connected to an edge of the shield by a slit, which is held closed by a releasable flap. Instrumentation can be inserted through the aperture to contact a patient over which the shield is draped. By releasing the flap and thereby opening the aperture toward the edge of the shield, the shield can be removed from the patient without removing the instrumentation inserted through the aperture. A secondary shield is releasably secured over the aperture, affording further protection. Because the shield is placed within the septic field during use, the shield includes a sterilizable or disposable outer covering. U.S. Pat. No. 3,967,129, issued Jun. 29, 1976 to Winkler, indicates a radiation shield in the form of a stranded curtain made up of bead-chains whose material and geometry are selected to produce a cross-sectional density that is the equivalent of 0.25 mm or more of lead and which curtain may be mounted on various radiological devices to shield against scattered radiation while offering a minimum of obstruction to the radiologist. U.S. Pat. No. 2,794,128, issued May 28, 1957 to Shasky, is for an “X-Ray Shield”, wherein the X-ray machine has a mounting plate with a plurality of clips attached thereto at one edge thereof. A shield of flexible opaque radiant material is affixed to the clips. U.S. Pat. No. 7,099,427, issued Aug. 29, 2006 to Cadwalader, provides a radiation attenuation system for use with Computed Tomography procedures. The system includes a shield made of a radiation attenuation material and may be useful in blocking or attenuating radiation, and assisting in the protection of at least one of a patient and a medical personnel present during the Computed Tomography procedure. The system may be useful for both Computed Tomography scanning procedures and Computed Tomography fluoroscopy procedures. FIGS. 4 and 5, show a shielding drape attached to the table and to the CT machine by means of hook and loop fasteners in addition to hook and loop fasteners, snaps, grommets, adhesives, or zippers, etc. This device is not retractably mounted to the CT machine. U.S. Pat. No. 6,674,087, issued Jan. 6, 2004 to Cadwalader, shows a radiation attenuation system including a polymeric resin comprising a web. The system also includes a radiation attenuation material dispersed at least partially in the web. The system has a radiation transmission attenuation factor of at least about 10% of a primary 100 kVp X-ray beam. A method of making a radiation attenuation system including a radiation attenuation material dispersed at least partially in a polymeric resin is also disclosed. The method includes extruding the radiation attenuation material and the polymeric resin thereby forming an extrusion. The method also includes forming the extrusion into a web. The web has a radiation transmission attenuation factor of at least about 10% of a primary 100 kVp X-ray beam. A shield for the attenuation of radiation is also disclosed. The shield may be disposable or may be sterilized between uses. U.S. Pat. No. 6,325,538, issued Dec. 4, 2001 to Heesch, describes a radiation field isolator shield apparatus that encloses the human torso (or part of a human torso) during X-ray procedures. The shield protects medical personnel from scatter radiation, is adjustable to fit different size torsos, and will move with the X-ray equipment as the position of the equipment is adjusted to examine different areas of the body. What is needed is a retractable cable for securing a radiation shield to a portable or stationary X-ray machine component to prevent loss of the shield. To insure the additional safety of each patient being X-rayed a new disposable plastic bag is used on each patent to encase the X-ray shield during use on a patient, so that the health of the patient is further protected by being shielded from infection disease cross contamination from other patients using the X-ray shield. An object of the present invention is to provide a retractable cable for securing a radiation shield to a portable or stationary X-ray machine component. The cable prevents the loss of the shield and insures the shields availability at all times. Disposable plastic shield covers are pulled from a dispenser on an X-ray machine component to encase the radiation shield during use on a patient, so that the health of the patient is further protected by being shielded from cross contamination of infectious diseases from other patients using the X-ray shield. The present invention achieves radiation protection and infection control, and keeps the shield consistently available and ready to use thereby improving the overall quality of patient care and meeting standard precautions safety performance compliance because the shield will always be with the X-ray machine equipment to be ready for any random unannounced accreditation compliance survey. In brief, the radiation shield securing and covering system of the present invention comprises a flexible lead-impregnated or other type of ionizing radiation shield for the protection of patients during ionizing radiation exposure, the flexible shield being attached to an X-ray machine component by a long retractable cable in a cable casing locked onto the X-ray machine component. The flexible shield has an elongated horizontal opening adjacent to a top edge for dual usage including a hand hold for manipulating the flexible shield during usage and a means to hang the flexible shield onto the casing by hanging the elongated opening over two horizontally spaced hooks on the casing for storage to insure that the flexible shield is always available for use with the X-ray machine. The system of the present invention further comprises sanitary disposable shield covers from a dispenser mounted on an X-ray machine component, the sanitary disposable shield covers used to enclose the shield for each usage to prevent exposure of patients to any contamination from the shield and to dispose of the shield cover after use to prevent the spread of communicable diseases between patients using the shield and from handling by technicians. An advantage of the present invention is that it insures that a patient will be protected from radiation in body areas surrounding the actual part of the body being X-rayed. Another advantage of the present invention is that it protects the patient from infectious diseases which might spread from other patients if the radiation shield were not covered. One more advantage of the present invention is that it insures that the radiation shield will always be with the portable or stationary X-ray machine. In FIGS. 1-3, a radiation shield securing and covering system 20 comprises a radiation shield 31 attached by a retractable cable 26 to a cable casing 25 with hooks 28 through a shield hand opening 29 to support the shield stored on a post 30 (tower) or other convenient location on a portable X-ray machine 40 and a dispenser 21 for sanitary disposable bags 23 to cover the shield in use. The radiation shield 31 comprises a flexible sheet of radiation attenuation material, which may be impregnated with lead shielding, for preventing passage of all ionizing radiation through the shield to protect a patient from all ionizing radiation exposure on areas of the patient covered by the shield. The shield 31 further comprises a means for handling the sheet of material during use with a patient and a means for hanging the material on an X-ray machine component. Preferably, the means for handling the shield and means for hanging the shield comprises an elongated horizontal opening 29 adjacent to a top end of the shield to receive at least one hand of a user during use of the shield with the cable 26 extended, as shown in FIG. 1, and alternately to receive a pair of hooks 28 on the cable casing 25 for hanging the shield 31 on the X-ray machine component, as shown in FIG. 2. Alternately, there may be at least one hook attached to any X-ray machine component for hanging the shield 31 for storage with the X-ray machine or attached on or adjacent to a permanently fixed X-ray machine. The retractable cable 26 is attached at a first end by a means for permanently securing the cable to a radiation shield, such a plate 19 at the end of the cable attached by rivets or bolts, and at a second end to a retractable spool 18 in the cable casing 25 locked onto an X-ray machine component to insure that the shield is always with the X-ray machine to shield each patient being X-rayed from all ionizing radiation exposure on areas of the patient covered by the shield. The cable casing 25 comprises a rigid structure having the two hooks 28 horizontally spaced on the casing to fit within the elongated horizontal opening 29 to support the shield 31 hanging on the hooks for storage of the shield. The cable casing 25 houses a spring loaded spool 18 to retract the cable 26 after use of the shield 31. The cable casing 25 preferably further comprises a means for locking the cable casing onto the X-ray machine component, which may be an integrated lock with a keyhole 24 on the outside of the casing or the casing 25 may be secured by a strong permanent adhesive or by welding or other secure attaching means to insure that the shield 31 stays with the X-ray machine. A plurality of sanitary disposable bags 23 are fabricated to encompass the radiation shield 31, as shown in FIG. 2, the plurality of disposable bags removably stored within a dispenser 21 of the disposable bags secured to an X-ray machine component for dispensing one of the plurality of disposable bags 23 for each patient being X-rayed and mounting the disposable bag over the shield for each use of the shield with a patient and for disposing of the disposable bag after each use of the shield with a patient to prevent the spread of contagious diseases between patients using the shield and from technicians handling the shield. The radiation shield is made of a soft and flexible usually lead-impregnated radiation attenuation material designed to shield against all ionizing radiation exposure. The system of the present invention is designed to be securely mounted and conveniently stored on any mobile or stationary X-ray machine component. The radiation shield is permanently attached to a lengthy retractable and flexible cable of high strength material to prevent removal of the shield. The cable casing is preferably locked onto the X-ray unit component or mounted with a strong permanent adhesive or welded or otherwise permanently attached. The cable container holds the shield when not in use. The radiation shield is available in various sizes and thicknesses. In use, the radiation shield attaching and covering system of the present invention is user friendly, reliable, and effective when used as intended. When placed in the impervious protective barrier, the radiation shield prevents the potential spread of infectious diseases caused by patient to patient or patient to technologist contact contamination. The radiation shield is removed from the protective barrier after the exposure and the barrier is discarded into the properly designated waste receptacle. Using the radiation shield attaching and covering system of the present invention will significantly improve patient satisfaction and confidence regarding radiation protection and infection control regardless of the patient's isolation precaution status. Real patient safety equals quality patient care. The system of the present invention is structured to meet all national and state regulatory, quality assurance, and accreditation readiness compliance. It is understood that the preceding description is given merely by way of illustration and not in limitation of the invention and that various modifications may be made thereto without departing from the spirit of the invention as claimed. Not Applicable. |
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claims | 1. A charged particle beam writing apparatus comprising:a storage device configured to input layout information of a plurality of chips on which pattern formation is to be achieved, and store the layout information;a writing group setting unit configured to set, using the layout information, a plurality of writing groups each being composed of at least one of the plurality of chips and each having writing conditions differing from each other;a frame setting unit configured to set, for each of the plurality of writing groups, a frame which encloses a whole of all chip regions in the each of the plurality of writing groups;a region dividing unit configured to virtually divide the frame into a plurality of stripe regions in a predetermined direction, with respect to the each of the plurality of writing groups;an order setting unit configured to set, using the plurality of stripe regions of all the plurality of writing groups, an order of each of the plurality of stripe regions such that a reference position of the each of the plurality of stripe regions is located in order in the predetermined direction regardless of the plurality of writing groups; anda writing unit configured to write a pattern in the each of the plurality of stripe regions onto a target workpiece according to the order which has been set, by using a charged particle beam. 2. The apparatus according to claim 1, wherein the writing conditions include at least one of multiplicity, a stage movement path of a stage with the target workpiece thereon, a speed of the stage, a dividing height of the plurality of stripe regions, and a dose of the charged particle beam. 3. The apparatus according to claim 1, wherein the frame is set such that it encloses the whole of all the chip regions in the each of the plurality of writing groups while circumscribing chip regions located at an outer peripheral side. 4. The apparatus according to claim 1, wherein the frame is set such that it encloses the whole of all the chip regions in all the plurality of writing groups while circumscribing chip regions located at an outer peripheral side. 5. The apparatus according to claim 1, wherein when at least part of the plurality of stripe regions of different writing groups of the plurality of writing groups overlap each other, after a stripe region of one of the different writing groups has been written, a stripe region of another of the different writing groups is to be written. |
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abstract | A three-dimensional image capturing device comprises a plurality of laser devices, and an imaging device, such as a CCD, having a plurality of photo-diodes. Each of the laser devices radiates a pulse modulated laser beam so as to detect distance information or data relating to a topography of a measurement subject. The laser beam is radiated onto the measurement subject and a reflected light beam is sensed by the CCD. Signal charge corresponding to a distance from the image capturing device to the measurement subject is accumulated in each of the photo-diodes, and thus the above distance information is sensed. Each laser beam, respectively radiated from each of the laser devices, shares illuminating area at the distance of the measurement subject, so that radiant energy of each laser beam can be reduced by sharing a single distance measurement operation among the plurality of laser devices. |
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claims | 1. A nuclear fuel rod for fast reactors comprisinga metallic nuclear fuel slug;a nuclear cladding tube; andan oxide coating layer on an inner surface of the nuclear cladding tube before fuel fission,wherein the oxide coating layer is consisting essentially of any one selected from the group consisting of chromium oxide (Cr2O3), vanadium oxide (V2O3) and zirconium oxide (ZrO2). 2. The nuclear fuel rod of claim 1, wherein the oxide coating layer has a thickness of 0.1-100 μm. 3. The nuclear fuel rod of claim 1, wherein the oxide coating layer is formed on the inner surface of the nuclear cladding tube by oxidation in an acid solution, high-temperature oxidation, electrolytic oxidation or vapor-phase deposition. 4. The nuclear fuel rod of claim 3, wherein the oxide coating layer is formed by the oxidation in an acid solution by steps comprising:polishing an inner surface of the nuclear cladding tube by mechanical or chemical polishing;dipping the polished nuclear cladding tube in an acid solution; andwherein the acid is selected from the group consisting of nitric acid, citric acid, oxalic acid, sulfuric acid and perchloric acid. 5. The nuclear fuel rod of claim 3, wherein the oxide coating layer is formed on the inner surface of the nuclear cladding tube by the high-temperature oxidation by steps comprising:polishing an inner surface of the nuclear cladding tube by mechanical or chemical polishing;heating the polished nuclear cladding tube in a vacuum of 1.0×10−7-1.0×10−4 torr at 400-600° C. in a chamber; andinjecting oxygen into the chamber, containing the nuclear fuel rod, to a pressure of 1.0×10−5-1.0×10−1 torr. 6. The nuclear fuel rod of claim 3, wherein the oxide coating layer is formed on the inner surface of the nuclear cladding tube by the electrolyte oxidation by steps comprising:polishing an inner surface of the nuclear cladding tube by mechanical or chemical polishing;connecting the polished nuclear cladding tube to a metal network consisting of any one selected from the group consisting of platinum, gold, iron and aluminum, andapplying electric current to the electric circuit in an electrolyte solution at a current ratio of 0.60-2.0 for 15 minutes to 5 hours. 7. The nuclear fuel rod of claim 3, wherein the oxide coating layer is formed on the inner surface of the nuclear cladding tube by the vapor-phase deposition by steps comprising:polishing an inner surface of the nuclear cladding tube by mechanical or chemical polishing;sputtering the polished nuclear cladding tube with argon ions;heating the ion-sputtered nuclear fuel rod at 200-300° C. to remove native oxides from the cladding tube surface; andforming the oxide coating layer on the inner surface of the polished nuclear cladding tube in a vacuum of 1.0×10−8-1.0×10−6 torr. |
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abstract | A nuclear reactor trip apparatus includes a remote circuit breaker trip device operatively connected to a reactor trip breaker to release a control rod into a nuclear reactor core, an active power source, a passive power source, and a local circuit breaker trip device operatively connected to the reactor trip breaker including a sensor to trigger the local circuit breaker trip device upon sensing a predefined condition. The active power source is electrically coupled to energize the remote circuit breaker trip device under normal operating conditions. The passive power source is electrically coupled to energize the remote circuit breaker trip device based on a loss of the active power source. |
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060027363 | description | DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 shows a fuel assembly 1 consisting of a bundle of parallel fuel rods 2 held by spacers 3 arranged with a certain spacing along the length of the rods 2. The spacers 3 consist of grids whose cells each receive one fuel rod. Some positions in the pattern of the grids are occupied by guide thimbles 4 which are longer than fuel rods 2. The guide thimbles 4 are connected at one of their ends to a nozzle 5 constituting the top nozzle of the fuel assembly, and at their other end to a second nozzle constituting the bottom nozzle. When the assembly is in a storage position under water in a pit, the top nozzle 5 is accessible from the top of the pit. This top nozzle 5 has leaf springs 7 which hold the assembly within the core of the reactor in which the top core plate comes to rest on the springs 7. The nozzle also includes studs 8 which project relative to its upper face. FIG. 2 shows the framework 9 of the fuel assembly, including the guide thimbles 4, spacers 3 and the end nozzles 5 and 6. This framework 9 acts as a housing for the fuel rods 2 of the bundle which may be inserted into or extracted from the framework when the upper nozzle 5 is removed. In order to replace or withdraw rods, quick dismountable connections between the end of the guide thimbles 4 and the top nozzle 5 are provided. FIGS. 3 and 4 show a top nozzle of a fuel assembly including an adaptor plate 10 into which the guide thimbles are engaged inside openings 11 passing through this adaptor plate and accessible from the upper part of the fuel assembly. The instrumentation guide thimble for the fuel assembly situated in the central part is received in an opening 12 of specific shape. The top nozzle of the assembly consists of the adaptor plate and of a frame 14 joined together via a skirt 13 welded to the plate 10 and to the frame 14. The frame 14 has bosses 8 including the centering openings and the clamping collars 8' for holding the springs 7. As can be seen in FIG. 4, the through-holes 11 allowing the guide thimbles 4 to be fixed are placed in defined positions corresponding to the positions of the twenty-four guide thimbles of the assembly. Holes 15 for the passage of water pass through the adaptor plate 10 of the nozzle between the through-openings 11 of the guide thimbles. FIGS. 5, 6 and 7 show a first embodiment of means for fixing the end part 4' of a guide thimble of the fuel assembly represented in FIG. 1 inside an opening 11' passing through the adaptor plate 10' of a dismountable nozzle of a fuel assembly according to the invention. In FIG. 5, the fixing means have been represented in their assembled position, the guide thimble being engaged and fixed inside the adaptor plate 10' of the nozzle. In FIG. 6, the fixing means have been represented separately in their disassembled position. In FIG. 7, the fixing elements have been represented in their assembled position at the end of the guide thimble and inside the opening in the adaptor plate, the guide thimble being in a disengaged position relative to the opening in the adaptor plate. The fixing means include a bearing sleeve 16, the opening 11' in the adaptor plate 10' and a locking and unlocking ring 18. The end of the guide thimble 4' has no machining nor any particular forming. The bearing sleeve 16 includes, at one of its ends, a collar 16a having a planar upper bearing surface 16f intended to constitute a bearing rim coming into contact with a planar lower bearing face 10'a of the adaptor plate 10', around the opening 11'. The collar 16a of the bearing sleeve 16 additionally has four indentations 16d evenly distributed about the collar 16a and intended to allow the passage of fuel rods of the assembly when they are being extracted or refitted into the assembly, after the top nozzle 5' has been dismounted. Above the bearing rim 16f of the collar 16a, the sleeve 16 includes a smooth cylindrical part 16b and then a smooth cylindrical part 16c, the diameter of the cylindrical part 16c being slightly less than the diameter of the smooth part 16b. The cylindrical part 16b constitutes a surface for bearing on a corresponding cylindrical centering and positioning part of the opening 11' in the adaptor plate 10'. The bearing sleeve 16 additionally includes stops 16e projecting radially outwards relative to the cylindrical surface 16c and evenly distributed around the periphery of the hoop 16c of the bearing sleeve 16 and separated by axial passages 16'e between two successive stops 16e. In the embodiment represented in FIGS. 5 to 7, the bearing sleeve 16 includes four stops 16e arranged at intervals of 90.degree. about the axis of the sleeve. More generally, the bearing sleeve 16 includes at least two projecting stops 16e separated by at least two axial passages 16'e between two successive stops which extend longitudinally over a certain length of the hoop 16c of the sleeve 16. Below the collar 16a, the sleeve 16 includes a rim projecting downwards and via which the sleeve 16 can be fixed by a weld (17) or other fixing means onto the end of the thimble 4' engaged inside the bore in the sleeve over the entire height of the sleeve. The internal bore in the sleeve 16 has a diameter slightly greater than the outside diameter of the guide thimble 4', so that the sleeve 16 can be slipped over the end of the thimble 4' in the assembled position, as represented in FIGS. 5 and 7. The lower part of opening 11' in the adaptor plate 10' is machined in order to constitute, four bearing stops 11'a arranged at 90.degree. about the axis of the opening 11', machined on just part of the opening 11 and separated by axial passages 11'b whose width in the circumferential direction is very slightly greater than the width of the stops 16e of the bearing sleeve 16, so as to allow the end of the guide thimble 4' on which the bearing sleeve 16 is fixed to be engaged in the axial direction inside the opening 11' until the rim 16f of the collar 16a of the sleeve 16 comes to bear on the planar lower surface 10'a of the adaptor plate. The number, dimension and arrangement of the projecting stops allow the bearing sleeve 16 integral with the end of the guide thimble 4' to be engaged axially inside the opening in the adaptor plate. The shape and width of the axial passages 11'b of the opening 11' correspond substantially to the shape and width of the stops 16e of the sleeve and the shape and dimension of the stops 11'a of the opening 11' correspond substantially to the shape and to the width of the axial passages 16'e of the sleeve 16. The stops 11'a include bearing surfaces perpendicular to the axis of the opening, inside the opening 11. The adaptor plate 10' is additionally machined, inside the opening 11', above bearing surfaces for the stops 11'a, into a smooth cylindrical part 11'c of the opening 11', in order to constitute eight radial cavities 11'f arranged at 45.degree. from one another about the axis of the opening 11' and therefore two sets of four cavities arranged at 90.degree. from one another. Above the cavities 11'f, the opening 11' has a frustoconical part 11'd flared outwards and emerging at the upper end of the opening 11'. The locking ring 18 is in the shape of a cylindrical hoop 18a whose outside diameter is slightly less than the inside diameter of cylindrical part 11'c of the opening 11'. The ring 18 includes four stops 18d projecting radially towards the inside of the cylindrical hoop constituting the standing part 18f of the guide ring 18 and separated by axial passages 18e. The dimension of the projecting stops 18d in the circumferential direction corresponds to the dimension in the circumferential direction of the stops 11'a machined inside the opening 11'. The hoop of the ring 18 additionally includes parts 18b in the form of small elastic bosses which can deform elastically in radial directions. The cross-section of the small bosses 18b corresponds to the cross-section of the cavities 11'f of the opening 11', so that the small radially deformable bosses 18b projecting radially towards the outside of the hoop of the ring 18 can be accommodated in cavities 11'f when the ring 18 is engaged inside the cylindrical part 11'c of the opening 11' above the stops 11'a, as represented in FIGS. 5 and 7. The cylindrical hoop of the ring 18 has a diameter very slightly less than the inside diameter of the smooth cylindrical part 11'c of the opening 11'. In the embodiment represented in FIGS. 5 to 7, the ring 18 includes four small elastically deformable bosses 18b arranged at 90.degree. from one another about the axis of the ring 18. The upper part of ring 18 in addition includes four openings 18c in the form of crenellations which are distributed at 90.degree. about the axis of the ring 18 and arranged each substantially equidistant between two small elastically deformable bosses 18b. In order to fit and fix the end of a guide thimble 4' in an opening 11' in the adaptor plate 10', firstly, the means for fixing the guide thimble 4' are assembled as represented in FIG. 7. The bearing sleeve 16 is fixed and welded to the end of the guide thimble and the ring 18 is engaged inside the smooth cylindrical part 11'c of the opening 11' in the adaptor plate 10'. The ring 18 is oriented so that the stops 18d of the ring 18 come into perfectly superposed positions relative to the stops 11'a of the opening 11'; simultaneously, of course, the axial passages 11'b between the stops 11'a and the axial passages 18e between the stops 18d of the ring 18 find themselves in perfectly aligned positions. In this position, the elastic tabs 18b engage in a first series of four cavities 11'f arranged at 90.degree. from one another about the axis of the opening 11'. It should be noted that the end part of the ring 18 including crenellations 18c is accessible from the top of the adaptor plate 10', owing to the presence of the flared end part 11'd of the opening 11'. A tool including stubs capable of engaging in the crenellations 18c of the ring 18 can be inserted inside the flared end part 11'd of the opening 11'. The tool therefore makes it possible to turn the ring 18 about its axis, which is coincident with the axis of the opening 11' in which the ring 18 is mounted with a small amount of radial clearance. The stops 11'a of the opening 11' and the stops 18d of the ring 18 which have identical shapes have a cylindrical inside surface having, as axis, the axis of the ring and the axis of the opening which are coincident in the position of engagement of the ring 18 in the opening 11' as represented in FIGS. 5 and 7. The internal cylindrical surface of the stops 11'a and 18d has a diameter slightly greater than the diameter of the cylindrical part 16c of the bearing sleeve 16 and substantially equal to the diameter of the cylindrical part 16b of the bearing sleeve 16, so that in the position of engagement of the sleeve inside the opening 11' as represented in FIG. 5, the cylindrical surface 16b of the sleeve 16 is in perfect contact with the internal surface of the stops 11'a which provide perfect centering of the bearing sleeve 16 and of the thimble 4' inside the opening 11'. The distance in the axial direction between the bearing ring 16f and the lower rim 16h of the bearing stops 16e of the bearing sleeve 16 is slightly greater than the sum of the dimensions in the axial direction of the bearing stops 11'a and 18d placed in a superposed position in the axial direction, when the ring 18 is fitted, as represented in FIG. 7. In order to mount and fix the nozzle on the end of the guide thimble 4' equipped with the sleeve 16, as represented in FIG. 7, the nozzle including the adaptor plate 10' is engaged over the end of the guide thimble 4' via its opening 11', oriented such that the bearing stops 16e of the bearing sleeve are inserted by sliding axially through the aligned axial passages 11'b and 18e. The adaptor plate 10' is engaged over the end of the guide thimble 4' until the bearing rim 16f comes into contact with the lower surface of the stops 11'a constituting the lower surface 10'a of the adaptor plate, at the periphery of the opening 11'. Owing to the separation of the rims 16f and 16h, the lower rim 16h of the bearing stops 16e of the sleeve is then slightly above the upper surface 18h of the bearing stops 18d of the ring 18. The guide thimble can therefore be locked quickly by inserting an end part of a tool into the flared opening 11'd of the adaptor plate and into the crenellations 18c of the ring 18. The ring 18 can then be turned inside the opening 11' and around the sleeve 16 whose cylindrical surface 16c has a diameter slightly less than the inside diameter of the bearing stops 18d of the ring 18. The ring 18 is turned through 45.degree., so as to cause the small elastically deformable bosses 18b to pass from one set of four cavities 11'f in the opening 11' arranged at 90.degree. to the second set of openings. Owing to their elasticity, the small bosses 18b can leave the cavities and then engage in the next cavities in order to immobilize the ring 18 in its locked position by snap-fitting. In the locked position of the ring 18, obtained by rotating through 45.degree. starting from the position represented in FIG. 7, the bearing stops 18d come to face the axial passages 11'b. In this way, the bearing sleeve 16, the bearing rims 16h of whose stops 16e are above the face 18h of a bearing stop 18d of the ring 18, itself resting on the bearing stops 11'a of the opening 11', is immobilized and locked in the axial direction relative to the adaptor plate 10'. All the guide thimbles of the assembly are simultaneously engaged in the adaptor plate and then fixed and locked via the rings 18. In order to dismount the nozzle 5' including the adaptor plate 10', the locking ring 18 of each of the guide thimbles is turned so as to cause the small elastic bosses to pass from one set of cavities of the opening of the adaptor plate to another. The bearing stops 18d therefore return to the position represented in FIG. 7 in which the axial passages 11'b and 18e arranged in the extension of one another are also in the extension of a bearing stop 16e of the sleeve 16. Since the four bearing stops of each of the guide thimbles are in the alignment of the axial passages, the nozzle can be separated from the guide thimbles by raising this nozzle in the axial direction of the guide thimbles. The means for fixing the guide thimbles represented in FIGS. 5, 6 and 7 therefore make it possible very simply and very quickly to fix or dismount the nozzle. The fixing means are additionally arranged inside the opening 11' and have no part projecting above the nozzle. The guide thimble is flush with the upper face of the nozzle or slightly set back into the opening. FIG. 8 shows a ring 28 of the means for dismountably fixing a fuel assembly according to the first embodiment and according to an alternative. The ring 28, which fulfils the same function as the ring 18 represented in FIGS. 5, 6 and 7, is made of two elements 26 and 27 which are joined together before the ring 28 is introduced into an opening in the nozzle of the fuel assembly. The first element 26 or ring body 28 is in the form of a component of overall tubular shape which includes various functional parts machined onto its external surface and into its internal bore. The second element 27 is an open elastic ring produced by winding and folding a rod or wire of circular or square cross-section made of steel having good elasticity. The body 26 of the ring 28 is machined so that its lower part has two sectors 26a separated from one another by two cutouts 26b and 26'b cut from the wall of the tubular body. The internal part of the sectors 26a projects radially relative to the internal surface of the tubular body 26, so as to constitute two bearing stops 29 having a function similar to that of the stops 18d described above and to delimit between them, at the cutouts 26b and 26'b, two axial passages. A toric groove 30 is formed on the external part of the body 26, and elastic ring 27 can be engaged over the body 26 by undergoing diametral expansion and snap fitted into the groove 30. In order to immobilize the ring 27 on the body 26 in terms of rotation, one end 27a of the ring 27, folded inwards, is engaged in a radial hole 30a emerging in the groove 30. The upper part of ring body 26, above the groove 30, includes two sets 32 and 32' of two stubs machined so that they project radially relative to the external standing surface of the ring body 26. The two sets of stubs 32 and 32' arranged at 180.degree. from one another about the axis of the ring 28 make it possible to retain the ring axially inside the nozzle in its unlocked position. The elastic ring 27 is folded in two zones situated at 180.degree. from one another about the axis of the ring in order to constitute two immobilizing stubs 27b and 27'b. When the elastic ring 27 is fixed onto the ring body 26, as represented in FIG. 8, the stubs 27b and 27'b project radially outwards relative to the outer surface of the body 26 and of the groove 30 and placed in perfectly defined positions on the periphery of the ring 28. The upper periphery of body 26 of the ring 28 has two notches 33 and 33' intended to identify the orientation of the ring 28 when it is being inserted in its service positions, inside the opening 31 of a fuel assembly nozzle 34, represented in FIG. 9. Provided on the edges of the opening 31 (FIG. 9) are two notches 35 and 35' which come into coincidence with the notches 33 and 33' of the ring 28, in the locked position of the ring. The upper part of body 26 of the ring 28 includes four sectors projecting inwards arranged at 90.degree. from one another separated by crenellations 36 in which branches of a tool allowing the ring 28 to be turned about its axis after it has been fitted in the opening 31 can be engaged. The opening 31 (FIG. 9) is machined so that it has two internal stops 37 and 37' projecting radially towards the inside of the opening 31 and separated from one another by two axial passages 38. The stops 37 and 37' are machined over only part of the length of the opening 31, so as to have bearing surfaces perpendicular to the axis of the opening 31, inside the opening. The stops 37 and 37' and the axial passages 38, which have a position similar to that of the stops 11'a and of the axial passages 11'b represented in FIG. 6, have an angular extent in the circumferential direction similar to that of the stops 28 of the ring 29 and of the axial passages between those stops. The upper part of the opening 31 is flared outwards in the form of a frustoconical surface 39 allowing the introduction and travel of the tool for operating on the ring 28 after it has been inserted into the opening 31. Two notches 40 and 40' are machined in the upper part of the opening 31 at a distance of 180.degree. about the axis of the opening 31. Two notches 41 are also machined in the frustoconical upper part 39 of the opening 31, at a distance of 180.degree. and at 90.degree. from the notches 40 and 40'. The notches 40 and 40' are arranged so as to receive the stubs 27b and 27'b of the ring 27 in the locked position of the ring 28. In this position, the stops 29 of the ring cover the axial passages 38 of the opening 31. The ring 28 can be engaged axially in the opening 31 in its orientation corresponding to the locked position identified by bringing the notches 33 and 33' of the ring 28 into coincidence with the corresponding notches 35 and 35' of the opening 31. The sets of stubs 32 and 32' of the ring 28 therefore face two notches 42 of the opening 31 and the immobilizing stubs 27b and 27'b then face the notches 40 and 40'. The ring 28 can therefore be inserted into the opening 31 without difficulty. In this position, the ring 28, whose stops 29 close off the axial passages 38 of the opening 31, can lock a guide thimble such as the guide thimble 4' represented in FIGS. 5, 6 and 7 equipped with a bearing sleeve such as the sleeve 16. The asial dimensions of the stops 29 and 37, 37' are such that their sum is substantially equal to or slightly less than the axial distance between the edges 16f and 16h via which the sleeve 16 bears on the nozzle and on the stops of the ring 28, respectively. The ring 28, in its locked position inside the opening 31, in which the stops 29 come to bear on the stops 37 and 37' of the opening, therefore fixes the guide thimble 4' onto the nozzle of the assembly. In order to unlock the guide thimble link, the ring 28 is turned through 90.degree. inside the opening 31, using a tool which has branches which are accommodated in the crenellations 36 of the ring, inside the frustoconical part 39 of the opening 31. The stubs 27b and 27'b of the elastic ring 27 can retract diametrally by deformation of the ring at the beginning of the rotation and leave the notches 40 and 40'. After the ring has been rotated through 90.degree., the stubs 27b and 27'b reach the notches 41 and snap-fit into the notches 41 owing to the elasticity of the ring. The ring 28 is then held in an unlocked position in which the axial passages of the ring 28 between the stops 29 are aligned with the axial passages 38 of the opening 31. The guide thimble is no longer held inside the opening 31 of the nozzle. However, the ring 28 remains held axially inside the opening 31 by the sets of stubs 32 and 32' inserted into a groove 43 machined inside the opening 31 below the cavities 43. It is equally possible to use a ring which does not have immobilizing stubs such as 32, and 32' and to provide indexing openings 40, 40' which have an outwardly inclined engagement part. The ring is forcibly engaged in the openings 40 and 40'. In the unlocked position, the ring is retained by the rim of the groove 43, the openings 41 having no part emerging on the outside. FIGS. 10, 11 and 12 show a second embodiment of the means for fixing the end of a guide thimble 4" inside an opening 11" passing through the adaptor plate 10" of a dismountable nozzle 5" of a fuel assembly according to the invention. In FIG. 10, the fixing means have been represented in their assembled position, the guide thimble being engaged and locked inside the opening 11" of the adaptor plate of the nozzle. In FIG. 11, the fixing means have been represented in a non-assembled state and in positions allowing their mutual engagement and their assembly. In FIG. 12, the fixing means have been represented in the assembled state, the guide thimble not being engaged inside an opening in the adaptor plate. The fixing elements include a bearing sleeve 19 consisting of two components 20 and 21 and a ring 22. The two parts 20 and 21 of the sleeve 19 are engaged over one another and joined together by a weld 26 after the ring 22 has been engaged and mounted on the part 21 of the bearing sleeve. The production of the bearing sleeve 19 in two parts makes it possible to mount the ring 22 which is mounted captive and so that it can rotate on the bearing sleeve. After the bearing sleeve 19 and the ring 22 have been assembled, the bearing sleeve 19 is engaged over the end of the guide thimble 4" and fixed to the latter by a weld. The means of fixing the guide thimble also includes the opening 11" passing through the adaptor plate 10" which is machined to interact with the ring 22 and the bearing sleeve 19. The part 20 of the bearing sleeve is in the form of an annular component including a cylindrical internal bore 20a and a collar projecting outwards 20b including a bearing surface 20c perpendicular to the axis of the component 20 and four peripheral indentations 20d to allow the passage of four fuel rods 25, while they are being extracted or inserted into the fuel assembly, as represented in FIG. 13. The component 21 of the bearing sleeve 19 includes a cylindrical hoop 21c, whose outside diameter is slightly less than the inside diameter of the cylindrical hoop 20a of the component 20. As shown particularly in FIGS. 11 and 11A, the hoop 21c of the component 21 has oblong axial openings 21a and 21b passing through it, the openings 21a being arranged opposite each other across a diameter of the hoop 21c, and the openings 21b being arranged opposite each other across a second diameter of the hoop 21c forming an angle of 45.degree. with the diameter across which the openings 21a are aligned. The component 21 of the bearing sleeve 19 includes an upper part 21d whose thickness is greater than the thickness of the hoop 21c. The lower rim of the part 21d constitutes an annular bearing rim 21e. As shown in FIG. 10, the opening 11" passing through the adaptor plate 10" is machined to constitute four bearing stops 11"a arranged at 90.degree. from one another about the axis of the opening 11" separated by axial passages 11"b. The ring 22 includes a lower part 22a consisting of a cylindrical hoop whose wall is deformed in two diametrally opposite regions in order to constitute two elastically deformable radial parts 22b pointing towards the inside of the hoop 22a. The upper part of ring 22 includes four bearing stops 22c arranged at 90.degree. from one another and separated by passages 22d in the axial direction of the external lateral surface of the hoop of the ring 22. The width in the circumferential direction of the bearing stops 22c corresponds substantially to the width of the passages 11"b of the opening 11", and the width of the axial passages 22d in the circumferential direction corresponds substantially to the width in the circumferential direction of the stops 11"a of the opening 11". In this way, as will be explained later, the assembly formed by the bearing sleeve 19 and ring 22 which are fixed onto the end part of the guide thimble 4", as represented in FIG. 12, is capable of being engaged in the axial direction inside the opening 11". The internal bore of the ring 22 includes two successive parts having different diameters, the diameter of the upper part of the bore being greater than the diameter of the lower part of the bore. Between these two parts of different diameter of the interior bore of the ring 22, there is provided a rim 22e whose shape corresponds to the shape of the rim 21e of the component 21 of the bearing sleeve. The components 20, 21 and 22 represented in FIG. 11 are joined together and fixed to the end of the thimble 4" in the way represented in FIG. 12. Firstly, the ring 22 is engaged, via its internal bore, over the component 21 via the lower part of the hoop 21c. The rim 22e of the internal bore of the ring 22 comes into contact with the correspondingly shaped rim 21e of the component 21. The hoop 21c of the component 21 is engaged in the bore of the hoop 20a, over the entire length of the hoop 20a. The lower part of the shell 22a of the ring 22 rests on the end of the hoop 20a of the component 20. The component 20 and the component 21 of the bearing sleeve 19 are fixed by a weld 26. The end of the guide thimble 4" is engaged inside the component 21 over its entire length and a connecting weld is made between the component 21 of the bearing sleeve and the end part of the guide thimble 4". The end part of the thimble 4", the bearing sleeve 19 and the ring 22 are therefore in their assembled position, represented in FIG. 12. The elastically deformable parts 22b of the ring 22 are engaged in the slots 21a of the bearing sleeve 19. The ring 22 is thus held on the bearing sleeve 19 in a position whose orientation is defined. In this position, the adaptor plate 10" of the dismountable nozzle 5" can be engaged over the end of the guide thimble 4" so that the bearing stops 22c move by sliding inside the passages of axial direction 11"b of the opening 11" of the adaptor plate. Simultaneously, the bearing stops 11"a of the opening 11" of the adaptor plate move by sliding inside the axial passages 22d of the ring 22 held in a fixed orientation at the end of the thimble 4". The adaptor plate 10" is engaged on the thimble 4" until the bearing rim 20c of the component 20 of the bearing sleeve 19 comes into contact with the lower parts of the stops 11'a, at the peripheral part of the opening 11" of the adaptor plate. The distance in the axial direction between the rim 20c and the lower rim of the bearing stops 22c of the ring 22 is such that in this position, the lower bearing rims of the stops 22c are above the upper rims of the bearing stops 11"a of the opening 11". The ring 22 is then turned, using a tool including actuating parts which are engaged from above the adaptor plate 10" between the bearing stops 22c of the ring 22 inside the upper part of the opening 11", until the elastically deformable parts 22b of the ring 22 have passed from the slots 21a to the slots 21b of the hoop 21c of the component 21 of the sleeve. The ring 22 is mounted captive between the components 20 and 21 of the bearing sleeve 19 and is free to rotate about the component 21, particularly via its bearing rim 22e, which is engaged over the external rim 21e of the component 21. When the elastically deformable parts 22b have engaged in the slots 21b of the component 21 of the sleeve, the ring 22 is indexed into the locked position of the guide thimble, the lower bearing rim of the stops 22c being located vertically in line with the upper rims of the bearing stops 11"a in the opening 11" of the adaptor plate 10". A set of openings of the adaptor plate 10" is simultaneously engaged over the set of guide thimbles of the assembly. The end part of each of the guide thimbles 4" is then locked in succession onto the adaptor plate 10". In order to unlock each of the thimbles of the assembly, the tool allowing the ring 22 of each of the assemblies for fixing the guide thimbles to be turned is used to place this ring in an unlocked position, in which the elastically deformable parts 22b engage in he openings 21a in the sleeve. The stops 22c of the ring 22 are then in alignment with the axial passages 11"b between the bearing stops 11"a of the opening 11" of the adaptor plate. When all the guide thimbles of the assembly are unlocked, the dismountable top nozzle is separated from the ends of the guide thimbles by lifting the nozzle in the axial direction of the assembly. The fuel assemblies according to the invention therefore include quick means for locking or unlocking the connections between the guide thimbles and the adaptor plate of a dismountable nozzle. Furthermore, the means for fixing the guide thimble are entirely arranged inside the opening in the nozzle. In the case of the first embodiment represented in FIGS. 5 to 7 and of its alternative represented in FIGS. 8 and 9, the locking and unlocking ring remains fixed inside the adaptor plate of the fuel assembly, and loads are transmitted between each of the guide thimbles and the nozzle of the assembly via the bearing stops of the sleeve and the bearing stops of the ring which come to rest on the bearing stops of the opening in the adaptor plate. In the case of the second embodiment represented in FIGS. 10, 11 and 12, the locking and unlocking ring remains fixed to the bearing sleeve of the guide thimble and the loads exerted between the guide thimble and the adaptor plate are transmitted via the ring whose bearing surfaces come into contact with the bearing surfaces of the adaptor plate. In any case, the means for fixing the guide thimble are arranged entirely inside the nozzle and the end of the guide thimble is flush with or slightly set back relative to the external face of the nozzle. Furthermore, no radioactive waste is produced when dismounting the fixing, in contrast with the case of fuel assemblies including a thimble fixed into the nozzle by an immobilizing sleeve which has to be formed at the moment of dismounting, and which is not recovered. Once the assembly has been dismounted, the immobilizing sleeves constitute waste which has to be disposed of; the disposal of radioactive waste requires precautions and gives rise to additional service costs of the nuclear reactor. Although a dismountable assembly including guide thimbles has been described, the invention applies equally to the case of nuclear fuel assemblies including solid ties fixed dismountably to the nozzles at their ends. The bearing sleeves, locking rings and through-openings in the adaptor plate of the assembly may have a shape different from the shapes which have been described. In particular, the ring and the opening in the adaptor plate may include a different number of bearing stops having shapes different from those which have been described. The ring may include one or more small bosses or one or more stubs in order to immobilize it in the opening of the nozzle or on the bearing sleeve. The bearing sleeve of the guide thimble may comprise one or more components with or without bearing stops and with or without cavities for immobilizing the ring in its locked and unlocked positions. Those parts of the elastically deformable ring intended to be accommodated in the cavities of the opening of the adaptor plate or of the sleeve may have shapes different from those which have been described. The invention applies to any fuel assembly for nuclear reactors cooled by light water including a dismountable nozzle. |
042630975 | description | Generally, the present invention is directed to methods and apparatus for driving a toroidal plasma current by asymmetrically altering the magnetically trapped particle population of the plasma. In connection with various of the apparatus aspects of the present invention, there is provided an improvement in toroidal plasma confinement systems comprising means for assymmetrically altering the trapped particle population of a plasma confined by the system to provide ohmic current in the plasma. Generally, conventional component elements of such toroidal plasma systems are well-known. For example, toroidal plasma confinement systems for the generation and containment of high-temperature plasmas may comprise means for providing a strong, toroidal magnetic field in a toroidal plasma zone in which the plasma is to be embedded, and which may be provided by passage of electrical current through one or more conductive coils encircling the minor toroidal axis. Such systems also comprise means for generating a plasma in the plasma zone, which may include means for providing at least an initial toroidal plasma current which current in turn generates a poloidal magnetic field component. The combination of the poloidal magnetic field and the toroidal magnetic field produces resultant magnetic field lines that lie on closed, nested surfaces, and the plasma is subjected to confining, constricting forces generated by the current flowing in it. Such conventional aspects of toroidal plasma systems are known to the art and need not be described in detail herein. As indicated, the apparatus of the present invention, in addition to conventional toroidal plasma elements, further comprises means for asymmetrically altering the trapped plasma particle population to produce a plasma current. Such asymmetric, trapped particle population altering means preferably comprises means for selectively trapping plasma electrons in a predetermined direction with respect to the minor toroidal axis. Such selective trapping means may comprise means for providing a radio frequency field (including resolvable components of such field) which propagates in a direction parallel to the plasma-confining magnetic field, which has its electric field vector perpendicular to the magnetic field, and which is at resonance with a plasma resonance frequency to increase electron perpendicular velocity to asymmetrically trap plasma electrons. The apparatus may further include means for asymmetrically trapping plasma ions in a manner which is current-complementary to the electron trapping. As indicated, a preferred aspect of the present invention involves asymmetrical trapping of charged particles in the toroidal plasma. In a high temperature toroidally confined plasma, there is a population distribution with respect to the energy of the plasma particles, and with respect to the velocity vectors of the particles. If a charged particle such as an electron has a velocity component which is perpendicular to the magnetic field, it will describe a generally circular orbit in a magnetic field of constant strength. If in addition to the perpendicular velocity component, the particle further has a velocity component parallel to the constant magnetic field, the particle will generally describe a simple spiral path in motion through the constant magnetic field. However, in a toroidal magnetic confinement system, the magnetic field is not of uniform strength, and this non-uniformity affects the plasma particle paths in a relatively complicated manner. Because of the variation of magnetic field strength with respect to the radial distance from the major axis, with the field strength being greater at shorter radii, the existence of a parallel velocity component in the particle motion results in particles travelling into increasing, or decreasing magnetic fields. As the particle moves into a magnetic field which is increasing in strength, the parallel velocity decreases in the stronger field. For a combination of parallel and perpendicular velocity components of charged particle motion in a confining toroidal magnetic field, there is a magnetic field strength for which a particle having such velocity components will stop moving in a direction parallel to the magnetic field, and will reflect back in the opposite direction. For a given parallel velocity component, moreover, it is found that the larger the perpendicular velocity component of a given charged particle with respect to the magnetic field, the sooner the particle stops and is reflected. In a tokamak system, under given conditions of operation, there is a statistical population with respect to particle velocity components. Some of the particles in the distribution spectrum will have a parallel velocity which is large enough (with respect to their respective perpendicular velocity components) so that the particles will slow down but will pass through the high magnetic field region. These particles are not trapped and continue to propagate around the toroidal system in the same general direction with a velocity component parallel to the magnetic field. However, there are statistically also a number of particles for which the parallel velocity is not sufficiently large (with respect to their respective perpendicular velocity components) to permit the particles to pass through the high magnetic field. These particles are "trapped, " and reflect back and forth with respect to the minor axial direction. These "trapped" particles do not contribute to the net toroidal current. The velocity distribution of particles is a dynamic coulomb collisional process so that trapped plasma particles may, through collision or other interaction, be changed in respect of their velocity components so that they have sufficient parallel velocity to pass through the high magnetic field region of the toroidal magnetic field. Such particles thus become detrapped. In the conventional operation of a toroidal plasma component system this detrapping is statistically symmetrical in respect of the minor toroidal axis, and makes no net contribution to plasma current. Similarly and concomitantly with the normal particle detrapping, charged particles which are not trapped may acquire velocity components which are insufficient to pass through the high magnetic field regions, and accordingly become trapped. This charged particle trapping rate is also statistically symmetrical with respect to the minor toroidal axis in conventional toroidal plasma system, and also does not have a net effect on the plasma current. Such toroidal magnetic confinement systems may be considered to be a magnetic mirror with symmetrical mirror strength. However, if an effectively asymmetrical toroidal mirror could be provided, the net ohmic current can be affected. Asymmetrical mirror systems will now be generally discussed prior to describing a specific embodiment of apparatus of the present invention. In a simple magnetic mirror confinement system with asymmetric mirror strength, charged particles trapped initially between mirrors will escape due to Coulomb collisions. Since the Coulomb collisions are predominantly small angle scattering, over a period of time, substantially all particles trapped in the asymmetrical magnetic mirror will eventually escape through the weak mirror as Coulomb collisions redistribute the particle energy distribution, thus producing mechanical momentum. In accordance with the present invention, an asymmetric magnetic mirror is effectively provided by the interaction of a specified radio frequency field with the symmetrical magnetic mirror of a toroidal magnetic confinement system. The theoretical aspects of this interaction are discussed in the following description with respect to the asymmetrical trapping of plasma electrons. If initially empty magnetic mirrors are placed in a plasma where particles are all initially untrapped, a radio frequency field may be applied to increase the perpendicular energy of particles and to cause a selective trapping of particles. The radio frequency field is a travelling wave and the heating rate is larger for particles travelling in one direction. This will result in asymmetric trapping, thereby producing an increase in momentum (and thus temperature) in the over-all particle ensemble of the confined plasma. As indicated previously in an axisymmetric torus configuration, such as the magnetic confinement configuration of tokamak and doublet plasma systems, electrons are trapped in a magnetic mirror produced by a toroidal magnetic field. For purposes of illustration, a simple plasma of unifrom density and temperature will be utilized in the following discussion which in the absence of any electric field, has an isotropic and Maxwellian particle velocity distribution. In sphereical coordinates in velocity space, the velocity components of such a simple plasma in directions parallel to the confining magnetic field and perpendicular to the confining magnetic field may be represented as follows: ##EQU3## where suffixes .perp. and .parallel. denote components perpendicular and parallel to the magnetic field, respectively. The distribution function, f, of particles may be defined at the minimum of magnetic field strength on a flux surface, since all orbits pass through the minimum field. The undisturbed distribution function, f.sub.o, is a Maxwellian function and may be given by: ##EQU4## The trapped particles of the toroidally confined plasma are in the region EQU .theta..sub.c <.theta.<.pi.-.theta..sub.c (3) where sin .theta..sub.c =(B.sub.min /B.sub.max).sup.1/2, B.sub.min and B.sub.max are the minimum and the maximum field strength of a toroidal system. When a radio frequency electric field is provided which propagates parallel to the lines of flux of the magnetic field, and which is oriented such that the electric field plane of the radio frequency wave is perpendicular to the magnetic field, selective interaction with the parallel velocity of charged particles such as electrons may be provided. The frequency and the wave number of the field may, for example, be chosen such that the Doppler-shifted frequency is at resonance with a particle resonance frequency, such as the cyclotron resonance frequency. EQU .omega.-k.sub..parallel. v.sub..parallel.=.OMEGA. (4) where .omega. and k.sub..parallel. are the frequency and the wave number of the radio frequency field and .OMEGA. is the particle frequency. The acceleration or heating of particles may be regarded as stochastic (i.e., after a particle passes through a region of radio frequency field with a length l, the phase relation is substantially lost before the next passage), such that the heating process may be described as a diffusion in velocity space. For the case of the cyclotron heating, the equation of motion may be represented as follows: ##EQU5## where E.sub.195 is the radio frequency field and .OMEGA..sub.e is the electron cyclotron frequency. The perpendicular velocity gain .DELTA.v.perp. per pass through the radio frequency field (such as provided by appropriate antenna elements) is roughly given by ##EQU6## The number of passages per unit time may be represented by v.sub..parallel. /L where L is the length of the system and is equal to 2.OMEGA.R.sub.o q for a circular cross-section tokamak plasma confinement system. R.sub.o is the major radius and q is the safety factor in the preceding equation. Then the diffusion coefficient, D.perp., may be represented by the following relationship: ##EQU7## For the case of resonance occuring at v.sub..parallel. =v.sub..parallel.o, the following further relationship may be provided. EQU .omega.=.OMEGA..sub.e +k.sub..parallel. v.sub..parallel.o (8) The diffusion coefficient, D.perp., may then be considered to be: ##EQU8## For the resonance to be reasonably sharp, the following condition should be substantially observed: EQU k.sub..parallel. l>>1 (10) For electron cyclotron resonance heating, k.sub.81 .congruent..omega./c and Equation (10) becomes ##EQU9## This condition may be readily satisfied. However, in a toroidal plasma confinement system, the magnetic field strength is not uniform, and the resonance condition is satisfied with different values of undisturbed parallel velocity v.sub..parallel.o on different flux surfaces of the confining magnetic field. By rewriting Equation (8) the following relationship may be obtained: EQU v.sub..parallel.o =c(1-.OMEGA..sub.e /.omega.) (12) Therefore, in order that the undisturbed parallel velocity v.sub..parallel.o at the minimum region of magnetic field strength, be undirectional, the variation .alpha..OMEGA..sub.e in the cyclotron frequency should not exceed .sqroot.2T/m.sub.e c.sup.2 .OMEGA..sub.e. The equation for the electron distribution function is given by ##EQU10## The righthand side of the preceding equation contains the terms responsible for electron-ion collisional drag and for the cooling of electrons by either transport of collisions. Equation (13) may be linearized with the substitutions f=f.sub.o +f.sub.1 and f.sub.1 .ltoreq..ltoreq.f.sub.o, to provide the following relationship: ##EQU11## The heating rate, W, may be represented by: ##EQU12## The preceding relationship may be used in the calculation of the heating rate, W, as follows. By partial integration, Equation (15) becomes: ##EQU13## The heating rate solution of this equation may be approximated by ##EQU14## where .DELTA.v.sub..parallel. =.vertline.v.sub..parallel. o.vertline./k.sub..parallel. l and .DELTA.v.sub..parallel. <<.vertline.v.sub..parallel.o .vertline.. Then we have ##EQU15## In steady state operation of a toroidal plasma system, the heating due to the application of a radio frequency trapping (or detrapping) field is balanced by energy loss of the plasma represented by the root mean square of Equation (14). By representing the loss term by 3nT/.tau..sub.E is the energy confinement time, the following relationship may be provided: EQU W.ltoreq.3nT/.tau..sub.E. (19) The preceding inequality is used to account for cases in which additional heating methods are used in the system, and the present invention does contemplate embodiments including additional or auxiliary heating means. The trapping rate may now be discussed in view of the preceding disclosure. In this connection, the particle flux .GAMMA. across the .theta.=.theta..sub.c boundary of a toroidal plasma system may be represented by: ##EQU16## By using Equation (17), the following additional relationship for the particle trapping flux, .GAMMA., may be obtained. ##EQU17## This asymmetrical particle trapping flux is balanced by collisional detrapping in a steady state operation of the system after equilibrium is reached. Since the trapping is asymmetrical with respect to the parallel velocity component v.sub..parallel., and detrapping is symmetric, the untrapped population will gain a net momentum. The change in trapped population n.sub.1 may be calculated by equating the flux .GAMMA. with the collisional detrapping flux as follows: EQU .GAMMA..apprxeq..nu.n.sub.1 (.pi.-.theta..sub.c).sup.-2 (22) where .nu. is the collision frequency. In a steady state, this momentun gain is balanced by the collision between plasma electrons and plasma ions. The current density, j, generated may be represented by ##EQU18## where .sigma. is electrical conductivity. By combining Equations (22) and (23), the following ratio relationship may be provided: EQU n.sub.1 /n.sub.o .apprxeq.(.pi.-.theta..sub.c).sup.2 j/(ev.sub..parallel.o n.sub.o). (24) For typical tokamak operating parameters, the current density j is much less than the total current flux at the minimum (i.e., j<<ev.sub..parallel.o n.sub.o) and therefore EQU n.sub.1 /n.sub.o <<1 (25) Accodingly, the linearization of Equation (13) is justified. By using Equation (18), the flux .GAMMA. may be represented in terms of the heating rate, W, as follows: ##EQU19## The appropriate combination of Equations (19), (23) and (26) results in the following relationship: ##EQU20## In a typical tokamak system, .theta.c is given by EQU cos.theta..sub.c =.sqroot..epsilon. (28) where .epsilon. is the inverse aspect ratio. For a tokamak plasma system, Equation (24) becomes approximately: ##EQU21## The magnetohydrodynamic stability condition limits the current density to a value given by ##EQU22## where R is the major radius, B.sub.t is the toroidal magnetic field, and q is the safety factor. Typically, the valve of j for a large tokamak plasma system may be 5.times.10.sup.5 amp/m.sup.2. Since the right-hand side of Equation (29) is proportional to T.sup.2, it may be considered to represent the condition for the lower limit on temperature. ##EQU23## For j=5.times.10.sup.5 amp/m.sup.2, .tau..sub.E =1 sec, and .epsilon.=1/3 we obtain EQU T.gtoreq.1.4.times.10.sup.4 eV (32) It should be noted that the indicated temperature value is not far from the optimum operating temperature of a tokamak fusion reactor in accordance with known principles. In steady state radio frequency trapping (or detrapping) heating, over an extended time period the plasma ions will gain momentum due to the friction with electrons. The ion momentum may be cancelled, for example, bt applying counter-current radio frequency ion cyclotron resonance energy, at an appropriately much lower power level, in accordance with principles previously set forth herein. It has been shown that a plasma current in a toroidal plasma system such as a tokamak system may be sustained by using a radio-frequency heating induced, asymmetrical trapping (or detrapping) phenomenon. Although electron cyclotron resonance frequencies are used in the preceding description for discussion purposes, other resonances such as the lower hybrid wave may be utilized, and may be preferred inpractice. Electron cyclotron resonance has the disadvantage of requiring a very short wave length microwave generator, and also the wave will not penetrate the plasma if the plasma frequency is larger than the cyclotron frequency. In the selection of other suitable wave resonances, it should be recognized that the wave utilized should have a resonance and should heat the electron perpendicular energy for asymmetrical trapping, and should heat the electron parallel energy for asymmetrical detrapping. Turning now to the drawings, the invention will now be more particularly described with respect to the embodiment of apparatus illustrated in FIG. 1. Illustrated in FIG. 1 is a toroidal plasma confinement apparatus 10 of the tokamak type which is adapted for providing a plasma 12 of circular cross section. The boundary 14 of the plasma 12 is schematically represented by a closed, equidensity surface, in terms of mass density, which encloses substantially all of the plasma (e.g., 95% or more of the plasma mass). The plasma 12 is contained in a toroidal zone 16 defined by a toroidal conducting shell 18 of circular cross section and which is generally radially symmetrical about the longitudinal major toroidal axis 20 of the apparatus 10. It will be appreciated that while the illustrated plasma 12 boundary 14 toroidal zone 16 and conducting shell 18 are of circular cross section, they may have other shapes such as a doublet shape (or higher multiplet). The conducting shell 18 is provided with appropriate access ports for vacuum and gas supply, in accordance with known construction. The interior walls of the shell 18 may be protected by a liner (not shown) fabricated of graphite, silicon carbide, or some other suitable low atomic number material which minimizes the impurity effects of wall material sputtered back into the plasma as a result of charged particle bombardment of the liner. External of the shell 18 is the vacuum chamber 30, which is made of an electrically insulating material and which may have a thin metallic coating to avoid introduction of an excessive amount of impurities into the plasma zone. The vacuum chamber is hermetically sealed, and is provided with conduits 32 as an access port. Surrounding the vacuum chamber 30 are toroidal field producing coils 31 which produce the toroidal magnetic field in the plasma zone within the conducting shell 18. The toroidal coils 31 may be supplied current from a suitable d-c power source (not shown) such as a lead acid battery bank. Externally of the vacuum chamber 30, but internally of the toroidal coils 31, is an additional set of magnetic coils 34 which may be driven by an appropriate capacitor bank power system (not shown). The coils 34 are electric field induction coils, which function to ionize the plasma 12 and induce an initial plasma current. A radially symmetrical manifold array 36, which may be connected to a vacuum system (not shown) via outlet ports and piping 38, communicates with the interior of the vacuum chamber 30 by means of ports 32. Associated piping and ports for hydrogen (e.g. deuterium-tritium mixtures) supply for plasma generators are also provided. These previously described elements or toroidal apparatus 10 are conventional in the plasma art and need not be further described in detail. The embodiment of apparatus 10 further includes means 40 for selectively trapping electrons in the toroidal magnetic field. In the embodiment illustrated in FIG. 1 this selective trapping is carried out by each of a plurality of substantially identical antenna elements 42, 43, 44, 45 which are vertically oriented with respect to the major axis of the toroidal system and located adjacent to the interior surface of the shell 18 in the region of higher magnetic field strength. The four antenna elements 42, 43, 44, 45 are regularly spaced at equidistant intervals about the interior wall of the plasma confinement zone such that the antenna elements are spaced at successive 90.degree. intervals in a plane perpendicular to the major axis of the apparatus 10. The antenna elements each comprise a plurality of substantially identical waveguide units 50 which are more fully illustrated in FIGS. 2 and 3. As shown in FIGS. 2 and 3, the waveguide units 50 of each antenna element are disposed in uniform, vertically oriented array in adjacent relationship conforming to the toroidal interior surface of the plasma zone. Each of the waveguide units 50 is provided with a waveguide channel 52 communicating with a suitable radio frequency generator (not shown) and transmission line (not shown). The radio frequency generators may comprise a plurality of amplifiers driven by a single source, to produce the desired output power. The radio frequency generator supplies r-f energy at a predetermined wavelength adapted to increase the perpendicular velocity component of plasma electrons in accordance with previously discussed principles. In order to provide the appropriate r-f field within the plasma zone, each of the waveguide units is provided with a plurality of slot radiators 54 having a length dimension of approximately half the free space wave length, .lambda., of the r-f output of the radio frequency generators. The slot radiators as shown in FIG. 3 are spaced at one wave length, .lambda., intervals along the longitudinal direction of each of the waveguide units 50, and the slot radiators of each of the waveguide units 50 are adjacently disposed to form radiating surfaces of the respective antenna elements 42, 43, 44, 45 having a regular array of slot radiators thereon. The antenna enters at the top of the shell 18 and is confined to the higher field strength region to provide for entry of r-f energy to the system. As indicated, the waveguide units 50 are each provided with a suitable transmission line and radio frequency power source. In this connection, the waveguide units 50 of an antenna element 42, 43, 44, or 45 may be supplied with radio frequency energy in particular phase relationship with respect to the other units 50 or the antenna element, such that the antenna element may provide a relatively narrow r-f beam which may be adjusted in propagation angle with respect to the toroidal magnetic field. The desired phase relationship may be provided by appropriately phased individual r-f power sources for each waveguide unit, such as by inserting an appropriate phase shifting array between an r-f source and the r-f power amplifiers in a known manner. The electric field component of the r-f beam is vertical with respect to the illustration of FIG. 1 (i.e., in a plane passing through or parallel to major axis 20). The provision of a propagation angle which may be shallow with respect to the minor axis provides for increasing damping at the cyclotron layer, and accordingly increases absorption efficiency. The electric field component is thus also perpendicular to the toroidal field, and the full, confining magnetic field (because the poloidal field is relatively weak with respect to the toroidal field). In operation of the illustrated embodiment, a toroidal magnetic field is provided, and plasma is created in a conventional manner in the toroidal plasma zone with capacitor bank discharge through the inductive coils to provide an initial pulsed ohmic flow in the plasma and an initial poloidal field. This produces a plasma population with trapped and untrapped electrons. The trapping means is then operated to asymmetrically trap plasma electrons to provide for continuation of the ohmic current in the original direction of the initial plasma current flow and maintenance of the initial poloidal field. Thus, through the operation of the selective trapping means 40, electrons are selectively detrapped in one direction, and an enormous current flow resulting from the selective asymmetric detrapping of electrons is produced to provide for a continuous current in the plasma. Since the resulting current flow is along the minor axial direction, the current flow produces the poloidal confining field for continuous compression and confinement of the plasma and accomodates steady-state operation of the plasma system. The ions, which in a hydrogen plasma will be protons, may be similarly trapped in a current complementary direction by a similar antenna radiator system and radio frequency generator source operating at an appropriate wavelength for interaction with the proton particles. Apparatus and methods in accordance with the present invention have particular utility in the study and analysis of the properties and behavior of plasmas, and in particular, the study of analysis of toroidal plasmas which are magnetically confined under prolonged or steady-state conditions. The systems may also be used as auxiliary toroidal plasma heating systems in conjunction with other heating systems. The illustrated embodiment is particularly adapted for use in the generation, confinement, study and analysis of hydrogen plasmas (i.e., hydrogen, deuterium, tritium and mixtures thereof such as deuterium-tritium mixtures) at high temperatures, although the invention may also be used in the production of plasmas containing highly stripped elements of higher atomic number. Accordingly, the methods and apparatus of the present invention find utility as analytical techniques and instrumentation in respect of matter in the plasma state. In this connection, the apparatus may be provided with conventional diagnostic and measurement elements including magnetic probes, inductive pickup loops, particle detectors, photographic and spectrographic systems, microwave and infra-red detection systems and other appropriate elements, the data outputs of which may be utilized directly or recorded, such as by transient data recorders. The various aspects of the invention may also find utility as, or in the design or development of, fusion systems, which of course, need not necessarily be net power producers in order to be utilizable as neutron or other particle or fusion product generators, isotope generators, etc. It is of course further understood that although a specific embodiment of the present invention is illustrated and described, various modifications thereof will be apparent to those skilled in the art and, accordingly, the scope of the present invention should be defined only by the appended claims and equivalents thereof. For example, the invention may be utilized in toroidal plasma systems with elongated plasma cross section such as doublet or higher multiplet cross section produced by suitably shaped conducting shells or by appropriately designed field shaping coils. Various features of the invention are set forth in the following claims. |
summary | ||
claims | 1. An electronic blackbody cavity comprising:an inner surface;a chamber surrounded by the inner surface;an opening configured to allow an electron beam enter the chamber; anda porous carbon material layer on the inner surface, wherein the porous carbon material layer comprises a plurality of carbon material particles, and a material of the plurality of carbon material particles consists of carbon atoms, and the plurality of carbon material particles defines a plurality of micro gaps. 2. The electronic blackbody cavity of claim 1, wherein the plurality of carbon material particles comprise at least one of linear particles and spherical particles. 3. The electronic blackbody cavity of claim 2, wherein a diameter of a cross section of each of the linear particles is less than or equal to 1000 micrometers, and a diameter of each of the spherical particles is less than or equal to 1000 micrometers. 4. The electronic blackbody cavity of claim 2, wherein the linear particles are carbon fibers, carbon micron-wires, or carbon nanotubes. 5. The electronic blackbody cavity of claim 2, wherein the spherical particles are carbon nanospheres or carbon microspheres. 6. The electronic blackbody cavity of claim 1, wherein the porous carbon material layer is a carbon nanotube array or a carbon nanotube network structure. 7. The electronic blackbody cavity of claim 6, wherein the carbon nanotube network structure is a carbon nanotube sponge, a carbon nanotube film structure, a carbon nanotube paper, or a network structure. 8. The electronic blackbody cavity of claim 1, wherein a thickness of the porous carbon material layer is in a range from 200 micrometers to 600 micrometers. 9. The electronic blackbody cavity of claim 1, wherein the porous carbon material layer is a super-aligned carbon nanotube array, and a height of the super-aligned carbon nanotube array is in a range from 350 micrometers to 600 micrometers. 10. The electronic blackbody cavity of claim 1, wherein a size of each micro gap of the plurality of micro gaps is less than or equal to 100 micrometers. 11. A secondary electron detection device comprising:an electronic blackbody cavity comprising:an inner surface;a chamber surrounded by the inner surface;an opening configured to allow an electron beam enter the chamber; anda first porous carbon material layer on the inner surface, wherein the first porous carbon material layer comprises a plurality of first carbon material particles, and a material of the plurality of first carbon material particles consists of carbon atoms, and the plurality of first carbon material particles defines a plurality of micro gaps; anda secondary electron detection element located in the chamber. 12. The secondary electron detection device of claim 11, wherein the plurality of first carbon material particles is selected from carbon fibers, carbon micron-wires, carbon nanotubes, carbon nanospheres and carbon microspheres. 13. The secondary electron detection device of claim 11, wherein the first porous carbon material layer is a carbon nanotube array or a carbon nanotube network structure. 14. The secondary electron detection device of claim 13, wherein the carbon nanotube network structure is a carbon nanotube sponge, a carbon nanotube film structure, a carbon nanotube paper, or a network structure. 15. The secondary electron detection device of claim 11, wherein the secondary electron detection element comprises a secondary electron probe, the secondary electron probe comprises a second porous carbon material layer, and the second porous carbon material layer is insulated from the first porous carbon material layer. 16. The secondary electron detection device of claim 15, wherein the second porous carbon material layer consists of a plurality of second carbon material particles and a plurality of second micro gaps, the plurality of second micro gaps are defined by the plurality of second carbon material particles. 17. The secondary electron detection device of claim 16, wherein the plurality of second carbon material particles is selected from a group consisting of carbon fibers, carbon micron-wires, carbon nanotubes, carbon nanospheres and carbon microspheres. 18. The secondary electron detection device of claim 15, wherein the second porous carbon material layer is a carbon nanotube array or a carbon nanotube network structure. 19. The secondary electron detection device of claim 18, wherein the carbon nanotube network structure is a carbon nanotube sponge, a carbon nanotube film structure, a carbon nanotube paper, or a network structure. 20. The secondary electron detection device of claim 15, wherein a material of the plurality of second carbon material particles consists of carbon atoms. |
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claims | 1. An X-ray generation tube comprising:a target for generating an X-ray through irradiation with an electron beam;an electron source provided opposed to the target; anda grid electrode having multiple electron passage apertures,wherein the grid electrode is disposed between the target and the electron source so that a part of a source-side electron beam emitted from the electron source passes through the multiple electron passage apertures and irradiates the target,wherein the source-side electron beam shows a current density distribution,wherein the grid electrode has an aperture ratio distribution,wherein a region of the source-side electron beam, in which a current density is largest, is aligned with a region of the grid electrode, in which an aperture ratio is smallest,wherein the grid electrode causes the part of the source-side electron beam to pass through the multiple electron passage apertures so as to form a target-side electron beam on the target side of the grid electrode, andwherein a current density at a beam center of the target-side electron beam is lower than a current density at a beam center of the source-side electron beam. 2. The X-ray generation tube according to claim 1, wherein when the source-side electron beam shows the current density distribution, the electron beam shows an irradiation density distribution on the target in a beam diameter direction of the source-side electron beam. 3. The X-ray generation tube according to claim 1, wherein the grid electrode has the aperture ratio distribution in a beam diameter direction. 4. The X-ray generation tube according to claim 1, wherein the aperture ratio distribution comprises at least one of a surface density distribution of the multiple electron passage apertures or an aperture area distribution of the multiple electron passage apertures. 5. The X-ray generation tube according to claim 4, wherein the aperture ratio distribution is formed by the surface density distribution of the multiple electron passage apertures and the aperture area distribution of the multiple electron passage apertures. 6. The X-ray generation tube according to claim 1, wherein the grid electrode further comprises an extraction electrode of the electron source. 7. The X-ray generation tube according to claim 1, wherein the electron source comprises an impregnated hot cathode. 8. The X-ray generation tube according to claim 1, wherein the target comprises a transmission type target including a target layer disposed on a side opposed to the grid electrode, and a transmissive substrate for supporting the target layer. 9. The X-ray generation tube according to claim 8, wherein the transmissive substrate comprises a diamond substrate. 10. The X-ray generation tube according to claim 9, wherein the diamond substrate has a substrate thickness of 500 μm to 2 mm. 11. The X-ray generation tube according to claim 9, wherein the diamond substrate comprises one of polycrystal diamond and single crystal diamond. 12. The X-ray generation tube according to claim 8, wherein the target layer contains at least a metal selected from the group consisting of tantalum, tungsten, molybdenum, silver, gold, and rhenium. 13. The X-ray generation tube according to claim 8, wherein a thickness of the target layer is 1 μm or more to 12 μm or less. 14. An X-ray generation device comprising:the X-ray generation tube according to claim 1;a tube voltage circuit to be electrically connected to each of the target and the electron source, so as to output a tube voltage to be applied between the target and the electron source; anda grid potential circuit for defining a voltage between the grid electrode and the target. 15. An X-ray imaging system comprising:the X-ray generation device according to claim 14; andan X-ray detector for detecting an X-ray which is emitted from the X-ray generation device and passes through an object. 16. An X-ray generation tube comprising:a target for generating an X-ray through irradiation with an electron beam;an electron source provided opposed to the target;a grid electrode having multiple electron passage apertures; anda focusing lens electrode,wherein the grid electrode is disposed between the target and the electron source so that a part of a source-side electron beam emitted from the electron source passes through the multiple electron passage apertures and irradiates the target,wherein the source-side electron beam shows a current density distribution,wherein the grid electrode has an aperture ratio distribution,wherein a region of the source-side electron beam, in which a current density is largest, is aligned with a region of the grid electrode, in which an aperture ratio is smallest,wherein the focusing lens electrode focuses the source-side electron beam,wherein the focusing lens electrode defines, between the focusing lens electrode and the target, a crossover that is a virtual point at which a beam diameter of the target-side electron beam becomes smallest,wherein the focusing lens electrode further defines a crossover conjugate point at a position conjugate to the crossover,wherein the focusing lens electrode further defines, on the electron source side, a focus center conjugate point at a position conjugate to a focus center on the target, andwherein the grid electrode is disposed at a position from the crossover conjugate point to the focus center conjugate point. 17. The X-ray generation tube according to claim 16, wherein when the source-side electron beam shows the current density distribution, the electron beam shows an irradiation density distribution on the target in a beam diameter direction of the source-side electron beam. 18. The X-ray generation tube according to claim 16, wherein the grid electrode has the aperture ratio distribution in a beam diameter direction. 19. The X-ray generation tube according to claim 16, wherein the aperture ratio distribution comprises at least one of a surface density distribution of the multiple electron passage apertures or an aperture area distribution of the multiple electron passage apertures. 20. The X-ray generation tube according to claim 19, wherein the aperture ratio distribution is formed by the surface density distribution of the multiple electron passage apertures and the aperture area distribution of the multiple electron passage apertures. 21. The X-ray generation tube according to claim 16, wherein the grid electrode further comprises an extraction electrode of the electron source. 22. The X-ray generation tube according to claim 16, wherein the grid electrode is positioned so as to be overlapped with the focus center conjugate point. 23. The X-ray generation tube according to claim 16, wherein the electron source comprises an impregnated hot cathode. 24. An X-ray generation device comprising:the X-ray generation tube according to claim 16;a tube voltage circuit to be electrically connected to each of the target and the electron source, so as to output a tube voltage to be applied between the target and the electron source; anda grid potential circuit for defining a voltage between the grid electrode and the target. 25. An X-ray imaging system comprising:the X-ray generation device according to claim 24; andan X-ray detector for detecting an X-ray which is emitted from the X-ray generation device and passes through an object. |
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description | Field of the Invention The present invention relates to the generation and processing of extreme ultraviolet radiation. It refers to an optical collector for collecting extreme ultraviolet radiation according to the preamble of claim 1. It further refers to a method for operating such an optical collector, and a EUV source with such a collector. Discussion of Related Art Extreme ultraviolet radiation (EUV) is emitted by hot dense plasmas which can be produced by exciting a target material e.g. tin, with a focused laser beam, creating a laser produced plasma (LPP). A part of the radiation emitted from this plasma is in the EUV spectrum of wavelengths between 10 and 100 nm. The major share of emitted energy lies outside this wavelength band, comprising ultraviolet, visible, infrared and reflected laser radiation. To achieve a high power output and a high brilliance of the radiation source, the emitted radiation is collected and collimated to an intermediate focus for further usage. This is done by ellipsoidal collector optics. FIG. 7 shows a simplified configuration of a EUV source. The EUV source 10 comprises a chamber 11 containing an elliptic or nearly elliptic multilayer (Mo/Si) collector or mirror 15 and a target delivery system 17, which is attached to the chamber 11 by means of a mechanical support 16 and emits a chain of droplets 19 of the target material. A high power (100 W to 20 kW) and high repetition rate (10 Hz to 500 kHz) drive laser 12 ignites the target material at a EUV production site 20. The focused drive laser pulse 14 enters the chamber 11 through a flanged window 13. The spatial and temporal characteristics of the laser pulse match the target size and location in order to maximize conversion efficiency (CE), i.e. the ratio of EUV energy and laser energy. An optical system 23 is used to detect and control the droplets 19 coming from the target delivery system 17. The collector 15 collects the EUV light 18 generated at the EUV production site 20. The collector 15 has a first focus at the EUV production site 20, and a second focus 21, called intermediate focus (IF), where the EUV light 18 is bundled for further use in a subsequent EUV lithography tool (not shown in FIG. 7). The collector 15 has an aperture 22 for the laser light to reach the EUV production site 20. The EUV target delivery system 17 delivers the plasma source material to the EUV production or ignition site 20. The source material is in the form of liquid droplets 19 of either pure material, e.g. Sn, Xe or Li, or of a suspension of target material in a solution, e.g. water or alcohol. The delivery of the droplets 19 of source material takes place at a constant repetition rate and droplet or target size. Target sizes are in the range of 10-100 pm in order to minimize the amount of neutral particles being present after the plasma formation. As has been mentioned before, the targets or droplets 19 reach the EUV production site 20 at the first focal point of the EUV collector 15. Similar configurations are shown in documents WO 2006/091948(A1) or WO 2009/025557(A1) or WO 2010/017892(A1). The out of band emissions which are partially absorbed in the reflective optics lead to increased temperatures of the collector surface. To avoid thermally induced deformations and a deterioration of the multilayer coating, the collector 15 has to be cooled. However, any gas absorbs the EUV radiation and therefore the radiation sources and collimating optics are operated in a vacuum. This prohibits convection cooling of the collector surface within the chamber 11. Therefore cooling has to be implemented in another way. For a normal incidence collector the radiation hitting the collector surface is not homogeneous. Due to directionally varying emissions and varying distance between the collector surface and the plasma, there are regions of the collector surface with higher heat load than others, which results in temperature gradients across the surface. Both elevated temperature level and temperature gradients induce thermal stresses which lead to collector deformation. Deformations of the collector surface can be reduced by a rigid design of the collector surface. The choice of material also has a strong influence on the deformations in operation. Mechanical forces on the reflective part of the collector can induce or compensate for deformations. Document JP 8211211 proposes a design for high power laser optics, which are cooled from the back side. To avoid deformations of the reflective part by the pressure of the coolant the mirror is designed stiffer than the cooling ducts which mitigates all pressure induced deformations to the back structure. Document DE 19955574(A1) describes a gas cooled reflector for high power laser radiation. The design is such, that the thickness of the reflector substrate is reduced to a minimum (e.g. 1 to 25 mm) to enhance convective cooling of the mirror without losing the required stiffness to prevent vibrations or deformations. Further a cooling scheme based on convection on the collector back side is proposed. Ribs, which are designed on the collector back side to enhance manufacturability, serve for cooling enhancement by surface extension and flow perturbation as a secondary benefit. Documents US 2007058244(A1), US 2009289205(A1) and EP 2034490(A1) disclose normal incidence EUV collector designs and reflector arrangements, without any reference to thermal management, cooling or deformation control of the proposed optics. Document U.S. Pat. No. 7,641,340(B1) describes a cooling setup for optical surfaces in near vacuum based on heat transfer through a liquid in a narrow gap between the back side of the optics surface and a temperature controlled member. This heat transfer is based on conduction and the liquid is kept in position by interfacial surface tension. It is an object of the present invention to provide an optical collector, especially for being used in a EUV source, which is able to focus the collected radiation independent of the heat load on said collector during operation, and to provide a method for operating such an optical collector, and a EUV source with such an optical collector. The optical collector according to the invention collects the extreme ultraviolet radiation or EUV light generated at a central EUV production site. The collector, which comprises a reflective shell, is characterized in that means are provided for compensating thermally induced deformations of the reflective shell. According to an embodiment of the invention the reflective shell is mounted on and supported by a support structure, such that a cooling channel is established between the back side of the reflective shell and the support structure, that the thickness of the reflective shell is substantially reduced, such that the convective heat transfer between the back side of the reflective shell and a cooling medium flowing through the cooling channel dominates the process of removing heat from the reflective shell with respect to heat conduction, and that a cooling circuit is connected to the cooling channel to supply a cooling medium to the cooling channel with a controlled coolant pressure and/or mass flow and/or temperature. According to another embodiment of the invention the reflective shell is of near ellipsoidal shape and axisymmetric with respect to an axis, and the cooling channel is funnel-shaped with respect to the axis. According to another embodiment of the invention the cooling channel is connected to the cooling circuit through a plurality of inlet ports and exit ports. According to another embodiment of the invention volutes are provided between the inlet ports and the cooling channel and the exit ports and the cooling channel. According to another embodiment of the invention the cooling medium enters the cooling channel near the axis and exits the cooling channel far from the axis. According to another embodiment of the invention flow disturbing means are provided at predetermined locations within the cooling channel. According to another embodiment of the invention the flow disturbing means comprises a plurality of obstacles, especially in the form of turbulators, which are mounted on the side of the cooling channel opposite to the back side of the reflective shell and/or on the back side of the reflective shell. According to just another embodiment of the invention the cooling circuit is a closed circuit comprising a heat exchanging means, a compressor and a control valve, whereby a control is provided for controlling the compressor and/or the control valve and/or the heat exchanging means. The inventive method for operating the optical collector is characterized in that the pressure and/or the mass flow and/or the temperature of the cooling medium flowing through the cooling channel is used to compensate for thermally induced deformations of the reflective shell. According to an embodiment of the inventive method the pressure and/or the mass flow and/or the temperature of the cooling medium is controlled in dependence of an input signal being characteristic of a deformation of the reflective shell. According to another embodiment of the inventive method a gas is used as the cooling medium. According to just another embodiment of the inventive method the gas is one of the gases including hydrogen, helium, argon, neon, krypton, xenon, chlorine, nitrogen, fluorine, bromine, and iodine, or a mixture of two or more of said gases. The EUV source according to the invention comprises a target delivery system, which emits a chain of droplets of the target material, a high power drive laser, which ignites the target material at a EUV production site, and an optical collector, which collects the EUV light generated at the EUV production site, whereby the optical collector is a collector according to the invention. This invention is about a cooling scheme for the thermo-mechanical management of ellipsoidal collector optics as they are used in EUV radiation sources. The purpose of this optics is to collect radiation coming from its plasma source and focus it to an intermediate focus. The invention comprises an approach to solve two major problems, which collector optics in EUV sources are facing: The heat load coming from the plasma leads to elevated material temperatures and temperature gradients across the collector, which induce deformations of the reflective surface of the collector. On the other hand the application of the collected radiation requires a very small spot size in the focus of the reflected radiation. This is to ensure a high brilliance of the radiation source. The induced deformations of the reflective shell of the collector compromise the required focusing quality of the collector. The novel design and control strategy allow to adjust the temperature distribution in the collector material and to compensate for the thermally induced deformations: In a first step, the thickness of the reflective shell is substantially reduced, which leads to a dominating influence of convective heat transfer on the local temperature. Lateral distribution of heat by conduction is reduced, compared to heat transport across the thickness of the shell. This allows to locally influence the temperature by locally adjusting the convective heat transfer to the cooling medium (gas) on the back side. In regions with higher heat load, the local heat transfer is enhanced by flow acceleration, redirection or perturbation of the gas flow. Hence, approximately uniform temperature (+−1 [deg.] C.) of the reflective shell can be achieved despite the non-uniformly distributed heat load. The thin design of the reflective shell on one hand and the stiffness of the support structure on the other hand only allow certain modes of deformation of the reflective shell. Finite Element simulations show that an increase in coolant pressure induces a local surface rotation, which is opposite to the local surface rotation induced by an increase in material temperature (decrease in coolant mass flow) over a large extent of the reflective surface. In other words, an increase in coolant pressure makes the ellipsoidal surface bulge in one direction, whereas an increase in material temperature induces deformations in the opposite direction, bringing the deformed contour closer to its non-deformed shape. This makes compensation of local surface rotation, which is detrimental for the focusing of the collected radiation down to a small spot, possible. Hereby, the pressure in a closed cooling loop of the collector has to match the required level to compensate for temperature induced deformations at the respective operating point. However, the shape of the reflective shell is not necessarily perfectly ellipsoidal. Some deformations due to operation conditions can be compensated in manufacturing already, Therefore, the “cold” shell is not perfectly ellipsoidal anymore. The basic collector setup according to an embodiment of the invention is shown in FIG. 1. The collector 15 comprises an axisymmetric rigid support structure 24, which supports an axisymmetric reflective shell 25. A cooling medium 26 is injected into the collector support structure 24 at one or more inlet ports 27 arranged around the aperture 22 of the collector 15. In a first circumferential volute 28 the flow of the cooling medium 26 is distributed around the central axis 30, before it enters a funnel-shaped cooling channel 29 running along the back side of the reflective shell 25. After having passed the back side of the reflective shell 25, the cooling medium 26 is collected in a second circumferential volute 31, from which one or more exit ports 32 are releasing the cooling medium 26, which is a gas, back into a closed cooling circuit 33, which comprises at least a heat exchanging means 34 and a compressor 35. The pressure and/or the mass flow and/or the inlet temperature of the cooling medium 26. may be controlled by means of the compressor 35 and/or a control valve 41 and/or the heat exchanging means 34 being part of the cooling circuit 33. The operation of the compressor 35 and/or the control valve 41 and/or the heat exchanging means 34 is controlled by a control 40, which receives an input signal 42 (e.g. from temperature and/or deformation sensing means) being characteristic of the deformation of the reflective shell 25. The way to shape the temperature distribution of the collector 15 is depicted in FIG. 2. The section view indicates a cooling channel 29 of defined local width. Inserts in the form of ribs or turbulators 36 (wedge shaped in this case) are distributed on the inner surface of the support structure 24 at predetermined positions to accelerate and direct the cooling medium flow 26 towards the back side of the reflective shell 25. In the regions where these turbulators 36 are installed and act as barriers, the heat transfer from the back side of the reflective shell 25 to the flow of the cooling medium 26 is enhanced. Similar turbulators may also or alternatively provided on the back side of the reflective shell 25. FIG. 3 compares experimentally obtained radial temperature profiles (deviation from average temperature Tmean in dependence of the radial position) of the collector 15. The reduced temperature in regions with installed turbulators (curves A), compared to the original temperature profile (curve B) proves a cooling enhancement in those regions. The influence of different parameters like turbulator spacing, location, size and orientation to shape the temperature profile were investigated and can partially be seen in this figure, too. Deformation modes of the thin reflective shell 25 of the collector 15, as they are induced by substrate temperature and coolant pressure changes are indicated in FIG. 5 (the deformed shell is referenced by numerals 25′ and 25″). The stiff or fixed regions close to the inner and outer support 37 and 38, respectively, are facing smaller deformations than the central ellipsoidal part 39 of the reflective shell 25. The shape of the deformations is such that, at a certain position the surface rotation due to an increased temperature (25′) is opposite to the surface rotation, which is induced by increasing the coolant pressure (25″). The relative extent of these deformations is such that, depending on the radial position, up to 1 bar of coolant pressure increase is required to compensate an increase of 10 [deg.] C. in material temperature of the shell 25. This can be seen from FIG. 4, which shows the incremental surface rotation due to surface temperature and coolant pressure change for different surface angles. The reflective shell 25 may not necessarily have a uniform thickness. In some cases, it may be advantageous, that the thickness of the reflective shell 25 slightly varies over the shell surface in order to produce desired modes of thermally or mechanically induced deformations. How a deformed collector surface without compensation affects the spot size of the intermediate or second focus 21 of a EUV source 10 can be seen from the ray tracing results in FIG. 6. The reflected ray is deviated from the intermediate focus due to collector deformations up to 1.2 mm under operating conditions if a perfect ellipsoid is used as mirror geometry. Due to the thin design of the present solution a compensation of thermally induced deformations is indispensable to achieve a sufficiently small focus spot size. Although the invention has been explained above in connection with EUV radiation, it may also be useful for X rays, i.e. in an overall wavelength range from 1 nm to 100 nm. |
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056423896 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a light water reactor with a reactor pressure vessel, a core being composed of fuel elements and being disposed in the lower half of the reactor pressure vessel, and a column of water covering the core and being used as a coolant and a moderator, the column having an initial level range during normal operation. 2. Summary of the Invention It is accordingly an object of the invention to provide a light water reactor, in particular a boiling water reactor with a high degree of inherent safety, which overcomes the disadvantages of the heretofore-known devices of this general type and which increases the degree of inherent safety of such a boiling water reactor by the use of passively operating safety devices. With the foregoing and other objects in view there is provided, in accordance with the invention, a light water reactor, comprising a reactor pressure vessel having an interior, a core disposed in a lower half of the pressure vessel, fuel assemblies disposed in the core, and a column of water covering the core and acting as a coolant and a moderator, the column having an initial level range during normal operation; a passively operating safety device; and fluid lines connected between the safety device and the interior of the pressure vessel, the fluid lines having means for automatically transmitting an actuation criterion to the safety device, with at least a drop of a level in the pressure vessel to a value below the initial level range serving as the actuation criterion. In accordance with another feature of the invention, the pressure vessel has a steam space; the safety device is a switching vessel in the form of a pressure vessel with a fluid space and a gas cushion space, the switching vessel has heat exchanging pipes being submerged in the fluid space and having one end communicating with the steam space and another end communicating with the reactor water column during normal operation or when the initial level range is present; the switching vessel initiates condensation in the heat-exchanging pipes if a flow of steam occurs from the reactor interior into the heat exchanging pipes, when dropping below the initial level region of the reactor water; and including at least one of pilot and main fittings, an increase in pressure due to absorbed condensation heat in the switching vessel being used as a derived actuation criterion for passive actuation of the at least one of pilot and main fittings. In accordance with a further feature of the invention, there are provided control rods to be inserted into the core, the at least one of pilot and main fittings actuated when the derived actuation criterion has been fulfilled, include live steam penetration fittings, the at least one of pilot and main fittings actuate a closing of the live steam penetration fittings as a safety measure and/or actuate a reactor scram as a safety measure by quickly inserting the control rods in the core. In accordance with an added feature of the invention, there is provided a condensation chamber, and blow-off units connected to the at least one of pilot and main fittings being actuated when the derived actuation criterion has been fulfilled, the blow-off units blowing-off steam in the condensation chamber to depressurize the pressure vessel or a primary loop. In accordance with an additional feature of the invention, there is provided a containment in which the pressure vessel is disposed; the safety device being an open flooding reservoir disposed outside the pressure vessel in the containment and having a flooding water column with a water level being geodetically higher than the reactor water column; at least one connecting line serving as a fluid line connected between the interior of the pressure vessel and the flooding water column, the at least one connecting line having a non-return fitting being held in a closed position by a reactor-side overpressure in normal operation of the reactor pressure vessel and in the initial level range of the reactor water, and the non-return fitting being opened due to pressure equalization and flooding water being added to the pressure vessel through the connecting line when reaching or dropping below another level range of the reactor water column after pressure in the pressure vessel is reduced to a value approaching that of pressure in the containment. In accordance with yet another feature of the invention, there is provided a condensation chamber below the flooding reservoir for blowing-off excess reactor steam. In accordance with yet a further feature of the invention, the at least one connecting line has a first line section connected to the pressure vessel, a second line section connected to the flooding reservoir and an interior, the non-return fitting is connected between the first and second line sections, and the first line section slopes down toward the non-return fitting for largely preventing a transfer of heat by convection from the reactor water to an interior of the connecting line. In accordance with yet an added feature of the invention, the reactor core has an upper edge, and the connecting line has a lower end connected to the pressure vessel at a point above the upper edge of the reactor core. In accordance with yet an additional feature of the invention, there is provided a water reservoir containing water; the pressure vessel having a steam space; the safety device being an emergency condenser having heat exchanging pipes being disposed in the water of the water reservoir; an inlet pipe configuration interconnecting the emergency condenser and the steam space during normal operation of the reactor, and a drainage pipe configuration interconnecting the emergency condenser and a lower region of the reactor water column at a point above the reactor core; water or condensate in the heat exchanging pipes stagnates during normal operation, but reactor steam flows through the inlet pipe configuration into the heat exchanging pipes and condenses there if the level of the reactor water drops to another level below the initial level range, so that condensate flows back into the pressure vessel through the drainage pipe configuration. In accordance with again another feature of the invention, in this embodiment as well there is provided a condensation chamber below the water reservoir for blowing-off excess reactor steam. In accordance with again a further feature of the invention, the inlet pipe configuration has an inlet and a connection to the heat exchanging pipes and slopes downward from the inlet to the connection, and the drainage pipe configuration has a connection to the heat exchanging pipes and an outlet end and slopes downward from the connection to the outlet end. In accordance with again an added feature of the invention, the heat exchanging pipes have first and second pipe legs and a reversing bend and are essentially hairpin shaped with respective upward and downward slopes, the first pipe leg being connected to the inlet pipe configuration and the second pipe leg being connected to the drainage pipe configuration. In accordance with a concomitant feature of the invention, the drainage pipe configuration has a downwardly running, hairpin shaped pipe bend located on a section in a gap between the pressure vessel and the flooding reservoir, the bend forming a circulation block during normal operation. The advantages which can be realized with the invention lie primarily in the fact that the new light water reactor is particularly well suited for the new generation of boiling water reactors having a specific power density which is preferably reduced as compared to today's power reactors, and in which a greater passive cooling water supply is made available within the plant. The new light water reactor is preferably suited for a power or output range of up to approximately 1000 MWe, whereby essential components can be taken from the base of experience with today's power reactors having approximately twice the output. In particular, the following advantages can be realized by means of the invention: at least one safety-relevant redundancy should be passively operated (disconnect, pressure release, isolation, after-cooling, level maintenance), PA1 the holding time in which active measures (replacement measures) must be taken, can be extended to approximately seven days, PA1 active measures can then either be in the form of the start-up of existing systems or of the simple addition to the water reservoir, such as by means of fire department connections, PA1 to temper the effects of extremely unlikely core meltdowns, at least one fall back position (such as in-vessel control of the core melt, or ex-vessel cooling of an escaped core melt) is available. 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 light water reactor, in particular a boiling water reactor with a high degree of inherent safety, 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. |
abstract | A packing seal is provided for a system for sealing the shaft of a primary motor-driven pump unit of a nuclear reactor, intended to ensure sealing between the primary circuit and the atmosphere. The packing seal including a rotary active surface and a floating active surface, in which a face of the floating active surface and/or the rotary active surface is micro- or nano-structured by an array of holes or pillars, each hole or pillar having lateral dimensions and a height of between 10 nm and 5 μm, the distance between two consecutive holes or pillars being between 10 nm and 5 μm. |
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048184683 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention .sup.123 I has many advantages as a radionuclide for medicinal purposes. The radiation dose resulting from .sup.123 I is much reduced as compared to .sup.131 I or .sup.125 I. For most scanning situations .sup.123 I allows scanning to be accomplished with an acceptable dose. In addition, the gamma radiation emitted is ideal for imaging with scintillation cameras. The relatively short half-life of .sup.123 I allows other radionuclides to be used as well in diagnostic procedures without interference. The radiations resulting from .sup.123 I are readily shielded, so as to decrease radiation hazard to personnel. While the half-life is relatively short, the .sup.123 I half-life is sufficiently long to allow for purification and chemical labeling of compounds, delivery to the clinician, and utilization of the .sup.123 I by the clinician. Finally, .sup.123 I does not have undesirable particulate radiation. In preparing the .sup.123 I there are a number of significant considerations. Important to the process is the production of .sup.123 I without the concomitant formation of other radionuclides which cannot be conveniently separated from the desired radionuclide and have undesirable properties, for example, particulate radiation. Because the equipment employed for the preparation of radionuclides is expensive and large amounts of energy are utilized, it is desirable that the use of the energy employed be highly efficient as it relates to the yield of the desired radionuclide. Other considerations include the cost of the target material, ease of processing, speed of processing and the like. DESCRIPTION OF THE PRIOR ART U.S. Pat. No. 3,694,313 discloses a process for preparing .sup.123 I from .sup.122 Te powder with alpha particles while passing a low flow rate helium stream through the powder to remove the xenon which is formed. U.S. Pat. No. 3,226,298 teaches irradiating tellurium dioxide with thermal neutrons at a temperature of at least about 550.degree. C. and then separating radioactive iodine-131 by distillation. Fusco, et al, J. of Nuclear Medicine 13, 729 (1972) describes the preparation of .sup.123 I by proton irradiation of .sup.127 I in a batch process. Weinreich, et al, Int. J. of Applied Radiation and Isotopes, 25, 535 (1974) teaches the preparation of .sup.123 I by irradiating solid sodium iodide in the presence of a continuous helium stream. SUMMARY OF THE INVENTION A method is provided for preparing medicinally and isotopically pure .sup.123 I by irradiating an XI (X is alkali metal or iodine) target with high energy particles to produce .sup.123 Xe. The target material is maintained in the liquid state, providing reflux as required, with a continual stream of helium, optionally containing xenon, passing through the target area, while maintaining the target temperature in a predetermined range. The helium carrier aids in temperature control and sweeps out the .sup.123 Xe radionuclide which is trapped in a cold trap and then purified by pumping the radioactive .sup.123 Xe to the final decay vessel. |
058752234 | summary | TECHNICAL FIELD The present invention relates to a design of a spacer for retaining elongated elements in a fuel assembly for a light-water nuclear reactor. More particularly, the invention relates to the design of a spacer sleeve for such a spacer. BACKGROUND OF THE INVENTION A fuel assembly in a boiling water nuclear reactor comprises a long tubular container, often with rectangular or square cross section, which is open at both ends forming a continuous flow passageway, through which the coolant of the reactor may flow. The fuel assembly comprises a large number of equally long tubular fuel rods, arranged in parallel in a certain definite, normally symmetrical pattern. The fuel rods are retained at the top by a top tie plate and at the bottom by a bottom tie plate. To allow coolant to flow past the fuel rods in the desired way, it is important that these be spaced from each other and prevented from bending or vibrating when the reactor is in operation. For this purpose, a plurality-of spacers are used, distributed along the fuel assembly in the longitudinal direction. A fuel assembly for a pressurized-water nuclear reactor has, in principle, the same construction as a fuel assembly for a boiling water nuclear reactor, except that the fuel rods are not enclosed by some tubular container and that the number of fuel rods is larger. In connection with repair and service of a nuclear reactor, foreign matter may enter the coolant. The foreign matter then moves with the coolant which is circulated in the reactor core. The foreign matter may consist of metal chips or pieces of metal wire. In those cases when the foreign matter adheres to the spacers or to other locations in the fuel assembly, it may give rise to wear damage on the elongated elements. The wear damage may have serious consequences, especially if it occurs on parts which are particularly fragile such as the fuel rods. This may be the case if the debris adheres to a spacer such that, because of the upwardly-flowing coolant, it is set into vibration thus wearing against one or more of the fuel rods which are positioned by the spacer. To avoid damage of the above kind, it is known to design various forms of debris-capturing means which are intended to be arranged below the fuel assembly in such a way that the coolant is forced to pass therethrough before it is passed into the fuel assembly. By arranging debris-separating means in this way, the main part of the foreign matter is prevented from entering the fuel assembly proper. A disadvantage with additional parts introduced in a fuel assembly is that they almost always lead to the increase of the pressure drop across the fuel assembly. The present invention relates to an alternative way of reducing the risk of wear on the fuel rods caused by foreign matter adhering to the upstream edge of the spacer. SUMMARY OF THE INVENTION According to one aspect of the present invention, a reduced risk of wear on the fuel rods by foreign matter is achieved by an alternative design of already known spacers. The invention is applicable to already-known spacers of the type comprising a grid structure of sleeves. By designing the upstream edge of such spacers with a wavy form, foreign matter captured towards the upstream edge of the spacer may be oriented such that it will not make contact with the elongated fuel rods positioned by the spacer. The wavy edge is suitably made such that that part of the upstream edge, which is arranged adjacent another sleeve to be joined together with this sleeve in the grid structure of the spacer, encounters the upwardly-flowing coolant after the coolant has encountered the edge between the joints. In this way, any foreign matter is oriented such that it is arranged between the elongated elements transversely of the flow direction when being captured. The captured foreign matter will thus make contact with that part of the wavy edge which is disposed at the joint with adjacently located sleeves in the grid structure and diagonally across the flow channel which is formed between the sleeves in an orthogonal grid structure, thus as far away from the rod surfaces as possible. In a particularly preferred embodiment of the invention, the sleeves are provided with elongated embossments adapted to coincide with that part of the edge which is arranged between the joints. The elongated embossments are adapted to substantially make contact with the fuel rods. By forming the spacer with a wavy edge, it can be given a low flow resistance while at the same time foreign matter which adheres to the upstream edge of the spacer is efficiently captured and oriented such that it does not make contact with and thus does not cause wear on the elongated elements. The low flow resistance is achieved by making the flow-preventing transverse area in a cross section through that part of the space which is provided with the wavy edge smaller than in a spacer with a substantially straight edge. |
abstract | Disclosed herein are systems and methods for a modular reconfigurable shielding system for one or more storage containers in temporary or long term storage. The system comprises shield panels which may be used to shield external faces of containers in a storage configuration to reduce the overall amount of shielding required in a storage facility. Reducing the amount of shielding reduces the storage footprint of each container thus increasing storage capacity and efficiency of the storage facility. The modularity of the shield panels allows storage containers to be easily added and removed from the storage configuration. Additionally, modular shielding allows the amount and type of shielding to be easily reconfigured for differing requirements and storage contents. |
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summary | ||
050911392 | summary | This invention relates to a thermal limit monitor system for a nuclear power plant. More particularly, an apparatus and process is disclosed for preventing in real time thermal limit violations caused by requested power increases. BACKGROUND OF THE INVENTION This invention relates to boiling water nuclear reactors. Such nuclear reactors increase their power output by two well known expedients. The first of these expedients is the increase in coolant flow through the reactor. Simply stated, increased coolant flow increases the amount of moderator present in the reactor. Fast neutrons from the nuclear reaction are moderated in greater number, promoting additional nuclear fission reactions and power output increases. Alternately, the nuclear reaction can be controlled by so-called "control rods". These rods when inserted within a reactor core absorb thermal neutrons and inhibit the nuclear reaction. When control rods are withdrawn, less thermal neutrons are absorbed. Instead of being absorbed, the thermal neutrons find their way into the promotion of further nuclear fission reactions. Power output increases, Those having skill in this art will realize that the above description constitutes a gross simplification; this simplification can help in the understanding of materials that follow. Nuclear fuels are typically arranged in fuel bundles. The fuel bundles themselves contain side-by-side tubes, the tubes being filled, and sealed at both ends with the fissionable material trapped inside. The water coolant in the reactor is relied upon to both moderate the fast neutrons and extract heat from the individual fuel rods. In the absence of the extraction of the heat from the individual fuel tubes, damage to the fuel can occur. One type of damage that can occur to tubes within a fuel bundle results from a departure from nucleate boiling. In nucleate boiling individual steam bubbles form on the tube surface (at so called bubble nucleation) as heat is transferred to the coolant. As the bubbles rapidly form and leave the tube surface a very agitated coolant condition exists at the tube surface promoting a very efficient heat transfer process--nucleate boiling. When a departure from nucleate boiling occurs a steam film forms adjacent to the wall of the tube. The steam film is inefficient in extracting heat from the tube. When such a steam bubble forms, it is possible that the metal of the tube can become overheated from the nuclear reaction and the structural integrity of the tube can be lost. To make absolutely certain that this type of casualty does not occur, all fuel bundles in boiling water reactor configurations are assigned bundle power limits to prevent a departure from nuclear boiling. Other types of damage to a fuel rod can occur as a result of an overpower condition even while operating in the nucleate boiling regime. The power level of a fuel rod determines the temperature distribution within the rod. A higher power level requires a higher rod operating temperature to drive the nuclear generated heat out of the rod to the coolant. Operation of fuel rods at too high a power level can result in fuel melting or fuel expansion that strains the confining tube the extent that tube failure occurs. These types of rod failure mechanisms depend on the power generated per unit length of fuel rod tube. A third type of catastrophic tube failure condition is possible during severe loss of coolant accident (LOCA). During a LOCA the moderator coolant is lost between the fuel rod tubes. The loss of the heat transfer medium causes the residual decay heat from the nuclear fuel to rapidly heat up the fuel tubes to high temperatures. At these high temperatures radiation heat transfer between tubes is a significant heat transfer process. It is a characteristic of radiation heat transfer to tend to transfer heat from hotter fuel tubes in the fuel bundle to colder tubes. Thus the peak fuel tube cladding temperature during a LOCA has been found to be limited by controlling the average fuel rod power at each axial elevation of a fuel bundle prior to a LOCA. This is possible because fuel rod residual decay heat power during a LOCA is directly proportional to operating fuel rod power prior to the LOCA. If fuel tubes become too hot (in excess of approximately 2200.degree. F.), the zircaloy alloy tubing metal chemically reacts vigorously within the steam environment. The chemical reaction releases combustible hydrogen gas and embrittles fuel tube cladding. High temperature cladding has reduced integrity for containing fuel and radioactive materials and is subject to shattering from the thermal shock of rapid cool down when the reactor system is reflooded with water during LOCA recovery. Limits are therefore imposed on the maximum average fuel rod operating power in a fuel bundle at each axial elevation prior to a LOCA, to limit the peak fuel rod tube cladding temperature that could be reached during a LOCA. The types of operating thermal limits can therefore easily be summarized. First, since the overall power output of a fuel bundle can result in a departure from nuclear boiling the overall power output of each fuel bundle is monitored to maintain nucleate boiling. The bundle power at which departure from nucleate boiling is predicted to occur, the critical power, is divided by the monitored bundle power and the ratio parameter termed the bundle critical power ratio, CPR. The CPRs of all bundles must exceed unity to prevent a departure from nucleate boiling. Second, it is of concern that no rod anywhere within a fuel bundle at any point exceed design temperatures. Since fuel rod temperatures are determined by the rod power per unit axial length, operating limits on rod linear power (power per unit length) are established. The operating linear powers of all sections of all fuel rods are effectively monitored and compared to the limits during operation. Finally, within each fuel bundle the average linear power at each elevation is determined and compared to limits to assure acceptable consequences during a potential LOCA. The classification of the above thermal limits is also subdivided. A first thermal limit is chosen and denominated as an "operating thermal limit". This operating thermal limit is a limitation of normal day to day steady operation. It is the object of routine nuclear plant operational power increases not to exceed these so-called operating thermal limits. Operating thermal limits include margin allowances for unplanned power increases or heat transfer degradation as might occur during abnormal system transients or accidents. In addition to the operating thermal limits, there is a second and more stringent limits known as safety thermal limits. The safety thermal limits reside at or near the point where damage to the fuel tubes can occur. Obviously, the goal of plant operation is to remain within operating thermal limits so that safety limits are never violated. Plant instrumentation is provided to assure that operating and safety limits are not violated on operator initiated power increases by core flow increases and control rod withdrawal. SUMMARY OF THE INVENTION In a boiling water reactor, the power output of the reactor is monitored by conventional local power range monitors. Preferably, these local power range monitors each measure the amount of thermal neutron flux present and output proportional electrical signals. These electrical signals give the power range of the reactor in the vicinity of the monitor. In a boiling water reactor, monitors are distributed throughout the whole reactor core in vertical strings. Each vertical string has a group of typically four power monitors attached to it. These power monitors are spaced in elevation such that the whole boiling water reactor core can be monitored both in columns and in rows. For purposes of both the prior art monitoring of the reactor and the monitor here, the reactor is subdivided into square columnar blocks of 16 fuel bundles in each block. For each block, there are assumed to be four monitor strings located at the four corners of the block. As there are four local power range monitors on each string and these local power range monitors are spaced equally vertically, the region is covered by a total of 16 local power range monitors. A region of such fuel bundles is controlled by four discrete control rods. If any or a combination of the four discrete control rods is withdrawn, the neutron flux increases, and thus the power will increase. Such power increase will be indicated on an immediate basis by the local power monitors. In prior automatic fuel protection instrumentation schemes, the prevention of exceeding thermal limits has been confined to the withdrawal of control rods with mandatory human supervising action required to maintain operating limits. Increases in flow that would violate operating or safety limits have not been automatically monitored and censured. Instead the reactor core is constrained to operating thermal limits at reduced core flows such that the power increase associated with a core flow increase to maximum system capability will not result in a violation of fuel safety thermal limits. Thus operator errors or flow control system failures that could result in violating of operating limits, but not safety limits, are recognized. The design philosophy which allows the unplanned short duration violation of operating limits relies on the small likelihood of an additional concurrent abnormal transient or accident event which could cause further degradation to violate safety limits. Sufficient instrumentation inputs are provided to the plant process computer such that the reactor operator is periodically provided a complete picture of the performance of reactor fuel in relationship to established operating limits. There is, however, no automatic enforcement of compliance to fuel thermal operating limits. The current situation is similar for operator initiated power increases by control rod withdrawal. Established operating limits assure that a single erroneous control rod withdrawal will not degrade fuel performance from operating limits to a safety limit violation. However, in this instance complete control rod withdrawal is not covered by the established operating limits. The local power increase associated with the completed withdrawal of some limiting control rods is so high that to do so would require very restrictive operating limits that could sometimes require reactor total power to be restricted below the design level in order to meet the requirement. Instead, during control rod withdrawal an automatic monitoring system is provided which utilizes the local power monitor signals as input to override the operator requested control rod withdrawal (viz. block further withdrawal) as necessary to assure fuel safety limits are not violated assuming withdrawal is initiated with fuel near the control rod on operating thermal limits. In current boiling water reactor (BWR) nuclear power stations, the analogous monitoring device is called a rod block monitor or RBM. The RBM uses the in-core power (neutron flux) monitors for its basic monitoring information source. The core power and thermal limit status then can be related by processing the readings of the local power monitors. The 16 local power monitors of each four corner strings are assigned to two channels in the prior art RBM: the bottom (A) and above the mid-plane (C) detectors in one channel, and the top (D) and the below the mid-plane (B) detectors in another channel. The average of the (typically 8) detector inputs in each channel forms an RBM signal. Block/Alarm occurs when the signal exceeds a preset setpoint. The RBM rod block setpoint to prevent safety limit violation is determined based on a theoretical core power and thermal limit calculation response prior to the beginning of each fuel cycle (i.e., the period between reactor refuelings). The calculation is based on the assumption that initially the core is operating at the operating limit, and that a rod withdrawal error is initiated from a hypothetically worst control rod pattern which gives the worst thermal limit change with control rod withdrawal. With such a continuous rod pull, the relative amount of RBM channel output increase which is accompanied by a thermal limit change from the operating limit to the safety limit is defined as the rod block setpoint. This rod block setpoint is thus dependent on assumed conservative initial conditions. Typically this setpoint is determined only for the rated power rated flow condition. Consequently, this current method is not based on comprehensive study of the correlation between thermal limit change and RBM signal change, and does not consider the true existing absolute thermal margins of the core. Experience has shown that current RBM setpoints restrict (block) control rod withdrawal much more often than necessary and is conservative. However, it can be seen that with such a system based upon the assumption of initial operation within an operating limit, that defeat of the safety system would be possible. Simply stated, by making assumptions of operation within thermal operating limits in succession and requesting rod withdrawals in succession, multiple sequential requests could cause violation of the thermal limits. However, since conservative values between instrument response and core power increase are normally chosen, these conservative values while assuring and contributing to the remarkable safety record of nuclear power plants to date, unnecessarily inhibit operation of the plant in maneuvering from a low power state to a higher power state. Further, since the effects of flow increase are ignored in such rod blocks, a level of automatic safety precaution is omitted which would be desirable to include. It should be understood that nuclear reactors can be continuously monitored by online computers. Typically, these online computers recurrently put together three dimensional core thermal performance profiles which accurately predict both the thermal state of the core as well as the local power range monitor readings. Unfortunately, even though such computations are now performed by modern fast computers in the order of once every two minutes, they are insufficient in their speed to provide "real time" rapid response predictions of the consequences of planned reactor flow or control rod position changes relative to fuel thermal limit performance. Accordingly, there is a need for an automated thermal limit monitor which will inhibit in real time requests made for increased power that would violate either operating or safety limits, whether it be based upon rod withdrawal or increases in coolant flow. SUMMARY OF THE INVENTION A computed model of reactor power output is read periodically to computer memory and retained in memory in a three dimensional matrix. This retention occurs between regular updates on the order of every two minutes. The reactor is conventionally monitored in groups of 16 fuel bundles each. Each 16 bundle group is monitored in real time as to its thermal neutron flux by four vertical strings of local power range monitors, each string having one of four power monitors disposed at four different elevations extending the height of the fuel in core. Each bundle group is controlled by four control rods and is assumed to be subject to uniform flow change with overall reactor flow change. The automated thermal limit monitor (ATLM), takes as inputs all power range monitor information from the BWR reactor core on a continuous basis to two channels, one channel for determining operating limits, the other channel for determining safety limits. (Redundant functional configurations can be implemented in each channel if desired for increased reliability but is not assumed in the reference configuration discussed.) These signals are processed inside the system according to different algorithm requirements for the protection of fuel thermal limits, i.e., minimum critical power ratio (MCPR) and maximum linear heat generation rate (MLHGR). (Extension of the MLHGR procedures discussed to the singular maximum average planar linear heat generation thermal limit parameter (MAPLHGR) is straight forward.) The system also takes as input the on-line absolute core thermal parameters limits, together with a set of built-in parameters called A and B factors which are functions of core power and control rod position, and the operating thermal parameter limit (or safety limit) at the current power and flow conditions. Based on the above information, the system calculates signal setpoint values for MCPR and MLHGR, respectively. The ratio of the instantaneously scanned power monitor value to that value at some initial state forms the ATLM signal. These setpoint values (normalized to some initial state) are compared with the instantaneously scanned ATLM signals continuously to determine whether a control rod withdrawal block command or core flow block command should be issued. If an instantaneously scanned and processed ATLM value approaches its setpoint, then rod block (or flow block) will be issued. This then assures that the core thermal limits are not violated on rod withdrawal or flow increases. This invention disclosure not only describes the system configuration and functional logic of rod block and flow block, it also describes the design bases of the A and B factors in the system algorithm which are fundamental to the whole ATLM system. The configuration concept, functional logic, and the form and design of the A and B factors constitute the bulk of the ATLM design invention disclosure. An object of this invention is to disclose a system for blocking requests for core power increase in real time based upon a current model of the reactor thermal profile. An advantage of the disclosed process and apparatus is that it is applicable both to requests for rod withdrawal and to requests for flow increase. An additional advantage is that manipulation of the plant can include rod blockage when operating thermal limits versus safety thermal limits are in danger of violation. No longer is it required to have a system for monitoring requests for increased power theoretically issuing block orders based upon safety limits. A further advantage of the disclosed system is that it can be utilized in a backup module to monitor and block requests for power increase when safety limits are approached. It is ideal for the high degree of operating safety redundancy required in nuclear plants. An additional advantage of the disclosed system is that the operator is assisted in real time of avoiding violation of operating thermal limits. This avoidance of violation is based upon the absolute and current operating thermal state of the reactor. Consequently, the operator is assisted in achieving optimized radial and axial power shapes during power ascension to rated condition throughout rated power operation. Yet another advantage of this invention is that since the system is based on actual online local power range monitor results, the reactor can be operated with better flexibility within its thermal limits. Since blockages only occur based upon the difference between the actual operating state of the reactor and the requested power increase, overly conservative practices relating to local power range monitor output are no longer required. The disclosed protocol within its metes and bounds assures operation within the operating thermal limits. Summarizing the functional operational objectives of the system it will be found that the disclosed system: a) Adapts core thermal limit information from the plant process computer and the local power information from the NMS (Neutron Monitoring System). to perform comparisons based on its own algorithm independent of the process computer, and to issue rod block (or flow block) commands when the absolute operating thermal limit is approached. In the event the operating limit rod block function fails, a backup module will issue a rod block command when the safety limit is approached. b) Through rod block function and estimated thermal limit by the ATLM, the operator is assisted not only in avoiding violation of operating thermal limit but also in achieving optimized radial and axial power shapes during power ascension to rated condition and throughout rated power operation. c) Utilizes actual on-line core monitor results for better flexibility in rod withdrawal maneuvers. With ATLM, the rod(s) can be withdrawn until the operating limit is reached. d) With its independent protection algorithm which is based on absolute core thermal limits, the ATLM allows for automated control rod operation. The RBM will not be able to allow for automated control rod operation because it is not based on absolute core thermal limit and it assumes the core is always on or having a margin from the operating limit. Consequently, it cannot automatically provide the operating limit protection the ATLM can for automated control rod operation where repeated requests are made to withdraw a control rod that would result in a thermal limits violation if allowed to proceed if only RBM is used. |
description | 1. Field of the Invention The present invention relates to an arrangement of devices suitable to downsize a synchrotron. The invention also relates to a synchrotron using such an arrangement and a particle therapy system using the synchrotron. 2. Description of the Related Art In the aging society of recent years, as one of cancer treatments, a radiation treatment, which applies less load on a human body and enables the quality of life to be maintained at a high level after the treatment, has attracted attention. A particle therapy system that uses a charged particle beam (such as protons or carbon) accelerated by a synchrotron provides a high dose concentration to an affected part and has been expected as a promising system. The particle therapy system includes an injector, the synchrotron and an irradiation device. The injector supplies a charged particle beam to the synchrotron. The synchrotron accelerates the charged particle beam so that the speed of the charged particle beam becomes close to the speed of light. The irradiation device irradiates a patient with the charged particle beam extracted from the synchrotron on the basis of the position and shape of an affected part of the patient. There is a demand to reduce the size and cost of the particle therapy system in order to expand use of the particle therapy system. As one of methods for extracting the beam from the synchrotron, there is an extraction method called a slow extraction method (resonance extraction method). The slow extraction method is different from a quick extraction method in which the entire charged particle beam is extracted during one circulation of the charged particle beam in the synchrotron. When the slow extraction method is used, the charged particle beam can be slowly extracted during a plurality of circulations of the charged particle beam in the synchrotron. The extracted beam is mainly used for a particle therapy or a physics experiment. FIG. 4 illustrates a first example of a conventional synchrotron. A synchrotron 200 includes an injection deflection device 201 (SM, ESI), deflection magnets 202 (BM), focusing quadrupole magnets 203 (QF), defocusing quadrupole magnets 204 (QD), a radio frequency acceleration cavity 205 (RF-cavity), a resonance excitation multi-pole magnet 206 (SXFr, SXDr; only one resonance excitation multi-pole magnet is illustrated in FIG. 4), an extraction radio frequency device 207 (RF-KO), a first extraction deflector 208 (ESD) and a second extraction deflector 209 (SMI). The injection deflection device 201 causes a beam that is accelerated by a pre-accelerator 101 to be injected into the synchrotron 200. The deflection magnets 202 each deflect the injected beam and cause the beam to circulate in the synchrotron 200. The focusing quadrupole magnets 203 each cause the beam to stably circulate in the synchrotron 200 and focus the beam in a horizontal direction in order to prevent an increase in the size of the beam. The defocusing quadrupole magnets 204 each defocus the beam in the horizontal direction. The radio frequency acceleration cavity 205 accelerates and decelerates the beam. The resonance excitation multi-pole magnet 206 forms a separatrix for an oscillation (betatron oscillation) of the beam in order to cause the beam to be slowly extracted. The extraction radio frequency device 207 increases the amplitude of the oscillation of the beam and thereby leads the beam to the outside of the separatrix. The first extraction deflector 208 and the second extraction deflector 209 deflect the beam, change a path of the beam and cause the beam to be extracted from the synchrotron in order to introduce the accelerated and/or decelerated beam into an irradiation device. In order to extract the beam from the synchrotron using the slow extraction method, the resonance excitation multi-pole magnet 206 excites resonance and forms the separatrix, and the extraction radio frequency device 207 increases the amplitude of the beam and thereby leads the beam to the outside of the separatrix. The amplitude of the beam that is led to the outside of the separatrix is further increased, and the beam propagates into the first extraction deflector 208. Then, the beam that propagates into the first extraction deflector 208 is deflected by the first extraction deflector 208, thereby being distanced from a beam that circulates in the synchrotron. The charged particle beam that is deflected by the first extraction deflector 208 is further deflected by the defocusing quadrupole magnet 204 (located on the downstream side of the first extraction deflector 208) toward the outer side of the synchrotron 200 in the horizontal direction. The charged particle beam that is deflected by the defocusing quadrupole magnet 204 toward the outer side of the synchrotron 200 in the horizontal direction passes through the deflection magnet 202 and is deflected by the focusing quadrupole magnet 203 (located on the downstream side of the defocusing quadrupole magnet 204) toward the inner side of the synchrotron 200 in the horizontal direction. Then, the charged particle beam is deflected by the second extraction deflector 209 toward the outer side of the synchrotron 200 in the horizontal direction and extracted from the synchrotron 200. FIGS. 4 to 6 illustrate arrangements of main parts of synchrotrons described in “DESIGN OF SYNCHROTRON AT NIRS FOR CARBON THERAPY FACILITY”, Proceedings of APAC 2004, p 420-422, Gyeongju, Korea, “A NOVEL PROTON AND LIGHT ION SYNCHROTRON FOR PARTICLE THERAPY”, Proceedings of EPAC 2006, p 2305-2307 Edinburgh, Scotland, and “LATTICE DESIGN OF A CARBON-ION SYNCHROTRON FOR CANCER THERAPY”, Proceedings of EPAC 2008, p 1803-1805, Genoa, Italy (hereinafter referred to as Non-Patent Documents 1 to 3). The synchrotron illustrated in FIG. 4 is described above as a conventional technique. As well as the synchrotron illustrated in FIG. 4, the The synchrotrons illustrated in FIGS. 5 and 6 each have a plurality of quadrupole magnets 203,204 that are arranged between a first extraction deflector 208 (ESD described in Non-Patent Documents 1 and 3 and SS2 described in Non-Patent Document 2) and a second extraction deflector 209 (SM1 described in Non-Patent Documents 1 and 3 and SS4 described in Non-Patent Document 2) in order to prevent an increase in the size of a beam. In each of these cases, the number of devices is large. Thus, there is a limitation in reducing the size of the synchrotron. In addition, the extracted beam is deflected back to the inner side of the synchrotron (or to the side of a circulating beam) by the focusing quadrupole magnets 203 arranged between the first extraction deflector 208 and the second extraction deflector 209. In order to compensate for the deflection, it is necessary to set a deflection angle of the first extraction deflector 208 to a large angle. As the first extraction deflector 208, a device that is called an electrostatic deflector (ESD) (electrostatic extraction septum described in Non-Patent Document 2) is used in order to reduce beam loss. In order to increase a deflection angle per unit length of the electrostatic deflector, it is necessary to increase the intensity of an electric field. There is, however, a limitation to the intensity of the electric field in order to avoid discharge. Thus, in order to extract a charged particle beam with higher energy than protons or helium from the synchrotron, an electrostatic deflector that has a long length in a circumferential direction of the synchrotron and can deflect the beam at a sufficient angle needs to be arranged. This prevents the synchrotron from being downsized. As an invention that solves those problems, JP-A-10-162999 describes that defocusing quadrupole magnets 204 are arranged on inlet and outlet sides of a deflection magnet arranged between a first extraction deflector 208 and a second extraction deflector 209 as an example, as illustrated in FIG. 7. In this case, since the number of quadrupole magnets is increased, there is a limitation in downsizing the synchrotron. JP-A-10-162999 describes an example in which the deflection magnet is divided into magnets, a focusing quadrupole magnet 203 is arranged between the divided magnets, and defocusing quadrupole magnets 204 are arranged on the inlet side of an upstream-side magnet among the divided magnets and on the outlet side of a downstream-side magnet among the divided magnets. In this case, the number of devices is increased, and there is a disadvantage in downsizing the synchrotron. An object of the present invention is to downsize a synchrotron by reducing the number of quadrupole magnets and reducing the length of an extraction deflector while suppressing an increase in the size of a beam. In addition, another object of the present invention is to provide a particle therapy system that includes the synchrotron. In one aspect of the present invention, a plurality of deflection magnets 202 and a single defocusing quadrupole magnet 204 are arranged between a first extraction deflector 208 and a second extraction deflector 209, the single defocusing quadrupole magnet 204 is arranged between deflection magnets among the plurality of deflection magnets 204, and focusing quadrupole magnets 203 are arranged on the inlet side (upstream side) of the first extraction deflector 208 and on the outlet side (downstream side) of the second extraction deflector 209. According to the one aspect of the present invention, the plurality of deflection magnets are arranged between the first extraction deflector 208 and the second extraction deflector 209. The single quadrupole magnet is arranged between the deflection magnets among the plurality of deflection magnets. The quadrupole magnets are arranged on the inlet side of the first extraction deflector 208 and on the outlet side of the second extraction deflector 209. Thus, the number of quadrupole magnets arranged between the first extraction deflector 208 and the second extraction deflector 209 can be reduced while an increase in the size of the beam is suppressed. This reduces a space in which devices are arranged. In addition, the single quadrupole magnet that is arranged between the deflection magnets among the plurality of deflection magnets (arranged between the first extraction deflector 208 and the second extraction deflector 209) is the defocusing quadrupole magnet. The quadrupole magnets that are arranged on the inlet side of the first extraction deflector 208 and on the outlet side of the second extraction deflector 209 are the focusing quadrupole magnets. Thus, an effect of deflecting the extracted beam toward the outer side of the synchrotron in a horizontal direction can be added, and there is no effect of deflecting the extracted beam (that has been deflected by the first extraction deflector 208) back to the side of a circulating beam by means of the quadrupole magnet. Thus, a deflection angle (kick angle) of the first extraction deflector 208 can be set to a small angle, and an incident angle of the beam on the second extraction deflector 209 can be set to a large angle. That is, the number of quadrupole magnets can be reduced and the first extraction deflector 208 and the second extraction deflector 209 can be downsized. As a result, the synchrotron can be downsized. Embodiments of the present invention are described below with reference to the accompanying drawings. The configuration of a synchrotron according to a first embodiment of the present invention is described below with reference to FIG. 1. A particle therapy system includes a beam injection system 100, a synchrotron 200 and a beam transport/irradiation system 300. The beam injection system 100 has a pre-accelerator and a transport system. The pre-accelerator accelerates a charged particle beam (hereinafter also referred to as beam) until the beam has energy that is sufficient for the beam to be injected into the synchrotron 200. The transport system transports the beam. The synchrotron 200 accelerates the injected beam until the beam has desired energy. The beam transport/irradiation system 300 transports the beam accelerated and extracted from the synchrotron 200 to a target to be irradiated and irradiates the target with the beam. In addition, the particle therapy system includes a control system (including an injection control device 110, a synchrotron control device 210 and a beam transport/irradiation system control device 310) and a central control device 400. The injection control device 110 controls the beam injection system 100 via a power source 100a thereof. The synchrotron control device 210 controls the synchrotron 200 via power sources 201a-209a thereof. The beam transport/irradiation system control device 310 controls the beam transport/irradiation system 300 via a power source 300a thereof. The central control device 400 controls the entire particle therapy system. The synchrotron 200 includes an injection deflection device 201, deflection magnets 202, focusing quadrupole magnets 203, defocusing quadrupole magnets 204, a radio frequency acceleration cavity 205, a resonance excitation multi-pole magnet 206, an extraction radio frequency device 207, a first extraction deflector 208 and a second extraction deflector 209. The injection deflection device 201 causes the beam to be injected into the synchrotron 200. The deflection magnets 202 each deflect the injected beam. The focusing quadrupole magnets 203 each focus the beam. The defocusing quadrupole magnets 204 each defocus the beam. The radio frequency acceleration cavity 205 accelerates and decelerates the beam. The resonance excitation multi-pole magnet 206 forms a separatrix for an oscillation (betatron oscillation) of the beam. The extraction radio frequency device 207 increases the amplitude of the oscillation of the beam and thereby leads the beam to the outside of the separatrix. The first extraction deflector 208 and the second extraction deflector 209 deflect the beam, change a path of the beam and cause the beam to be extracted from the synchrotron 200. As one of slow extraction methods for extracting the beam from the synchrotron, there is a diffusion resonance extraction method. In the diffusion resonance extraction method, the resonance excitation multi-pole magnet 206 excites resonance and forms the separatrix, and the extraction radio frequency device 207 increases the amplitude of the beam and thereby leads the beam to the outside of the separatrix. The amplitude of the beam that is led to the outside of the separatrix is further increased. Then, the beam propagates into the first extraction deflector 208. The first extraction deflector 208 has an effect of separating a beam to be extracted from the synchrotron 200 from a beam that circulates in the synchrotron 200. Thus, the thickness of a septum needs to be small as much as possible, and beam loss needs to be reduced as much as possible. In the first embodiment, an electrostatic deflector is used as the first extraction deflector 208. In the present embodiment, two deflection magnets and a single defocusing quadrupole magnet are arranged between the first extraction deflector 208 and the second extraction deflector 209 so that a separation of the extracted beam from the circulating beam at an inlet of the second extraction deflector 209 is ensured efficiently by a small deflection angle. The defocusing quadrupole magnet is arranged between the two deflection magnets in order to suppress an increase in the size of the circulating beam. A focusing quadrupole magnet 203 is arranged on the upstream side of the first extraction deflector 208, while a focusing quadrupole magnet 203 is arranged on the downstream side of the second extraction deflector 209 (on a path of the circulating beam). In the present embodiment, the plurality of deflection magnets 202 are arranged between the first extraction deflector 208 and the second extraction deflector 209. The single quadrupole magnet 204 is arranged between two of the deflection magnets 202. The quadrupole magnet 203 is arranged on the upstream side of the first extraction deflector 208 (or the quadrupole magnet 203 and the first extraction deflector 208 are arranged in this order from the upstream side in a traveling direction of the beam that circulates in the synchrotron). The quadrupole magnet 203 is arranged on the downstream side of the second extraction deflector 209 (or the second extraction deflector 209 and the quadrupole magnet 203 are arranged in this order from the upstream side in the traveling direction of the beam that circulates in the synchrotron). In this configuration, the number of quadrupole magnets arranged between the first extraction deflector 208 and the second extraction deflector 209 can be reduced while an increase in the size of the beam is suppressed. Thus, a space in which devices are arranged can be reduced. In the present embodiment, the single quadrupole magnet that is arranged between the deflection magnets 202 arranged between the first extraction deflector 208 and the second extraction deflector 209 is the defocusing quadrupole magnet 204. The quadrupole magnet that is arranged on the upstream side of the first extraction deflector 208 is the focusing quadrupole magnet 203. The quadrupole magnet that is arranged on the downstream side of the second extraction deflector 209 is the focusing quadrupole magnet 203. In this configuration, an effect of deflecting the extracted beam toward the outer side of the synchrotron in the horizontal direction can be added, and there is no effect of deflecting the extracted beam (that has been deflected by the first extraction deflector 208) back to the side of the circulating beam by means of the quadrupole magnet. Thus, the deflection angle (kick angle) of the first extraction deflector 208 can be set to a small angle and an incident angle of the beam on the second extraction deflector 209 can be set to a large angle. Thus, the number of quadrupole magnets can be reduced, while the first extraction deflector 208 and the second extraction deflector 209 can be downsized. As a result, the synchrotron can be downsized. In the present embodiment, a distance between the focusing quadrupole magnet 203 (arranged on the upstream side of the first extraction deflector 208) and the defocusing quadrupole magnet 204 (arranged between the first extraction deflector 208 and the second extraction deflector 209) and a distance between the defocusing quadrupole magnet 204 (arranged between the first extraction deflector 208 and the second extraction deflector 209) and the focusing quadrupole magnet 203 (arranged on the downstream side of the first extraction deflector 209) can be set to equal to each other. If the distances are largely different from each other, the size of the beam increases in long regions located between the quadrupole magnets in general. In the present embodiment, since the distances are equal to each other, the number of quadrupole magnets arranged between the first extraction deflector 208 and the second extraction deflector 209 can be reduced while an increase in the size of the beam is suppressed. Thereby, the space in which the devices are arranged can be reduced. In addition, the quadrupole magnet that is arranged between the first extraction deflector 208 and the second extraction deflector 209 is the defocusing quadrupole magnet 204. Thus, the effect of deflecting the extracted beam toward the outer side of the synchrotron in the horizontal direction can be added, and there is no effect of deflecting the extracted beam (that has been deflected by the first extraction deflector 208) back to the side of the circulating beam by means of the quadrupole magnet. As a result, the kick angle of the first extraction deflector 208 can be set to a small angle and the incident angle of the beam on the second extraction deflector 209 can be set to a large angle. Thus, the number of quadrupole magnets can be reduced, and the first extraction deflector 208 and the second extraction deflector 209 can be downsized. As a result, the synchrotron can be downsized. In the present embodiment, the diffusion resonance extraction method is used as the slow extraction method. In addition, there are a method for extracting the beam by changing the size of the separatrix, a method in which a device that is called a betatron core is used (refer to Non-Patent Document 3), a method for causing the beam to contact a scatterer and thereby deflecting the beam, and the like. These methods are to lead the beam to the first extraction deflector 208. When any of the methods is used, the same effects as described above can be obtained. In the present embodiment, the distance between the focusing quadrupole magnet 203 (arranged on the upstream side of the first extraction deflector 208) and the defocusing quadrupole magnet 204 (arranged between the first extraction deflector 208 and the second extraction deflector 209) and the distance between the defocusing quadrupole magnet 204 (arranged between the first extraction deflector 208 and the second extraction deflector 209) and the focusing quadrupole magnet 203 (arranged on the downstream side of the first extraction deflector 209) are equal to each other. The distances, however, may not be equal to each other. The distances may be different from each other as long as an increase in the size of the beam is in an acceptable range. The configuration of a synchrotron according to a second embodiment of the present embodiment is described below with reference to FIG. 2. In the present embodiment, three deflection magnets 202 and a single defocusing quadrupole magnet 204 are arranged between the first extraction deflector 208 and the second extraction deflector 209. In order to suppress an increase in the size of a beam circulating in the synchrotron, the defocusing quadrupole magnet 204 is arranged between a deflection magnet that is among the three deflection magnets 202 and arranged on the most upstream side in the traveling direction of the beam circulating in the synchrotron and a deflection magnet that is among the three deflection magnets 202 and arranged on the second most upstream side in the traveling direction of the beam circulating in the synchrotron. In addition, a focusing quadrupole magnet 203 is arranged on the upstream side of the first extraction deflector 208 (or the quadrupole magnet 203 and the first extraction deflector 208 are arranged in this order from the upstream side in the traveling direction of the beam circulating in the synchrotron). A focusing quadrupole magnet 203 is arranged on the downstream side of the second extraction deflector 209 (or the second extraction deflector 209 and the quadrupole magnet 203 are arranged in this order from the upstream side in the traveling direction of the beam circulating in the synchrotron). In the present embodiment, the difference between a distance between the focusing quadrupole magnet 203 (arranged on the upstream side of the first extraction deflector 208) and the defocusing quadrupole magnet 204 (arranged between the first extraction deflector 208 and the second extraction deflector 209) and a distance between the defocusing quadrupole magnet 204 (arranged between the first extraction deflector 208 and the second extraction deflector 209) and the focusing quadrupole magnet 203 (arranged on the downstream side of the second extraction deflector 209) can be small, compared with an arrangement in which the defocusing quadrupole magnet 204 is arranged on the inlet side (upstream side) of the deflection magnet that is among the three deflection magnets 202 and arranged on the most upstream side (or compared with an arrangement in which the defocusing quadrupole magnet 204 is arranged on the outlet side (downstream side) of the deflection magnet that is among the three deflection magnets 202 and arranged on the most downstream side). In this configuration, the number of quadrupole magnets arranged between the first extraction deflector 208 and the second extraction deflector 209 can be reduced while an increase in the size of the beam is suppressed. Thus, a space in which devices are arranged can be reduced. The quadrupole magnet that is arranged between the first extraction deflector 208 and the second extraction deflector 209 is the defocusing quadrupole magnet 204. Thus, the effect of deflecting the extracted beam toward the outer side of the synchrotron can be added, and there is no effect of deflecting the extracted beam (that has been deflected by the first extraction deflector 208) back to the side of the circulating beam by means of the quadrupole magnet. Thus, the kick angle of the first extraction deflector 208 can be set to a small angle, and the incident angle of the beam on the second extraction deflector 209 can be set to a large angle. The aforementioned effects make it possible to reduce the number of quadrupole magnets and downsize the first extraction deflector 208 and the second extraction deflector 209. As a result, the synchrotron can be downsized. In the present embodiment, the single defocusing quadrupole magnet 204 (arranged between the first extraction deflector 208 and the second extraction deflector 209) is arranged between the deflection magnet that is among the three deflection magnets 202 and arranged on the most upstream side in the traveling direction of the beam circulating in the synchrotron and the deflection magnet that is among the three deflection magnets 202 and arranged on the second most upstream side in the traveling direction of the beam circulating in the synchrotron. The single defocusing quadrupole magnet 204 that is arranged between the first extraction deflector 208 and the second extraction deflector 209 may be arranged between the deflection magnet that is among the three deflection magnets 202 and arranged on the second most upstream side in the traveling direction of the beam circulating in the synchrotron and the deflection magnet that is among the three deflection magnets 202 and arranged on the most downstream side in the traveling direction of the beam circulating in the synchrotron. The configuration of a synchrotron according to a third embodiment of the present invention is described below with reference to FIG. 3. In the present embodiment, a combined function magnet or combined function magnets (n-indexed magnet) 202CB are arranged between the first extraction deflector 208 and the second extraction deflector 209. The combined function magnets 202CB each have a defocusing quadrupole function obtained by combining the function of the deflection magnet with the function of the defocusing quadrupole magnet. In the present embodiment, since the combined function magnet 202CB has the defocusing quadrupole function, the effect of deflecting the extracted beam toward the outer side of the synchrotron can be added and there is no effect of deflecting the extracted beam (that has been deflected by the first extraction deflector 208) back to the side of the circulating beam by means of the quadrupole magnet. Thus, the kick angle of the first extraction deflector 208 can be set to a small angle, and the incident angle of the beam on the second extraction deflector 209 can be set to a large angle. The aforementioned effects make it possible to reduce the number of quadrupole magnets and downsize the first extraction deflector 208 and the second extraction deflector 209. As a result, the synchrotron can be downsized. In the third embodiment described above, a combined function magnet or combined function magnets 202CB are arranged between the first extraction deflector 208 and the second extraction deflector 209. Alternatively, for instance, a combined function magnet and a deflection magnet may be arranged between the first extraction deflector 208 and the second extraction deflector 209. Such a modified embodiment also provides the same advantages as the third embodiment. |
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052221130 | description | DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Referring to the drawing, reference numeral 1 identifies the X-ray source in the microscope. This X-ray source is a plasma focus source of the kind described in U.S. Pat. No. 4,596,030 incorporated herein by reference. This plasma focus source supplies a point-shaped plasma for short times. The plasma emits X-radiation at a dominant emission wavelength on the Lyman-.alpha. line of six-times ionized nitrogen. The plasma focus source 1 is driven by a capacitor bank 2 which is electrically charged in the time between discharges. The X-radiation emanating from the plasma focus 1a is focussed with the aid of a reflecting condenser 3 on the specimen mounted on a specimen holder 4. The reflecting condenser 3 has the form of a rotational ellipsoid and reflects the X-radiation incident on its mirror surfaces at a grazing incidence. The reflecting condenser 3 is closed off at one or both ends thereof by respective foils 15 and 16 which protect the sensitive mirror surfaces against contamination. The foils are produced from a material such as polyimide which is absorbent as little as possible in the spectral range of the X-radiation. A so-called microzone plate 5 is mounted above the specimen plane. This microzone plate defines the actual imaging optics of the X-ray microscope. The spacing of the microzone plate 5 from the specimen plane is greatly exaggerated in the schematic. Actually, the microzone plate has a diameter of 20 to 50 .mu.m and is disposed only a few tenths of a millimeter above the specimen to be investigated. The microzone plate 5 images the specimen greatly enlarged on a detector 6. The detector 6 is a solid-state camera in the form of a CCD-camera such as a camera having the product number NXA 1011 of the Valvo company which is a corporation doing business in Germany. The detector 6 is sensitized for the X-radiation in that the cover glass is removed and the photosensitive surface is covered with a fluorescence colorant such as Gd.sub.2 O.sub.2 S:Tb. The CCD-camera 6 is mounted on a carrier 7 which can be displaced along the optical axis as indicated by the arrow with the aid of an adjusting device 8 for the purpose of focussing or magnification changing. The focussing itself is preferably done by changing the distance between the microzone plate and the specimen. The components of the X-ray microscope described above are arranged in a cylindrical column 9 mounted on the capacitor bank 2. The column 9 is at a vacuum and the space around the specimen stage 4 can be filled with a gas such as helium or hydrogen which is only slightly absorbent in the range of the X-radiation used and the space is separated from the vacuum system by means of two X-ray transparent foils (not shown). The signal lines of the CCD-camera 6 are passed through the adjusting device 8 and are connected to an electronic unit 10 which reads out the image of the CCD-camera 6. This camera electronic unit 10 is synchronized via a control unit 11 with the electronics (not shown) for the operation of the plasma focus source in such a manner that after each X-ray pulse supplied by the plasma focus source 1, an image is taken in and stored in an image memory 13. The images stored there can be viewed by means of a monitor 12 likewise connected to the electronic unit 10. Variations from the configuration described herein are within the scope of the invention. Accordingly, an X-ray film cassette can be used in lieu of the CCD-camera 6. In addition, other mirror optics can be used in lieu of the reflecting condenser in the form of a rotation ellipsoid operating at grazing incidence. An example of such other mirror optic is a mirror arrangement of the so-called Schwarzschild type which is described, for example, on page 566 of the reference text of K. Mutze et al entitled "ABC der Optik", published by Werner Dausien (1972). It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims. |
abstract | A focused ion beam device is described comprising a gas field ion source with an analyzer for analyzing and classifying the structure of a specimen, a controller for controlling and/or modifying the structure of the specimen according to the analysis of the analyzer, an emitter tip, the emitter tip has a base tip comprising a first material and a supertip comprising a material different from the first material, wherein the supertip is a single atom tip and the base tip is a single crystal base tip. Furthermore, the focused ion beam device has a probe current control and a sample charge control. A method of operating a focused ion beam device is provided comprising applying a voltage between a single emission center of the supertip and an electrode, supplying gas to the emitter tip, analyzing and classifying the structure of a specimen, and controlling the structure of the specimen. |
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claims | 1. An anti-scatter X-ray raster, for placing between a radiation detector and an object under study, said anti-scatter X-ray raster comprising: a plurality of channels for X-ray transporting connected together to form a cellular structure, walls of the said channels comprising a material capable of absorbing X-rays, wherein said channels are tubular with the orientation of the walls of all said channels being in a same in a longitudinal direction and the walls are in a form of cylindrical surface or a lateral surface of a prism and form a honeycomb structure and the walls of the neighboring channels are fused with each other; and an input end of said channels and an output end of said channels, wherein the input end and output end of the said channels are placed in two parallel planes, being perpendicular to the longitudinal direction of the said channels, wherein the largest cross size d of a single channel and its length H meet a relationship 2d/H greater than xcex8 c where xcex8 c = p /E is the critical angle of total external reflection of X-rays from the walls of the channels transporting X-rays, for the material of the walls, xcfx89 p is the plasma frequency of the material of the channels"" walls, E is energy of radiation quanta. 2. A raster according to claim 1 , wherein the walls of the channels for X-ray transporting comprise lead glass. claim 1 3. A raster according to claim 1 , wherein the walls of the channels for X-ray transporting comprise metal. claim 1 4. A raster according to claim 1 , wherein the walls of the channels for X-ray transporting comprise heavy metal. claim 1 5. A raster according to claim 1 , wherein the walls of the channels for X-ray transporting comprise a dielectric. claim 1 6. A raster according to claim 1 , wherein the channels for X-ray transporting are hollow. claim 1 7. A raster according to claim 1 , wherein the channels for X-ray transporting are filled with light metal. claim 1 8. A raster according to claim 1 , wherein the channels for X-ray transporting are filled with an organic material. claim 1 9. A raster according to claim 1 , wherein the channels for X-ray transporting are formed of glass mono or polycapillaries. claim 1 10. A raster according to claim 9 , wherein the walls of the channels for X-ray transporting comprise lead glass. claim 9 11. A raster according to claim 1 , wherein said raster comprises a parallelepiped cells, formed by the channels. claim 1 12. An anti-scatter X-ray raster, for placing between a radiation detector and an object under study, said raster comprising: a plurality of tubular channels for X-ray transporting, walls of said tubular channels comprising a material capable of absorbing X-rays, wherein an orientation of said walls of said tubular channels changes from the center of the raster to a periphery of the raster, wherein said walls of said tubular channels form truncated cones or truncated pyramids with a common top and form a honeycomb structure, said walls of the neighboring channels are fused with each other; inputs and outputs of said channels are placed on two concentric spherical surfaces with a center coinciding with said common top of the truncated cones or truncated pyramids, the walls of neighboring channels are spliced with each other such that the largest cross size d of a single channel for and its length H meet a relationship 2d/H greater than xcex8 c , where xcex8 c = p /E is the critical angle of total external reflection of X-rays from the walls of the channels transporting X-rays, for the material of the walls, xcfx89 p is the plasma frequency of the material of the channels"" walls, E is energy of radiation quanta. 13. A raster according to claim 12 , wherein the walls of the channels for X-ray transporting comprise lead glass. claim 12 14. A raster according to claim 12 , wherein the walls of the channels for X-ray transporting comprise metal. claim 12 15. A raster according to claim 12 , wherein the walls of the channels for X-rays transporting comprise heavy metal. claim 12 16. A raster according to claim 12 , wherein the walls of the channels for X-ray transporting comprise a dielectric. claim 12 17. A raster according to claim 12 , wherein the channels for X-ray transporting are hollow. claim 12 18. A raster according to claim 12 , wherein the channels for X-ray transporting are filled with light metal. claim 12 19. A raster according to claim 12 , wherein the channels for X-ray transporting are filled with an organic material. claim 12 20. A raster according to claim 12 , wherein the channels for X-ray transporting comprise glass mono or polycapillaries. claim 12 21. A raster according to claim 20 , wherein the walls of the channels for an X-ray transporting are made of lead glass. claim 20 22. A raster according to claim 12 , wherein said raster is formed as a narrow parallelepiped of cells, formed of the channels for X-ray transporting. claim 12 23. An anti-scatter X-ray raster, for placing between a radiation detector and an object under study, comprising: 2d/H greater than xcex8 c , a plurality of tubular channels for X-ray transporting, walls of the said channels comprising a material being capable of absorbing X-rays, wherein an orientation of the walls changes from a center of the raster to a periphery of the raster, wherein the walls of the tubular channels form truncated cones or truncated pyramids with a common top and form a honeycomb structure, said walls of the neighboring channels are fused with each other; and inputs and outputs of said tubular channels are placed in two parallel planes, which are perpendicular to an axis of one of the tubular channels, placed in the central zone of the raster, the walls of the neighboring channels are spliced with each other, wherein the largest cross size d of a singe channel for an X-rays transporting and its length H meet a relationship satisfy the correlation: where xcex8 c = p /E is the critical angle of total external reflection of X-rays from the walls of the channels transporting X-rays, for the material of the walls, xcfx89 p is the plasma frequency of the material of the channels"" walls, E is energy of radiation quanta. 24. A raster according to claim 23 , wherein the walls of the channels comprise lead glass. claim 23 25. A raster according to claim 23 , wherein the walls of the channels comprise metal. claim 23 26. A raster according to claim 23 , wherein the walls of the channels comprise heavy metal. claim 23 27. A raster according to claim 23 , wherein the walls of the channels comprise a dielectric. claim 23 28. A raster according to claim 23 , wherein the channels are hollow. claim 23 29. A raster according to claims 23 , wherein the channels are filled with light metal. 30. A raster according to claim 23 , wherein the channels are filled with an organic material. claim 23 31. A raster according to claim 23 , wherein the channels are formed of glasxcx9cmono or polycapillaries. claim 23 32. A raster according to claim 31 , wherein the walls of the channels comprise lead glass. claim 31 33. A raster according to claim 23 , wherein said raster is made parallelepiped of cells formed by the channels. claim 23 |
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summary | ||
summary | ||
abstract | A method and system of treating an interior surface on an internal cavity of a workpiece using a charged particle beam. A beam deflector surface of a beam deflector is placed within the internal cavity of the workpiece and is used to redirect the charged particle beam toward the interior surface to treat the interior surface. |
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claims | 1. A vapor-cell system comprising a bidirectional solid-state electrochemical charge-depletion capacitor and a vapor-cell region configured to allow at least one optical path into a vapor phase within said vapor-cell region,wherein said charge-depletion capacitor includes:(i) a first electrode disposed in contact with said vapor-cell region;(ii) a second electrode electrically isolated from said first electrode; and(iii) an ion conductor interposed between said first electrode and said second electrode,wherein said first electrode is permeable to mobile ions and/or neutral atoms formed from said mobile ions;wherein said ion conductor is ionically conductive for said mobile ions, andwherein said second electrode does not contain a second-electrode material that is capable of forming said mobile ions. 2. The vapor-cell system of claim 1, wherein said charge-depletion capacitor stores electrical charge by reduction-oxidation reactions, electrosorption, intercalation, or combinations thereof. 3. The vapor-cell system of claim 1, wherein said charge-depletion capacitor has an actuation voltage of about 100 V or less. 4. The vapor-cell system of claim 3, wherein said charge-depletion capacitor has an actuation voltage of about 10 V or less. 5. The vapor-cell system of claim 1, wherein said vapor-cell system is characterized by a vapor-cell time constant for said mobile ions of less than 1 second. 6. The vapor-cell system of claim 5, wherein said vapor-cell time constant is about 100 milliseconds or less. 7. The vapor-cell system of claim 1, wherein said vapor-cell vapor phase contains an alkali metal, an alkaline earth metal, or a combination thereof. 8. The vapor-cell system of claim 1, wherein said vapor-cell vapor phase contains mercury, ytterbium, aluminum, cadmium, or a combination thereof. 9. The vapor-cell system of claim 1, wherein said ion conductor is ionically conductive for at least one ionic species selected from the group consisting of Rb+, Cs+, Na+, K+, and Sr2+. 10. The vapor-cell system of claim 1, wherein said ion conductor is characterized by an ionic conductivity at 25° C. of about 10−7 S/cm or higher. 11. The vapor-cell system of claim 10, wherein said ion conductor is characterized by an ionic conductivity at 25° C. of about 10−5 S/cm or higher. 12. The vapor-cell system of claim 1, wherein said ion conductor contains said mobile ions. 13. The vapor-cell system of claim 1, wherein said ion conductor contains immobile ions having opposite charge of said mobile ions. 14. The vapor-cell system of claim 1, wherein said ion conductor comprises alumina, β-alumina, β″-alumina, yttria-stabilized zirconia, NASICON, LISICON, KSICON, or combinations thereof. 15. The vapor-cell system of claim 1, wherein said first electrode is fabricated from a metal selected from the group consisting of platinum, molybdenum, tungsten, and combinations thereof. 16. The vapor-cell system of claim 1, wherein said first electrode is in the form of a mesh, a grid, a porous material with open porosity, a parallel line pattern, a microwire array, a nanowire array, a lithographically patterned network, or a combination thereof. 17. The vapor-cell system of claim 1, wherein said second electrode is not in contact with said vapor-cell region. 18. The vapor-cell system of claim 1, wherein said second electrode is not permeable to said mobile ions or neutral atoms formed from said mobile ions. 19. The vapor-cell system of claim 1, wherein said second-electrode material is not capable of forming second-electrode ions, different than said mobile ions, which are mobile in said ion conductor. 20. The vapor-cell system of claim 1, wherein said second electrode is fabricated from a metal selected from the group consisting of platinum, molybdenum, tungsten, and combinations thereof. 21. The vapor-cell system of claim 1, said system further comprising an atom chip contained within said vapor-cell region. 22. The vapor-cell system of claim 1, wherein said vapor-cell system is configured to allow three optical paths into said vapor phase. 23. A magneto-optical trap apparatus, said apparatus comprising:(a) a bidirectional solid-state electrochemical charge-depletion capacitor;(b) a vapor-cell region configured to allow three orthogonal optical paths into a vapor phase within said vapor-cell region;(c) a source of laser beams configured to provide said three orthogonal vapor-cell optical paths through said vapor-cell gas phase, to trap a population of cold atoms; and(d) a magnetic-field source configured to generate magnetic fields within said vapor-cell region,wherein said charge-depletion capacitor includes:(i) a first electrode disposed in contact with said vapor-cell region;(ii) a second electrode electrically isolated from said first electrode; and(iii) an ion conductor interposed between said first electrode and said second electrode,wherein said first electrode is permeable to mobile ions and/or neutral atoms formed from said mobile ions;wherein said ion conductor is ionically conductive for said mobile ions, andwherein said second electrode does not contain a second-electrode material that is capable of forming said mobile ions. 24. An atomic-cloud imaging apparatus, said apparatus comprising:(a) a bidirectional solid-state electrochemical charge-depletion capacitor;(b) a vapor-cell region configured to allow three orthogonal optical paths into a vapor phase within said vapor-cell region;(c) a source of laser beams configured to provide said three orthogonal vapor-cell optical paths through said vapor-cell gas phase, to image a population of cold atoms; and(d) a magnetic-field source configured to generate magnetic fields within said vapor-cell region,wherein said charge-depletion capacitor includes:(i) a first electrode disposed in contact with said vapor-cell region;(ii) a second electrode electrically isolated from said first electrode; and(iii) an ion conductor interposed between said first electrode and said second electrode,wherein said first electrode is permeable to mobile ions and/or neutral atoms formed from said mobile ions;wherein said ion conductor is ionically conductive for said mobile ions, andwherein said second electrode does not contain a second-electrode material that is capable of forming said mobile ions. |
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042808723 | description | In FIG. 1, the reference numeral 1 generally designates the core of a fast reactor, the constructional detail of which is already well known and therefore does not appear to be of interest to anyone versed in the art. It can briefly be mentioned that the reactor core is constituted by a series of fuel assemblies 2, only the lower ends of which are shown diagrammatically in this figure. Said fuel assemblies are each provided in particular with a bottom end-fitting 2a which is adapted to engage in cylindrical support columns 3 carried in a horizontal diagrid 4. Said diagrid is formed by a top bearing plate 5 and a bottom support plate 6, said plates being braced by the columns 3 which receive the bottom end-fittings 2a of the fuel assemblies 2. A manifold 7 is thus defined between the plates 5 and 6 for a liquid metal which serves to cool the fuel assemblies during operation of the reactor. Said liquid metal is introduced under a suitable circulation pressure within the manifold 7 through large-section ducts 8 which are connected on the one hand to the diagrid and on the other hand to circulating pumps (not shown in the drawings), is admitted through lateral slots formed in the support columns 3, then into the bottom end-fittings 2a of the fuel assemblies and then flows upwards within these latter, the flow path of the liquid metal being shown diagrammatically by means of arrows in full lines. The diagrid 4 is in turn carried on a metallic structure 9 formed by mechanically welded sheet metal members 10. The constructional detail of said metallic support structure does not have any direct bearing on the invention and is therefore not shown in detail in the drawings. Beneath the diagrid 4, the support structure 9 comprises only a lateral cylindrical shell 11 joined to a base plate 12. Said base plate is in turn supported by means of a cylindrical shell 13 or the like on the bottom wall 14 of the pressure vessel of the reactor. In accordance with conventional practice, the pressure vessel contains the entire reactor core, the volume of liquid metal which is necessary for cooling the core and finally the pumps and heat exchangers which are arranged at intervals around the core, these structural elements having been omitted from the drawings. In accordance with another known arrangement, the bottom wall 14 of the pressure vessel and especially the sides are provided internally with a parallel lining plate or baffle wall 15 which extends over the entire surface of the side wall of the pressure vessel and delimits an annular region 16 with said wall. Said region is reserved for the circulation of a by-pass flow of liquid metal derived from the diagrid 4 which supports the fuel assemblies 2 of the reactor core. Said by-pass flow results in particular from leakages of liquid metal which take place at the bottom end-fittings 2a of the fuel assemblies 2 and flow beneath the diagrid 4 in the direction of the broken-line arrows. The leakage flow of liquid metal accordingly supplies the region 16 after passing through orifices 17 formed in the bearing shell 13 of the diagrid support structure 9. The support structure 9, especially its lateral cylindrical shell 11 and its base plate 12, serves to delimit together with the bearing shell 13, the diagrid 4 and the bottom wall 14 of the pressure vessel, an enclosed region or space 18 which contains a single collecting tray 19 in accordance with the invention. Said tray is capable of collecting debris from the molten reactor core as a result of a major accident which has produced a temperature rise of sufficient magnitude. In the example construction shown in the drawings, the collecting tray 19 is constituted by two walls 20 and 21 each having a circular peripheral contour and, as shown in cross-section in FIG. 1, a slightly conical profile which is upwardly inclined from the periphery to the center of the tray. The wall 20 is advantageously formed by a series of plates 22 placed in adjacent relation and provided from one plate to the next with an overlapping zone 23 in order to form a continuous surface. The wall 21 is flat and continuous. Said walls 20 and 21 are separated by a clearance space 24 so that the wall 20 can thus constitute a thermal shield for the wall 21. Finally, raised edges 25 and 26 respectively are formed at the ends of said walls 20 and 21. By virtue of this arrangement, the tray 19 is capable of collecting in a suitable manner any molten debris which may fall from the reactor core fuel assemblies 2. The collecting tray 19 is provided in the central portion with a vertical chimney 27 located in the axis of the pressure vessel 14 beneath the diagrid 4. Said chimney delimits internally a vertical passage 28 which makes it possible for the liquid metal contained within the enclosed space 18 to circulate around the collecting tray 19 if necessary. The upper end of said chimney 27 is rigidly fixed to an inclined cover-plate 30 by means of a series of small vertical columns 29. Said inclined cover-plate is mounted above the chimney 27 in such a manner as to ensure that any debris which may fall from the reactor core in the event of melt-down are deflected towards the interior of the collecting tray 19 and not directly towards the bottom wall of the pressure vessel 14 while at the same time preventing any possible accumulation of vapor of the liquid metal coolant beneath said cover-plate. The collecting tray 19 is supported on a structure 31 on a bearing surface 32 in the form of a shell which is provided within the space 18 and extends substantially parallel to the bottom wall 14 of the pressure vessel. In accordance with a particular feature of the invention, the lateral extremity of said surface 32 is connected by means of a member 33 to the diagrid support structure 9 and in particular to the bearing shell 13 of this latter. Preferably, the member 33 is constituted by a series of adjacent sheet metal elements 34 each provided with an overlapping edge 35 from one member to the next, thus forming a continuous structure for preventing any debris from the reactor core which may be carried down by the circulation of liquid metal from being deposited on the bottom wall 14 of the reactor vessel. Said liquid metal within the enclosed space 18 remains practically stagnant during normal reactor operation except for the small flow which is derived from leakages at the bottom end-fittings 2a of the fuel assemblies 2 and fed to the annular space 16 by being caused to flow beneath the bearing surface 32 within the region 36 delimited with the bottom wall 14 of the reactor vessel. This by-pass flow is introduced into said region 36 from a vertical duct 37 arranged in the axis of the chimney 27 and rigidly fixed in position with respect to the surface 32 by means of lateral gusset-plates 38. That wall of the bearing surface 32 which is directed towards the bottom wall 14 of the reactor vessel is provided with shoes 39 so that said surface 32 can rest on said bottom wall in the event of accidental failure of a suspension arm 40 welded between the diagrid support structure 9 and a plate 41 fixed separately against the surface 32 which is therefore directly carried by the diagrid support structure during normal operation. By way of alternative and as illustrated in FIG. 3, the bottom bearing shell 32 is extended to the cylindrical bearing shell 13 and is only supported by an annular reinforcement 33a welded to the underface of said bottom bearing shell. The members 33 and 40 are dispensed with in this alternative embodiment. The structure 31 which carries the collecting tray 19 is preferably formed by an array of radial and vertical ribs or plates 43 provided with notches which serve to lighten these ribs and to limit thermal stresses within these latter during reactor operation and with holes 45 for the circulation of liquid metal between the sectors defined by said radial ribs. Moreover, said ribs are advantageously braced with respect to each other by means of tubular and circumferential stiffening members 46, the profile of which can more clearly be seen in the cross-section B-B of FIG. 1 as shown at the top portion of FIG. 2. If necessary, the collecting tray 19 and the bearing surface 32 are provided with sleeves 47 and 48 respectively. Thus a device known as a "neutron guide" 49 of a type known per se is permitted to extend through said sleeves to a point located near the bottom wall 14 of the reactor vessel in order to produce activation of an ionization chamber (not shown) provided on the opposite side of said vessel wall. By virture of the position of the collecting tray 19 within and at the bottom portion of the enclosed space 18, the core catcher as thus constructed is not only permitted to extend entirely beneath the reactor core 1 but also to have the maximum area by extending in particular beyond the limits of the reactor core. In consequence, the entire quantity of debris collected in the tray can be distributed over the surface of this latter to a very small depth. This accordingly avoids the need for a complex design of core catcher in the form of a large number of adjacent but separate cups as was the case in the prior art. It can be mentioned by way of indication that, in the design solution contemplated by the invention and consisting of a single collecting tray, the depth of molten fuel corresponding to the complete core of a 1200 MWe reactor will be of the order of 7 cm, thus permitting of efficient cooling and removing any potential danger of criticality. During operation, cooling of the molten fuel contained in the collecting tray 19 is produced by the mass of liquid metal confined within the enclosed space 18 and circulated by convection between the hot zone constituted by the tray 19 itself and the cold zone formed by those regions of the support structure 9 and of the diagrid 4 which are in contact with the cold liquid metal contained in the external region 50. The position of the collecting tray 19 in the lowest portion of the enclosed space 18 is thus conducive to the most profitable use of the heat-transfer surface formed by the walls which provide a separation between the volume of liquid metal heated by the collecting tray and the colder volume contained in the reactor vessel itself. The slightly conical shape of the bottom of the collecting tray also makes it possible to improve the conditions of this circulation to an appreciable degree. |
062927515 | summary | TECHNICAL FIELD OF THE INVENTION This invention relates to methods and apparatus for correcting errors associated with the use of an inertial measurement unit (IMU) to track positions, locations, or movements. BACKGROUND OF THE INVENTION Inertial Measurement Units (IMUs) typically use accelerometers and gyros to track accelerations in order to calculate changes in position. Because of inherent errors in the sensors used in IMUs, random errors in the calculated position build with time. One current method of eliminating these errors is to use a second position sensor (e.g., a GPS or an odometer input) along with a Kalman filter to minimize errors from each of the position sensors. A second method is to stop and perform a Zero Velocity Update (ZVU) to re-calibrate the sensors at the beginning of a period of interest. Most applications using IMUs require good absolute position accuracy over long distances, such as for use in a plane or a tank. Such applications are ideal for use of an IMU coupled with a secondary data source such as a Global Positioning System (GPS) to bound and correct errors in the IMU. A typical IMU operating in conjunction with the GPS may be capable of 10 meters in accuracy relative to a fixed reference point after traversing a distance of 100 miles. In contrast, some applications, such as to which this invention applies, requires extremely accurate relative position data over short distances. In such applications, it is necessary to determine with high accuracy how far the IMU has moved since the last ZVU was performed. Neither of the two methods described above are suitable when very high relative positional accuracy is required over very short distances. For example, where a vehicle is used to detect and destroy a land mine, 3 centimeters of accuracy in 6 meters of travel is required. These high levels of accuracy preclude the use of coarse sensors such as an odometer or GPS to eliminate the errors. The nature of these applications also prevents a ZVU from being performed at the beginning of each period of interest (i.e., sensing of a mine or false alarm). Other solutions to the problem of accumulation of errors from an IMU include the use of more expensive sensors with lower noise, and using additional external equipment. As an example, survey quality differential Real Time Kinematic (RTK) GPS can provide highly accurate positional data with the use of a ground based station at a known point, which is disadvantageous in some situations. Thus, to achieve the requisite high levels of accuracy would generally require an IMU using extremely accurate sensors costing approximately $100,000. Therefore, there is a need for methods and apparatus for generating highly accurate position data over short periods of travel using a less expensive IMU. SUMMARY OF THE INVENTION An object of the present invention is, therefore, to provide methods and apparatus for generating highly accurate position data over short periods of travel using a relatively inexpensive IMU. This invention utilizes a method of estimating the random velocity errors in order to remove a portion of these errors from the position data. The invention allows the use of a relatively inexpensive IMU by providing a method of estimating the accumulated error at the beginning and end of the period of interest, and then correcting for these errors. The method employs a ZVU at the end of the period of interest and uses a simple algorithm along with existing data from the IMU to correct for the accumulated errors and thereby provide more accurate position data. The invention may be employed in a system for detecting and disabling mines as described herein, and may also be used to refine the accuracy of position determination in other applications as well. The present invention provides several key advantages: (1) it provides highly accurate relative position data over short distances; (2) does not require external or ground-based equipment; (3) does not require stopping for calibration at the beginning of the period of interest; (4) does not require stopping for any length of time to gather data; (5) does not require the use of a second data source; and (6) allows the use of less expensive inertial sensors. According to the present invention, a conventional IMU is provided for obtaining relative position data. A Zero Velocity Update (ZVU) is performed prior to the commencement of motion to calibrate the IMU. At some time after the commencement of motion a period of interest begins. At the start of the period of interest, the time and position of the IMU is recorded. At a later time, the period of interest ends. At the end of the period of interest, the motion of the IMU is stopped and the time and position of the IMU is again recorded. The velocity indicated by the IMU at the end of the period of interest is also recorded. Because the IMU is now at rest, any velocity indicated by the IMU is the result of errors accumulated during the time of motion of the IMU. The accumulation of error as a function of time is approximated by a function, f(t). From this function, the approximate amount of error at both the beginning and the end of the period of interest can be calculated. This error can then be subtracted from the position data for both the beginning and ending points of interest to minimize the error in the indicated relative change in position between these points. The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. |
abstract | An apparatus and method for irradiating a product or product stack with a relatively even radiation dose distribution (low dose uniformity ratio (DUR). The apparatus comprises a radiation source for producing radiation in the range of X-rays or greater, an adjustable collimator for producing a radiation beam of a desired geometry, a turn-table capable of receiving a product stack and a control system capable of adjusting the adjustable collimator to vary the geometry of the radiation beam as the product stack is rotated in the radiation beam. Also disclosed is the modulation of the radiation beam energy and power and varying the angular rotational velocity of the product stack in a radiation beam to achieve a low dose uniformity ratio in the product stack. The invention also discloses a radiation detection system integrated with a control system for automatic processing, and monitoring of product stacks for delivery of a precise radiation dose distribution and a relatively flat dose distribution in a product stack. |
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048636711 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, an embodiment of the present invention will be described with reference to FIG. 1. The system comprises a toroidal vacuum chamber 1 which is substantially axisymmetric, a coil 2 which generates a magnetic field in a toroidal direction mainly within the vacuum chamber 1, current transformer coils 3 which drive current in the toroidal direction in order to generate and maintain a plasma column 7 within the vacuum chamber 1, and coils 41, 42, 43 and 44 which generate magnetic fields for holding the equilibrium of the plasma 7, as well as magnetic field coils 51, 52, 53, 54, 55, 56, 57 and 58 which serve to cause the rotation of a magnetic surface 81. Electric power is supplied by power sources 61, 62, 63 and 64 for feeding the individual coils 41-44 and 51-58. The current transformer coils 3 serve to induce a magnetic flux change on the center axis of the system. Although they are illustrated as having the air-core setup, it is the same as in the conventional Tokamak system that iron cores may well be employed. The current transformer coils 3 are connected in series with the power source 62, and are fed with pulses. The equilibrium field coils 41, 42, 43 and 44 serve to establish a magnetic field perpendicular to the plane of a plasma ring, and are disposed to be symmetric in the vertical direction. The number of the equilibrium field coils is not always four. In addition, the waveform of power feed from the power source 63 is substantially the same as the waveform of a plasma current, and the coils 41-44 are connected in series. These are the same as in the conventional Tokamak system. The toroidal coil 2 is connected and fed with power similarly to that of the conventional Tokamak system. Although the eight rotating coils 51-58 are illustrated, an elliptical magnetic surface 81 can be rotated even by six coils. A method of power feed in the case of rotating the elliptical magnetic surface with the eight coils will be described. The elliptical magnetic surface 81 is established by a quadrupole magnetic field. In establishing the quadrupole magnetic field, forward and reverse currents of two cycles around the plasma column are necessary. If the eight coils are arranged at substantially equiangular intervals, alternating currents which have a phase shift of: EQU 2.times.360.degree./8=90.degree. between the respectively adjacent coils is supplied. Then, the elliptical magnetic surface is rotated 1/2 revolution in one cycle of the alternation. In order to rotate a triangular magnetic surface by the use of the eight coils, the following measure may be taken: Since a triangular deformation is established by a hexapole magnetic field, alternating currents having a phase difference of: EQU 3.times.360.degree./8=135.degree. between the respectively adjacent coils are supplied, whereby the magnetic surface rotation of 1/3 revolution is achieved in a cycle of the alternation. The relationship among the number of coils, the sectional shape and the magnitude of revolution becomes as follows: Letting the number of coils be 2M, and the sectional shape be an N-gonal shape, the phases of the respectively adjacent coils may be endowed with a difference of: EQU 360.degree..times.N/(2M). If this value is 180.degree. or greater, a magnetic field which attains the desired N-gonal shape at every point of time cannot be generated, or the rotating direction reverses meaninglessly. To avoid this drawback, N must be smaller than M, and the smallest number for the deformation is N=2 corresponding to the elliptical deformation. The magnitude of revolution per alternating cycle for the N-angled shape change is 1/N, and does not depend upon the number of coils. In general, the number of coils may be odd as well. In this case, 2M in the above expression may be substituted by (2M'+1). The power source 64 for the magnetic surface rotating coils supplies alternating currents of various phases. FIG. 2 shows the arrangement of the power source and the method thereof for feeding power to the coils. The power source 64 is composed of a signal generator 65, phase shifters 66, 67 and power amplifiers 68, 69. The signal generator 65 produces an alternating waveform. As the waveform, a sinusoidal wave promises the smoothest operation, but another alternating waveform such as a triangular wave, square wave or saw-tooth wave may well be used. The phase shifters 66 and 67 shift the phases of signals therebetween, making it possible to supply the coils 51-58 with currents of waveforms whose phases shift in succession. In the present example, the phases are shifted every 90.degree. between the adjacent coils in order that the elliptical magnetic surface to-be-changed may be rotated by the eight coils. Therefore, the coils 51 and 55, 52 and 56, 53 and 57, and 54 and 58 become the same phases, respectively. Among these four sets, the set of the coils 51 and 55 and the set of the coils 53 and 57, and the set of the coils 52 and 56 and the set of the coils 54 and 58 become the opposite phases with the phase shifts of 180.degree., respectively. Accordingly, the phase shifters 66 and 67 may provide the signals having the phase shift of 90.degree., and any other phase shifter is unnecessary. In principle, the phase shifter 66 may be directly connected so as to afford null phase difference. In the case where the set of eight coils is arranged at the equal intervals and where the elliptical magnetic surface is rotated, the two phase shifters 66, 67 and the two amplifiers 68, 69 suffice in this manner. The arrangement of connection in the case of generating and rotating a triangular magnetic surface by the use of eight coils is shown in FIG. 3. The phase difference between the respectively adjacent coils is 360.degree..times.3/8=135.degree., so that the coils 51 and 55 have a phase shift of 540.degree., namely, the opposite phases. The coils 52 and 56 and the coils 51 and 55 have opposite phases therebetween, respectively, and the former set lags just 135.degree. over the latter set. In a power source 70, accordingly, the combinations of phase shifters 72-75 and amplifiers 76-79 to be connected to a signal generator 71 are required in four sets. In general cases, the phase shifters and the amplifiers which are equal in number to the coils are sufficient. The alternating current coils may well be non-axisymmetric. An example is a shape in which the coils turn helically around the vacuum chamber 1 as shown in FIG. 4 where the coils are numbered 51'-58'. In this case, the shape of the plasma column 7 does not become axisymmetric, but it becomes a shape twisted at the same pitch as that of the helix. When the helical coils are supplied with alternating currents having phase differences, the twisted plasma column can be rotated. By constructing the plasma confinement system as in the foregoing embodiment, the plasma column can be rotated, so that the unstable plasma part is quickly moved to the stable part, and the instability of the plasma can be eliminated. In addition, heat load concentration ascribable to a diverter flux is simultaneously solved by the rotation of a heat flux inflow position during the rotation of the magnetic surface. More specifically, the rotating coils are arranged so that a magnetic neutral point may be formed during the formation of the deformed magnetic surface, and the neutral point is rotated simultaneously with the movement of the whole magnetic surface during the feed of the alternating currents. Then, the diverter heat load is distributed on the entire inside surface of the chamber and is not locally concentrated. When the magnetic surface is rotated, the magnetic neutral point (separatrix configuration) is simultaneously rotated. Therefore, an impurity particle flux to be separated and emitted can be prevented from continuing to enter a fixed position. When the plasma is rotated, centrifugal forces act on particles, and heavy ions move toward the exterior of the plasma. The centrifugation is effective when the thermal velocities of ions exceed the rotating velocity of the plasma. In the nuclear fusion plasma, solely heavy hydrogen and tritium play the principal roles, and all the other particles are impurities. Since heavy impurities have low thermal velocities, the rotation of the magnetic surface can serve the separation and emission of the impurities more effectively. In other words, the impurity inflow flux can be expanded over the entire inside surface of the chamber. Since the mean inflow flux per unit area decreases to about 1/5, the lifetime of the chamber against sputtering becomes 5 times longer. According to the present invention, the period of time for which a plasma column faces the outer side of a toroid accounts for about 1/2 of the whole period of time, so that the growth rate of instability becomes 1/2. Accordingly, the energy confinement time is approximately doubled. In a nuclear fusion apparatus conforming to the system of the invention, the merit appears as a reactivity increment, and the invention is effective to raise the efficiency of the overall plant. |
abstract | A safety system for a nuclear plant includes a plurality of catalytic recombiner elements each triggering a recombination reaction with oxygen when hydrogen is entrained in an onflowing gas flow, so that reliable elimination of the hydrogen from the gas mixture is ensured with an especially high degree of operational safety even based on comparatively extreme conditions or scenarios of the aforementioned type. The recombiner elements and/or the flow paths each connecting two recombiner elements on the gas side are configured in such a way that a pressure pulse triggered in the gas medium by an ignition during the recombination reaction in a first recombiner element triggers a gas displacement process having a flow rate of at least 5 m/s in the onflow region of a second, adjacent recombiner element. A nuclear plant with a safety system is also provided. |
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claims | 1. A containment of a nuclear power plant, comprising:a containment structure having formed therein a pressure chamber and a condensation chamber with a base, said condensation chamber having a cooling liquid therein, the cooling liquid having a surface defining a horizontal;a vertical condensation tube having an upper end communicating with said pressure chamber and a lower end immersed in the cooling liquid in said condensation chamber;said lower end of said condensation tube being formed with an elbow leading into an outlet nozzle;said elbow having an elbow angle causing a lower end of said elbow to be immersed obliquely with respect to the horizontal; andsaid outlet nozzle of said condensation tube being formed by a tube section having a beveled end defining an outlet opening directed towards the surface defining the horizontal. 2. The containment according to claim 1, wherein said elbow angle of said elbow of said condensation tube is between 70° and 85°, whereby said lower end of said elbow is immersed in the cooling liquid in said condensation chamber with an oblique downward inclination. 3. The containment according to claim 2, wherein said elbow angle of said elbow is 82°. 4. The containment according to claim 1, wherein a portion of said condensation tube is embedded in a wall of said condensation chamber. |
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claims | 1. An x-ray beam conditioning system comprising:a Kirkpatrick-Baez side-by-side optic includinga first diffractive element, anda second diffractive element, one diffractive element being a crystal. 2. The x-ray beam conditioning system of claim 1 wherein both diffractive elements are mosaic crystals with high mosaicity and low d-spacing. 3. The x-ray beam directing system of claim 1 wherein the crystal is selected from the group consisting of a perfect crystal and a mosaic crystal and has a low d-spacing. 4. The x-ray beam conditioning system of claim 3 wherein the other diffractive element is a multilayer optic. 5. The x-ray beam conditioning system of claim 3 wherein the other diffractive element is a mosaic crystal with large d-spacing. 6. The x-ray beam conditioning system of claim 1 wherein the diffractive element is a multilayer optic selected from the group consisting of an elliptical mirror and a parabolic mirror and has graded d-spacing. 7. The x-ray beam conditioning system of claim 6 wherein tin graded d-spacing is lateral grading. 8. The x-ray beam conditioning system of claim 6 wherein tin graded d-spaclng is depth grading. 9. The x-ray beam conditioning system of claim 6 wherein tin graded d-spacing is lateral grading and depth grading. 10. The x-ray beam conditioning system 1 wherein at least one diffractive element is an asymmetric Johansson crystal. 11. The x-ray beam conditioning system of claim 1 wherein a: least one diffractive element is a Johanseon crystal, a Johann crystal, or a logarithm crystal. 12. The x-ray beam conditioning system of claim 1 wherein both diffractive elements are equidistant from the origin from where the x-ray beam is emitted. 13. The x-ray beam conditioning system of claim 1 wherein the diffractive elements are located at different distances from the origin from where the x-ray beam is emitted. 14. The x-ray beam conditioning system 1 wherein at least one diffractive element is a crystal with low d-spacing for use in a plane where high convergence is provided. 15. The x-ray beam conditioning system of claim 1 further comprising at least two working corners. 16. The x-ray beam conditioning system of claim 1 further comprlsing an entrance aperture and an exit aperture. 17. An x-ray beam conditioning system comprising:a first crystal with a first active zone, the first crystal being positioned along a beam line in a first reflective plane, the beam line being defined by an x-ray field originating at an origin; anda multilayer reflective element with a second active zone, the reflective element being positioned along the beam line in a second reflective plane that is perpendicular to the first reflective plane, and the first active zone reflecting an incident beam to the second active zone. 18. The x-ray beam conditioning system of claim 17 wherein the crystal and the reflective element define a first center point and a secnd center point, respectively, the first center point and the second center point being equidistant from the origin. 19. The x-ray beam conditioning system of claim 18 wherein the first center point is positioned a first distance from the origin, and the seond center point is positioned a second distance from the origin, the first distance being less than the second distance. 20. The x-ray beam conditioning system of claim 18 wherein the first center point is positioned a first distance from the origin, and the second center point is positioned a second distance from the origin, the first distance being greater than the second distance. 21. The x-ray beam conditioning system of claim 17 wierein the reflective element is a muitilayer optic. 22. The x-ray beam conditioning system of claim 21 wierein the multilayer optic is elliptically curved. 23. The x-ray beam conditioning system of claim 21 wierein the muitilayer optic is parabolically curved. 24. The x-ray beam conditioning system of claim 21 wierein the multilayer optic is spherically curved. 25. The x-ray beam conditioning system of claim 21 wherein the multilayer optic has graded d-spacing. 26. The x-ray beam conditioning system of claim 25 wherein the graded d-spacing is laterally grading. 27. The x-ray beam conditioning system of claim 26 wherein the graded d-spacing is depth grading. 28. The x-ray beam conditioning system of claim 26 wherein the graded d-spacing is lateral grading and depth grading. |
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description | The present disclosure relates generally to systems for and methods of attenuating radiation. More particularly, the present disclosure relates to systems for and methods of attenuating radiation during a radiological examination of a patient. Radiation barriers or shields are used to attenuate (e.g., deflect, absorb, etc.) the flux of electromagnetic radiation originating from a radiation source and directed towards a patient. Radiation can have beneficial and/or negative effects. One beneficial effect of radiation relates to radiological examinations. For purposes of this disclosure, the phrase radiological examination refers generally to any procedure wherein radiation is applied to a patient for the purpose of producing an image or representation of the patient. Radiological examinations may provide a non-invasive means capable of obtaining an image of the internal composition of the patient. Radiological examinations may be employed in a variety of applications including, but not limited to, medical procedures. During a radiological examination, medical personnel (e.g., technicians, assistants, nurses, physicians, surgeons, etc.) are often positioned near the patient undergoing the procedure. Medical personnel positioned near the patient during the procedure are susceptible to both primary beam radiation and scatter radiation. Scatter radiation is a secondary radiation generated when the primary radiation interacts with the object being impinged. Scatter radiation typically has a frequency range lower than the primary radiation beam and generally moves in a variety of uncontrollable (e.g., random, pseudo-random, etc.) directions. Scatter radiation, like primary radiation, can cause damage to living tissue. During a radiographic imaging procedure, the primary radiation beam is likely to scatter after impinging the patient mass. Conventional radiation attenuating safeguards, such as table drapes or standard patient shields used during conventional radiographic imaging procedures, may not provide the medical personnel with a desired level of protection from the scatter radiation. Thus, there is a need for an improved radiation attenuation system for and method of shielding an object from primary beam radiation during radiographic imaging of the object. There is also a need for a radiation attenuation system that is configured to shield persons positioned near an object undergoing radiographic imaging from primary beam radiation. There is further a need for a radiation attenuation system that is configured to shield an object or persons positioned near the object undergoing radiographic imaging from scatter radiation. One embodiment of the invention relates to a radiation attenuation system. The radiation attenuation system includes a first shield panel formed of a first radiation attenuating material, a second shield panel formed of a second radiation attenuating material, and a frame disposed below the first shield panel and the second shield panel. The frame includes a first end portion defining a first array of slots and a second end portion defining a second array of slots. The first array of slots and the second array of slots are configured to receive the first shield panel and the second shield panel such that the second shield panel is spaced apart from the first shield panel to form a first trough sized to fit a limb of a patient. Another embodiment relates to a radiation attenuation system for the scanning of a leg of a patient. The radiation attenuation system includes a first shield panel, a second shield panel, a third shield panel, and a frame disposed below the first shield panel, the second shield panel, and the third shield panel. The frame includes a connecting portion extending from a first end to a second end, at least one first arm defining a first array of slots and extending outward from the connecting portion between the first end and the second end, and at least one second arm defining a second array of slots and extending outward from the connecting portion between the at least one first arm and the second end. The first array of slots and the second array of slots are configured to receive the first shield panel, the second shield panel, and the third shield panel such that the second shield panel and the third shield panel are spaced apart from the first shield panel to form a pair of troughs sized to fit the legs of the patient. Another embodiment relates to an apparatus for attenuating radiation scattered from a patient undergoing radiological examination on a table. The apparatus includes a frame configured to be supported by the table, and a first shield panel formed of a radiation attenuating material and supported by a first portion of the frame. The first shield panel at least partly defines a trough configured to receive a limb of the patient and attenuates radiation scattered from the patient. Another embodiment relates to a method of attenuating radiation during a radiological examination of a patient. The method includes the steps of providing a frame configured to be supported by a platform; providing a first radiation attenuation plate and a second radiation attenuation plate; receiving on the frame a limb of the patient; receiving by the frame the first radiation attenuation plate along on a first side of the limb of the patient; receiving by the frame the second radiation attenuation plate along on a second side of the limb of the patient, opposite the first radiation attenuation plate; and attenuating radiation directed at the limb of the patient in a direction parallel to the first radiation attenuation plate and the second radiation attenuation plate. The frame may receive the first radiation attenuation plate and the second radiation attenuation plate in slots formed in the frame such that the plates are removably coupled to the frame. The frame may receive the limb of the patient such that the limb is supported by the platform. The limb of the patient may be a leg. The method may include the steps of receiving on the frame a second limb of the patient such that the first radiation attenuation plate is positioned between the limbs of the patient; providing a third radiation attenuation plate; and receiving by the frame the third radiation attenuation plate along on a side of the second limb of the patient, opposite the first radiation attenuation plate. The method may include the steps of receiving by the frame a sheet disposed between the limb of the patient and the frame. The foregoing is a summary and thus, by necessity, contains simplifications, generalizations, and 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, inventive features, and advantages of the devices and/or processes described herein will become apparent in the detailed description set forth herein and taken in conjunction with the accompanying drawings. Referring to FIGS. 1 through 5, a radiation attenuation system 20 and components thereof are shown according to exemplary embodiments. Generally, radiation attenuation system 20 includes one or more radiation shields or barriers supported in a manner and at a position that may be useful in attenuating (e.g., blocking, reflecting, absorbing, etc.) primary beam radiation and/or secondary or scatter radiation generated during lateral radiographic imaging of an object (e.g., patient, etc.). For purposes of the present disclosure, the phrase “lateral radiographic imaging,” unless expressly stated otherwise, is used broadly to refer to not only literal lateral imaging of an object (i.e., end-to-end wherein the primary radiation beam is emitted in a horizontal direction that is substantially parallel to a ground surface or a support surface for the object), but also partially lateral or oblique imaging of the object (i.e., wherein the primary radiation beam is emitted at an angle (e.g., 20, 30 or 40 degrees, etc.) relative to a ground surface or a support surface for the object). For example, lateral radiographic imaging need not be strictly horizontal or strictly in the coronal plane of the patient. The radiation attenuation system 20 generally includes a plurality of radiation shields or barriers provided in the form of rigid panels (show, e.g., as plates 24). The panels are removably coupled to and held upright by a frame 26. The panels are received in slots formed in the frame and can be removed from the frame for storage. The radiation attenuation system 20 is configured to be a reusable device that may be utilized for multiple patients. A wide array of medical procedures exist where radiological examinations are employed to obtain an image of the anatomy of a patient or portions thereof. For example, portions of a patient's anatomy may be irradiated during: (i) diagnostic procedures (e.g., Computed Tomography (CT) scanning, x-ray photography, or any other imaging procedure) allowing non-invasive investigation of anatomical regions of a patient (e.g., internal tissue, organs, etc.); or (ii) various invasive procedures, such as the fluoroscopic guidance and/or manipulation of instruments during surgical procedures (e.g., CT fluoroscopy, etc.). To obtain an image through a radiological examination, a primary radiation beam (i.e., entrance radiation) is applied to the patient. Preferably, radiation is selectively focused on to those areas to be examined (i.e., target areas) to minimize the patient's overall radiation exposure. Typically, the target areas are irradiated directly without any obstruction or impairment provided between the primary radiation beam and the patient. Those areas above and/or below the target area that are not being examined (i.e., secondary areas) may be covered with a radiation barrier or shield to prevent and/or reduce radiation exposure for those areas. Such shields are formed of a radiation attenuating material (e.g., lead apron, radiation attenuating polymeric matrix, etc.) and may be placed directly upon the patient. According to an exemplary embodiment, the radiation attenuating material is a polymeric matrix charged with an attenuating filler. Examples of suitable radiation attenuation materials are disclosed in U.S. Pat. No. 4,938,233, entitled “Radiation Shield,” and U.S. Pat. No. 6,674,087, entitled “Radiation Attenuation System,” both of which are hereby incorporated by reference in their entireties. It should be noted that for purposes of this disclosure, the term “coupled” is used broadly to mean the joining or combining of two or more members (e.g., portions, layers, materials, components, etc.) directly or indirectly to one another. Such joining or combining may be relatively stationary (e.g., fixed, etc.) in nature or movable (e.g., adjustable, etc.) in nature. Such joining or combining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another (e.g., one-piece, etc.) or with the two members or the two members and any additional intermediate member being attached to one another. Such joining or combining may be intended to be relatively permanent in nature or alternatively may be intended to be relatively detachable or removable in nature. The radiation barriers are configured to protect one or more individuals present during a procedure (e.g., technicians, assistants, nurses, physicians, surgeons, etc.), referred to generally herein as medical personnel. One or more medical personnel are likely to be positioned near the patient during the procedure, and as such, are likely to be positioned close to the primary radiation beam (i.e., between the emitter and receiver) and/or an area likely to be exposed by scatter radiation. Medical personnel present during the radiographic imaging of the patient may also be susceptible to radiation exposure from the primary radiation beam (e.g., during a fluoroscopy procedure, etc.), but are more likely to be susceptible to radiation exposure from secondary or incidental scatter radiation. The radiation barriers protect against scatter radiation by absorbing at least a portion of the primary radiation beam and scatter radiation. The frame 26 positions the radiation barriers in an upright orientation, forming a trough or channel with an open top into which a portion of the patient's body to be scanned (e.g., an arm or leg) may be received. The open top of the radiation attenuation system 20 provides medical personnel with access to an area of interest on the patient (e.g., target area, etc.). During a procedure, a radiographic visualization or imaging device (e.g., fluoroscope, etc.) will likely be positioned such that a radiation emitter of the device is located at a first end (e.g., inferior end) of the patient and that a corresponding radiation receiver of the device is located at an opposite second end (e.g., superior end). The panels act as radiation barriers positioned between the emitter and the receiver, parallel to the radiation beam, to limit stray radiation. Referring to FIGS. 1-2, the radiation attenuation system 20 is shown according to an exemplary embodiment. The radiation attenuation system 20 is configured to receive a portion of a patient 10 during a medical procedure including lateral radiographic imaging. For example, according to an exemplary embodiment, the radiation attenuation system 20 is configured for use with the lower limbs of the patient 10. In other exemplary embodiments, the radiation attenuation system 20 may be configured for use with another portion of the patient 10, such as an upper limb, torso, head, etc. The radiation attenuation system 20 includes one or more upright plates 24 coupled to a frame 26 supported by a platform 28 (e.g., table, examination table, operating table, etc.) and positioned below the patient 10. As shown, a sheet 30 may be provided between the patient 10 and the plates 24 and/or the frame 26. The sheet 30 serves as a lining between the patient 10 and the plates 24 and/or the frame 26 to limit the contact between the patient 10 and the plates 24 and the frame 26 thereby maintaining the cleanliness and/or hygiene of the radiation attenuation system 20. The radiation attenuation system 20 may further include a drape 32 that lies over the patient 10. The sheet 30 and the drape 32 may be formed from any suitable textile material, such as a woven or knit textile or a non-woven textile. The sheet 30 and the drape 32 may be formable (e.g., deformable), compliant, and/or relatively “stretchable” (e.g., elastic). The sheet 30 may be formed from a variety of fibers (e.g., cotton, paper, polyester, etc.) and may be configured to be disposable in whole or in part, thereby minimizing ancillary sources of contamination that may arise from multiple uses. In some embodiments, the sheet 30 and/or the drape 32 may be formed at least partially of a radiation attenuating material. The radiation attenuation system 20 may be used regardless of the position of the patient. For example, the patient may be provided in a supine position wherein the patient is positioned on his or her back with the legs of the patient being straight or bent, a prone position wherein the patient is positioned face down, and/or a lateral position wherein the patient is positioned on one side. When the emitter and receiver are placed above and below the patient (e.g., in substantially vertical alignment, above and below the examination table, etc.), the beam may pass substantially transverse to a longitudinal axis of the trough, and radiographic images of the coronal or sagittal planes may be obtained. Accordingly, with a patient in the supine or prone positions, the primary radiation beam may pass towards the front or back of the patient, and with a patient in the lateral position, the primary radiation beam may pass through the side of the patient. It is contemplated that the emitter and receiver may be oriented longitudinally with respect to the trough such that the beam may pass substantially along a superior-inferior axis so as to obtain radiographic images of the transverse plane. Referring to FIG. 2, the in an situation where the emitter is located below the platform 28 and emits as primary beam upward through the patient, the beam will begin to scatter when it makes first contact with the patient mass (e.g., the back of the patient's leg). Radiation scattered downward (e.g., low flying scatter) may be reflected by the medical personnel's apron. Lateral or upward scatter is attenuated and/or reflected up through the top of the trough. According to one embodiment, the height of the plates 24 is such that a radiation shadow (e.g., umbra, penumbra, etc.) is formed to the side of the platform 28, which substantially shields nearby medical personnel. According to an exemplary embodiment, the height of the plates 24 is such that a radiation shadow is formed to the side of the platform 28 such that medical personnel standing near the platform are within an umbra of the plates 24. According to another embodiment, the cross-section of the trough is configured such that radiation escaping the top of the trough to the side of the platform on which medical personnel are standing passes over the top of the medical personnel. The plates 24 are positioned proximate the area of interest being scanned such that they attenuate the scatter radiation. According to an exemplary embodiment, the plates 24 are rigid transparent panels. In one embodiment, the plates 24 may be formed of an acrylic lead material (e.g., leaded acrylic, lead acrylic, etc.). In another embodiment, the plates 24 may be formed of a leaded glass material. In still other embodiments, the plates 24 may be formed of any appropriate radiation attenuation material including, but not limited to, bismuth, barium, lead, tungsten, antimony, copper tin, aluminum, iron, iodine, cadmium, mercury, silver, nickel, zinc, thallium, tantalum, tellurium, and uranium. Anyone of the aforementioned radiation attenuation materials alone or in a combination of two or more of the radiation attenuation materials may provide the desired level of radiation attenuation. According to one embodiment, the plates 24 may be formed of a medium having a radiation attenuation material suspended therein. According to an exemplary embodiment, the radiation attenuating material is a polymeric matrix charged with an attenuating filler. It should be noted that the radiation attenuating member is not limited to such radiation attenuating materials, and according to the various alternative embodiments, may be formed of any suitable radiation attenuating material including more conventional attenuating materials (e.g., lead-based materials, etc.). The radiation attenuation factor of the plates 24 may vary depending upon the intended application of radiation attenuation system 20, for example, attenuating direct or scattered radiation. Further, higher powered beams (kVp) and larger patients tend to cause greater scattering of the radiation. According to one exemplary embodiment, the radiation attenuating member may have a radiation attenuation factor of nearly 100 percent (%) with reference to a 60 kVp x-ray beam. According to another embodiment, the radiation attenuating member may have a radiation attenuation factor of approximately 30 percent (%) with reference to a 90 kVp x-ray beam. The plates 24 may also at least partially attenuate gamma rays. According to an exemplary embodiment, the plates 24 have a thickness of between 4 mm and 24 mm. According to another embodiment, each plate 24 has a thickness of between 4 mm and 18 mm. According to a preferred embodiment, the plates 24 have a thickness of between 6 mm and 18 mm. According to a particularly preferred embodiment, the plates 24 have a thickness of between 8 mm and 12 mm. According to an exemplary embodiment, the plates 24 are configured to attenuate the radiation for a peripheral procedure involving the legs of the patient 10. In one embodiment, the radiation attenuation system 20 includes an inner plate 24a positioned between the legs of the patient 10 and a pair of outer plates 24b positioned along the outside of either of the legs of the patient 10. According to an exemplary embodiment, the plates 24 have a height of between approximately 8 in. and 14 in. The plates 24 are held in an upright orientation by the frame 26. Referring to FIGS. 3-4, the frame 26 is a low-profile structure that is provided between the patient 10 and a supporting structure, such as the platform 28. According to an exemplary embodiment, the frame 26 is I-shaped body with a first end portion including a pair of first arms 40 (e.g., superior end portion, proximal end portion, etc.) and a second end portion including a pair of second arms 42 (e.g., inferior end portion, distal end portion, etc.). As shown in FIG. 1, the frame 26 may lie between the buttocks and the heels of the patient 10 in the supine position. The first arms 40 and the second arms 42 are coupled together by a connecting portion 44 (e.g., rib, rail, leg, etc.) shown to be perpendicular to the arms 40, 42. According to an exemplary embodiment, the frame 26 includes a single connecting portion 44 extending between the arms 40, 42 and under a gap between the legs of the patient 10. In other exemplary embodiments, the frame 26 may include additional connecting portions, such as connecting portions extending from the distal ends of the arms 40 and 42. In still other exemplary embodiments, the arms 40, 42 may be coupled together by a connecting portion in the form of a panel that extends along the entire length of the arms 40, 42. The length of the connecting portion 44 of the frame 26 may vary depending on the desired length of the radiation attenuation system 20. Any number of radiation attenuation systems 20 of various lengths (e.g., having plates 24 and frames 26 with various lengths) may be provided to be used with patients of various sizes. Due to the placement of the frame 26 between the buttocks and the heels of the patient 10 and the relatively low profile of the frame 26, one or more of the elements of the frame 26 (e.g., the first arms 40, the second arms 42, and the connecting portion 44) may have a rectangular cross-section without causing undue discomfort for the patient. In another exemplary embodiment, one or more of the elements of the frame 26 may have rounded edges. In another exemplary embodiment, the first arms 40 and/or the second arms 42 may include hollows or cutouts configured to comfortably receive the legs of the patient 10. The frame 26 includes a multitude of slots 50 configured to receive the plates 24. The slots 50 are formed are formed in the arms 40 and 42, with the slots 50 on the first arms 40 forming an array that is aligned with corresponding array of slots 50 on the second arms 42. The connecting portion 44 may define a slot 50 (e.g., a longitudinal slot) running along the length of the connecting portion 44 (e.g., to receive the inner plate 24a). The slots 50 have a width and a depth to facilitate the assembly and use of the radiation attenuation system 20 with minimal components and no additional tools. According to an exemplary embodiment, the width of the slots 50 is equal to or less than the thickness of the plates 24, such that the plates 24 can be inserted (e.g., slid) into the slots 50 by hand. The plates 24 may be held loosely in the slots 50 or may be held in the slots 50 with an interference fit between the plates 24 and the frame 26. According to an exemplary embodiment, the depth of the slots 50 is great enough that the plates 24 may be supported by the frame 26 in an upright orientation without additional support. The slots 50 may have a depth that is less than the height of the frame 26 such that the slots 50 extend only part of the way through the frame 26 or may extend through the entire frame 26 and divide the frame 26 into separate portions that are coupled together, for example, as shown in FIG. 6. In some embodiments, the frame 26 may include slots 50 of varying widths to accommodate plates 24 having varying thicknesses. The frame 26 is a relatively lightweight structure formed of a material that need not be opaque to the radiation utilized in the procedure. According to an exemplary embodiment, the frame 26 is molded from a semi-rigid, relatively resilient material, such as a high-density polypropylene foam, high density polyethylene, HDPE foam, rubber, etc. In other exemplary embodiments, the frame 26 may be formed from a more rigid material, such as acrylic, glass, etc. When formed from a resilient material, the slots 50 may, in a relaxed state, have a width that is less than the thickness of the plates 24, and the plates 24 cause the portions of the frame 26 defining the slots 50 to deform such that the plates 24 are held in place with an interference fit. Although not required, the frame 26 is preferably formed from a radiotranslucent material so as not to interfere with the imaging of the patient. In other embodiments, the frame 26 may be formed from multiple materials. For example, the frame 26 may include a main body formed of a relatively rigid material and inserts formed of a relatively resilient material in which the slots 50 are formed. The multiple materials may be formed with a two-shot molding process or may be formed separately and coupled together, such as with an adhesive. In other embodiments, the top of the frame may include a layer of softer, deformable material to increase the comfort of the patient. Referring now to FIG. 5, in one embodiment, the slots 50 may extend through the entire height of the arms 40 (and/or of the arms 42), and divide the arms 40 into an inner portion 52 and an outer portion 54. The inner portion 52 is coupled to the outer portion 54 with a hinge member 56 that is configured to allow the outer portion 54 to pivot relative to the inner portion 52 about an axis 58, thereby varying the width of the slot 50 to facilitate the insertion of the plate 24 into the slot 50. According to one exemplary embodiment, the hinge member 56 is a pinned hinge coupled to the bottom surface of the arm 40. In other exemplary embodiments, the hinge member 56 may be another type of hinge, such as a flexible sheet coupled to the bottom surface of the arm 40 or a living hinge integrally formed with the inner portion 52 and the outer portion 54 of the arm 40. The slot 50 may be widened, for example, by lifting the frame 26 off of the platform 28 and allowing the outer portion 54 to pivot downward. The plate 24 may then be positioned in the slot 50 and the slot 50 narrowed by lowering the frame 26 onto the platform 28, forcing the outer portion 54 to pivot upward. The hinge member 56 may be pinned or otherwise held in place with a locking mechanism, such as when the outer portion 54 is pivot upward and the slot 50 is narrowed. In other embodiments, the hinge member 56 may lack a locking mechanism and the plate 24 may be retained in the slot 50 and the outer portion 54 may be held in position by the weight of the patient forcing the frame 26 against the platform 28. Although the radiation attenuation system 20 is shown as being an I-shaped structure configured to accommodate two limbs, in another embodiment, the radiation attenuation system 20 may be configured to accommodate a single limb. Such a radiation attenuation system 20 may include a frame 26 with a connecting portion 44 disposed on one or both sides of the radiation attenuation system 20 or running generally along the center of the radiation attenuation system 20 (e.g., under the limb). It is further contemplated that the radiation attenuation system 20 described above may be used with less than the full accompaniment of plates 24. According to various embodiments, plate 24a, one of plates 24b, both of plates 24b, or plate 24a and one of plates 24b may be removed from the frame 26 to create the desired attenuation scheme for the radiological examination. One or more of the components of radiation attenuation system 20 are generally non-toxic, recyclable, and/or biodegradable. According to an alternative embodiment, one or more of the components of radiation attenuation system 20 may be reusable. According to a preferred embodiment, one or more of the components of radiation attenuation system 20 may be sterilized between uses to minimize the likelihood of bacteriological or virus contamination. Sterilization may be performed in any convenient manner, including gas sterilization and irradiation sterilization. It is important to note that the construction and arrangement of the elements of the radiation attenuation system as shown in the illustrated embodiments is illustrative only. Although only a few embodiments of the present inventions have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited. For example, elements shown as integrally formed may be constructed of multiple parts or elements shown as multiple parts may be integrally formed, the operation of the interfaces may be reversed or otherwise varied, or the length or width of the structures and/or members or connectors or other elements of the system may be varied. It should be noted that the elements and/or assemblies of the system may be constructed from any of a wide variety of materials that provide sufficient strength or durability, in any of a wide variety of colors, textures and combinations. For example, the radiation attenuation material may be a relatively flexible material, or alternatively, may be a relatively rigid material. Further, drape 32 may not include the fenestration area if drape 32 is not going to be used for invasive procedures. Further, while lateral radiographic imaging is used above with reference to a primary radiation beam that is generally parallel to a patient table, the angle at which the primary radiation beam may emitted relative to a patient table during lateral radiographic imaging may be up to approximately 45 degrees (or any other degree of obliquity) relative to the patient table. Accordingly, all such modifications are intended to be included within the scope of the present inventions. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the present inventions. |
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abstract | The invention relates to a combined method in which a high-resolution image of a sample surface is recorded by means of scanning force microscopy and the locally high-resolution, chemical nature (which is correlated with this) of the sample surface is measured by means of mass spectroscopy. The surface is chemically analyzed on the basis of laser desorption of a restricted surface area. For this purpose, the surface is illuminated in a pulsed form at each point of interest using the optical near-field principle. The optical near-field principle guarantees analysis with a position resolution which is not diffraction-limited. A hollow tip of the measurement probe that is used allows unambiguous association between the chemical analysis and a selected surface area. The highly symmetrical arrangement allows good transmission of the molecular ions that are produced. |
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summary | ||
summary | ||
059129395 | abstract | A plasma source of soft x-rays provides the illumination for a microfluoroscope. In general, an x-ray relay optic collects part of the diverging plasma radiation and redirects it to a distant plane. At that plane, the fine-grained or grainless fluorescent screen of a microfluoroscope is placed to receive the radiation. A specimen is placed in direct contact with the screen, or in very close proximity, so that its x-ray shadow is projected onto the screen. The screen is very thin and transparent to visible or ultraviolet light so that a high-numerical-aperture optical microscope objective can closely approach and view the screen from the opposite side. The optical microscope views the fluorescent light emitted by the screen, which corresponds to the x-ray absorption shadow of the specimen. In general, a very thin, x-ray transparent vacuum window is used to separate the specimen, fluorescent screen, and microscope from the vacuum of the plasma source. Thin-film filters and/or monochromator devices are used to limit the wavelengths of soft x-rays which reach the fluorescent screen to the desired energy range. The use of the apparatus and process occurs with either a separate instrument or as an add-on feature to a conventional optical microscope. |
abstract | An extreme ultraviolet light source device in accordance with the present invention suppresses a surface that comes into contact with a target material in a molten state from being eroded by the target material, being reacted with the target material, and being cut by the target material. |
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046844805 | description | The object of the invention is explained in greater detail in the examples that follow. As ceramic starting powders, the following powder types have been used in the examples. Boron carbide powder (A) contained 77.3% by weight B and 0.3% by weight B.sub.2 O.sub.3 and had a particle size distribution of 100% finer than 100 .mu.m PA1 90% finer than 60 .mu.m PA1 70% finer than 40 .mu.m PA1 50% finer than 30 .mu.m PA1 30% finer than 20 .mu.m and PA1 20% finer than 15 .mu.m PA1 100% finer than 50 .mu.m PA1 90% finer than 15 .mu.m PA1 70% finer than 10 .mu.m PA1 50% finer than 8 .mu.m PA1 30% finer than 6 .mu.m and PA1 20% finer than 4 .mu.m. PA1 100% finer than 50 .mu.m PA1 90% finer than 15 .mu.m PA1 70% finer than 10 .mu.m PA1 50% finer than 8 .mu.m PA1 30% finer than 5 .mu.m and PA1 20% finer than 2 .mu.m PA1 28 parts by weight boron carbide powder (A), PA1 65 parts by weight silicon carbide powder (C), PA1 7 parts by weight graphite powder, PA1 18 parts by weight phenolic resin powder and PA1 6 parts by weight furfural PA1 60 parts by weight boron carbide powder (B) PA1 20 parts by weight silicon carbide powder (C) PA1 10 parts by weight graphite powder PA1 19 parts by weight phenolic resin powder and PA1 6 parts by weight furfural. PA1 93 parts by weight boron carbide powder (B) PA1 7 parts by weight graphite powder PA1 19 parts by weight pheonolic resin powder and PA1 5 parts by weight furfural. Boron carbide powder (B) contained 78.8% by weight B, 0.24% by weight B.sub.2 O.sub.3 and had a particular size distribution of Silicon carbide powder (C) contained 98.4% by weight SiC and had a particle size distribution of The graphite powder was a screened natural graphite fraction of 40 .mu.m and finer. The lexural strength was determined according to the 3-point method with samples which measured 45.times.4.5.times.3.5 mm, a span of 30 mm amd a rate of load application of 1.8 N/mm.sup.2 per second. For the corrosion test, the plates were immersed for 2000 or 3000 hours in water near its boiling point, and the flexural strength was again determined. The percent decrease in the flexural strength refers to the initially measured value at room temperature. EXAMPLE 1 were homogenously mixed. The powder mixture was pressed under a pressure of 28 MPa into plates 2 mm thick. The plates were stacked between glass plates and cured by heating for 15 hours at 180.degree. C. The plates were then stacked between graphite plates and heated to 1050.degree. C. in the absence of air, the time for heating to 1050.degree. C. was 19 hours and the plates were held at this temperature for 7 hours. Properties of the plates produced: ______________________________________ density 2.0 g/cm.sup.3 boron content: 19.0% by weight corresponds to 19.5% by volume B.sub.4 C silicon content: 36.5% by weight corresponds to 32.5% by volume SiC free carbon content: 20.0% by weight corresponds to 18.0% by volume free C B.sup.10 loading: near 0.014 g Boron 10/cm.sup.2 flexural strength: 35 N/mm.sup.2 compression strength: 60 N/mm.sup.2 modulus of elasticity: 22,000 N/mm.sup.2 radiation resistance: 10.sup.11 rad (no measurable change in the flexural strength and the dimension) flexural strength after immersion for 2000 hours in water at 93.degree. C.: 25 N/mm.sup.2 flexural strength after immersion for 3000 hours in water at 93.degree. C.: 24 N/mm.sup.2 corresponds to a drop of 31.4% compared to the initial value. ______________________________________ EXAMPLE 2 Under the same conditions as described in Example 1, the following homogeneous powder mixture was prepared and compressed and the plates cured and fired in the absence of air: Properties of the plates produced (2mm): ______________________________________ density 1.85 g/cm.sup.3 boron content: 41.0% by weight corresponds to 39.0% by volume B.sub.4 C silicon content: 17.5% by weight corresponds to 14.5% by volume SiC free carbon content: 19.0% by weight corresponds to 16.0% by volume free C B.sup.10 loading: near 0.028 g Boron 10/cm.sup.2 flexural strength: 25 N/mm.sup.2 compression strength: 50 N/mm.sup.2 modulus of elasticity: 16.000 N/mm.sup.2 radiation resistance: 10.sup.11 rad (no measurable change the flexural strength and the dimensions) flexural strength after immersion for 2000 hours in water at 93.degree. C.: 17.0 N/mm.sup.2 flexural strength after immersion for 3000 hours in water at 93.degree. C.: 16.0 N/mm.sup.2 corresponds to a drop of 36% compared to the initial value. ______________________________________ EXAMPLE 3 (for comparison) Under the same conditions as described in Example 1, the following homogeneous powder mixture was prepared and compressed and the plate cured and fired in the absence of air. Properties of the plates produced (2 mm): ______________________________________ density: 1.70 g/cm.sup.3 boron content: 64.0% by weight corresponds to 55% by volume B.sub.4 C free carbon content: 16.0% by weight corresponds to 12% by volume free carbon B.sup.10 loading: 0.04 g Boron 10/cm.sup.2 flexural strength 16 N/mm.sup.2 compression strength: 50 N/mm.sup.2 modulus of elasticity: 11.500 N/mm.sup.2 radiation resistance: 10.sup.11 rad (no measurable change in flexural strength and the dimensions) flexural strength after immersion for 2000 hours in water at 93.degree. C. 8.5 N/mm.sup.2 flexural strength after immersion for 3000 hours in water at 93.degree. C.: 7.5 N/mm.sup.2 corresponds to a drop of 52.3% compared to the initial value. ______________________________________ |
claims | 1. A bottom nozzle of a light-water reactor fuel assembly, comprising a skirt, support blocks, transverse blades and longitudinal blades, wherein the skirt is a hollow structure and a bottom thereof is provided with corner legs which are protruded downwards, a cavity is defined in the hollow structure, the transverse blades are equidistantly and uniformly configured in the cavity to form a transverse thin strip layer, the longitudinal blades are equidistantly and uniformly configured in the cavity to form a longitudinal thin strip layer, both ends of the transverse blades and longitudinal blades are connected with the skirt, the transverse blades are located above longitudinal blades, projections of the transverse blades and the longitudinal blades in a level plane are intersectant to form interleaved grids, and the support blocks run through and are fixed on the transverse blades and the longitudinal blades, wherein a gap is formed between lower ends of the transverse blades and upper ends of the longitudinal blades to form a water passage subdivision layer, and wherein the transverse blades and the longitudinal blades are in wave structures, and the transverse blades and the longitudinal blades are flipped in orientation vertically 180 degrees with respect to each other, such that downward-facing wave crests of the transverse blades are directly above corresponding upward-facing wave crests of the longitudinal blades. 2. The bottom nozzle according to claim 1, wherein lower ends of the transverse blades are connected to upper ends of the longitudinal blades. 3. The bottom nozzle according to claim 1, wherein the support blocks are located at intersections of the grids. 4. The bottom nozzle according to claim 1, wherein the support blocks, the transverse blades and the longitudinal blades are in an integrated structure. 5. The bottom nozzle according to claim 1, wherein projections of the transverse blades and longitudinal blades in a level plane are orthogonal. 6. The bottom nozzle according to claim 1, wherein an enhanced strip is connected between each support block and its adjacent transverse thin strip, or between each support block and its adjacent longitudinal thin strip. 7. The bottom nozzle according to claim 1, wherein the support blocks are provided with connecting holes which are capable of receiving guide thimbles of a light-water reactor fuel assembly, and the connecting holes are stepped holes each of which has a narrow top and a wider bottom. 8. A light-water reactor fuel assembly, comprising a bottom nozzle, a top nozzle, spacer grids, guide thimbles and fuel rods, the fuel rods and the guide thimbles being inserted into the spacer grids respectively, the spacer grids having upper ends connected and mating with the top nozzle and lower ends connected and mating with the bottom nozzle, and the bottom nozzle comprising a skirt, support blocks, transverse blades and longitudinal blades, wherein the skirt is a hollow structure and a bottom thereof is provided with corner legs which are protruded downwards, a cavity is defined in the hollow structure, the transverse blades are equidistantly and uniformly configured in the cavity to form a transverse thin strip layer, the longitudinal blades are equidistantly and uniformly configured in the cavity to form a longitudinal thin strip layer, both ends of the transverse blades and longitudinal blades are connected with the skirt, the transverse blades are located above longitudinal blades, projections of the transverse blades and the longitudinal blades in a level plane are intersectant to form interleaved grids, and the support blocks run through and are fixed on the transverse blades and the longitudinal blades, wherein a gap is formed between lower ends of the transverse blades and upper ends of the longitudinal blades to form a water passage subdivision layer, and wherein the transverse blades and the longitudinal blades are in wave structures, and the transverse blades and the longitudinal blades are flipped in orientation vertically 180 degrees with respect to each other, such that downward-facing wave crests of the transverse blades are directly above corresponding upward-facing wave crests of the longitudinal blades. 9. The light-water reactor fuel assembly according to claim 8, wherein lower ends of the transverse blades are connected to upper ends of the longitudinal blades. 10. The light-water reactor fuel assembly according to claim 8, wherein the support blocks are located at intersections of the grids. 11. The light-water reactor fuel assembly according to claim 8, wherein the support blocks, the transverse blades and the longitudinal blades are in an integrated structure. 12. The light-water reactor fuel assembly according to claim 8, wherein projections of the transverse blades and longitudinal blades in a level plane are orthogonal. 13. The light-water reactor fuel assembly according to claim 8, wherein an enhanced strip is connected between each support block and its adjacent transverse thin strip, or between each support block and its adjacent longitudinal thin strip. 14. The light-water reactor fuel assembly according to claim 8, wherein the support blocks are provided with connecting holes which are capable of receiving guide thimbles of a light-water reactor fuel assembly, and the connecting holes are stepped holes each of which has a narrow top and a wider bottom. |
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abstract | An ion implantation method for reducing energy contamination in low energy beams is disclosed in this invention. The ion implantation method requires the use of a target chamber for containing a target for implantation in vacuum and an ion source chamber with an ion source for generating an ion beam. A means for conducting a mass analysis of the ion beam, such as an analyzer magnet, is also needed. The ion source chamber includes a beam deceleration optics that includes a beam deceleration means for decelerating the ion beam for producing a low energy ion beam. The beam deceleration optics further includes a beam steering means for generating an electrostatic field for steering the ion beam to a targeted ion-beam direction and separating neutralized particles from the ion beam by allowing the neutralized particles to transmit in a neutralized-particle direction slightly different from the targeted ion-beam direction. The ion beam steering means further includes a beam stopper for blocking said neutralized particles from reaching said target of implantation that minimizes energy contamination from high energy neutralized particles. |
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061920959 | description | PREFERRED EMBODIMENT OF THE INVENTION .sup.133 Xe Radioactive Stent In a half-life of 5.25 days, xenon-133 undergoes .beta.-disintegration, whereupon it emits .beta.-rays at a maximum energy of 350 keV, as well as 81 keV of .gamma.-rays and internal conversion electrons due to .gamma.-decay. This means that not only .beta.-rays but also internal conversion electrons are expected to contribute to intravascular irradiation. In addition, due to their low energy, .beta.-rays are only applied to intimae and will not affect other parts of the blood vessels. As a further advantage, .sup.133 Xe which is gaseous is easy to handle and has a higher ionization efficiency than .sup.32 p to be ion injected more efficiently with an ion injector. Ion Injection with Ion Injector As shown in FIGS. 1 and 2, ion injection is performed in vacuo with a uniform irradiating unit 10 provided within an ion injector 8 and this is in order to achieve uniform ion injection into the surfaces of cylindrical stents 2 made of stainless steel, tantalum or its alloys. Since the created ion beam has a larger diameter and a shorter length than the stents, uniform irradiation of the entire surface of each stent has to be assured by using a uniform irradiating unit equipped with a rotating table 3 capable of not only rotation but also vertical movements. Connecting Nuclear Reactor to Ion Injector Xenon- 133 is a nuclear fission product which is constantly generated by nuclear fission in fuel rods in a nuclear reactor upon irradiation of 1.sup.235 U with neutrons. If the fuel rods are connected to an ion source 9 in the ion injector via piping, the gaseous .sup.133 Xe generated in the fuel rods can be transferred through the piping to the ion source in the ion injector. Radioactive stents can be mass produced by allowing the supplied .sup.133 Xe to be continuously ion injected into the surfaces of stents by means of the ion injector. Stated more specifically, if neutrons impinge on .sup.235 U in the fuel rods 5 in the nuclear reactor 4, the resulting nuclear fission of .sup.235 U gives rise to .sup.133 Xe in a gaseous form. The generated .sup.133 Xe gas passes through the piping 6 to enter a Xe purifier 7, where it is worked up to the pure form. The pure .sup.133 Xe gas moves on through the piping 6 to be supplied into the ion source 9 within the ion injector 8 . The supplied .sup.133 Xe gas is ionized to yield an ion beam, which is introduced into the irradiating unit 10 in the ion injector and directed to one of the stents positioned on the vertically movable rotating table 3 in the irradiating unit. Since the rotating table is capable of not only rotation on its shaft but also vertical movements, all stents erected on the table are uniformly irradiated with the ion beam, whereby .sup.133 Xe is uniformly injected into the surfaces of the stents. The following example is provided for the purpose of further illustrating the present invention. EXAMPLE Gaseous 1.sup.33 Xe (40 MBq) was transferred to a 3.8-L sample container via a vacuum line. The container was also charged with ca. 3 cm.sup.3 of concentrated .sup.129 Xe isotope as a mass indicator in mass spectrometry. The container was connected to a Nielsen-type ion source in an ion injector, from which 40 keV or 60 keV of .sup.133 Xe was ion injected into the surfaces of stents each having a length of 14 mm and an outside diameter of 1.4 mm. To assure uniform irradiation of the surface of each stent, the ion injector was equipped with a vertically movable rotating irradiator (see FIG. 1). While the .sup.133 Xe ion beam 1 was flying in a fixed path, the rotating table 3 not only moved vertically but also rotated, thereby permitting the .sup.133 Xe ion beam 1 to impinge uniformly on the surfaces of eight stainless steel stents 2 erected on the rotating table 3 . The radioactivities of the stents thus injected with .sup.133 Xe were measured with a Ge semiconductor detector and the results are shown in Table 1, from which one can see that stents having radioactivities of up to 98 kBq were produced by ion injection of .sup.133 Xe as a .beta.-emitter. TABLE 1 Stent NO. Radioactivity, kBq 1 74.5 2 36.9 3 40.7 4 24.9 5 93.4 6 97.9 The radioactive stents produced by the above-described method were kept in place for 4 weeks in the abdominal aortas of rabbits; they proved to retard the growth of vascular smooth muscles. FIG. 2 shows a general layout for connecting a nuclear reactor to the ion injector in such a way as to enable mass production of .sup.133 Xe radioactive stents. Xenon-133 produced in the fuel rods 5 in the nuclear reactor 4 passes through the piping 6 to enter the Xe purifier 7, where it is deprived of .sup.131 I and other impurities; the pure .sup.133 Xe also passes through the piping 6 to be transferred into the ion source 9 in the ion injector 8, where it is ionized and accelerated; the accelerated ion beam of .sup.133 Xe is injected into the surfaces of stents erected on the rotating table in the uniform irradiating unit 10 of the ion injector. The .sup.133 Xe radioactive stents produced in accordance with the present invention proved to be capable of retarding the growth of vascular smooth muscles of the abdominal aortas of rabbits. Therefore, if such .sup.133 Xe radioactive stents are applied to patients suffering from arteriosclerosis, it is expected that they can retard the growth of vascular smooth muscles, thereby preventing the restenosis of opened blood vessels. If a uniform irradiator is employed in an ion injector connected to a nuclear reactor, radioactive stents featuring uniform irradiation with .sup.133 Xe can be produced in high volume. |
description | The present invention relates in general to electron beam duplication lithography. Referring to FIG. 4, there is illustrated a prior art apparatus for performing electron beam duplication lithography using a photo cathode. A quartz substrate 41 forms the base of a mask plate 40 on which a chromium (Cr) light shield pattern 42 is formed. On the surface of substrate 41 and between the portions of the Cr light shield pattern 42, a photo cathode film 43 is deposited in a defined pattern. The photo cathode material 43 emits electrons when bombarded by light energy, such as ultra violet light 46. An exemplary photo cathode material is cesium iodide (CsI), which is a low work function material. An ultra violet light source (not shown) irradiates ultra violet light 46 through the backside of quartz substrate 41, bombarding the photo cathode film 43, resulting in a secondary emission of electrons 47 from the photo cathode patterned film 43. The emitted photo electrons 47 are accelerated by an electric field applied by acceleration electric source E, and may be focused into an electron beam 47 by a focusing magnetic field (magnetic field lens) 48 created by magnetic coils (not shown), onto electron beam resist film 45 deposited on substrate plate 44. In this manner, the “lithography” is not created by light but by exposure of the resist film 45 to an electron beam. The result is that the pattern formed by light shield pattern 42 and photo cathode film 43 is duplicated when portions of resist film 45 are bombarded by the electron beams 47. The electron beams change the molecular structure of the resist such that the portion of the resist bombarded by electrons is easy to dissolve in specific chemicals for the resist (“developer” chemicals). However, there are several disadvantages to the prior art technique illustrated in FIG. 4. Because the mask plate is itself a passive light emission device using a photo cathode, there is a need for an ultra violet lamp. Furthermore, the wave length of ultra violet light is limited to about 0.1 micrometers(μm), and thus, duplication lithography below 0.1 micrometers is very difficult, if not impossible. Additionally, the lifetime of the photo electron plane is limited to a duplication cycle of approximately 50 cycles when using CsI for the photo electron plane. Moreover, although the quartz substrate 41 is quite conductive to ultra violet light, quartz is a relatively expensive material especially in large areas. Furthermore, it is difficult to achieve a duplication that is precisely one-to-one between the pattern to be duplicated and the pattern that is created, without molding the surface of the photo cathode pattern 43 to be concave, which will result in surface roughness on the concave surface and a duplication that is even still difficult to produce in a one-by-one manner. The present invention addressed the foregoing needs by an electron beam duplication lithography apparatus utilizing a field emission cathode for emitting electrons to the electron beam resist film. One advantage of the present invention is that duplication lithography of a fine pattern with features below 0.1 micrometers is possible. Another advantage of the present invention is that a high duplication directivity of one-by-one is achievable. Yet another advantage of the present invention is that it does not require an ultra violet light source, nor a quartz substrate. The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be obvious to those skilled in the art that the present invention may be practiced without such specific details. Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views. In solving needs of the prior art, the present invention provides an electron beam duplication lithography apparatus and method for focusing electrons emitted from a mask plate as a result of an application of an electric field between a mask plate and a duplication plate. Irradiation of electrons from the mask plate is assisted through an electric field lens or magnetic field lens, or a combination thereof from an electron field emission material formed into a pattern on a flat surface of a substrate. The result is that a congruent or similar pattern is lithographed by electron beam exposure onto an electron beam resist film from a field emission film having the congruent or similar pattern to be created. Because there is no use of a photo cathode, it is possible to realize a longer lifetime of the mask plate. Moreover, it is possible to construct the mask plate using a conductive substrate or having a conductive film coated glass substrate or ceramic substrate or a metal substrate, at a lower cost. Moreover, it is possible to achieve higher current densities with a field emitter, resulting in a lessening of the exposure time of the resist film, resulting in a faster lithography process, which will increase the manufacturing throughput. Because the mask plate surface is flat, it is possible to more effectively duplicate in a one-to-one manner, plus there is no inherent limit to the size of the cathode. The whole pattern can be exposed in parts of it at a time. It is also possible to realize more precise duplication lithography below the 0.1 micrometer level. A field emission device can use low work function materials, such as a diamond-like carbon thin film. As a result, the two plates can be positioned closer together resulting in higher current densities, resulting in the increased efficiency, all without a degradation of the mask plate, since the diamond-like carbon thin film is more resistant to damage over its lifetime. Referring to FIG. 1, there is illustrated a cross-section view of an electron beam duplication lithography apparatus in accordance with an embodiment of the present invention. The apparatus may be operated in a vacuum chamber. The mask plate 10 is a cathode using a substrate 11 with an electron emission device 12 formed in a predetermined pattern on the substrate 11. The substrate 11 could be made from a conductive film coated glass, ceramics, silicon, metal, etc. The electron emission material 12 can be diamond-like carbon (DLC) film, diamond film, carbon film, carbon nanotube (CNT) film, porous silicon film, or any other field emission material. Furthermore, though the surface of the material is relatively flat, the present invention should not be limited to exclude micro-tip and other projection-like features of the field emission material. In this example, electron beams 15 emit from the plural patterned field emission devices 12 connected to the cathode electrode, and are focused to irradiate onto electron beam resist film 14 on duplicated plate 13. In one exemplary embodiment of the present invention, the mask plate 10 and the duplicated plate are in parallel with each other and separated between 50 micrometers and five millimeters apart. The substrates 11 and 13 may be conductive, or conductive films may be deposited thereon in order that an exemplary applied voltage from one kilovolt to ten kilovolts can be provided for promotion of emission of electrons from the electron emission device 12 toward the electron beam resist film 14. A magnetic lens (focusing magnetic field) 16 is formed parallel to the electron beams 15 to focus the electron beams 15 as they are irradiated toward the electron beam resist film 14. The magnetic field 16 may be created by any well known means. The magnitude of the magnetic field may be a function of the gap between the two plates and the field strength of the electrical field. The result of the apparatus in FIG. 1 is that an electron emission type plate is provided that is self-emitting of electrons and the field emission device 12 is planar and patterned to thereby etch a duplicated pattern into the electron beam resist film 14. As noted, to assist in preventing spreading of emitted electrons, the electron beam 15 can be focused with a magnetic field 16, but it is also possible to use an electric field lens. Also, some type of grid electrode can also be utilized to focus the electron beams 15. Further, it is possible to have a better defined pattern into the electron beam resist material 15 by placing the plates closer together, which can also result in a lowering of the voltage needed to create the acceleration voltage E. In this case, if needed, exposure of the resist film 14 on substrate 13 can be formed in sections over the entire substrate surface. FIG. 2 illustrates an exemplary duplicated pattern lithographed in accordance with an embodiment of the present invention by electron beam duplication lithography, such as using the apparatus illustrated in FIG. 1. On the duplicated plate 21 is a pattern 22 where the resist material 14 has been patterned by electron beam lithography from an electric field emission device 12. Such electric field emission device 12 will have the same pattern as the keyhole pattern 22 shown in FIG. 2. In FIG. 2, the exemplary duplicated pattern 22 is arranged in an array, but a more complex shaped pattern is possible using the present invention. Furthermore, inner circuitry can be formed different from circuitry around the periphery of the plate 21. The lithograph time t is defined by the emission current density J and the sensitivity S of the electron beam resist material used 14 as follows:t=S/J For example, when J is equal to 10 mA/cm2, and the electron beam resist material 14 has a sensitivity of 10 to 100 micro-Coulombs/cm2, for a one-to-one duplication lithography, it is possible to perform such a process in 10 milliseconds. FIGS. 3A, 3B, and 3C show cross-sections of alternative embodiments of the mask plate 10 shown in FIG. 1. The exemplary mask plate illustrated in FIG. 3A shows that the patterned field emission material 32a is formed with a dielectric or conducive material 33a onto substrate 31a where the surfaces of layers 32a and 33a are substantially coplanar. In FIG. 3B, the patterned field emission material 32b is recessed so that its top surface is lower than the top surface of the dielectric or conductive material 33b. In FIG. 3C, the field emission material 32c is patterned onto substrate 31c, and the dielectric or conductive material is then coated in between the patterned field emission material 32c and over its edges to cover the edged portions of the electric field emission device 32c. Note, it is also possible to merely coat a single layer of field emission material 32c onto substrate 31c, and then to realize the effective pattern of the field emission from gaps through the dielectric or conductive material 33c. The buried layers 33a, 33b, and 33c function to assist by concentrating the electrons emitted from the field emission material because the sidewalls are at least coated by the conductive or dielectric material. The reason is that otherwise, the edges of the field emission devices 32a, 32b, and 32c will more readily yield electron emissions resulting in a corresponding decrease in electron emissions from the non-edged portions. This may result in non-uniformity of the emission of electrons. However, with the methods illustrated in FIGS. 3A, 3B and 3C, it is possible to suppress the irregular lithography by realizing an improvement in the uniform emission of electrons from the entire field emission material that is unexposed. With the electron beam lithography of the present invention, it is possible to realize high resolution lithography, lithography of a pattern having features below 0.1 micrometers, and improved productivity with a quicker lithography process, and a focus depth of +/−15 micrometers. Referring to FIGS. 5A–5L there is illustrated a process for creating a mask plate, such as the mask plates illustrated in FIGS. 1 and 3A–3C. In FIG. 5A, a substrate 51 is provided. In FIG. 5B, an indium tin oxide (ITO) layer 52 is deposited onto substrate 51. In FIG. 5C, a field emitter material 53 is deposited onto the ITO layer 52. In FIG. 5D, an electron-beam sensitive or photosensitive resist layer 54 is deposited onto the field emitter layer 53. In FIG. 5E, the resist material 54 is exposed by an E-beam or light with pattern and developed to form a patterned layer of resist 54. Note, an alternative approach may be to deposit a hard-mask layer on top of the field emitter material 53, then deposit the resist material, then expose the resist material then develop it to then etch the hard-mask layer. The resist is then removed leaving a structure that is the same as above, except that the top layer is a hard-mask layer and not a resist material. Such a hard-mask layer could be used to withstand a harsh etch of oxygen plasma. In FIG. 5F the field emitter material 53 is etched in oxygen plasma. In FIG. 5G, the resist material (or hand-mask layer) 54 is removed. In FIG. 5H, a layer of silicon dioxide (SiO2) is deposited on top of the field emitter 53 and ITO 52 layers. In FIG. 5I, an E-beam sensitive resist layer 56 is deposited onto the silicon dioxide layer 55. In FIG. 5J, the E-beam resist layer 56 is pattern exposed to an electron beam, developed and patterned using standard techniques in the photo mask industry. In FIG. 5K, the silicon dioxide layer 56 is etched using fluorocarbon plasma dry etch technology. In this case, line and space width is dependent on the required width. In FIG. 5L, the resist layer 56 is removed. Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. |
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claims | 1. A radiation imaging apparatus comprising:a detection unit for detecting a radiation distribution transmitted through an object;an imaging unit which includes said detection unit; anda grid for suppressing scattered light which is detachably mounted on an outside of said imaging unit,wherein said imaging unit includes a buffer member on a side surface facing a surface side which radiation strikes,said grid includes a grid body placed on the surface side which the radiation strikes, and a fixing unit for fixing the grid body to said imaging unit, andsides constituting the fixing unit include a side which does not protrude from an outer shape of said imaging unit when viewed from the surface side which the radiation strikes. 2. The apparatus according to claim 1, wherein said imaging unit includes a handle, anda side of said fixing unit which is perpendicular to a side located near the handle when viewed from the surface side which the radiation strikes does not protrude from the outer shape of said imaging unit. 3. The apparatus according to claim 2, wherein a side of the buffer member of said imaging unit which is parallel to the side located near the handle when viewed from the surface side which the radiation strikes includes a notched portion, andthe fixing unit is positioned by the notched portion at a side parallel to the side located near the handle, and the parallel side is a side which does not protrude from the outer shape of said imaging unit. 4. The apparatus according to claim 2, wherein the fixing unit includes bent portions, each having a substantially U-shaped cross-section, which hold said imaging unit therebetween, and is mounted on said imaging unit while holding, therebetween, the side including the handle of said imaging unit and an opposite side. 5. The apparatus according to claim 3, wherein the fixing unit includes a lock portion which locks to the handle and bent portions, each having a substantially U-shaped cross-section, which are arranged to hold said imaging unit therebetween at a position of the notched portion, and is mounted on said imaging unit while holding said imaging unit by the lock portion and the bent portions. 6. The apparatus according to claim 1, wherein the fixing unit of said grid has a shape which is bent toward said imaging unit on an incident surface side of said imaging unit so as to cover a gap corresponding to a thickness of the grid body between the grid body and the fixing unit, and so as not to protrude from a side surface. |
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summary | ||
059303190 | abstract | A nuclear reactor includes a propagation space for core melt. The propagation space has a coolant conduit leading to a coolant reservoir and a device which opens in a temperature-dependent manner. The coolant conduit in the propagation space is a spray conduit having a spraying area which covers the cross-section of the propagation space over a large area. The device is controlled in such a way that it opens when the core melt enters the propagation space. Spraying gives rise to a crust on the core melt which reduces heat radiation. At the same time, the propagation space fills with a steam atmosphere which drastically reduces the thermal load on building structures. |
description | The present application is a continuation of U.S. patent application Ser. No. 10/064,172 filed Jun. 18, 2002, now U.S. Pat. No. 6,836,535 which is a continuation-in-part of U.S. patent application Ser. No. 10/063,420 filed Apr. 22, 2002, both of which are incorporated herein by reference. The present invention relates generally to diagnostic imaging and, more particularly, to a method and apparatus of dynamically filtering radiation emitted toward a subject during radiographic imaging. Typically, in radiographic imaging systems, an x-ray source emits x-rays toward a subject or object, such as a patient or a piece of luggage. Hereinafter, the terms “subject” and “object” may be interchangeably used to describe anything capable of being imaged. The beam, after being attenuated by the subject, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is typically dependent upon the attenuation of the x-rays. Each detector element of the detector array produces a separate electrical signal indicative of the attenuated beam received by each detector element. The electrical signals are transmitted to a data processing system for analysis which ultimately produces an image. In computed tomography (CT) imaging systems, the x-ray source and the detector array are rotated about a gantry within an imaging plane and around the subject. X-ray sources typically include x-ray tubes, which emit the x-rays as a beam at a focal point. X-ray detectors typically include a collimator for collimating x-ray beams received at the detector, a scintillator for converting x-rays to light energy adjacent the collimator, and a photodiode for receiving the light energy from an adjacent scintillator and producing electrical signals therefrom. Typically, each scintillator of a scintillator array converts x-rays to light energy. Each photodiode detects the light energy and generates a corresponding electrical signal. The outputs of the photodiodes are then transmitted to the data processing system for image reconstruction. There is increasingly a need to reduce radiation dosage projected toward a patient during an imaging session. It is generally well known that significant dose reduction may be achieved by using a “bowtie” filter to shape the intensity profile of an x-ray beam. Surface dose reductions may be as much as 50% using a bowtie filter. It is also generally known that different anatomical regions of a patient may advantageously mandate different shaped bowtie filters to reduce radiation dosage. For example, scanning of the head or small region of a patient may require a bowtie filter shaped differently than a filter used during a large body scanning session. It is therefore desirable to have an imaging system with a large number of bowtie filter shapes available to best fit each patient. However, fashioning an imaging system with a sufficient number of bowtie filters to accommodate the idiosyncrasies encountered during scanning of numerous patients can be problematic in that each individual patient cannot be contemplated. Additionally, manufacturing an imaging system with a multitude of bowtie filters increases the overall manufacturing cost of the imaging system. Therefore, it would be desirable to design an apparatus and method of dynamically filtering the radiation emitted toward the subject during imaging data acquisition with a single filter. The present invention is a directed method and apparatus of dynamically filtering radiation projected toward a subject for data acquisition overcoming the aforementioned drawbacks. The present invention includes a filtering apparatus for a CT imaging system or equivalently for an x-ray imaging system. The filtering apparatus is designed such that its shape may be changed prior to or during an imaging session. The shape of the filtering apparatus can be modulated to mirror an attenuation pattern of a subject thereby optimizing radiation dose exposure to the subject. Furthermore, by implementing two opposing filters that are orthogonally oriented with respect to one another, the x-ray attenuation may be controlled along the x as well as z axes to shape the x-ray intensity. A number of filtering apparatuses are contemplated. In accordance with one aspect of the present invention, a method of diagnostic imaging comprises the steps of positioning a subject to be scanned into a scanning bay and projecting a radiation beam along a beam path toward the subject. The method further includes positioning a filter having an attenuation profile in the beam path. The attenuation profile of the filter is then modulated to define a desired attenuation profile. The method further includes acquiring diagnostic data of the subject and reconstructing an image of the subject from the diagnostic data. In accordance with another aspect of the present invention, a method of acquiring diagnostic data of a subject comprises the steps of determining an attenuation pattern for acquiring diagnostic data of a subject to be scanned and presetting a first filter to a desired attenuation profile. The method further includes the step of projecting high frequency electromagnetic energy toward the subject to acquire diagnostic data of the subject. During the projection of high frequency electromagnetic energy, a second filter having an attenuation profile is translated such that the attenuation profiles of the first filter and the second filter is a function of the attenuation pattern of the subject. In accordance with a further aspect of the present invention, a method of diagnostic imaging includes the steps of positioning a subject to be scanned on a table in a scanning bay and projecting high frequency electromagnetic energy toward the subject. The method further includes dynamically filtering the high frequency electromagnetic energy with at least one filter and acquiring imaging data of the subject. A set of images of the subject from the imaging data are then reconstructed. With the subject removed from the scanning bay, high frequency electromagnetic energy is again projected toward the detector absent the subject and table and dynamically filtered with the at least one filter. The method further includes acquiring scan data attributable to the at least one filter and generating a set of calibration data attributable to the at least one filter to be used in reconstructing artifact free images of the subject. In accordance with yet another aspect of the present invention, a radiation emitting system comprises a scanning bay configured to position the subject to be scanned in a path of radiation as well as a radiation projection source configured to project radiation toward the subject. The system further includes a radiation filter having a variable attenuation profile. A computer is also provided and programmed to determine an attenuation pattern of the subject and modulate the variable attenuation profile of the radiation filter as a function of the attenuation pattern of the subject. In accordance with a further aspect of the present invention, a radiation emitting imaging system is provided. The imaging system includes a scanning bay and a moveable table configured to move a subject to be scanned fore and aft along a first direction within the scanning bay. The system further includes an x-ray projection source configured to project x-rays toward the subject. A first attenuator is provided and configured to attenuate x-rays along a first axis. A second attenuator is also provided and configured to attenuate x-rays along a second axis. Both the first attenuator and second attenuator are translatable in the first direction. The imaging system further includes a computer programmed to calibrate the first attenuator to have a desired attenuation profile and calibrate the second attenuator to have a desired attenuation profile. The computer is further programmed to move the subject along the first direction and simultaneously therewith, translate at least one of the first attenuator and the second attenuator in the first direction. In accordance with yet another aspect of the present invention, a computer readable storage medium is provided and has stored thereon a computer program representing a set of instructions that when executed by a computer causes the computer to move a subject to be scanned into a scan position. The set of instructions further causes the computer to determine an attenuation pattern of the subject and manipulate an attenuation profile of a filter configured to filter x-rays projected toward a subject. The computer is also instructed to acquire imaging data of the subject and reconstruct at least one image therefrom. In accordance with another aspect of the present invention, a filtering apparatus to filter radiation projected toward a subject to be scanned is provided. The filtering apparatus includes a body having a plurality of hollow tubes parallelly arranged and configured to receive and discharge attenuating fluid to define an attenuation profile as a function of an attenuation pattern of the subject. In accordance with a further aspect of the present invention, a filtering apparatus to filter radiation projected toward a subject to be scanned includes a body constructed so as to be capable of having a plurality of attenuating rods. Each of the attenuating rods is placeable in the body such that an attenuation profile as a function of an attenuation pattern of the subject is defined. In accordance with yet another aspect of the present invention, a filtering apparatus to filter radiation projected toward a subject to be scanned comprises a flexible bladder containing attenuating fluid. The flexible bladder is configured to be manipulated to modulate the attenuating fluid such that an attenuation profile as a function of an attenuation pattern of the subject is defined. In accordance with yet another aspect of the present invention, a pre-subject filter having variable attenuation for a radiographic imaging system is provided. The filter includes a first end having a first attenuation profile and a second end having a second attenuation profile. The second attenuation profile is larger than the first attenuation profile. The pre-subject filter is contoured to continuously change the attenuation profile from the first end to the second end. In accordance with a further aspect of the present invention, a CT system includes a rotatable gantry having an opening defining a scanning bay. This system also includes a movable table configured to translate a subject to be scanned along a first axis within the scanning bay. An x-ray projection source configured to project x-rays toward the subject is also provided. The system further includes a pre-subject filter configured to filter x-rays projected toward the subject when the filter has a shaped cross-section that changes shape as a function of z-axis position. The system also includes a computer programmed to determine attenuation pattern of the subject and translate the filter along the first axis with respect to the attenuation pattern of the subject. The computer is then programmed to acquire imaging data of the subject. In accordance with yet a further aspect of the present invention, a method of diagnostic imaging comprises the steps of positioning a subject to be scanned and to a scanning bay and projecting a radiation beam along a beam path toward the subject. The method also includes positioning a filter having variable attenuation in the beam path and translating a filter in at least one direction to reduce radiation exposure to sensitive anatomical regions of the subject. The method further includes acquiring imaging data of the subject and reconstructing an image of the subject from the imaging data. In accordance with another aspect of the present invention, a radiographic imaging system is provided and includes a scanning bay with a movable table configured to move a subject to be scanned fore and aft along a first direction within the scanning bay. The imaging system further includes an x-ray projection source configured to project x-rays in an x-ray beam toward the subject. A pair of cam filters formed of attenuating matter is also provided and controlled by a computer programmed to determine a region-of-interest of the subject and position the pair of cam filters to limit x-ray exposure to the patient area outside the region-of-interest. In accordance with yet another aspect of the present invention, a cam filter assembly for use with a radiation emitting imaging system is provided. The cam filter assembly includes a pair of cam filters wherein the attenuation varies with thickness of the cam filter. The pair of cam filters is also configured to operate in tandem to manipulate a beam of radiation projected toward a subject to limit radiation exposure to the patient area outside the region-of-interest of the subject. Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings. The present invention is described with respect to a radiographic imaging system such as the CT system shown in FIGS. 1–2 and the x-ray system shown in FIGS. 3–4. However, it will be appreciated by those skilled in the art that the present invention is equally applicable for use with other radiographic imaging systems. Moreover, the present invention will be described with respect to the emission and detection of x-rays. However, one skilled in the art will further appreciate, that the present invention is equally applicable for the emission and detection of other high frequency electromagnetic energy. Referring to FIGS. 1 and 2, a “third generation” CT imaging system 10 is shown as including a gantry 12. The present invention, however, is applicable with other CT systems. Gantry 12 has an x-ray source 14 that projects a beam of x-rays 16 through filter 15 toward a detector array 18 on the opposite side of the gantry 12. Detector array 18 is formed by a plurality of detectors 20 which together sense the projected x-rays that pass through a medical patient 22. Each detector 20 produces an electrical signal that represents the intensity of an impinging x-ray beam and hence the attenuated beam as it passes through the patient 22. During a scan to acquire x-ray projection data, gantry 12 and the components mounted thereon rotate about a center of rotation 24. Rotation of gantry 12 and the operation of x-ray source 14 are governed by a control mechanism 26 of CT system 10. Control mechanism 26 includes an x-ray controller 28 that provides power and timing signals to an x-ray source 14, a gantry motor controller 30 that controls the rotational speed and position of gantry 12, and filter controller 33 that controls filter 15. A data acquisition system (DAS) 32 in control mechanism 26 samples analog data from detectors 20 and converts the data to digital signals for subsequent processing. An image reconstructor 34 receives sampled and digitized x-ray data from DAS 32 and performs high speed reconstruction. The reconstructed image is applied as an input to a computer 36 which stores the image in a mass storage device 38. Computer 36 also receives commands and scanning parameters from an operator via console 40 that has a keyboard. An associated cathode ray tube display 42 allows the operator to observe the reconstructed image and other data from computer 36. The operator supplied commands and parameters are used by computer 36 to provide control signals and information to DAS 32, x-ray controller 28 and gantry motor controller 30. In addition, computer 36 operates a table motor controller 44 which controls a motorized table 46 to position patient 22 and gantry 12. Particularly, table 46 moves portions of patient 22 through a gantry opening 48. Referring now to FIGS. 3–4, an x-ray system 50 incorporating the present invention is shown. The x-ray system 50 includes an oil pump 52, an anode end 54, and a cathode end 56. A central enclosure 58 is provided and positioned between the anode end 54 and the cathode end 56. Housed within the central enclosure 58 is an x-ray generating device or x-ray tube 60. A fluid chamber 62 is provided and housed within a lead lined casing 64. Fluid chamber 62 is typically filled with coolant 66 that will be used to dissipate heat within the x-ray generating device 60. Coolant 66 is typically a dielectric oil, but other coolants including air may be implemented. Oil pump 52 circulates the coolant through the x-ray system 50 to cool the x-ray generating device 60 and to insulate casing 64 from high electrical charges found within vacuum vessel 68. To cool the coolant to proper temperatures, a radiator 70 is provided and positioned at one side of the central enclosure 58. Additionally, fans 72, 74 may be mounted near the radiator 70 to provide cooling air flow over the radiator 70 as the dielectric oil circulates therethrough. Electrical connections are provided in anode receptacle 76 and cathode receptacle 78 that allow electrons 79 to flow through the x-ray system 50. Casing 64 is typically formed of an aluminum-based material and lined with lead to prevent stray x-ray emissions. A stator 70 is also provided adjacent to vacuum vessel 68 and within the casing 64. A window 82 is provided that allows for x-ray emissions created within the system 50 to exit the system and be projected toward an object, such as, a medical patient for diagnostic imaging. Typically, window 82 is formed in casing 64. Casing 64 is designed such that most generated x-rays 84 are blocked from emission except through window 82. Referring now to FIGS. 5–9, a number of filter embodiments will be described. It should be noted that each of the embodiments described may be implemented as a pre-patient bowtie filter in a CT imaging system similar to filter 15 shown in FIGS. 1–2 or as a pre-patient filter 86 for an x-ray system similar to that shown in FIGS. 3–4. Specifically, a number of filter embodiments will be described wherein each of the filters may be modulated or “morphed” to define a desired attenuation profile specific to the particular imaging needs of an imaging session. For example, the attenuation profile of the filter may be modulated such that radiation exposure to particular organs is reduced without sacrificing or jeopardizing radiation exposure to other particular regions of interest. As a result, organs or regions of interest either sensitive to radiation exposure or not subject of the imaging session are not unnecessarily subjected to radiation exposure. Additionally, the attenuation profile of the filter may be modulated as a function of viewing angle. For example, the attenuation profile of the filter may be manipulated to filter radiation for a wider region of interest for a top view data acquisition position and likewise be manipulated to have a more narrow profile for a side view data acquisition position. The attenuation profile of the filter may also be modulated as a function of filter position along an imaging axis. For example, the attenuation profile of the filter may be dynamically manipulated during translation of the subject and/or filter to reduce radiation exposure in dose avoidance or reduction regions located between regions of interest. “Dose avoidance” and “dose reduction” refers to certain organs or anatomical regions where reduced radiation exposure is desired during an imaging session. While complete blockage of radiation to these areas is desired, reducing but not eliminating radiation exposure to these regions is acceptable. Therefore, it remains desirable to develop an attenuation profile that reduces if not eliminates radiation exposure to certain anatomical regions of the subject but SNR may be sacrificed with respect to these “avoidance” or “reduction” regions. Referring now to FIG. 5, one embodiment of the present invention is shown. In this embodiment, filter 100 includes a body 102 defined by a plurality of hollow tubes 104. Hollow tubes 104 are configured to receive attenuating fluid such as a contrast agent. As shown, a selected number of the hollow tubes have been flooded with the attenuating fluid to define an attenuation profile. The attenuation profile defined by the attenuating fluid flooded into the hollow tubes is only one example. That is, any number of the hollow tubes may be filled with attenuating fluid to define a desired attenuation profile. The attenuating fluid is stored in a reservoir (not shown) and a computer or control mechanism floods the tubes to define the desired attenuation profile needed for the imaging session or for a moment in the imaging session. That is, depending upon the needs of the imaging session, the tubes may be filled and flushed dynamically throughout the imaging session to vary the attenuation profile during data acquisition. A number of techniques of removing or flushing attenuating fluid from a tube are contemplated including a computer controlled system of valves (not shown) that apply compressed gas to the chambers. Alternately, a series of honeycombed cavities may be equivalently implemented in place of the hollow tubes. Referring now to FIG. 6, another embodiment of the filter in accordance with the present invention is shown. In this embodiment, filter 106 includes a body 108 defined by a number of attenuating rods 110. Operation of filter 106 is similar to operation of filter 100 of FIG. 5. With filter 106, each attenuating rod 110 is positioned within the body such that the plurality of attenuating rods as a whole defines the desired attenuation profile. Filter 106 may be used to filter radiation in a couple of ways. First, that portion of the plurality of attenuating rods 110 having attenuating rods removed may be placed in the x-ray beam path or, conversely, the attenuating rods 110 disposed from the rest of the attenuating rods may be slid into the x-ray beam path. A control and/or computer may be programmed to reposition the attenuating rods to define the desired attenuation profile. Referring now to FIG. 7, another preferred embodiment of a filtering apparatus 112 includes a flexible bladder 114 containing attenuating fluid positioned between an upper plate 116 and a lower plate or base 117. Bladder 114 is sufficiently flexible such that the attenuating fluid contained therein may be modulated or manipulated to define the desired attenuation profile. Bladder 114 may contain attenuating liquid, gelatin, beads, or the like. Upper plate 116 is fabricated from a flexible x-ray transparent material such as plastic that, in response to an applied force, alters the shape of the flexible bladder 114. In one embodiment, the upper plate responds to a force applied by at least one of a number of moveable rods 118. The moveable rods 118 are controlled by a computer to distort the upper plate such that the flexible bladder is likewise distorted. Base plate 118 supports the flexible bladder and is fabricated from a solid x-ray transparent material. Alternatively, base plate 117 could be fabricated to contain x-ray spectral filtration material. It should be noted that flexible bladder 114, upper plate 116, and base plate 117 are each fabricated from an x-ray transparent material so that x-rays are attenuated primarily by the attenuating fluid rather than the bladder or plates. Referring now to FIG. 8, another embodiment of a filtering apparatus in accordance with the present invention is shown. In this embodiment, filter 120 includes a first bladder 122 and a second bladder 124. Each bladder 122, 124 is designed to contain attenuating fluid such as attenuating liquid, gelatin, or beads. Filter 120 further includes an intermediary plate 126 disposed between bladder 122 and bladder 124. Filter 120 further includes an upper plate 128 and a lower plate 130. Each plate 128, 130 is formed from a plurality of parallelly aligned slots 132, 134. The slots 132 and 134 of each plate 128 and 130, respectively, impart or release a force applied to bladders 122 and 124. That is, each slot 132 of plate 128 moves perpendicularly with respect to plate 126 to impart a desired force onto bladder 122 such that the attenuating fluid contained within bladder 122 defines a desired attenuation profile. Slots 134 of plate 130 operate in a similar fashion to define a desired attenuation profile for bladder 124. For example, slots 132 may be moved by a computer controlled mechanism such as step actuators to impart a force on bladder 122 to define an attenuation profile along an x axis whereas slots 130 of plate 134 respond to another set of step actuators to define an attenuation profile along a z axis. Collectively, slots 132 and 134 cooperatively define a desired attenuation profile that mirrors a dual-axes attenuation pattern of the subject. The attenuation pattern of the subject may be determined from a scout scan of the subject. Additionally, filter 120 may be implemented with only one of the bladders 122, 124 and only one of the plates 128–130 of slots 132, 134. In this alternate single bladder embodiment, an attenuation profile is defined only along one axis. Moreover, in accordance with another embodiment, the flexible bladders 122, 124 may be manipulated by step actuators (not shown) directly without plates 128 and 130. Shown in FIG. 9 is a representation of a filtering apparatus in accordance with another aspect of the present invention during translation in a first direction. In this embodiment, filtering apparatus 136 comprises an x axis filter 138 and a z axis filter 140. Filtering apparatus 136 is designed to filter x-ray beams 142 projected toward a subject 144 by an x-ray source 146. Filters 138 and 140 may comprise any one of the dynamic filters described with respect of FIGS. 5–8. Accordingly, an attenuation profile of filter 138 and an attenuation profile of filter 140 are defined for a moment of x-ray projection. Preferably, the attenuation profiles are defined prior to the imaging session based on the attenuation pattern of the subject 144 determined from a scout scan, but, alternately, the attenuation profiles may be defined during x-ray projection or from a data base of patient demographic information. As shown in FIG. 9, the attenuation profile of filter 138 is set as is the attenuation profile of filter 140. Collectively, attenuation profiles will mirror the attenuation patterns of the subject 144 in both the x and z axis. In operation, as the subject 144 is translated in a first direction by a moveable table filter 138 is synchronously translated in the first direction as well. As a result, the collective attenuation profile of filters 138 and 140 mirror the attenuation pattern of the subject 144 during translation of the patient in the first direction along the z axis. As such, the dosage applied to various anatomical regions of the patient may be optimized to eliminate over exposure of radiation to the patient. While FIG. 9 shows translation of the z axis filter 140, the x axis filter 138 could likewise be translated with patient movement. Referring now to FIG. 10, a perspective view of a pre-subject filter in accordance with another aspect of the present invention is shown. In this embodiment, the pre-subject filter 148 includes a first end 150 and a second end 152. A body region 154 is disposed therebetween to connect first end 150 and second end 152 to one another. As shown, filter 148 has a cross-section that narrows from the second end 152 to the first end 150. That is, first end 150 has a filtering region that is narrower than the filtering region of second end 152. Additionally, the attenuation profile of first end 150 is larger than the attenuation profile of second end 152. That is, the filtering material is thicker at the first end 150 than at the second end 152. In the illustrated embodiment, the filtering material thickness changes linearly from the first end 150 to the second end 152. Filter 148 is designed such that it may be translated in a direction along the z-axis of a radiographic imaging system. That is, filter 148 may be translated such that the attenuation achieved by filter 148 generally complements the attenuation pattern of the subject to be scanned. As a result, anatomical regions or organs sensitive to radiation exposure may be protected against unnecessary radiation exposure. Furthermore, filter 148 is configured to be translated in a transverse direction as well. As a result, filtration with respect to the attenuation pattern of the subject may be achieved. To further reduce radiation exposure to the subject, filter 148 may be repositioned as a function of view angle. The filter can be easily calibrated prior to patient scanning by collecting and storing data representing the filter attenuation at two or more filter positions. During patient scanning, the appropriate attenuation profile is determined for correction during image reconstruction by interpolation and/or extrapolation. Referring now to FIG. 11, a schematic representation of a pair of cam filters configured to operate in tandem to manipulate an x-ray beam projected toward a subject in accordance with the present invention is illustrated. As shown, a pair of cam filters 156, 158 is configured to operate in tandem to manipulate an x-ray beam 159, schematically shown as a dashed line about a vertical axis between the filters, to limit radiation exposure outside the desired region-of-interest (ROI) of a subject. By operating filters 156, 158 in tandem, the profile of an x-ray may be manipulated. For example, the filter 156, 158 may be spaced closer to the beam path 159 to create a narrow beam profile 160 and spaced apart to create a wider beam profile 162. Additionally, one filter 156 may be moved away from the beam 159 and the other filter 158 moved closer to the beam 159 to cause the beam profile to be off-center. Filters 156, 158 are configured to be oriented along an x-axis of the subject to be scanned and may also be translated along the length of the subject to manipulate the beam profile with respect to the attenuation pattern of the subject to reduce radiation exposure to radiation sensitive or dose reduction regions of the subject. In a further embodiment, the intensity of the x-ray beam along the x-axis may be manipulated by configuring the filters to have a varying attenuation profile. For example, each filter may be configured such that the thickness of the attenuation material varies with the length of the filter. As such, different portions of the filter may be placed in the x-ray beam path to alter the filtering of the x-ray beam. Alternately, the filters could be formed to have a constant thickness but the density of the filtering material varies along the length of the filter. Other embodiments are contemplated including fabricating the filters to have different sections or cores wherein each section has a different filtering power and depending upon the clinical needs of the imaging session, different sections are placed in the beam path. In another embodiment, each filter has an elliptical shape to reduce x-ray intensity drop off rate. As is indicated previously, a scout scan may be performed of the subject to determine a filter contour that best fits the complement of the patient's attenuation pattern. Accordingly, special needs of the imaging session for the patient such as dose avoidance or reduction regions or regions of increased x-ray necessity may be accounted for in defining the patient's attenuation pattern. Also, as indicated previously, the attenuation profile of filters may be preset prior to the imaging session or dynamically modulated during the imaging session to mirror or complement the attenuation pattern of the subject. In a further embodiment of the present invention, one or more dynamic filters may be used to filter radiation during the acquisition of imaging data of a subject. A set of images can then be reconstructed according to well known reconstruction techniques of the subject based on the filtered imaging data. However, the imaging data is susceptible to the presence of artifacts and the set of images associated with the one or more filters itself. Accordingly, the patient is removed from the scanning bay and another set of scan data is acquired wherein the one or more filters are dynamically defined as they were during the imaging of the patient. As a result, a set of calibration data is obtained attributable to the one or more dynamically configured filters. Therefore, a set of images of the of the patient can be reconstructed using the calibration data and usual correction methods. The present invention has been described with respect to a number of embodiments of a dynamic filter to be implemented in a radiographic imaging system. The various embodiments may be utilized to dynamically modulate the attenuation profile of the filter prior to and/or during the imaging session to mirror the attenuation pattern of the subject and thereby reduce radiation exposure to the patient. Accordingly, in accordance with one embodiment of the present invention, a method of diagnostic imaging comprises the steps of positioning a subject to be scanned into a scanning bay and projecting a radiation beam along a beam path toward the subject. The method further includes positioning a filter having an attenuation profile in the beam path. The attenuation profile of the filter is then modulated to define a desired attenuation profile. The method further includes acquiring diagnostic data of the subject and reconstructing an image of the subject from the diagnostic data. In accordance with another embodiment of the present invention, a method of acquiring diagnostic data of a subject comprises the steps of determining an attenuation pattern for acquiring diagnostic data of a subject to be scanned and presetting a first filter to a desired attenuation profile. The method further includes the step of projecting high frequency electromagnetic energy toward the subject to acquire diagnostic data of the subject. During the projection of high frequency electromagnetic energy, a second filter having an attenuation profile is translated such that the attenuation profiles of the first filter and the second filter is a function of the attenuation pattern of the subject. In accordance with a further embodiment of the present invention, a method of diagnostic imaging includes the steps of positioning a subject to be scanned on a table in a scanning bay and projecting high frequency electromagnetic energy toward the subject. The method further includes dynamically filtering the high frequency electromagnetic energy with at least one filter and acquiring imaging data of the subject. A set of images of the subject from the imaging data are then reconstructed. With the subject removed from the scanning bay, high frequency electromagnetic energy is again projected toward the detector absent the subject and table and dynamically filtered with the at least one filter. As a result, a set of calibration data is obtained attributable to the one or more dynamically configured filters. Therefore, a set of images of the patient can be reconstructed using the calibration data and usual correction methods. In accordance with yet another embodiment of the present invention, a radiation emitting system comprises a scanning bay configured to position the subject to be scanned in a path of radiation as well as a radiation projection source configured to project radiation toward the subject. The system further includes a radiation filter having a variable attenuation profile. A computer is also provided and programmed to determine an attenuation pattern of the subject and modulate the variable attenuation profile of the radiation filter as a function of the attenuation pattern of the subject. In accordance with a further embodiment of the present invention, a radiation emitting imaging system is provided. The imaging system includes a scanning bay and a moveable table configured to move a subject to be scanned fore and aft along a first direction within the scanning bay. The system further includes an x-ray projection source configured to project x-rays toward the subject. A first attenuator is provided and configured to attenuate x-rays along a first axis. A second attenuator is also provided and configured to attenuate x-rays along a second axis. Both the first attenuator and second attenuator are translatable in the first direction. The imaging system further includes a computer programmed to calibrate the first attenuator to have a desired attenuation profile and calibrate the second attenuator to have a desired attenuation profile. The computer is further programmed to move the subject along the first direction and simultaneously therewith, translate at least one of the first attenuator and the second attenuator in the first direction. In accordance with yet another embodiment of the present invention, a computer readable storage medium is provided and has stored thereon a computer program representing a set of instructions that when executed by a computer causes the computer to move a subject to be scanned into a scan position. The set of instructions further causes the computer to determine an attenuation pattern of the subject and manipulate an attenuation profile of a filter configured to filter x-rays projected toward a subject. The computer is also instructed to acquire imaging data of the subject and reconstruct at least one image therefrom. In accordance with another embodiment of the present invention, a filtering apparatus to filter radiation projected toward a subject to be scanned is provided. The filtering apparatus includes a body having a plurality of hollow tubes parallelly arranged and configured to receive and discharge attenuating fluid to define an attenuation profile as a function of an attenuation pattern of the subject. In accordance with a further embodiment of the present invention, a filtering apparatus to filter radiation projected toward a subject to be scanned includes a body constructed to be capable of having a plurality of attenuating rods. Each of the attenuating rods is placeable in the body such that an attenuation profile as function of an attenuation pattern of the subject is defined. In accordance with yet another embodiment of the present invention, a filtering apparatus to filter radiation projected toward a subject to be scanned comprises a flexible bladder containing attenuating fluid. The flexible bladder is configured to be manipulated to modulate the attenuating fluid such that an attenuation profile as a function of an attenuation pattern of the subject is defined. In accordance with yet another embodiment of the present invention, a pre-subject filter having variable attenuation for a radiographic imaging system is provided. The filter includes a first end having a first attenuation profile and a second end having a second attenuation profile. The second attenuation profile is larger than the first attenuation profile. The pre-subject filter continuously varies the attenuation profile in the z-axis between the first end and the second end. In accordance with a further embodiment of the present invention, a CT system includes a rotatable gantry having an opening defining a scanning bay. This system also includes a movable table configured to translate a subject to be scanned along a first axis within the scanning bay. An x-ray projection source and configured to project x-rays toward the subject. The system further includes a pre-subject filter configured to filter x-rays projected toward the subject. The system also includes a computer programmed to determine attenuation pattern of the subject and translate the filter along the first axis with respect to the attenuation pattern of the subject. The computer is then programmed to acquire imaging data of the subject. In accordance with yet a further embodiment of the present invention, a method of diagnostic imaging comprises the steps of positioning a subject to be scanned and to a scanning bay and projecting a radiation beam along a beam path toward the subject. The method also includes positioning a filter having variable attenuation in the beam path and translating a filter in at least one direction to reduce radiation exposure to sensitive anatomical regions of the subject. The method further includes acquiring imaging data of the subject and reconstructing an image of the subject from the imaging data. In accordance with another embodiment of the present invention, a radiographic imaging system is provided and includes a scanning bay with a movable table configured to move a subject to be scanned fore and aft along a first direction within the scanning bay. The imaging system further includes an x-ray projection source configured to project x-rays in an x-ray beam toward the subject. A pair of cam filters formed of attenuating matter is also provided and controlled by a computer programmed to determine a region-of-interest of the subject and position the pair of cam filters to limit x-ray exposure to the patient area outside the region-of-interest. In accordance with yet another embodiment of the present invention, a cam filter assembly for use with a radiation emitting imaging system is provided. The cam filter assembly includes a pair of cam filters wherein each cam filter has an attenuation power that varies with thickness of the filter. The pair of cam filters is also configured to operate in tandem to manipulate a beam of radiation projected toward a subject to limit radiation exposure to a region-of-interest of the subject. The present invention has been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims. |
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claims | 1. A method of use for a radiopharmaceutical pig, the radiopharmaceutical pig comprising a base and a cap removably attachable to the base,the base comprising:a radiation-blocking base shielding element having an open end, a closed end, and at least one wall extending between the open and closed ends, the closed end and the at least one wall defining an interior of the base shielding element; anda polymeric base shell that completely encloses an entirety of the base shielding element, the base shell defining a hollow section of the base; and the cap comprising:a radiation-blocking cap shielding element having an open end, a closed end, and at least one wall extending between the open and closed ends, the closed end and the at least one wall defining an interior of the cap shielding element; anda polymeric cap shell that completely encloses an entirety of the cap shielding element, the cap shell defining a hollow section of the cap,the method comprising:placing a syringe having a radiopharmaceutical therein into the hollow section of the base of the pig; andattaching the cap of the pig to the base of the pig so that the cap shielding element and the base shielding element are in overlapping relationship with each other, and so that an inner base shell portion of the base shell and an inner cap shell portion of the cap shell are in overlapping relationship with each other to thereby enclose the syringe and the radiopharmaceutical in the syringe within the pig. 2. The method of claim 1 further comprising attaching a label to the syringe. 3. The method of claim 1 further comprising attaching a label to the pig. 4. The method of claim 1 further comprising placing the pig with the syringe and the radiopharmaceutical enclosed therein in a delivery container. 5. The method of claim 1 further comprising transporting the pig with the syringe and the radiopharmaceutical enclosed therein to a medical facility. 6. The method of claim 1 wherein the attaching comprises engaging threads on the cap of the pig with threads on the base of the pig. 7. The method of claim 6 wherein the engaging comprises rotating the cap no more than three hundred and sixty degrees (360°) with respect to the base. 8. The method of claim 6 wherein the engaging comprises rotating the cap no more than ninety degrees (90°) with respect to the base. 9. The method of any one of claims 6-8 further comprising at least one locking detent associated with the threads. 10. The method of claim 1 wherein the syringe comprises a barrel and a plunger, wherein the placing includes the barrel of the syringe being received in the hollow section of the base, and the attaching includes the plunger of the syringe being received in the hollow section of the cap. 11. The method of claim 1 wherein the cap shell and the base shell comprise polycarbonate resin. 12. The method of claim 1 wherein at least one of the base and the cap is elongate. 13. The method of claim 12 wherein both the base and the cap are elongate. 14. The method of claim 1 wherein an exterior of at least one of the base shell and the cap shell comprises a plurality of flat surfaces. 15. The method of claim 14 wherein the exterior of each of the base shell and the cap shell comprises a plurality of flat surfaces. 16. The method of claim 1 wherein the base shielding element comprises lead. 17. The method of claim 1 wherein the base shielding element is made of lead. 18. The method of claim 1 wherein the base shielding element comprises tungsten. 19. The method of claim 1 wherein the base shielding element is made of tungsten. 20. The method of claim 1 wherein the base shielding element comprises a metallic-filled polymer. 21. The method of claim 1 wherein the base shielding element is made of a metallic-filled polymer. 22. The method of claim 1 wherein the cap shielding element comprises lead. 23. The method of claim 1 wherein the cap shielding element is made of lead. 24. The method of claim 22, wherein the base shielding element is made of lead. 25. The method of claim 1 wherein the cap shielding element comprises tungsten. 26. The method of claim 1 wherein the cap shielding element is made of tungsten. 27. The method of claim 1 wherein the cap shielding element comprises a metallic-filled polymer. 28. The method of claim 1 wherein the cap shielding element is made of a metallic-filled polymer. 29. The method of claim 1 wherein polymeric material is molded about the base shielding element to form the base shell. 30. The method of claim 1 wherein polymeric material is molded about the cap shielding element to form the cap shell. 31. The method of claim 1 wherein polymer material is molded about the base shielding element to form the base shell, and polymer material is molded about the cap shielding element to form the cap shell. 32. The method of claim 1 wherein the cap shell further comprises an annular flange adapted for face-to-face engagement with a portion of the base shell when the cap is attached to the base. 33. The method of claim 1 wherein the syringe comprises finger grips that are disposed between a portion of the base shell and a portion of the cap shell after the attaching. 34. The method of claim 1 wherein the hollow section of the base is devoid of a removable inner liner. |
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056639937 | description | BEST MODE FOR CARRYING OUT THE INVENTION Referring now to the drawings, particularly FIG. 1, there is illustrated a nuclear fuel bundle assembly generally designated 10, incorporating the feature of the present invention. Briefly, the nuclear fuel bundle assembly 10 includes a lower tie plate 12, an upper tie plate 14, a plurality of fuel rods 16 extending between the lower tie plate 12 and upper tie plate 14. A plurality of spacers 18 (one shown) are disposed at vertically spaced locations along the height of the fuel bundle for maintaining the fuel rods and water rods in predetermined lateral positions relative to one another. The fuel bundle assembly 10 is encased within a casing or channel 20. In conventional fashion, coolant/moderator liquid flows into an opening through the lower tie plate 12 and into and about the fuel rods 16 within the channel 20 and upwardly through the spacers 18, whereby steam is generated for use in, for example, the production of electricity. In this fuel bundle assembly, a pair of water rods 22, 24 structurally interconnect the upper and lower tie plates 14, 12, and no other structural connections between the upper and lower tie plates are employed. While only a pair of water rods are disclosed and discussed herein, it will be appreciated that one or more additional water rods may be employed to structurally interconnect the upper and lower tie plates to one another. Alternatively, a single water rod may be employed for the same purpose. It will be appreciated however, that the invention disclosed herein is equally applicable to other fuel bundle assemblies where, for example, fuel rods configured as tie rods serve as the load bearing members of the bundle. The water rods or tubes 22 and 24 extend vertically through central regions of the fuel bundle, although other locations may be appropriate. The water rods in the exemplary embodiment are threadedly attached at their lower ends to the lower tie plate 12 (FIG. 2) and extend upwardly within the fuel bundle through the spacers 18 for coupling to the upper tie plate 14 in the manner described in commonly owned copending application Ser. No. 08/380,587 filed Jun. 30, 1995, and now allowed. That application is incorporated herein by reference. The invention here has to do with the lower end plugs 26, 28, respectively, of the water rods 22, 24 by which the latter are secured to the lower tie plate 12. With reference specifically to FIGS. 2 and 3, the end plug 26 (end plug 28 is identical, and both are made of Zircaloy), it may be seen from FIG. 3 that the end plug is secured to the lower end of the water rod 24, by welding for example, and is in threaded engagement within a cylindrical boss 30 provided in the lower tie plate. With the water rods so attached to the lower tie plate, and attached to the upper tie plate in the manner described in the '587 application, it may be appreciated that the water rods serve as the sole load bearing means within the fuel bundle assembly 10. In other words, the entire fuel bundle assembly may be lifted out of the reactor core via the handle 32 which is structurally connected to the water rods by means of the latch mechanism disclosed in the '587 application. For other structural arrangements, however, the water rod end plug may be received in the lower tie plate in various other ways, and this invention is not limited to any particular fastening technique. As already noted above, in this invention, the water rods 22, 24 and specifically the water rod end plugs 26 and/or 28 incorporate a flow restriction or metering mechanism best seen in FIG. 3. The end plug 26 includes a coolant entrance end at 34 and a coolant exit end at 36. At the coolant entrance end 34, an enlarged inlet counterbore 38 opens to the upstream coolant flow. This opening is reduced to a smaller diameter center bore 40 which extends through the plug to an exit where it opens to another larger counterbore 42. The center bore 40 has a greater axial length than either the inlet or outlet counterbores. The exterior of the metering device is formed with an annular locating shoulder 44 on which seats the lower end of the water rod, where the two are welded together by conventional welding techniques. The threaded cylindrical exterior portion of the end plug terminates at a slightly reduced neck portion 46 Which merges with a tapered transition 48, which in turn merges with a cylindrical portion 50 terminating at the shoulder 44. In the exemplary embodiment, the reduced diameter center bore 46 may have a diameter of about 0.297 inches, but it will be appreciated that the center bore 40 may be altered in accordance with the desired regulation of flow through the water rod. In an alternative arrangement, because the water rod inlet may in fact bypass a debris filter arrangement in the vicinity of the lower tie plate, a debris screen 52 (FIG. 4) may be incorporated into the metering device inlet counterbore 38, with flow openings sized and arranged to provide the desired pressure drop and flow characteristics. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. |
044118570 | summary | BACKGROUND OF THE INVENTION Complete shutdown of the operation of a nuclear reactor, commonly referred to as a scram, is required under any condition wherein continued operation could cause damage to the reactor. A scram is generally effected by releasing vertically disposed "safety" rods carrying neutron-absorbing material at their lower ends, thus allowing the rods to drop to a level wherein they position the absorber material within the reactor core. The inertia of long safety rods limits the speed at which they can be moved to scram position. Furthermore, it is possible that seismic shocks can interfere with the release of absorber carrying rods by bending them so that they cannot slide in their bearings. All scram control mechanisms must, of course, provide a means for returning safety rods to their raised position when an adverse operating condition has been eliminated. As shown in the description of scram mechanisms presented in the text titled "Fast Reactor Technology: Plant Design", published by M.I.T. Press in 1966, electromagnets have previously been used to hold reactor safety rods in a raised position until an unsafe reactor operating condition occurs, at which time the electromagnets are de-energized to release the rods. An electromagnet is incorporated in some latch mechanisms of embodiments of the invention disclosed herein, but the construction of safety rod release apparatus in accordance with the invention differs from that of known devices. Furthermore, known safety rod release devices use only one release means, whereas in preferred embodiments of this invention a plurality of release latches provide for two types of scram. SUMMARY OF THE INVENTION It is an object of this invention to provide an improved means for rapidly inserting a neutron absorber into a nuclear reactor core to control fission therein. Another object of the invention is to provide a nuclear reactor control apparatus having (1) plural latch assemblies for quickly releasing, under different conditions, a shaft which carries a neutron absorber, and (2) an additional lead screw drive means for moving the absorber into and out of a reactor core. A major difference between preferred embodiments of this invention and known apparatus for shutting down a nuclear reactor is that in the latter there is a single release mechanism that is actuated to permit a safety rod to move downwardly and thereby position a neutron absorber within a reactor core, whereas the invention provides (1) a first release mechanism that operates to drop an entire safety rod, and (2) a second release mechanism that operates to separate from the lower end of the safety rod a small segment thereof that holds the neutron absorber. The entire safety rod is released when a condition occurs that cannot affect the lowering of the rod, such as, for example, the failure of a coolant pump. However, when a condition occurs that may affect the movement of the entire safety rod (such as an earthquake), the absorber-holding segment is released from the lower end of the safety rod and allowed to move within the reactor core. The long safety rod could be bent by seismic shock and thus jammed in a position wherein the neutron absorber is held outside the reactor core. The small absorber holding segment of the rod will not be affected by seismic shock and, in addition, it can be moved more rapidly within the reactor core than the entire safety rod because its inertia is much less than that of the rod. Another advantage of using a plurality of release mechanisms is that the position of the safety rod can be detected during a scram of the entire safety rod (normal scram) using known types of position sensors such as reed switches and magnets. |
044629567 | claims | 1. A device for partitioning off the core of a pressurized nuclear water reactor, said reactor core being constituted by prismatic assemblies juxtaposed inside a core casing laterally bounding a space surrounding said core in which a cooling liquid circulates in the longitudinal direction of said assemblies, a transverse lower support plate and a transverse upper support plate also being disposed at either side of said core in the longitudinal direction, said device comprising (a) a set of boxes (8, 9, 10, 11) each including at least two plates (12-13, 14-15, 27-29, 28-30) rigidly assembled at right angles and disposed in the longitudinal direction of said assemblies (24); and (b) a plurality of transverse plates (32) perpendicular to said longitudinal plates and rigidly assembled to the latter, each of said boxes (8, 9, 10, 11) being removably disposed side by side inside the core casing (1) and bearing on said core casing without being attached thereto, so that the faces of said longitudinal plates directed towards the reactor core serve as bearing faces for said assemblies (24) disposed at the periphery of said core, each of said boxes (8, 9, 10, 11) being intercalated between said lower support plate (2) and said upper support plate (7) and fixed at its upper ends to said upper support plate by a flexible coupling (46, 47, 48) allowing each of said boxes to be displaced longitudinally. 2. A device according to claim 1, wherein at least one part of said longitudinal plates (14, 15) of said boxes is assembled together by keys (19) engaged in grooves (18a, 18b) provided in said plates in the longitudinal direction, over the whole length of said plates (14, 15). 3. A device according to claim 1, wherein said flexible coupling comprises a centering piece in two parts (46 and 47) telescoping in the longitudinal direction, with a spring (48) disposed between them, fixed to a reinforcing plate (41) disposed at the end of said box (10) which approaches said upper support plate 7 when it is put in position, said upper support plate (7) bearing a bearing device 49 which centers on the piece (46, 47) when said upper support plate (7) is put in position, causing said spring (48) to be compressed. 4. A device according to claim 1, wherein said flexible coupling comprises a centering piece (50) solid with said upper support plate (7), leaf springs (54) inserted between a reinforcing plate (52) at the end of said box (10) and said upper support plate (52) to engage with said centering piece (50) borne by said upper support plate (7). 5. A device according to claim 3 or 4, wherein said box (10) is associated at one of its ends with a flexible coupling apparatus (46, 47, 48) and at its other end with a centering piece (43) in said lower support plate (2). 6. A device according to any one of claims 1 to 4, wherein at least one part of said boxes (8, 9, 10, 11) includes a longitudinal plate (27, 28) associated with several longitudinal stiffening plates (29, 30) disposed perpendicularly to said longitudinal plate (27, 28) and rigidly fixed to said plate at its outer face directed towards said core casing (1). 7. A device according to any one of claims 1 to 4, wherein each of said boxes (8, 9, 10, 11) bears on said core casing (1) through transverse reinforcing plates (32) bearing on bearing rings (35) solid with the inner surface of said core casing (1). 8. A device according to any one of claim 1 to 4, including protective neutron-absorbent apparatuses (60, 61) or apparatuses for producing radio-active elements inside said boxes (8, 9, 10, 11) and fixed to said transverse reinforcing plates (32). 9. A device according to any one of claims 1 to 4, including apparatuses (63) for measuring, sampling or injecting liquid poison in the boxes and borne by said transverse reinforcing plates (32). |
047175346 | description | DETAILED DESCRIPTION The present invention provides a nuclear fuel cladding and a fuel rod containing the same, where the cladding is a composite material having a boron-containing burnable absorber integrally incorporated therein. Referring now to FIG. 1, there is illustrated a transverse cross-section of the composite cladding 1. The composite cladding 1 is composed of an outer tubular layer 3 of zirconium alloy having a first thickness, and an intermediate layer 5 having a thickness less than the thickness of tubular layer 3, formed from a mixture of a boron-containing material, such as zirconium boride, and a zirconium alloy, bonded to the inner wall 7 of the outer tubular layer 3. An inner layer 9 of zirconium metal, which has a thickness less than the thickness of the intermediate layer 5 is bonded to the inner surface 11 of the intermediate layer 5. The outer tubular layer 3 is formed from a zirconium alloy which contains less than about 5 percent by weight of alloying elements, usable in nuclear reactors. Such zirconium alloys contain elements which increase the mechanical properties of zirconium metal and/or the corrosion resistance of zirconium metal. The elements that are used in the formation of such alloys include niobium, oxygen, tin, iron, chromium, nickel, molybdenum, copper, vanadium and the like. Especially useful alloys are a zirconium alloy containing about 2.5 percent niobium and the zirconium alloys known as Zircaloy-2 and Zircaloy-4. Zircaloy-2 contains, by weight, about 1.2-1.7 percent tin; 0.07-0.20 percent iron; 0.05-0.15 percent chromium; and about 0.03-0.08 percent nickel; the balance being zirconium. Zircaloy-4 contains, by weight, about 1.2-1.7 percent tin; 0.12-0.18 percent iron, and 0.05-0.15 percent chromium, the balance being zirconium. The intermediate layer 5 is also formed from a zirconium alloy, of the alloys defined relative to the outer tubular layer 3, and preferably of the same alloy as that of the outer tubular layer, and has admixed therewith a boron-containing burnable absorber. The boron-containing burnable absorber is selected from boron compounds such as natural boron, enriched boron (boron having a higher percentage by weight of the isotope B.sup.10 than natural boron) zirconium boride (ZrB.sub.2), boron carbide (B.sub.4 C), boron nitride (BN), and the like. The boron-containing burnable absorber is dispersed throughout the zirconium alloy, in an amount of less than 3 percent by weight of the alloy, and the mixture formed into an intermediate layer that is bonded to the inner surface of the outer zirconium alloy tubular layer. The inner layer 9 is a layer of zirconium metal and has a thickness less than the thickness of the intermediate layer 5, and is bonded to the inner surface of the intermediate layer such that a composite tubular cladding is produced that has a boron-containing burnable absorber integrally incorporated therein. The inner zirconium layer prevents a problem of stress corrosion and possible failure of the tubular cladding by "pellet-clad interaction". This term is used to describe the attack on the cladding by volatile fissile materials such as iodine, cadmium, or other volatile elements released by the fuel during operation of the reactor. Such attack, coupled with cladding operating stresses, can produce stress crack corrosion of the metallic cladding and eventual penetration of the wall of the tubular cladding. Also, during irradiation, the boron-containing burnable absorber results in helium gas being produced in the intermediate layer, and the inner layer of zirconium metal prevents the penetration of such helium gas into the interior space of the tubular cladding. Since the intermediate layer has a thicker zirconium alloy tubular layer 3 on its outer surface, and a thinner zirconium layer 9 on its inner surface, this intermediate layer 5 is subject to neither the coolant for the reactor which contacts the outer tubular layer 3, nor the fuel pellets and emission products thereof which contact the inner layer 9. The outer tubular layer 3 has the largest cross-sectional area and, as such, serves the normal function of a cladding, the mechanical integrity and strength to contain the fuel pellets and resist corrosion from the fuel, emission products, and the coolant in which the fuel elements are positioned. As illustrated in FIG. 3, the outer zirconium alloy tubular layer 3 has a thickness A of at least about 15 mils. The intermediate layer 5, the zirconium alloy containing the boron-containing burnable absorber has a thickness B, less than the thickness A, and is preferably a thickness of about 3-5 mils. The thickness will vary dependent upon the type of boron-containing burnable absorber used and the amount of burnable absorber desired. The inner zirconium metal layer 9 has a thickness C, less than the thickness B, and is preferably a thickness of about 1-2 mils. This layer is the thinnest layer, and is used to isolate the intermediate layer from the fuel pellets. The overall thickness of the component cladding, A+B+C, is preferably between 18-22 mils, with A>B>C. In most instances, due to the large thickness of the outer tubular layer A, the thickness of the outer tubular layer A will be at least twice the thickness of the sum of the thicknesses of the intermediate layer and the inner layer, i.e. A>2(B+C). The intermediate layer, which contains the boron-containing burnable absorber can be fabricated to provide specific desired burnable absorber contents. The concentration of the burnable absorber in a specific application will depend on the requirements of the nuclear system, manufacturability, and the irradiation behavior during operation of the reactor in which the fuel element is used. For the same nuclear system requirements, the concentration of the burnable absorber can be adjusted by either altering the thickness of the intermediate layer or the B.sup.10 enrichment of the boron-containing burnable absorber. As an example of how the amount of boron-containing absorber can be determined, using a 5 mil thick intermediate layer of zirconium boride (ZrB) in a Zircaloy-4 alloy, the following describes the key parameters. The symbols and their typical values are as follows: ______________________________________ (Typical) Symbol Unit Description Value ______________________________________ D in Clad OD 0.374 .tau. mil Thickness of Zr--ZrB.sub.2 layer 5 B mg/cm B-10 concentration per 0.6 unit length E B-10 enrichment 0.19 (Nat) 1.0 (Enriched B) .rho.1 gr/cc ZrB.sub.2 density 6.09 .rho.2 gr/cc Zircaloy-4 density 6.55 F.sub.B Fraction of Boron in ZrB.sub.2 0.1917 C w/o w/o of ZrB.sub.2 in Zircaloy-4 <3 V v/o v/o of ZrB.sub.2 in Zircaloy-4 <3 ______________________________________ C and V are related as ##EQU1## The B-10 content per unit length is obtained by ##EQU2## For typical light water reactors, ZrB.sub.2 concentration in the mixture layer can be easily in manufacturability range by adjusting the layer thickness and boron-10 enrichment. The composite tubular cladding may be formed by various processes. For example, an intermediate layer can be formed by powder metallurgy techniques in a thicker construction than that desired in the final tube and inserted in an outer tubular member also of a thicker construction than that desired in the final product and the two structures subjected to cold working to reduce the same, such as pilgering, to give the desired diameter and thickness, and bonding, of these two layers and then the zirconium inner layer coated on the inner surface of the intermediate layer, and bonded thereto, to form the desired component tubular cladding. As illustrated in FIGS. 2 and 3, a nuclear fuel element 13 using the cladding 1 of the present invention is used to hermetically seal fuel pellets 15. The fuel pellets 15, as is conventional, are preferably sintered pellets of enriched uranium dioxide, or mixed uranium-plutonium dioxide. The pellets are retained within the cladding 1 by a bottom Zircaloy end plug 17 which has previously been welded to the composite tubular cladding, and a welded Zircaloy top end cap 19. A void space or plenum 21 is provided between the top pellet and the Zircaloy top end cap 19 and a biasing means, such as spring 23 restrains the pellets 15 within the cladding 1, with clearance spaces 25 (FIG. 3) left between the pellets and the inner layer 9 of the composite cladding 1. The clearance space and plenum are filled with a high purity, inert atmosphere having high thermal conductivity, such as high purity helium pressurized to about 2 to 5 atmosphere (STP). The present composite cladding provides the benefits associated with use of a boron-containing burnable absorber in a fuel rod while separating the burnable absorber handling from the fuel pellet manufacturing line. Also, helium gas resulting from irradiation of the burnable absorber is prevented from entering the interior space of the tube and improved properties are provided to prevent pellet clad interaction. In addition, the present invention provides more flexibility as the amount of burnable absorber usable and the pattern of such absorber in the fuel rod later in the manufacturing stage of the fuel rod. |
summary | ||
description | In FIG. 1 is thus shown a curve over the neutron energy in relation to the flow per lethargic unit both for a known installation curve 1, and for a Studsvik installation having a conventional radiation filter, curve 2, and for a radiation installation according to the invention, curve 8. FIG. 2 shows a group of curves of maximum radiation dose in healthy tissue expressed in Gray Equivalent (Gy equivalent) in relation to probable tumour control or tumour decomposition. The ideal beam for treatment of a brain tumour at the depth of 8 cm (most difficult case) is thereby shown by the graph 3 having the designation BNCTxe2x80x941 which is the optimum curve for radiation treatment of such a brain tumour, which curve 3 has been calculated by means of a computer as known per se. The graphs 4, 5 and 6 of the diagram relate to the results for corresponding cases for the most important of the BNCT beams which are available in the west world. The beams are designated according to the following: The outcome for the beam having a conventional filter in the R2-0 reactor at Studsvik is shown by the graph having the designation S544, curve 7. As evident from the diagram the beam at R2-0 can be expected to give a substantially better treatment result than any of the other beams, corresponding to the presently known technics for radiation treatment of brain tumours, what is observed in that the curve shows that the radiation dose against healthy tissue is substantially less (curve located to the left) than from known installations, curves 4, 5 and 6. The curve 9, marked with S577, corresponds to a treatment in the reactor R2-0 in the case that the reactor is completed by an additional filter, by means of which neutrons are filtered off up to a certain energy the value of which is determined based on the depth at which the tumour is located, whereby consequently the outcome of the radiation can be improved. The technical problem of providing such improvement is to find a filter material which selectively removes neutrons having low energy, up to energies in the area of some few keV without concurrently therewith too much dampening, by spreading processes in the filter material, the intensity of neutrons at the higher energies which are required for the radiation treatment, or without too much affecting the direction spreading of the therapy beam. It is evident that the curve 9 nearly exactly coincides with the calculated optimum radiation curve 3. This is very surprising, and gives a great hope of future successful radiation of deeply located brain tumours, and hopefully healing of brain tumour cancer and also other types of tumours for which the BNCT method is not useful. When treating tumours at less depths in the tissue the treatment result can be optimized in that the energy distribution zone is displaced from the distribution which is the optimum for deeply located tumours (1 keV-40 keV) to less energies. This can be provided in that the neutrons from the reactor are braked by means of a block comprising for instance Al and D2O having various thickness and chosen so that the intensity of neutrons are maximized in the energy area which is optimized for the treatment. For shallow tumours the thickness of the block is adapted so that a solely thermal energy distribution is obtained. For tumours at greater depth in the tissue the thickness of the D2O block is reduced so that the average energy of the neutrons is displaced towards the epithermic area. This method, however, has as an effect that the beam contains a tail of low energetic neutrons of down to thermal energies. This gives a non-desired dose load at and closely inside the surface. Said tail of low energetic beams can be eliminated by using the above mentioned Li6 filter having a thickness which is adapted so that neutrons having the non-desired energies are eliminated from the beam. The said additional filter has to fulfil several different demands for modifying the spectrum. Firstly the absorbing filter material must have such probability of capture and spreading that neutrons having an energy up to the desired keV area are effectively captured at the same time as the spreading of neutrons is minimized. Extensive spreading of neutrons affect the beam unfavourably and affects the direction of the beam. Further the filter must provide an absorption/capture process which is not accompanied by gamma radiation. It has shown that Li6 fulfils said high demands on the filter material. It is further important that the original neutron beam has such intensity that the remaining beam, after having passed the additional filter has sufficient intensity for making a radiation possible within a reasonable period of time. In the above mentioned reactor R2-0 at Studsvik the epithermical (E greater than 0.4 eV) neutron flow originally was 1.4xc3x971010 n/cm2/s at the patient position, and when mounting a lithium plate the neutron flow was 3.6xc3x97109/cm2/s, which is a quite sufficient flow of radiation giving suitable treatment times. In this case the patient was placed at about 75 cm distance from the output surface of the conventional filter Alxe2x80x94AIF3xe2x80x94Bi. In FIG. 3 is diagrammatically, and in a vertical cross section, shown an installation for radiation treatment of a patient 10 having a deeply located brain tumour, for instance at a depth of 8 cm. In the illustrated case the neutron source is a nuclear reactor, in which the core 11 is mounted hanging in the pool 12, and in which the radiation first passes a lead jacket 13 and thereafter a conventional filter 14 which is most clearly shown in FIG. 5. Said conventional filter, which is likewise encapsulated in an about 10 cm thick lead jacket 15 comprises, as seen in the radiation direction, an aluminum plate 16, a relatively thick plate 17 of Alxe2x80x94AIF3, a thin plate of titanium, a thin layer of cadmium and a plate 20 of bismuth. The plates can have the following approximate thickness, which, as mentioned previously, gives a neutron flow at the illustrated installation of 1.4xc3x971010n/cm2/s at a reactor effect of 1 MW: As discussed above it is not appropriate that the beam contains neutrons having very low energy. To this end there is used an additional filter 21 which is mounted between the conventional filter 14 and the output 22 of the radiation tube. Said additional filter 21 also is useful for filtering off radiation having too low energy, for instance energies lower than about 1 keV. A specially useful material for said additional filter 21 has shown to be lithium which is enriched in the isotope Li6. The case illustrated in the drawing relates to radiation of a brain tumour 23 located at a depth of about 8 cm in the brain of a patient. In this case it has shown useful that the lithium filter has a thickness of about 2 cm considering the energy spectrum obtained and the depth of the tumour. For treatment of tumours at other depths than 8 cm, like in the above related case, the thickness of the lithium filter is varied so that a relatively thin lithium filter is used for a more shallowly located tumour and a relatively thicker lithium filter is used for a more deeply located tumour. In FIG. 4 is shown the neutron cross section for capture/absorption and for spreading of Li6. From the figure is evident that the absorption is high for low neutron energies and is reduced to a neglectible value at some tenth keV. The spreading cross section is sufficiently low over the entire energy interval which is of interest for a BNCT beam. Both cross sections show a peak at ≈250 keV, the effect of which is to further improve the quality of the beam by filtering off harmful neutrons at high energies. Clinical experiments with neutron radiation of glioblastoma patients were started in Brookhaven, USA in the year 1951. In the experiments there were used low energetic (thermal) neutrons and boron carrying substances having low selectivity for specific boron deposition/capture in the tumour. For reasons which are easy to understand to-day the results were not successful and the activity was ceased. At the end of the 1960th the experiments were resumed in Japan, now with better selectivity in the boron deposition, but still with beams of thermal neutrons. About 200 patients having glioblastoma have so far been treated. The reporting from the experiments in Japan have indicated a substantial improvement of the therapeutic effects as compared with the radiation therapy with photons which is a routine method all over the world. The Petten group system having the above mentioned radiation designation HFR, also marked in FIG. 2, the Petten Group in the Netherlands, curve 5 of FIG. 2 has, for historical reasons, chosen another boron element (BSH), and there are reasons to expect that the results thereof will be only little successful. The installation in Finland now also is ready to be used, and the first patient radiation treatments are expected to take place during the year 1999. In the Finnish project it is intended to use BPA as the boron carrier. Glioma is the common name for those tumours which are formed by tumour transformation of the support cells of the brain, the so called glia cells. There is a series of types of glioma. The largest type of said types is also the most malignant, namely glioblastoma multiformae. The average surviving time for patients having glioblastoma is about nine months, and there is practically no hope that a patient is healed. The treatment which is used to-day is surgical treatment followed by convention radiation treatment and eventually also treatment with cytostatics. The basic reason for the difficulty of treating glioblastoma is the fact that the tumour cells grow extremely infiltratively. When the tumour is shown for the first time at X-ray examination it can therefore be presupposed that tumour cells already have been spread in the larger part of the brain tissue, even if said cells are present in a very low concentration. This is the explanation for the fact, which has been observed since long, namely that it is quite impossible to heal gliastoma by surgical operation. It is true that radiation treatment has a greater influence on tumour cells than on normal brain cells, but the difference is too little for the radiation treatment to be healing, even if the entire brain should be radiation treated. The same arguments also are valid for cytostatics. One of the difficulties in transferring active substances to the tumour cells is the fact that only some few substances pass the so called blood-brain barrier between the blood vessels and the brain tissue. At the type of BNCT which is used at Brookhaven boron atoms are coupled to the amino acid phenylaianine. Normally phenylalanine passes the blood-brain barrier and is also selectively captured by quickly growing cells. It seems that BPA has the same characteristics. Theoretically it is therefore reasonable to believe hat BPA can be enriched in all the tumour cells of the entire brain volume. The experiments which have been made are supporting said belief. Supposing that a suitable spectrum of neutrons can be obtained it seems that a neutron radiation from both sides of the head might generate a neutron flux in the brain tissue which flux is relatively uniform. An important factor for this development is the filter structure which has been invented according to the Studsvik project. At the survey of the present situation for BNCT at Lund, Sweden, in the summer 1999, it was considered that a radiation should be obtained in the tumour, by a xe2x80x9ctwo beamxe2x80x9d neutron radiation and BPA, corresponding to 30 Gy in a single dose radiation, whereas the radiation in normal brain tissue should be 10 Gy. In this connection it should be reminded that the radiation which is routinely used against metastasis has a lowest dose of 25 Gy. The combination of BPA+the theoretically optimum neutron radiation which can be provided at the Studsvik installation must be considered utterly promising. It is considered quite reasonably to count upon a clear improvement of the therapeutic effect. Further improvements thereafter can be obtained (if considered necessary) by chemical improvements of the carrier molecules. |
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claims | 1. Lead substitute material for radiation protection purposes in the energy range of an X-ray tube having a voltage of from 60 to 140 kV, wherein for nominal overall lead equivalents of from 0.25 to 2.00 mm the lead substitute material comprisesfrom 12 to 22 wt. % of a silicone-based material,from 1 to 39 wt. % Sn or Sn compounds,from 16 to 60 wt. % W or W compounds, andfrom 16 to 60 wt. % Bi or Bi compounds. 2. Lead substitute material for radiation protection purposes in the energy range of an X-ray tube having a voltage of from 60 to 140 kV, wherein for nominal overall lead equivalents of from 0.25 to 2.00 mm the lead substitute material comprisesfrom 12 to 22 wt. % of the silicone-based material,from 40 to 60 wt. % Sn or Sn compounds,from 7 to 15 wt. % W or W compounds andfrom 7 to 15 wt. % Bi or Bi compounds. 3. Lead substitute material according to claim 1, wherein the lead substitute material additionally comprises up to 40 wt. % of one or more of the following elements: Er, Ho, Dy, Tb, Gd, Eu, Sm and/or their compounds and/or CsI. 4. Lead substitute material according to claim 3, whereinthe lead substitute material additionally comprisesup to 20 wt. % of the elements and/or their compounds and/or CsI. 5. Lead substitute material according to claim 4, whereinthe lead substitute material additionally comprises up to 8 wt. % of the elements and/or their compounds and/or CsI. 6. Lead substitute material according to claim 1, whereinthe lead substitute material additionally comprises up to 40 wt. % of one or more of the following elements: Ta, Hf, Lu, Yb, Tm, Th, U and/or their compounds. 7. Lead substitute material according to claim 6, whereinthe lead substitute material additionally comprises up to 20 wt. % of the elements and/or their compounds. 8. Lead substitute material according to claim 7, whereinthe lead substitute material additionally comprises up to 8 wt. % of the elements and/or their compounds. 9. Lead substitute material for radiation protection purposes in the energy range of an X-ray tube having a voltage of from 60 to 90 kV according to claim 3, whereinfor nominal overall lead equivalents of from 0.25 to 0.6 mm the lead substitute material comprisesfrom 12 to 22 wt. % of the silicone-based material,from 49 to 65 wt. % Sn or Sn compounds,from 0 to 20 wt. % W or W compounds,from 0 to 20 wt. % Bi or Bi compounds andfrom 5 to 35 wt. % of one or more of the elements Gd, Eu, Sm and/or their compounds and/or CsI. 10. Lead substitute material according to claim 1, whereinthe silicone-based material comprises silicone rubber. 11. Lead substitute material according to claim 10, whereinthe silicone rubber comprises dimethyl silicone rubber, phenylmethyl silicone rubber, phenyl silicone rubber and polyvinyl silicone rubber. 12. Lead substitute material according to claim 1, wherein it comprises fillers and processing aids. 13. Lead substitute material according to claim 1, whereinit comprises a structure of protective layers of different compositions. 14. Lead substitute material according to claim 13, whereinit comprises a structure of at least two protective layers of different compositions which are separate or joined together, wherein the protective layer(s) more remote from the body comprise(s) predominantly the elements having a lower atomic number, or their compounds, and the protective layer(s) close to the body comprise(s) predominantly the elements having a higher atomic number, or their compounds. 15. Lead substitute material according to claim 13 whereinit comprises a structure of at least two protective layers of different compositions which are separate or joined together, wherein at least in one layer at least 50% of the total weight consists of only one element from the group Sn, W and Bi or their compounds. 16. Lead substitute material according to claim 14, whereinit comprises a structure of at least two protective layers of different compositions which are separate or joined together, wherein the protective layer(s) more remote from the body comprise(s) predominantly the elements or their compounds having a higher X-ray fluorescent yield, and the protective layer(s) close to the body comprise(s) the elements or their compounds having a lower X-ray fluorescent yield. 17. Lead substitute material according to claim 14, whereina weakly radioactive layer is embedded between two non-radioactive protective layers which are separate from or joined to the radioactive layer. 18. Lead substitute material according to claim 1, whereinthe metals or metal compounds are granular and their particle sizes exhibit a 50th percentile according to the following formula D 50 = d · p 10 mm whereinD50 represents the 50th percentile of the particle size distribution,d represents the layer thickness in mm andp represents the proportion by weight of the particular material component in the total weight, and the 90th percentile of the particle size distribution D90≦2·D50. 19. Radiation protection clothing of lead substitute material according to claim 1. |
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045333955 | claims | 1. A solid fixation end product of harmful water-containing waste materials and cement (fixation matrix) which is resistant to leaching by water or salt solutions, said product being made by mixing the water-containing waste material and cement while they are subjected to evaporation to a degree that the end product, after subsequent setting, is characterized by (a) a content of harmful waste materials of 20 to 50% by weight on the basis of the dry weight of the waste materials in the end product, and (b) a content of water in the end product corresponding to a water-to-cement ratio (water-cement number) of 0.2 to 0.45. (a) a content of harmful waste materials of 33-50% by weight on the basis of the dry weight of the waste materials in the end product, and (b) a content of water in the end product corresponding to a water-to-cement ratio (water-cement number) of 0.20 to 0.40. 2. A solid waste material end product as claimed in claim 1, wherein the waste material includes ion exchange resins charged with harmful compounds, characterized by an ion exchange resin content of 26 to 50%. 3. A solid end product of harmful water-containing waste materials and cement (fixation matrix) which is resistant to leaching by water or salt solutions, said product being obtained by mixing the water-containing waste material and cement while they are subjected to evaporation to degree that the end product, after subsequent setting, is characterized by 4. A method of producing solid fixation products of harmful water-containing waste materials and cement (fixation matrix) wherein the water-containing waste materials and the cement are mixed and, while being mixed, are subjected to evaporation at a temperature of 100.degree. C. to 180.degree. C. until sufficient water is evaporated so as to provide in the final fixation product a content of 20 to 50% by weight of waste material on the basis of the dry weight of the waste material in the fixation product and the mixture is then filled into forms for hardening. 5. A method according to claim 4, wherein the mixing and evaporation time is so adjusted as to obtain in the fixation product a water-to-cement ratio of 0.2 to 0.45. 6. A method according to claim 4, wherein evaporation and mixing is performed in a continuous manner in a continuous mixing apparatus. 7. A method according to claim 4, wherein evaporation and mixing is performed in a batch-wise manner in a vessel. 8. A method according to claim 4, wherein a setting retardant is added before the mixture is subjected to evaporation and mixing. 9. A method as claimed in claim 4, wherein evaporation and mixing is performed under a vacuum of 20 to 50 m bar. |
052873900 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT Outline of Contents I. Overview Description of Control Complex PA0 II. Panel Overview PA0 III. DIAS PA0 IV. DPS PA0 V. Control Room Integration PA0 VI. Panel Modularity PA0 APPENDIX (Validity Algorithm) PA0 1. Conditions that may cause a trip in less than 10 minutes. PA0 2. Conditions that may cause major equipment damage. PA0 3. Personnel/Radiation hazard. PA0 4. Critical Safety Function violation. PA0 5. Immediate Technical Specification Action Required. PA0 6. First-Out Reactor/Turbine Trip. PA0 1. Conditions that may cause a trip in greater than 10 minutes. PA0 2. Technical specification action items that are not Priority 1. PA0 3. Possible equipment damage. PA0 1. Sensor deviations. PA0 2. Equipment status deviations. PA0 3. Equipment/process deviations not critical to operation. PA0 PAMI--Post Accident Monitoring Instrumentation. PA0 Instrument--The performance accuracy of a sensor and its transmitter (i.e., if accuracy is .+-.1%, the instrument uncertainly is 2%). PA0 Expected Process--The difference in temperature (or other unit of measurement) between sensors measuring the same process parameter due to expected variation in the the process temperature (or other unit of measurement) at different sensor locations. PA0 Calculated Signal--A single signal that the algorithm calculates to represent all sensors measuring the same parameter. PA0 Process Representation--A single signal that is output for displays and alarms where a single value is needed as opposed to multiple sensor values. The "process representation" will always be the "calculated signal" unless a failure has occurred. After a failure it may be the output of a single sensor selected by the operator or algorithm. PA0 Valid--A "calculated signal" that has been verified to be accurate by successfully deviation checking all of its inputs with their average. PA0 Valid PAMI--A "valid" "process representation" that deviation checks successfully against the "PAMI" sensors. PA0 Validation Fault--A failure of the validation and display algorithm to calculate a "Valid" "Calculated Signal". PA0 PAMI Fault--A failure of the "Calculated Signal" to deviation check successfully against the "PAMI" sensors. PA0 Fault Select--The "calculated signal" that is the output of the sensor closest to the last "valid" signal at the time validation initially failed. PA0 Operator Select--A "process representation" that is the output of the sensor that the operator has selected after a "PAMI Fault" or a "Validation Fault". PA0 Good--A label given to a sensor that deviation checks successfully against the "Operator Select" or "Valid" "Process Representation". PA0 Bad--A label given to a sensor that fails to deviation check successfully against the "Valid" "Process Representation". PA0 Suspect--A label given to deviates the most from the average "calculated signal" when any deviation check fails. PA0 "Validation Fault Operator Select Permissive"--The permissive that allows the operator to select an individual sensor as the "Process Representation" when the algorithm is unable to calculate a "valid" signal. PA0 "PAMI" Fault Operator Select Permissive--The permissive that allows the operator to select an individual sensor as the "Process Representation" when the "valid" "calculated signal" does not deviation check successfully against "PAMI" indication. PA0 1. The algorithm checks to see if there are 2 or more "good" sensors. PA0 2. The algorithm averages all "good" sensors (A,B,C,D). Go to step 3. PA0 3. Deviation check all good sensors against the average (within sum of 1/2 instrument uncertainty and expected process variation). PA0 4. (Step applicable if process has a Category 1 PAMI Sensor. If there is no PAMI sensor(s) in this process the step is not performed, go to step 6. PA0 5. The algorithm checks to see if the "calculated signal" on the previous scan was a "Fault Select" sensor. PA0 6. The algorithm checks to see if there is either the "Validation Fault Operator Select Permissive" or the "PAMI Fault Operator Select Permissive". PA0 7. Check to see if the operator has selected a sensor as the "process representation". PA0 8. Does the "operator select" sensor deviation check against the PAMI sensor (within sum of PAMI instrument uncertainty and expected process variation). PA0 9. Is the "process representation" "valid" or "operator select". PA0 10. The algorithm checks to see if the "process representation", is at or above the maximum numerical range, or at or below the minimum numerical range for the sensors. PA0 1. Determine a "process representation" temperature in each of the 4 cold legs (1A, 1B, 2A, 2B) through a combination of deviation checking and averaging (the details are described later). PA0 2. From the results in step 1, determine a T.sub.cold "process representation" for each RCS loop (loop 1 and loop 2) by averaging the corresponding A, B data. PA0 3. From the results in step 2, determine a RCS T.sub.cold "process representation" for normal display and alarms by averaging loop 1 and 2 data. PA0 1. The leg 1A, 1B, 2A, 2B, loop 1, 2 and RCS T.sub.cold "process representation" shall always be displayed on the applicable DIAS display and/or CRT page(s) where a single "process representation" is needed as opposed to multiple sensor values. PA0 2. The T.sub.cold algorithm and display processing is identical to the generic validation algorithm with the following modifications: PA0 3. Using a menu (as described in the generic validation algorithm) on DIAS or the CRT the operator may view any of the 12 sensor values or 7 "calculated signals". PA0 Note: To simplify the discussion of sensor tag numbers, the following letters will be used to designate sensors in a cold leg. PA0 1. Determination of "calculated signal" and faults, as described below (steps 1-8): PA0 2. "Process Representation" selection (steps 9, 10) (similar to steps 6 and 7 of the generic validation algorithm). PA0 3. PAMI Check of "operator select" sensor (step 11) (identical to step 8 of the generic validation algorithm). PA0 4. Bad Sensor Evaluation and Range Check (step 12, 13) (similar to steps 9, 10 of the generic validation algorithm. PA0 1. The algorithm checks to see if there two "good" narrow range sensors (A and B). PA0 Note: A sensor is "good" if it was not declared a "bad" sensor on the previous scan. PA0 2. The algorithm averages A and B, go to step 3. PA0 3. Deviation check both "good" narrow range sensors (A and B) against the average (within sum of 1/2 narrow range uncertainty and expected process variation) PA0 4. The algorithm checks to see if the average or selected narrow range sensor is in-range. PA0 5. The algorithm deviation checks narrow range sensors (A and B) against sensor C (within sum of wide range instrument uncertainty and expected process variation). PA0 6. The algorithm checks to see if the "valid" average or selected sensor deviation checks satisfactorily against the PAMI sensor (C). (Within sum of 1/2 wide range uncertainty and expected process variation). PA0 7. Deviation check C against D (within sum of wide range instrument uncertainty and expected process validation). PA0 8. The algorithm checks to see if the "calculated signal" on the previous scan was a "fault select" sensor. PA0 9. Step 9 is identical to step 6 of the generic validation algorithm. PA0 10. Step 10 is identical to step 7 of the generic validation algorithm except for the following. The operator may select any sensor A, B or C from that cold leg or A, B, C from the opposite cold leg (A or B) as the "process representation". PA0 11. This step is identical to step 8 of the generic validation algorithm. PA0 12. This step is identical to step 9 of the generic validation algorithm except that wide range instrument uncertainties are used on all deviation checks except when narrow range sensors are being deviation checked against a narrow range signal, in this case narrow range instrument certainties will be used. PA0 13. This step is identical to step 10 of the generic validation algorithm. PA0 Note: To simplify the discussion of the cold leg (1A,1B,2A or 2B) "process representation" inputs to the loop 1 or loop 2 algorithm, A will designate the input from leg 1A or 2A and B will designate the input from leg 1B or 2B leg T.sub.c. PA0 1. The algorithm averages the "process representation" inputs from the A and B cold legs and outputs the average as the loop (1 or 2) T.sub.c "process representation".. PA0 2. The algorithm checks to see if A and B are "valid" PA0 3. The algorithm checks to see if A or B is "operator select". PA0 4. The algorithm checks to see if A or B is "fault select". PA0 5. Deviation check A and B against the average. (Within sum of 1/2 wide range instrument uncertainty and expected process variation). PA0 6. The algorithm checks to see if A and B are narrow range. PA0 7. The algorithm checks to see if either or both inputs is out-of-range. PA0 8. The algorithm checks to see if A and B inputs are PAMI. PA0 5. The algorithm checks to see if signal 1 or 2 is "fault select". PA0 6. This step is identical to step 10 of the generic validation algorithm. Go to step 1 and repeat the algorithm. PA0 1. The "process representation" pressure shall always be displayed on the applicable DIAS display and/or the CRT page(s) where a single "process representation" is needed as opposed to multiple sensor values. PA0 2. The pressure algorithm and display processing is identical to the generic validation algorithm with the following modifications: PA0 3. Using a menu (as described in the generic validation algorithm) the operator may view any of the 12 sensors values or single "calculated signal". PA0 1. The algorithm checks to see if there are 2 or more "good" (1500-2500 psig narrow range) sensors. PA0 2. The algorithm averages all "good" (1500-2500) range sensors (A, B, C, D, E and F). Go to step 3. PA0 3. Deviation check all "good" (1500-2500) range sensors against the average (within sum of 1/2 narrow range uncertainty and expected process variation). PA0 4. The algorithm checks to see if the average is in-range. PA0 5. The algorithm checks to see if there are 2 or more "good" 0-1600 psig range sensors (G, H, I and J). PA0 6. The algorithm averages all "good" 0-1600 psig range sensors (G, H, I and J). Go to step 7. PA0 7. Deviation check all "good" 0-1600 psig range sensors against the average (within sum of 1/2 of the 0-1600 psig range uncertainty and expected process variation). PA0 8. The algorithm checks to see if the average is in-range. PA0 9. The algorithm checks to see if both of the 0-4000 psig range sensors (K and L) are "good". PA0 10. The algorithm averages K and L, the 0-4000 psig range sensors. Go to step 11. PA0 11. Deviation check K and L against the average (within sum of 1/2 0-4000 psig range uncertainty and expected process variation). PA0 12. Does the "valid" "calculated signal" deviation check against the PAMI sensors. Use method a if the "valid" "calculated signal" is in the 1500-2500 psig or 0-1600 psig range, and method b if in the 0-4000 psig range. PA0 13. The algorithm checks to see if the "calculated signal" output of the previous scan was a "fault select" sensor. PA0 14. Step 14 is identical to step 6 of the generic validation algorithm. PA0 15. Step 15 is identical to step 7 of the generic validation algorithm. PA0 16. Step 16 is identical to step 8 of the generic validation, except that the deviation criteria are the same as those specified in step 12 of this pressurizer pressure validation and display algorithm. PA0 17. This step is identical to step 9 of the generic Validation algorithm, except that the deviation criteria checks are the same as those specified in step 12 of this pressurizer pressure validation and display algorithm. PA0 18. The algorithm checks to see if the "process representation" is at or above the maximum numerical range (1600 psig for the 0-1600 psig sensors, 2500 psig for the 1500-2500 psig sensors and 4000 psig for the 0-4000 psig sensors) or at or below the minimum numerical range (0 psig for the 0-1600 psig and 15-4000 psig sensors and 1500 psig for the 1500-2500 psig sensors). A. Alarm and Messages PA1 B. Indicator PA1 C. CRT PA1 D. Controller PA1 E. Display Formats PA1 F. Display Integration PA1 A. Discreet Indicators PA1 B. Validity Algorithm Summary PA1 C. Alarm Processing and Display PA1 A. CRT PA1 B. IPSO PA1 Pump: A hollow pump indicates that the pump has been activated by the operator to automatic control signal. A solid pump indicates that the pump has been deactivated by the operator or automatic control signal. PA1 Valve: A hollow valve indicates that the valve is fully open and a solid valve indicates that the valve is fully closed. A valve not fully open or closed has a mixed solid/hollow shape, i.e., left side solid/right ride hollow. PA1 Valve Open and Operable--Red Color Coding. PA1 Valve Closed and Operable--Green Color Coding. PA1 Non-Instrumental Valve--Grey Color Coding (Position is Operator Inputted). PA1 Valve Not Operable--Grey Color Coding with Alarm Coding. PA1 Loss of Indication--Grey Color Coding with Alarm Coding and mixed hollow/solid shape. PA1 The critical function information provided on the 1st level display page that is associated with the critical function. PA1 Information related to success path availability and performance of the success paths that can support that critical function. PA1 High level information presented using a mimic format with the critical function/success path related information. PA1 A time trend of the most representative critical function parameter. PA1 1. RCP 1A PA1 2. RCP 1B PA1 3. RCP 2A PA1 4. RCP 2B PA1 5. RCP SealBleed PA1 6. RCS PA1 7. .sup.T hot PA1 8. .sup.T cold PA1 9. Pressurizer Pressure PA1 10. Pressurizer Level PA1 1. When validation fails and a "FAULT SELECT" sensor is selected for the "process representation". PA1 2. When the "Valid" output does not correlate to the PAMI sensor(s). PA1 1. The "process representation" is always displayed on the applicable DIAS display and/or CRT page(s) where a single "process representation" is needed as opposed to multiple sensor values. Each plant process parameter is evaluated individually to determine the type of display required and location (DIAS and CRT or CRT only). PA1 2. The "process representation" is always a "valid" value unless there is a: PA1 Both of these are explained below. PA1 3. The "process representation" is always used for alarm calculations and trending (where a single value is normally trended). This can be "valid", "fault select" or "operator select" data, depending on the results of the algorithm calculations as described below. PA1 4. Using a menu on DIAS or the CRT, the operator may view any of the values (A,B,C,D or calculated output) without changing the "process representation". PA1 5. A "Fault Select" value will be displayed automatically as the "process representation" when the validation algorithm is unable to yield "valid" data. The "fault select" value is the output of the sensor closest to the last "valid" signal at the time validation initially failed. On DIAS (if applicable), this information will be labeled "fault select". On the CRT(s) graphic pages, this information is preceded by an asterisk(*) to indicate suspect data. The "fault select" "process representation" is automatically returned to a "valid" "process representation" when the validation algorithm is able to calculate "valid" data. PA1 6. An "operator select" sensor may be selected for the "process representation" only when there is a: PA1 The "operator select" "process representation" will replace the "valid" or "fault select" "process representation". On DIAS (if applicable), this information will be labeled "operator select". On the CRT(s), this information will be preceded by an asterisk(*) on graphic displays and labelled "operator select" in the data base. The "operator select" "process representation" is automatically replaced by the calculated "valid" signal when both the "Validation Fault" and the "PAMI Fault" clear. PA1 1. Normal operation PA1 2. Heatup/cooldown. PA1 3. Cold shutdown/refueling. PA1 4. Post-trip. PA1 1. Unacknowledged Alarm--If there is an unacknowledged alarm associated with an alarm tile, the alarm tile will flash at a fast rate (i.e., 4 times/sec using a 50/50 duty cycle as depicted by the long rays in FIG. 9). This condition takes precedence over all other alarm tile states for group alarms. PA1 2. Cleared Alarm/Return to Normal (Reset Alarm)--When an alarm condition clears, the corresponding alarm tile flashes at a slow rate (i.e., 1 time/sec using a 50/50 duty cycle as depicted by the short rays in FIG. 9) until this condition has been acknowledged. This condition takes precedence over the remaining two states for grouped alarms. PA1 3. Alarm--If an alarm condition exists and alarm states 1 and 2 above do not exist, then the alarm tile is lit without flashing (as depicted by the absence of rays in FIG. 9). PA1 4. No Alarm--If there is no alarm condition associated with an annunciator tile, then the alarm tile is not lit (not depicted in FIG. 9). To indicate that the alarm tile's bulb is functioning, a lamp test feature is provided. PA1 A) First Level Display Page Set (Major Plant System/Function Groupings) 142 PA1 B) Control Room Workstation) 144 PA1 C) Alarm tiles 146 PA1 1) The operator selects the "Alarm List" menu option 140 (FIG. 4) followed by the "Elec." menu option 148 (FIG. 12). This accesses the categorized alarm listing of the type shown in FIG. 1 beginning with the electrical alarms. PA1 2) If the operator wishes to view alarms associated with a specific alarm, e.g., RCP1A, he selects the following menu options from page 84 (FIGS. 4 and 12) PA1 A. Categorized Alarm List--The operator selects "Alarm List" followed by the tile, e.g., "RCP1A", menu option. The categorized alarm list is accessed with RCP1A alarms at the top of the page. PA1 B. Messages--The operator can use the alarm tile menu options in the same method that the control panel alarm tiles are used. The selection of an alarm tile menu option provides the alarm message and a menu with display pages that can provide supporting information about the alarm condition. PA1 1) Alarm acknowledgement via the annunciator tiles--Alarms can be acknowledged by depressing alarming/unacknowledged annunciator tiles or a CRT annunciator tile representation. This action changes the annunciator tile from a flashing condition to a solid condition when all alarm conditions associated with the tile have been acknowledged and silences any audible sound (described later) associated with the alarm condition. Alarm messages are viewed on the message window (when using the physical tile) and the workstation's CRT message line (see FIG. 16). PA1 2) Alarm acknowledgement using alarm listing pages--Alarms can be acknowledged on the categorized listing by touching alarm tile touch targets associated with the alarm tile categories (see FIG. 14). Upon touching the alarm tile's representation, all alarms associated with that tile are acknowledged. This means of alarm acknowledgement may be the most useful for acknowledging multiple alarms remote to the operator's location. PA1 1. Unacknowledged Priority 1 or 2 Alarms. PA1 2. An Alarm Reminder Tone for Priority 1 or 2 Unacknowledged or Cleared Conditions. PA1 3. Cleared Priority 1 Alarms, or Cleared Priority 2 Alarms. PA1 All new/unacknowledged priority 2, 3 and operator aid features change from a fast flash rate to a steady highlighted condition, i.e., tiles and CRT alarm representations. PA1 Any cleared alarm conditions, i.e., slow flash rate, are not presented as alarm information. PA1 Any new alarm condition or cleared alarm condition coming in after the "STOP FLASH" button has been activated, is normally displayed to the operator (i.e., flashing). However, the operator may redepress the alarm "STOP FLASH" button to suppress these conditions. PA1 1) Primary Systems (example, see FIG. 19) PA1 2) Secondary Systems PA1 3) Power Conversion PA1 4) Electrical Systems PA1 5) Auxiliary Systems PA1 6) Critical Functions PA1 1) The next higher level (when applicable) display page in the hierarchy, item (c). This feature is more meaningful on a 3rd level display page since the next higher level page is a level 2 display page which is not normally on the menu. PA1 2) Display pages of systems that are connected to or support the process of the presently displayed page (h,i). PA1 3) All six first level display pages (b,c,d,e,f,g). PA1 4) The IPSO display page (a). PA1 5) The last page viewed on the monitor (j). PA1 (1) Display Page Access Using Alarm Tiles--This mechanism for display page access may be most useful for obtaining display pages associated with the workstation's process. By pressing a workstation alarm tile from display 78, such as 80 (FIG. 15), region 4 of the workstation CRT's display page menu changes to a new menu with display page options associated with the alarm tile's descriptor. For example as shown in FIG. 23, an RCP1A alarm tile provides menu options associated with RCP 1A. The desired display page will then be a direct access menu option. PA1 (2) Accessing CRT Information from the Discrete Indicators--Each discrete indicator 82 such as shown in FIG. 7, has a CRT access touch target 158. This button provides for access to supporting information for the process parameter that is presently displayed on the discrete indicator. By touching the CRT target on the discrete indicator, region 4 of the menu options on the workstation's CRT changes to menu options containing display pages with supporting and diagnostic information associated with the process parameter. PA1 (3) Display Page Access Using a Display Page Directory --Any display page of the display page hierarchy can be accessed using the presently displayed menu. For example, if the operator is viewing the Feedwater System display page and wants to access the CVCS display page, the following sequence takes place (refer to FIGS. 22 and 4): The operator selects "by touch" the "DIRECTORY" menu option (option 1 in region 2 on FIG. 22) followed by the "PRIMARY" menu option (option b in region 3 on FIG. 22). This accesses the primary section of the display page hierarchy from the display page library (see FIG. 4). Each display page within the primary section of the display page hierarchy is a touch target on this display page, and now the operator can select the CVCS display page. Any page in the display page hierarchy can be accessed using this feature. The "DIRECTORY" menu option is followed by the desired hierarchy associated with one of the six first level display pages, menu options b,c,d,e,f or g on FIG. 22. PA1 Failure to satisfy the safety function status checks, (post-trip). PA1 Poor performance of a success path/system that is being used to support a critical function. PA1 An undesirable priority 1 deviation in a power production function (pre-trip). PA1 Unavailability of a safety system (less than minimum availability as defined by Reg. Guide. 1.47). PA1 (a) Feedwater and Condensate System Status Information (i.e., operational status, alarm status) PA1 (b) Steam Generator Levels, Dynamic Representation PA1 (c) Steam Generator Safety Valve Status PA1 (d) Atmospheric Dump Valve Status PA1 (e) Main Steam Isolation Valve Status PA1 (f) Turbine Bypass System Status PA1 (a) Plant net electric output, digital value. PA1 (b) Alarm information for deviations in important processes associated with the main turbine and turbine generator. PA1 (c) Power distribution operational and alarm status to the plant busses and site grid. PA1 (a) Circulation water system status. PA1 (b) Alarm information for critical deviations in condenser pressure conditions. PA1 Containment Isolation Actuation PA1 Safety Injection Actuation PA1 Main Steam Isolation PA1 Containment Purge Isolation PA1 High Containment Airborne Radiation PA1 High Activity Associated, with Any Release Path PA1 High Coolant Activity PA1 (a) Diesel Generator Status PA1 (b) Status of Power Distribution within the Power Plant PA1 (c) Instrument Air System Status PA1 (d) Service Water System Status PA1 (e) Component Cooling Water System Status PA1 CCW--Component Cooling Water PA1 CD--Condensate PA1 CI--Containment Isolation PA1 CS--Containment Spray PA1 CW--Circulating Water PA1 EF--Emergency Feedwater PA1 FW--Feedwater PA1 IA--Instrument Air PA1 SDC--Shutdown Cooling PA1 RCS--Reactor Coolant PA1 SI--Safety Injection PA1 SW--Service Water PA1 TB--Turbine Bypass PA1 Yes, go to step 2 PA1 No, go to step 5 PA1 Note: A sensor is "good" if it was not declared a "bad" sensor on the previous scan or a "suspect" sensor on a previous pass. PA1 If all deviation checks are satisfactory do the following: PA1 a. Clear the "Validation Fault" alarm, if previously present PA1 b. Clear the permissive that allows the operator to select a sensor after a validation fault (i.e., "Validation Fault Operator Select Permissive"), if previously present. PA1 c. Declare any "suspect" sensor "bad" and output a sensor deviation alarm on that sensor. PA1 d. Output the average as the "valid" "calculated signal". PA1 e. Go to step 4 PA1 If any deviation checks are unsatisfactory, the following occurs: PA1 a. The sensor with the greatest deviation from the average is flagged as "suspect", then the algorithm checks to see if this the first or second pass on this scan. PA1 Does the "valid" signal deviation check against the PAMI sensor(s) PA1 a. Yes, Output the "PAMI" message and if not previously present, remove the "PAMI Fault Operator Select Permissive", clear the "PAMI Fault" alarm if present, go to step 6. PA1 b. No, Perform the following: PA1 If the previous scan was not "fault select", a "validation fault" has just occurred. Do the following: PA1 a. Generate a "Validation Fault" alarm PA1 b. Declare all "suspect" sensors "good". PA1 c. Enable the permissive for the operator to select an individual sensor output for "process representation", the ("Validation Fault Operator Select Permissive"). PA1 d. Deviation check all sensors against the last "valid" signal. Select the sensor that deviates the least from the last "valid" signal as the "fault select" sensor. PA1 e. Output the signal from the "fault select" sensor as the "calculated signal". PA1 f Go to step 6. PA1 If the previous scan was "fault select", validation had failed previously and already picked a "fault select" sensor. Continue to output the "fault select" sensor as the "calculated signal", go to step 6. PA1 Note: It is important that the sensor initially fault selected be retained since over time other failed sensors may erroneously appear more accurate. PA1 Note: A validation fault enables one Operator Select Permissive and failure of the "valid" algorithm output to deviation check satisfactorily against "PAMI" gives the other Operator Select Permissive. PA1 If there is no Operator Select permissive, output the "calculated signal", as the "process representation", go to step 9. PA1 If there is an Operator Select permissive, go to step 7. PA1 Yes, output the signal from the selected sensor as the "process representation", go to step 8. PA1 No, output the "calculated signal" as the "process representation", go to step 9. PA1 Note: This step outputs the "calculated signal" as the "process representation" when the operator has the option to select a sensor, but does not use that option. PA1 Yes, output the "PAMI" message on the "process representation" display. PA1 No, remove the "PAMI" message on the "process representation" display. PA1 No, go to step 10 ("bad" sensor evaluations are not performed when the "process representation" is from a "fault select" sensor). PA1 Yes, Deviation check all "bad" sensors (A, B, C, D) against the "valid", or "operator select" signal by the following methods: PA1 Yes, Output the message "Out-of-Range" along with the "process representation" signal. On the CRT place an asterisk (*) preceding the "process representation". Go to step 1 and repeat the algorithm. PA1 No, go to step 1 and repeat the algorithm. PA1 Note: "Out-of-range" informs the operator that the actual process value may be higher or lower than the sensor is capable of measuring. In the case of process measurements with multiple ranges of sensors this check will cause the selection of sensors in a new range. PA1 Note: On the RCS panel, RCP Differential Pressure, SG Differential Pressure and Pressurizer Level Reference Leg Temperature use this generic validation algorithm directly. The T.sub.cold, T.sub.hot, Pressurizer Level and Pressurizer Pressure algorithms this generic algorithm with additional steps and minor modifications to accommodate: PA1 a. Steps 1-5 (Determination of "Calculated Signal" and Faults) of the generic validation algorithm are modified to account for the following (steps 1-8 perform these functions): PA1 b. The (Determination of "Calculated Signal" and Faults) and the remainder of the generic Validation algorithm (steps 6-10 are performed independently for each of the cold legs (1A, 1B, 2A, 2B). PA1 c. Two additional algorithms were added: PA1 A--1st narrow range sensor (safety) (465.degree.-615.degree. F.) PA1 B--2n narrow range sensor (safety) (465.degree.-615.degree. F.) PA1 C--wide range sensor (PAMI) (50.degree.-750.degree. F.) PA1 D--wide range sensor in opposite cold leg (i.e., when discussing loop 1A, this will be the wide range sensor in loop 1B, PAMI) (50.degree.-750.degree. F.) PA1 Cold leg 1A, 1B, 2A and 2B temperature "calculated signal" will be calculated using sensors A,B,C. A validation attempt will be made using narrow range sensors, if that is unsuccessful, the cold leg "calculated signal" will be validated using wide range sensors. In the event that validation fails using both narrow and wide range sensors, the the algorithm will select the sensor closest to the last "valid" signal as the "fault select" "calculated signal". PA1 Yes, go to step 2 PA1 No, go to step 5 PA1 If both deviation checks are satisfactory, go to step 4 to see if the average is in range. PA1 If any deviation checks are unsatisfactory go to step 5. PA1 The average or selected sensor goes in-range at 96% and 4% of narrow range. PA1 The average or selected sensor goes out-of-range at 98% and 2% of narrow range. PA1 Note: Hysteresis is needed to prevent frequent shifts at end-of-range. Out-of-range occurs at 98% and 2% to insure that no out-of-range sensors are used to calculate a "valid" output (i.e.: worst case sensors would read 100% or 0%). PA1 If in-range, clear the "Validation Fault" alarm, if present, disable the "Validation Fault Operator Select Permissive", and output the average or selected narrow range sensor as the "valid" "calculated signal". Go to step 6. PA1 If out-of-range, attempt the wide range validation, go to step 7. PA1 If either sensor A or B passes the deviation check, the algorithm selects the sensor (A or B) that is closest to C. This sensor is selected for further checks. The sensor that deviates the most from sensor C is flagged as a "bad" sensor, if not previously "bad" and its associated sensor deviation alarm is generated if not previously generated. Go to step 4. PA1 If both A and B do not deviation check against C, go to step 7 and attempt wide range validation. PA1 If satisfactory, do the following: PA1 a. Disable the "PAMI fault operator select permissive" PA1 b. Output the "PAMI" message with the "valid" "calculated signal". PA1 c. Clear the "PAMI Fault" alarm, if present. PA1 d. Go to step 9. PA1 If unsatisfactory, do the following: PA1 a. Remove the "PAMI" message PA1 b. Enable the "PAMI Fault Operator Select Permissive". PA1 Note: To validate the single wide range sensor in a cold leg, the algorithm deviation checks it against the wide range sensor in the other cold leg of that loop (i.e., if in loop 1, 1A wide range sensor is deviation checked against the 1B wide range sensor). PA1 If the previous scan was not "fault select", a validation fault has just occurred. Do the following: PA1 a. Generate a "validation fault" alarm. PA1 b. Enable the "Validation Fault Operator Select Permissive". PA1 c. Deviation check all sensors (A, B, C) against the last "valid" signal. Select the sensor that deviates the least from the last "valid" signal as the "fault select" sensor. PA1 d. Output the signal from the "fault select" sensor as the leg T.sub.c "calculated signal". PA1 e. Go to step 9. PA1 If the previous scan was "fault select", validation had failed previously and the algorithm has already picked a "fault select" sensor. Continue to output the signal from the "fault select" sensor as the "calculated signal", go to step 9. PA1 Yes, output average as "valid", go to step 5. PA1 No, go to step 3. PA1 Yes, go to step 4. PA1 No, output the average as "fault select", go to step 5. PA1 Yes, output the average as "fault select", go to step 5. PA1 No, output the average as "operator select, go to step 5. PA1 If the deviation checks are satisfactory, clear the "T.sub.c Cold Leg (1A/1B or 2A/2B) Temp Deviation" alarm, if present, go to step 6. PA1 If either deviation check is unsatisfactory, generate the "T.sub.c Cold Leg (1A/1B or 2A/2B) Temp Deviation" alarm, go to step 6. PA1 Yes, output the average as narrow range, go to step 7. PA1 No, output the average as wide range, go to step 7. PA1 If either or both are out-of-range, output this T.sub.c loop "process representation" signal with the message "out-of-range", go to step 8. PA1 If both are in-range, this T.sub.c loop "process representation" is not output with the message, "out-of-range", go to step 8. PA1 Yes, output the "PAMI" message with the loop (1 or 2) T.sub.c "process representation", the loop T.sub.c algorithm is repeated, go to step 1. PA1 No, do not output the "PAMI" message with the loop (1 or 2) T.sub.c "process representation", the loop T.sub.c algorithm is repeated, go to step 1. PA1 No, output the "process representation" from step 2 as "fault select", go to step 6. PA1 Yes, output the "process representation" from step 2 as "fault select", go to step 6. PA1 No, output the "process representation" from step 2 as "operator select", go to step 6. PA1 a. Steps 1-5 (Determination of "Calculated Signal" and Faults) of the generic validation algorithm are modified to account for the following. PA1 b. The remainder of the generic algorithm (steps 6-10) are renumbered to account for additional steps in the (Determinating of "Calculated Signal" and Faults). They are almost identical with the minor modifications described with each step. PA1 P - 101A - A PA1 P - 101B - B PA1 P - 101C - C PA1 P - 101D - D PA1 P - 100X - E PA1 P - 1OOY - F PA1 P - 103 - G PA1 P - 104 - H PA1 P - 105 - I PA1 P - 106 - J PA1 P - 190A - K PA1 P - 190B - L PA1 Yes, go to step 2 PA1 No, go to step 5 and attempt (0-1600 psig range validation) PA1 Note: A sensor is "good" it was not declared a "bad" sensor on the previous pass or a suspect sensor on a previous pass. PA1 If all deviation checks are satisfactory, go to step 4 to see if the average is in range. PA1 The average goes in-range at 96% and 4% of narrow range. PA1 The average goes out-of-range at 98% and 2% of narrow range. PA1 If in-range, do the following: PA1 a. Clear the "Validation Fault" alarm, if previously present. PA1 b. Remove the "Validation Fault Operator Select Permissive". PA1 c. Output the average as the "valid" "calculated signal". PA1 d Go to step 12. PA1 If out-of-range, attempt the (0-1600 psig) range validation, go to step 5. PA1 Yes, go to step 6 PA1 No, go to step 9 and attempt (0-4,000 range validation) PA1 If all deviation checks are satisfactory, go to step 8 to see if the average is in range. PA1 If any deviation checks are unsatisfactory, the following occurs: PA1 The average goes in-range at 96% and 4% of the 0-1600 psig range. PA1 The average goes out-of-range at 98% and 2% of the 0-1600 psig range. PA1 Hysteresis prevents frequent range shifts. Out-of-range occurs at 98% and 2% to insure that no out-of-range sensors are used to calculate a "valid" output (i.e., worst case sensors would read 100% or 0%). PA1 If in-range, do the following: PA1 a. Clear the "Validation Fault" alarm, if previously present. PA1 b Remove the "Validation Fault Operator Select Permissive". PA1 c. Output the average as the "valid" "calculated signal". PA1 d. Go to step 12. PA1 If out-of-range, attempt the 0-4000 psig range validation, go to step 9. PA1 Yes, go to step 10. PA1 No, (0-4000 psig) range validation is not possible, go to step 13. PA1 If both deviation checks are satisfactory, do the following: PA1 a. Clear the "validation fault" alarm, if previously present. PA1 b. Remove the "Validation Fault Operator Select Permissive", if previously present. PA1 c. Go to step 12. PA1 If either deviation check is unsatisfactory, go to step 13. PA1 Method (a) (within sum of 1/2 0-4000 psig range instrument uncertainty, plus process variation, plus instrument position constant). PA1 Method (b) (within sum of 1/2 0-4000 psig range instrument uncertainty, plus process variation). PA1 If the previous scan was not "fault select", a validation fault has just occurred, do the following: PA1 a. Generate a "Validation Fault" alarm. PA1 b. Deviation check all sensors (A,B,C,D,E,F,G,H,I,J,K or L) against the last "valid" signal. Select the sensor that deviates the least from the last "valid" signal as the "fault select" sensor. PA1 c. Output the signal from the "fault select" sensor as the pressurizer pressure "calculated signal". PA1 d. Enable the "Validation Fault Operator Select Permissive". PA1 e. Go to step 14. PA1 Yes, Output the message "Out-of-Range" along with the "process representation" signal. On the CRT place an asterisk (*) preceding the "process representation". Go to step 1 and repeat the algorithm. PA1 No, go to step 1 and repeat the algorithm. PA1 Note: "Out-of-range" informs the operator that the actual pressure may be higher or lower than the sensor is capable of measuring. 1. Mode and Equipment Dependance PA2 2. Subfunction Grouping PA2 3. Shape and Color Coding PA2 4. Alarms on CRT PA2 5. Determining Alarm Conditions PA2 6. Acknowledging Alarms PA2 a. "Fault Select" value or PA2 b. "Operator Select" value. PA2 a. "Validation Fault" or PA2 b. "PAMI Fault". PA2 Alarm Tiles 150 PA2 "Primary" 152 PA2 * If the first pass, the algorithm is repeated, beginning at step 1. PA2 * If it is the second pass validation fails, go to step 5. PA2 Note: The "PAMI Fault Operator Select Permissive" allows the operator to Select any Sensor for the "process representation" when the "calculated signal" (i.e. algorithm's "valid" output) does not agree with the PAMI sensor(s). PA2 Remove the "PAMI" message PA2 Generate a "PAMI Fault" alarm PA2 Enable the "PAMI Fault Operator Select Permissive" PA2 Go to step 6. PA2 Note: This step insures that the algorithm will attempt to validate using all sensors not previously determined "bad" on the next validation attempt. PA2 Deviation check "bad" sensors to be (within sum of instrument range uncertainty and expected process variation). PA2 1. Different numbers of sensors PA2 2. Multiple sensors ranges PA2 3. Data reduction in related process measurements. PA2 1. Only 3 cold leg sensors PA2 2. There are wide and narrow range temperature sensors in the same cold leg. PA2 1. An algorithm that averages the 2 cold leg "process representation" to get a loop T.sub.cold "process representation" (1A and 1B for loop 1 and 2A and 2B for loop 2) PA2 2. An algorithm that averages the 2 cold loop "process representation" to get an RCS T.sub.cold "process representation" (loop 1 and loop 2). PA2 Note: This feature allows the operator to select another sensor for the cold leg "process representation" when the algorithms's "valid" output does not correlate with postaccident monitoring indication (sensor c). PA2 If the deviation check is satisfactory, select C sensor as "valid", "calculated signal and do the following". PA2 a. Clear the "Validation Fault" alarm, if present PA2 b. Disable the "Validation Fault Operator Select Permissive", if it was enabled. PA2 c. Go to step 9. PA2 If the deviation check is unsatisfactory, validation fails, go to step 8. PA2 1. Three sensor ranges (0-1600 psig), (1500-2500 psig) and (0-4000 psig). PA2 The sensor with the greatest deviation from the average is flagged as a "suspect" sensor, then the algorithm checks to see if this the first or second pass on this scan. PA2 * If the first pass, the algorithm is repeated, beginning at step 1. PA2 * If it is the second pass, the (1500-2500) range validation fails, go to step 5 to attempt 0-1600 psig range validation. PA2 Note: Hysteresis prevents frequent range shifts. Out-of-range occurs at 98% and 2% to insure that no out-of-range sensors are used to calculate a "valid" output (i.e., worst case sensors would read 100% and 0%). PA2 The sensor with the greatest deviation from the average is flagged as a "suspect" sensor, then the algorithm checks to see if this is the first or second pass on this scan. PA2 * If the first pass, the 0-1600 psig range algorithm is repeated, beginning at step 5. PA2 * If it is the second pass, the 0-1600 psig range validation fails, go to step 9 to attempt 0-4000 psig range validation. PA2 Yes, do the following: PA2 a. Output the "PAMI" message, if not previously present. PA2 b. Remove the "PAMI Fault Operator Select Permissive", if previously present. PA2 c. Go to step 14. PA2 No, do the following: PA2 a. Remove the "PAMI" message, if previously present. PA2 b. Generate a "PAMI Fault" alarm, if not previously present. PA2 c. Enable the "PAMI Fault Operator Select Permissive" PA2 d. Go to step 14. PA2 Note: The (0-4000 psig) wide range sensors (K and L) are not located on the pressurizer, as are the other pressure sensors. The K and L sensors are positioned at the discharge of the reactor coolant pumps (RCPs) where they measure RCS pressure. During normal operation the pressure at this location is much higher (approximately 110 psi for a System 80 plant) than at the pressurizer, where sensors (A, B, C, D, E, F, G, H, I and J) are located. An additional deviation acceptance criteria (called instrument position constant) will be used when deviation checks are made with or against the K and L (0-4000 psig range) sensors. I. Overview Description of Control Complex FIG. 1 shows a control room complex in accordance with the preferred embodiment of the present invention. The heart of the main control room 10 is a master control console 12 which allows one person to operate the nuclear steam supply system from the hot standby to the full power condition. It should be appreciated that the control room, equipment and methods described herein, may be advantageously used with light water reactors, heavy water reactors, high temperature gas cooled reactors, liquid metal reactors and advanced passive light water reactors, but for present purposes, the description will proceed on the basis that the plant has a pressurized water NSSS. For such an NSSS, the master control console 12 typically has five panels, one each for the reactor coolant system (RCS) 14, the chemical volume and control system (CVCS) 16, the nuclear reactor core 18, the feed water and condenser system (FWCS) 20, and the turbine system 22. As will be described more fully below, the monitoring and control for each of these five plant systems, is accomplished at the respective panel in the master control console. Immediately overhead behind the core monitoring and control panel 18, is a large board or screen 24 for displaying the integrated process status overview (IPSO). Thus, the operator has five panels and the overhead IPSO board within easy view while sitting or standing in the center of the master control console To the left of the master control console is the safety related console 26, typically including modules associated with the safety monitoring, engineered safeguard features, cooling water, and similar functions. To the right of the master control console is the auxiliary system console 28 containing modules associated with the secondary cycle, auxiliary power and diesel generator, the switch yard, and the heating and ventilation system. Preferably, the plant computer 30 and mass data storage devices 32 associated with the control room are located in distributed equipment rooms 31 to improve fire safety and sabotage protection. The control room complex 10 also has associated therewith, a shift supervisor's office 34, which has a complete view of the control room, an integrated technical support center (TSC) 36 and viewing gallery outside the control area, and other offices 38 in which paper work associated with the operation of the plant may be performed. Similarly, desk, tables, and the like 40 are located on the control room floor for convenient use by the operators. A remote shut-down room 42 (FIG. 2) is also available on site for post-accident monitoring purposes (PAM). FIG. 2 is a schematic of the information links between the plant components and sensors, which for present purposes are considered conventional, and the various panels in the main control room. It is evident from FIG. 2 that information flows in both directions through the dashed line 46 representing the nuclear steam supply system and turbo generating system boundary. NSSS status and sensor information 48 that is used in the plant protection system 50 and the PAMS 58, passes directly through the NSSS boundary 46. Control signals 52 from the power control system pass directly through the NSSS boundary. Other control system signals 60,62 from the engineered safeguard function component control system 56 and the normal process component control system 64, are interfaced through the NSSS boundary via remote multiplexors 6. Each of the plant protection system, ESF component control system, process component control system, power control system and PAMs, is linked to the main control room 42, to each other, to the data processing system (DPS) 70 and to the discrete indication and alarm system (DIAS) 72. FIG. 2 illustrates one significant aspect of the present invention, namely, the integration of monitoring, control and protection information, during both normal and accident conditions, so that the operator's task in determining an appropriate course of action is considerably simplified. The way in which this is accomplished will be described in the following sections. II. Panel Overview FIGS. 3(a) and 3(b) are schematics of a sit/stand panel such as the reactor coolant system panel 14 from the master control console 12 in accordance with one embodiment of the invention. FIGS. 3(c) and 3(d) show an alternative embodiment for stand up only. The substantially flat upper portion or wall 74 of the panel is vertically oriented and the substantially flat lower or desk portion 76 is substantially horizontal, with the monitoring and alarm interfaces carried by the upper portion, and the control interfaces carried on the lower portion. A. Alarm and Messages The alarm functionality (see FIGS. 9, 15-18) includes alarm and message (A&M) interface 78 having a multiplicity of tiles 80 each having a particular acronym or similar cue 81 associated therewith, whereby an alarm condition is indicated by the illumination of that tile and the generation of an accompanying audible signal. The operator is required to acknowledge the alarm by either pushing the tile or some other interface provided for that purpose. The number of tiles associated with a particular panel is dependent on the number of different alarm conditions that can arise with respect to the monitored system, e.g, the reactor coolant system. Typically, hundreds of such tiles are associated with each panel. The alarms are prioritized into three (3) alarm classes (Priority 1, Priority 2, and Priority 3, prompting immediate action, prompt action and cautionary awareness). These RCS panel alarms are equipment status and mode dependent (Normal RCS, Heatup/Cooldown, Cold Shutdown/Refueling and Post Trip). When a high priority alarm actuates coincidentally with a low priority alarm on the same parameter, the lower priority alarm is automatically cleared. On improving conditions, the higher priority alarm will flash and sound a reset tone. The operator will acknowledge that the higher priority alarm has cleared. If the lower priority alarm still exists, its alarm window or indicator will turn on in the acknowledged state after the operator acknowledges that the higher alarm has cleared. B. Indicator The second monitoring interface are the process variable indicators, for example reactor coolant hot and cold leg temperatures, pressurizer level and pressure, and other RCS parameters. Discrete indicators 82 (see also FIGS. 7 and 8) provide an improved method of presenting the RCS panel parameters. Some RCS panel parameters require continuous validated display and trending on the master control console. Plant process and category 1 parameters like pressurizer level and RCS cold leg temperature fall into this category. Other RCS panel parameters are used less frequently. The discrete indicators 82 provide indication on parameters needed for operation when the Data Processing System (CRT information displays) is unavailable. These include Regulatory Guide 1.97 category 1 and 2 parameters, parameters associated with priority 1 or priority 2 alarms, other parameters needed for operation due to inaccessibility of local gages and parameters that the operator must view for surveillance when the Data Processing System is unavailable for a period of up to twenty-four (24) hours. These less frequently viewed parameters would be available on discrete indicators, with a menu available by operator selection. The menu would show alphanumeric listings of available data points. Lastly, parameters displayed on process controllers need not be available on discrete indicators. C. CRT Additionally, a CRT display 84 generates an image of the major vessels, pipes, pumps, valves and the like associated with, e.g., the reactor coolant system, and displays the alarms and values of the parameters which may be shown in bar, graph, trend line or other form on the other displays 78,82 (see FIGS. 4-6, 10, 12-14 and 19-23). From this CRT, the operator has access to all NSSS information. The information is presented in a three level structured hierarchy that is consistent with the operator's system visualization. FIG. 4 illustrates the NSSS primary side page directory 84, which accesses all CRT pages related to the functions of the RCS panel. D. Controller In the control portion 76 of the panel 14, a plurality of discrete, on-off switches 86 are provided at the left, for example, each switch pattern being associated with a particular reactor cooling pump whose operating parameters are displayed immediately above it, and analog control interfaces which can be in the form of conventional dials or the like (not shown), or touch screen, discrete control as indicated at 88. Process controllers are provided on the RCS panel to provide the operator with the ability to automatically or manually control process control loops. The process controllers allow control of throttling or variable position devices (such as electro-pneumatic valves) from a single control panel device. Process controllers are used for closed loop control of the following RCS panel process variables: pressure level, pressurizer pressure, RCP Seal Injection Flow and RCP Seal Injection Temperature. Process controllers are designed for each specific control loop utilizing a consistent set of generic display and control features. In a conventional control room, each process control loop has its own control device, usually referred to as a MANUAL/AUTO Station. For example, the RCP Seal Injection Sub-System has five process control loops, a seal injection flow control loop for each of the four RCPs and a seal injection temperature control loop for the entire sub-system. These five control loops each have their own MANUAL/AUTO station which occupy a large amount of control panel space and make cross loop comparisons cumbersome. Although these five process loops are controlled independently, process variations in one controlled parameter affect the other four process parameters. Conventional MANUAL/AUTO stations make it difficult for the operator to simultaneously interact with the five MANUAL/AUTO stations. The RCS panel process controllers for similar processes (related by function or system) are operated from a single control station, called a process controller. This single control station saves panel space, accommodates convenient cross channel checking and allows easier control loop interaction for multiple related controls. Component control features (i.e., actuation of switches controls) provide the primary method by which the operator actuates equipment and systems on the RCS panel. The RCS panel has forty-three components controlled from momentary type switches. Each switch contains a red status indicator for active or open and a green status indicator for inactive or closed. Blue status indicator lights/switches are used to indicate and select automatic control or control via a process controller. In addition to color coding, the red switch is always located above the green switch to reinforce color distinction. Each switch generates an active control signal when depressed and is inactive when released. Each switch is backlit to indicate equipment status position. E. Display Formats Process display formats use standard information placement for similar processes and equipment. Fluid system piping representations are where possible standardized, top to bottom, left to right, with avoidance of crossovers. Incoming and outgoing flow path connections are placed at the margins. Related data are grouped by task and analysis specifications for comparison, sequence of use, function, and frequency. Process representations/layout are based on the operator's process visualization to maximize the efficiency of his data gathering tasks. The operator's visualization of a system is often based on diagrams used with learning materials and plant design documentation associated with system descriptions. Graphic information is presented on display page formats to aid in rapid operator comprehension of processes. Graphic information includes the use of bar graphs, flow charts, trends, and other plots, (e.g., Temp. vs. Press.). Bar graphs are primarily used to represent flows, pressures and levels. Since level corresponds to a tank, the bar graph is placed with consistent spatial orientation with respect to the tank symbol. Level bar graphs are oriented vertically. Flow bar graphs when used are oriented horizontally. Bar graphs are also helpful for comparison of numeric quantities. Flowcharts are used when they aid in the operator's process visualization. Flowcharts are helpful for understanding control system processes such as the Turbine Control System. Operator's learning materials for process control systems are frequently in a flowchart format, and thus a similar format on a display page is easy to comprehend. Trends are used on display page formats when task analysis indicates that the operator should be informed about parameter changes over time. Additionally, the operator is able to establish trends of any data base points in the plant computers data base. In some situations, task analysis may indicate that more than one trend is important to monitor process comparisons. In other situations such as heatup/cooldown curves, two parameters may be placed on the different ordinate axis of a graph. When more than one trend curve occupies the same coordinate axes, two ordinate vertical axes can be used for parameters that have different units. Scale labels are divisible by 1, 2, 5 or 10. Tick marks between scale labels are also divisible by 1, 2, 5 or 10. Trended information is typically presented on display pages with a scale of 30 minutes. However, the operator is able to adjust the scale to suit his needs. Logarithmicaxes be established using multiples of 10. If full range is less than 10, an intermediate range label is located to fall near the middle of the scale. Different colors are used for trends occupying the same coordinates. When multiple curves use a common scale, the scale is gray and the curves are color coded. When multiple ordinate scales are used, they are color coded in correspondence to the curve. The colors used for trends will not include the alarm color or normal status color to avoid associating process parameter with normal or alarm conditions. Color is used to aid the operator in rapidly discriminating between different types of information. Since the benefits of color coding are more pronounced with fewer colors, coding on informational displays (i.e., IPSO, CRTs, alarm tiles) is limited to seven colors. In addition, color coded information has other representational characteristics to aid in discrimination of data and discrimination by color deficient observers. The following colors are used in the information display to represent the following types of information. The colors used have been carefully selected to yield satisfactory contrast for red-green deficient color observers. ______________________________________ Color Representation Characteristics ______________________________________ Black Background color. Green Component Off/Inactive, Valve Closed and Operable. Red Component On/Activated, Valve Open and Operable. Yellow Alarm Status-Good attention-getting color. Grey Text, labels, dividing lines, menu options, piping, inoperable and non-instrumented valves, graph grids, and other applications not covered by other coding conventions. Light Blue Process parameter values. White System's response to operator touch, e.g., menu selection until appropriate system response occurs. ______________________________________ Shape coding is used in the information system to aid the operator to identifying component type, operational status, and alarm status. Component shape coding is based on symbology studies which included shape coding questionnaires given to nuclear power plant personnel. FIGS. 5 and 6 show the shapes used to represent components in the control room. An attribute of shape, hollow/solid, is reflective of the status of the component. Hollow shape coding indicates that the component is active, whereas solid shape coding is used to represent inactive components. An example of shape coding for a pump and valve is described as follows. Information coding on valves is provided by these additional characteristics/representations: F. Display Integration Information associated with safety related concerns is integrated as a part of the control room information to allow the operator to use safety related information, where possible, during normal operation. This is a better design from a human factors view than that of previous control rooms because in stressful situations, people tend to use information that they are most familiar with. In many situations, safety related parameters are only a subset of the parameters that monitor a particular process variable. Operators of present control room designs typically use control or narrow range indications during process control and should use separate safety related indications when monitoring plant safety concerns. In this invention, the parameters typically used for monitoring and control are validated for accuracy against the safety related parameter(s), where available. If a parameter deviates beyond expected values from the associated safety related information, a validation alarm is presented to the operator. In response to an alarm condition, the operator can review the individual channels associated with the parameter on either a diagnostic CRT page or the discrete indicator displaying that parameter. At this time, he can select the most appropriate sensor for display. The operator is informed when the validation algorithm is able to validate the data. The resultant output of the validation algorithms are used on IPSO, the normally displayed format of a discrete indicator, and the higher level display pages on the CRT display system that contain the parameter. The Regulatory Guide 1.97 category 1 information is also displayed, by discrete indication display, at a single location on the safety monitoring panel. Critical Function and Success Path (availability and performance) information is accessible throughout the information hierarchy (see FIGS. 10, 24, 25, 26, 27, 32-35). Alarms provide guidance to unexpected deviation in critical functions as well as success path unavailability or performance problems. Priority 1 alarms alert the operator to the inability to maintain a critical function as well as the inability of a success path to meet minimum functional requirements. Lower priority alarms provide subsystem/train and component unavailability or poor performance. IPSO provides overview information that is most useful for operator assessment of the Critical Functions Priority 1 alarms associated with the Critical Functions or Success Paths supporting the critical function are presented on IPSO critical function matrix. Supporting information relating to these alarm conditions is available by using the alarm tiles or the critical function section of the CRT display page hiearchy. The critical function section of the display page hierarchy contains the following information: Level 1 Display Page--"Critical Functions: this page provides more detail on the critical function matrix presented on IPSO. Specifically, more detail on alarm conditions (descriptor, priority). This will help guide the operator to the appropriate level two critical function display page. A 2nd level page exists for each of the 12 critical functions. Each page contains: The 3rd level display pages in the critical function hierarchy are a duplicate of display page existing elsewhere in the hierarchy. For example, a safety injection display page display page under Inventory Control also exists within the primary section of the display page hierarchy. III. Discrete Indicator and Alarm System A. Discrete Indicators The discrete indicators 82 provide an improved method of presenting safety related parameters. Major process parameters such as Regulatory Guide 1.97 Category 1, require continuous validated display and trending on the master control console. The discrete indicators also provide indication and alarms on parameters needed for operation when the Data Processing System (DPS) is unavailable. These include Regulatory Guide 1.97 Category 1, 2 and 3 parameters, parameters associated with priority 1 or priority 2 alarms, and other surveillance related parameters. Though the DPS is a highly reliable and redundant computer system, its unavailability is considered for a period of up to twenty-four hours. The less frequently viewed parameters are available on discrete indicators, with a menu available by operator selection. Each discrete indicator has the capability to present a number of parameters associated with a component, system, or process. The discrete indicators present various display formats that are based on fulfilling certain operator information requirements. When monitoring or controlling a process such as pressurizer pressure, it is desirable that the operator use a "process representation" value in the most accurate range. For this type of information, the discrete indicator 82, such as shown in FIGS. 7 and 8 presents a bold digital value 90 in field 92 and an analog bar graph 94 of the validated average of the sensors in the most accurate range. The preferred validation technique is described in the Appendix, and validated status is indicated in field 96. This validated data is checked against post-accident monitoring indication (PAMI) sensors when applicable. When in agreement with the PAMI, as shown at field 98 the indicator may be used for post-accident monitoring. This has the advantage of continuing to allow the operator to utilize the indicator he is most familiar with and uses on a day-to-day basis. The operator, upon demand, can display any individual channel on the discrete indicator digital display, by touching a sensor identification such as 102. The use of validated parameters is a benefit operators by reducing their stimulus overload and task loading resulting from presentation of multiple sensor channels representing a single parameter. When the parameter cannot be validated, the discrete indicator displays the sensor reading that is closest to the last validated value. A validation alarm is generated for this condition. The discrete indicator continues to display this sensor's value until the operator selects, another value for indication. The field 96 on the discrete indicator that usually read "VALID" displays "FAULT SEL" in reverse image. This indicates that the value is not validated and has been selected by the computer. In this circumstance, the operator should review the available sensors that can be used for the "process representation". If the operator makes a sensor selection (which is enabled by a validation fault or failure of the "VALID" signal to agree with PAMI), the field 96 with "FAULT SEL" will be replaced by the message "OPERATOR SELECT", which is displayed in reverse image. When the validation algorithm can validate the data and all faults have cleared, the validation fault alarm will clear and the algorithm will replace the "FAULT SELECT" or "OPERATOR SELECT" "process representation" in field 92 with the "VALID" "calculated signal". Parameters that are required for monitoring the overall performance of plant processes or responding to priority 1 or 2 alarms are provided on discrete indicators. The most representative process parameter is the normally displayed value. Through menu options, the operator can view the other process related parameters. There are ten discrete indicators provided for the RCS panel. The indicators are: FIG. 7 illustrates that two related discrete indicators can be shown on a single display. On the left side of the display 82 validated pressurizer pressure is shown whereas at the right, pressurizer level is shown. The pressure display includes the following: digital "process representation" value 90 with units of measurement (2254 psig), quality 96 of the display (VALID), indication 98 that the display is acceptable for post accident monitoring (PAMI), bar chart 94 with the process value, a 30 minute trend 104, normal operating range (NORMAL) 106, instrument range (1500-2500) and units of measurement for the bar chart (psig). In the upper right hand corner of the PRESS display, there are two buttons, "CRT" and "MENU" when touched, the selected button backlights, indicating selection. When the operator removes his hand, the actual selection is processed. The "CRT" button changes the CRT menu options on the CRT 84 located at the same panel as the discrete indicator where the button is pushed e.g., RCS panel 14 as shown in FIG. 3. This "CRT" option identifies the CRT pages most closely associated the parameters on the discrete indicator. The "MENU" button selects the discrete indicator menu (FIG. 8). The upper section of the menu page is nearly identical to the normal display. It contains the digital "process representation" value 90 with units of measurement (2254 psig), quality of display (valid), indication that the display is acceptable for post accident monitoring (PAMI), CRT and MENU buttons. The lower section of the menu page contains selector buttons, such as 102 for all sensor inputs and "calculated signals" of this discrete indicator. The selector buttons 102 backlight when touched, indicating selection. When the operator removes his finger, the actual processing of the selection takes place. There are 13 buttons for pressure: four for 0-1600 psig pressurizer pressure: P-103, P-104, P-105 and P-106; six for 1500-2500 psig pressure: P-101A, P-101B, P-101C, p-101D, P-100X and P-100Y; two for 0-4000 psig RCS pressure: P-190A and P-190B; and one for the "calculated signal" pressure: CAL selected). When selected, the "CALC PRESS" button displays the "calculated signal" (i.e., the output of the algorithm). The "calculated signal" of the algorithm can be a "valid" signal. If the algorithm were to fail and select an individual sensor for the "calculated signal", the "valid" message would be replaced by the message "fault select". This message "fault select" would be displayed in reverse image on the discrete indicator. This message would be displayed on the discrete indicator any time "CALC PRESS" is selected until the algorithm outputs a "VALID" signal to replace the "FAULT SELECT" sensor. To change the display, the operator would touch the button containing the sensor he wished to view. For example: by touching the button marked "P-103", the digital display would display the output from the 0-1600 psig range sensor P-103. The message "VALID" below the digital value would be replaced by the message "P-103". Additionally, the "PAMI" message would be removed because P-103 is not a PAMI sensor. The button "ANAL/ALARM OPER SEL" selects the signal used for the "process representation" in DIAS. It selects whatever sensor is displayed on the digital display. The signal select button gives the operator the option to "operator select" any of the sensors for analog display and alarm processing when a fault exists, such as: If a fault were present and the operator elected to select P-103 for the "process representation", he would select the menu, select P-103 for display and then touch the "ANAL/ALARM OPER SEL" button. The message in field 96 below the digital display would read "P-103 0P SEL" in reverse image. Any time P-103 was selected for display, it would have the message "OP SEL" displayed in reverse image, indicating that the output from P-103 is being used for the "process representation". After selecting an "operator select" sensor for the "process representation", it is expected that the operator will depress the button marked "ANALOG DISPLAY". This would return to the analog 94 and trend display 104 (FIG. 7) for the operator selected sensor with the message "OP SEL" in reverse image. The "ANAL/ALARM OPER SEL" button is not normally displayed on the discrete indicator menu page; it automatically displays when the "operator select permissive" is enabled after a fault. The "ANAL/ALARM OPER SEL" button is removed from the menu page when the "operator select permissive" is disabled after all faults are corrected. The button "ANALOG DISPLAY" removes the menu page and replaces it with the bar graph (analog) and trend display for whatever sensor or "calculated signal" is currently selected as the "process representation" (normally the "valid" "calculated signal" output). Other validated process parameter discrete indicators operate in an identical manner. Menu driven discrete indicators contain all level 1 and 2 displays for a functional group of indication. B. Validation Algorithm Summary To reduce an operator's task loading and to reduce his stimulus overload, a generic algorithm is used. This algorithm takes the outputs of all sensors measuring the same parameter and generates a single output representative of that parameter, called the "Process Representation". A generic validation approach is used to ensure that it is well understood by operators. This avoids an operator questioning the origin of each valid parameter. This generic algorithm averages all sensors [(A,B,C and D) (sensor quantity may be parameter specific)] and deviation checks all sensors against the average. If the deviation checks are satisfactory, the average is used as the "Process Representation" and is output as a "valid" signal. If any sensors do not successfully pass the deviation check against the average, the sensor with the greatest deviation from the average is taken out and the average is recalculated with the remaining sensors. When all sensors used to generate the average deviation check satisfactorily against the average, this average is used as the "valid process representation". This "valid process representation" is then deviation checked against the post-accident monitoring system sensors (if present). If this second deviation check is satisfactory, the "process representation" is displayed with the message "Valid PAMI" (Post-Accident Monitoring Indication), indicating that this signal is suitable for monitoring during emergency conditions, since it is in agreement with the value as determined by the PAMI sensors. As long as agreement exists, this indicator may then be utilized for post-accident monitoring rather than utilizing the dedicated PAMI indicator. This provides a Human Factors Engineering advantage of allowing the operator to use the indicator he normally uses for any day-to-day work and which he is most familiar with. The validation process, as described, reduces the time an operator takes to perform the tasks related to key process related parameters. To insure timely information, all validated outputs are recalculated at least once every two seconds. Additionally, redundancy and hardware diversity are provided in the calculating devices insuring reliability. The following section describes the algorithm and display processing on the DIAS and CRT displays. It should be appreciated that the discrete validation is accomplished using a generic algorithm that is applicable to different parameters. In this manner, the operators understand how the validated reading has been determined for every parameter and, again, this reinforces their confidence. This algorithm always has an output and allows the operator selection for display when validation is not possible. The discrete indicators continuously display all vital information yet allow easy access via a function or organized menu system to enable the operator to access less frequently needed information. There is no need for separate backup displays, since the backups are integrated in the subsidiary levels of retrieval. Such displays vastly reduce the amount of indicator locations required on the panel and yet provide all vital indication in a easy to use format, thereby reducing stimulus overload. The Appendix in conjunction with FIGS. 37 and 38 provide additional details on the preferred implementation of the algorithm. Alarm Processing and Display Another feature of the monitoring associated with each panel, is the reduction of the number of alarms that are generated, in order to minimize the operator information overload. Cross channel signal validation is accomplished prior to alarm generation, and the alarm logic and set points are contingent on the applicable plant mode. The alarms are displayed with distinct visual cueing in accordance with the priority of the required operator response. For example, priority 1 dictates immediate action, priority 2 dictates prompt action, priority 3 is cautionary, and priority 4, or operator aid, is merely status information. The types of alarm conditions that exist within each category are described below: Priority 1 Priority 2 Priority 3 The alarms are displayed using techniques that help the operator quickly correlate the impact of the alarm on plant safety or performance. These techniques include grouping of displays which highlight the nature of the problem rather than the symptom denoted by the specific alarm condition. Another is the fixed spatial dedication of alarm displays allowing pattern recognition. Another is the plant level pictorial overview display on the IPSO board which shows success paths and critical functions impacted by the priority 1 alarms. To insure that all alarms are recognized by the operator without task overload, all alarms can be either individually acknowledged, or acknowledged in small functionally related groups. All alarms can be acknowledged at any control panel. Momentary audible alerts for alarm state changes require no operator action to silence. Periodic momentary audible reminders are provided for unacknowledged conditions. The operator can affectuate a global alarm stop flash which will automatically resume in time, to allow for deferred acknowledgement. In addition to alarms, an information notification category "Operator Aids" has been established for information that may be helpful for operations but is not representative of deviations from abnormal conditions. Conditions classified as "Operator Aids" include: channel bypass conditions, approach to interlocks and equipment status change permissive. Some parameters have more than one alarm on the same parameter (i.e., Seal Inlet Temperature Hi Hi and Hi) To limit the operator's required response, the lower priority is automatically cleared without a reset tone or slow flash rate when the higher priority alarm actuates after actuation of the lower priority alarm. The Hi Hi alarm will be acknoweldged by the operator; therefore, the operator acknowledgement of the cleared lower priority alarm is unnecessary. When the condition improves to the point where the higher priority alarm clears the condition will sound a reset tone and the alarm tile will flash slowly. The operator will acknowledge that the higher priority alarm has cleared. If the lower priority alarm condition still exists, its alarm window or indicator will turn on in the acknowledged state after the operator acknowledges that the higher priority alarm has cleared. If the condition improves such that it clears both the high and low priority alarms before operator acknowledgement, then operator acknowledgement of the cleared high priority alarm will also clear the lower priority condition. 1. Mode and Equipment Dependency A key feature of the alarm system is its mode dependent and equipment status dependent logic. These features combine to greatly reduce the number of alarms received during significant events and limit those alarms to conditions that actually represent process or conditions that actually represent process or component deviations pertinent to the current plant state. Mode and equipment dependency is implemented both through alarm logic changes and setpoint changes. An alarm of mode dependency is the reduction in the low pressurizer alarm setpoint to avoid a nuisance alarm on a normal reactor hip. Equipment dependent logic is used to actuate a low flow alarm only when an upstream pump is supposed to be operating. Four modes have been selected which correspond to significant changes in the alarm logic based on the plant state. These modes are: The alarm modes are manually entered by the operator with the exception of the post-trip mode. Upon a reactor trip, the alarm logic automatically switches to the post-trip mode with no operator action required. All equipment dependent alarm features are actuated automatically without operator action. 2. Subfunction Grouping The RCS panel has over 200 conditions that can cause an alarm. To reduce the operator's stimulus overload due to the quantity of alarms and improve his alarm comprehension, many alarms are grouped into subfunctional groups 108, 110, 112 (FIG. 15). The subfunctional group alarm tiles have a variety of related subfunctional group alarm messages that are read on the panel alarm message window 114 (adjacent to the alarm tile) or CRT. In cases where key process related parameters are alarmed, there is a single alarm message for each alarm tile (i.e., RCS Pressure Low). This single alarm message allows the operator to quickly identify the specific process related problem. As shown in FIG. 16, some alarms are grouped by similar component rather than process function, and are augmented by a message such as 116. As shown in FIG. 9, each alarm tile can be in one of the following states: 3. Shape and Color Coding Alarm information is identified by a unique tile color, preferably yellow 118. The parameter/component descriptor or concise message 120 within the tube is shown in blue. Grey color coding is used for the tile color 122 for Return to Normal conditions. Shape coding is used to identify alarm priority, i.e., 1, 2 or 3. A single bright color is used for alarm information to maximize the attention-getting quality of this information. The shape coding used for identifying alarm priorities uses representational features of decreasing levels of salience. Shape coding of alarm priorities also allows retention of priority information for Return to Normal conditions. For priority 1 alarms, the alarm tiles, mimic diagram components, symbols, process parameters, and menu option fields have their descriptor presented in reverse image (i.e., blue letters 12 on a yellow 118 solid rectangular background 124) using the alarm color coding. The descriptor is presented in blue to provide good contrast for readability. In addition, the alarm tiles and menu option fields on the CRT use the same representation. For priority 2 alarms, the alarm tiles, mimic diagram parameters, components, menu options and symbols have a thin (1 line) box 126 using the yellow alarm color code 118 around their descriptor, which is blue. For priority 3 alarms, the alarm tiles, mimic diagram parameters, components, menu options, and symbols have brackets 128 around their descriptors 120. For all alarms, English Descriptors on the CRT's message line are also represented with the alarm representation formats when they are in alarm. 4. Alarms On CRT Each CRT page in the data processing system provides the operator with an overview of the existence of any unacknowledged alarm conditions and a general overview of where they exist within the plant. The standard menu provided with each display page contains the IPSO and all first level display pages as menu options (see FIG. 10 menu region 130). These menu option fields provide the existence of unacknowledged alarms in their sector of the display page hierarchy and their alarm status/priority by using the alarm highlighting feature as described above. If an alarm tile (i.e., in the DIAS) is in alarm, a first level display page menu option field, such as 132, in the menu options 130 shows that an alarm condition exists in an associated area of the display page hierarchy. The alarm tiles in menu 130 are categorized into the first level display page set corresponding to the console groupings or by critical function, as shown in FIG. 11. In addition to alarm information represented on the first level display page menu options, the following display page features are also used to represent the existence of alarms. Display page menu options 134 that provide access to levels 2 and 3 display pages are lit with the above described alarm representation if information on the corresponding page is in alarm (e.g., if an unacknowledged alarm exists the display page menu option is highlighted to show the highest priority unacknowledged condition). The operator can by selecting option 136 call up a level 2 display page directory containing a pictorial diagram of the level 3 display pages in a hierarchical format associated with a first level display page (see FIGS. 12 and 15). Each of the level 2 and 3 display pages represented on this diagram provide alarm notification if information on that display page is in an unacknowledged alarm state. This alarm information is most useful for determining where alarms exist within an area of the display page hierarchy. For example, the operation would be notified by the display page menu 130 (FIG. 10) that an unacknowledged alarm(s) exists in the auxiliary systems by grey alarm shape coding (return to normal) and slow flashing of alarm coding on the PRT menu option field. He can then access that directory/hierarchy to see what page(s) contains alarm information by touching the menu option "DIRECTORY" 136 followed by PRT. When the primary display directory comes up (FIG. 12), the field(s) representing the display page(s) that contains the alarm condition(s) (such as PZR LEVEL 138) will be highlighted. The desired page that contains the alarm information (similar to FIG. 15) is accessed by touching the flashing field. The descriptors of components and plant data on the process display pages of the CRT (FIG. 13) are alarm coded and flashed to provide indication of alarms and their acknowledgement status. A component's descriptor can provide this alarm information if a parameter associated with the component is in alarm. This is true even if the parameter in alarm is not represented on the display pages, e.g., low pump lube oil pressure is represented by alarm coding of the associated component's symbol. To view the exact information that is in alarm, the operator can access a lower level display page, or use the alarm system features that are described later. 5. Determining Alarm Conditions and Acknowledging Alarms With reference again to FIG. 16, each category 1 and 2 alarm annunciator tile in the DIAS may notify the operator of more than one possible alarm condition. To quickly determine the actual alarm conditions, a message window 114 is provided in the display area 78 on the panel. By depressing an unacknowledged alarming annunciator tile, such as 134, an English description 116 of the specific alarm condition is provided on the message window 114. The alarm tile 134 remains flashing until all alarm conditions associated with the alarm tile have been acknowledged. The English descriptors of additional alarms can be accessed by redepressing the alarm tile 134. At the same time that a message appears on the message window of a DIAS alarm display 78, an alarm message line is presented on the bottom of the display page 84 on the panel CRT (see FIG. 13). The CRT alarm message contaings the following information: Time, Priority, Severity (e.g., Hi, Hi-Hi), Descriptor, Setpoint, and real time process value (coded as described to show the alarm priority and alarm condition). If additional unacknowledged alarms exist that are associated with the tile, the number of additional unacknowledged alarms is specified within a circle 136 at the right hand side of the message area (see FIG. 13). In addition to this alarm message, menu options/fields appear on the display page menu (Region 4) and provide direct access to the display pages that can be used to obtain supporting or diagnostic information of the alarm condition. The display regions are shown in FIG. 22. The alarm tiles that are in alarm on the DIAS display 78 of a given panel can be accessed and acknowledged on any CRT panel by procedure similar to accessing and acknowledging the alarms via the alarm tiles. By selecting the "Alarm Tiles" menu option followed by an alarming display page menu option, i.e., first level display page set (region 3), the alarm tiles that are in alarm, that are associated with the display page, are provided in region 4 of the display page menu. One tile is depicted and is a touch target that provides access to other tiles. The operator acknowledges and reviews these CRT alarm tiles by touch and obtains alarm messages and supporting display page touch targets in the same format as described above. This means of responding to alarming alarm tiles is most useful for responding to alarms at workstations that are remote to the operator's location. All alarm conditions associated with an annunciator tile in the DIAS display are held in a buffer. The buffer containing alarm conditions is arranged in the following format: ______________________________________ 1. First-In Unacknowledged 2. . . . . . N Last-In Unacknowledged N + 1 First-In Cleared/Return to Normal N + 2 . . . . . . n Last-In Cleared/Return to Normal n + .sup.1 Acknowledged Alarms n + 2 . . . . . . ______________________________________ Depressing an alarm tile provides access to the alarm condition that is at the top of the buffer. Acknowledging unacknowledged alarms moves these alarm conditions to the bottom of the buffer. Acknowledging cleared alarms drops them from the buffer. Previously acknowledged alarm(s) (n+1,n+2,..) can be reviewed when there are no unacknowledged or cleared unacknowledged alarm conditions present. Upon reviewing these alarms, they move to the bottom of the buffer. Alarm messages for priority 3 alarms and operator aids are only generated by the computer and only appear on the message line 132 of the CRT page (FIG. 3); there will be no English descriptor provided on the message window of the DIAS display 78. One annunciator tile is provided at each annunciator workstation for all priority 3 alarms and 1 alarm tile is provided on the workstation for operator aids that are associated with these workstation. When an alarm condition changes priority, the following changes occur in the alarm handling system. When a higher priority alarm comes in on the same parameter, the previous alarm is automatically cleared (i.e., no operator acknowledgement necessary since he will need to acknowledge the higher priority condition) without a reset tone or slow flash rate. When an alarm condition improves to the point where the high priority alarm clears, the operator will need to acknowledge that the higher priority alarm has cleared; however, if the lower priority alarm still exists, it will turn on (upon operator acknowledgement of the higher priority cleared condition) and automatically go to the acknowledged state (i.e., no operator action required). The new lower priority alarm condition will be observed by the operator when reading the alarm message in response to clearing the highest priority alarm. The invention provides a means of listing and categorizing alarms, and accessing supporting display pages. In this system, alarms are provided on alarm listing display page accessible from the fields 138 of the DIAS display 78 and 140 of the CRT display 84 shown in FIGS. 15 and 13, respectively. The categories of alarms in this listing are as follows (see FIG. 14): A workstation's alarm tiles in alarm are listed by priority. Alarms associated with the alarm tiles are listed as they are contained in the alarm tile's alarm buffer. These alarm categories provide alarm data consistent with operator's information needs in response to alarm conditions. When accessing the Categorized Alarm Listing, the operator can easily select the data in the category he wishes to see. Using the "Alarm List" menu option 14 (FIG. 4) followed by a display page feature that represents alarm condition(s), (FIG. 12), the operator can view the specific alarm conditions that he is interested in (FIG. 14). Three examples of accessing alarm data in the categorized list from page 84 (FIG. 4) follow. The display page's menu changes to a representation of the alarm tiles that are in alarm and are associated with the Primary Systems (see FIG. 14). At this time, the operator can request one of two different types of information formats associated with the displayed alarm tiles: Alarm information is also provided on all process display mimic diagrams which contain a component or parameter which is in an alarm condition. Color, and shape coding is used to indicate alarm conditions, as described earlier. Parameters in alarms that are associated with a component can cause the represented component's descriptor to be highlighted to indicate an alarm condition if the parameter is not visible on the display page, e.g., pump lube oil pressure may not be listed on a level two display page, so the pump's descriptor may be alarm coded. If the operator desires to see the exact alarm condition associated with a component, he would access the appropriate lower level display page. Alternatively, he could touch the "Alarm Tiles" menu option followed by touching the component's descriptor and respond to the alarm using alarm tile representations. This action also accesses menu options associated with display pages that provide more detail about the component. The following means of alarm acknowledgement is provided with the invention. Each of these methods of alarm acknowledgement clears unacknowledged alarm indicators in the other alarm formats. When an alarm condition clears, the operator needs to be notified. Notification is accomplished by flashing the annunciator tiles and associated process display page information at a slow rate. Acknowledging or resetting the cleared alarm indications takes place in a mechanism similar to acknowledgement of new alarms, i.e., touching an alarm tile or CRT alarm representation/feature. Distinct sounds/tones are provided in the control room to indicate the following alarm information: An audible alarm, tone 1 or 3, is only present for 1 second and tone 2 will repeat periodically, once every minute, until all new or cleared alarms are acknowledged. In situations where multiple unacknowledged alarms exist, the operator needs to direct his attention at the highest priority new alarm conditions. In this situation, all other unacknowledged alarms, i.e., new priority 2, 3 and all cleared alarm conditions, are added noise that distracts the operator from most important alarm conditions. In the control room, a "STOP FLASH" and "RESUME" button exists at the MCC, ACC and ASC. When the "STOP FLASH" button is depressed, the alarm system's behavior exhibits the following characteristics: The alarm reminder tone informs the operator about any unacknowledged new or cleared alarm conditions that exist. To identify these conditions for acknowledgment, the operator selects a "resume" button which returns all unacknowledged and cleared conditions to their normal representational alarm status. The alarm suppression button is backlit after selection to show that the alarm suppression feature is active. So that the operator can provide quick, direct access to supporting information thereby enhancing the operator response to alarm conditions, a single operator action provides alarm acknowledgement, display of alarm parameters, and selection options for CRT display pages appropriate for the alarm condition. The invention provides redundancy and diversity in alarm processing and display such that the operators have confidence in intelligent alarm processing techniques and such that plant safety and availability are not impacted by equipment failures. Priority 1 and 2 alarms are processed and displayed by two independent systems. Two-system redundancy is invisible to the operators through continuous cross-checking and integrated operator interfaces. FIGS. 16-18 show a schematic alarm response using the tiles in accordance with the invention. The illustrated group of tiles is associated with the reactor coolant pump seal monitoring in the reactor cooling system panel shown in FIG. 3. The priority 2 seal/bleed system trouble alarm is illuminated to alert the operator, who then can read a more complete message in the message window, which indicates a high control bleed-off pressure. Such a message is provided for priority 1 and 2 alarms. The same message in more complete form is displayed on the panel CRT. The CRT also identifies menu options that indicate useful supporting display pages. Alternatively, the operator may directly access a listing of all the alarms in a particular group. Thus, overview of the alarm conditions is provided with the tiles, and the detail is provided with the associated messages. A given alarm is rendered more or less important at a particular point in time, depending on the equipment status and the mode of operation of the NSSS. Alarm handling is reduced by validation of the parameter signals, and clearing automatically lower priority alarms when one of the higher priority alarms is actuated on the same condition. IV. Data Processing System A. The CRT Display The CRT shown 84 in the center of the panel in FIG. 3 is part of the data processing system which processes and displays all plant operational data. Thus, it is linked to all other instrumentation and control systems in the control room. FIGS. 2, 28 and 30 schematically show the relationship of the data processing system with the control system, plant protection system, and discrete indication and alarm system. The data processing system 70 receives from the control system 64, the same sensor data that is used by the control system for executing the control logic. Likewise, it receives from the discrete indication and alarm system 72 the validated sensor data that is used by the discrete indication and alarm system for generating the discrete alarms and displays. The plant protection system 50 does not use internally validated data for its trip logic, and this "raw" signal is for each channel passed along to the data processing system 70 which performs its own signal validation logic 154 on the plant protection system signals, and passes on the internally validated signal to the validated signal comparison logic 156. In that functional, area, the validated signals from the control system 64, the plant protection system 50 and the discrete indication and alarm system 72 are compared and displayed on the CRT 84. It should be appreciated that both the validated signal from the comparison logic 156 and the validated signal from the plant protection system are available for display on the CRT 84. Thus, the CRT display within each panel includes signal validation and all CRTs in the plant are capable of accessing any information available to the other CRTs in the plant. Moreover, on any given CRT, the alarm tile images from any other panel may be generated and the alarms acknowledged. Detailed display indicator windows may be accessed as well. The CRTs have a substantially real time response, with at most a two-second delay. The CRT display pages contain all the power plant information that is available to the operator, in a structured, hierarchic format. The CRT pages are very useful for information presentation because they allow graphical layouts of power plant processes in formats that are consistent with operator visualization. In addition, CRT formats can aid operational activities, where appropriate, by providing trends, categorized listing, messages, operational prompts, as well as alert the operator to abnormal processes. The primary method the operator obtains information formats on the CRTs is through a touch screen interface which operates in a known manner. The touch screens are based on infrared beam technology. Horizontal and vertical beams exist in a bezel mounted around the face of each color monitor. When the beams are obstructed by the user, the coordinates are cross-referenced with the display page data base to determine the selected information. Messages and Supporting Display page option touch targets can be accessed onto panel CRTs by touching other panel features, e.g., discrete indicators and alarm tiles. IPSO is available as a display page and forms the apex of the display page hierarch (See FIGS. 10, 22 and 24). Three levels exist below IPSO, where each level hierarchy provides consistent information content to satisfy particular operational needs. The structure of the hierarchical format is based on assisting the operator in the performance of his tasks as well as providing quick and easy access to all information displayed via the CRTs. The display formats on the top level provide information for general monitoring activities, while the lowest level formats contain information that is most useful for supporting diagnostic activities. Level 1 display pages provide information that is most useful for general monitoring activities associated with a major plant process. These display pages inform the operator of major system performance and major equipment status and provide direction to lower level display pages for supportive or diagnositc information. The level 1 display pages are as follows: Level 2 display pages provide information that is most useful for controlling plant components and systems. These pages contain all information necessary to control the system's processes and functions. Parameters which must be observed during controlling tasks appear on the same display, even though they may be parts of other systems. Proposed operating procedures or guides for controlling components are utilized for determining which parameters to display. FIG. 20 is a sample display for Reactor Coolant Pump 1A and 1B Control. The operator would normally monitor the "Primary System" display page to assess RCS performance. If the operator wishes to operate or adjust RCP 1A or 1B, the operator would access the control display page. All information for Reactor Coolant Pump Control is on the control display to preclude unnecessary jumping between display pages. Level 3 display pages provide information that is most useful for diagnostic activities of the component and processes represented in level 2 display pages. Level 3 display pages provide data useful for instrument cross-channel comparisons, detailed information for diagnosing equipment or system malfunctions, and trending information useful for determining direction of system performance changes, degradation or improvement. FIG. 21 shows a diagnostic display of the Seal and Cooling section of RCP1A; the pump portion, the supporting oil system, and the motor section are presented on a separate display page due to display page information density limits. Display page access is accomplished through the use of menus placed on the bottom of the display pages. Each display page contains one standard menu format that provides direct, i.e., single touch, access to all related display pages in the information hierarchy. The menu has fields (see FIG. 10) where display page title are listed. By selecting a field (a thru j), the specified display page is accessed. The menu option fields associated with a display page includes the following (see FIG. 22). To access a display page described by a menu option, the operator would select the menu option (a-k) by touching the desired menu option field on the monitor. The menu option is highlighted (using black letters on a white background) until the display page appears. Since the menu options provide direct access to a minimum set of display pages in the display page hierarchy, alternate means are available for quickly accessing other display pages. Three options are available to the operator: In addition to the menu options described above, menu options exist for "LAST PAGE", "ALARM LIST", "ALARM TILES", "OTHER", and horizontal paging options ("Keys"). The "LAST PAGE" (option j on FIG. 22) provides direct access to the last page that was on the monitor. This is very useful to operators for comparison of information between two display pages, or retrieval of information that the operator was previously involved with. The "ALARM LIST" (option n on FIG. 22) provides for quick access to the alarm listing display pages. The "ALARM TILES" (option m on FIG. 22) provides for quick access to the alarm tile representations of active alarm tiles in the area above Region 4(see FIG. 23) of the workstation's CRT menu. This allows an operator to access alarm information associated with specific tiles on any workstation's CRT. This method of alarm access is further described in Section 5 of this document. The "OTHER" (option k on FIG. 22) provides access to display pages or information that does not fall into the categories of information described by the presently displayed menu options. B. IPSO Another part of the data processing system is the integrated process status overview (IPSO board). Although the number of displays and alarms stimulating the operator at any one time can be considerably reduced using the panels having the discrete alarm, discrete display, and CRT displays described above, the number of stimuli is still relatively high and, particularly during emergency operations, may cause delay in the operator's understanding of the status and trends of the critical systems of the NSSS. A single display is needed that presents only the highest level concerns to the operator and helps guide the operator to the more detailed information as it is needed. Although some attempts have been made in the past to present a large board or display to the operator, such displays to date have not included a significant consolidation of information in the nature to be described below. The IPSO board presents a high level overview of all high level concerns including overview of the plant state, critical safety and power functions, symbols representing key systems and processes, key plant data, and key alarms. IPSO information includes trends, deviations, numeric values of most representative critical function parameters, and the existence and system location of priority 1 alarms including availability and performance status for systems supporting the critical functions. This is otherwise known as success path monitoring. The IPSO board also can identify the existence and plant area location of other unacknowledged alarms. Thus, IPSO bridges the gap between an operator's tendency toward system thinking and a more desirable assessment of critical functions. This compensates for reduction in the dedicated displays to help operators maintain a field plant conditions. It also helps operators maintain an overview of plant performance while being involved in detailed diagnostic tasks. IPSO provides a common mental visualization of the plant process to facilitate better communication among all plant personnel. In FIG. 25, the condition illustrated is a reactor trip. At the instance illustrated, the temperature rise in the reactor is 27.degree. and the average temperature rise is higher than desired and rising as indicated by the arrow and "+". The pressurizer pressure is higher than desired, but it is falling. Likewise, the steam generator water level is higher than desired but falling. FIG. 24 shows a CRT display page hierarchy wherein the IPSO is at the apex, the first level display page set contains generic monitoring information for each of the secondary, electrical, primary, auxiliary, power conversion and critical function systems, the second level of display pages relates to system and/or component control, and the third level of display pages provides details and diagnostic information. IPSO is a continuous display visible from any control room workstation, the shift supervisor's office, and Technical Support Center. The IPSO is centrally located relative to the master control console. The IPSO also exists as a display page format that is accessible from any control room workstation CRT as well as remote facilities such as the Emergency Operations Facility. The IPSO large panel format is 4.5 feet high by 6 feet wide. Its location, above and behind the MCC workstation, is approximately 40 feet from the shift supervisor's office (the furthest viewable point). One of the beneficial aspects of IPSO is the use of IPSO information to support operator response to plant disturbances, particularly when a disturbance effects a number of plant functions. IPSO information supports the operator's ability to respond to challenges in plant power production as well as safety-related concerns. IPSO supports the operator's ability to quickly assess the overall plant's process performance by providing information to allow a quick assessment of the plant's critical safety functions. The concept of monitoring plant power and safety functions allows a categorization of the power and safety-related plant processes into a manageable set of information that is representative of the various plant processes. The critical functions are: ______________________________________ Critical To: Function Power Safety ______________________________________ 1. Reactivity Control X X 2. Core Heat Removal X X 3. RCS Heat Removal X X 4. RCS Inventory Control X X 5. RCS Pressure Control X X 6. Steam/Feed Conversion X 7. Electric Generation X 8. Heat Rejection X 9. Containment Environment Control X 10. Containment Isolation X 11. Radiological Emissions Control X X 12. Vital Auxiliaries X X ______________________________________ A 3.times.4 alarm matrix block 166 containing a box 162 for each critical function exist in the upper right hand corner of IPSO (see FIG. 25 and the CRT display of IPSO in FIG. 10). The matrix provides a single location for the continuous display of critical function status. If a priority 1 alarm condition exists that relates to a critical function, the corresponding matrix box 164 will be highlighted in the priority 1 alarm presentation technique. Critical Function alarms are representative of one of the following priority 1 conditions: The 3.times.4 matrix representation is an overview summary of the 1st level critical function display page information (FIG. 32). The operator obtains the details associated with critical function and Success Path alarms in the Critical Function section of the display page. Each critical function can be maintained by one or more plant systems. Information on IPSO is most representative of the ability of supporting systems to maintain the critical functions. For some critical functions, the overall status of the critical function can be assessed by a most representative controlled parameter(s). For these critical functions, the process parameter's relationship to the control setpoint(s) and indication of improving or degrading trends is represented on IPSO to the right of the parameter's descriptor. An arrowhead as explained in FIG. 26 is used if the integral of the parameter's value is greater than an acceptable narrow band control value, indicating that the parameter is moving toward or away from the control setpoint. The arrowhead's direction, up or down, indicates the direction of change of the process parameter. If these parameters deviate beyond normal control bounds, a plus or minus sign is placed above or below the control setpoint representation. The following bases were used for the selection of parameters or other indications that are used on IPSO to provide the monitoring of the overall status of the critical functions. 1. Reactivity Control Reactor power is the only parameter displayed on the IPSO as a means of monitoring reactivity. Using Reactor Power, the operator can quickly determine if the rods have inserted. He can also use Reactor Power to determine the general rate and direction of reactivity change after shutdown. Reactor Power is displayed on IPSO with a digital representation 166 because a discrete value of this parameter is most meaningful to both operators and administrative personnel. The IPSO also provides an alarm representation on the reactor vessel if there is a priority 1 alarm condition associated with the Core Operating Limit Supervisory System. 2. Core Heat Removal A representative Core Exit Temperature 168 and Subcooled Margin 170 the parameters presented on IPSO for determining if Core Heat removal is adequate. If Core Exit Temperature is within limits, then the operator can be assured of maintaining fuel integrity. The Subcooling Margin is used because it gives the operator the temperature margin to bulk boiling. Core Exit Temperature is represented on IPSO by using a dynamic representation (i.e., trending format), since there is a distinct upper bound that defines a limit to core exit temperature, and setpoints for representational characteristics can be easily defined. Subcooled Margin is also represented on IPSO using a dynamic representation since there is a lower bound which defines an operational limit for maintaing subcooling. 3. RCS Heat Removal T.sub.H, T.sub.C, S/G Level 172, and T.sub.ave 174 are used on IPSO to provide the operator the ability to quickly assess the effectiveness of the RCS Heat Removal Function. In order to remove heat from the Reactor Coolant, S/G Level must be sufficiently maintained so that the necessary heat transfer can take place from the RCS to the steam plant. A dynamic representation is used so the operator can observe degradiations or improvements in deviant condition at a glance. T.sub.H and T.sub.C are used on IPSO because they are needed by the operator to determine how much heat is being transferred from the reactor coolant to the secondary system. A digital value of these parameters is used since a quick comparison of these parameters is desired for observing the delta T. In addition, an indication of their actual values are used often and would be helpful to an operator in locations where the discrete indicator displaying T.sub.h and T.sub.c is not easily visible. T.sub.ave is presented on IPSO using a dynamic representation to allow quick operator assessment of whether this controlled parameter is within acceptable operating bounds. 4. RCS Inventory Control Pressurizer Level 176 is presented on the IPSO using a dynamic representational indication to allow the operator to quickly access if the RCS has the proper quantity of coolant and observe deviations in level indicative of improving or degrading conditions. 5. RCS Pressure Control Pressurizer Pressure 178 and Subcooled Margin is used as the indications on IPSO to determine the RCS Pressure Control A dynamic representation is used on IPSO to notify the operator of changing pressure conditions that may indicate RCS depressurization or over pressurization. A dynamic representation is used on IPSO for saturation margin. A saturation condition in the RCS can adversely affect the ability to control pressure by the pressurizer. Also, if pressure is dropping, the subcooled margin monitor representation on IPSO depicts a decrease in the margin to saturation. 6. Steam/Feed Conversion The processes associated with Steam/Feed Conversion can be quickly assessed by providing the following information on IPSO: 7. Electric Generation The processes associated with Electric Generation can be quickly assessed by providing the following information on IPSO: 8. Heat Rejection The processes associated with heat rejection can be quickly assessed by providing the following information on IPSO: 9. Containment Environment Control Containment Pressure and Containment Temperature are the parameters which are used on the IPSO to monitor the control of the Containment Environment. These are presented on IPSO using a dynamic representation to allow assessment of trending and relative values. The Containment Pressure variable is used on the IPSO to warn the operator about an adverse overpressure situation which could be the result of a break in the Reactor Coolant System. The Containment Temperature also helps indicate a possible break in the Reactor Coolant System; it also can indicate a combustion in the Containment Building. 10. Containment Isolation The Containment Isolation Safety function is monitored on the IPSO with a Containment Isolation system symbol representation. This symbol will be driven by an algorithm which presents the effectiveness of the following containment isolation situations when the associated conditions warrant containment isolation: 11. Radiological Emissions Control Radiation symbols exist on IPSO which presents notification of high radioactivity levels such as inside containment, and (2) radiation associated with radioactivity release paths to the environment. These symbols will only be presented on IPSO when high radiation levels exist. These indications are presented in the alarm color in a location relative to the sensor in any of the following situations occurs: 12. Vital Auxiliaries Vital Auxiliaries are monitored on IPSO by providing the following information: The systems represented on IPSO are the major heat transport path systems and systems that are required to support the major heat transport process, either power or safety related. These systems include systems that require availability monitoring per Reg. Guide 1.47, and all major success paths that support the plant Critical Functions. The following systems have dynamic representations on IPSO: System Information presented on IPSO includes systems operational status, change in operational status (i.e., active to inactive, or inactive to active) and the existence of a priority one alarm(s) associated with the system. Alarm information on systems can also help inform an operator about success path related Critical Function alarms. Priority 1 alarm information is also presented on IPSO by alarm coding the descriptors of the representative features on IPSO as described above. V. Integration of Control Room FIG. 27 presents an overview of the integrated information presentation available to the operator in accordance with the invention. From the integrated process status overview or board, the operator may observe the high priority alarms. If the operator is concerned with parameter trends, he may view the discrete indicators. If he is interested in the system and component status, he may view the settings on the system controls. Thus, the IPSO information is displayed either on the board or at the panel CRT, and the other information from the operator's panel or any other panel, is available to the operator on his CRT. From the IPSO overview, the operator may navigate through the CRT or DIAS display pages. Moreover, the operator has direct access to either of these types of information from any of the control panels and when a system control is adjusted or set, the results are incorporated into the other alarm and display generators in the other panels. As shown in FIGS. 2 and 28-31, in general overview, the integration of the system means that each panel including the main console, the safety console, and the auxiliary console, includes a CRT 84 which is driven by the data processing system 70. The data processing system utilizes the plant main computer and, although being more powerful, it is not as reliable as the DIAS 72 computers (which may be distributed microprocessors-based or mini-computer based). Also, it is slower because it is menu driven and performs many more computations. It is used primarily for conveying the most important information to the operator and thus important alarm tiles can be viewed on each CRT and acknowledged from any CRT. Any information available on one CRT is available at every other CRT. The indicator and alarm system 72 for a given panel is related to the controls, but the discrete (i.e. quick and accurate) aspects of the alarms and indicator displays 78,82 and controls of that panel are not available at any other panel. Basically, information is categorized in three ways. Category 1 information must be continuously displayed at all times and this is accomplished in DIAS 72. Category 2 information need not be continuously available, but it must nevertheless be available periodically and this is also the responsibility of DIAS 72. Category 3 information is not needed rapidly and is informational only, and that is provided by the DPS 70. In the event of the failure of DPS, some essential information is provided by DIAS. The DPS and DIAS are connected to the IPSO board by a display generator 180. From the IPSO, the operator can obtain detailed information either by going to the panel of concern, or paging through the CRT displays. It should be appreciated that DIAS and DPS do not necessarily receive inputs for the same parameters, but, to the extent they do receive information from common parameters, the sensors for these parameters are the same. Moreover, the validation algorithms used in DIAS and DPS are the same. Furthermore, the algorithms used for the discrete alarm tiles and the discrete indicators include as part of the computation of the "representative" value, a comparison of the DIS and DPS validated values. FIG. 29 is a block diagram representing the discrete indicator and alarm system in relation to other parts of the control room signal processing. The DIAS system preferably is segmented so that, for example, all of the required discrete indicator and discrete alarm information for a given panel N is processed in only one segment. Each segment, however, includes a redundant processor. The information and processing in DIAS 1 is for category 1 and 2 information which is not normally displayed directly on IPSO. IPSO normally receives its input from the DPS. However, in the event of a failure of DPS, certain of the DIAS information is then sent to the IPSO display generator for presentation on the IPSO board. It should also be appreciated that both DIAS and the DPS utilize sensor output from all sensors in the plant for measuring a given parameter, but that the number of sensors in the plant for a given parameter may differ from parameter to parameter. For example, the pressurizer pressure is obtained from 12 sensors, whereas another parameter, for example, from the balance of plant, may only be measured by two or three sensors. Some systems, such as the plant protection system, do not employ validation because they must perform their function as quickly as possible and employ, for example, a 2 out of 4 actuation logic from 4 independent channels. In the event the validation for a given parameter differs as determined within two or more systems, an alarm or other cue will be provided to the operator through the CRT. One of the significant advantages of the present invention is that the DPS need not be nuclear qualified, yet it can be confidently used because it obtains parameter values from the same sensors as the nuclear qualified DIAS. These are validated in the same manner and a comparison is made between the validated DPS parameters and the validated DIAS parameters, before the DPS information is displayed on the CRTs or the IPSO. The nuclear qualification of the alarm tiles and windows, and the discrete indicator displays in the DIAS are preferably implemented using a 512.times.256 electroluminescent display panel, power conversion circuitry, and graphics drawing controller with VT text terminal emulation, such as the M3 electroluminescent display module available from the Digital Electronics Corporation, Hayward, California. The control function of each panel is preferably implemented using discrete, distributed programmable controllers of the type available under the trademark "MODICON 984" from the AEG Modicon Corporation, North Andover, Massachusetts, U.S.A. Thus, the computational basis of the DIAS is with either distributed, discrete programmable microprocessors or mini computers, whereas the computational basis of the DPS is a dedicated main frame computer. The ESF control system and the process component control system are shown schematically in FIG. 31, whereas the plant protection system is preferably of the type based on the "Core Protection Calculator" system such as described in U.S. Pat. No. 4,330,367, "System and Process for the Control of a Nuclear Power System", issued on May 18, 1982, to Combustion Engineering, Inc., the disclosure of which is hereby incorporated by reference. Another aspect of integration is the capability to display the critical functions and success path in IPSO as described above. Since the major safety and power generating signal and status generators are connected to both DIAS and DPS, the operator may page through the critical functions in accordance with the display page hierarchy shown in FIGS. 32 through 35. In FIG. 33, the operator is informed that the emergency feed is unavailable in the reactant coolant system. In FIG. 34, the operator is informed that the emergency feed is unavailable and the reactor is in a trip condition. Under these circumstances, the operator must determine an alternative for removing heat rom the reactor core and by paging to the second level of the critical function display page which, although shown for inventory control (FIG. 35), would have a comparable level of detail for heat removal. This type of information with this level of detail and integration is available for all critical functions under substantially all operating conditions, not only during accidents. VI. Panel Modularity It should be appreciated that, as mentioned above, the discrete tile and message technique significantly reduces the surface area required on the panel to perform that particular monitoring function. Similarly, the discrete display portion of the monitoring function, including the hierarchical pages, is condensed relative to conventional nuclear control room systems. The control function on a given panel can be consolidated in a similar fashion. Thus, a feature of the present invention is the physical modularity of each panel constituting the master control console, and more generally, of each panel in the main control room. In essence, the space required for effective interface with the operator for a given panel, becomes independent of the number of alarms or displays or controls that are to be accessed by the operator. For example, as shown in FIG. 3, six locations on each side of the CRT may be allocated for alarm and indicator display purposes. Preferably, the top two on each side are dedicated to alarms 78 and the other four on each side dedicated to the indicator display 82. An identical layout is provided for each panel in the control room. This permits significant flexibility and cost savings during the construction phase of the plant because the hardware can be installed and the terminals connected early in the construction schedule, even before all system functional requirements have been finalized. The software based systems are shipped early with representative software installed to allow preliminary checking of the control room operations. Final software installation and functional testing are conducted at a more convenient point in the construction schedule. This method can accelerate plant construction schedules for the instrumentation and control systems significantly. Since the instrumentation and control requirements for a given plant are often not finalized until late in the plant design schedule, the present invention will in almost every case significantly reduce costly delays during construction. This is in addition to the obvious cost savings in the ability to fabricate uniform panels, both in the engineering phase normally required to select the locations of and lay out the alarms and displays, and in the material savings in fabricating more compact panels. Furthermore, such modularity in the plant facilitates the training of operators and, when operators are under stress during emergencies, should reduce operator error because the functionality of each panel is spatially consistent. Thus, each modular control panel has spatially dedicated discrete indicators and alarms, preferably at least one spatially dedicated discrete controller at 88, a CRT 84, and interconnections with at least one other modular control panel or computer for communication therewith. For example, communication via the DPS includes, among other things, the ability to acknowledge an alarm at one panel while the operator is located at another panel, and the automatic availability at every other panel of information concerning the system controlled at one panel. FIG. 36 (a) illustrates the conventional sequence for furnishing instrumentation and control to a nuclear power plant and 36(b) the sequence in accordance with the invention. Conventionally, the input and outputs are defined, the necessary algorithms are then defined, and these specify the man machine interface. Fabrication of all equipment then begins and all equipment is installed in the plant at substantially the same time before system testing can begin. In contrast, the modularity of the present invention permits fabrication of hardware to begin immediately in parallel with the definition of the input/output. Likewise, the hardware can be installed and generically tested in parallel with the definition of the man machine interface and the definition of the algorithms that are plant specific. The hardware and software are then integrated before final testing. In a conventional nuclear installation, the equipment is installed during the fourth year of the entire instrumentation and control activity, whereas with the present invention, equipment can be installed during the second or third year. With further reference to FIG. 2, the process component control system and the engineered safety features component control system 56 use programmable logic controllers similar to the Modicon equipment mentioned above including input and output multiplexors and associated wires and cabling, all of which can be shipped to the plant before the plant specific logic and algorithms have been developed. This equipment is fault tolerant. The data processing system 70 uses redundant plant main frame computers, along with modular software and hardware and associated data links. Such hardware can be delivered and the modular software that is specific to the plant installed, just prior to integration and system testing. The DIAS 72 also uses input/output multiplexors and a fault tolerant arrangement, with programmable logic processors or mini-computers, with the same advantages as described with respect to the process control and engineered safety features control systems. APPENDIX Detailed Examples of Validation Algorithm This Appendix describes the details of the generic validation and display algorithm implemented in the DPS and DIAS. Definition of Terms Used in Discussion Validation and Display Algorithm The sensor inputs (A, B, C, D) are all read and stored at the time the algorithm begins. The algorithm uses these stored inputs to perform all steps (1-10), which comprise a scan. When the algorithm is repeated (after step 10), the sensor inputs are read and stored again, for use on the new scan. Determination of "Calculated Signal" and Faults (steps 1,2,3,4,5) Validation Attempt (steps 1, 2, 3) Note: If the deviation check fails on the first pass, the algorithm has used one or more bad sensors to calculate the average. Performing a second pass eliminates the one bad sensor or determines that multiple sensors are bad. PA3 Note: Failing to pass the deviation check on the second pass indicates that there failures. The algorithm cannot be sure to correctly eliminate only the bad sensors, therefore the algorithm must fail. This insures that the algorithm does not calculate a incorrect "valid" signal for this case. Normally without two or more simultaneous failures, the algorithm will detect multiple non-simultaneous deviations, sequentially eliminate them from the algorithm and still determine a "valid" signal. PA3 a. Remove "bad" data flags and make them "good" on all sensors passing the deviation check, if present and clear its associated sensor deviation alarm. PA3 b. Maintain "bad" data flags on all sensors failing the deviation check. PA3 c. Go to step 10. PA3 Note: If the deviation check fails on the first pass, the algorithm has used one or more bad sensors to calculate the average. Performing a second pass eliminates the one bad sensor or determines that multiple sensors are bad. PA3 Note: Failing to pass the deviation check on the second pass indicates that there are two or more simultaneous (1500-2500) range sensor failures. The algorithm cannot, be sure to correctly eliminate only the bad sensors, therefore the (1500-2500) range validation must fail. The 0-1600 psig range validation is attempted. This insures that the algorithm does not calculate an incorrect signal for this case. Normally without two or more simultaneous failures, the algorithm will detect multiple non-simultaneous deviations, sequentially eliminate them from the algorithm and still determine a "valid" signal. PA3 Note: If the deviation check fails on the first pass, the algorithm has used one or more bad sensors to calculate the average. Performing a second pass eliminates the one bad sensor or determines that multiple sensors are bad. PA3 Note: Failing to pass the deviation check on the second pass indicates that there are two or more simultaneous 0-1600 psig range sensor failures. The algorithm cannot be sure to correctly eliminate only the bad sensors, therefore the 0-1600 psig range validation must fail. The 0-4000 psig range validation is attempted. This insures that the algorithm does not calculate an incorrect signal for this case. Normally without two or more simultaneous failures, the algorithm will detect multiple non-simultaneous deviations, sequentially eliminate them from the algorithm and still determine a "valid" signal. Valid--PAMI Check (step 4) Failed Validation (step 5) "Process Representation" Selection (steps 6, 7) PAMI Check of "Operator Select" Sensor (step 8) Bad Sensor Evaluation (step 9) Range Check (step 10) T.sub.cold Validation Algorithm (FIG. 37) There are 12 sensors used to measure cold leg temperatures in the RCS. During most operational sequences, the operator is looking for a single "process representation" of all cold leg temperatures in the RCS. This value will be provided in the DIAS with a display labeled "RCS T.sub.cold ". For consistency, this value, which is determined by DIAS, is also used on the Integrated Process Status Overview (IPSO) board. To insure reliability, DPS compares DIAS's RCS T.sub.cold "process representation" with its own RCS T.sub.cold and alarms any deviations (DPS/DIAS RCS T.sub.c Calculation Deviation). A three step validation algorithm is used to determine this value: The three step process determines "valid" "process representation" temperatures for cold legs 1A, 1B, 2A and 2B, cold loop 1 and 2 and RCS T.sub.c. For situations when a "valid" cold leg "process representation" temperature cannot be calculated the algorithm will select the sensor closest to the last "valid" signal as the "fault select" "process representation" temperature. This automatic fault selection insures a continuous output of the RCS T.sub.cold "process representation" for display and alarms. After a failure the operator may select an individual sensor for that cold leg (1A, 1B, 2A, 2B) "process representation". This selection will allow calculation of loop 1, loop 2 and RCS T.sub.cold "process representation", with "operator select" data. The following section describes the algorithm and display processing on the DIAS and CRT displays. These selections include the following: ______________________________________ T-112CA/122CA 465-615.degree. F. T.sub.cold Loop 1A/2A T-112CB/122CB 465-615.degree. F. T.sub.cold Loop 1B/2B T-112CC/122CC 465-615.degree. F. T.sub.cold Loop 1A/2A T-112CD/122CD 465-615.degree. F. T.sub.cold Loop 1B/2B T-111CA/111CB/ 50-750.degree. F. T.sub.cold Loop 1A/1B/2A/2B, 123CA/123CB PAMI Loop 1A Tc Calculated Signal Loop 1B Tc Calculated Signal Loop 2A Tc Calculated Signal Loop 2B Tc Calculated Signal Loop 1 Tc Calculated Signal Loop 2 Tc Calculated Signal RCS Tc Calculated Signal ______________________________________ Validation Algorithms The algorithms described below are calculated and displayed independently by both DPS and DIAS. Method to Determine Cold Leg 1A, 1B, 2A, or 2B T.sub.cold "Process Representation" The determination of the Cold Leg "Process Representation" will be performed in four parts: Cold Deg (1A, 1B, 2A or 2B Validation and Display Algorithm Determination of "Calculated Signal" and Faults (steps 1-8) Narrow Range Validation Attempt (Steps 1-5) Range Selection (Step 4) Valid PAMI Check (Step 6) Wide Range Validation Attempt (Step 7) Failed Validation (Step 8) T.sub.c Leg (A or B) "Process Representation" Selection (Steps 9, 10) PAMI Check of "Operator Select" Sensor (Step 11) Bad Sensor Evaluation (Step 12) Range Check (Step 13) Method to Determine Loop 1 and 2 T.sub.cold "Process Representation" The loop 1 and 2 T.sub.c "Process representation" will be calculated by averaging the "process representation" from the A and B cold legs (1A and 1B for loop 1), (2A and 2B for loop 2). Method to Determine RCS T.sub.cold The R T.sub.cold "process representation" will be calculated by averaging the "process representation" inputs from loop 1 and 2 T.sub.cold. Range Check Pressurizer Pressure Validation Algorithm (FIG. 38) There are 12 sensors used to measure pressurizer and RCS pressure. During most operational sequences, the operator is looking for a single "process representation" of all pressurizer/RCS pressure readings. This value will be provided in DIAS with a display labeled "PRESS". For consistency, this value, which is determined by DIAS, is also used on the lPSO board. To insure reliability, DPS compares DIAS's Press "process representation" with its own Press "process representation" and alarms any deviations (DPS/DIAS Press Calculation Deviation). The algorithm determines a "valid" "process representation" for pressurizer/RCS pressure. For situations when a "valid" pressure "process representation" cannot be calculated, the algorithm will select the sensor closest to the last "valid" signal as the "fault select" "process representation" pressure. This automatic fault selection insures continuous output of the pressurizer/RCS "process representation" pressure for displays and alarms. After a failure the operator may select an individual sensor for the pressure "process representation" as the "fault select" "process representation". The following section describes the algorithm and display processing on the DIAS and CRT displays. These selections include the following: ______________________________________ P-103, 104, 105, 106 0-1600 psig Pressurizer Pressure P-101A, 101B, 101C, 1500-2500 psig Pressurizer Pressure 101D, 100X, 100Y P-190A, 190B 0-4000 psig RCS Pressure, PAMI CALC PRESS Calculated Signal ______________________________________ Validation Algorithm To simplify the discussion of sensor tag numbers, the following letters will be used to designate pressure sensors: The algorithm described below is calculated and displayed independently by both DPS and DIAS. The pressurizer pressure "calculated signal" will be calculated using sensors A, B, C, D, E, F, G, H, I, J, K and L. An attempt will be made to use the narrow 1500-2500 psig range sensors (A, B, C, D, E and F) (pressure is normally in this range). If pressure is outside the 1500-2500 psig range, the 0-1600 psig range sensors (G, H, I and J) will be used. If pressure cannot be calculated using these sensors, the 0-4000 psig range sensors (K and L) will be used. In the event that the validation fails all of these three ranges, the algorithm will select the sensor closest to the last "valid" signal as the "fault select" "calculated signal". This "fault select" "calculated signal" will be used as the "process representation" until the operator selects an "operator select" sensor to replace it or the algorithm is able to validate data. Pressurizer Pressure Validation and Display Algorithm Determination of Calculated Signal and Faults (steps 1-13) 1500-2500 psig Range Validation Attempt (steps 1-4) If any deviation checks are unsatisfactory, the following occurs: Range Selection (step 4) 0-1600 psig Range Validation Attempt (steps 5-8) Range Selection (step 8) 0-4000 psig Range Validation Attempt (steps 9, 10, 11) Valid-PAMI Check (step 12) Failed Validation (step 13) Pressurizer Pressure "Process Representation" Selection (steps 14, 15) PAMI Check of "Operator Select " Sensor (step 16) Bad Sensor Evaluation (step 17) Range Check (step 18) |
abstract | Each of a plurality of electrostatic lens has inner walls of a plurality of lens apertures, which are formed by an electrode laid out around each beam axis, and high-resistance portions which are bonded to the electrode and are laid out on two sides of the electrode in the beam axis direction, and a low-resistance portion which is bonded to the high-resistance portions on a side opposite to the electrode in the beam axis direction. |
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053533232 | claims | 1. An X-ray exposure apparatus comprising: X-ray generating means for generating X-rays; a main chamber having an X-ray window for passing said X-rays and an X-ray mask attached thereto facing said X-ray window, and filled with X-ray low attenuation gas, for guiding said X-rays from said X-ray window to said X-ray mask; gas supplying means for supplying X-ray low attenuation gas into said main chamber and having a portion with a small-diameter passage cross section formed at least at a part thereof; gas discharging means for discharging gas from said main chamber and having a portion with a small-diameter passage cross section formed at least at a part thereof; and flow-rate control means for controlling a flow rate of gas to be supplied to said gas supplying means to thereby control pressure in said main chamber, and wherein a diameter of said small-diameter portion of said gas supplying means is set at a value smaller than that of said gas discharging means so that pressure in said main chamber is substantially equal atmospheric pressure. X-ray generating means for generating X-rays; a main chamber having an X-ray window for passing said X-rays and an X-ray mask attached thereto facing said X-ray window, and filled with X-ray low attenuation gas for guiding said X-rays from said X-ray window to said X-ray mask; gas supplying means for supplying X-ray low attenuation gas into said main chamber and having a first portion with a small-diameter passage cross section formed at least at a part thereof: 2. The X-ray exposure apparatus according to claim 1, wherein said gas supplying means includes a pressure control chamber whose internal pressure is controllable and a restrictor provided between said pressure control chamber and said main chamber and having an orifice of a predetermined diameter, and said gas discharging means has a gas discharging passage connected to said main chamber and wider than said diameter of said orifice. 3. The X-ray exposure apparatus according to claim 2, wherein said gas supplying means has a differential pressure gauge attached to said pressure control chamber for measuring a difference between pressure in said pressure control chamber and atmospheric pressure, and flow-rate control means for controlling a flow rate of gas to be supplied to said pressure control chamber, based on a signal output from said differential pressure gauge. 4. The X-ray exposure apparatus according to claim 1, wherein said gas supplying means has a pipe coupled to said main chamber to supply said gas thereto and narrower than said small-diameter portion of said gas discharging means. 5. The X-ray exposure apparatus according to claim 1, wherein said gas discharging means has a pipe connected to said main chamber and a shield valve provided between said pipe and said main chamber for closing said pipe. 6. The X-ray exposure apparatus according to claim 1, wherein said gas discharging means has a pipe connected to said main chamber and an oxygen analyzer for measuring an amount of oxygen in said pipe. 7. The X-ray exposure apparatus according to claim 1, wherein said gas discharging means has a pipe connected to said main chamber, and an outer tube provided around said pipe, with a gas retainer formed between said pipe and said outer tube. 8. The X-ray exposure apparatus according to claim 1, wherein said gas supplying means has a gas tank and a pipe for coupling said gas tank to said gas retainer. 9. The X-ray exposure apparatus according to claim 1, wherein said gas supplying means has bypass means for supplying a large amount of gas in said main chamber at a time of activating said X-ray exposure apparatus. 10. The X-ray exposure apparatus according to claim 1, wherein said gas discharging means has a pipe connected to a vicinity of a bottom portion off said main chamber, and having a gas outlet port extending upward and then bent to be open downward. 11. An X-ray exposure apparatus comprising: 12. The X-ray exposure apparatus according to claim 11, wherein said gas supplying means includes a pressure control chamber whose internal pressure is controllable and a restrictor disposed between said pressure control chamber and said main chamber and having an orifice of a predetermined diameter, and said gas discharging means has a gas discharging passage connected to said main chamber and having a larger diameter than said diameter of said orifice. |
054223830 | description | The following examples will further illustrate the present invention. Parts are by weight. In the present specification, the term "average particle diameter" is intended to refer to a Stokes diameter when the particles have a diameter of less than 1 .mu.m and to an equivalent volume diameter when the particles have a diameter of 1 .mu.m or more. EXAMPLE 1 Preparation of Composition Particles by Dry-Mixing Method (Method A) Each of the four colorants shown below was charged into a high speed jet impact-type mixer (Hybridizer NHS-1 manufactured by Nara Machinery Inc.) together with cordierite (SS-200 manufactured by Marusu Yuyaku Inc., average particle diameter: 10 .mu.m, white LB absorber) and the contents were mixed for 5 minutes at a revolution speed of 8,000 rpm to obtain composite particles having an average particle diameter of 10 .mu.m and a weight ratio of the colorant to the cordierite of 1:9. Colorant 1. Titanium dioxide (TiO.sub.2), Tipaque R-830 manufactured by Ishihara Sangyo Inc., white pigment, average particle diameter: 0.255 .mu.m, hereinafter referred to as Ti-W; PA1 2. Titanium yellow (mixture of TiO.sub.2, NiO.sub.2 and Sb.sub.2 O.sub.3, Tipaque TY-70 manufactured by Ishihara Sangyo Inc., yellow pigment, average particle diameter: 1.05 .mu.m, hereinafter referred to as Ti-Y; PA1 3. FeOOH, Mapicotan YP-100N manufactured by Tone Sangyo Inc., orange yellow pigment, average particle diameter: 0.2-1.0 .mu.m, hereinafter referred to as Fe-O; PA1 4. cupric oxalate, light blue, average particle diameter: 1.0 .mu.m, hereinafter referred to as Cu-B. PA1 A: very clear PA1 B: clear PA1 C: slightly unclear PA1 D: unclear PA1 1. Polyethylene (hereinafter referred to as Resin-PE) PA1 2. Polycarbonate (hereinafter referred to as Resin-PC) PA1 3. Polystyrene (hereinafter referred to as Resin-PS) PA1 5. Niobium (V) oxide, white colorant, average particle diameter: 1.68 .mu.m, hereinafter referred to as Nb-W PA1 1. Cordierite (the same as used in Example 1) PA1 2. Zeolite: Zeolite 4A manufactured by Union Showa Inc. average particle diameter: 10 .mu.m, white particles PA1 3. Zirconium silicate: Micropax manufactured by Hakusui Chemical Industries Inc., average particle diameter: 2.0 .mu.m, white particles, hereinafter referred to as Zr-silicate PA1 4. Calcium silicate: Niat 400 manufactured by Interpace Inc., average particle diameter: 6.0 .mu.m, white particles, hereinafter referred to as Ca-silicate PA1 EPIKOTE 828: Bisphenol A epoxy resin manufactured by Yuka-Shell Epoxy Inc. PA1 EPIKOTE 1002: Bisphenol A epoxy resin manufactured by Yuka-Shell Epoxy Inc. PA1 Anhydride A: Methyltetrahydrophthalic anhydride PA1 Anhydride B: Benzophenone tetracarbolylic anhydride PA1 Phenol Resin: Phenol novolak resin (Tamanol 754, hydroxyl equivalent: 104, manufactured by Arakawa Chemical Industry Inc.) PA1 TPP: Triphenylphosphine PA1 Silica: Amorphous silica Micron S-COL (manufactured by Micron Inc., average particle size: 28 .mu.m) PA1 Fe-O: Colorant (Example 1) PA1 Cordierite: LB absorber (Example 1) PA1 CoA-Fe-O: Composite particles obtained in Example 2 PA1 CoD-Fe-O: Composite particles obtained by the wet-mixing method (Method D shown in Example 6 using Fe-O (1 part) as a colorant and cordierite (9 parts) as an LB absorber, average particle diameter: 12 .mu.m) Each of the thus obtained four kinds of composite particles (hereinafter referred to as CoA-Ti-W, CoA-Ti-Y, CoA-Fe-O and CoA-Cu-B) were press-molded into a tablet having a diameter of 16 mm and a thickness of 1.0 mm and the tablet was irradiated with a laser beam (CO.sub.2 laser, energy 4J/cm.sup.2) using a laser beam marking device (TEA Unimark 400-4J manufactured by Ushio Electric Co., Ltd.) to obtain bar mark (line width: 2 mm). Irradiation was performed only once or repeated five times. The thus obtained marks were observed with native eyes to evaluate the visibility thereof on the basis of the following ratings: The results are summarized in Table 1. TABLE 1 ______________________________________ Visibility Colorant Once Five times Color of Mark ______________________________________ Ti-W C A black Ti-Y C A black Fe-O B A black Cu-B C A black ______________________________________ Comparative Example 1 Example 1 was repeated in the same manner as described except that no cordierite was used. The results are shown in Table 2. TABLE 2 ______________________________________ Visibility Colorant Once Five times ______________________________________ Ti-W C C Ti-Y C C Fe-O C B-C Cu-B C C ______________________________________ EXAMPLE 2 Preparation of Laser Beam Absorbing Plate A thermoplastic resin shown below was blended with a quantity of respective one of the composite particles obtained in Example 1. The blend was mixed at a temperature sufficient to melt the resin and then molded into a plate having a width of 20 mm, a length of 50 mm and a thickness of 1 mm. Laser marking test was carried out in the same manner as described in Example 1. The results are summarized in Table 3. The color of the marks was black. Thermoplastic Resin: TABLE 3 ______________________________________ Composite Particles Visibility Resin Kind Amount (parts*) Once Five times ______________________________________ Resin-PE CoA-Ti-W 10 C B Resin-PE CoA-Ti-Y 10 C B Resin-PE CoA-Fe-O 2 B A Resin-PE CoA-Cu-B 10 C B Resin-PC CoA-Ti-W 10 C B Resin-PC CoA-Ti-Y 10 C B Resin-PC CoA-Fe-O 2 B A Resin-PS CoA-Ti-W 10 C B Resin-PS CoA-Ti-Y 10 C B Resin-PS CoA-Fe-O 2 B A ______________________________________ EXAMPLE 3 Preparation of composite Particles by Singering Method (Method B) A colorant (4 g) shown in Table 4 and cordierite (36 g, the same as used in Example 1) were charged in a planetary ball mill (P-5 manufactured by Flitch Japan Inc.) together with 50 g of water and the contents were mixed for 1 hour. The resulting dispersion was filtered and the solids phase was dried and sintered at 1,300.degree. C. for 1 hour. The sintered mass was then pulverized into particles having an average particle diameter of 15 .mu.m. Preparation of Laser Beam Absorbing Plate The thus obtained composite particles (CoB-Ti-W, CoB-Ti-Y and CoB-Nb-W, 10 parts) were each mixed with a resin (100 parts) shown in Table 4 and the resulting composition was molded into a plate in the same manner as that in Example 2. The plate was then irradiated with a laser beam marking in the same manner as that in Example 1 to give black marks whose visibility was shown in Table 4. For the purpose of comparison, the resin (100 parts), the colorant (1 part) and cordierite (9 parts) were simultaneously mixed and the resulting composition was formed into a plate in the same manner as that in Example 2. The laser marking on the comparative samples was white to gray and had visibility shown in Table 4. Colorant TABLE 4 ______________________________________ Experiment 1* 2 3* 4 5* 6 7 ______________________________________ Resin Resin-PC 100 100 100 100 100 100 Resin-PE 100 Colorant Ti-W 1 Ti-Y 1 Nb-W 1 Cordierite 9 9 9 Composite CoB-Ti-W 10 10 CoB-Ti-Y 10 CoB-Nb-W 10 Visibility Once D B D B D C B Five times D A D A D B A ______________________________________ *Comparative samples EXAMPLE 4 Preparation of Composite Particles by Dry-Mixing Method (Method A) Using the combination of a colorant and an LB absorber shown below, the following five composite particles (CoA-Ti-W, ZeA-Ti-W, ZrA-Ti-W, CaA-Ti-W and CoA-Nb-W) were prepared by the Method A shown in Example 1. CoA-Ti-W: Ti-W and cordierite ZeA-Ti-W: Ti-W and zeolite ZrA-Ti-W: Ti-W and zirconium silicate CaA-Ti-W: Ti-W and calcium silicate CoA-Nb-W: Nb-W and cordierite LB absorber: Preparation of Laser Beam Absorbing Plate The thus obtained composite particles were each mixed with a resin (100 parts) shown in Table 5 and the resulting composition was molded into a plate in the same manner as that in Example 2. The plate was then irradiated with a laser beam marking in the same manner as that in Example 1 to give grayish black or black marks whose visibility was shown in Table 5. For the purpose of comparison, the resin (100 parts), the colorant (1 part) and the LB absorber (9 parts) shown in Table 5 were simultaneously mixed and the resulting composition was formed into a plate in the same manner as that in Example 2. The laser marking on the comparative samples was white to gray and had visibility shown in Table 5. TABLE 5 ______________________________________ Experiment 1* 2 3* 4 5* 6 ______________________________________ Resin Resin-PC 100 100 100 100 100 100 Resin-PE Colorant Ti-W 1 1 1 Nb-W LB absorber Cordierite 9 Zeolite 9 Zr-silicate 9 Ca-Silicate Composite CoA-Ti-W 10 ZeA-Ti-W 10 ZrA-Ti-W 10 CaA-Ti-W CoA-Nb-W Visibility Once D C D C D C Five times D B D B D B ______________________________________ Experiment 7* 8 9* 10 11* ______________________________________ Resin Resin-PC 100 100 100 100 Resin-PE 100 Colorant Ti-W 1 Nb-W 1 LB absorber Cordierite 9 Zeolite Zr-silicate Ca-Silicate 9 Composite CoA-Ti-W 10 ZeA-Ti-W ZrA-Ti-W CaA-Ti-W 10 CoA-Nb-W 10 Visibility Once D C D C C Five times D B D B B ______________________________________ *Comparative samples EXAMPLE 5 Preparation of Composite Particles by Sintering Method (Method B) Using the combination of a colorant and an LB absorber shown below, the following five composite particles (CoB-Ti-W, ZeB-Ti-W, ZrB-Ti-W, CaB-Ti-W and CoB-Nb-W) were prepared by the Method B shown in Example 3. CoB-Ti-W: Ti-W and cordierite ZeB-Ti-W: Ti-W and zeolite ZrB-Ti-W: Ti-W and Zr silicate CaB-Ti-W: Ti-W and Ca silicate CoB-Nb-W: Nb-W and cordierite Preparation of Laser Beam Absorbing Plate The thus obtained composite particles were each mixed with a resin (100 parts) shown in Table 6 and the resulting composition was molded into a plate in the same manner as that in Example 2. The plate was then irradiated with a laser beam marking in the same manner as that in Example 1 to give black marks whose visibility was shown in Table 6. For the purpose of comparison, the resin (100 parts), the colorant (1 part) and the LB absorber (9 parts) shown in Table 6 were simultaneously mixed and the resulting composition was formed into a plate in the same manner as that in Example 2. The laser marking on the comparative samples was white to gray and had visibility shown in Table 6. TABLE 6 ______________________________________ Experiment 1* 2 3* 4 5* 6 ______________________________________ Resin Resin-PC 100 100 100 100 100 100 Resin-PE Colorant Ti-W 1 1 1 Nb-W LB absorber Cordierite 9 Zeolite 9 Zr-silicate 9 Ca-Silicate Composite CoB-Ti-W 10 ZeB-Ti-W 10 ZrB-Ti-W 10 CaB-Ti-W CoB-Nb-W Visibility Once D B D C D B Five times D A D B D A ______________________________________ Experiment 7* 8 9* 10 11 ______________________________________ Resin Resin-PC 100 100 100 100 Resin-PE 100 Colorant Ti-W 1 Nb-W 1 LB absorber Cordierite 9 Zeolite Zr-silicate Ca-Silicate 9 Composite CoB-Ti-W 10 ZeB-Ti-W ZrB-Ti-W CaB-Ti-W 10 CoB-Nb-W 10 Visibility Once D C D C B Five times D B D B A ______________________________________ *Comparative samples EXAMPLE 6 Preparation of composite Particles by Precipitation Method (Method C) Into a three-necked flask were charged 10 g of cordierite (the same as used in Example 1) and 100 ml of water and the mixture was heated to 100.degree. C. With stirring, a solution of titanium sulfate (16.68 g) dissolved in 25.02 ml of water was poured dropwise into the flask. The resulting mixture was refluxed for 6 hours with stirring. The resulting precipitates were filtered and washed with water until the pH of the washed water became 6-7. The scanning electric microscope analysis revealed that the cordierite particles were each covered with titanium oxide. The precipitates thus obtained were then calcined at 800.degree. C. to obtain composite particles CoC-Ti-W having an average particle diameter of 15 .mu.m and a weight ratio of Ti-W to cordierite of 3:7. Preparation of composite Particles by Wet-Mixing Method Using Binder (Method D) Into a planetary ball mill were charged 8 g of polyethylene glycol (weight average molecular weight: 6000), 10 g of water and 10 g of Ti-W (titanium dioxide). The contents were mixed and thereafter added with 300 g of water. Further mixing of the contents gave a first suspension. Polyethylene glycol (the same as above, 3 g) was dissolved in 1,500 ml of water, into which 190 g of cordierite (the same as used in Example 1) were mixed with stirring to obtain a second suspension. With stirring, the first suspension was added to the second suspension. The resulting mixture was filtered and the separated solids were dried to obtain composite particles CoD-Ti-W having an average particle diameter of 10 .mu.m and a weight ratio of Ti-W to cordierite of 1:19. The scanning electric microscopic analysis revealed that titanium dioxide deposits on the surfaces of cordierite particles. The thus obtained composite particles CoC-Ti-W and CoD-Ti-W as well as CoA-Ti-W (Example 1) and CoB-Ti-W (Example 3) were each formed into a disc in the same manner as that in Example 1. Laser marking was carried out in the same manner as that in Example 1 to give the results shown in Table 7. TABLE 7 ______________________________________ Visibility Composite Once Five times Color of Mark ______________________________________ CoA-Ti-W C A black CoB-Ti-W B A black CoC-Ti-W B A black CoD-Ti-W C A gray-black ______________________________________ EXAMPLE 7 Using the colorants and the LB absorbers shown in Table 8, various composite particles were prepared by the same dry-mixing method (Method A) shown in Example 1. Each composite was formed into a disc in the same manner as that in Example 1. Laser marking was carried out in the same manner as that in Example 1 to give the results shown in Table 8. TABLE 8 ______________________________________ Compo- LB Visibility Color of site No. Absorber Colorant Once Five times Mark ______________________________________ 1 cordierite Ti-W C A black 2 cordierite Ti-Y C A black 3 cordierite Fe-O B A black 4 cordierite Cu-B C A black 5 Zr-silicate Ti-W C B black 6 Zr-silicate Ti-Y C B black 7 Zr-silicate Fe-O B A black 8 Zr-silicate Cu-B C A black 9 zeolite Ti-W C B black 10 zeolite Ti-Y C B black 11 zeolite Fe-O B A black 12 zeolite Cu-B C B black 13 Ca-silicate Ti-W C B black 14 Ca-silicate Ti-Y C B black 15 Ca-silicate Fe-O B A black 16 Ca-silicate Cu-B C B black ______________________________________ EXAMPLE 8 The ingredients shown in Table 9 below were blended in the amounts shown in Table 9 to obtain compositions of Sample Nos. 1-8. In Table 9, the amounts are parts by weight and abbreviations and trademarks are as follows: Each of Samples Nos. 1-8 was applied on a surface of an aluminum plate (50 mm.times.50 mm.times.1.5 mm) and the coating was heated at 120.degree. C. to form a cured resin layer (thickness: 0.5 mm) thereon. Bar mark (line width: 0.2 mm) was then marked on the coated resin layer by irradiation with a laser beam (CO.sub.2 laser, wavelength: 10.6 .mu.m, energy: 4 J/cm.sup.2) using a commercially available laser beam marking device (TEA Unimark 400-4J, manufactured by Ushio Electric Co., Ltd.). The color of the mark and the visibility were as summarized in Table 9. TABLE 9 __________________________________________________________________________ Sample No. 1* 2 3 4* 5 6 7 8 __________________________________________________________________________ Resin composition EPIKOTE 828 100 100 100 100 100 100 EPIKOTE 1002 100 100 100 Anhydride A 87 87 87 87 87 87 Anhydride B 20 Phenol Resin 15 BDMA 1.5 1.5 1.5 1.5 1.5 1.5 TPP 1.0 1.0 Filler Silica 80 80 80 80 80 80 Fe-O 2 1 Cordierite 18 19 Composite particles CoA-Fe-O 20 10 20 20 CoD-Fe-O 20 10 Color of Mark brown black black red brown brown black black Visibility Once C B B D C C B B Five times B A A D B B A A __________________________________________________________________________ *Comparative sample EXAMPLE 9 Example 8 was repeated in the same manner as described except that CoB-T-W, CoB-Ti-Y or CoB-Nb-W (obtained in Example 3) was used as the composite particles. The results are summarized in Table 10. EXAMPLE 10 Example 8 was repeated in the same manner as described except that CoA-T-W (obtained in Example 2), CoB-T-W (obtained in Example 3), CoC-Ti-Y (obtained in Example 6) or CoD-Ti-W (obtained in Example 6) was used as the composite particles. The results are summarized in Table 11. Comparative samples gave gray marks while the samples according to the present invention gave black or grayish black marks. EXAMPLE 11 Example 8 was repeated in the same manner as described except that CoA-T-W, ZeA-Ti-W, ZrA-Ti-W, CaA-Ti-W or CoA-Nb-W (obtained in Example 4) was used as the composite particles. The results are summarized in Table 12. Comparative samples Nos. 1, 3, 5, 7 and 9 gave gray marks while the samples Nos. 2, 6 and 11 according to the present invention gave black marks. The samples Nos. 4, 8 and 10 of the present invention gave grayish black marks. EXAMPLE 12 Example 8 was repeated in the same manner as described except that CoB-T-W, ZeB-Ti-W, ZrB-Ti-W, CaB-Ti-W or CoB-Nb-W (obtained in Example 5) was used as the composite particles. The results are summarized in Table 13. Comparative samples Nos. 1, 3, 5, 7 and 9 gave gray marks while the samples Nos. 2, 6, 10 and 11 according to the present invention gave black marks. The samples Nos. 4 and 8 of the present invention gave gray marks. In Tables 10-13, the symbol "*" indicates comparative sample. TABLE 10 __________________________________________________________________________ Sample No. 1* 2 3* 4 5* 6 7 __________________________________________________________________________ Resin composition EPIKOTE 828 100 100 100 100 100 100 EPIKOTE 1002 100 Anhydride A 87 87 87 87 87 87 Anhydride B 20 BDMA 1.5 1.5 1.5 1.5 1.5 1.5 TPP 1.0 Filler Silica 80 80 80 80 80 80 80 Ti-W 2 Ti-Y 2 Nb-W 2 Cordierite 18 18 18 Composite particles CoB-Ti-W 20 20 CoB-Ti-Y 20 CoB-Nb-O 20 Color of Mark gray black gray black gray gray- black black Visibility Once D B D B D C B Five times C A C A C B A __________________________________________________________________________ TABLE 11 __________________________________________________________________________ Sample No. 1* 2 3 4 5 6* 7 8 9 10 11 12 __________________________________________________________________________ Resin composition EPIKOTE 828 100 100 100 100 100 100 100 100 100 100 EPIKOTE 1002 100 100 Anhydride A 87 87 87 87 87 87 87 87 87 87 Anhydride B 20 Phenol resin 15 BDMA 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 TPP 1.0 1.0 Filler Silica 80 80 80 80 80 80 80 80 80 80 50 50 Ti-W 5 2 Cordierite 45 18 Composite particles CoA-Ti-W 50 20 CoB-Ti-W 50 20 50 50 CoC-Ti-W 50 20 CoD-Ti-W 50 20 Visibility Once C C C B B D C C C B B B Five times B A B A A C B B B A A A __________________________________________________________________________ TABLE 12 __________________________________________________________________________ Sample No. 1* 2 3* 4 5* 6 7* 8 9* 10 11 __________________________________________________________________________ Resin composition EPIKOTE 828 100 100 100 100 100 100 100 100 100 100 EPIKOTE 1002 100 Anhydride A 87 87 87 87 87 87 87 87 87 87 Anhydride B 20 BDMA 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 TPP 1.0 Filler Silica 80 80 80 80 80 80 80 80 80 80 80 Ti-W 2 2 2 2 10 Nb-O 2 Cordierite 18 18 Zeolite 18 Zr-silicate 18 Ca-silicate 18 Composite particles CoA-Ti-W 20 20 ZeA-Ti-W 20 ZrA-Ti-W 20 CaA-Ti-W 20 CoA-Nb-O 20 Visibility Once D C D C D C D C D C C Five times C B C B C B C B C B B __________________________________________________________________________ TABLE 13 __________________________________________________________________________ Sample No. 1* 2 3* 4 5* 6 7* 8 9* 10 11 __________________________________________________________________________ Resin composition EPIKOTE 828 100 100 100 100 100 100 100 100 100 100 EPIKOTE 1002 100 Anhydride A 87 87 87 87 87 87 87 87 87 87 Anhydride B 20 BDMA 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 TPP 1.0 Filler Silica 80 80 80 80 80 80 80 80 80 80 80 Ti-W 2 2 2 2 Nb-O 2 Cordierite 18 18 Zeolite 18 Zr-silicate 18 Ca-silicate 18 Composite particles CoA-Ti-W 20 20 ZeA-Ti-W 20 ZrA-Ti-W 20 CaA-Ti-W 20 CoA-Nb-O 20 Visibility Once D B D C D B D C D C B Five times C A C B C A C B C B A __________________________________________________________________________ EXAMPLE 13 Preparation of Composite Particles by Dry-Mixing Method (Method A) In accordance with the Method A described in Example 1, cupric oxalate and cordierite were processed to obtain composite particles CoA-Cu-1 having an average particle diameter of 10 .mu.m and a weight ratio of cupric oxalate to cordierite of 3:17 and CoA-Cu-2 having an average particle diameter of 15 .mu.m and a weight ratio of cupric oxalate to cordierite of 3:7. Preparation of composite Particles by Precipitation Method Into a three-necked flask were charged 34 g of cordierite (the same as used in Example 1) and 100 ml of water and the mixture was heated to 50.degree. C. With stirring, a solution of anhydrous cupric sulfate (5.8 g) dissolved in 60 ml of water was poured dropwise into the flask. Then, a solution of oxalic acid dihydride (7.2 g) dissolved in 50 ml of distilled water was added dropwise to the mixture in the flask with stirring. The resulting mixture was stirred for 30 minutes and a greater part of the water was removed in vacuo. The remaining mixture was filtered and the solids phase was dried at 110.degree. C., thereby to obtain composite particles CoC-Cu-1 having an average particle diameter of 15 .mu.m and a weight ratio of cupric oxalate to cordierite of 3:17. The above procedure was repeated in the same manner as described except that the amounts of the cordierite, anhydrous cupric sulfate and oxalic acid dihydride were changed to 14 g, 5.8 g and 7.2 g, respectively, thereby to obtain composite particles CoC-Cu-2 having an average particle diameter of 10 .mu.m and a weight ratio of cupric oxalate to cordierite of 3:7. Using the thus obtained composite particles, Example 8 was repeated in the same manner as described. The results are shown in Table 14. TABLE 14 ______________________________________ Sample No. 1* 2 3 4* 5 6 ______________________________________ Resin Composition EPIKOTE 100 100 100 100 100 100 828 Anhydride A 87 87 87 87 87 87 BDMA 1.5 1.5 1.5 1.5 1.5 1.5 Silica 50 50 50 50 50 50 Cu oxalate 7.5 15 Cordierite 42.5 35 CoA-Cu-1 50 CoA-Cu-2 50 CoC-Cu-1 50 CoC-Cu-2 50 Color of -- gray gray- gray gray- black Mark black glack Visibility Once D C B D B B Five times D B B C B A ______________________________________ *Comparative sample The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all the changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. |
054810612 | description | BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will now be described with reference to the attached drawings. First, the volume change of cement accompanying hardening will be described. FIG. 1 shows the relationship between the length change accompanying hardening and the mechanical strength (compressive strength) of a cement-solidified body. Herein, various solid bodies were prepared by incorporating 20% by dry weight of an ion exchange resin into various cements exhibiting different volume changes upon hardening. The volume change upon hardening of cement was regulated primarily by regulating the formation of ettringite (3CaO.Al.sub.2 O.sub.3. 3CaSO.sub.4. 32H.sub.2 O). As a result, it Has been found that when the length change upon hardening (hardening and curing conditions: in the air at 35.degree. C. for 14 days) is 0 to +0.5%, a high compressive strength can be attained. Moreover, the solid bodies were immersed in water for 30 days to measure the compressive strength. As a result, it has been found that they have maintained the strength before immersion. The reason for such a high water resistance is believed to reside in that not only the absence of any through capillary voids serves to inhibit the water absorption causative of a volume increase of the ion exchange resin, but also the cement has a sufficient strength to absorb any tensile stress occurring as a result of water absorption. Accordingly, a cement-solidified body having improved mechanical strength and water resistance can be attained by using cement whose length change upon hardening is 0 to +0.5. The mechanism permitting the regulation of a length change upon hardening and the cement properties and an expanding agent for attaining the object of the present invention will now be described with reference to some particular examples. Generally, in the hydration of cement, the true volumes of water and the cement after hardening are always smaller due to the hardening and shrinkage than those before hardening. Accordingly, from the microscopic viewpoint, it is not possible to avoid the occurrence of voids. However, it is possible to prevent the voids from communicating with one another, i.e., to inhibit the formation of through voids, i.e., to apparently, viz from the macroscopic viewpoint, inhibit shrinkage. What is provided in line with this thought is one designated as a "non-shrinkable or expansible cement". The expansible cement forms crystals having minute voids which do not mutually communicate. In the case of cement solidification of the above-described ion exchange resin, main crystals each comprise ettringite. However, in the case of calcium hydroxide or mixed system thereof as well, similar effects can be exerted. In order to form these crystals, it is necessary to add to cement in advance an expanding agent for promoting the formation of the crystals. In order to form ettringite, for example, a calcium solfoaluminate material whose major components are calcium sulfate and haunite (3CaO. 3Al.sub.2 O.sub.3.CaSO.sub.4) may be used as an expanding agent. Moreover, in the case of calcium hydroxide, calcium oxide or a limy material containing the same may be used as an expanding agent. Subsequently, the effect of the water absorptivity of radioactive wastes on the fluidity of cement was investigated. FIG. 2 shows the results on the measurement of the viscosity of cement mixture against sodium sulfate contents. Herein, the water to cement ratio was set at 0.4. As a result, it has been found that when the Na.sub.2 SO.sub.4 content reaches about 25% by weight, a rapid increase in the viscosity occurs. This is because Na.sub.2 SO.sub.4 absorbs water present in the cement, thereby forming a hydrate of the formula Na.sub.2 SO.sub.4.10H.sub.2 O and, when Na.sub.2 SO.sub.4 reaches 25% by weight, the stoichiometrical amount of water present in the cement is absorbed. Moreover, since the molecule of water is linked to Na.sub.2 SO.sub.4 so weakly that it is lost by efflorescence under 10 conditions of a temperature of 20.degree. C. and a relative humidity of 60% (believed to be average conditions within cement when allowed to stand at ordinary temperatures), it has been found that this water moves toward the cement with the progress of the hardening of the cement. Consequently, the addition of excess water is not an effective measure since there occur problems such as a decrease in the strength and difficulty in increasing the amount of packing of Na.sub.2 SO.sub.4 as will be described later. Therefore, the present inventors have attempted to ensure predetermined fluidity for cement by adding a material miscible with water but not absorbed by Na.sub.2 SO.sub.4. The present inventors have contemplated the use of a hydrophilic material as such a material and have added a polyalkylsulfonate hydrophilic material. The results are shown in FIG. 2. As shown by a solid line A, it has been found that when a hydrophilic material is added, predetermined fluidity can be maintained even when the water absorptive Na.sub.2 SO.sub.4 content of the waste is increased. By contrast, as shown by a broken line B, it is apparent that when no hydrophilic material is added, the viscosity increases. Besides the above-described polyalkylsulfonate material, organic compounds having a hydrophilic group (hereinafter referred to as "organic compounds having a hydrophilic group"), such as a polyhydric alcohol or a salt of a polybasic carboxylic acid, may also be used as the hydrophilic material. Moreover, a polymer emulsion, such as a latex emulsion, may be used as the hydrophilic material. When this polymer emulsion (hereinafter referred to as a "hydrophilic polymer") is used, not only predetermined fluidity is ensured as in the case of the above-described hydrophilic material, but also the tackiness of the polymer can be utilized. This enables the bonding strength between minute hydrated cement particles to be enhanced, thereby exerting an effect of increasing the strengths, especially, tensile strength. Therefore, even when a large amount of water-absorptive radioactive waste is contained, predetermined fluidity of cement can be ensured by adding the hydrophilic material. The results of an investigation on the amount of addition of water are shown in FIG. 3, which shows the results on the measurement of the mechanical strength at varied water to cement ratio when Na.sub.2 SO.sub.4 was added in an amount of 30% by weight. Herein, as an expandable cement, 2% of a polysulfonate hydrophilic material was employed. As a result, it has been found that a solid body having high strength can be obtained when the water to cement ratio is 0.15 to 0.6, especially 0.15 to 0.45. This is because when the water to cement ratio is small, there is no sufficient amount of water for hydration of cement and when the water to cement ratio is large, excess water causes the number of voids to be increased. Moreover, similarly the results of the solidification conducted by incorporating an ion exchange resin in an amount of 20% by dry weight are shown in FIG. 4, In the solidification, an ion exchange resin (water content: 50%) from which the adherent water had been removed was used. The water content of the ion exchange resin is not included in the calculation. The solidification was conducted at varied water to cement ratios. Of the two axes of abscissae, the lower axis indicates the water to cement ratio wherein the water content of the ion exchange resin is not included in the calculation as described above. It is apparent from the results that the cement is hardened even when the water to cement ratio is 0. Then, the water content of the resin within the cement-solidified body was measured and was found to be identical with the equilibrium water content under conditions of a temperature of 20.degree. C. and a relative humidity of 60%. Consequently, a corrected value was calculated assuming that water acted on the hydration of the cement in an amount equal to that desorbed from the 50% water-containing resin at a temperature of 20.degree. C. and at a relative humidity of 60%. The upper axis of abscissa of FIG. 4 indicates the corrected values by designating them as the water to cement ratio after correction. It is apparent that when the water to cement ratio is 0.15 to 0.45, a solid body having a high mechanical strength can be obtained. This result is in agreement with that of cement solidification of sodium sulfate as shown in FIG. 3. From the results of FIGS. 3 and 4, it is apparent that an acceptable cement-solidified body can be produced by determining the water to cement ratio between 0.15 and 0.45 on the assumption that the amount of adsorbed water at a temperature of 20.degree. C. and at a relative humidity of 60% onto the waste packed into the solid body does not affect the effect of the cement. Detailed description will now be made with respect to a solidification unit used for carrying out the present invention. FIG. 5 shows a schematic view of such a solidification unit. In the figure, numeral 1 designates a tank for accommodating powdery sodium sulfate, numeral 2 a tank for accommodating an ion exchange resin (water content: 50%), numeral 3 an agitator, numeral 4 a kneading tank, numeral 5 a tank for accommodating cement, numeral 6 a tank for supplying an organic compound having a hydrophilic group, numeral 7 a tank for supplying a polymer emulsion, numeral 8 a tank for accommodating water, numeral 9 a cement mixer, numeral 10 a 200-l drum, numeral 11 a belt conveyor, and numerals 20 to 27 valves. The detail of solidification process will now be described in order of procedures. Sodium sulfate is a main component of a concentrated liquid waste and obtained by drying a concentrated liquid waste with a centrifugal thin-film dryer. When solidifying the powder of dried sodium sulfate, the powder is fed from the sodium sulfate powder tank 1 through the valve 20 into the kneading tank 4. A cement mixture serving as a solidifying agent is prepared by feeding to the cement mixer 9 cement from the cement tank 5 through the valve 22, an organic compound having a hydrophilic group from the supply tank 6 through the valve 23, a hydrophilic polymer from the tank 24 for supplying a polymer emulsion through the valve 24, and water from the water tank 8 through the valve 25, and mixing them with one another in, the mixer 9. In this case, the cement is one exhibiting a length change upon hardening as shown in FIG. 1, i.e., a coefficient of linear expansion of 0 to 0.5% and the water to cement mixing ratio is regulated to 0.15 to 0.45 as shown in FIG. 3. The cement mixture regulated so as to satisfy the above-described requirements is fed into the kneading tank 4 to be kneaded with the sodium sulfate powder by means of the agitator 4. The kneaded mixture is solidified after packed into the drum 10, which is transferred by the belt conveyor 11, through the valve 27. On the other hand, when solidifying an ion exchange resin, the adherent water is preliminarily removed from the ion exchange resin with a centrifugal dryer or the like, and the ion exchange resin is then stored in the ion exchange tank 2 in such a state that the resin has a water content of about 50%. This resin may be fed through the valve 21 into the kneader 4 and solidified in the same manner as that described above with respect to sodium sulfate. However, in this case, the water to cement mixing ratio is regulated by making use of the amount of water desorbed from all of the ion exchange resins at a relative humidity of 70% so that the water to cement ratio afters correction as shown in FIG. 4 is 0.15 to 0.45. An example with respect to the solidification of an ion exchange resin will now be described in more detail with reference to FIG. 6. FIG. 6 shows the relationship between the amount of packing of an ion exchange resin and the compressive strength. As can be seen from the figure, the cement solidification according to the present invention ensure an amount of packing of the ion exchange resin larger than that of the case of the conventional cement solidification. Comparison of the amounts of packing at a compressive strength of 20 kg/cm.sup.2 shows that the amount of packing in the conventional cement solidification is 54 kg of dried resin per 200 l of the solid body while the amount of packing in the present invention is 66 kg of dried resin per 200 of the solid body. That is, the present invention enables an increase in the amount of packing by about 20%. Although the conventional cement solidification brings about a lowering in the strength during immersion when the amount of packing is large, the lowering in the strength in the present invention is very small. As with the above-described example, this example also enables the formation of a solid body having excellent water resistance and a large amount of packing of the waste. In the above-described example, sodium sulfate is solidified in powder form. However, it is also possible to solidify sodium sulfate in solution form. In this case, since the concentration of the sodium sulfate solution can be increased at most up to 20 wt. %, the amount of packing of the waste cannot be increased. Further, in the above-described examples, sodium sulfate and ion exchange resins are separately solidified. However, the same effect can be attained by solidifying them as a mixture. Further, in the above-described examples, both the hydrophilic polymer and the organic compound having a hydrophilic group are used. They may also be used alone. The number of tanks used can be reduced when the hydrophilic polymer and the organic compound having a hydrophilic group can be preliminarily mixed with cement. In the present invention, fibrous materials, such as carbon or,glass fiber, may also be used for the purpose of enhancing the tensile strength. Further, the use of cement capable of providing a solid body in which minute air bubbles are not connected to each other not only enables the formation of a light-weight solid body having excellent transportability but also makes the solid body less susceptible to lowering in the strength due to the floating of the waste in cement even when said waste has a low specific gravity. Industrial Applicability The present invention enables the formation of solid bodies having high strength, which makes it possible to increase the amount of packing of the wastes into the solid bodies. Further, since the wastes can be formed into compact solid bodies, the water resistance of the solid bodies is high, which makes it possible to remarkably suppress the leaching rate of wastes, e.g., radioactive wastes, incorporated in the solid bodies. Therefore, the present invention is useful for solidification and storage of general industrial wastes containing heavy metals or other hazardous materials as well as radioactive wastes. |
description | A stimulable phosphor sheet of the invention comprises at least two partitioned stimulable phosphor films laminated one on another. The partitioned stimulable phosphor film comprises plural partitions that divide the stimulable phosphor film on its plane to give plural stripe sections, and a stimulable phosphor layer placed in each stripe section. The partitioned stimulable phosphor films are laminated in such manner that the partitions of one stimulable phosphor film are arranged to cross the partitions of another stimulable phosphor film. The partitioned stimulable phosphor film is described in detail by referring to FIG. 1 of the attached drawings. In FIG. 1, the partitioned stimulable phosphor film 1 is composed of partitions 2 and stimulable phosphor layers placed in the areas between the partitions. For accomplishing appropriate resolution and image quality, the mean width of the partition preferably is in the range of 0.5 to 50 xcexcm. The stripe of the phosphor layer preferably has a mean width in the range of 5 to 300 xcexcm. A ratio of a total surface of the stimulable phosphor layer 3 to a total surface of the phosphor film 1, that is a ratio of effective phosphor layer, preferably is in the range of 40% to 98%. In the stimulable phosphor sheet of the invention, the partition of the stimulable phosphor film preferably has a light-scattering length for the stimulating rays which is shorter than that of the stimulable phosphor layer. In particular, the partition preferably has a light-scattering length of 0.05 to 20 xcexcm for the stimulating rays and a light-absorption length of 1,000 xcexcm or longer for the stimulating rays, while the stimulable phosphor layer has a light-scattering length of 20 to 1,000 xcexcm for the stimulating rays and a light-absorption length of 1,000 xcexcm or longer for the stimulating rays. The term of light-scattering length indicates a mean distance in which a light travels straight until it is scattered, and therefore a shorter light-scattering length means that the phosphor layer or partition highly scatters a light. The term of light-absorption length indicates a mean free distance in which the stimulated emission is absorbed, and therefore a longer light-absorption length means that the phosphor layer or partition shows a lower light absorbance. The light-scattering length and light-absorption length can be determined by calculation according to Kubeluka-Munk theory. In FIG. 1, the top and bottom of the partition 2 are exposed over each surface of the stimulable phosphor film 1. However, the top and/or bottom of the partition 2 may be buried in the stimulable phosphor sheet. The partition preferably has a height corresponding to 1/3 to 1/1 of the thickness of the stimulable phosphor film 1. In FIG. 2, a set of four partitioned stimulable phosphor films 1 which are to be laminated in the illustrated mode to give a stimulable phosphor sheet in which the partitions of one stimulable phosphor film are arranged to perpendicularly (namely at an angle of approximately 90xc2x0) cross the partitions of another stimulable phosphor film. Each partitioned stimulable phosphor film preferably is identical to each other. In FIG. 3, a set of four partitioned stimulable phosphor films which are to be laminated in the illustrated mode to give a stimulable phosphor sheet. In the illustrated mode, the partitions of the top stimulable phosphor film are arranged to cross the partitions of the second stimulable phosphor film at an angle of 45xc2x0; the partitions of the second stimulable phosphor film are arranged to cross the partitions of the third stimulable phosphor film at an angle of 90xc2x0; and the partitions of the third stimulable phosphor film are arranged to cross the partitions of the fourth (i.e., bottom) stimulable phosphor film at an angle of 45xc2x0. Each partitioned stimulable phosphor film preferably is identical to each other. The stimulable phosphor sheet of the invention comprises plural partitioned thin stimulable phosphor films which are so arranged as to form square, rhombic, or triangle plural cells which are observed in the direction perpendicular to the plane of the phosphor sheet. Thus, the specific arrangements of partitions of the adjoining partitioned stimulable phosphor films results in producing imaginary cell structures in the phosphor sheet, to define scattering of the stimulating rays in the cells. In the radiation image reproducing procedure, the stimulable phosphor sheet of the invention is preferably moved in the direction parallel to the partitions of the top partitioned phosphor film, while the stimulating rays are scanned in a direction perpendicular to the direction of movement. The stimulable phosphor sheet of the invention can be preferably produced in the process illustrated in FIG. 4 through FIG. 7. The preferred process is further described below, by referring to the case that the stimulable phosphor layer comprises stimulable phosphor particles and binder, and the partition comprises low light-absorbing fine particles and polymer material. In the first step, a stimulable phosphor film is prepared. As the stimulable phosphor, a phosphor giving a stimulated emission of a wavelength in the region of 300 to 500 nm when it is irradiated with stimulating rays of a wavelength in the region of 400 to 900 nm is preferably employed. In Japanese Patent Provisional Publications No. 2-193100 and No. 4-310900, some examples of the stimulable phosphors are described in detail. Examples of the preferred stimulable phosphors include divalent europium or cerium activated alkaline earth metal halide phosphors (e.g., BaFBr:Eu, BaF(BrI):Eu), and cerium activated oxyhalide phosphors. Most preferred stimulable phosphors are rare earth metal activated alkaline earth metal fluorohalide phosphors having the following essential formula (I): MIIFX:zLnxe2x80x83xe2x80x83(I) in which MII is an alkaline earth metal such as Ba, Sr, or Ca; Ln is a rare earth metal such as Ce, Pr, Sm, Eu, Tb, Dy, Ho, Nd, Er, Tm, or Yb; X is a halogen atom such as Cl, Br, or I; and z is a value satisfying the condition of 0 less than zxe2x89xa60.2. MII of the formula (I) preferably comprises Ba in an amount of 50 atomic % or more. Ln preferably is Eu or Ce. It should be noted that the formula (I) does not mean F:X=1:1, but means to have a crystalline structure of BaFX. Thus, the formula (I) does not accurately indicate stoichiometric amounts of the constitutional elements. It is generally preferred that F is slightly rich in comparison with X, because F+ center (Xxe2x88x92 center) produced in such composition efficiently gives a stimulated emission when the phosphor is stimulated with a light in the region of 600 to 700 nm. The stimulable phosphor of the formula (I) can further contain one or more of the following additive components: bA, wNI, xNII, yNIII In the above formulas, A is a metal oxide such as Al2O3, SiO2 or ZrO2, in which source of the metal oxide preferably is extremely fine particles having a mean diameter (of primary particles) of 0.1 xcexcm or less and has little reactivity to MIIFX particles to keep the MIIFX particles from coagulation; NI is a compound of an alkali metal such as Li, Na, K, Rb, or Cs; NII is a compound of an alkaline earth metal such as Mg and/or Be; and NIII is a compound of a monovalent or trivalent metal such as Al, Ga, In, Tl, Sc, Y, La, Gd, or Lu. The metal compounds preferably are halide compounds such as those described in Japanese Patent Provisional Publication No.59-75200. In the formulas, each of b, w, x, and y is a value which means an amount of each source material, based on one molar amount of MIIFX, under the conditions of 0xe2x89xa6bxe2x89xa60.5, 0xe2x89xa6wxe2x89xa62, 0xe2x89xa6xxe2x89xa60.3, and 0xe2x89xa6bxe2x89xa63. Accordingly, the value of b, w, x, or y does not necessarily mean the amount of each element or compound existing in the finally produced phosphor. Further, each additive compound may exist as such in the finally produced phosphor or may react with MIIFX in the course of the preparation of the stimulable phosphor. Furthermore, the stimulable phosphor of the formula (I) may contain one or more of the following compounds or reaction products thereof: Compounds of Zn and Cd described in Japanese Patent Provisional Publication No. 55-12145; Metal oxides such as TiO2, BeO, MgO, CaO, SrO, BaO, ZnO, Y2O3, LA2O3, In2O3, GeO2, SnO2, Nb2O5, Ta2O5, and ThO2 described in Japanese Patent Provisional Publication No. 55-160078; Compounds of Zr and Sc described in Japanese Patent Provisional Publication No. 56-116777; Compounds of B described in Japanese Patent Provisional Publication No. 57-23673; Compounds of As and Si described in Japanese Patent Provisional Publication No. 57-23675; Tetrafluoroborate compounds described in Japanese Patent Provisional Publication No. 59-27980; Hexafluoro compounds such as monovalent or divalent salts of hexafluorosilicic acid, hexafluorotitanic acid, or hexafluorozirconic acid described in Japanese Patent Provisional Publication No. 59-47289; and Compounds of transitional metals such as V, Cr, Mn, Fe, Co, and Ni described in Japanese Patent Provisional Publication No. 59-56480. Moreover, other additives may be incorporated, provided that the incorporated additives do not disturb the preparation of the essential phosphor composition of the formula (I). The rare earth activated alkaline earth metal fluorohalide phosphors of the formula (I) generally have an aspect ratio of 1.0 to 5.0. The stimulable phosphor particles favorably employed for the production of the stimulable phosphor sheet of the invention have an aspect ratio of 1.0 to 2.0, more preferably 1.0 to 1.5. The particle size preferably is in the range of 1 xcexcm to 10 xcexcm, more preferably 2 xcexcm to 7 xcexcm, in terms of Median diameter (Dm), and "sgr"/Dm ("sgr" is a standard deviation of the particle size distribution) preferably is not more than 50%, more preferably not more than 40%. The particles may be in the form of parallelepiped, regular hexahedron, regular octahedron, tetradecahedron, intermediate polyhedron, or amorphous. The phosphor particles of tetradecahedron are preferred. Examples of the binders include natural polymers such as proteins (e.g., gelatin), polysaccharides (e.g., dextran) and gum arabic; and synthetic polymers such as polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethyl cellulose, vinylidene chloride-vinyl chloride copolymer, polyalkyl (meth) acrylate, vinyl chloride-vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, linear polyester, and thermoplastic elastomers. The polymer material may be crosslinked. The stimulable phosphor particles and binder are placed in an appropriate solvent to prepare a dispersion. The ratio of binder and stimulable phosphor particles in the phosphor dispersion generally is in the range of 1:1 to 1:100 (binder:phosphor, by weight), preferably 1:8 to 1:40. The phosphor dispersion is coated on a temporary support such as glass plate, metal plate, or plastic sheet, and dried to give a stimulable phosphor film A illustrated in FIG. 4. The produced stimulable phosphor film may be compressed under heating, so as to increase the density of the phosphor film. Alternatively, the stimulable phosphor film can be prepared by depositing or sintering stimulable phosphor material on a heat-resistant support such as metal plate. The partition film B is described below. Examples of the low light-absorbing fine particles are fine particles of white inorganic materials such as aluminum oxide (i.e., alumina), titanium dioxide, yttrium oxide, zirconium oxide, gadolinium oxide, tellurium oxide, ruthenium oxide, and lead oxide. Certain stimulable phosphor particles may be employed as the low light-absorbing fine particles. Preferred are alumina particles and yttrium oxide. The low light-absorbing fine particles preferably have a mean particle diameter of 0.01 to 5.0 xcexcm. There are no specific limitation with respect to the polymer binder for production of the partition film B, and the binders described hereinbefore for the production of the stimulable phosphor film A can be employed. In order to shorten the light-scattering length of the partition, however, a ratio of Kf (i.e., refractive index of the low light-absorbing fine particles) to the refractive index of the polymer binder preferably is in the range of 1.1 to 3.0. Therefore, the polymer binder preferably is polyurethane, polyacrylate, polyethylene, polystyrene, or a fluororesin. For the production of the partition film, a dispersion is prepared by mixing the low light-absorbing fine particles and the polymer binder in a solvent. The polymer binder and the low light-absorbing fine particles are mixed generally at a ratio of 1:80 to 1:3 (by weight), preferably 1:20 to 1:10 (by weight). The dispersion is coated on a temporary support, and dried to give a partition film B illustrated in FIG. 4. The preparation of the stimulable phosphor film A is repeated to produced a plurality of stimulable phosphor films, and the preparation of the partition film B is repeated to produced a plurality of partitions films. The stimulable phosphor films and partition films are then placed alternately to give a laminate illustrated in FIG. 5. The laminate of FIG. 5 is then heated under pressure in the manner illustrated in FIG. 6, to give a laminate block in which the stimulable phosphor films and partition films are bonded to each other. The laminate block is then sliced along the surface perpendicular to the planes of the phosphor films and partition films, so that a partitioned stimulable phosphor film such as that illustrated in FIG. 1 is produced. The slicing procedure is repeated to give a plurality of partitioned stimulable phosphor films. The partitioned stimulable phosphor films are then laminated in the manner illustrated in FIG. 2 or FIG. 3, and heated under pressure in the manner such as that illustrated in 6, to produce a stimulable phosphor sheet of the invention. The stimulable phosphor sheet of the invention may have a support and a transparent cover film as illustrated in FIG. 8 in which the stimulable phosphor sheet 4 has a support 5 and a transparent cover film 6, so as to keep the phosphor sheet from deterioration and to facilitate handling of the phosphor sheet. The stimulable phosphor sheet also can have a light-reflective layer on one surface side (or between the phosphor sheet and the support, if the support is provided), so as to increase the sensitivity of the phosphor sheet. As the support, a sheet or a film of flexible resin material having a thickness of 50 xcexcm to 1 mm is generally employed. The support may be transparent or may contain light-reflecting material (e.g., alumina particles, titanium dioxide particles, and barium sulfate particles) or voids, for reflecting the stimulating rays or the stimulated emission. Further, it may contain light-absorbing material (e.g., carbon black) for absorbing the stimulating rays or the stimulated emission. Examples of the resin materials include polyethylene terephthalate, polyethylene naphthalate, aramid resin and polyimide resin. The support may be a sheet of other material such as metal, ceramics and glass, if needed. On the phosphor sheet-side surface of the support, auxiliary layers (e.g., light-reflecting layer, light-absorbing layer, adhesive layer, electroconductive layer) or many hollows may be provided. On the other side surface, a friction-reducing layer or an anti-scratch layer may be formed. On the surface not facing the support, the stimulable phosphor sheet may have a protective cover film. In order not to affect the simulating rays or the stimulated emission, the cover film preferably is transparent. Further, for efficiently protecting the stimulable phosphor sheet from chemical deterioration and physical damage, the protective film should be both chemically stable and physically strong. The cover film can be provided by fixing a before-hand prepared transparent plastic film (e.g., polyethylene terephthalate) on the stimulable phosphor sheet with adhesive, or by coating the phosphor sheet with a solution of cover film material and drying the coated solution. Into the cover film, fillers of fine particles may be incorporated so as to reduce blotches caused by interference and to improve the quality of the resultant radiation image. The thickness of the cover film generally is in the range of approx. 0.1 to 20 xcexcm. For enhancing the resistance to staining, a fluororesin layer is preferably provided on the cover film. The fluororesin layer can be formed by coating the surface of the cover film with a solution of a fluororesin in an organic solvents, and drying the coated solution. The fluororesin may be used singly, but generally a mixture of the fluororesin and a film-forming resin is employed. In the mixture, an oligomer having polysiloxane structure or perfluoroalkyl group can be further added. Into the fluororesin layer, a filler of fine particles may be incorporated so as to reduce blotches caused by interference and to improve quality of the resultant radiation image. The thickness of fluororesin layer generally is in the range of 0.5 to 20 xcexcm. In the formation of the fluororesin layer, additives such as a crosslinking agent, a film-hardening agent and an anti-yellowing agent can be used. In particular, the crosslinking agent advantageously improves durability of the fluororesin layer. The light-reflective layer can comprise a white pigment such as alumina pigment, titanium dioxide pigment, or a barium sulfate pigment, or phosphor particles giving no stimulated emission. In the light-reflective layer, the pigment or particles are dispersed and supported in a binder. The present invention is further described by the following examples. 1) Stimulable phosphor (BaF(Br,I):Eu) particles (median of the particle sizes; 5 xcexcm) and a thermoplastic high molecular weight-polyester resin were dispersed in an organic solvent in a weight ratio of 5:1. The prepared phosphor dispersion was coated on a temporary support having a releasing surface, and dried to give a dry phosphor film. The phosphor film thus formed was then peeled from the temporary support to give a stimulable phosphor film A (thickness: approx. 100 xcexcm). The stimulable phosphor film A was subjected to measurement of transmittance at a stimulating wavelength (600 nm) and a stimulated emission wavelength (400 nm), to determine the light-scattering length and light-absorbing length. It was confirmed that the light-scattering length at the stimulating wavelength was such long as to give 66 xcexcm and the light-absorbing length was such long as a length of longer than 1,000 xcexcm. 2) Particles of yttrium oxide (mean particle size: 0.6 xcexcm) and a thermoplastic high molecular weight-polyester resin were dispersed in an organic solvent in a weight ratio of 15:1. Thus prepared yttrium oxide particle-containing dispersion was coated onto a temporary support having a releasing surface, and dried to give a yttrium oxide particle-containing dry film. The dry film was then peeled from the temporary support to give a partition film B (thickness: approx. 30 xcexcm). The partition film B was subjected to measurement of transmittance at a stimulating wavelength (600 nm) and a stimulated emission wavelength (400 nm), to determine the light-scattering length and light-absorbing length. It was confirmed that the light-scattering length at the stimulating wavelength was such short as to give 4 xcexcm and the light-absorbing length was such long as a length of longer than 1,000 xcexcm. 3) The stimulable phosphor films A and the partition films B were alternately piled up to form a laminate consisting of 360 films. The la te was then heated under pressure (pressure: approx. 1 kg/cm2, temperature: 100xc2x0 C.) for 1 hour to produce a laminate block. 4) The laminate block was repeatedly sliced in the manner illustrated in FIG. 7 using a wide microtome, to produce plural partitioned stimulable phosphor film (thickness: 100 xcexcm, width of partition: approx. 30 xcexcm, width of stimulable phosphor layer: approx. 100 xcexcm). 5) Three, six or nine partitioned stimulable phosphor films are laminated in such manner that the partitions of the adjoining films perpendicularly cross each other, as illustrated in FIG. 2. Thus, three stimulable phosphor sheets (thickness: approx. 300 xcexcm, approx. 600 xcexcm, or approx. 900 xcexcm) were prepared. The procedures of Example 1 were repeated except for placing a light-reflecting layer on one surface of the stimulable phosphor sheet of approx. 600 xcexcm thick by coating the yttrium oxide particle-containing dispersion employed in 2) above, to produce a stimulable phosphor sheet having a light-reflecting layer on one side. The procedures of Example 1 were repeated except for fixing a transparent polyethylene terephthalate film (thickness: 300 xcexcm) on one surface of the stimulable phosphor sheet of approx. 600 xcexcm thick, using an adhesive, to produce a stimulable phosphor sheet having a transparent cover film. The laminate block prepared in Example 1-3) was sliced in the manner illustrated in FIG. 7 to give three stimulable phosphor sheets (thickness: 320 xcexcm, 590 xcexcm, and 910 xcexcm) having partitions extending one dimensionally. Stimulable phosphor (BaF(Br,I):Eu) particles (median of the particle sizes: 5 xcexcm) and a thermoplastic high molecular weight-polyester resin were dispersed in an organic solvent in a weight ratio of 20:1. The prepared phosphor dispersion was coated on a temporary support having a releasing surface, and dried to give a dry phosphor film. The dry phosphor film was peeled off from the temporary support to obtain a stimulable phosphor sheet having a thickness of approx. 290 xcexcm, approx. 600 xcexcm, or approx. 880 xcexcm which had no partitions on its surface. The stimulable phosphor sheets obtained in Examples 1 to 3 and Comparison Examples 1 and 2 were exposed to irradiation of X-rays (tube voltage: 80 kVp, 80 mA, radiation dose: 10 mR). Subsequently, a He-Ne laser beam was scanned on the irradiated stimulable phosphor sheet, and the stimulated emission was collected on the side on which the laser beam was scanned. The amount of the stimulated emission was detected to determine the sensitivity. Independently, the stimulable phosphor sheet was exposed to X-rays in the same manner except for placing a CTF chart on the phosphor sheet. The scanning with the laser beam and the collection of the stimulated emission were carried out in the same manner to obtain radiation image data. The sharpness was evaluated using the obtained radiation image data. In the exposure to X-rays, the CTF chart was so placed on the stimulable phosphor sheet that the partitions of the phosphor sheet on the top partitioned phosphor film and the stripes of the CIF were arranged perpendicularly to each other (first run) or aligned in parallel (second run). The stimulated emission produced from the stimulable phosphor sheet of Example 3 was collected from both surface sides The results are set forth in Table 1. From the results of Table 1, it is confirmed that the stimulable phosphor sheet of the invention (Example 1) gives a reproduced radiation image of high sharpness not only in the first run but also in the second run, as compared with the stimulable phosphor sheet of Comparison Example 1. This is favorable for reproducing a radiation image for diagnosis. The stimulable phosphor sheet of Comparison Example 2, which is a conventional stimulable phosphor sheet) also gives a reproduced radiation image of relatively high sharpness not only in the first run but also in the second run, as compared with the stimulable phosphor sheet of Comparison Example 1. However, in the case that the thickness of the stimulable phosphor sheet, the phosphor sheet of Comparison Example 2 decreases the sensitivity rapidly, while its sensitivity increases only slightly. The stimulable phosphor sheets of Examples 2 and 3 show sensitivity apparently higher than that of the stimulable phosphor sheet of Example 1. The procedures of Example 1 were repeated except for laminating, in order, three (six or nine) partitioned stimulable phosphor films in such manner that the partitions of a upper film crossed the partitions of a lower film at an angle of 60xc2x0. Thus, three stimulable phosphor sheets (thickness: approx. 300 xcexcm, approx. 600 xcexcm, or approx. 900 xcexcm) were prepared. The procedures of Example 1 were repeated except for so slicing the laminate block as to give plural partitioned stimulable phosphor films having different thicknesses in the range of 50 to 600 xcexcm, in the step 4). The plural partitioned stimulable phosphor films having different thickness are laminated in such manner that the partitions of one of the adjoining films crossed perpendicularly the partitions of another film. In this manner, four stimulable phosphor sheets set forth in Table 2 were prepared. The three stimulable phosphor sheets of Example 4 and the four stimulable phosphor sheets of Example 5 were evaluated in their sensitivity and sharpness in the same manner as described above. It was confirmed that these stimulable phosphor sheets showed satisfactory sensitivity and sharpness. |
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abstract | Ion sources, systems and methods are disclosed. In some embodiments, the ion sources, systems and methods can exhibit relatively little undesired vibration and/or can sufficiently dampen undesired vibration. This can enhance performance (e.g., increase reliability, stability and the like). In certain embodiments, the ion sources, systems and methods can enhance the ability to make tips having desired physical attributes (e.g., the number of atoms on the apex of the tip). This can enhance performance (e.g., increase reliability, stability and the like). |
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description | 1. Field of the Invention The present invention generally relates to a UV light irradiating apparatus or a method for irradiating a semiconductor substrate. 2. Description of the Related Art Traditionally, UV processing apparatuses have been used in the reforming of various processing targets using ultraviolet light or in the production of substances through processes that utilize photochemical reactions. The trend of increasingly integrated devices in recent years has created needs for refined wiring designs and multi-layer wiring structures, which has made it vital to reduce inter-layer volumes to increase the processing speeds of devices while reducing their power consumptions. Low-k (low-dielectric-constant film) materials are used to reduce inter-layer volumes. However, reducing the dielectric constant of a material also reduces its mechanical strength (elastic modulus, or EM), which makes it difficult for the low-k material to withstand the stresses received in subsequent processes such as CMP, wire bonding and packaging. One method to address the aforementioned problem is to cure the low-k material with UV irradiation to improve its mechanical strength (examples are found in U.S. Pat. No. 6,759,098 and U.S. Pat. No. 6,296,909). UV irradiation causes the low-k material to shrink and harden, thereby increasing its mechanical strength (EM) by 50 to 200%. Separately, optical CVD based on photochemical reaction has been studied for years as a way to respond to another demand stemming from the recent trend of highly integrated devices, which is to obtain various thin films free from heat or plasma damages by utilizing thermal CVD or PECVD-based film deposition processes. UV irradiation has the effect of enhancing the mechanical strength of a low-k film by breaking the —CH3 bond or —Si—O bond in film and then re-bonding the broken components to build an O—Si—O network. This effect is stronger with UV light with short wavelengths because such light generates higher energy. Various types of lamps can be used for UV curing, such as excimer lamps and mercury lamps. Among these, mercury lamps produce light of various wavelengths and generate a lot of heat as a result, and therefore these lamps require cooling. Normally mercury lamps are cooled by a blower supplying cooling air. Since the oxygen in cooling air absorbs UV light with a wavelength of 250 nm or shorter and converts it to ozone, however, the quantity of effective UV light reaching the irradiation target will decrease. As a result, the curing efficiency will drop and the throughput will also be affected. Furthermore, generated ozone is harmful and thus the exhaust gas must be treated with a scrubber method, etc. If the input power to the lamp is increased in an attempt to increase the quantity of effective UV light with a wavelength of 250 nm or shorter, more heat will generate and the temperature of the curing target, i.e., the substrate on which a low-k film has been deposited, will also increase. Accordingly, there is a limit to how much the input power can be increased. To solve at least one of the aforementioned problems, an embodiment of the present invention changes the lamp cooling method from air-cooling to water-cooling. Since this eliminates the need for use of atmospheric air for cooling, the required UV light with a wavelength of 250 nm or shorter will not be absorbed by the oxygen in cooling air, which in turn enables effective UV processing. UV light with a wavelength of 250 nm or shorter is effective in curing low-k films. In particular, UV light with a wavelength in a range of 200 to 250 nm is very effective. A lot of air is needed to cool mercury lamps, but as noted above, effective light with a wavelength of 250 nm or shorter is absorbed by the oxygen in air and converted to harmful ozone. Use of nitrogen is not practical in view of the large quantity of nitrogen required. These concerns will no longer be necessary if the aforementioned embodiment is used. In another embodiment, the atmosphere in the lamp unit is replaced with N2 to prevent UV light with a wavelength of 250 nm or shorter from being absorbed by the oxygen in cooling air. Another problem, as mentioned before, is that if the intensity of UV light with a wavelength of 250 nm or shorter is raised to improve the curing efficiency, the greater heat generated from the lamp will increase the temperature of the irradiated substrate. Consequently, the intensity of UV light can only be increased to a certain level. In an embodiment, a water-cooled lamp is used to increase the intensity of UV light without causing problems associated with heat. For purposes of summarizing the invention and the advantages achieved over the related art, certain objects and advantages of the invention are described in this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. Further aspects, features and advantages of this invention will become apparent from the detailed description of the preferred embodiments which follow. The present invention will be explained with reference to preferred embodiments. However, the preferred embodiments are not intended to limit the present invention. In an embodiment, the present invention provides a UV light irradiating apparatus for irradiating a semiconductor substrate with UV light, comprising: (i) a reactor in which a substrate-supporting table is provided, said reactor being provided with a light transmission window; (ii) a UV light irradiation unit connected to the reactor for irradiating a semiconductor substrate placed on the substrate-supporting table with UV light through the light transmission window, said UV light irradiation unit including at least one UV lamp; and (iii) a liquid layer forming channel disposed between the light transmission window and the UV lamp for forming a liquid layer through which the UV light is transmitted, said liquid layer being formed by a liquid flowing through the liquid layer forming channel. The above embodiment may further include, but may not be limited to, the following embodiments: In an embodiment, the liquid layer may be formed by the flowing liquid which has substantially or nearly no absorption of UV light having a wavelength of 250 nm or lower. In an embodiment, the liquid constituting the liquid layer may be water. In an embodiment, the liquid layer forming channel may be formed with a glass capable of transmitting UV light having a wavelength of 250 nm or lower. In an embodiment, the liquid layer forming channel may be formed by two transparent walls for passing the liquid therebetween. In a preferred embodiment, a distance between the two walls may be about 5 mm to about 15 mm (preferably 7 mm to 12 mm). The thickness of the wall (e.g., made of a quartz glass) may be about 1 mm to about 2 mm. In an embodiment, the liquid layer forming channel may be formed by a double walled enclosure comprising an inner wall and an outer wall for passing the liquid between the walls, said enclosure enclosing the UV lamp. In an embodiment, the UV lamp may have an elongated shape. In an embodiment, the double walled enclosure may have a liquid inlet port for introducing the liquid between the inner and outer walls and a liquid outlet port for discharging the liquid from between the inner and outer walls. In an embodiment, the double walled enclosure may have an inert gas inlet port for introducing inert gas into an interior enclosed by the inner wall and an inert gas outlet port for discharging the inert gas from the interior. In an embodiment, the liquid layer forming channel may be disposed in parallel to and closer to the UV light transmission window than to the UV lamp. In an embodiment, the UV light transmission window may constitute the liquid layer forming channel. In an embodiment, the UV irradiation unit may be provided with a reflection plate disposed along an inner wall of the UV irradiation unit, said reflection plate being angled to reflect UV light from the UV lamp toward the UV light transmission window. In an embodiment, the liquid layer forming channel may have a liquid inlet port for introducing the liquid into the channel and a liquid outlet port for discharging the liquid from the channel and may be provided with a temperature sensor disposed at the liquid outlet port for detecting a temperature of the liquid at the liquid outlet port. In an embodiment, the liquid layer forming channel may be provided with a flow controller disposed upstream of the liquid inlet port for controlling the liquid flow according to the temperature detected by the temperature sensor. In another embodiment, the present invention provides a method for irradiating a semiconductor substrate with UV light, comprising: (i) placing a semiconductor substrate on a substrate-supporting table in a reactor; (ii) forming a liquid layer by passing a liquid through a liquid layer forming channel disposed between a UV lamp provided in a UV light irradiation unit and a light transmission window provided between the reactor and the UV light irradiation unit; and (iii) irradiating the semiconductor substrate with UV light emitted from the UV lamp through the liquid layer and the light transmission window. The above embodiment may further include, but may not be limited to, the following embodiments: In an embodiment, the liquid layer may be formed by passing the liquid which has substantially or nearly no absorption of UV light having a wavelength of 250 nm or lower. In an embodiment, the liquid constituting the liquid layer may be water. In an embodiment, the substrate may have a low-k film (or ultra low-k film) subjected to the UV light irradiation. In an embodiment, the liquid layer forming channel may be formed by a double walled enclosure which encloses the UV lamp and may comprise an inner wall and an outer wall, wherein the liquid layer forming step comprises passing the liquid between the inner and outer walls. In an embodiment, the liquid layer forming step may further comprise introducing inert gas into an interior enclosed by the inner wall and discharging the inert gas from the interior. In an embodiment, the liquid layer may be formed in parallel to and closer to the UV light transmission window than to the UV lamp. In an embodiment, the UV light transmission window may serve as the liquid layer forming channel, and the liquid layer may be formed in the UV light transmission window. In an embodiment, the UV irradiation unit may be provided with a reflection plate disposed along an inner wall of the UV irradiation unit, wherein the irradiation step may further comprise reflecting UV light from the UV lamp using the reflection plate toward the UV light transmission window. In an embodiment, the liquid layer forming step may comprise introducing the liquid into the channel, discharging the liquid from the channel, detecting a temperature of the liquid discharging from the channel, and controlling the flow of the liquid introduced into the channel according to the detected temperature. In an embodiment, the liquid flow may be controlled to control the temperature of the liquid discharging from the channel at 40° C. or lower. The present invention will be explained in detail below with reference to preferred embodiments and drawings. The preferred embodiments and drawings are not intended to limit the present invention. In all of the aforesaid embodiments, any element used in an embodiment can interchangeably be used in another embodiment unless such a replacement is not feasible or causes adverse effect. Further, the present invention can equally be applied to apparatuses and methods. The UV irradiation apparatus shown in FIG. 1 comprises a UV unit 18, water-cooled filter 11, irradiation window 5, gas introduction ring 9, reactor chamber 6, heater table 7, and vacuum pump 12. The gas introduction ring 9 has multiple gas outlet ports 8, through which gas is discharged toward the center between the arrows. A cold mirror 1 is fitted along the interior walls of the UV unit 18 to transmit IR light but cause UV light to reflect upon the mirror, so that UV light will go through the irradiation window 5 effectively. Another cold mirror 2 is also placed above a UV lamp 3 for the same purpose. The water-cooled filter 11 has a cooling-water inlet 14 and cooling-water outlet 10, where the cooling-water inlet 14 is connected to a cooling-water supply port 16 on a chiller unit (heat exchanger) 13 to allow cooling water in the chiller unit 13 to be supplied into the water-cooled filter 11. The cooling-water outlet 10 is connected to a cooling-water return port 17 on the chiller unit 13 to return cooling water to the chiller unit 13 after it has passed through the water-cooled filter 11. The chiller unit 13 has a temperature controller 19 and a flow controller 15 to control the temperature and flow rate of cooling water. The UV irradiation apparatus is not limited to the one illustrated in this figure, and any apparatus can be used as long as it can irradiate UV light. However, the following explanation applies to the structure of the apparatus shown in this figure. In this figure, the chamber 6 can be controlled at various conditions between vacuum and near atmosphere, and the UV irradiation unit 18 is placed on top. In this figure, the UV light source 3 and heater 7 are opposingly positioned in parallel with each other, and the irradiation window glass 5 is opposingly positioned between the UV light source 3 and heater 7 in parallel with the two. The irradiation window 5 is used to irradiate uniform UV light, and made of synthetic quartz, for example. This window can be made of any material, as long as it can shield the reactor 6 from atmosphere but allow UV light to transmit through. The UV light source 3 in the UV irradiation unit 18 has multiple tubes that are arranged in parallel with one another. As shown in FIG. 1, this light source is properly arranged to achieve uniform intensity, and a reflector 2 (which looks like a lamp shade of the UV lamp) is provided to allow UV light from each UV tube to be reflected toward the thin film, where the angle of the reflector 2 is adjustable to achieve uniform intensity. The lamp 3 is made of glass, such as synthetic quartz, that allows UV light to transmit through, and is positioned inside the unit 11 in which cooling water flows. Cooling water flowing through the unit 11 is circulated by the chiller unit 13 positioned outside the unit. The unit 11 is also filled with nitrogen to eliminate oxygen, so that ozone will not generate as a result of UV irradiation. In this apparatus, the substrate processing section 6 that can be controlled at various conditions between vacuum and near atmosphere is separated from the UV emitting section 18 by a flange 9 in which the irradiation window glass 5 is set. The space between the UV emitting section and irradiation window glass 5 has been replaced by nitrogen, which also serves to prevent absorption of UV light by the oxygen in air and consequent generation of ozone. In this embodiment, the UV light source 3 is structured in such a way that it can be easily removed and replaced. Also in this embodiment, gas is introduced through the flange 9, where multiple gas inlet ports are provided and arranged symmetrically to create a uniform processing atmosphere. In the UV irradiation process, the chamber 6 is filled with gas selected from Ar, CO, CO2, C2H4, CH4, H2, He, Kr, Ne, N2, O2, Xe, alcohol gases, and organic gases, and its pressure is adjusted to a range of approx. 0.1 Torr to near atmosphere (including 1 Torr, 10 Torr, 50 Torr, 100 Torr, 1,000 Torr, and values between any two numbers of the foregoing), and then a processing target, or semiconductor substrate carried in through the substrate transfer port via the gate valve, is placed on the heater 7 whose temperature has been set to a range of approx. 0° C. to approx. 650° C. (including 10° C., 50° C., 100° C., 200° C., 300° C., 400° C., 500° C., 600° C., and values between any two numbers of the foregoing, but preferably in a range of 300° C. to 450° C.), after which UV light with a wavelength in a range of approx. 100 nm to approx. 400 nm (including 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, and values between any two numbers of the foregoing, but preferably in a range of approx. 200 to 250 nm) is irradiated at an output in a range of approx. 1 mW/cm2 to approx. 1,000 mW/cm2 (including 10 mW/cm2, 50 mW/cm2, 100 mW/cm2, 200 mW/cm2, 500 mW/cm2, 800 mW/cm2, and values between any two numbers of the foregoing) onto the film on the semiconductor substrate by keeping an appropriate distance from the UV light source (the distance between the water-cooled filter 11 and irradiation window 5 may be approx. 5 to 40 cm, while the distance between the irradiation window 5 and substrate may be approx. 0.5 to 10 cm). Use of UV light with a wavelength of preferably 300 nm or shorter, or more preferably 250 nm or shorter, will maximize the effect of UV irradiation (such as curing of low-k film) while suppressing heat generation. The irradiation time may be in a range of approx. 1 sec to approx. 60 min (including 5 sec, 10 sec, 20 sec, 50 sec, 100 sec, 200 sec, 500 sec, 1,000 sec, and values between any two numbers of the foregoing). The chamber is evacuated via the exhaust port. This semiconductor manufacturing apparatus performs a series of processing steps according to an automatic sequence, where the specific processing steps include gas introduction, UV irradiation, stopping of irradiation, and stopping of gas supply. FIGS. 2(a) and 2(b) are a schematic side view and a schematic front view, respectively, of a water-cooled filter used in an embodiment. This water-cooled filter encloses the UV lamp 3, storing the vertically long UV lamp 3 and sealed by covers 27, 28 on both ends to create an interior space 29. One cover 28 has an inlet 25 through which to introduce an inert gas, such as nitrogen gas, into the interior space 29, while the other cover 27 has an exhaust port 26 through which to exhaust the inert gas after it has passed through the interior space 29. The covers 27, 28 need not hermetically seal the interior space 29 (because the interior will reach high temperatures), but instead it is sufficient for them to maintain the interior space 29 at a positive pressure to prevent entry of atmospheric air (oxygen). The covers 28, 27 also have a cooling-water inlet 14 through which to introduce cooling water, and a cooling-water outlet 10 through which to discharge cooling water, respectively. The water-cooled filter comprises double-walled quartz glass 21 with cooling water 22 flowing in between the walls. In an embodiment, the thickness of the quartz glass is approx. 1 to 2 mm, while the thickness of the water layer is approx. 5 to 15 mm. In FIG. 2, the water-cooled filter surrounds three UV lamps. However, each UV lamp may be stored in a separate cylindrical water-cooled filter, or five to 10 UV lamps may be stored in a single water-cooled filter. In an embodiment, the UV lamp generates light covering a wide wavelength range from DUV to infrared, and mercury lamps are particularly suited for this application. Mercury lamps are classified by the internal lamp pressure into various types from low-pressure to ultrahigh-pressure types associated with wavelengths of 185 nm, 254 nm, 365 nm, etc., and any type can be selected as deemed appropriate (light with a wavelength shorter than 300 nm is effective in curing low-k films). Mercury lamps break the —CH3 bond or —Si—O bond in a low-k film and then allow the broken components to re-bond to build an O—Si—O network to enhance the mechanical strength of the film. The atmosphere in which the substrate is kept is normally replaced with an inert gas to prevent oxidization of the low-k film. Normally N2, He, Ar, etc., is used as this inert gas. In an embodiment, KrCl excimer (222 nm) lamps may be used. KrCl excimer lamps are associated with relatively weak output, but they have a wavelength of 250 nm or shorter and can efficiently improve film quality. The water-cooled filter is not limited to the configuration illustrated in FIG. 1 and FIG. 2, and any other embodiment may be used such as one where a water layer is provided between the UV lamp and irradiation window. For example, an embodiment in which water flows between two glass sheets can be considered. FIG. 3 and FIG. 4 each shows a schematic diagram of a water-cooled filter 31 according to such embodiment. All other components of the structure can be the same as those shown in FIG. 1. Since the same reference numbers are used to indicate the same components, their explanation is omitted. In this embodiment, the entire surface of the irradiation window is covered with a filter glass made of synthetic glass, etc. The filter is filled with water, and this water is temperature-controlled by the chiller unit. As shown in FIG. 4, the water-cooled filter 31 basically comprises two synthetic quartz sheets 41 positioned with a specific distance kept in between (such as the same as or around 1.5 or 2 times the thickness of the water layer mentioned above), and is hermetically sealed, except that a cooling-water inlet 34 is provided on the right end and a cooling-water outlet 30 is provided on the left end so that cooling water 42 can flow inside. The water-cooled filter 31 is provided near the irradiation window 5, and in an embodiment the distance between the two is around several millimeters to several centimeters. It is also possible to have the irradiation window itself constituted by a water-cooled filter. By using a water-cooled filter, heat from the UV lamp can be suppressed more effectively. Also, UV light with a wavelength of 250 nm or shorter effective in processing semiconductor films can be transmitted without absorption loss, and consequently semiconductor films can be processed effectively. Use of a cold filter comprising synthetic glass coated with an organic film, etc., is effective in cutting off heat. However, such a filter is not effective because it also absorbs light with a wavelength of 250 nm or shorter. In an embodiment of the present invention, no filter including a cold filter is used and water is used instead to shield heat. Water is known to absorb infrared with a long wavelength of 1 μm or longer, without absorbing any other light with a shorter wavelength. Since IR light with a wavelength of 1 μm or longer does not affect film quality, absorption of light in this wavelength range does not present problems. In an embodiment, the lamp is enclosed with a glass that transmits UV light with a wavelength of 250 nm or shorter, and then this glass is enclosed with another layer of glass. By filling the space between the two glass layers with water, a water filter is constituted. The double glass layers of this filter are fully sealed and do not leak water filled in between. Also, this filter is connected to the water-cooling unit installed externally to the UV irradiation unit to circulate the cooling water inside. In an embodiment, the filter is filled with an inert gas such as nitrogen, Ar, He, etc., and no oxygen exists that absorbs UV light with a wavelength of 250 nm or shorter. This filter resolves the heat problem, allowing the intensity of effective curing UV light with a wavelength of 250 nm or shorter to be raised without raising the substrate temperature. By the way, light with a wavelength of around 170 to 180 nm may break the Si—CH3 bond and thereby promote the formation of unnecessary bonds, such as the Si—H bond with H attached to a broken component of Si—CH3 bond. Accordingly, the key wavelength range of UV light may preferably be 200 to 250 nm, and UV light meeting this condition may be transmitted to the substrate. To control the intensity of UV light, the method shown in FIG. 5 can be used, for example. The apparatus in FIG. 5 uses a UV illuminometer 54 to measure the intensity of UV light irradiated from the UV lamp 3 at positions before and after the irradiation window 5, and sends the results as signals to an intensity monitor 53, where the signals are recognized as intensity data and output to a UV controller/power unit 52 to control the power to the UV lamp 3. In this embodiment, the water-cooled filter is installed in the irradiation window 5. Also, a substrate to be placed inside the UV irradiation chamber 6 is transferred from a load lock chamber 50 into the UV irradiation chamber by means of a load lock arm (LL arm) 51 installed in the load lock chamber 50. Following the transfer of the substrate, the susceptor 7 in the UV irradiation chamber will rise to a position where a specified gap is achieved from the irradiation window. In conventional apparatus where the lamp is cooled with a blower using atmospheric air, the lamp unit inevitably contained atmospheric air. Nitrogen or other gas can be used to cool the lamp to prevent absorption of UV light with a wavelength of 250 nm or shorter, but this is not practical from the cost-effectiveness viewpoint because a large quantity of gas will be required. Since use of a water-cooled filter eliminates the need for air cooling using a blower, the lamp unit can be always filled with nitrogen to remove oxygen. In an embodiment, cooling water from the water-cooled filter uses pure water, ion exchanged water, etc., and its flow rate is controlled to achieve a temperature of approx. 25° C. at the inlet to the lamp (cooling-water inlet) and approx. 35 to 40° C. at the outlet (cooling-water outlet) so as to prevent the dissolved oxygen in cooling water from forming air bubbles to absorb/scatter UV light. As shown in FIG. 1 and FIG. 3, the chiller unit 13 has the temperature controller 19 and flow controller 15 for monitoring the temperature of cooling water (such as the outlet temperature) and adjusting the flow rate. If the outlet temperature of cooling water is high, the circulation rate is increased. If the temperature is low, the circulation rate is decreased. In an embodiment, the inlet temperature should be kept to around room temperature because if the inlet temperature is lower than room temperature, bedewing may occur. A desirable method to keep the temperature of cooling water at the outlet to 40° C. or below and thereby suppress formation of air bubbles, is to supply cooling water of room temperature into the filter by approx. 5 to 20 SLM. Examples of how UV light with a wavelength of 200 to 250 nm would effectively improve film quality are shown in FIG. 6 and FIG. 7. Here, change in film quality is evaluated by reduction in film thickness. FIG. 6 shows the wavelength distribution of a high-pressure mercury lamp and the UV transmittance through a SiC film (CVD, 4MS=150 sccm, NH3=1,000 sccm, He=500 sccm, Pressure=500 Pa, RF (27 MHz)=500 W, RF (400 kHz)=150 W, Depo temperature=400° C., Film thickness=50 nm). The UV light transmittance through the SiC film was calculated from the extinction coefficient measured by ellipsometry and the film thickness. The SiC film is not sensitive to light with a wavelength of 300 nm or longer and transmits such light almost 100%. On the other hand, it absorbs light with a wavelength shorter than 300 nm, and this tendency is prominent with a light whose wavelength is 250 nm or shorter. With this mercury lamp, wavelengths shorter than 200 nm are not significant. Accordingly, if this mercury lamp is used to irradiate UV light onto a SiC film formed as a cap layer for a low-k film, the result would be the same as irradiating a low-k film with UV light with a wavelength of 200 to 250 nm. FIG. 7 shows the result of how much a low-k film (CVD, TMDOS (tetra-methyl-disiloxane)=100 sccm, Isopropyl alcohol=400 sccm, O2=50 sccm, He=150 sccm, Pressure=800 Pa, RF (27 MHz)=1,800 W, Temperature=400° C., Film thickness=500 nm) would shrink when irradiated with UV light directly and over a SiC film. Under UV irradiation over the same duration, the film without SiC shrank more than the film with SiC. This is because UV light having the effect of shrinking low-k films was shielded by SiC. As shown in FIG. 6, light not transmitting through SiC had a wavelength shorter than 300 nm (notably 250 nm or shorter). This indicates that UV light having the effect of shrinking low-K films has a wavelength shorter than 300 nm. In this experiment, UV curing effect was reduced by 35% by the SiC film. Since UV light shielded to this extent mainly has a wavelength of 250 nm or shorter, it can be concluded that light with a wavelength of 250 nm or shorter is especially useful for UV curing. These results find that to enhance the curing efficiency of low-k films, it is effective to increase the quantity of UV light with a wavelength of 250 nm or shorter. However, an attempt to increase the input power with the aim of increasing UV light with a wavelength of 300 nm or shorter, or preferably 250 nm or shorter, will lead to a proportional increase in light of other wavelengths, and more problematically heat generation. Increased heat generation pushes up the temperature of the cured substrate, which is a problem when curing interlayer insulation films where the temperature must be controlled at 400° C. or below. Accordingly, effective means for obtaining a greater quantity of UV light with a wavelength of 250 nm or shorter include: 1) cutting off the heat generated by the UV lamp and increasing the power input to the lamp, and 2) replacing the atmosphere around the lamp with nitrogen to reduce absorption of UV light by oxygen. The water-cooled filter used in an embodiment satisfies both of these conditions. As explained above, embodiments of the present invention establish a method to improve the curing efficiency by specifying wavelengths of UV light effective in curing low-k films, resolving the heat problem of high-pressure mercury lamps with the use of a water-cooled filter, and also replacing the curing atmosphere with nitrogen to suppress ozone generation, consequently increasing the quantity of UV light effective for curing. In the present disclosure where conditions and/or structures are not specified, the skilled artisan in the art can readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation. It will be understood by those of skill in the art that numerous and various modifications can be made without departing from the spirit of the present invention. Therefore, it should be clearly understood that the forms of the present invention are illustrative only and are not intended to limit the scope of the present invention. |
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047117583 | description | DESCRIPTION OF THE PREFERRED EMBODIMENTS With initial reference to FIG. 15, the cask 38 of the present invention includes a generally cylindrical container 40 having a basket 42 disposed therein. Basket 42 provides an array of storage slots 44, configured much a matrix of vertically disposed pigeon holes, each accommodating a cell 46 for a spent fuel assembly 20 or a canister for consolidated fuel. As will be discussed in detail subsequently, container 40 and basket 42 are fabricated separately, whereupon basket 42 is inserted into container 40 to provide cask 38. Turning next to FIG. 6, container 40 includes a base element 48 having an upper proportion configured to receive a lid element 50. The cavity 52 provided within element 48 has substantially cylindrical interior walls 54 rising from floor 56, which is substantially horizontal during long-term storage. Elements 48 and 50 include carbon steel portions 58 to which inner cladding layers 60 of stainless steel are affixed. Carbon steel portions 58 are approximately 30 cm thick and served to protect the environment from gamma rays. Layer 60 can be applied to base element 48, for example, by placing element 48 on a turntable and rotating it while welding a continuous spiral path around the interior using stainless steel welding rods, thereby applying a stainless steel surface which completely covers floor 56 and interior walls 54 of element 48. During this cladding operation, excess stainless steel is applied to provide rings 62, 64, 66, 68 and 70, which project slightly into the interior of element 48 for reasons which will be discussed subsequently. After rings 62-70 have been deposited they are machined to provide smooth, cylindrical surfaces. With continuing reference to FIG. 6, carbon steel portions 58 of elements 48 and 50 are surrounded with a layer about 7.6 cm thick of neutron absorbing material 72, which may be a resin. A suitable resin for use as material 72 is commercially available from BISCO Products, Inc., 1420 Renaissance Drive, Park Ridge, Ill. 60068, under Stock Number N.S.-3. Surrounding material 72 is outer layer 74 of stainless to protect container 40 from the environment. Container 40 also includes cooling fins 76 of carbon steel, preferably treated to protect the carbon steel from chemical attack by the environment. Fins 76 are welded to portion 58 and extend through material 72 and layer 74. In this embodiment container 40 is approximately 4.8 meters high and has an outer diameter of about 2.5 meters, excluding fins 76, and an inner diameter of approximately 1.7 meters. When loaded with spent fuel, cask 38 has a mass of over 100,000 kilograms. Although not illustrated, it is advantageous to affix a pair of trunions at the top and bottom of base element 48 in order to facilitate handling. Turning next to FIG. 3, basket 42 includes grid assemblies 78, 80, 82, 84 and 86, which are supported in a column by legs 88. Grid assemblies 78-86 are substantially identical, except that their diameters differ slightly for reasons to be discussed subsequently. Referring next to both FIGS. 4 and 5, the construction of a grid assembly will now be described. Matrix 90 includes plates 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116 and 118. These plates are approximately 23 cm high and 2.0 cm thick. The bottom portion of plate 96, for example, includes 5 downwardly oriented slots 120 which extends midway into the plate and which divide the plate into six segments. Similarly, plate 110, for example, has 5 upwardly oriented slots 122. The slots 120 in plate 96 and the slots 122 in plate 110 are about 26.3 cm apart, and it will be apparent that such dimensions provide storage slots 44 which are positioned about 26.3 cm apart, center-to-center. During assembly, plates 94, 96, 98, 100 and 102 are held at right angles to plates 108, 110, 112, 114 and 116, and the slots 120 are then inserted into slots 122, in the manner illustrated by Arrow A, to provide intersections which extend from the tops of the plates to the bottoms. Thereafter the plates are joined by full length fillet welds running along opposite sides of the intersections, so that each intersections is provided with two welds. Fabrication of matrix 90 is completed by welding plates 92 and 104 to the ends of plates 110, 112 and 114 and by welding plates 106 and 118 to the ends of plates 96, 98 and 100. Turning next to FIG. 7, after matrix 90 is fabricated blocks 124-154 are welded to plates 92-118 to provide matrix 90 with an approximately circular metallic periphery. Matrix 90, with blocks 124-154 attached thereto, is then mounted on a turntable and machined to provide a circular periphery 156 having a top bevel 158 and a bottom bevel 160. Fabrication of the grid assembly is completed by drilling holes 162 through blocks 128, 136, 144 and 152 in order to slidingly accommodate legs 88. It will be apparent that the construction described above provides generally disk-shaped grid assemblies having plates which define twenty four square apertures and having peripheries which are in heat-conducting contact with the plates. With reference next to both FIGS. 3 and 6, the grid assemblies 78-86 of basket 42 are positioned on legs 88 so that they will be level with respective rings 62-70 on wall 54 when the bottoms 164 of legs 88 contact floor 56 of container 40. That is to say, the top grid assembly 78 corresponds to top ring 62 and is supported on legs 88 at a position which aligns the periphery 156 of grid assembly 78 with ring 62 when basket 42 is inserted into container 42. This alignment is illustrated in FIG. 9, wherein it will be noted the rings are provided with bevels 166. Similarly, the second grid assembly 80 corresponds to the second ring 64 and is supported on legs 88 at a position which aligns the periphery 156 of grid assembly 80 with ring 64 when basket 42 is inserted into container 40; the third grid assembly 82 corresponds to the third ring 66 and is supported on legs 88 at a position which aligns the periphery 156 of grid assembly 82 with ring 66 when basket 42 is inserted into container 40; the fourth grid assembly 84 corresponds to the fourth ring 68 and is supported on legs 88 at a position which aligns the periphery 156 of grid assembly 84 with ring 68 when basket 42 is inserted into container 40; and, finally, the bottom grid assembly 86 corresponds to bottom ring 70 and is supported on legs 88 at a position which aligns the periphery 156 of grid assembly 86 with ring 70 when basket 42 is inserted into container 40. With continuing reference to FIG. 3, grid assemblies 78-86 are supported on legs 88 by bottom rings 168, which are affixed to legs 88. For reasons to be discussed subsequently, top rings 170 are affixed to legs 88 at positions spaced slightly above the upper surfaces of grid assemblies 78-86, the distances between rings 170 and the upper surfaces of the grid assemblies in FIG. 3 being exaggerated for purposes of illustration. It will be apparent that the grid assemblies are confined between their respective bottom and top rings 168 and 170, but each grid assembly is able to move with respect to legs 88 by a distance which is equal to the difference between the thickness of the grid assembly and the spacing between rings 168 and 170. After assembly of basket 42, it is mounted on a turntable and the peripheries 156 of grid assemblies 78-86 are machined again to ensure that slight manufacturing deviations have not resulted in peripheries that are eccentric with respect to one another. Moreover, the peripheries 156 are machined to slightly different diameters, the diameters decreasing from the top grid assembly 78 of basket 42 to the bottom grid assembly 86. In the preferred embodiment the diameter of grid assembly 78 is approximately 169.875 cm; the diameter of grid assembly 80 is 0.635 cm less than the diameter of grid assembly 78; the diameter of grid assembly 82 is 0.635 cm less than the diameter of grid assembly 80; the diameter of grid assembly 84 is 0.635 cm less than the diameter of grid assembly 82; and the diameter of grid assembly 86 is 0.635 cm less than the diameter of grid assembly 84. Accordingly, it will be apparent that the peripheries 156 of grid assemblies 78-86 define concentric cylinders which have diameters progressively differing by 0.635 cm, and that the diameter of top grid assembly 178 is approximately 2.54 cm greater than the diameter of bottom grid assembly 86. The plates 92-118, blocks 124-154, and rings 168 and 170 of the basket 42 are made of a metal which conducts heat. In the preferred embodiment aluminum is used for basket 42, although other metals such as copper would also be suitable. The storage slots 44 provided by basket 42 can be used for storing fuel assemblies 20 or for storing spent fuel in consolidated form, or both simultaneously. In such consolidated storage, the rods 26 are removed from the fuel assemblies 20 and placed in a consolidation canister which holds a greater number of fuel rods than the number in a single fuel assembly. In order to prepare cask 38 for consolidated storage, assembly 42 is inserted into container 40, as will be described subsequently, and consolidation canisters loaded with spent fuel are transferred under water to storage slots 44. If one or more storage slots 44 are to be devoted to the storage of fuel assemblies 20, however, these storage slots are provided with cells for receiving the fuel assemblies 26 before assembly 42 is inserted into container 40. Turning next to FIGS. 10 and 11, a cell 46 will now be described. Shell element 174, of stainless steel about 0.19 cm thick, has four elongated sides defining a region having a square cross section sufficiently large to accommodate a fuel assembly 20. The cross sectional area is determined by the dimensions of the particular fuel assembly design, so as to provide a snug fit. The bottom end of 176 of element 174 is open and the top end of element 174 is provided with outwardly bent flanges 178 which serve to funnel the fuel assembly 20 into cell 46. Stainless steel wrapper portions 180, about 0.08 cm thick, are welded to shell element 174 in order to support sheets 182 of a "neutron poison" such as boron carbide. Sheets 182, which are about [0.19] cm thick, are present to moderate neutrons emitted from fuel assemblies 20 when cask 38 is in pool 30 while the fuel assemblies are being loaded into it. That is to say, sheets 182 serve to maintain the criticality factor K.sub.eff at less than one in order to obviate the possibility of a self-sustaining chain reaction while cask 38 contains both water and fuel assemblies 20. Sheets 182 limit the nuclear interaction between fuel assemblies which are, of course, designed to promote chain reactions when they are present in a reactor. In fact, neutron poison is unnecessary when consolidated fuel is stored. It is worth noting that sheets 182 have served their purposes after the water has been drained from cask 38 during the loading process, since water thermalizes neutrons and, after drainage, the potential for a chain reaction is reduced. Turning next to FIGS. 12, 13 and 14, the mounting of cells 46 in the storage slots 44 provided by basket 42 will now be described. Each cell 46 is fastened, for example by welding, to the bottom grid assembly 86. The bottom ends 176 of cells 172 are disposed slightly above the bottoms 164 of legs 88 in order to facilitate water drainage. The cells 46 are not fixedly attached to the remaining grid assemblies 78, 80, 82, and 84, since otherwise differential expansion of the cells 46 with respect to basket 42, as the temperature within cask 38 rises following drainage of the water, would create appreciable strains in the structure which might lead to unacceptable performance. Instead of fastening cells 46 to grid assemblies 78-84, heat conducting wedges are used to position the cells within grid assemblies 78-84 while nevertheless permitting the cells to move axially with respect to the grid assemblies. In order to avoid an electrolytic reaction the wedges are preferably made of the same metal, such as aluminum or copper, as the plates 92-118 of grid assemblies 78-84. For example FIG. 13 illustrates a top view of a portion of grid assembly 78 and a cell 46, illustrated for the sake of clarity without its flanges 178. In FIG. 13 it will be apparent that one side of the cell 46 slidably rests against plate 98 and another side slidably rests against plate 114. The other sides of the cell 46 receive lateral support by means of wedges 184, 186, 188, and 190, with a narrow gap 192 being left between wedge 186 and cell 46 and with a narrow gap 194 being left between wedge 188 and cell 46. Gaps 192 and 194 are exaggerated in FIG. 13 for purposes of illustration. The installation of wedges 184 and 186, for example, is illustrated in FIG. 14. After cell 46 is inserted into the storage slot 44, wedge 184 is affixed to plate 112 by fillet weld 196. Wedge 186 is then inserted and, using a feeler gauge, gap 192 is adjusted to provide a predetermined spacing between wedge 186 and cell 46 when cask 38 reaches its maximum temperature, such as 375.degree. C., during storage of spent fuel. This predetermined gap thickness preferably ranges from about 0.005 cm to 0.025 cm. After the gap adjustment, wedge 186 is affixed to wedge 184 by fillet weld 198, and weld 200 is applied to join plate 112, wedge 184, and wedge 186. In the same way, wedges 188 and 190 are adjusted and welded to provide gap 194, preferably also ranging from 0.005 cm to 0.025 cm wide. The remaining cells 46 are, of course, wedged into the apertures provided by grid assembly 78, and into the apertures provided by grid assemblies 80, 82, and 84, in the same manner. After cask 38 is loaded with fuel assemblies 20 and drained of water it is preferably flooded with an inert gas, such as helium or nitrogen, although air may be employed instead. Helium, in particular, readily transmits heat through narrow gaps such as gaps 192 and 194. Accordingly, it will be apparent that heat from a cell 46 is directly transmitted to the plates of a grid assembly via the two sides of the cell which contact the plates, and indirectly via gaps 192 and 194 and wedges 184-190 to the remaining plates. Gaps 192 and 194 are sufficiently narrow to prevent cells 46 from rattling around within basket 42 during manufacture, loading, and transportation of cask 38 to a remote storage location. Gaps 192 and 194 also, as indicated previously, serve to permit linear movement of cells 46 with respect to basket 42 during temperature changes. This differential linear expansion of cells 46 with respect to basket 42 can amount to 2 centimeters or more within the range of temperatures encountered during and after the insertion of fuel assemblies into cells 46. Moreover, wedges 184-190 position cells 46 within assembly 42 and ensure a cell-center to cell-center spacing, in the present embodiment, of about 26.2 cm. This uniform spacing, in addition to poison sheets 82, ensures that the credicality factors K.sub.eff remains less than 1 before the water is drained from cask 38. From the previous discussion it will be recalled that the top grid assembly 78 has a diameter of 169.875 cm in the preferred embodiment, and that the remaining grid assemblies 80-86 have decreasing diameters. Rings 62-70 in container 40 are also machined to have different diameters. In the preferred embodiment top ring 62 has a diameter of approximately 170.18 cm, that is, approximately 0.305 cm greater than the diameter of grid assembly 78. The diameter of ring 64 is 0.635 cm less than the diameter of ring 62; the diameter of ring 66 is 0.635 cm less than the diameter of ring 64; the diameter of ring 68 is 0.635 cm less than the diameter of rings 66; and the diameter is reduced by 0.635 cm again for bottom ring 70. Thus, rings reduced by 0.635 cm again for bottom ring 70. Thus, rings 62-70, like the peripheries 156 of grid assembly 78-86, defined concentric cylinders having a common axis and diameters differing by 0.635 cm. Moreover, the diameter of each ring 62-70 is, when container 40 and basket 42 are being fabricated at normal shop temperatures, 0.305 cm greater than the diameter of the corresponding grid assembly 78-86. The stepped diameters of grid assemblies 78-86 and rings 62-72 facilitate insertion of basket 42, after cells 46 had been wedged into place in the manner previously described, into container 40. Assembly 42 and the cells 46 are relatively massive and the fit between assembly 42 and container 40 is relatively tight, so that a slight axial misalignment between container 40 and assembly 42, or a slight longitudinal displacement of container 40 with respect to assembly 42, might cause assembly 42 to jam, or become lodged within container 40 before it is fully inserted, were it not for the stepped diameters. During the initial stages of the insertion operation, as assembly 42 and the cells 46 mounted therein are suspended over container 40 and are being lowered into it, the difference in the diameters of grid assembly 86 and ring 62 provides over 1.5 cm clearance as assembly 86 passes ring 62. This clearance can be visually checked and any misalignment can be corrected. When basket 42 is lowered further into container 40, there is about 1.22 cm clearance between grid assembly 86 and ring 64 and between grid assembly 84 and ring 62. These clearances can be visually checked again, and any asymmetries corrected. Due to the stepped diameters it is not until grid assembly 86 is lowered to ring 70 that the diametrical differences become 0.305 cm. Thus, the stepped diameters of ring 62-70 and of grid assemblies 78-86 not only facilitate monitoring of the insertion process, they also effectively multiply the tolerance for inaccuracy throughout most of the insertion process. It should also be noted that bevels 158 and 160 of grid assemblies 78-86 and bevels 166 of rings 62-70 also reduce the likelihood that basket 42 will jam within container 40 when basket 42 is being inserted or removed. Such removal might be necessary, for example, should basket 42 lodge in container 40 before it is fully inserted. FIG. 15 illustrates cask 38 after basket 42 with cells 172 is fully installed in container 40. An operational summary of cask 38 can now be presented. Cask 38 is opened and lowered to cask pad 36 of pool 30, and fuel assemblies 20 are transferred to cells 46. After lid element 50 is bolted into place, gas is introduced into cask 38 as water is being drained. The temperature within cask 38 rises as the water is drained, so that a long drying time is not necessary. As the temperature within cask 38 rises, grid assemblies 78-86 expand radially and the 0.305 cm diameter difference between grid assemblies 78-86 and their respective rings 62-70 disappears as result of differential expansion between assembly 42 and container 40. The peripheries 156 of grid assemblies 78-86 are pressed against their respective rings 62-70 to provide heat flow paths between assembly 42 and container 40. For example, FIG. 9 illustrates grid assembly 78 pressed against its corresponding ring 62 when the interior of cask 38 reaches its equilibrium temperature. It should be noted that this differential expansion of grid assemblies 78-86 into contact with their corresponding rings 62-70 is a self-correcting feature. Consider, for example, the situation if the equilibrium temperature were to change during spent fuel storage so as to separate the grid assemblies 78-86 from their respective rings 62-70. Such a separation would impede heat transfer from grid assembly 78-86 to rings 62-70, and thence to the environment. This in turn would raise the temperature of grid assemblies 78-86, pressing them again against their corresponding rings 62-70 so as to reestablish the heat-conducting relationship at a new equilibrium temperature. At thermal equilibrium grid assemblies 78-86 interfere with rings 62-70 in the sense that their diameters would overlap were they not pressing against each other. This condition may be deemed "diametral interference" and results in stress where the peripheries 156 of grid assemblies 78-86 contact the surfaces of rings 62-70. With the cask dimensions given, and assuming that the difference in diameters of grid assemblies 78-86 with respect to rings 62-70 is initially 0.305 cm, with a manufacturing tolerance of plus or minus 0.038 cm, at thermal equilibrium the diametral interference ranges from about 0.0305 cm to about 0.107 cm when cask 38 contains 24 spent fuel assemblies 20, each generating a kilowatt of heat. The resulting stress ranges from about 1,000-4,000 PSI (69 million-276 million dyes/cm.sup.2). It has been determined experimentally that the contact temperature differences between stainless steel and aluminum at these pressures range from approximately 0.degree. C. to 1.7.degree. C. Cask 38 could be modified by replacing rings 62-70 with vertically disposed tracks affixed to walls 54 and by affixing corresponding tracks at the periphery of basket 42. The tracks would preferably be tapered to facilitate insertion. However, the use of vertical tracks rather than horizontal rings would tend to complicate manufacture. Another alternative would be to manufacture basket 42 so that the diameters of grid assemblies 78-86 are the same as or slightly larger than the diameters of rings 62-70. Under this alternative container 40 would be heated and/or basket 42 would be chilled, as by frozen CO.sub.2, prior to the insertion operation. Basket 42 would then be tightly fitted to container 40 when the elements are returned to normal shop temperature. This alternative would exclude borated water from the interface between grid assemblies 78-86 and rings 62-70, thus ensuring that contaminants do not enter this interface to degrade heat flow. From the foregoing discussion it will be apparent that the spent fuel storage cask of the present invention provides a basket formed of grid assemblies which define storage slots for receiving spent fuel and which, after the basket is inserted into the container, expand to provide heat-conducting interfaces between the grid assemblies and the walls of the container. Although the foregoing discussion has described the preferred embodiments with reference to pressurized water reactors, in which case the water in pool 30 would be borated, it will be apparent to those skilled in the art that the present invention could be used with spent fuel from a boiling water reactor. It will be understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations, and the same are intended to be comprehended within the meaning and range of equivalence of the appended claims. |
056299648 | abstract | A neutron absorbing apparatus which includes two adjacent neutron absorbing plates and a mounting assembly with latching means configured to be easily secured to fuel assemblies while the fuel assemblies remain under water in a fuel storage rack, thereby eliminating the need to remove the fuel assemblies or the fuel storage rack for installation. The two neutron absorbing plates are positioned orthogonally to form a chevron cross section which can be placed about the fuel assemblies by insertion in the existing space between the fuel assemblies and the cell walls of a fuel storage rack. A prescribed orientation of the chevron configured neutron absorbing plate in the cells of the fuel storage rack together with the selected use of a single neutron absorbing plate economically provides sufficient neutron absorption in all radial directions about the fuel assemblies to maintain safe storage condition sin closely packed fuel storage racks. |
description | The present invention relates to a radiation detector, a method of manufacturing a radiation detector, and a lithographic apparatus comprising a radiation detector. A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g., comprising part of, one, or several dies) on a substrate (e.g., a Silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate. In device manufacturing methods using lithographic apparatus, an important factor is the yield, i.e., the percentage of correctly manufactured devices, is the accuracy within which layers are printed in relation to layers that have previously been formed. This is known as overlay and the overlay error budget will often be 10 nm or less. To achieve such accuracy, the substrate must be aligned to the reticle pattern to be transferred with great accuracy. A number of sensors is used at substrate level for evaluating and optimizing imaging performance. These may include transmission image sensors (TIS). A TIS is a sensor that is used to measure at substrate level the position of a projected aerial image of a mark pattern at mask (reticle) level. The projected image at substrate level may be a line pattern with a line width comparable to the wavelength of the exposure radiation. The TIS measures aforementioned mark pattern using a transmission pattern with a photocell, i.e., a radiation detector, underneath it. The sensor data may be used to measure the position of the reticle with respect to the substrate table in six degrees of freedom, i.e., three degrees of freedom related to translation and three degrees of freedom related to rotation. Moreover, magnification and scaling of the projected mark pattern may be measured. At wavelengths between 10-200 nm, the radiation-sensitive surface of the radiation detector of a conventional TIS deteriorates within a limited time frame. As a result, the TIS has a limited lifetime. With the continual desire to image ever smaller patterns to create device with higher component densities, there is pressure to reduce the wavelengths used. In order to maintain or reduce overlay errors, there is a desire for a more robust TIS. The inventors have determined that it may be desirable to provide a radiation detector at substrate level with high sensitivity that can be used to detect radiation with wavelengths between 10-200 nm with an improved lifetime over radiation detectors according to the prior art. To that end, the invention provides a radiation detector. The radiation detector has a radiation sensitive surface. The radiation-sensitive surface is sensitive for radiation with a wavelength between 10-200 nm. The radiation detector comprises a silicon substrate, a dopant layer, a first electrode and a second electrode. The silicon substrate is provided in a surface area at a first surface side with a doping profile of a certain conduction type. The dopant layer is provided on the first surface side of the silicon substrate. The dopant layer comprises a first layer of dopant material and a second layer. The second layer is a diffusion layer which is in contact with the surface area at the first surface side of the silicon substrate. The first electrode is connected to the dopant layer. The second electrode is connected to the silicon substrate. The surface area at the first surface side of the Silicon substrate and the second layer are arranged to form the radiation-sensitive surface. Additionally, in an embodiment, the invention provides a method of manufacturing a radiation detector. The method comprises: providing a silicon substrate with a first surface side and a second surface side opposite thereto, depositing a layer of dopant material on top of the first surface of the silicon substrate such that in the silicon substrate a diffusion layer is formed, partly covering the layer of dopant material with a first contact layer comprising a metallic material such that first regions and second regions are formed, wherein the layer of dopant material is covered with the first contact layer in the first regions and remains exposed in the second regions, depositing a second contact layer comprising a metallic material at the second surface side of the silicon substrate. Finally, an embodiment of the invention provides a lithographic apparatus comprising an illumination system, a support structure, a substrate holder, a projection system, and a radiation detector as described above. The illumination system is configured to provide a beam of radiation. The support structure is configured to support a patterning device that serves to impart the beam of radiation with a pattern in its cross-section. The substrate holder is configured to hold a substrate in a substrate plane. The projection system is configured to expose the patterned beam on the substrate. The radiation detector is substantially positioned in the substrate plane. FIG. 1 schematically depicts a lithographic apparatus according to one embodiment of the invention. The apparatus includes an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation or EUV radiation), a support structure (e.g., a mask table) MT constructed to support a patterning device (e.g., a mask) MA and connected to a first positioner PM configured to accurately position the patterning device in accordance with certain parameters, a substrate table (e.g., a wafer table) WT constructed to hold a substrate (e.g., a resist coated wafer) W and connected to a second positioner PW configured to accurately position the substrate in accordance with certain parameters, and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W. The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping, or controlling radiation. The support structure supports, i.e., bears the weight of, the patterning device. It holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure may be a frame or a table, for example, which may be fixed or movable as required. The support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system. Any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device.” The term “patterning device” used herein should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section such as to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit. The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam which is reflected by the mirror matrix. The term “projection system” used herein should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system.” As here depicted, the apparatus is of a transmissive type (e.g., employing a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g., employing a programmable mirror array of a type as referred to above, or employing a reflective mask). The lithographic apparatus may be of a type having two (dual stage) or more substrate tables (and/or two or more mask tables). In such “multiple stage” machines the additional tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposure. The lithographic apparatus may also be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g., water, so as to fill a space between the projection system and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that liquid is located between the projection system and the substrate during exposure. Referring to FIG. 1, the illuminator IL receives a radiation beam from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such cases, the source is not considered to form part of the lithographic apparatus and the radiation beam is passed from the source SO to the illuminator IL with the aid of a beam delivery system BD comprising, for example, suitable directing mirrors and/or a beam expander. In other cases the source may be an integral part of the lithographic apparatus, for example when the source is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system. The illuminator IL may comprise an adjuster AD for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and/or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may comprise various other components, such as an integrator IN and a condenser CO. The illuminator may be used to condition the radiation beam, to have a desired uniformity and intensity distribution in its cross section. The radiation beam B is incident on the patterning device (e.g., mask MA), which is held on the support structure (e.g., mask table MT), and is patterned by the patterning device. Having traversed the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF (e.g., an interferometric device, linear encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g., so as to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor (which is not explicitly depicted in FIG. 1) can be used to accurately position the mask MA with respect to the path of the radiation beam B, e.g., after mechanical retrieval from a mask library, or during a scan. In general, movement of the mask table MT may be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT may be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner) the mask table MT may be connected to a short-stroke actuator only, or may be fixed. Mask MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks as illustrated occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the mask MA, the mask alignment marks may be located between the dies. The depicted apparatus could be used in at least one of the following modes: 1. In step mode, the mask table MT and the substrate table WT are kept essentially stationary, while an entire pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e., a single static exposure). The substrate table WT is then shifted in the X and/or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure. 2. In scan mode, the mask table MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e., a single dynamic exposure). The velocity and direction of the substrate table WT relative to the mask table MT may be determined by the (de-)magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) of the target portion in a single dynamic exposure, whereas the length of the scanning motion determines the height (in the scanning direction) of the target portion. 3. In another mode, the mask table MT is kept essentially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, generally a pulsed radiation source is employed and the programmable patterning device is updated as required after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above. Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed. FIG. 2 schematically depicts an arrangement of the substrate table WT depicted in the lithographic apparatus of FIG. 1. On the substrate table WT, two fixed marks TIS1 and TIS2 are provided. The fixed markers TIS1 and TIS2 have integrated into them an image sensor that can be used to determine a location of an aerial image of an object mark on the mask MA by scanning the image sensor through the aerial image. The image sensor is substantially positioned in the substrate plane, i.e., the plane in which substrate W is located if positioned on the substrate table WT. Consequently, the relative position of the image of the object mark on the mask MA and the fixed marks TIS1, TIS2 can be determined. If the substrate table WT is provided with a substrate W comprising substrate marks, e.g., substrate marks P1, P2, P3, P4 as depicted in FIG. 2, an alignment sensor (not shown) may previously obtain relative positions of the substrate marks P1, P2, P3, P4. The knowledge of the relative positions of the substrate marks P1, P2, P3, P4 obtained by the alignment sensor combined with the knowledge of the relative position of the image of the object mark on the mask MA and the fixed marks TIS1, TIS2 measured by the image sensors within TIS1, TIS2, allow the substrate W to be positioned at any desired position relative to the projected image of the mask MA with great accuracy. FIG. 3 schematically depicts a cross-sectional view of a radiation detector 1, e.g., TIS1 or TIS2 in FIG. 2, or at least part thereof, according to an embodiment of the invention. The radiation detector 1 comprises a silicon (Si) substrate 3, hereinafter referred to as Si-substrate 3. In at least a surface area 10 of the Si-substrate 3, the Si-substrate 3 is provided with doping profile of a certain conduction type. That is, the doping profile may be of a conduction type in which the conduction takes place by means of electrons, i.e., n-type conduction, or of a conduction type in which the conduction takes place by means of holes, i.e., p-type conduction. On top of the radiation-sensitive surface of the radiation detector, a dopant layer 5 is provided. In case the doping profile within the surface area 10 of the Si-substrate 3 relates to n-type conduction, dopant layer 5 is an acceptor layer. In case the doping profile within the surface area 10 of the Si-substrate 3 relates to p-type conduction, the dopant layer 5 is a donor layer. The radiation detector further comprises two electrodes, i.e., a first electrode 7 and a second electrode 9. The dopant layer 5 may be covered by an isolation layer 11. The first electrode 7 is connected to the dopant layer 5. The first electrode 7 may partly cover the dopant layer 5, as depicted in FIG. 3. This partial overlap ensures a proper connection between the first electrode 7 and the dopant layer 5. As the contact between the first electrode 7 and the dopant layer 5 is larger in size due to the overlap, charge may be removed within a shorter period of time, which may increase the speed in which the radiation detector 1 reacts to short radiation pulses. The first electrode 7 may comprise one or more metallic materials or may be formed from metallic stacks including metallic materials like aluminum (Al), titanium nitride (TiN), titanium (Ti), gold (Au), nickel (Ni) and chrome (Cr). The second electrode 9 is connected to the Si-substrate 3. The connection may be made with a second surface side of the Si-substrate 3, the second surface side being opposite to the first surface side as is depicted in FIG. 3. A connection as depicted in FIG. 3 between the second surface side of the Si-substrate 3 and the second electrode 9 ensures a homogeneous influence of the second electrode 9. Also the second electrode 9 may comprise one or more metallic materials or may be formed from a metallic stack including metallic materials like Al, TiN, Ti, Au, Ni and Cr. The dopant layer 5 comprises two layers; a first layer 5a of dopant material and a second layer 5b which is a diffusion layer. In an embodiment, the dopant material is an acceptor material, like boron (B), gallium (Ga), aluminum (Al) or indium (In). Alternatively, the dopant material may be a donor material like phosphorus (P), arsenic (As) or antimony (Sb). Embodiments of the invention will further be described with reference to boron as acceptor material. In this case, the second layer 5b is a layer of a BxSi1-x-compound, i.e., boron (B) encompassed in a silicon structure as suitable under the circumstances, x being a value between zero and one. In an embodiment, the first layer 5a of boron has a thickness of 2-20 nm. As the transparency of the first layer 5a for radiation with wavelengths between 10-200 nm is not 100%, the first layer 5a is kept relatively thin to ensure a high sensitivity. In an embodiment especially suitable for radiation with wavelengths between 150-200 nm, the second layer 5b of a BxSi1-x-compound has a thickness of 1-10 nm. This thickness is sufficient to provide a charge response which, due to aforementioned thickness of the second layer 5b, may be transported without undue delays away via the first electrode. In an embodiment, especially suitable for radiation with wavelengths between 10-150 nm, the second layer 5b of BxSi1-x has a thickness of 50-1000 nm. In an embodiment, the Si-substrate 3 comprises an epitaxial layer of crystalline silicon. In this case, the acceptor layer 5 has been provided on a surface of aforementioned epitaxial layer. Due to the n-type semiconductor doping profile in at least the surface area 10 of the Si-substrate 3, deposition of the first layer 5a of boron causes development of a pn-junction between the surface area of the Si-substrate 3 and a developing diffusion layer 5b of a BxSi1-x-compound. The n-type semiconductor doping profile in at least the surface area and the diffusion layer are so arranged as to form a radiation-sensitive surface of the radiation detector. The radiation-sensitive surface is sensitive for radiation with a wavelength between 10-200 nm. In use, the radiation-sensitive surface, i.e., the surface area of the Si-substrate 3 and the diffusion layer 5b, is at least partly depleted which makes the surface sensitive to aforementioned radiation. The boron layer 5a and BxSi1-x-compound layer 5b improve hardness, i.e., the ability to withstand degradation, of the radiation detector 1 while they, when their thickness is sufficiently chosen, are sufficiently transparent with respect to the radiation of interest, i.e., wavelengths between 10 and 200 nm. In an embodiment, the second layer 5b comprises 2 sub-layers, i.e., a first sub-layer of mono-crystalline BxSi1-x and a second sub-layer of non-monocrystalline BxSi1-x. The first sub-layer of mono-crystalline BxSi1-x is an important layer with respect to transfer of charge from the radiation-sensitive surface of the Si-substrate 3 and the first electrode 7. The second sub-layer of non-monocrystalline BxSi1-x is located between the first sub-layer and the first layer of boron 5a. The second sub-layer has high sheet resistance but is conductive. The presence of the first layer and the second sub-layer of non-monocrystalline BxSi1-x suppresses electron injection from Si-substrate 3. Consequently, the transition between the second layer of BxSi1-x 5b and the Si-substrate 3 is junction-like. The second sub-layer of non-monocrystalline BxSi1-x may have a thickness of 0-2 nm. Thus, aforementioned variation in thickness of second layer 5b of BxSi1-x is, in case aforementioned two sub-layers are present, mainly due to variation in thickness of the first sub-layer of crystalline BxSi1-x. FIG. 4 schematically depicts an elevated side view of the embodiment of the radiation detector depicted in FIG. 3. From FIG. 4, it can be seen that the first electrode 7 may be configured as a conductive grid. A conductive grid as depicted in FIG. 4 enables an increased charge removal velocity. As the boron layer is semi-metallic and the BxSi1-x has high sheet resistance, the read-out speed, which is correlated with the charge removal velocity, becomes slower if the sheet resistance of the BxSi1-x-layer increases. The resistance depends on the distance between the electrode and the location in the BxSi1-x-layer where a charge is induced. The conductive grid limits the maximum value of aforementioned distance. In order to ensure an efficient charge removal, the conductive grid may be circumvented by a conducting ring-shaped electrode (not shown in FIG. 4), which may be located outside the area covered by the radiation-sensitive surface of the radiation detector 1. The conductive grid forms grid cells. Typical areas of grid cells are 5×5, 10×10 and 20×20 μm2. A typical width of the conductive tracks in the conductive grid is 1.0-1.5 μm. In an embodiment, the conductive grid structure comprises aluminum. Aluminum is a conductive material that may be used in cleanroom environments without additional conditions regarding restricted use. The radiation-sensitive surface of radiation detector 1 comprises first regions 12 and second regions 13. In the first regions 12, the first layer 5a, i.e., the layer of Boron, is connected to the first electrode 7. In the second regions 13, the first layer 5a, i.e., the layer of Boron, is covered with an isolation layer 11. The isolation layer 11 is substantially transparent for radiation with a wavelength between 10-200 nm. In an embodiment, the second regions 13 have a cumulative surface area of 10-25 mm2. The isolation layer 11 may be silicon-oxide (SiO2), e.g. provided by means of some type of chemical vapor deposition (CVD) like plasma enhanced CVD or low pressure CVD as will be understood by a person skilled in the art. It must be understood that the isolation layer 11 is an optional layer. Process flows exist to provide a metallic grid without use of isolation layer, e.g., an oxide layer. FIG. 5 schematically depicts an assembly of radiation detectors according to embodiments of the invention, e.g., the embodiment of a radiation detector 1 as depicted in FIGS. 3 and 4. In the assembly shown in FIG. 5, an embodiment of a radiation detector 1 is used in which the conductive grid 7 is connected with an outer ring-shaped electrode 15 as discussed with reference to FIG. 4. The first electrodes 7 of the respective radiation detectors 1a-d may be controlled by connecting the first electrodes of the respective radiation detectors 1a-d with a corresponding bond pad, e.g., one of bond pads 19. In an embodiment, metal tracks from the first electrodes towards a corresponding bond pad are used for this purpose. The second electrode of the respective detectors 1a-d is common and may be connected by directly contacting directly the second electrode 9. The assembly of radiation detectors, in FIG. 5 four radiation detectors 1a-d arranged in a symmetric order, is suitable for measuring radiation provided at different illumination settings, e.g., annular illumination, dipole illumination and quadrupole illumination. FIG. 6 schematically depicts a flow diagram of a method of manufacturing an embodiment of a radiation detector according to the invention. First, in action 61, a silicon (Si) substrate is provided. The Si substrate has a first surface and a second surface opposite thereto. Subsequently, in action 63, a layer of boron (B) is deposited on top of the first surface. Aforementioned deposition is performed such that in said Si substrate a layer of BxSi1-x is formed. Optimal formation takes place at locations where no oxide is present. In order to ensure an oxide-free surface, etching of an oxide layer to the Si-substrate surface before aforementioned deposition may be performed. Subsequently, in action 65, the layer of B is partly covered with a first contact layer comprising a metal, e.g., an electrode 7 or conductive grid as schematically depicted in FIGS. 3 and 4. As a result of the partly covering, first regions and second regions are formed. The layer of B is covered with the first contact layer in the first regions, e.g., the regions where the conductive grid as depicted in FIGS. 4 and 5 is located. The layer of B remains exposed in the second regions, e.g., in the grid cells discussed with reference to FIG. 4. Subsequently, in action 67, the layer of B in aforementioned second regions is covered with an insulation layer. The isolation layer may be silicon-oxide (SiO2). The layer may be provided by means of some type of chemical vapor deposition (CVD) like plasma enhanced CVD or low pressure CVD as will be understood by a person skilled in the art. Finally, in action 69, a second contact layer comprising a metal is deposited on top of the second surface of the Si-substrate. Embodiments of the radiation detector may be used in many applications. Possible applications include use as an energy sensor, a spot sensor, and a slit sensor of a high volume EUV lithographic apparatus. Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion,” respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool and/or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers. Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention may be used in other applications, for example imprint lithography, and where the context allows, is not limited to optical lithography. In imprint lithography a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured. The terms “radiation” and “beam” used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g., having a wavelength of or about 365, 355, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g., having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams. The term “lens”, where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components. While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, the invention may take the form of a computer program containing one or more sequences of machine-readable instructions describing a method as disclosed above, or a data storage medium (e.g., semiconductor memory, magnetic or optical disk) having such a computer program stored therein. The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below. |
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